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 ON THE 3 3 '^■^ 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 ''The profit of the earth is for all : the king himself is served by the field." — Eeclea, v. 9. 
 
 BY JAS. FiWl' JOHNSTON, M.A., F.R.SS. L. & E., 
 
 FELLOW OF THE GEOLOGICAL AND CHEMICAL SOCIETIES, 
 
 Honorary Member of the Royal Agricultural Society, Foreign Member of the Royal 
 Swedish Academy of Agriculture, &c. &c ; Chemist to the Agricultural 
 Chemistry Association of Scotland, and Reader in Chemistry 
 and Mineralogy in the University of Durham. 
 
 NEW EDITION, WITH AN APPENDIX, 
 
 CONTAINING SUGGESTIONS FOR EXPERIMENTS IN PRACTICAL AGRICULTURE. 
 
 NEW YORK: 
 C. M. SAXTON, AGRICULTURAL BOOK PUBLISHER, 
 
 No. 123 FULTON STREET. 
 
 1850. 
 

 VENERABLE CHARLES THORP, D.D. F.R.S., &c., «Scc.. 
 
 ARCHDEACON OF DUKHAM, AND WARDEN OP THE UNIVERSITY OP DURHAM. 
 
 My dear Sir, — 
 I cannot moi'e appropriately dedicate tiie following Lectures than to the head 
 of the University witli which I am officially connected, and within the walls 
 of which the earlier Lectures were first delivered. 
 
 In publishing this Volume I am only endeavouring to follow out the enlight- 
 ened intentions of yourself and the other Founders of the University of Dur- 
 ham, who have contributed so largely of their fortune and their influence for 
 the promotion and diffusion of sound and us ful learning. That you have so 
 long and so successfully laboured to carry these intentions into effect, is ano- 
 ther reason why I desire to dedicate my work especially to you. 
 
 I need scarcely add how much pleasure it affords me to embrace this public 
 opportunity of testifying my own personal regard and esteem. 
 Believe me, rr.y dear Sir, 
 
 With much respect, 
 7- Your obedient humble servant, 
 
 JAMES F. W. JOHNSTON. 
 
 
 
PREFACE. 
 
 The First Part of the following Lectures was addressed 
 to a Society* of practical agriculturists, most of whom pos- 
 sessed no knowledge whatever of scientific Chemistry or Ge- 
 ology. They commence, therefore, with the discussion of 
 those elementary principles which are necessary to a proper 
 understanding of each branch of the subject. Every thing 
 in such Lectures, which is not — or may not be — easily un- 
 derstood by those to whom they are addressed, is worse than 
 useless. It has been my wish, therefore, to employ no scien- 
 tific terms, and to refer to no philosophical principles, which 
 I have not previously explained. 
 
 To many who may take up the latter portions of the work, 
 some points may appear obscure or difficult to be fully un- 
 derstood ; such persons will, I hope, do me the justice to be- 
 gin at the beginning, and to blame the Author only when that 
 which is necessary to the understanding of the later is not 
 to be found in the earlier Lectures. 
 
 For the sake of clearness, I have, in the following pages, 
 divided the subject into four Parts — the study of each pre- 
 ceding Part preparing the way for a complete understanding 
 of those which follow. Thus, Part I. is devoted to the or- 
 ganic elements and parts of plants, the nature and sources 
 of these elements, and to an explanation of the mode in which 
 they become converted into the substance of plants ; — Part 
 II., to the inorganic elements of plants, comprehending the 
 study of the soils from which these elements are derived, and 
 
 * The Durham County Agricultural Society, and the Members of the Dur- 
 ham Farmers' Club. 
 
VI PREFACE. 
 
 the general relations of geology to agriculture ; — Part III., to 
 the various methods, mechanical and chemical, by which 
 the soil may be improved, and especially to the nature of 
 manures^ by which soils are made more productive, and the 
 amount of vegetable produce increased; — and Part IV., to 
 the results of vegetation^ to the kind and value of the food 
 produced under different circumstances, and its relation to 
 the growth and feeding of cattle, and to the amount and 
 quality of dairy produce. 
 
 By this method I have endeavoured to ascend from the 
 easy to the apparently difficult ; and I trust that the willing 
 and attentive reader will find no difficulty in keeping bv niy 
 side during the entire ascent. 
 
 The Author has much pleasure in now presenting these 
 Lectures to the public in a complete form-. He has only to 
 express a hope that the delay which has occurred in the pub- 
 lication of the latter part of the work has enabled him to ren- 
 der it more useful, and therefore more worthy of the public 
 approbation. 
 
 Note. — The rapid sale of a large impression having rendered a second 
 edition of the first and second Parts necessary hefore the entire comple- 
 tion of the work, such alterations, corrections, and additions only have 
 been made as could be introduced without altering the original paging of 
 the work. Several oversights, however, have been corrected, and some 
 omissions supplied, which presented themselves in the earlier edition. 
 
CONTENTS. 
 
 F^aRT z. 
 
 ON THE ORGANIC CONSTITUENTS OF PLANTS. 
 
 LECTURE I. 
 
 IMPORTANCE OF AGRICULTURE. 
 
 introduction -. P-H I Hydrogen, its properties and relations to 
 
 Different kinds and'state's of malter 21 | vegetable life p. 25 
 
 Carbon, its properties and relations to ve- i Nitrogen, its properties and relations to 
 
 getable life 23 j vegetable life ....26 
 
 Oxygen, its propertieVdnd relations to ve- | Rewards of study 27 
 
 getable life 
 
 .24 
 
 LECTURE IL 
 
 CHARACTERISTIC PROPERTIES OF ORGANIC SUBSTANCES. 
 
 On the constitution of the atmosphere 31 
 
 The nature and laws of chemical combi- 
 nation 32 
 
 Of water, and its relations to vegetable life.. 36 
 Of the cold produced by the evaporation 
 of water, and its influence on vegetation . .43 
 
 Characceristic properties of organic sub- 
 stances 28 
 
 Relative proportions of organic elements.. 29 
 Of the form or state of combination in 
 which the organic elements enter into 
 and minister to the growth of plants .31 
 
 LECTURE III. 
 
 CARBONIC AND OXALIC ACIDS, THEIR PROPERTIES AND RELATIONS. 
 
 Carbonic acid, its properties and relations 
 to vegetable life 45 
 
 Oxalic acid, its properties and relations to 
 vegetable life 47 
 
 Carbonic oxide, its constitution and pro- 
 perties... 48 
 
 Light carburetted hydrogen, the gas of 
 marshes and of coal mines 49 
 
 Ammonia, its properties and relations to 
 vegetable life 50 
 
 Nitric acid, its constitution and properties . .56 
 
 Questions to be considered 57 
 
 LECTURE IV. 
 
 SOURCE OF THE ORGANIC ELEMENTS OF PLANTS. 
 
 Source of the carbon of plants 58 
 
 Form in which carbon enters into the cir- 
 culation of plants 63 
 
 Source of the hydrogen of plants 64 
 
 Source of the oxygen of plants 66 
 
 Source of the niti-ogen of plants ,...ib. 
 
 Form in which the nitrogen enters into 
 
 the circulation of plants 68 
 
 Absorption of ammonia by plants 70 
 
 Absorption of nitric acid by plants 72 
 
 Conclusions 74 
 
 LECTURE V. 
 
 HOW DOES THE FOOD ENTER INTO THE CIRCULATION OF PLANTS 1 
 
 General structure of plants, and of their 
 
 several parts 75 
 
 The functions of tlie root 76 
 
 The course of the sap 85 
 
 Functions of the .stem 88 Effects of marling 
 
 Functions of the leaves 89 
 
 Functions of the bark 96 
 
 Circumstances by which the functions of 
 the various parts of plants are modified . . 97 
 
 .101 
 
CONTENTS OF PART I. 
 
 LECTURE VI. 
 
 SUBSTANCES OP 'WHICH PLANTS CHIEFLY CONSIST. 
 
 Woody fibre or lignin — its constitution 
 
 and properties p. 103 
 
 Starch — its constitution and properties. . . .106 
 
 Gum — its constitution and properties 108 
 
 Of Sugar— its varieties and ciiemical con- 
 stitution 109 
 
 Mutual relations of woody fibre, starch, 
 
 gum, and sugar Ill 
 
 Mutual transformations of woody fibre, 
 starch, gum, and sugar 112 
 
 Of the fermentation of starch and sugar, 
 and of the relative circumstances under 
 which cane and grape sugars generally 
 occur in nature p. 115 
 
 Of substances which contain nitrogen. — 
 Gluten, vegetable albumen, and diastase. 116 
 
 Vegetable Acids. — Acetic acid, oxalic acid, 
 tartaric acid, citric acid, malic acid 121 
 
 General observations on the substances 
 of which plants chiefly consist 126 
 
 LECTURE VII. 
 
 CHEMICAL CHANGES BY WHICH THE SUBSTANCES OF WHICH PLANTS CHIEFLY 
 CONSIST ARE FORMED FROM THOSE ON WHICH THEY LIVE. 
 
 Chemical changes which take place du- 
 ring germination, and during the devel- 
 opement of the first leaves and roots — 130 
 
 Of the chemical changes from the for- 
 mation of the true leaf to the expansion 
 of the flower 134 
 
 On the production of oxalic acid in the 
 leaves and stems of plants .137 
 
 Of the chemical changes between the 
 opening of the flower and the ripening 
 of the fruit or seed 139 
 
 Of the chemical changes which take place 
 aft«r the ripening of the fruit and seed.. 143 
 
 Of the rapidity with which these changes 
 take place, and the circumstances by 
 which they are promoted 'it. 
 
 LECTURE VIII. 
 
 HOW THE SUPPLY OF FOOD FOR PLANTS IS KEPT UP IN THE GENERAL 
 VEGETATION OP THE GLOBE. 
 
 Of the proportion of their carbon which 
 
 ?ilants derive from the atmosphere ..145 
 the relation which the quantity of car- 
 bon extracted by plants from the air, 
 bears to the whole quantity contained 
 
 in the atmosphere 147 
 
 How the supply of carbonic acid in the 
 
 atmosphere is renewed and regulated .. 148 
 General conclusions in relation thereto.. .155 
 
 Of the supply of ammonia to plants 156 
 
 Of the supply of nitric acid to plants 159 
 
 Theory of the action of nitric e^Ad and 
 
 ammonia 163 
 
 Comparative influence of nitric acid and 
 
 of ammonia in different climates 166 
 
 Stimulating influence of these compound*. i>. 
 Concluding obser\'ations regarding the 
 
 organic constituents of plants 166 
 
PiLRT IZ. 
 
 ON THE INORGANIC ELEMENTS OF PLANTS. 
 
 LECTURE IX. 
 
 INORGANIC CONSTITUENTS OF VEGETABLE SUBSTANCES. 
 
 Of the relative proportions of inorganic 
 
 matter in vegetable substances p. 178 
 
 Kind of inorganic matter found in plants. . 180 
 Of the several elementary bodies usually 
 met with in the ash of plants 182 
 
 Of those compounds of the inorganic ele- 
 ments which enter directly into the 
 circulation, or exist in the substance 
 and ash of plants 133 
 
 LECTURE X. 
 
 INORGANIC CONSTITUENTS OF PLANTS CONTINUED. 
 
 Inorganic constituents of plants continued .200 
 Tabular view of the constitution of the 
 compounds of the inorganic elements 
 
 above described 214 
 
 On the relative proportions of the differ- 
 ent inorganic compounds present in 
 the ash of plants 216 
 
 To what extent do the crops most usual- 
 ly cultivated exhaust the soil of inor- 
 ganic vegetable food 1 220 
 
 Of the alleged constancy of the inorganic 
 constituents of plants, in kind and 
 quantity ■ 225 
 
 LECTURE XL 
 
 NATURE AND ORIGIN OF SOILS. 
 
 Of the organic matter in the soil 229 
 
 General constitution of the earthy part of 
 
 the soil 230 
 
 Of the classification of soils from their 
 
 chemical constituents 232 
 
 Of the distinguishing characters of soils 
 
 and subsoils , 235 
 
 Of the general origin of soils 236 
 
 On the general structure of the earth's 
 crust 237 
 
 Relative positions and peculiar charac- 
 ters of the several strata 239 
 
 Classilication of the stratified rocks, their 
 extent, and the agricultural relations of 
 the soils derived from them 241 
 
 LECTURE XIL 
 
 COMPOSITION OF THE GRANITIC ROCKS, 
 
 Composition of the granitic rocks 257 
 
 Of the degradation of the granitic rocks, 
 
 and of the soils formed from them ...260 
 Of the trap rocks, and the soils formed 
 
 from them 263 
 
 Of superficial accumulations of foreign 
 
 materials, and of the means by which 
 
 they have been transported 266 
 
 AND OF THEIR CONSTITUENT MINERALS. 
 
 Of the occurrence of such accumulations 
 in Great Britain, and of their influence 
 in modifying the character of the soil.. 270 
 
 How far these accumulations of drift in- 
 terfere with the general deductions of 
 Agricultural Geology 272 
 
 Of superficial accumulations of peat 275 
 
 LECTURE XIII. 
 
 EXACT CHEMICAL CONSTITUTION OF SOILS. 
 
 Of the exact nature of the organic con- 
 stituents of soils, and of the mode of 
 separating them,. . 277 
 
 Of the exact chemical constitution of 
 the earthy part of the soil 281 
 
 Of the exact chemical constitution of 
 certain soils, and of the results to be 
 
 deduced from them 282 
 
 or the physical properties of soils 290 
 
 Conclusion 297 
 
F^RT III. 
 
 ON THE IMPROVEMENT OF THE SOIL BY MECHANICAL AND 
 CHEMICAL MEANS, 
 
 LECTURE XIV. 
 
 THE QUALITIES OF THE SOIL MAY BE CHANGED BY ART. 
 
 Connection between the kind of soil and 
 the kind of plants that grow upon it. p. 304 
 
 Of draining, and its effects 306 
 
 Practical effects of draining 311 
 
 Of the theory of springs p. 312 
 
 Of ploughing'and subsoiling 318 
 
 Of deep-ploughing and trenching 321 
 
 Improvement of the soil by mixing 323 
 
 LECTURE XV. 
 
 IMPROVEMENT OF THE SOIL BY CHEMICAL MEANS. 
 
 Of saline manures 327 
 
 Theory of the action of potash and soda. 328 
 Sulphates of potash, soda, magnesia, and 
 
 lime (gypsum) 331 
 
 Theory of the action of these sulphates.. 332 
 
 Nitrates of potash and soda 335 
 
 Effect of these nitrates on the quantity 
 
 of various crops 336 
 
 Effect of the nitrates on the qualify of 
 
 the crop 339 
 
 Cases in which they have failed 341 
 
 Theory of the action of these nitrates... 343 
 Special effeCts-ef^the nitrates of potash 
 
 and soda .344 
 
 Use of common salt 345 
 
 Chlorides of calcium and magnesium. ..347 
 Phosphate of Hme and earth of bones... 348 
 
 Silicates of potash and soda 349 
 
 Salts of ammonia ib. 
 
 Of mixed saline manures 352 
 
 Wood ashes.. ib. 
 
 Use of kelp 355 
 
 Straw ashes 356 
 
 Turf peat or Dutch-ashes 359 
 
 Crushed granites and lavas 361 
 
 Results of experiments with mixed ma- 
 nures ....362 
 
 LECTURE XVL 
 
 OF THE USE OF LIME AS A MANURE. 
 
 Of the composition of common and 
 magnesian limestones 364 
 
 Of the burning and slaking of lime 366 
 
 Changes which the hydrates of lime 
 and magnesia undergo by prolonged 
 exi)osure to the air 367 
 
 States of chemical combination in which 
 lime may be applied to the land 3G9 
 
 Of the various natural forms in which 
 carbonate of lime is applied to the land. 370 
 
 Effects of marl, and of the coral, shell, 
 and lime-stone sands upon the soil. . . .374 
 
 Of the use of chalks, as a manure 375 
 
 Is lime indispensable to the fertility of 
 the soil! 377 
 
 States of combination in which lime ex- 
 ists in the soil 373 
 
 Of the quantity of lime which ought to 
 be added to the soil 381 
 
 Ought lime to be applied in large doses 
 at distant intervals, or in smaller quan- 
 tities more frequently repeated? 383 
 
 Form and state of combination in which 
 
 lime ought to be applied to the land. . .386 
 Use and advantage of the compost form. -388 
 
 When ought lime to be applied 7 3S9 
 
 Of the effects produced by lime upon 
 
 the land and upon the crops 390 
 
 Circumstances by which the effects of 
 
 lime are modified 393 
 
 Effects of an overdose of lime 395 
 
 L'-ngth of time during which lime acts.. 396 
 
 Of the sinking fif lime into the soil 397 
 
 Why liming must be repeated 398 
 
 Theory of the action of lime 400 
 
 or lime as the food of plants ib. 
 
 The chemical action of^ lime is exerted 
 chiefly on the organic matter of the soil.401 
 
CONTENTS OF PART III. 
 
 Of the forms in which organic matter 
 usaally exists in the soil, and the cir 
 cumstances under which its decom- 
 position may take place p. 401 
 
 General action of alkaline substances 
 upon organic matter 403 
 
 Special effects of caustic lime upon the 
 several varieties of organic matter in 
 the soil 404 
 
 Action of mild (or carbonate of) lime 
 upon the vegetable matter of the 
 soil 406 
 
 Of the comparative utility of barned and 
 
 unburned lime p. 408 
 
 Action of lime on organic substances 
 
 which contain nitrogen 409 
 
 How these chemical changes directly 
 
 benefit vegetation 412 
 
 Why Hme must be kept near the surface.ib. 
 Action of lime upon th6 inorganic or 
 
 mineral matter of the soil 413 
 
 Action of lime on animal and vegetable 
 
 life 415 
 
 Use of silicate of lime 416 
 
 LECTURE XVII. 
 
 OF ORGANIC MANURES. 
 
 Of green manuring or the application of 
 vegetable matter in a green stale 417 
 
 Important practical results obtained by 
 green manuring 418 
 
 Of the plants which in different soils 
 and climates are employed for green 
 manuring 419 
 
 Will green manuring alone prevent land 
 from becoming exhausted 1 421 
 
 Of the practice of green manuring 422 
 
 Of natural manuring with recent vegeta- 
 ble matter ib- 
 
 Weisht of roots left in the soil by the 
 different grasses and clevers 423 
 
 Improvement of the soil by laying down 
 to grass 424 
 
 Improvement of the soil by the planting 
 of trees 429 
 
 Of the use of sea- weed as a manure 431 
 
 Of manuring with dry vegetable sub- 
 stances 433 
 
 Use of rape-dust 434 
 
 Use of decayed vegetable matter as a 
 manure 436 
 
 Use of charred vegetable matters — soot, 
 &c., as manures 437 
 
 Of the theoretical value of different 
 vegetable substances as manures 440 
 
 LECTURE XVIII. 
 
 ANIMAL MANURES, 
 
 Of flesh, blood, and skin 443 
 
 Of wool, woollen rags, hair, and horn. . .445 
 
 Of the composition of bones 446 
 
 On what does the fertilizing action of 
 
 bones depend 1., ., 447 
 
 Of the application of bone-dust to pas- 
 ture lands 451 
 
 Of animal charcoal, the refuse of the su- 
 gar refineries, and animalized carbon. .452 
 Of fish, fish refuse, whale blubber, and 
 
 oil.... 453 
 
 Relative fertilizing value of the animal 
 
 manures already described 454 
 
 Of the droppings of fowls— pigeons' 
 
 dung and guano 456 
 
 Results of experiments with guano 459 
 
 Of liquid animal manures— the urine of 
 man, of the cow, the horse, the 
 
 sheep, and the pig 460 
 
 Of the waste of liquid manure — of urate 
 and of sulphated urine 463 
 
 Of solid animal manures- night soil, 
 the dung of the cow, the horse, the 
 sheep, and the pig 465 
 
 Of the quantity of manure produced 
 from the same kind of food by the 
 horse, the cow, and the sheep. ... - .468 
 
 Of^ the relative fertiUzing values of dif- 
 ferent animal excretions 469 
 
 Influence of circumstances on the quali- 
 ty of animal manures 470 
 
 Of the changes which the food under- 
 goes in passing through the bodies of 
 animals ....472 
 
 Of farm-yard manure, and the loss it un- 
 dergoes by fermenting 474 
 
 Of top-dressing with fermenting ma- 
 nures 477 
 
 Of eating off with sheep 478 
 
 Of the improvement of the soil by irri- 
 gation 479 
 
P^RT IV. 
 
 ON THE PRODUCTS OF THE SOIL, AND THEIR USE IN THE FEEDING 
 
 OF ANIMALS. 
 
 LECTURE XIX. 
 
 OF THE PRODUCE OF THE SOIL. 
 
 Of the maximum or greatest possible and 
 the average or actual produce of tiie 
 
 land p. 487 
 
 Of the circumstances by which the pro- 
 duce of food is affected — climate, sea- 
 son, soil, «fec 488 
 
 Ir^uence on tiie mode of culture on the 
 
 produce of food 490 
 
 Of the theory of the rotation of crops. . . . 492 
 
 Why land becomes tired of clover 494 
 
 Of the theory of fallows 495 
 
 Of wheat and wheaten flour 49S 
 
 Of the composition of wheaten flour.... 499 
 Of the influence of soil and climate on 
 
 the composition of wheaten flour 501 
 
 Influence of variety of seed, of mode of 
 culture, of timeof cutting, and of special 
 manures on the composition of wheat. 502 
 Of the effects of germination and of bak- 
 ing upon the flour of wheat 5(X1 
 
 Of the supposed relation between the per- 
 centage of gluten in flour, and the 
 
 weight of br«a*i obtained from it 507 
 
 Of the composition of barley, and the in- 
 fluence of different manures upon the 
 relative proportions of its several con- 
 stituents 508 
 
 Effect of malting upon barley 509 
 
 Of the composition of oats, and effect of 
 manures in modifying that composition. 510 
 
 Of the composition of rye, and the effect 
 of dilferenl manures upon its composi- 
 tion p. 510 
 
 Composition of rice, Indian corn, and 
 buck- wheat 511 
 
 On the alleged general etfeci of different 
 manures \n modifying the amount of 
 gluten and albumen in wheat, barley, 
 oats, and rye 513 
 
 Composition of peas, beans, and vetches. 515 
 
 Etfect of soils and n;anures on the quality 
 of peas and beans 518 
 
 Of the composition o I potatoes, and the 
 effect of circumstances in modifying 
 their composition £20 
 
 Of the composition of the im-nip, theceir- 
 rot, the beet, anii'heparsjiip. 523 
 
 Of the composition of the green stems of 
 peas, vetches, clover, spurry, and 
 buckwheat 525 
 
 Of the composition of the grasses when 
 made into hay 526 
 
 Of hemp, line, rape, and other oil-bearing 
 seeds 528 
 
 General differences in composition among 
 the different kinds of vegetable food... 529 
 
 Average composition and produce of nu- 
 tritive matter per acre, by each of the 
 usually cultivated crops 530 
 
 LECTURE XX. 
 
 OF MILIC AND ITS PRODUCTS. 
 
 Of the properties and composition of 
 milk 533 
 
 Of the circumstances by which the com- 
 position or quality of milk is modified. 534 
 
 Of the circumstances which atfect the 
 quantity of the milk 540 
 
 Of the mode of separating and estimating 
 the several constituents of milk 542 
 
 Of the sugar of milk, and of the acid of 
 milk or lactic acid &13 
 
 Of the mutual relations which exist be- 
 tween lactic acid and the cane, grape, 
 and milk sugars 544 
 
 Of the souriog aad preserving of milk. . . 546 < 
 
 Of the separation and measurement of 
 cream — the galactometer — the compo- 
 sition of cream, and ilie preparation of 
 cream cheese 547 
 
 Of the separation of butter by churning 
 orotlierwise 549 
 
 Of the composition of butter 551 
 
 Of the average quantity of butter yielded 
 by milk and cream, and of the yearly 
 produce of a cow 552 
 
 Of the circumstances which affect the 
 quality of butter 553 
 
 Of the fatty substances of which butter 
 consists, and of the acid of butter (buty> 
 
CONTENTS OP PART IV. 
 
 lie acid), and the capric and caproic 
 
 acids P-557 
 
 Of casein or the curd of milk and its pro- 
 perties 561 
 
 Of the relations of casein to the sugars 
 
 and fats 562 
 
 Of the rancidity and preservation of butter 563 
 Of the natural and artificial curdling of 
 
 milk 566 
 
 Of the preparation of rennet 567 
 
 Theory of the action of rennet 569 
 
 Of the circumstances by which the quali- 
 ty of cheese is affected 573 
 
 Circumstances under which cheese of 
 different qualities may be obtained from 
 the same milk 575 
 
 Of the average quantity of cheese yielded 
 by different varieties of milk, and of 
 the produce of a single cow p. 580 
 
 Of the fermented liquor from milk, and of 
 milk vinegar 581 
 
 Of the composition of the saline constitu- 
 ents of milk ib. 
 
 purposes served by milk in the animal 
 economy, , 582 
 
 On the churning of milk in the French 
 chum ib. 
 
 Quantity of milk dnd batter yielded by 
 Ayrshire cows 583 
 
 Profit of making butter and cheese com- 
 pared with that of selling the milk 584 
 
 LECTURE XXI. 
 
 OF THE FEEDING OF ANIMALS, AND THE PURPOSES SERVED BY THE POOD. 
 
 Of the subsLances of which the parts of 
 animals consist , 586 
 
 Whence does the body obtain these sub- 
 stances 1 are they contained in the 
 food? 589 
 
 Of the respiration of animals, and of the 
 purposes served by the starch, gum, 
 and sugar contained in vegetable food. . 591 
 
 Of the origin and purposes served by the 
 fat of animals 594 
 
 Of the natural waste of the parts of the 
 body in a full grown animal, 597 
 
 Of the kind and quantity of food necessa- 
 ry to make up for the natural waste in 
 the body of a full-grown animal 598 
 
 The health of an animal can be sustained 
 only by a mixed food 600 
 
 Of the kind and quantity of additional 
 food required by the fattening animal.. 601 
 
 Kind and quantity of additional food re- 
 quired by a growing animal. 602 
 
 Kind and quantity of additional food re- 
 quired by a pregnant animal 604 
 
 Kind and quantity of additional food re- 
 quired by a milking animal 605 
 
 Influence of size, condition, warmth, ex- 
 ercise, and light on the quantity of food 
 necessary to make up for the natural 
 waste 607 
 
 Influence of the form or state in which 
 the food is given on the quantity re- 
 quired by an animal , . 611 
 
 Influence of soil and culture on the nutri- 
 tive value of agricultural produce 612 
 
 Car. we correctly estimate the feeding 
 properties of different kinds of produce 
 under all circumstances 1 613 
 
 Effect of different modes of feeding on 
 the manure and on the soil 615 
 
 Summary of the views illustrated in this 
 lecture 617 
 
 Concluding section •• 619 
 
jBLPPEirDZX. 
 
 1. Suggestions for experiments in 
 
 practical agriculture , , p. 1 
 
 ^ 11. Effect of sudden alternations of 
 
 temperature 11 
 
 III. Results of experiments in practical 
 
 agriculture made during the spring 
 
 and summer of 1841 — 
 
 At AskeHall 13 
 
 At Erslcine 16 
 
 At Barochan — 
 
 1. On hay 17 
 
 2. On winter rye 18 
 
 3. On wheat 19 
 
 4. On potatoes 20 
 
 5. On moss oats ..21 
 
 6. On oats, with sulpliate and ni- 
 
 "■ trate of soda, as a top-dressin;?. .22 
 
 7. On peas and bean.s, with sulpliate 
 
 of soda 23, 
 
 • ■ 8. On nitrate ofsoda as a top-dress- 
 ing for gooseberry and currant 
 bushes 23 
 
 IV. Suggestions for comparative ex- 
 
 periments with guano and other 
 manures ..24 
 
 V. Of the examination and analysis of 
 
 soilsTTT. 27 
 
 Determinationof the physical pro- 
 
 ?erties of the soil ib. 
 the organic matter present in 
 
 tliesoil 29 
 
 Of the soluble saline matter in the 
 
 soil 31 
 
 Determination of the quantity of 
 
 the several constituents of the 
 
 soluble saline matter ... .33 
 
 Of the insoluble earthy matter of 
 
 the soil.. 37 
 
 VI. Different theories of the action of 
 
 gypsum 39 
 
 Vn. Suggestions for experiments with 
 
 the silicates of potash and soda. . .40 
 Vm. Results of experiments in practical 
 agriculture made in 1&12— 
 A. Experiments on turnips — 
 
 1. Made at Lennox Love 42 
 
 2. Made at Barochan 43 to 46 
 
 3. Made at Southbar 46 
 
 4. Made at Muirkirk ib. 
 
 5. Effect of gypsum on the tur- 
 
 nip crop 47 
 
 VIII. Results of experiments in practi- 
 cal agriculture made in 1842 — 
 B. Experiments on potatoes — 
 
 1. Those of Mr. Campbell, of 
 
 Craigie •?• ^^ 
 
 2. Those of Mr. Fleming, of 
 
 Barochan 47 to 51 
 
 C Experiments upon barley 51 
 
 C Experiments upi^n oat.s — 
 
 1. Those of Lord Blantyre 52 
 
 2. Those of Mr Fleming 53 
 
 E. Experiments upon wheat — 
 
 1. Those of Lord Blantyre 53 
 
 2. Those of Mr. Fleming 54 
 
 3. Those of Mr. Burnet, of Gad- 
 
 girth ib 
 
 F. Experiments upon pasture and 
 
 other grasses — 
 
 1. Those of Ml. Alexander 55 
 
 '2. Those of Mr. Fleming 56 
 
 3. Tiio3eofMr.Campb.;li,ofIsla.ib. 
 
 G. Experiments upon mixed crops 
 
 by Mr. Alexander 57 
 
 II. Experiments upon beans — 
 
 1. Those of Mr. Alexander ib. 
 
 2. Those of Lord Blantyre ib. 
 
 I. Effect of the top-dressings ap- 
 
 plied in 1841 upon the crop 
 of 1842 58 
 
 II. Remarks upon the experiments 
 
 of 1842 ib. 
 
 A. The experiments on turnips... 59 
 
 B. The experiments on potatoes.. 64 
 
 C. The experiments on barley... 67 
 
 D. The experiments on oats ib. 
 
 E. The experiments on wiieat....68 
 
 F. The experiments on grass 71 
 
 G. The experiments on mixed 
 
 crops 73 
 
 II. The experiments on beans, ...ib. 
 IX. Results of additional experiments 
 
 made in 1842 75 
 
 Remarks on these experiments.. .73 
 X. Experiments in practical agricul- 
 ture made in 1843 by Mr. 
 Fleming, of Barochan — 
 
 1. With guano upon potatoes... 83 
 
 2. On hay 85 
 
 3. On oats 86 
 
 4. On turnips. 87 
 
 Remarks on these experiments. ..89 
 
LECTURES 
 
 ON THE 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 fo 
 
 AGRICULTURE. 
 
 ON THE ORGANIC ELEMENTS OF PLANTS, 
 
LECTURE I. 
 
 Importance of Agriculture— Relation of the growth of food to the population of Great Britain — 
 Recent progress and prospects of English Agriculture— Application of Chemical and Geo- 
 logical Science to the art of culture — to the improvement of soils — the rotation of crops — 
 the application of manures, &c.— Outline of the Course of Lectures — Number and nature 
 of the elementary bodies — The organic elements Carbon, Hydrogen, Oxygen, and Nitro 
 gen, their properties and their relations to vegetable life. 
 
 Were I about to address you in a single or detached Lecture only, I 
 should think it my duty to select sonae one branch of the art of culture 
 for special illustration, and without much introductory matter to pro- 
 ceed at once to the exposition of the principle or principles on which it 
 depended. As the present, however, is only the first of a Series of Lec- 
 tures I hope to have the honor of delivering to you, I may be permitted 
 to introduce my subject with a few prefatory remarks, which will here 
 find their appropriate place. 
 
 In regard to the importance of Agriculture it may appear superfluous 
 in me to address you. That art on which a thousand millions of men 
 are dependent for their very sustenance — in the prosecution of which 
 nine-tenths of the fixed capital of all civilized nations is embarked — and 
 probably two hundred millions of men expend their daily toil — that art 
 must confessedly be the most important of all ; the parent and precursor 
 of all other arts. In every country then, and at every period, the in- 
 vestigation of the principles on which the rational practice of this art is 
 founded, ought tp have commanded the principal attention of the great- 
 est minds. To what other object could they have been more benefi- 
 cially directed ? 
 
 But there are periods in the history of every country when the study 
 of Agriculture becomes more urgent, and in that country acquires a 
 vastly superior importance. When a tract of land is thinly peopled, 
 like the newly settled districts of North America, New Holland, or 
 New Zealand, a very defective system of culture will produce food 
 enough not only for the wants of the inhabitants, but for the partial sup- 
 ply of other countries also. But when the population becomes more 
 dense, the same imperfect or sluggish system will no longer suffice. 
 The land must be better tilled, its special qualities and defects must be 
 studied, and means must gradually be adopted for extracting the maxi- 
 mum produce from every portion susceptible of cultivation. 
 
 The British islands are in this latter condition. Agriculture now is 
 of vastly more importance to us as a nation, than it was towards the 
 close even of the last century. In 1780, the island of Great Britain 
 contained about 9 millions of inhabitants; it now contains nearly 20. 
 The land has not increased in quantity, but the consumption of food has 
 probably more than doubled. The importation from abroad has not in- 
 creased to any itiiportant extent; by improved management, therefore, 
 the same area of land has been caused to yield a double produce. 
 
 But the population will continue to increase; can we expect that the 
 food raised from the land will continue to increase in the same ratio? 
 
i2 ON IMPROVEMENTS IN AGRICULTURE. 
 
 This is an important question, to which we can give only an imperfect 
 and somewhat unsatisfactory answer. 
 
 The superficial area of Great Britain comprises about 57 millions ^^f 
 acres, of which 34 millions are in cultivation, about 13 millions are in- 
 capable of culture, and the remaining 10 millions are wastelands suscep- 
 tible of improvement. The present population, therefore, is supported 
 by the produce of 34 millions of acres, or every 34 acres raises food for 
 about 20 people. Suppose the 10 millions of acres which are suscepti- 
 ble of improvement to be brought into such a stale of culture as to 
 maintain an equal proportion — the most favourable supposition — they 
 would raise food for an additional population of about 6 millions, or 
 would keep Great Britain independent of any large and constant foreign 
 supply till the number of its inhabitants amounted to 26 millions. 
 But at the present rate of increase this will take place in about 20 
 years,* so that by 1860, unless some general improvement take place 
 in the agriculture of the country, the demands of the population will 
 have completely overtaken the productive powers of the land. 
 
 But though we cannot say how far the fertility of the soil may be in- 
 creased, or how long it may be able lo keep a-head of the growing 
 numbers of the people, we have our own past experience, the example 
 of other countries, and the indications of theory, all concurring to per- 
 suade us that the limit of its productive powers can neither be predicted 
 nor foreseen. 
 
 If we glance at the history of British agriculture during the last half 
 century — from the introduction of the green crop system or the alternate 
 iusbandry from Flanders into Norfolk, up to the present time — we find 
 the results of each successive improvement more remarkable than the 
 former. The use of lime, a more general drainage of the soil, the in- 
 vention of improved ploughs and other agricultural implements, as well'' 
 as the introduction of better and more economical modes of using them, 
 the application of bone manure, and more recently of thorough draining 
 and subsoil ploughing, have all tended not only to the raising of crops 
 at a less cost^ but in far greater abundance, and on spots which our 
 forefathers considered wholly unfit for the growth of corn. 
 
 The result of each new improvement, I have said, has seemed more 
 astonishing than the former. For after a waste piece of land has been 
 brought into an average state of productiveness, we are not prepared for 
 any great improvement upon it by new labours; nor could we readily 
 believe that, half a century after such land had been in culture, its pro- 
 duce or its value should at once be doubled, by a better draining, a 
 deeper ploughing, or by sprinkling on its surface a small quantity of a 
 saline substance imported ft-om a foreign country. 
 
 Yet the example of the Chinese shows us that the productive powers 
 of the soil are not to be easily estimated. Nothing repays the labours 
 of the husbandman more fully than the willing soil — nothing is more 
 grateful for his attention, or offers surer rewards to patient industry, or 
 to renewed attempts at improvement. 
 
 In China we see a people whom we call semi-barbarians, multiply- 
 ing within their own limits till their numbers are almost incredible; 
 
 * For more precise data and calculations see Porter^s Progress c^f the Nation. 
 
PROSPECTS OF SCIENTIFIC AGRICULTURE. 13 
 
 practising from the most remote ages, and in the most skilful manner, 
 various arts which the progress of modern science has but recently in- 
 troduced into civilized Europe; cultivating their soil with the most assid- 
 uous labour, and stimulating its fertility by means which we have hith- 
 erto neglected, despised, or been wholly ignorant of — but which the dis- 
 coveries of the present time are pointing out as best fitted to secure the 
 amplest harvests — and have thus been enabled to compel their limited 
 soil to yield a sufficient sustenance to its almost unlimited population.* 
 
 Experience and example, therefore, encourage us to look forward to 
 still further improvements in the art of culture, and, independent of such 
 as may be derived from purely mechanical principles, theoretical 
 cnemistry seems to point out the direction in which important advances 
 of another kind may reasonably be anticipated. The Chinese are said 
 to be not only familiar with the relative value and efficiency of the va- 
 rious manures, but also to understand how to prepare and apply without 
 loss that which is best fitted to stimulate and support each kind of plant. 
 How far this statement is exaggerated we are unable at present to de- 
 termine, but it is in this direction that chemistry appears likely to pro- 
 mote the advance of European agriculture. The practical farmer al- 
 ready rejoices in having in one ton of bone dust the equivalent of 14 
 tons of farm-yard manure; some of the most skilful living chemists 
 predict that methods will hereafter be discovered for comi)ressing into a 
 still less bulky form the substances required by plants, and that we 
 shall live to see extensive manufactories established for the preparation 
 of these condensed manures.f 
 
 * An intelligent correspondent reminds me that tlie agricultural skill of the Chinese is 
 questioned by recent writers on the customs of that country. This doubt is founded chiefly 
 on the rudeness of iheir agricultural implements and the scarcity of cattle, whether horses 
 or cows, amon;^ tlicm. But in this densely peopled country the hoe they employ serves 
 the purpose of every other implement (Davis^s China, ii. 282), and where the place of cat- 
 tle is supplied by an equivalent number of men, there can be no couiparative want of 
 valuable manure. The population of China, however, is probably not so dense in all the 
 provinces as it has hitlierlo been supposed. Many writers have estimated ihe entire 
 population at 300 millions, while recent statists reduce it to 175 millions. Taking even the 
 higher estimate, the population is not more dense than in England and Holland — the area 
 of China proper being 1,200,000 square miles, or eight times that of France. It is considera- 
 bly less dense, indeed, if we take into account the number of horses and catile which in 
 Europe are reared and fed on the produce of the land. We may hereafter expect more ac- 
 curate information, however, especially regarding the interior of this interesting' country. — 
 See Apjyendiz A. 
 
 1 Should the opinions above expressed appear too sanguine to some, or be treated by any 
 of my readers as wjera'y theuretical, I would refer them to the words of Mr. Sniilh of Dean- 
 ston, the inventor of the subsoil plough, and the introducer of Ihe greatest practical im- 
 provement in modern agriculture. After stating that a< /cas^ Ihree/ourth-'i of the ichole ara- 
 ble land in the country is under very indifferent culture, chielly from tlie want of complete 
 draining and deep working, and, adverting to the increased produce it may be made to 
 yield, he says, -'it is not at all improbable that Brilain may become an e.xporting country in 
 grain in the course of the next iwcnty years." — Remarks on Thoroiigh Draining and Deep 
 Ploughing, by James Smith, Esq., of Deanston Works, p. 22. Were the population to 
 remain stationury, Mr. Smith maybe right; at all events, this opinion shows that even 
 practical men do not despair of altaining to a pitch of improvement in agriculture which 
 theoretical writers dare not venture to predict. 
 
 But among ail persons of enlarged information a similar opinion prevails. Thus the 
 eloquent author of a recent work on the principles of population says, '' the single alteration 
 of substituting the kilchen-garden husbandry of Flanders in our plains, and the terraced 
 culture of Tuscany in our hills, for the present system of agricultural management, would 
 at once double the produce of the British islands, and procure amjile subsistence for twice 
 the number of its present inhabitants." — Alison's Princijjles of Po2ndation, I. p. 216. These 
 hopes are not to be rejected or suppressed ; for, though they may never be fully realized, 
 yet they are, as it were, the seeds of exertion, from which ample harvests of good may 
 hereafter be reaped. 
 
14 NEGLECT OF SCIENTIFIC AGRICULTURE IN SCHOOLS. 
 
 Thus much may be said in regard to the future hopes and prospects 
 of scientific agriculture.* But how few practical men are acquainted 
 with what is already known of the principles of the important art by 
 whicli they live ! Trained u\) in ancient methods — attached generally 
 to conservative principles in every shape — the practical agriculturists, 
 as a body, have always been more opposed to change than any otlier 
 large class of the community. They have been slow to beUeve in the 
 superiority of any methods of culture which differed from their own, 
 from those of their fathers, or of the district in which they live — and, 
 even when the superiority could no longer be denied, they have been 
 almost as slow to adopt them. 
 
 But the asvakening spirit of the time is making itself felt in the re- 
 motest agricultural districts ; old prejudices are dying out, and the cul- 
 tivators of this most ancient, most important, and noblest of all the arts, 
 are becoming generally anxious for information, and eager for improve- 
 ment.! 
 
 Two circumstances have contributed to retard the approach of this 
 better state of things. 
 
 In the first place, the agricultural interest in England has hitherto 
 expended its main strength in attempting to secure or maintain impor- 
 tant political advantages in the state. The encouragement of experi- 
 mental agriculture has been in general neglected, while the diffusion 
 of practical knowledge has been either wholly overlooked or considered 
 subordinate to other objects. No national efforts have been made for 
 the general improvement of the methods of culture. While for the 
 other important classes of the community special schools have been es- 
 tablished, in which the elements of all the branches of knowledge most 
 necessary for each class have been more or less completely taught, and 
 a more enlightened, because better instructed, race of men gradually 
 trained up, no such schools have been instituted for the benefit of the 
 agriculturist. In our Universities, in which the holders of land, those 
 most interested in its improvement, are nearly all educated, a lesson 
 upon agriculture, the right arm of the State, has hitherto scarcely ever 
 been givemtT With the practice of the art, the theory has also been 
 
 Those who have access to the Journal of the Royal English Agricultural Society will 
 find in the first number a [)aiier by Mr. Pusey, "On the present state of the science of Agri- 
 culture in England," in which much valuable information is conlained, and of a more prac- 
 tical kind tlian I have been able to introduce. Tiiis paper ought to be printed in a separate 
 form, and circulated widely among ihose who are not members of the Royal English Agri 
 cultural Society. 
 
 t This opinion has been confirmed by the numerous communications I have received 
 from all parts of the country since the publication of these Lectures was announced, and in 
 wiiich I am assured that the want of knowledge is generally felt, and a supply in a sufficient- 
 ly elementary form desired, by all classes of agriculturists. I conclude, therefore, that Lie- 
 big means tlie following sentence to ap|Hy to his German countrymen : " What can be ex- 
 pected from the present (generation of) farmers, which recoils with seeming distrust and 
 aversion from all the means of assistance otTered it by chemistry, and which does not un- 
 derstand the art of making a rational application of chemical discoveries." I do not think 
 chemists ought in fairness to blame the practical airriculturists for not understanding the 
 art of applying chemical discoveries to the improvement of the culture of the land. They 
 must first know what the discoveries are ; and the error has hitherto been, that no steps 
 have been taken to diffuse this preliminary knowledge. 
 
 t However satisfied young men may be to avoid the labor of additional study while at 
 College, how many in after life regret that their early attention had not been directed to 
 some of those branches of knowledge which are applicable to common life. Thus the late 
 Lord Dudley, in his letters to the Bishop of LlandafT, invariably laments, " as mistakes in 
 
ENCOURAGEMENT OF AGRICULTURAL LITERATURE. 15 
 
 neglected. Scientific men have had no inducement to devote their 
 time and talents to a subject which held out no promise of reward, 
 either in the shape of actual emolument or of honorary distinction. 
 And thus has arisen the second of those circumstances, by which I con- 
 sider the approach of a better state of things to have been retarded — 
 namely, the want of an Agricultural Literature. 
 
 With the exception of a small number of periodical publications, 
 none of these even too well supported, by which attempts have been 
 zealously made to diffuse important information among the practical 
 farmers — it cannot be denied that the press has not been encouraged to 
 do its utmost on behalf of agricultural knowledge in general — while the 
 single work of Sir Humphry Davy is nearly all that chemical science 
 has, in this country, been induced to contribute to the advancement of 
 agricultural theory during the last forty years.* 
 
 Many of you have probably read this work of Sir Humphry Davy, 
 and are prepared to acknowledge its value. Yet how many things 
 does iie pass over entirely, how many things leave unexplained ! Since 
 his time, not only have numerous [)ractical observations and discoveries 
 been made, but the entire science of animal and vegetable chemistry 
 has been regenerated. We are not, therefore, to expect in his work a 
 view of the present state, either of our theoretical knowledge^ or of our 
 practical agriculture. It belongs rather to the history of tlie progress of 
 isnowledge, than to the condition of existing information. Hence the 
 merits of the agricultural chemistry of Davy are not to be tried by its 
 accordance with actual knowledge, but with what was known in 18V2, 
 when its distinguished author read his course of lectures for the last 
 time before the Board of Agriculture. 
 
 We may with certainty predict, hov/ever, that neither the practice 
 nor the theory of agriculture will be permitted to experience in future 
 that want of general encouragement under which during the last half 
 
 his early life, his unacquaiiilance with the rudiments of ao;riciilture — his ignorance of bota- 
 ny and geology."— (See also a note to the Review of these Letters in the Quarterly Review 
 for December, 1840.) 
 
 For this state of things we shall soon have at least a partial remedy. It is a remarkable 
 fact that nearly all the new rducational institutions of the higher class, on the Continent of 
 Europe, of wliicli so many have been founded within the present century, and all those 
 which have been established in America, I believe, without exception, have incorporated 
 into their cour.se of general sludy one or more of the newer sciences. Can we have a more 
 consentaneous and universal testimony to their value and importance than this? Tlie Uni- 
 versity of Lonilon has been inckiccd, by the same piiblic demand for this species of instruc- 
 tion, to include Chemistry and Botany in its course of arts ; and circumslances only have 
 caused Geoloiry to be omitted for a time. Its numerous affiliated institutions have followed 
 its steps; and hence the Catholic College of St. Cuthbert, at Ushaw, has in this respect an- 
 ticipated its I'roicstant neighbor at Durham. 
 
 But should the agricultural interest rest satisfied with this introduction of one or two 
 liranches, suppose it generally done, into the University course of study? Many are of 
 opinion that it ought not, and that the general interests of practical agriculture woidd bn 
 manifestly promoted, among other means, by the establishment of agricultural colleges, in 
 which all the branches necessary to be known by enlightened agriculturists of every class 
 should be specially and distinctly taught. Whether such Colleges might be beneficially 
 annexed to the existing Universities, is "a question deserving of serious consideration. 
 
 • The latest edition of Lord Dundonald's "Treatise on the intimate connection between 
 Chemistry and Agriculture," which I have seen, is dated London, 1S03. 
 
 I should be doing injustice to a good chemist and a zealous agriculturist, were I not to 
 direct the attention of my readers to a series of excellent articles on chemical agriculture 
 by Dr. Madden, inserted in the numbers of the Quarterly Journal of Agriculture for the last 
 two years. 
 
 Since the above went to press, Three Lectures on Agriculture have appeared from the 
 pen of Dr. Daubeny, of Oxford, whose name will secure them an extended circulation. 
 
16 GENERAL SCIENCE AND AGRICULTURE. 
 
 century they have in England been pennitled to languish. The public 
 mind has been awakened, and the establishment of Agricultural Associ-' 
 ations. provincial and local, are nianifesiations of the interest now felt 
 upon the subject in all parts of the country. It requires only the general 
 exhibilion of such an interest, and the adoption of sonjc general means of 
 encouragement, to stimulate both practical ingenuity and scientific zeal 
 to expend themselves on this most valuable branch of national industry. 
 
 Science is never unwilling to lend her hand to the practical arts ; on 
 the contrary, she is ever forward to profiler her assistance, and it is not 
 till her advances have been rejected or frequently repulsed, that she re- 
 frains from aiding in their advancement. 
 
 Need I advert, in proof of this, to the unwearied labours of the vege- 
 table [physiologists — or to the many valuable observations and experi- 
 ments recorded in the memoirs of scientific chemists. In these memoirs, 
 or in professedly scientific works, such observations have not unfre- 
 quently been permitted to rest; — the public mind being unprepared 
 either to appreciate their value or to encourage the exertions of those who 
 were willing to give them a practical and popular form. 
 
 And how numerous are the branches of science connected with this 
 art ? Need I speak of botany, which is, as it were, the foundation on 
 which the first elements of agriculture rest; or of vegetable physiology, 
 to the indications of which it has hitherto almost exclusively looked for 
 improvement and increased success; or of zoology, which alone can 
 throw light on the nature of the numerous insects that prey upon your 
 crops, and so often ruin your hopes, — and which can alone be reason- 
 ably expected to arm you against their ravages, and instruct you to ex- 
 tirpate them ? Meteorology among her ot her labours tabulates the highest, 
 the mean, and the lowest, temperatures, as well as the quantity of rain 
 which falls during each day and each month of the year. Do you 
 doubt the importance of such knowledge to the proper cultivation of the 
 land ? Consider the destructive eiTccts of a late frost in s[)ring, or of a 
 continued heat in summer, and your doubts will be shaken. A wet sea- 
 son in our climat3 brings with it many evils to the practical agriculturist ; 
 but whatT^ect must the rain have on the soil, in countries where nearly 
 as much falls in a month, as in England during the course of a whole 
 year ;* — where every thing soluble is speedily washed from the land, and 
 nothing seems to be left but a mixture of sand and gravel ? It may 
 indeed be said with truth, that no department of natural science is inca- 
 j)able of yielding instruction — that scarcely any knowledge is superflu- 
 ous — to the tiller of the soil. 
 
 It is tlius that all branches of human knowledge are bound together, 
 and all the arts of life, and all the cultivators of them, mutually de- 
 ])endent. And it is by lending each a helping hand to the others, that 
 tlie success of all is to be secured and accelerated ; while with the gene- 
 ral progress of the whole the advance of each individual is made sure. 
 
 The recent contributions and suggestions of geology are the best proof 
 of the readiness of the sciences of observation to give their aid to the 
 promotion especially of agricultural knowledge. The geologist can 
 best explain the immediate origin of your several soils, the cause of the 
 
 • Kt Canton, in the month of May thp fall nf ram is often as mn"li as 20 inches. 
 
GKOLOGT CONNECTED WITH AGRICULTURE. 17 
 
 diversities which even in the same farm, it may be in the same field, 
 they not unfrequently exhibit;* the nature and differences among your 
 subsoils, and the advantages you may expect from breaking them up or 
 bringing them to the surface. 
 
 Geology is essentially a popular science, and the talents of its emi- 
 nent English cultivators are admirably fitted to make it still more so. 
 Hence, a certain amount of knowledge of this science has been of late 
 years very generally diffused, and its relations to agriculture are be- 
 comincr every day better understood. The Highland Society of Scot- 
 land, among its many other useful exertions, has done very much to 
 connect agriculture and geology with the sphere of its own labours, 
 while the Journal of the Royal Agricultural Society of England mani- 
 fests a similar desire on the part of that numerous and talented body, to 
 illustrate the connection of agriculture with geology and chemistry, in 
 the southern division of the island. That Dr. Buckland, Mr. Murchi- 
 son, and Mr. De la Beche have each engaged to make a gratuitous sur- 
 vey of the subsoils in several extensive agricultural districts, at the re- 
 quest of the Council of this Society,f shows that, where their services are 
 estimated, our most eminent scientific men will not hesitate to devote them 
 to the development of the most important branches of national industry. 
 
 The time, therefore, is peculiarly favourable for the increase and diffii- 
 sion of agricultural knowledge. The growth of our population re- 
 quires it — practical men are anxious to receive instruction — scientific 
 men are eager to impart what they know, and to make new researches 
 for the purpose of clearing up what is unknown — are we not justified, 
 therefore, in anticipating hereafter a constant and general diffusion of 
 light, a steady progress of agricultural improvement ? 
 
 "Having thus glanced at the state and prospects of scientific agricul- 
 ture in general, and especially of the art of culture in England, permit 
 me to advert to a few of those questions of daily occurrence among you, 
 to which chemistry alone can give a satisfactory answer. I shall not in 
 this place allude to the subject of manures — which form alone an entire 
 chapter of most recondite chemistry, and which I shall take up in its 
 proper place, but I shall select a few isolated topics, the bearing of 
 chemical knowledge upon which is sufficiently striking. 
 
 Some soils are naturally barren, but how few of our agriculturists are 
 able, in regard to such soils generally, to say why ; how few who pos- 
 sess the knowledge requisite for discovering the cause ! Of these bar- 
 ren lands some may be improved so as amply to repay the outlay ; some, 
 from their locality or from other causes, are in the present state of our 
 knowledge irreclaimable. How important to be able to distinguish be- 
 tween these two cases ! 
 
 • I cannot refer to a plainer, more simple, or more beautiful illustration of this fact than 
 that which is presented in a short paper by Sir John Johnstone, Bart., inserted in the Jour- 
 nal of the English Agricultural Society, I. p. 271, entitled "On the Application of Geology to 
 Agriculture." See also an able paper by the Rev. Mr. Thorpe, of which a valuable report is 
 contained in the Doncaster Chronicle of December 5th, and which will be published in the 
 proceedings of the Geological and Polytechnic Society of the West Riding of Yorkshire. 
 
 t Journal of the Royal Agricultural Society, Report of their Council, I. p. 188. 
 
 To form a just idea of the value and importance of such surveys, it is only necessary to 
 read chap, xv., pp. 463 to 480, of Mr. De la Beche's " Geological Report on Cornwall and De- 
 von," or Professor Hitchcock's "Report on a re-examination of the Economic Geology of 
 Massachusetts." 
 
18 CHEMISTRY AND AGRICULTURE. 
 
 Some apparently good soils are yet barren in a high degree. In en- 
 deavouring to improve such soils, practical men have no general rule — 
 they can have none. They work in the dark — like a man who makes 
 experiments in a laboratory, without a teacher or wilhout a book, till, 
 after many blunders and much expense, he discovers some fact, to him- bi 
 self new, but to others long known, and forming only one of many ana- i 
 logous facts, flowing from a common, and probably well understood, 
 principle. 
 
 " The application of chemical tests to such a soil," says Sir Humphry 
 Davy, " is obvious. It must contain some noxious ])rinciple, [or be de- 
 ficient in some necessary element. — J.] which may be easily discovered 
 and probably easily destroyed. Are any of the salts of iron present, 
 they may be decomposed by lime. Is there an excess of siliceous sand, 
 the system of improvement must depend on the application of clay and 
 calcareous matters. Is there a defect of calcareous matter, the remedy 
 is obvious. Is an excess of vegetable matter indicated, it may be re- 
 moved by liming, ))aring, and burning. Is there a deficiency of vege- 
 table matter, it is to be supplied by manure." — [Agricultural Chemistry, 
 Lecture I.] 
 
 What was true in regard to the applications of chemistry in the time 
 of Sir Humphry Davy is more true in a high degree of the chemistry 
 of our time. Not only is the nature of soils better understood, but we 
 know in many cases what a soil 7uiist contain before it will produce a 
 given crop. Why do [)ine forests settle themselves on the naked and 
 apparently barren rocks of Scotland and of Northern Europe, content if 
 their young roots can find but a crevice in the mountain to shelter themx? 
 Why does the beech luxuriate in the alluvial soils of Southern Sweden, 
 of Zealand, and Continental Denmark ? Why does the birch spring 
 up from the ashes of the pine forest — why the rapid rush of delicate 
 grass from the burned prairies of India and of Northern America? 
 Whence comes the thick and tender sward of the mountain limestone 
 districts — whence the gigantic wheat stalk of a virgin soil ? Why do 
 the same forest trees propagate themselves for ages on the same spots 
 without impoverishing the soil — why do the natural grasses, the longer 
 they are uniMsturbed, render the land only the more fertile ? 
 
 These, one would think, are scarcely chemical questions, and yet to 
 all of them, and to a thousand such, chemistry alone can and will give 
 a satisfactory answer. 
 
 The rotation of crops is a practical rule, the benefit of which has 
 been proved by experience ; it becomes a true philosophical principle 
 of action, when we discover the causes from which this benefit springs. 
 Botany has thrown considerable light, and of an interesting and impor- 
 tant kind, upon this practice, but chemistry has fully cleared it up and 
 established the principle. 
 
 Sir Humphry Davy speaks of the use of hme. Can you explain the 
 mysterious, and apparently fickle and diversified, agency of this sub 
 stance in reference to vegetation ? Are the advantages so frequently 
 attendant upon its use to be ascribed to the chemical character of the 
 soil to which it is applied, to the kind and quantity of the vegetable 
 matter it contains, or to the geological nature of the rocks on which it 
 rests? Are they dependent upon the drainage and exposure of the 
 
THEORETICAL KNOWLEDGE STILL VERT DEFECTIVE. 19 
 
 land — on the kind of crop to be raised — on the general climate of the 
 district — on the maxima and minima of temperature — or on the quanti- 
 ty of rain which falls? 
 
 So with gypsum. Why are its effecfs lauded in one district, doubted 
 in another, and decried in a third! Are no rules or principles to b^ 
 discovered, by which these diversified effects are to be ex[)lained, and 
 the true purpose and fit use of these and other mineral substances clear- 
 ly pointed out? Such principles are yet to be sought for; but if 
 sought by the way of well devised and accurately conducted experi- 
 ment, they are sure to be discovered. 
 
 The land is exhausted by frecjuent cropping. What language more 
 lamiliar, what statement more true than this? Yet how few under- 
 stand what exhaustion im[)lies; how few can explain either how it 
 takes place, by what means it can be remedied, or how, if left to her- 
 self, nature at length does apply a remedy ! 
 
 Have you any doubt in regard to the prevaiUng ignorance on this 
 subject? To be satisfied, you have only to look with an experienced 
 eye on the agricultural practice of the county of Durham. Are there 
 not thousands of acres in llie centre of this county which exhibit a de- 
 gree of unproductiveness not natural to the soil ; — which have been 
 overcro[)[)ed, and worn out, and impoverished? A soil comparative- 
 ly fertile by nature has been rendered unfertile by art. That which 
 was naturally good has been rendered as un[)roductive and unprofitable 
 as that which was naturally bad. Has this state of things arisen from 
 ignorance, from design, or from necessity ? By whichever of these it 
 has been immediately caused, it is clear that the requisite degree of 
 knowledge on the part of the owners of the soil would have retarded if 
 not wholly prevented it. 
 
 The same knowledge will enable them to reclaim these lands again, 
 and gradually restore them to a more fertile condition ; for the changes 
 which the soil undergoes in such circumstances are all chemical 
 changes, — either in the relative quantities of the substances it contains, 
 or in the state of combination in which they exist. 
 
 The art of culture indeed is almost entirely a chemical art, since 
 nearly all its processes are to be explained only on chemical principles. 
 If you add lime or gypsum to your land, you introduce new chemical 
 agents. If you irrigate your meadows, you nmst demand a reason 
 from the chemist for the abundant growth of grass which follows. Do 
 you find animal manure powerful in its action, is the effect of some 
 permanent, while that of others is speedily exhausted ? — does a mixture 
 of animal and vegetable manure prepare the land best for certain kinds 
 of grain? — do you employ common salt, or gypsum, or saltpetre, or ni- 
 trate of soda, with advantage ? — in all these cases you observe chemical 
 results which you would be able to control and modify did you possess 
 the requisite chemical knowledge. 
 
 It is not wonderful that even theoretical agriculturists should be far 
 behind in the knowledge of those principles on which their most impor- 
 tant operations depend. The greatest light has been thrown upon the 
 art of culture by the researches of organic chemistry, a branch which 
 may be said to have started, if not into existence, at least into a new 
 life, within the last ten years. Every day too is adding to the number 
 
20 OUTLINE OF THE COURSE OF LECTURES. 
 
 and value of its discoveries, and the agriculturist may well be pardoned 
 for not keeping ])ace with the advances of a department of science, 
 which even the professed and devoted chemist can scarcely overtake. 
 
 I might advert also to the mechanical operations of ploughing, wheth- 
 er common or subsoil, of fallowing, draining, weeding, and many 
 others, as being only so many methods by which chemical action is in- 
 duced or facilitated ; — to the growth of plants, and even to such ob- 
 servetl differences as that of the relative quantity of leaves and tubers in 
 the potatoe, and of grain and straw in our corn-fields, as interesting 
 cases on which scientific chemistry throws a flood of light. I might 
 shew how the feeding of your cattle and the raising and management 
 of dairy produce are not beyond the province of chemistry, but that the 
 only approach to scientific principle yet made, even in these branches 
 of husbandry, is derived from the results of chemical research. 
 
 But I do not dwell on any of these points: they will all hereafter 
 come under our review in their appropriate order, and will afford me an 
 opportunity of laying before you many important facts, as well as, I 
 hope, valuable practical deductions and observations. 
 
 While, however, I feel justified in saying thus much of the light 
 which existing chemical knowledge throws on the natural processes of 
 vegetation, and on the artificial methods of practical agriculture, I 
 would not lead you to suppose that our knowledge is by any means 
 complete, that there are not many points over which much darkness 
 still rests — that some of the theoretical views now entertained are not 
 crude, adopted too hastily, and generalized too rapidly. But a similar 
 confession may be made in reference to all the modern sciences of ob- 
 servation without diminishing their importance or detracting from the 
 value of the facts they embody. Human science is progressive in all 
 its branches, and to refuse to follow the indications of existing know- 
 ledge because it is to some extent uncertain, would be as foolish as to 
 refuse to avail ourselves of the morning's light, because it is not equal 
 to that of the midday sun. 
 
 1 advance, therefore, to the special object of these lectures, and I shall 
 first present you with a rapid outline of the method which I intend to 
 follow. It is indispensable that this method should be simple, and that 
 every consecutive portion should be so fitted to clear the way for, and 
 thpjw light upon, what is to follow, that we may be able to advance 
 fror« the first rudiments to the most difficult and abstruse parts of our 
 subject, without any chance of the illustrations being even difficult to 
 comprehend. This end I do not hope perfectly to attain, but it will be 
 my constant aim, and, with due attention on your part, I do not fear 
 that we shall fail in arriving at a perfect understanding of the various 
 points to which I shall have occasion to direct your attention. 
 
 I propose, therefore, to bring before you — 
 
 I. The constitution of vegetable substances with the properties of the 
 elementary and compound bodies which either enter into the substances 
 of plants or contribute to their growth and nourishment. 
 
 II. The general structure and functions of the several parts of plants 
 
ORGANIC AND INORGANIC MATTER. 21 
 
 — their mode of growth — and the manner in which their fooa is ab- 
 sorbed, changed, and converted into parts of their substance. 
 
 III. Tlie origin, nature, and principal differences of soils — with the 
 circumstances on which their relative fertility depends, or under which 
 it is modified. 
 
 IV". The nature and differences of manures, and their mode of action, 
 whether directly in supplying food to the plant, or indirectly in hasten- 
 ing and increasing their growth. 
 
 V. The nature and diversities of the food.raised as the result of cul- 
 ture — especially in reference to their several equivalents or powers of 
 supporting animal life. 
 
 Under this head the feeding of cattle and the variations in the quan- 
 tity and quality of dairy produce, will form subjects of consideration. 
 
 These different branches, I believe, comprehend the whole subject 
 of chemical agriculture ; in regard to all of them we shall derive either 
 from chemistry or geology much important information. 
 
 § 1. Different kinds and states of matter. 
 
 All the forms of matter which present themselves to our view, 
 whether in the solid crust of the globe on which we live, in the air 
 which forms the atmosphere by which we are surrounded, or in the bo- 
 dies of animals and plants — all are capable of being divided into the two 
 great groups of organic and inorgariic matter. The solid rocks and soils, 
 the atmosphere, the waters of the seas and oceans, every thing which 
 neither is nor has been the seat of Hfe, may generally be included under 
 the head of inorganic matter. The bodies of all living animals and 
 plants, and their dead carcases, consist of organic or organized matter. 
 These generally exhibit a kind of structure readily visible by the eye, 
 as in the pores of wood, and in the fibres of hemp, or of the lean of 
 beef,* and are thus readily distinguished from inorganic matter, in 
 which no such structure is observable. 
 
 But in many substances of organic origin also, no structure is obser- 
 vable. Thus, sugar, starch, and gum, are formed in plants in great 
 abundance, and yet do not present any pores or fibres ; they have never 
 been endowed with organs, yet being produced by the agency of living 
 organs, they are included under the general name of organic matter. 
 So when animals and plants die, their bodies undergo decay, but the 
 matter of which they are composed is considered as of organic origin, 
 not only as long as any traces of structure are observable, but even after 
 all such traces have disappeared. Thus coal is a substance of organic 
 origin, though almost all traces of the vegetable matter from which it 
 has been derived, have been long ago obliterated. ^ 
 
 Again, heal chars and destroys wood, starch, and gum, forming black 
 substances totally unlike the original matter acted upon. By distillation, 
 wood yields tar and vinegar ; and by fermentation, sugar is converted 
 first into alcohol, and then into vinegar. All substances derived from 
 vegetable or animal products by these and similar processes are included 
 under the general designation of organic bodies. •: 
 
 * The pores of wood and fibres and minute vessels in animals being the organs or instru* 
 ments of life, the substances themselves are called organized or organic. 
 
 2 
 
22 NUMBER OF ELEMENTARY BODIES. 
 
 1 
 
 Now if we take a portion of almost any of those numerous forms 
 of matter which we meet with either in the inorganic or in the organic 
 kingdoms, we find, that on subjecting it to certain chemical processes, it 
 is capable of being resolved or separated into more than one substance. 
 Thus coal when put into a gas retort is resolved into tar, coal gas, and 
 certain other substances. Wood, when treated in the same way, yields 
 pyroligneous acid, tar, and water, and leaves behind a residue of char- 
 coal. If again we subject charcoal to the action of heat (not in the 
 open air), or to any other process we can devise, we can never separate 
 any thing further from it. After all our operations we obtain only 
 charcoal. 
 
 So a piece of common lead' ore, when healed in a similar manner, 
 will, if pure, give offsulphuronly, and leave the lead behind, from which 
 nothing but lead can afterwards be extracted. 
 
 Thus it is evident that wood and the ore of lead differ from charcoal 
 and metallic lead in this respect, that the former consist of more than one 
 kind of matter, the latter of one kind of matter only. Hence ciiarcoal 
 and lead are called simple or elementary bodies, while wood and all oth- 
 er substances which are capable of being resolved into two or more 
 different kinds of matter are called compound bodies. 
 
 The diversified forms of matter which present themselves to our no- 
 tice in the mineral crust of the globe, and in the organs and vessels of 
 plants and animals, are absolutely without number. We can no more 
 reckon them than we can the stars of heaven. Yet it is one of those re- 
 sults of modern chemistry which to the mind not yet familiarized 
 with chemical discoveries appears most wonderful, — that these num- 
 berless forms of matter are capable of being resolved into, and there- 
 fore are composed or made up of, only 65* of those simj)le or ele- 
 mentary substances, the nature of which has been above explained. 
 Occasionally these elementary substances occur in a separate state, as 
 in native [so called when found in the malleable state,] gold and silver,. 
 but they are generally found associated together, forming substances 
 from whicluseveral of the 55 simple bodies may be extracted. 
 
 All the material substances in nature consist of one or more of these 
 55 elementary bodies. This is sufficiently sur[)rising, yet it is, if ])os- 
 sible, still more remarkable that nearly the entire mass of every vege- 
 table substance may be resolved into one or more o^ four only of these 
 simple substances. 
 
 When a portion of animal or vegetable matter is burned it either en- 
 tirely drsappears or leaves behind it only a small quantity of ash. Ani- 
 mal and vegetable oils and fats, gum, sugar, and starch, when burned, 
 disappear entirely ; a piece of wood or of lean meat leaves a small 
 quantity of earthy (inorganic) matter behind. 
 
 Now all that disappears when any portion of vegetable matter, of any 
 kind, is burned, consists generally of three, and only in some rare cases 
 
 * The names of these elementary bodies are as follows :— Oxygen, hydrogen, nitrogen, 
 sulphur, selenium, phosphorus, chlorine, bromine, iodine, fluorine, carbon, boron, silicon, 
 potassium, sodium, litliium. barium, strontium, calcium, maunesium, aluminium, glucinium, 
 yttrium, zirconium, ihoriiim, cerium, lanthanium, manganese, iron, cobalt, nickel, zinc, 
 cadmium, load, tin, bismuth, copper, uranium, mercury (quicksilver), silver, palladium, 
 iridium, platinum, gold, osmium, titanium, tantalum (columbium), tungsten, molybdenum, 
 Tanadium, chromium, antimony, tellurium, arsenic. 
 
PROPERTIES OF CARBON. 23 
 
 of more than four, of the elementary bodies. These four are carbon, 
 oxygen, hydrogen, and nitrogen. With the exception of the matter ir 
 destructible by fire (the ash), chemical analysis* has hit herto failed to detect 
 the presence,*^in any notable quantity, f)f more than these four substances. 
 The same remarks apply with almost equal truth to animal substances. 
 The destructible part of these also consists of the same four elements. 
 
 To the agriculturist, therefore, an acquaintance with these four con- 
 stituent parts of all that lives and grows on the face of the globe is 
 indispensable. It is impossible for him to comprehend the laws by 
 which the operations of nature in the vegetable kingdom are conducted, 
 nor the reason of the processes he himself adopts in order to facilitate or to 
 modify these operations, without this previous knowledge of the nature 
 of the elements — the raw materials as it were — out of which all the 
 products of vegetable growth are elaborated. 
 
 I shall first, therefore, exhibit to you briefly the properties of these 
 organic constituents of plants, in order that we may be prejjared for the 
 further inquiries — by whatmeansor in what form they enter into the cir- 
 culation of |)lants — and how, when they have so entered, they are con- 
 verted into those substances of which the skeleton of the plant consists 
 or which are produced in its several organs. 
 
 § 2. Carbon — its properties and relations to vegetable life. 
 
 Carbon is the name given by chemists to the substance of wood char- 
 coal in its purest form. When wood is distilled in close vessels, or 
 burned in heaps covered over, so as to prevent the free access of air, 
 wood charcoal is left behind. When this process is well performed, the 
 charcoal consists of carbon with a slight admixture only of earthy and 
 saline matters, which remain behind on burning the charcoal in the air. 
 
 Healed in the air, charcoal burns with little flame, and, with the ex- 
 ception of the ash which is left, entirely disappears. It is converted into 
 a kind of air known among chemists by the name ofcarbonic acid, which 
 ascends as it is formed and mingles with the atmosphere. 
 
 Charcoal is light and porous, and floats upon water, but plumbago or 
 black lead and the diamond, which are only other forms of carbon, are 
 heavy and dense. The former is 2i, and the latter 3|, times heavier 
 than v/ater. The diamond is the purest form of carbon, and at a high 
 temperature it burns in the air or in oxygen gas, and, like charcoal, dis- 
 appears in the state ofcarbonic acid gas. 
 
 Of this carbon all vegetable substances contain a very large ])ortion. 
 It forms from 40 to 50 per cent., by weight, of all the parts of plants 
 which are cultivated for the food of animals or of man, [that is, of these 
 plants in their dried state.] In the economy of nature, therefore, it per- 
 forms a most important part. 
 
 The light porous charcoals obtained from wood [especially from the 
 willow, the pine, and the box], and from animal substances, possess 
 several interesting properties, which are of practical application in the 
 art of culture. 1°. They have the power of absorbing in large quanti- 
 ty into their pores, the gaseous substances and vapours which exist in 
 
 ' Under the general name of chemical analysis are comprehended the various processes 
 by which, as above explained, natural forms of matter may be resolved or separated into 
 the several elements or simple substances of which they consist. 
 
24 PROPERTIES OF OXYGEN. 
 
 the atmosphere ;* and on this properly, as I shall explain hereafter, the 
 use of charcoal powder as a manure probably in some measure depends. 
 2°. They also separate from water any decayed animal matters or col- 
 ouring substances which it may hold in solution ; hence its use in filters 
 for purifying and sweetening impure river or spring waters, or for clari- 
 fying syrups and oils. This action is so powerful that port wine is 
 rendered perfectly colourless by filtering through a well prepared char 
 coal. 
 
 In or upon the soil charcoal for a time will act in the same manner, 
 will absorb from the air moisture and gaseous substances, and from tlie 
 rain and from flowing waters organized matters of various kinds, any 
 of which it will be in a condition to yield to the plants which grow 
 around it, when they are such as are likely to contribute to their 
 growth. 
 
 3°. They have the property also of absorbing disagreeable odours in || 
 a very remarkable manner. Hence animal food keeps longer sweet •' 
 when placed in contact with charcoal — hence also vegetable substances 
 containing much water, such as potatoes, are more completely preserved ^i 
 by the aid of a quantity of charcoal — and hence the refuse charcoal of the I] 
 sugar refiners is found to deprive night-soil of its disagreeable odour, and 
 to convert it into a dry and portable manure. 4°. They exhibit also 
 the still more singular property of extracting from water a portion of the ' 
 saline substances they may happen to hold in solution, and thus allow- 
 ing it to escape in a less impure form. The decayed (half carbonized) 
 roots of grass, which have been long subjected to irrigation, may act in 
 one or all of these ways on the more or less impure water by which 
 they are irrigated — and thus gradually arrest and collect the materials 
 which are fitted to promote the growth of the coming crop. 
 
 § 3. Oxygen — its properties and relations to vegetable life. ! 
 
 Oxygen is a substance with which we are acquainted only in the gas- 
 eous or aeriform state. f By the unaided senses it cannot be distin- 
 guished from common air, being void of colour, taste and smell. But 
 if a lighted^aper be plunged into it, the flame is wonderfully increased 
 both in size and brilliancy, and the taper burns away with great 
 rapidity. 
 
 The effect of this gas upon animal life is of a similar kind. When 
 a living animal is introduced into a large vessel filled with oxygen, the 
 rapidity of the circulation is increased, all the vital fuiictions are stimu- 
 lated and excited, a state of fever comes on, and after a time the ani- 
 mal dies. 
 
 By these two characters, oxygen is distinguished from every other ele- 
 mentary body. It exists in the atmosphere to the amount of 21 percent, 
 of its bulk, and in this state of air is necessary to the existence of ani- 
 mals and of j)lants, and to tiie support of combustion on the face of the 
 globe. It exists also largely in water, every nine pounds of this liquid 
 containing eight pounds of oxygen. 
 
 * Thus of ammonia they absorb 95 times their own bulk, of sulphuretted hydrogen 55 times, 
 of oxygen 9 limes, ofhydrojien nearly twice their bulk, and of aqueous vapour so much as to 
 increase their weigiit from 10 to 20 per cent. 
 
 t In this state it is readily obtained by healing in a glass retort the red oxide of mercury 
 of the shops, or a white salt known by the name of chlorate of potash 
 
PROPERTIES OF HYDROGEN. 25 
 
 But the quantity of tliis substance which is stored up in the solid rocks 
 is still more remarkable. Nearly one-half of the weiglit of the solid 
 rocks whicii compose the crust of our globe, of every solid substance we 
 see aroLinTl us — of the houses in which we live, and of the stones on 
 which we tread — of the soils which you daily cultivate, and much more 
 than one-half by weight of the bodies of all living animals and plants, 
 consist of this elementary body oxygen, known to us, as I have already 
 said, only in the state of a gas. It may not appear surprising that any 
 one elementary substance sliould have been formed by the Creator in 
 such abundance as to constitute nearly one-half by weight of the entire 
 crust of our globe, but it must strike you as remarkable, tliat this should 
 also be the element on the presence of which all animal life depends — 
 and as nothing less than wonderful, that a substance which we know 
 only in the state of thin air, should, by some wonderful mechanism, be 
 bound up and imprisoned in such vast stores in the solid mountains of 
 the globe, be destined to pervade and refresh all nature in the form of 
 water, and to beautify and adorn the earth in the solid parts of animals 
 and plants. But all nature is full of similar wonders, and every step 
 you advance in the study of the principles of the an by which you live, 
 you will not fail to mark the united skill and bounty of the same great 
 Contriver. 
 
 Oxygen gas is heavier than common air in the proportion of about 11 
 to 10 [its specific gravity by experiment is 1-1026, air being 1] ; it is 
 also capable of being absorbed by water to a certain extent. One hun- 
 dred measures of water dissolve 6i of this gas. [De Saussure. Ac- 
 cording to Dr. Henry, 100 volumes of water absorb only 3i of oxygen.] 
 Rain, spring, and river waters, always contain a portion of oxygen 
 which they have derived from the atmosphere, and this oxygen, as they 
 trickle through the soil, ministers to the growth and nourishment of plants 
 in various ways. Some of these will be explained in a subsequent lecture. 
 
 In an atmosphere of pure oxygen gas, plants refuse to vegetate, and 
 speedily perish. 
 
 § 4. Hydrogen — its properties and relations to vegetable life. 
 
 Hydrogen is also known to us only in the state of gas, and when per 
 fectly pure agrees with oxygen and common air in being without colour, 
 taste, or smell. It is not known to occur in nature in a free or simple 
 state, nor does it exist so abundantly as either carbon or oxygen. It 
 forms a small per centage of the weight of all animal and vegetable 
 substances, and constitutes one-ninth of the weight of water, but with 
 the exception of coal, it does not enter as a constituent into any of the large 
 mineral masses that exist in the crust of the globe. 
 
 "When a lighted taper is plunged into this gas it is immediately ex- 
 tinguished, but if in contact with the air the gas itself takes fire and burns 
 with a pale yellow flame. If previously mixed with air or with oxygen 
 gas, it kindles and burns with a loud explosion. During this combus- 
 tion water is formed. [See the Second Lecture.] 
 
 It does not support life, animals cease to breathe when introduced into 
 it, and plants gradually wither and die. It is the lightest of all known 
 substances, being about 14* times lighter than common air, so that if the 
 stopper be removed from a bottle in which it is contained it almost imme- 
 
Such are the several elementary bodies of which the organic or de- 
 Biructible part of vegetable substances is formed. With one exception 
 they are knov^^n to us only in the form of gases ; and yet out of these 
 gases much of tlie solid parts of animals and of plants are made up. 
 When alone, at the ordinary temperature of the atmosphere they form 
 invisible kinds of air; w^hen united, they constitute those various forms 
 of vegetable matter which it is the aim and end of the art of culture to 
 raise with rapidity, with certainty, and in abundance. How difficult 
 to understand the intricate processes by which nature works up these 
 
 * Heniy De Saussure says, that pure water absorbs 4 per cent of its bulk of thig gas. 
 
 26 PROPERTIES OF NITROGEN. --_ 
 
 m 
 
 diately escapes, [its specific gravity, by experiment, is 0-0687, air be- 
 ing 1.] It is the element which is employed to give buoyancy to 
 balloons ; and by this great levity and its relations to flame it is readily 
 distinguished from all other known substances. 
 
 Water absorbs it only in very small quantities, 100 gallons taking^p 
 no more than about Ij gallons of liydrogen gas. But, as already ob- 
 served, this gas does not exist in nature in a free state — is not necessary, 
 therefore, to the growth of plants or animals in this state — and lience its 
 insolubility in water is in unison with the general adaptation of every 
 property of every body, to the health and growth of the highest orders 
 of living beings. 
 
 Hydrogen gas is readily obtained from water by putting into it a few 
 pieces of metallic iron or zinc, and adding a little sulphuric acid (oil of 
 vitriol). Bubbles of the gas are liberated from the surface of the meto.1, 
 ascend through the water, and may be collected on the surface. 
 
 § 5. Nitrogen — its properties and relations to vegetable life. 
 
 Nitrogen is also known to us only in the form of gas. It exists in the .» 
 atmosphere (o the amount of 79 per cent, of its bulk. It is without | 
 colour, taste, or smell. Animals and plants die in this gas, and a taper 
 is instantly extinguished when introduced into it ; the gas itself under- 
 going no change. It is lighter than atmosjiheric air, in the proportion 
 of 97i to 100, [its density is 0-976, air being 1.] It is an essential . 
 constituent of the air we breathe, serving to temper the ardour with I 
 which combustion would proceed and animals live iij undiluted oxygen 
 gas. It forms a part of very many animal and of some vegetable sub- 
 stances, but it is not known to enter into the composition of any of the 
 great mineral masses of which the earth's crust is made up. In coal 
 alone, which is of vegetable origin, it has been delected to the amount 
 ofoneortwo percent. It is therefore much less abundant in nature : 
 than any of the other so called organic elements — and it exhibits much f 
 less decided properties than any of them ; yet we shall hereafter see 
 that it performs certain most important functions in reference both to the 
 growth oFplants and to the nourishment of animals. 
 
 One hundred volumes of water dissolve about li volumes of this 
 gas.* Spring and rain waters absorb it as they do oxygen, from the at- 
 mospheric air, and bear it in solution to the roots, by which it is not un- 
 likely that it may be conveyed directly into the circulation of plants. 
 
REWARDS OF STUDY. 27 
 
 raw materials into her many beautiful productions — yet how interest- 
 ing it must be to know her ways, how useful even partially to find them 
 
 out 
 
 Permit me, in conclusion, to submit to you one reflection. We have 
 seen that oxygen, hydrogen, and nitrogen, are all gaseous substances, 
 which when pure are destitute of colour, taste, and smell. They can- 
 not be distinguished by the aid of our senses. Man in a state of nature 
 — uneducated man — cannot discern that they are different. Yet so 
 simple an instrument as a lighted taper at once shows them to be totally 
 unlike each other. This simple instrument, therefore, serves us in- 
 stead of a new sense, and makes us acquainted with properties the ex- 
 istence of which, without such aid, we should not even have suspected. 
 Has the Deity then been unkind to man, or stinted in his benevolence 
 in withholding the gift of such a sense ? On the contrary, he has given 
 us an understanding which when cultivated is better than twenty new 
 senses. The chemist in his laboratory is better armed for the investi- 
 gation of nature, than if his organs of sense had been many times mul- 
 tiplied. He has many instruments at his command, each of which, 
 like the taper, tells him of properties which neither his senses nor any 
 other of his instruments can discover ; and the further his researches 
 are carried, the more willing does nature seem to reveal her secrets to 
 him, and the more rapidly do his chemical senses increase. Do you 
 think that the rewards of study and patient experimental research are 
 confined to the laboratory of the chemist, and that the Deity will prove 
 less kind to you, whose daily toil is in the great laboratory of nature 1 
 As yet 3^ou see but faintly the reason of many of your commonest oper- 
 ations, and over the results you have comparatively little control — but 
 the light is ready to spring up, the means are within your reach — you 
 have only to employ your minds as diligently as you labour with your 
 hands, and ultimate success is sure. 
 
LECTURE IL 
 
 Characteristic properties of organic substances— Relative proportions of organic elements — 
 Variable proportions of inorganic elements in plants — Form in which the organic elo 
 ments are taken up by plants — The atmosphere, its constitution and x'elations to vegetablo 
 life — Nature and laws of chemical combination — Water and its relations to vegetable life 
 
 § 1. Characteristic properties of organic substances. 
 
 Of the four elementary substances described in the former lecture, the 
 organic part of all animal and vegetable substances consists. What is 
 understood by the term organic has also been explained. 
 
 But organic substances possess certain characters by which they are 
 distinguished from the inorganic or dead matter of the globe, and on 
 which their connection with the principle of life, and with the art of 
 culture, entirely depends. These characteristic properties are chiefly 
 the following : 
 
 1°. They are all easily decomposed or destroyed by a moderately 
 high temj)erature. If wood or straw be heated in the air, as over the 
 flame of a candle, it becomes charred, burns, and is in a great measure 
 dissipated. So sugar and starch darken in colour when heated, black- 
 en, and take fire. The same is true of all vegetable substances. But 
 limestone, clay, and other earthy or stony matters, undergo no appar- 
 ent chanire in such circumstances — they are not decomposed. 
 
 2°. When exposed to the air, especially if it be warm and moist, 
 vegetable and animal substances putrify and decay.* They decom- 
 pose of their own accord, and after a time almost entirely disappear. 
 Such is not the case with inorganic matters. If the rocks and stones 
 crumble, their particles may be washed away by the rains to a lower 
 level, but they never putrify or wholly disappear. 
 
 3°. They consist almost entirely of two or more of the four organic 
 elements only. The mineral substances we meet with on the earth's 
 surface, and'collect for our cabinets, often contain portions of many ele- 
 mentary bodies; but, with few exceptions, the organic part of all plants, 
 that which lives and grows, contains only the four simple substances 
 described in my former lecture. 
 
 4°. They are distinguished also by this important character, that 
 they cannot be formed by human art. Many of the inorganic com- 
 pounds which occur in the mineral crust of the globe can be produced by 
 the chemist in his laboratory, and were any corresponding benefit likely 
 to be derived from the expenditure of time and labour, there is reason to 
 believe that, with a few exceptions, nature might be imitated in the for- 
 mation of any of her mineral productions. But in regard to organic sub- 
 stances, whether animal or vegetable, the chemist is perfectly at fault. 
 He can form neither woody fibre, nor sugar, nor starch, nor muscular 
 fibre, nor any of those substances which constitute the chief bulk of ani- 
 mals and plants, and which serve for the food of animated beings. 
 
 • For an explanation of the exact nature and end of this putrefaction, see the subsequen 
 Lecture, ^'Onllie decay ofanimai and vegetable substances." 
 
PROSPECTS OF SCIENCE. 29 
 
 This is an important and striking, and is, I believe, liltely to remain a 
 permanent distinction, between most substances of organic and of inor- 
 ganic origin. 
 
 Looking back at the vast strides which organic chemistry has made 
 within the last twenty years, and is still continuing to make, and trust- 
 ing to ihe continued progress of human discovery, some sanguine chem- 
 ists venture to anticipate the time when the art of man shall not only 
 acquire a dominion over that principle of life, by the agency of which 
 plants now grow and alone produce food for man and beast, but shall be 
 able also, in many cases, to imitate or dispense with the operations of that 
 principle : and to predict that the time will come when man shall man- 
 ufacture by art those necessaries and luxuries for which he is now wholly 
 dependent on the vegetable kingdom. 
 
 And, having conquered the winds and the waves by the agency 
 of steam, is man really destined to gain a victory over the uncertain sea- 
 sons too? Shall he come at last to tread the soil beneath his feet as a 
 really useless thing — to disregard the genial shower, to despise the influ- 
 ence of the balmy dew — to be indifferent alike to rain and drought, to 
 cloud and to sunshine — to laugh at the thousand cares of the husband- 
 man — to pity the useless toil and the sleepless anxieties of the ancient 
 tillers of the soil ? Is the order of nature, through all past time, to be re- 
 versed — are the entire constitution of society, and the habits and pur- 
 suits of the whole human race, to be completely altered by the pro- 
 gress of scientific knowledge ? 
 
 By placing before man so many incitements to the pursuit of know- 
 ledge, the will of the Deity is ,that out of ihis increase of wisdom he 
 should extract the means of increased happiness and enjoyment also. 
 But set man free from the necessity of tilling the earth by the sweat of 
 his brow, and you take from him at the same time the calm and tran- 
 quil pleasures of a country life — the innocent enjoyments of the return- 
 ing seasons — the cheerful health and happiness that wait upon labour 
 in the free air and beneath the bright sun of heaven. And for what? — 
 only to imprison him in manufactories, to condemn him to the fretful 
 and feverish life of crowded cities. 
 
 To such ends, I trust, science is not destined to lead ; and he is not 
 only unreasonably, but thoughtlessly sanguine, who would hope to de- 
 rive from organic chemistry such power over dead matter as to be able 
 to fashion it into food for living animals. With such consequences be- 
 fore us it seems almost sinful to wish for it. 
 
 Yet, that this branch of science will lead to great ameliorations in the 
 art of culture, there is every reason to believe. It will explain old meth- 
 ods — it will clear up anomalies, reconcile contradictory results by ex- 
 plaining the principles from which they flow — and will suggest new meth- 
 ods by which better, speedier, or more certain harvests may be reaped. 
 
 § 2. Relative proportions of organic elements. 
 
 Though the substance of plants consists chiefly of the four organic ele- 
 ments, yet these bodies enter into the constitution of vegetables in very 
 different proportions. This fact has already been adverted to in a gen- 
 eral manner: it will appear more distinctly by the following statement 
 of the exact quantities of each element contained in 1000 parts by 
 
 2* 
 
30 RELATIVE PROPERTIES OF ORGANIC ELEMENTS. 
 
 weight of some of the more important kinds of vegetable substance you 
 are in the habit of cultivating : — 
 
 
 Hay from 
 
 young Clover 
 
 3 mos. old. 
 
 Oats. 
 
 Clover- 
 Seed. 
 
 After-math 
 Hay. 
 
 Peas. 
 
 Wheat. 
 
 Hay. 
 
 Potatoes. 
 
 Carbon . 
 
 507 
 
 507 
 
 494 
 
 471 
 
 465 
 
 455 
 
 458 
 
 441 
 
 Hydrogen 
 
 66 
 
 64 
 
 58 
 
 56 
 
 61 
 
 57 
 
 50 
 
 58 
 
 Oxygen 
 
 389 
 
 367 
 
 350 
 
 349 
 
 401 
 
 431 
 
 387 
 
 439 
 
 Nitrogen 
 
 38 
 
 22 
 
 70 
 
 24 
 
 42 
 
 34 
 
 15 
 
 12 
 
 Ash . . 
 
 . not stated 
 
 40 
 
 28 
 
 100 
 
 31 
 
 23 
 
 90 
 
 50 
 
 1000* lOOOf 1000* lOOOf lOOOt 1000* lOOOf lOOOf 
 The numbers in the above table represent the constitution of the 
 plants and seeds, taken in the state in which they are given to cattle or 
 are laid up for preservation, and then dried at 230° Fahrenheit. By 
 this drying they lost severally as follows : 
 
 uu par 
 ditto 
 
 [S oi iroiaiues . . lusi 
 ofWhea^ . . — 
 
 . . . /^^ p 
 . . . ,166 
 
 .11 IS 1^1 
 
 ditto 
 
 ditto 
 
 of Hay ... — 
 
 . . . 158 
 
 ditto 
 
 ditto 
 
 of Aftermath Hay — 
 
 . 136 to 140 
 
 ditto 
 
 ditto 
 
 of Oats . . . — 
 
 . . . 151 
 
 dittc 
 
 ditto 
 
 of Clover Seed . — 
 
 . . . 112 
 
 dhto 
 
 ditto 
 
 of Peas ... — 
 
 . . . 86 
 
 ditto 
 
 n 
 
 In crops as they are reaped, therefore, and even as they are given for 
 food, much water is present. When artificially dried, the carbon ap- 
 proaches to one-half of their weight — the oxygen to more than one- 
 third§ — the hydrogen to little more than 5 per cent. — and the nitrogen 
 rarely to more than 2i per cent. These proportions are variable, but 
 they represent very nearly the relative weights in which these elements 
 enter into the constitution of those forms of vegetable matter which are 
 raised in the greatest quantity for the support of anitnal life. 
 
 But, besides the organic part, vegetable substances contain an inor- 
 ganic portion, which remains behind in the form of ash when the plant is 
 consumedJjy fire, or of dust when it decomposes and disappears in 
 consequence of natural decay. 
 
 In the dried hay, oats, &c., of which the com])osition is represented 
 in the above table, we see that the quantity of ash is very variable, in 
 oats being as small as 4 per cent., while of hay every hundred pounds 
 left 10 of ash. A similar diflference is observed generally to prevail 
 throughout the vegetable kingdom. Each variety of plant, when 
 burned, leaves a weight of ash, more or less peculiar to itself. Herba- 
 ceous plants generally leave more than the wood of trees — and differ- 
 ent parts of the same plant yield unlike quantities of inorganic matter.|I 
 
 • Boiissingault Annates de China, et de Phys. (1838) lxvii. p. 20 to 38. 
 T Ditto ' ditto (1839) Lxxi. p. 113 to 136. 
 
 i Ditto ditto (1838) lxix. p. 356, 
 
 § This ^ill appear no way inconsi.stent with the statement in the former Lecture, that 
 oxygen constitutes one-half by weight of all living plants, when it is recollected that of tlie 
 water driven off in drying lliese plants eight-ninths by weight consist of oxygen, and ttiat 
 600 lbs. of grass, for example, yield only from 80 to 100 lbs. of hay. 
 
 11 Thus of the oak, the dried bark left 60 of ash — the dried leave.s 53 — the dried albumuiQ 
 4— and the dried wood only 2 parts in a thousand of ash.— i?e Saussure. 
 
ON THE CONSTITUTION OF THE ATMOSPHERE. 31 
 
 These facts are of great importance in the theory and in the enhghtened 
 practice of agriculture. They will hereafter come under special and 
 detailed consideration, when we shall have examined the nature of the 
 soils in which plants grow, and shall be prepared to consider the chemi- 
 cal nature, the source, and the functions, of the inorganic compounds 
 which exist in living animal and vegetable substances. 
 
 § 3. Of the form or state of combination in which the organic elements 
 enter into and minister to the growth of plants. 
 
 From the details already presented in the preceding Lecture, in re- 
 gard to the properties of carbon and nitrogen, and the circumstances 
 under which they are met with in nature, — it will readily occur to you 
 that neither of these elementary bodies is likely to enter directly, or in a 
 simple state, int^ the circulation of plants. The former (carbon) being 
 a solid substance, and insoluble in water, cannot obtain admission into 
 the pores of the roots, the only parts of the plants with which, in nature, 
 it can come in contact. The latter (hydrogen) does not occur either in 
 the atmosphere or in the soil in any appreciable quantity, and hence, in 
 its simple state, forms no part of the food of plants. Oxygen and nitro- 
 gen, again, both exist in the atmosphere in the gaseous state, and the 
 former is known to be inhaled, under certain conditions, by the leaves 
 of plants. Nitrogen may also in like manner be absorbed by the leaves 
 of living plants, but, if so, it is in a quantity so small as to have hitherto 
 escaped detection. The two latter substances (oxygen and nitrogen) 
 are also slightly soluble in water, and, besides being inhaled by the 
 leaves, may occasionally be absorbed in minute quantity along with the 
 water taken in by the roots. But by far the largest proportion of these 
 two elementary bodies, and the whole of the carbon and hydrogen 
 which find their way into the interior of plants, have previously entered 
 into a state of mutual combination — -forming what are called distinct 
 chemical compounds. Before describing the nature and constitution of 
 these compounds, it will be proper to explain, 1°. the constitution of the 
 atmosphere in which plants live, and, 2°. the nature of chemical com- 
 bination and the laws by which it is regulated. 
 
 §4. On the constitution of the atmosphere. 
 
 The air we breathe, and in which plants live, is composed principal- 
 ly of a mixture of oxygen and nitrogen gases, in the proportion very 
 nearly of 21 of the former to 79 of the latter. It contains, however, as 
 a constituent necessary to the very existence of vegetable life, a small 
 per centage of carbonic acid. On an average this carbonic acid 
 amounts to about ■2/o^th part* of the bulk of the air. On the shores 
 of the sea, or of great lakes, this quantity diminishes; and it becomes 
 sensibly less as we recede from the land. It is also less by day than 
 by night (as 3*38 to 4*32), and over a moist than over a dry soil. 
 
 The air is also imbued with moisture. Watery vapour is every 
 where diffused through it, but the quantity varies with the season of 
 the year, with the climate, with the nature of the locality, with its alti- 
 
 • 0'04 per cent. The mean of 104 experiments made by Saussure at Geneva at all timp3 
 ofthe year and of the day gave 415 volumes in 10000. The maximum was 5-74, and th« 
 minimum 315. 
 
32 NATURE OF CHEMICAL COMBINATION. 
 
 tude, and with its distance from the equator. In temperate climates, 
 it oscillates on the same spot between i and IJ per cent, of the weight 
 of the air ; being least in mid-winter and greatest in the hot months of 
 Slimmer. There are also mingled with the atmosphere, traces of the 
 vast variety of substances which are capable of rising from the surface 
 of the earth in the form of vapour; such, for example, as are given off 
 by decaying animal or vegetable matter — which are the produce of 
 disease in either class of bodies— or which are evolved dnring the oper- 
 ations of nature in the inorganic kingdom, or by the artificial processes 
 of man. Among these accidental vapours are to be included those 
 miasmata, wiiich, irt certain parts of the world, render whole districts 
 unhealthy, — as well as certain compounds of ammonia, which are infer- 
 red to exist in the atmosphere, because they can be detected in rain 
 water, or in snow which has newly fallen. 
 
 In this constitution of the atmosphere we can discover many beauti- 
 ful adaptations to the wants and structure of animals and plants. The 
 exciting effect of pure oxygen on the animal economy is diluted by the 
 large admixture with nitrogen ; — the quantity of carbonic acid present 
 is sufficient to supply food to the plant, while it is not so great as to 
 prove injurious to the animal ; — and the watery vapour suffices to 
 maintain the requisite moisture and flexibility of the parts of both or- 
 ders of beings, without in general being in such a proportion as to prove 
 hurtful to either. 
 
 The air also, by its subtlety, diffuses itself everywhere. Into every 
 pore of the soil it makes its way. When there, it yields its oxygen or 
 its carbonic acid to the dead vegetable matter or to the living root. A 
 shower of rain expels the half-corrupted air, to be succeeded by a purer 
 portion as the water retires. The heat of the sun warms the soil, and 
 expands the imprisoned gases, — these partially escape, and are, as be- 
 fore, replaced by other air when the rays of the sun are withdrawn. 
 
 By the action of these and other causes a constant circulation is, to 
 a certain extent, kept up, — between the atmosphere on the surface, 
 which plays among the leaves and stems of plants, and the air which 
 mingles with the soil and ministers to the roots. The precise effect and 
 the importance of this provision will demand our consideration in a fu- 
 ture lecture. 
 
 § 5. Tlie nature and laws of chemical comhination. 
 
 The terms combine and comhination in chemical language have a 
 strict and precise application. If sand and saw-dust be rubbed togeth- 
 er in a mortar they may be intimately intermingled, but by pouring wa- 
 ter on the mass we can separate the particles of wood and leave the 
 sand unchanged behind. So if we stir oatmeal and water together, we 
 may cause them perfectly to mix together, but by the aid of a gentle 
 heat we can expel the water and obtain dry oatmeal in its original 
 condition. Or, by putting salt into water, it will dissolve and disappear, 
 and form what is called a solution, but by boiling it down, as is done 
 in our salt-pans, the water may be entirely removed and the salt 
 procured of the weight originally employed and possessed of its original 
 properties. 
 
 In none of these cases has any chemical action taken place, or any 
 
chemictil decomposition. 33 
 
 permanent change been produced, upon any of the substances. The two 
 former were merely mixtures. 
 
 In all cases of chemical action a jjennanent change takes place in sojne 
 of tiie substances employed ; and this change is the result either of a chem- 
 ical combination, or of a chemicMl (hroni position. 
 
 Thus when sulphur is burned in the air, it is converted into white va- 
 pours possessed of a powerful ana very unpleasant odour, and which 
 continue to be given oii' until the whole of the sulphur is dissipated. 
 
 Here a solid substance is permanently changed into noxious va})ours 
 which disappear in the air, and this change is caused by tlie combination 
 of the sulphur with the oxygen of the atmosphere. 
 
 In like manner when limestone is put into a kiln and strongly heated 
 or burned, it is changed or converted into quicklime — a substance very 
 different in its properties from the natural limestone employed. But 
 Jiis is a case of chemical decomposition. The limestone consists of 
 lime and carbonic acid. By the heat these are separated, the latter is 
 driven off and the former remains in the kiln. 
 
 Again, when a jet of hydrogen gas is kindled in the air or in oxygen 
 gas, it burns with a pale yellow flame. If a cold vessel be held over 
 this flame, it speedily becomes bedewed with moisture, and drops of wa- 
 ter collect upon it. How remarkable the change wiiich hydrogen un- 
 dergoes during this combustion! It unites with the oxygen of the 
 atmosphere and forms water. How different in its properties is this 
 water from either the oxygen or the hydrogen by the union of which it is 
 formed! The former a liquid, the latter gases; the former an enemy 
 to all combustion, while of the latter, the one (hydrogen) burns readily, 
 the other (oxygen) is the very life and support of combustion in all oth- 
 er bodies. 
 
 1°. It appears, therefore, that chemical combination or decomposition 
 is always attended by a permanent change. 
 
 2°. That when combination takes place, a new substance is formed 
 differing in its properties from any of those from which it was produced, 
 or of which it consists. 
 
 When two or more elementary bodies thus unite together to form a 
 new substance, this nev/ substance is called a chemical compound. 
 Thus water is a compound (not a mixture) of the two elementary bodies 
 oxygen and hydrogen. 
 
 Now when such combination takes place, it is found to do so always 
 in accordance with certain fixed laws. Thus : 
 
 I. Bodies unite logether only in constant and definite proportions. We 
 can mix together oxygen and hydrogen gases, for example, in any pro- 
 portion, a gallon of the one with any number of gallons of the other, but 
 if we burn two gallons of hydrogen gas in any greater number of gallons 
 of oxygen, they will only consume or unite with one gallon of the oxy- 
 gen, the rest of this gas remaining unchanged. A quantity of water will 
 be formed by this union, in which the whole of the hydrogen will be 
 contained, combijied with all the oxygen that has disappeared. Under 
 no circumstances can we burn hydrogen so as to cause it to consume 
 more oxygen, or from a given weight of hydrogen to produce more than 
 a known weight of water. And as oxygen is nearly sixteen times 
 heavier than nitrogen, it is obvious that one gallon of the former is about 
 
34 EQUIVALENT NUMBERS — ISOMERIC BODIES 
 
 eight times heavier than two gallons of the latter, so that by weight these 
 two gnses, when thus burned, unite together nearly in the proportion 
 of 1 to 8, — one pound of hydrogen forming nine pounds of water. 
 
 Again, when pure carbon is burned in the air, it unites with a fixed 
 and constant weight of oxygen to form carbonic acid ; it never unites 
 with more, and it does not form carbonic acid when it unites with less. 
 
 Now this law of fixed and definite* proportions is found to hold in re- 
 gard to all bodies, and in all cases of chemical combination. Thus we 
 have seen that — 
 By weight. By weight. 
 
 1 of hydrogen combines with 8 of oxygen to form water. 
 
 So 6 of carbon combine ... 8 carbonic oxide, 
 
 and 14 of nitrogen 8 nitrous oxide. 
 
 Hence 1 of hydrogen, 6 of carbon, and 14 of nitrogen unite respec- 
 tively with the weight (8) of oxygen. These several numbers, there- 
 fore, are said to be equivalent to each other (they are equivalent numbers). 
 Or they represent the fixed and definite proportions in which these seve- 
 ral substances combine together (they are definite projyortionah). Some 
 chemists consider these numbers to represent the relative weights of the 
 atoms or smallest particles of which the several substances are made up, 
 and hence not unfrequently speak of them as the atomic weights of these 
 substances, or more shortly their atoms. 
 
 For the sake of brevity, it is often useful to represent the simple or 
 elementary bodies shortly by the initial letter of their names. Thus 
 hydrogen is represented by H, carbon by C, and nitrogen by N, and 
 these letters are used to denote not only the substances themselves, but 
 that quantity which is recognised as its equivalent, proportional, or 
 atomic weight. Thus : 
 
 Equivalent 
 Symbol. or atomic Name. 
 
 weights. 
 
 H denotes 1 by weight, of hydrogen. 
 
 C . . . 6 carbon. 
 
 O . . . 8 ■ oxygen. 
 
 N . . . 14* nitrogen. 
 
 Chemical combination is expressed shortly by placing these letters in 
 juxta-position, or sometimes in brackets, with the sign plus (+) between 
 them. Thus HO or (H + O) denotes the combination of one atom or 
 equivalent of hydrogen with one of oxygen, that is, water ; and at the 
 same time a weight of water (9), equal to the sum of the atomic weights 
 (1 _j_ 8) of hydrogen and nitrogen. 
 
 A number prefixed or appended to a symbol, denotes that so many 
 equivalents of the substapce represented by the symbol are meant, as 
 that number expresses. Thus 2 H O, 3 H O, or 3 (B + O), mean two 
 or three equivalents of water, 3 H, or H3 three equivalents of hydrogen, 
 and 4 C or C4, 2 N or N21 four of carbon and two of nitrogen respec- 
 tively. 
 
 H. Not only are the quantities of the substances which unite together 
 definite and constant, but the properties or qualities of the substances 
 formed are in general equally so. The properties of pure water or o** 
 
 • More correctly 1, 6 13, 8013, and 14-19. 
 
 i 
 
LAW OF MULTIPLE PROPORTIONS. 36 
 
 carbonic acid are constant and invariable under whatever circumstances 
 they may be formed, and the elements of which they consist, when they 
 combine together in the same proportions, are never known to form any 
 other compounds but water and carbonic acid. 
 
 This law, however, though generally, is not universally true. Many 
 substances are known which contain the same elements united together 
 in the same proportions, and which, nevertheless, possess very ditierent 
 properties. Oil of turpentine and oil of lemons are in this condition. 
 They both consist of the same elements, carbon and hydrogen, united 
 together in the same proportions, and yet their sensible properties as well 
 as their chemical relations* are very dissimilar. 
 
 Cane sugar, starch, and gum, all of them abundant products of the 
 vegetable kingdom, consist also of the same elements, carbon, hydro- 
 gen, and oxygen, united together in the same proportions, and may even 
 be represented by the same formula (Cjo Hjo O,o),f and yet these 
 substances are as unlike to each other in their properties, as many 
 bodies are of which the chemical composition is very different. To 
 compounds thus differing in their properties, and yet containing the 
 same elements, in the same proportions, chemists have given the name 
 of Isomeric bodies. I shall have occasion to make you more familiar 
 with some of them hereafter. 
 
 3°. Another important law by which chemical combinations are 
 regulated, is known bv ti.e name of the law of multiple proportions. 
 Some substances are observed to be capable of uniting together in more 
 than one proportion. Thus carbon unites with oxygen in several pro- 
 portions, forming carbonic oxide, carbonic acid, oxalic acid, &c. Now 
 when such is the case, it is found that the quantity (the weight) of each 
 substance which enters into the several compounds, if not actually re- 
 presented by the ecjuivalent number or atomic weight, is represented by 
 some simple multiple of that number. Thus two equivalents of carbon 
 unite with 2, 3, or 4 equivalents of oxygen, to form carbonic oxide, 
 oxalic acid, and carbonic acid respectively, — while one of nitrogen unites 
 with 1, 2, 3, 4, or 5 of oxygen to form a series of compounds, of which 
 the last (N O5), nitric acid, is the only one I shall have frequent occa- 
 sion to speak of in the present lectures. 
 
 This law of multiple proportions, though of great importance in 
 chemical theory, 1 do not further illustrate, as we shall have very little 
 occasion to refer to it in the discussion of the several topics which will 
 hereafter come before us. 
 
 Having thus briefly explained the nature and laws of chemical com ■ 
 bination, I proceed to make you acquainted with those chemical com- 
 pounds of the organic elements which are known or are supposed to 
 minister to the growth of plants. - 
 
 The number of compounds which the four organic elements form 
 with each other is almost endless ; but of this number a very few only 
 
 * By the chemical relations of a substance are meant the effects which are produced 
 upon it by contact with other chemical substances. 
 
 t Th\s foTTnula means that starch, gum, and sugar, consist of 12 equivalents of carbon 
 united to 10 of hydrogen and 10 of oxygen. 
 
36 RELATIONS OF WATER TO VEGETABLE LIFE. 
 
 are known to minister directly to the growth or nourishment of plants. 
 Of these, water, carbonic acid, ammonia, and nitric acid, are the most 
 important ; but it will be necessary shortly to advert to a few others, of 
 the occurrence or production or action of which we may hereafter iiave 
 occasion to speak. 
 
 § 6. Of water and its relations to vegetable life. 
 
 Water is a compound of oxygen and hydrogen in the proportion, as 
 already staled, of 8 of the former to 1 of the latter by weight, or of 1 
 volume of oxygen to 2 of hydrogen. 
 
 [t is more universally ditllised throughout nature than any other 
 chemical compound witli which we are acquainted, performs most im- 
 portant functions in reference to animal and vegetable life, and is en- 
 dowed with properties by which it is wonderfully adapted to the exist- 
 ing condition of things. 
 
 We are familiar with this substance in three several states of cohe- 
 sion, — in the solid form as ice, in the fluid as water, and in the gaseous 
 as steam. At 32° F. and at lower temperatures, it continues solid, at 
 higher temperatures it melts and forms a liquid (water), which a 
 212° F. begins to boil and is converted into steam. By this change its 
 bulk is increased 1700 times, and it becomes nearly two-fifilis lighter 
 than common air, [common air being 1, steam is 0-62. j It therefore 
 readily rises into and diffuses itself through the atmosphere. 
 
 I. There are only one or two circumstances in which water in tne solid 
 form materially atiecls or interferes with the labours of the agriculturist. 
 
 1°. During the frost of a severe winter, the soil contracts and appears 
 to shrink in. But the water contained in its pores freezes and expands, 
 and the minute crystals of ice thus formed separate the particles of the 
 soil from each other. This expansion of the water in dry soils may not 
 be equal to the natural contraction of the soil itself, yet still it is suffi- 
 cient to cause a considerable separation of the earthy particles through- 
 out the whole frozen mass. When a niilder temperature returns, and a 
 thaw commences, the soil expands and gradually returns to its former 
 bulk ; but-th« outer layers thaw first, and the particles being previously 
 separated by the crystals of ice, and now loosened by the thaw, fall off 
 or crumble down, and thus the soil becomes exposed to the mellowing 
 action of the atmosphere, which is enabled everywhere to pervade it. 
 On heavy clay land this effect of the winter's frost not unfrequently 
 proves very beneficial.* 
 
 2°. In the form of snow it has been often supposed to be beneficial to 
 winter wheat and other crops. That a heavy fall of snow will shelter 
 and protect the soil and crop from the destructive effects of any severe 
 cold which may follow, there can be no doubt. It forms a light porous 
 covering, by which the escape of heat from the soil is almost entirely 
 prevented. It defends the young shoots also from those alternations of 
 temperature to which the periodical return of the sun's rays continually 
 
 * This alternate contraction and expansion is often injurious to the practical farmer in 
 throwing out his winter wheat. Some varieties are said to be more thrown out than others, 
 and this peculiarity is sometimes ascribed to the longer and stronger roots which shoot from 
 one variety than from another ; it may, however, be occasionally owing to the different na- 
 ture of the soils in which the trials have been made, or when, in the same soil, to the differ- 
 ent states of dryness at different times. 
 
ACTION AND PROPERTIES Of SNOW. 37 
 
 exposes them ;* and when a thaw arrives, by slowly melting, it allows 
 the lender herbage gradually to accustom itself to the milder atmosphere. 
 
 In this manner there is no doubt that a fall of snow may often be of 
 great service to the practical farmer. But some believe that winter 
 wheat actually thrives under snow. On this point I cannot speak from 
 personal knowledge, but I will here mention two facts concerning snow, 
 which may possibly be connected with its supposed nourishing quality. 
 
 In the first place, snow generally contains a certain quantity of ammo- 
 nia, or of animal matter which gives off ammonia during its decay. 
 This quantity is variable, and is occasionally so small as to be very dif- 
 ficult of detection. Liebig found it in the snow of the neighbourhood of 
 Giessen, and I have this winter detected traces of it in the snow which 
 fell in Durhamf during two separate storms. This ammonia is present 
 in greater quantity in the first portions that fall and lie nearest the plant. 
 Hence if the plant can grow beneath the snow, this ammonia may aflfect 
 its growth ; or when the first thaw comes it may descend to the root, and 
 may there be imbibed. Rain water also contains ammonia, but when 
 rain falls in large quantity it runs off the land, and may do less good than 
 the snow, which lies and melts gradually. [For the properties of am- 
 monig, see Lecture III.] 
 
 Another singular property of snow is the power it possesses of ab- 
 sorbing oxygen and nitrogen from the atmosphere, in proportions very 
 different from those in which they exist in the air. The atmosphere, as 
 already stated, contains 21 percent, of oxygen by volume (or bulk), but 
 the air which is present in the pores of snow has been found by various 
 observers to contain a much smaller quantity. Boussingault [Annalen 
 der Physick (Poggendorf), xxxiv., p. 211,] obtained from air disengaged 
 by melting snow 17 per cent, of oxygen only, and De Saussure found 
 still less. The diflficulty of respiration experienced on very high moun- 
 tains has been attributed to the nature of the air liberated from snow 
 when melted by the sun's rays. Whether the air retained among the 
 pores of the snow, which in severe winters covers our corn-fields, be 
 equally deficient in oxygen with that examined by Boussingault, and 
 whether, if it be, the abundance of nitrogen can at all affect vegetation, 
 are matters that still remain undetermined. 
 
 II. In the fluid state, that of water, the agency of this compound in 
 reference to vegetable life, though occasionally obscure, is yet every- 
 where discernible. 
 
 Pure water is a colourless transparent fluid, destitute of either taste or 
 
 ' The effects of such alternations are seen on the occurrence of a night's frost in spring. 
 If the sun's rays fall in the early morning, on a frozen shoot, it droops, withers, and black- 
 ens—it is destroyed by the frost. If the plant be in a shaded spot, where the sun does not 
 reach it till after the whole atmosphere has been gradually heated, and the frozen tissue 
 slowly thawed, its leaves sustain little injury, and the warmth of the sun's rays, instead of 
 injuring, cherish and invigorate it. This effect of sudden alternations of temperature on or- 
 ganic matter explains many phenomena, to which it would here be out of place to advert. 
 
 A thick light covering of porous earth not beaten down preserves the potatoe pit from the 
 effects of the frost better than a solid compact coating of clay, in the same way as snow 
 protects the herbage better than a sheet of ice ; and it is because of the porosity of the 
 covering, that ice may be preserved more effectually, and for a longer period, in a similar 
 pit, than in many well-constructed ice-houses. 
 
 t By adding two drops of sulphuric acid to four pints of snow water, evaporating to dry- 
 ness, and mixing the dry mass with quicklime or caustic potash. The residual mass con- 
 tJiined a brown organic matter, mixed with the sulphate of ammonia. 
 
38 WATER NECESSARY TO LIFE — ITS SOLVENT POWER. 
 
 smell. It enters largely into the constitution of all living animals and 
 plants, and forms upwards of one half of the weight of all the newly 
 gathered vegetable substances we are in the habit of cultivating or col- 
 lecting for the use of man. [See page 30.] 
 
 Not only does it enter thus largely into the constitution of all ani- 
 mals and plants, but in the existing economy of nature its presence in 
 large quantities is absolutely necessary to the persistence of animal and 
 vegetable life. In the midst of abundant springs and showers, plants , 
 shoot forth with an amazing rapidity, while they wither, droop, and die, i 
 when water is withheld. How much the manifestation of life is de- ] 
 pendent upon its presence, is beautifully illustrated by some of the hum- 
 bler tribes of plants. Certain mosses can be kept long in the herbarium, 
 and yet will revive again when the dried specimens are immersed in ^i 
 water. At Manilla a species of "Lycopodium grows upon the rocks, II 
 which, though kept for years in a dried state, revives and expands its 
 foliage when placed in water [the Spaniards call it Triste de Corazon, 
 Sorrow of the Heart. — BurneVs Wanderings, \>. 72.] Thus life lingers 
 as it were, unwilling to depart and rejoicing to display itself again, when 
 the moisture returns.* 
 
 There are, however, three special properties of water, which are in 
 a high degree interesting and important to the practical agriculturist, 
 and to which I beg to direct your particular attention. These are: 
 
 1°. Its solvent power; 
 
 2^. Its affinity for certain solid substances ; and, 
 
 3°. The degree of affinity by which its own elements are held to- 
 gether. 
 
 1°. When pure boiled water is exposed to the air, it gradually ab- 
 sorbs a quantity of the several gases of wiiich the atmosphere is com- 
 posed, and acquires more or less of a sparkling appearance and an agree- 
 able taste. The air which it thus absorbs amounts to about J^th of its 
 own bulk, and is entirely expelled by boiling. When thus expelled, 
 this air, like that obtained from snow, is found on examination to contain 
 the oxygen, nitrogen, and carbonic acid in proportions very different from 
 those in which they exist in the atmosphere. In the latter, oxygen is 
 present to the amount of only 21 per cent, by volume, while the air ab- 
 sorbed by water contains 30 to 32 per cent, of the same gas. In like 
 manner, the mean quantity of carbonic acid in the air does not exceed 
 y-g4^fj^th parts (0*05 per cent.) of its bulk, while that expelled from water, 
 which has been long exposed to the air^ varies from 11 to GO ten thou- 
 sand parts (0-11 to 0-6f per cent.) 
 
 * In some species of animals, life is in like manner suspended by the absence of water. 
 The inhabitants of some land and even marine shells may be dried and preserved for a long 
 time in a state of torpor, and afterwards revived by immersion in water. The Cerithium 
 Armatum has been brought froxn tiie Mauritius in a dry state, while snails are said to have 
 beeu revived after beinu dried for 15 years. The vibrio tritici (a species of worm), was re- 
 stored by Mr. Bauer, after an apparent death of nearly six years, by merely soaking it in 
 water. The Purcularia Anastobea, a small microscopic animal, may be made to undergo 
 apparent death and resuscitation many times, by alternate drying and moistening. Accord- 
 ing to Spallanzani, animalculi have been recovered by moisture, after a torpor of 27 years. 
 These facts tend to lessen our surprise at the alleged longevity of the seeds of plants. 
 
 t Of these gases when unmixed, water absorbs very different quantities. Thus 1(X) vo- 
 lumes of water at 60° F., absorb 3-55 of oxygen, 1-53 of hydrogen, 147 of nitrogen, (flewy,) 
 106 of carbonic acid, or 7800 of ammonia. 
 
ITS AFFINITY FOR SOLID SUBSTANCES. 39 
 
 Thus when water falls in rain or trickles along the surface of the 
 land, it absorbs these gaseous substances, carries them with it wherever 
 it goes, conveys them to the roots, and into the circulation of plants, and 
 thus, as we shall hereafter see, makes them all minister to the growth 
 and nourishment of living vegetables. 
 
 Again, water possesses the power of dissolving many solid substances. 
 If sugar or salt be mixed with water in certain quantities, they 
 speedily disappear. In like manner, many other bodies, both simple 
 and compound, are taken up by this liquid in greater or less quan- 
 tity, and can only be recovered by driving off the water, through the aid 
 of heat. 
 
 Thus it happens that the water of our springs and rivers is never 
 pure, but holds in solution more or less of certain solid substances. 
 Even rain Avater, washing and purifying the atmosphere as it descends, 
 brings down portions of solid matter which had previously risen into the 
 air in the form of vapour, and as it afterwards flows along or sinks into 
 the surface of the soil, it meets with and dissolves other solid substances, 
 the greater portion of which it carries with it wherever it enters. In 
 this way solid substances are conveyed to the roots of plants in a fluid 
 form, which enables them to ascend with the sap ; and the supply of 
 these naturally solid substances is constantly renewed, by the succes- 
 sive passage of new portions of flowing water. We shall hereafter be 
 able to see more clearly and to aj)preciate more justly this beautiful ar- 
 rangement of nature, as well as to understand how indispensable it is to 
 the continued fertility of the soil. 
 
 Nor is it merely earthy and saline substances which the water dis- 
 solves, as it thus percolates through the soil. It takes up also sub- 
 stances of organic origin, especially portions of decayed animal and ve- 
 getable matter, — such as are supposed to be capable of ministering to 
 the growth of plants, — and brings them within reach of the roots. 
 
 This solvent power of water over solid substances is increased by an 
 elevation of temperature. Warm water, for example, will dissolve 
 Epsom salts or oxalic acid in much larger quantity than cold water 
 will, and the same is true of nearly all solid substances which this fluid 
 is capable of holding in solution. To this increased solvent power of 
 the water they absorb, is ascribed, among other causes, the peculiar 
 character of the vegetable productions, as well as their extraordinary 
 luxuriance, in many tropical countries. 
 
 2°. But the affinity which water exhibits for many solid substances is 
 little less important and remarkable. 
 
 When newly burned lime is thrown into a limited quantity of water 
 the latter is absorbed, while the lime heats, cracks, swells, and finally 
 falls to a white powder. When thus perfectly slaked, it is found to be 
 one-third heavier than before — every three tons having absorbed- one 
 ton of water. This water is retained in a solid form, more solid than 
 water is when in the state of ice, and it cannot be entirely separated 
 from the lime without the application of a red heat. When you lay 
 upon your land, therefore, four tons of slaked lime, you mix with your 
 soil one ton of water, which the lime afterwards gradually gives up, 
 either in whole or in part, as it combines with other substances. To 
 this fact wo shall return when we hereafter consider the various ways 
 
40 USES OF WATERY VAPOUR IN VEGETATION. 
 
 in which lime acts, when it is employed by the farmer for the purpose 
 of improving his land. [See the subsequent lecture, " On the action of 
 lime when employed as a manure.''^'] 
 
 For clay also, water has a considerable affinity, though by no means 
 equal to that which it displays tor quicklime. Hence, even in well- 
 drained clay lands, the hottest summer does not entirely rob the clay of 
 its water. It cracks, contracts, and becomes hard, yet still retains 
 water enough to keep its wheat crops green and flourishing, when the 
 herbage on lighter soils is drooping or burned up. 
 
 A similar affinity for water is one source of the advantages which are 
 known to follow from the admixture of a certain amount of vegetable 
 matter with the soil ; though, as in the case of charcoal, its porosity* 
 is probably more influential in retaining moisture near the roots of 
 the plants. f 
 
 3°. The degree of affinity by which the elements of water are held 
 together, exercises a material influence on the growth and production 
 of all vegetable substances. 
 
 If I burn a jet of hydrogen gas in the air, water is formed by the 
 union of the hydrogen with the oxygen of the atmosphere, for which it 
 manifests on many occasions an apparently powerful affinity. But if 
 into a vessel of water I put a piece of iron or zinc and then add sulphuric 
 acid, the water is decom'posed and the hydrogen set free, while the 
 metal combines with the oxygen. 
 
 So in the interior of plants and animals, water undergoes continual 
 cZecom position and recomposition. In its fluid state, it finds its way 
 and exists in every vessel and in every tissue. And so slight, it would 
 appear, in such situations, is the hold which its elements have upon 
 each other — or so strong their tendency to combine with other substan- 
 ces, that they are ready to separate from each other at every impulse — 
 yielding now oxygen to one, and now hydrogen to another, as the pre- 
 duction of the several compounds which each organ is destined to elab- 
 orate respectively demands. Yet with the same readiness do they 
 again re-attach themselves and cling together, when new metamorphoses 
 require it. It is in the form of water, indeed, that nature introduces 
 the greate^^ortion of the oxygen and hydrogen which perform so im- 
 portant a part in the numerous and diversified changes which take place 
 in the interior of plants and animals. Few things are really more won- 
 derful in chemical physiology, than the vast variety of transmutations 
 which are continually going on, through the agency of the elements of 
 water. 
 
 III. In the state of vapour water ministers most materially to the 
 life and growth of plants. It not only rises into the air at 212° Fahr. 
 when it begins to boil, but it disappears or evaporates from open vessels 
 at almost every temperature, with a rapidity proportioned to the previ- 
 ous dryness of the air, and to the velocity and temperature of the at- 
 mospheric currents which pass over it. Even ice and snow are grad- 
 
 * Affinity for water causes vegetable matter to combine chemically with M, porosity causes 
 it merely to drink in the water mechanically, and to retain it, unchanged, in its pores. 
 
 t For an exposition of the intimate relation of water to the chemical constitution of the 
 solid parts of living vegetables, see a subsequent Lecture, " On the nature and production 
 of the substances of which plants chiefly consist." 
 
FORMATION OF CLOUDS AilD RAIN. 41 
 
 ually dissipated in the coldest weather, and sometimes with a degree 
 of velocity which at first sight seems truly surprising.* 
 
 It thus happens that the atmosphere is constantly impregnated with 
 watery vapour, which in this gaseous state accompanies the air where- 
 ever it penetrates, permeates the soil, pervades the leaves and pores of 
 plants, and gains admission to the lungs and general vascular system of 
 animals. We cannot appreciate the influence which, in this highly 
 comminuted form, water exercises over the general economy of organic 
 nature. 
 
 But it is chiefly when it assumes the form of rain and dew, and re- 
 descends to the earth, that the benefits arising from a previous conversion 
 of the water into vapour become distinctly appreciable. The quantity 
 of vapour which the air is capable of holding in suspension is depend- 
 ent upon its temperature. At high temperatures, in warm climates, or 
 in warm weather, it can sustain more — at low temperatures less. 
 Hence when a current of comparatively warm air loaded with moisture 
 ascends to or comes in contact with a cold mountain top, it is cooled 
 down, is rendered incapable of holding the whole of the vapour in sus- 
 pension, and therefore leaves behind in the form of a mist or cloud, a 
 portion of its watery burden. In rills subsequently, or springs, the 
 aqueous particles which float in the midst, re-appear on the plains be- 
 neath, bringing nourishmentf at once, and agreateful relief to the thirsty 
 soil. 
 
 So when two currents of air charged with moisture, but of unequal 
 temperature, meet in the atmosphere, they mix, and the mixture has 
 the mean temperature of the two currents. But air of this mean tem- 
 perature is incapable of holding in suspension the mean quantity of wa- 
 tery vapour ; hence, as before, a cloud is formed, and the excess of 
 moisture falls to the earth in the form of rain. In descending to refresh 
 the earth, this rain discharges in its progress another office. It washes 
 the air as it passes through it, dissolving and carrying those accidental 
 vapours which, though unwholesome to man, are yet fitted to minister 
 to the growth of plants. 
 
 The dew, celebrated through all times and in every tongue for its sweet 
 influence, presents the most beautiful and striking illustration of the agen- 
 cy of water in the economy of nature, and exhibits one of those wise and 
 bountiful adaptations, by which the whole system of things, animate and 
 inanimate, is fitted and bound togetlier. 
 
 All bodies on the surface of the earth radiate, or throw out rays 
 of heat, in straight lines — every warmer body to every colder ; and the 
 entire surface is itself continually sending rays upwards through the 
 clear air into free space. Thus on the earth's surface all bodies strive, 
 as it were, after an equal temperature (an equilibrium of heat), while 
 
 * Mr. Howard states that a circular patch of snow 5 inches in diameter lost in the month 
 of January 150 grains of vapour between sunset and sunrise, and 56 grains more before the 
 close of the day, when exposed to a smart breeze on a house-top. From an acre of snow 
 this would be equal to 1000 gallons of water during the night only. — Prout' s Bridgewater 
 Treatise, p. 302; EncyclupcBd. MetropoL, art. Meteorology. 
 
 In Von Wrangell's account of his visit to Siberia and the Polar sea, translated by Major 
 Sabine (p. 390), it is stated that, in the intense cold, not only living bodies — but the very 
 snow — smokes and fills the air vfith vapour. , 
 
 t For the nature of this nourishment see the subsequent Lectures, " On the inorganic con-i 
 etituents of plants." 
 
42 DESCENT OF DEW. — UNIVERSAL BOUNTY OF NATURE. 
 
 the surface as a whole tends gradually towards a cooler state. But 
 while the sun shines this cooling will not take place, for the earth then 
 receives in general more heat than it gives offi and if the clear sky be 
 shut out by a canopy of clouds, these will arrest and again throw back 
 a portion of the heat, and prevent it from being so speedily dissipated. 
 At night, then, when the sun is absent, the earth will cool the most ; on 
 clear nights also more than when it is cloudy, and when clouds only 
 partially obscure the sky, those parts will become coolest which look to- 
 wards the clearest portions of the heavens. 
 
 Now when the surface cools, the air in contact with if must cool also ; 
 and like the warm currents on the mountain side, must forsake a portion 
 of the watery vapour it has hitheito retained. This water, like the float- 
 ing mist on the hills, descends in particles almost infinitely minute. 
 These particles collect on every leaflet, and suspend themselves from 
 every blade of grass, in drops of " pearly dew." 
 
 And mark here a beautiful adaptation. Different substances are en- 
 dowed with the property of radiating their heat, and of thus becoming 
 cool with different degrees of rapidity, and those substances which in 
 the air become cool first, also attract first and most abundantly the par- 
 ticles of falling dew. Thus in the cool of a summer's evening the grass 
 plot is wet, while the gravel walk is dry ; and the thirsty pasture and ev- 
 ery green leaf are drinking in the descending moisture, while the naked 
 land and the barren highway are still unconscious of its fall. 
 
 How beautiful is the contrivance by which water is thus evaporated or 
 distilled as it were into the atmosphere — largely perhaps from some par- 
 ticular spots, — then diffused equably through the wide and restless air, — 
 and afterwards precipitated again in refreshing showers or in long-mys- 
 rerious dews!* But how much more beautiful the contrivance, I might 
 almost say the instinctive tendency, by which the dew selects the objects 
 on which it delights to fall ; descending first on every living plant, copi- 
 ously ministering to the wants of each, and expending its superfluity 
 only on the unproductive waste. 
 
 And equally kind and bountiful, yet provident, is nature in all her 
 operations, and through all her works. Neither skill nor materials are 
 ever wastect; and yet she ungrudgingly dispenses her favours, apparent- 
 ly without measure, — and has subjected dead matter to laws which 
 compel it 'to minister, and yet with a most ready willingness, to the 
 wants and comforts of every living thing. 
 
 And how unceasingly does she press this her example not only of un- 
 bounded goodness, but of universal charity — above all other men — on 
 the attention of the tiller of the soil. Does the corn spring more 
 freshly when scattered by a Protestant hand — are the harvests more 
 abundant on a Catholic soil, — and does not the sun shine alike, and the 
 dew descend, on the domains of each political party ? 
 
 The beauty of this arrangement, appears more striking when we consider that the whole 
 ofthe watery vapour in (he air, if it felt at once in the form of rain, would not amount to 
 more than 5 inches in depth on the whole surface ofthe globe. In England the fall of rain 
 varies from 22 inches (London, York, and Edinburgh) to 63 (Keswick), while in some fejv parts 
 of the world (St. Domingo) it amounts to as much as 150 inches. The mean fall of rain 
 over the.whole earth is estimated at 32 or 33 inches ; but if we suppose it to be only 10 or 15 
 Inches, the water which thus falls will require to be two or three times re-distilled in the course 
 of every year. This is exclusive of dew, which in many countries amounts to a very 
 large quantity.— See Front's Bridgetcater Treatise, p. 309. 
 
 I 
 
COLD PRODUCED BY EVAPORATION, AND ITS INFLUENCE. 43 
 
 So science, from her daily converse with nature, fails not sooner or 
 later to take her hue and colour from the perception of this universal 
 love and hounty. Party and sectarian differences dwindle away and 
 disappear from the eyes of him who is daily occupied in tiie contempla- 
 tion of the boundless munificence of the great Impartial; he sees him- 
 self standing in one common relation to all his fellow-men, and feels 
 himself to be most completely performing his part in life, when he is 
 able in any way or in any measure to contribute to the general welfare 
 of all. 
 
 It is in this sense too that science, humbly tracing the footsteps of the 
 Deity in all his works, and from them deducing his intelligence and his 
 universal goodness — it is in this sense, that science is of no sect, and of 
 no party, but is equally the province, and the property, and the friend of all. 
 
 § 7. Of the cold produced by the evajyoration of water, and its 
 influeiice on vegetation. 
 
 Beautiful, however, and beneficent as are the provisions by which, in 
 nature, watery vapour is made to serve so many useful purposes, there 
 are circumstances in which, and often through the neglect of man, the 
 presence of water becomes injurious to vegetation. 
 
 The ascent of water, in the form of vapour, permits the soil to dry, 
 and fits it for the labours of the husbandman ; while its descent in dew 
 refreshes the plant, exhausted by the heat and excitement of a long 
 summer's day. But the same tendency to ascend in vapour, gives rise 
 to the cold ^pproductive character of lands in which water is present in 
 great excess. This character you are familiar with in what are called 
 cold clay soils. 
 
 The epithet cold, applied to such soils, though derived probably from 
 no theoretical views, yet expresses very truly their actual condition. 
 The surface of the fields in localities where such lands exist, is in reality 
 less warm, throughout the year, than that of fields of a different quality, 
 even in their immediate neighbourhood. This is readily proved, by 
 placing tlie bulb of a thermometer immediately beneath the soil in two 
 such fields, when in the hottest day a marked diflference of temperature 
 will, in general, be perceptible. The difference is dependent upon the 
 following principle : — 
 
 When an open pan of water is placed upon the fire, it continues to 
 acquire heat till it reaches the temperature of 212° F. It then begins to 
 boil, but ceases to become hotter, ^team, however, passes off, and the 
 
 I water diminishes in quantity. But while the vessel remains upon the 
 fire the water continues to receive heat from the burning fuel as it did 
 before it began to boil. But since, as already stated, it becomes no hot- 
 
 •ter, the heat received from the fire must be carried off' by the steam. 
 
 Now this is universally true. Whenever water is converted into 
 steam, the ascending vapour carries off much heat cdong with it. 
 
 This heat is not missed, or its loss perceived, when the vapour or 
 steam is formed over a fire ; but let water evaporate in the open air 
 
 i from a stone, a leaf, or a field, and it must take heat with it from these 
 objects — and the surface of the stone, the leaf, or the field, must become 
 colder. That stone or leaf also must become coldest from which the 
 
 1 largest quantity of vapour rises. 
 
44 WET AND COLD SOILS IMPROVED BY DRAINING. 
 
 Now, let two adjoining fields be wet or moist in different degrees, that 
 which is wettest will almost at all times give off the largest quantity of 
 vapour, and will therefore be the coldest. Let spring arrive, and the 
 genial sun will gently warm the earth on the surface of the one, while 
 the water in the other will swallow up the heating rays, and cause them 
 te re-ascend in the watery vapour. Let summer come, and while the 
 soil of the one field rises at mid-day to perhaps 100° F. or upwards, that 
 of the other may, in ordinary seasons, rarely reach 80° or 90°— -in wet 
 seasons may not even attain to this temperature, and only in long 
 droughts will derive the full benefit of the solar rays. I shall hereafteri 
 more particularly advert to the important influence which a hightempe-l 
 rature in the soil exercises over the growth of plants, the functions of 
 their several parts, and their power of ripening seeds — as well as to 
 certain beautiful adaptations by which nature, when left to herself, id 
 continually imparting to the soil, especially in northern latitudes, those! 
 qualities which fit it for deriving the greatest possible benefit from thr 
 presence of the sun's rays. In the mean time you are willing to con 
 cede that warmth in the soil is favourable to the success of your agricul 
 tural pursuits. What, then, is the cause of the coldness and poverty, 
 the fickleness and uncertainty of produce, in land of the kind now al- 
 luded to ? It is the presence of too much water. What is the remedy ? 
 A removal of the excess of water. And how ? By effectual drainage. 
 
 There are other benefits to the land, which follow from this removal 
 of the excess of water by draining, of which it would here be out of 
 place to treat ; but a knowledge of the above principle shows you that 
 the first effect upon the soil is the same as if you were t^place it in a 
 warmer climate, and under a milder sky — where it could bring to ma- 
 turity other fruits, and yield more certain crops. 
 
 The application of this merely rudimentary knowledge will enable 
 you to remove from many improvable spots the stigma of being poor and 
 cold; an appellation hitherto applied to them, — not because they are by 
 nature unproductive, but because ignorance, or indolence, or indifference, 
 has hitherto prevented their natural capabilities from being either ap- 
 preciated or made available. 
 
 Note. — In reference to the supposed fertilizing effect of snow, adverted to in the above 
 lecture, I may mention a fact observed by Heyer, and quoted by Liebig, (p. 125), that willow 
 branches immersed in snow water put forth roots tiiree or four times longer than when put 
 into pure distilled water, and that the latter remained clear while the snow water became 
 coloured. This shows that snow contains something not present in distilled water, which 
 is capable of accelerating the growth of plants. The experiment would have been more 
 indtructive in regard to natural operations, had the eflfect of the snow water been com- 
 pared with that of an equal bulk of rain water, collected under similar circumstances. 
 
LECTURE III. 
 
 Carbonic and oxalic acids, their properties and relations to vegetable life— Carbonic oxide 
 and ligiit carburetted hydrogen, tlieir properties and production in nature — Ammonia, its 
 properties and relations to vegetable life. 
 
 § 1. Carbonic acid, its j^roperties and relations to vegetable life. 
 
 When charcoal is burned in the air it combines slowly with oxygen, 
 and is transformed into carbonic acid gas. In oxygen gas it burns more 
 rapidly and vividly, producing the same compouq^. 
 
 This gas is colourless, like oxygen, hydrogen, and nitrogen, but is 
 readily distinguished from all these, by its acid taste and smell, by its solu- 
 bility in water, by its great density, and by its reddening vegetable blues. 
 Water at 60 F. and under the ordinary pressure of the atmosphere, dis- 
 solves rather more than its own bulk of this gas (100 dissolve 106), and, 
 however the pressure may be increased, it still dissolves the same bulk. 
 
 All gases diminish in bulk uniformly as the pressure to which they 
 are subjected is increased. Thus under a pressure of two atmospheres 
 they are reduced to one-half their bulk, of three atmospheres to one- 
 third, and so on. When water, therefore, is saturated with carbonic 
 acid under great pressure, as in the manufacture of soda water, though 
 it still dissolves only its own bulk, yet it retains a weight of the gas 
 which is proportioned to the pressure applied. For the same reason 
 also, when the pressure is removed, as in drawing the cork from a bot- 
 tle of water so impregnated, the gas expands and escapes, causing a 
 lively effervescence, and the water retains only its own bulk at the ex- 
 isting pressure. This solution in water has a slightly sour taste, and 
 reddens vegetable blues. These properties it owes to the presence of 
 the gas, which is therefore what chemists call an acid body, and hence its 
 name of carbonic acid. [Acids have generally a sour taste, redden 
 vegetable blues, or combine with bases, such as lime, soda, potash, &c., 
 to form salts.'] ■ 
 
 This gas is one-half heavier than atmospheric air, its density being 
 1*524, and hence it may be poured through the air from one vessel to 
 another. Hence also, when it is evolved from crevices in the earth, in 
 caves, in wells, or in the soil, this gas diffuses itself through the atmos- 
 phere and ascends into the air, much more slowly than the elementary 
 gases described in the previous lecture. Where it issues from the earth 
 in large quantity, as in many volcanic districts, it flows along the surface 
 like water, enters into and lills up cracks and hollows, and sometimes 
 reaches to a considerable distance from its source, before it is lost among 
 the still air. 
 
 Burning bodies are extinguished in carbonic acid, and living beings, 
 plunged into it, instantly cease to breathe. Mixed with one-ninth of its 
 bulk of this gas the atmospheric air is rendered unfit for respiration. It 
 is, however, the principal food of plants, being absorbed by their leaves 
 and roots in large quantity. Hence the presence of carbonic acid in the 
 atmosphere is necessary to the growth of plants, and they have beenob^ 
 
 3 
 
46 CARBONIC ACID. — EVIDENCE OF UNITY OF DESIGN. 
 
 served to thrive belter when tlie quantity of this gas in the air is con- 
 siderably augmented. Common air, as has been already staled, does 
 not coniain more on an average than 2 7,^00^*'' of its bulk of carbonic acid, 
 but De Saussure found that plants in the sunshine grew better when it 
 was increased to -^th of the bulk of the air, but beyond this quantity 
 they were injured by its presence, even when exposed to the sun. 
 AVhen the carbonic acid amounted to one-half, the plants died in seven 
 days ; when it reached two-thirds of the bulk of the air, they ceased to 
 grow altogether. In the shade any increase of carbonic acid beyond 
 that which naturally exists in the atmosphere of our globe, was found 
 to be injurious. 
 
 These circumstances it is of importance to remember. Did the sun 
 always shine on every part of the earth's surface, the quantity of carbo- 
 Die acid in the atmosphere might probably have been increased with ad- 
 Tantage to vegetation. But every such increase would have rendered 
 the air less tit for the Respiration of existing races of animals. Thus 
 we see that not only the nature of living beings, both plants and ani- 
 mals, but also the periodical absence of the sun's rays, have been taken 
 into account in the present arrangement of things. 
 
 In perpetual sunshine plants would flourish more luxuriantly in air 
 containing more carbonic acid, but they would droop and die in the 
 shade. This is one of those \)CooCs of unity of design which occasion- 
 ally force themselves upon our attention in every department of nature, 
 and compel us to recognise the regulating superintendence of one mind. 
 The same hand which mingled the ingredients of the atmosphere, also 
 set the sun to rule the day only, — tempering the amount of carbonic 
 acid to the time of his periodical i)resence, as well as to the nature of 
 animal and vegetable life. 
 
 Carbonic acid consists of one equivalent of carbon and two of oxygen, 
 and is represented by COo. It unites with bases (potash, soda, lime, 
 &c.), and forms compounds known by the name of carbonate. Thus 
 fearlash is an vra^nxe carhonates of i^otash, — the common soda of the 
 shops, corhonate of soda, — and limestone or chalk, carbonates of lime. 
 From thesej^om pounds it may be readily disengaged by pouring upon 
 them diluted muriatic or sulphuric acids. From limestone it is also 
 readily expelled by heat, as in the common lime-kilns. During this 
 process the limestone loses nearly 44 per cent, of its weight, [43-7 when 
 pure and dry,] a loss which represents the quantity of carbonic acid dri- 
 ven off. [Hence by burning limestone on the spot where it is quarried, 
 nearly one-half of the cost of transport is saved,] 
 
 Common carbonate of lime, in its various forms of chalk, hard lime 
 stone, or marble, is nearly insoluble in water, but it dissolves readily in 
 water containing carbonic acid. Thus, if a current of this gas be pass- 
 ed through lime-water, the liquid speedily becomes milky from the 
 formation and precipitation of carbonate of lime, but after a short time 
 the cloudiness disappears, and the whole of the lime is re-dissolved. 
 The application of heat to this clear solution expels the excess of car- 
 bonic acid, and causes the carbonate of lime again to fall. 
 
 By exposure to the air, we have already seen that water always ab- 
 sorbs a quantity of carbonic acid from the atmosphere. As it after- 
 wards trickles through the rocks or through soil containing lime, it grad- 
 
CARBONIC ACID RENDERS LIME SOLUBLE. 47 
 
 ually dissolves a portion of this earth, equivalent to the quantity of gas 
 it holds in solution, and thus reaches the surface impregnated with cal- 
 careous matter. Or it carries it in its progress helow the surface to the 
 roots of plants, where its earthy contents are made available, either di- 
 rectly or indirectly, to the promotion of vegetable growth. To the lime 
 thus held in solution, spring and other waters generally owe their hard- 
 ness, and ii is the expulsion of the carbonic acid, by lieat, that causes 
 the deposition of the sediment so often observed when such waters are 
 boiled. 
 
 I propose hereafter to devote an entire lecture to the consideration of 
 the action of lime upon land, as it is employed for agricultural pur- 
 poses, but 1 may here remark, that this solvent action of the carbonic 
 acid in rain water is one of the ])rincipal agents in removing the lime 
 from your soils, and in rendering 'a fresh application necessary after a 
 certain lapse of time. It is the cause also of that deposit of calcareous 
 matter at the mouths of drains which you not unfrequently see in lo- 
 calities where lime is laid abundantly upon the land. The greater the 
 quantity of rain, therefore, which falls in a district, the less permanent 
 will be the effects of liming the land — the sooner will it be robbed of 
 this important element of a fertile soil. Still carbonic acid is only one 
 of several agents which act almost unceasingly in thus removing the 
 lime from the land, a fact I shall hereafter have occasion more fully to 
 explain. 
 
 In nature, carbonic acid is produced under a great variety of circum- 
 stances. It is given oif from the lungs of all animals during respira- 
 tion. It is formed during the progress of fermentation. Fermented li- 
 quors owe their sparkling qualities to the presence of this gas. Dur- 
 ing the decay of animal and vegetable substances in the air, in com- 
 post heaps, or in the soil, it is evolved in great abundnnce. In certain 
 volcanic countries it issues in large quantity from springs and from 
 cracks and fissures in the surface of the earth ; while the vast amount 
 of carbon contained in the wood and coal daily consumed by burning, 
 is carried up into the atmosphere, chiefly in the form of carbonic acid. 
 We shall hereafter consider the relation which exists between these 
 several sources of supply and the proportion of carbonic acid per- 
 manently present in the air and so necessary to the support of vegetable 
 life. 
 
 § 2. Oxalic acid, its properties and relations to vegetable life. 
 
 Oxalic acid is another compound of carbon and oxygen, which, though 
 not known to minister either to their growth or nourishment, is yet found 
 largely in the interior of many varieties of plants. In an unconibined 
 state it exists in the hairs of the chick pea. In combination with potash 
 it is found in the wood sorrel (oxalis acetosella), in the common sorrel, 
 and other varieties o^ rumex, — in which it is the cause of the acidity of 
 the leaves and stems, — in the roots of these plants also, in the leaves and 
 roots of rhubarb, and in the roots of tormentilla, bistort, gentian, saponaria, 
 and many others. It is this combination with potash, formerly extracted 
 from wood sorrel, which is known in commerce by the name o^ salt of 
 sorrel. In combination with lime it forms the principal solid parts of 
 
48 PnOPERTIES OF OXALIC ACID. 
 
 many lichens, especially of the^arme^i*^ and variolari<^,'* some of which 
 contain as much oxalate of lime as is equivalent to 15 or 20 parts of pure 
 acid in 100 of the dried plant. 
 
 The crystallized oxalic acid of the shops forms transparent colourless 
 crystals, of an intensely sour taste. These crystals dissolve readily in " 
 twice their weight of cold water, and the solution, when sufficiently di- 
 lute, is agreeably acid to the taste. This acid is exceedingly poisonous. 
 Half an ounce of the crystals is sufficient to destroy life in a very short 
 time, and a quarter of an ounce after the lapse of a few days. It con- 
 sists solely of carbon and oxygen in the proportion of two equivalents 
 of the former to three of the latter. Its symbol is C0O3. It combines 
 with bases, and forms salts which are known by the name of oxalates^ 
 and it is characterised by the readiness with which it combines whh lime ' 
 to form oxalate oflifne. If a solution of the acid be poured into lime wa- 
 ter, the mixture immediately becomes milky from the formation of this , 
 compound, which is insoluble in water.f It is this oxalate of li/ne which 
 exists in the lichens, while oxalate of potash exists in the sorrels. 
 
 Oxalic acid is one of those compounds of organic origin which we can- 
 not form, as we can form carbonic acid by the direct union ofits elements. 
 In all our processes for preparing it artificially, we are obliged tohave re- 
 course to a substance previously organized in the living plant. It may 
 be prepared from sugar, starch, or even from wood, by various chemical 
 processes. The usual method is to digest potato starch with five times its 
 weight of strong nitric acid (aquafortis), diluted with ten of water, till red 
 fumes cease to be given offj and then to evaporate the solution. The ox- 
 alic acid separates in crystals, or, as it is usually expressed, crystallizes in 
 tlie solution thus concentrated by evaporation. 
 
 It is not known to exist in the soil or in the waters which reach the 
 roots of plants. Where it is found in living vegetables, therefore, it must, 
 like the other substances they contain, have been formed or elaborated 
 in the interior of the plant itself. By what very simple changes the 
 production of this acid is or may be effected, we shall see in a subse- 
 quent lecture. 
 
 ^3. Carbonic oxide, its constitution and properties. 
 
 When carbonic acid {CO2) is made to pass through a tube containing 
 
 red-hot charcoal, it undergoes a remarkable change. Its gaseous form 
 
 remains unaltered, but it combines with a second equivalent of carbon 
 
 (becoming C0O2), which it carries off in the aeriform state. The new 
 
 ' The parmdia cruciata a.m\ variolaria communis are mentioned as peculiarly rich in this 
 acid, which used to be extracted from thorn for sale. A species of parmelia, collected after 
 the droufjlils on the sands of Persia and Georgia, contains 66 per cent, of oxalate of lime, 
 with ahout23 per cent, of a gelatinous substance similar to that obtained from Iceland moss. 
 This lichen is u.sed for food by the Kiryhuis. A similar lichen is collected about Bagdad for 
 a similar purpose. 
 
 t Substances that arc insoluble are generally without action on the animal economy, and 
 may be introduced into tiie sto'iiach without producins any injurious effect. Hence tliis ox- 
 alate of liine, thougli it contains oxalic acid, is not poisonous. Hence also, if oxalic acid be 
 present in the stomach, its poisonous action may be taken away by causing lime water or 
 milk of lime to be swallowed in sufficient quantity. The acid combines with the lime, as in 
 the experiment described in the text, and forms insoluble oxalate of lime. The common 
 may;nesia of the shops will serve the same pm-posc, forming an iiisohible oxaJale of magnesia. 
 It is by performing experiments under circumstances where the resuks are visible— as in 
 glass vessels — that we are enabled to predict the results in circumstances where the phe- 
 nomena are not visible, and to act with as much confidence as if we could really see them. 
 
LIGHT CARBURETTED HYDROGEN. 49^ 
 
 gas thus producea is known by the name of carbonic oxide. It consists 
 of one equivalent of carbon united to one of oxygen, and is represented 
 by Co O2, or simply CO. 
 
 This gas is colourless, without taste or smell, lighter than common air, 
 nearly insoluble in water, extinguishes flame, does not support life; 
 burns in the air or in oxygen gas with a blue flame, and during this 
 combustion is converted into carbonic acid. It is produced along with 
 carbonic acid during the imperfect combustion of coals in our fires and 
 furnaces, but is not knov/n to occur in nature, or to minister directly to 
 the growth of ])lants. 
 
 There exists a general relation among the three compounds of carbon 
 and oxygen above described, to which it may be interesting to advert, 
 in connection with the subject of vegetable physiology. This relation 
 appears when we compare together their chemical constitution, as re- 
 presented by their chemical formulas : — 
 
 Carbmiic acid consists of one of carbon and two of oxygen; or CO2 ; 
 
 Carbonic oxide, of one of carbon and one of oxygen, or CO ; 
 
 So that if carbonic acid be present in a plant, and be there deprived 
 of one equivalent of its oxygen, by any vital action, it will be converted 
 into carbonic oxide. 
 
 Oxalic acid consists of two of carbon and three of oxygen, or C2O3. 
 
 If we add together the formulae for 
 
 Carbonic acid = COo and 
 Carbonic oxide = CO, we have 
 
 Oxalic acid = CoOg. 
 
 Hence this acid may be formed in the interior of plants, either by the 
 direct union of carbonic oxide and carbonic acid, or by depriving two of 
 carbonic acid (2CO2 or C0O4) of one equivalent of oxygen. 
 
 When in a subsequent lecture we have studied the structure and func- 
 tions of the leaves of plants, we shall see how very easy it is to under- 
 stand the process by which oxalic acid is formed and deposited in the in- 
 terior of plants, and by which carbonic oxide also may he, and probably 
 is, produced. 
 
 § 4. Light carhuretted hydrogen — the gas of marshes and of coal mines. 
 
 During the decay of vegetable matter in moist places, or under water, 
 a light inflammable gas is not unfrequently given o&, which differs in its 
 properties from any of those hitherto described. In summer it may often 
 be seen rising up in bubbles from the bottom of stagnant pools and 
 from marshy places, and may readily be collected. 
 
 This gas is colourless, without taste or smell, and is little more than 
 half the weight of common air, [its specific gravity, by experiment, is 
 0-5576.] A lighted taper, plunged into it, is immediately extinguished, 
 while the gas takes fire and burns with a pale yellow flame, yielding 
 more light, however, than pure hydrogen gas, which it otherwise re- 
 sembles. Animals introduced into it, instantly cease to breathe. 
 
 It consists of one equivalent of carbon (C) united to two of hydrogen 
 (2H or H2), and is represented by CHg. When burned in the air or 
 
50 PROPERTIES OF AMMONIA. 
 
 in oxygen gas, the carbon it contains is converted into carbonic acid 
 (COo), and the h^'^drogen into water (HO). 
 
 Like oxalic acid this gas cannot, by any known process, be produced 
 from the direct union of the carbon and hydrogen of which it consists. 
 It is readily obtained, however, by heating acetate of potash in a retort, 
 with an equivalent proportion of caustic baryta. [AceLate of potash is 
 ))repared by pouring vinegar (acetic acid) on common pearlash and 
 evaporating the solution.] 
 
 In nature it is largely evolved in coal mines, and is the principal com- 
 bustible ingredient in those explosive atmospheres which so frequently 
 cause disastrous accidents in mining districts. 
 
 This gas is also given off along with carbonic acid during the fermen- 
 tation of compost heaps, or of other large collections of vegetable mat- 
 ter. It is said also to be generally present in well manured soils, 
 [Persoz, Chimie Moleculaire, p. 547,] and is supposed by many to con- 
 tribute in such cases to the nourishment of plants. It is, however, very 
 sparingly soluble in water, so that in a state of solution, it cannot enter 
 largely into the pores of the roots, even though it be abundantly present 
 in the soil. Haw far it can v/iih propriety be regarded as a general 
 source of food to plants, will be considered in the following lecture. 
 
 § 5. Ammonia^ its jnoperties and relations to vegetable life. 
 
 Ammonia is a compound of hydrogen and nitrogen. It is possessed 
 of many interesting properties, and is supposed to perform a very im- 
 portant part in the process of vegetation. It will be' proper, therefore, 
 to illustrate its nature and properties with considerable attention. 
 
 Ammonia, like the nitrogen and hydrogen of which it is composed, is 
 a colourless gas, but, unlike its elements, is easily distinguished from 
 all other gaseous substances by its smell and taste. 
 
 It possesses a powerful penetrating odour (familiar to you in the smell 
 of hartshorn and of common smelling salts), has a burning acrid alka- 
 line* taste, extinguishes a lighted taper as hydrogen and nitrogen do, but 
 does not itself take fire like the former. It instantly suffocates animals, 
 kills living vegetables, and gradually destroys the texture of tlieir parts. 
 
 It is absorbed in large quantities by porous substances, such as char- 
 coal — which, as already stated, absorbs 95 times its own bulk of am- 
 iiioniacai gas. Porous vegetable substances in a decaying state likewise 
 absorb it. Porous soils also, burned bricks, burned cla3s and even com- 
 mon clay and iron ochre, which are mixed together on the surface of 
 most of our fertile lands — all these are capable of absorbing or drinking 
 in, and retaining within their pores, this gaseous substance, when it hap- 
 pens to be brought into contact with them. 
 
 But the (]uantity absorbed by water is much greater and more sur- 
 prising. If the mouth of a bottle filled with this gas be immersed in 
 water, the latter will rush uj) and fill the bottle almost instantaneously; 
 and if a sufficient supply of ammonia be present, a given quantity of 
 water will take up as much as G70 times its bulk of the gas. 
 
 This solution of ammonia in water is the spirit of hartshorn of the 
 5hops. When saturated [that is, when gas is supplied till the water re- 
 
 • The term alkaline, as applied to taste, will be best unrierstood by describing it as a taste 
 imilar to that of the common soda and pearlash of the shops. 
 
ITS COMBINATION WITH ACIDS. 61 
 
 fuses to take up any- more,] it is lighter than pure water, [its specific 
 gravity is 0-875, water being I,] has the pungent penetrating odour of the 
 gas, and its hot, burning, alkahne taste — is capable of blistering the 
 skin, and decomposing or destroying the texture of animal and vegeta- 
 ble substances. 
 
 You will remark here the effect which combination has in investing 
 substances with new characters. The two gases hydrogen and nitrogen, 
 themselves without taste or smell, and absorbed by water in minute 
 quantity only, form by their union a compound body remarkable both 
 for taste and sniell, and for the rapidity with which water absorbs it. 
 
 Ammonia possesses also alkaline properties,* it restores the blue 
 colour of vegetable substances that have been reddened by an acid, and 
 it combines with acid substances to form salts. 
 
 Among gaseous substances, therefore, there are some which, like car- 
 bonic acid, have a sour taste and redden vegetable blues ; others which, 
 like ammonia, have an alkaline taste and restore the blue colour; and 
 a third class which, like oxygen, hydrogen, and nitrogen, are destitute of 
 taste and do not affect vegetable colours. These last are called neu- 
 tral or indifferent substances. 
 
 AjTimonia, as above stated, combines with acids and forms salts, 
 which at the ordinary temperature of the atmosphere are all solid sub- 
 stances. Hence if carbonic acid gas be mixed with ammoniacal gas, 
 a white cloud is formed consisting of minute particles of solid carbonate 
 of ammonia — the smelling salts of the shops. Hence also a feather 
 dipped into vinegar or dilute muriatic acid (spirit of salt), and then in- 
 troduced into ammoniaccil gas, forms a similar white cloud, and be- 
 comes covered with a white down of solid acetate or of muriate of ammonia 
 (sal ammoniac). The same appearance is readily seen by holding the 
 feather to the mouth of a bottle containing hartshorn (liquid ammonia), 
 from which ammoniacal gas continually escapes, and by its lightness rises 
 into the air, and thus comes in contact with the acid upon the feathers. 
 
 The fact of the production of a solid body by the union of two gases 
 (ammonia and carbonic or muriatic acid gases) is one of a very inter- 
 esting nature to the young chemist, and presents a further illustration 
 of the changes resulting from chemical combination as explained in 
 the previous lecture. 
 
 Ammonia is little more than half the weight of common air, [more 
 nearly three-fifths, its specific gravity being 0'59, that of air being 1,] 
 hence when liberated on the earth's surface it readily rises into and 
 mingles with the atmosphere. It consists of hydrogen and nitrogen 
 united together in the proportion of three equivalents of hydrogen (3H 
 or Ho) and one of nitrogen (N), [see Lecture H,] and hejice. it is re- 
 presented by the symbol (N + 3H), or more shortly by NH3. 100 
 parts by weight contain 82i of nitrogen and 17i of hydrogen, [correct- 
 ly 82-545 and 17-455 respectively.] 
 
 In nature, ammonia exists in considerable quantity It is widely, 
 
 * In the previous lecture, the term acid was explained as applying to substances possess- 
 ed of a sour taste, and capable of reddening vegetable blues or combining with basts (pot- 
 ash, soda, magnesia, «fec.) to form salts ; alkalies are such as possess an alkaline taste (see 
 previous Note), restore the blue colour to reddened vegetable substances, or combine with 
 acids to form salts. Of salts, nitrate of soda, saltnetrc (nitrate of potash), and glauber salts 
 (sulphate of soda), are examples. 
 
I 
 
 52 ITS EXISTENCE -IN NATURE, AND SPECIAL PROPERTIES. 
 
 almost universally, ditrused, but is not known to form large deposits on 
 any part of the earth's surface, or to enter as a constituent into any 
 of the great mineral masses of which the crust of the globe is com- 
 posed. It exists most abundantly in a state of comhination — in the 
 forms, for example, of muriate (sal ammoniac), of nitrate, and of carbon- 
 ate of ammonia. It frequently escapes into the atmosphere in an un- 
 combined state, especially where animal matters are undergoing decay, 
 but it rarely exists in this free state for any length of time. It speedily 
 unites with the carbonic acid of the air, with one or other of the numer- 
 ous acid vapours which are continually rising from the earth, or with 
 the nitric acid which is formed at the expense of the nitrogen and oxy- 
 gen of which the atmosphere consists. 
 
 The influence of ammonia on vegetation appears to be of a very 
 powerful kind. It seems not only to promote the rapidity and luxu- 
 riance of vegetation, but to exercise a powerful control over the func- 
 tions of vegetable life. In reference to the nature and extent of this 
 action, int) which we shall hereafter have occasiou to inquire, ther 
 are several special properties of ammonia which it will be of irapor-] 
 tance for us previously to understand. 
 
 1°. It has a powerful affinity* for acid substances. Hence the 
 readiness with which it unites with acid vapours when it rises into the 
 atmosphere. Hence also when formed or liberated in the soil, in the 
 fold-yard, in the stable, or in compost heaps, it unites with such acid 
 substances as may be presejit in the soil, &c. and forms saline com- 
 pounds or salts. All these salts appear to be more or less influential in 
 the processes of vegetable life. 
 
 2*^. Yet this affinity is much less strong than that which is exhibited 
 for the same acids by })otash, soda, lime, or magnesia. Hence if any 
 of these substances be mixed or brought into contact with a salt of am- 
 monia, the acid of the latter is taken up by the potash or lime, while 
 the ammonia is separated in a gaseous state. Thus when sal ammo- 
 niac in powder is mixed with twice its weight of quick-lime, ammoni- 
 acal gas is liberated in large quantity. This is the method by which 
 pure ammonia is generally prepared ; and one of the many functions 
 performedjyy lime when employed for the improvement of land, espe- 
 cially on soils rich in animal anil vegetable matter, is that of decompo- 
 sing the salts, especially the organic salts, of ammonia, — as will be 
 more fully explained when we come to treat at length of this important 
 part of agricultural practice. f 
 
 3°. The salts which ammonia forms with the acids are all, like am- 
 monia itself, very soluble in water. Hence two consequences follow. 
 First, that whicli rises into the air in the form of gas, and there com- 
 bines with the carbonic or other acids, is readily dissolved, washed out 
 
 • By affinity \s meant the tendency which bodies have lo unite and to remainunited or 
 combined. Tims ammonia forms a solid substance with the vapour of vine<^ar the mtiment 
 the two substances come into contact; they have, therefore, a strons tendency to unite, or 
 an ajfimty for each otlier. • 
 
 t See Lecture XVI. "On the ttse nflime." Owing to this property the action of lime upon 
 compost heaps is ofte^ri injurious, by causing the evolution of the ammonia produced durin.' 
 the decomposition of the animal matters they contain. Tliis escape of ammonia, even 
 when imperceptible by tlie sense of smell, is easily detected by holding over the hpap a fea- 
 ther dipped in vinegar or in spirit of salt (muriatic acid), when white fumes are immediate- 
 ly perceived if ammonia be present. 
 
DECOMPOSES GYPSUM. 53 
 
 and brought to the earth again by the rains and dews ; so that at the 
 same time the air is purified for the use of animals, and the ammo- 
 nia brought down for the use of plants. And second, whatever salts of 
 ammonia are contained in the soil, being dissolved by the rain, are in 
 a condition to be taken up, when wholesome, by the roots of plants; or 
 to be carried off by the drains when injurious to vegetation. 
 
 4°. I have already alluded to the fact of this gas being absorbed by 
 porous substances, and to its presence, in consequence, in porous soils, 
 and in burned bricks and clay. With the purer kinds of unburned 
 clay, however, and with the oxide of iron contained in red (or ferrugi- 
 nous)* soils, ammonia is supposed to form a chemical compound of a 
 weak nature. In consequence of its affinity or feeble tendency to com- 
 bine with these substances, they attract it from the air, and from decay- 
 ing animal or vegetable matters, and retain it more strongly than many 
 porous substances can, — yet with a sufficiently feeble hold to yield it 
 up, readily as is supposed, to the roots of [)lants, when their extremities 
 are pushed forth in search of food. In this case the carbonic, acetic, 
 and other acids given off, or supposed to be given off by the roots, exer- 
 cise an influence to which more particular allusion will be made here- 
 after. 
 
 6°. In tlie state of carbonate it decomposes gypsum, forming carbon- 
 ate of lime (clialk) and sulphate (jf ammonia. f The action of gypsum 
 on grass lands, so undoubtedly beneficial in many parts of the world, 
 has been ascribed to this single proi)erty ; it being supposed that the 
 sulphate of ammonia formed, is peculiarly favourable to vegetation. 
 This question will come properly under review hereafter. I may here, 
 however, remark that if this be the sole reason for the efficiency of gyp- 
 sum, its a])plication ought to be beneficial on all lands not already 
 abounding either in gypsum or in sulphate of ammonia. J But if the 
 
 * Soila reddened by the presence of oxide of iron. 
 
 t Gypsum is sulphate of lime — consisting of sulphuric acid (oil of vitriol) and quicklime. 
 Carbonate of ammonia consists of carbonic acid and ammonia. When the two substances 
 act upon each other in a moist state — the two acids change places — the sulphuric acid, as it 
 were, pi-efei'rhig the ammonia, the rarbonic acid the lime. 
 
 t Liebig says — "tlie striking fertility of a mcafiow on which gypsnm is strewed depends 
 only on its fi.'cing in the soil the ammonia of the atmosphere, which would otherwise be vola- 
 tilized with the water which evaporates." — Organic Chemistry applied to Agriculture, p. 86. 
 {Ry fixing is meant the forminir o( sulphate with the ammonia. Rain water is supposed to 
 bring down with it carbonate of ammonia (common smelling salts), which acts upon the sul- 
 phate ofi li7ne (iiypsum) in such a way that sulphate of ammonia And carbonate ofi lime are 
 produced. The carbonate of ammonia readily volatilizes or rises again into the air, the sul- 
 phate does not — hence the use of the wonifix.] 
 
 When we come to consider the subject of mineral manures in general, we shall study 
 more in detail the specific action of gypsum in promoting vegetation — a very simple calcula- 
 tion, however, will serve to shew that the above theory of Liebig is far from affording a satis- 
 factory explanation of all the phenomena. 
 
 Supposing the gypsum to meet with a sufiicient supply of ammonia in the soil, and that it 
 exercises its full influence, 100 lbs. of common tinbur 7i ed gypsun\ will fix or form sulphate 
 with nearly 20 lbs. of ammonia containing 16^ lbs. of nitrogen. One hundred weight, there- 
 fore, (112 lbs.) will form as much sulphate as will contain 22i lbs. of ammonia, and if intro- 
 duced without loss into the interior of plants will furnish them with 18| lbs. of nitrogen. 
 
 1°. In the first volume of British Husbandry, pp. 322, 323, the following experiment is 
 recorded : 
 
 Mr. Smith, of Tunstal, nearSittingbourne, top-dressed one portion of a field of red clover 
 with powdered gypsum at the rate of five bushels (or four hundred weight*) per acre, and 
 compared the produce with another portion of the same field, to which no manure had- been 
 
 [* A ton of pure gypsum, when crushed, will yield 25 bushels. It should, however, al- 
 ways be applied by weight.] 
 
 3* 
 
54 MODE IN WHICH GYPSUM ACTS. 
 
 results of experimental farming in this country are to be trusted, this is 
 by no means the case. The action neither of this, nor probably of any 
 other inorganic substance applied to the soil, is to be explained by a 
 reference in every case to one and the same property only. 
 
 7°. The presence or evolution of ammonia in a soil containing animal 
 and vegetable matter in a decaying state, induces or disposes this mat- 
 ter to attract oxygen from the air more rapidly and abundantly. The 
 result of this is, that organic acid compounds are formed, which combine 
 
 applied. The first crop was cut for hay, and the second ripened for seed. The following 
 were the comparative results per acre : 
 
 HAY CROP. SEED. STRAW. 
 
 cwt. grs. lbs. cwt. qrs. lbs. 
 
 Gypsumed 60 ■ 3 21 22 3 12 
 
 Unmanured .....20 020 500 
 
 Excess of produce . . 40 3 1 17 3 12 
 
 The excess of produce in all the three crops upon the gypsumed land is very large : let ug 
 calculate how much nitrogen this excess would contain. In a previous lecture (II. p. 30) it 
 was stated as the result of Boussingauit's analyses, that dry clover seed contained 7 per 
 cent, of nitrogen, and the same experimenter found in the hay of red clover li per cent (or 
 70 and 15 lbs. respectively in 1000.) 
 
 The seed as it was weighed by Mr. Smith would still contain one-ninth of its weight of 
 water, and, consequently, only 6>Jrd per cent, of nitrogen, [see Lecture II. p. 30.] Let it 
 be taken at 6 per cent, and let the straw be supposed to contain only 1 |)er cent, of nitro- 
 gen, the quantity of this element being found to diminish in the grasses after the seed has 
 ripened, and averaging 1 per cent, in the straw of wheat, oats, and barley, the weight of ni- 
 trogen reaped iti the whole crop will then be as follows : 
 
 1. 40 cwt. of hay (44,S0 lbs.) at lA per cent, of nitrogen, contain 67 lbs. 
 
 2. 85 lbs. of seed at 6 per cent, contain 5'lbs. 
 
 3. 17 cwt. 3 qrs. 12 lbs. or 2000 lbs. of straw at 1 per cent, contain 20 lbs! 
 
 Total nitrogen in the excess of crop, 92 lbs. 
 
 But, as above shewn, the five bushels or four cwt. of gypsum could fix only 90 lbs. of am- 
 monia containing 74 lbs. of nitrogen, leaving, therefore, 18 lbs. or one-fifth of 'the whole, to be 
 derived from some other source. 
 
 Now this result supposes that none of the gypsum or sulphate of ammonia was carried 
 away by the rains, but that the whole remained in the soil, and produced its greatest possible 
 effect on the clover — a72d all hi one season. 
 
 But the effect of Ihe gyp.sum does not disappear with the crop to which it is actually ap- 
 plied. Its beneficial action is extended to the succeeding crop of wheat, and on grass lands 
 the amelioration is visible for a succession of years. If, then, the increased produce of a 
 single year may contain more nitrogen than the gypsum can be supposed to yield this sub- 
 stance must exercise some other influence over vegetation than is involved in its supposed 
 action on the indefinite (luantity of ammonia in the atmosphere. 
 
 2°. Again,~1VIr. Barnard, of Little Bordean, Hants, applied 2i cwt. per acre on two-year 
 old sainfoin, on a clayey soil. The increased produce of the'first cutting was a Ion per 
 acre, and in October fully a ton, the undressed part yielding scarcely any hay at all while 
 the dressed part gave U tons. The second year no gypsum was applied, and the diflference 
 IS said to have been at least as great. 
 
 Supposing the increascl produce in all to have been 4 tons of hay, and thenitro<^en it con- 
 tained to have been only one per cent.— the 4 tons (8960 lbs.) would contain about^go lbs of 
 nitrogen. But 2| cwt. would fix only 46 lbs. of nitrogen in the form of ammonia ; and there- 
 ,,^J '^n">Posing it to have produced its maximum eflfect, there remain 44 lbs. or nearly one 
 halj of the whole, unaccounted for by the theonj. 
 
 I would not be understood to place absolute reliance on the results of the above experi- 
 ments ; but the way in which such results may be easily applied for the purpose of te^tino- 
 theoretical views, will I hope, convince the intelligent practical agriculturist how important 
 It IS that the results of some of the experiments he is every year making should be accu- 
 rately determined by trejght and measure. By this means data would gradually be accu- 
 mulated, on which we might hope to found more unexceptionable explanations of the phe- 
 nomena of vegetation, than the results obtained in our laboratories have hitherto enabled 
 us to advance. cuau.cvi 
 
 In a subsequent note it will be shewn that the mode in which the nitrates of soda and 
 potash act-in other words, the theory of their action upon vegetation-may be tested by a 
 ^mi ar simp e calciilation, and the importance of precise experiments made on the farm 
 will then still further appear. It is in the hope of^inducing some of my readers to make 
 comparative trials and publish accurate results, that I have introduced into the Appendix 
 (No. I.) an ouUme of the mode m which such experiments may most usefully be performed. 
 
INFLUENCE OF AMMONIA OVER PLANTS. 55 
 
 with the ammonia, and form ammoniacal salts.* On the decomposi- 
 tion of these salts by lime or otherwise — the organic acids which are se- 
 parated from them, are always more advanced towards that state in 
 which they again become fit to act as food for plants. 
 
 8°. But the most interesting, and perhaps the most important proper- 
 ty of ammonia, is one which I have already had occasion to bring under 
 your notice, as possessed by water also, and as peculiarly fitting that 
 fluid for the varied functions it performs in reference to vegetable life. 
 This property is the ease with which it undergoes decomposition, either 
 in the air, in the soil, or in the interior of plants. 
 
 In the air it is diffused through, and intimately mixed with, a large 
 excess of oxygen gas. In the soil, especially near the surface, it is also 
 continually in contact with oxygen. By the influence of electricity in 
 the air, and of lime and other bases in the soil, it undergoes a constant 
 though gradual decomposition (oxidation), hs hydrogen being chiefly 
 converted into water, and a portion of its nitrogen into nitric acid.f 
 
 In the interior of plants this and other numerous and varied decom- 
 positions in all probability take- place. 
 
 The important influence which ammonia appears to exercise over the 
 irrowih of plants — the evidence for which I shall presently lay before 
 you— is only to be explained on the supposition that numerous transfor- 
 inations of organic substances are efTected in the interior of living vege- 
 tables — which transformations all imply the separation from each other, 
 or the re-arrangement of the elements of which ammonia consists. In 
 the interior of the plant we have seen that water, .ever present in great 
 abundance, is also ever ready to yield its hydrogen or its oxygen as oc- 
 casion may require, while these same elements are never unwilling to 
 unite again for the formation of water. So it is, to a certain degree, 
 with ammonia. The hydrogen it contains in so large a quantity is ready 
 to separate itself from the nitrogen in the interior of the plant, and, in con- 
 cert with the other organic elements introduced by the roots or the leaves, 
 to aid in producing the different solid bodies of which the several parts 
 of plants are made up. The nitrogen also becomes fixed in the coloured 
 petals of the flowers, in the seeds, and in other parts, of which it appears 
 to constitute a necessary ingredient — passes ofi'm the form of new com- 
 pounds, in the insensible perspiration or odoriferous exhalations of the 
 
 plant, or returning with the downward circulation, is thrown off by the 
 
 root into the soil from which it was originally derived. Much obscurity 
 still rests on the actual transformations which take place in the interior 
 of plants, yet we shall be able in a future lecture, I hope, to arrive at a 
 tolerably clear understanding of the general nature of many of them. _ 
 
 Such are the more important of those properties of ammonia, to which 
 we shall hereafter have occasion to advert. The sources, remote as 
 well as immediate, from which plants derive this, and other compounds 
 we have described as contributing to the nourishment and growth of 
 plants, will be detailed in a subsequent section. 
 
 • Organic adds generally contain more oxygen in proportion to their carbon and hydro- 
 gen, than those which are alkaline or neutral. 
 
 t It will he remembered that ammonia is represented by NH3, water by HO, and nitric 
 acid by NO5. It is easy to see, therefore, how, by means of oxygen, ammonia should be 
 converted into water and nitric acid. 
 
66 PROPERTIES OF NITRIC ACID. 
 
 § 6. Nitric acid, its constittition and properties. 
 
 When the nitre or saltpetre of commerce is introduced into a retort, 
 covered with strong sulphuric acid (oil of vitriol*) and heated over a lamp 
 or a charcoal fire, red fumes are given off, and a transparent, often 
 brownish or reddish li(]uid, distils over, which may be collected in a bot- 
 tle or other receiver of glass. This liquid is exceedingly acid and cor- 
 rosive. In small quantity it stains the skin and imparts a yellow colour 
 to animal and vegetable substances. In larger quantity it corrodes the 
 skin, producing a painful sore, rapidly destroys animal and vegetable 
 life, and speedily decomposes and oxidizesf all organic substances. 
 Being obtained from nitre, this liquid is called nitric acid. It consists of 
 nitrogen combined with oxygen, one equivalent of the former (N) being 
 united to 5 of the latter (O5), and is represented by NO5. 
 
 This acid contains much oxygen, as its formula indicates, and its ac- 
 tion on nearly all organic substances depends upon the ease with which 
 it is decomposed, and maybe made to part with a portion of this oxygen. 
 
 In nature, it never occurs in a free state ; but it is found in many in- 
 tertropical (hot) countries in coihbination with potash, soda, and lime — in 
 the state of nitrotes. It is an important character of these nitrates that, Uke 
 the salts of ammonia, they are all very soluble in water. Those of so- 
 da, lime, and magnesia attract moisture from the air, and in a damp at- 
 mosphere gradually assume the liquid form. 
 
 Saltpetre is a compound of nitric acid with potash (nitrate of potash). 
 It is met with in the surface soil of many districts in Upper India, and 
 is separated by washing the soil and subsequently evaporating (or boil- 
 ing down) the clear liquid thus obtained. When pure, it does not be- 
 come moist on exposure to the air. It is chiefly used in the manufac- 
 ture of gunpowder, but has also been recommended and frequently and, 
 successfully tried by the practical husbandman, as an influential agent 
 in promoting vegetation. 
 
 In combination with soda, it is found in deposits of considerable thick- 
 ness inthe district of Arica in Northern Peru, from whence it is im- 
 ported into this country, chiefly for the manufacture of nitric and sulphu- 
 ric acids. -More recently its lower price has caused it to be extensively 
 employed in husbandry, especially as a top-dressing for grass lands. 
 Like the acid itself, these nitrates of potash and soda, when present in 
 large quantities, are injurious to vegetation. This is probably one cause 
 of the barrenness of the district of Arica in Peru, and of other countries, 
 where m consequence of the little rain that falls, the nitrous incrusta- 
 tions are accumulated upon the soil. In small quantity they appear to 
 exercise an important and salutary influence on the rapidity of growth 
 and on the amount of produce of raanv of the cultivated grasses. This' 
 salutary mfluence is to be ascribed, either in whole or in part, to the 
 constitution and nature of the nitric acid which these salts contain. It 
 
 w,v.'„?S""'^f'^''^ is a compound of oxygen and sulphur, which is prepared by buminff sul- 
 phur wth cera.n precautions in lai-e leaden chambers. It is also obtained directlvbl dis- 
 
 of SI;47T! ThSvvP^o^r "^ ''T ^\ " '''"^' temperature in an iron still-hence'tsLme 7 
 oryitnol. It IS a heavy, oily, acid, and remarkably corrosive liquid. In a concentrated state 
 U is exceedmgly destructive both to animal and to vegetable life conceniratea state 
 
 -UY!!°" f substance combines with oxygen, either in consequence of exposure to the air 
 ^ 'nv nt)ipr r.ircumstances, it is said to become oxidized. i^woure 10 me air 
 
QUESTIONS TO BE CONSIDERED. 57 
 
 is chiefly with a view to the explauafion I shall hereafter attempt to 
 give of the nature of this saUitary action, that I have thought it neces- 
 sary here to make you acquainted with this acid compound of nitrogen 
 and oxygen, in connection with the alkaline compound (ammonia) of iJie 
 same gas with hydrogen. 
 
 Having thus shortly described both the organic elements themselves, 
 and such chemical compounds of tliese elements as appear (o be most 
 concerned in promoting the growth of plants, we are prepared for enter- 
 ing upon the consideration of several very important (juestions. These 
 questions are — 
 
 1°. From what source do plants derive the organic elements of which 
 they are composed ? 
 
 2°. In what form do plants take them up— -or what proof have we 
 that the com pounds above described really enter into j)lants? 
 
 3°. By what organs is the food introduced into the circulation of 
 plants? In consecjuence of what peculiar structure of these several 
 parts are plants enabled to take up the com pounds by which they appear 
 to be ^ei\ ; and what are the functions of these parts, by tlie exercise of 
 which tlie food is converted and appropriated to their own sustenance 
 and further growth? 
 
 4"^. By what chemical changes is the food assimilated by plants, that 
 is — after being introduced into the circulation, through what series of 
 chemical changes does it pass, before it is converted by the plant into 
 portions of its own substance ? 
 
 5°. By what natural laws or adaptations is the supply of those com- 
 pounds, which are the food of plants, kept up ? Animals are supported 
 by an unfailing succession of vegetable crops, — by the operation of what 
 invariable laws is food continually provided for plants ? 
 
 These questions we shall consider in succession 
 
LECTURE IV. 
 
 Source of tlie organic elements of plants— Source of the carbon — Form in which it enters 
 into the circulation of plants — Source of the hydrogen — Source of the oxygen— Source of 
 the nitrogen — Form in which nitrogen enters into the circulation of plants — Absorption of 
 ammonia and nitric acid by plants. 
 
 The first af the series of questions stated at the close of the preceding 
 lecture, regards the source from which plants derive the organic ele- 
 ments of which they are composed. They are supported, it is obvious, 
 at the conjoined expense of the earth and the air — how much do they 
 owe to each, and for which elements are they chiefly and immediately ' 
 indebted to the soil, and for which to the atmosphere ? We must first 
 consider the source of each element separately. 
 
 § 1. Source of the carbon of plants. 
 
 We have already seen reason to believe that carbon is incapable of 
 entering directly, in its solid state, into the circulation of plants. It isA 
 generally considered, indeed, that solid substances of every kind are un- ■ 
 fit for being taken up by the organs of plants, and that only such as are 
 in I he liquid or gaseous state, can be absorbed by the minute vessels of 
 which the cellular substances of the roots and leaves of plants are com- 
 posed. Carbon, therefore, must enter either in the gaseous or liquid 
 form, but from what source must it be derived ? There are but two 
 sources from which it can be obtained, — the soil in which the plant 
 grows — and the air by which its stems and leaves are surrounded. 
 
 In the soil much vegetable matter is often present, and the farmer 
 adds vegetable manure in large quantities with the view of providing 
 food for his intended crop. Are plants really fed by the vegetable mat- 
 ter which exists in the soil, or by the vegetable manure that is added to 
 it? 
 
 This question has an important practical bearing. Let us, therefore, 
 submit it Tcra thorough examination. 
 
 1°. We know, from sacred history, what reason and science concur 
 in confirming, that there was a time when no vegetable matter existed 
 in the soil which overspread the earth's surface. The first plants must 
 have grown without the aid of either animal or vegetable matter — that 
 is, they must have been nourished from the air. 
 
 2°. It is known that certain marly soils, raised from a great depth 
 beneath the surface, and containing apparently no vegetable matter, 
 will yet, without manure, yield luxuriant crops. The carbon in such 
 cases must also have been derived from the air. 
 
 ■3°. You know that some plants grow and increase in size when sus- 
 pended in the air, and without being in contact with the soil. 
 
 Vou know, also that iriany plants — bulbous flower roots for example 
 — will grow and flourish in pure water only, provided they are open to 
 the access of the atmospheric air. Seeds also will germinate, and, 
 when duly watered, will rise into plants, though sown iu substances 
 that contain no trace of vegetable matter. 
 
WHENCE PLANTS DERIVE THEIR CARBON. 59 
 
 Thus De Saussure found that two beans, when caused to vegetate in 
 (he open air on pounded flints, doubled the weight of the carbon they 
 originally contained. 
 
 Under similar circumstances Boussingault found the seeds of trefoil 
 increased in weight 2i times, and wheat gave plants equal in weight, 
 when dry, to twicethat of the original grains, [Ann. de Chim. etde Phys. 
 Ixvii:, p. 1.] The source of the carbon in all these cases cannot be 
 doubted. 
 
 4°. When lands are impoverished, you lay them down to grass, and 
 the longer they lie undisturbed the richer in vegetable matter does the 
 soil become. When broken up, you find a black fertile mould where 
 little trace of organic matter had previously existed. 
 
 The same observation applies to lands long under wood. The vege- 
 table matter increases, the soil improves, and when cleared and plough- 
 ed it yields abundant crops of corn. 
 
 Do grasses and trees derive their carbon from the soil ? Then, how, 
 by tlieir growth, do they increase the quantity of carbonaceous matter 
 which the soil contains ? It is obvious that, taken as a whole, they 
 must draw from the air not only as much as is contained in their own 
 substance, but an excess also, which they impart to the soil. 
 
 5°. But on this jioint the rapid growth of peat may be considered as 
 absolutely conclusive. A tree falls across a little running stream, dams 
 up the water, and produces a marshy spot. Rushes and reeds spring 
 up, mosses take root and grow. Year after year new shoots are sent 
 forth, and the old plants die. Vegetable matter accumulates; a bog, 
 and finally a iliick bed of peat is formed. 
 
 Nor does this peat form and accumulate at the expense of one spe- 
 cies or genus of plants only. Latitude and local situation are the cir- 
 cuinstances which chiefly efifect this accumulation of vegetable matter 
 on the soil. In our own country, the lowest layers of peat are formed 
 of aquatic plants, the next of mosses, and the highest of heath. In 
 Terra del Fuego, "nearly every patch of level ground is covered by 
 two species of plants (rt5^eZia pumila of Brown, and donatia magellan- 
 ica), which, by their joint decay, compose a thick bed of elastic peat." 
 " In the Falkland Islands, almost every kind of plant, even the coarse 
 grass which covers the whole surface of the island, becomes converted 
 into this substance."* 
 
 Whence have all these plants derived their carbon ? The quantity 
 originally contained in the soil is, after a lapse of years, increased ten 
 thousand fold. Has dead matter the power of reproducing itself? 
 You will answer at once, that all these plants must have grown at the 
 expense of the air, must have lived on the carbon it was capable of af- 
 fording them, and as they died must have left this carbon in a state un 
 fit to nourish the succeeding races. 
 
 This reasoning appears unobjectionable, and, from the entire group of 
 •acts, we seem justified in concluding that plants every where, and 
 under all circumstances, derive the whole of their carbon from the at- 
 mosphere. 
 
 * Darwiii's Researches in Geology and Natural History^ pp. 349-50. Dr. Gerville informs 
 me that the aslelia approaches more nearly to the junceseor rush in6e,and VciQdonaliaio our 
 tufted saxifrages, than to any other British plants. 
 
60 THE VEGETABLE MATTER OF THE SOIL. 
 
 In certnin cxfretne cases, as in those of plants growing in the air and 
 in soils perfectly void of organic matter, this conclusion must be abso 
 lutcly true. The phenomena admit of no other interpretation. But is 
 it as strictly true of the more usual fonns of vegetable life, or in the or- 
 dinary circum-sfances in which ])lants grow spontaneously or are culti- 
 vated by the art of man ? Has the vegetable matter of the soil no 
 connection with the growth of the trees or herbage ? — does it yield them 
 no regular sujiplies of nourishment ? Does nature every where form a 
 vegetable mould on which her wild flowers may blossom and her pri- 
 meval forests raise their lofty heads ? Has the agricultural experience 
 of all ages and of all countries led the practical farmer to imitate nature 
 in i)re|)aring such a soil ? Does nature work in vain ? — is all this ex- 
 ])eri<,'ncc to be at once rejected ? 
 
 While we draw conclusions, legitimate in kind, we must be cautious 
 Jiovv, in degree, we extend them beyond our premises. 
 
 The consideration of one or two facts will shew that our general con- 
 clusion must either be iDodified or more cautiously expressed. 
 
 1°. It is true that ))lants will, in certain circumstances, grow in a soil 
 containing no sensible quantity of organic matter — but it is also true, 
 gcrierallij, that they do not luxuriate or readily ripen their seed in such a 
 soil. 
 
 2°. It is consistent with almost universal observation, that the same 
 soil is more productive when organic matter is present, than when it is 
 wholly absent. 
 
 3°. That if the crop be carried off a field, less organic matter is left 
 in the soil than it contained when the crop began to grow, and that by 
 constant croi)ping the soil is gradually exhausted of organic matter. 
 
 Now it must be granted that tillage alone, without cropping, would 
 gradually lessen the amount of organic matter in the soil, by continually 
 exposmg it to the air and hastening its decay and resolution into gaseous 
 substances, which escape into the atmosphere. But two years' open 
 fallow, whh constant stirring of the land, will not rob it of vegetable 
 inatter so effectually as a year of fallow succeeded by a crop of wheat. 
 ISome of thej'egetable inaiter, therefore, which the soil contained when 
 the seed was sown, must be carried off the field in the crop. 
 
 The conclusion therefore seems to be reasonable and legitimate, that 
 the crop which we remove from a field has not derived all its carbon di- 
 rect.y Ironi the air— but has extracted a portion of it immediately from 
 tlie sod. It IS to supply this supposed loss, that the practical farmer 
 luKls It necessary to restore to the land in the form of manure— amon-^ 
 other substances— the carbon also of which the straw or hay had robbed 
 the sou. *^ 
 
 But liow is this reconcileable with our previous conclusion, that the 
 whole of the carbon is derived from the air ? The difficulty Is of easy 
 solution. *^ '' 
 
 A seed germinates in a soil in which no vegetable matter exists- it 
 sprouts vigorously, increases then slowly, grows languidly at the expense 
 ot the air, and the plant dies stunted or immature. But in dyin^ it im- 
 parls vegetable matter to the soil, on which the next seed thrives better 
 —draw^ig sujjport not only from the air, but by its roots from the soH 
 also. 1 he death of this second plant enriches the soil further, and thus, 
 
HOW THE VEGETABLE MATTER, INCREASES. 61 
 
 while each succeeding plant is partly nourished by food from the earth, 
 yet each, when it ceases to live, imparls to the soil all the carbon which 
 during its life it has extracted from the air. Let the quantity which 
 each plant thus returns to the soil, exceed what it has drawn from it by 
 only one ten-thousandth of the whole, and — unless other causes inter- 
 vene — the vegetable matter in the soil must increase. 
 
 Thus while it is strictly true that the carbon contained in all plants 
 has beeii originally derived from the air, it is not true that the ivhole of 
 what is contained in any one crop we raise, is directly derived from the 
 atmosphere — the proportion it draws from the soil is dependent upon nu- 
 merous and varied circumstances. 
 
 The history of vegetable growth, therefore — in so far at least as the 
 increase of the carbon is concerned — may be thus simply stated : 
 
 1°. A plant grows partly at the expense of the soil, and partly at that 
 of the air. When it reaches maturity, or when winter arrives, it dies. 
 The dead vegetable matter decays, a part of it is resolved into gaseous 
 matter and escapes into the air, a part remains and is incorporated with 
 the soil. If that which remains be greater in quantity than that which 
 the plant in growing derived from the soil, the vegetable matter will in- 
 crease; if less, it will diminish. 
 
 2°. In warm climates the decay of dead vegetable matter is more 
 rapid, and, tlierefore, the portion left in the soil will be less than in 
 more temperate regions — in other words, the vegetable matter in the 
 soil will increase less rapidly — it may not increase at all. 
 
 3°. As we advance into colder countries, the decay and disappearance 
 of dead vegetable mattef, in the form of gaseous substances which escape 
 into the atmosphere, become more slow — till at length, between the par- 
 allels of 40° and 45°, it begins to accumulate in vast quantities in favour- 
 able situations, forming peat bogs of greater or less extent. While the 
 living plant here, as in warm climates, derives carbon both from the 
 earth and from the air, the dead plant, during its slow and partial decay, 
 restores little to the atmosphere, and therisfore adds rapidly to the vege- 
 table matter of the soil. 
 
 4°. Again, in one and the same climate, the decay of vegetable mat- 
 ter, and its conversion into gaseous substances, is more rapid in propor- 
 tion to the frecjuency with which it is disturbed or exposed to the action 
 of the sun and air. Hence this decay may be comparatively slow in 
 shady woods and in fields covered by a thick sward of grass ; and in such 
 situations organic matter may accumulate, while it rapidly diminishes 
 in an uncovered soil, or in fields repeatedly ploughed and subjected to 
 frequent cropping.* 
 
 Being thus fitted, by oature, to draw their sustenance — now from the 
 earth, now from the air, and now from both, according as they can most 
 readily obtain it — plants are capable of living, — though rarely a robust 
 life, — at the expense of either. The proportion of their food which they 
 actually derive from each source, will depend upon many circumstan- 
 ces — on the nature of the plant itself — on the period of its growth — on 
 the soil in which it is planted — on the abundance of food presented to 
 
 * In removing a crop we take away both what the plants have received from the earth and 
 what they have absorbed from the air— the materials, in short, intended by nature to restore 
 the loss of vegetable matter arising from the natural decay. 
 
62 PLANTS PARTLY SUPPORTED BY THE AIR AND BY THE SOIL. 
 
 cither exfremity-— on the warmth and moisture of the climate — on the du- 
 ration and intensity of the sunshine, and other circumstances of asimilar 
 kind— so that the only general law seems to be, tliat, like animals, plants 
 have also the power of adapting themselves, to a certain extent, to the 
 conditions in which they are placed ; and of supporting life hy the aid of 
 such sustenance as may be within their reach. 
 
 ^ Such a view of the course of nature in the vegetable kingdom, is con- 
 sistent, I believe, with all known facts. And that the Deity has bounti- 
 fully iitted the various orders of plants — with which the surface of the 
 earth is at once beautified and rendered capable of supporting animal 
 life— to draw their nourishment, in some spots more from the air, in oth- 
 ers more from the soil, is only in accordance with the numerous provisions 
 we everywiiere perceive, for the preservation and continuance of the 
 presenJ condition of things. 
 
 By taking a one-sided view of nature, y^e may arrive at startlino- 
 conclusions— correct, if taken as partial truths, yet false, if advanced as 
 general propositions— and fitted to lead into error, such as have not the 
 requisite knowledge to enable them to judge for themselves— or such as, 
 doubtful of their own judgment, are willing to yield assent to the author- 
 ity of a name. 
 
 Of this kind appears, at first sight, to be the statement of Liebicr, that 
 "when a plant is quite matured, and when the organs by whichit ob- 
 tmns food from the atmospliere are formed, the carbonic acid of the soil 
 IS no further required"— and that, -during the heat of summer it derives 
 Its carbon exclusively from the atmosphere."— [Organic Chemistry ap- 
 plied to Agriculture, p. 48.] . 
 
 ^ A little consideration will shew us that, while the proposition contained 
 in the former quotation may be entertained and advanced as a mailer of 
 opi,uo7i— the latter is obviously incorrect. In summer, when the sun 
 shines the brightest, and for the greatest number of hours, the evapora- 
 tion from the leaves of all plants (their insensible perspiration) is the 
 ^^[^^^?^^77^^'®i ^^'S^^^ supply of water, therefore, must at this season be 
 absorbed by the roots, and transmiited upwards to the leaves.— [Lindlev's 
 Iheory ofJHorticulture, p. 46.]— But this water, before it enters the roots, ' 
 has derived carbonic acid and other soluble substances from the air and 
 from the soil in as large quantity at this period as at any other during 
 the growth of the plant; and these substances it will carry with it in its 
 progress through the roots and the stem. 
 
 Are the functions of the root chanced at this stage of the plants' 
 growtii ? Do they now absorb pure water only, carefully separatincrand 
 refusing to admit even such substances as are held in solution?" Or 
 do the same materials wliich minister to the growth'of the plant in its 
 earlier stages, now pass upwards to the leaf and return again in the 
 course of the circulation unchanged and unemployed, to b"e a^rain re- 
 jected at the roots ? Does all this take place in the height of sSmmer, 
 while the plant is still raj)idly increasing in size ? The^ opinion is nei- 
 ther supported by facts nor consistent with analogy. 
 
 But such an opinion,— however the words above quoted may mislead 
 some,— IS not intended to be advanced by Liebig; for, in the 'following 
 page he says, that "the power which roots possess of taking up nourish- 
 ment does not cease so long as nutriment is present." In summer, 
 
LEAVES AND ROOTS ABSORB CARBONIC ACID. 
 
 63 
 
 therefore, as well as in spring or in autumn, the plant must be ever ab- 
 sorbine; nourishment by these roots, if the soil is capable of atlording it — 
 and thus, in the general vegetation of the globe, the increase of carbon 
 in growing plants must, at every season of the year, be partly derived 
 frorn the vegetable matter of the soil in which they grow. 
 
 § 2. Form in ivhich carbon enters into the circulation of plants. 
 Supposing it to be established that the wliole of the carbon contained 
 in plants has originally been derived from the air — we have only to in- 
 quire in what state this element exists in the atmosphere, in order to 
 satisfy ourselves as to the form- of combination in winch it is and has 
 been received into the circulation of plants. In considering the consti- 
 tuiion of the atmosphere in the preceding lecture, it was stated that car- 
 bonic acid, a compound of carbon and oxygen, is always present in it — 
 and that, though this gas is diffused through the air in comparatively 
 small quantity only, yet it is everywhere to be detected, — while no 
 other compound of carbon is to be found in it in any appreciable cjuanti- 
 ty. We must conclude, therefore, tliat from this gaseous carbonic acid 
 the whole of the carbon contained in plants has been j^rimariiy derived. 
 This conclusion is confirmed by the observation so frecjuently made, 
 that the leaves of plants in sunshine absorb carbonic acid, and that 
 plants die in an atmosphere from which this gas is entirely excluded. 
 
 But we have seen reason to believe that, under existing circumstan- 
 ces, plants also extract a portion of the carbon they contain from the 
 soil' in which they grow. In what state or forin of combination do the 
 roo/5 absorb carbon? 
 
 The most abundant product of the decay of vegetable matter m the 
 soil, is the same carbonic acid which plants inhale so largely from the 
 atmosphere by their leaves. In a soil replete with vegetable matter, 
 therefore, the roots are surrounded by an atmosphere more or less 
 charged with carbonic acid. Hence if they are capable of inhalirig 
 gaseous substances, this gas will enter the roots in the aeriform state— if 
 not, it must enter in solution in the water, which the roots drink in so 
 largely, to supply the constant waste caused by the insensible perspira- 
 tion of the leaves. • ^ j 
 
 During the early fermentation of artificial manures there is also de- 
 veloped In the soil a variable proportion of light carburetted hydrogen 
 (Lecture III., ]). 49), whicli is supposed by some to enter occasionally 
 into the roots. That it does enter, however, is doubtful,— and we are 
 safe, I think, in considering this compound not only as an uncertain 
 source of the carbon of plants, but as one from which, in the most fa- 
 vourable circumstances, they can derive only a small supply. 
 
 Thus, from the earth as from the air, the most unfailing supply of food 
 is the gaseous carbonic acid. 
 
 But as the water passes through the soil it takes up inorganic substan- 
 ces-potash, soda, lime, magnesia— and conveys them through the roots 
 into the circulation of the plants. Can it refuse to take up and to perform 
 a similar office to the soluble organic substances it meets with, as it sinks 
 through the soil ? Or do the spongioles of the roots keep a perpetual 
 v/atch over the entering waters, to prevent the introduction of every so- 
 luble form of carbon but that of carbonic acid ? Or, supposing such 
 
64 ROOTS ABSORB ORGANIC SUBSTANCES ALSO 
 
 substances introduced into the interior of the plant, are none of them 
 digested there and converted to the general purposes of food ? A state- 
 ment of two or three facts will afford a satisfactory reply to these several 
 questions. 
 
 1°. When plants are made to grow in infusions of madder the radicle 
 fibres are tinn[ed of a red colour. 
 
 2^. The flower of a white hyacinth becomes red after a few hours, 
 when ihe earth in which it is planted is sprinkled with the juice of the 
 2)hytolaca decandra (Biol). 
 
 Therefore organic substances can enter into the roots^ and thence into 
 the circulation, of ihe plant. 
 
 3°. The colour of the madder does not usually extend upwards to 
 the leaves and flowers of the plant. 
 
 4°. The colour imparted to the flower of the white hyacinth disap- 
 pears in the sunsliine in the course of a few days. 
 
 Organic colouring matters, therefore, undergo a chemical change either 
 in the stem, in the leaf or in the jioicer — some sooner, some later — and 
 the same is probably the case with most other organic substances which 
 gain admission into the interior of plants. 
 
 5°. Sir Humphry Davy introduced plants of mint into weak solutions 
 of sugar, gum, jelly, the tanning principle, &c., and found that tliey 
 grew vigorously in all of them. He then watered separate spots of grass 
 with the same several solutions, and with common water, and found all 
 to thrive more than that to which common water was applied — while 
 those treated with sugar, gum, aTid gelatine grew luxuriantly. — [Davy's 
 Agricultural Chemistry, Lecture VI.] 
 
 Therefore different organic substances — being introduced into the cir 
 culation and there changed — are converted by plants into their own sub- 
 stance, or act as food, and nourisJi the jdant. 
 
 We may consider it, therefore, to be satisfactorily established that, 
 while a plajit sucks in by its leaves and roots much carbon in the form of 
 carbonic acid, it derives a variable portion of its immediate sustenance 
 (of its carbon) from the soluble organic substances that are within reach 
 of its roots. 
 
 This fact is-never doubted by the practical husbandman. It forms 
 the basis of many of his daily and most important operations, while 
 the results of these operations are further proofs of the fact. 
 
 The nature of the soluble substances which are formed during the de- 
 cay of animal and vegetable substances — and which the roots of plants 
 are supposed to take up — will be considered in a subsequent lecture.* 
 
 § 3. Source of the hydrogen of plants. 
 
 The source of the hydrogen of plants is less doubtful, and will re- 
 quire less illustration, than the source of the carbon. This elementary 
 substance is not known to exist in nature in an uncombined state, and, 
 therefore, it must, like carbon, enter into plants in union w'ith some other 
 element. 
 
 1°. Water has been already shewn to consist of hydrogen in combina- 
 
 • This part of the subject might have been discussed here without appearing out of place 
 ^but it will come in more appropriately, I think, wlien treating of the nature and mode of 
 action of vegetable manures. 
 
SOURCE OF THE HYDROGEN OF PLANTS. 65 
 
 tion with oxygen. In the form of vapour, this compound pervades the 
 atmosphere, and plays among the leaves of plants, while in the liquid 
 state it is diffused through the soil, and is unceasingly drunk in by the 
 roots of all living vegetables. In the interior of plants — at least during 
 their growth — this water is continually undergoing decomposition, and 
 it is unquestionably the chief source of the hydrogen which enters into 
 the constitution of their several parts. In explaining the properties of 
 water I have already dwelt upon the apparent facility with which its 
 elements are capable either of separating from, or of re-i>niting to, each 
 other, in the vascular system of animals or of plants. The reason and 
 precise results of these transformations we shall hereafter consider. 
 
 2°. In light carburetted hydrogen (CH2), given otf as already stated 
 during the decay of vegetable matter, and said to be always present in 
 highly manured soils, this element, hydrogen, exists to the amount of 
 nearly one-fourth of its weight. On the extent, therefore, to which this 
 gaseous compound gains admission into the roots of plants, will de- 
 pend the supply of hydrogen which they are capable of drawing from 
 this source. Had we satisfactory evidence of the actual absorption of 
 this (marsh) gas by the roots or leaves of plants, in any quantity, we 
 should have no difficulty in admitting that plants might, from this source, 
 easily obtain a considerable supply both of carbon and of hydrogen. It 
 would be also easy to explain how (ihat is, by what chemical changes,) 
 it is capable of being so appropriated. But the extent to which it really 
 acts as food to living vegetables is entirely unknown. 
 
 3°. Ammonia is another compound, containing much hydrogen, [its 
 formula being NH3, or one equivalent of nitrogen and three of hydro- 
 gen,] which, as I have already stated, exercises a manifest influence on 
 the growth of plants. If this substance enter into their circulation in 
 any sensible quantity, — if, as some maintain, it be not only universally 
 diffused throughout nature, but is constantly affecting, and influencing at 
 all limes, the universal functions of vegetation — there can be no doubt 
 that the hydrogen it contains must, to an equal extent, be concerned in 
 the production of the various organic substances which are formed or 
 elaborated by the agency of vegetable life. How far this probable in- 
 terference of the hydrogen of ammonia with the functions of the vegeta- 
 ble organs, will tend to explain" or illustrate the influence actually exert- 
 ed by this compound, we shall, by and by, more accurately inquire. In 
 the mean time, the quantity of ammonia, which actually enters into the 
 circulation of plants in a state of nature, is too little known, and making 
 the largest allowance, probably too minute, to permit us to consider it as 
 an irnt)oriant source of hydrogen to the general vegetation of the globe. 
 
 4°. The soluble organic substances, which enter into the circulation 
 of plants through the roots, as shewn in the ]:)receding section, do not 
 consist of carbon and water only, but of combinations of carbon with 
 hydrogen and oxygen in various proportions. From these substances, 
 therefore, plants derive an uncertain and indefinite supply of hydrogen 
 in a state already half-organized, and probably still more easily assimi- 
 lated or converted into portions of their own substance, than when this 
 element is combined with oxygen in the form of water. 
 
 We may, therefore, conclude generally in regard to the source of the 
 hydrogen of plants — that though .there are undoubtedly several other 
 
66 SOURCE OF THE OXYGEN AND NITROGEN. 
 
 forms of combination in which this element may enter into their circula- 
 tion, in uncertain quantity — yet that all-pervading water is the main 
 and constant source from which the hydrogen of vegetable substances is 
 derived. 
 
 § 4. Source of the oxygen of plants. 
 
 We can at once perceive, and without difficulty, the various sources 
 of the oxygen of plants •, though it is difficult in this case also to say 
 how much they derive from each. 
 
 1°. The water which they imbibe so largely consists in great part of 
 oxygen, and is easily decomposed, [eight-ninths of the weight of water 
 are oxygen.] This alone would yield an inexhaustible supply. 
 
 2°. The atmosphere contains 21 per cent, of its bulk of oxygen, and 
 the leaves of plants in certain circumstances are known to absorb this 
 oxygen. The air in which tliey live, therefore, might be another 
 source. 
 
 3°. Carbonic acid contains 72 per cent, by weight of oxygen, and 
 this gas is also known to be absorbed in large quantity from the atmos- 
 phere by the leaves of plants — while its solution in water is admitted 
 readily by the roots. 
 
 From any one of these sources an ample supply of oxygen might 
 readily be obtained, and it may be considered as a proof of the vast im- 
 portance of this element to the maintenance of animal and vegetable 
 life, that it is everywhere placed so abundantly within the reach of 
 Jiving beings. It is from the first of these sources, however, from the 
 water they contain, that plants are believed to derive their principal 
 supply. The reasons on which this opinion is founded will appear 
 when we shall have considered the functions of the several parts of 
 plants, and the chemical changes to which the food is subjected in the 
 course of the vegetable circulation. 
 
 § 5. Source of the nitrogen of plants. 
 
 The quantity of nitrogen present in plants is very small, compared 
 with that of any of the other elements which enter into their constitu- 
 tion. Of tlii&^you will be reminded, by a reference to the analyses of 
 hay, oats, and potatoes, exhibited in the second lecture (page 30), which 
 shew that the nitrogen contained in these several crops, when perfectly 
 dried at 240° F., is respectively 1|, 2^, and l^ per cent. In the state 
 in which they are usually given to cattle they contain a still less per 
 centage of nitrogen, in consequence of the quantity of water still present 
 in them.* Thus raw potatoes as they are given to cattle contain only ^ 
 of a per cent, of nitrogen, hay 1^ per cent., and oats lyV* P^'" cent., or a 
 hundred pounds of each contain 5 ounces, 1 pound 5 ounces, and 1 pound 
 14 ounces respectively. 
 
 It would appear at first sight as if this small quantity of nitrogen 
 could be of little importance to the plant, especially since, as we shall 
 hereafter see, it does not enter as a constituent into those vegetable sub- 
 stances, such as woody fibre, starch, sugar, and gum, which plants pro- 
 duce in the greatest abundance, and of which their own stems and 
 
 • 0'33, 1-29, and 1-87 per cent.— the potatoes containing also 72 percent, of water, the hay 
 14, and the oats 15 per cent. 
 
QUANTITY OF NITROGEN IN PLANTS. &t 
 
 branches chiefly consist. The same remark, however, applies to this, 
 as to many other cases which present themselves to the chemist, during 
 his analyses, especially of organized substances, — that those elements 
 which are present only in small quantity are as necessary — as essential 
 — to the constitution of the particular substance in which they occur, as 
 other elements are of which they contain much ; and that if these small 
 quantities are removed or absent, not only are the physical and chemi- 
 cal properties of the substance materially altered, but it is found also to 
 exercise a very different influence on animal and vegetable life. This 
 latter observation will present itself to you in a very striking light, when 
 we come hereafter to study the nutritive properties of the several kinds 
 of food by which animals are chiefly supported, — and shall see on what 
 elementary body their relative nutritive properties depend, or by the 
 amount of which their relative value appears at least to be indicated. 
 
 But a consideration of the absolute quantity of nitrogen contained in 
 an entire crop will satisfy you that though small in comparative amount, 
 [that is, compared with the carbon and oxygen which phints contain,] 
 this element cannot be without its due share of importance in reference 
 to vegetable life. Hay, as above stated, contains, as it is stacked, 1|* 
 per cent, of nitrogen, or a ton of hay contains 30 lbs. of this element. A 
 good crop of hay, on land which is depastured during the winter, will 
 amount to 2 or 2* tonsf per acre. Taking 2 tons as an average, the hay 
 from one acre will contain 60 lbs. of nitrogen, or from 100 acres 6000 lbs., 
 equal to 2| tons of nitrogen. 
 
 Allowing, therefore, nothing for the aftermath, and supposing the 
 other crops to contain no more nitrogen than the hay does, the farmer of 
 five hundred acres will annually carry into his stack-yard at least 13 
 tons of nitrogen in the form of hay, straw, grain, and other produce. J. 
 
 Nature performs all her operations on a large scale, and the quantity 
 of materials she employs are large in a corresponding degree. Hence, 
 though comparatively small, the nitrogen in vegetable substances is ab- 
 solutely large. You cannot suppose, when viewed in this light, that 
 nitrogen is an element of little consequence in reference to vegetable 
 life ; or that in nature it should be so constantly and universally dif- 
 fused without reference to some important end. If I may be allowed a 
 famiUar illustration of the mod-e in which small quantities of matter will 
 affect the sensible properties of large masses, I would recall to your 
 minds the effects of seasoning upon food, in imparting, when added in 
 small quantity only, an agreeable relish to what would otherwise be 
 
 * In different crops of hay BoussingauU found in tliree several years the following pro- 
 portions of nitrogen: — 
 
 Hay dried at 
 280° F. 
 
 1-04 of nitrogen per cent. 
 115 " " 
 
 1-3 " " 
 
 20 " « 
 
 t The Rev. Mr, Ogle, of Kirkley, Northumberland, informs me that some of hvg land 
 near the Hall has yielded annually at this rate for 100 years, and without other manure than 
 the droppings from the cattle which have fed upon it. 
 
 t This average estimate gives but an inaccurate idea of the quantity actually contained 
 in some species of crops. Thus red clover with the aid of gypsum will yield 3 tons of hay 
 per acre. This hay contains more than twice the quantity of nitrogen (Boussingault) that 
 common hay does, hence an acre of such hay would contain at least 180 lbs. of nitrogen. 
 (See Lecture II., p. 30.) 
 
 
 Hay, 
 
 as commonly 
 stacked. 
 
 In 1836 
 
 
 118 
 
 " 1&38 
 
 
 1.3 
 
 " 1839 
 
 
 1-5 
 
 Aftermath 
 
 
 2-4 
 
6S THE ATMOSPHERE THE PRIMARY SOURCE OF NITROGEN. 
 
 insipid. But I need not dwell on this point, since I shall hereafter have 
 occasion to draw your attention to certain facts in reference to the con- 
 stitution of the atmosphere, which will satisfy you that, hy the agency 
 of comparatively feeble causes, gigantic effects are coniinually produced, 
 in nature, — and that we can scarcely fall into a graver error in reason- 
 ing of natural processes, than by overlooking the agency of forms of mat- 
 ter which present themselves to our senses in minute quantity only. In 
 reference to insect life this truth has been long established. In the coral 
 reefs you are familiar with the wonderful results of the persevering la- 
 bour of minute animals in one element. When I come to explain the 
 nature and origin of soils, I shall have occasion to show that even the 
 element on which you labour — the earth, oil the cultivation of which 
 your thoughts and hands are daily employed — is occasionally indebted 
 for some of its most valuable properties to a similar agency, often un- 
 seen by you, and though working for your good, unheeded and un- 
 thought of. 
 
 Whence, then, is this nitrogen derived by plants? The primary 
 source it is not difficult to see. We can arrive at it by a train of reason- 
 ing similar to that which led us to the atmosphere as the original source 
 of th.e carbon of plants. Nitrogen does not constitute an ingredient of any 
 of the solid rocks,* nor do we know any other source than the atmosphere 
 from which it can be obtained in very large quantity. It exists, as we 
 have seen, in many vegetables, and it is more largely present in animal 
 substances, but these organized matters must themselves have drawn 
 this element from a foreign source, and the atmosphere is the only one 
 from which we can fairly assume it to have been originally derived. 
 
 But though the nitrogen, like the carbon of plants, may thus be traced 
 to the atmosphere — as its orginal source — it does not follow that this 
 element is either absorbed directly from the air, or, in an uncombined 
 and gaseous state. Though the leaves of trees and herbs are continually 
 surrounded by nitrogen, the constitution of plants may be unfitted for 
 absorbing it by their leaves. The nitrogen may not only require to be 
 in a state of combination before it can enter into the circulation, but it 
 may also be capable of gaining admission only by the roois. These 
 points are considered in the following section. 
 
 § 6. Form in which the nitrogen enters into the circulation of plants. 
 
 The question as to the form in which nitrogen enters into the circula- 
 tion of plants is one which at the present moment engages much attention. 
 It will be proper, therefore, to discuss it with considerable care. 
 
 1°. It is considered an essential part of good tillage to break up and 
 loosen the soil, in order that the air may have access to the dead vege- 
 table matter, as well as to the living roots which descend to considerable 
 depths beneath the surface. When thus admitted to the roots, it is im- 
 possible that some of the nitroiien of the atmosphere, as well as some of 
 its oxygen, may be directly absorbed and ap])ropriated by the plant. 
 To what extent this absorption of nitrogen may proceed, however, we 
 
 * Except coal, and coal itself is of vegetable origin. Throughout all rocks in which or- 
 ganic remains are found, more or less animal matter containing nitrogen is to be met with, 
 but these remains are only accidentally present, and they must have derived their nitrogen 
 during life, either directly or indirectly, from the atmosphere. 
 
RAIN WATER DISSOLVES IT. 
 
 69 
 
 have as yet no experimental results from whicli we can form any esti- 
 mate. Whether it takes place at all or not, is wholly a matter of opinion. 
 
 2°. The leaves of plants, as will be more fully explained hereafter, absorh 
 certain gaseous substances from the atmosphere, and we might, therefore, 
 expeci that some of the nitrogen of the air would, by this channel, be 
 admitted into their circulation. This view, however, is not confirmed 
 by any of the experiments hitherto made with the view of investigating 
 the action and functions of the leaves.* We are not at liberty, there- 
 fore, to assume that any of the nitrogen which plants contain has in this 
 way been derived directly from the air. It may be the case ; but it is 
 not yet proved. 
 
 3°. There is little dobbt, however, that nitrogen enters the roots of 
 plants in a state of solution. But the quantity they thus absorb is un- 
 certain — it is sup|X)sed to be small, and must be variable. 
 
 When water is exposed to the air in an open vessel it gradual]}'' ab- 
 sorbs oxygen and nitrogen, though, as has been stated in a previous lec- 
 ture, in proportions different from those in which they exist in the atmos- 
 phere. The whole quantity of the mixed gases thus taken up amounts 
 to about 4 per cent, of the bulk of the water (Humboldt and Gay-Lus- 
 sac), and in rain water about | of the whole consist of nitrogen. One 
 hundred cubic inches of rain water, therefore, will carry into the soil 
 about 2| inches of nitrogen gas. But in passing through the soil, the 
 water meets with other soluble substances before it reaches the roots, 
 especially the deep-seated roots of plants. It takes up carbonic acid, 
 and it dissolves solid substances, and in doing so it is a property of water 
 to give off a portion of the other gases which it had previously absorbed 
 from the air. 
 
 But let us suppose that rain water actually takes to the roots, and car- 
 ries with it into the circulation of the plant, 2 per cent, of its bulk of 
 nitrogen, and let us calculate how much of the nitrogen it contains a 
 crop of hay could in this way derive from the air. 
 
 * See subsequent lecture " On the structure and functions of the several parts of plants.^' 
 The experiments above referred to were made upon plaJits growing in close vessels, the 
 air contained in which was measured and examined (analysed) both before the plajits were 
 introduced and after they had been some time in the vessel. In these experiments tlie 
 bulk of the nitrogen present has sometimes been observed to increase, but never to diniin- 
 itfh, in quantity. The conclusion seems satisfactory, that no nitrogen is abstracted directly 
 from the atmosphere by the leaves of plants. Yet Boussingault' very justly remarks, tliat 
 a diminution in the bulk of the nitrogen too small to be detected in the ordinary mode of 
 making these experiments, would be sufficient to account for a considerable portion of tliat 
 comparatively small quantity of nitrogen which is present in all livinn; plants. While, there- 
 fore, we accord l;heir due weight to these researches of the vegetable physiologists, we are 
 not to consider Ihem as by any means decisive of the question. With this rational and cau- 
 tious conclusion, Liebig is not satisfied ; he says, '• We have not the slightest reason for be- 
 lieving tliat the niti-ogei) of the atmosphere fakes part in the processes of assimilation of plants 
 and animals ; on the contrary, we know that many plants emit tJie iiitrogen which is ab- 
 sorbed by their roots either in tlie gaseous form or in solution in water." (p. 70.) But if 
 they occa.sionally expire nitrogen by their leaves why must this nitrogen be exactly that 
 portion whicli has previously been absorbed by the roots in Uie uncombined state, and the 
 quantity of which-is so uncertain and so indefinite'? 
 
 [* Boussingault details a series of experiments in the course of which he made peas, tre- 
 foil, wheat, and oats, grow in the same pure siliceous sand containing no organic matter, ana 
 watered them with the same distilled water. The absolute quantity of nitrogen increased 
 sensibly in the peas and trefoil during their growth ; in the wheat and oats no change could 
 be detected by analysis. Trom these results he is inclined to infer that the green leaves or 
 tlie former have the power of sensibly absorbing niti-ogen from tlie atmosphere, while tJiose 
 of the latter have not tliis power — at least under the circimislances in which the experi- 
 ments were made. This conclusion, however, is not certain^ as will presently be shewn.— 
 See Ami. de Chim. et de Pkys. Ixvii. p. 1, and Ixix. p. 353.] 
 
 A. 
 
70 ABSORPTION OF AMMONIA BY PLANTS. 
 
 The quantity of rain that falls at York from the first of March to the 
 middle of June — during which time the grass grows and generally ri- 
 pens — is about five inches.* On a sijuare foot, therefore, there fall 720 
 cubic inches of water, containing 2 per cent, of their bulk, or 14 cubic 
 inches of nitrogen, weighing 4} grains. This gives 28 lbs. for the quan- 
 tity of nitrogen thus brought to the soil over an entire acre. But if we 
 consider how the rain falls in our climate, we cannot suppose the grass 
 in a field to absorb by its roots, and afterwards perspire by its leaves, 
 more than one-third of the whole. This quantity would carry with it 9 
 lbs. of nitrogen into the circulation of the plants — or little more than a 
 seventh part of the 60 lbs. which, as we havg seen, are taken ofT the 
 field in a crop of hay. 
 
 Such a calculation as this affords at the best but a very rude approxi- 
 mation to the truth — it seems, however, to justify us in concluding that 
 plants can derive from the air, and in an uncombined state, only a small 
 portion of the nitrogen they are found to contain — and that they proba- 
 bly draw a larger supply from certain compounds of this elementary sub- 
 stance with hydrogen and oxygen — which are known to come within 
 the reach of their roots and leaves. 
 
 The most important of these compounds, and those perhaps the most 
 extensively concerned in influencing vegetation, are ammonia and nitric 
 acid, the properties of which have been described in the preceding 
 lecture. f 
 
 § 7. Absorption of ammonia hy plants. 
 
 That ammonia enters directly into the circulation of plants is ren- 
 dered probable by a variety of considerations. 
 
 1°. Thus it is found to be actually present in the juices of many 
 plants. In that of the beet-root, and in those of the birch and maple 
 trees, it is associated with cane sugar (Liebig.) In the leaves of the 
 tobacco plant, and of scurvy grass, in elder flowers, and in many fungi, 
 it is in combination with acid substances, and may be detected by 
 mixing their juices with quick-lime. — [Schiibler Agricultur Chemie, 
 II., p. 56.] 
 
 2°. Some plants actually perspire ammonia. Among these Is the 
 Chenopodium Olidum (stinking goosefoot), which is described by Sir 
 William Hooker as "giving out a most detestable odour, compared to 
 putrid salt fish." In the odoriferous matter given off ammonia is con- 
 tained, and may be detected by putting a glass shade over the plant, 
 and after a time introducing a feather moistened with vinegar or dilute 
 muriatic acid. — [Chevalier Jour. dcPharm. X., p. 100.] It is also pre- 
 sent in the odoriferous exhalations of many sweet-smelling plants and 
 flowers. — [Schiibler, L, p. 152.] 
 
 3°. Nearly all vegetable substances, when distilled with water, 3'ield 
 an appreciable fjuantity of ammonia. Thus the leaves of hyssop, and 
 
 * The result of experiments made in 1834 by Prof. Phillips and Mr. Edward Gray. The 
 mean annual fall of rain at York is about 22 inches. — (See fifth Report of the British Associa- 
 tion, p. 173.) 
 
 t It will be recollected that ammonia consists nf one equivalent of nitrogen (N) united to 
 three of hydrogen (H3), being represented by NIIj; and that nitric acid consists of one of ni. 
 trogen(N) and five of oxygen (Os), its formula being NO5.— See Lecture III., p. 34. 
 
AMMONIA OBTAINED FROM VEGETABLES. 71 
 
 the flowers of the lime tree, yield distilled waters in which ammonia 
 can be detected (Schiibler), the seeds of plants thus distilled yield it in 
 abundance (Gay-Lussac), and traces of it may be found in most vege- 
 table extracts (Liebig). 
 
 4°. Ammonia is also given off, among other products, when wood is 
 distilled in iron retorts for the manufacture of pyroligneous acid, and by 
 a similar treatment it may be obtained from many other vegetable sub- 
 stances. 
 
 The above facts, however, are not to be considered as proofs that am- 
 monia enters directly into the circulation of plants either by their roots 
 or by their leaves. Tbat which is associated with sugar in the beet, may 
 have been formed by tire same converting power which, in the interior 
 of the plant, has jiroduced the sugar from carbonic acid and water. So, 
 that exhaled by the leaves of the goosefoot, which grows in waste places, 
 especially near the sea, may have been produced during the upward 
 flow of the sap or during its passage over the leaf And we kmoiv that 
 the nitrogen does not exist in the state of ammonia in the seeds of plants, 
 or in wood, or in coal — though from all of them it may be obtained by 
 the processes above described. 
 
 The production of ammonia, by the agency of a high temperature, 
 may be illustrated by a very familiar experiment often performed, 
 though for a very different purpose. The juice and dried leaf of tobac- 
 co contain nitre (nitrate of potash) and a little ammonia. But when 
 tobacco is burned, ammonia in sensible quantity is given off along with 
 the smoke, chiefly in the state of carbonate of ammonia. This may be 
 shown by bringing a lighted cigar near to reddened litmus paper, when 
 the blue colour will be restored ; or to a red rose, when the leaves will 
 become green ; or to a rod dipped in vinegar or in dilute muriatic acid, 
 when a white cloud will appear. — [Runge, Einleitung in die iechnische 
 Cliemie, p. 375.] 
 
 In this case a portion of the ammonia given off by the tobacco has 
 most probably been formed during the combustion, at the expense of the 
 nitrogen contained in the nitrate of potash which is present in the leaf. 
 
 5°. But there are other circumstances which are strongly in favour of 
 the o|)inion, that ammonia not unfrequently does enter, as such, into the 
 circulation of plants. 
 
 Thus it is proved, by long experience, that plants grow most rapidly 
 and most luxuriantly when supplied with manure containing substances 
 of animal origin. These substances are usually applied to the roots or 
 leaves in a state of fermentation or decay, during which they always 
 evolve ammonia. Putrid urine and night-soil are rich in anmionia, 
 and they are among the most efficacious of manures. This ammonia 
 is supposed to enter into the circulation of plants along with the water 
 absorbed by their roots, and sometimes even by the pores of their leaves. 
 We can scarcely be said to have as yet obtained decisive proof that it 
 does so enter, but probabilities are strongly in favour of this supposition ; 
 and when we come hereafter to consider minutely the mode in which it 
 is likely to act, when within the plant, we shall find the probabilities 
 derived from practical experience to be strengthened by the deductions 
 of theory. 
 
 But though the facts so long observed in reference to the action h an- 
 
72 OTHER IMMEDIATE SOURCES OF NITROGEN. 
 
 imal manures upon vegetation, justify us in believing that ammonia 
 actually enters into the roots, and perhaps into the leaves, of plants — we 
 ought not hastily to conclude that all the nitrogen which plants are ca- 
 pable of deriving from decaying animal matter must enter into their cir- 
 culation in the form of ammonia. Other soluble compounds containing 
 nitrogen are formed during the decay of animal substances — they ac- 
 tually exist largely in the li(|uid manures of the stable and fold-yard, 
 and they can scarcely fail, when applied (o the soil, to be to a certain 
 extent absorbed by the roots of plants. This urea is a substance con- 
 taining much nitrogen, which exists in the urine or excrements of most 
 animals, and by its decomposition produces carbonate of ammonia. 
 But being very soluble, this substance may enter directly info tiie roots, 
 and may be there decomposed, and made to give up its nitrogen to the 
 living plant. To other compound substances of animal origin the same 
 observation may apply,* — so that while the fact, that animal manure in 
 a state of fermentation is very beneficial to vegetation, may be consid- 
 ered as rendering it highly probable that the ammonia which such 
 manure contains, enters directly and supplies much nitrogen to the 
 growing plants, it must not be entirely left out of view that, in nature, a 
 portion of the nitrogen, derived from animal substances, may be ob- 
 tained immediately from other compounds in which ammonia does not 
 exist. 
 
 To what amount ammonia actually enters into the circulation of 
 plants, or how much of the nitrogen they contain it actually supplies, 
 we have no means of ascertaining. Were it abundantly present in the 
 soil, its great solubility would enable it to enter, with the water absorbed 
 by the roots, in almost unlimited quantity. In a subsequent section we 
 shall consider the conditions under which ammonia is produced in nature, 
 the comparative abundance in vi^hich it exists on the earth's surface, 
 and the extent of the influence it may be supposed to exercise on the 
 general vegetation of the globe. 
 
 §8. Absorption of 7dtric acid hy plants. 
 1°. That ammonia is actually present in the juices of many livirig 
 vegetables hasHbecn adduced, as a kind of presumptive evidence, that 
 this compound is directly absorbed by plants. A similar presumjnion 
 is offered in favour of the direct entrance of nitric acid, by its invariable 
 presence in combination with potash, soda, lime, or magnesia, in the 
 juices of certain common and well known plants. Thus it is said to be 
 always contained in the juices of the tobacco plant, of the sunflower, of 
 the goosefoot,f and of common borage. The nettle is also said to con- 
 tain it, and it has been detected in the grain of barley. J It exists pro- 
 bably in the juices of many other plants in which it has not hitherto 
 
 • TliU3 it may be applied more sfi-on2;ly to the hipparic acid, which cxisis in the urine of 
 the horse, and otiicr lierbivorous animals. Tliis acid decomposes naturally into benzoic 
 acid and ammonia. The sweet-scented vernal-Eirass {Anlhoxavthum Odoratum) by which 
 hay is perlumed, owes its agreeable odour lo the presence of this benzoic acid. It may, 
 therefore, be supposed that, where cattle and horses sraze, the grasses actually absorb the 
 hippuric acid contained in tlie urine, which readies Ihejr roots, decompose it as it*&.scend3 
 with the sap, appropriate its nitrogen, and exhale the odoriferous benzoic acid. 
 
 t Chenopodium, probably in all the species of this genus. — See Liebig, p. 82. 
 
 X Grisenthwaite {Neic Theory of Agriculture, p. 105) says, it is always present in barley in 
 the form of nitrate of soda. — See Appendix. 
 
ABSORPTION OF NITRIC ACID ITS EFFECT ON VEGETATION. 73 
 
 been sought for. Were we, therefore, entitled, from the mere presence 
 of this acid in plants, lo infer that it had really entered by their roots or 
 leaves, we should have no hesitation in drawing our conclusion. But, 
 like ammonia, it may have been formed in the interior of the living ve- 
 getable ;* and hence the fact of its presence proves nothing in regard to 
 the state in which the nitrogen it contains, entered into the circulation of 
 the plant. 
 
 2°. But nitric acid, like ammonia, exerts a powerful influence on the 
 growing crop, whether of corn or of grass. Animal matters, as we have 
 seen, give off ammonia during their decay, and manures are rich and 
 efficacious in proportion to the quantity of animal manure they contain. 
 The crop produced also is valuable and rich in nitrogen in like propor- 
 tion. Therefore, as already stated, it is inferred that ammonia enters 
 directly into the living plant, and supplies it with nitrogen. 
 
 The effect of nitric acid is similar in kind, and perhaps equal in de- 
 gree. Applied to the young grass or sprouting shoots of grain, it has- 
 tens and increases their growth, it occasions a larger produce of grain, 
 and this grain, as when ammonia is employed, is richer in gluten, and 
 more nutritious in its qualify. f An equal breadth of the same field 
 yields a heavier produce, and that produce, weight for weight, contains 
 more when saltpetre or nitrate of soda have been ajjplied in certain 
 quantities to the young ])Iants which grow upon it. It is reasonable to 
 conclude, therefore, that the acid of the nitrates, in some form or other, 
 
 * Wlien the beet-root arrives at maturity, the swg-ar begins to diminish, and saltpetre or 
 other nitrates to be formed, probably at the expense of the ammonia which the juice pre- 
 viously contained.— Docroizelles, Jour, de Phar., X., p. 42. 
 
 t The analogous effects of ammoiiiacal manures and of the nitrates on the relative quan- 
 tities of gluten and starch in grain, are shown by the following experiments : 
 
 Hermbstaedt sowed equal quantities of the same wheat, on equal plots of the same ground, 
 and manured them with equal weights of ditferent manures. Then from lUO parts of each 
 sample of grain produced, he obtained starcii and gluten in the following proportions : 
 
 Gluten. Starch. Produce. 
 
 Without manure 9-2 66-7 3 fold. 
 
 With vegetable manure (rotted 
 
 polatoe haulm) 9-6 6.5-94 5 « 
 
 With cow dung 12-0 6?-3 7 " 
 
 With pigeons' dung 12-2 63-2 9 « 
 
 Witliliorsedung 137 6164 10 » 
 
 With goats' dung 32-9 424 12 » 
 
 With sheep dung 329 428 12 " 
 
 With dried night-soil 3314 4144 14 " 
 
 With dried ox-blood 34 24 413 14 " 
 
 With dried human urine - - - 351 39 3 12 "^ 
 
 The manures employed by Hermbstaedt are sup/wsed, during fermentation, to evolve 
 more ammonia in the order in which they are here placed, beginning at the top of the list; 
 while the amount and kindof Uie produce obtained by the use of each, aflford the chief evi- 
 dence in favour of the opinion that this ammonia actually enters into and yields nitrogen to 
 the plant. 
 
 Mr. Hyett found in flour raised on two patches of the same land in Gloucestershire, the 
 one dressed with nitrate of soda, the other undressed, the following proportions : 
 
 Gluten. Starch. 
 
 In the nitrated - - - 2325 49-5 
 
 In the unnitrated - - 19* 55-5 
 
 And Mr. Daubeny, [Three Lectures on Agriculture, p. 76,] in flour from wheat top-dressed 
 with saltpetre, found — 
 
 In the nitrated 15 per cent, of gluten. 
 
 In the unnitrated - - - - 13 " ■ " 
 These differences are not so striking as in the cnse of ammonia, but they are precisely 
 the same in kind, and lead to the same general conclusion in regard to the nature of the in- 
 fluence of the nitrates on vegetation. Accurate and repeated experiments on the precise 
 effects of the nitrates are still much to be desired. 
 
 [<- Schiibler. Grundsdtze der Agricuttur Chemie, II. p. 170.] 
 
/4 GENERAL CONCLUSIONS. 
 
 is capable of entering into the circulation of living plants — and of yield- 
 ing to them, in whole or in part, the nitrogen they contain. 
 
 But here, again, as in the case of ammonia, we are at fault in regard 
 to tlie (juantity of nitrogen which plants in a state of nalure actually 
 derive from nitric acid or the nitrates. The compounds of this acid with 
 potash, soda, lime, and magnesia (the nitrates of these substances), are 
 all very soluble in water. The quantity of this fluid, therefore, which 
 enters by the roots of plants, could easily convey into their circulation 
 far more of these nitrates than would be alone sutficient to supply the 
 whole of the nitrogen they require — for the formation of all their parts 
 and products. But so it might of ammonia or its salts, as has already 
 been shown. I shall hereafter lay before you certain considerations 
 which may probably lead us to approximate conclusions in regard to 
 llie relative influence exercised by these two compounds on the general 
 vegetation of the globe. 
 
 Conclusions. — Respecting the form in which nitrogen enters into the 
 circulation of plants, we have therefore, I think, fairly arrived at these 
 deductions : 
 
 1°. That the nitrogen of the atmosphere may, to a small extent, enter 
 directly into the living vegetable either in the form of gas or in solution 
 in water, but that supposing nitrogen lobe in this way appropriated* by 
 the plant, the quantity so taken up could form only a small (juantity of 
 that which vegetables actually contain. 
 
 2°. That ammonia is capable of entering Into plants in very large 
 quantity, and of yielding nitrogen to them, and that in European agri- 
 culture, which employs fermenting animal manure as an important 
 means of promoting vegetable growth, it does appear to yield to cultiva- 
 ted plants a considerable portion of the nitrogen t!)ey contain. 
 
 3°. That nitric acid, in like manner, is capable of entering into and 
 giving up its nitrogen to plants ; and that where this acid is employed as 
 an instrument of culture, the crops obtained owe ])art of their nitrogen 
 to the quantity of this compound which has been ai)plied to the grow- 
 ing plants. TJie same inference may fairly be drawn in regard to the 
 effect of nitric acid — when, in the form of nitrates, it exists or is pro- 
 duced naturally in llie soil. 
 
 4°. That other compound bodies, such as are contained in urine, or are 
 produced during the decay of animal matter, may also enter into the 
 circulation of plants, and yield nitrogen to promote their growth. 
 
 On the whole, however, there seem strong reasons for believing that 
 plants are mainly dependent on ammonia and nitric acid for the nitro- 
 gen they contain ; and that they obtain it most readily, and with least 
 labour, so to speak, from these compounds, — though nature has kindly 
 fitted them for deriving a stinted supply from other sources, when these 
 substances are not present in sufficient abundance. 
 
 How far each of these comjjounds is employed by nature, as an in- 
 strument in promoting the general vegetation of the globe, will be con- 
 sidered in "a subseijucnt lecture. 
 
 * Liebig and others say that plants are incapable of appropriating or assimilating the nitro 
 gen wliich enters into their circulation in the simple state. We shall consider this ques- 
 tion hereafter. 
 
LECTURE V. 
 
 How does the food enter into the circulation of plants — Structure of the several parts of 
 plants— Functions of the root— Course of the sap— Cause of its ascent— Functions of 
 the stem— of the leaves— and of the bark — Circumstances by which the exercise of these 
 
 functions is modified. 
 
 Hav^ing now taken a general view of the source froffi which plants 
 derive the elementary substances of which their solitl parts consist, and of 
 the stales of combination in which these elements enter into the vegeta- 
 ble circulation, — the next step in our inquiry is — hoio are these substan- 
 ces admitted into the- interior of living plants — and under what condi- 
 tions or regulations? We are thus led to study the structure and func- 
 tions of the several parts of plants, and the circumstances by which the 
 exercise of these functions is observed to be modified. 
 
 § 1. General structure of plants^ and of their several j'xirts. 
 
 Plants consist essentially of three parts — the roots, the stem, and the 
 leaves. The former spread themselves in various directions through 
 the soil, as the latter do through the air, and the stem is dependent for its 
 food and increase on the rapidity with which the roots shoot out and ex- 
 tend, and on the number and luxuriance of the leaves. 
 
 We shall obtain a clearer idea of the relative structure of these several 
 parts by first directing our attention to that of the stem. 
 
 The stem consists apparently of four parts — the pith, the wood, the 
 bark, and the medullary rays.. The pith and the medullary rays, how- 
 ever, are similarly constituted, and arc only prolongations of one and 
 the same substance. The pith forms a solid cylinder of soft and spongy 
 matter, which ascends through the central part of the stem, and varies 
 in thickness with the species and with the age of the trunk or branch. 
 The wood surrounds the pith in the form of a hollow cylinder, and is itself 
 covered by another hollow cylinder of bark. In trees or branches of 
 considerable age the wood consists of two parts, the oldest or heart tvood, 
 often of a brownish colour, and the newer external wood or alburnum^ 
 which is generally softer and less dense than the heart wood. The bark 
 also is easily separated into two portions, the inner bark or liher, and 
 the epidermis or outer covering of the tree. The ]:>ith and the bark are 
 connected together by thin vertical columns or partitions, which inter- 
 sect the wood and divide it into triangular segments. A cross section 
 of the trunk or branch of a tree exhibits these thin columns extending 
 in the form of rays, or like the spokes of a wheel, from the centre to 
 the circumference. Though they form in reality thin and continuous 
 vertical plates, yet from the appearance they present in the cross sec- 
 tion of a piece of wood, they are distinguished by the name of medulla- 
 ry rays. 
 
 These several parts of the stem are composed of bundles of small 
 tubes or hollow cylindrical vessels of various sizes, and of different 
 kinds, the structure of which it is unnecessary for us to study. 
 
76 STRUCTURE OF THE STEMS, ROOTS, AND LEAVES OF PLANTS. 
 
 are all intended to contain liquid and gaseous substances, and to convey 
 them in a vertical, and sometimes in a horizontal, direction. The 
 tubes which compose the wood and bark are arranged vertically, as may 
 readily be seen on examining a piece of wood even with the naked eye, 
 and are intended to convey the sap upwards to the leaves and down- 
 wards to the roots. Those of whicli the pith and medullary plates con- 
 sist are arranged horizontally, and appear to be intended to maintain a 
 lateral intercourse between the pith and the bark — perhaps even to place 
 the heart of the tree within tlie influence of the external air. 
 
 Tlie i-oot, thmigh prior in its origin to the stem, may nevertheless for 
 the ]iurpose of illustration be considered as its downward and lateral 
 prolongation into the earth — as the branches are its upward prolonga- 
 tion into the air.* When they leave the lower part of the trunk of the 
 tree, they differ little in their internal structure from the stem itself. 
 As they taper off, however, first the heart wood, then the pith, gradual- 
 ly disappear, till, towards their extremities, they consist only of a soft 
 central v/oody part and its covering of soft bark. These are connected 
 with, or are respectively prolongations of, the new wood and bark of the 
 trunk and branches. At the extreme ])ainls of the roots the bark be- 
 comes white, soft, spongy, and full of |)ores and vessels. It is by these 
 spongy extremities only, or chiefly, that li(]uid and gaseous substances 
 are capable either of entering into, or of making their escape from, the 
 interior of the root. 
 
 Tlie branches- and twigs are extensions of the trunk; and of the 
 former, the leaves may be considered as a still further extension. The 
 fibres of the leaf are minute ramifications of the woody matter of the 
 twigs, are connected through them with the wood of tiie branches and 
 stems, and from this wood receive the sap which tliey contain. Tlie 
 green part of the leaf may be considered as a special expansion of the 
 bark, by which it is fitted to act upon the air, in the same way as the 
 spongy mass into which the bark is changed at the extremity of the root, 
 is fitted to act upon the wafer and other substances it meets with in the 
 soil. For as the fibres of the leaf are connected with the wood of the 
 stem, so the green part of the leaf is connected with its bark, and from 
 this green partthe sap first begins to descend towards the root. 
 
 §2. The functions of the root. 
 The position in which the roots of plants in their natural state are ge- 
 nerally placed, has hitherto i)revented their functions from being so ac- 
 curately investigated as those of the leaves and of the stem. While, 
 therefore, the main purposes they are intended to serve are universally 
 
 * The coiTfctness of this comparison is proved by the fact that, in many trees, the branch 
 if plantHfl will become a root, and (he root, if exposed to the air, will gradually be trans- 
 formed into a branch. The banana in the forest, and the currant tree in onr gardens, are 
 familiar instances of trees spontaneously plantinii their branches, and cruising them to per- 
 form the fnnclions of roots. In like manner, " if the stem of a yonnj; plum ov cherry-tree, 
 or of a willow, be bent in the autumn so that one-hnlfofthe top can be laid in the earth and 
 one-half of the root he at the same time taken carefully up — sheltered at first and after- 
 wards gradually exposed to the cold — and if in the following year th^ remaining fiart of the 
 (op and root be treated in the same way, the branches of the top will become roots, and the 
 ramifications of the ruots will bef^ome bnmche.s, producing leaves, flowers, and fruit in due 
 season. — ['Lo\n\ori^» Ihicychjiadia of Ai^ricuUiire.], The tree is thus reversed in position, 
 and the roots and branches being thus mutually convertible caimot be materially unlike in 
 Jfeneral structure. 
 
ROOTS ABSORB AQUEOUS SOLUTIONS, AND OXYGEN. 77 
 
 Known and understood, the precise way in which these ends are accom- 
 plished by tiie roots, and the powers with which they are invested, are 
 still to a considerable degree matters of dispute. 
 
 I. It appears certain that they are possessed of the power of absorb- 
 ing water in large quantity from the soil, and of transmitting it upwards 
 to the stem. The amount of water thus absorbed depends greatly upon 
 the nature of the soil and of the climate in which a plant grows, but 
 much also upon the specific structure of its leaves and the extent of its 
 foliage. 
 
 II. The analogy of the leaves and young twigs would lead us to 
 suppose that, when in a proper state of moisture, the roots should 
 also be capable of absorbing gaseous substances from the air which 
 pervades the soil. Experiment, however, has not yet shown this to be 
 the case. 
 
 We know, however, that they are capable of absorbing gases through 
 the medium of water. For if the roots of a plant are placed in water 
 containing carbonic acid in the state of solution, this gas is found gradu- 
 ally to disappear. It is extracted from the water by the root^s. And if 
 the water in whicli the roots are immersed be contained in a bottle only 
 partially filled v/ith the liquid, while the remainder is occupied by at- 
 mospheric air, the oxygen in this air will also slowly diminish. It will 
 be absorbed by the roots through the medium of the water.* 
 
 Again, if in the place of the atmospheric air in this bottle, carbonic 
 acid be substituted, the plant will droop and in a few days will die. The 
 same will take place, if instead of common air or carbonic acid, nitro- 
 gen or hydrogen gases be introduced into the bottle. The plant will not 
 live when its roots are exposed to the sole action of any of the three. 
 
 It is obvious, therefore, that the roots of plants absorb gaseous sub- 
 stances from the air which surrounds their roots, at least indirectly and 
 through the medium of water. It appears also that from this air they 
 have the power of selecting a certain portion of oxygen when this gas is 
 present in it. Thirdly, that though they can absorb carbonic acid to a 
 limited amount without injury to the plant, yet that a copious supply of 
 this gas, unmixed with oxygen, is fatal to vegetable life. This deduction 
 is confirmed by the fact that, in localities where carbonic acid ascends 
 through fissures in the subjacent rocks and saturates the soil, the growth 
 of grass is found to be very much retarded. And, lastly, since nitrogen 
 is believed not to be in itself noxious to vegetable life, the death of the 
 plant in water surrounded by this gas, is supposed to imply that the pre- 
 sence of oxygen is necessary about the roots of a growing and healthy 
 plant, and that one of the special functions of the roots is constantly to 
 absorb this oxygen. 
 
 This supposition is in accordance with the fact that, in the dark, the 
 leaves of plants absorb oxygen from the atmosphere ; for we have al- 
 ready seen reason to expect that, from their analogous structure, the roots 
 and leaves in similar circumstances should perforrn also analogous func- 
 tions. At the same time, if the roots do require the access and presence 
 
 * It will be recollected that water absorbs about 4 per cent, of its bulk of air from the at- 
 mosphere, of which about ene-third is oxygen. If the roots extract this oxygen from the 
 water, the latter will again drink in a fresh portion from the atmospheric air which floata 
 above it. 
 
 4* 
 
78 DO SOLID SUBSTANCES ENTER THE ROOTS? 
 
 of oxygen in the soil, it would further appear that those of some plants 
 require it more than those of others ; inasmuch as some genera, like the 
 grasses, love an open and friable soil, into which the air is more com- 
 pletely excluded. — [Sprengel, Cheniie, II., p. 337.] 
 
 III. We have in a former lecture (IV. p. 64) concluded from facts 
 there stated, that solid substances, which are soluble in water, accom- 
 pany this liquid when it enters into the circulation of the plant. This 
 appears to be true both of organic and inorganic substances. Potash, 
 soda, lime, and magnesia thus find their way into the interior of plants, 
 as well as those substances of animal and vegetable origin lo which the 
 observations made in the fourth lecture were intended more especially to 
 apply. Even silica,* considered to be almost insoluble in water, enters 
 by the roots, and is found in some cases in considerable quantities in the 
 stem. Some persons have hence been led to conclude that solid sub- 
 stances, undissolved, if in a minute state of division, may be drawn into 
 the pores of the root and may then be carried by the sap upwards to the 
 stem. 
 
 Considered as a mere question of vegetable mechanics, argued as such 
 among ])hysioiogists, it is of little moment whether we adopt or reject 
 this opinion. One ph3'siologist may state that the pores by which the 
 food enters into the roots are so minute as to baffle the powers of the best 
 constructed microscope, and, therefore, that to no particles of solid mat- 
 ter can they by possibility give admission — while another may believe 
 solid matter to be capable of a mechanical division so minute as to pass 
 through the pores of the finest membrane. As to the mere fact itself, it 
 matters not which is right, or which of the two Ave follow. The adoption 
 of the latter opinion implies in itself merely that foreign substances, 
 unnecessary, perhaps injuriousto vegetable life, may be carried forward 
 by the flowing juices until in some still part of the current, or in some 
 narrower vessel, they are arrested and there permanently lodged in the 
 solid substance of the plant. 
 
 By inference, however, the adoption of this opinion implies also, that 
 the inorganic substances found in plants, — those which remain in the 
 form of ash when the plant is burned, — are accidental on\y , not essential 
 to its constitution. For since they may have been introduced in a mere 
 state of minute mechanical division suspended in the sap, they ought to 
 consist of such substances chiefly as the soil contains in the greatest 
 abundance, and they ought to vary in kind and relative quantity with 
 every variation in the soil. In a clay land the ash should consist chiefly 
 of alumina, f in a sandy soil chiefly of silica. But if, as chemical in- 
 quiry appears to indicate, the nature of the ash is not accidental, but es- 
 sential, and in some degree constant, even in very diflerent soils, this 
 latter inference is inadmissible;^ — and in reasoning backwards from this 
 fact, we find ourselves constrained to reject the opinion that substances 
 are capable of entering into the roots of plants in a solid state — and this 
 without reference at all to the mechanical question, as to the relative size 
 of the pores of the spongy roots or of the ]iarticles into which solid mat- 
 ter may be divided. 
 
 ' Silica is the name given by chemists to the pure matter of flint or of rock crystal. Sand 
 and sandstones consist almost entirely of fjllica. 
 
 t Alumina is the pvure earth of clay. 
 
SELECTING POWER OF THE ROOTS. 79 
 
 IV. "We are thus brought to the consideration of the alleged selecting 
 power of the roots, which, if rightly attributed to them, must be con- 
 sidered as one of the most important functions of which they are pos- 
 sessed. It is a function, however, the existence of which is disputed by 
 many eminent physiologists. But as the adoption or rejection of it will 
 materially influence our reasonings, as well as our theoretical views, ia 
 regard to some of the most vital processes of vegetation, — it will be pro- 
 per to weigh carefully the evidence on which this power is assigned to 
 the roots of plants. 
 
 1°. The leaves, as we shall hereafter see, possess in a high degree 
 the. power of selecting from the atmosphere one or more gaseous sub- 
 stances, leaving the nitrogen, chiefly, unchanged in bulk. The absorp • 
 tion of carbonic acid and the diminution of the oxygen in the experi 
 ments above described, appear to be analogous effects, and would seem 
 to imply in the roots the existence of a similar power. 
 
 2°. Dr. Daubeny found that pelargoniums, barley {hordeum vulgare), 
 and the winged pea {lotus tetragonolohus), though made to grow in a 
 soil containing much strontia,* appeared to absorb none of this earth, foi 
 none was found in the ash left by the stem and roots of the plant when 
 burned. In like manner De Saussure observed that polygonum persi- 
 caria refused to absorb acetate of lime from the soil, though it freely took 
 up common salt. — [Lindley's Theory of Horticulture, p. 19.] 
 
 3°. Plants of different species, growing in the same soil, leave, when 
 burned, an ash which in every case contains either different substances, 
 or the same substances in unlike proportions. Thus if a bean and a 
 grain of wheat be grown side by sida, the stem of the plant from the lat- 
 ter seed will be found to contain silica, from the former none.f 
 
 4°. But the same plant grown in soils unlike in character and com- 
 position, contains always — if they are present in the soil at all — very 
 nearly the same kindj of earthy matters in nearly the same proportion. 
 Thus the stalks of corn plants, of the grasses, of the bamboo, and of many 
 others, always contain silica, in whatever soil they grow, or at least are 
 capable of growing with any degree of luxuriance. 
 
 With the view of testing this point, Lampadius prepared five square 
 ])atchesof ground, manured them with equal quantities of a mixture of 
 horse and cow dung, sowed them with equal measures of the same 
 wheat, and on four of these patches strewed respectively five pounds of 
 finely powdered quartz (siliceous sand), of chalk, of alumina, and of 
 carbonate of magnesia, and left one undressed. The produce of seed 
 from each, in the^above order, weighed 24i, 28|, 26i, 2li, and 20 ounces 
 respectively. The grain, chaff", and straw, from each of the patches 
 left nearly the same quantity of ash— tlie weights varying only from- 3*7 
 to 4-08 per cent., and the roots and chaff'being richest in inorganic mat- 
 ter. The relative proportions of silica, alumina, lime, and magnesia, 
 
 * Watered with a solution of nitrate of strontia. Strontia is an earthy substance resem- 
 Ming lime, which is found in certain rocks and mineral veins, but which has not hitherto been 
 observed in the ashes of plants. 
 
 t It is not strictly correct that the bean will absorb no silica, but the quantity it will take up 
 will be only one-thirteenth of that taken up by the wheat plant— the per centage of silica in 
 the ash of bean straw beinff, according to Sprcngel, only 0-22, while in wheat straw it is 2-87 
 per cent. Pea straw contains four times as much as that of the bean, or 0996 per cent. 
 
 X For more precise information on this point, see the subsequent lectures, " Onthe inor- 
 ganic constituents of plants^" (Part II.) 
 
80 PLANTS MAY ABSORB POISONOUS SUBSTANCES. 
 
 were the same in all. — [Meyen JahreshericJit, "1839, p. 1.] Provided, 
 therefore, the substances which plants prefer be present in the soil, the 
 kind of inorganic matter they take up, or of ash they leave, is not mate- 
 rially affected by the presence of other substances, even in somewhat 
 larger (]uantity. 
 
 These facts all point to the same conclusion, that the roots have the 
 power of selecting from the soil in which they grow, those substances 
 which are best fitted to promote the growth or to maintain the healthy 
 condition of the plants they are destined to feed. 
 
 5°. It lias been stated above that the roots of certain plants refuse to 
 absorb nitrate of strontia and acetate of lime, though presented to them 
 in a state of solution — the same is true of certain coloured solutions which 
 have been found incapable of finding their way into the circulation of 
 plants whose roots have been immersed in them. On the other hand, 
 it is a matter of frequent observation that the roots absorb solutions con- 
 taining substances which speedily cause the death of the plant. Arsenic, 
 opium, salts of iron, of lead, and of copper, and many other substances, 
 are capable of being absorbed in quantities which prove injurious to the 
 living vegetable — and on this ground chiefly many physiologists refuse to 
 acknowledge tliat the roots of plants are by nature endowed with any 
 definite and constant power of selection at all. But tliis argument is of 
 equal force against the possession of such a ]X)wer by animals or even by 
 man himself; since, with our more perfect discriminating powers, aided 
 by our reason too, we every day swallow with pur food what is more or 
 less injurious, and occasionally even fatal, to human life.* 
 
 On the whole, therefore, it appears most reasonable to conclude that 
 the roots are so constituted as (1°) to be able generally to select from the 
 soil, in preference, those substances which are most suitable to the nature 
 of the plant — (2°) where these are not to be met with, to admit certain 
 others in their steadf — (3°) to refuse admission also to certain substan- 
 ces likely to injure the plant, though unable to discriminate and reject 
 every tiling hurtful or unbeneficial which may be presented to them in 
 a state of solution. 
 
 The objectjifjnature, indeed, seems to be to guard the plant against 
 the more common and usual dangers only — not against such as rarely 
 present themselves in the situations in which it is destined to grow, or 
 against substances which are unliJiely even to demand admission into its 
 roots. How useless a waste of skill, if I may so speak, would it have 
 been to endow the roots of each plant with the power of distinguishing 
 and rejecting opium and arsenic and the thousand otlier })oisonous sub- 
 stances which the physiologist can present to them, but which in a state 
 of nature — on its natural soil and in its natural climate — the living vege- 
 table is never destined to encounter ! 
 
 ' I may here remark that it is by no means an extraordinary power which these circum- 
 stances seem to sliow the roots of plants to possess, ii tlie presence of oxvcen, nitrogen, 
 and carbonic acid, in equal quantitie?, water will prefer and will select the lallcr. From a 
 mixture of lime and magnesia, acetic or sulphuric acid will select and separate the former. 
 Is it unreasonable to suppose the roolsof plants— the organs ofa living being— to be endowed 
 with powers of discrimination at least as great as those possessed by dead matter? 
 
 t This conclusion is not strictly contained in the premises above slated, but the facts from 
 which it is drawn will be fully explained in treating of the inorganic constituents of plants. 
 'i is introduced here for the pm-pose of giving a complete view of what appears to be the 
 • ■••--'r<5 '^'■'^is''riminj»tion posscsseid bv the root. 
 
EXCRETORY PbWER OF THE ROOTS. 81 
 
 V. Another function of tiie roots of plants, in regard to which physiol- 
 ooists are divided in opinion at the present day, is what is called their 
 excretory poiver. 
 
 1°. When barley or other grain is caused to germinate in pure chalk, 
 acetate ofhme* is uniformly found to be mixed with it after the germi- 
 nation is somewhat advanced {J3ecquerel and Mateucci, Ann. de Cliem. 
 et de Phys., 1 v., p. 310.) In this case the acetic acid must have been given 
 off (excreted) by the young roots during the germination of the seed. 
 
 This fact mav be considered as the foundation of the excretory theory 
 as it is called. 'This theory, supported by the high authority of Dccan- 
 doUe, and illustrated by the apparently convincing experiments of Ma- 
 caire, {Ann. de Chim. el de Phys., lii., p. 2-25,) has more recently been met 
 by counter-experiments of Braconnot, (Ixxii. p. 27,) and is now in a great 
 measure rejected by many eminent vegetable physiologists. It may m- 
 deed be considered as quite certain that the ai)plication of this theory by 
 Decandolie and others to the explanation of the benefits arising from a 
 rotation of crops, is not confirmed, or pmue^Z to be correct, by any exper- 
 iments on the subject that have hitherlo been published. f 
 
 According to Decandolie, plants, like animals, have the ])0wer of se- 
 lecting from their food, as it passes through their vascular system, such 
 portions as are likely to nourish them, and of rejecting, by their roots, 
 * Acetate of lime is a combination of acetic acid or vinegar with lime derived from the chalk, 
 t The discordant results of Macaire and Braconnot were as follow : 
 
 1<^ Macaire observed that when plants of Cho-ndrilla Muralis were grown m ram water 
 they imparted to it something of the smell and taste of opium. Braconnot conhrnied this, 
 but altribuled it to wounds in the roots which allowed tiie proper juice of the plant to escape. 
 He says it is almost impossible to free the young roots from the soil m which they have gi-own, 
 without injuring theiu and causing the sap to exude. .,.,.. 
 
 2° Euphorbia Peplus (Petty Sparge) imparted to the water in which it grew a gummi- 
 resinous substance of a very acrid taste. In the hajids of Braconnot it yielded to l.he water 
 scarcely any organic mailer, and Uiat only slightly bitterish. .,.,-, 
 
 3° Braconnot washed the soil in whicli plants of /Ju/p/iorim Breuni and Asdepias Incar- 
 nala were growing in pots, and obtained a solution containing earthy and alkaline salts with 
 only a trace of organic matter. , , ^ 
 
 He also washed the soil in which the Pi'ppy (Papaver Somniferum) had been grown ten 
 vears succes-^iv-ly. The sola' Ion, besiiies iuorganic earthy and alkaline saits, gave a consid- 
 erable fiuaatiry of acetic acid (in the form of acetate of lime) and a trace of brown organic 
 matter. He infers tliat these several plants do not excrete any organic matter m sufficient 
 CMiantity to be injiu-ious to themselves. . ,., i . r tit „., 
 
 4° Macaire obsei'ved that when separate portions of the roots of the same plant ot Mercu- 
 rialis Atmua were immersed in separate vessels, the one containing pure water and the 
 other a solution of acetate of lead,— the solution of lead was absorbed by the plant,-Twas to 
 be traced in every part of it, and aflei-wards was partially transmitted to the pure water. Bra- 
 connot observed Uie same residts, but he found the entrance of the lead into the second vessel 
 to be owing to the asceat of the fluid up the outer surface of the one root and down the exterior 
 of the other, and that, by preventing the possibihty of this passage, no lead could be detected 
 -mong the pure water. ... ^ -n i n^ 
 
 Tlie conclusion^ of Macaire, therefore, in favour of the rotation theory of Decandolie 
 
 scure and so littJe known as to justify the presumption tliat some other explanation inust 
 be t^iven of iheiieneral system ot" rotation." Various illustrations have been given by ditter- 
 ent^'ob'^ervers of tJiis supposed excreting power of the roots. Among the most recent are 
 those oi Nietner, who ascribes the luxuriant rye crops obtained without manure after three 
 years of clover, to the excretions of this plant in the soil, which, like tJiose of the ppa and 
 bean to the whe-U, lie supposes *o be nourishing food to the rye. He also states that the 
 beet or the turnip after tobacco has an unpleasant taste, and is scarcely eatable, which he 
 attributes t ) tlie excretions of the tobacco plant. Meyen ascribes the etfect of the clover to 
 (he "recn manure supplied by its roots and stubble and tliat of the tobacco to the undecom- 
 posed organic substances contained in the sap and substance of the roots and stems of this 
 plant of which so large a quantity is left behind in the field.— [Mey en's Jahresbencht, IQ3J, 
 p. 5.]— These objections of Meyen are not without their weight, but we shall hereafter see 
 lliut they embocjy only half the truth. 
 
82 EXPERIMENTS OF DE SAUSSURE. 
 
 when the sap descends, such as are unfit to contribute to their support, 
 or would be hurtful to them if not rejected from their system. He further 
 supposes that, after a time, the soil in which a certain kind of plant 
 grows becomes so loaded wiih this rejected matter, that the same plant 
 refuses any longer to flourish in it. And, thirdly, that though injurious 
 to the plant from which it has been derived, this rejected matter may be 
 wholesome food to plants of a different order, and hence the advantage to 
 be derived from a rotation of crops. 
 
 There seems no good reason to doubt that the roots of plants do at 
 times — it may be constantly — reject organic substances from their roots. 
 The acetic acid given off during germination, and the same acid found 
 by Braconnot in remarkable quantity in the soil in which the poppy 
 {papaver somniferum) has grown — may be regarded as sufficient evi- 
 dence of the fact — but the quantity of such organic matter hitherto de- 
 tected among what may be safely viewed as the real excretions of plants, 
 seems by far too small to account for the remarkable natural results at- 
 tendant upon a rotation of crops. 
 
 The consideration of these results, as well as of the general theory of 
 such a rotation, will form a distinct topic of consideration in a subsequent 
 part of these lectures. I shall, therefore, only mention one or two facts 
 wiiich seem to me capable of explanation only on the supposition that 
 the roots of plants are endowed with the power of rejecting, and that 
 they do constantly reject, when the sap returns from the leaf, some of 
 the substances which they had previously taken up from the soil. 
 
 1°. De Saussure made numerous experiments on the (juantity of ash 
 pe cent, left by the same plant at different periods of its growth. Among 
 other results obtained by him, it appeared — 
 
 A. That the quantity of incombustible or inorganic matter in the dif- 
 ferent parts o£.the plant was different at different periods of the year. 
 Thus the dry leaves of the horse chestnut, gathered in May, left 7*2 per 
 cent., towards the end of July 8-4 per cent., and in the end of Septem- 
 ber 8-6 per cent, of ash; the dry leaves of the hazel in June left 6-2, 
 and in September 7 ])er cent. ; and those of the poplar (populus nigra) 
 in May 6-6, and in September 9-3 per cent, of ash. These results are 
 easily explained on the supposition that the roots continued to absorb 
 and send up to the leaves during the whole summer the saline and 
 earthy substances of which the ash consisted. But — 
 
 B. He observed also that the quantity of the inorganic substances in 
 — or the ash left by — the entire plant, diminisfied as it approached to 
 maturity. Thus liie dry plants of the vetch, of the golden rod [solida- 
 go vulgaris); of^ the turnsol {helianthus annuus), and of wheat, left res- 
 pectively of ash, at three different periods of their growth, [Davy's 
 Agricultural Chemistry, Lecture HI,] — 
 
 Before flowering. 
 per cent. 
 Vetch ...... 15 
 
 Golden rod ... 9-2 
 Turnsol .... 14-7 
 
 Wheat .... 7-9 
 
 This diminution in the proportion of ash, might arise either from an 
 increase in the absolute quantity of vegetable matter in the plants ac- 
 
 In flower 
 
 Seeds ripe, 
 
 2)er cent. 
 
 jier cent. 
 
 12-2 
 
 6-6 
 
 5-7 
 
 5-0 
 
 13-7 
 
 9-3 
 
 5-4 
 
 3-3 
 
PROPORTION OF SILICA IN THE ASH OF PLANTS. 83 
 
 companying their increase in size — or from a portion of the saline and 
 earthy matters tiiey contained being again rejected by the roots. But 
 if the former be the true explanation, the relative proportions of the 
 several substances of which the ash itself consisted, in the several cases, 
 should have been the same at the several periods when the experiments 
 were made. But this was by no means the case. Thus, to refer only 
 to the quantity of silica contained in the ash left by each of the above 
 plants at the several stages of their growth, the ashes of the 
 
 Before flowering. In flower. Seeds ripe. 
 
 per cent. per cent. per cent. 
 
 Vetch contained . . . 1'5 l-o 1-75 
 
 Golden rod 1-5 1-5 3-5 
 
 Turnsol ...... 1-5 1-5 3-75 
 
 Wheat 12-5 26-0 51-0 
 
 If, then, the proportion of silica in the ash increased in some cases 
 four-fold, while the whole quantity of ash left by the ])lant decreased, it 
 appears evident that some part of that which existed in the plant during 
 the earlier periods of its growth must have been excreted or rejected by 
 the roots, as it advanced towards maturity. 
 
 2°. This conclusion is confirmed and carried farther by another con- 
 sideration. The quantity of ash left by the ripe wheat plant, in the 
 above experiments of De Saussure, amounted to 3*3 per cent. ; — of 
 which ash, 51 percent., or rather more than one-half, was silica. This 
 silica, it is believed, could oiily have entered into the circulation of the 
 plant in a state of solution in water, and could only be dissolved by the 
 agency of potash or soda. But, according to Sprengel, the potash, soda, 
 and silica, are to each other in the grain and straw of wheat, in the pro- 
 portions of — 
 
 Potash. Soda. Silica- 
 
 Grain .... 0-225 0-24 0-4 
 
 Straw .... 0-20 0-29 2-87 
 
 Or, supposing the grain to equal one-half the weight of the straw — 
 their relative proportions in the whole plant will b^^nearly as 21 potash, 
 27 soda, 205 silica, or the weight of the silica is upwards of four times 
 the weights of the potash and soda taken together. 
 
 Now silica re(iuires nearly half its weight of potash to render it .solu- 
 ble in water,* or three-fifths of its weight of a mixture of nearly equal 
 parts of potash and soda. The quantity of these alkaline substances 
 found in the plant, therefore, is by no means sufficient to have dissolved 
 and brought into its circulation the whole of the silica it contains. One 
 of two things, therefore, must have taken place. Either a portion of 
 the })otash and soda present in the plant in the earlier stages of its 
 growth must have escaped from its roots at a later stage, f leaving the 
 silica behind it — or the same quantity of alkali must have circulated 
 through the plant several limes — bringing in its burden of silica, deposit- 
 
 * A soluble glass may be made by melting together in a crucible for six hours 10 parts of 
 carbonate of potash, 15 of silica, and 1 of cliarcoal powder. 
 
 t De Saussure {}ops not state the exact relative quantitios of potash and soda at the several 
 periods of the growtli of wheat, tliough they appear to have graikally diminished. It 
 seems, indeed, to be- true of many plant.s, that the potash and soda they contain diminishes 
 in quantity as their age increases. Thus tfie weight of potash in the juice of the ripe or 
 sweet grai)e, is said to be less than in the unripe or sour grape — and the leaves of the potato 
 have been found more rich in potasli before than after blossoming (Liebig). 
 
84 CAN THE ROOTS MODIFY THE F30D OF PLANTS? 
 
 ing it in the vascular system of tl-ie plant, and again returning to the 
 soil for a fresli sup[)ly. In either case tJie roots must have allowed it 
 egress as well as ingress. But the fact, that the j9ro/?or^ion of silica in 
 the [)lant goes on increasing as it continues to grow, is in favour of the 
 latter view — and renders it very prohahle that the same (juantity of al- 
 kali returns again and again into the circulation, bringing with it sup- 
 plies of silica and probably of other substances which the plant requires 
 from the soil. And while this view appears to be the more probable, it 
 also presents an interesting illustration of what may j}''of->cibly he the 
 kind of function discharged by the potash and other inorganic substances 
 found in tiie substance of plants — a question we shall hereafter have oc- 
 casion to consider at some length. 
 
 The above considerations, therefore, to which I might add others of a 
 similar kind, satisfy me that the roots of plants do possess the power of 
 excreting various substaYices which are held in solution by the sap on its 
 return from the stem — and which having performed their functions in 
 the interior of the plant are no longer fitted, in their existing condition, 
 to minister to its sustenance or growth. Nor is it likely that this excre- 
 tory ]io\ver is restricted solely to the emission of inorganic substances. 
 Other soluble matters of organic origin are, no doubt, permitted to es- 
 cape into the soil — tliongh whether of such a kind as must necessarily 
 be injurious to the plant from which they have been extruded, or to such 
 a degree as alone to render a rotation of crops necessary, neither reason- 
 ing nor experiment has hitherto satisfactorily shown. 
 
 VI. The roots have the power of absorbing, and in some measure of 
 selecting, food from the soil — can they also modify or alter it as it passes 
 through them? A colourless sap is observed to ascend through the 
 roots. From the very extremity up to the foot of the stem a cross sec- 
 tion exhibits little trace of colouring matter, even when the soil contains 
 animal and vegetable substances wliich are soluble, and which give dark 
 coloured solutions, [such as the liquid manure of the fold-yanl.] Does 
 such matter never enter the root ? If it does, it must be speedily changed 
 or transfonned into*ew compounds. 
 
 We havejisj^et too few experiments upon this subject to enable us to 
 decide with any degree of certainty in regard to this function of the root. 
 
 It is probable, however, that as the sap passes through the plant, it is 
 constantly, though gradually, undergoing a series of changes, from tiie 
 time when it first enters tJie root till it again reaches it on its return from 
 the leaf 
 
 Can we conceive the existence of Rwy powers in the root, or in the 
 whole plant, of a still more refined kind ? The germinating seed gives 
 off acetic acid into the soil, — does this acetic acid dissolve lime from the 
 soil and return with it again, as some suppose (Liebig), into the circula- 
 tion of the plant?* Is acetic acid produced and excreted by the seed 
 for this very refined purpose? We have concluded that in the wheat 
 plant the potash and soda probably go and come several times during its 
 growth, and the ripening of its seed. Is this a contrivance of nature to 
 
 * Draconnot found acetate of lime in very small quantities to be singularly hurtful to vege- 
 tation, and acetate of magnesia a little less so.. He otilv mentions, however, some experi- 
 ments upon merairialis wmua, [Attn, de Chim. et de P/d/s. Ixxii. p. 3G,] and as Saussure 
 found that some plants actually refused to take it up at all, those acetates may not be equally 
 "-i'lrious to all plants. 
 
THE SAP ASCENDS THROUGH THE WOOD. 85 
 
 make up for the scarcity of alkaline substances in the soil — or would the 
 same mode of operation be employed if potash and soda were present 
 in greater abundance ? Or where the alkalies are present in greater 
 abundance, might not more work be done by them in the same 
 time, — might not the plant be built up the faster and the larger, when 
 there were more hands, so to speak, to do the work ? Is the action of 
 inorganic substances upon vegetation to be explained by the existence 
 of a ])o\ver resident in the roots or other parts of plants, by which such 
 operaiions as this are directed or superintended? There are many 
 mysteries connected with the nature and phenomena of vegetable life, 
 which we have been unable as yet to induce nature to reveal to us.* 
 But the morning light is already kindling on the tops of the mountains, 
 and we may hope that the deepest vallies will not forever remain obscure. 
 
 § 3. Tke course of the sap. 
 
 If the trunk of a tree be cut off above the roots, and the lower extrem- 
 ity be immediately plunged into a solution of madder or other colouring 
 substances, the coloured liquid will ascend and will gradually tinge the 
 wocmI. This ascent will continue till the colour can also be observed 
 in the nerves of the leaf. If at this stage in the experiment the trunk 
 be cut across at various heights, the wood alone will appear coloured, 
 the bark remaining entirely untinged. But if the process be allowed 
 si ill to continue when the coloured matter has reached the leaf, and after 
 some further time the stem be cut across, the bark also will appear dyed, 
 and the tinge will be perceptible further and further from the leaf the 
 longer the experiment is carried on, till at length both bark and wood 
 will be coloured to the very bottom of the stem. 
 
 Or if the root of a living plant, as in the experiment of Macaire de- 
 tailed in a preceding note, be immersed in a metallic solution — such 
 as a solution of acetate of lead, — which it is capable of absorbing with- 
 out immediaK'. injury, and different portions of the plant be examined 
 after the lapse of different periods of time, — first the stem, afterwards 
 the leaves, then the bark of the upper part of the stem, and lastly that 
 of the lower part of the stem, will exhibit traces of lead. 
 
 These experiments show that the sap which enters by the roots as- 
 cends through the vessels of the wood, diffuses itself over the surface 
 of leaves, and then descends by the bark to the extremities of the root. 
 
 But what becomes of the sap when it reaches the root? Is it deliver- 
 ed into the soil, or does it recommence the same course, and again, re- 
 peatedly perhaps, circulate through the stem, leaves, and bark ? This 
 <|uestion has been partly answered by what has been stated in the pre- 
 ceding section. When the sap reaches the extremity of the root, it ap- 
 pears to give off to the soil both solid and fluid substances of a kind and 
 
 * The roots of treea will travel to comparatively great distances, and in various directions, 
 in search of water: the roots of sainfoin (Esparsette) will penetrate 10 or 12 feet through the 
 calcareous rubbly subsoil, or down the fissures of limestone rocks on which they deUght to 
 grow. Is this the result of some perceptive power in the plant — or is it merely by accident 
 that the roots display these tendenciea'? 
 
 Those who are in any degree acquainted with the speculations of the German physiolo- 
 gists of the greatest name — in regard to the^owZ and even the immortality of plants — will not 
 accuse me of goin^ very far in allutling to the possible existence of some sucli perceiitive 
 
86 CAPILLARY ATTRACTION. 
 
 to an amount which probably differ with every species of j)lant. The 
 remainder of llie sap and of the substances it holds in solution must be 
 diffused through the cellular spongy terminations of the roots, and, with 
 the new supply of liquid imbibed from the soil, returned again to the 
 stem with the ascending current. 
 
 But what causes the sap thus to ascend and descend ? By what 
 power is it first sucked up through the roots, and afterwards forced down 
 again from the leaves? Several answers have been given to this ques- 
 tion. 
 
 1°. When the end of a wide tube, either of metal or of glass, is 
 plunged into water, the liquid will rise within the lube sensibly to the 
 same level as that at which it stands in the vessel. But if a capillary* 
 lube be employed instead of one with a wide bore, the liquid will'rise, 
 and will permanently remain at a considerably higher level within than 
 without the tube. The cause of this rise has been ascribed to an attrac- 
 tion which the sides of the tube have for the licjuid, and which is suffi- 
 ciently strong to raise it and to keep it up above the proper level of the 
 water. The force itself is generally distinguished by the name o^ capil- 
 lary attraction. 
 
 Now, the wood of a tree, as we have seen, is composed of a mass of 
 fine tubes, and through these the sap has been said to rise by capillary 
 attraction. But if the top of a vine be cut off when it is juicy and full 
 of sap, the liquid will exu(.le from the newly formed surface, and if the 
 air be excluded, will flow for a length of time, and may be collected in 
 a considerable quantity [Lindley's Theory of Horticulture, p. 47, note]. 
 Such a flow of the sap is not to be accounted for by mere capillary at- 
 traction — the sides of tubes cannot draw up a fluid beyond their own 
 extremities. 
 
 2°. To supply the defect of this hypothesis, De Saussure supposed 
 that the fluid at first introduced by capillary attraction into the extremi- 
 ties of the root, was afterwards ])ropelled upwards by the alternate con- 
 traction and expansion of thc/tybes of which the wood of the root and 
 stem is comjjosed. This alternate contraction and expansion he also 
 supposed to be caused by a peculiar irritating property of the sap itself, 
 which caused^cach successive part of (he tube into which it found ad- 
 mission to contract for the purpose of expelling it. Mr. Knight also as- 
 cribed the ascent of the sap to a similar contraction of certain other parts 
 of the stem. Being once raised, he supposed it to return again or de- 
 scend by its own weight — but in drooping branches it is obvious that the 
 sa[) must be actually driven or drawn upwards from the leaves on its re- 
 turn to the root. These ex})lanations, therefore, are still unsatisfactory. 
 
 3^. If one end of an open glass tube be covered with a piece of mois- 
 tened bladder or other fine animal membrane, tied tightly over it, and a 
 strong solution of sugar in water be then poured into the open end of the 
 tube, so as to cover the membrane to the do|)th of several inches, and if 
 the closed end be then introduced to the depth of an inch below the sur- 
 face of a vessel of pure water, the water will after a short time pass 
 through the bladder inwards, and the column of lifjuid in the tube will 
 increase in height. This ascent will continue, till in favourable circum- 
 
 * Glass tubes perforated by a very fine bore, like a human hair, are called capillary tabes, 
 Buch are those of which thermometers are usually made. 
 
CAUSE OF THE ASCENT OF THE SAP. 87 
 
 Stances the fluid will reach the height of several feet, atul will How out 
 or run over at the open end of the tube. At the same time the water in 
 the vessel will become sv/eet, indicating that while so much liquid has 
 passed through the membrane inwards, a quantity has also passed out- 
 wards, carrying sugar along with it.* To these opposite effects Duiro- 
 chet, who first drew attention to the fact, gave the names of Endosmose, 
 denoting the inward progress, and Exosmose,\he outward progress of the 
 fluid. He supposed them to be due to the action of two opposite cur- 
 rents of electricity, and he likens the phenomena observed during the 
 circulation of the sap in plants, to the aj)pearances presented during the 
 above experiment. 
 
 Without discussing the degree pfprobabilhy which exists as to the in- 
 fluence of electricity in producing the phenomena of endosmose and ex- 
 osmose, it must be admitted that the apjjearances themselves bear a 
 strong resemblance to those presented in the absorption and excretion of 
 fluids by the roots of plants — and point very distinctly to at least a 
 kindred cause. 
 
 Thus, if the spongy termination of the root represent the thin porous 
 membrane in the above experiment — the sap with which the tuhes of 
 the wood are filled, the artificial solution introduced into the experimen- 
 tal tube — and the water in the soil, the water or aqueous solution into 
 which the closed extremity of the tube is introduced, — we have a series 
 of conditions precisely similar to those in the experiment. Fluids ought 
 consequently to enter from the soil into the roots, and thence to ascend 
 into the stem, as in nature they ap[)car to do. 
 
 This ascent, we have said, will continue tiil the fluid in the tubes of 
 the wood (the sap) is reduced to a density as low as that of the liquid 
 entering the roots from the soil. But in a growing tree, clothed with 
 foliage, this will never happen. The leaves are continually exhaling 
 aqueous vapour, as one of their constant functions, and sometimes in 
 very large (juantity. The sap, therefore, when it reaches the leaves, is 
 concentrated or thickened, and rendered more dense by the separation 
 of the water, so that when it descends to the root, and again begins its 
 upward course, it will admit of large dilution before its density can be 
 so far diminished as to approach that of the comparatively pure water 
 which is absorbed from the soil. And this illustration of the ascent of 
 the sap appears the more correct from the obvious purpose it points out 
 — (in addition to others long recognised) — as served by the evaporation 
 which is constantly taking place from the surface of the leaf. 
 
 Still the cause of the ascent of the sap is not the more clear that we 
 can imitate it in some measure by an artificial experiment. But it will 
 be conceded by the strictest reasoners on physical phenomena, that to 
 have obtained the command, or even a partial control, over a natural 
 
 * Instead of sugar, common salt, gum, or other soluble substances may be dissolved in 
 the water introduced at first into the tube, and tlie denser this solution the larger the quantity 
 of water which will enter by the membrane, and the greater the height to which the column 
 will rise. It ceases in all cases to rise only when tlie portions of liquid within and without 
 the membrane attain nearly to the same density [i. e. contain nearly the same weight of solid 
 matter in solution.] Instead of pure water the vessel into which the extremity of the tube 
 is plunged may also contain a weak solution of some soluble substance — such as lime or soda 
 — in which case while llie sugar, orsalt, or gum, will pass outwards, in smaller quantity, the 
 lime or soda will pass inwards, along with the currents of water in which they are severally 
 dissolved. 
 
88 DECOMPOSITION TAKES PLACE IN THE STEM. 
 
 power, is a considerable step towards a clear conception of the nature of 
 that power itself. If the phenomena of endosmose can hereafter be 
 clearly and indubitably traced to the agency of electricity we shall have 
 advanced still another step, and shall be enabled to devise other means 
 by which a more perfect imitation of nature may be elTected, or a more 
 complete control asserted over the phenomena of vegetable circulation. 
 
 § 4. Functions of the stem. 
 
 The functions of the stem are probably as various as tbose of the 
 root, though the circumstances under which they are performed neces- 
 sarily involve these functions in considerable obscurity. 
 
 The pitli which forms the central part of the stem consists, as I have 
 already stated, of tubes disposed horizontally. When a coloured fluid 
 is permitted to enter the lower part of the stem in the experiments 
 above described, the pith remains untinctured in the centre of the col- 
 oured wood. It does not, therefore, serve for the conveyance of the sap. 
 Nor does it seem to be vitally necessary to the health and growth of the 
 plant, since Mr. Knight has shov/n that, from the interior of many trees, 
 it may be removed without apparent injury, and in nature, as trees ad- 
 vance in age, it gradually diminishes in bulk, and in some species be- 
 comes apparently obliterated. 
 
 The vessels of the wood, which surrounds the pith, perform proba- 
 bly both a mechanical and a chemical function. They serve to convey 
 upwards to the leaf the various substances which enter by the roots. 
 This is their mechanical function. But during its progress upwards, 
 the sap appears to undergo a series of changes. When it reaches the 
 leaves it is no longer in the state in which it ascended from the root into 
 the stem. The difficulty of extracting the sap from the wood, at dif- 
 ferent heights, has prevented very rigorous experiments from being 
 made on its nature and contents at the several stages of its ascent. 
 These it is obvious must vary with the species and age of the })lant, and 
 with the season of the year at which the experiment is made. But the 
 general result to be drawn from such observations as have hitherto been 
 made, is, that those substances which enter directly into the root, when 
 mingled with such as have already passed through the circulation of the 
 plant, undergo, during their ascent, a gradual preparation for that state 
 in which they become fit to minister to the growth of the plant. This 
 preparation is completed in a great measure in the leaf, though further 
 changes still go on as the sap descends through the bark. This deduc- 
 tion is strengthened by the fact that gaseous substances of various kinds 
 and in varying (quantities exist in the interior of the wood of the grow- 
 ing plant. These gaseous subtances, according to Boucherie, are in 
 some cases equal in bulk to one-twentieth part of the entire trunk of the 
 tree in which they exist. They probably move upwards along with 
 the sap, and are more or less completely discharged into the atmosphere 
 through the pores of the leaves. That these gaseous substances not 
 only differ in quantity, but in kind also, with the age and species of 
 the tree, and with the season of the year, may, I think, be considered 
 as almost amounting to a proof that they have not been inhaled direct- 
 ly by the roots, but are the result of chemical decompositions which 
 
FUNCTIONS OF THE STEM AND LEAVES. 89 
 
 have taken place on the stem hself, as the sap mounted upwards to- 
 wards the leaves. 
 
 We have seen that the roots exercise a kind of discriminating power 
 in admitting to the circulation of the plant the various substances which 
 are present in the soil. The vessels of the stem exhibit an analogous 
 power of admitting or rejecting the solutions of different substances into 
 which they may be immersed. Thus Boucherie states that, when the 
 trunks of several trees of the same species are cut off above the roots, 
 and the lower extremities immediately plunged into solutions of differ- 
 ent substances, some of these solutions will quickly ascend into and pen- 
 etrate the entire substance of the tree immersed in them, while others 
 will not be admitted at all, or with extreme slowness only, by the ves- 
 sels of the stems to. which they are respectively presented. On the 
 other hand, that which is rejected by one species will be readily admit- 
 ted by another. Whether this partial stoppage of, or total refusal to ad- 
 Juit, certain substances, be a mere contractile effort on the part of the 
 vessels, or be tlie result of a chemical change by which their exclusion 
 is effected or resisted, does not as yet clearly aj)pear. That it does not 
 depend upon the lightness and porosity of the wood, as might be sup- 
 posed, is shown by the observation that the poplar is less easily pene- 
 trated in this way than the beech, and the willow than the pear tree, 
 the maple, or the plane. 
 
 These various functions of the woody part of the stem are performed 
 chiefly by the newer wood- or alburnum, or, as it is often called, the sap 
 wood of the tree. As the heart wood becomes older, the tubes of which 
 it cojisists are either gradually stopped up by the deposition of solid 
 subs'tances which have entered by the roots, or by the formation of 
 chemical compounds, which, like concretions in the bodies of animals, 
 slowly increase in size till the vessels become entirely closed — or they 
 are by degrees compressed laterally by the growth of wood around them, 
 so as to become incapable of transmitting the ascending fluids. Per- 
 haps the result is in most cases due in part to both these causes. This 
 more or less perfect stoppage of the oldest vessels is one reason why the 
 course of the sap is chiefly directed through the newer tubes.* 
 
 The functions of the bark, which forms the exterior portion of the 
 stem, will be more advantageously described, after we shall have con- 
 sidered the purposes served by the leaves. 
 
 § 5. Functions of the leaves. 
 
 The vessels of wliich the sap wood is composed extend upwards into 
 the fibres of the leaf. Through these vessels the sap ascends, and from 
 their extremities diffuses itself over the surface of the leaf. Here it un- 
 dergoes important chemical changes, the extent, if not the exact nature, 
 of which v/ill appear from a shorr description of the functions which the 
 leaves are known or are believed to discharge. 
 
 1°. When the roots of a living plant are immersed in water, it is a 
 
 * As the newest roots are prolongations of the newest wood, it may be supposed that the 
 fact of these roots being the chief absorbents from the soil, is a sufficient reason why that 
 which is absorbed by them should also pass up through the wood with which they are most 
 closely connected. But that the pores of the heart wood are really incapable of transmit- 
 ting fluids, is shown by plunging the newly cut stem of a tree into a coloured solution — the 
 newer wood will be dyed, while more or less of the central portion will remain unchanged. 
 
 / 
 
90 ESCAPE OF WATERY VAPOUR FROM THE LEAVES. 
 
 matter of familiar observation that the water gradually diminishes in 
 bulk, and will at length entirely disappear, even when evaporation info 
 the air is entirely prevented. The water which thus disap[)ears is taken 
 up by the roots of the plant, is carried up to the leaves, is there spread 
 out over a large surface exposed to the sun and to the air, and in ihe 
 form of vapour escapes in considerable proportion through the pores of 
 the leaves and diffuses itself through the atmosphere. 
 
 The quantity of water which thus escapes from the surface of the 
 leaves varies with the moisture of the soil, with the species of plant, 
 with the temperature and moisture of the air, and with the season of the 
 year. According to the experiments of Hales, it is also dependent on 
 the presence of the sun, and is scarcely perceptible during tlie night. 
 He found that a sun-flower, 3^ feet high, lost from its leaves during 12 
 hours of one day 30, and of another day 20 ounces of water, while during 
 a warm night, without dew, it lost only three ounces, and in a dewy 
 niglit underwent no diminution m weight.* 
 
 This loss of watery vapour by the leaf is ascribed to two different 
 kinds of action. First, to a natural perspiration from the pores of' the 
 leaf, similar to the insensible perspiration which is continually proceed- 
 ing from the skins of healthy animals ; and second, to a mechanical 
 evaporation like that which gradually takes place from the surface of 
 moist bodies when exposed to hot or dry air. The relative amount of 
 loss due to each of these two modes of action respectively, must differ 
 very much in different species of plants, being dependent in a great 
 measure on the special structure of the leaf. In all cases, however, the 
 natural perspiration is believed very greatly to exceed the mere mechan- 
 ical evaporation — though the results of Hales, and of other experimen- 
 ters, show that both processes proceed with the greatest rapidity under the 
 influence of a warm dry atmosphere, aided Ijy the direct rays of the sun. 
 
 Among the several purposes served by this escape of watery vapour 
 from the surface of the leaf, it is of importance for us to notice the direct 
 
 * When the escape of vapour from the leaves is more rapid than the supply of water from 
 the roots, Ihe-ieaves droop, dry, and wither. Such is sometimes the case with growing 
 crops in very hot weather, and it always happens when a twig or flower is plucked and sep- 
 arated from the stem or root. When thus separated the leaves still continue to give off wa- 
 tery vapour into the air, and consequently 'the sap ascends from the iwig or stalk to supply 
 the place of the water tlius exhaled. 
 
 But as the sap ascends it must leave the vessels empty of fluid, and air must X'ush in to 
 fill the empty space. This will continue till nearly all the fluid has risen from the stem into 
 tlie leaf, and the vessels of the wood are full of air. But if the stem of the twig or flower be 
 placed in water this liquid will rise into it, air will be excluded, and the freshness and bloom 
 of llie leaves and flowers will be longer preserved. If the water into which they are intro- 
 duced contain any substances in solution, lliese will rise along with the water, and will gi-ad. 
 ually make their way througli all Ihe vessels of the wood, till they can be detected in the 
 haves. By this means even large trees may in a short time be saturated with saline solu- 
 tions, capable of preserving them from decay. It is only necessary to cut down or .«aw 
 through the tree and insert its lower extremity into the prepared solution, when the action 
 of the sun and air upon the leaves will cause it spontaneously to ascend. Thus corrosive 
 sublimate (Ihe subject of Kyan's Patent) may be injected with ease, or pyroagnile of iron, 
 (iron dissolved in wood vinegar,) which Boucherie recommends as eijually eflnicient and 
 much more economical, [Ann. de Chim. et de Phys. Ixxiv. p. 113.] The process is finished 
 when the liquid is found to have risen to Ihe leaf. Coloured solutions may in the same way 
 be injected and Ihe wood linged to any required shade. One of the chief benefits attendant 
 upon the cutting of wood in the winter, appears to be that the absence of leaves prevents the 
 exhaustion of the sap and the ascent of air into the vessels of the wood — the oxygen of this 
 air tending to induce decay. But the sap may be retained, and the air excluded almost as 
 effectually, at any other season of the year, by stripping the tree of its leaves and branches a 
 few days before it is cut down. 
 
OTHER VOLATILE SUBSTANCES EXHALED. 91 
 
 chemical influence it exercises over tlie growth of the plant. As the water 
 disappears from the leaf, the roofs must absorb from the soil at least an 
 equal supply. This water brings with it the soluble substances, organ- 
 ic and inorganic, which the soil contains, and thus in proportion (o the 
 activity with which the leaves lose their watery vapour, will be the 
 quantity of those substances which enter from the soil into the general 
 circulation of the plant. This enables us to understand how substances, 
 very sparingly soluble in water, should yet be found in the interior of 
 plants, and in very considerable quantity, at almost every stage of their 
 growth. 
 
 2°. Besides watery vapour, however, the leaves of nearly all plants 
 exhale at the same lime other volatile compounds in greater or less 
 abundance. In the petals of flowers, we are familiar with such exha- 
 lations — often of an agreeable and odoriferous character. In the case of 
 plants and trees also which emit a sensible odour, we readily recognise 
 the fact of volatile substances being given ofl" by the leaves. But even 
 when the sense of smell gives us lio indication of their emission from a 
 single leaf or a single plant, the introduction of a number of such in- 
 odorous plants into the confined. atmosphere of a small room after a time 
 satisfies us that even they part with some volatile matter from their 
 leaves, which makes itself perceptible to our imperfect organs only when 
 in a concentrated state. The probability^ therefore is, that the leaves ol" 
 all plants emit, along with the watery vapour which they evolve, cer- 
 tain other volatile substances also, though often in quantities so minute 
 as to escape detection by our unaided senses. By the emission of these 
 substances the plant probably relieves itself of what would prove inju- 
 rious if retained, though of the chemical nature and composition of these 
 exhalations little or nothing has yet been ascertained. 
 
 3°. If the branch of a living plant be so bent that some of its leaves, 
 can be introduced beneath the e(\ge of an inverted tumbler full of wafer, 
 and if the leaves be then exposed to the rays of the sun, bubbles oi' gas 
 will be seen to form on the leaf, and gradually to rise through the water 
 and collect in the bottom of the tumbler. If this gas be examined it 
 will be found to be pure oxygen. 
 
 If the water contain carbonic acid gas, or if during the experiment a 
 little carbonic acid be introduced, this gas will be found gradually to dis- 
 appear, while the oxygen will continue to accumulate. 
 
 Or if the experiment be made by introducing a living plant into a large 
 bell-glass full of common atmospheric air, allowing it to grow there for 
 12 hours in the sunshine, and then examining or aivilysing the air con- 
 tained in the glass, the result will be of a precisely similar kind. The 
 per centage of oxygen in the air will have increased.* And if the ex- 
 periment be varied by the introduction of a small quantity of carbonic 
 acid gas into the jar, this gas will be found as before to diminish in (]uan- 
 tity, while the oxygen increases. The conclusion drawn from these 
 experiments, therefore, is, that the leaves qfjjlanls, when exjyoscd to the 
 rays of the sun, absorb carbonic acid from the air and give q^j^jwre oxy- 
 gen gas. 
 
 It has been already stated that the proportion of carbonic acid present 
 
 • It will be remembered that atmospheric air contains about 21 per cent, of oxygen g^ 
 
92 OXYGEN IS EMITTED DURING THE DAY, 
 
 in llie atmosphere is exceedingly small, [about l-2500th of this bulk — 
 see Lecture II., p. 30 ;] but if for tlie purpose of experiment we increase 
 this proportion in a gallon of air to five or (en per cent., introduce a liv- 
 ing plant into it, and expose it to the sunshine, the carbonic acid will 
 gradually disajjpear as before, while the ox^'gen will increase. And if 
 we analyse the air and estimate the exact bulk of each of these gases 
 present in it at the close of our experiment, we shall.find that the oxygen 
 has increased a;enerally by as much as the carbonic acid has dnninished. 
 That is to say^ if five cubic inclies of the latter have disappeared, five 
 cubic inches will have been added to the bulk of the oxygen. The 
 above general conclusion, therefore, is rendered more precise by this ex- 
 periment, which appears to show that under the injluence of the sun's 
 rays the leaves of plants absorb carbonic acid from the air, and at the same 
 time give off a^ equal bulk of oxygen gas. 
 
 And as carbonic acid (COo) contains its own bulk of oxygen gas* 
 combined with a certain known weight of carbon, it is further inferred 
 that the oxygen given oflT by ilie leaves is the same which has been pre- 
 viously absorbed in the form of carbonic acid, and therefore it is usually 
 stated as a function of the leaves — that in the sunshine they absorb car- 
 bonic acid from the air, decompose it in the interior of the leaf rctainits 
 carbon, and again reject or emit the oxygen it contained. 
 
 This conclusion presents a very simple view of the relations of oxygen 
 and carbonic acid respectively to the living leaf in the presence of the 
 sun, and it appears to be fairly deduced from the facts above stated. 
 It has occasionally been observed, however, that the bulk of oxygen 
 given oflfby the leaf has not been precisely equal to that of the carbonic 
 acid absorbed, [see Persoz, Chimie Moleculaire, p. 54,'] and hence it is 
 also fairly concluded that a portion of the oxygen of the carbonic acid 
 which enters tlie leaf is retained, and made available in the production 
 of the various substances which are formed in the vascular system of 
 different plants. On the other hand it is stated by Sprengel, that if com- 
 pounds containing much oxygen be presented to the roots of plants, and 
 thus introduced into the circulation, they are also decomposed, and the 
 oxygen they^-contain in part or in whole given off by the leaves, so that, 
 under certain circumstances, the bulk of the oxygen which escapes is 
 actually greater than that of the carbonic acid which is absorbed by the 
 leaves. Such is the case, for example, when the roots are moistened 
 with water containing carbonic, sulphuric, or nitric acids. — [Sprengel 
 Chemie, IT., p. 344.] 
 
 It is of importance to note these deviations from apparent simplicity 
 in the relative bulks of the two gases which are respectively given off 
 and absorbed by all living vegetables. There are numerous cases of the 
 formation of substances in the interior of [)lants v^diich theory would fail 
 to account for with any degree of ease, were these apparent anomalies 
 to be neglected. This will more distinctly appear when in a subsecpient 
 lecture we shall inquire hoiv or by what chemical changes the substan- 
 ces which plants contain, or of which they consist, are produced from 
 the food which they draw from the air and from the soil. 
 
 * This the reader will i-ecollectis proved by burning chai'coal in a bottle of oxygen gas till 
 combustion ceases, when nearly the whole of the oxygen is converted into carbonic acid, but 
 • -i-ianse of bulk.— See Lecture III., p. 45. 
 
AND CARBONIC ACID DURING THE NIGHT. 33 
 
 The most general and probable expression, therefore, for the function 
 of the leaf, now under consideration, appears to be that in the sunshine 
 the leaves absorb from the air carbonic acid, and at the same time 
 evolve oxygen gas, the bulk of the latter gas given otf being nearly 
 equal to that of the former which is taken in — the relative bulks of the 
 two gases varying more or less with the species of plant, as well as 
 with the circumstances under which it is caused or is fitted to grow.* 
 
 4°. Such is the relation of the leaf to the oxygen and carbonic acid 
 .of the atmosphere in the presence of the sun. During the night their 
 action is reversed, they emit carbonic acid and absorb oxygen. This is 
 proved by experiments similar to those above described. For if the 
 plant which has remained under the bell-glass for 12 hours in the sun- 
 shine — during which time the oxygen has sensibly increased, and the 
 carbonic acid diminished in bulk — be allowed to remain in the same air 
 through the following night, the oxygen will be found to have decreased, 
 while the carbonic acid will be present in larger quantity than in the 
 evening of the previous day. 
 
 The carbonic acid thus given off during the night is supposed to be 
 partly derived from the soil through the roots, and partly from the sub- 
 stance of the plant itself. The oxygen absorbed either combines with 
 the carbon of the plant to form a portion of the carbonic acid which is 
 at the same time given off or is employed in producing some of the 
 oilier oxidixed [containing oxygen in considerable quantity] compounds 
 that exist in the sap. 
 
 As a general rule, the quantity of carbonic acid given off during the 
 night is far from being equal to that which is absorbed during the day. 
 Still it is obvious that a plant loses carbon precisely in proportion to the 
 amount of this gas given off. Hence, when the days are longest, the 
 plant will lose the least, and where the sun is brightest it v/ill gain the 
 fastest; since other things being equal, the decomposition of carbonic 
 acid proceeds most rapidly where the sky is the clearest, and the rays 
 of the sun most powerful. Hence we see why in Northern regions, 
 where spring, summer, and autumn are all comprised in one long day 
 — vegetation should proceed with such rapidity. The decomposition of 
 the carbonic acid goes on without intermission, the leaves have no night 
 of rest, but nature has kindly provided that, where the season of 
 warmth is so fleeting, there should be no cessation to the necessary 
 growth of food for man and beast. 
 
 This comparison of the functions performed by the leaf, during the 
 day and night respectively, explains the chemical nature of the blanching 
 of vegetables practised by the gardener, as well as the cause of the pale 
 colour of plants that grow naturally in the absence of light- 
 When exposed to the sun, the leaves of these sickly vegetables evolve 
 oxygen, and gradually become green and healthy. Woody matter is 
 formed, and the stems become strong and fibrous. 
 
 The light of the sun, in the existing economy of nature, is indeed 
 equally necessary to the health of plants and of animals. The former 
 
 * As the oxygen given off by the leaves is always the result of a chemical decomposition, 
 by which the carbonic acid or other compound is deprived of a portion, at least, of its oxy- 
 gen or de-oxidized, this function of the leaves ia the presence oj the sun is often spoken bf 
 as their de-oxidizing power. 
 
 5 
 
94 LEAVES SOMETIMES EMIT CHLORINE. 
 
 become pale and sickly, and refuse to perform their most importani 
 chemical functions when excluded from the light. The bloom disap- 
 pears from the human cheek, (he body wastes away, and the spiril 
 sinks, when the unhappy prisoner is debarred from the sight of tlie blessed 
 sun. In Ais system, too, the presence of light is necessary to the perfor- 
 mance of those chemical functions on which the healthy condition of the 
 vital fluids depends. 
 
 The processes by which oxygen and carbonic acid are respectively 
 evolved in plants have been likened by physiologists to the resi)iration 
 and digestion of animals. It is supposed that when plants respire they 
 give off carbonic acid as animals do, and that when they digest they 
 evolve oxygen. Respiration also, it is said, proceeds at all times, diges- 
 tion only in the light of the sun. Though these views are confessedly 
 conjectural, they are founded upon striking analogies, and may reason- 
 ably be entertained as matters of opinion. 
 
 6°. Other sj)ecies of decomposition also, besides that of^ de-oxidization, 
 go on in the leaf, or are there made manifest. Thus when plants grow 
 in a soil containing much common salt (chloride of sodium) or other 
 chlorides, they have been observed by Sprengel and Meyen to evolve 
 chloride* gas from their leaves. This takes place, however, more dur- 
 ing the night than during the day. Some plants also give off ammonia, 
 (Lecture IV., p. 70,) while others (crucifercc), according to Dr. Daube- 
 ny, [in his Three Lectures on Agriculture, p. 59,] emit from their leaves 
 pure nitrogen gas. 
 
 The evolution of chlorine implies the previous decomposition of the 
 chlorides, which have been absorbjgd from the soil; while that of nitro- 
 gen may be due to the decomposition of ammonia, of nitric acid, or 
 of some other compound containing nitrogen, which has entered into the 
 circulation by the roots. The exact mode and nature of the decompo- 
 sition of these substances, and the purposes served by them in the vegeta- 
 ble economy', will come under our consideration in a subse(|uent lecture. 
 
 The leaf has been described (p. 76) as an expansion of the bark. 
 It consists internally of two layers of veins or vascular fibres laid one 
 over the otheivthe upper connected with the wood — the lower with the 
 inner bark. It is covered on both sides by a thin membrane (epider- 
 mis), the expansion of the outer bark. This thin membane is' studded 
 ■with numerous small pores or mouths (stomata), which vary in size and 
 in number with the nature of the j)lant, and with the circumstances in 
 which it is intended to grow. It is from the pores in the upper pan of 
 the leaf that substances are supposed to be exhaled, while every thing 
 that is inhaled enters by those which are observed in the under side of 
 the leaf.f This opinion, however, is not universally received, it being 
 admitted by some that the power both of absorbing and of emitting 
 may be possessed by the under surface of the leaf. 
 
 7°. We have seen that the chief supply of the fluids which constitute 
 
 * Chlorine is a gas ofagreenish yellowcolour, having an unpleasant taste and a suffocating 
 odour. When it combines with other substances it forms chlorides. It exists in, and im- 
 parts its smell to, c/doride of lime, which is employed for disinfecting purposes, and it 
 forms upwards of half the weight of common salt. 
 
 t This is illustrated by the action of a cabbage leaf on a wound. If the upper side be ap- 
 plied, the sore is protected and quickly heals, while the under side draws it and produces a 
 constant discharge. 
 
FUNCTIONS OF THE FLOWER-LEAVES. 95 
 
 the sap of plants, is derived from the soil. The under side of the 
 leaves of plants is also siq^posed by some to be capable of absorbing 
 moisture from the air, either in the form of watery vapour, or when it 
 falls ujDon the leaves in the state of dew. Like the roots also they may 
 absorb with the dew any substances the latter happens to hold in solu- 
 tion. And thus plants may, in some degree, be nourished by the vola- 
 tile organic substances which ascend from the earth during the heat of 
 the day, and which are again in a great measure precipitated with the 
 evening dew. 
 
 Whether the leaves ever absorb nitrogen gas from the air has not as 
 yet been determined with sufficient accuracy. If they do, it must in gene- 
 ral be in very small quantity only, since it has hitherto escaped detec- 
 tion. In like manner it is doubtful how far they regularly absorb any 
 other substances which tiie air is supposed to contain. Thus it is known 
 that nitric acid exists in the air in very minute (}uantity. Some chem- 
 ists also believe that ammonia is extensively diffused through the atmos- 
 phere in an exceedingly diluted state. Do the leaves of plants absorb 
 these substances? Is the absorption of them one of the constant and ne- 
 cessary functions of the leaves ? The reply to these questions must be 
 very uncertain, and any principle which professes to be based upon such 
 a reply must be regarded only as a matter of opinion. 
 
 8°. The petals of flower-leaves perform a somewhat different function 
 from those of the ordinary leaves of a plant. They absorb oxygen at 
 all times- — though more by day than by night — and they constantly emit 
 carbonic acid. The bulk of the latter gas evolved, however, is less than 
 that of the oxygen taken in. The absorption of oxygen gas, and the 
 constant production of carbonic acid, is, in some flowers, so great as to 
 cause a perceptible increase of temperature — and to this slow combus- 
 tion, so to speak, the proper heat observed in the flowers of many plants 
 has been attributed. 
 
 According to some authors, the flower-leaves also emit pure nitrogen 
 gas. — [Sprengel, Chemie, II., p. 347.] This fact has not yet been deter- 
 mined by a sufficient number of accurate experiments; it is in accord- 
 ance, however, with the results of Boussingault, that, when a plant 
 flowers and approaches to maturity, the nitrogen it contains becomes 
 less. If confirmed, this evolution of nitrogen would throw an interest- 
 ing light on the most advantageous employment of green crops, both for 
 the purposes of manure and for the feeding of cattle. 
 
 9°. When the leaves of a plant begin to decay, either naturally as in 
 autumn, or from artificial or accidental causes, they no longer absorb 
 and decompose carbonic acid, even under the influence of the sun's rays. 
 On the contrary, they absorb oxygen, like the petals of the flower, new 
 compounds are formed within their substance — their green colour disap- 
 pears — they become yellow — they wither, die, and drop from the tree — 
 their final function, as the organs of a living being, is discharged. They 
 then undergo new changes, are subjected to a new series of influences, 
 and are made to serve new purposes in the economy of nature. These 
 we shall hereafter find to be no less interesting and important in refer- 
 ence to a further end, than are the functions of the living leaf to the 
 growth and nourishment of the plant.-^[See subsequent lecture, " On the 
 law of the decay of organic substances."] 
 
96 CHEMICAL ru>;cTio>s of the bark. 
 
 § G. Functions of the hark. 
 
 The inner bark being connected with the under layer of vessels hi the 
 leaf, receives from tliem the sap after it has been changed by the action 
 of the air and hght, and transmits it downwards to the root. 
 
 The outer bark, especially in young twigs and in the stalks of the 
 grasses, so closely resembles the leaves in its appearance, that we can 
 have no difficulty in admitting that it must, not unfrequently, perform 
 similar functions. In the Cactus, the Stapelia, and other plants which 
 produce no true leaves, this outer bark seems to perform all the functions 
 which in other vegetable tribes are specially assigned to the abundant 
 foliage. During its descent through the inner bark, therefore, the sap 
 must in very many cases undergo chemical changes, more or less analo- 
 gous to those which usually take place in the leaf. 
 
 It is by means of the inner bark that the stems of trees, such as 
 our forest and fruit trees, are enlarged by the deposition of annual 
 layers of new wood. The woody fibre is formed or prepared in 
 the leaf, and as the sap descends it is deposited beneath the inner sur- 
 face of the inner bark. It thus happens that, as the sap descends, it is 
 gradually deprived of the substances it held in solution when it left the 
 leaf, and in consequence it becomes difficult to say how much of the 
 change, which the sap is found to have undergone when it reaches the 
 root, is due to chemical transformations produced during its descent, and 
 how much to the deposition of the woody fibre and other matters it has 
 parted with by the way. 
 
 Among other evidences of such changes really taking place during 
 the descent of the sap, I may mention an observation of Meyen [Jahres- 
 bericht, 1839, p. 27], made in the course of his experiments on the re- 
 production of the bark of trees. In these experiments he enclosed the 
 naked wood in strong glass tubes, and in three cases out of eight the 
 tubes were burst and shattered in pieces. This could only have arisen 
 from the disengagement of gaseous substances, the result of decomposi- 
 tion. While, therefore, such gases as enter by the roots or are evolved 
 in the vesseisTjf the wood during the ascent of the sap, escape by the 
 leaf along with those which are disengaged in the leaf itself, it is proba- 
 ble that those which are produced as the residt of changes in the bark, 
 descend with the downward sap, and are discharged by the root.* 
 
 In the bark of the root it is probable that still further changes fake 
 place — and of a kind which can only be efTected during the absence of 
 light. This is rendered probable by the fact that the bark of the root 
 frequently contains substances which are not to be met with in any 
 other part of the plant. Thus from the bark of the fresh root of the ap- 
 ple tree a substance named ])hloridzinc, possessed of considerable medi- 
 cal virtues, may be readily extracted, though it does not exist in the 
 bark either of the stem or of the branches. 
 
 In fine, as the food which is introduced into the stomachs of animals, 
 undergoes continual and successive chemical changes during its pro- 
 gress through the entire alimentary canal — so, numerous phenomena 
 indicate that the sap of plants is also subjected to unceasing transforma- 
 
 * Sprengel says that the stems and twigs, and the stalks of the grasses, all absorb oxygen 
 and give off carbonic acid. — Chemie, II., p. 341. 
 
FUNCTIONS OF THE ROOT MODIFIED BY THE SOIL. 97 
 
 tions, — in the root and in ihe stem as well as in the leaves, — at one time 
 in the dark, at anotlier under the influence of the sun's rays, — exposed 
 when in the leaf to the full action of the air, — and when in the root al- 
 most wholly secluded from its presence ; — the new compounds pro- 
 duced in every instance being suited either to the nature of the plant or 
 the wants and functions of that part of it in which each transformation 
 takes place. 
 
 To some of these transformations it will be necessary to advert more 
 particularly, when we come to consider the special changes by which 
 those substances of which plants chiefly consist, are formed out of these 
 compounds on which they chiefly live. 
 
 § 7. Circumstances hy which the functions of the various parts of plants 
 
 are rnodified. 
 Plants grow more or less luxuriantly, and their several parts are 
 more or less largely developed, in obedience to numerous and varied 
 circumstances. 
 
 I. In regard to the special functions of the root, we have already seen 
 that the access of atmospheric air is in some cases indispensable, while 
 in others, by shooting vertically downwards, the roots appear to shun 
 the approach of either air or light. It is obvious also that a certain de- 
 gree of moisture in the soil, and a certain temperature, are necessary 
 to the most healthy discharge of the functions of the root. In hot wea- 
 ther the plant droops, because the roots do not absorb water from the 
 soil with sufficient rapidity. And though it is probable that, at every 
 temperature above that of absolute freezing, the food contained in the 
 soil is absorbed and transmitted more or less slowly to the stem, yet it is 
 well known that a genial warmth in the soil stimulates the roots to in- 
 creased activity. The practice of gardeners in applying bottom heat in 
 the artificial climate of the green-house and conservatory is founded on 
 this well-known principle. 
 
 But the nature of the soil in which plants grow has also much influ 
 ence on the way in which the functions of the root are discharged. As 
 a general fact this also is well known, though the special qualities of the 
 soil on which the greater or less activity of vegetation depends, are far 
 from being generally understood. If the soil contain a sensible quantity 
 of any substance which is noxious to plants, it is plain that their roots 
 will be to a certain degree enfeebled, and their functions in consequence 
 only imperfectly discharged. Or if the soil be deficient either in organic 
 food, or in one or other of those inorganic substances which the plants 
 necessarily require for the production of their several parts, the roots 
 cannot perform their office with any degree of efficiency. Where the 
 necessary materials are wanting the builder must cease to work. So in 
 a soil which contains no silica, the grain of wheat may germinate, but 
 he stalk cannot be prodiiced in a natural or healthy state, since silica is 
 indispensable to its healthy construction. 
 
 II. The ascent of the sap is modified chiefly by the season of the 
 year, by the heat of the day, and by the genus and age of the plant or 
 tree. 
 
 There seems reason to believe that the plant never sleeps, that even 
 during the winter the circulation slowly proceeds, though the first 
 
98 ALSO THE RAPIDITY OF THE CIRCULATION. 
 
 genial sunshine of the early spring stimulates it to increased activit}''. 
 The general increased temperature of the air does not produce this ac- 
 celeration in so remarkahle a manner as the direct rays of the sun. The 
 sap will flow and circulate on the side of a tree on which ilie sunshine 
 falls, while it remains sensibly stagnant on the other. This is shown by 
 the cutting down similar trees at more and more advanced periods of 
 the spring", and immersing their lower extremities in coloured solutions. 
 The wood and bark on one side of the tree will be coloured, while, on 
 the other, both will remain unstained. If a similar dilference in the 
 comparative rapidity of the circulation on opposite sides of a trunk or 
 branch be supposed to prevail more or less throughout the year, we can 
 readily account for the annual layers of wood being often thicker on 
 the one half of the circumference of the stem than on the other. 
 
 The sap is generally supposed to flow most rapidly during the spring, 
 but if trees be cut down at ditTerent seasons, and immersed as above 
 described, the coloured solution, according to Boucherie, reaches the 
 leaves most rapidly in the autumn.* 
 
 The heat of the day, other circumstances being the same, materially 
 affects, for the time, the rapidity of the circulation. The more rapidly 
 watery and other vapours are exhaled from the leaves, the more quick- 
 ly must the sap flow upwards to supply the waste. IC on two succes- 
 sive days the loss by the leaves be, as in the experiment of Hales, above 
 described, (p. 90,) as 2 to 3, the ascent of the sap must be accelerated 
 or retarded in a similar proportion. Hence, every seiisible variation in 
 the temperature and moisture of the air, must also, to a certain extent, 
 modify the flow of the sap ; must cause a greater or less transport of that 
 food which the earth supplies, to be carried to every part of the plant, 
 and must thus sensibly affect the luxuriance and growth of the whole. 
 
 But the persistance of the leaves is a generic character, which has 
 considerable influence upon the circulation in the evergreens. In the 
 pine and the holly, from w^hich the leaves do not fall in the autumn, the 
 sap ascends and descends during all the colder months, — at a slower 
 rate, it is true, than in the hot days of summer, yet much more sensibly 
 than in the oak and ash, which spread their naked arms through the 
 wintery air. This is illustrated by the experiments of Boucherie, who 
 has observed that in December and January the entire wood of resinous 
 trees may be readily and thoroughly penetrated by the spontaneous as- 
 cent of saline and other solutions, into which their stems may be im- 
 mersed. 
 
 III. From what has just been stated, it will appear that the mechani- 
 cal functions of the stem are subject to precisely the same influences as 
 the ascent of the sap. As the tree advances in age, the vessels of the 
 interior will become more or less obliterated, and the general course of 
 the sap will be gradually transferred to annual layers, more and more 
 
 * Boucherie makes a distinction, not hitherto insisted upon by physiologists, between the 
 circulation on the surface of the tree by which the buds and young twigs are supported, and 
 the interior circulation, whicli is not perfect until a latter period of the year. Hence in the 
 spring, though the sai) is tlowing rapidly through tlie bark and the newest wood, coloured 
 solutions will not penetrate tiie interior of the tree with any degree of rapidity. In autumn, 
 on tlic other hand — when the fear of approaching winter has already descended upon the 
 bark — the time of most active circulation has only arrived for the interior layers of the older 
 wood. It is this season consequently that he finds most favourable for impregnating the 
 trunks of trees with those solutions which are likely to preserve them from deca.y.—A7in, do 
 Chim. 6t de Phys.^ Ixxiv., p. 135. 
 
CHEMICAL RAYS IN THE SUN-BEAM. 99 
 
 removed from the centre. It is this transference of the vital circula- 
 tion to newer and more perfect vessels that enables the tree to grow and 
 blossom and bear fruit through so long a life. In animals the vessels 
 are gradually worn out by incessant action. None of them, through 
 old age, are permitted to retire from the service of the body — and the 
 whole system must stop when one of them is incapacitated for the 
 further performance of its appointed duties. 
 
 In regard to the chemical functions of the stem, it is obvious that they 
 are not assigned to the mere woody matter of the vessels and cells. 
 They take place in these vessels, but the nature and extent of the chemi- 
 cal changes themselves must be dependent upon the quantity and kinds 
 of matter which ascend or descend in the sap. The entire cliemical 
 functions of the plant, therefore, must be dependent upon and must be 
 modified by the nature of the substances which the soil and the air re- 
 spectively present to the roots and to the leaves. 
 
 tV. In describing the functions of the leaf, I have already had occa- 
 sion to advert to the greater number of the circumstances by which the 
 discharge of those functions is most materially affected. We have seen 
 tliat the purposes served by the leaf are entirely different according as 
 the sun is above or below the horizon ; that the temperature and mois- 
 ture of the air may indeed materially influence the rapidity with which 
 its functions are discharged — but that the light of the sun actually deter- 
 mines their nature. Tims the leaf becomes green and oxygen is given 
 off' in the presence of the sun, while in his absence carbonic acid is dis- 
 engaged, and the whole plant is blanched. 
 
 How necessary light is to the health of plants may be inferred from 
 the eagerness with which they appear to long for it. How intensely 
 does the sun-flower watch the daily course of the sun, — how do the 
 countless blossoms nightly droop when he retires, — and the blanched 
 plant strive to reach an open chink through which his light may reach 
 it!* 
 
 That the ivarmth of the sun has comparatively little to do with this, 
 specific action of his rays on the chemical functions of the leaf, is illus- 
 trated by some interesting experiments of Mr. Hunt, on the efl^ect of 
 rays of light of different colours on the growing plant. He sowed cress 
 seed, and exposed different portions of the soil in which the seeds were 
 germinating, to the action of the red, yellow, green, and blue rays, 
 which were transmitted by equal tliicknesses of solutions of these seve- 
 ral colours. " After ten days, there was under the blue fluid, a crop of 
 cress of as bright a green as any which grew in full light and far more 
 abundant. The crop was scanty under the green fluid, and of a pale 
 yellow, unhealthy colour. Under the yellow solution, only two or three 
 plants appeared, but less pale than those under the green, — while be- 
 neath the red, a few more plants came up than under the yellow, though 
 they also were of an unhealthy colour. The red and blue bottles being 
 now mutually transferred, the crop formerly beneath the blue in a few 
 
 * A potato has been observed to grow up in quest of light from the bottom of a well 
 twelve feet deep— and in a dark cellar a shoot of 20 feet in length has been met with, the 
 extremity of which had reached and rested at an open window. In the leaves of blanched 
 vegetables peculiar chemical compounds are formed. Thus in the stalk of the potato a 
 poisonous substance called solanin is produced, which disappears again when the stalk is ex- 
 posed to the hght and becomes green. 
 
100 FUNCTIONS OF TilK GRTKN 1 WIGS. 
 
 days appeared bligliled, while on the patcli previously exposed to the 
 red, some additional plants sprung up."* 
 
 Besides the rays of heat and of light, the sun-beam contains what 
 have been called chemical rays, not distinguishable by our senses, but 
 capable of being recognized by the chemical effects they produce. 
 These rays appear to differ in kind, as the rays of different coloured 
 light do. It is to the action of these chemical rays on the leaf, and 
 especially to those which are associated with the blue light in the solar 
 beam, that the chemical influence of the sun on the functions of the leaf 
 is principally to be ascribed. 
 
 It cannot be doubled that the warmth and moisture of a tropical cli- 
 mate act as powerful stimulants — assistants it may be — to the leaf, in 
 the absorption of carbonic acid from the air, and in that rapid apj)ropria- 
 tion (assimilation) of its carbon by which the growth of the plant is has- 
 tened and promoted. But the bright sun, and especially the chemical in- 
 fluence of liis beams, must be regarded as the main agent in the wonderful 
 develoj)ment of a troi)ical vegetation. Under this influence the growth 
 by the leaves at the expense of the air must be materially increased, 
 and the plant be rendered less dependent upon the root and the soil for 
 the food on which it lives. f 
 
 V. The rapidity with which a plant grows has an important influence 
 upon the share which the hark is permitted to take in the general 
 nourishment of the whole. The green shoot performs in some degree 
 the functions of the leaf. In vascular plants, therefore, which in a con- 
 genial climate may almost be seen to grow, the entire rind of a tall tree 
 may more or less eflectually absorb carbonic acid from the atmos])here, 
 during the presence of the sun. The broad leaves of the palm tree, 
 when fully developed, render the plant in a great degree independent of 
 the soil for organic food — and the large amount of absorbing surface in 
 the long green tender stalks of the grasses, and of their tropical ana- 
 logues, must materially contribute to the same end. Hence the ])ro- 
 portion of organic matter derived from the air, in any crop we reap, 
 must always be the greater the more rapid its general vegetation has 
 been. 
 
 ' It is a fact familiarly known to all of you, that, besides those circum- 
 stances by which we can perceive the special functions of any one or- 
 gan to be modified, there are many by which the entire economy of the 
 plant is materially and simultaneously aflected. On this fact the ])rac- 
 tice of agriculture is founded, and the various processes ado[)ted by the 
 practical. farmer are only so many modes by which he hopes to influ- 
 
 * London and Edinburgh Journal of Science, Fehniary^ 1S40. 
 
 Might not our cheap blue glass be used with advantage in glazing hot-houses, conserva- 
 tories, &c. ? 
 
 t The effect of continued sunshine may be often seen in our corn fields in May, when, 
 under the influence of propitious weather, the young plants are shooting rapidly u\\ When 
 such a field is bounded by a lofty hedge running nearly north and south, the ri i^i-s nenr< •^t 
 the hedge on either side will be in the shade for nearly one-half of the day, and will itiv.iri.i- 
 bly appear of a paler green and less healthy colour, ff the hedge be studded wlih fM-casion: 1 
 large trees, the spots on which the shadows of those trees rest will be indicued by distinct 
 pale green patches stretching further into the field than the first, and sonieiimcs even tli; n 
 the second ridges. 
 
EFFECT OF MARLING. REWARDS OF NATURE. 101 
 
 ence and promote the growth of the whole plant, and the discharge of 
 the functions of all its parts. 
 
 Though manures in the soil act immediately through the roots, they 
 stimulate the growth of the entire plant; and though the application of 
 a top-dressing may be supposed first to atTect the leaf, yet the beneficial 
 result of the experiment depends upon the influence which the dressing 
 may exercise on every part of the vegetable tissue. 
 
 In connection with this part of the subject, therefore, I shall only 
 further advert to a very remarkable fact mentioned by Sprengel, which 
 seems, if correct, to be susceptible of important practical applications. 
 He states that it has very frequently been observed in Holstein, that if, 
 on an extent of level ground sown with corn, some fields be marled, and 
 others left unmarled, the corn on the latter portions will grow less iuxuri- 
 a?itly and will yield a poorer crop thari if the ivliole had been unmarled. 
 Hence he adds, if the occupier of the unmarled field would not have a 
 succession of poor crops, he must marl his land also.* 
 
 Can it really be that nature thus rewards the diligent and the impro- 
 ver? Do the plants which grow on a soil in higher condition take from 
 the air more than their due share of the carbonic acid or other vegetable 
 food it may contain, and leave to the tenants of the poorer soil a less pro- 
 portion than they might otherwise draw from it ? How many interest- 
 ing reflections does such a fact as this suggest ! What new views does 
 it disclose of the fostering care of the great Contriver — of his kind encour- 
 agement of every species of virtuous labour ! Can it fail to read to us a 
 new and special lesson on the benefits to be derived from the application 
 of skill and knowled2:e to tire cultivation of the soil ? 
 
 ' Wenn namlich auf einer Feldflur Stiick um Stiick gemergelt worden ist, so wachsen 
 die Friichte auf den nicht gemergelten Feldern, auch wenn hier alle friiheren verhaltnisse 
 ganz dicselben bleiben,niclit melirsogut, als eliedem; wodurch die Besitzer jener Felder, 
 wenn sie nicht fortwaiirend geringe Erndten haben wollen, geniithigt sind, gleichfalls zu 
 mergeln. Aus dieser hiJchst vichrigen Ersclieinung, die man sehi- hdujig in Holsteinschen 
 bemerkt, «fec. — ^prengel^C/iernie/ur Landwirth^chqft, I., p. 303. 
 
 5* 
 
LECTURE VI. 
 
 Substances of which plants chiefly consist— Woody fibre, Starch, Gum, Sugars— Their mu- 
 tual relations and transformations — Gluten,Vegetable Albumen, Diastase — Acetic, TartariCi 
 Malic, Citric, and Oxalic Acids — General observations. 
 
 From what has been stated regarding the structure of plants, it will be 
 understood in what way the food is introduced into their circulation. The 
 next inquiry appears to be how — by what chemical changes — is the food, 
 when introduced, converted into those substances of which plants chiefly 
 consist. But in order that we may clearly understand this point, it ia 
 necessary that we know first the nature and chemical constitution of the 
 substances which are most largely formed from the food in the interior 
 of the plant. To this point, therefore, I must previously direct your 
 attention. 
 
 If you were to collect all the varieties of plants which are within your 
 reach — whether such as are cultivated and used for food-^r such as 
 grow more or less abundantly in a wild state — and were to extract their 
 several juices, and to separate from each of these juices the chemical 
 compounds it contains — you would gradually gather together so many 
 different substances, all possessed of different properties, that you would 
 scarcely be able to number them. 
 
 But if at the same time you compared the weight of each substance 
 thus collected with that of the entire plant from which it is derived, you 
 would find also that the quantity of many of them is comparatively so 
 minute that only a very small portion of the vital energies of the plant 
 can be expended in producing them, — that they may be entirely neglect- 
 ed in a general consideration of the great products of vegetation. Thus 
 though quinine and morphine, the active ingredients in Peruvian bark 
 and in opium, are most interesting substances, from their effect upon the 
 human constitution, and their use in medicine, yet they form so small a 
 fraction of the mass of the entire trees or plants from which they are ex- 
 tracted, that it would be idle to attempt to convey to you any notion of 
 the way in which plants grow and are fed, by showing you how such 
 substances as these are produced from the food on which plants live. 
 
 While, however, the examination would satisfy you that almost 
 every species of plant produced in small quantity one or more sub- 
 stances peculiar to itself, you would observe, at the same time, that 
 every plant yielded a certain quantity of two or three substances com- 
 mon to and produced by all, and in most cases constituting the greater 
 portion of their bulk. Thus all trees and herbs produce wood or woody 
 fibre, and of this substance you know that their chief bulk consists. 
 Again, all the grains and roots you cultivate contain starch in large 
 quantity, and the production of this starch is one of the great objects of 
 the art of culture. The juices of trees, and of grasses, and of cultivated 
 roots, contain sugar and gum, and sometimes in such quantity as to 
 make their extraction a source of profit both to the grower and to the 
 
CONSTITUTION OF WOODY FIBRE. 103 
 
 manufacturer. The flour of grain contains sugar also, and along with it 
 two other substances, in small quantity, gluten and vegetable albumen, 
 which are of much importance in reference to the nutritive qualities of 
 the different v arieties of flour. Sugar is also present in the juices of 
 fruits, but it is there associated with various acid (sour) substances 
 which disappear to a certain extent or change into sugar as the fruit 
 ripens. 
 
 Of these few substances the great bulk of vegetables of all kinds con- 
 sists. They constitute nearly the whole mass of those various crops 
 which the art of culture studies to raise for the use of man and beast. 
 To the study of these substances, therefore, I shall at present confine 
 your attention, and if I shall afterwards be able to make you under- 
 stand how these few compound bodies are produced in the interior of a 
 plant from the food it takes up, I shall succeed in conveying to yoii as 
 much information in regard to this most interesting branch of our subject 
 as will be necessary to a general explanation not only of the natural 
 growth and increase of plants, but of the nature and efficacy of those 
 artificial means which the practical farmer employs, in order to hasten 
 their growth or enlarge their increase. 
 
 § 1. Woody fibre or lignin — its constitution and 2'>'roper lies. 
 
 1°. When a portion of the stem of a herbaceous plant, or of the new- 
 ly cut wood of the trunk or branch of a tree, is reduced to small pieces, 
 and boiled in successive portions of water and alcohol, as long as any 
 thing is taken up, a white fibrous mass remains, to which the name of 
 woody fibre or lignin has been given. This substance has no taste or 
 smelf, and is perfectly insoluble' in water. It is nearly identical in its 
 chemical constitution and properties, whether it be obtained from the 
 porous willow, or from the solid box tree, and the fibres of linen and of 
 cotton consist essentially of the same substances. 
 
 According to the analysis of Dr. Prout, this woody fibre when dried 
 
 at 350° F., consists of 
 
 From Box Wood. From the Willow. 
 
 Carbon 50-0 49-8 
 
 Hydrogen .... 5*55 5*58 
 
 Oxygen .... 44-45 44-62 
 
 ToJT" 100 
 
 It will be recollected that water consists of oxygen and hydrogen, 
 combined in the proportion, by weight, of 8 of the former to 1 of the lat- 
 ter. (See Lecture IL, p. 36.) Now^ if the hydrogen above given be 
 multipUed by 8, the product will be found to be almost exactly the 
 weight of the oxygen given — since 
 
 5-55 X 8 = 44-40, and 
 5-58 X 8 = 44-64. 
 In woody fibre, therefore, the hydrogen and oxygen exist in the same 
 proportion as in water, and its composition, therefore, might be repre- 
 sented by 
 
 Carbon 50-0 
 
 Water 50-0 
 
 100 
 
104 COMPOSITION OF WOOD. 
 
 did we not know that woody fibre, when heated or distilled, cannot be 
 resolved into carbon (charcoal) and water alone, and, therefore, cannot 
 be supposed to consist of .these alone. 
 
 It is a remarkable character of this substance, however, that these two 
 elements, hydrogen and oxygen, exist in it in the proportions to form 
 water, and we shall find the knowledge of this fact of great importance 
 to us, wlien we come to inquire how this constituent of vegetables is 
 formed — from the food on which they live. 
 
 2°. If a portion of the wood of a tree be dried and analyzed witlwut 
 
 being previously digested in water, alcohol, and ether, as long as any 
 
 thing is taken up, the proportion of the constituents is found to vary 
 
 slightly with the species of tree, but in all cases the hydrogen is in larger 
 
 quantity than is necessary to form water with the oxygen they contain. 
 
 Thus, according to Payen, the dry wood of the following trees consists of 
 
 Ebony. Walnut. Oak. Beech. 
 
 Carbon . . . 52-85 51-92 50-00 49-25 
 
 Hydrogen . . 6-00 5 96 6-20 6-10 
 
 Oxvsen ... 41-15 42-12 43-80 44-65 
 
 100 100 100 100 
 
 The carbon in these several kinds of wood differs as much as three 
 per cent., but in each of them the product of the hydrogen, when multi 
 plied by 8, is considerably greater than the per centage of oxygen. 
 
 3°. When the solid substance of wood is examined under the micro- 
 scope it is observed to consist of two i)ortions or kinds of matter, that of 
 which ihe original sides of the cells and tubes is composed, called the 
 cellular matter — the true woody fibre — and of a solid substance by which 
 the cells are internally coated and strengthened, called the incrusting 
 matter. It is in this latter substance that the excess of hydrogen, exhi- 
 bited by the preceding anal3^sis, is supposed to exist, the true woody 
 fibre containing always the hydrogen and oxygen in the proportions ne- 
 cessary to form water.* 
 
 ' Payen at first considered this incrusting matter as a peculiar substance, for which he 
 proposed the name of scZerogene. His first mode of separating it from the cellular matter 
 was by treating the finely rasped wood (of the oak and beech) with nitric acid, which dis- 
 solved out the incrusting matter and left the cellular matter behind. His second mode was 
 to digest the wood with dilute sulphuric acid, by which the cellular matter was dissolved 
 out, and the incrusting matter left. It is obvious, however, that no reliance whatever can be 
 placed on the analyses of substances so treated, since they cannot fail to have luidergone a 
 chemical change by being exposed to the action of these strong acids. Further examination 
 has satisfied Payen that the incru.sting matter consists of at least three substances, of which 
 one is soluble in water, alcohol, and ether, another in alcohol only, while the third is insolu- 
 ble in any of these liquids. They are composed, according to his analyses, of 
 
 Soluble in Soluble in 
 
 Insoluble. alcohol only. water and alcohol. 
 
 Carbon ... 48 628 63-53 
 
 Hydrogen ... 6 59 704 
 
 Oxygen ... 46 313 24-43'' 
 
 100 100 100 
 
 It is impossible to say how far the substances analysed by Payen are to be considered as 
 pure, or as actually existing in the pores, or in the incrusting matter of the woody fibre, but 
 it is obvious that the presence of a variable quantity of siich substances will necessarily 
 cause that excess of hydrogen, in the entire wood, which appears in the analysis of the ebo- 
 ny, walnut, oak, and beech woods, given in the text. That such an excess of hydrogen 
 above what is necessary to form water with the oxygen, does exist in the wood of most trees 
 
 [^ Meyen's Jaliresbericht, 1839, p. 10,] 
 
COMPOSITION OF CELLULAR MATTER. 105 
 
 It IS exceedingly difficult in any case to separate the cellular from the 
 incrusting matter of wood, so as to obtain the means of determining by 
 analysis tlie exact ditference in their elementary constitution. Under 
 the impression that in very light and })orous substances he should ob- 
 tain the ceHular matter in a purer form, Payen analysed the fibre of 
 cotton — the pith of the elder, the cellular substance of the cucuiriber, of 
 the mushroom, and of other fungi, the spongy matter which forms the 
 extremities of the roots of plants, and various other similar substances, 
 and in all these varieties he found the hydrogen and oxygen to exist in 
 the proportions to form water. The mean of his analyses was *^'ery 
 nearly as follows — which for the purpose of comparison I shall contrast 
 with that of Dr. Prout : 
 
 Woody fibre of box and Cellular matter of vascu- 
 
 willovv— Dr. Prout. lar plants— Payen. 
 
 Carbon . . . 50-00 44-80 
 
 Hydrogen . . 5-55 6-20 
 
 Oxygen . . . 44-45 49-0 
 
 100 100* 
 
 In both these analyses the hydrogen is very nearly 8 times that of 
 the oxygen. All these substances, therefore, may be represented by 
 carbon and water, though the woody fibre of Dr. Prout contains 5 per 
 cent, more carbon than the cellular matter of Payen. 
 
 If we calculate the number of equivalents of each element contained 
 in these two varietiesf of vegetable fibre composed as above exhibited, 
 we find in the one 12 of carbon, 8 of hydrogen, and 8 of oxygen ; in 
 the other, 12 of carbon, 10 of hydrogen, and 10 of oxygen. They may 
 therefore, be conveniently represented by the following formulae : 
 
 Woody Fibre by Cj2 Hg Cg 
 
 Cellular Fibre. . . . by C^a Hjo C^o 
 It is not unlikely that both of these forms of matter may exist, as 
 well in the perfect wood of trees as in the less consolidated pith of the 
 elder, or in the fibres of cotton — and that they may occur intermingled 
 also in varying proportions with other substances, containing hydrogen 
 in excess.:^ 
 
 in its natural state, is a fact to which it will be Important to advert when we consider here- 
 after the chemical changes which the food undergoes in the interior of the plant. 
 * Mey en' s Jahresbericht, 1839, p. 10. 
 
 t This is done very simply by dividing the carbon by 6, and the oxygen by 8 (see page 
 36), thus- 
 Carbon - - - 50^6 = 8-33 : which numbers 5 12 
 Hydrogen • • 555 = 5-£5 } are to each / 8 
 Oxygen - • - 44-45 -f- 8 = 55 5 ( other as ) 8 
 
 t The existence of a variety of cellular fibre identical in constitution with common starch, 
 as this of Payen is, (see subsequent section; p. 106,) was previously rendered probable by 
 the observations of Dr. Schleiden, that the embryo of the Scholia latlfoHa, consisting of 
 pores and vessels, the sides of which exhibit distinct concentric layers, is entirely soluble 
 in water, with the exception of the outer ripd ; and that its solution becomes blue on the 
 addition of iodine. It would appear as if the cellular substance were in this case wholly 
 composed of Starch. (PoggeTidorf's Annalen. xliii., p. 398.) It may, however, be in such a 
 state of tenuity in the embryo of this plant, as to be easily changed into starch by the action 
 of hot water; and it is still by no means certain that the cellular fibre analyzed by Payen 
 may not also have undergone a change by the treatment to which it was previously subject- 
 ed. I am unable, however, to speak decidedly on this subject, as I have not seen the de- 
 tails of M. Payen's several papers. (See subsequent section, on the mutual transformattona 
 of woody fibre, starch, gum, and sugar, p. 112.) 
 
J 06 PER CEr^TAGF, OF Vv'OODY FIBRE IN PLANTS. 
 
 I have spoken of these varieties of woody fibre as constituting a large 
 portion of the entire mass of vegetable matter produced during the 
 growth of plants. That such is the case in the more gigantic vegetable 
 productions, of which the great forests consist, is sufficiently evident 
 and so far the general statement is easily seen to be correct. It is also 
 true of the dried stalks of the grasses and the corn-growing plants, of 
 which it forms nearly one-half the weight, — but in roots and some 
 plants which are raised for food, the quantity of woody fibre, especially 
 in the earlier stages of their growth, is comparatively small.* Thus in 
 the beet root it forms only 3 per cent, of the whole weight when taken 
 from the ground. If suffered to remain in the soil till it becomes old, 
 or if the growth be very slow, the beet becomes more woody, as many 
 other roots do, and the quantity of ligneous fibre increases. 
 
 § 2. Starch — Us constitution and properties. 
 
 Next to woody fibre, starch is probably the most abundant product of 
 vegetation. To the agriculturist it is a substance of much more interest 
 and importance than the woody Or cellular fibre, from the value it pos- 
 sesses as one of the staple ingredients in the food of man and animals — 
 and from its forming a large portion of the weight of the various grains 
 and roots which are the principal objects of the art of culture. 
 
 1°. When the flour of wheat, barley, oats, Indian corn, &c., is mixed 
 up into a dough with water, and this dough washed on a linen cloth 
 with pure water, a milky liquid passes through, from which, when set 
 aside, a white })owder gradually falls. This white powder is \\\e starch 
 of wheaten or other flour. 
 
 2°. When the pith of the sago palm is washed, in a similar manner, 
 with water upon a fine sieve, a white powder is deposited by the milky 
 liquid which passes through. This, when collected, forced through a 
 metal sieve to granulate (or corn) it, and dried by agitation over the 
 fire, is the sago of commerce. 
 
 * The. foUowingJable shows the per centage of woody fibre contained in some commop 
 plants in the green state, and when dried in the air, and at 212° : 
 
 IN THE GREEN STATE. 
 
 Dried in the air. Dried at 212°. Woody fibre. Water, 
 
 percent. percent. percent, percent. 
 
 Barley straw, ripe 50 — — — 
 
 Oat straw, do. — 47 — — 
 
 Maize straw, do. 24 — — — 
 
 Stallis of the field pea - ... — — 10>^ 80 • 
 
 Eifild bean straw 51 — — — 
 
 Wliite turnip — — 3 92 
 
 Common beet (beta vulgaris) - — — 3 86 
 
 Young twigs of common furze- — — 21 50 
 
 Rape straw, ripe — 55 12)^ 77 
 
 Tare straw, do. 37 — — — 
 
 Vetch plant (v. saliva) - - - 42 — 10^ 77 }i 
 
 Do. (V. cracca) in flower — — 5>^ 68 
 
 Do. (V. narbonensis) do. — — 11 >^ 80 
 
 White lupin, in flower, ... — — 7 86 
 
 Lucerne, in flower, .... — — 9 73 
 
 Rye grass, do. — — 11 .68 
 
 Red clover, do. — — T . 79 
 
 White clover, do. — — 4)^ 81 
 
 Trefoil (medium) do. - - - ~ — 8>| 73 
 
 Sainfoin (esparsette) .... — — 7 76 
 
 Trefoil (agrarium) in flower - — — 12 68 
 
 Do. (rubens) do. • . — — 15 60 
 
PREPARATION AND DECOMPOSITION OF STARCH. IQT 
 
 3°. When the raw potato is peeled and grated on a fine grater, and 
 the pulp thus produced well washed with water, potato starcli is ob- 
 tained in the form of a fine white powder, consisting of rounded, glossy 
 and shining particles. 
 
 4°. When the roots of the Maranta Arundinacea ofthe West India 
 Islands are grated and washed like the potatoe, they yield the arrow 
 root of commerce. From the root of the Manioc, the cassava is pro- 
 cured by a similar process, and this, when dried by agitation on a hot 
 plate, is the tapioca of the shops. By this method of drying, both sago 
 and tapioca undergo a partial change, which will be explained in a sub- 
 sequent section (see p. 113.) 
 
 The substances to which these several names are given are, when 
 pure, similar in their properties, and identical in their chemical consti- 
 tution. They are all colourless, tasteless, without smell, when dry 
 and in a dry place may be kept for any length of time without under- 
 going alteration, are insoluble in cold water or alcohol, dissolve readily 
 in boiling water, giving a solution which gelatinizes (becomes a jelly) 
 on cooling — and in a cold solution of iodine* they all become blue. 
 
 When dried at 212°, they consist, according to Dr. Prout, with whose 
 analysis those of other chemists agree, of 
 
 Carbon 44-0 per cent., or 12 atoms. 
 
 Hydrogen .... 6-2 per cent., or 10 atoms. 
 Oxygen 49-8 per cent., or 10 atoms. 
 
 100 
 Starch, therefore, may he represented by the formula Cio Hjo Oio* 
 which is identical with that deduced in the preceding section for the 
 cellular fibre of Payen. Both substances, therefore, contain the same 
 elements (carbon, hydrogen and oxygen), united in the same propor- 
 tions, and in both, as well as in the common fibre of wood, the hydrogen 
 and oxygen exists in the proportion to form water. 
 
 That starch constitutes a large portion ofthe weight of grains and roots, 
 usually grown for food, will appear from the following table, which ex- 
 hibits the quanthy present in 100 lbs. of each substance named : 
 
 Starch per cent. 
 
 Wheat flour 39 to 77 
 
 Rye " 50 to 61 
 
 Barley " 67 to 70 
 
 Oatmeal 70 to 80 
 
 Rice flour 84 to 85 
 
 Maize " 77 to 80 
 
 Buckwheat 52 
 
 Pea and Bean meal 42 to 43 
 
 Potatoes, containing 73 to 78 of water, . 13 to 15 
 
 It thus exists most largely in the seeds of plants, and in some roots. 
 It is frequently deposited, however, among the woody fibre of certain 
 trees, as in that of tlie willow, and in the inner bark of others, as in 
 
 • Iodine is a solid substance, of a lead-grey colour, possessed of a peculiar powerful 
 odour, and forming when heated a beautiful violet vapour. It exists in small quantity in sea 
 water, and in some marine plants. Its solution in water readily shows the presence of 
 starch, by the blue colour it imparts to it. 
 
108 VARIETIES OF GUM. 
 
 those of the beech and the pine.* Hence the readiness with which a 
 branch of the willow takes root and spiouts, and hence also the occa- 
 sional use of the inner bark of trees for food, especially in northern coun- 
 tries, and in times of scarcity. In some roots which abound in sugar, 
 as in those of the beet, the turnip, and the carrot, only 2 or 3 per cent. 
 of starch can be detected. 
 
 § 3. Gum — its constitution and proj^er ties. 
 
 The variety of gum with which we are most familiar is gum arahic, 
 or Senegal, the produce of various species of acacia, which grow in the 
 warmer regions of Asia, Africa, and America. It exudes from the 
 twigs and stems of these trees, and collects in rounded more or less 
 transparent drops or tears. It is also produced in smaller quantities in 
 many of our fruit trees, as tlie apple, the plum, and the cherry ; it is 
 present in some herbaceous plants, as in the althsea and malva officinalis 
 (common and marsh mallow) ; and it exists in lint, rape, and many 
 other seeds. When treated with boiling water these plants and seeds 
 give mucilaginous solutions. 
 
 Many varieties of gum occur in nature, but they are all characterised 
 by being insoluble in .alcohol, by dissolving or becoming gelatinous in 
 hot or cold water, and by giving mucilaginous — viscid and glutinous — 
 solutions, which may be employed as a paste. 
 
 Three distinct species of gum have been recognised by chemists: 
 
 1°. Arahin — of which gum arable and gum Senegal almost entirely 
 consist. It is readily soluble in cold ivater, giving a viscid solution, usu- 
 ally known by the name of the mucilage of gum arable. 
 
 2°. Cerasin — which exists in the gum of the cherry-tree. It is inso 
 luhle in cold water, but dissolves readily in boiling water. When thus 
 dissolved it may be dried without losing its solubility, and is therefore by 
 boiling supposed to be changed into arabin. 
 
 3°. Bassorin — existing in what is called bassora gum — and forming 
 a large portion of gum tragacanth.f It swells and becomes gelatinous in 
 cold water, ^but does not dissolve in water either cold or hot. 
 
 By these characters, the three kinds of gum are not only readily dis- 
 tinguished, but may be easily separated from each other. Thus if a 
 native gum or an artificial mixture contain all the three, simple steeping 
 in and subsequent washing with cold water, will separate the arabin — 
 boiling water will then take up the cerasin^ and the bassorin will remain 
 behind. 
 
 These different kinds of gum all possess the same chemical constitu- 
 tion. According to the analyses of Mulder, they consist of 
 Carbon . . . 45*10 per cent., or 12 atoms. 
 Hydrogen . . 6-10 " or 10 " 
 
 Oxygen . . . 48'80t " or 10 " 
 
 100 
 
 * Its presence is readily detected in such wood by a drop of the solution of iodine — which 
 ^ives a permanent blue to starch, but to the woody fibre only a brownish stain. 
 
 t This gum exists along with starch in the roots of the various species of orchis, especially 
 of those which are used for making salep (Meyen). 
 
 Berzelius Arsberdttelse, 1839, p. 443. 
 
VARIETIES AND CONSTITUTION OF SUGAR. 109 
 
 In these analyses, as in those of starch and woody fibre, we see that 
 the per centage of oxygen is equal to that of the liydrogen multiplied by 
 8, and consequently that these two elements are, as already stated, in 
 the proportion to form water. But we see also that the carbon is in the 
 proportion of 12 atoms or equivalents to 10 of each of the other con- 
 stituents, and therefore gum may be represented by C^g -Hj q Oj ^ — a 
 formula which is identical with that already given for starch and cellu- 
 lar fibre. 
 
 It appears, therefore, that not only may g-wm, starch, and cellular jihre be 
 represented by carbon and water, but that they all consist of carbon and 
 the elements of water, united together in the same proportions. 
 
 Gum not only exists in many seeds, and exudes as a natural product 
 from the stems and twigs of many trees, but is also contained in the 
 juices of many other trees, from which it is not known to exude ; and in 
 the sap of most plants it may be detected in greater or less quantity. It 
 may be considered, indeed, as one of those substances which are pro- 
 duced most largely and most abundantly in the vegetable kingdom, 
 since, as will hereafter appear, it is one of those forms of combination 
 through which organic matter passes in the interesting series of changes 
 it undergoes during the development and growth of the plant. 
 
 § 4. Of Sugar — its varieties and chemical constitution. 
 
 1°. Cane Sugar. — Sugar, identical in constitution and properties with 
 that obtained from the sugar-cane, and generally known by the name of 
 cane-sugar, exists in the juices of many trees, plants, and roots. In the 
 United States of North America the juice of the maple tree is extensive- 
 ly collected in spring, and when boiled down yields an abundant supply 
 of sugar. In the Caucasus that of the walnut is extracted for the same 
 purpose. The-juice of the birch also contains sugar, and it may be ob- 
 tained, in lesser quantity, from the sap of n^any other trees. In the 
 juice of the turnip, carrot, and beet, it is also present, and in France and 
 Germany the latter root is extensively cultivated for the manufacture of 
 beet sugar. In the unripe grains of corn, at the base of the flowers of 
 many grasses and clovers when in blossom, and even in many small 
 roots, as in that of the quicken or couch-grass (triticum repens), the pre- 
 sence of sugar may likewise be readily detected. 
 
 Sugar is principally distinguished by its agreeable sweet taste. 
 When pure, it is colourless and free from smell. It dissolves readily 
 in alcohol and in large quantity in water. The solution in water, when 
 much sugar is present, has an oily consistence, and is known by tlje name 
 of syrup. From this syrup the sugar gradually deposits itself in the 
 form o^ sugar candy. If the syrup be boiled on too hot a fire, it chars 
 slightly, becomes discoloured, and a quantity of molasses is formed. 
 Pure cane-sugar, free from water, consists of 
 
 Carbon . . . 44-92 per cent., or 12 atoms. 
 Hydrogen . . 6-11 " or 10 '* 
 
 Oxygen . . . 48-97 " or 10 " 
 
 100 
 If we compare these numbers with those given for starch and gum in 
 the preceding sections, we see that they are almost identical — so that 
 
110 CANE, GRAPE, MANNA, AND LIQUORICE SUGARS. 
 
 cane-sugar also contains oxygen and hydrogen in the proportions to form 
 water, and may likewise be represented by the formula C,2 Hjo O,o. 
 
 2°. Grape sugar. — In the juice of the grape a peculiar species of su- 
 gar exists, which, in the dried raisin, presents itself in the form of little 
 rounded grains. The same kind of sugar gives their sweetness to the 
 gooseberry, the currant, tlie apple, pear, plum, apricot, and most other 
 fruits. It is also the sweet substajice of the chesnut, of the brewers' 
 wort, and of aU fermented liquors, and it is the solid sugar which floats 
 in rounded grains in liquid honey, and which increases in apparent 
 quantity as the honey, by keeping, becomes more and more solid. 
 
 Grape sugar has neaily all the sensible characrers of cane sugar, with 
 tlie exception of being less soluble in water and also less sweet, — 2 parts 
 of the latter imparting an etjual sweetness witli 5 of the former. 
 
 In chemical constitution they ditfer considerably. Thus grape sugar 
 dried at 250° F., consists of 
 
 Carbon . . . 40-47 per cent., or 12 atoms. 
 Hydrogen . . 6-59 " or 12 " 
 
 Oxygen . . . 52-94 " or 12 " 
 
 100 
 
 The oxygen here is still eight times greater than the hydrogen, and, 
 therefore, in this variety of sugar also, these elements exist in the pro- 
 portions to form water. But for every 12 equivalents of carbon, dry 
 grape sugar contains 12 of hydrogen and 12 of oxygen. It is conse- 
 quently represented by C[2 H,o Ojo, and contains the elements of two 
 atoms of water (H2 Oo) more than cane sugar.* 
 
 3°. Manna sugar, sugar of liquorice, S^'c. — Besides the cane and grape 
 sn2;ars which occur in large quantity in the juices of plants, there are 
 (jiher varieties which occur less abundantly, and are therefore of less in- 
 terest in the study of the general vegetation of the globe. Among these 
 is manna, which partly exudes and is partly obtained by incisions from 
 certain species of the ash tree which grow in the warmer countries of 
 Southern Et«epe (Sicily and Italy), and in Syria and Arabia. It also 
 exists, it is said, in the juice of the larch tree, of common celery, and of 
 certain trees which are met with in New South Wales. LiquoFice root 
 also contains a species of black sugar, which is known in this country 
 under the names of Spanish and Italian juice, from the countries where 
 it is grown. In the mushroom and o\h.ex fungi a colourless variety, ap- 
 parently peculiar, has' also been met with, — and milk owes its sweet- 
 ness to a species of sugar formed in the interior of the animal along with 
 the other substances which the milk contains. 
 
 These several kinds of sugar differ more or less, not onU'^ in sensible 
 and chemical properties, but also in chemical constitution, from the more 
 abundant cane and grape sugars — but they form too smalJ a part of the 
 general products of vegetation, and are of too little consequence in practi- 
 
 * Solutions of cane and grape sugar are readily distinguished from each other by the fol- 
 lowing chemical characters: — I. lithe solution be heated and a few drops of sulphuric acid 
 then added, cane sugar will be decomposed, blackened, and made to fall as a black or brown 
 powder — while a solution of arape sugar will at the most be only slightly discoloured. 2. If, 
 instead of sulphuric acid, caustic potash be employed, the cane sugar will be unchanged, 
 wliile the grape sugar will be blackened and thrown down. 
 
MUTUAL RELATIONS OF WOODY FiBRK, STAHCII, GUM, ETC. Ill 
 
 cal agriculture to render it necessary to do more than thus shortly ad- 
 vert to their existence.* 
 
 § 5. Mutual relations of woody fibre, starch, gum, and sugar. 
 It may be interesting now to consider for a moment the mutual rela- 
 tions of the several substances, woody fibre, starch, gum, and sugar — 
 above described — which occur so largely in tlie vegetable kingdom, and 
 are serviceable to man for so many difterent purposes. These relations 
 will be best seen on comparing the formulas by which they are respec- 
 livel}' represented. Thus — 
 
 Woody Fibre (lignin) is represented by C,2 Hg O3 
 Cellular Fibre (according to Payen) by C^g H-io ^\o 
 Starch (dried at 212° F.) by C^a Hio 0,0 
 
 Gum (any of tlie 3 varieties) by C12 Hio Oi 
 
 Cane Sugar (free from water) by C12 Hio Oi 0* 
 
 Grape Sugar (dried at 130° F.) by C12 H12 Oi2f 
 
 In these formuhe we observe — 
 
 1°. That the eqivalents of the oxygen are erpial to those of the hydro- 
 gen in all the formulas, ajid, therefore, that all these substances may be 
 supposed to consist of caibon and water. 
 
 2°. The formulas for cellular fibre, starch, gum, and cane sugar, are 
 identical. They consist of tlie same elements united together in the same 
 jrro portions. 
 
 Tliis is one of those facts which not only appear very remarkable to 
 the unlearned, but are scarcely capable of being clearly comprehended 
 and explained, even by those who have most profoundly studied this 
 branch of natnral science. Starch and sugar — how diilerent their 
 properties ! how unlike their uses ! how unequal their importance to the 
 human race ! yet they consist of the same weights of the sanie substances, 
 difTerently conjoined. The skilful arcljitect can put together the same 
 proportions of the same stone and cement— atjd the painter can combine 
 the same colours so as to produce a thousand varied impressions on the 
 sense of sight. In the hand of Deity matter is infinitely more plastic. 
 At His bidding the same particles can unite in the same quantity so as 
 to produce the most unlike impressions — and on all our senses at once. 
 
 3°. A knowledge of the above close relations in composition, nmong 
 a class of substances occurring so abundantly in the vegetable kingdom, 
 imparts a degree of simplicity to our ideas of this otherwise complicated 
 subject. It does not appear so mysterious that we should have wo/^dy 
 fibre, and starch, and gum, and sugar, occurring together in variable 
 quantities, when we know that they are all made up of the same ma- 
 terials, in the same or nearly the same proportions— or that one of these 
 should occasionally disappear from a plant, to be replaced in whole or 
 in part by another. 
 
 * For a list of plants from which sugar has been extracted, see Thomson's OrsrameChemiS' 
 /jn/(1838), p. 647. 
 
 t Crystallized cane sugar (sugar candy) loses 53 percent, of water in favourable circum- 
 stances. This is equal to one equivalent (HO), so that if dry sugar be Ci'2 Hio Oio, crystallized 
 sugar is Cis Hii Ou— or C12 Hio Oio+HO, since there is no doubt that this one equivalentof 
 the hydrogen and oxygen exists in crystallized sugar in the state of water. Jn like manner, 
 crystallized honey or grape sugar— as it occurs in honey or in the dried grape — loses 9 per 
 cent, of water when heated to 250"^ F. This is equal to two equivalents (2HO), so that crys- 
 tallized grape sugar is represented by C12 Hi4 O14 or C12 H12 Oi2-f2HO. 
 
112 MUTUAL TRANSFORMATIONS OF STARCH, GUM, ETC. 
 
 A further question, however, arises in our minds. We naturally ask, 
 — does nature, in thus removing one of these compounds, and supplying 
 its place by another, actually form from its elements the new substance 
 introduced, or does she produce it by a mere change or transformation 
 of those previously existing. A satisfactory reply to this question may 
 be derived from the facts detailed in the following section. 
 
 § 6. Mutual transformations of woody fibre, starch, gum, and sugar. 
 
 I. WOODT FIBRE. 
 
 1°. Action of heat. — If wood be reduced to the state of fine saw-dust, be 
 then boiled in water to separate everything soluble, afterwards dried by 
 a gentle heat, and then heated several times in a baker's oven, it will be- 
 come hard and crisp, and may be ground in the mill into a fine meal. The 
 powder thus obtained is slightly yellow in colour, but has a taste and 
 smell similar to the flour of wheat; it ferments when made into a paste 
 with yeast or leaven, and when baked gives a ligiit homogeneous bread. 
 Boiled with water, it yields a stiff tremulous jelly, like that from 
 starch (Autenrieth. — Schubler, Agricultur Chemie, i., p. 224.) By the 
 agenc}^ of heat, therefore, it appears that the woody fibre may be changed 
 into starch. 
 
 2°. Action of sulphuric acid. — If to tliree parts of the sulphuric acid 
 of the shops (oil of vitriol) one part of water be added, and a portion of 
 delicate woody fibre be immersed in it for half a minute, and the whole 
 then rubbed in a mortar with a few drops of a solution of iodine — the 
 woody fibre will assume a blue colour, showing that it is in part at least 
 changed into starch* (Schleiden). 
 
 Again, if three parts of fine saw-dust or of fragments of old linen be 
 rubbed in a mortar with four of the sulphuric acid of the shops added 
 by degrees — it will, in a quarter of an hour, be rendered completely so- 
 luble in water. If the solution in water be freed from acid by chalk, and 
 then evaporated, a substance resembling gum arable is obtained (Bra- 
 connot). According to Schleiden, the fibre may be seen under the mi- 
 croscope gradually to change from without inwards, first into starch and 
 then into gum. 
 
 Further, if this gum be digested with a second portion of sulphuric 
 acid diluted with 8 or 10 times its weight of water, it will be gradually 
 converted into grape sugar ; or the fibre of wood or linen may be changed 
 directly into sugar by the prolonged action of dilute sulphuric acid. 
 
 3°. Ajction of potash. — If saw-dust be mixed with from two to eight 
 times iis weight of hydratef of potash and as much water, and boiled 
 till a crust forms on the surface, and if dilute sulphuric acid be then added 
 till the whole is slightly sour, the undestroyed woody fibre will give an 
 
 • It will be recollected that starch is characterized by giving a blue colour with a solution of 
 iodine (see p. 107). 
 
 The simplest way of trying this experiment is, to take a quantity of clean cotton — to wet 
 it with water, squeezing out again as much as possible — then to spread it out upon a flat dish 
 and moisten it quickly and thoroughly with the acid diluted as above. After half a minute, 
 add tlie solution of iodine, stir quickly with a glass rod, and immediately add water, when 
 the blue compound of iodine and starch will speedily deposit itself —(Schleiden, Pog. Annal., 
 xliii., p. 396.) 
 
 t Hydrate of potash is tlie caustic substance which is obteuned by boiling common pearl- 
 ash with quick lime. 
 
ACTION OF HEAT ON STARCH. 110 
 
 instantaneous deep blue on the addition of iodine, showing that starch 
 has been formed. . 
 
 Woody fibre, therefore, may be changed into starch, either by the un- 
 aided action of heat, by that of sulphuric acid, or by boiling with caustic 
 potash, — ai>d the starch thus produced may be further transformed, first 
 into gum and then into grape sugar, by the prolonged action of dilute 
 sulphuric acid, assisted by a moderate heat. 
 
 II. STARCH. 
 
 1°. Action of heat. — When flour, potato, or arrow-root starch is 
 spread out upon a tray, then introduced into an oven and gradually 
 heated to a temperature not exceeding 300° F., it slowly changes, ac- 
 quires a yellow or brownish tint according to the temperature employed, 
 and becomes entirely soluble in cold water. It is changed into gum. 
 Under the names of starch-gum, or British-gum, this substance is large- 
 ly manufactured in this country, and is successfully substituted for gum 
 arable by the calico-printers in thickening many of their colours.* 
 
 The gum thus prepared not unfretjuently also possesses a sweet taste, 
 from the further change of a portion of the gum into sugar. 
 
 2°. Action of water. — When starch is dissolved in boiling water, and 
 is then allowed to stand in the cold either in a close vessel or exposed to 
 the air, it gradually changes into gum or sugar. The process, however, 
 is slow, and months must elapse before the whole of the starch is thus 
 spontaneously transformed in the presence of water (De Saussure). It 
 takes place more rapidly when starch and water are boiled together for 
 a length of time. 
 
 3°. Action of sulphuric acid. — From what has been already stated in 
 regard to the action of this acid on woody fibre it will readily be supposed 
 that native starch, of any variety, is likely to undergo transformation 
 when subjected to its influence. 
 
 In reality, if 50 parts of starch, 12 of sulphuric acid, and 139 of water 
 be taken, and if the starch be thoroughly moistened with a portion of the 
 water, and then poured into the mixture of the acid with the remainder 
 of the water, and heated to 190° F., the starch will be entirely convert- 
 ed into gum. By further and more prolonged heating this gum is 
 changed into grape sugar. The gum or sugar may be obtained iq a 
 separate state by adding to the solution either chalk or lime, which will 
 combine with and carry down the acid.f One hundred pounds of starch 
 treated in this way will yield from 105 to 122 lbs. of dry grape sugar. 
 
 The rapidity with which this transformation takes place depends 
 partly upon the temperature and partly upon the proportion of acid em- 
 ployed. Thus 100 lbs. of starch mixed with 600 of water and 10 of 
 sulphuric acid, will be converted into grape sugar by boiling for seven 
 hours. If by increasing the pressure the temperature be raised to 250° 
 F., the transformation will be effected in a few minutes. With only one 
 
 * During the baking of bread this conversion of starch into gum takes place to a consider- 
 able extent. Thus Vogel found that flour which contained no gum gave, when baked, a 
 bread of which 13 per cent., or nearly one-fifth of the whole weight, consisted of gum. 
 Thus one cf the effects of baking is to render the flour-starch more soluble, and therefore C?) 
 more easily digestible. 
 
 t It forms gypsum with it (sulphate of lime) which is a compound of lime and sulphuric 
 acid. 
 
114 CHANGE OF CANE INTO GRAPE SUGAR, 
 
 pound of acid and the same quantity of starch and water, the change 
 ■will be effected in three hours by a temperature of 230° F. This mode 
 of convertinc; potato starch into grape sugar is said to be extensively 
 practised in France, for the purpose of subsequently fermenting the 
 sugar and converting it into brandy. 
 
 III. GUM. 
 
 Action of sulphuric acid. — If powdered gum arabic be rubbed in a 
 mortar with the sulphuric acid of the shops, a brownish solution is ob- 
 tained, which, when diluted with water and treated with chalk, yields a 
 gummy substance similar to that obtained in the same way from starch 
 and woody fibre. Prolonged digestion with diluted acid converts a por- 
 tion of this gum into sugar. — [Berzelius, Traite de Chemie, (1831), v., 
 p. 217.] 
 
 IV. CANE SUGAR. 
 
 1°. Action of heat. — When crystallized cane sugar is heated to 320° 
 F. it melts, and if the temperature be raised to 360° F. it gives ofTtwo 
 atoms of water and is changed into caramel. This caramel is an un- 
 crystallizable sugar, which is generally present in artificial syrups, and 
 is often of a brownish colour. It contains the elements of an atom of 
 water less than cane sugar, and is represented by Cj^ Hg Og. It is 
 not known to occur in the natural juices of plants. 
 
 2°. Action of sulphuric acid. — When cane sugar is digested with di- 
 lute sulphuric acid, aided by a gentle heat, it is rapidly converted into 
 grape sugar. The acid of grapes (tartaric acid) and many other vege- 
 table acids produce a similar change. 
 
 It is obvious that this conversion of cane into grape sugar can only 
 take place in the presence of water, inasmuch, as has already been 
 shown (p. 110), grape sugar contains the elements of two atoms of water 
 more than cane sugar, or 
 
 Cane sugar. Water. Dry grape sugar. 
 
 Ci2 H,o Ou, + 2HO = C^2 Iii2 0|2' 
 
 We may revert now to the question with which we concluded the 
 preceding section. Since these different substances are so closely allied 
 in chemical constitution, and occur so often in connection with each 
 other in the vegetable kingdom, does nature, when her purposes demand 
 the change, actually transform them, the one into the other, in the inte- 
 rior of the plant? The answer may now be safely given, that she cer- 
 tainly does. What we can so readily perform by our rude art may be 
 still more en>;i!y effected in the living vegetable. That which is starch 
 or gum in one part of the plant, may become cane or grape sugar in 
 another, and woody fibre in a third. Thus by re-arranging the same 
 kind an(jl quantity of the several elements, may the various and unlike 
 forms of matter which constitute the main products of vegetation be 
 readily produced. 
 
 Still the facility is only apparent. We can assure ourselves of the 
 fact of such conversions, because we can at will induce them. But who 
 operates upon these substances in the interior of the plant? Whose 
 mind and will directs these changes — prescribing when, where, and in 
 
GRAPE SUGAR ALONE FERMENTS. 115 
 
 what order they shall fake place ? How much depends upon the re- 
 fined and little understood mechanism of the vegetable structure- — lujw 
 much on the living principle itself! What is this living principle — 
 how can it direct !* 
 
 § 7. Of the fermentation of starch and sugar — and of the relative circum- 
 stances under ivhich cane and grape sugars generally occur in nature. 
 It will be of use to us, in connection with the above transformations, 
 to advert to the property possessed by starch and nearly all the known 
 varieties of sugar of entering into fermentation under favourable cir- 
 cumstances. When flour is made into a paste with leaven or yeast it 
 begins to rise and ferment, — sooner or later, according to the kind of 
 flour and the quantity of ferment added. When to a decoction of malt 
 or to a solution of starch or of cane or grape sugar in water, a portion of 
 yeast is added, fermentation is speedily induced ; and if not arrested by 
 unfavourable circumstances it will continue until the whole of the 
 starch or sugar disappears. 
 
 In all these cases it is grape sugar alone that undergoes fermentation. 
 [Rose, Poggen. Annal., lii., p. 297.] The starch of the moist dough or 
 of the solution is partially transformed into grape sugar before fermenta- 
 tion commences. Such is the case also with the decoction of malt and 
 with cane sugar. The fermentation commences soon after the first por- 
 tion of grape sugar is formed, and proceeds more or less rapidly accord- 
 ing as this transformation is more or less speedily effected. Hence, in 
 the art of brewing, the necessity of cautiously regulating the tempera- 
 ture by which this change of the starch and sugar is promoted and hast- 
 ened. 
 
 The fermentation itself is the result not of a mere transformation of 
 one form of matter into another having the same elementary constitu- 
 tion, but of a decomposition of one substance into two others unlike itself 
 either in properties or in chemical composition. The grape sugar is re- 
 solved into alcohol (spirits of wine), which remains in the liquid, and into 
 carbonic acid, which escapes in the form of gas and causes the fermen- 
 tation. Thus alcohol being represented by C4 Hg O2, and carbonic acid 
 by CO2, 
 
 2 of alcohol = Cg H12 O4 and 
 
 4 of carbonic acid = C4 O3 make up 
 
 1 of grape sugar ^=^^12^12^12' 
 
 It is an interesting fact that the cane and grape sugars occur in na- 
 ture in circumstances which are entirely consistent with the statement 
 in the preceding section, regarding the action of acids on the former 
 variety of this natural product. Fruits contain grape sugar, which in- 
 creases in quantity as they ripen or become less sour. In the sugar 
 cane, the beet root, and the maple and birch trees, cane sugar exists, 
 but in their juices no acid is associated with the sugar. On the contra- 
 ry, ammonia is known to be present in most of them along with the 
 cane sugar. Hence it is inferred, that as in our hands and in our exper- 
 iments cane sugar is changed by the agency of acids into grape sugar", and 
 
 • " Oanst thou by searching find out God— Canst thou find out the AJmighty unto perfection 1" 
 
116 SUBSTANCES CONTAINING NITROGEN. 
 
 with remarkable ease by that acid which exists in the ripe grape, so it is 
 in the interior of plants. Where sugar occurs in connection with an acid 
 in the juice of a plant, it is grape sugar in whole or in great part, be- 
 cause in the presence of an acid body cane sugar cannot permanently ex- 
 ist, but is gradually transformed into the sugar of gra[)es. It ihus ap- 
 pears also why fruits so readily enter into fermentation, and why,-even 
 when preserved with cane sugar, they will, in consetjuence of the acid 
 they retain, slowly change the latter into grape sugar, and thus induce 
 fermentation.* 
 
 § 8. Of substances ivhick contain Nitrogen. — Gluten, Vegetaole 
 Albumen, and Diastase. 
 
 The substances described in the preceding sections consist of carbon, 
 hydrogen, and oxygen only, and of them the great bulk of the vegeta- 
 'ble productions of the globe consists. But there are certain other sub- 
 stances occurring along with starch and sugar, into which nitrogen enters 
 as a constituent, and which, though not formed in the vegetable king- 
 dom in very large quantity, are yet of such interest and importance in 
 other resj)ects, as to make it necessary shortly to advert to them. 
 
 1^. Gluten. — When the flour of wheat is made into a dough, and this 
 dough is washed with water upon a fine sieve, a milky liquid passes 
 through, from whicli starch gradually subsides. This has been already 
 stated. But on the sieve, when the water ceases to go through milky, 
 there remains a soft adherent, tenacious, and elastic substance, which 
 can be drawn out into long strings, has scarcely any colour, taste, or 
 smell, and is scarcely diminished by washing either with hot or with 
 cold water. This substance is the gluten o^ wheat. The flour of other 
 kinds of grain also yield it by a similar treatment, though generally in 
 much smaller quantity. This appears from the following table : — 
 
 The grain of 
 
 Wheat contains 8 to 35 per cent, of gluten. 
 Rye .... 9 to 13 " " 
 
 Barley ... 3 to 6 " " 
 
 Oats .... 2 to 5 " 
 
 When the moist gluten is dried in the air or at the temperature of 
 boiling water, it diminishes much in bulk, and hardens into a brittle 
 semi-transparent yellow substance resembling horn or glue. In this state 
 it is insoluble in water, but dissolves readily in vinegar, in alcohol either 
 cold or hot, and in solutions containing caustic potash, or soda, [the 
 common pearl-ash or soda of the shops boiled with quick-lime.] 
 
 2°. Vegetable Albumen. — To the white of egg the name of albumen 
 (albus, white) has been given by chemists. It ]K)Ssesses the well known 
 {)roperty of coagulating or of forming a white solid insoluble substance, 
 when it is heated either alone or after being mixed with water. 
 
 When the starch has subsided from the milky liquid which passes 
 
 * Milk also, in favourable circumstances, as when kept at a temperature of 100° F., ufn- 
 detBoes fermentation, and in some countries of Asia a spirituous liquor is prepared from 
 mares' and asses' milk. In this case the milk first becomes sour, tiien the acid thus form- 
 ed converts the mitk sugar into grape sugar, and finally Uiis sugar enters into fermenta- 
 tion. This takes place more readily in consequence of the presence of the decomposing 
 cheesy matter (casein) of the milk — as is shown by the fact that the introduction of a small 
 quantity of the curd of milk into a solution of grape sugar will cause it to ferment. 
 
GLUTEN, VEGETABLE ALBUMEN, AND DIASTASE. 117 
 
 through the sieve in preparing the gluten of wheat, the water rests trans- 
 parent and colourless above the white sediment. If this water be heated, 
 it will become more or less troubled, and white films or particles will 
 separate, which may be easily collected, and which possess all the pro- 
 perties of coagulated albumen, or boiled white of egg. To this sub- 
 stance the name oi" vegetable albumen has been given. When the fresh 
 prepared gluten of wheat is boiled in alcohol a portion of albumen gene- 
 rally remains undissolved, showing that water does not completely wasli 
 it out from the gluten. 
 
 Vegetable albumen, when fresh and moist, has neither colour, taste, 
 nor smell, is insoluble in water or alcohol, but dissolves in vinegar and 
 in caustic potash or soda. When dry it is brittle, more or less coloured, 
 and opaque. In the seeds of plants, it exists only in small quantity-^ 
 thus the grain of 
 
 Wheat contains | to 1| per cent. 
 Rye . . . 2 to3| " 
 Barley . . • yV *» i 
 Oats ... I to ^ " 
 It occurs more largely however in the fresh juices of plants, in those 
 of cabbage leaves, turnip roots, and many others. When these juices 
 are heated the albumen coagulates and is readily separated. 
 
 Gluten and vegetable albumen appear to be as closely related as sugar 
 and starch are to each other. Like these two substances, they consist 
 of the same elements, united together in the same proportions, and are 
 capable of similar mutual transformations. According to the most re- 
 cent analyses, those of Dr. Scheerer, they consist of 
 
 Carbon = 64-76 
 Hydrogen = 7-06 
 Oxygen =20-06 
 Nitrogen = 18-12 
 
 100 
 
 When exposed to the air in a moist state these substances undergo de- 
 composition. They ferment, emit a most disagreeable odour, and pro- 
 duce, among other compounds, vinegar and ammonia. 
 
 The important influence which gluten and vegetable albumen are 
 supposed to exercise over the nourishing properties of the different kinds 
 of food in which they occur, will be considered in a subsequent part of 
 these lectures.* 
 
 3°. Diastase. — When cold water is poured upon barley newly malted 
 and crushed, is permitted to remain over it for a quarter of an hour, is 
 then poured off", filtered, evaporated to a small bulk over boiling water, 
 again filtered if necessary, and then mixed with much alcohol, a white 
 tasteless powder falls — to which the name o^ diastase has been given. 
 
 ' There occur in the animal kingdom — in the bodies of animals — three other forms of the 
 substance above described under the names of gluten and vegetable albumen. These are 
 albumen or white of egg, already mentioned, — casein, the curd of cheese,— and fibrin, the 
 substance of the muscular fibre of animals. • 
 
 1^. Casein. — When the curd of cheese is well washed with water, and then boiled in 
 alcohol to free it from oily matter, it forms the casein of chemists. While moist it is soft 
 and colourless, but as it dries it hardens, assumes a yellow colour, and becomes semitrans- 
 parent. Even when moist it is perfectly insoluble either in cold or in hot water. It is solu- 
 
 6 
 
118 PRODUCTION OF DIASTASE. 
 
 If unmalted barley be so treated no diastase is obtained. This sub- 
 stance, therefore, is formed during the process of malting. 
 
 If wheat, or barley, or potatoes, which by steeping in water yield no di- 
 astase, be made to germinate (or sprout), and be afterwards bruised and 
 treated as above, diastase will be obtained. It is therefore produced 
 during germination. 
 
 If the shoot of a potato be cut off within half an inch of its base, this 
 lower portion, with the part of the potato to which it is immediately at- 
 tached, separated from the rest — and the three parts {the upper portion 
 of the shoot — the lower portion with its attached fragment of potato — 
 and the remaining mass of the potato) treated with water, — only that 
 portion will yield diastase in which the base of the shoot is situated. 
 "When a seed sprouts, therefore, this substance is formed at the base of 
 the germ, and there remains during its growth. 
 
 If the same portion of the potato, or if the grain of barley or wheat is 
 
 ble, however, in water containing vinegar, or to which a litUe carbonate of potash or soda 
 has been added. It may be kept for any length of time in a dry place, without undergoing 
 decay. The changes undergone by old cheese are chiefly due to the oily and other sut? 
 stances with which the curd is mixed. It has been remarked, that when the gluten of wheat 
 is left for a length of time in a moist state it undergoes a kind of fermentation and gradually 
 acquires the smell and taste of cheese (Rouelle.) 
 
 2°. Fibrin. — When lean beef or mutton is long washed in watertill it becomes colourless, 
 and is then boiled in alcohol to separate the fat, a colourless, elastic, fibrous mass is obtained, 
 which is the fibrin of chemists. In recently drawn blood it exists in the liquid state, but coa- 
 gulates spontaneously when exposed to the air, and forms the greater part of the clot of 
 blood. It dissolves in a solution of caustic potash or of nitre, and in vinegar. 
 
 3°. Albumen. — This substance in the liquid state exists in the white of egg, and in the 
 serum, of the blood. It coagulates by heating to 160° F , or if previously mixed with water 
 by raising to 212° F. 
 
 These three substances, in addition to their well Known sensible properties, are distin- 
 guished as follows : 
 
 1°. Liquid casein m milk, is not coagulated by heating alone — the addition of rennet orof 
 a little acid (vinegar or spirit of salt) is necessary, when it curdles readily. 
 
 2°. Liquid albumen in white of egg, coagulates by heat alone, as when an egg is put into 
 hot water. 
 
 3°. Liquid fibrin in the blood coagulates by mere exposure to the air, or more rapidly by 
 agitation in contact with the air. 
 
 Like starch and sugar tliese three substances are mutually convertible by known means. 
 T\\us fibrin, if unboiled, dissolves by digestion at 80° F. in a saturated solution of nitre, and 
 acquires the properties of liquid albumen; and if to liquid albumen a little caustic potash be 
 added, and afterwards much alcohol, it will be thrown down in the form and with the pro- 
 perties of casein. 
 
 All these substances appear to contain the same organic constituents in the same propor- 
 tions. 
 
 Boussingault first showed the identity in chemical constitution of gluten and vegetable al- 
 bumen. — [Pog. An., xl., p. 2.53.] Mulder afterwards proved a similar identity between vege- 
 table albumen and the white of egg, fibrin, and casein. — [Ann. de Chim. et. de Pliys., Ixv., p. ' 
 301.] Mulder supposes them to differ from each other by the presence in unlike quantities 
 of a small admixture of sulphur, phospliorus or phosphate of lime. 
 
 Those who arc not familiar with the history and with the nature of chemical research, can 
 form no idea of the time and latxiur which has by different chemists been expended on fhis 
 one branch. The persevering industry of Dr. Mulder, of Rotterdam, appeared to have 
 cleared up tlie entire subject by a long series of investigations and analyses,— [for an out- 
 line of his results, see Berzelius Arsberattlese, 1839, p. 611,] — when first Vogel, then Prosper 
 Denis, and latest Liebig and Dr. Scheerer, have arrived at different results. Our ideas are 
 thus again unfixed, and our partial generalizations set aside for future emendation. 
 
 The analysis inserted in the text, as representing the composition of gluten and vegetable 
 albumen, is that given by Dr. Scheei-er for the purest form oi fibrin. I have selected it in 
 preference to the results either of Boussinganlt orof Mulder, because it is the most recent, 
 and has been obtained with a knowledge of all the previous researches, — and assuming the 
 chemical identity of this entire gwoup of substances, is the most likely to represent their 
 constitution with accuracy. It differs from the analysis of Mulder only in stating the nitro- 
 gen at 2 per cent, higher than was done by that chemist. The recent improvements in the 
 mode of determining the true quantity of nitrogen in organic substances, appear to justify 
 us in expecting the result of Scheerer to be in this respect the more correct. 
 
DIASTASE CHANGES STARCH INTO SUGAR. llU 
 
 examined, when the first true leaves of the plant have been fully 
 formed and expanded, the diastas'3 will be found to have in great part, 
 if not entirely, disappeared. This substance, therefore, is first formed 
 when the seed begins to sprout, performs a function which makes its 
 presence necessary at the base of the germ, and which function being 
 discharged when the true leaves are formed, it then disappears. What 
 is the nature of this temporary function, why the diastase must reside at 
 the base of the sprout in order to discharge it, and why it should so early 
 cease, will appear from a detail of the properties of this singular sub- 
 stance. 
 
 Properties of diastase. — If the solution obtained from malt be digested 
 with potato, flour, or other starch, at a temperature between 120° and 
 140° F., the latter will gradually dissolve and will form a colourless 
 transparent solution. When this solution is carefully evaporated a yel- 
 lowish white powder is obtained, perfectly soluble in water, to which 
 the name of dextrine has been given, [because its solution turns to the 
 right a ray of polarized light when passed through it.] This dextrine 
 has the same composition as starch. It is merely starch changed or 
 transformed in such a way as to become soluble in cold water, — a 
 change analogous to that which it undergoes by simply boiling in water. 
 
 But if the digestion be continued after the starch is dissolved, the so- 
 lution will gradually acquire a sweet taste, and if it be now evaporated 
 it will yield, instead of dextrine, a mixture of gum and grape sugar. 
 And if the digestion be still further prolonged, the whole of the starch 
 will be converted into grape sugar only. — [See above, § 6, p. 113.] 
 
 Thus diastase (like sulphuric acid) possesses the property of trans- 
 forming starch entirely — first into gum, and then into grape sugar. The 
 intermediate stage of dextrine has not been recognized in the action of 
 sulphuric acid, nor is it easy to arrest the action of diastase exactly at 
 this point — the most carefully prepared dextrine always containing a 
 mixture of gum and sugar. One part of diastase will convert into sugar 
 2000 ptirts of starch. 
 
 A solution of diastase, when allowed to stand, soon undergoes decom 
 position, and after being boiled, it has no further effect upon starch. It 
 has not been analysed, because it is difficult to obtain it in a pure state. 
 It contains nitrogen, however, for, when moistened and exposed to the 
 air, it decomposes, and, among other products, yields ammonia.* 
 
 The functions of diastase — one of the purposes at least for which it is 
 produced in the living seed, and situated at the base of the germ — will 
 now be in some measure understood. The starch in the seed is the food 
 of the future germ, prepared and ready to minister to its wants when- 
 ever heat and moisture concur in awakening it to life. But starch is it- 
 self insoluble in water, and could not, therefore, accompany the fluid sap 
 when it begins to move and circulate. For this reason diastase is 
 formed at the point where the germ first issues from the mass of food. 
 There it transforms the starch, and renders it soluble, so that the young 
 vessels can take it up and convey it to the point of growth. When the 
 starch is exhausted its functions cease. It is then itself transformed and 
 
 • It will be recollected that ammonia contains nitrogen, being represented by NH3. — See 
 Lecture III., p. 51. 
 
120 ADAPTATIONS IN THE PRODUCTIONS OF DIASTASE. 
 
 carried into the general circulation. Or when, as in the potato, much 
 more starch is present than is in many cases requisite, its function ceases 
 long before the whole of the starch disappears. Its presence is necessa- 
 ry only until the leaves and roots are fully formed — when the plant is 
 enabled to provide for itself, and becomes independent of the starch of 
 the seed. When this period arrives, therefore, the production of dias- 
 tase is no longer perceived. 
 
 This I have said is one of the purposes which appears to be served by 
 diastase in the vegetable economy. That it is the only one we have no 
 reason to believe. There may be others quite as interesting which we 
 do not as yet understand. This is rendered more probable by the fact 
 that the diastase contained in one pound of malted barley is capable of 
 converting into sugar five pounds of starch.* (Liebig.) And tiiough 
 at the temperature at which the seed germinates, more of this substance 
 may be necessary to transform the same weight of starch than is re- 
 quired in our hands, when aided by artificial heat, — yet as we never in 
 the ordinary course of nature find any thing superfluous or going to 
 waste, there is reason to believe that the diastase may be intended also 
 to contribute directly to the nourishment and growth of the plant. As 
 it contains nitrogen, it must be derived from the gluten or vegetable al- 
 bumen of tlie seed ; and as a young plant of wheat, when already many 
 inches from the ground, contains no more nitrogen than was originally 
 present in the seed itself (Boussingault), this diastase may only be the 
 result of one of those transformations of which glutenf is susceptible, 
 and by which it is rendered soluble, and capable of aiding in the pro- 
 duction of those parts of the substance of the growing plant into which 
 nitrogen enters as a necessary constituent. 
 
 It may not be uninstructive if we pause here for a moment and con- 
 sider the beauty of the arrangements we have just been describing. In 
 passing through a new and interesting country we do not hesitate, at 
 times, to stop and gaze, and leisurely admire. We cannot otherwise 
 fully realize and appreciate its beauty. So in the domains of science, 
 we cannot be ever hurrying on — we must linger occasionally, not only 
 that we may jnore carefully observe, but that we may meditate and 
 feel. 
 
 You see how bountifully nature has provided in the seed for the nour- 
 ishment of the young plant, how carefully the food is stored up for i;, 
 and in how imperishable a form — how safely covered also and protected 
 from causes of decay ! For hundreds of years the princij)le of life will 
 lie dormant, and for as many the food will remain sound and undimin- 
 ished till the time of awakening comes. Though buried deep in the 
 earth, the seed defies the exertions of cold or rain, for the food it contains 
 is unaffected by cold and absolutely insoluble in water. But no sooner 
 
 * It is the diastase in malt which dissohes the slarch of the barley in the process of brew- 
 ing, but as tlie diastase contained in malt is sulRcient to dissolve so large a quantity of starch, 
 it is obviously a waste of labour to malt the whole of the barley employed. One of malt to 
 three of barley would probably be siithcient in most cases to obtain a wort containing the 
 whole of the slarch in solution. Advantaae is taken of this property in the manufacture of 
 the while beer of Lou vain, and of other places in Flanders, and in Germany, where the light 
 colour is secured by adding a large quantity of Hour to a decoction of a small quantity of 
 barley. 
 
 t That diastase is merely transformed gluten we cannot say, because the exact chemicsd 
 constitution of diastase is as yet unknown. 
 
VEGETABLE ACIDS. 121 
 
 is the sleeping germ recalled to life, by the access of air and warmth 
 and duly tempered moisture, than a new agent is summoned to its aid, 
 and the food is so ciianged as to be rendered capable of minislering to its 
 e^irly wants. The first movement of the nascent germ — (and how it 
 rdoves, by what inherent or impartial force, who siiall discover to us ?) 
 — i-is the signal for the appearance of this agent — diastase — of which, 
 previous to germination, no trace could be discovered in the seed. At 
 the root of the germ, where the vessels terminate in the farinaceous 
 matter, exactly where it is wanted, this substance is to be found ; — there, 
 and there only, resolving and transforming the otherwise unavailable 
 store of food, and preparing it for being conveyed either to the ascending 
 sprout or to the descending root. And when the necessity for its pre- 
 sence ceases — when ihe green leaf becomes develo|)ed, and the root has 
 fairly entered the soil — when tiie plant is fitted to seek food for itself — 
 then this diastase disappears, it undergoes itself a new conversion, and is 
 prepared in another form to contribute to the furl her increase of the plant. 
 How beautiful and jjrovident are all these arrangements! — how plas- 
 tic the various forms of organic matter in the hands of the All-Intelli- 
 gent I — how nicely adjusted in time and place its diversified changes ! 
 What an apparently lavish expenditure of forethought and kind previ- 
 sion, in beiialf even of the meanest plant that grows ! 
 
 § 9. , Vegetable Acids. — Acetic acid, Oxalic acid, Tartaric acid, 
 f Citric acid, Malic acid. 
 
 Another class of comj^ound substances remains to be shortly consid- 
 ered, — those, namely, which possess sour or acid properties, and which 
 are known to be present in large c|uantity in many plants, and more 
 especially in the greater number of unripe fruits. They do not, taken 
 as a whole, form any large portion of the entire produce, either of the 
 general vegetation of the globe or of those plants which are cultivated 
 for food; yet the growth of fruit — as in the grape, orange, and apple 
 countries — is sufficiently extensive, and the general interest in the cul- 
 tivation of fruit trees sufficiently great, to require that the nature of the 
 substances contained in fruits, and the peculiar changes by which they 
 are formed, should be in some measure considered and explained. 
 
 I.— ACETIC ACID. 
 
 Acetic acid or vinegar is the most extensively diffused, and the most 
 largely produced, of all the organic acids. It is formed during the ger- 
 mination of seeds, and it exists in the juices of many plants, but it is 
 most abundantly evolved during the fermentation, whether natural or 
 artificial, of nearly all vegetable substances. When pure it is a colour- 
 less licjuid, having a well known agreeably acid taste. It may be 
 boiled and distilled over without being decomposed. The vinegar of the 
 shops is generally very much diluted, but it can be prepared of such a 
 strength as to freeze and become solid at 45° F., and to blister the skin 
 and produce a sore when applied to any part of the body. When 
 mixed with water it readily dissolves lime, magnesia, alumina, &c., 
 forming salts called acetates, which are all soluble in water, and may, 
 therefore, be readily washed out of the soil or of compost heaps by 
 heavy falls of rain. 
 
122 PREPARATION OF ACETIC ACID. 
 
 When perfectly free from water, acetic acid consists of — 
 Carbon . . . 47'5 per cent., or 4 atoms 
 Hydrogen . . 5-8 ' " or 3 *' 
 
 Oxygen . . . 46-7 " or 3 " 
 
 100 
 
 It is therefore represented by the formula C4 H3 O3 — in which, as in 
 those given in the preceding sections for starch, sugar, &:c., ihe numbers 
 representing the atoms of hydrogen and oxygen are ecjual, and conse- 
 quently these elements are in the proporiion to form water. Hence, 
 vinegar, like sugar, may be represented by carbon and water. 
 
 Let us consider for a moment the several processes by which this acid 
 IS usually formed. 
 
 1°. By the distillation of loood. — This a method by which wood 
 vinegar — often called pyroligneous acid — is prepared in large (|uantity. 
 Wood which has been dried in the air is put into an iron retort and distil- 
 led. The principal products are vinegar, water, and tarry matter. 
 The decomposition is of a complicated description, but by comparing 
 the constitution of woody fibre with that of vinegar, we can readily see 
 the nature of the changes by which the latter is produced. 
 Woody Fibre is = C,o Hg Og 
 3 of Vinegar are = Cjo Hg Oj 
 
 Difference = H^ O, ; or the elements 
 
 of one atom of water. One portion of ihe woody fibre, therefore, com- 
 bines with the elements of an atom of wat^r, obtained by the decompo- 
 sition of another portion, and thus vinegar is produced. 
 
 2°. Manufacture of Vinegar from Cane Sugar. — It is a well known 
 fact in domestic economy, that if cane sugar be dissolved in water, a 
 little vinegar added to it, and the solution kept for a length of time at a 
 moderate temperature, the whole will be converted into vinegar without 
 any sensible fermentation. This process is frequently followed in the 
 preparation of household vinegar, and was formerly adopted to some ex- 
 tent in our cheniical manufactories. It will be recollected that we re- 
 presented Cajje Sugar by C12 H,o Oio, while 
 
 SofVlJNEGAR = C12 Hg Og 
 
 Difference H^ O^ ; or the elements 
 
 of an atom of water, which cane sugar must lose in order to be convert- 
 ed into vinegar. Whether the change in this instance takes place by 
 the direct conversion of cane sugar into vinegar, or whether the former 
 is previously transformed into grape sugar, has not been satisfactorily de- 
 termined. 
 
 3°. Manufacture of Vinegar from Alcohol. — In Germany, where 
 common brandy is cheaper than vinegar, it is found profitable to manu- 
 facture this acid from weak spirit. For this purpose it is mixed with a 
 little yeast, and then allowed to trickle over wood shavings moistened 
 with vinegar, and contained in a cask, the sides of which are perforated 
 with holes for the admission of a current of air. By this method oxy- 
 gen is absorbed from the air, and in 24 hours the alcohol in the spirit is 
 converted into vinegar and water. 
 
TARTARIC ACID IN THE GRAPE. 123 
 
 The explanation of this process is also simple, alcohol being repre- 
 sented by C4 Hg O^. Thus — 
 
 Alcohol = C4 He O2 ") ( Vinegar = C4 H3 O3 
 
 4 of Oxygens O^ '^_J 3 of Water = H3 O3 
 
 '() 
 
 Sum ^ C4 H, O, J ( Sum = C. Ho O, 
 
 4°. Production of Vinegar by fermentation . — When vegetable mat- 
 ters are allowed to ferment, carbonic acid is given off and vinegar is 
 formed. In such cases this acid is the result of a series of changes, du- 
 ring which that portion of the vegetable matter which has at length 
 reached the state of vinegar has most probably passed through the seve- 
 ral previous stages of grape, sugar, and alcohol. The carbonic acid, as 
 has already been explained (p. 115), is given off during the fermentation 
 of the grape sugar, and the consequent formation of alcohol. 
 
 To simple transformations, similar to those above described, we can 
 trace the origin of the vinegar which is met with in the Uving juices of 
 plants, and among the products of their decay. 
 
 II. — tartaric acid. * 
 
 The grape and the tamarind owe their sourness to a peculiar acid to 
 whicli the name of tartaric acid has been given. It is also present, along 
 with other acids, in the mulberry, in the berries of the sumach {rhus co- 
 riarii), and in the sorrels, and has been extracted from the roots of the 
 couch-grass and the dandelion. 
 
 When new wine is decanted from the lees, and set aside in vats or 
 casks, it gradually deposits a hard crust or tartar on the sides of the ves- 
 sels. This substance is known in commerce by the name of argol, and 
 when purified is familiar to you as the cream of tartar of the shops. It 
 is a com[)ound of tartaric acid with potash, and from it tartaric acid is 
 extracted for use in medicine and in the arts. The principal use of the 
 acid is in certain processes of the calico printers. 
 
 The pure acid is sold either in the form of a white powder or of trans- 
 parent crystals, which are colourless, and have an agreeable acid taste. 
 It dissolves readily in water, and causes a violent effervescence when 
 mixed with a solution of the carbonate of potash or of soda. As it has 
 no injurious action upon the system, it is extensively used in artificial 
 soda powders and effervescing draughts. When added in sutficient 
 quantity to a solution containing potash, it causes a white crystalline 
 powder to fall, which is cream of tartar (or bitartrate of potash), and from 
 lime water it throws down a white chalky precipitate of tartrate of lime. 
 Both of these compounds are present in the grape. 
 When perfectly free from water this acid consists of — 
 
 Carbon . . . = 36-81 or 4 atoms. 
 
 Hydrogen . . = 3-00 or 2 atoms. 
 
 Oxygen . . . = 60* 19 or 5 atoms. 
 
 100 
 It is therefore represented by the formula C4 Hg O5. 
 
 If we compare the numbers by which the atoms of hydrogen and ox- 
 ygen in this acid are expressed, we see that these elements are not in the 
 proportion to form water, and that this substance, therefore, cannot, like 
 
124 CONSTITUTION OF TARTARIC AND CITRIC ACIDS. 
 
 SO many of those we have hitherto had occasion to notice, be represented 
 by carbon and the elements of water alone. 
 It may be represented by 
 
 4 of Carbon . . = C, ) 
 
 2 of Water . . = Ho O^ > or, 4C+2H+30 
 and 3 of Oxygen . . = Oo S 
 
 Tartaric Acid = C4 H^ O5 
 And, though this mode of rej^resentaiion does not truly exhibit the con- 
 stituiion of the acid, inasmuch as we have no reason to believe that it 
 really contains water as such — yet it serves to show very clearly that in 
 the living ])lant this acid cannot be formed directly from carbon and the 
 elements of water, as starch and sugar may, but that it requires also 
 three atoms of oxygen in excess to every five of carbon and two of water. 
 AVe shall, in the following lecture, see how nicely the functions of the 
 several parts of the plant are adjusted, — at one period to the formation of 
 this acid, and at another to its conversion into sugar during the ripening 
 of the fruit. 
 
 III. CITRIC ACID, OR ACID OF LEMONS. 
 
 This acid gives their sourness to the lemon, the lime, the orange, the 
 cranberry, the red whortleberry, tlie bird-cherry, and the fruits of the 
 dog-rose and the woody night-shade. It is also found in some roots, as 
 in those of the dahlia joinnata, and the asarum europa^um {asarrabacca), 
 and mixed with much malic acid, in the currant, cherry, gooseberry, 
 raspberry, strawberry, common whortleberry, and the fruit of the haw- 
 thorn. 
 
 When extracted from the juice of the lemon or lime, and afterwards 
 purified, it forms transparent colourless crystals, possessed of an agreea- 
 ble acid taste ; efTervesces like tartaric acid with carbonate of soda, and 
 like it, therefore, is much employed for effervescing draughts. With 
 potash it forms a soluble salt, which is a citrate of potash, and from lime 
 water it throws down a white, nearly insoluble, sediment of d^raic 0/ 
 lime, which rc-dissolves when the acid is added in excess. In combi- 
 nation with limc-it exists in the tubers, and with potash in the roots, of 
 the Jerusalem artichoke. 
 
 When free from water, citric acid consists of 
 
 Carbon .... 41*49 = 4 atoms. 
 
 ' Hydrogen . . . 3-43 = 2 atoms. 
 
 Oxygen .... 55-08 = 4 atoms. 
 
 100 
 and is therefore represented by C4 H2 O4. 
 
 This formula differs from that assigned to the tartaric acid only in 
 containing one atom of oxygen less, O4 instead of O5. In the citric 
 acid, therefore, there are 2 atoms of oxygen in excess, above what is 
 necessary to form water with the 2 of hydrogen it contains. 
 
 IV. MALIC ACID. 
 
 The malic and oxalic acids are more extensively diffused in living 
 plants than any other vegetable acids. If acetic acid be more largely 
 
CONSTITUTION OF MALIC AND OXALIC ACIDS. 125 
 
 formed in nature, it is chiefly as a product of the decomposition of or- 
 ganic matter, when it has already ceased to exist in, or to form part of, 
 a living pUmt. 
 
 Along with the citric acid, it has been already stated that the malic 
 occurs in many fruits. It is found more abundantly, however, and is the 
 chief cause of the sour taste, in the unripe apple, [hence its name malic 
 acid,] the plum, the sloe, the elderberry, the barberry, the fruit of the 
 mountain ash, and many others. It is associated with the tartaric acid 
 in the grape and in the Agave americana. 
 
 This acid is not used in the arts or in medicine, and therefore is not 
 usually sold in the shops. It is obtained most readily, in a pure state, 
 from the berries of the mountain ash. It forms colourless crystals, 
 which have an agreeable acid taste. It combines with potash, soda, 
 lime, and magnesia, and forms maiates, and, in combination with one or 
 more of these bases, it usually occurs in the fruits and juices of plants. 
 The m.alate of lime is soluble, while the citrate, as already stated, is 
 nearly insoluble, in water. Tliis malafe exists in large quantity in the 
 juice"of the house-leek {sempervivwn tectorum),\n\he Sedum telephium, 
 the Arum maculatum, and many other juicy and fleshy-leaved plants. 
 
 When perfectly free from water, the malic acid has exactly the same 
 chemical constitution as the citric, and is represented by the same for- 
 mula C4 H2 O4. These two acids, therefore, bear the same relation 
 to each other as we have seen that starch, gum, and sugar do. They 
 are what chemists call isomeric, or are isomeric bodies. We cannot 
 transform them, however, the one into the other, by any known means, 
 though there is every reason to believe that they may undergo such 
 transformations in the interior of living plants. Hence probably one 
 reason also why the malic and citric acids occur associated together in 
 so many different fruits. 
 
 V. OXALIC ACID. 
 
 This acid has already been treated of, and its properties and composi- 
 tion detailed, in a preceding lecture (Lecture III., p. 47). It forms co- 
 lourless transparent crystals, having an agreeably acid taste, and it 
 effervesces with the carbonates of potash and soda, but on account of its 
 poisonous qualities, it is unsafe to administer it as a medicine. It oc- 
 curs in combination with potash in the sorrels, in rhubarb, and in the 
 juices of many lichens. Those lichens which incrust the sides of rocks 
 and trees, not unfrequently contain half their weight of this acid in com- 
 bination with lime. It can be formed artificially by the action of nitric 
 acid on starch, sugar, gum, and many other organic substances. 
 
 When perfectly free from water, oxalic acid contains no hydrogen ; 
 but consists of — 
 
 Carbon . . . 33-75 = 2 atoms 
 
 Oxygen . . . 66-25 = 3 " 
 
 100 
 and it is represented by C^ O3. When heated with strong sulphuric 
 acid, it is decomposed and resolved into gaseous carbonic acid (CO2) and 
 carbonic oxide (CO) in equal volumes. This change is easily under- 
 stood since CO2 -|- CO = C2 O3. 
 
 6* 
 
12fe 
 
 STARCH CONVERTED IJS TO WOODY FIBRE. 
 
 §10. General observations on the substances of which plants chiefly consist. 
 
 It may be useful here shortly to review the most important facts and 
 conclusions which have been adverted to in tlie present lecture. 
 
 1°. Tlie great bulk of plants consists of a series of substances capable 
 of being represented by, and consequently of being formed in nature 
 from, carbon and the elements of water only. Such are woody fibre, 
 starch, gum, and the several varieties of sugar (p. 111). 
 
 2°. Yet the crude mass of wood, as it exists in a full-grown 
 tree, containing various substances in its pores, cannot be represented 
 by carbon and the elements of water alone. It ap])enrs always to 
 contain a small excess of hydrogen, which is greater in some trees than 
 in others. Thus in the chesnut and the lime, this excess is greater than 
 in the pines, while in the latter it is greater than in the oak and the ash. 
 [For a series of analyses of ditferent kinds of wood by Peterson and 
 Schodler, see Thomson's Organic Chemistry, p. 849.] 
 
 3°. These substances are, in many cases, mutually convertible even 
 in our hands. They are probably, therefore, still more so in nature. 
 
 It is to be observed, however, that all the transformations we can as 
 yet effect are in one direction only. We can produce the above com- 
 pounds from each other in llie order of lignin or starch, gum, cane sugar, 
 grape sugar- — that is, we can convert starch into gum, and gum into 
 sugar, but we cannot reverse the process, so as to form cane from grape 
 sugar, or starch from gum. 
 
 The only apparent exception to this statement with which we are at 
 present acquainted, occurs in the case of starch. When this substance 
 is dissolved in cold concentrated nitric acid, and then mixed largely with 
 water, a substance [the Xyloidin of Braconnot] falls to the bottom, 
 which is a compound of the nitric acid with woody fibre (C,2 H3 O3.) 
 [Pelouze, see Berzelius Arsberdttelse, 1839, p. 416.] In this instance, 
 if the above observation is correct, there appears to be an actual con- 
 version of starch into woody fibre. 
 
 But what ice are as yet unable to perform may, nevertheless, be easily 
 and constantly^ffected in the living plant. Not only may what is starch 
 in one part of the tree be transformed and conveyed to another part in 
 the form of sugar, — but that which, in the form of sugar or gum, passes 
 upwards or downwards with the circulating sap, may, by the instrumen- 
 tality of the vital processes, be deposited in the stem in the form of 
 wood, or in the ear in that of starch. Indeed we know that such actu- 
 ally does take place, and that we are still, therefore, very far from being 
 able to imitate nature in her power of transforming even this one group 
 of substances only. 
 
 4°. Among, or in connection with, the great masses of vegetable mat- 
 ter which consist mainly of the above substances, we have had occasion 
 to notice a few which contain nitrogen as one of their constituents — and 
 which, though forming only a small fraction of the products of vegetable 
 growth, yet appear to exercise a most important influence in the general 
 economy of animal as well as vegetable life. The functions performed 
 by diastase in reference to vegetable growth, and to the transformations 
 of organized vegetable substances, have already been in some measure 
 illustrated, — we shall hereafter have an opportunity of considering more 
 
IMPORTANCE OF THE VEGETABLE ACID. 127 
 
 fully t :e influence which gluten and vegetable albumen exercise over • 
 the general efficiency of the products of vegetation in the support of ani- 
 mal life, and over the changes which these products must undergo, be- 
 fore they can be converted into the substance of animal bodies. In a 
 former lecture (Lecture IV., p. 66), I have had occasion lo draw your 
 attention lo the comparatively small proportion in which nitrogen exists 
 in the vegetable kingdom, and to show that it must nevertheless be con- 
 sidered as much a necessary and constituent element in their composi- 
 tion as the carbon itself; the very remarkable properties we have al- 
 ready discovered in the compounds above mentioned strongly confirm 
 this fact, and illustrate in a striking manner the influence of apparently 
 feeble and inadequate causes in producing important natural results. 
 
 5°. With the exception of acetic acid, which in constitution is closely 
 related to sugar* and gum, all the acid substances to which it has been 
 necessary to advert, contain an excess of oxygen above what is neces- 
 sary to form water with the hydrogen they contain. Thus 
 
 Vinegar =C^ H3 O3 contains no excess of oxygen. 
 
 Tartaric Acid = C4 H2 Og . . 3 of oxygen in excess. 
 
 Malic Acid ? n u r\ o " 
 
 iTRic Acid ^ a ^ % 
 
 Oxalic Acid =r: C2 O3 . . 3 
 
 It requires a little consideration to enable us to appreciate the true im- 
 portance of these aiul other organic acids, in the vegetable economy. At 
 first sight they appear to form a much smaller part of the general pro- 
 ducts of vegetation than is really the case. We must endeavour to 
 conceive the quantity actually produced by a single tree loaded with 
 thousands of lemons, oranges, or apples, — or again, how much is formed 
 during the growth of a single comparatively small plant of garden rhu- 
 barb in spring, if we would obtain an adequate idea of the extent to 
 which these acids are constantly formed in nature. On the other hand, 
 we must recollect also that the greater portion of the acid of fruits disap- 
 pears as they ripen, if we would understand the true nature of the in- 
 terest which really attaches to the study of these substances, of the 
 changes to which they are liable, and of the circumstances under which 
 in nature these changes take place. 
 
 6°. I will venture here to draw your attention for a moment to the na- 
 ture and extent of that remarkable power over matter, which the chem- 
 ist, as above explained, appears to possess. Such a consideration will 
 be of value not only in illustrating how far we really can now, or may 
 hereafter, expect to be able to influence or control natural operations, 
 [see Lecture II., p. 32,] but what is })robably of more value still, exhibit- 
 ing the true relation which man bears to the other parts of creation ; and, 
 in some measure, the true position he is intended to occupy among them, 
 
 1°. We have seen that the chemist can transform certain substances 
 one into the other, in a known order ; but that as yet he cannot reverse 
 that order. Thus far his power over matter is at present limited; but 
 this limit he may at some future period be able to overpass, and we 
 
 " It is identical in constitution with caramel (p. 114)— the uncrystallizable sugar of syrups. 
 For 
 
 Vinegar. Caramel. 
 
 (C4 H3 O3 X 3) = C12 H9 09. 
 
128 POWER OF THE CHEMIST OVER MATTER. 
 
 know not how far. The discovery of a new agent, or of a new mode 
 of treatment, may enable him to accomplish what he has not as yet the 
 means or the skill to perform. 
 
 2°. He has it in his power to form, actually to produce, some of the 
 organic or organized substances which occur in living plants. He can 
 form gum, and grape sugar, in any quantity. Tlius far he can imitate 
 and take the place of the Living principle itself 
 
 Numerous other cases are known, in which he displays a similar 
 power. By the action of nitric acid upon starch or sugar, [see Lecture 
 in., p. 47,] he can form oxalic acid, which, as has already been shown, 
 occurs very largely in the vegetable kingdom. By the action of heat, 
 upon citric acid, he can decompose it and produce an acid which is 
 ]net with in the Wolfsbane (Aconitum napellus), and hence is called 
 aconitic acid.* Also by the action of sulphuric acid he can change 
 salicine nm\ pJilorizinc — substances extracted respectively from the bark 
 of the willow and from that of the root of the apple tree — into a resinous 
 matter and grape sugar. So, of the compounds which are found in the 
 solids and fluids of animal bodies, there are son^e which he has also 
 succeeded in forming by the aid of his chemical art. 
 
 Elated by such achievements, some chemists appear willing to hope 
 that all nature is to bd subjected lo their dominion, and that they may 
 hereafter be able to rival the living principle in all its operations. It is 
 true that what we now know, and can accomplish, are but the begin- 
 nings of what we may fairly exj)ect hereafter to etlect- But it is of con- 
 sequence to bear in mind the true j)osition in which we now stand, and 
 the true direction in which all we at present know seems to indicate that 
 our future advances in knowledge, and in control over nature, are likely 
 to proceed. And this leads me to observe — 
 
 3°. That our dominion is at preseiit limited solely to transforming 
 and decomjiosing. We can transform woody fibre into gum or sugar — 
 we can7iot form either gum or sugar by the direct union of their elements. 
 We can resolve salicine by the acid of sulphuric acid into resin and 
 grape sugar ; but we cannot cause the elements of which they consist to 
 unite together in our hands, so as to form any one of the three. We 
 cannot even cause the resin and the sugar lo re-unite and rebuild the sali- 
 cine from which they were derived. 
 
 So we can by heat drive off the elements of water from the citric and 
 cause the aconitic acid to appear ; but we cannot persuade the unwilling 
 compounds, when thus separated, to return to their former condition of 
 citric acid ; and, if we could, we should still be as far removed from the 
 power of commanding or compelling the direct union of carbon, hydro- 
 gen, and oxygen, in such proportions, and in such a way, as to build up 
 either of the two acids in question. 
 
 Again, we can actually form oxalic acid by the action of nitric acid 
 
 " These two acids differ from eacii other only i y the elements of an atom of water. Thus 
 Citric Acid . . = C4 " 04 
 Aconitic Acid . = C.j Hi O3 
 
 Difference . . = Hi O or HO, one of water. 
 It is easy to sec, therefore, how, by the evohuion of tlie elements of an atom of water, the 
 one aci'l ma" ^>e changed into the other. The scientific reader will excuse me (if on the 
 grounds of simplicity alone) for representing, both here and in the text, the citric acid by 
 C H2 O4, instead of by C12 H5 Ou + 3H0, which l,iebig and his pupils prefer. 
 
TRL'E TKOSrECTS OF CHEMICAL SCIENCE. 129 
 
 upon starcli, or wood, or sucjar, or any other of a great variety of vegeta- 
 ble substances — but we cannot prepare it by the direct union of its ele- 
 ments. We can only as yet procure it from substances which have 
 already been organized — which have been themselves produced by the 
 agency of the living principle. 
 
 The same remarks apply with slight alteration to those substances of 
 animal origin to which I iiave above alluded as being within the power 
 of the chemist to jiroduce at will. There is hardly an exce[)ti()n to the 
 rule, that in producing organic substances, as they are called, the chem- 
 ist must employ other organic substances which are as yet beyond his 
 art — which, so far as we know, can only be formed under the direction 
 of the living principle. Thus the sum of the chemist's power in imita- 
 ting organic nature consists, at present, in his. ability — 
 
 1°. To transform one substance found only in the organic kingdom 
 into some other substances, produced more or less abundantly in the 
 same kingdom of nature. This power he exercises when he converts 
 starcli into sugar, or fibrin into albumen or casein. 
 
 2°. Toresolve a more complex or compound substance into two or 
 more which are less so, and of which less complex substances some may 
 be known to occur in vegetable or anitnal bodies. 
 
 3°. To decompose organic compounds by meansofhischemical agents, 
 and as the result of such decompositions to arrive at one or more com- 
 pounds, such as are fornied under the direction of the living princi])le. 
 
 In no one case can he form the substances of which animals and plants 
 chiefly consist, out of those on which animals and plants chiefly live. 
 
 But this is the common and every-day result of the agency of the liv- 
 ing prmciple. Is there as yet, then, any hope that the chemical labo- 
 ratory shall supersede the vascular system of animals and plants; or 
 that the skill of the chemist who guides the operations within it, shall 
 ever rival that of the principle of life which presides over the chemical 
 changes that take place in animal and vegetable bodies ? 
 
 The true place, therefore, of human skill — the true ])rospects of chem- 
 ical science — are pointed out by these considerations. No science has 
 accumulated so many and such various treasures as chemistry has done 
 during the last 20 years — none is at present so widely extending the 
 bounds of our knowledge at this moment as the branch of organic chem- 
 istry — men may therefore be excused for entertaining more sanguine 
 expectations from the progress of a favourite science than sober reason- 
 ing would warrant. Yet it is of importance, I think, and especially in 
 a moral point of view, that amid all our ardour, we should entertain 
 clear and just notions of the kind and extent of knowledge to which we 
 are likely to attain, and — as knowledge in chemistry is really power 
 over matter — to what extent this power is likely ever to be carried. 
 
 At present, if we judge from our actual knowledge, and not from our 
 hopes — there is no prospect of our ever being able to imitate or rival 
 living nature in actually compounding from their elements her nume- 
 rous and varied productions. That we may clearly understand, and be 
 able to explain many of her operations, and even to aid her in effecting 
 them, is no way inconsistent with an inability to imitate her by the re- 
 sources of art. This will, I trust, appear more distinctly in the subse- 
 quent lecture. 
 
LECTURE VIL 
 
 Chemical changes by which the substances of which plants chiefly consist are formed from 
 those on which they live.— Changes during germination— during the growth of the plant— 
 during the ripening of fruit. — Autumnal changes. 
 
 Having thus considered the nature and chemical constitution of those 
 substances wliich constitute by far the largest part of the solids and 
 fluids of living vegetables, we are now prepared for the further question 
 — hy what chemical changes these substances of which plants consist, arc 
 formed out of those on which tJiey live 1 
 
 The growth of a plant from the germination of the seed in spring till 
 the fall of the leaf in autumn, or the return of the succeeding spring- 
 time, may in perennial plants be divided into four periods — during which 
 they either live on different food, or expend their main strength in the 
 production of different substances. These periods may be distinguished 
 as follows : — 
 
 1°. The period of germination — from the sprouting of the seed to the 
 formation of the perfect Jeaf and root. 
 
 2°. From the expansion of the first true leaves to the period of flow- 
 ering. 
 
 3°. From the opening of the flower to the ripening of the fruit and 
 seed. 
 
 4°. From the ripening of the seed or fruit, till the fall of the leaf and 
 the subsequent return of spring. On the ripening of the fruit the func- 
 tions of annual plants are in general discharged, and they die; but per- 
 ennial plants have still important duties to perform in order to prepare 
 them for the growth of the following spring. 
 
 The explanation of the chemical changes to which our attention is to 
 be directed will be more clear, and perhajis more simple, if we consider 
 them in relation to these several i)eriods of growth. 
 
 § 1. Chemical changes wJiich take place during germination and during 
 the development of the first leaves and roots. 
 
 The general nature of the chemical changes which take place during 
 germination is simple and easy to be comprehended. 
 
 Let us first consider shortly the phenomena which have been observed 
 to accompany germination, and the circumstances which are most fa- 
 vourable to its rapid and healthy progress. 
 
 1°. Before a seed will begin to sprout, it must be placed for a time in 
 a sufficiently moist situation. We have already seen how numerous 
 and important are the functions which water performs in reference to 
 vegetable life (Lecture IL, p. 36,) in every stage of a plant's growth. 
 In the seed no circulation can take i)lace — no motion among tJie parti- 
 cles of matter — until water has beer largely imbibed ; nor can the food 
 be conveyed through the growing vessels, unless a constant supply of 
 fluid be afforded to the seed and its infant roots. 
 
 2°. A certain degree of warmth — a slight elevation of temperature- 
 is also favourable, and in most cases necessary, to germination. 
 
EFFECT OF AIR AND LIGHT ON GERMINATION. 131 
 
 The degree of warmth which is required in order that seeds may be- 
 gin to grow, varies with the nature of the seed itself. In Northern Si- 
 beria and other icy countries, plants are observed to spring up at a tem- 
 perature but slightly raised above the freezing point (32° F.,) but it is 
 familiar to every practical agriculturist, that the seeds he yearly con- 
 signs to the soil require to be protected from the inclemency of the 
 weather, and sprout most quickly when they are stimulated by the 
 warmth of approaching spring, or by the heat of a summer's sun. 
 
 The same fact is familiarly shown in the malting of barley, where 
 large heaps of grain are moistened in a warm atmosphere. When ger- 
 mination commences, the grain heats spontaneously, and the growth 
 increases in rapidity as the hea{) of corn attains a higher temperature. 
 It thus ap])ears that some portion of that heat which the growth of the 
 germ and radicles requires, is provided by natural processes in the grain 
 itself; in some such way as, in the bodies of animals, a constant supply 
 of heat is kept up by the vital processes — by which supply the cooling 
 effect of the surrounding air is continually counteracted. 
 
 We iiave seen in the* preceding lecture, that the transformations of 
 which starch and gum are susceptible, take place with greater certainty 
 and rapidity under the influence of an elevated temperature. It will 
 presently appear that such transformations are also alfected during ger- 
 mination ; there is reason, therefore, to believe that the external warmth 
 which is retpiired in order that germination may begin, as well as the 
 internal heat naturally developed as germination advances, are both 
 employed in etieciing these transformations. And, as the young sprout 
 shoots more rapidly under the influence of a tropical sun, it is probable 
 that those natural agencies. in general, by which such chemical transfor- 
 mations are most rapidly promoted, are also those by which the pro- 
 gress of vegetation is in the greatest degree hastened and promoted. 
 
 3°. It has been observed that seeds refuse to germinate if they are en- 
 tirely excluded from the air. Hence seeds which are buried beneath 
 such a depth of soil that the atmospheric air cannot reach them, will 
 remain long unchanged, evincing no signs of life — and yet, when turned 
 up or brought near the surface, will speedily begin to sprout. Thus in 
 trenching the land, or in digging deep ditches and drains, the farmer is 
 often surprised to find the earth, thrown up from a depth of many feet, 
 become covered with young plants, of species long extirpated from or 
 but rarely seen in his cultivated fields. 
 
 4°. Yet light is, generally speaking, prejudicial to germination. 
 Hence the necessity oi^ covering the seed, when sown in our gardens and 
 corn fields, and yet of not so far burying it that the air shall be excluded. 
 In the usual method of sowing broad-cast, much of the grain, even after 
 harrowing, remains uncovered : and the prejudicial influence of light in 
 preventing the healthful germination of such seeds is no doubt one rea- 
 son why, by the method of dibbling, fewer seeds are observed to fail, and 
 an equal return of corn is obtained from a much smaller expenditure of 
 seed. 
 
 The reason why light is prejudicial to germination, as well as why 
 the presence of atmospheric air is necessary, will appear from the fol- 
 lowing observation : — 
 
 5°. When seeds are made to germinate in a limited portion of atmos- 
 
132 SEEDS SPROUT ONLY IN THE PRESEiNCE OF OXYGEN. 
 
 plieric air, tlie bulk of the air undergoes no material alteration, but on 
 examination its oxygen is found to have diminished, and carbonic acid 
 to have taken its place. Therefore, daring germination, seeds absorb 
 oxygen gas and give oj/' carbonic acid. 
 
 iicnce it is easy io uncierstand why the presence of air is necessary 
 to germination, and why seeds refuse to sprout in hydrogen, nitrogen, 
 or carbonic acid gases. 2%e?/ cannot sj^rout unless oxygen be witldn 
 ihcir reach. 
 
 We liave seen also in a ])revious lecture that the leaves of plants in 
 the sunsliine give oil" oxygen gas and absorb carbonic acid, — while in 
 the dark the reverse takes place. So it is with seeds which have begun 
 to germiiiafe. When exposed to the liglit they give off oxygen instead 
 of carbonic acid, and thus the natural process is reversed. But it is ne- 
 cessary to the growth of the young germ, that oxygen should be absorb- 
 ed, and carbonic acid given of — and as this can take place to the rec^uir- 
 ed extent only in the dark, the cause of the prejudicial action of light is 
 suffieienily apparent as well as the propriety of covering the seed with a 
 thin layer of soil. ^ 
 
 G°. During germination, vinegar (acetic acid) and diastase are pro- 
 duced. That such is the case in regard to the latter substance, has been 
 proved in the previous lecture, (p. 118.) That acetic acid is ibrmed is 
 shown by causing seeds to germinate in powdered chalk or carbonate of 
 lime, when after a lime acetate of Lime- may be washed out from the 
 chalk (Braconnot) in which they have been made to grow. The acid 
 contained in tiiis acetate must have been formed in the seed, and after 
 wards excreted or thrown out into the soil. 
 
 7°. When the germ has shot out from the seed and attained to a sen- 
 sible length, it is found to be possessed of a sweet taste. This taste is 
 owing to the presence ol grape sugar in the sap which has already be- 
 gun to circulate through its vessels. 
 
 It has not been clearly ascertained whether the vinegar or the dias- 
 tase is first produced when germination commences, but there seems 
 little doubt that the grape sugar is formed subsequently to the appear- 
 ance of both. 
 
 8^. The young shoot which rises upwards from the seed consists of 
 a mass of vessels, which gradually increase in length, and after a short 
 time expand into the first true leaves. The vessels of this first slioot do 
 not consist of unmixed woody fibre. It is even said that no true wood 
 is formed till the first true leaves are developed. — [Lindley's Theory of 
 Horticulture.'] The vessels of the young sprout, therefore, and of the 
 early radicles, probably consist of the cellular fibre of Payen. They 
 are umiuestionably tijrmed of a substance which is in a state of transition 
 between starch or sugar and woody fibre, and which has a constitution 
 analoge'usf to that of both. 
 
 I:laving thus glanced at the phenomena which attend upon germina- 
 tion, let us now consider the chemical changes by which these phenom- 
 ena are accompanied. 
 
 1°. The seed absorbs oxygen and gives off carbonic acid. We have 
 
 • Acetate of lime is a compound of acetic acid (vinegar) and lime, and may be prepared by 
 dissolving chalk in vinegar. It is very soluble in water. 
 
 t By analogous I mean which may be represented by carbon and water. 
 
HOW AND WHY VINEGAR IS FORMED. 133 
 
 already seen that the starch of the seed (Cio H^o Oio) "^^y ^^ repre- 
 sented by carbon and water, — -by 12C -f lOHO. Now it appears that 
 in contact with tlie oxygen of the atmosphere, a portion of the starch is 
 actually separated into carbon and water, the carbon at the moment of sepa- 
 ration uniting with the oxygen, and forming carbonic acid (COo). This 
 acid is given off' into the soil in the form of gas, and thence partially es- 
 capes into the air; but for wliat immediate purpose it is evolved, or how 
 its formation is connected with the further development of the germ, has 
 not hitherto been explained. 
 
 2°. The formation of acetic acid (vinegar) from the starch of the 
 grain is also easy to comprehend. For, as we have already seen, 
 Starch . . . =Cj2 H. o Ojo 
 3 of Vinegar . . = Cjo Hg Og 
 
 Difference = Hi Oj ; or the elements of 
 
 an atom of water. Tljerefore, in this early stage of the growth of the 
 germ a portion of the starch is deprived of the elements of an atom of 
 water, and at the same time transformed into vinegar. 
 
 Why is this vinegar formed 1 It is almost as ditlicult to answer this 
 (|uestion as to say why carbonic acid is evolved from the seed, though 
 both undoubtedly serve v/ise and useful ends. 
 
 It has been explained in the preceding lecture how the action of dilute 
 acids gradually changes starch into cane sugar, and the latter into grape 
 sugar. While it remains in the sap of the sprouting seed, the vinegar 
 may aid the diastase in transforming the insoluble starch into soluble 
 food for the plant, and may be an instrument in securing the conversion 
 of the cane sugar, which is the first formed, into grajpe sugar, — since 
 cane sugar cannot long exist in the presence of an acid. 
 
 After the acetic acid is rejected by the plant, it may act as a solvent 
 on the lime and other earthy matters contained in the soil. Liebig sup- 
 poses the especial function of this acid — the reason why it is formed in 
 the germ and excreted into the soil — to be, to dissolve the lime, &c., which 
 the soil contains, and to return into the pores of the roots, bearing in so- 
 lution the earthy substances which the plant requires for its healthy 
 erowtb. This is by no means an unlikely function. It is only conjec- 
 Tural, however, and since the experiments of Braconnot have shown that 
 acetate of lime, even in small quantity, may be mjurious to vegetation, 
 it becomes more doubtful how far the formation of this compound in the 
 soil, and the subsequent conveyance of it into the circulation of the plant, 
 can be regarded as the special purpose for which acetic acid is so gene- 
 rally produced during germination. 
 
 3°. The early sap of the young shoot is sweet ; it contains grape su- 
 gar. This sugar is also derived from the starch of the seed. Being 
 rendered soluble by the diastase formed at the base of the germ, the 
 starch is gradually converted into grape sugar as it ascends. The rela- 
 tion between these two compounds has been already pointed out. 
 
 Starch =Ci2 H^o O,o 
 
 Grape Sugar . . . =Ci2Hi2C)i2 
 
 Difference . . . . = Hg Oo ; or the ele- 
 
 ments of two atoms of water. The water which is imbibed by the seed 
 
134 HOW THE SUGAR IS FORMED IN THE SPROUT. 
 
 from the soil, forms an abundant source from which the whole of the 
 starch, rendered soluble by the diastase, can be supplied with the ele- 
 ments of the two atoms of waier which are necessary to its subsequent 
 conversion into grape sugar 
 
 4°. The diastase is formed when the seed begins to sprout, at the ex- 
 pense of the gluten or vegetable albumen of the seed, but as its true 
 constitution is not yet known, we cannot explain the exact chemical 
 changes by which its production is effected. 
 
 5°. When the true leaf becomes expanded, true wood first appears 
 in sensible ({uantity. By what action of the sun's rays upon the leaf 
 the sugar already in solution in the sap is converted into woody fibre, 
 we cannot explain. The conversion itself is in o:ppearayice simple 
 enough, since 
 
 Grape Sugar . . . = C^o Hj2 Ojo. and 
 Woody Fibre . . . = C^o Hg O3 
 
 Difference . . . , = H, O4 ; or the former 
 
 must part with the elements of four atoms of water only, to be prepared 
 for its change into the latter. But the true nature of the molecular* 
 change by which this transformation is brought about, as well as the 
 causes which lead to it and the immediate instruments by which it is 
 effected, are all still mysterious. 
 
 §2. Of the chemical changes which take place from the formation of the 
 true leaf to the expansion ofthcjlower. 
 
 "When the true leaf is formed the plant has entered upon a new stage 
 of its existence. Up to this tmie it is nourished almost solely by the 
 food contained in the seed, — it henceforth derives its sustenance from the 
 air and from the soil. The apparent mode of growth is the same, the 
 stem shoots upwards, the roots descend, and they consist essentially of 
 the same chemical substances, but they are no longer formed at the ex- 
 pense of the starch of the seed, and the chemical changes of which they 
 are the result are entirely ditTerent. 
 
 1°. The leaf absorbs carbonic acid in the sunshine, and gives off* ox- 
 ygen in eq4Mdrbulk.f It is in the light of the sun that plants increase in 
 size — their growth, therefore, is intimately connected with this absorp- 
 tion of carbonic acid. 
 
 If carbonic acid be absorbed by the leaf and the whole of its oxygen 
 given off' agaln,t carbon alone is added to the plant by this function of 
 the leaf. But it is added in the ])resence of the water of the sap, and 
 thus is enabled by uniting with it to form, as it may he directed, or as 
 may be necessary, any one of those numerous compounds which may 
 
 * All bodies are supposeil to consist of particles or jno/ccziZes of exceeding minuteness, 
 and all chemical chan<:es which r^ike place in the same mass of matter are supposed to be 
 owin^ to the diflForeiit ways in which these jiarticles arrans^e tliemselves. We may form a 
 remote idea of the way in whii;ii different positions of the same particles may produce dif- 
 ferent substances, by consiilering how different fiiiures in Mosaic may be produced by dif- 
 ferent arrangements of the same number of equal and similar fragments of various colours. 
 
 t Such \s,sensihlij the result of experiment. How far this result can be considered as uni- 
 versally true, will be examined hereafter 
 
 X It will be recollected that carbonic acid contains its own bulk of oxygen gas : if, therefore, 
 the leaf give off the same bulk of oxygen as it absorbs of carbonic acid, the result must be as 
 stated in the text. 
 
HOW PLANTS ARE NOURISHED BY CARBONIC ACID ? 135 
 
 be represented by carbon and water, (p. Ill,) and of which, as we have 
 seen, the solid parts of plants are chiefly made up. 
 
 There are two ways in which we may suppose the oxygen given off 
 by the leaf to be set free, and the starch, sugar, and gum, to be subse- 
 quently formed. 
 
 A. The action of light on the leafof the plant may directly decompose 
 the carbonic acid after it has been absorbed, and cause the oxyen to sep- 
 arate from the carbon, and escape into the air; — while at the same in- 
 stant the carbon thus set free, may unite with the wai^r of the sap in 
 different |:)roportions, so as to i)r()duce either sugar, gum, or starch. 
 Suppose 12 atoms of carbonic acid (12 COo) to be thus decomposed, and 
 their carbon to unite with 10 of water (10 HO), we should have 
 from 12 of Carbonic Acid . = C^n 
 
 which united lo 10 of Water . . . = H^o Oio 
 
 would give 1 of Gum or of Cane Sugar = C^o Hjo Ok, 
 Vv hile 24 of oxygen would be s^iven off, the whole of which would have 
 been derived from the carbonic acid absorbed by the plant. 
 
 B. Or the action of the sun's rays may be directed, in the leaf, to the 
 decomposition, not of carbonic acid, but of the u'a/erofthe sap. The oxy- 
 gen of the water may be separated from the hydrogen, while at the same 
 instant the latter element (hydrogen) may unite with the carbonic acid 
 to produce the sugar or starch. The result here is the same as before, 
 but the mode in which it is brought about is vary differently represented, 
 and appears much more complicated. Thus, suppose 24 of water 
 (24 HO) to be decom[)ose{i, and to give off" their oxygen into the air, 24 of 
 oxvgen would be evolved as in the former case, the whole o^ which would 
 be derived from the decomposition of water, while there would remain 
 24 of Hydrogen . . = H , 
 
 Let this act on 12 of Carbonic Acid = Cjo O04 
 
 and we have as the result C^o H24 O24; 
 
 Starch, «fcc. Water. 
 
 or . Ci2 Hin Ojo + 14 HO. 
 
 According to this mode of representing the chemical changes, water is 
 first decomposed and its oxygen evolved, then its hydrogen again com- 
 bines with the carbon and oxygen of the carbonic acid, and forming two 
 products — water and sugar or starch. This view is not only more com - 
 jilicated, but it supposes the same action of light to be — continually, at 
 the same tiine, and in the same circumstances — both decomposing wa- 
 ter and re-forming it from its elements. While, therefore, there can be 
 no doubt, for other reasons not necessary to be stated in this place, that 
 the light of the sun really does decompose water in the leaves of plants, 
 and more in some than in others — yet it ajipears probable that the oxygen 
 evolved by the leaf is derived in a great measure from the carbonic acid 
 which is absorbed; and that the principal part of the solid substance of 
 living vegetables, in so far at least as it is derived from the air, is pro- 
 duced by the union of the carbon of this acid with the elements of the 
 water in the sap.* "> 
 
 * I ought not to pass unnoticed the opinion of Persoz (Chemie Moleculaire), that the 
 starch, gum, &c., of plants are formed by the union of carbonic oxide (CO) with the neces- 
 
136 IS CARBONIC ACID ABSORBED FROM THE SOIL ? 
 
 We have seen reason to conclude (p. 63) that, while plants derive 
 much of their sustenance from the air, they are also fed more or less 
 abundantly by the soil in which they grow. From this soil they ob- 
 tain through their roots the carbonic acid which is continually given off 
 by the decaying vegetable matter it contains. This carbonic acid will 
 ascend to the leaf, and will there undergo decomposition along with that 
 which is absorbed by the leaf itself. At least we know of no function 
 of the root or stem by which the carbonic acid derived from the soil can 
 be decomposed and deprived of its oxygen before it reaches the leaf. 
 
 It is distinctly stated, indeed, by Sprengel, [see above, p. 92,] that 
 when the roois of a plant are in the presence of carbonic acid, the oxy- 
 gen given off by the leaf is greater in bulk than the carbonic acid ab- 
 sorbed. But there is one observation in connection with this point which 
 it seems to me of importance to make. The leaves supply carbon to 
 the plant only in the form of carbonic acid, and they give off a bulk of 
 oxygen gas not exceeding that of the acid taken in, [see note, below.] 
 But if the carbon derived from the soil be also absorbed in the form of 
 carbonic acid, and if the oxygen contained in this portion of acid is also 
 given off by the leaf — either the quantity drawn from the soil must be 
 small, compared with that inhaled from the air, or the oxygen given off 
 by tlie leaf must, in the ordinary course of vegetation, be sensibly great- 
 er than the bulk of the carbonic acid which it absorbs. 
 
 We are too little familiar with the chemical functions of the several 
 parts of plants to be able.to pronounce a decided opinion on this point; 
 but it appears evident that one or other of the three following conditions 
 must obtain : — 
 
 («). Eitlier in the general vegetation of the globe the bulk of the oxy- 
 gen gas given off by the leaf during the day must always be considera- 
 bly greater than that of the carbonic acid absorbed by it; or 
 
 (b). The root or stem must have the power of decomposing carbonic 
 acid and of separating and setting free its oxygen ; or 
 
 (c). The plant can derive no considerable portion of its carbon from 
 the soil, in the form of carbonic acid. 
 
 If the experiments hitherto made by tlie vegetable physiologists be 
 considered ^ so decisive a character as to warrant us in rejecting the 
 two former conditions, the third becomes also untenable. 
 
 sary proportions of oxygen and hydrogen derived from the water of the sap. This opinion 
 implies that, in the leaf, carbonic acid (CO2 ) is decomposed into carbonic oxide and oxy- 
 gen (CO -|- O), and that water likewise is decomposed,— the oxygen produced by both de- 
 compositions being given off either into the air by the leaves, or into the soil by the roots. 
 The production of grape sugar, therefore, according to this hypothesis, would be thus repre- 
 sented : — There are retained, and given ofif. 
 From 12 of Carbonic Acid = 12C02 - - - C12 O12 O12 
 From 12 of Water- - - = 12HO - - - H12 O12 
 
 C12H12O12 O24 
 
 grape sugar 
 
 Of the 24 of oxygen thus given off, the opinion of Persoz is, that only one-half is evolved 
 by the leaf, — and the principal fact on which his opinion rests is that observed by De Saus- 
 sure, that plants of Viiica minor gave off by their leaves, in his experiments, only two-thirds 
 of the oxygen contained in the carbonic acid they absorbed. This result has led Berzelius 
 also to conjecture that the leaves of plants do not retain merely the carbon of the carbonic 
 acid, but some compound of carbon with oxygen, containing much less of this element than 
 the carbonic acid tlo.^s(7'm?7e c?e C/^e/n/e, V, p. (59). The principal objection to this view, 
 however, is the quantity of oxygen it supposes to be rejected by the root. The experiments 
 on which it is founded require coufirmation and extension. 
 
HOW SUGAR IS TRANSFORMED INTO STARCH. 137 
 
 3°. Without dwelling at present on this point, the above considera- 
 tions may be regarded as giving additional strength or probability to the 
 conclusions v/e formerly arrived at (p. 63) from other premises — that 
 ♦he roots, besides carbonic acid, absorb certain other soluble organic 
 compounds, which are always present in the soil in greater or less 
 quantity, and that the plant appropriates and converts these into its own 
 substance. Some of these organic compounds may readily, and by ap- 
 parently simple changes, be transformed into the starch and woody fibre 
 of the living vegetable. The illustration of this fact will be reserved 
 until, in the second part of these lectures, I come to treat of the vegeta- 
 ble portion of soils, and of the chemical nature and constitution of the 
 organic compounds of which it consists, or to which it is capable of giv- 
 ing rise. 
 
 4°. The chemical changes above explained («), show how, from 
 carbonic acid and the elements of water, substances possessed of ihe 
 elementary constitution of sugar and gum may, by the natural processes 
 of vegetable life, obtain the elements of which they consist, and in the 
 requisite proportions. They throw no light, however, upon the me- 
 chanism by which these elements are constrained, as it were, to assume 
 first the form of gum or sugar, or soluble starch, and afterwards, in 
 another part of the plant, of insoluble starch and woody fibre. 
 
 It is known that the sap deposits, starch and woody fibre in the stem, 
 only in its descent from the leaf, — and it is, therefore, inferred that the 
 action of light upon the sap, as it passes through the green parts, is ne- 
 cessary to dispose the elements to arrange themselves in the .form of 
 vascular fibre or liguin. And as, by the agency of nitric acid, starch 
 appears to be convertible into woody fibre (p. 126), it is not unlikely 
 that the soluble substances, containing nitrogen, which are present in 
 the sap may — as diastase does u{)on starch — exercise an agency in trans- 
 forming the soluble sugar, gum, &c., of the sap into the insoluble starch 
 and woody fibre of the seed and the stem. We are here, however, upon 
 uncertain ground, and I refrain from advancing any further conjectures. 
 
 Two great steps we have now made. We have seen how the germ 
 lives and grows at the expense of the food stored up in the seed— and 
 how, when it has obtained roots and leaves, the plant is enabled to ex- 
 tract from the air and from the soil such materials as, in kind and quan- 
 tity, are fitted to build up its several parts during its future growth. 
 That considerable obscurity still rests on the details of what takes place 
 in the interior of the plant, does not detract from the value of what we 
 have already been able to ascertain. 
 
 § 3. On the production of oxalic acid in the leaves and stems of plants. 
 
 In the preceding section we have studied the origin of those sub- 
 stances only which form the chief bulk of the products of vegetation, 
 and which are characterized by a chemical constitution of such a kind 
 as enables them to be represented by carbon and water. But during 
 the stage of vegetable growth we are now considering, other compounds 
 totally different in their nature are also produced, and in some plants in 
 sufficient quantity to be deserving of a separate consideration. Such is 
 the case with oxalic acid. 
 
 The circumstances under which this acid occurs in nature have al- 
 
138 TRODUCTION OF OXALIC ACID IN PLANTS. 
 
 ready been dot.-iilcd. It is found in srnnll (|uanfi(ic3 in ninny plants. 
 Tlio pola.sli in t'onisl trees is su[)i)08(;(l to be in conibinalion with oxalic 
 aeid, whih; in the lichens o.vidale of time serves a purpose similar to that 
 ])cii'orn)cd by the woody iibre of the more perfect plant; it forms the 
 skeleton by which the vegetable structure is supported, and tbrougli 
 which its vascular system is dillused. 
 
 Tiie produciion of this acid in the living j)lant is readily understood 
 when iis chemical constitution (Co O;,) is compared with that of car- 
 bonic aciil (COo). For 
 
 2 of Carbonic Acid = C^ O^ 
 1 of Oxalic Acid = C2 O3 
 
 DiHerencc . . . O, 
 
 That is to say, 2 of carbonic acid arc transformed into 1 of oxalic acid 
 by the loss of 1 eijuivalent of oxygen — or generally, far/;o«?'c acid hy the 
 loss of one-four tit, of its o.riji>cn. mny be converted into oxalic acid. 
 
 But the leaf .absorbs carbonic acid and gives oll'oxygen. In the lichens, 
 tlierefoRi, which contain so much oxalic acid, a large j)ortion of the car- 
 bonic acid absorbed is, by the action of light, de|)rivcd of only one-fourth 
 of its oxygen, and is thus ch.'uiged into oxalic acid. The same is true to 
 a smalh^r extiuit of the sorrel leav(;s and stems, which owe their sour- 
 ness to the pr(;sence of oxalic acid — of the leaves and stems of rhubarb 
 also — in a still smaller di'gree of the beech and other large trees, in 
 which nuich potash, and probably also of marine plants, in which 
 much soda is (bund to exist. It must be owing to the peculiar structure 
 of the leaves of each g(Mius or natural order of plants, that the same ac- 
 tion of the same light decomi)oscs the carbonic acid in ditVerent degrees 
 — evolving in some a less proportion of its oxygen, and causing in such 
 ])laulsthe formation of a larger (piantity of oxalic acid. 
 
 The fact of the ])roduction of this oxalic acid, to a very considerable 
 amount in many plants, is a further jjroof of the uncertainty of those 
 cxp(;riments from which physiologists have concluded that the leaves 
 of pl.anis (Muit a bulk of oxygen sensibly e(|ual to that of the carbonic 
 aciil absorbed.* 
 
 I have rctcTred the |)r()duction of more or less oxalic acid in dillerent 
 plants to the special structure of each, and this must be true, where, in 
 the same circumstances, dillbrent results of this kind arc observed to 
 take place — as where sorrels and sweet clovers grow side by side. Yet 
 tlu! inllu(M)ee of light of dillerent degriies of intensity on the same j)lant, 
 is beautifully shown by the leaves of the Scnipcrvivam, arhorcuni, of the 
 Porbd.acaria afra, and oilier [AiiniswhicJi arc sour in the morning, tasteless 
 
 * Wor<> we pi'rinill(>il, ii) I1h> abscnro of dorisivc experiments, to state as true what tlico- 
 rcliciil coi'isiilrialiims [ilaiiily iiidirale, we tshoiild say-- 
 
 1'^. Tlial plaiils couiaiiiiiig imicli oxalic or oilier similar aeids, and not deriving much car- 
 bonic arid iVoni tlie soil, must give oinVom their leaves a bulk of* oxygon lesa than that of the 
 carbonic acid ahsorlxMl. 
 
 '2'^. That ulauls conlainiiitr no sensible cpianlily of such acids, nor fed by carlionic acid 
 from the .soil, may evolve oxygen sensibly niuiil in bulk to IIk; cart)oiiic acid absorbed. 
 
 ;j°. That if lilile of these aciils be ()resent, and much carbonic acid be absorbed from the 
 soil, I hi; volume of oxyjjen jiivenollby the green parts of the plant must be sensibly g-rea/er 
 than that of the carbonic acid they absorb. 
 
 4'^. Thai llui leaves of the pines and other trees containing much turpentine — in vvliich 
 liydrogen is in excess-nmst at all limes jjive olToxynen in j,ne(i/cr bulk than the carbonic 
 acid Ihey absorb. They must decompose water as well as caibonic acid, and evolve the 
 oxygen of both. 
 
ACTIOff OF THE FLOWKR LEAVES ON THE AIR. 139 
 
 in the middle of Ihe day, and hitler in tlie cveni7i<r. — [Sprons^o , CJicmir, 
 II., p. 321.] l)iirini^lli(; h'l^IiI tlicoxyi^cii linsaccimiulalcd ill llu'sc plaiiLs 
 and foroiod acids coiitainiiiu; oxygen in oxc(\ss ([). 1LJ7.) As I Ik; day ad- 
 vances tliis oxygon is (^ivcn oil"; nndcr (Ijo inllucnccof ligiil ihc acidsarc 
 decomposed, and the sourness disaj)pears. 
 
 In the juices of plants before iJie period of llowcritiij;, other acids arc 
 met with besides the oxalic acid, though in much smaller quantity. As 
 the most im[)ortant of these, Jiowcwer, occur mor(! abundantly in fruits, 
 we shall consider the tJieory of their formation in the following section. 
 
 § 4. Of the chemical changes which take place between the opening of the 
 jlower and the ripening of the fruit or seed. 
 
 The op(!ning of tiie flower is the first and most striking step taken by 
 the plant towards the production olthe seed by which its species is to be 
 perpetuated. That at this jxMiod anew sericsofcdicmical changes coin- 
 niences in the plant is obvious Irom the ft I lowing facts : — 
 
 1°. That ih(! flower leaves absorb oxygen and emit carbonic acid botii 
 by day* and by night (p. 95.) 
 
 2°. That they also occasionally emit pure nitrogen gas. 
 
 3°. ^rhat the juice of the maple ceases to be sweet wh(!n the flowers 
 are matured (Ijiebig,) and that, in \\m sugar can(; and bcuit root, the sugar 
 becomes less abundant when the plant lias begun to blossom. 
 
 These facts sufliciently indicate the conuMcncement (jf new changes 
 in the interior of plants at this period of their growth. That such changers 
 go on until the ripening of the seed is also evident from these further ob- 
 servations : — 
 
 1°. That the husk of the future seed, as in tluj corn-lx^aring grasses 
 (wheat, oats, &c.,) is fdled at first with a milky Tupud, which b(;come8 
 gradually sweeter and more dcuise, and finally consolidates into a mix- 
 ture of starch and gluten, such as is presented by the flour of didi'rent 
 species of corn. 
 
 2'^. That the fruil in which the seeds of many plants is enveloped is 
 at first tasteless, afterwards more or less sour, and linally svt'ecst. In a 
 few fruits only, as in iIk; IIuk!, tlu; lemon, and the tamarind, docs a suf- 
 ficient (juantity of acid remain to be sensjbh! to the taste, when the seed 
 has become perfectly ri|)(>. The acid and cellular fibre both diminish 
 while the sugar increases. 
 
 3*^. That fruits, while green, act upon the air like the green biavesarid 
 twigs — but thai, as tli(!y approach maturity, they also absorb or retain 
 oxygen gas (i)e Saiissnre.) Tin; same absorption of oxygen takes ])lace 
 when unripe fruits are |)luck(Ml and left to ripen in the air (Berard.) 
 After a time tlie latter also emit carbonic acid. 
 
 I. FORMATION' OF THE SEED. 
 
 In the case of wheat, barley, or otiier plants, which yield farinaceous 
 seeds, we have seen tliat ])revious to flowering the chief energy of tijc 
 living plant is expended in the ])roduclion of the woody fibre of whi(di 
 its stem and growing branches mainly consist; and we have also been 
 able to understand, in some degree, how this woody fibre is produced 
 from the ordinary l()()d of the j)lant. When the flower expands, how- 
 
 " By day tlie absorjiiion is ilio Rreatcr, but the bulk of tli^ oxygen token in is always 
 greater tlian that of tlie carbonic acid given off. 
 
140 FORMATION OF THE SEED, AND RIPENING OF THE FRUIT. 
 
 ever, the plant has in general, and especially if an annual plant, reached 
 nearly to maturity, and woody fibre is little required. The most im- 
 portant of irs remauiing functions is the production of the starch and glu- 
 ten of the seed, and of the substances which form the husk by which the 
 seed is enveloped. 
 
 In the first stages of the plant's growth, the starch of the seed is 
 transformed into gum and sugar, and subsequently, when the leaves are 
 expanded, into woody fibre. In the last stages of its existence, when it 
 is producing the seed, the sugar of the sweet and milky sap is gradually 
 transformed into starch — that is to say, a process exactly the converse 
 of ilie former takes place. 
 
 We are able, in some measure, to explain the mode and agency by 
 which the former transformation is effected — the latter, however, is still 
 inex])licable. We can ourselves, b}' the agency of diastase, transform 
 starch into sugar ; and, therefore, can readily believe such transforma- 
 tions to be effected in the young plant ; — but we as yet know no method 
 of re-converting sugar into starch ; and, therefore, we can only hazard 
 conjectures as to the way in which this change is brought about in the 
 interior of the plant during the formation of the seed. 
 
 It is said that nitrogen is given off' by the flower leaf. We know that 
 this element is present in the colouring matter of the petal, and that it is a 
 necessary constituent of the albumen and gluten, which are always as- 
 sociated with the starch of the seed. It is plain, then, that the nitrogene- 
 ous substances [substances containing nitrogen,] contained in the sap at 
 all periods of the plant's gnnvth, are carried u|) in great quantity to the 
 flower and seed vessel. These substances are supposed to be concerned as 
 immediate agents in effecting the transformations which there take place. 
 More than this, however, we cannot as yet venture even to conjecture. 
 
 II.— RIPENING OF THE FRUIT. 
 
 In these plants, again, which invest their seed with a pulpy fruit — in 
 the grape, the lemon, the apple, the plum, &c. — other changes take 
 place, at this period, of a more intelligible kind, and other substances are 
 formed, on the production of which less obscurity rests. Atone stage of 
 their growtlTTTliese fruits, as has been already stated, are tasteless — in the 
 next, they are sour — in the third, they are more or less entirely sweet. 
 
 I. In the tasteless state they consist of little more than the substance 
 of tlie leaf — of vascular, or woody fibre, filled with a tasteless sap, and 
 tinged with the colouring matter of the green parts of the plant. For a 
 time, this young fruit appears to perform in relerence to the atmosphere 
 the usual functions of the leaf — it absorbs carbonic acid and gives off' oxy- 
 gen, and thus extracts from the air a portion of the food by which its growth 
 is ]iromotcd, and its size gradually increased. 
 
 II. But after a time this fruit becomes sour to the taste, and its 
 acidity gradually increases — while at the same time it is observed to 
 give off a less comparative bulk of oxygen than before. Let us consi- 
 der shortly the theory of the production of the more abundant vegetable 
 acids,contained in fruits. 
 
 1°. The tartaric acid which occurs in the grape is represented by 
 C, H, O5 (p. 124). 
 
 There are two ways in which we may suppose this acid to be formed 
 
FORMATION OF TARTARIC, MALIC, AND CITRIC ACIDS. 141 
 
 in the fruit — either directly from the elements of carbonic acid and wa- 
 ter with the evolution of oxygen gas — or from the gum and sugar al- 
 ready present in the sap aided by the ahsorplion of oxygen from the at- 
 mosphere. Thus 
 
 A. 4 of Carbonic Acid = C4 Og 
 2 of Water . . = H2 O2 
 
 ■ Tfii'f nrif* Acifl 
 
 Sum . . = C4 H2 Oio or C4 Ho O5 + 50. 
 That is, one equivalent of tartaric acid may be formed from 4 of carbon- 
 ic acid absorbed by the leaf or fruit, and 2 of the water of the sap, while 
 5 of oxygen are at the same time given off by the leaf. Or, 
 
 B. If Grape Sugar be 0^2 H^o O12 
 
 ^ of Grape Sugar = C4 H3 O3 
 
 3 of Oxygen . . = O3 
 
 Tartaric Acid. Water. 
 
 Sum . . = C4 H3 Og or C4 H2 O5 + HO. 
 
 Th?t is, by the absorption from the air of a quantity of oxygen equal to 
 that which it already contains, grape sugar may be converted into tar- 
 taric acid and water. 
 
 In the sorrels and other sour-leaved plants, which contain tartaric acid 
 in their general sap, tlie acid may be formed by either of the processes 
 above explained. In the sunshine their green jparts absorb carbonic 
 acid and evolve oxygen. If any of these green parts give off only | of 
 the oxygen contained in the carbonic acid they drink in, tartaric acid 
 may be produced (A.) In the dark they absorb oxygen and give off 
 carbonic acid. If the bulk of this latter gas which escapes be less than 
 that of the oxygen which enters, a portion of the sugar or gum of the 
 sap may, as above explained (B.), be converted into tartaric acid. 
 
 We have as yet no ex[)eriments which enable us to say by which of 
 these modes the tartaric acid is really produced in such plants — or 
 whether it may not occasionally be compounded by both methods. 
 
 In green fruits also, in the sour grape for example, it may, in like 
 manner, be produced by either method. The only experiments we yet 
 possess, those of De Saussure, though not sufficient to decide the point, 
 are in favour of the former explanation (A.) In the estimation of this 
 philosopher, the proportion of the oxygen of the carbonic acid which is 
 retained by the fruit, is sufficient to account for the acidity it gradually 
 acfiuires. 
 
 2°. Malic and citric acids. — These acids are represented (p. 127) by 
 the common formuljf! C4 Ho O4. They may be produced from water 
 and carbonic acid, if three-fourths only of the oxygen of the latter be 
 given off. Thus 
 
 4 of Carbonic Acid = C^ Oo 
 
 2 of Water . . = H2 Og 
 
 Malic Acid. 
 
 Sum . . = C4 H2 Oio = C4 H2 O4 -f 60. 
 
 That such a retention of one-fourth of the oxygen of the carbonic acid 
 occasionally takes place in the green fruit, is consistent with the obser- 
 vations of De Saussure. The lime and the lemon are fruits on which 
 the most satisfactory experiments might be made with the view of fi- 
 nally determining tiiis point. 
 
 .ai4. 
 
142 CONVERSION OF ACIDS INTO SUGAR. 
 
 III. This formation of acid proceeds for a certain time, the fruit be- 
 coming sourer and sourer; the acidity then begins to diminish, sugar is 
 formed, and (he fruit ripens. The acid rarely (li.sapj)ears entirely, even 
 from iIk; swect(!st fruits, until they begin to ^ecay ; a considerable j)or- 
 lion of ii, however, must be converted into grape sugar, as the fruit ap- 
 proaches to maturity. This conversion may take place in either of two 
 ways. 
 
 1°. By the direct evolution of the excess of oxygen. Thus 
 3 ofTAKTAiuc Acid = C,2 Hg 0,5 
 G of Water . . . = Ho 0„ 
 
 ■ Orape Sugar. 
 
 Sum. . . = Ci3 H,2 O2, = Cjo H,o 0,2 + 90. 
 
 Or grape sugar may be formed from 3 of tartaric acid and G of the water 
 oftlie sap, by the evolution, at the same time, of 9 of oxygen. Citric 
 and malic acids, in the same proportion, would form grape sugar by the 
 evolution of G of oxygen only. 
 
 Do fruits, wlien they have reached their sourest state, begin thus to 
 give oil" an excess of oxygen? 1 know of no experiments which as yet 
 decide the point. 
 
 2°. By the absorption of oxygen and the evolution of carbonic acid. 
 Thus in the case of tartaric acid, 
 1 of Tartaric Acid = C4 H2 O5 
 1 of OXYUKN . . . = O, 
 
 ■ joth of Grape Carbonic 
 
 Su!{ar. Acid. 
 
 Sum . . . = C, H^ Go = C, U., O, + 2 CO. 
 Where one of oxygen is absorbed and two of carbonic acid given off. 
 Or in the case of tlie malic and citric acids, 
 
 1 of Malic Acid = C^ Hj O^ 
 
 2 of OXYGKN . . = Oy 
 
 >6th of Grape Carbonic 
 
 Sugar. Acid. 
 
 Sum . . = C, H, O, = C, H, O3 + 2 CO^ 
 
 Where 2 of oxygen are absorb(!d and 2 of carbonic acid given o(!". 
 
 We knouTtrom the exi)criments of Berard tljat, when unripe fruits 
 are plucked, they do not ripen if excluded from the access of oxygen 
 gas — but that in the air they ripen, absorbing oxygen at the same time, 
 and giving oiX carbonic acid. This second method (2°) therefore ex- 
 hibits the more prcjbable theory of the ripening of fruits after they are 
 plucked; and if — as iJi'ey become coloured — fruits imitate the j^etals of 
 the flower in absorbing oxygen from the air and giving off catbonic acid, 
 it will also represent the changes which take place when they are per- 
 mitted to ripen on the tree. 
 
 During the ripening of the fruit, it has been stated tliat the woody or 
 cellular iilirc; it contains gradually diminishes, and is converted into su- 
 gar. This is familiarly noticed in some s|)ecies of hard or winter pears. 
 In sour fruit, the cellular fibre seldom exceeds 2^ per cent, of their 
 whole weight ; — in ripe fruits, however, it is still less, and as the con- 
 stitution of this substance is so analogous to that of grape sugar, there is 
 no difhculty in understanding that it may be readily converted into the 
 latter, though the immediate agency by which the transformation is 
 effected is as yet unknown to us. 
 
 / 
 
CHANGES AFTER THE TRUIT HAS RIPENED. 143 
 
 § 5. Of the chemical changes which take place after the ripening of 
 the fruit and seed. 
 
 AVhen the seed is fully ripe, the functions of annual plants are dis- 
 charged. They no longer recjiiire lo absorb and decomi)ose carbonic 
 acid, for their growth is at an end. Their leaves begin, therefore, to 
 take in oxygen only, become yellow, and prepare along with the entire 
 plant, for being finally resolved again into tliose more elementary sub- 
 stances from which they were originally compounded. 
 
 On trees and perennial j)lants, however, a further labour is imposed. 
 In the ripened seed they have deposited a sui)()ly of food sufficient to 
 sustain the germ that may spring from it, until it is able to seek food for 
 itself; but the young buds already formed, — and which are to shoot out 
 from the stem and branches in the ensuing spring, — are in reality so 
 many young |)lants for which a store of food has yet to be laid up in the 
 inner bark, and in the wood of tlie tree or shrub itself. 
 
 In the autumn, tlie sap of trees and permanent shrubs continues to 
 flow rapidly till the leaf withers and falls, and the food of the plant is 
 converted partly into woody fibre, as was the case during the earlier 
 period of the year, and partly into starch. The former is deposited be- 
 neath the inner bark to form the new layer of wood by which the tree is 
 annually enlarged ; the latter — partly in the same locality, as in the 
 birch and pine — partly throughout the substance of the wood itself, as in 
 the willow — while in the pafm trees and cycadea3, it is intermingled 
 with the central pith. The chemical changes by which the food is ca- 
 pable of being converted into these substances have already been con- 
 sidered. They proceed during the entire autumn, do not cease so long 
 as the sap continues to move, and even in the depth of winter slowly and 
 silently operate in storing up farinaceous matter — in readiness, like the 
 starch in the seed, to minister to the nourishment of the young bud, when 
 the warmth of the coming spring shall awaken it from its long sleep. 
 
 § 6. Of the rapidity tvith which these changes take place, and the 
 circumstances by which they are promoted. 
 
 But remarkable as those chemical changes are, llie rapidity with 
 which they sometimes take place is no less surprising. 
 
 From carbonic acid and water we have seen that the plant, by very 
 intelligible processes, can extract the elements of which its most bulky 
 parts consist — andean build them up in many varied ways, most of which 
 are probably beyond the reach of imitation. But who can understand or 
 explain the extraordinary activity which pervades the entire vascular 
 system of the plant, when circumstances are favourable to its growth? 
 
 A stalk of wheat has been observed to shoot up three inches in as 
 many days, of barley six inches in the same time, and a vine twig 
 almost two feet, or eight inches a day (Du Hamel). Cucumbers have 
 been known lo acquire a length of twenty-four inches in six days, and 
 in the Botanic Garden at Brussels I was shown a bamboo five inches in 
 diameter, which had increased in height nine feet in twenty-seven days, 
 sometimes making a prog&ess of six to eight inches in a day. In our 
 climate we meet with few illustrations of the rapidity with wliich plants 
 are capable of springing up in the most favourable circumstances, and 
 the above examples probably give us only an imperfect idea of the ve- 
 
144 INFLUENCE OF SALINE SUBSTANCES AND MAKUHES. 
 
 locity with which the bamboo, the palm, the tree fern, and other vascu- 
 lar plants, may grow in their native soil and climate. And with what 
 numerous and complicated chemical changes is the production of every 
 grain of the substance of these plants attended — how rapidly must tlie 
 food be selected and absorbed from the air and from the soil — how 
 quickly transformed and assimilated ! 
 
 The long period of time during which, year after year, these changes 
 may proceed in the same living vessels, or in the same tree, is no less 
 wonderful. Oaks have lived to an age of 1500 or 2000 years — yew 
 trees fo 3000 years— and other species are mentioned as having flour- 
 ished from 4500 to 6000 years ; while even a livmg rose tree {rosa 
 canina) is quoted by Sprengel as being already upwards of 1000 years 
 old. — [Sprengel, Lehre vom Dilnger, p. 76.] 
 
 The rapidity of the growth of a plant, and the length of its life, are 
 equally affected by circumstances. On a knowledge of these circum- 
 stances, and of the means of controlling or of producing them, the en- 
 lightened practice of agriculture is almost entirely dependent. 
 
 Over the natural conditions on which vegetation in general depends, 
 we can exercise little control. By hedge-rows and plantations we can 
 shelter exposed lands, but, except in our conservatories and hot-houses, 
 the plants we can expect to cultivate with profit will always be deter- 
 mined by the general climate in which we live. So the distribution of 
 rain and sunshine are beyond our control, and though it is ascertained 
 that a thundery condition of the atmosphere is remarkably favourable to 
 vegetable growth, [Sj)rengel, Lehre vom Dilnger, p. 73], we cannot 
 hope that such a state of the air will ever be induced at the pleasure or 
 by the agency of man. But under the same natural conditions of cli- 
 mate, there are many artificial methods by the use of which it is within 
 our power to accelerate the growth, and to increase the produce, of the 
 most valuable objects of ordinary culture. 
 
 Thus the germination of seeds in general is hastened by watering with 
 a solution of chlorine (Davy), or of iodine or bromine (Blengini), and 
 Davy found that radish seed which germinated in two days when wa- 
 ered witli solutions of chlorine or sulphate of iron, required three when 
 watered with very dilute nitric acid, and five with a weak solution of 
 sulphuric acid. 
 
 It is familiarly known also in ordinary husbandry, that the applica- 
 tion of manures hastens in a similar degree the develoj)n)ent of all the 
 parts of plants during every period of their growth — and largely increases 
 the return of seed obtained from the cultivated grains. Ammonia and 
 Its compounds likewise, and nitric acid and its compounds, with many 
 other saline substances existing in the mineral kingdom and occurring in 
 soils, or which are produced largely in our manufactories, have been 
 found to produce similar effects. 
 
 It would be out of place here to enter upon the important and interest- 
 ing field opened up to us by a consideration of the influence exercised 
 by these and other substances, in modifying both in kind and in degree the 
 chemical changes which take ])lace in living vegetables. The true mode 
 of action of such substances — their precise effects — the circumstances 
 under which these effects are most certainly produced — and the theoreti- 
 cal views on which they can be best accounted for — will form a subject of 
 special and detailed examination in the third part of the present lectures. 
 
LECTURE VIII. 
 
 How the supply of food for plants is kept up in the general vegetation of the globe. — Propor- 
 tion of their food drawn by plants from tlie air.— Supply of carbonic acid. —Supply of ammo- 
 nia and nitric acid. — Production of both in nature. — Theory of their action on living vege- 
 tables. — Concluding observations. 
 
 Having shown in the preceding Lecture in what way, and by what 
 chemical changes, the substances of which plants chiefly consist raay 
 be produced from those on which they live, — there remains only one 
 further subject of inquiry in connection with the organic constituents of 
 plants. 
 
 Plants, as we have already seen, derive mucli of their sustenance from 
 the carbonic acid of the atmospliere ; yet of this gas the air contains only 
 a. very small fraction, and in so far as experiments have yet gone, this 
 fractional quantity does not appear to diminish — how, then, is the sup- 
 ply of carbonic acid kept up ? 
 
 Again, plants most probably obtain much of their nitrogen either from 
 ammonia or from nitric acid ; and yet, neither in the soil nor in the air 
 do these compounds permanently exist in any notable quantity, — whence 
 then is the supply of these substances brought within the reach of ])lants? 
 
 The importance of these two que.stions will appear more distinctly, if 
 we endeavour to estimate how much of iheir carbon plants really draw 
 from the atmosphere — and how much of the nitrogen they contain must 
 be derived from sources not hitherto pointeid out. „ 
 
 . § I. Of the 2)Toportion of their carhon which plants derive from the 
 
 atmosphere. 
 
 On this subject it is perhaps impossible to obtain perfectly accurate 
 results. Several series of experiments, however, have been published, 
 which enable us to arrive at very useful approximations in regard to the 
 proportion of their carbon which plants, growing in a soil of ordinary 
 fertility, and in such a climate as that of Great Britain, actually extract 
 from the air by which they are surrounded. 
 
 1°. In an experitnent made in 1824, upon common borage (Borago 
 officinalis), Lampadius found that after a growth of five months (from 
 the 3rd of April to the 6tli of September) this plant produced ten times 
 as much vegetable matter as the soil in which it grew had lost during 
 the same period.* In other words, it had drawn nine-tenths of its car- 
 hon from the air. 
 
 2°. The experiments of Boussingault were made, if not with more 
 care, at least upon a greater number of plants, and were protracted 
 through a much longer period. It is necessary that we should under- 
 stand the principle on which they were conducted, in order that we 
 may be prepared to place confidence in the determinations at which he 
 arrived. 
 
 * The above experiment may have been correctly made, but the result appears at first 
 Bight too startling to be readily received as indicative of the proportion of their sustenance 
 drawn by plants from the air in the general vegetation of the globe. 
 
146 
 
 TROPORTION OF CARBON DRAWN FROM THE AIR. 
 
 If we were to examine the soil of a field on wliich we are about to 
 raise a crop of corn — and should find it to contain a certain per-centage, 
 say 10 per cent, of vegetable matter (or 5 per cent, of carbon) ; — and 
 after the crop ijs raised and reaped should, on a second examination, 
 find it to contain exactly the same quantity of carbon as before, wc 
 could not resist the conviction, that, with the exception of what was 
 originally in the seed, the plant during its growth had drawn from the 
 air all the carbon it contained. The soil having lost none, the air must 
 have yielded the whole supply. 
 
 Or if after examining the soil of our field we mix with it a supply of 
 farm-yard manure, containing a icnown weight, say one ton of carbon, 
 and when the crop is reaped find as before that the per-centage of vege- 
 table matter in the soil has sullercd no diminution,* we are justified in 
 concluding that the crop cannot, at the utmost, have derived from the 
 soil any greater weight of its carbon than the ton contained in the ma- 
 nure which had been added to it. 
 
 Sucli was the ])rinciple on which Boussingault's experiments were 
 conducted. He determined the [jcr-ccntage of carbon in the soil before 
 the exj)eriment was begun — the weight added in the form of manure — 
 the quantity contained in the series of crops raised during an entire rota- 
 tion or course of cropping, until in the mode of culture adopted it was 
 usual to add manure again — and lastly, the pro[)oriion of carbon re- 
 inaining in the soil. By this method he obtained the following results 
 in pounds per English acre, in three dillerent courses of cropping, and 
 
 on the same land : — 
 
 Difference, or 
 
 Carbon derived Remarks. 
 
 from the air. 
 
 ' The first was a 5 years' 
 course — of potatoes or 
 red beet witii manure, 
 wheat, clover, wheat, 
 oats; the second and 
 most productive rota- 
 tion was abandoned on 
 account of the climate ; 
 the third was a 3 years' 
 ^ course. 
 
 The result of the first course indicates that — the land remaining in 
 equal condition at the end of the four years as it was at the beginning — 
 the crops collected during these years contained three times the (juantity 
 of carbon present in the manure, and therefore the plants^ during their 
 growth, must on the lohole have derived two-thirds of their carbon from 
 the air. 
 
 It will be shown in a subsequent section that even when the soil is 
 lying naked the animal and vegetable matter it contains is continually 
 undergoing diminution, owing to decomposition and the escape of vola- 
 tile substances into the air. It is fair, therefore, to assume that a con- 
 
 * I need scarcely remark that, in the hands of a good farmer, who keeps his land in good 
 heart — the quantity of organic matter in the soil at the end of his course of cropping should 
 be as great, at least, ais it was at the beginning of his rotation, before the addition of the 
 manure. 
 
 
 Carbon 
 
 in the 
 
 manure. 
 
 Carbon 
 
 in 
 the crops 
 
 First Course 
 
 2513 
 
 7544 
 
 Second do. 
 
 _ 
 
 ^HM 
 
 Third do. — 
 
 5031 
 
 6839 « 
 
 3921 
 
WEIGHT OF CARBON IN THK ATMOSPHERE. 147 
 
 siderable portion of the carbon of the manure and of the soil would 
 naturally disappear during the four years' cropping above-mentioned, 
 and that, therefore, the proportion of carbon derived from the air in 
 Boussingault's experiments, must liave been really considerably greater 
 than is indicated by the numerical results. 
 
 Let two-thirds of the entire quantity of carbon contained in a series of 
 crops be taken as the average proportion, [Lecture IL, p. 31,] which, on 
 cultivated land in our climate, must be derived from the air in the form 
 of carbonic acid — and let the average weight of the dry crop reaped be 
 estimated at a ton and a half per acre. Then, if the crop contain half 
 its weight of carbon,* the plants grovt'n on each acre must annually ex- 
 tract from the air 10 cwt. or 1120 lias, of carbon in the form of carbonic acid. 
 
 § 2. Of the relation which the quantity of carbon extracted by plants from 
 the air, bears to the whole quantity contained ivi the atmosphere. 
 
 But the question will here at once suggest itself to you — docs not the 
 quantity thus extracted from the air really form a very large proportion 
 of the whole weight of carbon which is contained in the atmosphere ? A 
 simple calculation will give us clear ideas in regard to this interesting 
 point. 
 
 We have already seen that, by the resuhs of De Saussure, the aver- 
 age quantity of carbonic acid in the atmosphere of our globe may be 
 estimated at ^^'o o P^''^^ of its entire bulk. This is equal very nearly 
 to T.^,\^ of its "weight. f Or taking the whole weight of the atmosphere 
 at 15 lbs. on the square inch — that of the carbonic acid will be 0-009 lbs. 
 or 63 grs. per square inch. But as carbonic acid contains only 27j per 
 cent, of its weight of carbon, the weight of this element which presses 
 on each square inch of the earth's surface is only 17^ (17-39) grs. Upon 
 an acre this amounts to 7 tons-t 
 
 But if the crop on each acre of cultivated land annually extracts from 
 the air half a ton of carbon, the whole of the carbonic acid in the atmos- 
 phere would sustain such a vegetation over the entire globe for 14 years 
 only. And if we even suppose such a vegetation to extend over one 
 hundredth part of the earth's surface only, it still appears sufficient to 
 exhaust the carbonic acid of the air in 1400 years. 
 
 * Boussingault states, that of all the plants usually cultivated for food— so far as his experi- 
 ments have jrone— the Jerusalem arliclioke draws the larppst portion of its suf^•tenance from 
 the air— or yields the greatest weight of food from the smallest weight of manure. It is true 
 generally indeed that all those plants, "which, like the Jerusalem artichoke and the white 
 carrot, grow freely on sandy soils containing little vegetable matter and with the addition 
 of little manure, extract the greatest proportion of their sustenance from the air. Ruch 
 plants, therefore, are likely to prove the most profitable articles of culture where such soils 
 and a scarcity of manure simultaneously prevail. 
 
 t The mean of 225 experiments made by De Saussure between 1827 and 1829 gave as 
 above stated about 4-10000 or l-2500th part fortlie mean bulk of the carbonic acid in the air, 
 which is nearly 6-lOOOths of its whole weight. Among these observations the maximum 
 was 5-8 ten-thousandths, the minimum 3-15. If we take the maximum hulk at 6-10000th3 
 of the air— the maximum iceight of the carbonic acid is nearly 9-lOOOOtlis of that of the at- 
 mosphere. In elementary works it is grtierally staled in round numbers at l-lOOOth of the 
 weight of the air, but if the best experimental results we possess are to be any guide to us, 
 this is at least one-third too high. 
 
 It is also of consequence to remark, that this estimate of the whole weight of the carbonic 
 acid in the air is founded on the supposition that, in the highest regions of the atmosphere, 
 the carbonic acid is present in a proportion nearly equal to that in which it is found immS' 
 diately above the earth's surface — which is by no means established. 
 
 t 15-583 lbs.— an acre being 4840 square yards, containing each 1296 square inchess 
 
148 HOW THE SUPPLY OF CARBONIC ACID IS RENEWED. 
 
 A very short period, compared even with the limits of authentic his- 
 tory, has yet ehipsed since experiments began to be made on the true 
 constitution of the atmosphere ; we have no very trustworthy data, 
 therefore, on which to found a confident opinion in regard to the perma- 
 nence of the proportion of carbonic acid which it now contains. The 
 later observations of De Saussure do give a considerabl}'^ lower estimate 
 of the quantity of this acid in tlie air than that which was deduced from 
 the results of the earlier experimenters; but the imperfection of the 
 modes of analysis formerly adopted was too great, to justify us in rea- 
 soning rigorously from the inferences to which they led. We cannot 
 safely conclude from them that the proportion of carbon in the atmos- 
 phere has really diminished to any sensible extent during this limited 
 period; while the recorded identity of all the phenomena of vegetation 
 renders it probable that the proportion has not sensibly diminished even 
 within historic times. 
 
 From what sources, then, is tlie supply of carbonic acid in the atmos- 
 phere kept up? — and if the proportion be permanent, by what compen- 
 sating ])rocesses is the quantity which is restored to the atmosphere 
 produced and regulated? 
 
 § 3. How the supply of carhonic acid in the atmosfhere is renewed 
 
 and regulated. 
 On comparing, in a previous lecture, the quantity of rain which falls 
 with that of the watery vapour actuall3'^ present in the air, we saw rea- 
 son to believe that even in a single year the same portion of water may 
 fall in rain or dew and ascend again in watery vapour several succes- 
 sive times. Is it so also with the carbon in tlie air ? Does that which 
 feeds the growing plant to-day, again mount up in the form of carbonic 
 acid at some future time, ready to minister to the sustenance of new- 
 races, and to run again the same round of ever-varying change ? Such 
 is, indeed, the general history of the agency of the carbonic acid of the 
 atmosphere ; but when once it has been fixed in the plant it must pass 
 through many successive changes before it is again set free. The con- 
 ditions, also, under which it is restored to the atmosphere are so diver- 
 sified, and ths~agencies by which, in each case, it is liberated, are so 
 very distinct, as to require that the several modes by which the carbon 
 of plants is reconverted into carbonic acid and returned to the air, should 
 be made topics of separate consideration. 
 
 I. ON THE PRODUCTION OF CARBONIC ACID BY RESPIRATION. 
 
 The air we breathe when it is drawn into the lungs, contains o^'o-^th 
 of its bulk of carbonic acid ; when it returns again from the lungs, the 
 bulk of this gas amounts, on an average,* to Trjth of the whole ; or its 
 quantity is increased one hundred times. 
 
 The actual bulk of the carbonic acid emitted from the lungs of a sin- 
 gle individual in 24 hours varies exce.edingly ; it has been estimated- 
 however, on an average, to contain upwards of five ounces of carbon. f 
 
 * It varies in different individuals from 2 to 8 per cent, of the expired air. In animals it 
 varies also witli the spi^rics. Thn air from the lungs of a cat contains from 5| to 7 per cenl., 
 of a dO!! from "^Ho Ci^, of a rahbit from 4 to G. and of a pigeon from 3 to 4 per cent, of the 
 whole bulk. — Dulong, AjduiI. de Chim. etde Phys.^ third /Series, /., p. 4.55. 
 
 t Davy, and Allen, and Pepys, estimated the weijrhr of carbon evolved in a day at upwards 
 of 11 ounces, a quantity which all wi-itcrs liave concurred in rccoivin"' with PM^^nir-i'^" 
 
THE COMBUSTION OF ORGAMC MATTER. 149 
 
 A full grown man, therefore, gives off from his lungs, in the course of a 
 year, upwards of 100 lbs. of carbon in the form of carbonic acid. 
 
 If the (juantity of carbon thus evolved from the lungs be in proportion 
 to the weiglit of the animal, a cow or a horse ought to give off six times 
 as much as a man.* From indirect ex[)eriments, however, Boussin- 
 gault estimated the quantity of carbon actually lost in this way by a cow 
 at 2200 grammes in 24 hours, and by ahorse at 2400 grammes. — [Ann. 
 de Chim. eide Phys., Ixxi., pp. 127 and 136.] These quantities are equal 
 to 6 or 7 times the amount of carbon given off from the lungs of a man. 
 
 If we suppose each inhabitant of Great Britain, young and old, to ex- 
 pire only 80 lbs. of carbon in a year, the twenty millions would emit 
 seven hundred thousand tons ; and, allowing the cattle, sheep, and all 
 other animals, to give off twice as much more, the whole weight of 
 carbon returned to the air by respiration in this island would be about 
 two millions of tons, or the (piantity abstracted from the atmosphere by 
 four millions of acres of cultivated land. 
 
 Whence is all this carbon derived ? It is a portion of that which has 
 been conveyed into the stomach in the form of food. Suppose the car- 
 bon contained in the daily food of a full grown man to amount to one 
 pound — which is a large allowance— then it appears that, by the ordi- 
 nary processes of respiration, at least one-third of the carbon of his food 
 is daily returned into the air. 
 
 In other animals the proportion returned may be different from what 
 it is in man, yet the life of all depends on the emission to a certain ex- 
 tent of the same gas.f And since all are sustained by the produce of 
 the soil, it is obvious that the process of animal respiration is one of 
 those methods by which it has been provided that a large portion of the 
 vegetable productions of the globe should be almost immediately re- 
 solved into the simpler forms of matter from which it was originally 
 compounded, and again sent up into the air to minister to the wants of 
 new races. 
 
 II. — ON THE PRODUCTION OF CARBONIC ACID BY COMBUSTION. 
 
 Another important source of carbonic acid is familiar to us in the re- 
 sults of artificial combustion. 
 
 In the previous lecture I have shown how, by the action of the sun's 
 rays upon the leaf, the carbonic acid absorbed from the atmosphere is 
 deprived of its oxygen, and its carbon afterwards united to the elements 
 of water for the production of woody fibre. During the process of com- 
 bustion, this labour of the living leaf is undone — the carbon is made to 
 combine anew with the oxygen of the atmosphere, and the vegetable 
 matter is resolved again into carbonic acid and water. 
 
 Thus, when wood (woody fibre) is burned in the air, oxygen disap- 
 pears, and carbonic acid and watery vapour are alone produced. The 
 theory of this change is simple. 
 
 * Estimating tlie ordinary weight of a man at 150, Eind of a cow at 800 to 9!X) lbs. — See 
 Sprengel, Lehre vmn Diinger, p. 208. 
 
 ' That the proportion Tmist be less in the largjor animals is certain, since the daily food of 
 a cow may be staled generally as eqnivalent to 25 lbs. of hay, containing upwards of 10 lbs. of 
 carbon. If one- third of this were given off from the lungs, the quantity of carbon (.3^ lbs.) 
 evolved would be ten times greater than was indicated by the experiments of Boussingault, 
 and nearly double of what the weight of a cow, comparea with tnatof a man, requires. 
 
 •7* 
 
150 PRODUCES CARBONIC ACID AJND WATER. 
 
 It will be recollected (p. 135) that in forming an equivalent of woody 
 fibre or of sugar, 24 of oxygen were given off, chiefly by the leaf — so in 
 again resolving these substances into carbonic acid and water, 24 of oxy 
 gen are absorbed. Thus— 
 
 1 of Woody Fibre = C^a Hg O3 
 24 of Oxygen . = O24 
 
 12 of 8 of 
 
 Carbonic Acid. Water. 
 
 Sum. . . ^CisHg O30 = I2CO2 + 8HO. 
 
 Or, 1 of Cane Sugar ^CisHioOm 
 24 of Oxygen . . = O24 
 
 12 of 10 of 
 
 Carbonic Acid. Water. 
 
 Sum. . . =Ci2 Hxo O34 =12CO2 + 10HO. 
 
 The same law holds in regard to all other vegetable substances. They 
 are resolved into carbonic acid and water, in proportions which neces- 
 sarily vary with the chemical constitution of each. 
 
 It applies also to all bodies of vegetable origin, among which nearly 
 all combustible minerals may be reckoned. The peat and coal we burn 
 in onr houses and manufactories, when supplied with a sufficiency of 
 atmospheric air, are resolved during combustion inlo carbonic acid and 
 watery vapour. 
 
 Some vegetable substances contain a small quantity of nitrogen. 
 When these are burned, this nitrogen escapes inlo the atmosphere, — 
 generally in an uncombined state, — and mingles with the air. So in 
 animal substances, nearly all of which contain nitrogen as an essential 
 constituent. During perfect combustion the whole of the carbon is dis- 
 sipated in the form of carbonic acid, while the nitrogen rises along with 
 it in an elementary state. 
 
 The result of this uniform subjection of all combustible matter to the 
 operation of this one law, is the constant production on the surface of 
 the globe of a vast quantity of carbonic acid ; — the re-conversion of large 
 masses of organic matter into the more elementary compounds from 
 which it was originally formed. 
 
 How interesting it is to contemplate the relations, at once wise and 
 beautiful, by which through the operation of such laws, dead organic 
 matter, intelligent man, and living plants, are all bound together ! The 
 dead tree and the fossile coal lie almost useless things in reference to 
 animal and vegetable life, — man employs them in a thousand ways as 
 ministers to his wants, his comforts, or his dominion over nature — and 
 in so doing, himself directly though unconsciously ministers to the wants 
 of those vegetable races, which seem but to live and grow for his use and 
 sustenance. 
 
 It is impossible to say what proportion of the carbon absorbed during 
 the general vegetation of the globe, is thus annually restored to the at- 
 mosphere by the burning of vegetable matter. That it must be very 
 great, will appear from the single fact, that by far the greater part of the 
 globe is dependent for its supply of fuel on the annual produce of its 
 forests; — while even in those more favoured countries where mineral 
 coal abounds, the quantity of wood consumed by burning falls but little 
 short of the entire yearly growth of the land. 
 
LAW OF THE DECAY OF VEGETABLE MATTER. 151 
 
 In connection with this subject, I must draw your attention to one in- 
 teresting, as well as irn])ortant, fact. I have spoken of coal as a sub- 
 stance of vegetable origin, and there is no doubt that all the carbon it 
 contains «nce floated in the air in the form of carbonic acid. But the 
 period when it was so mixed with the atmosphere is remote almost be- 
 yond conception. When, therefore, we raise coal from its ancient bed 
 and burn it on tlie earth's surface, ivc add to the. carbon of the air a por- 
 tion which has not previously existed in the atmosphere oj our time. 
 
 The coal consumed in Great Britain alone is estimated at 20 millions 
 of tons, containing on an average at least 70 per cent., or 14 millions of 
 tons of carbon. But if the annual produce of an acre of cultivated land 
 contain half a ton (p. 147) of carbon derived from the air, the coal con- 
 sumed in this country would supply carbonic acid to the crops grown 
 upon 28 millions of acres. Or, since in Great Britain about 34 millions 
 of acres are in cultivation (p. 12), the coal we annually consume jnoduces 
 a quantity of carbonic acid ichich is alofie sufficient to supply food to the 
 crops that grow upon seven-eighths of the arable land of this country. 
 
 IH. P.10DUCTION OF CARBONIC ACID BY THE NATURAL DECAY OF VEGE- 
 TABLE MATTER. LAW OF THIS DECAY. 
 
 Over large tracts of country in every part of the globe, the vegetable 
 productions of the soil are never cropped or gathered, but either accumu- 
 late — as occasionally in our peat bogs; or decay and gradually disappear 
 ' — as in the jungles of India or in the tropical forests of Africa and South- 
 ern America. 
 
 The final results of this decay are the same as those which attend 
 upon ordinary combustion, but the conditions under which it takes place 
 being different, the immediate results are to a certain extent different 
 also. 
 
 When a vegetable substance is burned in the air, the oxygen of the at- 
 mosphere is the only material agent in effecting the decomposition. 
 The carbon of the burning body unites directly with this oxygen and 
 forms carbonic acid. 
 
 In the natural process of decay, however, at the ordinary temperature 
 of the atmosphere, vegetable matter is exposed to the action of both air 
 and water ; these both co-operate in inducing and carrying on the decom- 
 position, and hence carbonic acid is not, as in the case of combustion, the 
 chief or immediate result. 
 
 A detail of all the steps through which vegetable matter is known to 
 pass before it is finally resolved into carbonic acid and water, would be 
 difficult for you to understand, and is here unnecessary. A general 
 view of the way in which by the united agency of air and water, the 
 decay of organic substances is effected and promoted, may be made 
 very intelligible, and will sufficiently illustrate the subject for our pre- 
 sent purpose. 
 
 In combustion, as we have seen, the ichole of the vegetable substance 
 is resolved directly into carbonic acid and water, at the expense of the 
 oxygen of the atmosphere. In natural decay a small and variable por- 
 tion only is so changed, but to the extent to which this change does take 
 place carbonic acid is directly formed and sent up into the air. Suppose 
 such a change — a slow combustion in reality — to take place to a certain 
 
152 BY NATURAL DECAY IT IS FINALLY RESOLVED 
 
 extent, and let us consider what becomes of the remainder of the vegeta 
 ble matter. 
 1°. If we add 
 
 6 of Carbonic Acid . . = Cg Oja • 
 
 to 6 of Light Carburetted ) p tt 
 
 Hydrogen (CH2) $ " ^^ «i2 
 
 we have the sum . . = Cjo H12 O12; or, one of 
 grape sugar; — that is, one of grape sugar may be formed out of the ele- 
 ments of 6 of carbonic acid, and 6 of light carburetted hydrogen. Or, 
 conversely, grape sugar being already produced, it may be resolved or 
 decomposed into these two compounds in the same proportions, without 
 the aid of the oxygen of the atmosphere. 
 2°. So if to 
 
 1 of Woody Fibre = Cjo H^ O3 
 we add 4 of Water . . = H4 O4 
 
 Carbonic Light Carbu- 
 
 Acid, retted Hydrogen. 
 
 we have, as before, C,2 H12 O12 ^= 6CO2 + 6 Clio; 
 Or by the aid of the elements of 4 aioms of water, woody fibre may be 
 resolved into 6 of carbonic acid and as many of light carburetted 
 hydrogen. 
 
 3°. Again, in the case of a vegetable acid, if to 
 
 1 of Tartaric Acid = C4 H2 Og 
 we add 1 of Oxygen . . = Oj 
 
 Carbonic Light Carbu- 
 
 Acid. retted Hydrogen, 
 we have C, Ho O, = 3 COo + CHo ; 
 That is, by the aid of one of oxygen from the air, one of tartaric acid 
 may be resolved into 3 of carbonic acid, and 1 of light carburetted 
 hydrogen. It is easy to see how any other of the more common vegeta- 
 ble productions may — either at the expense of its own elements, as in 
 grape sugar — or by the aid of those of water, as in woody fibre — or of 
 the oxygen of the atmosphere, as in tartaric acid — be resolved into car- 
 bonic acid andjight carburetted hydrogen, in certain proportions. 
 
 Now, such a resolution does really take place to a considerable extent 
 in nature, during the decay of organic substances in moist situations. 
 Hence the evolution of light carburetted hydrogen from dead vegetable 
 matter in marshy places and stagnant pools — hence the production of 
 the same gas in compost heaps, and especially in rich and heated farm- 
 yard manure — and hence also its occurrence in such vast quantities in 
 many of our coal mines. 
 
 You will now be able to appreciate one of the reasons why this light 
 carburetted hydrogen has been supposed by some physiologists (p. 50) 
 to contribute as food to the ordinary nourishment of plants. It is pro- 
 duced in nature in many and varied situations, and it has been found 
 by experiment to exercise a visible influence upon the growth of plants; 
 — being so produced where young plants grow, is it never imbibed by 
 them 1 — being possessed of this influence, is it entrusted with no control 
 over the general vegetation of the globe ? 
 
 However this may be, by far the greatest portion of both these gases 
 <&8capes into the air ; — the carbonic acid to fulfil those purposes which 
 
INTO CARBONIC ACID AND WATER. 153 
 
 have already been considered, — the light carburetted liydrogen to under- 
 go a further change, by which it also is resolved into carbonic acid and 
 water. Thus, if to 
 
 1 of Light Carburetted Hydrogen = CHo we add 
 4 of Oxygen = O4 
 
 Carbonic Acid. Water. 
 
 We have CH2 O, or COo + 2HO 
 
 Or one of this gas with 4 of oxygen may be changed into 1 of carbonic 
 acid and 2 of water. 
 
 Now, Avhen this gas escapes into the air it becomes diffused through a 
 large excess of oxygen, and is thus ready, at any instant, to be decom- 
 posed. Through the atmosphere streams of electricity are continually 
 flowing, and every wandering spark that passes athwart a portion of 
 this mixture decomposes so much of the Hght gas, and produces in its 
 stead the equivalent proportions of carbonic acid and watery vapour. 
 Thus it happens that of the vast quantity of this and other combustible 
 gases which are continually escaping into the air, so few traces are dis- 
 cernible even by the aid of the most refined processes of art. By a wise 
 provision of nature such substances as are void of use to either animals 
 or plants, if not speedily removed from the air altogether, are there con- 
 verted into such new forms of matter as are fitted to minister to the ne- 
 cessities of living beings. 
 
 Though therefore in the natural decay of vegetable matter in the pre- 
 sence of air and moisture, a certain portion of its carbon escapes into the 
 air in the form of light carburetted hydrogen, this compound is but a 
 step towards the final change into carbonic acid and water. In the soil 
 the vegetable matter is continually undergoing decay, various sub- 
 stances are produced in greater or less quantity, some solid, some liquid, 
 a#d some gaseous like the light gas of which we have been speaking, — 
 but all of them, like this gas, are only hastening — some by one road, so 
 to speak, and some by another — towards that final destination which 
 sooner or later they are all fated to reach ; when in the form of carbonic 
 acid and water they shall be in a condition to minister again to the nour- 
 ishment of all plants. 
 
 While in the soil some part of this vegetable matter assumes forms 
 which are capable of entering again into the roots of li\T.ng plants, and, 
 without further resolution in the air, of being converted by the living 
 plant into portions of its own substance. The nature and composition 
 of these forms of matter, so far as they are known, will be considered in 
 a subsequent lecture. — [See Part II., Lectures XI.-XIII., " On the 
 constitution of soils/*] 
 
 It is upon the final result of this natural decay to which all vegetable 
 matter is subject, that the carbonic acid of the atmosphere depends for 
 its largest sui)plies. The rapidity with which organized bodies perish, 
 and become resolved into gaseous compounds, depends partly upon the 
 climate and partly on the. nature of the sub.stances themselves, — but all 
 hurry forward to the same end, and it is with diHiculty that we are able 
 for a time to arrest or even to retard their steps. It is by this perpetual 
 and active obedience of all dead matter to one fixed law that the exist- 
 ing condition of things is maintained ; — and thus it happens that either 
 by the respiration of the animals which live upon it, by the process of 
 
154 EVOLUTION OF CARBONIC ACID IN VOLCANIC COUNTRIES. 
 
 combustion, or by that of spontaneous decay, the entire crop of vegeta- 
 ble produce is ajjparently^ year by year — taking the average of a series 
 of years — resolved into the forms of matter from which it was originally 
 built up ; — and the substances on which plants feed at length restored to 
 the air in the precise proportion in which they have been taken from it. 
 
 VI. NATURAL EVOLUTION OF CARBONIC ACID IN VOLCANIC COUNTRIES. 
 
 The above apparent conclusion would be absolutely true, were there 
 no causes in operation by which the restoration to the air of a portion of 
 the carbon of animal and vegetable substances is prevented — and no 
 other sources, independent of existing organic matter, from which car- 
 bonic acid may be supplied to the air. 
 
 If the whole of the carbon be not returned to the air, the carbonic acid 
 of the atmosphere may be undergoing diminution ; while — if a large 
 supply be constantly poured into the air from sources independent of 
 vegetable matter, the proportion of carbonic acid may be continually on 
 the increase. 
 
 We have seen that the combustion of fossil coal adds to the air a 
 large quantity of carbonic acid which has never before existed in the at- 
 mosphere of our time. In many volcanic districts also, carbonic acid is 
 observed to issue in large (juantity from cracks and fissures in the earth ; 
 — accompanied sometimes by water, forming mineral springs, from 
 which the copious emisson of gas is readily perceived ; more frequently, 
 perhaps, rising up alone, and thus escaping general observation. 
 
 It must obviously be exceedingly difficult to estimate the quantity of 
 gas which rises into the air in such circumstances over an extensive 
 tract of country, fractured and broken up by volcanic agency — where 
 the outlets are numerous, and the rate at which the gas escapes very 
 variable. That in many localities it must be very great, however, 
 there can be no (juestion. In the ancient A^olcanic district of the Eifel, 
 comprising an area of many square miles around the Laacher See, on 
 the left bank of the Rhine, the annual evolution of carbonic acid from 
 springs and fissures has been estimated by Bischof at not less than 
 100,000 tons^ontaining 27,000 tons of carbon. In many other districts, 
 especially where active volcanoes exist, the volume of gas given off 
 may be quite as great, though no attempts have hitherto been made to 
 estimate its real amount. 
 
 Yet though absolutely large, the quantity of carbonic acid disengaged 
 in this way from the earth, is really small when compared either with 
 the entire quantity supposed to be present in the atmosphere, or with 
 that which is required for the growth of the yearly vegetation of the 
 globe. Suppose that from a thousand spots on the earth's surface a 
 quantity of carbonic acid equal to the above estimate of Bischof escapes 
 constantly into the air, the weight of carbon (27 millions of tons) thus 
 diffused through the atmosphere would be only e(iual to that which is 
 yearly drawn from the air by 54 millions of acres of land under cultiva- 
 tion (p. 147), and only twice as much as that contained in the coal 
 which is annually consumed in Great Britain alone. 
 
 Still if the whole of the carbon contained in the produce of the general 
 vegetation of the globe be ultimately restored to the air, — either by the 
 respiration of animals, by the natural and slow decay of vegetable mat- 
 
155 CARBON PERMANENTLY WITHDRAWN FROM THE AIR. 
 
 ter, or by the more rapid process of combustion, — the constant addition 
 of carbonic acid derived from volcanoes, and from the combusiion of fos- 
 sil coal, should gradually, though slowly, augment the proportion of this 
 gas in the air we breathe ; — unless it be per])etually undergoing a per- 
 manent diminution, to at least an equal extent, from the operation of 
 other causes. In reference to this point there are three circumstances 
 which are proper to be considered : — 
 
 1°. It has been observed that, as we recede from the land and ap- 
 proach the centre of great lakes, or sail into the open sea, the quantity 
 of carbonic acid in the air gradually diminishes. It is therefore inferred 
 that the sea is constantly, and to a sensible extent, absorbing carbonic 
 acid from the atmosphere, without afterwards restoring it, so far as is 
 yet known, by any compensating ])rocess. 
 
 2°. The waters which flow info the sea or great lakes constantly 
 bear down with them portions of animal and vegetable matter. These 
 fall along with the mud which tlie waters hold in suspension, and are 
 permanently imbedded in the deposits of clay, silt, and sand, which are 
 continually in the course of formation. 
 
 3°. In many parts of the world, especially in the latitudes north and 
 south of 45°, vegetable matter accumulates in the form of peat, becomes 
 buried beneath clay and sand, and thus is prevented from undergoing 
 the ordinary process of natural decay. 
 
 It is impossible to say how much carbon is permanently withdrawn 
 from the atmosphere by these several agencies. There is reason to be- 
 lieve that it is quite as great as the quantity added to the air by the 
 combustion of coal, and by the evolution of carbonic acid in volcanic 
 districts. Indeed, the supply from these two sources appears to return 
 only a small portion of that carbonic acid which is abstracted from the 
 air by the agencies just stated, and which have been in operation during 
 every geological epoch. 
 
 Conclusions. — The general conclusions, therefore, which we seem jus- 
 tified in drawing in regard to the supply of carbonic acid to the atmos- 
 phere are as follow : — 
 
 1°. That a large portion of the carbonic acid absorbed by plants is 
 immediately and directly restored to the air by the respiration of the 
 animals which feed upon vegetable productions. 
 
 2°. That a still larger portion is more slowly returned by the gradual 
 re-conversion of vegetable substances into carbonic acid and water dur- 
 ing the process of natural decay. • 
 
 3°. That nearly all the remainder is given back in the results of or- 
 dinary combustion. 
 
 4°. That a further portion, which has not previously existed in the 
 atmosphere of our time, is conveyed to ii by the burning of fossil fuel, 
 and by the emission of carbonic acid from cracks and fissures in the 
 surface of the earth ; yet that the quantity thus added cannot be sup- 
 posed to exceed that which is constantly and permanently separated 
 from the atmosphere by other causes. 
 
 The balance of all the evidence we possess is probably in favour of 
 the opinion that the carbonic acid in the atmosphere is slowly diminish- 
 
156 AMMONIA IN THE AIR — HOW DECOMPOSFD. 
 
 ing; we have, however, no satisfactory evidence either from theory or 
 experiment that it has undergone any sensible diminution in our time.* 
 
 § 4. Of4he supply of ammonia to plants. 
 
 In a previous lecture it has been shown that in our cultivated fields 
 plants derive a portion of their nitrogen from the manure which is added 
 to the soil. But the quantity of this element present in the manure, 
 supposing it all taken up and apjiropriated by (he plant, is seldom etjual 
 to that contained in the scries of crops which this manure assists in raising. 
 
 Thus, in the experiments of Boussingault already described (p. 144), 
 the manure added previous to the first, or four years' course, contained 
 
 157 parts of nitrogen, while the crops contained 251 parts, — or nearly 
 two-tJdrds more than could be derived from the artificial manure. 
 
 Whence is ti)is excess of nitrogen derived, and in what form does it 
 enter into the plant? Liebig replies to these (|uestions, that the whole 
 of the nitrogen absorbed by plants enters in the state of ammonia, and 
 that the excess above what is present in the manure is drawn either 
 from tlie soil or from the air. This opinion, advanced by so high an 
 authority, demands our attentive consideration. 
 
 Ammonia has been detected in many clays, and traces of it may be 
 discovered in most soils, but it is not known to be a natural or essential 
 constituent of any of the solid rocks of which tiie crust of the globe is 
 com))osed. These clays and soils, therefore, may be supposed to have 
 derived their ammonia from the atmosphere ; and Liebig ascribes the 
 fertilizing action of the air upon stiff'clays when fallowed, of burned clay 
 when applied as a top-dressing, and of gypsum on grass lands [see note 
 to page 53], to the larger quantity of ammonia which the surface of the 
 soil is by these means caused to absorb and retain. 
 
 There is no question that ammonia is present in the atmosphere in 
 small and variable quantity (p. 37). Whence is this ammonia derived, 
 and is its quantity sufficient to supply the demands of the entire vegeta- 
 tion of the globe ? 
 
 When animal substances undergo decay, nearly all the nitrogen they 
 contain is ultimately separated from the other constituents in the form of 
 ammonia, ^©uring the decay of plants also, a portion of their nitrogen 
 escai)es in the state of ammonia. Of the ammonia thus formed, much 
 ascends into the air, chiefly in combination with carbonic acid as carbonate 
 of ammonia (smelling salts), and much remains in the soil. Were the 
 whole of the nitrogen contained in plants and animals to assume the 
 form of ammonia when they decay, and to remain in the soil or in the 
 air, it would always be within the reach either of the roots or leaves of 
 the living races; and thus the same ammonia [or ammonia containing 
 the same nitrogen — supposing the hydrogen to have been changed] 
 might again and again return into the circulation of new vegetable tribes, 
 and be always alone sufficient to supply all the demands of the exist- 
 ing vegetation of the globe. 
 
 But of the ammonia thus formed, a portion is daily washed from the 
 soil by the rains and carried to the sea, and much more probably is 
 
 ' In another work (C7jc7?i/faZ Geology) now preparing for pnblicatinn, I have discussed 
 this question in connection witli purely Geological considerations and without reference to 
 our time ; but it would be out of place to introduce here any train of reasoning which is not 
 calculated to throw light on the phenomena of the existing vegetation oi the globe. 
 
AMMONIA KVOLVED FROM VOLCANOES. 157 
 
 washed from tne air by the waters of the sea itself, or by the rains which 
 fall directly into the wide oceans ; and we know of no compensating 
 process by which this ammonia can be restored to the air, and again 
 made useful to vegetation. 
 
 Besides, of that which still remains in the air much must undergo 
 decomposition by natural processes. In treating in a preceding section 
 of the evolution of light carburetted hydrogen during the slow decay of 
 vegetable matter (p. 153), I have shown how, in consequence of its ad- 
 mixture with the oxygen of the atmosphere, this gas is finely decom- 
 posed, while carbonic acid and water are produced. Ammonia in like 
 manner will burn in oxygen gas, and when mixed with atmospheric air 
 may be decomposed by the electric spark — water at tfie same time being 
 formed and nitrogen set free. Thus, 
 
 if with 1 of Ammonia =: NH3 
 
 we mix 3 of Oxygen = O3 
 
 ^ . 3 of water. 1 of nitrogen. 
 
 we have the sum NH3 O3 = 3 HO + N 
 
 or, when diffused through the air, 1 of ammonia, with the aid of 3 of 
 oxygen, will yield 3 of watery vapour, while the nitrogen may* mingle 
 with the air in an elementary form. Can we doubt that ammonia 
 is thus decom})Osed in the air? Not to speak of other forms assumed 
 by the electricity of the atmosphere, can the thunder-storms of the tropi- 
 cal regions pass unheeded the ammoniacal vapours they must meet 
 with in their course ? 
 
 I conclude, then, that of the ammonia which is formed from the nitro- 
 gen actually existing in animal and vegetable substances during their 
 decay, only a comparatively small portion ever returns again to minister 
 to the wants of new races. f 
 
 But if plants obtain all their nitrogen from ammouia,t how is this 
 waste re[)aired — whence are new supplies constantly derived ? 
 
 We have seen that, in certain yoicanic countries, carbonic acid is 
 evolved in vast quantities from rents and fissures in the earth. In some 
 of these districts — and this has been observed more especially in Italy 
 and Sicily, and it is said also to some extent in China — ammonia is 
 likewise given off, in combination generally with some acid, and most 
 freijuently with the muriatic acid in the form of sal-ammoniac (muriate 
 of ammonia). " This ammonia,'" Liebig is correct in saying, '•'■ has not 
 been produced by the animal organism ;" but he assumes a very doubt- 
 ful position when he adds, ''it existed before the creation of human be- 
 ings ; it is a part, a 'primary constituent of the globe itself ''' — [Orgaaic 
 Chemistry applied to Agriculture, p. 112.] 
 
 Where, we might ask, has this ammonia existed during all past time 
 — from what deep caverns of the earth does it now escape ? 
 
 • 1 say may, because it may at the same time combine with oxygen and form nitric acid. 
 — See the following section, p. 239. 
 
 1 1 might add, that of the ammonia which does return, and is again absorbed, a portion is 
 subsequently decomposed in the interior of living plants, as is shown by the evolution of 
 nitrogen from the common leaves of some and the flower leaves of others. 
 
 X " Wild plants obtain more iiilrogcnfrum the at7nosj)here, in the form of ammonia, than they 
 require for their growth, for the water which evaporates through their leaves and blossoms 
 emits, after a time, a putrid smijU— a peculiarity possessed only by such bodies as contain 
 nitrogen."— [Liebig, Organic Chemistry a'ppiiod to Agrictdture, p. 85.] Does the fact hero 
 stated, justify tlie conclusion which appears to be drawn from it 1 
 
158 INDIRECT PRODUCTION OF AMMONIA. 
 
 This opinion of Liebig, as well as the pariimount influence he as- 
 cribes to ammonia over the vegetation of the globe, are based chiefly on 
 the fact that we know of no means by which ammonia can be formed 
 by the direct union of the hydrogen and nitrogen of which it consists. 
 
 But the production of ammonia, by the indirect union of these ele- 
 ments, is daily going on in nature, and can even be effected by differ- 
 ent processes of art. Thus — 
 
 1°. When organic substances, which contain no nitrogen, are oxidized 
 in the air, ammonia is not unfrequently formed (Berzelius). Hence 
 it must be produced in unknown quantity during the annual decay of 
 all vegetable substances. 
 
 2°. When organic substances are oxidized in the presence of air and 
 wafer — as when moist iron filings are exposed to the air (Chevallier), 
 or when certain oxidized substances are decomposed in the air by 
 nieans of potassium (Faraday), or when metals, such as tin filings, are 
 rapidly oxidized by means of nitric acid, ammonia is also })roduced in 
 variable quantity. Hence the absorption of oxygen, even by the inor- 
 ganic substances of the soil, may irive rise to the formation of ammonia. 
 But, 
 
 3°. The fact which most clearly illustrates the production of am- 
 monia in nature, both on the siu^face of the earth, in the soil, and far in 
 the interior near the seat of volcanic fires, is this, that if a currant of 
 moist air be made to pass over red-hot charcoal, carbonic acid and am- 
 monia are simultaneously formed.* This is in reality only a repetition 
 in another form of what takes place, as above stated, when vegetable 
 matter decays, or iron filings rust in moist air. Tiie carbon and the iron 
 decompose the watery vapour in the air, and cotnbine with its oxygen, 
 while, at the instantf of its liberation, the hydrogen of the water com- 
 bines with the nitrogen of the air, and forms ammonia. 
 
 The source of the ammonia evolved in volcanic districts, therefore, is 
 no longer obscure. The existence of combustible matter in such dis- 
 tricts, and at great depths beneath the surface, can in fev/ cases be 
 doubted, and the passage of a mixed atmosphere of common air and 
 steam over such combustible matter, at a high temperature, appears to 
 be alone necessary to the production of ammonia. It is unnecessary, 
 then, to have recourse to doubtful speculations in order to account for 
 the natural reproduction of ammonia, to a certain extent, in the place 
 
 * This experiment is easily performed by drawing a. current of mixed atmospheric air 
 and steam tlirouj^h a red-hot gun-barrel filled with well-burned charcoal, and causing the 
 current, on leaving the barrel, to pass through water acidul.ited with mimalic acid. After 
 a time, the water, on evajtoration, will be found to contain traces of sal-ammoniac. What 
 thus takes place in asmall experiment of this kind must more readily and more largely 
 take place in the interior of the earth, where combustible substances at a high temperature 
 happen to be exposed to a current of atmospheric air, mixed with watery vapour. 
 
 t A bt'avitiful illnslration of the tendency which elementary substances have to unite with 
 each otlicr at the instant of tiieir liberation in what chemists call their nascent state, is men- 
 tioned by Runge. — Einlcitung in die technische Chemie, p. 373. 
 
 If 1 part of hydrate of potash and 20 of iron filings be heated together, hydrogen only is 
 given (iff. 
 
 If 1 of nitrate of potash and 20 of iron fih"ngs be heated together, nitrogen only is given off. ' 
 
 But if 40 of iron fiJings be mixed witli 1 of hydrate andl of nitrate of potash, and then 
 healed, ammonia becomes perceptible. 
 
 The nitrogen and hydrogen being given off together, at the same instant, some portions 
 of each find Uieniselves in a condition to unite, and tlius ammonia is produced. The same 
 result must foUow in many natural operations, wlien hydrogen and nitrogen are set free 
 from a previous state of combination, at the same time, and in the presence of one another. 
 
NITRIC ACID EXISTS LARGELY IN NATURE. 159 
 
 ot that which is constantly undergoing decomposition by the agency of 
 causes such as those above described. 
 
 But is the indefinite quantity of ammonia reproduced by these indi- 
 rect methods sutBcient to replace all that is lost? Can it be supposed 
 to impart to plants all the nitrogen they require ? These questions will 
 be considered in the following section. 
 
 § 5. Of the supply of nitric acid to jjlants. 
 
 In regard to the action of nitric acid upon vegetation it is known — 
 
 1°. That when, in the form of nitrates of soda, potash, &c., it is. 
 spread upon the soil, it greatly promotes the growth and luxuriance of 
 ihe crop and increases its produce ; and 
 
 2°. That, when other circumstancs are favourable to vegetation— as 
 m certain districts in India— the i)resence of an appreciable quantity of 
 these nitrates adds largely to the fertility of the soil.* 
 
 The saiue efiects are un(|ues(ionably produced by the addition of am- 
 inoiiia or by its natural presence in the soil. Tiie beneficial influence 
 of boih con]]jounds, ihen, being recognized, the relative extent to which 
 eacli operates upon the general vegetation of the globe will be main- 
 ly determined by the circumstances and the quantity in which they res- 
 ])ectively exist or are reproduced. 
 
 In regard to the existence of nitric acid, it is not known to form a 
 necessary constituent of any of tlie solid rocks of which the crust of the 
 globe is com[)osed, but is dilTused almost universally through the soil 
 which overspreads the surface. In the hotter regions of the earth, in 
 India, in Africa, and in South America (p. 56), it "in many places accu- 
 mulates in sufificient quantity to form incrustations of cons*iderable thick- 
 ness over very large areas, and in many more it can be separated by 
 washing the soil. Even in the climates of Northern Europe, it is rare- 
 ly absent from the water of artificial wells, into which tlie rains, aftei 
 filtering through the surface, are permitted to make their way.f 
 
 On the whole, nitric acid and its compounds api)ear to exist, ready 
 formed in nature, in larger quantity than either ammonia or any of its 
 compounds. 
 
 K ^S*" '''^ following, and other interesting notices, regarding Indian agriculture, I am in- 
 debted to Mr Fleming, of Barochan, in Renfrewshire, whose long residence in the districts 
 to which he alludes, as well as the interest he takes in practical agriculture, renders liis tes- 
 timony very valuable : 
 
 "The districts of Chaprah, Tirhoot, and Shahabad, near Patna, where a large proportion 
 of the salipetre sent (nnn Bengal is produced, are considered tlie most fertile in Bengal, 
 
 nrnrtllpintr 9 anil c^nmtitim^.T "} „^„r^„ 1., m, , .: _^il J- r_.^ .• 1 1 ' 
 
 .^ „ - -- igly 
 
 pregnated with saltpetre an(J other salts as to be quite brackish, and they consider onions, 
 turnips, and peas, most benefitted by this irrigation. Grain crops also grow most luxuriant- 
 ly on lands yielding saltpetre, where there is enough of rain within a week or two after the 
 seed is sown, but if a drought follows the sowing, and continues for 3 weeks or a month, the 
 leal becomes yellow, and the crop fails. 
 
 "The Hindoos do not generally manure their lands, as the dung of the cattle is used for 
 fuel, but the Quirees collect the ashes of cow dung and of burned wood, and use it as a ma- 
 nure in some cases, chiefly for the poppy plant. 
 
 " The Hindoos have for ages been well acquainted with the rotation of crops, and the ad- 
 vantages of fallowing land, although a great proportion of the land is almost constantly in 
 rice, Indian coi-n, or millet, during the rainy season, and in wlieat or peas during the dry 
 season." 
 
 t It occurs in the wells of the neighbourhood of Berlin (Mitscherlich), in the form of ni- 
 trates of potash, lime, and masnesia, in the wells around Stockholm, and may be expected 
 m all wells that are dug (Berzelius).— 7Vaz7e de Chemie, iv., p. 71. 
 
160 FORMATION OF NITRIC ACID. 
 
 Of these nitrates, as they do of ammonia, the rivers must be continu- 
 ally bearing a portion to the sea, but there are in nature unceasing pro- 
 cesses of reproduction, by which not only this waste of the nitrates is 
 repaired, but that further waste, also, which is caused by their absorp- 
 tion into the roots and subsequent decomposition in the interior of plants. 
 Let us shortly consider these processes of reproduction. 
 
 1°. When a succession of electric sparks is passed through common 
 air, nitric acid (NO5) is slowly but sensibly formed. The currents of 
 electricity which in nature traverse the atmosphere must produce the 
 same effect, and the passage of each flash of lightning through the air 
 must be attended by the formation of some portion of this acid. 
 
 After a thunder-storm plants appear wonderfully refreshed ; in thun- 
 dery weather they grow most luxuriantly, and other things being equal, 
 those seasons in which there is much thunder are observed to be the 
 most fruitful. Some have ascribed these results to the immediate agency 
 of electricity on the growth of plants. — [Sprengel, Cheviie, I., p. 99.] 
 It is not equally possible that they maybe connected with this necessary 
 production of nitric acid ? 
 
 In the rain which fell during 17 thunder-storms, Liebig found nitric 
 acid always present and generally in combination with lime and am- 
 monia. In the rain which fell on 60 other occasions, he could detect it 
 only twice. In minute quantity nitric acid is difficult to detect. How 
 much then must be formed in a thunder-storm, even in our climate, to 
 make the presence of this acid always appreciable in the rain that falls 
 — how vast a quantity in those warmer climates where such storms are 
 so frequent and so appalling! 
 
 2°. When a mixture of ammonia with oxygen gas is exploded by 
 passing an electric spark through it, a quantity of nitric acid is formed, 
 even when the oxygen is not sufficient to oxidize the whole of the am- 
 monia* (Bischof). Hence, if in the air, as we have seen reason to be- 
 lieve, the ammonia given off from decaying animal matters, and from 
 other sources, be decomposed by the atmospheric electricity, — there will 
 necessarily be formed at the same instant a portion of nitric acid, at the 
 expense of tjie nitrogen of the ammonia itself. This nitric acid will, as 
 necessarily, combine with some of* the ammonia which still remains in 
 the air. Hence the existence and production of nitrate of atmnonia in 
 the atmosphere, and the consequent presence of tliis acid along with am- 
 monia in rain water. 
 
 Thus the very cause which in the preceding section was shown to 
 operate in constantly diminishing the amount of ammonia in the air, 
 and the operation of which certainly renders improbable the existence 
 of this compound in the atmosphere in the large quantity supposed by 
 some [see especially Liebig's Organic Chemistry aiJplied to Agriculture^ 
 p. 74], this same cause is at the same moment constantly reproducing 
 nitric acid. And, though much of what is thus produced must neces- 
 sarily, as in the case of ammonia, be carried down to the sea by the 
 rains, or be directly absorbed by the waters of tiie ocean themselves, yet 
 
 * It was shown above (p. 157), that I of ammonia ( NII3 ) requires 3 of oxyj^en to decom- 
 pose it, forming 3 of water, and setting the nitrogen free. But, in reality, as Bischof has 
 shown, the nitrogen is not wholly set free, but a portion both of its hydrogen and nitrogen 
 combine with oxygen (are oxidized) at the same instant, forming simultaneously both water 
 (HO), and nitric acid ( NO5 ). 
 
ARTIFICIAL NITRE BEDS. 161 
 
 it is obvious that in whatever proportion we may suppose the ammonia 
 of the air to reach the leaves and roots of plants, in no less proportion 
 must the nitric acid, with which it is associated, he enabled to enter into 
 the circulating system of the various tribes of living vegetables, that 
 flourish on every quarter of the globe. 
 
 3°. Again, we have seen that, during the decay of vegetable substan- 
 ces in moist air, ammonia is formed at the expense of the hydrogen of 
 the water and of the nitrogen of the air. In consequence of, or in con- 
 nection with, such decay, nitric acid is also largely produced in nature. 
 
 The most familiar, as well as the most instructive examples of this 
 formation of nitric acid is in the artificial nitre beds of France and the 
 north of Europe. These are formed by mixing earth of different kinds 
 with stable manure or other animal and vegetable inatters, and exposing 
 the mixture to the air in long ridges or conical heaps, which are occa- 
 sionally watered with liquid manure, and turned over, to expose fresh 
 portions to the air. After a time, perhaps once a year, the whole is 
 washed, when the water which comes off is found to contain a variable 
 quantity of the nitrates of potash, soda, lime, and magnesia, which are 
 employed for the manufacture of saltpetre. In these nitre beds it has 
 been observed that the production of nitric acid either does not take place 
 at all, or only with extreme slowness, unless animal and vegetable mat- 
 ter be present in considerable proportion. And yet the quantity of nitric 
 acid which is formed is much greater than could be produced by the 
 oxidation of the whole of the nitrogen contained in the organic matters 
 present jn the mixture.* It is also observed that the nitre beds are more 
 productive when a portion from one outer face of the heap is lixiviated 
 from time to time, and the washed earth added to the other side, than 
 when the whole is lixiviated at once, and again formed into a heap and 
 exposed to the air. 
 
 It appears, therefore, that organic matters are in our climate necessa- 
 ry to cause the formation of nitric acid to commence, but that after it has 
 begun it will proceed in the same heap for an indefinite period, and at 
 the expense apparently of the nitrogen of the air only. 
 
 Compost heaps are in general only artificial nitre beds, often unskil- 
 fully y^repared and badly managed, producing, however, a certain quan- 
 tity of nitrates, to the presence of which their effect on vegetation may 
 not unfrequently be ascribed. To this fact we shall hereafter recur. 
 . The soils in'the plains of India, and in other similar spots in the trop- 
 ical regions, may be regarded as natural nitre beds, in which, the decay 
 of organic matter being vastly more rapid than in our temperate regions, 
 the production of nitric acid is rapid in pro})ortion.f 
 
 4°. But in many localities in which the presence of organic matter is 
 
 * Dumas, Traite de Chemie, II., p. 725. He adds, that 100 lbs. of nitre contain the nitrogen 
 of 75 lbs. of ordinary animal matter, supposed in a dry state, or of 300 or 400 lbs. in its ordi- 
 nary state of moisture, — a much greater relative proportion of animal matter than is ever 
 added to the heap. 
 
 t We are as yet too little acquainted with the natural history of the district of Arica in 
 Soutli America, in which, as already stated (p. 56), the nitrate of soda has been acciimulateu 
 in such large quantity, to be able to say to what specicd cause the accumulation is due. But 
 as, from the description of Mr. Darwin, the locality appears to have been the site of an an- 
 cient lake, it is not unlikely that the nitrate may have been derived from the successive 
 washings of a soil similar to that of India, by, rains or periodical floods, which for a long pe- 
 riod emptied themselves into or fed thelaKe. 
 
IXjH nitre caves. NITRIC ACID TORMED IN THE SOIL. 
 
 not. to be recognized in sensible quantity, tiie production of this acid is 
 observed to proceed with a constant and steady ])ace. Thus, from the 
 walls of certain caves in Ceylon a layer is yearly pared otF, which 
 yields an abundant crop of saltpetre (Dr. John Davy). The celebrated 
 Mammoth cave in Kentucky, situated in a limestone ridge, yields an 
 inexhaustible supply of nitrate of lime. During the war with Great 
 Britain, fifiy men were constantly emj)loyed in lixiviating the earth of 
 this cave, and in about three years the washed earth is said to become 
 as strongly impregnated as at first. Through the cave a strong current 
 of air is continually rushing — inwards in winter, and outwards during 
 the summer months. On the })laster of old walls, especially in damp 
 situations, an efflorescence of this and other nitrates is frequently ob- 
 served over every part of Europe. Jn China, according to Davis, the 
 old plaster of the houses is so much esteemed as a manure, that parlies 
 will often purchase it at the expense of a coating of new plaster. Old 
 clay walls, and especially the walls of clay-built huts, are said to be 
 very fertilizing to the land, when applied as a top-dressing, and in some 
 parts of England, where the land is poor, the people are said to pile up 
 the soil in the form of walls, in order to improve its quality. These lat- 
 ter facts seem to indicate that both in China and England nitric acid is 
 produced in similar circumstances, and that to its production the ferti- 
 lizing action of the old plaster, and of the weathered clay, is alike to be 
 attributed. 
 
 In the cultivated soil also, this acid is formed in ordinary circum- 
 stances. Braconnot found nitrate of potash in the botanic garden at 
 Nancy, in a portion of soil in which pop])ies {j^apaver somniferum) had 
 grown luxuriantly for ten years in succession — in larger quantity in the 
 soil surrounding the interlaced roots of an csclcpias incarnata, growing 
 in an ordinary llower-pot, with a hole in the bottom — as well as in moss 
 earth, in which a plant of euphorbia hreoni had been grown in a pot. — 
 \^Ann. dc Chim. et de Phys., Ixxii., p. 33 to 35.] There is little reason 
 to doubt, indeed, that nitrates are to be found, in greater or less quantity, 
 in all cultivated soils. 
 
 I shall not enter into a detailed inquiry how this nitric acid is formed. 
 It is })robabte~rhat as in the atmosphere ammonia may be decomposed 
 and give rise to the formation of nitric acid, so in the soil this acid may 
 result from a similar decomposition, proceeding more slowly, but accord- 
 ing to the same natural laws. In warm climates, indeed, it appears 
 certain that the ammonia which is evolved or formed during the decay 
 of animal and vegetable substances, does speedily, and to a great extent, 
 undergo oxidation,* and thus give rise to the greater abundance of nitric 
 acid with which the tropical soils abound. 
 
 Thus, in the economy of nature, much ammonia is decomposed in the 
 soil also, and hence another cause for the constant diminution of the 
 quantity of this compound in addition to those already detailed in the 
 preceding section. 
 
 But, besides the portion of this nitric acid, which owes its existence to 
 
 • For the perfect oxidation of 1 of ammonia, no less than 8 of oxygen are required. Thus 
 
 lof lof 3 of 
 
 Ammonia. Nitric Acid. Water. 
 NH3-t-80 = N05 + 3HO. 
 
QUANTITY IN WHICH IT IS REPRODUCED. 163 
 
 the decomposition of ammonia, much, by far the greatest proportion in 
 all probability, derives its origin from tiie union of the elements of the 
 atmospiiere itself. This direct union is effected in the air, as lias been 
 already shown, by the agency of atmospheric electricity; but it also 
 takes place in the soil during the oxidation of the other elements con- 
 tained in the organic matters which are there undergoing decay. The 
 combination of the elements of ammonia in such circumstances proceeds 
 on the i)rinciple that bodies, themselves undergoing oxidation, dispose 
 other substances in contact with them (in this instance the nitrogen of 
 the air) to unite with oxygen also. The presence of lime, potash, &c. 
 in the soil, furtlier induces to this oxidation by the tendency of these sub- 
 stances to combine with the acid which is formed by this union of the 
 elements of which nitric acid consists. — It is impossible precisely to es- 
 timate the quantity of nitric acid produced in these various ways, through 
 these various agents, and in these varied circumstances, or to balance it 
 accurately against the amount of ammonia continually reproduced, as 
 we have seen, in nature, wherever the necessary conditions present 
 themselves. But, as I formerly concluded, that the amount of nitric 
 acid actually existing in the superficial deposits of our globe is greater 
 than that of ammonia, so I tliink that, in regard to the reproduction also 
 of these two compounds, the balance is in favour of the former. 
 
 Since, tlien, nitric acid is fitted, by the solubility of its compounds, to 
 enter into the circulation of plants in any quantity — since, when applied 
 to them, it does undoubtedly promote, in a remarkable degree, the growth 
 of plants — and since, in nature, it is continually reproduced in every 
 country, and under such varied circumstances — 1 cannot withhold my- 
 self from the conclusion, that, over the general vegetation of the globe, 
 it holds with ammonia at least an equal sway, and is appointed to exer- 
 cise at least an equal influence over the growth of plants, both in their 
 natural and in their cultivated state; 
 
 Still the influence of each is not unvaried by locality or by climate. 
 The extent of dominion exercised by the nitrates probably diminishes as 
 we recede from the e(]uator, while that of ammonia increases, — it may 
 be in an e(|ual proportion. The reason of this probable variation will 
 appear in the following section. 
 
 § 6. Theory of the action of nitric acid and ammonia. 
 These two compounds act so far in common as to yield a supply of 
 nitrogen to the plants into which they enter. They do so, however, un- 
 der conditions which may be considerably different, and may be attend- 
 ed by unlike chemical changes. 
 
 I. THEORY OF THE ACTION OF NITRIC ACID. 
 
 1°. The nitric acid of the nitrates entering into the circulation of the 
 roots will ascend to the leaf, and will there be decomposed in the same 
 way as the carbonic and other similar acids arc, by the action of the 
 sun's rays. It is only in the light of day that carbonic acid is decom- 
 posed in the green parts of plants — so must it be, generally, with the 
 nitric acid which ascends to the leaf. Its oxygen will be given off', 
 while its nitrogen may be retained in the circulating system of the plant. 
 The extent to which this decomposition will take place at each passage 
 
164 THEORY OF THE ACTION OF NITRIC ACID AND OF AMMONIA. 
 
 of the sap through the leaf will depend, In some degree, on the nature 
 of the base (whether potash, soda, or lime,) with which the acid is in 
 combination, but much more on the intensity of the light to which the 
 green parts of the plant are exposed, and on the temperature of the air in 
 which the plant happens to grow. 
 
 2°. It is still uncertain whether this acid is capable of being decom- 
 posed in tjie roots or stems of plants where it is excluded from the light, 
 though it is very probable that it may be so, especially in cases where 
 the juices naturally contain substances in which hydrogen is present in 
 excess, or where such compounds make their way into the circulation 
 of plants from the manure that may be applied to their roots. 
 
 Thus in the pines, in which turpentine (C40 H30) naturally abounds, 
 $uch a decomposition may the more readily occur, inasmuch as it would 
 not necessarily imply the production and evolution of any gaseous sub- 
 stance. Thus 
 
 1 of Oil OF Turpentine, = C40 H32 with the oxygen of 
 
 1 of Nitric Acid (NO5) =: O5 gives 
 
 1 of Resin, = C40 H32 Og 
 
 By uniting with the oxygen of the nitric acid, therefore, oil of turpen- 
 tine, in such trees, might be changed into resin during its passage 
 through the stem, while the nitrogen, being set free, might, at the mo- 
 ment of its liberation, unite with other elements to form those parts or 
 productions of the tree into which this element enters as a necessary 
 constituent. 
 
 The above must be considered merely as an illustration of the kind of 
 changes which may possibly take place in the interior of certain plants, 
 and in the absence of light, when the nitrates happen to be present. 
 Were I to affirm that such changes actually do occur in the presence 
 of nitric acid, the theoretical chemist would have a right to expect that 
 several collateral questions should be discussed, the consideration of 
 which would here be out of place. 
 
 3°. The nitrates may also act in another way, which does not involve 
 the necessity of the total decomposition of the acid they contain. We 
 know that inTiature many substances are capable of inducing chemical 
 changes in other compound bodies, without themselves undergoing de- 
 composition. Some beautiful illustrations of this have already been 
 given in a previous lecture, when treating of the action of sul|)huric acid 
 upon starch and woody fibre, [Lecture VI.. pp. 113, 114.] But the fact 
 which most immediately bears on the influence of the nitric acid in the 
 living plant, is that mentioned in p. 126, — that by solution in this acid 
 in the cold, starch is converted into a substance having the composition 
 of woody fibre. In the interior of the plant changes of this kind may 
 be produced by simple contact only, with the nitric acid, so that, with- 
 out being decomposed, it may be materially serviceable in promoting 
 those molecular changes which are necessary to the healthy and rapid 
 growth of the plant. 
 
 II. theory OF THE ACTION OF AMMONIA. 
 
 1°. Ammonia" is capable of contributing to the growth of the plant, 
 by means of the hydrogen, as well as of the nitrogen it contains. We 
 
iS AMMONIA DECOMPOSED IN THE DARK ? 165 
 
 have seen [notes to pages 136 and 138,] that, according to the results 
 of the best Experiments, the whole of the oxygen of the carbonic acid 
 absorbed, is not given off by the leaves of all plants even in the sun- 
 shine, — while in the dark this gas is largely and directly imbibed from 
 the air. If in the sap of a plant there be present at the same time a 
 quantity of ammonia, the hydrogen of this ammonia may unite directly 
 with the oxygen of the carbonic acid, forming water and a proportionate 
 quantity of one or other of the several compounds (p. 112), which iiiay 
 be represented by carbon and water. Thus 
 
 3 of Carbonic Acid, = C3 Oq and the hydrogen of 
 
 2 of Ammonia (NH3) = Hg 
 
 j^ of Grape 3 of 
 
 Sugar. Water. 
 
 give . . . . C3 He Oe = C3 H3 O3 + 3HO 
 
 so that where ammonia is present, and circumstances are favourable, 
 sugar or starch may be formed in variable quantity, without the neces- 
 sary evolution of oxygen gas. This change will take place in the inte- 
 rior of the leaf. And, if the direct decomposition of carbonic acid, and 
 the evolution of its oxygen by the agency of the sun, take place at the 
 same time — with a rapidity proportioned to the intensity of the light, — 
 this .simultaneous production of sugar, &c., from the presence of ammo- 
 nia, must aid the increase and growth of the plant ; and may be one 
 main cause of the fertilizing action of this compound, which has been so 
 long and so generally recognized. 
 
 When the hydrogen of the ammonia is thus worked up, the quantity 
 of oxygen which escapes from the leaf must be less in proportion ; and 
 hence another cause (p. 138) for those discrepancies which have been 
 observed in regard to the bulk of oxygen given off, compared with that 
 of the carbonic acid taken in, by the leaves of different plants. 
 
 But at the same time the nitrogen is set free. This nitrogen will 
 either be again compounded in the plant with other elements, or, if not 
 required for its healthy growth — that is, if more largely present than is 
 required by the plant — it will be directly emitted by the leaves, or sent 
 downwards and permitted to escape by the root. Hence the reason 
 why pure nitrogen is evolved from the leaves of some plants (p. 95), 
 and why ammonia exercises a beneficial action upon vegetation, in 
 cases where all the nitrogen it contains is neither retained nor required 
 by ihe plant. 
 
 Does this decomposition necessarily require the agency of light? 
 May it not take place in the absence of the sun ? 
 
 I will mention one or two facts which seem to throw light upon this 
 point. 
 
 1°. Plants grow in the dark. Though feebk and blanched, they in- 
 crease largely in bulk; they rnust, therefore, have the power of assimi- 
 lating their food to a certain extent, independent of the sun's rays. 
 
 2°. Several species of Poa, Plantago, Trifolium arvense, Cheiran- 
 thus, &c., become green in the perpetual darkness of mines (Hum- 
 boldt). 
 
 3°. When a little hydrogen is mixed with the air, plants become 
 greenish, even in the dark (Sennebier) ; and when exposed to the sun, 
 the green becomes unusually intense in such a mixture (Ingenhouss). 
 
 8 
 
166 MODirrmG effect of climate. 
 
 The immediate and visible effect of an application of ammonia, or of 
 soot, or of any lop-dressing containing ammonia, is to render the green 
 colour much more intense, and in the darkest weather. It is therefore 
 prohable, I think, that the hydrogen of the ammonia contributes to this 
 immediate effect, and that the ammonia itself may be decomposed and 
 its elements appropriated to the nourishment of the living vegetable, 
 either by the unaided vital powers of the plant, or in the presence of a 
 feeble light only. Like water, ammonia is peculiarly liable to decom- 
 position, not always of that perfect kind which, /or the sake of simplicity, 
 I have endeavoured to explain in the present lecture, yet such as to ren- 
 der the elements of which it consists available to the general nourish- 
 ment of the plant. 
 
 § 7. Comparative influence of nitric acid and of ammonia in different 
 
 climates. 
 
 It follows, from what is above stated, that the beneficial influence of 
 ammonia upon vegetation will be readily perceived in all climates in 
 which plants are found to flourish. Its effects will be greater and more 
 rapid where the heat and light are more intense, — only because by these 
 agents the functions of all life are stimulated. 
 
 Not so with the nitric acid in the nitrates. In the presence of organic 
 compounds, that is, in the sap of the plant, it is less easily decomposed 
 than ammonia. It requires the interference of more powerful agents — 
 of a higher temperature, or of more brilliant light, — and thus its efficacy 
 upon vegetation will be more dependent upon season and climate. 
 
 Now, we have seen that in tropical countries the nitrates are produced 
 in the greatest abundance, and there the high temperature and the bril- 
 liant sun should render them most useful to vegetation. Such is well 
 known to be the case, and it may be regarded as one of those bountiful 
 adaptations with which all nature is full — that in these warmer regions, 
 the ammonia produced in the soil is first converted into nitric acid, that 
 it may remain fixed, and that this acid again is decomposed by the same 
 agents (light and heat), when it enters the living plant, and is required 
 to minister to its growth. On the other hand, it may no less be regarded 
 as a wise provision, that in colder and more uncertain climates, where 
 warm and brilliant summers are less to be depended upon, that com- 
 pound of nitrogen (ammonia) should more abound, which is most easily 
 decomposed in the living plant, which is fitted in comparative darkness 
 to yield up its nitrogen, and by the hydrogen it contains, to compensate 
 in some slight degree for the partial absence of the sun's rays. 
 
 From these views, therefore, we should draw this further practical 
 conclusion — that in our climate, ammonia is sure to promote vegetation, 
 and in every season, while the nitrates will produce their maximum effect, 
 othei things being equal, in such only as have abundant warmth and 
 sunshine. Is this conclusion consistent with observation? Will it 
 serve to explain any of the apparent failures which have occasionally 
 been experienced in the employment of the nitrates? 
 
 § 8. Stimulating influence of these compounds. 
 There remains one other point in regard to the effect of these two 
 compounds upon vegetation, to which I would request your attention. 
 
STIMULATING INFLUENCE OF NITRIC ACID AND OF AMMONIA. 167 
 
 We have seen that the quantity of nitrogen contained in a crop raised 
 by the aid of farm-yard manure, is very much greater than that which 
 exists in the manure itself, and the views just exposed serve to indicate 
 the sources from which the excess is derived. But suppose that upon 
 two patches of ground, of equal (|ualiiy, the one of which is manured 
 and the other not, equal quantities of the same seed be sown, it is 
 consistent with experience — that the crop reaped from the manured 
 portion will not only contain more nitrogen than that reaped from the 
 unmanured portion, but so much more as shall considerably exceed that 
 contained in the manure itself. Thus suppose the crop raised from the 
 unmanured land to contain 100 lbs. of nitrogen, and that the manure laid 
 on the other portion contained 100 lbs. also, the crop which is reaped 
 from this latter portion, in favourable seasons, will exceed, and probably 
 very far exceed, 200 lbs. Hence the effect of the ammonia, &c., in the 
 farm-yard manure, is not merely to yield its own nitrogen to the plant, 
 but to enable it, in some way hitherto unexplained, to draw from other 
 sources a larger portion of the same element than it would otherwise do. 
 So also with the nitrates. If two equal portions of the same grass or 
 corn-field, in early spring, be measured off, and one of them be top- 
 dressed with nitrate of soda or with saltpetre, the weight of nitrogen con- 
 tained in the crop of hay or corn reaped from the latter, will generally 
 be found to exceed that contained in the crop from the former, by a 
 quantity much greater than that which was present in the nitrate with 
 which the land was dressed.* In addition, therefore, to the nitrogen di- 
 
 * The following calculations illustrate the statement in the text:— Mr. Gray, of Dilston, 
 [see Journal of Royal English Agricultural Society,] applied nitrate of soda to grass land in 
 the proportion of 112 lbs. to the acre. 
 
 The produce without nitrate amounted to 2 tons 81 stones 
 with 112 lbs. of nitrate to 3 tons 146 stones 
 
 Increase, 1 ton 65 stones, or 3150 lbs. 
 And 3150-7- 112 = 28 J^ lbs. the increase of hay from each pound of nitrate of soda.^ But al- 
 lowing this hay to contain only one per cent, of nitrogen, 28 lbs. will contain 4>^ ounces of ni- 
 trogen, which is nearly double the quantity actually present in the nitrate employed. 
 
 Again, in the case of a crop of grain— Mr. Hyett applied nitrate of soda to a field of wheat, 
 and compared the produce with that from an equal p ^rtion to which no top-dressing wa» 
 applied. 
 
 CORN. STRAW. 
 
 Bush. pks. pts. Cwt. qrs. lbs. 
 
 Nitrated 43 2 11 31 2 3 
 
 Without nitrate . . 33 2 6 23 1 21 
 
 Excess, 10 5 8 10 
 
 Calculating the bushel of corn at 60 lbs., the excess of com amounted to 600 lbs., containing 
 24X per cent, or 147 lbs. of gluten and albumen. The nitrogen in these substances, when 
 properly dried, is from 15 to 17 per cent. If we. suppose the gluten not to have been quite 
 dry, and allow only 14 per cent, of nitrogen, 147 lbs. would contain 203^ lbs. of tliis element. 
 But the nitrated corn contained 5 per cent, more gluten and albumen than the un-nitrated, 
 which in 33 bushels (2000 lbs.) gives 100 lbs. of gluten in excess, containing 14 lbs. of nitrogen. 
 And 8 cwt. of straw (900 lbs.) contained one-third of a per cent, of nitrogen, [Boussingault,] 
 or in all 3 lbs. 
 
 Therefore the quantity of nitrogen present in the nitrated crop above that in the un-nitrated 
 was as follows : 
 
 1°. In 600 lbs of wheat at 24>^ percent, of gluten 20X lbs. Nitrogen. 
 
 2°. In 2000lbs. of wheat at 5 percent, of gluten contained in excess, 14 lbs. do. 
 3°. In 900 lbs. of straw at one-third per cent 3 lbs. do. 
 
 Total nitrogen =37X lbs. 
 
 But the nitrogen in 1 cwt. of dry nitrate of soda, as already stated, is only 19 lbs. or little 
 [* Dry nitrate of soda contains about 16>^ per cent, of nitrogen, being 19 lbs. to the cwt., 
 qjBtevo and three-fifth ounces to the pound ; but as it is usually applied, it contains from 5 to 
 IWper cent, of water. The nitrogen, therefore, may be estimated at 2^ ounces in the pound.] 
 
168 HOW THIS INFLUENCE IS MANIFESTED. 
 
 rectly conveyed to the plant by these nitrates, they also exercise some 
 other influence, by which they enable the living vegetable to draw from 
 natural sources a much larger supply than they would otherwise be 
 capable of doing. What is this influence, and how is it explained ? 
 
 This I suppose to be that kind of influence to which writers on agri- 
 culture are in the habit of alluding, when they speak of certain substan- 
 ces stimulating plants, or acting as sthmdants to their growth, though the 
 term itself conveys to the mind no distinct idea of the mode of operation 
 intended to be indicated — of the way in which the effect is produced. 
 
 In the present case, this special action of ammonia and the nitrates, 
 and perhaps also of immediate applications of manure in general, ap- 
 pears to arise from their affording to the plant, in its early youth, a copi- 
 ous supply of nitrogenous food, by which it is enabled at once to shoot 
 out in a more healthy and vigorous manner. It thrusts forth roots in 
 greater numbers, and to greater distances, and is thus enabled to extract 
 nourishment from a greater extent and depth of soil than is ever reached 
 by the sickly plant — it expands larger and more numerous leaves, and 
 thus can extract from the air more of every thing it contains which is 
 fitted to supply the vvanls of the living vegetable; as the stout and 
 healthy savage can hunt and fish to support many lives, while the feeble 
 or sickly can scarcely secure sustenance for himself alone. Feed a wild 
 animal well the first few months of its life, and you may set it loose to 
 prey for itself; starve it in its infancy, and its growth and strength will 
 be stunted, and it may lead a wretched and hungry life. 
 
 Even in soils, then, and situations, which are capable of yielding to 
 the jilant every thing it may require for its ordinary growth, it is an im- 
 portant object of the art of husbandry to discover what substances are 
 especially necessary or grateful to particular crops, and to apply these 
 directly, and in abundance, to the new-born plant, — in order that it may 
 acquire sufficient strength to be able to avail itself in the greatest degree 
 of the stores of food which lie within its reach. 
 
 Concluding observations regarding the organic constituents of plants. 
 
 We have now^ considered the most important of those questions con- 
 nected with the organic elements of plants, which are directly interesting 
 to the practical agriculturist. We have seen — 
 
 1°. That all vegetable productions consist of two parts — one the or- 
 ganic part, which is capable of being burned away in the air — the other, 
 the inorganic part, which remains behind in the form of ash. 
 
 ^°. That this organic part consists of carbon, hydrogen, oxygen, and 
 nitrogen only. 
 
 3°. That plants derive the greater part of their carbon from carbonic 
 acid, of their hydrogen and oxygen from water, and of their nitrogen 
 from ammonia and nitric acid. 
 
 4^. That by far the largest portion of those substances which form 
 the ])rincipal mass of plants, such as starch and woody fibre, consists of 
 carbon united to oxygen and hydrogen in the proportions in which they 
 
 more than half the quantity, wliich in consequence of the presence and action of the nitrate 
 tlie wheat was enabled to obtain and appropriate above the? quantity appropriated by the 
 wheat in the un-nitrated part of the field. 
 
 It requires no further proof, therefore, to show that the nitrate of soda and the nitrates vm^ 
 act in some ot/ier way in refereiice to vegetation, than by simply supplying a portion of nitro^WI. 
 
CONCLUDING OBSERVATKJNS. 169 
 
 exist in water, — or, in other words, may be represented by carbon and 
 water in various proportions. 
 
 5°. That the food on which they live enters by the roots and leaves 
 of plants, — that the leaves, under the influence of the sun, decompose 
 the carbonic acid, give off' its oxygen, and retain its carbon, — and that 
 this carbon, uniting with the elements of water in the sap, forms those 
 several compounds of which plants chiefly consist. 
 
 6°. That the supply of carbonic acid in the atmosphere is kept up 
 partly by the respiration of animals, partly by the natural decay of dead 
 vegetable matter, and partly by combustion. That ammonia is sup- 
 plied to plants chiefly by the natural decay of animal and vegetable 
 substances — and nitric acid partly by the natural oxidation of dead or- 
 ganic matter, and partly by the direct union of oxygen and nitrogen, 
 through the agency of the atmospheric electricity. 
 
 7°. That while both of these compounds yield nitrogen to plants, they 
 each exhibit a special action on vegetable life, in virtue of the hydrogen 
 and oxygen they respectively contain — and exercise also a so-called 
 stimulating power, by which plants are induced or enabled to appro- 
 priate to themselves, from other natural sources, a larger portion of 
 all their constituent elements than they could otherwise obtain or 
 assimilate. 
 
 In illustrating these several points, it has been necessary to enter oc- 
 casionally into details which, to those who have heard or may read only 
 the later lectures, may not be altogether intelligible. I am not aware, 
 however, of having introduced any thing of which the full sense will 
 not appear on a reference to the statement by which it is preceded. 
 
 We are now to consider the inorganic constituents of plants, — their na- 
 ture, — the source (the soil) from which they are derived, — their uses in 
 the vegetable and animal economy, — how the supply of these substan- 
 ces is kept up in nature, — and how, in practical husbandry, the want of 
 them may be at once efficaciously and economically supplied by art. 
 This division of our subject, though requiring a previous knowledge of the 
 principles discussed in the foregoing lectures, will be more essentially 
 of a practical nature, and will lead us to consider and illustrate the 
 great leading principle by which the practical agriculturist ought to be 
 guided in the cultivation and improvement of his land. 
 
 We shall here also find much light thrown upon our path by the 
 results of geological inquiry ; and it is in the considerations I am now 
 about to bring before you, that I shall have to direct your attention most 
 especially to the principal applications of Geology to Agriculture. 
 
LECTURES 
 
 ON THE 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 ON THE INORGANIC ELEMENTS OF PLANTS. 
 
LECTURE IX. 
 
 Inorganic constituents of vegetable substances. — Relative proportions of organic and inor- 
 ganic matter in plants. — Unlike proportions in unlilce species. — Kind of inorganic matter 
 wliich exists in different species. — Nature and properties of the several inorgani'c elemen 
 tary bodies found in plants. 
 
 The consideration of the inorganic constituents of plants is no less 
 important to the art of culture than the study of their organic elements, 
 which has engaged our sole attention in the preceding part of these lec- 
 tures. 
 
 It has already been shown that when vegetable substances are heated 
 to redness in the air, the whole of the so-called organic elements — car 
 bon, hydrogen, oxygen, and nitrogen — are burned away and disappear ; 
 while there remains behind a fixed portion, commonly called the ash, 
 which does not burn, and which in most cases undergoes no diminution 
 when exposed to a red heat. This ash constitutes the inorganic portion 
 of plants. 
 
 The organic or combustible part of plants constitutes, in general, 
 from 88 to 99 per cent, of their whole weight, even after they are dried. 
 Hence the quantity of ash left by vegetable substances in the green 
 state is often exceedingly small. It therefore long appeared to many, 
 that the inorganic matter could be of no essential or vital consequence 
 to the plant — that being, without doubt, derived from the soil, it was 
 only accidentally present, — and that it might or might not be contained 
 in the juices and solid parts of the living vegetable, without materially 
 affecting either its growth or its luxuriance. 
 
 Were tliis the case, however, the quantity and quality of the a.sh left by 
 the same plant should vary with the soil in which it grew. If one soil 
 contained much lime, another much magnesia, and a third much potash, 
 whatever plant was grown upon these several soils should also contain 
 in greatest abundance the lime, the magnesia, or the potash, which 
 abounded in each locality — and the nature, at least, of the ash, if not 
 its proportion, should be nearly the same in every kind of plant which 
 is grown upon the same soil. 
 
 Careful and repeated experiments, however, have shown — 
 
 1°. That on whatever soil a plant is grown, if it shoots up in a 
 healthy manner and fairly ripens its seed, the quantity and quality of 
 the ash is nearly the same ; and 
 
 2^. That though grown on the same soil, the quantity and quality of 
 the ash left by no two species of plants is the same — and that the ash 
 differs the more widely in these respects, the more remote the natural 
 affinities of the several plants from which it may have been derived. 
 
 Hence there is no longer any doubt that the inorganic constituents 
 contained in the ash are really essential parts of the substance of plants, 
 — that they cannot live a healthy life or perfect all their parts without 
 them, — and that it is as much the duty of the husbandman to supply 
 these inorganic substances when they are wanting in the soil, as it has 
 always been considered his peculiar care to place within the reach of 
 
 8* 
 
178 
 
 WEIGHTS OF ASH LEFT BY DIFFERENT SPECIES. 
 
 the growing plant those decaying vegetable matters which are most 
 likely to supply it with organic food. 
 
 For the full establishment of this fact, we are indebted to Sprengel. 
 Others, as De Saussure, have published many important and very use- 
 ful analyses of the inorganic matters left by plants, but for the illustra- 
 tion of the important practical bearing of this knowledge of their inor- 
 ganic constituents on the ordinary processes of agriculture, we are, I 
 beHeve, in a great measure indebted to the writings and numerous ana- 
 lytical researches of Sprengel. 
 
 It is difficult to conceive the extent to which the admission of the es- 
 sential nature and constant quality of the inorganic matter contained in 
 plants, must necessarily modify our notions and regulate our practice in 
 every branch of agriculture. It establishes a clear relation between the 
 kind and quality of the crop, and the nature and chemical composition 
 of the soil in which it grows — it demonstrates what soils ought to con- 
 tain, and, therefore, how they are to be improved — it explains the ^flfect 
 of some manures in permanently fertilizing, and of some crops in per- 
 manently impoverishing the soil — it illustrates the action of mineral 
 substances upon the plant, and shows how it may be, and really is, in a 
 certain measure, /erZ by the dead earth : — over nearly all the operations 
 of agriculture, indeed, it throws a new and unexpected light. Of this, I 
 am confident, you will be fully satisfied when I shall have discussed the 
 various topics I am to bring before you in the present part of my lectures. 
 
 § 1. Of the relative proportions of inorganic matter in different 
 vegetable substances. 
 
 As above stated, the inorganic matter contained in different vegetable 
 productions varies from 1 to 12 per cent, of their whole weight. The 
 following table exhibits the weight of ash left by 100 lbs. of the more 
 commonly cultivated plants — according to the analyses of Sprengel 
 
 [Ckemie, vol. ii., passim] : — 
 
 Undried. Dried in air.* 
 
 Grain of Per ct. 
 Wheat . . 1-18 lbs, 
 Rye . . . ^'04 
 Barley . . 2-35 
 Do. dried at 212, 2-52 J. 
 Oats . . . 2-58 
 Field Beans . 2-14 
 Peas . 2-46 
 
 Dry straw of 
 Wheat 
 Oats 
 Barley 
 Rye 
 Beans 
 Peas 
 
 Perct. 
 3-51 lbs. 
 5-74 
 5-24 
 2-79 
 3-12 
 4-97 
 
 Potato 0-83 lbs. 
 
 Turnip 0-63 
 
 Do. white ... 0-8 J. 
 
 Carrot 0-66 
 
 Parsnip 0-82 
 
 Leaf of Potato . . 
 
 Turnip . . 
 
 do. white 
 
 ■65 lbs. 
 05 
 
 09 
 34 
 79 
 
 — Carrot 
 
 — Parsnip 
 
 — Cabbage 
 
 1-8 
 
 2-18 J. 
 1-98 
 3-00 
 0-53 
 
 2-91 
 
 10-42 
 
 15-76 
 
 7-55 
 
 Lucerne 
 Red Clover 
 White Clover 
 Rye Grass . 
 
 Green. 
 2-58 lbs. 
 1-57 
 1-74 
 1-69 
 
 In hay. 
 
 9-55 lbs 
 7-48 
 9-13 
 5-3 
 
 • Of the substances in this column the potato lost by drying in the air 69 perct. of water, 
 the turnip 91, the carrot 87, the turnip leaf 86, the carrot leaf, the parsnip, and the parsnip 
 leaf, each 81, and the cabbage leaf 93 per cent. 
 
IT VARIES WITH THE SPECIES OF PLANTS. 179 
 
 In the parts of trees dried in the air there are found of inorganic 
 matter — 
 
 In the Elm . . 1-88 11-8 
 
 Willow . 0-45 8-23 
 
 Poplar . . 1-97 9-22 
 
 Beech . . 0-36 6-69 
 
 Wood. Leaves. Wood. Leaves. 
 
 In the Oak . . 0-21 4-5 
 
 Birch . . 0-34 5-0 
 
 Pitch pine 0-25 3-15 
 
 Comm. furze 0-82 3-1 J. 
 
 In looking at 'the preceding tables, you cannot fail to be struck with 
 one or two points, which they place in a very clear light. 
 
 1°. That the quantity of inorganic matter contained in the same 
 weight of the different crops we raise, or of the different kinds of vegeta- 
 ble food we eat, or with which our cattle are fed, is very unlike. Thus 
 100 lbs. of barley, or oats, or peas, contain twice as much inorganic 
 (earthy and saline matter, that is,) as an equal weight of wheat or rye — 
 and the same is the case with lucerne and white clover hays, compared 
 with the hay of rye grass. 
 
 2°. The quantity contained in different parts of the same plant is 
 equally unlike. Thus 100 lbs. of the grain of wheat leave only l^^lbs. 
 of ash, while 100 lbs. of wheat straw leave 3|^ lbs. So the dry bulb of 
 the turnip gives only 7 per cent., while the dry leaf leaves 13 per cent, 
 of ash when it is burned. The dry leaves of the parsnip also contain 
 nearly 16 per cent., though in its root, when sliced and dried in the air, 
 there are only 4^ per cent, of inorganic matter. 
 
 In trees the same fact is observed. The wood of the elm contains 
 less than 2 per cent., while its leaves contain nearly 12 per cent. ; — the 
 wood of the oak leaves only ^th of a per cent., while from its leaves 4^ 
 per cent, or 22 times as much are obtained. The leaves of the willow 
 and of the beech also contain about twenty times as much as the wood 
 of these trees does, when it has been dried under the same conditions. 
 
 These differences cannot be the result of accident. They are con- 
 stant on every soil, and in every climate ; they must, therefore, have 
 their origin in some natural law. Plants of different species must 
 draw from the soil that proportion of inorganic matter which is adapted 
 to the constitution, and is fitted to supply the wants of each; — while of 
 that which has been admitted by the roots into the general circulation 
 of the plant, so much must proceed to and be appropriated by each part 
 as is suited to the functions it is destined to discharge. And as from 
 the same soil different plants select different quantities of saline and 
 earthy matter, so from the same common sap do the bark, the leaf, the 
 wood, and the seed, select and retain that proportion which the healthy 
 growth and developement of each requires. It is with the inorganic, as 
 with the organic food of plants. Some draw more from tlie soil, some 
 less, and of that which circulates in the sap, only a small portion is ex- 
 pended in the production of the flower, though much is employed in 
 forming the stem and the leaves. On the subject of the present section, 
 I shall add two other observations. 
 
 1°. From the constant presence of this inorganic matter in plants, and 
 from its being always found in nearly the same proportion in the same 
 species of plants, — a doubt can hardly remain that it is an essential part 
 of their substance, and that they cannot live and thrive without it. But 
 that it really is so, is placed beyond a doubt, by the further experimen 
 
180 QUALITY OF THE ASH FROM DIFFERENT PLANTS. 
 
 tal fact, that if a healthy young plant be placed in circumstances where 
 it cannot obtain this inorganic matter, it droops, pines, and dies. 
 
 2°. But if it be really essential to their growth, this inorganic matter 
 must be considered as part of the food of plants ; and we may as cor- 
 rectly speak of feeding or supplying food to plants, when we add earthy 
 and mineral substances to the soil, as when we mix with it a supply of 
 rich compost, or of well fermented farm-yard manure. 
 
 I introduce this observation for the purpose of correcting an erroneous 
 impression entertained by many practical men in regard to the way in 
 which mineral substances act when applied to the soil. By the term 
 manure they generally designate such substances as they believe to be 
 capable o^ feeding the plant, and hence reject mineral substances, such 
 as gypsum, nitrate of soda, and generally lime, from the list of manures 
 properly so called. And as the influence of these substances on vegeta- 
 tion is undisputed, they are not unfrequeutly considered as stimulants only. 
 
 Yet if, as I believe, the use of a wrong term is often connected 
 with the prevalence of a wrong opinion, and may lead to grave errors 
 in practice, — I may be permitted to press upon your consideration 
 the fact above stated — I may almost say demonstrated — that plants 
 do feed upon dead unorganized mineral matter, and that you are, there- 
 fore, really manuring your soil, and permanently improving it, when 
 you add to it such substances of a proper kind. 
 
 § 2. Of the kind of inorganic matter found in plants. 
 
 I have said above, of a proper kind — for it is not a matter of indiffer- 
 ence to a plant, what kind of earthy or saline matter it takes in by its 
 roots. Each species of plant, we have seen, withdraws from the soil a 
 quantity of inorganic matter, which is peculiar to itself, .and which, as a 
 whole, is nearly constant. 
 
 So also each species, in selecting for itself a nearly constant weight 
 of inorganic matter, while it chooses generally the same kind of saline 
 and earthy ingredients as other plants do, to make up this weight, yet 
 picks them out in proportions pecidiar to itself Thus for example, lime 
 is present in the ash of nearly all plants, but while 100 lbs. of the ash 
 of wheat contain 8 pounds of lime, the same weight of the ash of barley 
 contains only 4^ lbs. So also potash is contained in the ash of most 
 plants grown for food, but in the ash of the turnip, there are 37^ per 
 cent, of potash, while in that of wheat there are only 19 per cent. Again, 
 in different parts of the same plant, a like difference prevails. The ash 
 of the turnip bulb contains 16i percent, of soda, — that of the leaf, little 
 more than 12 per cent. On the other hand, the lime in that from the 
 bulb constitutes less than 12 per cent, of its weight, while in that of the 
 leaf it amounts to upwards of 34 per cent. 
 
 These relative proportions among the different kinds of inorganic mat- 
 ter contained in the ash of plants — like the whole weight itself of the 
 ash — is nearly constant in the same species, and in the same part of a 
 plant, when it is grown in a propitious soil. It is not, therefore, as I have 
 already said, a matter of indifference to the living vegetable, whether 
 it meets with this or with that kind of inorganic matter in the land on 
 which it grows — whether its roots are supplied with lime, or with potash, 
 Hth soda. The soil must contain all these substances, and in such 
 
 f\r \tr\ 
 
THE SOIL MUST CONTAIN WHAT THE PLANT REQUIRES. 181 
 
 quantity as easily to yield to the crop so much of each as the hind of plant 
 specially requires. And if one of these necessary inorganic forms of 
 matter be rare or wholly absent, the crop will as certainly prove sickly 
 or entirely fail, as if the organic food supplied by the vegetable matter 
 of the soil were wholly withdrawn. It is, therefore, as much the end of 
 an enlightened agricultural practice to provide for the various require- 
 ments of each crop in regard to inorganic food, as it is to endeavour to 
 enrich the land with purely vegetable substances. 
 
 Since, also, as above shown, not only the relative quantity of inor- 
 ganic matter, but its kind or quality, likewise, is different in different 
 plants, — it may be, that a soil on which one crop cannot attain to ma- 
 turity may yet surely and completely ripen another — a fact which is 
 proved by"every-day experience. The soil, which is unable to supply 
 with sufficient speed all the lime or the potash required for one crop, 
 may yet easily meet the demands of another, and afford an ample re- 
 turn to the husbandman when the time of harvest comes.* 
 
 On the other hand, this consoling, at once, and stimulating reflection 
 must arise in the mind of the practical agriculturist from the considera- 
 tion of the above facts — that if the soil contain all, the inorganic substan- 
 ces required by plants, and in sufficient quantity, it will grow, if rightly 
 tilled, any crop which is suited to the climate,— or conversely to make 
 it capable of growing any crop, he has only — along with his usual sup- 
 plies of animal or vegetable matter — to add in proper quantity these in- 
 organic substances also. 
 
 Here a crowd of questions cannot fail to start up in your minds. You 
 will ask, for example, 
 
 1°. What are the several inorganic substances usually present in 
 cultivated plants, and what their respective proportions ? 
 
 2°. Which of them are most generally present in the soil? 
 
 3°. In what form can those which are less abundant be added most 
 easily, most advantageously, and most economically ? 
 
 We shall consider in succession these, and along with them other 
 
 * On the same principle, also, some of the interesting facts connected with the grafting of 
 trees are susceptible of a satisfactory explanation. . .... . ,. v 
 
 The root of a tree selects from the soil the kind and ^waa??/ of inorganic matter which 
 are required for the healthy maturity of its own parts. Any other tree may be grrafted on it, 
 which in its natural state requires the same kind of inorganic matters in nearly the sanie 
 proportion. This is the case generally with varieties of the same species— more rarely 
 with trees or plants of different species— and least frequently with such as belong to differ- 
 ent genera The lemon may be grafted on the orange, because the sap of the latter con- 
 tains all the earthy and saline substances which the former requires, and can supply them 
 in sufficient quantity to the engrafted twig. But the f5g or the grape would not flourish or 
 ripen fruit on the same stock— because these fruits require other substances than the root of 
 the orange cares to extract from the soil, or in greater quantity than the sap of the orange 
 can supply them. , , ,, , . , „ , 
 
 It is not for want of organic food, for of this the sap of nearly all plants is full— and we 
 have seen in our previous lectures, how the sugar of the fig, the tartaric acid of the grape, 
 and the citric acid of the lemon, may all be produced by natural processes from the same 
 common organic food. When we plant a tree or sow a crop on a soil which does not con- 
 tain all that the tree or crop requires, the tree must slowly perish,— the crop cannot yield a 
 profitable return. So it is in grafting. Tlie sap of the stock must contain all that t/ie engrajted 
 bud or shoot requires in every stage of its groiclh. Or to recur to our former illustration— 
 if the potash or lime required by the grape be not taken up and in sulficient quantity by 
 the root of the orange, it will be in vain to graft the former upon the latter with the hope ol 
 Its coming to maturity or yielding perfect fruit. 
 
 Tliis principle may also serve to explain many other curious and hitherto obscure cir- 
 cumstances connected with the practice of the gardener. 
 
182 
 
 ELEMENTARY SUBSTANCES FORMED IN THE ASH. 
 
 subsidiary questions, which will hereafter present themselves to our 
 notice. 
 
 § 3. Of the several elementary bodies usually met with iri the ash of plants 
 What is understood by the term element or elementary body among 
 chemists has already been exi)lained (Lect. T., p. 22), as well as the 
 number and names of those elements with which we are at present ac- 
 quainted. 
 
 Of these elementary bodies we have seen thatthe organic part of plants 
 contains rarely more than four, namely, carbon, hydrogen, oxygen, and 
 nitrogen, in various proportions. In ihe inorganic part there occur nine 
 or ten others, generally in combination, either with oxygen or with one 
 another. 
 
 The names of these inorganic elements are as follow : 
 
 Forming 
 Chlorides. 
 Iodides, 
 sulphurets. 
 
 Sulphuretted Hydrogen.* 
 Sulphuric Acid. 
 Phosphoric Acid. 
 Potash. 
 
 Chloride of Potassium. 
 Soda. 
 
 Chloride of Sodium or ) 
 Common Salt. ^ 
 
 Chloride of Calcium. 
 Lime. 
 Magnesia. 
 Alumina. 
 Silica. 
 ^ Oxides. 
 
 ( SuLPHURETS. 
 
 Other elementary bodies, chiefly metallic, occur in some plants — occa- 
 sionally, and in very small quantity, — but, so far as is yet known, they do 
 not appear to be either necessary to their growth, or lo exercise any ma- 
 terial influence on the general vegetation of the globe. 
 
 Of all the above elementary bodies it may be said, generally, 
 
 1°. That with the exception of sulphur,f they are not known to exist 
 or lo be evolved, in any quantity, anywhere on the surface of the globe, 
 in their simple, elementary, or uncombined stale; and that, therefore, 
 in this state they in no way alTect the progress of vegetable growth, or 
 require to occupy the attention of the practical agriculturist. 
 
 2°. They all, however, exist in nature more or less abundantly in a 
 state of combination with other substances, and chiefly with oxygen, [for 
 an explanation of the meaning and of the laws of chemical combination, 
 see Lecture II., p. 32] — but in no state of combination are they known 
 lo be generally diffused through the atmosphere of the globe, so as to be 
 
 * Called also Hydro-sulphuric Acid. 
 
 1 Given oflf in vapour from active volcanoes, and from rents and fissures »n ancient volcanic 
 countries. 
 
 Name. In 
 
 combination with 
 
 Chlorine . 
 
 Metals 
 
 Iodine . . 
 
 do. 
 
 Sulphur . 
 
 do. 
 
 
 Hydrogen 
 
 
 Oxvgen 
 
 Phosphorus 
 
 do'. 
 
 Potassium . 
 
 do. 
 
 
 Chlorine 
 
 Sodium . . 
 
 Oxygen 
 
 
 Chlorine 
 
 Calcium . 
 
 do. 
 
 
 Oxygen 
 
 Magnesium 
 
 do". 
 
 Aluminium 
 
 do. 
 
 Silicon 
 
 do. 
 
 Iron and ) 
 
 do. 
 
 Manganese ^ 
 
 Sulphur 
 
CHLORINE AND MURIATIC ACID. 183 
 
 capable of entering plants by their leaves or other superior parts. They 
 must all, therefore, enter by the roots of plants, — must consequently ex- 
 ist in the land, — and must all be necessary constituents of that soil in 
 whicli the plants that contain them grow. 
 
 It will not be necessary, therefore, to consider so much the relative 
 ])roportions in which these elementary bodies themselves exist in plants, 
 as that of the several chemical compounds which they form with oxy- 
 gen, or with one another — in which states of combination they exist in 
 the soil, and are found in tlie circulation and substance of the plant. As 
 a preliminary to this inquiry, however, it will be proper to lay before 
 you a brief outline of the nature and properties of these compound 
 bodies themselves — and of the direct influence they have been found to 
 exercise upon vegetable life. 
 
 § 4. Of those coynpounds of the inorganic elements wliicli enter directly into 
 the circulation, or exist in the substance and ash of plants. 
 
 I- CHLORINE AND MURIATIC ACID. 
 
 Chlorine. — If a mixture of common salt and black oxide of manga- 
 nese [sold by this name in the shops] be j)ut into a flask or bottle of 
 colourless glass, and sulphuric acid (oil of vitriol) be poured upon it, a 
 gas of a greenish-yellow colour will be given off', and will gradually fill 
 the bottle. This gas is distinguished by tiie name of chlorijie. 
 
 It is readily distinguished from all other substances by its greenish- 
 yellow colour, an<l its pungent disagreeable smell. It extinguishes a 
 lighted taper, but phosphorus, gold leaf, metallic potassium and sodium, 
 and many other metals, take fire in it and burn of their own accord. It 
 is nearly 4i times heavier than common air, and therefore may be 
 readily poured from one vessel to another. Water absorbs twice its 
 own bulk of the gas, acquiring its colour, smell, and disagreeable astrin- 
 gent taste. 
 
 Animals cannot breathe it without suffocation — and, when unmixed 
 with air, it speedily kills all living vegetables. The solution of chlorine 
 in wafer was found by Davy to promote the germination of seeds. 
 
 l^t does not exist, and is rarely evolved, [see Lecture V., p. 94,] in 
 nature in a free or uncombined state, and therefore is not known to ex- 
 ercise any direct action upon the general vegetation of the globe. It 
 exists largely, however, in common salt (chloride of sodium), every 100 
 lbs. of this substance containing upwards of GO lbs. of chlorine. Indi- 
 rectly, therefore, it may be supposed to influence, in some degree, the 
 growth of plants, where common salt exists naturally in the soil, or is 
 artificially applied in any form to the land. 
 
 Muriatic acid, the spirit of salt of the shops, consists of chlorine in 
 combination with hydrogen. It is a gas at the ordinary temperature of 
 the atmosphere, but water absorbs between 400 and 500 times its bulk 
 of it, and the acid of the shops is such a solution in water, of greater or 
 less strength. 
 
 Muriatic acid has an exceedingly sour taste, corrodes the skin, and in 
 its undiluted state is poisonous both to animals and plants. It dissolves 
 common pearl ash, soda, magnesia, and limestone, with effervescence; 
 and readily dissolves also, and combines with, many earthy substances 
 which are contained in the soil. 
 
134 IODINE, SUIiPHUR, AND SULPHUROUS AC1I>. 
 
 When npjilied lo living vegetables in the state of an exceedingly 'di 
 lute solution in water, it has been supposed ujwn some soils, and in 
 some circumstances, to be favourable lo vegetation. Long experience, 
 however, on the banks of the Tyne, and elsewhere, in the neighbour- 
 hood of liie so-called alkali* work's, has proved that in the state of va- 
 pour its repeated application, even when diluted with much air, is in 
 many cases fatal to vegetable life. 
 
 Poured in a litjuid stale upon fallow land, or land preparing for a 
 crop, it may assist'lhe growth of the future grain, by previously forming, 
 with the ingredients of the soil, some of those compounds which have 
 been occasionally applied as manures, and which we shall consider 
 hereafter. 
 
 Chlorine is represented by CI, and muriatic acid by HCl. 
 
 II. — IODINE. 
 
 Iodine is a solid substance of a lead grey colour, which, when healed, 
 is converted into a beautiful violet vapour. It exists in combination 
 chiefly with sodium, as Iodide of Sodiwn, in sea water and in marine 
 plants ; but it has not hitherto been detected in any of tlie crops usually 
 raised for food. 
 
 Like chlorine, it is poisonous both to animals and jilants ; and was 
 found by Davy to assist and hasten germination. It may possibly exert 
 some hitherto unobserved influence upon vegetation, when it is applied 
 to the soil in districts where sea-ware is largely collected and employed 
 as a manure. 
 
 Iodine is slightly soluble in water, and this solution has been men- 
 tioned in a previous lecture (VI., p. 107), as affording a ready means 
 of detecting starch by the beautiful blue colour it gives with this sub- 
 stance. 
 
 III. — SULPHUR, SULPHUROUS AND SULPHURIC ACIDS, AND SUL- 
 PHURETTED HYDROGEN. 
 
 1°. Sulphur is a substance too well known to require any detailed 
 descri|)tion. In an uncoinbined state it occurs chiefly in volcanic coun- 
 tries, but it may sometimes be observed in the form of a thin pellicle, on 
 the surface of stagnant waters — or of mineral springs, which are natu- 
 rally charged with sulphurous vapours. In this state it is not known 
 materially to influence the natural vegetation in any part of the globe. 
 It has, however, been employed with some advantage in Germany as a 
 top-dressing for clover aad other crops to which gypsum in that country 
 is generally applied. The mode in which it may be supposed to act 
 will be considered hereafter.* 
 
 2°. Sulphurous acid. — When sulphur is burned in the air it gives off 
 a gaseous substance in the form of white fumes of a well known intensely 
 suffocating odour. These fumes consist of a combination of the sulphur 
 
 * In these works carbonate of soda (the common soda of the shops) and sulphate of soda 
 (glauber salt) are manufactured from common salt, and in one of tlie processes immense 
 quantities of muriatic acid are given oflffrom Uie furnace, and used to escape into the air by 
 the chimney. 
 
 t The refuse heaps of the alkali works on the Tync contain much sulphur and more gyp- 
 sum—but the fanners, iierhaps, naturally enough, considt-r that if tlie works (hemselves do 
 harm to their crops, the refuse of the works caimot do them much good. There are thou- 
 sands of tons of this mixture which may he had for the leading away. 
 
SULPHURIC ACID, AND SULPHURETTED HYDROGEN. 185 
 
 whicli disappears with the oxygen of the atmosphere, and are known 
 to chemists by the name of sulphurous acid. This compound is des- 
 tructive to animal and vegetable life, but as it is not known to be directly 
 formed to any extent in nature, except in the neighbourhood of active 
 volcanoes, it probably exercises no extensive influence on the general 
 vegetation of the globe. ^ 
 
 This gas possesses the curious propertyof bleaching many animal and 
 vegetable substances. Wool and straw for plaiting are bleached to an 
 almost perfect whiteness-when they are suspended in a vessel or room 
 into which a plate of burning sulphur has been introduced. Gardeners 
 sometimes amuse themselves also in bleaching roses and other red 
 llowers, by holding them over a burning sulphur match. Some shades of 
 red resist this action more or less perfectly, and the colour of the bleached 
 flowers may olten be restored-by dipping them in a dilute solution of 
 carbonate ot soda, or by holding them over a bottle of hartshorn (liquid 
 ammonia). ^ ' 
 
 3. Sulphuric acid.— Th\^ is the name by which chemists distinguish 
 the oil of vitriol of the shops. It is also a compound of suli)hur and oxy- 
 gen only and is formed by causing the fumes of sulphur to pass into 
 •large leaden chambers along with certain other substances, from which 
 tliey can obtain a further supply of oxyiren. 
 
 It is met with in the shops in the form^if an exceedingly sour corrosive 
 Jiquid, which decomposes, chars, and destroys all animal and vegetable 
 substances, and, except when very diluted, is destructive to life in every 
 form. It is rarely met with in nature, in an uncombined state,— -thou c^h 
 according to Boiissmgault, some of the streams which issue from the 
 volcanic regions of the Andes are rendered sout by the presence of a 
 quantity of this acid. J i 
 
 ]t combines with potash, soda, lime, magnesia, &c., and forms sul- 
 phates which exist abundantly in nature, and have often been benefi- 
 cially and profitably employed as manures. 
 
 Where the soil contains lime or magnesia, the acid may often be ap- 
 plied directly to the land, in a very dilute state, with advantage to clover 
 and other similar crops. It has in France, near Lyons, been observed 
 to act favourably when used in this way, while in Germany it has been 
 found better to apply it to the ploughed land, previous to sowing. A few 
 experiments have also been made in this country with partial success. 
 It IS deserving, however, of a further trial, and in more varied circum- 
 stances. 
 
 ^°' ,^'^^¥i'f^reU€d Hydrogen.— This gaseous compound of sulphur 
 with hydrogen, is almost universally known by its unpleasant smell. 
 Jt imparts their peculiar taste and odour to sulphurous springs, such as 
 tnat ot Harrogate, and gives their disagreeable smell to rotten eggs. It 
 IS often produced in marshy and stagnant places,* and fish ponds, where 
 
 • This appears to be especially the case on the coasts of Western Africa, where the 
 hot sun IS contmually beating on sea water, often shallow, frequently stagnant and always 
 ^denwih organic matter, either animal or vegetable (Daniell). nLV the mouth oMhl 
 Tees m this county where a shallow, dark blue, muddy, samphire-bear n- tra^tsLtches 
 for several m.es mland from Seaton Snook, (he presence of suIphurettShydro4nS 
 The Slake % '^e ,^f,f \V'«" <^",^ hot sum lir skiL aZg tife edgJof 
 
 dition of th J^p/ th ^h^ conditions are, a burnmg sun, a very gentle air, and such a con- 
 dition of the sea— that those parts and pools which are only reached by the sprin'- Udes 
 shall have been several days uncovered. ica^,iicu uy lue .yuu^ uues 
 
1S6 PHOSPHORUS AND PHOSPHORIC ACID. 
 
 vegetable matter is undergoing decay in the presence of water contain- 
 ing gypsuin, or other sulphates ; and it may occasionally be detected by 
 tjie sense of smell among the roots of the sod, in old pasture land, to 
 which a top-dressing is occasionally given. 
 
 As in the egg, so also in other decaying animal substances, especially 
 when the air is in some measure excluded, this gas is formed. In*pu- 
 trified cow's urine, and in night soil, it is present in considerable quan- 
 tity. 
 
 Sulphuretted hydrogen is exceedingly noxious to animal and vegeta- 
 ble life, when diffused in any considerable quantity through the air by 
 which they are surrounded. The luxuriance of the vegetation in the 
 neighbourhood of sulphurous springs, however, has given reason to be- 
 lieve that water impregnated with this gas, may act in a beneficial 
 manner when it is placed within reach of the roots of plants. It seems 
 also to be ascertained that natural or artificial waters which have a sul- 
 phurous taste, give birtli to a peculiarly luxuriant vegetaiion, when tbey 
 are employed in the irrigation of meadows. — [Sprengel, Chemie, I., 
 p. 355.] 
 
 The relative constitution of these three compounds of sulphur is thus 
 represented : — 
 
 One equivalent of Weighing 
 
 Sulphur 16 
 
 Sulphurous Acid . . 32 
 Sulphuric Acid ... 40 
 Sulphuretted Hydrogen 17 
 
 IV. PHOSPHORUS AND PHGSPHGRI-C ACID. 
 
 1°. PhospJiorus is a solid substance of a pale yellow colour, and of a 
 consistence resembling that of wax. When exposed to the air it slowly 
 combines with the oxygen of the atmosphere, and burns away with a 
 pale blue flame visible only in the dark. When rubbed, however, or 
 exposed to a slight elevation of temperature, even to the heat of the 
 hand, it readily bursts into a brilliant flame, emitting an intense light 
 accompaniet^ by dense white vapours. It does not occur in nature in 
 an uncombined state, and is not known to be susceptible of any useful 
 application in practical agriculture. 
 
 2°. Phosphoric Acid. — The white fumes given off* by phosphorus, or 
 rather into which it is changed, when burned in the air or iii oxygen 
 gas, consist of phosphoric acid. This compound is solid and colourless, 
 attracts moisture from the air with great rapidity, is exceedingly soluble 
 in water, has an intensely sour taste, and like sulphuric acid is capable 
 of corroding and destroying animal and vegetable substances. 
 
 It docs not exist in nature in a free state, and, therefore, is not directly 
 influential upon vegetaiion. It unites, hov^-ever, with potash, soda, lime, 
 &c., to form compounds, known by the name of jjhosphates. In these 
 states of combination, it is almost universally difflased throughout nature 
 — and appears to be essentially necessary to the healthy growth and 
 maturity of all living — certainly of all cultivated vegetables. 
 
 * For the properties of oxygen and hydrogen see above, pages 24 and 25, and for their 
 equivalent or atomic weights see page 34. 
 
 Is repre- 
 sented by 
 
 Or 1 of Sulphur 
 and 
 
 s 
 
 SOo 
 
 so; 
 
 SH 
 
 2 of Oxygen 
 
 3 of Oxygen 
 
 1 of Hydrogen.* 
 
■WOOD-ASH AND CARBONATE OF POTASH. 187 
 
 V. POTASSIUM, POTASH, CARBONATE, SULPHATE, OXALATE, TARTRATE, 
 
 CITRATE, AND SULPHATE OF POTASH, AND CHLORIDE OF POTASSIUM. 
 
 1°. Carhonate of Potash. — In countries where non-resinous trees 
 abound, it is usual lo burn the wood which cannot otherwise be employ- 
 ed — as in tlie clearings in Canada and the United States — for the pur- 
 pose of collecting the ash which remains. This ash is washed with 
 water and the wasliings boiled to dryness in iron pots. In this state it 
 forms the ^;o^-ash of commerce. When this potash is again dissolved 
 in water, and the clear litjuid decanted and boiled, ihe jjcarl-'d^h of the 
 shops is obtained. 
 
 This pearl-ash is an impure form of the carhonate of potash/)f chem- 
 ists. It readily dissolves in water, has a peculiar taste — distinguished 
 as an alkaline taste — and dissolves in vinegar or in diluted sulphuric or 
 muriatic acid, with much effervescence. The gas given otV during this 
 effervescence (or boiling up) is carbonic acid, the same which, as was 
 shown in a previous lecture, is obtained when a diluted acid is poured 
 upon chalk or common limestone. 
 
 This carbonate of potash has been long known to exercise a powerful 
 influence over the growth of plants. 
 
 IMie use of wood-ash as a fertilizer both of pasture and of arable land, 
 goes back to the most remote antiquity ; and though ihe crude wood-ash 
 contains other substances also, yet much of its immediate and most ap- 
 jiarent effect is due to the carbonate of ])Otash it contains. 
 
 From what has already been stated, at the commencement of the 
 ])resent lecture, in regard to the {)resence of potash in the parts and 
 juices of nearly all plants, you will already in some measure under- 
 stand why the carbonate of potash should be useful to vegetation, and — 
 since this alkali (potash) is present in greater quantity in some than in 
 others — why it should appear to be more especially favourable to the 
 growth of one kind of plant than of another. 
 
 In this way, it is explained why moss and coarse grasses are extirpa- 
 ted from meadows by a sprinkling of wood ashes — and why red clover, 
 lucerne, esparsette, beans, peas, flax, and potatoes, &c., are greatly 
 promoted in their growth by a similar treatment. This substance, how- 
 ever, has other functions lo perform in reference to vegetation, besides 
 that of simply supplying the crop with the potash it requires ; these func- 
 tions I shall explain more particularly hereafter, when you wil^perhaps 
 be better prepared for understanding the details into which it will be ne- 
 cessary to enter. 
 
 2°. Potash. — When 12 parts of carbonate of potash are dissolved in 
 water, and boiled with half their weight of newly-slaked quick-lime, 
 they are gradually deprived of their carbonic acid, and converted into 
 pure potash, — or as it is often calleff, from its effect on animal and ve- 
 getable substances, caustic jwtash. 
 
 The caustic liquid thus obtained decomposes or dissolves most animal 
 and vegetable substances, whether living or dead. When applied to 
 the skin, unless it be in a very diluted state, it destroys it, and produces 
 a painful sore. Potash does not occur in nature in this caustic or un- 
 combined state, and is not known, therefore, to exercise any direct in- 
 fluence upon natural vegetation. 
 
 When wood-ashes and quick-lime are mixed together in artificial 
 
188 POTASSIUM, CAUSTIC POTASH, AND CHLORIDE OF POTASSIUM. 
 
 composts, it is not unlikely that a portion of the carbonate of potash may 
 be rendered caustic, and, therefore, be more fit to act upon the vegetable 
 matter in contact with it — by rendering it soluble in water and thus ca- 
 pable of entering into the roots of plants. To this point I shall have 
 occasion to return hereafter. In the mean time, it is proper to remark, 
 that if pearl-ash be mixed, as above prescribed, with half its weight of 
 quick-lime, and then boiled with less than ten or twelve times its weight 
 of water, a part of the potash only is rendered caustic — the lime being 
 unable to deprive the pearl-ash (carbonate of potash) of its carbonic 
 acid, unless it be largely diluted. Hence, in dry composts, or mixtures 
 of this substance with quick-lime, it is unlikely that any large portion of 
 the potash can be at once brought to the caustic state. This fact is 
 really of importance in reference to the theory of the conjoined action of 
 quick-lime and wood or pearl-ash, when mixed together in artificial ma- 
 nures, and applied to the land. 
 
 3°. Potassium. — When dry caustic potash, obtained by evaporating 
 the caustic solution above described, is mixed with powdered charcoal 
 and iron filings, and exposed to an intense heat in an iron retort, it is de- 
 composed, and metallic jmtassium distils over, and is collected in the 
 form of white shining silvery drops. 
 
 It was one of the most remarkable discoveries of Sir H. Davy, that 
 potash was a compound substance, and consistedof this metal potassiuin 
 united to oxygen gas. 
 
 Potassium is remarkable for the strong tendency/it possesses to unite 
 again with oxygen and re-form potash. When simply exposed to the 
 air, it gradually absorbs oxygen from the atmosphere ; but if it be heat- 
 ed in the air, it takes fire and burns. When the combustion has ceased, 
 a quantity o^ caustic potash remains, the weight of which is nearly one- 
 iifth greater than that of the potassium employed. It even bursts into a 
 flame when thrown upon water, depriving that liquid of its oxygen, and 
 liberating its hydrogen, — and it was justly considered as the most aston- 
 ishing property of this metal, when first discovered, that it took fire 
 when placed upon the coldest ice. [For the composition of water, see 
 Lecture Ilu,- p. 36.] When thus burned in contact with water, potash 
 is formed, as before, and is found dissolved in the liquid when the ex- 
 periment is completed. 
 
 4°. Chloride of Potassium. — This is a compound of chlorine with po- 
 tassium, ^vhich, in taste, properties, and general appearance, has much 
 resemblance to common salt. It may be formed by dissolving pearl- 
 ash in dilute muriatic acid (spirit of salt) as long as any effervescence 
 appears, and afterwards evaporating to dryness. It exists in small 
 quantity in sea water, in the ash of most plants, and frequently in -Xhe 
 soil. It is not an article of manufacture, but is occasionally extracted 
 from kelp, and sold to the alum makers. Could it be easily and cheap- 
 ly obtained, there is no doubt that it might be employed with advantage 
 as a manure, and especially in those circumstances in which common 
 salt has been found to promote vegetation. The refuse of the soap-boil- 
 ers, where soap is made from kelp, contains a considerable quantity of 
 this compound. This refuse might be obtained at a cheap rate, and, 
 therefore, might be usefully collected and applied to the land where 
 such works are established. 
 
SULPHATE, NITRATE, OXALATES, AND CITRATES OF POTASH. 18D 
 
 5°. Sulphate of Potash. — This compound is formed by adding pearl- 
 ash to dilute sulphuric acid (oil of vitriol) as long as etiervescence ap- 
 pears, and then evaporating the solution. It is a vi^hite saline sub- 
 stance, sparingly soluble in water, and has a disagreeable bitterish taste. 
 It exists in considerable quantity in wood-ash, and in the ash of nearly 
 all plants, and is one of the most abundant impurities in the common 
 potash and pearl-ash of the shops. This sulphate itself is not an article 
 of extensive manufacture, but it exists in common alum to the amount 
 of upwards of 18 per cent, of its weight. 
 
 Dissolved in 100 times its weight of water, the sulphate of potash has 
 been found to act favourably on red clover, vetches, beans, peas, (fee, 
 and part of the effect of wood ashes on plants of this kind is to be attri- 
 buted to the sulphate of potash they contain. Turf ashes are also said 
 to contain this salt in variable quantity, and to this is ascribed a portion 
 of their efficacy also when applied to the land. 
 
 6°. Nitrate of Potash, or saltpetre, is a well known saline substance, 
 of which mention has already been made in the preceding lectures. [See 
 p. 56, and pp. 159 to 163.] It contains potash and nitric acid only, and 
 may be readily formed by dissolving pearl-ash in nitric acid, and eva- 
 porating the solution. It exists, and is continually reproduced in the 
 soil of most countries, and is well known to exercise a remarkable influ- 
 ence in accelerating and increasing the growth of plants. 
 
 7°. Oxalates of Potash. — These salts exist in the common and wood 
 sorrels, and in most of the other more perfect plants in which oxalic 
 acid is known to exist. [See pp. 47 and 137.] The salt of sorrel is the 
 best known of these oxalates. This salt has an agreeable acid taste, 
 and is not so poisonous as the uncombined oxalic acid. 
 
 When this salt is heated over a lamp, the oxalic acid it contains is de- 
 composed, and carbonate of potash is obtained. It is supposed that a 
 great part of the potash extracted from the ashes of wood and of the 
 stems of plants in general, in the state of carbonate, existed as an oxa- 
 late in the living tree, and was converted into carbonate during the com- 
 bustion of the woody fibre and other organic matter. This compound, 
 therefore, in all probability, performs an important part in the changes 
 which take place in the interior of plants, though its direct agency in 
 affecting their growth when applied externally to their roots has not 
 hitherto been distinctly recognized. It is probably formed occasionally 
 in farm-yard manure, and in decaying urine and night-soil, but nothing 
 very precise is yet known on this subject. 
 
 8°. Citrates and Tartrates of Potash. — These salts exist in many 
 fruits. The citrates abound in the orange, the lemon, and the lime — 
 the tartrates in the grape. When heated over a lamp, they are decom- 
 posed, and like the oxalates leave the potash in the state of carbonate. 
 
 In the interior of plants, both potash and soda are most frequently 
 combined with organic acids (oxalic, citric, tartaric, &c., for an ac- 
 count of the most abundant of which see Lecture VI., p. 121,) and the 
 compounds thus formed are generally what chemists call acid salts— 
 that is to say, they generally have a distinctly sour taste, redden vege- 
 table blues, and contain much more acid than is found to exist in cer- 
 tain other well known compounds of the same acids with potash. 
 
 The citrates and tartrates are not known to be formed in nature, ex- 
 
190 PHOSPHATES OF POTASH, AND CHLORIDE OF SODIUM. 
 
 cept in the living plant, and as they are too expensive to be ever em- 
 ployed as manures, it is the less to be regretted that few experiments 
 have yet been tried with the view of ascertaining their effect upon vege- 
 tation. 
 
 9°. Phosphates of Potash. — If to a known weight of phosphoric acid 
 (p. 18G) pearl-ash (carbonate of potash) be added as long as any effer- 
 vescence appears, and the solution be then evaporated, phosphate of 
 potash is obtained. If lo the solution before evaporation a second por- 
 tion of phosphoric acid be added, equal to the first, and the water be 
 then expelled by heat, Bi-jyhosphate of potash will remain, [so called 
 from his, twice, because it contains t^vice as much acid as the former, or 
 neutral 'Y>^osp\\ate.] 
 
 One or other of these two salts is found in the ash of nearly all plants. 
 Whether or not the elements of which they consist exist in this state of 
 combination in the living plant will be considered hereafter, in the mean 
 time it may be stated as certain that they are of the most vital impor- 
 tance not only in reference to the growth of plants themselves, but also 
 to their nutritive qualities when eaten by animals for food. 
 
 These phosphates are occasionally, perhaps very generally, present 
 in the soil in minute quantities, and there is every reason to believe 
 that could they be applied to the land in a sufficiently economical form, 
 they would in many cases act in a most favourable manner upon vege- 
 tation. They are contained in urine and other animal manures, and to 
 their presence a portion of the efficacy of these manures is to be ascribed. 
 
 VI. SODIUM, SODA, CARBONATE OF SODA, SULPHATE OF SODA, SULPHU- 
 
 RET OF SODIUM, CHLORIDE OF SODIUM. 
 
 1°. Chloride of Sodium, common or sea salt, exists abundantly in sea 
 water, and is found in many parts of the earth in the form either of in- 
 crustations on the surface or of solid beds or masses at considerable depths. 
 The rock salt of Cheshire is a well known example of this latter mode 
 of occurrence. 
 
 Common salt may also be detected in nearly all soils, it is found in 
 the ashes of all plants, but especially and in large quantity in the ashes of 
 marine plants (kelp), and is sometimes borne with the spray of the sea to 
 great distances inland, when the winds blow strong, and the waves are 
 high and broken. 
 
 On some rocky shores, as on that between Berwick and Dunbar, the 
 spray may be seen occasionally moving up the little coves and inlets in 
 the form of a* distinct mist driving before the wind, and the saline matter 
 has been known to traverse nearly half the breadth of the island before 
 it was entirely de])0sited from the air. 
 
 It is impossible lo calculate how much of the saline matter of sea water 
 may in this way be spread over the surface of a sea-girt land like ours; 
 but two things are certain — that those places which are nearer the sea 
 will receive a greater, and those more inland a lesser, portion; and that 
 those coasts on which sea winds prevail will be more largely and more 
 frequently visited than those on which land winds are more commonly 
 experienced. 
 
 It is well known that common salt has been employed in all ages and 
 in all countries for the purpose of promoting vegetation, and in no coun- 
 
SULPHATE OF SODA, SULPHURET OF SODIUM, CARBONATE OF SODA. 191 
 
 try -perhaps in larger quantity or more extensively than in England. 
 That it has often failed to benefit the land in particular localities, only 
 shows that the soil in those places already contained a natural supply of 
 this compound large enough to meet the wants of the croi)S which grew 
 upon it. The facts above stated as to the influence of the wind in top- 
 dressing the exposed coast-line of a country with a solution of salt, may 
 serve as an important guide both in reference to the places in which it 
 may be expected to benefit the land, and to the causes of its failing to 
 do so in particular districts. 
 
 2°. Sulphate of Soda, or Glauber's salt, is usually manufactured from 
 common salt by pouring upon it diluted sulphuric acid (oil of vitriol), 
 and applying heat. Muriatic acid (spirit of salt, so called by the old 
 chemists, because thus given oflf by common salt,) is given off in the 
 form of vapour, and sulphate of soda remains behind. It may also be 
 prepared, though less economically, by adding the conmion soda of the 
 shops to diluted sulphuric acid as long as any effervescence appears. 
 
 This well known salt is met with in variable quantity in the ashes of 
 nearly all plants, and is diflfused in minute proportion through most 
 soils. I have elsewhere [see A))pendix,] directed your attention to the 
 beneficial effect which it has been observed to exercise on the growth 
 especially of such plants as are known to contain a considerable propor- 
 tion of sulphuric acid. Among these are red clover, vetches, peas, &c. 
 And as this salt is manufactured largely in this country, and can be ob- 
 tained at the low price of ten shillings a cwt. in the dry state,* I have 
 recommended it to the practical farmer as likely to be extensivel^^jseful 
 as a manure for certain crops and on certain soils. The kind W crops 
 and soils have as yet in great measure to be determined by practical 
 trials. — [See the results of Mr. Fleming's Experiments, given in the 
 Appendix.] 
 
 3°. Sulphuret of Sodium. — When sulphate of soda is mixed with 
 saw-dust, and heated in a furnace, the oxygen of the salt is separated, 
 and sulphuret of sodium is produced. By a similar treatment sulphate 
 of potash is converted into sulphuret of potassium. These compounds 
 consist of sulphur and metallic sodium or potassium only. They do 
 not occur extensively in nature, and are not manufactured for sale; but 
 there is reason to believe that they would materially promote the vege- 
 tation of such plants as contain much sulphur in combination with pot- 
 ash or soda. The sulphuret of sodium is present,in variable quantity in 
 the refuse lime of the alkali works, already spoken of, and might be ex- 
 pected to aid the other substances of which it chiefly consists, in contri- 
 buting to the more rapid growth of pulse and clover crops. 
 
 4°. Carbonate of Soda. — I have described the above compounds of 
 soda before mentioning this its best known and most common form, be- 
 cause they are all steps in the process by which the latter is usually pre- 
 pared from common salt, by the soda manufacturers. 
 
 When the sulphuret of sodium is mixed with chalk in certain propor- 
 tions, and heated in a furnace, it is deprived of its sulphur, and is con- 
 verted into carbonate of soda, the common soda of the shops. 
 
 This well known salt, now sold in the state of crystals, [containing 62 
 
 • Not in crystals, the form in which it is commonly sold as a horse medicine. Theso 
 crystals contain upwards of half their weight (55 per cent.) of water. 
 
192 SODA OR CAUSTIC SODA. 
 
 per cent, of water,] at from 10s. to 12s. a cwt., has not as yet been ex- 
 tensively tried as a means of promoting vegetation. The lowness of its 
 price, however, and the fact that it is an article of extensive home man- 
 ufacture, conjoined with the encouragement we derive from theoretical 
 considerations — all unhe in suggesting the propriety of a series of ex- 
 periments with the view of determining its real value to the practical 
 agriculturist. The mode in which theory indicates that this compound 
 is likely to act in promoting vegetation — as well as the crops to which it 
 may be expected to be especially useful, will come under our considera- 
 tion hereafter. 
 
 Besides the common carbonate of soda above described, and which in 
 the neighbourhood of Newcastle is manufactured from common salt to 
 the amount of 30 or 40 thousand tons every year, there occur in nature 
 two other compounds of soda with carbonic acid, in which the latter 
 substance is present in larger quantity than in the soda of the shops. 
 The sesqui-carhonate, containing one half more carbonic acid, occurs in 
 the soil in many warm climates (Egypt, India, South America, &c.), 
 and at Fezzan, in Africa, is met with as a mineral deposit of such 
 thickness as m that dry climate to allow of its being employed as a 
 building stone. 
 
 The 6i-carbonate is contained in the waters of many lakes, in Hunga- 
 ry, in Asia, &c., and in many springs in all parts of the world. There 
 can be no doubt that the waters of such springs are fi'tted to promote the 
 fertility, especially of pasture land, to which they may be applied ehher 
 by arti^ial irrigation, or by spontaneous overflow from natural outlets. 
 Some or the Harrowgate waters contain a sensible quantity of this bi- 
 carbonate, and over a large portion of the Yorkshire coal-field, a bed of 
 rock is found, at various depths, the springs from which hold in solution 
 a considerable portion of this salt. The Hoi beck water of Leeds, ac- 
 cording to Mr. West, owes its softness to the presence of this carbonate, 
 and the water from the coal-mines in the neighbourhood of Wakefield 
 is occasionally so charged with it, as to form troublesome saline incrus- 
 tations on the bottoms of the steam boilers. Where these waters occur 
 in sufficient abundance, they should not be permitted to escape into the 
 rivers, unttTfliey have previously been employed in irrigating the land. 
 
 It has occasionally been observed that natural springs in some locali- 
 ties impart a degree of luxuriance to natural pasture, which is not to be 
 accounted for by the njere effect of a constant supply of water. In 
 such cases, the springs may be expected to contain some alkaline, or 
 other mineral ingredient, which the soil is unable to supply to the plants 
 which grow upon it, either in sufficient abundance, or with sufficient 
 rapidity. 
 
 5°. Soda or Caustic Soda. — When a solution of the common soda of 
 the shops is boiled with quick-lime, it is deprived of its carbonic acid, 
 and like the carbonate of potash (p. 187) is brought into the caustic state. 
 In this state it destroys animal and vegetable substances, and, unless 
 very dilute, is injurious to animal and vegetable life. 
 
 W hen common salt (chloride of sodium) is mixed with quick-lime in 
 compost heaps, it is deprived by the lime of a portion of its chlorine, 
 and is partially converted into this caustic soda. The action of the soda 
 in this state is similar to that of caustic potash. Not only does it readi- 
 
SODIUM, PHOSPHATES OF SODA, AND CARBONATE OF LIME. 193 
 
 ly supply soda to the growing plant, to which soda is necessary, but it 
 also acts upon certain other substances which the plants require, so as 
 to render them soluble, and to facilitate their entrance into the roots of 
 plants. To the presence of soda in this caustic state, the efficacy of 
 such composts of common salt and lime in promoting vegetation, is in 
 part to be ascribed. 
 
 6°. Sodium is a soft metal of a silver white colour, and, like potassi- 
 um, light enough to float upon water. It is obtained by heating caustic 
 soda with a mixture of charcoal and iron filings. It takes fire upon 
 water — though not so readily as potassium — and combines with its oxy- 
 gen to form soda. In the metallic state it is not known to occur in na- 
 ture, and, therefore, does not directly act upon vegetation. With oxy- 
 gen it forms soda, — with chlorine, chloride of sodium (common salt), — 
 and with sulphur, sulphuret of sodium, — all of which, as already stated, 
 are more or less beneficial to vegetation. 
 
 7°. Phosphates of Soda. — When the common soda of the shops is added 
 to a solution of phosphoric acid in water, till effervescence ceases, and 
 the solution is evaporated to dryness, phos[)hate of soda is formed, and 
 by the subsequent addition of as much more phosphoric acid — &i-phos- 
 phate. These salts occur more or less abundantly in the ash of nearly 
 all plants ; they are occasionally also detectTed in the soil, and one or 
 other of them is ahnost always present in urine and other animal ma- 
 nures. As we know from theory that these compounds must be grate- 
 ful to plants, we are justified in ascribing a portion of the efficacy of animal 
 manures, in promoting the growth of vegetables, to the presence of these 
 phosphates, as well as to that of the phosphates of potash (p. 190). 
 They are not known to occur in the mineral kingdom in any large quan- 
 tity, neither are they articles of manufacture, hence their direct action 
 upon vegetation has not hitherto been made the subject of separate ex- 
 periment. 
 
 VII. CALCIUM, LIME, CARBONATE OF LIME, SULPHATE OF LIME, NI- 
 TRATE OF LIME, PHOSPHATES OF LIME, CHLORIDE OF CALCIUM, SUL- 
 PHURET OF CALCIUM. 
 
 1°. Carbonate of Lime. — Chalk, marble, and nearly all the lime- 
 stones in common use, are varieties, more or less pure, of that com- 
 pound of lime with carbonic acid which is known to chemists as car- 
 bonate of lime. It occurs of various colours and of various degrees of 
 hardness, but in weight the compact varieties are very much alike, be- 
 ing generally a little more than 2i times (2'7) heavier than water. 
 They all dissolve with effervescence in dilute muriatic acid (spirit of 
 salt), and by the bubbles of gas which are seen to escape when a drop 
 of this acid is applied to them, limestones may in general be readily dis- 
 tinguished from other varieties of rock. They dissolve slowly also in 
 water which holds carbonic acid in solution ; and hence the springs 
 which issue from the neighbourhood of deposits of limestone are gene- 
 rally charged in a high degree with this mineral substance. 
 
 The value of this carbonate of lime in rendering a soil capable of pro- 
 ducing and sustaining a luxuriant vegetation depends, in part, it is true, 
 on the necessity of a certain proportion of lime to the growth and full 
 developement of the several parts of nearly all plants, but it performs also 
 
 9 
 
194 QUICK-LIME, CALCIUM, AND CHLORIDE OF CALCIUM. 
 
 Other important offices, which we shall hereafter have occasion more 
 fully to consider. 
 
 2°. Lime or Quick-lime. — When limestone is burned along with coal 
 or wood in kilns so constructed that a current of air can pass freely through 
 them, the carbonic acid is driven off', and the lime alone remains. Jn 
 this state it is generally known by the name of burned or quick-Wme, 
 from its caustic qualities, and is found to have lost nearly 44 per cent, of 
 its original weight. 
 
 The most remarkable property of quick-lime is its strong tendency to 
 combine with water. This is displayed by the eagerness with which this 
 liquid is drunk in by the lime in the act of slaking, and by the great heat 
 * which is at the same time developed. Slaked lime is a compound of 
 lime with water, and by chemists is called a hydrate of lime. It con- 
 tains 24 per cent, of its weight of water. 
 
 The action of quick-lime upon the land is one of the most important 
 which presents itself to the observation of the practical agriculturist. 
 Among other effects produced by it is that of hastening the decomposi- 
 tion of vegetable matter either in the soil or in compost heaps ; but this 
 effect is materially promoted by — if it be not wholly dependent upon 
 — the presence of air and moisture. By this decomposition carbonic 
 acid and other compound substances are produced, which the roots are 
 capable of absorbing and converting into the food of plants. 
 
 In this caustic state lime does not occur in nature, nor when exposed 
 to the -air does it long remain in this state. It gradually absorbs carb«nic 
 acid from the atmosphere, and is again converted into carbonate. This 
 change takes place more or less rapidly in all cases where quick-lime is 
 applied to the land, but the benefits an«4H£» from burning the lime do not 
 disappear when it is thus reconverted into «jarbonate. On the contrary, 
 the state of very fine pov/der, into which quick-lime falls on slaking, 
 enables the carbonate of lime, subsequently formed, to be intermixed 
 with the soil in a much more minute state of division than could be ob- 
 tained by any mechanical means. This we shall hereafter see to be a 
 most important fact, when we come to study in more detail the theory 
 of the action of lime in the several states of combination, and under the 
 varied conditions in which it is employed for the purpose of improving 
 the land. 
 
 3°. Calcium is a silver-white metal, which, by its union with oxygen, 
 forms lime. It is not known to exist in nature in an uncombined state, 
 is prepared artificially only with great difficulty, and therefore exercises 
 no direct action on vegetable growth. 
 
 4°. Chloride of Calcium. — When chalk or quick-lime is dissolved in 
 muriatic acid, a solution of chloride of calciiitn is obtained. This solu- 
 tion occurs in sea-water, in the refuse (mother-liquor) of the salt-pans, 
 and is allowed to flow away in large quantities as a waste from certain 
 chemical works. I have elsewhere stated the effects it has been ob- 
 served to produce upon vegetable growth, [see Appendix,] and have re- 
 commended the propriety of making experiments with the view of ren- 
 dering useful some of those materials which in our manufactories are 
 now suffered largely to run to waste. 
 
 5°. Sulphuret of Calcium is a compound of sulphur and calcium, 
 which may be formed by heating together chalk and sulphur in a covered 
 
SULPHATE AND NITRATE OF LIME. 195 
 
 cruciDie. It is sometimes produced in nature, where moist decaying 
 vegetable and animal matters are allowed to ferment in the presence of 
 gypsum ; it may sometimes also be delected in the soil, and in the waters 
 of mineral springs, and is contained largely in the recent refuse heaps 
 of the alkali works. Like the sulphurets of potassium and sodium, al- 
 ready described, it is fitted, when judiciously applied, to promote the 
 growth especially of those plants in which sulphur has been recognized 
 as a necessary constituent. 
 
 6°. Suljyhate of Lime, or gypsum, is a well known white crystalline 
 or earthy compound, which occurs as an abundant mineral deposit in 
 numerous parts of the globe. It is present in many soils, is contained 
 in the waters which percolate through such soils, and in those of springs 
 which ascend from rocky beds in which gypsum exists, and is detect- 
 ed in sensible proportions in the ashes of many cultivated plants. It 
 is extensively employed in the arts, and in some countries not less ex- 
 tensively as a means of promoting the fertility of the land. — [See Appen- 
 dix, p. 1.] 
 
 The gypsum of commerce contains nearly 21 per cent, of its weight 
 of water, which it loses entirely on being exposed to a red heat. In 
 some countries, a variety which is almost entirely free from water oc- 
 curs in rocky masses, and is distinguished by the name o^ Anhydrite. 
 
 Gypsum, when burned, has the property of being reduced with great 
 ease into the state of an impalpable powder. This powder, however, 
 combines so readily with the 21 per cent, of water it had previously lost, 
 that if it be mixed with water \^ the consistence of a paste so thin that it can 
 be poured into a mould, it sets and hardens in a few minutes into a solid 
 mass. In this way burned gypsum is employed in making plaster casts 
 and cornices. 
 
 Burned gypsum consists of lime and sulphuric acid only — in the pro- 
 j)ortions of"41i of the former, to 58i of the latter. Its use as a manure, 
 therefore, will be specially to promote the growth of those plants by 
 which these two substances are more abundantly required, and upon 
 soils in which they are already present in comparatively small propor- 
 tion. 
 
 7°. JSitrate of Lime. — The production of nitrate of lime in artificial 
 nitre-beds, on old walls, and on the sides of caves and cellars, especially 
 in damp situations, has already been alluded to in Lecture VIII., [p. 
 161.] It may be formed artificially by dissolving common limestone in 
 nitric acid, and evaporating the solution. It constitutes a \shite mass, 
 which rapidly attracts water from the air, and runs to a liquid. It is 
 produced naturally, and exists, as I believe, in soils containing lime, 
 more commonly than has hitherto been suspected. Its extreme solubili- 
 ty in water, however, renders it liable to be carried downwards into the 
 lower portions of the soil by every shower of rain — or to be actually 
 washed away, when long continued wet weather prevails. 
 
 When heated to dull redness with vegetable matter, the nitrate of 
 lime is decomposed, and is converted into carbonate, or when exposed 
 alone to a bright red heat, the nitric acid is expelled, and quick-lime 
 alone remains. Hence where it really exists in plants, it cannot be de- 
 tected in the ash, — and when present in soils, it must be separated by 
 
r 
 
 196 PHOSPHATE OF LIWE. 
 
 washing ihem in water, before they are exposed to a heat sufficient to 
 burn away the organic matter they contain. 
 
 The details already entered into in the preceding lecture (pp. 159 to 
 163) regarding the general action of nitric acid, in promoting the natural 
 vegetation of the globe, render it unnecessary for me to dwell here on the 
 special action of its compound with lime — more particularly as the entire 
 subject of the action of lime upon the land will hereafter demand from 
 us a separate consideration. 
 
 The nitrate of lime cannot, as yet, be formed by art, at a sufficiently 
 cheap rate to allow of its being manufactured for the use of the agricul- 
 turist. 
 
 Phosphates of Lime. — Lime combines with phosphoric acid in sev- 
 eral proportions, forming as many different compounds. Of these bj'' 
 far the most important and abundant in nature, certainly the most use- 
 ful to the agriculturist, is the earth of bones. It will be necessary, how 
 ever, to advert shortly to two others, with the existence of which it is 
 important for us to be acquainted. 
 
 A. Earth of Bones is the name given to the white earthy skeleton that 
 remains when the bones of animals are burned in an open fire until 
 every thing combustible has disappeared. This earthy matter consists 
 chiefly of a peculiar phosphate of lime, composed of 5Ii per cent, of 
 lime, and 48i of phosphoric acid. This compound exists ready formed 
 in the bones of all animals, and is the substance selected in the economy 
 of nature to impart lo them their strength and solidity. It is found in 
 smaller quantity in those of young anintals, while they are soft, and 
 cartilaginous, — and the softening of the bones, which in after-life occurs 
 as the result of disease, is caused by the unnatural abstraction of a greater 
 portion of this earthy matter than is replaced by the food. 
 
 This earthy phosphate constitutes about 57 per cent, of the dried bones 
 of the ox, is present in lesser quantity in the horns, hoofs and nails, and 
 is never absent even from the flesh and blood of healthy animals. It 
 exists in the seed of many plants, in all the varieties of grain which are 
 extensively cultivated for food, and in the ashes of most common plants. 
 The ashes^f leguminous, cruciferous, and composite plants, are es- 
 pecially rich in this compound. 
 
 If we consider that when animals die, their bones are chiefly buried in 
 the earth, and that over the entire globe, animal life, in one or other of 
 its forms, prevails, we shall not be surprised that, in almost every soil, 
 the earth of bones should be found lo exist in greater or less abundance. 
 Nor can we have any difficulty in conceiving, if such be the case, 
 whence plants draw their constant and necessary supplies of this 
 substance. 
 
 At the same time, it is true of this compound^ as of all the others we 
 have yet spoken cf, as occurring in, and as necessary to the growth of, 
 vegetables, — that some soils contain it in greater abundance than others, 
 and that from some soils, therefore, certain plants will not readily obtain 
 as much of this substance as they require. This is the natural principle 
 on which the use of bone-dust as a manure chiefly depends. 
 
 Hence of two inarls both containing carbonate of lime, that will be 
 inDsl useful to the land which contains also, as many do, a notable por- 
 tion of phosuhate of lime; and of two limestones, that will be preferred 
 
BOILED BONES AS A MANURE. 197 
 
 in an agricultural district in whicli animal remains most abound. I 
 shall liave occasion to illustrate this point more fully, when in a subse- 
 quent lecture I come to explain the natural origin of soils, and to trace 
 their chemical constituents to the several rocky masses from which they 
 appear to have been derived. 
 
 Before dismissing this topic, however, there are one or two proper- 
 ties of this bone earth which are of practical importance, and to which, 
 therefore, I must shortly request your attention. It is insoluble in water 
 or in solutions of soda or potash, but it dissolves readily in acids, such as 
 the nitric or muriatic, and also, though less easily and abundantly, in 
 common vinegar. It exists in milk, and is supposed to be held in solu- 
 tion by a peculiar acid found in this liquid, and which is distinguished by 
 the name oHactic acid (acid of milk). 
 
 It is slightly soluble also in a solution of carbonic acid, and of certain 
 other organic acids which exist in the soil, and it is by means of these 
 acids that it is supposed to be rendered capable of entering into the roots 
 of plants- Wherever vegetable matter exists, and is undergoing decay 
 in the soil, tlie water makes its way to the roots more or less laden with 
 carbonic acid, and thus is enabled to bear along with it not only common 
 carbonate of lime, as has been shown in a previous lecture (p. 47), but 
 also such a portion of phosphate as may aid in supplying this necessary 
 food to the growing plant.* 
 
 In the bones of animals the phosphate is associated with animal geJa- 
 line, which can be partially extracted by boiling bones in water under 
 a high pressure. It has becri observed, however, that the phos))hate, 
 when in a minute state of division, is slightly soluble in a solution of 
 gelatine, and hence bones, from which the jelly has been partially ex 
 tracted by boiling, will be deprived of a certain proportion of their earthy 
 matter also. They will have lost their gelatine, however, in a greater 
 ])roportion, and hence, if again thoroughly dried, they will contain a 
 larger per-centage of bone earth than when in their natural state. In 
 this country, bones are seldom boiled, I believe, either for the jelly they 
 give, or as in France and Germany for the manufacture of glue, though 
 in certain localities they are so treated in open vessels for the sake of the 
 oil they are capable of yielding. Such boiled bones are said to act more 
 quickly when applied to the land, but to be less permanent in their ef- 
 fects. This may be chiefly owing to their not being so perfectly dry as 
 the unboiled bones. Being thus moist, they will contain, in the same 
 weight, a comparatively smaller quantity both of the animal gelatine 
 
 * If to a solution of bone earth in muriatic acid (spirit of salt), liquid ammonia (hartshorn) 
 be added, the solution will become milky, and a white powder will fall, which is the ea^th, 
 of bones in an extremely minute state of division. If this powder be waslied by repeated affu- 
 sions of pure water, and be aftenvards well shaken with water which is saturated with car- 
 bonic acid, or ihroui^h winch a current of this gas is made to pass, a sensible portion of the 
 phosphate will be found to be taken up by the water. This will appear on decanting the 
 solution and evaporating it to dryness, when a quaniily of the white powder will remain be- 
 hind. The mean of 10 experiments made in this way save me 30 grains for the quantity of 
 phospliate taken up by an imperial galKm of water. Wliat takes place in this way in our 
 hands, happens also in the soil. Nut only does that which enters the root bear with it a por- 
 tion of this compound where it exists in the soil, but the superabundant water also which 
 runs off the surface or sinks through to the drains, carries with it to the rivers in its cours^ 
 a still larger quantity of this soluble compound, and thus gradually lessens that supply of 
 phosphate which either exists naturally in the soil, or has been added as a manure by the 
 practical agricultuilst. 
 
198 ACID OR BI-PHOSPHATE OP'LIME. 
 
 and of the earthy phosphate, while they will also be more susceptible of 
 speedy decomposition when buried in the soil.* 
 
 In solutions of common salt and of sal-amraoniac, the earth of bones 
 is also slightly soluble, and cases niay occur where the presence of 
 these compounds in the soil may facilitate the conveyance of the earthy 
 phosphate into the roots of plants. 
 
 B. Acid or Bi-Phosphate of Lime. — When burned bones are reduced 
 to powder, and digested in sulphuric acid (oil of vitriol), diluted with 
 once or twice its weight of water, the acid combines with a portion of the 
 lime, and forms suli)liate of lime (gypsum), while the remainder of the 
 lime and the whole of tlie phosphoric acid are dissolved. The solution, 
 therefore, contains an acid phosphate of lime, or one in which the phos- 
 phoric acid exists, in much larger quantity than in the earlh of bones. 
 The true bi-phosphate, when free from water, consists of 71i of phos- 
 phoric acid, and 28i of lime. It exists in the urine of most animals, and 
 is therefore an important constituent of liquid manures of animal origin. 
 
 If the mixture of gypsum and acid phosphate, above described, be 
 largely diluted with water, it will form a most valuable liquid manure, 
 especially for grass land, and for crops of rising corn. In this liquid 
 state, the phosphoric acid will diffuse itself easily and perfectly through- 
 out the soil, and there will speedily lose its acitl character by combining 
 with one or other of the basicf substances, almost alwa3^s present in 
 every variety of land. 
 
 Or if to the solution, before it is applied to the land, a quantity of pearl- 
 ash be added until it begin to turn milky, a mixture of the phosphates 
 with the sulphates of lime and of potash will be obtained, or — if soda be. 
 added instead of potash — of the phosphates with the sulphates of lime 
 and of soda ; either of which mixtures will be still more efficacious 
 upon the land, than the solution of the acid phosphates alone. 
 
 Or to the solution of bones in the acid, the potash or soda may be added 
 without further dilution, and the whole then dried up by the addition of 
 charcoal powder, or even of vegetable mould, till it is in a sufficiently 
 dry state to be scattered with the hand as a top-dressing, or buried in 
 the land byjneans of a drill. 
 
 I have above alluded to the employment of bones in France and Ger- 
 many, for the manufacture of glue. For this purpose the broken bones 
 are digested in weak muriatic acid, by which the earthy matter is dis- 
 solved, and the gelatine left behind. The gelatinous skeleton is boiled 
 down for glue, and the solution of the bone earth is thrown away. This 
 solution contains a mixture of tlie acid phosphate of lime with chloride 
 of calcium, — and might be used up in any of the ways above described, 
 with manifest benefit to the land. The glue prepared by this method, 
 however, is said to be inferior in quality, and as the process is not adopt- 
 ed in this country, the opportunity of making an economical application 
 of this waste material is not likely to be often presented to the English 
 farmer. 
 
 * The relative value of crushed bones in these two states, is indicated by the price of the 
 unboiled being about 7 guineas, while that of boiled is only about 4 guineas a ton. 
 
 t This word has already been used and explained — it is applied to potash, soda, ammonia, 
 lime, magnesia, and other substances, which have the property of combining with acids (sul- 
 phuric, nitric, &c.) and of thus TieutraUzing them, or depriving them of their acid qualities 
 and effects. 
 
NATIVE PHOSPHATE OF LIME. 199 
 
 C. Native Phosphate of Lime or Apatite. — In some parts of the world, 
 a hard mineral substance, commonly known by the name of Apatite, 
 occurs in considerable quantity. It consists cliiefly of a phosphate of 
 lime, which differs but slightly in its constitution from the earth of bones, 
 — containing 54^ per cent, of lime, while the latter contains only 51|- per 
 cent. The composition of this mineral would lead us to expect it to 
 possess a favourable action upon vegetation, and this anticipation has 
 been confirmed by some experiments made with it on a limited scale by 
 Sprengel. — [Chemie, I., p. 64.] 
 
 It occurs occasionally in mineral veins, especially such as are found 
 in the granitic and slate rocks. Masses of it are met with in Cumber- 
 land, in Cornwall, in Finland, in the iron mines of Arendahl in Nor- 
 way, and in many other localities. A variety of it distinguished by the 
 name oC phosphorite is said to form beds at Schlachenwalde in Bohemia, 
 and in the province of Estremadura in Spain. From the last of these 
 localities being the most accessible, the time may come when the high 
 price of bones may induce our enterprising merchants to import it, for 
 the purpose of being employed in a finely powdered state as a fertilizer 
 of the land. 
 
LECTURE X. 
 
 Inorganic constituents of plants continued. - -Magnesia, Alumina, Silica, and the Oxides of 
 Iron and Manganese. — Tabular view of the constitution of the inorganic substances de- 
 scribed. — Proportions in which these several substances are found in the plants cultivated 
 for food.— Extent to which these plants exhaust the soil of inorganic vegetable food. — State 
 in which tiie inorganic elements exist in plants. 
 
 § 1. Inorganic constituents of plants continued. 
 
 VIII. MAGNPISIUM, MAGNESIA, CARBONATE, SULPHATE, NITRATE, AND 
 
 PHOSPHATE OF MAGNESIA, CHLORIDE OF MAGNESIUM. 
 
 1°. Carbonate of Magnesia is a tasteless earthy compound, which in 
 some parts of the world forms rocky masses and veins of considerahlc 
 heiijht and thickness. It occurs more largely, however, in connection 
 with carbonate of lime in the magnesian limestones, so well laiown in 
 the eastern and northern parts of England, — and in similar rocks, dis- 
 tinguished by the name of dolomites or of dolomitic limestones, in va- 
 rious countries of Europe. The pure, exceedingly light, white magne- 
 sia of (he siiops, is jiartly extracted from the magnesian limestone, and 
 partly from the mother liquor of tiie salt pans, which generally contains 
 much magnesia. 
 
 When pure and dry, carbonate of magnesia consists of 43|^ of magne- 
 sia, and 51| of carbonic acid. It dissolves readily in diluted acids (sul- 
 phuric, muriatic, and acetic,) the carbonic acid at the same time esca- 
 ping with effervescence. 
 
 Existing as it does in many solid rocks, this carbonate of magnesia 
 may be expected to be present in the soil, and it is found in the ashes of 
 many ])lants. Of the ashes of some parts of jilants it constitutes one- 
 sixth of the entire weight. 
 
 When exjiosed to the air in a finely divided state, it gradually absorbs 
 a quantity oTmoisture from the atmosphere, eciual to two-thirds of its 
 own weight. In this state, it dissolves in 48 times its weight of water, 
 though, when dry, it is nearly insoluble. Like carbonate of lime it is 
 also soluble in water impregnated with carbonic acid, but in a some- 
 what greater degree. In this state of solution it may be readily carried 
 into the roots, and be the means of supplying to the parts of living ve- 
 getables a portion of that magnesia which is necessary to their perfect 
 growth. 
 
 Soils containing much of this carbonate of magnesia are said to be 
 highly absorbent of moisture, and to this cause is ascribed tlie coldness of 
 such soils. — [Sprengel, Chemie, I., p. 645.] This opinion is, however, 
 open to doubt. 
 
 2°. Magnesia or Caustic Magnesia, the calcined magnesia of the 
 shops. — When the carbonate of magnesia is heated to redness in the 
 open air, it parts with its carbonic acid much more readily than lime 
 does, and is brought inio the stale of pure or causlic magnesia. In this 
 state it does not occur in nature, but it is occasionally met with in com- 
 
CAUSTIC OR CALCINED MAGNESIA. 201 
 
 bination with about 30 per cent, of water. When magnesian lime- 
 stones or dolomites are burned, 'the quick-lime obtained often contains 
 caustic magnesia also in considerable quantity. This mixture is fre- 
 quently applied to the land, and, as is well known in many parts of 
 England, with injurious effects, if laid on in too large quantities. The 
 cause of this hot or burning nature, as it is called, of magnesian lime, is 
 not very satisfcictorily ascertained. I shall, however, state two or three 
 facts, which may assist in conducting us to the true cause. 
 
 1°. Quick-lime dissolves in 750 times its weight of water, at the or- 
 dinary temperature of the atmosphere, while pure magnesia requires 
 514-2 limes its weight. The magnesia, therefore, is not likely to injure 
 living plants cUrecfly by entering into their roots in its caustic state, since 
 lime which is seven times more soluble produces no injurious effect. 
 
 2°. It seems to be the result of experience, that magnesia in the state 
 of carbonate is but slightly injurious to the land ; some deny that in this 
 state it has any injurious effect at all. This I fear is doubtful ; we may 
 infer, however, with some degree of probability^ that it is from some 
 property possessed by magnesia in the caustic state, and not possessed, 
 or at least in an equal degree, either by quick-lime or by carbonate of 
 magnesia, that its evil influence ischiejiy to be ascribed. 
 
 3°. When exposed to the air, quick-lime speedily absorbs water and 
 carbonic acid from the air, forming first a hydrate'^' in fine powder, and 
 then a carbonate. Caustic magnesia absorbs both of these more slowly 
 than lime does, and in the presence of the latter, or when mixed with it, 
 must absorb them more slowly still, since the lime will seize on the 
 greater portion of the moisture and carbonic acid which exists in the air, 
 immediately surrounding both. When slaked in the air also, the lime 
 may be transformed in great part into carbonate, while the magnesia 
 still remains in the state of hydrate, and it is a property of this hydrate 
 to attract carbonic acid more feebly and slowly, even than the newly 
 burned magnesia as it comes from the kiln. Hence when buried in the 
 soil, after the lime has become nearly all transformed into carbonate, the 
 magnesia may still be all either in the dry caustic state, or in that of a 
 hydrate only. 
 
 4°. Now there exist in the soil, and probably are exuded from the 
 living roots, various acid substances, both of organic and of inorganic 
 origin, which it is one of the functions of lime, when apphed to the land, 
 to combine with and render innoxious. But these acid compounds unite 
 rather with the caustic magnesia, than with the lime which is already 
 in combination with carbonic acid — and {orm salts, j which generally are 
 much more soluble in water than the compounds of lime with the same 
 acids. Hence the water that goes to the roots reaches them more or 
 less loaded with magnesian salts, and carries into the vegetable circula- 
 tion more magnesia than is consistent with the healthy growth of the 
 plant. 
 
 It is hazardous to reason from the phenomena of animal to those of 
 
 * Compounds of substances with vvatpr are called hydrates (from the Greek word for wa- 
 ter.) Thus slaked lime, a compound of lime with water, is called hydrate of lime— and the 
 native compound of magnesia with water, alluded to in the text, is called hydrate of mag- 
 nesia. 
 
 t Compounds of the io^es,— potash, soda, lime, magnesia, &c.,— with actds,— sulphuric, 
 muriatic, nitric, acetic (or vinegar), «fec.,— are called salts. 
 
 9* 
 
202 MAGNESIUM, AND CHLORIDE OF MAGNESIUM. 
 
 vegetable physiology, yel if llrae and magnesia have the power of dif- 
 ferently affecting the animal economy, why may they not also very 
 differently affect the vegetable economy ? And since in the same cir- 
 cumstances, and in combination with the substances they meet with 
 in the same soils, magnesia is capable of entering more largely into 
 a plant by its roots — may not magnesia be considered capable of poi- 
 soning a plant, when lime in the same condition would only improve 
 the soil ? 
 
 I have said that it may be doubted whether magnesia in the state of 
 carbonate is wholly unhuriful to the land. This doubt rests on the fact 
 that the magnesia retains its carbonic acid more feebly than lime does 
 — and therefore its carbonate is the more easily decomposed wlien an 
 acid body comes in contact \\\\\\ both. Though, therefore, the mag- 
 nesian carbonate will not lay hold of all acid matter so readily and surely 
 as caustic magnesia may, still occasions may occur where acid matters 
 being abundant In the soil, so much carbonate of magnesia may be de- 
 composed and dissolved as to render the water absorbed by its roots 
 destructive to the health or life of a plant. 
 
 In reference to this point, however, it must be distinctly understood, 
 that magnesia is one of the kinds of inorganic food most necessary to 
 ]>lants, that a certain quantity of it in the soil is absolutely necessary to 
 the growth of nearly all cultivated plants, and that it is only when it is 
 conveyed to the roots in too large a quantity, that it proves injurious to 
 vegetable life. 
 
 5°. Magnesium is the metallic basis of magnesia. Little is known 
 of its properties, owing to the difficulty of preparing it in any consider- 
 able quantity for the purpose of experiment. It is a white metal, which, 
 when heated in the air, takes fire and burns, combining with the oxygen 
 of the atmosphere, and forming magnesia. It is not known to occur in 
 nature in an elementary form, and therefore is not supposed directly to 
 influence vegetation. 
 
 6°. Chloride of Magnesium. — When calcined or carbonated magne- 
 sia is dissolved in muriatic acid, and the solution evaporated to dryness, 
 a white massjs obtained which is s. chloride of magnesium, consisting of 
 magnesium and chlorine only. This compound occurs not unfrequently 
 in the soil, associated with chloride of calcium. It is met with also in 
 the ash of plants, while in sea water, and in that of some salt lakes, it 
 exists in very considerable (luantity. Thus 100 parts of the water of 
 the Atlantic have been found to contain 3i of chloride of magnesium, 
 while that of the Dead Sea yields about 24 parts of this compound.* 
 Hence it is present in great abundance in the mother liquor of the salt 
 y)ans, and it is from the refuse chloride in .this lifjuor that the magnesia 
 of the shops, as above staled, is frequently prepared. 
 
 The chloride of magnesium has not hitherto been made the subject of 
 direct experiment as a fertilizer of the land. From the fact, however, 
 that plants require much magnesia and some chlorine, there is reason to 
 believe that, if cautiously applied, it might prove beneficial in some soils, 
 and especially to grain crops. Its extreme solubility in water, however, 
 suggests the use of caution in its application. The safest method is to 
 
 " 100 parts of the water of the Dead Sea contain also about 10^ of chloride of calcium, 
 and nearly 8 of common salt. 
 
NITRATE, SULPHATE, AND PHOSPHATE OF MAGNESIA. 203 
 
 dissolve it in a large quantity of water, and to api)ly it to the young 
 plant by means of a wafer-cart. In this way the refuse of the salt 
 works might, in some localities, be made available to useful purposes. 
 
 Tlie chloride of magnesium is decomposed both by quick-lime and by 
 carbonate of lime ; hence when applied to a soil containing lime ir? 
 either of these states, chloride of calcium and caustic or carbonated mag 
 nesia will be produced. 
 
 7°. Nitrate of Magnesia is formed by dissolving carbonate of magne 
 sia in nitric acid, and evaporating the solution. It attracts moisture from 
 the air with great rajjidity, and runs into a liquid. It is probably formed 
 naturally in soils containing magnesia, in the same way as nitrate of 
 lime is known to be produced in soils containing lime. [See Lecture 
 VIII., p. 159.] No direct experiments have yet been made as to its 
 effects upon vegetation ; but there can be no doubt that it would prove 
 highly beneficial, could it be procured at a sufficiently cheap rate to ad- 
 mit of its economical application to the land. 
 
 8°. Sulphate of Magnesia — the common Epsom salts of the shops — 
 is formed by dissolving carbonate of magnesia in diluted sulphuric acid. 
 It exists in nearly all soils which are formed from, or are situated in, 
 the neighbourhood of rocks containing magnesia. In some soils it is so 
 abundant that in dry weather it forms a while efflorescence on the sur- 
 face. This has been observed to take place in Bohemia, Hungary, and 
 j)arts of Germany, and it may be frequently seen in warm summer 
 weather in the neighbourhood of Durham.* 
 
 This salt has been found by Sprengel to act upon vegetation precisely 
 in the same way as gypsum does, and on the same kind of plants. It 
 must be used, however, in smaller quantity, owing to its great solubili- 
 ty. Its higher price will prevent its ever being substituted for gypsum, 
 as a top-dressing for clover, &c., but it is worth the trial, whether corn 
 ])lants, the grain of which contains much magnesia, might not be bene- 
 fitted by the application of a small quantity of this sulphate — along with 
 such other substances as are capable of yielding the remaining constit- 
 uents which compose the inorganic matter of the grain. Its price'is not 
 too high to admit of this more restricted application. f 
 
 9°. Phosphate of Magnesia. — Magnesia exists in combination with 
 phosphoric acid, in the solids and fluids of all animals, though not so 
 abundantly as the phosphates of lime. In most soils phosphate of mag- 
 nesia is probable present in minute quantity, since in the ashes of some 
 varieties of grain it is found in very considerable proportion. 
 
 Its action upon vegetation has never been tried directly, but as it 
 exists in urine, and in most animal manures, a ))ortion of their efficac3'' 
 may be due to its presence. In turf ashes, which often prove a valua- 
 ble manure, it is sometimes met with in appreciable quantity, and their 
 beneficial operation in such cases has been attributed in part to the agen- 
 cy of this phosphate. 
 
 * It occasionally collects beneath the plaster of old waHs in Durham. In one of the lower 
 rooms of the old Exchequer buildings, I found it forming an extensive layer nearly half an 
 inch thick, beneath the damp plaster. The magnesia is derived from the magnesian lime- 
 stone, used both for mortar and for building stone. 
 
 t Its price in Newcastle in the state of crystals, is about 10s. a cwt. The Impure salt col- 
 lected at the alum works on the Yorkshire coast, might be obtained, I should suppose, for 
 little more than half this price. 
 
204 ALUMINA THE PRINCIPAL CONSTITUP:?? T OF CLAYS. 
 
 IX. ALUMINIUM, ALUMINA, SULPHATK AND PHOSPHATE OF 
 
 ALUMINA — ALUM. 
 
 1°. Aluminium is another of those rare and little known metals, the 
 existence of which was established by Sir H. Davy. In combination 
 with oxygen it forms alumitia, and in this state it exists in such abun- 
 dance in nature, as to form a large portion of the entire crust of the 
 globe. 
 
 2°. Alumina, the earth of Alum. — When common alum is dissolved 
 in water, and a solution of carbonate of soda or of ammonia is added to 
 it, a bulky white powder falls, which, when collected on a filter, well 
 washed and dried, is nearly pure alumina. This substance occurs on 
 the surface of the earth in a pure state only in some rare minerals, such 
 as the corundum, the sapphire, and the ruby, — but it constitutes a large 
 proportion of all the slaty and shaley rocks. It is the principal ingre- 
 dient also of all clays (pipe-clay for example) and clayey soils, which 
 increase in tenacity in proportion to the quantity of alumina they contain. 
 
 When pure, it is a white tasteless earthy substance, which adheres to 
 the tongue, has a density of 2-00, and is insoluble in water, but dissolves 
 readily in caustic potash and soda and in most acids, at least when new- 
 ly thrown down from a solution of alum. When heated to redness, 
 however, it becomes hard and dense, as in burned clay and fire bricks, 
 and can then only be dissolved with extreme difficulty, even by the 
 strongest acids. Though it exists so largely in the soil, it contributes 
 but little in a direct manner to the nourishment of plants. The ash they 
 leave contains in general but a very small per-centage of alumina, as 
 will more clearly appear hereafter, — the principal agency, therefore, of 
 this ingredient of the soil is most probably of an indirect, perhaps of a 
 mechanical kind. 
 
 It has been stated in a preceding Lecture (p. 23), that charcoal has 
 the property of absorbing gaseous substances, such as ammonia, from 
 the atmosphere, and that the action of charcoal powder, in promoting 
 vegetation, has been in a great measure ascribed to this property. The 
 same property, we have also seen (p. 136), is ascribed to gypsum, and 
 lience its fertilizing action has been explainf^d in a similar way. Alum- 
 ina is said to be equally absorbent of ammonia ; and the use of burned 
 clay as a top-dressing, so strongly recommended by General Beatson, 
 [Neiv System of Cultivation, London, 1820,] is ascribed to its power 
 of abstracting ammonia from the air, and fixing it in the soil ready to be 
 conveyed by the rains to the roots of the plants that grow upon it [Liebig, 
 p. 90.] It has been already shown (p. 136,) that this mode of ac- 
 counting for the action of gypsum is not satisfactory as a sole cause — in 
 the case of alumina, the fact of its absorbing ammonia is hypothetical,* 
 and therefore the explanation founded upon this fact is not to be impli- 
 citly relied upon. 
 
 3^. Sulphate of Alumina. — When alumina is digested in diluted sul- 
 
 Because clays of ipany varieties— pipe-clay for example — contain traces of ammonia, 
 which they evolve when moistened with a solution of caustic potash,— it is inferred that 
 fhey have absorbed this ammonia from the atmosphere. The same inference is drawn 
 from the fact of its presence in oxide of iron. — [Lieiaig's Organic Chemistry applied to Agri- 
 culture, p. 89.] — In neitiier case does the inference appear to me to be necessary. Much of 
 the ammonia may have been formed in the soil, during the oxidation of the iron itself, or 
 during the decay of vegetable and animal substances.— See above, Lecture VIII., p. 158. 
 
SULPHATE AND PHOSPHATES OF ALUMINA, ALUM. 205 
 
 phuric acid, it readily dissolves, and forms a solution of sulphate of 
 alumina. This solution is characterized by a remarkable and almost 
 peculiar sweetish astringent taste. When evajiorated to dryness it yields 
 a white salt, which dissolves in twice its weight of water only, and when 
 exposed to the air, attracts moisture rapidly, and spontaneously runs to 
 a li(|uid. This salt exists in some soils, especially in those of wet, 
 marshy, and peaty lands. 
 
 No experiments have yet been made with the view of determining its 
 direct influence ujion vegetation. 
 
 4°. Phosphates of Alumina. — In coiribination with phosphoric acid, 
 alumina forms one compound well known to mineralogists, by the name 
 o^ loavellitc. This mineral, however, occurs in too small (piantity to be 
 an object of interest to the agriculturist. 
 
 Phosphoric acid is disseminated in some form or other throughout our 
 clayey soils, though in very small and variable quantity. It is most 
 probable that in these soils a portion of the acid at least is in combina- 
 tion with the alumina in the state of phosphate. One of the most diffi- 
 cult problems in analytical chemistry is to effect a perfect separation of a 
 small proportion of phosphoric acid from alumina, and rigorously to esti- 
 mate its ([uantity ; hence iu the greater part of the analyses of s(/iU hitherto 
 published, this most important ingredient in a fertile soil (the jjhosphoric 
 acid), when in combination with, or in presence of alumina, has either 
 been altogether neglected, or rudely guessed at, or indicated by a rough 
 approximation only. We have no direct proof, therefore, of the extent 
 to which the phosphates of alumina exist in different soils. 
 
 5°. Alum. — The common alum of the shops owes its well known 
 sweetish astringent taste to the presence of the above sulphate of alumi- 
 na. It consists in lOQ parts of about 40 of sulphate of alumina, 14i of 
 potash, [described p. 189,] and 45|- of water. Alum is formed naturally 
 on many parts of the earth's surface, especially as an efflorescence on 
 certain soils, and on some rocks when exj)osed to the air, — as on the 
 alum shales of the Yorkshire coast. It is largely manufactured by cal- 
 cining, and afterwards washing these alum shales. 
 
 Alum has not been extensively tried as a manure. Its composition, 
 however, would lead us to expect it to exert a beneficial influence on the 
 growth of many plants — while the price, especially of the less pure va- 
 rieties, is such as to admit of its being applied to the land at a compara- 
 tively small cost. From some experiments made on a small scale, 
 Sprengel considers it highly worthy the attention of the practical agri 
 culturist. 
 
 X. — SILICA, SILICON, SILICATES OF POTASH, OF SODA, OF LIME, OF 
 MAGNESIA, AND OF ALUMINA. 
 
 1°. Silica. — The chief ingredient in all sand-stones and in nearly all 
 sands and sandy soils, is known to chemists by the name of silica. Flints 
 are nearly pure silex or silica — common quartz rock is another form of 
 the same substance — while the colourless and more or less transparent 
 varieties of. rock crystal and chalcedony present it in a state of almost 
 perfect purity- It exists abundantly in almost all soils, constituting 
 what is called their siliceous portion, and is found in the ashes of all 
 plants without exception, but especially in those of the grasses. Silica 
 
206 SILICA, SILICON, SILICATES OF POTASH AND SODA. 
 
 is without colour, taste, or smell, and cannot be melted by (he strongest 
 heat. As it occurs in the mineral kingdom — in the state of flint, of 
 quartz, or of sand — it is perfectly insoluble in pure water, either cold or 
 hot, does not dissolve in acid and very slowly in alkaline solutions. 
 When mixed with potash, soda, or lime, and heated in a crucible to a 
 high temperature, it melts and forms a glass. Window and plate glass 
 consists chiefly of silica, lime, and soda, flint glass contains litharge 
 [oxide of lead] in place of the lime. But though the various forms of 
 more or less pure silica, which are met with in the mineral kingdom, 
 are absolutely insoluble in water, yet it sometimes occurs in nature, and 
 can readily be prepared in a state in which pure water, and even acid 
 solutions, will take it up in considerable quantity. In this state it may 
 be obtained by reducing crown-glass to a fine powder, and digesting it 
 in strong muriatic acid, or by melting quartz sand in a large quantity of 
 potash or soda, and aftervtards treating the glass that is formed with di- 
 luted muriatic acid. 
 
 Silica is one of the most abundant substances in nature, and in com- 
 bination with potash, soda, lime, magnesia, and alumina, it forms a 
 large portion of all the so-called crystalline (granitic, basaltic, &c.) 
 rocks. The compounds of silica, with these bases, are called silicates. 
 By the action of the air, and other causes, these silicates undergo decom- 
 position, as glass does when digested with muriatic acid, and the silica 
 is separated in the soluble state. Hence its presence in considerable 
 quantity in the waters of many mineral and especially hot mineral 
 springs, and in appreciable proportion in nearly all waters that rise from 
 any considerable depth beneath the surface, or have made their way 
 through any considerable extent of soil. 
 
 In the substance of living vegetables it exists, for the most part, in 
 this state of combination — as well as in the form of an extrc mely deli- 
 cate tissue, of which the fibres are exceedingly minute, and therefore 
 expose a large surface to the action of any decomposing agent, or of any 
 liquid capable of dissolving it. In the compost heaps these silicates 
 undergo decompositi( n, — and the more readily the less they have been 
 previously drie_d, or the greener they -are, — and the silica of the plant is 
 liberated in a soluble state. Whether or not, when thus liberated, it 
 will be carried, uncorubined, into the roots of the plants by the water 
 they absorb, will depend upon the quantity of potash or soda in the 
 compost or in the soil, and upon other circumstances hereafter to be 
 explained. 
 
 2°. Silicon is known only in the state of a dark brown powder, which 
 has not as yet been met with in nature in an elementary form, and is 
 prepared by the chemist with considerable difficulty. When heated in 
 the air, or in oxygen gas, it burns, combines with oxygen, and is con- 
 vened into silica. Silica, therefore, in its various forms, is a compound 
 of silicon with oxygen. It consists of 48 per cent, of the former and 52 
 per cent, of the latter. 
 
 3°. Silicates of Potash and Soda. — When finely powdered (juariz, 
 flint, or sand, is mixed with from one-half to three times its weight of 
 dry carbonate of potash or soda, and exposed to a strong heat in a cruci- 
 ble, it readily unites with the potash or soda, and forms a glass. This 
 glass is a silicate or a mixture of two or more silicates of potash or soda- 
 
DECOMPOSED BY THE CARBONIC ACID OF THE AIR. 207 
 
 Silica combines with these alkalies* in various proportions. If it be 
 racked with much potash, the glass obtained will be readily soluble in 
 water; if with little, the silicate which is formed will resist the action 
 of water for any length of time. Window and plate-glass contain 
 much silicate of potash or soda. A large quantity of alkali renders 
 these varieties of glass more fusible and more easily worked, but at the 
 same time makes them more susceptible of corrosion or tarnish by the 
 action of the air. 
 
 The insoluble silicates of potash and soda exist also in many mineral 
 substances. In the felspar and mica, of which granite in a great mea- 
 sure consists, they are present in considerable quantity. The former 
 (felspar) contains one-third of its weight of an insoluble silicate of potash, 
 consisting of nearly equal weights of potash and silica. In the variety 
 called albite or cleavelandite, silicate of soda alone is found, while in 
 some other varieties a mixture of both silicates is present. In mica from 
 12 to 20 per cent, of the same silicate of potash occurs, but soda can 
 rarely be detected in this mineral. The trap-rocks also (whin, basalt, 
 green-stone), so abundant in many parts of our island, consist almost 
 entirely oi^ silicates. Among these, however, the siUcates of potash and 
 soda rarely exceed 5 or 6 per cent, of the whole weight of the rock, and 
 are often entirely absent. 
 
 These insoluble»silicates also exist in the stems and leaves of nearly 
 all plants. They are abundant in the stems of the grasses, especially 
 in the straw of the cultivated grains, and form a large proportion of the 
 ash which is left when those stems are burned [p. 178.] 
 
 It is important to the agriculturist to understand the relation which 
 the carbonic acid of the atmosphere bears to these alkaline silicates which 
 occur in the mineral and vegetable kingdom. Insoluble as they are in 
 water, they are slowly decomposed by the united action of the moisture 
 and carbonic acid of the air, the latter taking the potash or soda from the 
 silica, and torming carbofiates of these bases. In consequence of this 
 decomposition the rock disintegrates and crumbles down, while the so- 
 luble carbonate is washed down by the rains or mists, and is borne to 
 the lower grounds to enrich the alluvial and other soils, or is carried by 
 the rivers to the sea. 
 
 In some cases, as in the softer felspar of some of the Cornish granites, 
 this decomposition is comparatively rapid, in others, as in the Dartmoor 
 and many of the Scottish granites, it is exceedingly slow, — but in all 
 cases the rock crumbles to powder long before the whole of the silicates 
 are decomposed, so that potash and soda are always present in greater 
 or less quantity in granitic soils, and will continue to be separated from 
 the decaying fragments of rock for an indefinite period of time. 
 
 But the silica of the fel'^par, or mica, or zeoliticf trap, when thus de- 
 prived of the potash with which it was combined, is in that peculiar state, 
 in which, as above described [p. 206], it is capable of being dissolved 
 in small (|uantity by pure water, and more largely by a solution of 
 carbonate of potash or soda. Hence the same rains or mists which dis- 
 
 • Potash, soda, and ammonia are called alkalies; lime and magnesia are alkaline earths. 
 See Lecture III., p. 51, note. 
 
 t Tiie trap-rocks always more or less abound in zeolitic minerals, of which there is a great 
 variety, and in which nearly all the alkali present in these (trap) rocka is contained. 
 
208 SILICATES OF LIME IN THE TRAP-ROCKS. 
 
 solve the alkaline carbonates so slowly formed, take up also a portion of 
 the silica, and convey it in a state of solution to the soils or to the rivers. 
 Tiius, with the exception of the dews and rains which fall directly from 
 the heavens, few of the supplies of water by which plants are refreshed 
 and fed, ever reach their roots entirely free from silica, in a form in 
 which it can readily enter into their roots, and be appropriated to their 
 nourishment. 
 
 In the farm-yard and the compost-heap, where vegetable matters are 
 undergoing decomposition, the silicates they contain undergo similar de- 
 compositions, and, by similar chemical clianges their silica is rendered 
 soluble, and thus fitted, when mixed with the soil, again to minister to 
 the wants and to aid the growth of new races of living vegetables. 
 
 4°. Silicates of Lime. — A mixture of sand or flint with quick-hme 
 readily melts and forms a glassy silicate or a mixture of two or more 
 silicates of lime. These silicates are also [)resent in large quantity in 
 window and plate-glass, and in some of the crystalline* (granite and 
 trap) rocks. In felspar and mica, wliich abound, as we have seen, in 
 the alkaline sihcates, it is rare that any lime can be detected. In that 
 variety of granite, however, to which the name of syenite is given by 
 mineralogists, hornblende takes the place oi" mica, and some varieties of 
 this hornblende contain from 20 to 35 per cent, of silicate of lime. This 
 silicate (containing 38 per cent, of lime) is almost always present in the 
 basaltic and trap-rocks, and sometimes, as in the augiticf traps, in a 
 proportion much larger than that in which it exists in the unmixed horn- 
 blende. To this fact we shall have occasion to revert when we come 
 to consider the relative fertility of difierent soils and the causes on which 
 the dilierence of their several productive powers most probably depends. 
 
 Silicates of lime are also found in the ash, and probably $ exist in the 
 living stem and leaves of plants. 
 
 Like ihe similar compounds of potash and soda, the silicates of lime 
 are slowly decomposed by the united ageney of the moisture and the 
 carbonic acid of the atmosphere. Carbonate of lime is formed, and 
 silica is set at liberty. This carbonate of lime dissolves in the rains or 
 dews which descend loaded with carbonic acid, [see page 46,] and the 
 same waterslaTke up also a portion of the soluble silica and ditfuse both 
 substances uniformly through the soil in which the decomposition takes 
 place, or bear them from the higher grounds to the rivers and plains. 
 The sparing but constant and long-continued supply of lime thus af- 
 forded to soils which rest upon decayed traj), or which are wholly made 
 up of rotten rock, has a material influence upon their well-known agri- 
 cultural capabilities. 
 
 5°. Silicates of Magnesia. — In combination with magnesia in differ- 
 ent proportions, silica forms nearly the entire mass of those common 
 minerals known by the names of serpentine and talc. In hornblende 
 also and augite, silicates of magnesia exist in considerable quantity. 
 
 * So called because the minerals of which they consist are generally mct.crys;allized state. 
 
 t Rocks of wliich the mineral called augite forms a more or less considerable part. 
 
 J I say probably, because if uncomblned silica be present in hay or straw along with car- 
 bonate or oxalate of lime, the heat employed in completely bin^nlng away the organic matter 
 may be sufficient to cause the lime and silica to unite and form a silicate which will after- 
 wards be found in the ash, though none previously existed in the stem. 
 
SILICATES OF ALUMINA. 209 
 
 They must, therefore, be present in greater or less quantity in soils 
 which are directly formed from the decomposition of such rocks. Like 
 the silicates of lime, however — though more slowly than these — they 
 will undergo gradual decomposition by the action of the carbonic acid 
 of the atmosphere, and of the acids produced in the soil by vegetation 
 and by the decay of organic matter. The magnesia, like the lime, will 
 thus be gradually brought down, in a state of solution (p. 200), from the 
 higher grounds, or washed out of the 'soil, till at length it may wholly 
 disappear from any given spot.* 
 
 C°. Silicates of Alumina. — Silica combines with alumina also in vari- 
 ous proportions, forming silicates, which exist abundantly in nature in 
 the crystalline rocks, and may also, like the other silicates, be formed 
 by art. Felspar, mica, hornblende, and the augites, which abound in 
 the trap-rocks, all contain much alumina in combination with silica, and 
 we shall probably not be very far from the truth in assuming that up- 
 wards of one-half by weight of the trap-rocks in general — as well as of 
 the hornblendes, micas, and felspars, of which so large a part of the 
 granitic rocks is composed — consists of silicates of alumina. The alu- 
 mina itself in these several minerals varies from 11 to 38 per cent., but 
 generally averages about 20 per cent, of their entire weight. 
 
 These silicates, when they occur alone, unmixed or uncombined with 
 other silicates, decompose very slowly by the action of the atmosphere. 
 They disintegrate, however, and fall to powder, when the alkaline sili- 
 cates with which they are associated in felspar, &c., are decomposed and 
 removed by atmospheric causes. In tliis way the deposits of porcelain 
 clay, so cominon in Cornwall and in other countries, have been pro- 
 duced from the disintegration of the felspathic rocks, and the clayey soils 
 which occur in granite districts have not unfrequently had a similar origin. 
 
 When contained in the soil, the silicates of alumina undergo a slow 
 decomposi\ion from the action of the various acid substances to which they 
 are exposed. A portion of their alumina is dissolved and separated by 
 these acids, and in this soluble state is either conveyed to the roots of 
 plants or is washed from the soil by the rains — or by the waters that 
 arise from beneath. 
 
 The ash of plants contains only a very small proportion of alumina, 
 yet even this small quantity they cannot derive from the silicates of this 
 substance, since these are all insoluble in water — as alumina itself is. 
 They obtain it, therefore, from some of those soluble compounds of alu- 
 mina of which I have spoken as being either occasionally present (pp. 
 204-5), or as being naturally formed in the soil. 
 
 General remarTcs on these Silicates. — Of all these silicates it may be 
 remarked in general — 
 
 1°. That besides existing in the minerals above-mentioned, and from 
 which they are conveyed into the soil, they are also sloivly formed in the 
 
 ' I am indebted to Sir Charles Lemon for the analysis of a soil, on part of his own proper 
 ty, resting on serpentine, and bearing only Erica vagans, which illustrates the statement in 
 the text. This soil consists of silica 70, alumina with a trace of gypsum 20, oxide of iron 6-2, 
 and vegetable matter 3-8 per cent. If this soil has been formed from the rock on which it 
 rests, the magnesia has been wholly washed out. Its constitution, however, points rather to 
 a decayed felspar or slate rock, as the source from which it has been derived. 
 
210 GENERAL REMARKS ON THESE SILICATES. 
 
 soil itself, when the ingredients of which they severally consist are na- 
 turally present in, or are artificially added to, the soil. Hence, the ad- 
 dition of potash or soda to the land may cause the production of sili- 
 cates of these alkalies — probably soluble silicates — which water will 
 be capable of dissolving and bearing to the extremities of the roots. 
 Hence also, in a sandy soil, the addition of lime may give rise to the 
 production of insoluble silicates of this earth, — and the beneficial eflTect 
 of the lime upon the land may thus sooner cease to be observable than 
 in soils of a diiferent character, where it is not so liable to be locked up 
 in an insoluble state of combination ; and 
 
 2°. That with the exception of those of potash and soda, which con- 
 tain much alkali, these siHcates are all insoluble in water, and thus not 
 directly available to the nutrition of plants. Except thOse of alumina, 
 however, they are all slowly decomposed by atmospheric agents, and 
 their constituent elements thus brought, to a certain extent, within the 
 reach of plants; while, without exception, they are all capable of de- 
 composition in the soil by the agency of the acid substances, chiefly or- 
 ganic, which there exist, or which are produced during the grovvjh and 
 decay of vegetable substances. From this latter source, the chief supply 
 of the ingredients contained in the silicates, is, in most soils, derived by 
 living plants. 
 
 To this cause is attributed the surprising effect often observed to fol- 
 low from the addition of vegetable matter to a sandy soil on which a 
 previous addition of lime had ceased to produce any further beneficial 
 effect. The organic acids formed by the vegetable matter during its de- 
 cay decompose the silicates of lime i)reviously produced, and thus liber.- 
 ate the lime from its insoluble stale of combination. But when the sili- 
 cates have been all decomposed by this agency, the further addition of ve- 
 getable matter ceases necessarily to produce the same remarkable effects. 
 
 XI. THE OXIDES, SULPHURETS, SULPHATES, AND CARBONATES OF IRON. 
 
 1°. Oxides^ Iron. — It is well known that when metallic iron is ex- 
 posed to moist air, it gradually rusts and becomes covered with, or whol- 
 ly changed into, a crumbling ochrey mass of a reddish brown colour. 
 This powder is a compound of iron and oxygen only, containing 69j per 
 cent, of the former, and 30| per cent, of the latter. 
 
 When iron is heated in the smith's forge, and then beat on the anvil, a 
 scale flies off" which is of a black colour, and when crushed gives a black 
 powder. This also consists of iron and oxygen only, but the proportion 
 of oxygen is not so sjreat as in the red powder above described. In both 
 cases the iron has derived its oxygen from the atmosphere. 
 
 To these compounds of iron, with oxygen, the name oi^ oxides is given. 
 There are only two which are of interest to the agriculturist, namely, 
 
 CONSISTING OF 
 
 Iron. Oxyjren. 
 
 Symbol. 
 
 Colour. 
 
 77-23 22-77 
 
 Fe Of 
 
 Black 
 
 69-34 30-66 
 
 Fe,03 
 
 Red. 
 
 The ^rs< oxide* . 
 • The second oxide 
 
 * The first is also called the prot-ojcide, the second either the sesqui, or more usually the 
 oeroxide of iron. 
 
 t Iron is represented by the symbol Fe, the initial letters of its Latin name (ferrum). 
 
THE OXIDES or IRON. 211 
 
 Both of these ex st abundantly in nature, and are present to a greater 
 or less extent in all soils. The second or jogr-oxide, however, is by far 
 the most abundant on the earth's surface, and the reddish colour obser- 
 vable in so' many soils is principally due to the presence of this oxide. 
 
 The first oxide rarely occurs in the soil except in a state of combina- 
 tion w^ith some acid substance, — and so strong is its tendency to combine 
 with more oxygen, that when exposed to the air, even in a state of com- 
 bination, it rapidly absorbs this element from the atmosphere and 
 changes into per-oxide. This change is observable in all chalybeate 
 springs, in which, as they rise to the surface, the iron is generally held 
 in solution in the state of the first oxide. After a brief exposure to the 
 air, more oxygen is absorbed, and a reddish pellicle is formed on the 
 surface, which gradually falls and coats the channel along which the 
 water rnns, with a reddish sediment of insoluble per-oxide. 
 
 Both oxides are insoluble in jiure water, and both dissolve in water 
 containing acids in solution. The first oxide, however, dissolves in 
 much greater quantity in the same weight of acid, and it is the com- 
 pounds of this oxide which are usually present in the soil, and which, in 
 boggy lands, prove so injurious to vegetation.* 
 
 The second oxide possesses two properties which, in connection with 
 ]iractical agriculture, are not void of some degree of importance. 
 
 1°. In a soil which contains much vegetable matter in a slate of de- 
 cay, the per-oxide is frequently deprived of one-third of its oxygen by 
 the carbonaceous matter,f and is thus converted into the first oxide 
 which readily dissolves in any of the acid substances with which it may 
 be in contact. In this state of combination it is more or less soluble in 
 water, and in some localities may be brought to the roots of plants in 
 such quantity as to prove injurious to their growth. 
 
 2°. The red oxide of iron is said, like alumina (p. 197), to have the 
 property of absorbing ammonia, and probably other gaseous substances 
 and vapours, from the atmosphere and from the soil. In that which 
 occurs in nature, either in the soil or near the surface of mineral veins, 
 traces of ammonia can generally be detected. Since then ammonia is 
 so beneficial — according to some so indispensably necessary — to vegeta- 
 tion, the property which the per-oxide of iron possesses of retaining this 
 ammonia when it would otherwise escape from the soil, or of absorbing 
 it from the atmosphere, and thus bringing it within the reach of plants, 
 must also be indirectly favourable to vegetation — where the soil contains 
 it in any considerable quantity. 
 
 An important practical precept is also to be drawn from these two pro- 
 perties of this oxide. A red irony soil, to which manure is added, 
 should be frequently turned over, and should be kept loose and pervious 
 to the air, in order that the formation of prot-oxide" (first oxide) may be 
 
 ' " Tliat layer of soil (says Sprengel), is always especially rich in iron, over which the heel 
 of the plough glides in preparing Ihe land. The friction of the soil continually rubs off Ar- 
 ticles of iron, which absorb oxygen and change into ihe first oxide. Hence this part of the 
 soil is always darker in colour tlian the rest; hence also the reason why the soil after deep 
 ploughing, remains unproductive sometimes for several years." — Chemie, I., p. 4<!8. While 
 we admit tliat the presence of the first oxide of iron in the subsoil affects its fertility, when 
 brought to the surface, we may doubt whether viuch of that iron can have been derived 
 from the tear and wear of the plough. 
 
 t The carbon of the vegetable matter combines with the oxygen of the oxide to form car- 
 bonic acid. — See p. 63. 
 
212 SULPHDRETS, AND SULPHATES OF IRON. 
 
 prevented as much as possible ; and it may occasionally be summer- 
 fallowed with advantage, in order also that the per-oxide may absorb 
 from the air those volatile substances which are likely to prove benefi- 
 cial to the growth of the future crops. 
 
 2°. Sulphurets of Iron. — Iron occurs in nature combined with sulphur 
 in two proportions, forming a sulphuret and a 6i-sulphuret. These 
 
 consist respectively — 
 
 Iron. Sulphur. Symbol. 
 
 The sulphuret . . . 62-77 37-23 Fe S 
 The bi-sulphuret of . 45-74 54-26 Fe 83 
 and are both tasteless and insoluble in water. 
 
 1°. The first of these, the sulphuret (Fe S), occurs occasionally in 
 boggy and marshy soils, in which salts of iron exist, or into which they 
 are carried by rains or springs. It is notitself directly injurious to vege- 
 tation, but wlien exposed to the air it absorbs oxygen and forms sulphate 
 of iron, which, when present in sufficient quantity, is eminently so.* 
 
 2°. The hi- sulphur eU or common iron pyrites (Fe S.), is exceedingly 
 abundant in nature. It occurs in nearly all rocky formations — and in 
 most soils. It abounds in coal, and is the source of the sulphurous smell 
 which many varieties emit while burning. It generally presents itself 
 in masses of a yellow colour and metallic lustre, more or less perfectly 
 cr3'stallized in cubical forms, so brittle and hard as to strike fire with 
 steel, and of a specific gravity four and a half times greater than that of 
 water (Sp. gr. 4, 5). When heated in close vessels it parts with nearly 
 one-half of its sulphur, and hence is often distilled for the sulphur it 
 yields. 
 
 In the air it absorbs oxygen, in some cases — as in the waste coal 
 heaps — with such rapidity as to heat, take fire, and burn. By this ab- 
 sorption of oxygen (oxidation), sulphuric acid and sulphate of iron are 
 produced. In the alum shales the iron pyrites abounds, and these are 
 often burned for the purpose of converting the sulphur and sulphuric 
 acid (or the subsequent manufacture of alum. 
 
 3°. Sulphates of Iron. — Of the sulphates of iron which are known, 
 there is oidyl^ne — the common green vitriol of^ \he shops — that occurs in 
 the soil in any considerable quantity. There are few soils, ])erhaps, in 
 which its presence may not be detected, though it is in bogs and marshy 
 places that it is most generally and most abundantly met with. It is 
 often exceedingly injurious to vegetation in such localities, but it is de- 
 composed by quick-lime, by chalk, and by all varieties of marl, and 
 thus its noxious efi^ecls may in general be entirely prevented. To soils 
 which abound in lime, it may even be applied with a beneficial effect. 
 
 When a solution of this salt is exposed to the air it speedily becomes 
 covered with a pellicle of a yellow ochrey colour, which afterwards falls 
 as a yellow sediment. This sediment consists of ^er-oxide of iron, con- 
 taining a little sulphuric acid ; but by the separation of this oxide the 
 sulphuric acid is left in excess in the solution, which becomes sour, and 
 
 * Yet in small quantity it may be beneficial. Thus Sprengel mentions that the subsoil of 
 a moor near Hanover, which contains some of this sulphuret of iron, i)roduces astonishing 
 eflfects when laid as a top-dressing on the grass lands. The explanation of this is, that the 
 pyrites ab.sorb oxygen and is converted into sulphate, and thus re-produces the remarkable 
 effects observed on the addition of gypsum, of sulphuric acid, or of sulphate ol soda, to simi- 
 lar grass lands. 
 
CARBONATES OF IRON, OXIDES AND SALTS OF MANGANESE. 213 
 
 Still more injurious to vegetation than before. In boe^y places the 
 waters impregnated with iron are generally more or Tess in this acid 
 state, and lirae, chalk, and marl, with perfect drainage, are the only 
 available means by which such lands can be sweetene'd and rendered 
 fertile. 
 
 When iron pyrites is exposed to the air it slowly absorbs oxygen, and is 
 converted into sulphate of iron and sulphuric acid ; on the other hand, the 
 sour solution above mentioned, when placed in contact with vegetable 
 matter, where the air is excluded, parts with its oxygen to the decayino- 
 carbonaceous matter, and is again converted into iron pyrites. These 
 two opposite processes are both continually in progress in nature, and 
 often in the same locality, — the one on the surface, where air is present ; 
 the other in the subsoil, where the air is excluded. 
 
 4°. Carbonates of Iron. — When a solution of the sulphate of iron, 
 above described, is mixed with one of carbonate of soda, a yellow powder 
 falls, which is carbonate of iron. This carbonate is found abundantly in 
 nature. It is the state in which the iron exists in the ore (clay-iron ore,) 
 from which this metal is so largely extracted in our iron furnaces, and 
 in the similar ore often found in the subsoil of boggy places, whi^h is 
 distinguished b^' the name of bog-iron ore. 
 
 Like the carbonate of lime, it is insoluble in water, but dissolves with 
 considerable readiness in water charged with carbonic acid. In this 
 Slate of solution it issues from the earth in most of our chalybeate springs, 
 and it is owing to the escape of the excess of carbonic acid from the 
 water, when it reaches the open air, that the yellow deposit of carbonate 
 of iron more or less speedily falls. 
 
 The carbonate of iron, being insoluble in water, cannot be directly in- 
 jurious to vegetation. When exposed to the air it gradually parts with 
 its carbonic acid, and is converted into per-oxide of iron. 
 
 The ash of nearly all plants contains a more or less appreciable quan- 
 tity of oxide of iron. This may have entered into the roots either in the 
 state of soluble sulphate or of carbonate dissolved in carbonic acid, or of 
 some other of those numerous soluble compounds of iron with organic 
 acids, which may be expected to be occasionally present in the soiL 
 
 XII. MANGANESE ; OXIDES, CHLORIDES, CARBONATES, AND SULPHATES 
 
 OF MANGANESE. 
 
 ^ 1°. Manganese is a metal which, in nature, is very frequently asso- 
 ciated with iron in its various ores. It alsp resembles this metal in 
 many of its properties. In the metallic state, however, it is not an ob- 
 ject of manufacture, nor is it used for any purpose in the arts. 
 
 2°. Oxides of Manganese. — Manganese combines with oxygen in 
 several proportions. The first oxide is of a light green colour, the se- 
 cond and third are black. The first is not knownto occur in nature in 
 an uncombined state, the two others exist abundantly in the common 
 ores of manganese, and are extensively diffused, though in small quan- 
 tity, through nearly all soils. They are all insoluble'in water, but the 
 two former dissolve in acids and form salts. Traces of these two oxides 
 are also to be detected in the ash of nearly all plants. 
 • 3°. Chloride, Carbonate, and Sulphate of Manganese. — If any of 
 
214 
 
 COMPOSITION OF THE OXIDES AND CHLORIDES. 
 
 these oxides be dissolved in muriatic acid a solution of chloride of man-, 
 ganese will be obtained. 
 
 If this solution of chloride of manganese be mixed with one of car-^ 
 bonate of soda, a white insoluble powder will fall, which is carbonate of, 
 maganese. 
 
 If this carbonate be dissolved in diluted sulphuric acid, or if any of 
 the oxides be digested in this acid, a solution of sulphate of manganese 
 will be formed. 
 
 The carbonate of manganese, and its oxides, will also dissolve, though 
 more slowly, in acetic acid (vinegar), and in other organic acids which 
 may be present in the soil, and will form with them other soluble 
 salts. 
 
 The compounds of manganese exist in plants in much less quantity 
 than those of iron; but as its oxides, like those of iron, are insoluble in 
 pure water, this metal most likely finds its way into the state of one 
 or other of tke soluble compounds above described. 
 
 § 2. Tabular view of the constitution of the compounds of the inorganic 
 ^ elements above described. 
 
 Having in the preceding section briefly described the several compounds 
 of the inorganic elements of plants, which either enter into the constitution 
 of vegetable substances, or are supposed to minister to their growth — it 
 may prove useful hereafter, if I exhibit at one view the composition per 
 cent, of the various oxides, chlorides, sulphurets, and oxygen-acid salts,* 
 to which I have had occasion to direct your attention. 
 
 We shall have occasion to refer to the numbers in the following tables 
 in our subsequent calculations. 
 
 1°. — Oxygen per cent, in the oxides of the inorganic elements. 
 
 Oxygen 
 per cent. 
 Sulphurous Acid . . . 49*85 
 Sulphuric Acid . . . 59*86 
 Phosphoric Acid . . . 56*04 
 Potash .~7 . . . . 16-95 
 
 Soda 25*58 
 
 Lime 28*09 
 
 Magnesia 38*71 
 
 Alumina 
 
 Silica 
 
 Prot-oxide of Iron . . 
 Per-oxide of Iron . 
 Prot-oxide of Manganese 
 Sesqui-oxide do. . . 
 Per-oxide do. . . 
 
 Oxygen 
 
 per cent. 
 
 46*70 
 
 51-96 
 
 22-77 
 30-66 
 22-43 
 30-25 
 36*64 
 
 OO. 
 
 ■Chlorine or Sulphur per cent, in the chlorides and sulphurets. 
 
 Chloride of Potassium 
 
 ■ Sodium 
 
 Calcium 
 
 Magnesium 
 
 First Chloride of Iron 
 Second do. do. 
 
 Chlorine 
 per cent. 
 47*47 
 60*34 
 63*38 
 73-65 
 56*62 
 66*19 
 
 Sulphurel of Potassium 
 
 Sodium 
 
 ; Calcium . . 
 
 Iron . . . 
 
 Bi-Sulphuret of Iron, 
 (Iron Pyrites) . 
 
 Sulphur 
 per cent. 
 29*11 
 40*88 
 44*00 
 37-23 
 
 47-08 
 
 * So called because the acid they contain has oxygen for one of its constituenta 
 
COMPOSITION OF THE SALINE COMPOUNDS. 
 
 215 
 
 . — Cwnposition per cent, of the Saline combinations above described. 
 
 1 
 
 Acid. 
 
 31-91 
 
 Base. 
 68-09 
 
 Water, j 
 
 Carbonate of Potash 
 
 • j 
 
 Bi-carbonate of do. ... 
 
 48-38 
 
 51-62 
 
 
 Sulphate of do. ... 
 
 45-93 
 
 54-07 
 
 
 Nitrate of do. ... 
 
 53-44 
 
 46-56 
 
 
 Binoxalate of do. (Salt of sorrel) . 
 
 52-64 
 
 34-29 
 
 13-07 
 
 Bitartrate of do. (Cream of tartar) 
 
 70-28 
 
 24-96 
 
 4-76 
 
 Phosphate of do. ... 
 
 43-06 
 
 56-94 
 
 
 Bi-phosphate of do. 
 
 60-20 
 
 39-80 
 
 
 Carbonate of Soda (dry) . 
 
 41-42 
 
 58-58 
 
 
 (crystaUized) 
 
 15-43 
 
 21-81 
 
 62-76 
 
 Bi-carbonate of Soda 
 
 58-58 
 
 41-42 
 
 
 Nitrate of do. 
 
 63-40 
 
 36 60 
 
 
 Sulphate of do. (dry) 
 
 56-18 
 
 43-82 
 
 
 
 24-85 
 
 19-38 
 
 55-77 
 
 
 Phosphate of do. . . 
 
 53-30 
 
 46-70 
 
 
 Bi-phosphate of do. . . . '^ 
 
 69-54 
 
 30-46 
 
 
 Carbonate of Lime .... 
 
 43-71 
 
 56-29 
 
 
 Sulphate of do. (Gypsum) . 
 
 46-31 
 
 32-90 
 
 20-79 
 
 (burned) 
 
 ^•47 
 
 41-53 
 
 
 Nitrate of Lime .... 
 
 65-54 
 
 34-46 
 
 
 Phosphate of Lime (Apatite) . 
 
 45-52 
 
 54-48 
 
 
 Bi-phosj)hate of Lime 
 
 71-48 
 
 28-52 
 
 
 Earth of Bones .... 
 
 48-45 
 
 51-55 
 
 
 Carbonate of Magnesia 
 
 51-69 
 
 48-31 
 
 
 Bi-carbonate of do. 
 
 68-15 
 
 31-85 
 
 
 Sulphate of do. (Epsom salts) . 
 
 32-40 
 
 16-70 
 
 50-90 
 
 Nitrate oi' do. ... 
 
 72-38 
 
 27-62 
 
 
 Phosphate of do. ... 
 
 63-33 
 
 36-67 
 
 
 Sulphate of Alumina 
 
 70-07 
 
 29-93 
 
 
 Phosphate of do. 
 
 ♦ 
 
 67-57 
 
 32-43 
 
 
 Silicate of Potash (soluble) 
 
 49-46 
 
 50-54 
 
 
 Bi-siHcate of do. (do.) 
 
 66-19 
 
 33-81 
 
 
 Silicate of Soda (do.) 
 
 59-63 
 
 40-37 
 
 
 Bi-silicate of do. (do.) 
 
 74-71 
 
 25-29 
 
 
 Silicate of Lime . . . 
 
 61-85 
 69-08 
 
 38-15 
 30-92 
 
 
 
 
 Alumina .... 
 
 72-95 
 
 27-05 
 
 
 Carbonate of Iron . . . 
 
 38-63 
 
 61-37 
 
 
 Sulphate of do. (crystallized) 
 
 31-03 
 
 27-1& 
 
 41-78 
 
 Carbonate of Manganese . 
 
 38-27 
 
 61-73 
 
 
 Sulphate of do.. (crystallized) 
 
 33-20 
 
 29-54 
 
 37-26 
 
216 COMPOSITION OF THE ASH OF WHEAT AND OF BARLEY. 
 
 § 3. On the relative proportions of the different inorganic compounds 
 present in the ash of plants. 
 
 Having thus made you acquainled with the general properties and 
 composition of the several compound substances of which the ash of 
 plants consists, we now advance to the consideration of the relative ])ro- 
 portions in which these substances exist in the ash of the different kinds 
 of plants usually cultivated for food. 
 
 We have seen (p. 178) that difTerent species of plants leave very dif- 
 ferent quantities of ash when burned ; — the ash left by different species 
 contains also the above earthy and saline substances in very unlike pro- 
 portions. This fact has already been stated generally (j). 180) ; we are 
 now to illustrate it more fully, and -to show the important practical de- 
 ductions to which it leads. 
 
 I. OF THE ASH OF WHEAT. 
 
 According to. the analysis of Sprengel, 1000 lbs. of wheat leave 11*77 
 
 lbs., and of wheat straw 35-18 lbs. of ash, consisting of — 
 
 Grain of Straw of 
 
 Wheat. Wheat. 
 
 Potash 2-25 lbs. 0-20 lbs. 
 
 Soda 2-40 0-29 
 
 Lime 0-96 2-40 
 
 Magnesia ^ 0-90 0-32 
 
 Alumina, with a trace of Jroa 0*26 0-90 
 
 Silica 4-00 28'70 
 
 Sulphuric Acid .... 0-50 0-37 
 
 Phosphoric Acid .... 0-40 1-70 
 
 Chlorine 0-10 0-30 
 
 11-77 lbs. 35-18 lbs. 
 If the })roduce of a field be at the rate per acre of 25 bushels of 
 wheat, eacii^Olbs,, and if the straw* be equal to twice the weight of 
 the grain, the quantity of each reaped per acre will be 
 
 Grain . . . 1500 lbs. } r. ^ ror i l i 
 
 Straw . . . 3000 lbs. I ^''^"^ ^ P™^"^^ "^-^ ^"^'^^^^' 
 so that the quantity of the different inorganic corai)Ounds carried oS'from 
 the soil of each acre will be, in the grain i more than is represented in 
 the second column, and in the straw 3 times as niuch as is represented 
 in the third column. 
 
 II. — or THE ASH OF BARLEY. 
 
 A thousand pounds of the grain of barley (two-rowed, hordeum disti- 
 chon,) leave 23i lbs., and of the ripe dry straw 52-42 lbs. of ash. This ash 
 consists of — 
 
 * The proportion of the straw to the seed in grain of all kinds is very variable. In wheat 
 if is said to average twice the weight of the gi'ain, but it is very often, even in heavy crops, 
 3 to 3>^ times that weight. 
 
OF THE ASH OF OATS. 217 
 
 Grain. Straw. 
 
 Potash 2-78 lbs. 1-80 lbs. 
 
 Soda 2-90 0-48 
 
 Lime 1-06 5-54 
 
 Magnesia 1-80 0-76 
 
 Alumina 0-25 1*46 
 
 Oxide of Iron. . . . a trace. 0*14 
 
 Oxide of Manganese . — 0*20 
 
 Silica 11-82 38-56 
 
 Sulphuric Acid . . . 0-59 1-18 
 
 Phosphoric Acid . . 2-10 1-60 
 
 Chlorine 0-19 0-70 
 
 23-49 lbs. 52-42 lbs. 
 If the produce of a crop of barley amount to 38 bushels of 63 lbs. each 
 per acre, and the straw exceed the grain in weight one-sixth, the weight 
 of each reaped per acre will be about 
 
 2000 lbs. of grain, / ^ , r oo u x, i 
 
 2300 lbs. of straw, \ ^^"""^ ^ P'"^^"^^ ^^^^ ^"^^^^^ ' 
 and the inorganic matters carried off from the soil by each will be ob- 
 tained by multiplying those contained in the second column (above) by 
 2, and in the third by 2^. 
 
 III. OF THE ASH OF OATS. 
 
 In 1000 lbs. of the grain of the oat are contained about 26 lbs., and of 
 
 the dry straw about 57i lbs. of inorganic matter, consisting of — 
 
 Grain. Straw. 
 
 Potash 1-50 lbs. 8-70 lbs. 
 
 Soda 1-32 0-02 
 
 Lime 0-86 1*52 
 
 Magnesia 0-67 0-22 
 
 Alumina 0-14 0-06 
 
 Oxide of Iron 0-40 0-02 
 
 Oxide of Manganese . 0-00 0-02 
 
 Silica 19-76 45-88 
 
 Sulphuric Acid . . . 35 0-79 
 
 Phosphoric Acid. . . 0-70 0-12 
 
 Chlorine 0-10 0-05 
 
 25-80 lbs. 57-40 lbs. 
 If an acre of land yield 50 bushels, each 54 lbs., of oats, and two-thirds* 
 nQore in weight of straw, there will be reaped per acre, 
 Of grain 2250 lbs., ) r- j rm u t. i 
 
 Of straw 3750 lbs., \ ^'"""^ ^ P''°^"^^ °^^^ bushels; 
 and the weight of the inorganic matters carried off will be equal to 2i 
 times the quantities contained in the second column, and 3| times those 
 contained in the third column. 
 
 * Of all kinds of grain, the oat gives the most variable proportion of straw, that which is 
 obtained at one lime, and in one locality, being two or three times greater than that reaped 
 in anotiier. 
 
 10 
 
218 
 
 ASH OF RTE, BEANS, PEAS, AND VETCHES. 
 
 IV. OF THE ASH OF RYE. 
 
 The weight of ash contained in 1000 lbs. of the grain of rye is 10^ 
 and of the straw 28 lbs. This ash consists of 
 
 Grain. Straw. 
 
 Potash ^ .^.^ ,. ^ 5 0-32 lbs. 
 
 Soda I ^^^^^'' J 0-11 
 
 Lime 1-22 1-78 
 
 Magnesia 1-78 0-12 
 
 Alumina 0-24 ) j^.^c 
 
 Oxide of Iron. . . . 0-42 ^ 
 
 Oxide of Manganese . 0-34 — 
 
 Silica 1-64 22-97 
 
 Sulphuric Acid . . . 0-23 1-70 
 
 Phosphoric Acid . I 0-46 0*51 
 
 Chlorine 0-09 0-17 
 
 lbs., 
 
 10-40 lbs. 27-93 lbs. 
 Rye is remarkable for the quantity of straw it yields, which is often 
 from 3 to 4 times the weight of the grain. The return in grain reaches 
 about the same average as that of wheat. From an acre of land yield- 
 ing a crop of 25 bushels, each 54 lbs., there would be reaped 
 
 Of grain 1350 lbs. ; of straw 4000 lbs. ; 
 the whole weight of inorganic matters contained in which is equal to ^- 
 niore than is represented in the second column, added to 4 times the weights 
 contained in the third column. 
 
 V. OF THE ASH OF BEANS, FEAS, AND VETCHES. 
 
 The ash of the seed and straw of the field bean, the field pea, and the 
 common vetch {vicia sativa,) dried in the air, contains in 1000 lbs. the 
 several inorganic compounds in the following proportions : 
 
 
 FIELI 
 
 ) BEAN. 
 
 FIELr 
 
 ( PEA. 
 
 A 
 
 COMMON 
 
 A 
 
 VETCH. 
 
 
 Seed. 
 
 Straw. 
 
 Seed. 
 
 Straw. 
 
 Seed. 
 
 Straw. 
 
 Potash .... 
 
 4-15 
 
 16-56 
 
 8-10 
 
 2-35 
 
 8-97 
 
 18-10 
 
 Soda 
 
 8-16 
 
 0-50 
 
 7-39 
 
 — 
 
 6-22 
 
 0-52 
 
 Lime .... 
 
 1-65 
 
 6-24 
 
 0-58 
 
 27-30 
 
 1-60 
 
 19-55 
 
 Magnesia . . . 
 
 1-58 
 
 2-09 
 
 1-36 
 
 3-42 
 
 1-42 
 
 3-24 
 
 Alumina . . . 
 
 0-34 
 
 0-10 
 
 0-20 
 
 0-60 
 
 0-22 
 
 0-15 
 
 Oxide of Iron . 
 
 — 
 
 0-07 
 
 0-10 
 
 0-20 
 
 0-09 
 
 0-09 
 
 Oxide of Manganese 
 
 ! 
 
 0-05 
 
 — 
 
 0-07 
 
 0-05 
 
 0-08 
 
 Silica .... 
 
 1-26 
 
 2-20 
 
 4-10 
 
 9-96 
 
 2-00 
 
 4-42 
 
 Sulphuric Acid 
 
 0-89 
 
 0-34 
 
 0-53 
 
 3-37 
 
 0-50 
 
 1-22 
 
 Phosphoric Acid . 
 
 2-92 
 
 2-26 
 
 ]-90 
 
 2-40 
 
 1-40 
 
 2-80 
 
 Chlorine . . . 
 
 0-41 
 
 0-80 
 
 0-38 
 
 0-04 
 
 0-43 
 
 0-84 
 
 21-36 31-21 24-64 49-71 22-90 51-01 
 On comparing the numbers in these columns, we cannot fail to remark, — 
 1°. How much potash there is in the straw of the beau and the vetch. 
 2°. That while there is only a trace of soda in any of the three straws, 
 there is a considerable quantity in all the seeds. 
 
ASH OF THE TURNIP, CARROT, PARSNIP, AND POTATO. 219 
 
 3'^. How large a proportion of lime exists in the strmo of the pea and 
 of the vetch — compared with that of the bean — and how much larger the 
 proportion is in all the straws than in any of the grains — and 
 
 4°. That the quantity of sihca in pea straw is double of what is con- 
 tained in tlie straw of the vetch, and 4 times that of the bean straw. 
 
 The produce of straw from these three varieties of pulse is very bulky, 
 but varies in weight from 1 to 1^ tons — or is on an average about 2300 
 lbs. per acre. The produce of grain is still more variable. 
 
 The bean gives from 16 to 40 bushels, of about 63 lbs. 
 
 The pea . . 12 to 84 " " 64 lbs. 
 
 The vetch . . 16 to 40 " " 66 lbs. 
 
 The mean return from beans is estimated by Schwertz [Anleitung 
 Zum Praklischen Ackerbau, II., p. 346,] at 25 bushels (1600 lbs.), from 
 peas at 15 bushels (1000 lbs.), and from vetches at 17 bushels (1100 
 lbs.) per acre. 
 
 The quantify of the several inorganic matters, therefore, carried off 
 from an acre in the straw of these crops, will be about 2^ limes the 
 weights given in the table — and in the grains, wh"tre the crop is near 
 the above average, 1| times the weights in the tables for beans and for 
 peas, and for vetches very nearly the actual weights above given. 
 
 VI. OF THE ASH OF THE TURNIP, CARROT, PARSNIP, AND POTATO. 
 
 These four roots, as they are carried from the field, contain respective 
 ly in ten thousand pounds — 
 
 TURNIP. CARROT. PARSNIP. POTATO. 
 
 Roots. Leaves. Roots. Tops. 
 
 Potash . . . 23-86 32-3 35-33 20-79 40-28 81-9 
 
 Soda .... 10-48 22-2 9-22 7-02 23-34 0-9 
 
 Lime .... 7-52 62-0 6-57 4-68 3-31 129-7 
 
 Magnesia . . . 2-54 5-9 3-84 2-70 3-24 17-0 
 
 Alumina . . . 0-36 0-3 0-39 0-24 0-50 0-4 
 
 Oxide of Iron. . 0-32 1-7 0-33 0-05 0-32 0-2 
 
 Oxide of Manganese — — 0-60 — — — 
 
 Silica .... 3-88 12-8 1-37 1-62 0-84 49-4 
 
 Sulphuric Acid . 8-01 25-2 2-70 1-92 5-40 4-2 
 
 Phosphoric Acid . 3-67 9-8 5-14 1-00 4-01 19-7 
 
 Chlorine . . . 2-39 8-7 0-70 1-78 1-60 5-0 
 
 63-03 180-9 66-19 41-80 82-83 308-4 
 
 These roots, as already stated (note, p. 178), contain very much water, 
 so that, in a dry state, the pro2?or^?on of inorganic matter present in them 
 is very much greater than is represented by the above numbers. I 
 have, however, given the quantities contained in the crop as it is carried 
 from the field, as alone likely to be of practical utility. 
 
 The crops of these several roots vary very much in different localities, 
 being in some places twice and even thrice as much as in others — every 
 nine tons, however, which are carried off the ground, contain about 
 twice the weight of saline and earthy matters indicated by the numbers 
 in the table. 
 
220 ASH or THE GRASSES AND CLOVERS. 
 
 VII. OF THE ASH OF THE GRASSES AND CLOVERS. 
 
 The following table might have been much enlarged. I have 
 thought it necessary, however, to- introduce in this place only those 
 species of grass and clover which are in most extensive use. I have 
 also calculated the weights given below, for these plants in the stxite of 
 hay only, as the succulency of the grasses, — that is, the quantity of wa- 
 ter contained in the green crop, — varies so much that no correct esti- 
 mate could be made of the quantity of inorganic matter present in hay 
 or grass, from a knowledge of its weight in the green state only : 
 
 
 Rye Grass 
 
 Red 
 
 White 
 
 
 
 
 Hay. 
 
 Clover. 
 
 Clover. 
 
 Lucerne. 
 
 Sainfoin. 
 
 Potash .... 
 
 8-81 
 
 19-95 
 
 31-05 
 
 13-40 
 
 20-57 
 
 Soda 
 
 3-94 
 
 5-29 
 
 5-79 
 
 6-15 
 
 4-37 
 
 Lime .... 
 
 7-34 
 
 27-80 
 
 23-48 
 
 48-31 
 
 21-95 
 
 Magnesia . . 
 
 0-90 
 
 3-33 
 
 3-05 
 
 3-48 
 
 2-88 
 
 Alumina . . 
 
 0-31 
 
 0-14 
 
 1-90 
 
 0-30 
 
 0-66 
 
 Oxide of Iron . 
 
 — 
 
 — 
 
 0-63 
 
 0-30 
 
 — 
 
 Oxide of Manganese 
 
 -— 
 
 — 
 
 — 
 
 — 
 
 — 
 
 Silica .... 
 
 27-72 
 
 3-61 
 
 14-73 
 
 3-30 
 
 5-00 
 
 Sulphuric acid . . 
 
 3-63 
 
 4-47 
 
 3-53 
 
 4-04 
 
 3-41 
 
 Phosphoric acid . 
 
 0-25 
 
 6-57 
 
 5-05 
 
 13-07 
 
 9-16 
 
 Chlorine .... 
 
 0-06 
 
 3-62 
 
 2-11 
 
 3-18 
 
 1-57? 
 
 52-86 74-78 91-32 95-53 69-57 
 
 The above quantities are contained in a thousand pounds of the dry 
 hay of each plant. 
 
 On comparing the numbers opposite to potash, lime, magnesia, alu- 
 mina, silica, and ])hosphoric acid, we see very striking differences in 
 the quantities of these substances contained in equal weights of the 
 above different kinds of hay. These differences lead to very important 
 practical inferences in reference, — 
 
 1°. To the kind of soil in which each will grow most luxuriantly. 
 
 2°. To the artificial means by which the growth of each may be pro- 
 moted — in so^ar as this growtli depends upon the supply of inorganic 
 food to the growing plant. 
 
 3°. To the feeding properties of each, and to the kind of stock they 
 are severally most fitted to nourish. 
 
 To these and other important practical deductions suggested by the 
 above tabulated analyses — as well as by those ])reviously given — of the 
 inorganic matters contained in the several varieties of vegetable produc- 
 tions usually raised for food, we sliall hereafter have frequent occasion 
 to revert. In the mean time, a preliminary inquiry demands our at- 
 tention, which we shall proceed to consider in the following section. 
 
 § 4. To ivhat extent do the crops most usually cultivated, exhaust the soil 
 of inorganic vegetable food? 
 
 A bare inspection of the tabular results exhibited in the preceding 
 section gives but a faint idea of the extent to which the inorganic ele- 
 mentary bodies are necessarily withdrawn from the soil in the ordinary 
 course of cropping. 
 
EFFECT OF A THREE YEARS' COURSE OF CROPPING. 221 
 
 I. Let US consider the effect upon the soil of a still too common three 
 years' course of cropping— ^«^/o?^, ivheat, oals.* If the produce of such 
 a course be 25 bushels of wheat and 50 busliels of oats, there would be 
 carried from the soil every three years in pounds — 
 
 WHEAT. OATS. 
 
 , ' , , ^ , Total. 
 
 Grain. Straw. Grain. Straw. 
 
 Potash .... 3-3 0-6 3-75 32-7 40-35 
 
 Soda 3-5 0-9 3-3 — 7-7 
 
 Lime 1-5 7-2 2-5 5-7 16-9 
 
 Magnesia. ... 1-5 1-0 1-7 0-8 5-0 
 
 Oxide of Iron . . — — 1-0 — 1-0 
 
 Silica 6-0 86-0 50-0 172-0 314-0 
 
 Sulphuric Acid . . 0-75 1-0 0-9 3-0 5-65 
 
 Phosphoric Acid . 0-6 5-0 1-43 0-5 7-53 
 
 398-13 
 
 The gross weight carried off in these crops is large — amounting to 
 about 400 lbs. It will vary, however, with ihe kind of wheat and oats 
 which are grown, and may often be greater than this. — [See the follow- 
 ing section (§ 5) of the present Lecture.] The greatest portion of the 
 matter carried off, however — upwards of three-fourths of the whole — 
 consists of silica; the rest of the materials are equal to 
 60 lbs. of dry pearl-ash, 
 36 lbs. of the common soda of the shops, 
 28 lbs. of bone-dust, 
 12 lbs. of gypsum, 
 ' 5 lbs. of quick-lime, 
 
 5 lbs. of magnesia, — or for the last three may be substi- 
 tuted 33 lbs. of common Epsom salts and 17 lbs. of quick-lime. 
 
 The form in which the silica may be restored to the soil in a state in 
 which the plant can absorb it, will be considered hereafter. 
 
 Though large as a whole, the weight of each of the ingredients, taken 
 singly, is not great; and yet it is not difficult to understand that if a 
 constant drain be kept up on the soil year after year, and the practical 
 farming adopted is of such a kind as not to restore to the soil a due pro- 
 portion o^ each of the substances carried off— the time must come when, 
 under ordinary circumstances, the soil will no longer be able to supply 
 the demands of a healthy and luxuriant vegetation. 
 
 II. Let us next consider the effect of a four-years' course system in 
 withdrawing these inorganic substances from the soil. And for this 
 purpose let us adopt one suited to the lighter soils — as to that of Norfolk — 
 turnijJs, barley, clover and rye grass, wheat. 
 
 Let the crop of turnips amount to 25 tons of roots per acre, of barley to 
 38 bushels, of clover and rye grass each to one ton of hay, and of wheat 
 as before to 25 bushels. Then we have from the entire rotation in 
 pounds — 
 
 • Common, among other counties, in that of Durham. There are cases, however, in 
 which this three years' course may not be indefensible, and it never could be compared with 
 some of the so-called improved rotations in East Lothian in the time of Lord Kames; as for 
 instance, /c/Zoju, barley, clover, manure on the clover stubble, then wheat, barley, oats.— See 
 The Gentleman Farmer (1802), p. 147. 
 
222 EFFECT OF A FOUR-YEARS' COURSE. 
 
 BARLEY. WHEAT. 
 
 Tumip . ' . Red Rye , ' . Total. 
 
 Roots. Grain. Straw. Clover. Grass. Grain. Straw. 
 
 Potash ..... 145-5 5-6 4-5 45-0 28-5 3-3 0-6 233-0 
 
 Soda 64-3 5-8 1-1 12-0 9-0 3-5 0-9 96-6 
 
 Lime 45-8 2-1 12-9 63-0 16-5 1-5 7-2 149-0 
 
 Magnesia. . . . 15-5 3-6 1-8 7'5 2-0 1-5 1-0 32-9 
 
 Alumina .... 2-2 0-5 3-4 0-3 0-8 0-4 2-7 10-3 
 
 Silica 23-6 23-6 90-0 8-0 62-0 6-0 860 299-2 
 
 Sulphuric Acid . 49-0 1-2 2-8 10-0 8-0 0-8 1-0 72-8 
 
 Phosphoric do. . 22-4 4-2 3-7 15-0 0-6 0-6 5-0 51-5 
 
 Chlorine .... 14-5 0-4 1-5 8-0 0-1 0-2 09 256 
 
 970-9* 
 
 On comparing the numbers in the last column — containing the total 
 quantity of matter ahstracted — with those contained in the three years' 
 rotation (p. 221), we see liow very much larger an addition must be 
 made to the land every fourth year, if we are to restore to it any thing 
 like an equivalent for the inorganic matter carried off. 
 
 It will be especially observed that the quantity of potash, and of soda, 
 and indeed of nearly every ingredient except the silica, carried off in 
 this course of cropping, is much greater, even in proportion to the time 
 it occupies, than in the three-year shift — and that ni7ie-tentJis of the pot- 
 ash and soda loithdraivn from the soil are contained in the green crops. 
 
 To place the relative effect of the green and corn crops upon the soil 
 in a clearer light, I shall exhibit the several quantities of common and 
 artificial salts and manures which it would be necessary to add to each 
 acre at the beginning of this rotation, in order to supply the various inor- 
 ganic substances about to be taken from the land in the next four years' 
 cropping. These quantities are as follow, in pounds : — 
 
 For the For the 
 
 Total. Green Crops. Corn Crops. 
 
 Dry Pearl-ash 325 316 9 
 
 Crystallized Carbonate of Sodaf 333 290 43 
 
 CommotrSalt 43 38 5 
 
 G3'psum — 30 — 
 
 Quick-hme 150 100 7 
 
 Epsom Salts 200 150 50 
 
 Alum 83 27 56 
 
 Bone-dust 210 150 60 
 
 With the exception of the silica, the substances above-named, in the 
 quantities given, will replace all the inorganic matters contained in the 
 whole crop reared, the turnip tops alone not included. A single glance 
 at the second and third columns shows how much greater a proportion 
 of all these substances is necessary to return what the green crops have 
 taken from the land. 
 
 That the fertihty of the soil depends in some considerable degree on 
 
 • This is exclusive of the turnip tops, which I have omitted, from not knowing what pro- 
 portion their weight in the green state generally bears to that of the roots. 
 
 t Or for every 100 lbs. of the common carbonate of soda may be substituted 40 lbs. of 
 common salt or 60 Iba. of dry nitrate of soda. 
 
WHY WHEAT PREFERS A HEAVY SOIL. 223 
 
 t'le quantity of the alkaline and other compounds present in it, there can 
 be HO question, — since not only do we find extraordinary natural luxuri- 
 ance of vegetation where some of these happen to be present in the soil, 
 but we can often greatly increase the apparent productiveness of our 
 fields by spreading such substances over them in sufficient quantity. 
 
 How comes it, then, that the green crops which carry oflT all these 
 substances in the greatest quantity by very much, should yet least injure 
 the land, — nay, should rather renew and prepare it again for the growth 
 of crops of corn ? 
 
 This is one of the most interesting practical questions which can pre- 
 sent itself to us in the existing state of theoretical agriculture ; — but it 
 would carry us away from our more immediate object, were we prema- 
 turely to enter upon the discussion of it in this place. It will hereafter 
 demand our especial attention, when we shall have become familiar 
 with the nature and origin of soils. 
 
 I may be permitted, however, to draw your attention here for a mo- 
 ment — as neither out of place, nor uninteresting, for many reasons, — to 
 an opinion expressed by Liebig on the question luhy wheat prefers stiff 
 and clayey soils. " Again," he says, "liow does it happen that wheat 
 docs not iSiourish in a sandy soil, and that a calcareous soil is also un- 
 suitable for its growth, unless it be mixed with a considerable quantity 
 of clay? It is because these soils do not contain alkalies insufficient 
 quantity, the growth of wheat being arrested by this circumstance, even 
 should all other substances be presented in abundance." — [Organic 
 Clieynistry a^jplied to Agriculture, p. 151,] 
 
 Without dwelling on the fact that excellent crops of wheat are reaped 
 in some parts of our island from sandy and calcareous* soils — what kind 
 of crops, we may ask, can be reared with success on the lighter soils to 
 which wheat seems least adapted ? The turnip rejoices in light land, 
 and the potato not unfrequently attains the greatest perfection on a sandy 
 soil. Yet ten tons of potato roots, or twenty of turnip bulbs, — exclu- 
 sive of the tops — contain nearly ten times as much of the two alkalies, 
 potash and soda, as fifty bushels of wheat with its straw included. f 
 What ground is there, then, for the explanation given by Liebig — of the 
 peculiar qualities of the so-called wheat lands ? We might with far 
 greater show of reason assume the converse of his proposition, and infer 
 that wheat does not prefer sandy soils, because they are too rich in alkali! 
 It is singular, and would almost seem to strengthen this converse propo- 
 sition, that beans, peas, and vetches, which are so often resorted to as a 
 good preparative for wheat, contain also a much larger quantity of alkali 
 than the latter grain. Thus the grain and straw together of twenty-six 
 bushels of beans contain 71 lbs., of twenty bushels of peas 26 lbs.*, and 
 of twenty bushels of vetches 74 lbs. of potash and soda taken together. 
 
 As I have already stated, however, we are not yet prepared for dis- 
 cussing this very curious and interesting question. 
 
 * On the thin chalk soils of the Yorlrshire Wolds a crop of wheat is tiaken every four or 
 five years, yielding an avereige of 34 or 25 bushels. The rotation is turnips, barley, clover or 
 beans, wheat. 
 
 t According to the analyses of Sprengel given in the previous pages, ten tons of potatoes 
 contain 143 lbs. of alkalies, twenty tons of turnips 154 lbs., and fifty bushels of wheat with 
 its straw only 16 lbs. 
 
224 ARE THE INORGANIC CONSTITUENTS REALLY CONSTANT ? 
 
 § 5. Of the alleged constancy of the inorganic constituents of plants^ in 
 
 kind and quantity. 
 
 In the preceding lecture (Ix., p. 177), it was stated that the ash of the 
 same plant, if ripe and healthy, is nearly the same in kind and quality 
 in whatever circumstances (if favourable) of soil and climate it may 
 grow. This general observation, however, is consistent with certain 
 differences in the above respect, which are not without interest in their 
 bearing upon agriculture both in theory and j)ractice. Thus, 
 
 1°. The different parts of the same plant contain quantities of inor- 
 ganic matter, not only different in their gross weights, but unlike also in 
 the relative proportions of the several substances of whicli the entire ash 
 consists. Both of these points liave been previously illustrated (pp. 179, 
 180), and they are placed in the clearest light by the tabulated analyses 
 introduced into tiic ])receding section. 
 
 2°. The quantity and relative proportions of the different inorganic 
 substances also vary with the season of the year at which the examina- 
 tion is made. Thus, according to De Saussure, plants of the same wheat 
 whicli a month before flowering left 7-9 per cent, of ash, left when in 
 flower only 5*4, and when ripe 3'3 ]ier cent. The quantity of potash 
 in the potato leaf diminishes very nmch as the plant approaches to ma- 
 turity (MoUerat) — and the same has been observed in many saltworts 
 and other sea-side plants. In the young plant of the salsola clavifolia 
 there is much potash and no soda, but as its age increases the latter alkali 
 appears, and gradually takes the place of the former.* 
 
 It is probably true, therefore, of all plants — that the ash both in kind 
 and quantity is affected by the age at which the plant has arrived. It 
 would appear that the unlike chemical changes which take place in the 
 interior of the plant, at the successive periods of its growth, require the 
 presence of different chemical agents — or that the production of new 
 parts demands the co-operation of new substances. 
 
 3°. Similar differences are sometimes observed also when the same 
 plant is grown in different soils. Thus it is known that the straw of the 
 oat grown upon boggy land is very ditrerent in colour and lustre, from 
 that yielded hy^the same variety of seed, when grown upon sound and 
 solid soil. I lately examined two such portions of straw from the same 
 seed — grown on the same farm on the estate of Dunglass, the one on 
 boggy, the other on sound stiffMand, when the straw from the 
 Sound land left 6*64 per cent, of ash, and from the 
 Boggy land " 6*2 per cent, of ash; 
 
 while the silica contained in the ash from the 
 
 Sound land amounted to 3*42 per cent., and from the 
 Boggy land " to 1-90 per cent, of the weight of the straw. 
 
 A remarkable difference, therefore, existed in the relative proportions, 
 
 • Meyen, JaJircsbericht, 1839, p. 125. In regard to these salt-loving plants, which generally 
 abound in soda, a curious observation was Ion? ago made by Cadet. He states that if a plant 
 of common salt- wort (scUsola Sdli) be tnuisplaiitcd into an inland district — and seed from lids 
 plant be afterwards sown, the second race of plants will contain much potash, but scarcely a 
 trace of soda.— Ginclin's Ifaudbuch der Chemie, II. p. 1492. Potash may thus take the 
 place of soda for a time, but removed from its native habitat, the plant would in a few gene- 
 rations die out and disappear. 
 
THE ASH FROM WHEAT STRAW IS VARIABLE. 225 
 
 at least of the silica, in these two varieties of straw, and this difference 
 can be attributed only to the unlike nature of the soils in which the two 
 samples were grown. But on boggy soils the oat i)lant is unhealtliy, 
 and in general neither fills its ear, nor ripens a perfect seed ; — the dif- 
 ference in the ash in this case, therefore, cannot bo considered as entirely 
 opposed to the general proposition, that in a heallhy state, plants at 
 the same period of their growth always yield nearly the same weight 
 of ash. 
 
 But that different experimenters have obtained very unlike quantities 
 of ash, from the most common cultivated plants, aj)parently in a state 
 of health, when grown under diff^erent circumstances of soil and climate, 
 — does appear to contradict this general proposition. Thus 100 lbs. of 
 ripe wheat straiv leave of ash 
 
 4-3 lbs. De Saussure ; 
 4*4 lbs. Berthier; 
 3"5 lbs. Sprengel ; 
 15-5 lbs. Sir H. Davy ; 
 while the straw of one variety of red wheat grown on a clay-loam, at 
 Aykley Heads, near Durham, gave me 6-6 per cent., and that of two 
 other varieties of red wheat, grown near Dalton, in Ravensworth Dale, 
 Yorkshire, a country abounding in limestone — and on the same field — 
 left, respeciively 12*15 and lG-5 i)er cent, of ash. The difiference of 4 
 per cent, between these last two results, shows that the quantity of ash 
 depends much upon the variety of grain examined — though to what ex- 
 tent all the great differences obtained, as above shown, are to be ascribed 
 to this cause alone, it is impossible to say, until numerous other experi- 
 ments shall have been instituted. 
 
 One thing, however, is manifest, that the quantities of inorganic mat- 
 ter necessarily contained in a cro]) of wheat, given in a previous page 
 (p. 21C) on the authority of Sprengel, must be considered as probably 
 far below the mean proportion, since some varieties yield, in the form 
 of ash, about six times as much as is there stated. 
 
 Every one knows how uncertain general conclusions are, — or expla- 
 nations of natural j)hen()menn, — when deduced from single observations 
 only, and of this truth the above results present us with a useful illus- 
 tration. Thus Liebig, in his Organic Chemistry applied to Agri'culture 
 p. 152, to which we have had frequent occasion to refer — explains 
 why land will refuse to grow wheat, and may yet produce good cro))S 
 of oats or barley in the following manner : — "One hundred parts of the 
 stalks of wheat yield 15-5 parts of ashes (H. Davy) : the same quantity 
 of the dry stalks of barley 8-54 (Schrader), and one hundred parts of the 
 stalks of oats only 4-42. The ashes of all are of the same composition. 
 We have in these facts a clear proof of what plants retjuire for tlieir 
 growth. Upon the same field which will yield only one harvest of 
 wheat, two cro])s of barley and three of oats may be raised." 
 
 In this passage it has been assumed that the ash of wheat and other 
 straws is constant in quantity, that wheat straw always contains much 
 more than that of oats or barley, and that the ash is in each case of the 
 same composition (see above, pp. 216 to 217), — all of which premises 
 being incorrect, the conclusion must of course be rejected. 
 
 But the straw of barley and oats also, according to different authorities, 
 10* 
 
226 ASH FROM OAT AND BARLEY STRAW ALSO VARIABLE. 
 
 leaves very unlike quantities of ash. Thus, according to Sprengel and 
 
 Schrader, 100 lbs. of 
 
 Sprengel. Schrader. 
 
 Oat Straw leave . 5-74 lbs. 4-42 lbs. 6-6 J. 
 
 Barley straw . . 5*24 lbs. 8-54 lbs. 
 We cannot help conceding, therefore, generally, in regard to the cereal 
 grasses, that different varieties, at least, of the same plants may contain 
 inorganic matter itt different projwrtions. 
 
 But certain analyses which have been made seem to demand a still 
 further concession. Thus De Saussure found that the ash left by the 
 same tree or shrub — by the fir or the juniper for example — differed both 
 in kind and in quantity, according as it grew upon a granitic or calca- 
 reous soil. Berthier also found the ash of a piece of Norway pine (pi- 
 nus abies) to differ very much from that of the wood of the same pine 
 grown in France. From these and a few other observations, the con- 
 clusion has been very generally drawn by vegetable physiologists, that 
 the ash of plants in general is determined both in kind and quantity by 
 the soil in which they grow. 
 
 This is very likely to be true to a certain extent, as we have seen in 
 the straw of the bog oat above adverted to, but a sufficient number of 
 accurate comparative analyses of the ash of cultivated plants* has not 
 yet been published, to enable us to determine the precise mfluenceof the 
 soil in all cases. It is impossible, however, that the prevailing charac- 
 ter of the soil can have more than a general influence on the character ot 
 the ash of any living vegetable — so long as the plant retains a healthy 
 state. The experiments of De Saussure do not appear to have been 
 made with sufficient care,f while the only comparative experiment of 
 Berthier is open to objections of another kind. 
 
 I have said that the quantity and kind of the ash is likely to be affected 
 by the character of the soil to a certain extent. The following considera- 
 tions seem to embody nearly all the sources of such variation, of which 
 we can at present speak with any degree of certainty : — 
 
 1°. Plants at different periods of their growth require for the produc- 
 tion of their^everal parts, and therefore appropriate from the soil, differ- 
 ent inorganic substances ;t hence the ash will vary with the age of the 
 plant. 
 
 * Five samples of the same variety of wheat (Hunter's wheat) grown on different soils in 
 the neighbourhood of Haddington, gave me very nearly the same proportions of ash. Thus 
 the sample grown on a 
 
 Per cp/nt. 
 1°. Deep reddish clay loam, subsoil gravel, left 1776 
 
 2°. Red clay on gravel 1787 
 
 3°. Stiff clay on retentive subsoil 1903 
 
 4°. Li^ht clay on rather retentive subsoil . . 1917 
 
 5°. Light turnip land 1-824 
 
 These results approach very near each other. The differences are perhaps too slight to 
 justify us in concluding that the ash is greatest in quantity when the subsoil is most reten- 
 tive. 
 
 t The accuracy of De Saussure's analyses is rendered very doubtful by the fact that, in 
 the ash o{ all the different trees and shrubs he examined, he found a large quantity, in that 
 of the juniper as much as 43 per cent. o( alumina, and in that of the pine from 12 to 16 per 
 cent., while Berthier, whose skill is undisputed, found no alumina in the ash of any of the 
 numerous trees on which his experiments were made. 
 
 I This fact indicates an exceedingly interesting field of chemical research in connection 
 with practical agriculture. What substance will bring this or that seed into early leafl — 
 what will hasten its growth in middle life l-j-what will bring it to early maturity 1 The wheat 
 
SOME SUBSTANCES ACT AS MEDIA OR AGENTS ONLY. 227 
 
 2°. If the substances necessary for the perfection of one or more parts 
 of a plant abound^in the soil, its chief developement will take the direc- 
 tion of those parts. Thus one plant will run to leaf or straw, another to 
 flower and seed. Thus also in the grain of one crop of wheat more glu- 
 ten is produced than in that of another, and as this gluten appears to 
 contain the phosphates of lime and magnesia, as essential constituents, 
 the ash will necessaril}'- vary with the gluten of the seed. 
 
 3°. Some substances appear to enter into the circulation of plants not 
 so much as actual and necessary constituents of the parts of the A'egetable, 
 as to serve as media or agents by which other compounds, both organic 
 and inorganic, may be conveyed to the plant. Thus common salt ap- 
 pears to enter many plants for the purpose of supplying soda, its chlo- 
 rine being discharged by the leaf. Silica enters the plant chiefly in the 
 form of silicate of potash or soda. When it reaches its proper destina- 
 tion — the stalks of the grasses for instance — this silicate is decomposed 
 chiefly by the carbonic acid, which is always present in the pores of the 
 green stem, the silica is deposited and the alkali proceeds downwards 
 with the sap as a soluble carbonate, or in combination with some other 
 organic acid. Thus the same portion of alkali may return many times 
 into the circulation with this or with other materials which the parts of 
 the plant require, and every new burden it deposits will necessarily 
 cause a new variation in the relative proportions, of the several inorganic 
 constituents which are afterwards detected in the ash. 
 
 4°. As the water which enters by the roots always brings with it some 
 soluble substances/ the quantity of these conveyed into the plant will be 
 materially affected by the amount of evaporation from the leaves; and 
 hence, after a long drought, the leaves of the turnip, the potato, and 
 other plants, will yield a larger proportion of ash than will be obtained 
 from them in moist and rainy weather. 
 
 5°. In the mineral kingdom it is found that one substance may not 
 unfreijuently take the place, and perform the functions, of another. Thus 
 potash and soda replace each other in certain minerals, as do also lime 
 and magnesia and the phosphoric and arsenic acids. It has been sup- 
 ])osed that a similar interchange may take place in the vegetable king- 
 dom — that when the plant cannot get potash it will take soda — that 
 when it can get neither, it will appropriate lime, — and so on. Such a 
 conjectural interchange may possibly take place in a small degree, for a 
 limited time, and in certain plants, without materially affecting their ap- 
 parent health — but it is not by trusting to such resources of nature that 
 a luxuriant vegetation or plentiful crops will ever be reared by the prac- 
 tical agriculturist. 
 
 Admitting, however, all these sources of variation in the kind and 
 quantity of the ash obtained from different plants, the sound practical 
 conclusions from all we know on the subject at present seem to be — 
 
 1°. That certain inorganic substances, in certain proportions, are ne- 
 cessary to all plants usually cultivated for food — ^if they are to be reared 
 or maintained in a healthy state. 
 
 stalk and the potato require more potash while in rapid growth. This growth may be con- 
 tinued and prolonged by the presence of ammonia ; while lime is said to bring it sooner to 
 a close, and to give an earlier harvest. How valuable would be the multiplication of such 
 facts ! 
 
228 BASIS OF ENLIGHTENED TRACTICAL AGRICULTURE. 
 
 2°. That we must seek for these necessary substances in the inorganic 
 constituents which are present in the richest cro])S of every kind — in the 
 produce of the most fertile soils.* 
 
 3°. That where these necessary substances are not present in an}'' 
 soil, we may infer that it will prove unfit to yield a luxuriant crop of a 
 given kind; or, on the other hand, where these substances are not to be 
 detected in the ash of the plant, that the fault of the crop, if any, maybe 
 ascribed to their partial or total absence from the soil on which it grew. 
 
 These conclusions form the basis of an enlightened and scientific prac- 
 tical agriculture. This basis, however, requires to be strengthened and 
 enlarged by further experimental investigations. 
 
 ' "I have examined," says Sprengel, "the finest seed-corns from many locahties, and 1 
 have invariably found the quantities not only of the organic substances — starch, sugar, &c. — 
 but also of the inorganic compounds in all the celebrated seed-corns, so perfectly alike, that 
 one would have thought they had all grown on one and the same soil." — Lehre vom Dunger^ 
 p. 43. 
 
LECTURE XL 
 
 Nature and origin of soils. — Organic matter in the soil. — General constitution of the earthy 
 part of the soil. — Classification of soils from their chemical constituents. — Method of ap- 
 proximate analysis for the purposes of classification. — General origin of soils and subsoils. 
 — Structure of the earth's crust. — Stratified and unstratified rocks. — Crumbling or degra- 
 dation of rocks. — Diversity of soils produced.— Superficial accumulations.— Tabular view 
 of the character and agricultural capabilities of the soils of the different pans of Great 
 Britain. 
 
 Such are the inorganic compound.s wlirch minister to the growth of 
 plants, and snch the proportions in which they severally occur in the 
 living vegetable. Whence are these inorganic constituents all derived ? 
 
 We have seen that the atmosphere, when pure, contains no inorganic 
 matter, and that if dust, spray, or vapours occasionally float in the air, 
 and are carried by the winds to great distances — yet that they are 
 only accidentally present, and cannot be regarded as a source from 
 which the general vegetation of the globe derives a constant supply of 
 those mineral substances which are necessary to its healthy existence. 
 
 The soil on which they grow is the only natural source from which 
 their inorganic food can be derived. We are led, therefore, as tlte next 
 subject of our study, to inquire into the nature and origin of soils.* 
 
 § 1 . Of the organic matter in the soil. 
 
 Soils differ much as regards their immediate origin, their physical 
 properties, their chemical constitution, and their agricultural capabili- 
 ties ; yet all soils which in their existing state are capable of bearing a 
 profitable crop, possess one common character — they all contain organic 
 matter in a greater or a less proportion. 
 
 This organic matter consists in part of decayed animal, but chiefly of 
 decayed vegetable substances, sometimes in brown or black fibrous por- 
 tions, exhibiting still, on a careful examination, something of the origi- 
 nal structure of the organized substances from which they have been de- 
 rived — sometimes forming only a fine brown powder intimately inter- 
 mixed with the mineral matters of the soil — sometimes scarcely percep- 
 tible in either of those forms, and existing only in the state of organic 
 compounds more or less void of colour and at times entirely soluble in 
 water. In soils which appear to consist only of pure sand, or clay, or 
 chalk, organic matter in this latter form may often be detected in con- 
 siderable quantity. 
 
 The proportion of organic matter in soils which are naturally produc- 
 tive of any useful crops, varies from one-half to 70 per cent, of their 
 whole weight. With less than the former proportion they will scarcely 
 support vegetation — with more than the latter, they require much ad- 
 mixture before they can be brought into profitable cultivation. It is 
 
 • On the subject of this and the following lecture, the reader will consult with advantage 
 an excellent little work, " On the nature and property of soils," by Mr. John Morton. 
 
230 PROPORTION OF ORGANIC MATTER IN SOILS. 
 
 only in bog2;y and peaty soils that the latter large proportion is ever 
 found — in tfie best soils the organic matter does not average five percent., 
 and rarely exceeds ten or twelve. Oats and rye will grow upon land 
 containing only one or one and a half per cent. — barley where two or 
 three per cent, are present — but good wheat soils contain in general from 
 4 to 8 per cent., and, if very stiff and clayey, from 10 to 12 per cent, 
 may occasionally be detected. 
 
 Thougli, however, a certain proportion of organic matter is always 
 found in a soil distinguished for its fertility, yet the presence of such sub- 
 stances is not alone sufficient to impart fertility to the land. I do not 
 allude merely to such as, like peaty soils, contain a very large excess of 
 vegetable matter, but to such also as contain only an average proportion. 
 Thus of two soils in the same neighbourhood — the one contained 4*05 
 per cent, of organic matter, and was very fruitful — the other 4*19 per 
 cent., and was almost barren. This fact is consistent with what has been 
 stated in the two preceding lectures, in regard to the influence exercised 
 by the dead inorganic matter of the soil, on the general health and luxu- 
 riance of vegetation. 
 
 § 2. General constitution of the earthy part of the soil. 
 
 From what is above stated, it appears that, on a general average, the 
 earthy part of the soil in our climate does not constitute less than 96 per 
 cent, of its whole weight, when free from water. This earthy part con- 
 sists principally of three ingredients: — 
 
 1°. O^ Silica, siliceous sand, or siliceous gravel — of various degrees 
 of fineness, from that of an impalpable ])owder as it occurs in clay soils, 
 lo the large and more or less rounded sandstones of the gravel beds. 
 
 2°. Alumina — generally in the form of clay, but occasionally occur- 
 ring in shaly or slaty masses more or less hard, intermingled with the 
 soil. 
 
 3°. Lime, or carbonate of lime — in the form of chalk, or of fragments 
 more or less large of the various limestones that are met with near the 
 surface in different countries. Where cultivation prevails it often hap- 
 pens that aiUtrhe lime which the soil contains has been added to it for 
 agricultural purposes — in the form of (|uick-lime, of chalk, of shell-sand, 
 or of one or other of the numerous varieties of marl which different dis- 
 tricts are known to produce. 
 
 It is rare that a superficial covering is anywhere met with on the 
 surface of the earth, which consists solely of any one of these three sub- 
 stances — a soil, however, is called sandy in which the siliceous sand 
 greatly predominates, and calcareous, where, as in some of our chalk 
 and limestone districts, carbonate of lime is present in considerable abun- 
 dance. When alumina forms a large proportion of the soil, it constitutes 
 a clay of greater or less tenacity. 
 
 The term clay, however, or pure clay, is never used by writers on 
 agriculture to denote a soil consistingof alumina only, for none such ever 
 occurs in nature. The ipure porcelain clays are the richest in alumina, 
 but even when free from water they contain only from 42 to 48 per cent, 
 of this earth, with from 52 to 58 of silica. These occur, however, only 
 in isolated patches, and never alone form the soil of any considerable 
 
cni\:rosiTiON of porcelain and AORicrLTURAi. clays. £31 
 
 district. The strongest clay soils which are anywhere in cultivation 
 rarely contain more than 36 per cent, of alumina.* 
 
 Soils in general consist in great part of the three substances above 
 named in a state oi mechanical mixture. This is always the case with 
 the sihceous sand and with the carbonate of lime — but in the clays the 
 silica and the alumina are, for the most part, in a state of chemical com- 
 bination. Thus, if a portion of a stiff" clay soil be kneaded or boiled 
 with repeated portions of water till its coherence is entirely destroyed, 
 and if the water, with the finer ])arts which float in it, be then poured 
 into a second vessel, the whole of the soil will be separated into two por- 
 tions — a fine impalpable powder consisting chiefly of clay, poured ofT 
 with the water, and a quantity of siliceous or other sand in particles of 
 various sizes, which will remain in the first vessel. This sand was 
 only mechanically mixed with the soil. The fine clay retains still some 
 mechanical admixtures, but consists chiefly of silica and alumina chem- 
 ically combined. 
 
 Of the porcelain clays above alluded to, there are several varieties, 
 three of which, containing the largest proportion of alumina, cotwist res- 
 pectively of — 
 
 
 I. 
 
 11. 
 
 III. 
 
 Silica . , 
 
 . 47-03 
 
 46-92 
 
 46-0 
 
 Alumina . 
 
 . 39-23 
 
 34.81 
 
 40-2 
 
 Water . 
 
 . 13-74 
 
 18-27 
 
 13-8 
 
 100-00 100-00 100-Of 
 
 But, as already stated, these clays rarely form a soil — the stifTest 
 clays treated by the agriculturist containing a further portion of silica, 
 some of which is mechanically mixed, and can be partially separated by 
 mechanical means. 
 
 The strongest agricultural clays {pipe-clays) of which trustworthy 
 analyses have yet been published, consist, in the dry slate, of 56 to 62 
 of silica, from 36 to 40 of alumina, 3 or 4 of oxide of iron, and a trace of 
 lime. Clays of this composition are distinguished by the foreign agri- 
 cultural writers as pure clays. They are all probably made up of some 
 of (he varieties of porcelain clay, more or less intimately mixed with 
 siliceous and ochrey particles — in so minute a state of division that they 
 cannot be separated by the method of decantation above described. 
 
 These clays are adopted by the German and French writers as a 
 standard to which they can liken clay soils in general, and by compari- 
 son with which they are enabled distinctly to classify and name them. 
 As the use of the term clay in this sense has been introduced into Eng- 
 
 • In an interesting paper on subsoil ploughing by Mr. H. S. Thompson, in the report of 
 the Yorkshire Agricultural Society for 1837, p. 47, it is stated that the lias clays, which form 
 the subsoil in certain parts of Yorkshire, contain sometimes, in the dry state, as much as 54 
 per ce?tt of alumina {7) 
 
 t When heated to redness the whole of the water is driven off from these clays, and they 
 then consist respectively of— 
 
 Silica 54-5 57'4 534 
 
 Alumina 45 5 42 6 46 6 
 
 1000 1000 1000 
 
 which numbers are in accordance with those given at the foot of the preceding page. 
 
232 CLASSIFICATION OF SOILS. 
 
 lish agricultural books,* and as it is really desirable to possess a word to 
 which the above meaning can be attached, I shall venture in future to 
 employ it always strictly in this agricultural sense. 
 
 By alumina, then, I shall in all cases express the pure earth of alum, 
 which exists in clays, and to which tliey owe their tenacity — by clay, a 
 finely divided chemical compound, consisting very nearly of 60 of silica 
 and 40 of alumina, with a little oxide of iron, arid from ivhich no siliceous 
 or sandy matter can be sejjarated mechanically or by decantation. 
 
 Of this clay the eartliy part of all known soils is made up by mere 
 mechanical admixture with the other earthy constituents (sand and 
 lime), in variable proportions. On a knowledge of these proportions the 
 following general classification and nomenclature are founded. 
 
 § 3. Of the classification of soils from their chemical constituents. 
 
 Upon the principles above described soils may be classified as fol- 
 lows : — 
 
 1°. Pure clay (pipe-clay) consisting of about 60 of silica and 40 of 
 alumina and oxide of iron, for the most jjart chemically combined. It 
 allows no siliceous sand to subside when diilused through water, and 
 rarely forms any extent of soil. 
 
 2°. Strongest clay soil (tile-clay, unctuous clay) consists of pure clay 
 mixed with 5 to 15 per cent, of a siliceous sand, which can be separated 
 from it by boiling and decantation. 
 
 3°. Clay loam differs from a clay soil, in allowing from 15 to 30 per 
 cent, of fine sand to be separated from it by washing, as above described. 
 By this admixture of sand, its parts are mechanically separated, and 
 hence its freer and more friable nature. 
 
 4°. A loamy soil deposits from 30 to 60 per cent, of sand by mechani- 
 cal washing. 
 
 5°. A sandy loam leaves from 60 to 90 per cent, of sand, and 
 
 6°. A sandy soil contains no more than 10 per cent, of pure clay. 
 
 The mode of examining with the view of naming soils, as above, is 
 very simple. It is only necessary to spread a weighed quantity of the 
 soil in a thin^ayer upon writing paper, and to dry it for an hour or two in 
 an oven or upon a hot plate, the heat of which is not sufficient to dis- 
 colour the paper — the loss of weight gives the water it contained. While 
 this is drying, a second weighed portion may be boiled or otherwise 
 thoroughly incorporated with water, and the whole then poured into a 
 vessel, in which the heavy sandy parts are allowed to subside until the 
 fine clay is beginning to settle also. This point must be carefully 
 watched, the liquid then poured off, the sand collected, dried as before 
 upon paper, and again weighed. This weight is the quantity of sand 
 in the known weight o{ moist soil, which by the previous experiment has 
 been found to contain a certain quantity of water. 
 
 Thus, suppose two portions, each 200 grs., are weighed, and the one 
 in the'oven loses 50 grs. of water, and the other leaves 60 grs. of sand, 
 — then, the 200 grs. of^ moist are equal to 150 o^ dry, and this 150 of dry 
 
 * As in British Htisbandry^ p. 113, and in LoudoiCs Encydopoidia of Agriculture, p. 315, 
 where classifications of soils are given chiefly from Von Thaei-, though neither work ex- 
 hibits with sufficient prominence the meaning to be attached to agricultural clay, as distin- 
 guished from alumina, sometimes called pure clay by the chemist. 
 
MARLY AND CALCAREOUS SOILS, AND VEGETABLE MOULDS. 233 
 
 soil contain 60 of sand, or 40 in 100 (40 per cent.) It would, therefore, 
 be properly called a loam, or loamy soil. 
 
 But the above classification has reference only to the clay and sand, 
 while we know that lime is an important constituent of soils, of which 
 they are seldom entirely destitute. We have, therefore, 
 
 7°. Marly soils, in which the proportion of lime is more than 5 but 
 does not exceed 20 per cent, of the whole weight of the dry soil. The 
 marl is a sandy, loamy, or clay marl, according as the proportion of 
 clay it contains would place it under the one or other denomination, sup- 
 posing it to be entirely free from lime, or not to contain more than 5 per 
 cent., and 
 
 8°. Calcareous soils, in which the lime exceeding 20 per cent, becomes 
 the distinguishing constituent. These are also calcareous clays, calca- 
 reous loams, or calcareous sands, according to the proportion of clay and 
 sand which are present in them. 
 
 The determination of the lime also, when it exceeds 5 per cent., is 
 attended with no difficulty. 
 
 To 100 grs. of the dry soil diffused through half a pint of cold water, 
 and half a wine-glass full of muriatic acid (the spiritof salt of the shops), 
 stir it occasionally during the day, and let it stand over-night to settle. 
 Pour off" the clear liquor in the morning and fill up the vessel with water, 
 to wash away the excess of acid. When the water is again clear, pour 
 it off', dry the soil and weigh it — the loss will amount generally to about 
 one per cent, more than the quantity of lime present. The result will 
 be sufficiently near, however, for the purposes of classification. If the 
 loss exceed 5 grs. from 100 of the dry soil, it may be classed among the 
 marls, if more than 20 grs. among the calcareous soils. 
 
 Lastly, vegetable matter is sometimes the characteristic of a soil, 
 which gives rise to a further division of 
 
 9°. Vegetable moulds, which are of various kinds, from the garden 
 mould, which contains from 5 to 10 per cent., to the peaty soil, in which 
 the organic matter may amount to 60 or 70. These soils also are clayey, 
 loamy, or sandy, according to the predominant character of the earthy 
 admixtures. 
 
 The method of determining the amount of vegetable matter for the 
 purposes of classification, is to dry the soil well in an oven, and weigh 
 it; then to heat it to dull redness over a lamp or a bright fire till the 
 combustible matter is burned away. The loss on again weighing is the 
 quantity of organic matter. 
 
 Summary. — The several steps, therefore, to be taken in examining a 
 soil with the view of so far determining its constitution as to be able pre- 
 cisely to name and classify it, will be best taken in the following order : — 
 
 1°. Weigh 100 grarns of the soil, spread them in a thin layer upon 
 white paper, and place them for some hours in an oven or other hot 
 place, the heat of which may be raised till it only does not discolour the 
 paper. The loss is water. 
 
 2'-'. Let it now (after drying and weighing) be burned over the fire as 
 above described. The second loss is organic, chiefly vegetable matter, 
 with a little water, which still remained in the soil after drying. 
 
 3°. After being thus burned, let it be put into half a pint of water 
 
234 SUMMARY OF THE METHOD OF EXAMINATION. 
 
 with half a wine-glass full of spirit of salt, and frequently stirred. 
 When minute bubbles of air cease to rise from the soil on settling, this 
 process may be considered as at an end. The loss by this treatment 
 will be a little more than the true per cenfage of lime,* and it will gen- 
 erally be nearer the truth if that portion of soil be employed which has 
 been previously heated to redness. 
 
 4°. A fresli portion of the soil, perhaps 200 grs. in its moist state, may 
 now be taken and washed to determine the quantity of siliceous sand it 
 contains. II' the residual sand be supposed to contain calcareous matter 
 its amount may readily be determined by treating the dried sand with 
 diluted muriatic acid, in the same way as when determining the whole 
 amount of lime (3°.) contained in the unwashed soil.f 
 
 Let me illustrate this by an exam])le. 
 
 Kxample. — Along the outcrop of some of the upper beds of the green 
 sand in Berkshire, Wiltshire, and Hampshire, and probably also in 
 Buckingham and Bedford, occur patches of a loose friable grey soil 
 mixed with occasional fragments of flint, which is noted for producing 
 excellent crops of wheat every other year. It is known in the valley of 
 Kingsclere, at Wantage, and Newbury. I select a portion of this soil 
 from the latter locality for my present illustration. 
 
 1°. After being dried in the air, and by keeping some time in paper, it 
 was exposed for some hours to a temperature sufficient to give the white 
 paper below it a scarcely perceptible tinge : by this process 104|^ grs. 
 lost 4 grs. 
 
 2°. When thus dried, it was heated to dull redness. It first black- 
 ened, and then gradually assumed a pale brick colour, the change, of 
 course, beginning at the edges. The loss by this process was 4^ grs. 
 
 3°. Alter this heating, it was put into half a pint of pure rain water 
 with half a wine-glass full of spirit of salt. After some hours, when the 
 action had ceased, the soil was washed and dried again at a dull red 
 heat. The loss amounted to 3 grs. 
 
 The soil, therefore, contained 
 
 Water 4 grs. 
 
 - Organic matter (less than) . . 4^ 
 
 Carbonate of lime (less than) . 3 
 
 Clay and sand 93^ 
 
 1041 
 4°. By boiling and washing with water, 291 grs, of the undried soil 
 left 202i grs. of very fine sand chiefly siliceous, — 104i, therefore, would 
 have left 73 grs., or the soil contained per cent. — 
 
 ' A more rigrorous method of determining the lime when less than 5 per cent, will be 
 given in the following lecture. 
 
 t The weighings for the purposes here described may be made in a small balance with 
 grain weights, sold by the druggists for 5s. or 6s., and the vegetable matter may be burned 
 away on a slip of sheet iron or in an untinned iron table-spoon over a bright cinder or char- 
 coal fire— care being taken that no scale of oxide, which may be formed on the iron, be al- 
 lowed to mix with the soil when cold, and thus to increase its weight. Those who are in- 
 clined to perform the latter operation more neatly, may obtain for about 6s. each — from the 
 dealers in chemical apparatus— thin light platinum capsules from 1 to VK inches in diame- 
 ter, capable of holding 100 grs. of soil— and for a few shillings more a spirit lamp, over 
 which the vegetable matter of the soil may be burned away. With care, one of these little 
 capsules will serve a life-time. 
 
DIFFERENCE BETWEEN SOIL AMD SUBSOIL. 235 
 
 Water . . . '^ 3-9 per cent. 
 
 Organic matter (less than) . . 4'1 
 Carbonate of lime (less than) . 3-0 
 
 Clay 19-0 
 
 Sand (very fine) 70.0 
 
 100-0* 
 This soil, therefore, containing 70 per cent, of sand, separable by 
 decantalion, is properly a sandy loam. 
 
 § 4. Of the distinguishing characters of soils and subsoils. 
 
 Beneath the immediate surface soil, through which the plough makes 
 its way, and to which the seed is entrusted, lies what is commonly dis- 
 tinguished by the name of subsoil. This subsoil occasionally consists 
 of a mixture of the general constituents of soils naturally ditferent from 
 that which forms the surface layer — as when clay above has a sandy 
 bed below, or a light soil on the surface rests on a retentive clay beneath. 
 
 This?, however, is not aUvays the case. The peculiar characters of 
 the soil and subsoil often result from the slow o[)eration of natural causes. 
 
 In a mass of loose matter of considerable depth, spread over an extent 
 of country, it is easy to understand how — even though originally aUke 
 through its whole mass — a few inches at the surface should gradually 
 acquire different physical and chemical characters from the rest, and 
 how there should thus be gradually established important agricultural 
 distinctions between the first 12 or 15 inches (the soil), the next 15 (the 
 subsoil), and the remaining body of the mass, which, lying still lower, 
 does not come under the observation of the practical agriculturist. 
 
 On the surface, plants grow and die. Through the first few inches 
 their roots penetrate, and in the same the dead plants are buried. This 
 portion, therefore, by degrees, assumes a brown colour, more or less dark, 
 according to the quantity of vegetable matter which has been permitted 
 to accumulate in it. Into the subsoil, however, the roots rarely pene- 
 trate, and the dead plants are still more rarely buried at so great a depth. 
 Sill this inferior layer is not wholly destitute of vegetable or other or- 
 ganic matter. However comparatively impervious it may be, still water 
 makes its way through it, more or less, and carries down soluble organic 
 substances, which are continually in the act of being produced during the 
 decay of the vegetable matter lying above. Thus, though not sensibly 
 discoloured by an admixture of decayed roots and stems, the subsoil in 
 reality contains an appreciable quantity of organic matter which may 
 be distinctly estimated. 
 
 Again, the continual descent of the rains upon the surface soil washes 
 down the carbonates of lime, iron, and magnesia, as well as other soluble 
 earthy substances— it even, by degrees, carries down the fine clay also, 
 
 * Some of these numbers differ by a minute fraction from those in the preceding page : 
 this is because they are calculated from the more correct decimal fractions contained in my 
 own note-book. The organic matter is said to be less than the number here given, because 
 by simple drying, as here prescribed, the whole of the water cannot be driven off— a portion 
 being always retained by the clay, which is not entirely expelled, till the soil is raised nearly 
 to a red heat. Hence the loss by this second heating must always be greater than the actual 
 weight of organic matter present. The lime is also less than the number given, because, as 
 already stated, the acid dissolves a little alumina as well as any carbonate of magnesia which 
 may be present. 
 
236 HOW THfi SUBSOIL IS PRODUCED. 
 
 SO as gradually to establish a more or less manifest difference between 
 the upper and lower layers, in reference even to the earthy ingredients 
 which tliey respectively contain. 
 
 But, except in the case of very porous rocks or accumulations of earthy 
 matter, these surface waters rarely descend to any great depth, and hence 
 after sinking through a variable thickness of subsoil, we come, in gene- 
 ral, to eartliy layers, in which little vegetable matter can be detected, 
 and to which the lime, iron, and magnesia of the superficial covering 
 has never been able to descend. _^ 
 
 Thus the character of tlie soil is, that it contains more brown organic|B 
 chiefly vegetable, matter, in a state of decay — of the swftsoi/, that the or- 
 ganic matter is less in quantity and has entered it chiefly in a soluble 
 slate, and that earthy niatters are present in it which have been washed 
 out of the superior soil — and of the subjacent mass, that it has remained 
 nearly unaffected by the changes which vegetation, culture, and atmos- 
 pheric agents have produced upon the portions that lie above it. 
 
 From what is here staled, the effect of trench and subsoil ploughing, 
 in altering more or less materially the proportions of the earthy constitu- 
 ents in the surface soil, will be in some measure apparent. That which 
 the long action of rains and frosts has caused to sink beyond tlie ordinary 
 reach of the plough is, by such methods, brought again to the surface. 
 When the substances thus brought up are directly beneficial to vegeta- 
 tion or are fitted to improve the texture of the soil, its fertility is increased. 
 Where the contrary is the case, its productive capabilities may for a 
 longer or a shorter period be manifestly diminished. 
 
 § 5. On the general origin of soils. 
 
 On many parts of the earth's surface the naked rocks appear over 
 considerable tracts of country, without any covering of loose mate- 
 rials from which a soil can be formed. This is especially the case in 
 mountainous and granitic districts, and in the neighbourhood of active 
 or extinct volcanoes, where, as in Sicily, streams of naked lava stretch 
 in long black lines amid the surrounding verdure. 
 
 But overlie greater portion of our islands and continents the rocks 
 are covered by accumulations, more or less deep, of loose materials — 
 sands, gravels, and clays chiefly — the upper layer of which is more or 
 less susceptible of cultivation, and is found to reward the exertions of 
 human industry with crops of corn in greater or less abundance. 
 
 This superficial covering of loose materials varies from a few inches to 
 one or two hundred feet in depth, and is occasionally observed to consist 
 of different layers or beds, placed one over the other — such as a bed of 
 clay over one of gravel or sand, and a loamy bed under or over both. 
 In such cases the characters and capabilities of the soil must depend 
 upon which of these layers may chance to be uppermost — and its char- 
 acter may often be beneficially altered by a judicious admixture with 
 portions of the subjacent layers. 
 
 It is often observed, where naked rocks present themselves, either in 
 cliffs or on more level parts of the earth, that the action of the rains and 
 frosts causes their surfaces gradually to shiver off', crumble down, or 
 wear away. Hence at the base of cliffs loose matter collects — on com- 
 paratively level surfaces the crumbling of the rock gradually forms a soil— 
 
CRUMBLING OR DEGRADATION OF ROCKS. 237 
 
 while from those which are sufficiently inclined the rains wash away 
 the loose materials as soon as they are separated, and carry them down 
 to the vallies. 
 
 The superficial accumulations of which we have spoken, as covering 
 the rocks in many places to a depth of one or two hundred feet, consist 
 of materials thus washed down or otherwise transported — by water, by 
 winds, or by other geological agents. Much of these heaps of transported 
 matter is in the state of too fine a powder to permit us to say from whence 
 it has been derived — but fragments of greater or less size are always to 
 be found, even among the clays and fine sands, which are sufficient to 
 ]X)int out to the skilful geologist the direction from which the whole has 
 been brought, and often the very rocks from which the entire accumula- 
 tions have been derived. 
 
 Thus the general conclusion is fairly drawn, that the earthy matter of 
 all soils has been produced by the gradual decay, degradation, or crumb- 
 ling down of previously existing rocks. It is evident therefore — 
 
 1°. That whenever a soil rests immediately upon the rock from which 
 it has been derived, it may be expected to partake more or less of the 
 composition and characters of that rock. 
 
 2°. That where the soil forms only the surface layer of a considerable 
 depth of transported materials, it may have no relation whatever either 
 in rriineralogical characters or in chemical constitution to the immedi- 
 ately subjacent rocks. 
 
 The soils of Great Britain are divisible into two such classes. In 
 some counties an acquaintance with the prevailing rock of the district 
 enables us to predict the general characters and quality of the soil ; in 
 others — and nearly all our coal fields are in this case — the general 
 character and capabilities of the soil have no relation whatever to the 
 rocks on which the loose materials rest. 
 
 § 6. On the general structure of the earth'' s crust. 
 
 Beneath the soil, and the loose or drifted matters on which it rests, we 
 everywhere find the solid rock. This rock in most countries is seen — 
 in mines, quarries, and cliffs — to consist of beds or layers of varied thick- 
 ness placed one over the other. To these layers geologists give the 
 name of strata; and hence rocks which are thus made up of many se- 
 parate layers are called stratified rocks. 
 
 But in some places entire mountain masses are met with, in which no 
 parting into layers or beds is seen, but which appear to consist of one 
 unbroken rock of the same material from their upper surface down- 
 wards, and often as far beneath as we have been able to penetrate into 
 the earth. Such rocks are said to be unstratified. Among these are 
 included the granites, the trap, green-stone, or basaltic rocks, and the 
 lavas. Geologists have ascertained that all these unstratified rocks have, 
 like the volcanic lavas, been in a more or less perfectly melted state- 
 that their present appearance is owing to the action of fire — and hence 
 they are often called igneous* rocks. They often also exhibit a more or 
 less crystalline or glassy structure, or contain, imbedded in them, nu- 
 merous regular crystals of mineral substances ; hence they are some- 
 times called also crystalline rocks. The terms igneous, crystalline, and 
 
 * Somelimes pyrogenous, produced by fire ; but this is an unnecessarily hard word. 
 
238 
 
 STRATIFIED AND UNSTRATIFIED ROCKS. 
 
 unstratified, therefore, apply to the same class of rocks — the first indica- 
 ting their origin, the second their structure in the small, the third tlieir 
 structure in the large, as distinguislied from that of the rocks which occur 
 in heds. 
 
 The following diagram exhibits the general appearance of the strati 
 Red rocks as they are found to occur in contact with unstratified masses 
 in various parts of the globe : — 
 
 I 
 
 A represents an unstratified mountain mass or other similar rock rising 
 up through the stratified deposits. Tlie bending up of the edges of the 
 latter indicates that after the beds were deposited in a nearly level posi- 
 tion, the mass A was intruded or forced up through them, carrying tha||{ 
 broken edges of the beds along with it. o 
 
 B shows the more quiet way in which veins or dykes of unstratified 
 green-stone, or trap, or lava, cut through tiie beds without materially 
 displacing them — as if when in a fluid state it had risen up and filled a 
 previously existing crack or chasm. In Devonshire, in the North of 
 Scotland, and in Ireland, the granite rises in many places exactly as is 
 shown at A, and nearly all our coal fields exhibit in their whin dykes 
 numerous illustrations of what is shown at B. 
 
 C and D exhibit the manner in which the strata overlie one another 
 in nearly a horizontal position — 1, 2, 3, indicating different kinds of rock, 
 — as a lime-stone, a sand-stone, and a clay — which again are subdivided 
 into beds or thinner layers, by the partings exhibited in the wood-cut. 
 
 The stratified rocks lie sometimes nearly level or horizontal over large; 
 tracts of country — as in the above diagram, — sometimes they are mon? 
 or less inclined or appear to dip in one and to rise in the opposite direc- 
 tion — as if a surface, formerly level, had been pushed down at the one 
 end and rajsed up at the other, — and sometimes they seem to rest entire 
 ly upon their edges. Upon the mode in which they thus lie, the unifor 
 inity of the soil, in a district where it reposes immediately on the rocks 
 from which it is derived, is materially dependent. In the following dia- 
 gram the surface from A to E represents a tract of country in which the 
 
 rocks have in different parts these diflferent degrees of inclination, at A 
 vertical, at B more inclined, and from C to E nearly horizontal. Now, 
 it is obvious that if the outer surface of these several rocks crumble and 
 form a soil which rests where it is produced — then the quality of the soil 
 on every spot will be determined by the nature of the rock beneath. 
 Hence, in proceeding from E over the comparatively level strata, we 
 shall find the soil pretty uniform in quality till we come to the edge of 
 
VERTICAL, INCLINED, AND HORIZONTAL STRATA. 239 
 
 the bed D, thence it will again be uniform, though perhaps different from 
 the former, till we reach the stratum C, when again it will prove uni- 
 form over a considerable space till we begin to climb the hill to B. So 
 the whole hill-side in ascending to B will be of one and the same kind 
 of soil. But as we descend on the other side and pass B, we get upon 
 the edges of the beds, and then as we proceed from one bed to another, 
 the quality of the soil may vary every few yards, more or less, ac- 
 cording as the members of this group of beds are more or less differ- 
 ent from each other. But when we ascend the hill to A, where the 
 beds, besides being vertical, are also very thin, the soil may change at 
 almost every step, provided — which is, however, rarely the case among 
 the rocks (slate rocks) which occur most frequently in this position — pro- 
 vided the mineralogical characters of the several vertical layers be sen- 
 sibly unlike. Such dissimilarities in the angular position of the strata, 
 as are represented in the above diagram, are of constant occurrence, not 
 only in our islands, but in all parts of the globe ; and they illustrate very 
 clearly one important natural cause of that want of uniformity in the na- 
 ture and capabilities of the soil which is more or less observable in every 
 undulating and in some comparatively level countries also. 
 
 It may be stated, as the general result of an extended examination 
 of all the stratified rocks yet known — that they consist of alternations or 
 admixtures of three kinds of rock only — of sand-stones, of lime-stones, 
 and of clays. The sand-stoqes are of various degrees of solidity and 
 hardness, from the loose sand of some parts of the lower new-red and 
 green-sand formations, to the almost perfect quartz rock not unfrequently 
 associated with the oldest strata= The lime-stones vary in like manner 
 from the soft chalk to the hard mountain lime-stone and the cr^'stalline 
 statuary marble ; while the clays are found of all degrees of hardness 
 from that of the London and Kimmeridge clays, which soften in water, 
 to that of the roofing slates of Cumberland and Wales, — and even to 
 that of the gneiss rocks which rest immediately upon the granite, and 
 which appear to be only the oldest clays altered by the action of heat. 
 
 But the stratified rocks, though thus distinguishable into three main 
 varieties — rarely consist of any one of these substances in an unmixed 
 slate. The sand-stones not unfrequently contain a little clay or lime, 
 while the lime-stones and clays are often mixed with sand and with 
 each other. 
 
 If the stratified rocks thus consist essentially of these three substances, 
 the soils formed from them by natural crumbling or decay must have a 
 similar composition. A sandy soil will be formed from a sand-stone, — 
 a calcareous soil from a lime-stone, — a clay from a slate or shale, — and 
 from a mixed rock, a soil containing a mixture of two or more of these 
 earthy ingredients — in proportions which will depend upon the relative 
 quantities of each which are contained in the rock from which they have 
 been derived. 
 
 § 7. Relative positions and peculiar characters of the several strata. 
 
 1°. The several strata, or series of strata, wliich present themselves 
 in the crust of the globe, always maintain the same relative positions. 
 Thus the numbers 3, 2, 1, in the annexed diagram, represent three series 
 of beds known by the names of the magnesian lime-stone, the lower new- 
 
240 THESE STRATA ARE OFTEN CONTJNUOUS OVER LARGf: AREAS 
 
 X 
 
 =&--. 
 
 3^x\\rx 
 
 II 
 
 red sand-stone, ami the coal-nieuL-urrs, Jyniii <>\'tr each olher in ilieir 
 natural positions — the liiri^'-slone uppermost, the sand-stone next, and 
 the coal beneath boiii. Whenever liiese three rocks are met witli, near 
 each other, they always occupy the satne relative ])osition, the coal 
 never appears above this lime-stone, and the sand-stone, if present, is 
 always between the two other series of beds. The same is true of every 
 other grou[) of strata — the order in which ihey are placed over each olher 
 is universally the same. 
 
 2°. These beds are generally continuous also over very large areas — 
 or are found to stretch, without interruption, over a great extent of coun- 
 try. Hence when they dip beneath other beds, as they are seen to do 
 in the above diagrams, we can still, with a high degree of probability, 
 infer their presence at a greater or less depth, wherever we observe on 
 the surface those olher beds which are known usually to lie immediate- 
 ly above them. Thus, if in a tract of country consisting of the magne- 
 sian lime-stone (3) above-mentioned, it is known that deep vallies occur, 
 it becomes probable that the soil in those vallies will rest upon, and may 
 be formed from, the underlying red sand-stones or coal-measures ; and 
 that it will therefore possess very different agricultural capabilities from 
 the soil that generally prevails around it. Or in chalk districts, beneath 
 which usually lies the green-sand, the presence of a deep valley cutting 
 through the chalk almost necessarily implies in the hollow a very differ- 
 ent soil from that which is cultivated in the chalk wolds above. This is 
 the case in the valley of Kingsclere, where the peculiar wheat soil oc- 
 curs, of which an approximate analysis has been given in page 234. 
 
 3°. It has been already stated that the stratified rocks, though so very 
 numerous and so varied in appearance, yet consist generally of repeated 
 alternations of lime-stones, sand-stones, and clays, or of mixtures of two 
 or more oftliese earthy substances. But the several series of strata are 
 nevertheless distinguished from each other by peculiar and often well- 
 marked characters. 
 
 Thus some are soft, crumble readily, and soon form a soil, — while 
 others, though consisting of the same ingredients, long refuse to break 
 into minute fragments, and thus condemn the surface of the country 
 where they occur to more or less partial barrenness. 
 
 In others, again, the proportions of sand or lime are so varied, from 
 bed to bed, that the character of the mixture in each is entirely different 
 — so that while one, on crumbling down, will give a stiff clay, another 
 will produce a loam, and a third a sandy marl. 
 
 Or, in some rocks the remains of vegetables are present in considera- 
 ble quantity, — as in the neighbourhood of our coal-beds — or the bones or 
 shells of animals in greater or less abundance, by each of which the 
 agricultural characters and capabilities of the soils formed from them, 
 will be more or less extensively affected. 
 
 Or lastly, the mixture of other earthy substances gives a peculiar 
 
THEIR PECULIAR CHARACTERS ALSO CONTINUOUS. 241 
 
 character to many rocks. Thus the per-oxide of iron, which imparts 
 their red colour to many strata — as to the red sandstones — influences 
 not only the mineralogical character of the rock, but also the quality of 
 the soil which is formed by its decay. In like manner the presence of 
 magnesia, sometimes in large quantity, in man3^ lime-stones, })roduces 
 an important modification in the chemical constitution and mineralogical 
 characters of the rock, as well as in its relations to practical agriculture. 
 
 In consequence of these and other similar causes of diversity, if not 
 every stratum, at least every series of strata, exhibits distinguishing and 
 characteristic peculiarities, by means of which it may be more or less 
 readily recognized. On these peculiarities the special agricultural ca- 
 pabilities of those parts of the globe in which each series of beds occurs 
 are in a great degree dependent. 
 
 4". This peculiar character is also more or less continuous over very 
 large areas. Thus if a given stratum be found on the surface in any 
 part of England, and again in any part of Russia, the soil formed from 
 that bed will generally exhibit very nearly the same qualities in both 
 countries. A knowledge of (he geology, therefore, — that is, of the kind 
 of rock which appears on tiie surface in every part of a country— ena- 
 bles us to predict generally the kind of soil which ought to rest upon it, 
 if it be not covered by foreign accumulations ; while, on the other hand, 
 a knowledge of the agricultural capabilities of any one district in which 
 certain rocjvs are known to lie immediately beneath the soil, and of the 
 agricultural practice suited to that district, will indicate the probable ca- 
 pabilities of any other tract in which the same kind of rock is known to 
 appear on the surface, and of the kind of culture which may be most 
 successfully applied to it. 
 
 It is evident, then, that a familiar acquaintance with' the general 
 characters and relative positions of all the series of strata that have hith- 
 erto been observed, and of the classification of rocks considered geologi- 
 cally, to which this knowledge has led, must be fitted to throw much 
 light upon the principles of a general, enlightened, and philosophical 
 agriculture. 
 
 § 8. Classification of the stratified rocks, their extent, and the agricultu- 
 ral relations of the soils derived from' them. 
 
 It is a received principle, I may say rather, an obvious fact, that in 
 the crust of the earth, as in the wallsof a building, those layers which lie 
 lowest or undermost have been first deposited, or are the oldest. In re- 
 ference to this their relative age, the stratified rocks are divided into the 
 primary, the first deposited and most ancient— r-the secondary, which are 
 next in order — and the tertiary, which overlie both. 
 
 These three series of strata are again subdivided into systems, and 
 these into minor groups, called formations, — the several members of 
 each system and formation having such a common resemblance, either 
 in mineralogical character or in the kind of animal and vegetable re 
 mains found in them, as to show that they were deposited under very 
 nearly the same general physical conditions of the globe. 
 
 The following table exhibits the names, relative positions, thicknesses 
 and mineralogical characters of the stratified rocks, in descending order 
 as they occur in our islands. The annexed remarks indicate also the 
 
 11 
 
242 CLASSIFICATION OF THE STRATIFIED ROCKS. 
 
 districts where each of these groups of rocks forms the surface, and the 
 general agricultural character of the soils that rest upon them. 
 
 I. Tertiary Strata — characterized by containing, among other fos- 
 sils, the remains of animals, which are identical with existing species 
 
 NAME AND THICKNESS. MINERALOGICAL CHARACTERS. 
 
 1°. Craii. bOft. A mass of rolled pebbles mixed with 
 
 marine shells — ^resting on beds of sand 
 and sandy lime-stone ; the whole more 
 or less impregnated with oxide of iron. 
 Extent. — The Crag forms a stripe of land a few miles in width m the east- 
 ern part of Norfolk and Suffolk, and in the south-eastern part of the latter coun- 
 ty. It is a flat, and generally, it is said, a fertile arable district. 
 
 2°. Fresh-water Marls. 100/^. Marls and marly lime-stones, with 
 
 fresh-water shells divided into two se- 
 ries by an estuary deposit, containing 
 marine shells. 
 Extent. — On these beds reposes the soil of the northern half of the Isle of 
 
 Wight, the only part of England in which they appear at the surface. 
 
 2°. Londm Clay. 200 to 500 ft. Stiff, almost impervious, bro\\ni, blue, 
 
 and blackish clay, rich in marine shells, 
 and containing layers of lime-stone no- 
 dules. 
 Extent. — The greater part of the county of Middlesex, the south-eastern 
 half of Essex, and the southern half of Hampshire, rest upon the London Clay, 
 Soil. — The soil is naturally strong, heavy, wet, and tenacious, "sticking to 
 the plough like pitch," and shrinking and cracking in dry weather. Where it 
 is mixed with sand, it forms a fertile loam •, and hence where the sand of the 
 subjacent plastic clay is easily accessible, it may readily be improved by ad- 
 mixture. Repeated dressings of London manure convert it into rich meadow 
 land, and even where this cannot be obtained, the difficulty and expense of cul- 
 ture have caused a very large portion of it to be retained in pasture. That 
 which is under culture is said to be too strong for turnips and barley, but to 
 grow excellent crops of wheat and beans. 
 
 A°. Plastie^lay. 300 to AOO ft. Alternating beds of cky and sand, of 
 
 various colours and thicknesses. Some 
 of the beds of clay are pure white, and 
 so fine as to be used for making pipes. 
 
 Extent. — This formation surrounds the London clay with an indented, gen- 
 erally low, and flat belt, of varying breadth, occupying a large space in Hamp- 
 shii-e and Dorset, in Essex, Suffolk, and Norfolk, — stretching along the north- 
 ern part of Kent and Surrey, and throwing out arms into Berks, Buckingham, 
 and Hertford. 
 
 Son-. — The soil is veiy various, the alternate beds of sand and clay of differ- 
 ent qualities producing soils of the most unlike quality often within very short 
 distances. The greatest portion of this tract is in arable culture, but there are 
 extensive heaths and wastes in Berks, Hampshire, and Dorset. 
 
 In Norfolk and Suffolk, where the lower beds of this sand rest upon chalk, 
 the soil is readily changed, by an admixture with this chalk, into a good sandy 
 loam, which will yield large crops of turnips, barley, and wheat, instead of the 
 heath and bent, its sole original produce. This chalking is generally repeated 
 once in 8 years, at an expense of 50s. an acre. In Hampsliire and Berkshire, 
 the same method is adopted with great success, and the rich crops now reaped 
 from Hounslow Heath are the result of this method of improvement. 
 
SOIL OF THE UPPER AND LOWER CHALKS. 243 
 
 II. The Secondary Strata — contain no animal remains which 
 can be identified with existing species. Those which are found in them 
 are nearly all different from those which occur either in the tertiary 
 above or the primary strata below. 
 
 A. — Cretaceous System. 
 
 5°. Chalk. 600 ft. The upper part softer, and contain- 
 
 ing layers of flints, with many marine, 
 remains. Below, the chalk is harder, 
 and towards the bottom passes into 
 beds of marl — (chalk marl). 
 Extent. — The chalk occupies a very large area in the south-eastern part of 
 the island. It forms a broad band of from 15 to 25 miles in breadth, running 
 north-east and south-west from the extreme south-western part of Dorset, to 
 the extreme north of Norfolk, — it there turns nearly at a right angle, into the 
 centre of Lincolnshire, where it is 10 to 15 miles in breadth, and thence stretches 
 into Yorkshii-e, in the south-eastern part of which county it covers a large area, 
 and about Flamborough Head attains a breadth of 25 miles. In passing 
 through Berkshire and Surrey, it is partially inten-upted by the plastic clay 
 which it embraces on every side ; and hence, in following the outline of this for- 
 mation it encircles with a broad fringe the southern edges of Sussex and Surrey 
 and the northern borders of Kent. 
 
 Soil. — The soils formed from the upper chalk are all more or less mixed 
 with flints, and they produce naturally a very short but excellent sheep pastui'e. 
 A great portion of this chajk-land in Dorset, Wilts, and Berks, has been occu- 
 pied as a sheep-walk for ages, though under proper cultivation it is said to be 
 convertible into good arable land, producing barley, turnips, wheat, and sain- 
 foin. The lower chalk soils (chalk marl) consist of a deep, strong, calcareous 
 grey or white loam, very productive, and when mixed with the green sand be- 
 low it, becoming still richer, more friable, and more productive of every kind of 
 crop. It is better suited for wheat than the upper chalk, but is less adapted 'for 
 turnips. 
 
 The porous nature of the chalk renders the soil very dry, and in many locali- 
 ties the only method of obtaining a sufficient supply of water is by forming 
 ponds to catch and retain the rain-water. 
 
 In Norfolk and Suffolk, on the Lincolnshire, and more recently on tlie York- 
 shire Wolds, great improvement has been effected by dressing tire chalk-soil 
 with fresh chalk brought up from a considerable depth below, and laid on at the 
 rate of 50 to 80 cubic yards per acre. The explanation of this procedure is to 
 be found in the fact above stated, that the lower chalk marls, without flints, pro- 
 duce an excellent soil, fitted therefore, by admixtui-e with the poorer upper-chalk 
 soils, for materially improving their quality. It is, therefore, only in localities 
 where this lower chalk can be obtained, that the above method of improve- 
 ment can be with any material advantage adopted. This is proved by the 
 practice at Sudbury, in Suffolk, which rests upon the upper beds, where it is 
 found to be more profitable to import the lower chalk from Kent, to lay upon 
 these lands, than to dress them with any of the chalks (only upper beds) which 
 are immediately within their reach.* 
 
 6° . Green Sand. bOO ft. The upper beds consist of layers of 
 
 a Upper, 100. a greenish sand or sand- stone, often 
 
 b Gault,' 150. chalky. The gault is a solid compact 
 
 c Lower, 250. mass of an impervious blue clay, some- 
 
 times marly. The lower gi-een sand 
 contains a series of ochrey resting on a 
 
 " A rigorous chemical analysis of characteristic specimens of these two chalks might lead 
 to interesting results. 
 
244 UPPER GREEN SAND, WEALDEN, AND UPPER OOLITE ROCKS. 
 
 series of greenish sandy strata. The 
 whole of these beds are in many places 
 full of fossils. 
 
 Extent. — The Green Sand forms a narrow border round the whole of the 
 northern and western edge of the chalk, except in Yorkshire, where it has not 
 as yet been anywhere discovered at the surface. It skirts also the southern 
 edge of the chalk in SuiTey and Kent, and its eastern boundaiy in Hampshire, 
 where it attains a breadth of eight or ten miles. It forms likewise the southern 
 portion of the Isle of Wight. 
 
 Soil. — The upper beds, which are the greenest and most chalky, form an 
 open friable soil, easily worked, and of the most productive character. It con- 
 sists in general of an exceedingly fine sand, mixed with more or less of clay 
 and calcareous matter (see analysis, p. 234), coloured by greenish grains. It is 
 rich and productive of eveiy species of crop, and the peculiar richness of this 
 soil has been remarked not only in England but also in the United States of 
 North America. In some parts of Bedfordshire the soils of this formation form 
 the most productive garden lands in the kingdom. In other localities, again, 
 where the soil is formed from layers of black or of white silvery sand, it produ- 
 ces naturally nothing but heath. 
 
 The impervious gault clay forms in Cambridge and Huntingdon "a thin, 
 cold clay soil, which, when wet, becomes as sticky as glue, is most expensive- 
 to cultivate as arable land, and naturally produces a poor, coarse pasture." 
 Much of this tract, though unenclosed, is yet generally in arable culture, under 
 two crops and a naked fallow — the enclosed parts are chiefly in pasture, and 
 yield a rich herbage. 
 
 The lower green-sand presents itself over a comparatively small surface, 
 is in some localities (Sussex) laden with iron ochre, and is there naturally un- 
 productive. 
 
 B. — Oolitic System. 
 
 7°. Wealden. 950 ft. The upper part consists of a fresh- 
 
 a, Weald Clay, 300. water deposit of brown, blue, or fawn- 
 
 d Hastings Sand, 400. coloured clay, often marly and almost 
 c Purbeck lime-stone, 250. always close and impendous to water. 
 
 Beneath this are the iron or ochrey 
 Hastings sands, which again rest upon 
 the Purbeclc beds of alternate fresh- wa- 
 ter lime-stones and marls. 
 Extent. — The Wealden rocks appear at the surface only in Sussex and 
 Kent, of which they fonu the entire central portion. 
 
 Soil. — The soil formed from the Weald Clay is fine gi'ained and unctuous — 
 often pale coloured, and containing much fine grained siliceous sand. It forms a 
 paste which dries and hardens almost like a brick, so that the roots of plants 
 cannot penetrate it. From the expense of cultivating such land, much of it 
 is in wood (Tilgate Fc^rest). and some is in poor wet pasture. On the whole 
 of this tract, therefore, there is much room for improvement. The Hastings 
 sands produce a poor brown sandy loam which naturally yields only heath and 
 brash-wood. Much of this soU is in pasture, but, under proper cultivation, it 
 yields good crops of all kinds. Where the ruins of the Purbeck marls are in- 
 termixed with it, the soil is of a superior quality. 
 
 8°. Upper Oolite. 600 ft. The upper part of this formation con- 
 
 a Portland Beds, 100. sists of the oolite* limestones and cal- 
 
 b Kimmeridge Clay, 500. carcous sand-stones long worked at 
 
 Portland — the lower of the blue slaty 
 
 • So named because they consist of small c^s-'Shaped granules, like the roe of a fish. 
 
IMPERVIOUS SOIL OF THE OXFORD CLAY. 245 
 
 or greyish, often calcareous and bitu 
 minous beds of the Kimmeridge clay. 
 
 Extent. — The Upper Oolite xnins north-east along the northern edge ot 
 the green sand, from the western extremity of Dorset to the extreme north of 
 Norfolk. It is in general only 2 or 3 miles, but in a few places expands to 
 6 or 8 miles in breadth. It appears again on the western edge of the gi-een 
 sand in Lincolnshire, and in Yorkshire forms a stripe 5 or 6 miles in breadtli, 
 which crosses the countiy from Helmsley to Filey Bay. In the Isle of Port- 
 land also it is found, and it stretches in a narrow stripe along part of the south 
 coast of Dorset. 
 
 Soil. — The soil from the Portland rocks, in consequence of the prevalence 
 of siliceous and the absence of clayey matter, produces naturally, or when laid 
 down to grass, only a poor and benty herbage. Its loose and sandy nature 
 makes it also very cheap to work, and hence it is chiefly in arable culture. It 
 is easily affected by drought, but in damp seasons it produces abundant crops 
 — especially in those parts where the soil is naturally mixed with the detritus 
 of the over-lying Hastings sand, and of the calcareous Purbeck beds. 
 
 The Kimmeridge clay forms a tough, greyish, impervious, often however 
 very calcareous soil and subsoil. From the difficulty of working it, much of 
 the surface over which this formation extends is laid down to grass, and the old 
 pasture land affords excellent herbage. The celebrated pasture lands of the vale 
 of North Wilts rests partly on this clay. The relative thicknesses of the Portland 
 beds and the Kimmeridge clay will readily account for the fact of this clay be- 
 ing spread over by far the greatest part of the area occupied by this formation. 
 In Yorksliire, clay of a ga-eat thickness is the only member of this series that 
 has hitherto been observed. On this, as well as on the subjacent Oxford clay, 
 the judicious investment of capital might produce a much greater annual breadth 
 of corn. 
 
 9°. Middle Oolite. 500 ft. The uppermost bed in this fox-mation 
 
 Upper Calcareous Grit, } is a sand-stone containing a consider- 
 
 Coral Rag > 100. able quantity of lime — next is a coral- 
 
 Calcareous Grit, S l"^e lime-stone (coral rag) resting upon 
 
 Oxford Clay ) other sand-stones, which contain much 
 
 Kelloways Rock > 400. lii'f^s in their upper and little or none in 
 
 Blue Clay ' S their lower beds. Below these is an 
 
 enormous deposit of adhesive tenacious 
 dark blue clay, frequently calcareous 
 and bituminous, and towards the lower 
 part containing irregular beds of sand- 
 stones and lime-stones(Kelloways rock) 
 beneatli which the clay again recurs. 
 Extent. — The middle adjoins the upper oolite on the north and west — ac-' 
 companying it from the extremity of Dorset, into Wilts, Oxford, Huntingdon, 
 Lincolnshire, and Yorkshire. Until it reaches Huntingdon, it rarely exceeds 
 6 or 8 miles in width, but in this county and in Lincoln it expands to a width 
 of nearly 20 miles. In Yorkshire it nearly surrounds the vipper oolite, and 
 on the northern border of the latter formation attains a width from north to 
 south of 6 or 8 miles. 
 
 Soil. — The higher beds of both the upper and lower calcareous grits produce 
 good land. They contain lime intermingled with the other materials of the 
 siliceous sand-stone. The upper calcareous grits are no doubt improved by 
 their proximity to the KLmmeridfi^e clay above them, while the lower calcareous 
 grit is in like manner benefitted Ijy the lime of the super-incumbent coral rag. 
 The under beds of both groups are the more gritty, and form a poor, bairen, 
 cdmost worthless soil, much of which in Yorkshire is still unreclaimed. 
 Upon the hills of the coral rag itself occurs the best pastui'e which is met with 
 
S46 ARABLE LANDS OF THE OOLITE. 
 
 in that part ofthe North Riding of Yorkshire through which this formation 
 extends. 
 
 The Oxford clay, v/hich is by far the most important member of this forma- 
 tion, and forms the surface over by far tlie largest portion of the area occupied 
 by it — produces a close, heavy, compact clay soil, difficvilt to work, and which 
 is one of the most expensive of all the clays to cultivate. This is especially 
 the case in Bedford, Huntingdon, Northampton, and Lincoln, in which coun- 
 ties, neveriheless, a considerable extent of it is under the plough. In Wilts, 
 Oxford, and Gloucester, it is chiefly in pastiu-e, and as over these districts it as- 
 sumes the character rather of a clayey loam, the herbage is thick and luxuriant. 
 The impervious nature of this clay has caused the stagnation of water upon 
 its lower lying portions, the consequent accumulation of vegetable matter, and 
 the formation of bogs. The extensive fens of Lincoln, Northampton, Hunt- 
 ingdon, Cambridge, and Norfolk, rest upon the Oxford clay. This tract of 
 fenny country is 70 miles in length, and about 10 in average breadth. When 
 drained and covered with the clay from beneath, it is capable of being converted 
 into a most productive soil. In Lincolnshire, there are about a million acres 
 of fen, which have their drainage into the Wash, about 50,000 of which are at 
 present iri-eclaimable, on account of the state ofthe outlet. 
 
 In the neighbourhood ofthe Kelloways rock the clay becomes more loamy 
 and less difficult to work. 
 
 Both in Yorkshire and in the southern disti-icts, the Oxford clay is found to 
 favour the growth of the oak, and hence it is often distinguished by tlie name 
 of the oak tree clay. 
 
 10°. Inferior Oolite. 600/^ Thin, impure, rubbly beds of shelly 
 
 a Combrash, 30. lime-stone form the upper part of this 
 
 h Forest Marble, 50. series. These rest upon alternate beds 
 
 c Bradford Clay, 50. of oolitic shelly lime-stone and sand- 
 
 d Bath Oolite, 130. * stone, more or less calcareous, having 
 
 e Fuller's Earth, 140. pai-tings of clay ; these again upon beds 
 
 / Inferior Oolite, ) o^., of blue marly clay, immediately under 
 
 g Calcareous Sand, \ which are the thick beds ofthe light-co- 
 
 loured oolite lime-stone of Bath. Be- 
 neath these follow other beds of blue 
 clay, with Fuller's eartli, based upon 
 another oolitic lime-stone, which is fol- 
 lowed by slightly calcareous sands. 
 Extent.— ^This formation commences also at the south-westei-n extremity of 
 Dorset, and runs north-east, swelling out, here and there, and in Gloucester, 
 Oxford, and Northampton attaining a width of 15 to 20 miles. It occupies 
 nearly the whole of these three counties, covers almost the entire area of Rut- 
 'land, a lai'ge portion ofthe north-east of Leicester, and then, in a narrow stripe, 
 stretches north through Lincoln, and disappears at the Hmnber. It appears 
 again in the North Riding of Yorkshire, skirting the outer edge of the middle 
 oolite, on the north of which it attains a breadth of 15 miles, and stretches 
 across, with little interruption, from near Thirsk to the North sea. A small 
 patch of it appears farther north, on the south-eastern coast of Suthei'land, and 
 on the east and south of the Isle of Sky. 
 
 Soil. — It will be understood from what has been already stated in reference 
 to other formations, that one which contains so many different rocks, as this 
 does, must also present many diversities of soil. Where the tipper beds come 
 to the surface, the clay-partings give tlie character to the soil — fonning a calca- 
 reous clay, which, when dry or drained, is of good quality. In other places it 
 fonns a close adhesive clay, which is naturally almost sterile. The Bath oolite 
 weather? and crumbles readily. The soil upon it is thin, loose, and diy. The 
 rock is fuU of vertical fissures, which carry off the water and drain its surface. 
 
OLD PASTURES OF THE LIAS. 247 
 
 When free from fragments of the rock, the soil is often close and impervious, 
 and, though of a brown colour, deep, and apparently of good quality, it is really 
 worthless, or, as the farmers call it, dead and sleepy. Most of this land, how- 
 ever, is in arable cultivation. The heavy soils, which rest on the clay contain- 
 ing Fuller's earth, are chiefly in pasture. 
 
 The inferior oolite varies much in its character, containing, in some places, 
 much lime-stone, while in others, as in Yorkshire, it forms a thick mass of sand- 
 stones and clays, with occasional thin beds of coal. In Gloucester, Oxford, 
 'Northampton, and Rutland, these lower beds form a tract of land about 12 miles 
 in width. The soil is generally soft, sandy, micaceous, of a brown colour, and 
 of a good fertile quality. It is deep, contains many fragments of the subjacent 
 rock, is porous, and easily worked. Where the sand-stones prevail, it is of in- 
 ferior quality. In these counties it is principally enclosed, and in arable culture, 
 the sides of the oolitic hills and the clayey portions being in pasture. In York- 
 shire, much of the unproductive moor land of the North Riding rests upon this 
 formation. Nearly all the arable land in the county of Sutherland rests on the 
 narrow stripe of the lower oolite rocks which occurs on its south-east coast. 
 The debris of these rocks has formed a loamy soil, which, when well limed, 
 produces heavy crops of turnips. 
 
 11°. Lias. 500 to 1000 ft. This great deposit consists chiefly of 
 
 an accumulation of beds of blue clay, 
 more or less indurated — interrupted in 
 various places by beds of marl, and of 
 blue, more or less earthy, lime-stones, 
 which especially abound in the lowef 
 part of the series. The whole is full of 
 shells, and of the remains of large ex- 
 tinct animals. 
 Extent. — Wherever the lower oolites are to be traced in England, the lias 
 is seen coming up to the surface on its northern or western edge, pursuing an 
 exceedingly tortuous north-eastern course, throwing out m its course many 
 arms (outliers), and varying in breadth from '3 to 6 or 10 miles. It may be 
 traced from the mouth of the Tees, in Yorkshire, to Lyme Regis, in Dorset, the 
 continuity being broken only by the coal field of Somerset. In Scotland and 
 Ireland no traces of this formation have yet been detected. 
 
 Soil. — Throughovit the whole of this formation the soil is a blue clay, more 
 or less sandy, calcareous, and tenacious. Where the lime or sand prevails the 
 soil is more open, and becomes a loam ; where they are less abundant, it is of- 
 ten a cold, blue, unproductive, wet clay. This latter, indeed, may be given as 
 the natural character of the entire formation. Where it rests upon a gravelly 
 or open subsoil, or contains a large quantity of vegetable matter, it may be 
 cultivated to advantage, and it is found especially to produce good herbage. In 
 all situations, it is an expensive soil to work, and hence by far the greater por- 
 tion of it is in old pasture. The celebrated dairy districts of Somerset, Glou- 
 cester, Warwick, and Leicester, rest for the most part on the lias, as does also 
 much of the best grazing and pasture land in Nottingham and Yorkshire. 
 Through the long lapse of time an artificial soil has been produced on the un- 
 distm-bed surface of these clay districts, which is peculiarly propitious to the 
 growth of grass. With skilful drainage and judicious culture, it is capable of 
 producing heavy crops of wheat. 
 
 C, — New Red Sand-stone System. 
 
 The upper and lower red sand-stones 
 consist of alternate layers of sand, sand- 
 stones, and marls sometimes colourless, 
 but generally of a red colour — sprinkled 
 in the upper series with frequent green 
 
 12°. Upper and Lower > _^„ ^ 
 Red Sand-stones. ^ -' 
 
248 FERTILE MARLS OF THE NEW RED SAND-STONE. 
 
 spots. The lower beds are sometimes 
 full of rolled pebbles. Few of the sand- 
 stones of this formation are sufficiently- 
 hard to form building stones — many of 
 the layers consist of loose friable sand, 
 and the marls universally decay and 
 crumble to a fine red powder under the 
 influence of the weather. 
 Extent. — The new red sand-stone extends over a larger portion of the surface* 
 of England than any other formation. It commences at 1'orbay, in the south 
 of Devon, runs north-east into Somersetshire ; from Bristol ascends both sides 
 of the Severn, accompanies it into the vale of Gloucester, stretches along the 
 base of the Malvern hills, and north of the city of Worcester expands into a 
 gently undulating plain, nearly 80 miles in width at its broadest part, compre- 
 hending nearly the whole of the counties of Warwick and Stafford and the 
 greater part of that of Leicester. Fi-om this central plain it parts into two di- 
 visions. One of these runs west over the whole of Cheshire — (in which 
 county it contains salt springs and mines of rock salt) — the western part of 
 Flint, and on the south-west surrounds the county of Lancashire. It is there 
 interrupted by the rising of the older rocks in Westmoreland, but re-appears in 
 the eastern corner of this county, runs north-west through Cumberland, form- 
 ing the plain of Carlisle — and thence round and across the Solway Frith till it 
 finally disappears about 20 miles north of Dumfries. The other arm, proceed- 
 ing from the towns of Derby and Nottingham, runs due north through Notting- 
 ham and the centre of Yorkshire, skirting the outer edge of the lias, and finally 
 disappears in the county of Durham to the north of the i-iver Tees. The south- 
 ern portion of this arm has a width of 20 to 30 miles, until it reaches the neigh- 
 bourhood of Knaresborough, where it suddenly contracts to G or 8, and does 
 not again expand to more than 10 or 12 miles. 
 
 North of Dumfries-shire these rocks are not known to jccur in our island 
 In the north-east of Ireland they form a stripe of land a few miles in width, run- 
 ning from Lough Foyle to Lough Neagh, and thence, with slight interruptions, 
 to the south of Belfiist. 
 
 Soil. — These rocks, by their decay, almost always produce a deep red 
 soil. Where the red clay and marl predominate, this soil is a red clay or 
 clayey loam of the richest quality, capable of producing almost every crop, and 
 remarkable therefore for its fertility. It is chiefly in arable culture, because of 
 the comparative ease with which it is worked, but the meadows are rich, and 
 produce gooii^Serbage. Where the rocks are more sandy, and contain few 
 marly bands, the soil produced is poorer, yet generally forms a good sandy loam, 
 suitable for turnips and barley. 
 
 In Devonshire, as in the vale of Taunton and other localities, where the lias 
 and the red sand-stone adjoin each other, or nm side by side, the difference in 
 the fertility and general productiveness of the two tracts is very striking. On 
 the former, as already observed, good old grass land is seen, but the arable land 
 on the latter produces the richest and most luxuriant crops to be seen on any 
 soil in the kingdom. In this county, and in Somerset, the only manure it seems 
 to require is lime, on every repetition of which it is said to produce mcreased 
 crops. The same i-emarks as to its compai'ative fertility, apply with more or 
 less force to the whole of the large area occupied by this formation in our island 
 — wherever the soil has been chiefly formed by the decomposition of the rock 
 on which it rests. In some localities (Dumfries-shire) the vticaccoiis, marly 
 rock is dug up, and, after being crumbled by exposure to a winter's frost, is laid 
 on with advantage as a top-dressing to grass and other lands. 
 
 In the south of Lancashire, and along its western coast, and on the shores of 
 the Solway, in Dumfries- shire, a great breadth of this formation is covered with 
 peat. 
 
SOILS OF THE MAGNESIAN LIMESTONE AND COAL MEASURES. 249 
 
 13°. Magnesian Lime-stone. The magnesian lime-stone is gene- 
 
 rally of a yellow, sometimes of a giey, 
 colour. In the upper part it occasion- 
 ally presents itself in thin beds, which 
 crumble more readily when exposed to 
 the air. Jn some places, also, it assumes 
 a marly- character, forming masses 
 which are soft and friable; in general, 
 however, it is in thick beds, hard and 
 compact enough to be used for a build- 
 ing stone or for mending the roads. The 
 quantity of carbonate of magnesia it 
 contains varies from 1 to 45 per cent. 
 It is in the north of England generally 
 traversed by vertical fissures, which ren- 
 der the surface dry, and make water in 
 many places difficult to be attained. 
 Extent. — The magnesian limestone stretches in an almost vmbroken line 
 nearly due north from the city of Nottingham to the mouth of the river Tyne. 
 It is in general only a few miles in width, its principal expansion being in the 
 county of Durham, where it attains a breadth of 8 or 10 miles. 
 
 Soil. — It forms, for the most part, a hilly country, covered by a reddish 
 brown soil, often thin, light and poor, where it rests immediately on the native 
 rock — producing indifferent herbage when laid down to grass, but under skilful 
 management capable of yielding average crops of turnips and barley. In the 
 eastern part of the county of Durham tracts of the poorest land rest upon this 
 rock, but as this formation is for the most part covered with deep accumulations 
 of transported materials — the quality of the soil is in very many places more 
 dependent upon the character of this superficial covering tlian upon the nature 
 of the rock beneath. 
 
 During the slow degradation of this rock, the rains gradually wash out great 
 part of the magnesia it contains, so that it seldom happens that the soil formed 
 from it, though resting on the parent rock, contains so mnch magnesia as to be 
 necessarily hurtful to vegetation. 
 
 D. — Carboniferous System. 
 
 14°. Coal Measures. 300 ft. Consisting of alternate beds of indu- 
 
 rated bluish-black clay (coal shale), of 
 siliceous sand-stone generally grey in 
 colour and containing imbedded plants, 
 and of coal of various qualities and de- 
 grees of thickness. Beds of lime-stone 
 rarely appear in this formation till we 
 approach the lowest part of the series. 
 Extent. — Fortunately for the mineral resources of Great Britain, the coal 
 measures occupy a large area in our island. Most of the districts in which 
 they occur are so well known as to reqv\ire only to be indicated. The south 
 Welsh coal-field occupies the south of Pembroke, nearly the whole of Glamor- 
 gan, and part of Monmouth-shire. In the north of Somerset are the coal mea- 
 sures of the Bristol field, which stretch also across the Severn into the forest of 
 Dean. In the middle of the central plain of the new red sand-stone, lie the coal- 
 fields of Ashby-de-la-Zouch, of Coventiy, and DvTdley, and on its western 
 borders are those of Shropshire, Denbigh, and Flint (North Wales). To the 
 north of this plain extends on the right" the Yorkshire coal-field from Notting- 
 ham to Leeds, while on the left is the small coal-field of Newcasde-under-Line, 
 and the broader Lancashire field which crosses the country from near Liverpool 
 to Manchester. Almost the entire eastern half of the county of Durham, and 
 
 11* 
 
^.'0 MOOR-LANDS OF THE MILLSTONE GRIT. 
 
 of the low country of Northumberland, is covered with these measures -but 
 the largest area covered by these rocks is in that part of the low country of 
 k-^cotland which extends in a north-easterly direction from the west coast of 
 Ayrshire to the eastern coast of Fife. They there form a broad band, having 
 an average breadth of 30 miles, interrupted often by trap or green-stone rocks, 
 yet lying immediately beneath the loose superficial matter, over the largest por- 
 tion of this extensive district. They do not occur further north in our island. In 
 Ireland they form a tract of limited extent on the northern borders of the county 
 of Monaghan — cover a much larger area in the south-east in Kilkenny and 
 dueen's counties — and towards the mouth of the Shannon, spread on either 
 bank over a large portion of the counties of Clare, Kerry, and Limerick. 
 
 Soil. — The soil produced by the degradation of the sand-stones and shales 
 of the coal formation is universally of inferior quality. The black shales or 
 schists form alone a cold, stiff, ungrateful clay. The sand-stones alone form 
 thin, unproductive soils, or barren — almost naked — heaths. When the clay 
 and sand are mixed a looser soil is produced, which, by heavy liming, by drain- 
 ing, and by skilful culture, may be i-endered moderately productive. In the 
 west of the counties of Durham and Northumberland, and on the higher edges 
 of most of our coal fields, there are extensive tracts of this worthless sand-stone 
 surface, and thousands of acres of the improveable cold clays of the shale beds. 
 These latter soils appear veiy unpromising, and can only be rendered remune- 
 ratively productive in skilful hands. They present one of those cases in which 
 the active exertions of zealous agriculturists, and the efforts of the friends of 
 agriculture, might be expended with the promise of much benefit to the country. 
 
 15°. Millstone Grit. 600 ft. This formation consists in some lo- 
 
 " calities of an entire mass of coarse sand- 
 
 stone, of great thickness — in others of 
 alternations of sand-stones and shales, 
 resembling those of the coal-measures 
 — while in others, again, lime-stones, 
 more or less siliceous, are interposed 
 among the sand-stones and shales. 
 Extent. — A lai*ge portion of Devonshire is covered with these rocks — they 
 form also the high land which skirts to the north and west the coal-measures of 
 Yorkshire, Lancashire, and Durham, and over which is the first ascent to the 
 chain of mountains that run northward through these three counties. In Scot- 
 land, they have^iiot been observed to lie immediately beneath any part of the sur- 
 face. In the north of Ireland they cover a considerable area, stretching across 
 the county of Leitrim between Sligo and Lough Erne. 
 
 Soil.— The soils resting upon, and formed from, these rocks are generally of 
 a very inferior description. Where the sand-stones come to the surface, miles 
 of naked rock appear ; other tracts bear only heath, or, where the rains have 
 only a partial outlet, accumulations of peat. The shale-beds, like those of the 
 coal-measures, aflford a cold, unproductive, yet not unimproveable soil — it is 
 only where lime-stones occur among them that patches of healthy verdure are 
 seen, and fields which are readily susceptible of profitable arable culture. 
 
 It is true, therefore, of this fomiation in general, that the high grounds form 
 extensive tracts of moor-land. In the lower districts of countiy over which it 
 extends, the soil generally rests not on the rocks themselves, but on su[)erficial 
 accumulations of transported materials, which are often of such a kind as to 
 form a soil either productive in itself or capable of being rendered so by skilful 
 cultivation. 
 
 16°. Mountain ) q^.. ^ In this formation, as its name implies, 
 
 Lime-stone. \ *' lime-stone is the predominating rock. 
 
 It is generally hard, blue, and more or 
 
SWEET PASTURES OF THE MOUNTAIN LFME-STONE. 251 
 
 less full of organic remains. In some 
 localities, it occurs in beds of vast thick- 
 ness — (Derby and Yorkshire) — while 
 in others — (Northumberland) — it is di- 
 vided into numerous layers, with inter- 
 posed sand-stones and beds of shale, and 
 occasional thin seams of coal. 
 Extent, — The greater portion of the counties of Derby and Northumberland 
 are covered by this formation, and from the latter county it stretches along the 
 west of Durham through Yorkshire as far as Preston, in Lancashire — forming 
 the mountains of the well known Pennine chain, which throw out spurs to the 
 east and west, and thus present on the map an irregular outline and varying 
 breadth of country. In Scotland these rocks cover only a small portion of the 
 county of Berwick, immediately on the Border; but in Ireland, almost the en- 
 tire central part, forming upwards of one-half of the whole island, is occupied 
 by the mountain lime-stone formation. 
 
 Soil. — From the slowness with which this rock decays, many parts of it are 
 quite naked ; in others, it is covered with a thin light porous soil of a brown 
 colour, which naturally produces a short but thick and sweet herbage. Much 
 of the mountain lime-stone country, therefore, is in natural pasture. 
 
 Where the lime-stones are mixed or interstratified with shale beds, which de- 
 cay more easily, a deeper soil is found, especially in the hollows and towards 
 the bottom of the valleys. These are often stiff and naturally cold, but when 
 well drained and limed produce excellent crops of eveiy kind. In Northumber- 
 land, much of the mountain lime-stone country is still in moor-land, but the ex- 
 cellence of border farming is gradually rescuing one improveable spot after ano- 
 ther from the hitherto unproductive waste. In Yorkshire and Devonshire also 
 improvements are more or less extensively in progress, though, in all these dis- 
 tricts, there are large tracts which can never be re-claimed. 
 
 E, — Old Red Sand-stone or Devonian System. 
 
 17°. Old Red Sand- ? 500 to The upper part of this formation con- 
 
 stc^ie, \ 10 000 ft. sists of red sand-stones and conglomer- 
 
 01d*Red Conglomerate. * * ates (indurated sandy gravel), the mid- 
 Corn-stone and Marls. die of spotted, red and green clayey 
 
 Tile-stone marls, with m-egular layers of hard, of- 
 
 ten impure and siliceous lime-stones 
 (cornstones) likewise mottled, and the 
 lowest of thin hard beds of siliceous 
 sand-stones, sometimes calcareous, mot- 
 tled, and splitting readily into thin flags 
 (tile-stones). 
 Extent, — Though occasionally of vast thickness, the old red sand-stone does 
 not occupy a very extensive area in our island. In the south of Pembroke it 
 forms a tract of land on either side of the coal-field — surrounds on the north and 
 east the coal-field of Glamorgan, and immediately north of this county covers a 
 large area comprehending the greater portion of Brecknock and Hereford, and 
 part of Monmouth. ■ A small patch occurs in the Isle of Anglesey, and in the 
 north-eastern corner of Westmoreland — but it does not again present itself till 
 we reach the western flank of the Cheviot Hills. It there appears on either 
 side of the Tweed, and extends over a portion of Berwick and Roxburgh to the 
 base of the Lammermuirs. On the north of the same hills it again presents it- 
 self, and stretching to the south-west, forms a considerable tract of country in 
 the counties of Haddington and Lanark. On the north of the great Scottish 
 coal-field it fonns a broad band, which runs completely across the island in a 
 south-western direction along the foot of the Grampians, from Stonehaven to 
 
252 RICH WHEAT LANDS OF THE OLD RED SAND-STOJ?E. 
 
 the Firth of Clyde, is to be discovered in the Island of Arran, and at the Mull 
 of Cantire, and — along the prolongation of the same line — at various places on 
 the northern flank of the great mountain lime-stone formation of Ireland, and 
 especially in the counties of 1'yrone, Fermanagh, and Monaghan. In the 
 north of Scotland, it lines either shore of the Moray Firth, skirts the coast to- 
 wards Caithness, where it covers nearly the whole county, and still further 
 north, forms the entire surface of the Shetland Islands. Along the north-west- 
 ern coast, it also appears in detached patches till we reach the southern ex- 
 tremity of the Isle of Sky. 
 
 In Ireland, it occurs also on the extreme southern edge of the mountain lime- 
 stone, in Waterford and the neighbouring counties — and in the middle of this 
 formation on the upper waters of the Shannon, in the south of Mayo, and 
 round the base of the slate mountains ofTipperary. 
 
 Soil. — The soil on the old red sand-stone admits of very nearly the same 
 variations as on the new red sand-stone fonination. Where it is formed, as in 
 parts of Pembroke, from the upper sand-stones and conglomerates, it is either 
 worthless or it joroduces a poor hungiy soil, "which eats all the manure, and 
 drinks all the water." These upper rocks are sometimes so siliceous as to be 
 almost destitute both of lime and clay — in such cases, the soils they form are 
 almost valueless. 
 
 The marly beds and lime-stones of the second division, yield warm and rich 
 soils — such as the mellow lands of Herefordshire, and the best in Brecknock 
 and Pembroke shires. The soil in every district varies according as the partings 
 of marl are more or less numerous. These easily crumble, and where they 
 abound form a rich stiff wheat soil — like that of East Lothian and parts of Ber- 
 wickshire ;-^ where they are less frequent the soil is lighter and produces excellent 
 turnips and barley. "VVhere the subsoil is porous, this land is peculiarly fa- 
 vourable to the growth of fruit trees.* The apple and the pear are largely grown 
 in Hereford and the neighbouring counties, long celebrated for the cider and 
 perry they produce. 
 
 The tile-stones reach the surface only on the northern and western edges of 
 this formation in England. In Ayrshire, in Lanarkshire, in Ross-shire, and in 
 Caithness, larger tracts of land rest on these lower beds. In all these districts 
 rich corn lands are produced from the rocks of the middle series. The fertility 
 of Strathmore in Perthshire, and of other vallies upon this formation, is well 
 known — Easter Ross and Murray have been called the granary of Scotland, 
 and even in Caithness rich corn-bearing (oat) lands are not unfrequent. Yet 
 in the immediate neighboui'hood of these rich lands, tracts of tile-stone countiy 
 occur, which are either covered with useless bog (Ayrshire and Lanarkshire), 
 or with a thin covering of soil which is almost incapable of profitable culture. 
 In this latter condition is the moor of Beauly on the Cromarthy Firth, an area 
 of 50 square miles, which, till within a few years, lay as an unclaimed common 
 — and in the county of Caithness still more extensive tracts. ' 
 
 In South Devon and part of Cornwall a veiy fertile 'district rests also on the 
 middle series of these I'ocks. Instead of red sand-stones, however, the country 
 there consists of green slates, more or less siliceous, of sand-stones and of lime- 
 stones, which by their decay have formed a veiy productive soil. These rocks 
 in the above counties abound in fossil remains, and it is chiefly for this reason 
 that the term Devonian has been applied to the rocks of the old red sand-stone 
 formation. 
 
 ♦ The most loamy of these red soils of Hereford afford the finest crops of wheat and hops, 
 and bear the most prolific apple and pear trees, whilst the whole i-egion (eminently in the 
 heavier clayey tracts) is renowned for the production of the sturdiest oaks, which so abound 
 as to be styled the "weeds of Herefordshire." Thus, though this region contains no mines, 
 the composition of its rocks is directly productive of its great agricultural wealth. — Murchi- 
 son, Silurian System, I., p. 193. 
 
MUDDY S OILS OF THE LOWER LUDLOW ROCKS. 253 
 
 III. Primary Strata. — In these rocks slates abound, and lime- 
 stones are more rare. Organic remains are also less frequently met 
 with than in the superior rocks. These remains belong all to extinct 
 species, the greater part to extinct genera and families, and are frequent- 
 ly so wholly unlike to existing races that it is often difficult to trace any 
 resemblance between the animals which now live and those which appear 
 to have inhabited the waters of those ancient periods. 
 
 F. — Silurian System. 
 
 18°. Upper Silurian. 3800 ft. The upper Ludlow rocks consist of 
 
 1°. Ludlow formation. sand-stones more or less calcareous and 
 
 a Upper Ludlow ) argillaceous. These rest upon hard, 
 
 b Aymestry Lime-stone > 2000 somewhat crystaUine, earthy lime-stones 
 
 c Lower Ludlow S (Aymestry hme-stones.) The lower 
 
 oo -Tsr Ludlow rocks are masses of shale more 
 
 2-. Wenlocic formation. free from lime and sand than the upper 
 
 A ShT' i 1800 beds, and from the mode in wliich they 
 
 ■ ^iiaie ^ decay into mud are locally known by 
 
 the name of " mud-stones." 
 
 The Wenlock or Dudley formation 
 consists in the upper part of a great 
 thickness of lime-stone beds often argil- 
 laceous, and abounding in the remains 
 of mai'ine animals; and in the lower 
 part of thick beds of a dull clayey shale 
 — in its want of cohesion, and in its 
 mode of decay, very much resembling 
 the vmd-stones of Ludlow. 
 Extent.— The principal seat of these rocks in our island is in the eastern 
 counties of Wales, where they lie immediately beneath the surface over the 
 eastern half of Radnor, and the north of Montgomeiy. 
 
 Soil. — The prevailing character of the soils upon these formations is derived 
 from the shales and mud-stones — and from the earthy layers of the sand-stones 
 and lime-stones which decay more readily than the purer masses of these rocks. 
 The traveller is immediately struck in passing- from the rich red marls and 
 clays of the old red sand-stone in Hereford, on to the dark, almost black, soils 
 of the upper and lower Ludlow rocks in Radnor, not merely by the change of 
 colour, but by their obviously diminished value and productiveness. The up- 
 per Ludlow is crossed by many vertical cracks and fissures, and thus, though 
 clayey, the soil which rests upon it is generally dry, and susceptible of cultiva- 
 tion. 
 
 Not so the muddy soils of the lower Ludlow and Vv^enlock rocks. They are 
 generally more or less impervious to water, and being subject to the drainage 
 of the upper beds, form cold and comparatively unmanageable tracts. It is only 
 where the intermediate lime-stones (Aymestry and Wenlock lime-stones) come 
 to the surface and mingle their debris with those of the upper and lower rocks, 
 that the stiff clays become capable of bearing excellent crops of wheat. This 
 fact, however, indicates the method by which the whole of these cold wet clays 
 might be greatly improved. By perfect artificial drainage and copious limeing, 
 the unproductive soils of the lower Ludlow and of the Wenlock shales might be 
 converted into wheat lands more or less rich and fertile. It unfortunately hap- 
 pens, however, that in those districts of North and South Wales, where the 
 dark grey or black " rGtchy" land of the mud-stones prevails, lime is often so 
 scarce, or has to be brought from so great a distance, as to render this means of 
 improvement ahnost unattainable. 
 
254 MOUNTAINOUS COUNTRY OF THE SLATE ROCKS. 
 
 19°. Lower Silurian. 3700 ft. The Caradoc beds consist of thicK 
 
 Caradoc Sand-stones 2500 ^^^^^^ ^^ sand-stone of various colours, 
 Llandeilo Flags 1200 nesting upon, and covered by and oc- 
 
 ° casionally interstratined with, thm beds 
 
 of impure lime-stone. The Llandeilo 
 flags which lie beneath them consist of 
 thin calcareous strata, in some locali- 
 ties alternating with sand-stones and 
 shales. 
 Extent. — These rocks form patches of land in Shropshire and the north of 
 Montgomery — and skirt the southern and eastern edge of Caermarthen. None 
 of the Silurian rocks have yet been found to extend over any large portion of 
 either Scotland or Ireland. 
 
 Soil. — The Caradoc sand-stone, when free from lime, produces only a 
 naked surface or a barren heath. The Llandeilo flags form a fertile and arable 
 soil, as may be seen in the south of Caermarthen, where they are best devel- 
 oped, and especially on the banks of the Towey, which for many miles before 
 it reaches the town of Caermarthen runs over this formation. 
 
 In this formation, as in every other we have yet studied, the soil changes im- 
 mediately on the appearance of a new I'ock at the surface. The soil of the 
 Wenlock shale is sometimes more sandy as it approaches the Caradoc beds, 
 and on favourable slopes forms good arable land and sustains luxuriant woods, 
 but where the Caradoc sand-stones reach the surface, a wild heath or poor 
 wood-land stretches over the countiy, until passing over their edges we reach 
 the lime-containing soils of the Llandeilo flags, when fertile arable lands and 
 lofty trees again appear.* 
 
 G. — Cambrian System. 
 
 20°. Upper Sf Lower Cam- ) These rocks, which are many thou- 
 
 hrian Rocks. \ sand yards in thickness, consist chiefly 
 
 of thin slates, often hard and cleaving 
 readily, like roofing slates, occasionally 
 intermingled with sandy and thin lime- 
 stone beds. They contain few organic 
 remains. 
 Extent. — These rocks cover the whole of Cornwall, part of North and 
 South Devon, the western half of Wales, the entire centre of the Isle of Man, 
 and a larger-part of Westmoreland and South Cumberland. In Scotland, they 
 form a band between 30 and 40 miles in width, which crosses the island from 
 the Mull of Galloway to St. Abbs Head. They form also a narrow stripe of 
 land, which recrosses the island along the upper edge of the old red sand-stone 
 from Stonehaven to the Isle of Bute, and, further north, spi-ead over a consider- 
 able portion of Banff'shire. In the south-west of Ireland they attain a great 
 breadth, are narrower at Waterford, but form a broad band along the granite 
 mountains from that city to Dublin. They extend over a large portion of the 
 counties of Louth, Cavan, Monaghan, Armagh, and Down, — form a nairow 
 strii^e also along the coast of Antrim as far north as the Giant's Causeway, — 
 and, in the interior of Ireland, re-appear in the mountainous district of Tip- 
 perary. 
 
 Soil. — The predominance of slaty rocks in this formation imparts to the soils 
 of the entire surface over which they extend one common clayey character. 
 They generally form elevated tracts of country, as in Wales, Cumoerland, 
 Scotland, and Ireland, where the rigours of the climate combine with the fre- 
 quent thinness and poverty of the soil to condemn extensive districts to worth- 
 
 * Such a passage from one formation to another is exhibited in the diagrams inserted in 
 page 238. 
 
HEATHS AND BOGS ON THE GNEISS ROCKS. 255 
 
 less heath or to widely extended bogs. Yet the slate rocks themselves, especi- 
 ally when they happen to be calcareous, are capable of producing fertile soils. 
 Such are found in the valleys, on the hill sides, and by the margins of the lakes 
 that are often met with in the slate districts. More extensive stripes or bands 
 of such productive land occur also at lower levels, as in the north of Devon, and 
 in the south of Cornwall. In the latter county, the soils on the hornblende slate 
 (which lies near the bottom of the slate series)are extremely fertile, exhibiting a 
 striking contrast with those which are formed from the neighbouring Serpentine 
 rocks, that extend over a large area immediately north of the Lizard (see p. 265.) 
 
 Where the clay-slate soils occur, therefore, however cold and stiff they may 
 be, a favourable climate, drainage, if necessary, and lime, either naturally pre- 
 sent, or artificially added, appear to be the first requisites to insure fertility. 
 
 The mode in which these rocks lie, or the degree of inclination which the 
 beds exhibit, exercises an important influence upon the agricultural character 
 of the soils that rest upon them. In the diagram inserted in page 238, the 
 rocks (A) represent the highly inclined, often nearly vertical position, in which 
 the slate rocks are most frequently found. The soil formed from them must, 
 therefore, rest on the thin edges of the beds. Thus it happens in many lo- 
 calities that the rains cany down the soluble parts of the soil and of the manure 
 within the partings of the slates — and hence the lands are hungry and unprofit- 
 able to work. 
 
 On the slopes of the clay slate hills of the Cambrian and Silurian systems, 
 flourish the vineyards of the middle Rhine, the Moselle, and the Ahr. 
 
 H. — Mica-Slate and Gnsiss Systems. 
 
 21°. Mica-Slate, Gneiss Rock. The upper of these formations con- 
 
 sists of thin undulatinglayers of rock, 
 consisting chiefly of quartz and mica, 
 alternating occasionally with green 
 (chlorite) slates, common clay-slates. 
 quartz rock and hard crystalline ilni'i- 
 stones. The gneiss is a hard an 1 
 solid rock of a similar nature, consist- 
 ing of many thin layers distinctly vi- 
 sible, but firmly cemented, and as it 
 were half-melted together. 
 Extent. — Two-thirds of Scotland, comprehending nearly the whole country 
 north and west of the Grampians, consist of these rocks. In England there 
 is only a small patch of mica slate about Bolt Head and Start Point in South 
 Devon, and a somewhat larger in Anglesey ; but in Ireland, nearly the whole 
 of the counties of Donegal and Londonderry on the north, and a large portion 
 of Mayo, Connaught, and Galway, on the west, are covered by I'ocks belonging 
 to the mica slate system. 
 
 Soils. — These rocks are, in general, harder still than those of the Cambrian 
 system, and still more impervious to water, when not highly inclined. - They 
 crumble slowly, therefore, and imperfectly, and hence are covered with thin 
 soils, on which, where good natural drainage exists, a coarse herbage springs, 
 and from which an occasional crop of corn may be reaped — but on which, where 
 tiie water becomes stagnant, extensive heaths and bogs prevail. That they 
 contain, when perfectly decomposed and mellowed, the materials of a fertile soil, 
 is shown by the richness of many little patches of land, that occur in the shel- 
 tered valleys of the Highlands of Scotland, and by the margins of its many 
 lakes. In general, however, the mica-slate and- gneiss country is so elevated 
 that not only does an ungenlal climate assist its natural unproductiveness, but 
 the frequent rains and rapid flowing rivers bear down to the bottoms of the val- 
 lies or forward to the sea, much of the finer matter produced by the decay of the 
 rocks, — leaving only a poor, thin, sandy soil behind. 
 
256 FERTILITY DEPENDENT ON GEOLOGICAL STRUCTURE. 
 
 On these hard slate and gneiss rocks extensive pine forests in Sweden and 
 Norway have long lived and died. In these countries it is customary in many 
 places to burn down the wood, to strew the ashes over the thin soil, to harrow 
 in the seed — to reap thus one or two hax'vests of rye, and to abandon it again to 
 nature. A grove of beech first springs up, which is supplanted'by an after- 
 growth of pine, and finally disappears. 
 
 Such is a general description of the nature and order of succession of 
 the stratified rocks, as they occur in Great Britain and Ireland — of the 
 relative areas over wiiich they severally appear at the surface — and of 
 the kind of soils which they produce by their natural decay. The con- 
 sideration of the facts above stated,* shows how very much the fertility 
 of each district is dependent uj)on its geological structure — how much a 
 previous knowledge of that structure is fitted to enlighten us in regard to 
 the nature of the soils to be expected in any district — to explain anoma- 
 lies also in regard to the unlike agricultural capabilities of soils a[)par- 
 ently similar — to indicate to the purchaser where good or better lands 
 are to be expected, and to the improver, whether the means of amelio- 
 rating his soil by limeing, by marling, or by other judicious admixture, 
 are likely to be within his reach, and in what direction they are to be 
 sought for. There still remain some important branches of this suhject 
 to which, at the risk of fatiguing you, it will be my duty briefly to draw 
 your attention in the following lecture. 
 
 * For much of the practical information contained in this section, I have to express my 
 oblijraiioiis to the following works: — For the extreme southern counties, to De La Beche's 
 d'eological Report on Cornwall and Devon; and to a paper by Sir Charles Lemon, Bart., on 
 thf Agricultural Produce of Cornwall ; — for Wales and the Border counties, to Murchison's 
 Silurian System ; — for the Midland counties of England, to Morton on Soils, a work I have 
 in a |)revious note recommended to the attention of the reader ; for Yorkshire, to a paper by 
 Sir .Jnhn Johnston, Bart., in the Journal of the Royal Agricultural Society ; — and for the Old 
 Red Sand-stone of the north of Scotland, to the very interesting little work of Mr. Miller on 
 The Old Red Sandstone. The reader would read the above section with much greaft^r 
 profit if he were previously to possess liimself of Phillip's Outline Map of the Geology of the 
 British Islands, 
 
LECTURE XII. 
 
 rom])osition of the granitic rocks and of their censtltuent minerals— Cause and made of 
 their degradation— Soils derived from them— Superficial accumulations — Their mfluence 
 upon the character of the soils— Organic constituents, ultimate chemical constitution, and 
 pliysioal properties of soils. 
 
 It has been stated in the preceding Lecttire, (§ 6, p. 237), that the rocks 
 which present themselves at the surface of the earth are of two kinds, 
 distinguished by the terms stratified and unstratified. The former 
 crumble away, in general, more rapidly than the latter, and form a va- 
 riety of soils of which the agricultural characters and capabilities have 
 l)ecii shortly explained. The unstratified or crystalline rocks form soils 
 of so peculiar a character and possessing agricultural capabilities in 
 general so different from those of the stratified rocks which occur in the 
 same neighbourhood, and they, besides, cover so large and hitherto so 
 ur^f'ruitful an area in our island, as to entitle them to a separate and 
 somewhat detailed consideration. 
 
 § 1. Composition of the Granitic Rocks. 
 
 The name of Granite is given by mineralogists to a rock consisting of 
 a mixture more or less intimate of three simple minerals — Quartz, Mica, 
 and Felspar. When Mica is wanting, and Hornblende occurs in its 
 stead, the rock is distinguished by the name of Syenite. This mineral- 
 ogical distinction is often neglected by tte geologist, who describes large 
 tracts of country as covered by granitic rocks, though there may be 
 many hills or mountains of syenite. In a geological sense, the distinc- 
 tion is often of little consequence; in relation to agriculture, however, 
 tiie distinction between a granite and a syenite is of considerable im- 
 jiortance. 
 
 The minerals of which these rocks consist are mixed together in very 
 variable proportions. Sometimes the quartz predominates, so as to con- 
 stitute two-thirds or three-fourths of the whole rock, sometimes botii 
 mica and quartz are present in such small quantity as to form what is 
 then called a felspar rock. The mica rarely exceeds one-sixth of the 
 wijole, while the hornblende of the syenites sometimes forms nearly 
 one half of the entire rock. These differences also are often overlooked 
 by the geologist — though they necessarily produce important differences 
 in the composition and agricultural characters of the' soils derived from 
 the crystalline rocks. 
 
 A few other minerals occur occasionally among the granitic rocks, in 
 sufficient quantity to affect the composition of the soils to which they 
 give rise. Among these, the different varieties of tourmaline are in 
 many places abundant. Thus the schorl rock of Cornwall consists of 
 quartz and schorl (a variety of tourmaline), while crystals of schorl 
 are so frequently found in the granites of Devon, Cornwall, and the 
 
25J COMPOSITION OF GRANITE, FELSPAR, AND ALBITE. 
 
 Scilly Isles, as to be considered diaracteristic of a very large portion of 
 them (Dr. Boase). 
 
 These rocks decay with very different degrees of rapidity — accord- 
 ing to the proportions in which the several minerals are present in 
 them, and to the peculiar state of hardness or aggregation in which they 
 happen to occur. Both the mode of their decay, however, and the cir- 
 cumstances under which it takes place, as well as the character and 
 composition of the soils formed from them, are materially dependent 
 upon the composition of the several minerals of which the rocks consist. 
 This composition, therefore, it will be necessary to exhibit. 
 
 1^. Quartz has already been described (p. 206), as a variety of silica 
 — the substance of flints, and of siliceous sands and sand-stones. In 
 granite, it often occurs in the form of rock crystal, but it is more frequent- 
 ly disseminated in small particles throughout the rocky mass. It is 
 hard enough to scratch glass. 
 
 2°. Felspar is generally colourless, but is not unfrequently reddish or 
 flesh-coloured. On the colour of the felspar they contain, that of the 
 rjraniies most frequently depends. Several varieties of this mineral are 
 known to collectors. Besides the common felspar, however, it is only 
 necessary to specify Albite, which, in appearance, closely resembles fel- 
 sjinr, often takes its place in granite rocks, and in chemical constitution 
 differs from it only in containing soda, while the common felspar con- 
 tains; potash. These two minerals are readily distinguished from quartz 
 by their inferior hardness. They do not scratch glass, and, in general, 
 may easily be scratched by the point of a knife. 
 
 They concist respectively of — 
 
 
 Felspar. 
 
 Albite. 
 
 Silica . . 
 
 . . 65-21 
 
 69-09 
 
 Alumina . 
 
 . . 18-13 
 
 19-22 
 
 Potash . . 
 
 .• . 16-66 
 
 — 
 
 Soda . . 
 
 . . — 
 
 11-69 
 
 100-00 100-00 
 
 It is to be observed, however, that these minerals do not generally oc- 
 cur in naturean a perfectly pure state — for though they do not essential- 
 ly contain either lime, magnesia, or oxide of iron, they are seldom found 
 without a small admixture of one or more of these substances. It is also 
 f )und that while pure felspar contains only potash, and pure albite only 
 soda, abundance of a kind of intermediate mineral occurs which contains 
 both potash and soda. Such is the case with the felspar of the Siebeng<^- 
 nirije, on the right bank of the Rhine (Berthier), and with (hose con- 
 tained in the lavas of Vesuvius and the adjacent parts of Italy (Abich). 
 
 In these two minerals the silica is combined with the yiotash, soda, 
 and alumina, forming certain compounds already described under the 
 name o{ silicates (p. 207). 
 
 Felspar consists of a silicate of alumina combined with a silicate of 
 potash. Albite of the same silicate of alumina combined with a silicate 
 of soda. 
 
 3'^. Miica generally occurs disseminated through the granite in small 
 shining scales or plates, which, when extracted from the rock, split readi- 
 ly into numerous inconceivably thin layers. It sometimes occurs also 
 
COMPOSITION OF MICA AND HORNBLENDE. 259 
 
 in large masses, and is of various colours — white, grey, brown, green, 
 and black. It is soft and readily cut with a knife. The thin shining 
 particles that occur in many sand- stones, and especially between the 
 j;)artings of the beds, and give them what is called a micaceous charac- 
 ter, are only more or less weathered portions of this mineral. 
 
 Mica also consists of silicates, though its constitution is not always so 
 simple as that of felspar. In some varieties magnesia is present, whilst 
 in others it is almost wholly wanting, as is shewn by the following com- 
 position of two specimens from different localities. 
 
 Potash. Magnesian. 
 
 Mica. Mica. 
 
 46-10 40-00 
 
 31-60 12-67 
 
 8-65 19.03 
 
 Silica .... 
 Alumina . 
 Prot-Oxide of Iron 
 
 Magnesia 
 
 Potash .... 
 Oxide of Magnesia 
 Fluoric Acid . 
 Water .... 
 
 — 15-70 
 
 8-39 5-61 
 
 1-40 0-63 
 
 1-12 2-10 
 
 1-00 Titanic Acid 1-63 
 
 96-26 97-37 
 
 If we neglect the three last substances, which are present only in small 
 quantities, and recollect that the silica is in combination with all the 
 oi her substances which stand beneath it, we see that these varieties of 
 mica consist of a silicate of alumina, combined in the one with silicate 
 of iron and silicate of jpotas/i, and in the other with silicate of iron and 
 silicate of magnesia. 
 
 4°. Hornblende occurs of various colours, but that which forms a con- 
 stituent of the syenites and of the basalts is of a dark green or brownish 
 black colour, is often in regular crystals, and is readily distinguished 
 frou) quartz and felspar by its colour, and frotri black mica hy not split- 
 ting into thin layers, when heated in the flame of a candle. It consists 
 of silicates of alumina, lime, magnesia, and oxide of iron, or per cent, 
 of— 
 
 Basaltic Syenitic 
 
 Hornblende. Hornblende. 
 
 Silica ..... 42-24. 45-69 
 
 Alumina .... 13-92 12-18 
 
 Lime 12-24 • 13-83 
 
 Magn«sia .... 13-74 18-79 
 
 Prot-Oxide of Iron . 14-59 7-32 
 
 Oxide of Manganese 0-33 0-22 
 
 Fluoric Acid ... — 1-50 
 
 97-06 99-53 
 
 A comparison of these two analyses shows that the proportions of 
 magnesia and oxide of iron sometimes vary considerably, yet that the 
 hornblendes still maintain the same general composition. They are re- 
 markably distinguished from felspar by the total absence of j)otash and 
 soda, and by containing a large proportion of lime and magnesia. From 
 the potash-mica they are distinguished by the same chemical differen- 
 ces, and from the magnesian mica by containing lime to the amount of 
 
260 COMPOSITION OF SCHORL. 
 
 •gth part of their whole weight. Such differences must materially af- 
 fect the constitution and agricultural capabilities of the soils formed from 
 these several minerals, and they show the correctness of what I have 
 previously stated to you — that mineralogical differences in rocks which 
 may be neglected by the geologist, may be of great importance in ex- 
 plaining the appearances that present themselves to the philosophical 
 agriculturist. 
 
 4°. Schorl usually occurs in the form of long black needles or prisms 
 disseminated through the granitic rock, and generally (in Cornwall) at 
 the outskirts of the granite, where it comes into contact with the slate 
 rocks that surround it (De la Beche). It consists of a silicate of alumi- 
 na in combination with silicates of iron and of soda or magnesia. Two 
 varieties gave by analysis — 
 
 Schorl Tourmaline 
 
 from Devonshire. from Sweden. 
 
 Silica, 35-20 37-65 
 
 Alumina, .... 35-50 33-46 
 
 Magnetic Oxide of Iron, 17-86 9-38 
 
 Magnesia, .... 0-70 10-98 
 
 Boracic Acid, . . . 4-11 3-83 
 
 Soda 2-09 Soda & potash, 2-53 
 
 Lime, . . . . . 0-55 0-25 
 
 Oxide of Manganese, 0-43 — 
 
 96-44 98-08 
 
 This mineral, according to these analyses, is characterised by con- 
 taining from ^ to jL of its weight of magnetic oxide of iron,* and some- 
 times ■— of magnesia. The presence of Boracic acidf is also a remark- 
 able character of this mineral, but as neither the presence of this sub- 
 stance in any soil, nor its effect upon vegetation, have hitherto been ob- 
 served, we can form no opinion in regard to its importance in an agri- 
 cultural point of view. 
 
 § 2. Of the degradation of the Granitic rocks, and of the soils formed 
 from them. 
 
 The granites, in general, are hard and durable rocks, and but little af- 
 fected by the weather. The quartz they contain is scarcely acted upon at 
 all by atmospheric agents, and in very many cases the felspar, mica, 
 and hornblende yield with extreme slowness to their degrading power. It 
 is chiefly to the chemical decomposition of the felspar that the wearing 
 away of granite rocks is due, and the formation of a soil from their crum- 
 bling substance. 
 
 It has been stated that the felspars consist of a silicate of alumina in 
 combination with silicates of potash or of soda. New these latter sili- 
 cates are slowly decomposed by the carbonic acid of the air (see p. 207), 
 which combines with the potash and soda, and forms carbonates of these 
 alkalies. These carbonates are very soluble in water, and are, there- 
 
 ' This oxide is composed of the first and second oxides of iron described in p. 210. 
 
 t Boracic acid occurs in combination with soda in the common borax of the shops. It 
 combines with soda, potash, hme, &c., and forms borates. In the schorl it probably exists 
 in such a stale of combination. 
 
CLAY FROM TIIR FELSPAR ROCKS. 261 
 
 fore, washed away by the first shower of rain that falls. The insoluble 
 silica and the silicate of alumina are either left behind or are more slow- 
 ly carried away by the rains in the form of a fine powder (a fine porce- 
 lain clay), and deposited in the valleys or borne into the rivers and lakes, 
 — while the particles of quartz and mica, having lost their cement of fel- 
 spar, fall asunder, and form a more or less siliceous sand. 
 
 Granite soils, therefore, on all hanging grounds^ — on the sides and 
 slopes of hills, that is — are poor and sandy, rarely containing a sufficient 
 admixture of clay to enable them to support crops of corn — while at the 
 bottoms of the hills, whether on flat or hollow grounds, they are com- 
 posed, in great measure, of the fine clay which has resulted from the 
 gradual decomposition of the felspar. 
 
 This clay consists chiefly of the silicate of alumina contained natural- 
 ly in the felspar — it differs little, in short from that which has already 
 been described (p. 161), under the name of pure or pipe clay, which is 
 too stiff' and intractable to be readily converted into a prolific soil. 
 
 It will readily be understood how such soils — decomposed felspar soils 
 — must generally contain a considerable quantity of potash from the 
 presence of minute particles of silicate of potash still undecomposed ; 
 and it will be as readily seen that they can contain little or no lime, 
 since neither in felspar nor in mica has more than a trace of this eartli 
 been hitherto met with. 
 
 We have seen, however, that hornblende contains from ^th to |thof its 
 weight of lime, and as the same carbonic acid of the atmosphere which 
 decomposes the felspar, decomposes the silicates of the hornblende alsD, 
 it is clear that soils which are derived from the degradation of S3'cniri(; 
 rocks, especially if the proportion of hornblende present in them be large, 
 will contain lime as well as clay and silica. Thus consisting of a great- 
 er number of the elements of a fertile soil, they will be more easily 
 rendered fruitful also — must naturally be more fruitful — than those 
 which are formed from the granites, correctly so called. It is to the pre- 
 sence of this lime that the superior fertility of the soils derived from the 
 hornblende slates of Cornwall, already adverted to (p. 255), is mainly 
 to be ascribed. 
 
 Scliorl, as above stated, contains much oxide of iron, and sometimes 
 five or six per cent, of magnesia. It decomposes slowly, will give the 
 soil a red colour, and though it contain only a trace of lime, yet the ad- 
 mixture of its constituents with those of the felspar may possibly amelio- 
 rate the quality of a soil formed from the decay of the felspar alone. 
 
 It thus appears that a knowledge of the constitution of the minerals of 
 which the granites are composed, and of the proportions in which these 
 minerals are mixed together in any locality, clearly indicates what the 
 nature of the soils formed from them must be — an indication which per- 
 fectly accords with observation. The same knowledge, also, showing 
 that such soils never have contained, and never can, naturally, include 
 more than a trace of lime, will satisfy the improver, who believes the 
 presence of lime to be almost necessary in a fertile soil, as to the first 
 step to be taken in endeavouring to rescue a granitic soil from a state of 
 nature — will explain to him the reason why the use of lime and of shell 
 sand on such soils, should so long have been practised with the best ef- 
 
 .^- 
 
262 GRANITE ROCKS OF GREAT BRITAIN AND IRELAND. 
 
 fects, — and will encourage biin to persevere in a course of treatment 
 which, while suggested by theory, is confirmed also by practice. 
 
 Extent, of granitic rocks in Great Britain and Ireland. — In England, 
 the only extensive tracts of granite occur in Cornwall and Devon, pre- 
 senting themselves here and there in isolated patches from the Scilly 
 Isles and the Land's End to. Dartmoor in South Devon. In the latter 
 locality, the granite rocks cover an area of about 400 square miles. Pro- 
 ceeding northward, various small out-hursts* of granite appear in the 
 Isle of Anglesey, in Westmoreland, and in Cumberland, and north of 
 the Solway, in Kirkcudbright, it extends over 150 or 200 square miles ; 
 — but it is at the Grampian Hills that these rocks begin to be most ex- 
 tensively developed. With the exception, indeed, of the patches of old 
 red sandstone already noticed, nearly the whole of Scotland, north of the 
 Grampians — and of the western islands, excluding Skye and Mull, con- 
 sists of granitic rocks. 
 
 In Ireland, a range of granite (the Wicklow) mountains runs south by 
 west from Dublin to near New Ross — the same rock forms a consider- 
 able portion of the mountainous districts in the north-west of Donegal, and 
 in the south of Gal way — covers a less extensive area in Armagh, and pre- 
 sents itself in the form of an isolated patch in the county of Cavan. 
 
 Soils of the granitic rocks. — From what has been already stated in re- 
 gard to the composition of granite, it is clear from theory that no gene- 
 rally uniform quality of soil can be expected to result from its decompo- 
 sition, and this deduction is confirmed by practical observation. Where 
 (juartz is more abundant, or where the clay is washed out, the soil is 
 poor, hungry, and unfruitful — such, generally, is its character on the 
 more exposed slopes of the hills in the Western Isles, and in the north 
 of Scotland. — [Macdonald's Agricultural Survey of the Hebrides., p. 26.] 
 In the hollows and levels, where natural drainage exists, stiff clay soils 
 prevail, which are often cold and unfruitful, but arie capable of amelio- 
 ration where the depth of earth is sufficient, by draining and abundant 
 liming or marling. Where there is no natural drainage, vegetable mat- 
 ter accumulates, as we have seen to be the case on the surface of all im- 
 pervious rocks — and bogs are formed. In the north of Scotland, and in 
 .Ireland, and in the high lands of Dartmoor (Devon), these are every- 
 where seen in such localities, and it is said that two-thirds of the He- 
 brides are covered with peat bogs more or less reclaimable. 
 
 In Cornwall and Devon, the granitic soils {growan soils, as they are 
 there called) are observed to be more productive as the hills diminish 
 in height. Thus Dartmoor is covered only with heath, coarse grass, 
 and peat ; while in the Scilly Isles the growan land produces good crops 
 of wheat, potatoes, barley, and grass; and the same is observed at 
 Moreton Hampstead, in Devon, where tolerable crops of barley are grown, 
 and potatoes, which are highly esteemed in the Exeter market (De La 
 Beche). No doubt the climate has something to do with these differ- 
 ences ; but the less the elevation, and the consequent washing of the 
 rains, the more of the clay will remain mixed with the siliceous sand ; 
 
 • This expression is in some measure theoretical, and implies — what is the generally re- 
 ceived opinion — that the granite rocks were forced up from beneath in a fluid state, like the 
 lavas of existing volcanoes — ihat they, as well as the trap rocks, are, in short, only lavas of 
 a more ancient date (see p. 237). 
 
THK TnAP-li<>Li\« ChKKA-SroAK. 263 
 
 while in aid of both these causes, n snmll dilTorence in the composition 
 of its constituent minerals, often not to be detected by the eye, may ma- 
 terially affect the character of the granitic soils. 
 
 According to Dr. Paris, the presence of much mica deteriorates these 
 soils; while that which is formed at the edges of the granite, when it 
 comes in contact with the slate rocks, is of a more fertile quality. The 
 latter remark, however, does not universally apply, — especially where 
 the granite, as at the edges of Dartmoor, contains much schorl, (De La 
 Beche) — and the presence of mica, in the richest soils of the red marl, 
 would seem to imply that this mineral is fitted materially to promote 
 the fertility of a soil in which the other earthy ingredients are properly 
 adjusted. 
 
 The more elevated and thin granitic soils are said to be fitted for the 
 growth of larch ; the lower and deeper soils, which admit of the use of 
 the plough, have been found to yield a three-fold return of corn by the 
 use of lime alone. 
 
 § 4. Of the trap rocks, and the soils.formed from them. 
 Of the trap rocks there are several varieties, of which the most impor- 
 tant are distinguished by the names of Greenstone, Basalt, and Scr~ 
 pentine. 
 
 The Green-stones consist of a mixture more or less intimate of felspar 
 and hornblende, or of felspar and augite. They are distinguished fron) 
 the granites by the absence of mica and quartz, and by the presence of 
 the hornblende or augite, often in equal, and not unfrequently in greater 
 quantity than the felspar. In the granites, the felspar and quartz to- 
 gether generally form upwards of ^^ of the whole mass. 
 
 Augite is a mineral having much resemblance to hornblende, and, 
 like it, occurring of various colours. In the trap rocks it is usually of a 
 dark green approaching to black. It generally contains much lime and 
 oxide of iron in the state of silicates. The composition of two varieties 
 compared with that of basaltic hornblende is as follows : — 
 
 Black Augite Augite from the Basaltic 
 
 from Sweden. lava of Vesuvius. Hornblende. 
 
 Silica 53-36 50-90 42-24 
 
 Lime 22-] 9 22-96 12-24 
 
 Magnesia . . ." . . . 4-99 14-43 13-74 
 
 Prot-Oxide of Iron . . . 17-38 6-25 14-59 
 
 Prot-Oxide of Manganese . 0-09 — 0-33 
 
 Alumina . . . \ . . — 5-37 13-92 
 
 98-01 99-91 97-06 
 
 The predominance of this mineral (augite) or of hornblende in the 
 green-stone rocks must necessarily cause a very material difference in 
 the nature of the soils produced from their decay, compared with those 
 which are formed from the granitic rocks in which the felspars are the 
 predominating mineral ingredient. 
 
 2°. Basalt consists of a mixture, in variable proportions, of augite, 
 magnetic oxide of iron, and zeolite.* It differs in appearance from green- 
 
 ' '■'■With or without felspar." In addition to augite, magnetic iron, and zeolite, manj ba- 
 salts contain also a considerable portion of certain varieties of felspar, especially of one to 
 which the name oinepheline has been given. 
 
264 EXTENT AND SOIL OF THE TRAP-ROCK^. 
 
 Stone, chiefly by the darkness of its colour, and by the minuteness of the 
 particles of which it is composed, which, in general, cannot be distin- 
 guished by the naked eye. 
 
 Zeolite is a generic term applied to a great number of mineral species 
 which occur in the basalts, and often intermixed with I he green-stone 
 rocks. They differ from felspar in their greater solubility in acids, and 
 by generally containing lime, where the latter contains potash or soda. 
 
 It may be stated, indeed, as the most important agricultural distinc- 
 tion, between the granitic and the true* trap-rocks, that the latter abound 
 in lime, while in the former, it is often entirely absent. If in a green- 
 stone only one-fourth of its weight consist of augite, every 20 ton^"of the 
 rock may contain one ton of lime. If in a basalt the augite and zeolhe 
 amount to only two-thirds of its weight, every nine tons may contain a 
 ton of lime. 'The practical farmer cannot fail to conclude that a soil 
 formed from such rocks must possess very different agricultural capabil- 
 ities from the soils we have already described as being formed from the 
 decomposition of the granites. 
 
 3°. Serpentine is a greenish yellow mineral, consisting of silica in 
 combination with magnesia and a little iron, and occasionally a few 
 pounds in the hundred of lime or alumina. The distinguishing ingredi- 
 ent is the magnesia, which generally approaches to 40 per cent, of the 
 whole weight of the mineral. Hocks of serpentine are generally mixe<l 
 with magnetic iron ore, and with portions of other minerals in greater 
 or less abundance. 
 
 Extent of the trap rocks in the British Isles. — The serpentine rock oc- 
 curs to any extent only in Cornwall, about the Lizard Point, where it 
 covers an area of 50 square miles. The green-stones and basalts are 
 only met with here and there in small patches, until we get so far north 
 as the Cheviot Hills, which consist of these and other varieties of trap. 
 It is in the low country of Scotland, however, intermixed with and sur- 
 rounding the great coal district of that part of the island, that the greatest 
 breadth of trap is seen. It there stretc;hes across the island in a south- 
 west direction, and in detached masses, from the Friths of Tay and 
 Forth to the^ island of Arran, covering an area of 800 or 1000 square 
 miles. In the prolongation of the same line it re-appears in the north- 
 east of Ireland, and extends over the whole of the county of Antrim and 
 a small part of Londonderry and Armagh. In the most northerly portion 
 of this tract the well-known columnar basalt of the Giants' Causeway 
 occurs. On the west coast of Scotland the trap rocks cover nearly the 
 whole of the islands of Mull and of Skye — to the west of the former of 
 which islands lies Staffa with its celebrated basaltic caves. 
 
 Soil of the trap rocks. — The soil of the serpentine rocks at the Lizard 
 is far from fertile, retaining the water and thus forming swamps and 
 marshes. Even where a natural drainage exists it rarely produces good 
 grass, or average crops of corn. It is remarkable for growing a pecu- 
 liar, very beautiful heath — erica vagans — which so strictly limits itself 
 to the serpentine soil as distinctly to mark the boundary by which the 
 serpentine is separated from other rocks (De La Beche). From the 
 
 • iS(erj9cn<tn« is not (generally included among the true trap rocks: it is included among 
 them here as ii often is by geologists,.because in many places, as at the Lizard, it occurs 
 along with true green-stone 
 
FERTILITY OF THE GREEN-STONE SOILS. 265 
 
 composition of serpentine we might be led to suppose that the compara- 
 tive barrenness of the soils formed from it is due to the large quantity 
 of magnesia which this mineral contains ; and this may, in some cases, 
 be partly the cause. It would appear, however, that these soils often 
 contain very little magnesia, the long action of the rains and of other 
 agents having almost entirely removed it (see p. 209), and yet they still 
 retain their barrenness. But they contain no lime, and, therefore, after 
 draining, the first great step to take in order to improve such soils, is to 
 give them a good dose of lime. How this step is to be followed up will 
 depend upon the effect Which this treatment is found to produce. 
 
 The soil of the green-stones is generally fertile, and it is more so in 
 proportion as the hornblende or augite predominates — that is, generally, 
 in proportion to the darkness of its colour. 
 
 In Cornwall and South Devon, where scattered masses of trap occur, 
 consisting chiefly of hornblende and felspar, they "afford the most fertile 
 soils of any in the district when their decomposition has taken place to 
 a sufficient depth" (De La Beche). Wherever the trap rocks (locally 
 dun-stones) are observed at the surface, '* it is deemed a fortunate cir- 
 cumstance, being a certain indication of the fertility of the incumbent 
 soils." — [Worgan's Vieiv of the Agriculture of Cornwall, p. 10.] The 
 superior fertility of the neighbourhood of Penzance is owing to the pre- 
 sence of these rocks (Dr. Paris), and where their detritus has been mix- 
 ed with that of other rocks — as with the worthless granite soils — it ame- 
 liorates and improves their quality. 
 
 The same general character is exhibited by the trappean soils of other 
 districts of the island. The height of the Cheviot Hills renders the cli- 
 mate in many places unfavourable to arable culture, yet they produce 
 the sweetest pasture,* while the low country around them has been 
 largely benefitted by admixture with their crumbling fragments. The 
 whole of that lowland tract of Scotland, ovef which these rocks extend — 
 comprehending the cou'nties of Ayr, Renfrew, Lanark, Linlithgow, 
 Fife, and portions of Perth, Sterling, Edinburgh, and Haddington, — ex- 
 hibit the fertile or fertilizing character of the decomposing green-stone. 
 In Cornwall it is dug up as a marl and applied to the land, and in the 
 neighbourhood of Haddington I have seen a farming tenant {a leasehold- 
 er) renjoving twelve inches of trap soil from the entire surface of a field, 
 for the purpose of spreading a layer of an inch in depth over twelve 
 times the area in another part of his farm. There can be no doubt that 
 this mode of improvement is within the reach of many proprietors and 
 farmers — especially along the southern borders of Perthshire, and near 
 the more elevated of Ayr and Lanark. 
 
 To the north of Ireland, and to the Western Islands, the above re- 
 marks, with slight modifications, arising from local causes, will also ap- 
 ply. For example, where the surface is flat, and the rock impervious, 
 water will collect and heaths and bogs will be produced, which only 
 
 ' It is a singular fact observed here and there among the Cheviot Hills on the border, that 
 where sheep are folded or pastured on hills of trap which are covered with delicate herbage, 
 lliey are attacked by what is locally called the pining ill, — they pine away, become indolent, 
 and are unwilling to move. The cure is to drive them to a neAgnhounng sand stone pasture, 
 where they become again active, and begin to thrive. The pining hills on each farm are 
 well knov/n, and the tenant has no hesitation i;i pointing lo this and to that bill as those oa 
 which tlie sheep are sure to pine, if kept upon thi'm uiiiy. 
 
 12 
 
266 THE HYPERTHENE SOILS OF SKYE. 
 
 draining can remove. They apply also fo other countries where trap 
 rocks abound — the only fertile tracts of Abyssinia, for instance, being 
 found in vallies and on mountain slopes, where the soil is composed of 
 the detritus of trappean rocks (Dr. Riippell., 
 
 Yet there are exceptions to this general rule. 
 
 Where the felspar is largely predominant, the soil formed from the 
 Tock will partake more or less of the cold and barren character of the 
 stifter granitic soils. Such appears to be the case with some of the traps 
 which occur in the border counties of England and Wales (Murchison). 
 
 In the Isle of Skye, again, a local peculiarity of a different kind ob- 
 tains, the effect of which upon the soil is also to render it poor and un- 
 productive. In that island the singularly beautiful ridge of the Cuchul- 
 len Hills consists of a variety of trap in which the augite so far predomi- 
 nates as to form nearly the whole of the mountain masses, But the 
 augite in this case is a variety to which the name of hypersthene has 
 been given, and which contains much magnesia and oxide of iron, but 
 scarcely a trace of either lime or alumina. The rock is very hard, and 
 decays with extreme slowness; yet however rapid its decay might be, 
 it could never produce a fertile soil. We have seen that the serpentine 
 and granite soils are essentially deficient in lime, but a hypersthene soil 
 is in want both of lime and of clay. It would be still inore difficult, 
 therefore, to render the latter productive — even supposing, as in the case 
 of the serpentine soils, that the magnesia of the hypersthene* were most- 
 ly washed away by the rains. 
 
 Thus we perceive how eactly the study of the composition of the dif- 
 ferent varieties of the trap rocks explains the observed differences in the 
 quality of the soils derived from them. When the minerals they contain 
 abound in lime, the soils they yield are fertile — when those minerals 
 predominate in which lime is wanting, the soils are inferior, sometimes 
 scarcely capable of cultivatif>n. Again, the granites abound in potash; 
 but except in the syenites they rarely contain lime, and their soils are 
 generally poor. Let them be mixed with the trap soils, and they are 
 enriched. This would seem fairly and clearly to imply that the fertility 
 of the one is^mainly due to the presence of lime, and the barrenness of 
 the other to the absence of this earth. 
 
 On this subject I will only further add, that the more modern volcanic 
 lavas which overspread Italy, Sicily, parts of France, Spain, and Ger- 
 many, are closely related to the trap rocks in their general composition 
 — and the fertility which overspreads thousands of square miles of de- 
 composed lava streams and ejections of volcanic ashes in Italy and Si- 
 cily, is too well known to require any detailed description. 
 
 § 5. Of superficial accumulations of foreign materials, and of the means 
 by which they have been transported. 
 Abundant proof, I think, has now been advanced that a close relation 
 
 * The hypersthene of Skye has been found to consist of— 
 
 Silica 51-35 1 Protoxide of iron 3392 . 
 
 Lime 1 84 | Water 0-50 
 
 Magnesia 1109 I 
 
 I 9870 
 The composition probably varies in different parts of the rock, some containing more mag- 
 nesia and less iron than is here represented. 
 
TRANSPORTED MATERIALS OFTEN MASK THE ROCKS. 267 
 
 generally exists between the soil and the rocks on which it rests, and 
 that the geological structure of a country, as well as the chemical consti- 
 tution of the minerals of which its several rocky masses consist, have a 
 primary and fundamental influence upon the agricultural capabilities of 
 its surface. 
 
 And yet I should be leading you into a serious error, were I to permit 
 you to suppose that this intimate and direct relation is always to be ob- 
 served — that in whatever district you may happen to be, you will find 
 the soil taking its general character from the subjacent rocks — and that 
 where the same rocks occur, similar soils are always to be expected. 
 On the contrary, in very many localities the soil is totally different from 
 that which would be produced by the degradation or decomposition of 
 the rocks on which it rests. To infer, therefore, or to predict, that on a 
 given spot, where, according to the geological map, red sand-stone for 
 example prevails, a marly or other red sand-stone soil will necessarily 
 be found — or that where the coal measures are observed, poor, ungrate- 
 ful land must exist — would be to form or to state opinions which a visit 
 to the several localities would in many instances show to be completely 
 erroneous — and which would bring undeserved discredit upon geologi- 
 cal science. 
 
 In such cases as these geology is not at fault. New conditions only 
 have supervened which render the natural relation between soils and 
 rocks in those places less simple, and consequently more obscure. Yet 
 a further study of geological phenomena removes the obscurity — shows 
 to what cause it is owing that in many districts the soil is such as could 
 never have been formed from the subjacent rocks — again places the en- 
 lightened agriculturist in a condition to pronounce generally from what 
 rocks his soils have been derived — generally also what their agricultural 
 capabilities are likely to be, and by what mode of treatment those capa- 
 bilities may be most fully developed. 
 
 Of the surface of Great Britain and Ireland it may indeed be truly 
 said, that it exhibits extensive tracts in which the character of the soil is 
 directly influenced by, and may be inferred from, the character and 
 composition of the subjacent rock. To these districts the rules and ob- 
 servations contained in the preceding sections directly and clearly apply. 
 But other extensive tracts also occur in which the character of the soil is 
 independent of that of the rocks on which it immediately rests — the 
 cause of this apparent difficulty we are now to consider. 
 
 1°. I have already had occasion to explain to you in what way all 
 rocks crumble more or less rapidly, and give origin to soils of various 
 kinds. Were the surfaces of rocks uniformly level, and that of every 
 country flat, the crumbled materials would generally remain on the spots 
 where they were formed. But as already shown in the diagrams, in- 
 serted in page 238, the rocks rarely lie in a horizontal position, 
 but rest almost always more or less on their edges; and the surface in 
 such a country as ours is often mountainous or hilly, and everywhere 
 undulating. Hence the rains aie continually washing off the finer par- 
 ticles from the higher, and bearing them to the lower grounds — and on 
 occasions of great floods, vast quantities even of heavy materials are 
 borne to great distances, and spread sometimes. to a great depth and over 
 a great extent of country — [witness the still recent floods in Morayshire.] 
 
268 EFFECT OF RAINS, RIVERS, AND TIDES. 
 
 Thus the spoils of one rocky fonnafjoii are hortic from (heir uat'iN'e soU, 
 and are strewed over the surtuce of oiher kinds of rock of a totally dii- 
 ferent character. The fragments of the granite, gneiss, and slate rocks 
 of the high lands are scattered over the old red sand-stones whicli lie at 
 a lower level — and those of the blue lime-stone mountains over the mill- 
 stone grits, the coal measures, and the new red sand-stones, which stretch 
 away from their feet. 
 
 2°. But the effects produced by this natural cause, though they may 
 be judged of in kind, can never be estimated in degree by what we per- 
 ceive in our own temperate climates — in our country of small rivers and 
 gentle rains. How must such effects exceed in magnitude, in districts 
 where, — as in the Ghauts, that separate the level land of the Malabar 
 coast (the Concan) from the high table-land of the Deccan, — 120 inches 
 of rain occasionally fall in a single month, and 240 inches or 20 feet, on 
 an average, every year from June to September ! And to what vast 
 distances must materials be transported by great rivers, such as the Mis- 
 sissippi, the River of Amazons, the Ganges, and the Indus, which main- 
 tain a course of thousands of miles, before they empty themselves into 
 the sea? What necessary connection can the deposits of mud and sand 
 which yearly collect at the mouths and in the places overflowed by the 
 waters of these great rivers, have with the nature of the rocks on which 
 these transported materials may happen to rest? 
 
 3°. But the constant motion of the waters of the sea washes down 
 the cliffs on one coast, and carries away their ruins to be deposited, either 
 in its own depths, or along other more sheltered shores. Hence sand 
 banks accumulate — as in the centre of our own North Sea: or the land 
 gains upon the water in one spot what it loses in another — as may be 
 seen both on the shores of our own island, and on the opposite coasts of 
 Germany and France. 
 
 What necessary relation can the soils thus gained from the sea have 
 to the rocks on which they rest? Suppose the bottom of the North Sea 
 to become dry land, what necessary mineral relation would then exist 
 between the soils which would gradually be formed on its hundreds of 
 square miles-of sand-banks, and the rocks on which those sand-banks 
 immediately repose ? 
 
 4°. Again, the sea, in general, carries with it and deposits in its own 
 bosom the finest particles of clay, lime, and other earthy matters, and 
 leaves along its shores accumulations of fine siliceous sand. This sand, 
 when dry, the sea winds bear before them and strew over the land, form- 
 ing sand hills and downs, sometimes of considerable height and of great 
 extent. Such are to be seen here and there, in our own islands, but on 
 the Eastern shores of the Bay of Biscay, and on the coasts of Jutland, — 
 both exposed to violent sea winds, — they occur over much larger areas. 
 Before these winds tlie light sands are continually drifting, and, year by 
 year, advance further and further into the country, gradually driving 
 lakes before them, swallowing up forests and cultivated fields, with the 
 houses of the cultivators, and burying alike the fertile soils and the rocks 
 from which they were originally derived. [In the Landes, the ad- 
 vance of the downs is estimated at 66 to 70 feet every year.] 
 
 You have all read of the fearful sands of the African deserts, and of 
 
EFFECTS OF WIlfDS, AND OF GLACIERS. 260 
 
 fheir destructive march when the burning winds awaken. History tells 
 of populous cities and fertile plains, where nothing but blown sands are 
 now to be seen, and geology easily leads us back to still more remote 
 periods, when the broad zones of sandy desert were but narrow stripes 
 of blown sand along the shores of the sea, or beds of comparatively loose 
 sand-stone, which here and there came to the surface, and which the 
 winds have gradually removed from their original site, and wafted widely 
 over the land. 
 
 Wherever these sand- drifts spread, it will also be clear to you, that 
 there may be no necessary similarity between the loose materials on 
 the surface and the kind of rock over which these materials are strewed. 
 
 5°. Along with these I shall mention only one other great agent by 
 which loose materials are gradually transported to considerable dis- 
 tances. 
 
 It is observed in elevated countries, where the snow never entirely 
 melts, and where glaciers or sheets of ice hang on the mountain sides,— - 
 descending towards the plains as the winter's cold comes on, and again 
 retreating towards the mountain-tops at the approach of the summer's 
 heat — that the edges of the glaciers bear before them into the valleys, and 
 deposit along their edges, banks of conical ridges of sand and gravel 
 (Moraines). These consist of the fragments of the rocky heights, worn 
 and rounded by the friction of the sheets of ice beneath which they 
 have descended from above, and from the edges of which they finally 
 escape into the plain. 
 
 These ridges of sand and gravel accumulate till some more sudden 
 thaw than usual, or greater summer's heat arrives, when they are more 
 or less completely broken up by the rush of water that ensues, and are 
 dispersed over the subjacent tracts of level land. 
 
 When the rocks are of a kind to rub down so fine as to form much 
 mud as well as sand or gravel, the ridges are of a more clayey charac- 
 ter. And where the edges of the glaciers descend to the borders of lakes 
 or seas — as in the Tierra del Fuega — this mud is washed away and 
 widely spread by the waters, while the gravel and sand remain nearer 
 their original site ; or, finally, when the ice actually overhangs the wa- 
 ter, huge fragments break off now and then — loaded with masses of gra- 
 vel and sand, or even with rocks of large size, — which fragments float 
 away often to great distances and drop their stony burdens here and 
 there, as they gradually melt and disappear. 
 
 To these facts, let it be added, that recent geological researches, of a 
 very interesting kind, tend to show that nearly all the elevated tracts of 
 country in the temperate regions of Europe and America — in our own 
 island among other localities — have been covered with glaciers at a 
 comparatively recent period, (geologically speaking,) and that these gla- 
 ciers have gradually retreated step by step to their present altitudes, 
 halting here for a time, and lingering there ; — and we shall find reason 
 to believe that traces of transported materials — moved from their origi- 
 nal site by this agent also — are to be looked for on almost every geolo- 
 gical formation. 
 
 And such the geological observer finds to be in reality the case. 
 
270 DRIFTS IN GREAT BRITAIN. 
 
 § 6. Of the occurrence of such accumulations in Great Britain, and of 
 their influence in modifying the character of the soil. 
 
 Such accumulations, for example, present themselves over a large 
 portion of our own island. Thus, in Devonshire, the chalk and green 
 sand are so completely covered by gravels, consisting of the fragments 
 of older rocks from the higher grounds, mixed with chalk-flints and 
 chert,, that nearly the whole of this tract possesses one common charac- 
 ter of infertility, and is widely covered with downs of furze and heath 
 (De La Beche.) In like manner the chalk, green sand, and plastic clay 
 of a large portion of Norfolk and Suflfolk, and of parts of the counties of 
 Essex, Cambridge, Huntingdon, Bedford, Hertford, and Middlesex, are 
 covered with till, (stiff unstratified clay,) containing large stones, (boul- 
 ders,) or with gravels, in which are mixed fragments of rocks of various 
 ages, which must have been brought from great distances, and perhaps 
 from different directions (Lyell.) So over the great plain of the new 
 red sand-stone, in the centre and west of England — in Lancashire, 
 Cheshire, Shropshire, Staffordshire, and Worcestershire — drifted gra- 
 vels of various kinds are widely spread. It may indeed be generally 
 remarked, that over the bottoms of all our great vallies, such drifted 
 fragments are commonly diffused — that upon our wider plains, they are 
 here and there collected in great heaps — and that on the lower lands tbat 
 border either shore of our island, extensive deposits of clay, sand, or gra- 
 vel, not unfrequently cover to a great depth the subjacent rocks. 
 
 The practical agriculturist will be able to confirm this remark, in 
 whatever district almost he may live, by facts which have come within 
 his own knowledge and observation. I shall briefly explain, by way of 
 illustration, the mode in which such accumulations of drifted matter 
 overlie the eastern or lower half of the county of Durham. 
 
 The eastern half of the county of Durham reposes, to the north of the 
 city of Durham, chiefly upon the coal measures, (sand-stones and shales;) 
 to the south, chiefly on the raagnesian lime-stone and the new-red sand- 
 stone. These coal measures rise, here and there, into considerable eleva- 
 tions, as at Gateshead Fell near Newcastle, and Brandon Hill near Dur- 
 ham, where-tlie rocks lie immediately beneath the surface, and are cov- 
 ered by comparatively little transported matter. The magnesian lime- 
 stone, also, in many localities, starts up in the form of round hills or ridges, 
 on which reposes only a poor thin soil, formed in great measure by the 
 crumbling of the rock itself. Yet, generally speaking, this entire dis- 
 trict is overspread with a thick sheet of drifted matter, consisting of 
 clays, sands, and gravels. 
 
 This drift is made up of three separate layers, to be observed more or 
 less distinctly in taking a general survey of the county, though there are 
 few spots where they can all be seen reposing immediately one over the 
 other. 
 
 1°. The upper layer consists of clays — on the higher grounds, poor, 
 stiff, yellow — on the hill-sides and slopes of the valleys, often darker in 
 colour — but almost everywhere full of rounded trap boulders* from a few 
 
 • In some parts of Northumberland these trap boulders ai'e still more numerous. In the 
 country which stretches between the north and south Tyne, the old grass fields are full of 
 them. A friend of mine informs me that in ploughing out a nine-acre field on his estate in 
 that district, there were dug out and carried off no less than 900 tots of such rolled stones 
 great and small ! 
 
DRIFT NEAR THE CITY OF DURHAM. 
 
 271 
 
 pounds to many tons in weight. These are generally dug up when they 
 obstruct the plough, and are sold for mending the roads at about 5s. a 
 ton. This clay varies in depth, from one or two, to tifty or sixty feet. 
 
 2°. Beneath the clay occurs an accumulation of fine, generally yel- 
 low, more rarely red, sand, intermixed with occasional layers and 
 round hills of gravel — with frequent black streaks of rounded coal dust, 
 and here and there with nests of rounded lumps of coal, from half an 
 inch to five or six inches in diameter. This coal is sometimes so abun- 
 dant as to be collected and sold for burning. 
 
 The gravels, where they overlie the coal measures, consist chiefly of 
 rounded, and on the upper part occasionally of large angular masses 
 of coal sand-stones — with here and there a fragment of trap, of 
 mountain lime-stone, or of some of the older rocks to be met with in 
 the mountainous districts towards the west. Over the magnesian lime- 
 stone, however, in the south-eastern division of the county, towards the 
 foot of the south-eastern slope of the magnesian lime-stone hills, the gra- 
 vels which exhibit in some places (Wynyard) an irregular stratification, 
 contain many rounded masses of magnesian lime-stone, and even of 
 new-red sand-stone — the evident debris of adjacent rocks long ago bro- 
 ken up. 
 
 3°. The undermost layer which rests immediately upon the subjacer 
 rocks consists of a stiff unstratified blue clay often full of trap boulders 
 but containing also occasional large rounded masses of blue lime-stone 
 — and smaller pebbles of quartz, of granite, and of the older slate rocks. 
 In many localities this clay is wanting, and the sands or gravels rest im- 
 mediately upon the carboniferous or magnesian lime-stone rocks — while 
 m some tracts, both this and the upper clay appear to degenerate into a 
 stony most unmanageable clayey gravel. I am not aware that the 
 large whin (trap) boulders are ever met with in the beds of sand. 
 
 The following diagram exhibits the mode in which these drifted mate- 
 rials present themselves in the neighbourhood of the city of Durham. 
 The cross (+) indicates very nearly the site of Durham on the banks of 
 the river Wear. 
 
 No. 1 represents the coal measures. 
 
 2. The lower new-red sand-stone, here soft and pale yellow. 
 
 3. The magnesian lime-stone rising into a high escarpment from 3 to 
 6 miles south of the city. 
 
 4. Yellow loose sand — with rolled sand-stones and coal-drift — ^^occa- 
 sionally stratified. It forms the numerous picturesque round hills in the 
 neighbourhood of the city, and varies from a few feet to not less than 120 
 feet in thickness. 
 
 5 is the upper clay, with boulders. N indicates Framwellgate 
 Moor, where it is only a few feet thick. At S, on the southern slope of 
 the escarpment, it sometimes rests immediately on the rock as here re- 
 
272 
 
 THE SOILS OFTEN CHANGE FROM SAND TO CLAY. 
 
 presented — in which case it is difficult to decide whether it should be con- 
 sidered as the under or the upper clay — though in other spots both sand 
 and clay, or gravel and clay, present themselves. 
 
 It will at once occur to you from the inspection of this diagram, that 
 the general character of the soil in the county of Durham, wherever 
 such accumulations of drifted matter occur, is not to be judged from the 
 nature of the rocks on which they are known to rest. 
 
 Another fact, not unworthy of your attention, is the rapid alternations 
 of light and heavy soil, of sands or gravels and clays, which present 
 themselves in the same district, I may say in the same farm, and often 
 in the same field. This arises from the irregular thickness of ihe de- 
 posit of sand or gravel over which the upper clay rests. The surface 
 of this sand is undulating, as if it had formed a country of round hills 
 before the clay was deposited upon it. This appears in the following 
 diagram, which represents the way in which the several layers are seen 
 to occur in the Crindon cut on the Hartlepool railway : — 
 
 
 Here 1 is the magnesian lime-stone, not visible ; 2, the under clay, 
 with boulders ; 3, the sand rising in round hills, and here and there 
 piercing to the surface ; and 4, the upper boulder clay. 
 
 In the county of Durham it is a very usual expression that the tops 
 of the hills are light turnip soil — but that they fall off to day. Both the 
 meaning and the cause of this are explained by the above diagram. 
 
 Nor is this mode of occurrence rare among the alternate sands and 
 clays of which the superficial accumulations in various parts of the 
 country consist. Nearly the same circumstances give rise to the rapid 
 changes so ffequently observed in the character of the soil, as we pass 
 from field to~field, not in this county only, but in various other parts of 
 our island. 
 
 § 7. How far these accumulations of drift interfere with the general 
 deductions of Agricultural Geology. 
 
 Thus it appears, that over the eastern half of the county of Dur- 
 ham, and over large portions of other counties, the soils are found to 
 rest upon and to derive their character from accumulations of drifted 
 materials more or less different in their nature from the rocks that lie 
 beneath. 
 
 But in the preceding lecture I have endeavoured to show you that 
 •soils are derived from the rocks on which they rest, and to impress upon 
 you the close general relation which exists between the kind of rocks of 
 which a country is composed, and the kind of soils by which its surface 
 is overspread. 
 
 How are these apparent contradictions to be reconciled ? How is any 
 
DRIFT MIXED UP WITH THE DETRITUS OF THE SPOT. 273 
 
 degree of order to be evolved out of this apparent confusion? Are the<' 
 general indications of agricultural geology (Lecture xi., §8, ) still, in any 
 degree, to be relied upon? 
 
 They are, and for the following, among other reasons : 
 
 1°. It is still generally true that where a considerable extent of coun- 
 try rests upon any known rock, the soil in that district derives its usual 
 character from the nature of that rock. Thus though large portions of 
 Cheshire and Lancashire are covered with drift, yet the soil of these 
 counties, taken as a whole, has the general characters of the soils of 
 ihe new-red sand-stone, which in that part of England is so largely de- 
 veloped. 
 
 2°. Where the drift overspreads any large area, it is found to become 
 gradually mixed up with the fragments, large and small, of the rocks 
 upon which it reposes. Thus in the neighbourhood of Durham, the 
 round hills of sand and gravel with intermingled coal consist in great 
 part of the ruins of the sand-stones of the country itself — while the 
 clays, no doubt, are partly derived from the shale beds which occur in- 
 termingled with the sand-stones of the same coal measures. Hence the 
 soils of the northern half of this county, in general, still partake of the 
 usual qualities of those of the coal measures and mill-stone grit (pp. 
 249 and 250). In the western and higher part of the district they lie 
 more immediately on the rocks from which they have been derived, 
 while on the eastern half they rest on a mixture of the accumulated 
 ruins of the same rocks, which have been transported by natural agents 
 to a greater or less distance from their natural site. 
 
 It is true that there are mixed up with these many portions of other 
 rocks brought from a still greater distance, but these bear but a small 
 proportion to the entire mass, and hence have, generally speaking, but 
 little influence in altering the mineral character of the whole. 
 
 3°. It may indeed be stated as generally true, that the greater propor- 
 tion of the transported materials which lie upon any spot has been 
 brought only a comparatively small distance. Thus the sands and gra- 
 vels in the county of Durham — to the west of the magnesian lime- 
 stone — consist chiefly of the fragments of the coal measures. East and 
 south of the magnesian lime-stone escarpment (diagram, p. 271), they 
 become mixed with rounded masses of this lime-stone. On the new- 
 red sand-stone of the south-east of the county, they consist chiefly of 
 magnesian lime-stone mixed with fragments of the red sand-stone — 
 and on crossing the Tees, the debris of the lias hills begins to appear 
 among them. 
 
 In countries, therefore, where drifted sands and gravels prevail on the 
 surface, they generally consist of the fragments of rocks which lie at no 
 great distance — generally towards the higher ground — the natural ten- 
 dency being for the debris of one kind of rock, or of one formation, to 
 overlap to a greater or less extent the surface of the adjoining rock, or 
 formation. By this overlapping, the geographical position of a given 
 soil is removed to a greater or less distance beyond the line indicated by 
 the geological position of the rocks from which it is derived. Thus, a 
 coal measure soil may overspread part of the magnesian lime-stone — 
 a red sand-stone soil may partially cover the lias, and so on — the general 
 
 12* 
 
274 GENERAL DEDUCTIONS OF GEOLOGY STILL TRUE. 
 
 characters and distinctions of the soil peculiar to each rock being stil, 
 preserved beyond the spaces upon which they have been accidentally 
 intermingled. 
 
 4°. To this, and to each of the other statements above made, there are 
 Vnany local exceptions. For instance, what is true of sands and gravels, 
 will not so well apply to the fine mud of which many clays are formed. 
 Once commit these to the water, and if it has any motion, they may be 
 transported to very great distances from their original site. Rivers, 
 lakes, and seas, are the agents by which these extensive diffusions are 
 effected. The former produce what are called alluvial formations or de- 
 posits ; which are generally rich in all the inorganic substances that 
 plants require, and hence yield rich returns to the agricultural labourer. 
 They are usually, however, distinguished, and their boundaries marked, 
 by the geologist — so that the soils which repose upon them do not con- 
 tradict any of the general deductions he is prepared to draw, in regard to 
 the general agricultural capabilities of a country, from the kind of rocks 
 of which it consists. 
 
 Thus though the occurrence of extensive fields of drift over various 
 parts of almost every country, does throw, some further difficulty over 
 the researches of the agricultural geologist, and requires from liim the 
 application of greater skill and caution before he pronounce with cer- 
 tainty in regard to the agricultural capabilties of any syjot before he visit 
 it — yet it neither contradicts the general deductions of the geologist nor 
 the special conclusions he would be entitled to draw in regard to the 
 ability of any country, when rightly cultivated, to niaintain in comfort 
 a more or less numerous population. The political economist may still, 
 by a survey of the geological map of a country, pronounce with some 
 confidence to what degree the agricultural riches of that country might 
 by industry and skill be brought — and which districts of an entire conti- 
 nent are fitted by nature to maintain the most abundant population. 
 The intending emigrant may still, by the same means, say in what new 
 land he is most likely to find a propitious soil on which to expend his 
 labour — or such mineral resources as will best aid his agricultural pur- 
 suits ; — while a careful study of the geological map of his own country 
 will still enable the skilful and adventurous farmer to determine in what 
 counties he will meet with soils that are suited to that kind of practice 
 with which he is most familiar — or which are likely best to reward 
 him for the application of the newest and most approved methods of 
 culture. 
 
 Still there are some aids to this kind of knowledge yet wanting. We 
 have geological maps of all our counties, in which the boundaries of the 
 several rocky formations are more or less accurately pointed out, and 
 from these maps, as we have seen, much valuable agricultural informa- 
 tion may be fairly deduced. We have also agricultural maps of many 
 counties, compiled with less care, and often with the aid of little geolo- 
 gical knowledge, as that of Durham in Bailey's ' View of the Agricul- 
 ture of the County of Durham,' published in 1810. But agriculture 
 now requires geological maps of her own — which shall exhibit not only 
 the limits of rocky formations, but also the nature and relative extent 
 of the superficial deposits (drifts), on which the soils so often rest, and 
 from which they are not unfrequently formed. These would afford a 
 
AGRICULTURAL MAPS ACCUMULATIONS OF PP:AT. 275 
 
 sure basis on which to rest our opinions in regard to the agricultural ca- 
 pabiliiies of the several parts of a count}'' in which, though the rocks are 
 the same, the soils may be very different. To the study of these drifted 
 materials, in connection with the action of ancient glaciers (p. 269), the 
 attention of geologists is at present much directed, and from their labours 
 agriculture will not fail to reap her share of practical benefit — the geolo- 
 gical survey, also, so ably superintended by Mr. De La Beche, is col- 
 lecting and recording much valuable information in regard to the agri- 
 cultural geology of the southern counties — but it is not unworthy the con- 
 sideration of our leading agricultural societies — whether some portion of 
 their encouragement might not be beneficially directed to the preparation 
 of agricultural maps, which should represent, by different colours, the agri- 
 cultural capabilities of the several parts of each county, based upon a 
 knowledge of the soils and sub-soils of each parish or township, and of 
 tiie rocks, whether near or remote, from which they have been severally 
 derived. 
 
 Before leaving this subject, I will call your attention to one practi- 
 cal application of this knowledge of the extensive prevalence of drifts, 
 which is not without its value. Being acquainted with the nature of the 
 rocks in a country, and with its physical geography — that is, which of 
 these rocks form the hills, and which the valleys or plains — we can pre- 
 dict, in general, that the materials of the hills will be strewed to a greater 
 or less distance over the lower grounds, and that these lower soils will 
 thus be more or less altered in their mineral character. And when the 
 debris of the hills is of a more fertile character than that of the rocks 
 which form the plains, that the soils will be materially improved by this 
 covering: — the soil of the mill-stone grit, for example, by the debris of 
 the mountain lime-stone, or of a decayed green-stone or a basalt. On 
 the other hand, where the higher rocks are more unfruitful, and the low 
 lands are covered with sterile drifted sands brought down from the more 
 elevated grounds — a knowledge of the nature of the subjacent rock may 
 at once suggest the means of ameliorating and improving the unpromis- 
 ing surface-drift. Thus the loose sand of Norfolk is fertilized by the 
 subjacent chalk marl; and even sterile heaths (Hounslow), on which 
 nothing grew before, have, by this means, been made to produce luxu- 
 riant crops of every kind of grain. 
 
 § 8. Of superficial accumulations of Peat. 
 
 Of superficial accumulations, that of peat is one which, in the United 
 Kingdom, covers a very large area. In Ireland alone, the extent of bog 
 is estimated at 2,800,000 acres. None of the drifted materials we have con- 
 sidered, therefore, would appear so likely to falsify the predictions of the 
 geologist, who should judge of the soils of such a country from informa- 
 tion in regard to the rocks alone on wdiich they rest — from a geological 
 map for example — as the occurrence of these peat bogs. Yet there are 
 certain facts connected with the formation of peat, which place him in 
 some measure on his guard in reference even to accumulations of vege- 
 table matter such as these. 
 
 1°. There is a certain range of temperature within which alone peat 
 seems capable of being produced. Thus, at the level of the sea, it is 
 n?vcr found nearer the equator than between the 40° and 45° of latitude; 
 
276 WHERE PEAT IS TO BE EXPECTED. 
 
 •while its limit towards the poles appears to be within the 60th degree. 
 It is a product, therefore, chiefly of the temperate regions. 
 
 Still, on the equator itself, at a sufficient altitude above the sea, the 
 temperature may be cool enough to permit the growth of peat. Hence, 
 though on the plains of Italy no peat is formed, yet, on the higher Ap- 
 penines, it may be here and there met with, among the marshy basins, 
 and on the undrained mountain sides. 
 
 2°. The occurrence of stagnant water is necessary for the production 
 of peat. Hence, on impervious beds of clay, through which the rains 
 and springs can find no outlet, the formation of peat may be expected. 
 Thus on the Oxford clay repose the fens of Lincoln, Cambridge and 
 Huntingdon (p. 245). On impervious rocks also, peat bogs form for a 
 similar reason. The new-red sandystone is occasionally thus impervi- 
 ous, and on it, among other examples, repose the Chat moss, the tract of 
 peat, mostly in cultivation, which lies west of a line drawn between 
 Liverpool and Preston,, and the large extent of boggy country which 
 stretches round the head of the Solway Firth. On the old red sand- 
 stone, the mountain lime-stone, the slate, and the granite rocks, much 
 peat occurs, and it is on these latter formations that the extensive bogs of 
 Scotland and Ireland chiefly rest. 
 
 But though these two facts are of some value to the politician and to 
 the geologist in indicating in what countries and on what formations peal 
 may be expected to occur, yet they are of comparatively little impor- 
 tance to the practical agriculturist. It is of far more consequence to 
 him that the moment he casts his eye upon the face of a country he can 
 detect the presence or absence of peat — that none of the perplexities 
 which beset the nature and origin of other superficial accumulations at- 
 tach to this — that he can, at once, judge both of its source and of its agri- 
 cultural capabilities. Though produced on a given spot, because rocks 
 of a certain character exist there, yet its origm is always the same — its 
 qualities more or less uniform, — the improvement of which is susceptible 
 in some measure alike, — and the steps by which that improvement is to 
 be effected, liable to variation, chiefly according as this or that amelio- 
 rating substance can be most readily obtained. 
 
LECTURE XIII. 
 
 Exact chemical constitution of soils — their organic constituents — Analysis of soils — Compo- 
 sition of certain characteristic soils — Physical characters of soils. 
 
 I.N the two preceding lectures we have considered the general consti- 
 tuii.iti u!id origin of soils, and their relation to the geological structure of 
 liie country in which they are found, and to the chemical composition of 
 the ro<;ks on which they rest. We have also discussed some of the 
 causes of those remarkable differences which soils are known to present 
 in their relations to practical agriculture. But a more intinaate and pre- 
 cise acquaintance with the chemical constitution of soils is not unfre- 
 quently necessary to a complete understanding of the causes of these dif- 
 ferences — of the exact effect which its chemical constitution has upon the 
 fertility of a soil — and of the remedy which in any given circumstances 
 ought to be applied. 
 
 Some persons have been led to expect too much from the chemical 
 analysis of a soil, as if this alone were necessary at once to explain all its 
 qualities, and to indicate a ready method of imparting to it every desir- 
 able quality, — while others have as far depreciated their worth, and have 
 pronounced them in all cases to be more curious than useful. — [Boussin- 
 gault, ' Annal. de Chim. et de Phys.' Ixvii., p. 9.] The truth here, as 
 on most other subjects, lies in the middle between these extreme opinions. 
 
 If you have followed me in the views I have endeavoured to press upon 
 you in regard to the necessity of inorganic food to plants — which food 
 can only be derived from the soil, and which must vary in kind and 
 quantity with the species of crop to be raised, — you will at once perceive 
 that the rigorous analysis of a soil may impart most valuable knowledge 
 to the practical man in the form of useful suggestions for its improvement. 
 It may indeed show that to apply the only available substances to the 
 soil which are capable of remedying its defects, would involve an expense 
 for which, in existing circumstances, the land could never give an equiva- 
 lent return. Yet even in this latter case the results of analysis will not be 
 without their value to the prudent man, since they will deter him from 
 adding to his soil what he knows it already to contain, and will set him 
 upon the search after some more economical source of those ingredients 
 which are likely to benefit it most. 
 
 It will be proper, therefore, to tumour attention briefly to the conside- 
 ration of the exact chemical constitution of soils. 
 
 § 1. Of the exact nature of the organic constituents of soils, and of the 
 
 mode of separating them. 
 
 We have already seen in Lecture XL, p. 229, that all soils contain a 
 
 greater or less admixture of organic — chiefly vegetable — matter, the 
 
 total amount of which may be very nearly determined by burning the 
 
 dried soil at a red heat till all blackness disappears (p. 233). But this 
 
 vegetable matter consists of several different chemical compounds, the 
 
 nature and relative weights of which it is occasionally of consequence to 
 
 . be able to determine. 
 
278 NATURE OF THE ORGANIC CONSTITUENTS OF SOILS. 
 
 1°. Humus. — The general name of humus is given to the fine, brown 
 light powder which imparts their richness to vegetable moulds and gar- 
 den soils. It is formed from the gradual decomposition of vegetable 
 matter, exists in all soils, forms the substance of peat, and consists of a 
 mixture of several different compounds which are naturally produced 
 during the decay of the different parts of plants. It is distinguished into 
 mild^ sour, and coaly humus. 
 
 The mild gives a brown colour to water, but does not render it sour, 
 gives a dark brown solution when boiled with carbonate of soda, evolves 
 ammonia when heated with caustic potash or soda or with slaked lime, 
 and leaves an ash when burned which contains lime and magnesia. 
 The sour gives, with water, a brown solution of a more or less sour 
 taste, [or reddens vegetable blues — see page 45.] This variety is 
 less favourable to vegetation than the former, and indicates a want of 
 lime in the soil. The coaly humus gives little colour to water or to a 
 hot solution of carbonate of soda, leaves an ash which contains little 
 lime, occurs generally on the surface of very sandy soils, and is very un- 
 fruitful. It is greatly ameliorated by the addition of lime or wood 
 ashes. 
 
 2°. Humic acid. — When a fertile soil or a piece of dry peat is boiled 
 with a solution of the common carbonate of soda of the shops, a brown 
 solution, more or less dark, is obtained, from which, when diluted muri- 
 atic acid (spirits of salt) is added till the liquid has a distinctly sour 
 taste, brown flocks begin to fall. This brown fiocky matter is humic acid. 
 
 3°. Ulmic acid. — If, instead of a solution of carbonate of soda, one 
 of caustic ammonia, (the hartshorn of the shops,) be digested upon the soil 
 or peat by a gentle heat, a more or less dark brown solution is obtained, 
 which, on the addition of muriatic acid, gives brown flocks as before, 
 but which now consists o^ ulmic acid. 
 
 These two acids combine with lime, magnesia, alumina, and oxide of 
 iron, forming compounds (salts) which are respectively distinguished by 
 the names of humates and ulmates. They probably both exist, ready 
 formed, in the soil in variable proportions, and in combination with one 
 or raoreofjiie earthy substances above mentioned — lime, alumina, &c. 
 They are produced by the decay of vegetable matter in the soil, which 
 decay is materially facilitated by the presence of one or other of these 
 substances, and by lime especially — on the principle that the formation 
 of acid compounds is in all such cases much promoted by the presence 
 of a substance with which that acid may combine. They predispose 
 organic substances to the formation of such acids, and consequently to 
 the decomposition by which they are to be produced. Thege two acids 
 consist respectively of 
 
 Humic acid. Ulmic acid. 
 
 Carbon 63 57 
 
 Hydrogen 6 4^- 
 
 . Oxygen 31 38| 
 
 100 100 
 
 Some writers upon agriculture have supposed that these acids con- 
 tribute very materially to the support of growing plants. But Liebig 
 
CRENIC AND APOCRENIC ACIDS. 279 
 
 has very properly objected to this opinion,* that they are so very sparingly 
 soluble in water that we cannot suppose them to enter directly into the 
 roots — even were all the water they absorb to be saturated with them — 
 in such quantity as to contribute in a great degree to the organic matter 
 contained in almost any crop.f 
 
 We have indeed seen reason to conclude on other grounds, that only a 
 small, though a variable, proportion of the carbon of plants is derived 
 from the soil, yet of this proportion a certain quantity may enter by the 
 roots in the form of one or other of these acids, or of their earthy com- 
 pounds. They are readily soluble in ammonia; and animal manures 
 which give off this compound in the soil may therefore facilitate their 
 entrance into the roots of those plants which are cultivated by the aid of 
 such manures. They are also soluble in carbonate of potash and car- 
 bonate of soda, which are contained in wood ashes and in the ash of 
 weeds and of soils which are pared and burned. When these substan- 
 ces, therefore, are applied to the land, they may combine with, and, 
 among their other beneficial modes of action, may serve to introduce, 
 these acids in larger quantity into the plant. 
 
 When exposed to the air, the humates and ulmates contained in the 
 soil undergo decomposition, give off carbonic acid, and are changed into 
 carbonates. The admission of air into the soil facilitates this decompo- 
 sition, which is supposed to be continaally going forward — and it is in the 
 form of this gas that plants are considered by some to imbibe the largest 
 portion of that carbon for which they are indebted to the soil. 
 
 4°'. Crenic and Aprocrenic acids. — When soils are digested or washed 
 with hot water, a quantity of organic matter is not unfrequently dissolved, 
 which imparts to the water a brownish yellow colour. When the solu- 
 tion is evaporated to dryness, there remains besides, the soluble saline 
 substances of the soil, a variable portion of brown extractive looking 
 matter also, which is a mixture of the two acids here named, with the 
 ulmic and humic — all in combination with lime, alumina, and other bases. 
 When this residue is dried at 230° F., the two latter acids, and their 
 compounds, become insoluble, while the crenates and apocrenates, more 
 especially the former, remain soluble in water, and may be separated 
 by washing with this liquid. 
 
 These acids also are formed in the soil during the decay of vegetable 
 matter. They are distinguished from the two previously described by 
 containing nitrogen as an essential constituent, and by forming compounds 
 with lime, &c., which are, for the most part, readily soluble in water. 
 Hence they will both prove more nourishing to plants — in virtue of the 
 nitrogen they contain — and in consequence of their solubility, will be able, 
 where they exist, to enter more readily, and in greater abundance, into 
 the roots than either the ulmic or the humic acid. 
 
 Owing to this solubility, also, they are more readily washed out of the 
 soil by the rains, and hence are rarely present in any considerable quan- 
 
 ' Organic Chemistry applied lo Agriculture, first edition, pp. 1 1 and 12. 
 
 t Ulmic acid requires 2500 times its weight of water to dissolve it— ulmate of lime 2000 
 times, and ulmate of alumina 4200 limes — but all are still less soluble after they have been 
 perfectly dried, or exposed to the action of a hard winter's frost. The ulmates of potash, 
 soda, and alumina, are all dissolved in water with considerable ease. 
 
280 OTHER ORGANIC COMPOUNDS IN THE SOIL. 
 
 tity in specimens of soil which are submitted to analysis. They are fre- 
 quently, however, met with in springs and in the drainings of ihe land. 
 They have even been found in minute quantity in rain-water,* it is pro- 
 bable that they ascend into the air in very small proportion with the 
 watery vapour that rises. This exhibits another form, therefore, ia 
 which the rains may minister to the growth of plants (see page 36). 
 
 Both acids form insoluble compounds with the peroxide of iron — and 
 hence are found in combination with many of the ochrey deposits from 
 ferruginous springs, and with the oxide of iron by which so many soils 
 are coloured. The apocrenic acid has also a peculiar tendency to com- 
 bine with alumina, with which it forms a compound insoluble in water, 
 and in this slate of combination it probably exists not unfrequently, espe- 
 cially in clayey soils. 
 
 When heated with newly slaked quick-lime these acids give off am- 
 monia and carbonic acid. By the action of the air, and of lime in the 
 soil, they are probably decomposed in a similar manner, though with 
 much less rapidity. 
 
 5°. Mudesous acid is another dark brown acid substance, which is also 
 produced naturally in the soil. It resembles the apocrenic, in having 
 a strong tendency to combine with alumina. In union with this acid it 
 is slowly washed out of the soil by the rains, or filters through it when 
 the water can find an outlet beneath. This is seen to be the case in some^ 
 of the caves on the Cornish coast, where the waters that-trickle through 
 from above have gradually deposited on their roof and sides a thick in- 
 crustation of mudesite of alumina.f 
 
 Besides these acids, it is known that the malic and the acetic (vine- 
 gar) are occasionally produced in the soil during the slow decay of vege- 
 table matter of different kinds. It is probable that many other analo- 
 gous compounds are likewise formed — which are more or less soluble in^ 
 water, and more or less fitted to aid in the nourishment of plants. There 
 is every reason to believe, indeed, that organic substances in the soil pass 
 through many successive stages of decomposition, at each of which they 
 assume new properties, and become more or less capable of aiding in 
 the support of living races. The subject is difficult to investigate, be- 
 cause of the obstacles which lie in the way of exactly separating from 
 each other the small quantities of the different organic compounds that 
 occur mixed up together in the soil. But it seems quite clear, that while 
 some agricultural chemists have erred in describing the ulmic and hu- 
 mic acids as the immediate source of a large portion of the carbon of 
 plants, others have no less misstated — as I apprehend — the true course 
 of nature, who deny any direct influence to these and other substances 
 of vegetable origin, and limit their use in the soil to the supply of car- 
 bonic acid only, which, on their ultimate decomposition, they are capa- 
 ble of yielding to the roots. The resources of vegetable life are not so 
 limited; but as the human stomach can, and does, on occasion, convert 
 into nourishment many different compounds of the same elements, — so, 
 no doubt, many of those organic compounds which are produced in the 
 soil, or in fermenting manure during the decay of animal and vegetable 
 
 ' * Fiirsten zu Salm-Horstmar. Poggend. Annal. liv., p. 254. 
 t Known to mineralogists under the name of Pigotite. 
 
SEPARATION OF THESE ORGANIC SUBSTANCES. 281 
 
 bodies, — when once admitted, in consequence of their solubility, into the 
 circulating system of plants, — are converted into portions of their sub- 
 stance, and really do minister to their natural growth. 
 
 Separation of these Organic Constituents. — 1°. When on washing 
 with hot water a soil imparts a colour to the solution, the liquid must be 
 filtered and evaporated, to perfect dryness. On treating with water 
 what remains after the evaporation, the humic acid and humates remain 
 insoluble, while the crenic and apocrenic acids are taken up by the wa- 
 ter along with the soluble saline matter which the soil may have con- 
 tained. By evaporating this second solution to perfect dryness, weigh- 
 ing the residue, and then heating it to dull redness in the air, the loss 
 will indicate something more than the quantity of these acids present in 
 the soil. By burning the dried insoluble matter, also, the quantity of 
 humic acid present in it may in like manner be determined. 
 
 2°. After being washed with pure water, the soil is to be boiled with 
 a solution of carbonate of soda, repeated once or twice an long as a brown 
 solution, more or less dark, is obtained. Being filtered, and then ren- 
 dered sour by muriatic acid, brown flocks fall, which being collected on 
 the filter, perfectly dried and weighed, give the quantity of humic acid 
 in the soil. As this dry humic acid genei-ally contains some earthy 
 matter, it is more correct to burn it, and to deduct the weight of the ash 
 which may be left. 
 
 3°. The insoluble (coaly) humus still remains in the soil. On boiling 
 it now in a solution of caustic potash for a length of time, and till a fresh 
 solution ceases to become brown, the coaly humus is entirely dissolved — 
 being converted according to Sprengel into humic acid. The addition 
 of muriatic acid to this solution, till it has a sour taste, throws down the 
 humic acid in the form of brown flocks, which may be collected, dried, 
 and weighed as before. 
 
 4°. If there be any mudesite of alumina in the soil, it is also dis- 
 solved by the potash, but is not thrown down when the solution is ren- 
 dered sour by muriatic acid. The entire weight of organic matter in the 
 soil being therefore determined by burning it in the air, after being 
 perfectly dried, the difference between this weight and the sum of those 
 of the humic acid and insoluble humus will be the proportion of the 
 other acids present. Thus, if, by burning in the air, the soil lose 6 per 
 cent., and give 2 per cent, of humic acid, and 2 of insoluble humus, there 
 remain 2 per cent, for other organic substances in the soil. 
 
 In general, it is considered sufficient to ascertain only the whole loss 
 by burning, and the quantity taken up by carbonate of soda, the propor- 
 tion of the other substances present being in most cases so small as to be 
 capable of being precisely estimated by great precautions only. 
 
 § 2. On the exact chemical constitution of the earthy part of, the soil. 
 
 In reference to the general origin of soils — to their geological rela - 
 tions — and to the simplest mode of classifying them, — I have shown you 
 that the earthy part of nearly all soils consists essentially of sand, clay, 
 and lime (p. 230). But in reference to their chemical relations to the 
 plants which grow, or may be made to grow, upon them, it is necessary, 
 as. you are now aware, to take a more refined and exact view of their 
 
282 WHY REFINED ANALYSES ARE NECESSARY. 
 
 constitution. This will appear by referring to three important pnnci- 
 ples established in the preceding lectures. 
 
 1°. That the ash of plants generally contains a certain sensible pro- 
 portion of ten or twelve different inorganic substances (pp. 216 to 221). 
 
 2°. That they can, in general, only derive these substances from the 
 soil, which must, therefore, contain them (p. 181). And — 
 
 3°. That the fertility of a soil depends, among other circumstances, 
 upon its ability to supply readily and in sufficient abundance all the in- 
 organic substances which a given crop requires (p. 228.) 
 
 Now the quantity of some of these substances which is necessary to 
 ]>Ianls is so very small, that nothing but a refined analysis of a soil is 
 capable, in many cases, of determining whether they are present in it or 
 not — much less of explaining to what its peculiar defects or excellencies 
 may be owing — what ought to be added to it in order to render it more 
 productive — or why certain remarkable effects are produced upon it by 
 the addition of mineral or animal manures. 
 
 Thus, for example, half a grain of gypsum in a pound of soil indicates 
 the presence of nearly two cwt. in an acre, where the soil is a foot deep, — 
 a (juanlity much greater than need be added to a soil in which gypsum 
 is almost entirely wanting, in order to produce a remarkable luxuriance 
 in the red clover crop. In 100 grains of the soil, this quantity of gyp- 
 sum amounts only to seven-thousandths of a grain — (foVo» ^^ 0*007 
 grs.) — a proportion which only a very carefully conducted analysis 
 v%M)uld be able to detect, and yet the detecting of which may alone be able 
 to explain the unlike effects which are seen to follow the application of 
 gypsum to different soils. 
 
 Asjain, the phosphoric acid is a no less necessary constituent of the 
 fM')il than the sulphuric acid contained in gypsum. This acid is gener- 
 ally in combination either with lime, with oxide of iron, or with alu- 
 mina — and, as it is much more difficult even to detect than the sulphuric 
 acid, requires more care and skill to determine its quantity with any 
 decree of accuracy, — and is generally present even in fertile soils in a 
 still smallerjproporiion — it is obvious that safe and useful conclusions can 
 be drawn only from such analyses as have been made rigorously, accord- 
 ing to the best methods, and with the greatest attention to accuracy. 
 
 There are cases, no doubt, where a rough analysis may be of use, 
 where the cause of peculiarity is at once so obvious that further research 
 is unnecessary — as where mere washing with water dissolves out a 
 noxious substance, such as sulphate of iron (green vitriol). But such 
 cases are comparatively rare, and it more frequently happens, that the 
 cause of the special qualities of a soil only begins to manifest itself when 
 a carefully conducted analysis approaches to its close. I shall, therefore, 
 briefly describe to you the methods to be adopted, in order to arrive at 
 these more accurate experimental results. [As these methods of analysis 
 involve considerable detail, I have transferred thera^to the Appendix. — 
 See Appendix, p. 25.] 
 
EXACT CONSTITUTION OF SOME FERTILE SOILS. 283 
 
 §3. Of the exact chemical constitution of certain soils, and of the results 
 to be deduced from them. 
 
 But the importance of this attention to rigorous analysis will more 
 clearly appear, if I exhibit to you the constitution of a few of the nume- 
 rous soils analyzed by Sprengel, in connection with the agricultural quali- 
 ties and capabilities by which they are severally distinguished. 
 
 The following analyses are selected from a much greater number made 
 by Sprengel, and embodied in his work on soils, " Die Bodenkunde." 
 
 I. — FERTILE SOILS. 
 
 Soils are fertile which contain a sufficient supply of all the mineral 
 constituents which the plants to be grown upon them are likely to re- 
 quire. 
 
 1°. Pasture. — The following numbers exhibit the constitution of the 
 
 surface soil in three fertile alluvial districts of Hanover, where the land 
 
 has been long in pasture. 
 
 Soil near From the banks of the Weser 
 Osterbruch. near Hoya. near Weserbe 
 
 Silica, Quartz, Sand, and Silicates. 84-510 71-849 83-318 
 
 Alumina 6-435 9-350 3-085 
 
 Oxides of Iron 2-395 5-410 5-840 
 
 Oxide of Manganese .... 0-450 0-925 0-620 
 
 Lime 0-740 0-987 0-720 
 
 Magnesia 0-525 0-245 0-120 
 
 Potash and Soda extracted by water 0-009 0-007 0-005 
 
 Phosphoric Acid 0-120 0-131 0-065 
 
 Sulphuric Acid 0-046 0-174 0-025 
 
 Chlorine in common Salt . . 0-006 0-002 0-006 
 
 Humic Acid .0-780 1-270 0-800 
 
 Insoluble Humus .... 2-995 7-550 4-126 
 
 Organic matters containing Nitrogen 960 2-000 1-220 
 
 Water 0-029 0-100 0-050 
 
 100 100 100 
 
 These soils had all been long in pasture, the second is especially cele- 
 brated for fattening cattle when under grass. It will be observed that in 
 none of them is any of the mineral ingredients wholly wanting, though 
 in all the quantity of potash and soda capable of being extracted by 
 water is very small. This is ascribed to the fact of their having been 
 long in pasture, during which the supply of these substances is gradually 
 withdrawn by the roots of the grasses. It is well known how, in our or- 
 dinary soils, grass is often renovated — how the mosses, especially, are de- 
 stroyed — by a dressing of wood ashes, whichowetheir effect to the alkali 
 they contain. In the above soils the gradual decomposition of the sili- 
 cates would continue to supply a certain portion of alkaline matter for an 
 indefinite period of time. 
 
 You will perceive that the soil which is the most celebrated for its^^- 
 tening power, is also the richest in alumina, lime, phosphoric acid, sul- 
 phuric acid, and vegetable matter. 
 
284 
 
 THE SOIL OF RICH ARABLE LANDS. 
 
 29. Arable. — The following table exhibits the constitution of three 
 soils, celebrated for yielding successive crops of corn for a long period 
 without manure. 
 
 1. 
 
 2. 
 
 3. 
 
 From Nebtsein, 
 
 From the banks of the 
 
 From the polde, 
 
 near Olmutz, 
 
 Ohio, North America. 
 
 of Alt-Arenbergr 
 
 in Moravia. 
 
 Soil. 
 
 Subsoil. 
 
 in Belgium. 
 
 Silica and fine Sand . 77-209 
 
 87-143 
 
 94-261 
 
 64-517 
 
 Alumina . ... 8*514 
 
 5-666 
 
 1-376 
 
 4-810 
 
 Oxides of Iron . . . 6-592 
 
 2-220 
 
 2-336 
 
 8-316 
 
 Oxide of Magnesia . . 1-520 
 
 0-360 
 
 1-200 
 
 0-800 
 
 Lime ...... 0-927 
 
 0-564 
 
 0-243 
 
 Carbof 
 Lime 9-403 
 
 Magnesia 1-160 
 
 0-312 
 
 0-310 
 
 Carb.of ^ ^^^ 
 Mag. 10-361 
 
 Potash chiefly combined 
 
 
 
 
 with Silica .... 0-140 
 
 0-120 I 
 
 0-240 
 
 5 0-100 
 ) 0-013 
 
 Soda, ditto .... 0-640 
 
 0-025 S 
 
 Phosphoric Acid combined^ 
 
 
 
 
 with Lime and Oxide of 
 
 
 
 
 Iron 0-651 
 
 0-060 
 
 trace 
 
 1-221 
 
 Sulphuric Acid in gypsum 0-011 
 
 0-027 
 
 0-034 
 
 0-009 
 
 Chlorine in common salt. 0-010 
 
 0-036 
 
 trace 
 
 0-003 
 
 Carbonic Acid united to the 
 
 
 
 
 Lime — 
 
 0.080 
 
 — 
 
 — 
 
 Huinic Acid .... 0-978 
 
 1.304 
 
 — . 
 
 0-447 
 
 Insoluble Humus . . . 0-540 
 
 1.072 
 
 — 
 
 — 
 
 Organic substances con- 
 
 
 
 
 taining Nitrogen . 1-108 
 
 1-011 
 
 — 
 
 — 
 
 100 
 
 100 
 
 100 
 
 100 
 
 Of these soils, the first had been cropped for 160 years successively, 
 witliout eitherrnanure or naked fallow. The second was a virgin soil, 
 celebrated for its fertility. The third had been unmanured for twelve 
 years, during the last nine of which it had been cropped with beans 
 — barley — potatoes — winter barley and red clover — clover — winter bar- 
 ley — wheat — oats — naked fallow. 
 
 Though the above soils differ considerably, as you see, in the propor- 
 tions of some of the constituents, yet they all agree in this — that they are 
 not destitute of any one of the mineral compounds, which plants necessa- 
 rily require in sensible quantity. You will also observe how compara- 
 tively small a proportion of vegetable matter, less than half a per cent., 
 is contained in the fertile Belgian soil — a fact to which I shall by-and- 
 by recall your attention. 
 
 . 3°. Soils ivhich have a natural source of fertility. — Some soils, which 
 by their constitution are not fitted to exhibit any great degree of fertility, 
 or for a very long period, are yet, by springs or otherwise, so constantly 
 supplied with soluble saline, and other substances, as to enable them to 
 yield a succession of crops, without manure, and without apparent dete- 
 rioration. Such is the case with the following soil from near Rothen- 
 
SPRINGS OFTEN ENRICH THE SOILS. 285 
 
 felde, in Osnabruck, which gives excellent crops, though manured only 
 once in 10 or 12 years. 
 
 Silica and coarse Quartz Sand .... 86*200 
 
 Alumina 2-000 
 
 Oxides of Iron and a little Phosphoric Acid . 2*900 
 
 Oxide of Manganese 0*100 
 
 Carbonate and a little Phosphate of Lime . 4*160 
 
 Carbonate of Magnesia 0*520 
 
 Potash and Soda 0*035 
 
 Phosphoric Acid 0*020 
 
 Sulphuric Acid 0*021 
 
 Chlorine 0*010 
 
 Humic Acid 0*544 
 
 Insoluble Humus 3*370 
 
 Orgatiic matter containing Nitrogen . . . 0*120 
 
 100 
 
 You will see that, although in this soil all th^ inorganic substances are 
 really present, yet the potash and soda, the phosphoric and sulphuric 
 acids, and the chlorine, are not in such abundance as to justify us in ex- 
 pecting it to grow any long succession of crops, without exhibiting the 
 usual evidences of exhaustion. But it lies on the side of a hill which con- 
 tains layers of lime-stone and marl, through which the surface waters 
 find their way. These waters afterwards rise into the soil of the field, 
 impregnated with those various substances of which the soil is in want, 
 and thus, by a natural manuring, keep up a constant supply for each suc- 
 ceeding crop. 
 
 This example is deserving of your particular attention, inasmuch as 
 there are many soils, in climates such as ours, which are yearly refresh- 
 ed from a similar source. Few spring waters rise to the surface which 
 are not fitted to impart to the soil some valuable ingredient, and which, if 
 employed for the purposes of irrigation, would not materially benefit 
 (hose lands especially on which our pasture grasses grow. The same 
 may also be said of the waters which are carried off in some places so 
 copiously by drains. Whether these waters rise from beneath in springs, 
 or, falling in rain, afterwards sink through the soil, they in either case 
 carry into the brooks and rivers much soluble matter, which the plants 
 would gladly extract from them. On sloping grounds it would be a 
 praiseworthy economy to arrest these waters, and, before they escape, 
 lo employ them in irrigation. 
 
 The fact that nature thus on many spots brings up from beneath, or 
 down from the higher grounds, continual accessions of new soluble mat- 
 ter to the soil, will serve to explain many apparent anomalies, and to ac- 
 count for the continued presence of certain substances in small quantity, 
 although year by year portions of them are carried off the land in the 
 crops that are reaped, while no return is made in the shape of artificial 
 manure. It will also in some instances account for the fact that, after a 
 hard cropping, prolonged until the soil has become exhausted, a few 
 years' rest will completely re-invigorate it, and render it fit to yield 
 
286 
 
 IMPORTANCE OF DEPTH OF SOIL. 
 
 new returns of abundant corn. Other causes, as we shall hereafter see, 
 generally operate in bringing about this kind of natural recovery, but 
 there can be no question that in circumstances such as I have now 
 adverted to, this recovery may be effected in a much shorter period 
 of time. 
 
 4°. Tmjyortance of depth and uniformity of soil. — If the surface soil be 
 of a fertile quality, ample returns will be sure from many cultivated 
 crops. But where the subsoil is similar in composition to that of the 
 surface — not only may the fertility of the land be considered as almost 
 inexhaustible, but those crops also which send their roots far down will 
 be able permanently to flourish in it. This fact is illustrated by the 
 composition of the following soils from the neighbourhood of Bruns- 
 wick ; — 
 
 1. 
 
 Soil. 
 
 Silica and fine Quartz Sand . 94-724 
 
 Alumina 1'638 
 
 Oxides of Iron . .* . . ) 1-960 
 Oxides of Manganese . . ^ 
 
 Lime 1-028 
 
 Magnesia trace 
 
 Potash and Soda 0-077 
 
 Phosphoric Acid 0-024 
 
 Sulphuric Acid 0-010 
 
 Chlorine 0-027 
 
 Humic Acid 0-302 
 
 Insoluble Humus .... 0-210 
 
 100 
 
 Subsoil. 
 
 97-340 
 
 0-806 
 
 5 1-126 
 
 I 0075 
 
 0-296 
 
 0-095 
 
 0-112 
 
 0-015 
 
 trace 
 
 trace 
 
 0-135 
 
 100 
 
 2. • 
 
 Subsoil. 
 
 90-035 
 1-976 
 5-815 
 0-240 
 0-0'22 
 0-115 
 0-300 
 0-098 
 1-399 
 trace 
 
 100 
 
 The first of these soils produced excellent crops of all deep-roofed 
 plants — luc^ne, sainfoin (esparsette), hemp, carrots, poppies, &c. — and 
 with the aid of gypsum, red clover, and leguminous plants (vetches, 
 peas, and beans), in great luxuriance. The former of these facts is ex- 
 plained by the great similarity in constitution which exists between the 
 surface and the under soils. To deep-rooted plants also the magnesia, 
 in which the surface is deficient, is capable of being supplied by the under 
 soil. The effect of the gypsum is accounted for by the almost total ab- 
 sence of sulphuric acid in the subsoil, but which the application of gyp- 
 sum has introduced into the upper soil. 
 
 The second soil was taken from a field in which sainfoin died regu- 
 larly in the second or third year after it was planted. This was naturally 
 attributed to something in the subsoil. And by the analyses above 
 given, it was found to contain much sulphuric acid in combination with 
 oxide of iron, forming sulphate of iron (green vitriol). This salt being 
 noxious to plants, began to act upon the crop of sainfoin as soon as the 
 roots had gone so deep as to draw sufficient supplies from the subsoil, 
 and it thus gradually poisoned them, so that they died out in two or three 
 years. 
 
EXACT CONSTITUENTS OF SOME UNFRUITFUL SOILS. 
 
 287 
 
 II. BARREN OR UNFRUITFUL SOILS. 
 
 Soils are unfruitful or altogether barren, either when they contain too 
 little of one or more of the inorganic constituents of plants, or when some 
 substance is present in them in such quantity as to become hurtful or 
 poisonous to vegetation. The presence of sulphate of iron in the subsoil 
 just described is an illustration of the latter fact. In what way the defi- 
 ciency of certain substances really does allect the agricultural capabilities 
 of the soil will appear from the following analyses : — 
 
 1. 2. 3. 4. 
 
 Moor land soil, Another Sandy Soil on the 
 
 near Aurich, soil from soil from Muscliel- 
 
 East Friesland. the same Wettingen kalk, 
 
 neighbour- in Liine- near Miihl- 
 Soil. Subsoil. hood. burg- hausen. 
 
 Silica and auartz Sand . . 70-576— 95190 61 57G 96000 77-780 
 
 Alumina 1050— 2520 0-450 0500 9 490 
 
 Oxides of Iron 0-252— 1460 0524 2000 5 800 
 
 Oxide of Manganese . . . trace — 0048 trace ti-ace 0105 
 
 Lime do.— 0-336 0320 0001 0866 
 
 Magnesia 0012— 0125 Q-130 trace 0728 
 
 Potash trace — 0072 trace do. trace 
 
 Soda do. — 0180 do. do. do. 
 
 Phosphoric Acid .... do. 0034 do. do. 0003 
 
 Sulphuric Acid ...... do. 0-020 do. do. trace 
 
 Carbonic Acid — — — — 0-200 
 
 Chlorine trace — 0015 trace trace trace 
 
 HumicAcid 11-910- — 11-470 0200 0732 
 
 Insoluble Humus .... 16200— — 26 530 1-299 0200 
 
 Water _ _ _ _ 4 096 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 Each of these analyses is deserving of attention. 
 
 1°. That the barrenness of the moor-land soils (1 and 2) is to be at- 
 tributed to their deficiency in the numerous substances of which they 
 contain only traces, may almost be said to he proved by the fact — one- 
 long recognised and acknowledged on many of our own moor-lands and 
 peaty soils — that when dressed with a covering of the subsoil they be- 
 come capable of successful cultivation. The analysis of the sub.soil in 
 the second column shows that it contains all those mineral constituents in 
 which the soil itself is deficient — and to the eflect of these, therefore, the 
 improvement produced upon the soil by bringing it to the surface is alto- 
 gether to be attributed. 
 
 2°. The sandy soil, No. 3, is evidently barren for the same reason as 
 the moorland soils, 1 and 2. The soil No. 4 rests on lime-stone, and 
 was mixed with 7 per cent, of lime-stone gravel, and contains a great 
 number of the substances which plants require — but its unfruitfulness is 
 to be ascribed to the want of potash and soda, of sulphuric acid and of 
 chlorine. Wood ashes and a mixture of common salt with gypsum or 
 sulphate of soda, would probably have remedied these defects. 
 
 3°. Among the fertile soils to which I recently directed your attention 
 (p. 284) was one from Belgium, in which the proportion of organic 
 matter was less than half a per cent, of its whole weight. In the above 
 table, on the other hand, we have two nearly barren soils, containing 
 
288 WHAT RENDERS A SOIL FERTILE. 
 
 each 11 per cent, of humic acid, besides a much larger proportion of in- 
 soluble organic matter. It is obvious, therefore, that the fertility of a 
 soil is not dependent upon its containing this or that proportion of vege- 
 table matter, either in a soluble or an insoluble form. It is certainly 
 true ihat many very fertile soils do contain a considerable quantity of 
 organic matter, in a form in which it may readily j'ield nourishment to 
 the roots of plants. Yet such soils are not fertile merely in consequence 
 of the presence of this organic matter, as a source o{ organic food to the 
 plant. It may be present, and yet the soils, like those above-mentioned, 
 may remain barren. Where soils become fertile apparently by the 
 long accumulation of such vegetable matter in the soil, it is not mer.ely 
 because of the increase of purely organic substances, such as the humic 
 and ulmic acids, but, because, as I have already had occasion to mention 
 to you, the decaying vegetable matter which produces them contains 
 hlso, and yields to the soil, a considerable abundance of some of those 
 inorganic substances which plants necessarily require. The organic 
 matter is an indication of their presence in such soils. But they may 
 be present without the organic matter. They may either be duly pro- 
 portioned in the soil by nature — or they may be artificially mixed with 
 it, and then this use of the organic matter may be dispensed with. It is 
 of more importance to bear this in mind, because not only vegetable 
 physiologists, but some zealous chemists also, have laid great stress upon 
 the quantity of soluble and insoluble organic matter contained in a soil, 
 and have been led to consider it as a safe index of the relative fertility 
 of different soils. 
 
 The history of science shows, by many examples, that those men 
 who adopt extreme views, — who attempt to explain all phenomena of a 
 given kind, by reference to a single specific cause — have ever been of 
 very great use in the advancement of certain knowledge. Their argu- 
 ments, whether well or ill founded, lead to discussion, to further investi- 
 gation, to the discovery of exceptional cases, and, finally, to the general 
 adoption of modified views which recognise the action of each special 
 cause in certain special cases, but all in subordination to some more ge- 
 neral principle. 
 
 Thus, if some ascribe the fertility of the soil to the presence of the 
 alkalies in great abundance, others to that of the phosphates, others to 
 that of lime, others to that of alumina, and others, finally, to that of ve- 
 getable matter in a soluble state — all these extreme opinions are recon- 
 ciled, and their partial truths recognised, in one general principle, that 
 a soil to he fertile must contain all the substances which the plant we de- 
 sire to grow can only obtain from the soil, and in such abundance as 
 readily to supply all its wants ; while at the same time it must contain 
 nothing hurtful to vegetable life. 
 
 III. SOILS CAPABLE OF IMPROVEMENT BT THE ADDITION OF 
 
 MINERAL MATTER. 
 
 On the principle above stated depends in very many cases the mode 
 of improving soils by the addition of mineral substances, as well as the 
 method of explaining the remarkable effects occasionally pcoduced by 
 their mixture with the land. The following analyses will place this 
 matter in a clearer light : — 
 
COMPOSITION OF READILY IMrROVEABLE SOILS. 
 
 289 
 
 
 1. 
 
 2. 
 
 3. 
 
 4. 
 
 
 Soil near Pa- 
 dingbiittel, on 
 the Weser. 
 
 Near Draken- 
 burg:, on the 
 Weser. 
 
 Near Ganders- 
 
 heim, in 
 
 Brunswick. 
 
 Near 
 Bruns- 
 wick. 
 
 Silica and Quartz Sand 
 
 . 93-720 
 
 92-014 
 
 90-221 
 
 95-698 
 
 Alumina . 
 
 . 1-740 
 
 2-652 
 
 2-106 
 
 0-504 
 
 Oxide of Iron . 
 
 . 2-060 
 
 3-192 
 
 3-951 
 
 2-496 
 
 Oxide of Manganese . 
 Lime 
 
 . 0-320 
 . 0-121 
 
 0-480 
 0-243 
 
 0-960 
 0-539 
 
 trace 
 0-038 
 
 Magnesia . 
 
 . 0-700 
 
 0-700 
 
 " 0-730 
 
 0-147 
 
 Potash (chiefly in- combini 
 lion with Silica) 
 
 a- 
 . 0-062 
 
 0-125 
 
 0-066 ? 
 
 0-090 
 
 Soda (do.) 
 
 . 0-109 
 
 0-026 
 
 0-010 s 
 
 Phosphoric Acid 
 
 . 0-103 
 
 078 
 
 0-367 
 
 0-164 
 
 Sulphuric Acid 
 
 . 0-005 
 
 trace 
 
 trace 
 
 0-007 
 
 Chlorine in common Salt 
 
 . 0-050 
 
 trace 
 
 0-010 
 
 0-010 
 
 Humic Acid 
 
 . 0-890 
 
 0-340 
 
 0-900 
 
 0-626 
 
 Other Organic matter 
 
 . 0-120 
 
 0-150 
 
 0-140 
 
 0-220 
 
 100 
 
 100 
 
 100 
 
 100 
 
 The first of these soils produces naiuraWy beautiful red clover — the 
 second produces very had red clover. On comparing the constitution of 
 the two soils, we see the second to be deficient in sulphuric acid and 
 chlorine. A dressing of gypsum and common salt would supply these 
 deficiencies, and render it capable of producing this kind of clover. The 
 third soil is remarkable for growing luxuriant crops of ])ulse, when ma- 
 nured with gypsum. The almost total absence of sulphuric acid ex- 
 plains this effect. The fourth soil was greatly improved by soap-boiler's' 
 ash, which supplied it with lime, magnesia, manganese, and other sub- 
 stances. 
 
 I need not further multiply examples to show you how much real 
 knowledge is to be derived from a rigidly accurate analysis, not only in 
 regard to the agricultural capabilities of a soil, but also in regard to the 
 natural and necessary food of plants, and to the manner in which 
 mineral manures act in promoting and increasing their growth. The 
 illustrations I have already presented will satisfy you — 
 
 1°. That a fertile soil must contain all the inorganic constituents which 
 the plant requires, and none that are likely to do it an injury. 
 
 2°. That if the addition of a given manure to the soil render it more 
 fertile — it is because the soil was defective in one or more of those sub- 
 stances which the manure contained. 
 
 3°. That if a given application to the land fail to improve it — of gyp- 
 sum, of bone-dust, of common salt, for exam pie — it is because enough of 
 the substance applied is already present, or because something else is 
 still wanting to render the previous additions available. 
 
 4°. That the result of extended experience in our country, that the 
 clay soils are best for wheat, and sandy soils, such as that of Nor- 
 folk, for barley, is not to be considered as anything like a law of nature, 
 setting aside the clay land for the special growth of wheat, and denying 
 
 13 
 
290 PHYSICAL PROPERTIES OF SOILS. 
 
 to the sandy soils the power of yielding abundant crops of this kind of 
 grain. Almost every district can present examj^les of well cultivated 
 fields, where the contrary is proved — and the wheat crops which are 
 yearly reaped from the sandy plains of Belgium, demonstrate it on a 
 more extended scale. 
 
 Chemically speaking, a soil will produce any crop abundantly, pro- 
 vided it contain an ample supply of all that the crop we wish to raise 
 may happen to require. But, in practice, soils which do not contain all 
 these substances plentifully, are yet found to differ in their power of 
 yielding plentiful returns to the husbandman. Such differences arise 
 from the climate, the exposure, the colour, the fineness of the particles, 
 the lightness or porosity of the soil — from the quantity of moisture it is 
 capable of retaining, or from some other of its numerous physical pro- 
 perties. These physical properties, therefore, it is necessary shortly to 
 consider. 
 
 § 4. Of the physical properties of soils. 
 
 To the physical properties of soils was formerly ascribed a much 
 more fundamental importance than we can now attach to them. Crome 
 and Scliiibler regarded the fertility of a soil as entirely dependent upon 
 its physical properties. Influenced by this opinion, the former published 
 the results of an examination of numerous soils in the Prussian provin- 
 ces, which are now possessed of no scientific interest ; because they 
 merely indicate the amount of clay, sand, and vegetable matter whicli 
 these soils severally contained.* The latter completed a very elaborate 
 examination of the physical properties of soils, which is very useful and 
 instructive ;f but the defective nature of which, in accounting for their 
 agricultural capabilities, became evident to the author himself, when the 
 more correct and scientific views of Sprengel, illustrated in the preced- 
 ing section, afterwards became known to him. In giving, therefore, 
 their due weight to the physical properties, we must not forget that in 
 nature they are subordinate to the chemical constitution of soils. Plants 
 may grow u4)on a soil, whatever its physical condition — if all the food 
 they require be within their reach — while, however favourable the phy- 
 sical condition may be, notliing can vegetate in a healthy manner, if the 
 soil be deficient in some necessary kind of food, or contain what is de- 
 structive to vegetable life. 
 
 Of the physical properties of soils the most important are their den- 
 sity, their power of absorbing and retaining water and air, their capillary 
 action, their colour, and their consistence or adhesive power. There 
 are one <9t two others, however, to which it will be necessary shortly to 
 advert. 
 
 I. — MECHANICAL RELATIONS OF SOILS. 
 
 1°. The density and absolute weight of a soil. — Some soils are much 
 heavier than others, not merely in the ordinary sense of heavy and light, 
 as denoting clayey and sandy soils, but in reference to the absolute weight 
 of equal bulks. 
 
 * Recorded in his Grunds'dtze der Agricultur Chemie. 
 t /^^r Boden und acin verhdltmss zu den Geic'dchaen. 
 
ABSOLUTE WEIGHT AND FIRMNESS OF S0IL3. 291 
 
 Thus a cubic foot of dry 
 
 Siliceous or Calcareous Sand — weighs about . 110 lbs. 
 
 Half Sand and half Clay 95 
 
 Of common arable Land, from . . . . 80 to 90 
 Of pure agricultural Clay (page 231) ... 75 
 Of garden Mould, richer in vegetable matter . 70 
 Of a peaty Soil, from 30 to 50 
 
 Sandy soils, therefore, are the heaviest. The weight diminishes with 
 the increase of clay, and lessens still further as the quantity of vegetable 
 matter augments. 
 
 In practice, the denser a soil is, the less injury will be done to the 
 land by the passage of carts and the treading of cattle in the ordinary 
 operations of husbandry. In a theoretical point of view it is of conse- 
 quence to vegetation, chiefly in so far as, according to the experiments 
 of Schiibler, the denser soils retain their warmth for a longer period when 
 the sun goes down, or a cold wind comes on. Thus a peaty soil will 
 cool as much in an hour and a half as a pure clay in two, or a sand in 
 three hours. 
 
 2°. Of the state of division of the constituent parts of the soil. — 
 With the relative weight of different soils, their state of division is in 
 some degree connected. Some soils consist of an admixture of exceed- 
 ingly fine particles both of sand and clay — while in others, coarse sand, 
 stones and gravels, largely predominate. There can be no doubt that the 
 state of the soil in this respect has a material influence upon its produc- 
 tive character, and consequently upon its money value, since the labours 
 of the husbandman in lands of a stiffer and more coherent nature are 
 chiefly expended in bringing thein into this more favourable powdery con- 
 dition. In the description and examination of a soil, therefore, this pro- 
 perty ought by no means to be passed lightly over — since it is one in 
 regard to which a mere chemical analysis gives us little or no informa- 
 tion. 
 
 In some parts of the country, the farmer diligently gathers tho 
 stones off his land, while in others the practice is condemned as hurtful 
 to the arable crops. The latter fact is explained by supposing that 
 these stones in winter afford shelter to the winter-corn, and in warmer 
 seasons protect the ground in some degree from the drying winds, and 
 retain beneath them a supply of moisture of which the neighbouring 
 roots can readily avail themselves. 
 
 3°. Firmness and adhesive power of soils. — When soils dry in the 
 air they cohere and become hard and stiff in a greater or less degree. 
 Pure siliceous sands, alone, do not at all cohere when dry — while pure 
 clays become hard and very difHcult to pulverize. In proportion to the 
 quantity of sand whh which the latter are mixed, do their tenacity and 
 hardness diminish. The difficulty of reducing clays to a fine powder in 
 the open field, or of bringing them into a good tilth, may be overcome, 
 therefore, by an admixture of sand or gravel, but there are few localities 
 where the expense of such an operation does not present an insur- 
 mountable obstacle. Thorough draining, however, subsoil ploughing, 
 and careful tillage, will gradually bring the most refractory soils of this 
 character into a condition in which they can be more perfectly and more 
 economically worked. 
 
292 ADHESION OF SOILS TO THE PLOUGH. 
 
 Soils also adhere to the plough in cUiTerent degrees, and, therefore, pre- 
 sent a more or less powerful obstruction to its passage. All soils present 
 a greater resistance when wet than when dry, and all considerably more 
 to a wooden than to an iron plough. A sandy soil when wet offers a re- 
 sistance to the passage of agricultural implements, equal to about 4 lbs. 
 to the square foot of the surface which passes through it — a fertile vege- 
 table soil or rich garden mould about 6 lbs., and a clay from 8 to 25 lbs. 
 to the square foot. These differences will naturally form no inconsider- 
 able items in the calculations of the intelligent farmer when he estimates 
 the cost of working, and the consequent rent he can afford to pay for this 
 or that soil, otherwise equal in value. 
 
 II. RELATIONS OF SOILS TO WATER. 
 
 1°. Power of imbibing moisture from the air. — "When a portion of soil 
 is dried carefully over boiling water, or in an oven, and is then spread 
 out upon a sheet of paper in the open air, it will gradually drink in watery 
 vapour from the atmosphere, and will thus increase in weight. In hot 
 climates and in dry seasons this property is of great importance, restoring 
 as it does, to the thirsty soil, and bringing within the reach of plants, a 
 portion of the moisture which during the day they had so copiously ex- 
 haled. 
 
 Different soils possess this property in unequal degrees. During a 
 night of 12 hours, and when the air is moist, according to Schiibler, 1000 
 lbs. of a perfectly dry 
 
 Quartz Sand will gain lbs. 
 Calcareous Sand. . 2 
 Loamy Soil . . 21 
 and peaty soils, or such as are rich in vegetable matter, a still larger 
 quantity. 
 
 Sir Humphry Davy found this property to be possessed in the highest 
 degree by the most fertile soils. Thus, when made perfectly dry, 1000 
 lbs. of a 
 
 Very fertile Soil from East Lothian gained in an hour 18 lbs. 
 
 Very fertile Soil from Somersetshire 16 
 
 Soil worth 458. per acre from Mersea, in Essex . . 13 
 
 Sandy Soil worth 28s., from Essex 11 
 
 Coarse Sand worth only 15s 8 
 
 Soil of Bagshot Heath 3* 
 
 Fertile soils, therefore, possess this property in a very considerable de- 
 gree, and, though we cannot, by determining this property alone, infer 
 with safety what the fertility of a soil is likely to prove — since peaty 
 soils and very strong clays are still more absorbent of moisture, and 
 since this property is only remotely connected with the special chemical 
 constitution of a soil — yet among arable, sandy, and loamy lands, it cer- 
 tainly does, as Sir Humphry Davy states, afford one means of judging 
 of their relative agricultural capabilities. 
 
 2°. Power of containing or holding water. — If water be poured drop 
 by drop upon a piece of chalk or of pipe-clay, it will sink in and disap- 
 pear, but if the dropping be continued, the pores of the earth will by de- 
 
 • Sir H. Davy's Works, vol. vii., p. 326. 
 
 Clay Loam ... 25 lbs. 
 Pure Agricultural Clay 27 
 
RELATIONS OF SOILS TO WATER. 293 
 
 grees become filled with water, and it will at length begin to drop out 
 from the under part as it is added above. This property is exhibited in 
 a certain degree by all soils. The rain falls and is drunk in, the dew 
 also descends, and is thus taken possession of by the soil. But after much 
 rain has fallen, the earth becomes saturated, and the rest either runs otf 
 from the surface or sinks through to the drains. This happens more 
 speedily in some soils than in others. Thus from 106 lbs. of dry soil, 
 water will begin to drop — if it be a 
 
 Quartz Sand, when it has absorbed 25 lbs. 
 
 Calcareous Sand 29 
 
 Loamy Soil 40 
 
 English Chalk 45— J. 
 
 Clay Loam 50 
 
 Pure Clay 70 
 
 but a dry peaty soil will absorb a very much larger proportion (Schii- 
 bler), before it suffers any to escape. Useful arable soils are found to be 
 capable of thus containing from 40 to 70percent. of their weight of water. 
 If the quantity be less than this, the soils are said to be best adapted for 
 pine plantations, — if greater, for laying down to grass. 
 
 In dry climates this power of holding water must render a soil more 
 valuable, whereas in climates such as ours, where rains rather over- 
 abound, a simple determination of this property will serve to indicate 
 to the practical farmer on which of his fields it is most important to him, 
 in reference to surface water, that the operation of draining should be 
 first and most effectually performed. The more water the soil contains 
 within its pores, the more it has to part with by subsequent evaporation ; 
 and, therefore, the colder it is likely to be. The presence of this water also 
 excludes the air in a great degree, so that for these, as well as for other 
 reasons, it is desirable to afford every facility for the speedy removal of 
 the excess of water from such soils as absorb it, and are capable of con- 
 taining it, in a very large proportion. 
 
 3°. Power of retaining water lulien exposed to the air. — Unless when 
 rain or dew are falling, or when the air is perfectly saturated with mois- 
 ture, watery vapour is constantly rising from the surface of the earth. 
 The fields, after the heaviest rains and floods, gradually become dry, 
 though this, as every farmer has observed, takes place in some of his 
 fields with much greater rapidity than in others. Generally speaking, 
 those soils which are capable of arresting and containing the largest por- 
 tion of the rain that falls, retain it also with the greatest obstinacy, and take 
 the longest time to dry. Thus a sand will become as dry in one hour as a 
 pure clay in three, or a piece of peat in four hours. This, therefore, not 
 only explains, and shows the correctness of, the well-known distinctions 
 of warm and cold soils, but exhibits another strong argument in favour 
 of a perfect drainage of stiff' soils and of such as contain a large proportion 
 of decaying vegetable matter. 
 
 4°. Capillary power of the soil. — When water is poured into the sole 
 of a flower-pot, the soil gradually sucks it in and becomes moist even to 
 the surface. The same takes place in the soil of the open fields. The 
 water from beneath — that contained in the subsoil — is gradually sucked 
 up to the surface. Where water is present in excess, this capillary action, 
 as it is called, keeps the soil always moist and cold. 
 
294 CAPILLARY POWER OF THE SOIL. 
 
 The tendency of the water to ascend, however, is not the same in all 
 soils. In those which, like sandy soils and such as contain much vege- 
 table matter, are open and porous, it probably ascends most freely, while 
 stiff clays will transmit it with less rapidity. No precise experiments, 
 however, have yet been made upon this subject, chiefly, 1 believe, be- 
 cause this property of the soil has not hitherto been considered of such 
 importance as it really is, to the general vegetation of the globe. Let us 
 attend a little to this point. 
 
 I have already drawn your attention to the fact, that the specimens of 
 soil which are submitted to analysis generally contain very little saline 
 matter, and yet that in a crop reaped from the same soil a very consider- 
 able proportion exists. This I have attributed to the action of the 
 rains which dissolve out the soluble saline matter from the surface 
 soil, and as they sink, carry it with them into the subsoil; or from 
 sloping grounds, and during very heavy rains, partly wash it into the 
 brooks. Hence from the proportion of soluble matter present at any one 
 time in the surface soil, we cannot safely pronounce as to the quantity 
 which the whole soil is capable of yielding to the crop that may be grown 
 upon it. For when warm weather comes and the surface soil dries 
 rapidly, then by capillary action the water rises from beneath, bringing 
 with it the soluble substances that exist in the subsoil through which it 
 ascends. Successive portions of this water evaporate from the surface, 
 leaving their saline matter behind them. And as this ascent and eva- 
 poration go on as long as the dry weather continues, the saline matter 
 accumulates about the roots of the plants so as to put within their reach 
 an ample supply of every soluble substance which is not really defective 
 in the soil. I believe that in sandy soils, and generally in all light soils, 
 of which the particles are very fine, this capillary action is of great im- 
 portance, and is intimately connected with their power of producing 
 remunerating crops. They absorb the falling rains with great rapidity, 
 and these carry down the soluble matters as they descend — so that when 
 the soil becomes soaked, and the water begins to flow over its surface, 
 the saline iimtter being already buried deep, is in little danger of being 
 washed away. On the return of dry weather, the water re-ascends from 
 beneath and again diffuses the soluble ingredients through the upper soil. 
 
 In climates such as ours, where rains and heavy dews frequently fall, 
 and where the soil is seldom exposed for any long period to hot summer 
 weather unaccompanied by rain, we rarely see the full effect of this ca- 
 pillary action of the soil. But in warm climates, where rain seldom or 
 never falls, the ascent of water from beneath, where springs happen to 
 exist in the subsoil, goes on without intermission. And as each new 
 particle of water that ascends brings with it a particle, however small, 
 of saline matter (for such waters are never pure), which it leaves behind 
 when it rises into the air in the form of vapour, a crust, at first thin, but 
 thickening as time goes on, is gradually formed on the surface of the soil. 
 Such crusts are seen in the dry season — in India, in Egypt, and in many 
 parts of Africa and America. In hot, protracted summers they may be 
 seen on the surface of our own fields, but they disappear again with the 
 first rains that fall. Not so where rains are unknown. And thus on the 
 arid plains of Peru, and on extensive tracts in Africa, a deposit of saline 
 matter, sometimes many feet in thickness, is met with on the surface of 
 
ITS IMPORTANCE TO VEGETATION. 295 
 
 wide plains, in the hollows of deep valleys, and on the bottoms of ancient 
 lakes. Such an incrustation, probably so formed, is the bed of nitrate of 
 soda in Peru, from which all our supplies of that salt are drawn—such 
 are the deposits of carbonate of soda (urao) extracted from the soil in the 
 South American State of Colombia. 
 
 5°. Contraction of the soil on drying. — Some soils in dry weather di- 
 minish very much in bulk, shrink in, and crack. Thus, after being 
 soaked by rain, pure clay and peaty soils diminish in bulk about one- 
 fifth when they are again made perfectly dry — while sand has the same 
 bulk in either state. The more clay or vegetable matter, therefore, a 
 soil contains, the more it swells and contracts in alternate wet and dry 
 weather. This contraction in stiff clays can scarcely fail to be occa- 
 sionally injurious to young roots from the pressure upon the lender fibres 
 to which it must give rise, while in light and sandy soils the compres- 
 sion of the roots is nearly uniform in all weathers, and they are undis- 
 turbed in their natural tendency to throw out off-shoots in every direction. 
 Hence another good quality of light soils, and a less obvious benefit 
 which must necessarily result from rendering soils less tenacious by ad- 
 mixture or otherwise. 
 
 Ill, RELATIONS OF THE SOIL TO THE ATMOSPHERE. 
 
 Power of absorbing oxygen and other gaseous substances from the 
 air. — 1°. The importance of the oxygen of the atmosphere, first to the 
 germination of the seed, and afterwards to the growth of the plant, I have 
 already sufficiently insisted upon. It is of consequence, therefore, that 
 this oxygen should gain access to every part of the soil, and thus to all 
 the roots of the plant. This access 'can be facilitated by artificially 
 working the land, and thus rendering it more porous. But some soils, 
 in whatever state they may be in this respect, have been found to absorb 
 oxygen with more rapidity, and in larger quantity, than others. Thus 
 clays absorb more oxygen than sandy soils, and vegetable moulds or 
 peats more than clays. This difference depends in part upon the natural 
 porosity of these different soils, and in part also upon the chemical con- 
 stitution of each. If the clay contain iron or manganese in the state of 
 first or jsro^oxides, these will naturally absorb oxygen for the purpose of 
 combining with it, — while the decaying vegetable matter will in like 
 manner, in such as contain it largely, drink in much oxygen to aid their 
 natural decomposition. 
 
 2°. Besides the gases, oxygen and nitrogen, of which the air princi- 
 pally consists, the soil absorbs also carbonic acid from the atmosphere, 
 and portions of those various vapours, — whether of ammonia and other 
 effluvia which rise from the earth, or of nitric acid formed in the air,— 
 and these, in the opinion of some chemists, contribute very materially to 
 its natural fertility. This, however, is very much a matter of conjec- 
 ture, and no experiments have been made as to the relative capabilities 
 of different soils thus to extract vegetable food from the surrounding air. 
 One fact, however, seems to be clearly ascertained, that all soils, namely, 
 absorb gaseous substances of every kind most easily and in the greatest 
 abundance when they are in a moist state. The fall of rains, or the de- 
 scent of dew, therefore, will favour this absorption in dry seasons, and ii 
 will also be greatest in those soils which have the power of most readily 
 
296 POWER OF SOILS TO RETAIN HEAT. 
 
 extracting watery vapour from the air during the absence of the sun. 
 Hence the influence of the dews and of gentle showers on the progress 
 of vegetation, is not limited to the mere supply of water to the thirsty 
 ground, and of those vapours which they bring with them as they descend 
 to the earth, but is partly due also to the power which they impart to thj 
 moistened soil, of extracting for itself new supplies of gaseous matter 
 from the surrounding atmosphere. 
 
 IV. RELATIONS OF THE SOIL TO HEAT. 
 
 There are some of the relations of soils to heat, which have considera- 
 ble influence upon their power of promoting vegetation. These are the 
 rapidity with which they absorb heat from the air, the temperature they 
 are capable of attaining under the direct action of the sun's rays, and the 
 length of lime during which they are able to retain this heat. 
 
 1°. Power of absorbing heat. — It is an important fact, in reference to 
 thegrowtliof plants, that during sunshine, when the sun's rays beat upon 
 it, the earth acquires a much higher temperature than the surrounding 
 air- This temperature very often amounts to 110°, and sometimes to 
 nearly 150°, while the air in the shade is between 70° and 80° only. 
 Thus the roots of plants are supplied with that amount of warmth which 
 is most favourable to their rapid growth. 
 
 Dark-coloured — such as black and brownish red — soils absorb the 
 heat of the sun most rapidly, and therefore become warm the soonest. 
 They also attain a higher temperature — by a few degrees only, how- 
 ever (3° to 8°), — than soils of other colours, and thus, under the action 
 of the same sun, will more rapidly promote vegetation. In climates, 
 such as ours, where the presence of the sun is often wished for in vain 
 in time of harvest, this property of the soil possesses a considerable eco- 
 nomical value. In other parts of the world, where sunshine abounds, 
 it becomes of less importance. 
 
 Every one will understand that the above differences are observed 
 among such soils only as are exposed to the samg sun under the same 
 circumstances. Where the exposure or aspect of the soil is such as to 
 give it the prclonged benefit of the sun's rays, or to shelter it from cold 
 winds, it will prove more propitious to vegetation than many others less 
 favourably situated, though darker in colour and more free from super- 
 fluous moisture. 
 
 2°. Power of retaining heat. — But soils differ more in their power oJT 
 retaining the heat they have thus absorbed. You know that all hot bodies, 
 when exposed to the air, gradually become cool. So do all soils ; but a 
 sandy soil will cool more slowly than a clay, and the latter than a soil 
 which is rich in vegetable matter. The difference, according to Schub- 
 ler, is so great, that a peaty soil cools as much in one hour as the same 
 bulk of clay in two, or of sand in three hours. This may no doubt have 
 considerable influence upon growing crops, inasmuch as, after the sun 
 goes down, the sandy soil will be three hours in cooling, while the clavs 
 will cool to the same temperature in two, and rich vegetable mould in 
 pne hour. But on those soils which cool the soonest, dew will first l);\uin 
 to be deposited, and it is doubtful, where the soils are equally drained, 
 whether, in summer weather, the greater proportion of dew deposited (>;i 
 the clays and vegetable moulds mav not more than compensate to the 
 
POWER OP MODIFYING THE PHYSICAL CHARACTERS. 297 
 
 parched soil — for the less prolonged duration of the elevated tempera- 
 ture derived from the action of the sun's rays. It is also to be remem- 
 bered, that vegetable soils at least absorb the sun's heat more rapidly 
 than the lighter coloured sandy soils, and thus the plants which grow in 
 ^he former, which is sooner heated, may in reality be exposed to the 
 highest influence of the sun's warmth — for at least as long a period as 
 those which are planted in the latter. 
 
 The only power we possess over these relations of soils to heat, ap- 
 pears to be, that by top-dressing with charcoal, with soot, or with dark- 
 coloured composts, we may render it more capable of rapidly absorbing 
 the sun's heat, and by admixture with sand, more capable of retaining 
 the heat which it has thus obtained. 
 
 Sucn are the most important of the physical properties of soils. Over 
 some of them, the skilful farmer possesses a ready control. He can 
 drain his land, and thus render it cheaper to work and more easy to re- 
 duce to a fine powder. He can plough, subsoil, and otherwise work it 
 well, and thus can make it more open and porous, more accessible both 
 to air and water. When it is light and peaty, he can lay heavy matter 
 over it — clay, and sand, and lime-stone rubble — and can thus increase 
 its density. He can darken its colour in some localities with peat com- 
 posts, and can thus make it more absorbent of heat and moisture, as well 
 as more retentive of the rain that falls. But here his power ends, and 
 how far any of the changes within his power can be 'prudently attempted 
 will depend upon the expense which, in any given locality, the operation 
 would involve. And even after he has done all which mere mechanical 
 skill can suggest, the soil may still disappoint his hopes, and refuse to 
 yield him remunerating crops of corn. 
 
 ''A soil," says Sprengel, "is often neither too heavy nor too light, 
 neither too wet nor too dry, neither too cold nor too warm, neither too 
 fine nor too coarse ; — lies neither too high nor too low, is situated in a 
 propitious climate, is found to consist of a well-proportioned mixture of 
 clayey and sandy particles, contains an average quantity of vegetable 
 matter, and has the benefit of a warm aspect and favouring slope." — 
 [Bodenkunde, p. 203.] It has all the advantages, in short, which 
 physical condition and climate can give it, and yet it is unproductive. 
 And why ? Because, answers chemical analysis, it is destitute of cer- 
 tain mineral constituents which plants require for their daily food. The 
 physical properties, therefore, are only accessory to the chemical consti- 
 tution. They bring into favourable circumstances, and thus give free 
 scope to the operation, upon the seeds and roots of plants, of those che- 
 mical substances which Nature has kindly placed in most of our soils, or 
 by the lessons of daily experience is teaching the skilful labourer in her 
 fields to supply by art. 
 
 And yet the study of the physical properties of soils is not without its 
 use, even in a theoretical point of view. It shows both the use of the 
 fundamental admixture of sand, clay, and vegetable matter, of which 
 our soils consist, and for what special end all the mechnnical labours oi 
 the husbandman are undertaken, and why they are so necessary. Plants 
 
 13* 
 
298 GENERAL FUNCTIONS OF THE SOIL. 
 
 must be firmly fixed, tnerefore the soil must have a certain consistency, 
 — their roots must find a ready passage in every direction ; therefore the 
 soils must be somewhat loose and open. Except for these purposes, we 
 see li^ile immediate use for the sand and alumina which form so much 
 oi .at substance of soils — till we come to study their physical properties. 
 The siliceous sand is insoluble, and the alumina exists in plants in very 
 minute quantity only, while during the progress of natural vegetation, 
 the proportion of vegetable matter in the soil actually increases. The 
 immediate agency, therefore, of these substances is not chemical but 
 physical. 
 
 The alumina of the clays is of immediate use in absorbing and retain- 
 ing both water and air for the use of the roots — while the vegetable mat- 
 ter is advantageous in reference to llie same ends, as well as to the power 
 of absorbing quickly and largely the warmth of the sun's rays. The 
 soil, in short, in reference to vegetation, performs the four following dis- 
 tinct and separate, but each of them important and necessary, func- 
 tions : — 
 
 1°. It upiiolds and sustains tlie plant, affording it a sure and safe an- 
 chorage. 
 
 2°. It absorbs water, air, and heat, to promote its growth 
 
 These are its mechanical and physical functions. 
 
 3°. It contains and supplies to the plaul both organic and inorganic 
 food as its wants require ; and 
 
 4°. It is a workshop in which, by the aid of air and moisture, chemi 
 cal changes are continually going on ; by whicli changes these several 
 kinds of food are prepared for admission into the living roots. 
 
 These are its chemical functions. 
 
 All tlie operations of the husbandman are intended to aid the soil in the 
 performance of one or other of these functions. To the most importanf. 
 of these operations — the methods adopted by the practical farmer for 
 improving the soil — it is my intention, in the following division of these 
 Lectures, briefly to direct your attention. 
 
 4^ 
 
LECTURES 
 
 ON THE 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 JInrt Mil* 
 
 ON THE IMPROVEMENT OF THE SOIL BY ME- 
 CHANICAL AND CHEMICAL MEANS. 
 
 
LECTURE XIV. 
 
 The physical qualities and chemical constitution of a soil may be changed by art. — Nature 
 of the plants dependent upon tliat of the soil on which they grow. — Mechanical methods 
 of improving the soil. — Effects produced by draining. — Theory of springs. — Effect of 
 ploughing, subsoiling, deep ploughing and trenching. — Artificial improvement by mixing 
 with clay, sand, or marl. 
 
 The facts detailed in the preceding lecture may be considered as af- 
 fording sufficient proof that the abihty of the farmer to grow this or that 
 crop upon his land, is very much restrained by its natural character and 
 constitution. Each soil establishes upon itself — so to speak — a vegeta- 
 tion suited to its own nature, one that requires most abundantly those 
 substances which actually abound in the soil — and the art of man can- 
 not long change this natural connection between the living plant and the 
 kind of land in which it delights to grow. 
 
 But he" can change the character of the land itself. He can alter 
 both its physical qualities and its chemical constitution, and thus can fit 
 it for growing other races of plants than those it naturally bears — or, if he 
 choose, the same races in greater abundance, and with increased luxuri- 
 ance. It is, in fact, in the production of such changes, that nearly all the 
 labour and practical skill of the husbandman — apart from local peculiari- 
 ties of climate, &c. — is constantly expended. For the attainment of 
 this end he drains, ploughs, sub.soil-ploughs, and otherwise works his 
 land. For this end he clays, sands, marls, and manures it. By the.se 
 and similar operations the land is so changed as to become both able and 
 willing to nourish and ripen those peculiar plants which the agriculturist 
 wishes to raise. On this practical department of the art of culture, 
 the principles explained and illustrated in the preceding parts of these 
 lectures, throw much light. They not only explain the reason why cer- 
 tain practices always succeed in the hands of the intelligent former, but 
 why others also occasionally and inevitably fail — they tell him which 
 practices of his neighbours he ought to adopt, and which of them he had 
 better modify or wholly reject, — and they direct him to such new modes 
 of improving his land as are likely to add the most to its permanent 
 productive value. 
 
 The operations of the husbandman in producing changes upon the 
 land, are either mechanical or chemical. When he drains, ploughs, 
 and subsoils, he alters chiefly the physical characters of his soil— when 
 he limes and manures it, he alters its chemical con.stitution. These two 
 classes of operations, therefore, are perfectly distinct. Where a soil con- 
 tains all that the crops we desire to grow are likely to require, mere me- 
 chanical operations may suffice to render it fertile — but where one or 
 more of the inorganic constituents of plants are wanting, draining may 
 prepare the land to benefit by further operations, but it will not be alone 
 sufficient to remove its comparative sterility. I shall, therefore, con- 
 sider in succession these two classes of practical operations : — 
 
 1°. Mechanical methods of improving the soil, including draining, 
 ploughing, mixing with clay, sand, &c. 
 
304 PLANTS PECULIAR TO CERTAIN SOILS. 
 
 2°. Chemical methods, including limeing, marling, and the application 
 of vegetable, animal, and mineral manures. 
 
 To satisfy you fully, however, in regard to the absolute necessity 
 for such changes, if we would render the land fit to produce any given 
 crop, let me illustrate, by a few brief examples, the intimate relation 
 observed in nature between the kind of soil and the kind of plants that 
 grow upon it. 
 
 § 1. On the connection hetiveen the Mnd of soil and the kind of plants 
 
 that groiv upon it. 
 
 That a general connection exists between the kind of soil and the 
 kind of [)lants that grow upon it, is familiar to all practical men. Thus 
 clay soils are generally acknowledged to be best adapted for wheat — 
 loamy soils for barley — sandy loams for oats or barley — such as are more 
 sandy still for oats or r3'^e — and those which are almost pure sand, for 
 rye alone of all the corn-bearing crops. 
 
 But in a state of nature, we find special differences among the spon- 
 taneous produce of the soil, which are more or less readily traceable to 
 its chemical constitution in the spots where the plants are seen to 
 grow. Thus — 
 
 1°. On the sandy soils of the sea shores, and on the salt steppes oi 
 Hungary and Russia, the sand- worts, salt- worts, glass- worts, and other 
 salt-loving plants abound. When these sands are inclosed and drained, 
 i.he excess of the salt is gradually washed out by the rains, or in some 
 countries is removed by reaping the saUne plants annually, and burning 
 them for soda (barilla), when wholesome and nutritive grasses take their 
 place ; but the white clover and the daisy, and the dandelion, must first 
 appear, before, as a general rule, it can be profitably ploughed up and 
 sown with corn. 
 
 2°. The dry drifted sands, more or less remote from the sea, produce 
 no such plants. They are distinguished by their own coarse grasses, 
 among which the elymus arenarius (upright sealyme-grass) often, in our 
 latitudes, occupies a conspicuous place. On the downs of North Jut- 
 land, it was formerly almost the only plant which the traveller could 
 meet with over an area of many miles. ■ 
 
 3°. On ordinary sandy soils, leguminous plants are rare, and the herb- 
 age often scanty and void of nourishment. With the presence of marl 
 in such soils, the natural growth of leguminous plants increases. The 
 colt's-foot also, and the butter-bur, not only grow naturally where the 
 subsoil is marly, but infest it sometimes to such a degree as to be with 
 great difficulty extirpated. So true is this indication of the nature of 
 the soil, tliat in the lower vallies of Switzerland these plants are said to 
 indicate to the natives where they may successfully dig for marl, {Prize 
 Essays of the Highland Society, I., p. 134). On calcareous soils, again, 
 or such as abound in lime, the quicken or couch-grass is seldom seen as 
 a weed, {'S)])r engoi, Bodenkunde, p. 201), while the poppy, the vetch, and 
 the darnel abound. 
 
 4°. So peaty soils, when laid down to grass, slowly select for them- 
 selves a peculiar tribe of grasses, especially suited to their own nature, 
 among which the holcus lanatus (meadow soft-grass) is remarkably 
 abundant. Alter their constitution by heavy limeing, and they produce 
 
NATURAL ROTATION AMONG FOREST TREES. 305 
 
 luxuriant green crops and a great bulk of straw, but give a coarse thick- 
 skinned grain, more or less imperfectly filled. Alter them further by a 
 dressing of clay, or keep them in arable culture, and stiffen them with 
 composts, and they will be converted into rich and sound corn-bearing 
 lands. 
 
 5°. In the waters that gush from the sides of lime-stone hills — on the 
 bottoms of ditches that are formed of lime-stones or marls — and in the 
 springs that have their rise in many trap rocks, the water-cress appears 
 and accompanies the running waters, sometimes for miles on their 
 course. The mare's-tail {cquisetujn), on the other hand, attains its largest 
 size ])y th(^ marshy banks of rivulets in which not lime but- silica is 
 more abundantly present. So the Cornish heath {erica vagans) is found 
 only over the serpentine soils of Cornwall, and the red broom rape 
 {orobanche rubra, Hooker's Flora Scotica), only on decayed traps in 
 Scotland and Ireland. 
 
 These facts all point to the same natural law, that where other circum- 
 stances of climate, moisture, &c., are equal, the natural vegetation — that 
 ■which grows best on a given spot — is entirely dependent upon the chemical 
 constitution of the soil. '^ 
 
 But both the soil and the vegetation it willingly nourishes, are seen 
 to undergo slow but natural changes. Lay down a piece of land to grass, 
 and, after a lapse of years, the surface soil — originally, perhaps, of the 
 stiffest clay — is found to have become a rich, light, vegetable mould, 
 bearing a thick sward of nourishing grasses, almost totally different from 
 those which naturally grew upon it when first converted into pasture. 
 So in a wider field, and on a larger scale, the same slow changes are 
 exhibited in the vast natural forests that are known to have long covered 
 extensive tracts in various countries of Europe. 
 
 Thus it is a matter of history that Charlemagne hunted in the forest 
 of Gerardmer, then consisting of oak and beech — though now the same 
 forest contains only pines of various species. On the Rhine, between 
 Landau and Kaiserlautern, oak forests, of several centuries old, are seen 
 to be gradually giving way to the beech, while others of oak and beech 
 are yielding to the encroachments of the pine. In the Palatinate, the 
 Scotch fir {pinus sylvestris) is also succeeding to the oak. In the Jura, 
 and in the Tyrol, the beech and the pine are seen mutually to replace 
 each other — and the same is seen in many other districts. When the 
 time for a change of crop arrives, the existing trees begin to languish 
 one after another, their branches die, and finally their dry and naked 
 tops are seen surrounded by the luxuriant foliage of other races [Le Ba- 
 ron de Mortemart de Boisse, Voyage dans les Landes, p. 189.] These 
 facts not only show how much the vegetable tribes are dependent upon 
 the chemical nature of the soil — they indicate, likewise, the existence 
 of slow natural changes in the constitution of the soil, which lead neces- 
 sarily to a change of vegetation also. 
 
 We can ourselves, in the case of ancient forests, effect such changes. 
 When in the United States a forest of oak or maple is cut down, one of 
 pine springs up in its place ; while on the site of a pine forest, oak and 
 other broad -leaved trees speedily appear. 
 
 But if the full time for such changes has not come, the new vegeta- 
 tion may be overtaken, and smothered by the original tribes. Thus, 
 
306 OF DRAINING, AND ITS EFFKCTS. 
 
 when the pine forests of Sweden are burned down, a young growth of 
 birch succeeds, but after a time the pines again appear and usurp their 
 former dominion. The soil remains, still, more propitious to the growth 
 of the latter than of the former kind of tree. 
 
 We may, therefore, take a practical lesson from the book of nature. 
 If we wish to have a luxuriant vegetation upon a given spot, we must 
 cither select such kinds of seeds to sow upon it as are fitted to the kind 
 of s;)il, or we must change the nature of the land so as adapt it to our 
 crop. And, even when we have once prepared it to yield abundant re- 
 turns of a particular kind, the changes we have produced can only be 
 more or less of a temporary nature. Our care and attention must still 
 be bestowed upon it, that it may be enabled to resist the slow natural 
 causes of alteration, by which it is gradually unfitted to nourish those 
 vegetable tribes which it appears now to delight in maintaining 
 
 Let us now turn our attention, therefore, to the methods by which 
 these beneficial changes are to be effected and maintained. 
 
 § 2. Of draining, and its effects. 
 
 Among the merely mechanical methods by which those changes are 
 to be produced upon the soil, that are to fit it for the better growth of 
 valuable crops, draining is now allowed to hold the first place. That it 
 is an important step in heavy clay lands, and that it must be tha first step 
 in all cases where water abounds in the surface soil, will be readily con- 
 ceded ; but that it can be beneficial also in situations where the soils are 
 of a sandy nature — wliere the subsoil is light and porous — or where the 
 inclination of the field appears sufficient to allow a ready escape to the 
 water, does not appear so evident, and is not unfrequently, therefore, a 
 matter of considerable doubt and difficulty. It may be useful, then, 
 briefly to state the several effects v/hicli in different localities are likely 
 to follow an efficient drainage of the land : — 
 
 1°. It carries olf all stagnant water, and gives a ready escape to the 
 excess of what falls in rain. 
 
 2°. It arrests the ascent of water from beneath, whether by capillary 
 action or by tlie force of springs — and thus not only preserves the sur- 
 face soil from undue moisture, but also frees the subsoil from the linger- 
 ing presence of those noxious substances, whicJi in undrained land so fre- 
 quently lodge in it and impair the growth of deep-rooted plants. 
 
 3°. It allows the water of the rains, instead of merely running over 
 and often injuriously washing tlie surface, to make its way easily 
 through the soil. And thus, while filtering through, not only does the 
 rain-water impart to the soil those substances useful to vegetation, which, 
 as we have seen, [see Lecture II., p. 37, Lecture IV"., p. 69, and Lecture 
 VIII., p. 159,] it always contains in greater or less abundance ; but it 
 washes out of the upper soil, and, when the drains are deep enough, 
 out of the subsoil also, such noxious substances as naturally collect and 
 may have been long accumulating there — rendering it unsound and 
 hurtful to the roots. The latter is one of those l)enefits which gradually 
 follow the draining of land. When once thoroughly effected, ii consti- 
 tutes a most important permanent improvement, and one which can be 
 fully produced by no other available means. It will be permanent, 
 however, only so long as the drains are kept in good condition. The 
 
SECURES A DRY SEED-TIME AND AN EARLY HARVEST. 307 
 
 same openness of the soil which enables the rains to wash out those so- 
 luble noxious substances, which have been long collecting, permits them 
 to carry off also such as are gradually formed, and thus to keep it in a 
 sound and healthy state ; but let this openness be more or less impaired 
 by a neglect of the drainage, and the original state of the land will again 
 gradually return. 
 
 4°. Tliis constant descent of water through the soil causes a similar 
 constant descent of fresh air through its pores, from the surface to the 
 depth of the drains. When the rain falls, it enters the soil and more or 
 less completely displaces the air which is contained within its pores. 
 This air either descends to the drains or rises into the atmosphere. 
 When the rain ceases, the water, as it sinks, again leaves the pores of 
 (lie upper soil open, and fresh air consequently follows. It is in fact 
 sucked in after the water, as the latter gradually passes down to the 
 drains. Thus, where a good drainage exists, not only is the land re- 
 freshed by every shower that falls — not only does it derive from the 
 rains those important substances which occasionally, at least, are brought 
 down by them from the atmosphere, and which are in a great measure 
 lost where the waters must flow over the surface — but it is supplied also 
 with renewed accessions of fresh air, which experience has shown to be 
 so valuable in promoting the healthy growth of all our cultivated crops. 
 
 5°. But other consequences of great practical importance follow from 
 these immediate effects. When thus readily freed from the constant 
 ])rcsence of water, the soil gradually becomes drier, sweeter, looser, and 
 more friable. The hard lumps of the stiff clay lands more or less dis- 
 appear. They crumble more freely, offer less resistance to the plough, 
 and are in consequence more easily and economically worked. These 
 are practical benefits, equivalent to a change of soil, which only the 
 farmer of stubborn clays can adequately appreciate. 
 
 6"^. With the permanent state of moisture, the coldness of many soils 
 also rapidly disappears. The backwardness of the crops in spring, and 
 the lateness of the harvests in autumn, are less frequently complained 
 of — for the drainage in many localities produces effects which are equi- 
 valent to a change of climate. " In consequence of the drainage which 
 has taken place in the parish of Peterhead, in Aberdeenshire, during th^ 
 last 20 years, the crops arrive at maturity ten or fourteen days sooner 
 than they formerly did ;"* and the same is true to a still greater extent 
 in many other localities. 
 
 7°. On stiff clay lands, well adapted for wheat, wet weather in au- 
 tumn not unfrequently retards the sowing of winter corn — in undrained 
 lands, often completely prevents it — compelling the farmer to change his 
 system of cropping, and to sow some other grain, if the weather permit 
 him, when the spring comes round. An efficient drainage carries off the 
 water so rapidly as to bring the land into a workable state soon after the 
 rain has ceased, and thus, to a certain extent, it rescues the farmer from 
 the fickle dominion of the uncertain seasons. f To the skilful and in- 
 
 ' Mr. Gray, in the Prize Essays of the Highland and Agricultural Society, II., p. 17L 
 This opinion was given in 1830, since which lime many other extensive improvements have 
 been made in tiiat part of the island. 
 
 t "Formerly," says Mr. Wilson, of Cumledge, in his account of the drainage of a farm 
 in Berwickshire, " this part of the farm was so wet, that — though better adapted for wheat 
 than any other crop — the season for sowing was frequently lost, and after an expensive fal> 
 
308 IS EQUIVALENT TO A DEEPENING OF THE SOIL. 
 
 telligent farmer, who applies every available means to the successful 
 prosecution of his art, the promise even in our age and country is sure 
 — " that seed-time and harvest shall never fail." 
 
 8°. But on lands of every kind this removal of the superfluous water 
 is productive of another practical benefit. In its consequences it is equi- 
 valent to an actual deepening of the soil. 
 
 When land on which the surface water is in the habit of resting, be- 
 comes dry enough to admit the labours of the husbandman, it is still 
 found to be wet beneath, and the waters, even in drj' seasons, not unfre- 
 quently remain where the roots of the crops would otherwise be inclined 
 1o come. Or, if the surface soil permit a ready passage to the rains, and 
 waters linger only in the moist subsoil, still — though the farmer may 
 not be delayed in his labours — the subsoil repels the approach of the 
 roots of his grain, and compels them to seek their nourishment from the 
 surface soil only. But remove the waters, and the soil becomes dry to 
 a greater depth. The air penetrates and diffuses itself wherever the 
 waters have been. The roots now freely and safely descend into the 
 almost virgin soil beneath. And not only have they a larger space 
 through which to send their fibres in search of food, but in this hitherto 
 ungenial soil they find a store of substances — but sparingly present, it may 
 be, in tlie soil above — which the long-continued washing of the rains, 
 or the demands of frequent crops, may have rerrioved, but which may 
 i)ave been all the time accumulating in the subsoil, into which the 
 roots of cultivated plants could rarely with safety descend. It is not 
 wonderful then that the economical effects of draining should be found 
 by practical men to be not only a diminution in the cost of cultivation, 
 but a considerabl}^ augmented produce also both in corn and grass ; or 
 that this increased produce should alone be found sufficient to repay the 
 entire cost of thorough-draining in two or three years. 
 
 An obvious practical suggestion arises out of the knowledge of this 
 fact. The deeper the drains, provided the water have still a ready escape, 
 the greater the depth of soil which is rendered available for the purposes 
 of vegetable nutrition. Deep-rooted plants, such as lucerne, often fail, 
 even in moderately deep soils, because an excess of water or the 
 presence of some noxious ingredient which deep drains would remove, 
 prevents their natural descent in search of food. Even plants, which, 
 like that of wheat or clover, do not usually send down their roots so far, 
 will yet, where the subsoil is sound and dry, extend their fibres for three 
 or more feet in depth, in quest of more abundant nourishment. 
 
 Not only, then, do deep drains permit the use of the subsoil plough 
 without the chance of injury, — not only are they less liable to be choked 
 up by the accumulated roots of plants which naturally make their way 
 into ihem in search of water, — but they also increase the value and per- 
 manent fertility of the land, by increasing its available depth. In other 
 words, that kind of drainage which is most efficiently performed, with a 
 regard to the greatest nmiiber of contingencies, will not only be the most 
 permanent, but will also be followed by the greatest number of eccnomi- 
 cal advantages. 
 
 lowing and limeing, it was sown with oats in spring, of which it always produced very poor 
 crops. It is now so dry as to grow very good crops of turnip or rape, and except in two 
 instances, I have always sown my wheat in capital order." — Prize Essays of the Highland 
 and Agricultural Society, I., p. 243. 
 
EFFECT OF A GENERAL DRAINAGE OF THE SOIL. 309 
 
 9°. Nor do the immediate and practical benefits of draining end with 
 the attainment of these beneficial results. It is not till the land is ren- 
 dered dry that the skilful and enterprising farmer has a fair field on 
 which to expend his exertions. In wet soils, bones, wood-ashes, rape- 
 dust, nitrate of soda, and other artificial, manures, are almost thrown 
 away. Even lime exhibits but one-half of its fertilizing virtue, where 
 water is allowed to stagnate in the soil. Give him dry fields to work 
 upon, and the well-instructed agricvilturist can bring all the resources, 
 as well of modern science as of old experience, to bear upon them, with 
 a fair chance of success. The disappointments which the holder of un- 
 drained lands so often ineets with, he will less frequently experience. 
 An adequate return will generally be obtained for his expenditure in 
 manuring and otherwise improving his soil, and he will thus be encour- 
 aged to proceed in devoting his capital to the permanent amelioration of 
 his farm — not less for his own than for his landlord's benefit. 
 
 Viewed in this light, draining is only the first of a long scries of im- 
 })rovements, or rather it is a necessary preparative to the numerous im- 
 provements of which the soil of islands is susceptible — which improve- 
 ments it would be a waste of money to attempt, until an efficient system 
 of drainage is established. And when we consider how great a national 
 benefit this mere preparatory measure alone is fitted directly to confer 
 upon the country, you will agree with me -in thinking that every good 
 citizen ought to exercise his influence in endeavouring, in his own district, 
 more or less rapidly to promote it. It has been calculated that the drain- 
 age of those lands only, which are at present in arable culture (10 mil- 
 lions of acres), would at once increase their [)roduce by 10 millions of 
 quarters of the various kinds of grain now grown upon them ; — and that 
 a similar drainage of the uncultivated lands (15 millions of acres) 
 would yield a further increased produce of twice as much more. This 
 increase of 30 millions of quarters is equal to nearly one-half of our pre- 
 sent consumption* o^ all kinds of grain — so that were it possible to effect 
 at once this general drainage, a large superfluity of corn would be raised 
 from the British soil. 
 
 This general drainage, however, cannot possibly be effected in any 
 given time. The individual resources of the land-owners are not suflfi- 
 cient to meet the expense, f and such calculations as the above are use- 
 ful, mainly, in stimulating the exertions of those who have capital to 
 spare, or such an excess of income as can permit them to invest an an- 
 nual portion permanentlyl: in the soil. 
 
 10°. He who drains and thus improves his own land, confers a 
 benefit upon his neighbours also. In the vicinity of wet and boggy 
 
 * 65 millions of qnarters. See an excellent paper on this subject in the Quarterly Agri- 
 cultural Journal, xii., p. 505, by Mr. Dudgeon, of Spyelaw, in Roxburghshire, a county in 
 which the practical benefits of draining have been extensively experienced, and are therefore 
 well understood. 
 
 t To drain 25 millions of acres, at £,& an acre, w^ould cost 150 millions sterling, a sum equal, 
 probably, to the whole capital at present invested m farming the land. 
 
 X By an efficient drainage the soil is permanently benefitted, but it is not so clear that the 
 money it cosls \s permanently invested or \>\ir\e<i in \\\q soil. If the cost be repaid by the 
 increase of produce, in three years, the money is not invested, it is only lent for this period 
 to the soil "I drain so many acres every year," said the holder of a large Berwicitshire 
 farm to me, " and I find myself always repaid by the end of the third season. If I have 
 spare capital enough, therefore, to go on for three years, I can gradually drain any extent of 
 land, by the repeated use of the same sum of money." 
 
310 RENDERS A COUNTRY MORE SALUBRIOUS. 
 
 lands the hopes of the industrious farmer are often disappointed. Mists 
 are fretjuent and rains more abundant on the edges of the moor, and 
 mill-dews retard the maturity, and often seriously injure the crops. Of 
 undrained land, in general, the same is true to a less extent, and tlie 
 presence of one unimproved property in the centre of an enterprising 
 district, may long withhold from the adjoining farms that full measure 
 of benefit which the money and skill expended upon them would in 
 other circumstances have immediately secured. 
 
 So true is it in regard to every new exercise of human skill and in 
 every walk of life, that we are all mutually dependent, every one upon 
 every other; and that the kindly co-operation of all can alone secure 
 that ample return of good, which the culture either of the dead earth 
 or of the living intellect appears willing, and we may hope is ultimately 
 destined, to confer upon our entire race. 
 
 11°. I would not here willingly neglect to call your attention to a 
 higher benefit still, which the skilful drainage of an extensive district is 
 fitted to confer upon its whole population. Not only is this drainage 
 equivalent, as above stated, to a change of climate in reference to the 
 growth and ripening of plants, but it is so also in reference to the gene- 
 ral health of the people, and to the number and kind of the diseases to 
 which they are observed to be exposed. 
 
 I may quote in illustration of this fact the interesting observations of 
 Dr. Wilson on the comparative state of health of the labouring popula- 
 tion in the district of Kelso during the last two periods of ten years. In 
 his excellent paper on this subject, in the Quarterly Journal of Agricul- 
 ture, (volume xii., p. 317), he has shown that fever and ague, w^hich 
 formed nearly one-half of all the diseases of the population during the 
 former ten years, have almost wholly disappeared during the latter ten, 
 in consequence of the general extension of an efficient drainage through- 
 out the country ; while, at the same time, the fatality of disease, or the 
 comparative number of deaths from every hundred cases of serious ail- 
 ment, has diminished in proportion of 4-6 to 2*59. Such beneficial re- 
 sults, thougJrjnot immediately sought for by the practical farmer, yet 
 are the inevitable consequence of his successful exertions. Apart, there- 
 fore, from mere considerations of pecuniary profit, a desire to promote 
 the general comfort and happiness of the entire inhabitants of a district 
 may fairly influence the possessors of land to promote this method of 
 ameliorating the soil ; while the whole people, on the other hand, of 
 whatever class, ought "gratefully to acknowledge the value of those im- 
 provements which at once render our homes more salubrious and our 
 fields more fruitful." 
 
 The practical benefits of draining, therefore, may be stated generally 
 as follows : — 
 
 A . It is equivalent not only to a change of soil, but also to a change 
 of climate, both in reference to the growth of plants and to the health 
 of the population. 
 
 B. It is equivalent also to a deepening of the soil, both by removing 
 the water and by allowing those noxious ingredients to be washed out 
 
BENEFITS POROUS SOILS. — ORIGIN OF MOOR-LAND. 311 
 
 of the subsoil which had previously prevented the roots from descend- 
 ing. 
 
 C. It is a necessary preparation to the many other means of improve- 
 ment which may be applied to the land. 
 
 You will now be able to perceive in what way it is possible that 
 even light and sandy soils, or such as lie on a sloping surface, may be 
 greatly benefitted by draining. Where no open outlet exists under a 
 loamy or sandy surface soil, any noxious matters that either sink from 
 above, or ooze up from beneath, will long remain in the subsoil, and 
 render it more or less unwholesome to valuable cultivated plants. But 
 let such an outlet be made by the establishment of drains, and that 
 which rises from beneath will be arrested, while that which descends 
 from above will escape. The rain-waters passing through will wash 
 the whole soil also as deep as the bottom of the drains, and the atmos- 
 pheric air will accompany or follow them. 
 
 The same remarks apply to lands which possess so great a natural 
 inclination as to allow the surface water readily to flow away. Such a 
 sloping surface does not necessarily dry the subsoil, free it from noxious 
 substances, or permit the constant access of the air. Small feeders of 
 water occasionally make their way near to the surface, and linger long 
 in the subsoil before they make their escape. This is in itself an evil ; 
 but when such springs are impregnated with iron^the evil is greatly 
 augmented, and from such a cause alone a more or less perfect barren- 
 ness not unfrequently ensues. To bring such lands by degrees to a 
 sound and healthy state, a mere outlet beneath is often alone sufficient. 
 
 It is to this lingering of unwholesome waters beneath, that the origin 
 of many of our moor-lands, especially on higher grounds, is in a great 
 measure to be attributed. A calcareous or n ferruginous spring sends up 
 its waters into the subsoil. The slow access of air from above, or it 
 may be the escape of air from water itself, causes a more or less ochrey 
 deposit,* which adheres to and gradually cements the stones or earthy 
 particles, among which the water is lodged. Thus a layer of solid 
 stone is gradually formed — the moor-land fan of many districts — which 
 neither allows the roots of plants to descend nor the surface water to es- 
 cape. Hopeless barrenness, therefore, slowly ensues. Coarse grasses, 
 mosses, and heath, grow and, accumulate upon soils not originaliy in- 
 clined to nourish them, and by which a better herbage had previously 
 been long sustained. Of such lands many tracts have been reclaimed 
 by breaking up this moor-land pavement, but such an improvement, 
 unless preceded by a skilful drainage, can only be temporary. The 
 same natural process will again begin, and the same result will follow, 
 unless an outlet be provided for the waters from which the petrifying 
 deposit proceeds. 
 
 It ought to be mentioned, however, that where a ready passage and 
 escaf)e for the water is provided by an efficient drainage, and especially 
 in light and porous soils, the saline and other soluble substances they 
 
 * If the water contain s?</p/?a<e of iron, the ail' from above will impart to its iron an ad- 
 ditional quantity of oxygen, and cause a portion of it to fall in tlie slate oi peroxide. If the 
 iron or lime be present in the state of 6?carbonate, the escape of carbonic acid from the 
 water will cause a deposit of carbonate of iron or of lime. Any of these deposits will 
 cement the earthy or stony particles together. Iron, however, is sometimes held insola- 
 tion by an organic acid (crenic), wliich becomes insoluble, and falls along with the iron 
 when the latter has absorbed more oxygen from the atmosphere. 
 
312 THEORY OF SPRINGS. 
 
 contain will be liable, in periods of heavy rain, to be more or less com- 
 pletely washed out and carried off by the water that trickles through 
 them. While, therefore, the establishment of drains on all soils may 
 adapt and prepare them for further improvements, and may make them 
 more grateful for every labour or attention that may be bestowed ujion 
 ihem — yet after drainage the}'- must be more liberally dealt with than 
 before, if the increased fertility they at first exhibit is to be permanently 
 maintained or increased. 
 
 § 3. Of the theory of Springs. 
 
 In the general drainage of the*land a double object is sought to be at- 
 tained. In very rainy districts, the first wish of the farmer is to carry 
 off the surface water from his fields — but where less rain falls, that 
 which ascends from beneath in springs, attracts at least an equal share 
 of the husbandman's regard. In draining, with a view to the removal 
 of this latter source of superfluous moisture, a knowledge of the true 
 theory of springs, as indicated by an examination of certain geological 
 phenomena, is of the greatest possible service to the practical man, in 
 pointing out the sources from which the water that injures his land pro- 
 ceeds, as well as the lines along which it may be most efficiently and 
 most economically carried off. 
 
 1°. The rain whjph falls on the surface of an extensive tract of country 
 partly escapes into the rivers, and partly sinks into the earth. This 
 latter portion descends through the covering of soil and other loose ma- 
 terials till it reaches the rocks on which they rest. H these rocks are 
 porous, like many sand-stones, or are traversed by cracks and vertical 
 fissures, as many sand-stones and lime-stones are, it descends ihrouizh 
 them also till it reaches a bed, such as one of indurated clay, so close and 
 compact as to resist its further passage. By this ijn^Jervious bed the wa- 
 ter is arrested, and is, therefore, compelled to spread itself laterally, and 
 gradually to accumulate in the beds that lie above it. Thus, if the 
 
 C 
 
 outline from A to C in the annexed diagram represent the surface of an 
 undulating country, in which the subjacent rocks (1, 2, 3, 4) are covered 
 by a considerable thickness of loose materials, the rain which falls from 
 A to B will sink n^iore or less rapidly to the bed (1), and, if this be im- 
 p(3rmcable to water, will rest there, or will slowly drain off in the di- 
 rection of B and C along the inclined surface of the rock. But if (1) 
 be jiorous, it will sink through it to the surface of the bed (2), and 
 through this also, if permeable, to (3) or (4), until it reaches the stratum 
 through which it cannot pass. On the surface of this latter bed, or 
 am;)ng the rocks above it, the water will accumulate until, flowing 
 downwards towards C, it is enabled either to sink among the deeper 
 rocks or to make its escape again to the surface. 
 
 But if the rocks beneath, as is showai in the same diagram from E to 
 F, be traversed by vertical fissures passing through two or more, or, like 
 the one represented from B to E, through a great number of beds, the 
 
WATER IS ARRESTED BY IMPERVIOUS BEDS. 
 
 313 
 
 water that falls on the surface will readily find a passage downwards to 
 a considerable depth, and to the same cracks the water that lodges 
 among the unfissured rocks from D to E will also gradually make its way. 
 
 The practical effects of these several conditions on the drainage of a 
 country are very obvious. If the stratum (]) be impervious to water, 
 the surfcice from A to B may be full of water, and may urgently" de- 
 mand the intro(]uction of drains, whereas if (1) and (2) be porous, the 
 surface water will gradually sink, and the apparent necessity for artifi- 
 cial drainage will become much less striking. On the other hand, 
 where the rocks are filled with frequent cracks, as from B to C, the 
 surface water may descend and disappear so rapidly, as to render 
 useless the sinking of wells — and, as in dry summers, greatly to retard 
 the progress of the crops, or even seriously to injure the produce of the 
 harvest. Tn such a fissured state are the magnesian lime-stone rocks in 
 some parts of the county of Durham — and such is the consequent scar- 
 city of water, on some farms, that when, in long droughts, the supply 
 preserved in artificial tanks begins to fail, the cattle must be driven to 
 water sometimes for miles, to the nearest living brook. 
 
 2°. But water often finds its way to greater depths without passing 
 through the superior strata, and even where they are absolutely impervi- 
 ous to the rains that fall upon them. Thus along the country from A to 
 B, and especially towards A, the surface soil rests upon the upper edges 
 
 of the strata. Suppose now the beds 1, 2, 3, to be im{)ervious to water, 
 the rain that falls wherever these ?-ocks lie immediately beneatli the sur- 
 face will cither remain stagnant, or will flow ofi'by some natural drain- 
 age. Thus from the highest point C in the above diagram, the water 
 will descend on either liand towards a and b. At b it may remain slag- 
 nant, for it cannot descend through the bed (2), which forms the bottom 
 of the valley, and the same is true of the hollow c, in which otlier por- 
 tions of the water will rest. All this tract of countr}'-, therefore, will be 
 more or less cold, wet, and consequently unproductive. But let the bed 
 (4), the edge (or outcrop) of which forms the surface at a, be porous or 
 permeable, then the water which falls upon that spot or which descends 
 from the higher grounds about C and A, will readily sink and drain off, 
 descending from a towards d along the inclined bed till it finds an outlet 
 in the latter direction. 
 
 Thus it may readily happen that a naturally dry and fertile valley, as 
 at a, may exist at no great distance from others, b and c, which are 
 marshy and insalubrious, and in which artificial drainage alone can de- 
 velope the agricultural capabilities of the soil. It appears also that, 
 though in any district the rocks which lie immediaiely beneath the sur- 
 face may contain no water, and may allow none to pass through them, 
 yet that other beds, perhaps at a great depth beneath, may contain much. 
 It is, in fact, this accumulation of water beneath impervious beds that 
 
314 
 
 SPRINGS PRODUCED BY VALLEYS AND SLIPS. 
 
 gives rise to so many natural springs, and enables us by artificial wells 
 to bring water to the surface — often where tlie land would otherwise be 
 wholly uninhabitable. 
 
 3°. Thus in undulating countries, where hill-sides frequently pre- 
 sent themselves, or valleys are scooped out among the rocks, as in the 
 folloSving wood-cut, the water that has fallen over the high grounds to- 
 
 wards A, and has entered as above described, or has sunk down to the 
 several strata 1, 2, 3, &:c., will find a ready outlet along the slope of llie 
 valley, and will give rise to springs at a, b, c, or d, according as the wa- 
 ter has lodged in the one or the other of these beds. These springs will 
 fili the surface soil with water, which will also descend into the botiomof 
 the valley, and, if no sufficient outlet be provided for it, will, according 
 to its quantity, give rise to a lake, a bog, or a morass. On the slope to- 
 wards B the same springs are not to be expected, since the rains which 
 sink through the surface on this side of the valley, and lodge in the po- 
 rous rocks beneath, will, by the inclination of the beds, be drawn oflT in 
 the opposite direction, till a second valley or some other available outlet, 
 present itself for their escape. This explains why the land on one side 
 of avalle}' or of a hill is often much drier than on the other, and why, 
 even in the absence of the improver's skill, an apparently more fertile 
 soil may exist, and better crops be reaped. 
 
 4°. Again, such an outlet for the waters that rest among inclined strata 
 is not unfre([uently afforded, without the intervention of valleys, and 
 even in level or hilly countries, by the existence of slips or faults in the 
 rocks beneath. Such a slip or shifting of the beds is represented in the 
 
 annexed diagram, in which B D is a crack, along which the strata from 
 B to C appear to have slipped downwards, so that the thin bed (2), for 
 exanii)le, which terminates at b on the one side of the crack, begins again 
 at a lower level c on the other side, and so with the other beds that lie 
 above and below it. None of them is exactly continuous on the oppo- 
 site sides of the slip. From such cracks or faults in the beds, springs of 
 water often rise to the surface, even on hill toj)S, as at B, and they may 
 be thus thrown or forced out from either of two causes — 
 
 1. These slips are often of considerable width, and are usually found 
 to be filled with impervious clay. This is the case at least among the 
 coal measures, which have been the most extensively explored. The 
 effect of this wall of clay is to dam back at B D the water which de- 
 
SLIPS ARREST AND THROW UP THE WATER. 
 
 315 
 
 scends along the inclined beds towards C from the country beyond A, 
 and thus to arrest its further progress. But the pressure of the water 
 behind forces that which has reached the fault B D to seek a way up- 
 wards, and, as spaces not unfrequently exist between the wall of clay 
 and the rocks between which it stands, the water finds a more or less 
 ready outlet at the surface B, and either gushes forth as a living and 
 welcome spring, or oozes out unseen among the soil, rendering it cold, 
 wet, and unproductive. Thus from b the water accumulated in the bed 
 (2) may rise to the surface, or from/ that which exists in (4), or from 
 any other bed in which water exists, and from almost any depth. 
 
 2. But even where no such wall of clay exists, the waters may still 
 find their way to the surface along lines of fault, and from great depths. 
 Thus suppose the thin bed (2) to be full of water, and that it is covered 
 by an impervious bed (1), then the water which tends downwards from 
 a to h will be arrested at the fault, and dammed back by the impervious 
 extremity of (1) against which it now rests. If an outlet can be found, 
 it will therefore rise towards the surface. And as the rocks incline up- 
 wards in the direction of A, the pressure from behind may easily cause 
 the water to ascend to the summit of the hill at B, and to gush out in a 
 more or less copious spring. 
 
 5°. Where no natural outlets of the kind above described exist in a 
 district, there may be a great scarcity of water on the surface, while 
 abundance, as we have already seen (2°), may exist in the rocks be- 
 neath, ready and willing to rise if a passage be opened for it. Such is 
 the case with the site of the city of London, represented below : — 
 
 St. Alban's. 
 
 Hampstead. London. Thames. Sydenham. 
 
 Knockholt. 
 
 SECTION ACROSS THE LONDON BASIN FROM ST. ALBAN'S TO KNOCKHOLT. 
 
 iBuckland's Bridgewater Treatise, plate 69.) 
 
 1. Marine Sand. 2. London Clay (almost impermeable). 3. Plastic Clay and Sand. 
 4. Chalk, both full of water. 
 
 The rain-water which falls between a and A on the one hand, and 
 upon the plastic clay and chalk between d and B on the other, sinks into 
 these two beds and rests in them tillit finds an escape. It cannot rise 
 through the great thickness of impervious clay on which London and its 
 neighborhood stands, unless where wells are simk, as above represented 
 at a, 6, c, d, either into the plastic clay (3), or into the chalk (4), when 
 the water ascends copiously till it reaches the general level of the country 
 about St. Alban's, the lowest part of the basin where the permeable beds 
 form the surface. Hence in the vale of the Thames at &, it rises above 
 the surface, and forms a living spring, while at other places, as at a, c, c?, 
 it has still to be pumped up from a greater or less depth.* It is the ex- 
 
 * In January 1840, there were stated to be in the London clay upwards of 200 such wells, 
 of which 174 were in London, and of which latler 30 taken together were known to yield 30 
 14 
 
316 ARTEf?IAN WELLS. SPRINGS IN DESERTS AND PARCHED PLAINS. 
 
 istence of water beneath the surface where the soils rest on impermea 
 ble beds, and the known tendency of these waters to rise when a boring 
 is sunk to them, that have given rise to the establishment of 7lr^mrt?i* 
 wells, so frequently executed, and with so much success, in recent times. 
 There is probably no geological fact that promises hereafter to be of more 
 practical value to mankind, when good government and the arts of peace 
 shall obtain a permanent resting-place in those countries where, without 
 irrigation, the soil remians hopelessly barren. Wherever a living spring 
 bursts out in the sands of Arabia, in the African deserts, or in the parched 
 plains of South America, an island of perennial verdure delights the eye 
 of the weary traveller, and wherever in such countries the labour of man 
 has been expended in digging wells, and in raising water from them for 
 artificial irrigation, the same beauty and fertility always appear. It 
 has recently been found that the oases of Thebes and Garba, in Upper 
 Egypt, where the blown sands now hold a scarcely disputed dominion, 
 are almost riddled with wells sunk by the ancient Egyptians, but for the 
 greater part long since filled up. The re-opening of such wells might 
 restore to these regions their long-lost fertility, as the sinking of new 
 ones by our easier and more economical methods might reclaim many 
 other wide tracts, and convert them to the use of man. In contemplating 
 what man may do, when his angry passions and his prejudices do not 
 interfere with the exercise of his natural dominion over dead matter, it is 
 not unreasonable to hope that, guided by such indications of natural 
 science, human industry may hereafter, by slow degrees, re-establish its 
 power in long-deserted regions of country, spreading abundance over the 
 broad wilderness, staying the Arab's wandering foot, and fixing his 
 household in a permanent and plenteous home. 
 
 6°. It not unfrequently happens that alternate layers of sand and clay 
 overspread the rocks of a country, and act in arresting or in throwing out 
 the surface water in the same manner as the solid strata beneath. Thus 
 
 under the surface A B here represented, alternate layers of sand and clay 
 overspread the inclined beds of rock, and alone affect not only the qual- 
 ity but the state of dryness also of the soil. 
 
 The rain which falls on the upper bed of sand will sink no further 
 than the first bed of clay, and will appear as a spring, or will form a 
 wet band along the side of the hill, at a. That which falls or exists in 
 the second bed of sand will in like manner come to day at 6, c, and d, c, 
 
 millions of gallons weekly. This number of wells has since been increased, and is still 
 increasing. The borings "are generally carried down into the chalk, because the water which 
 ascends from the plastic clay has been found to bring with it much sand, which both ob- 
 structs the pipes and is injurious to the pumps. 
 
 So called from the district of Jr/ois, in France, in which it was formerly supposed that 
 such borings had been longest or most extensively practised. 
 
EFFECT OF ALTERNATE LAYERS OF SAND AND CLAY. 317 
 
 filling the two vallies more or less with water, and forming wet tracts of 
 country resting upon a lower bed of impervious clay. 
 
 In endeavouring to form a satisfactory opinion as to the best mode of 
 draining a piece of land, it is of great importance to be able to determine 
 not only the immediate natural source of the water we are desirous tore- 
 move, but also the probable quantity it may be necessary to carry off, 
 and the permanence of the supply. It is well known, for example, that 
 in many spots, when the accumulated waters are once carried off, there 
 remains only a small and probably intermitting supply, for which an 
 outlet is afterwards to be left and kept open ; while in other localities a 
 constant stream of water is seen to pass along the drains. In connection 
 with this point it is of consequence to make out whether the water is 
 thrown out by surface clays, as in this latter diagram, or flows from 
 among the solid rocks at a greater or less depth — as shown in the prece- 
 ding wood-cuts. That which is thrown out by beds of clay is in most 
 cases derived only from the rains that fall, and is. therefore, liable to in- 
 termit, to cease altogether, or to become more copious, according as the 
 season is dry or otherwise ; while that which escapes from a bed of rock, 
 being independent of the seasons, will seldom vary in quantity. Thus 
 it happens that where surface water only stagnates in the soil of a district, 
 a warm, dry, and long continued summer may cause it to yield a crop 
 of unusual excellence, while other soils fed by springs from beneath may, 
 even in such seasons, still retain moisture enough to render them unfit to 
 rear and ripen a profitable crop of corn. 
 
 7°. There remains one other interesting principle connected with this 
 subject, which I must briefly explain to you. Let C and D in the ac- 
 
 companying wood-cut be two impervious beds through which the w^ater 
 finds no escape, and from which the rains pass off only by the natural in- 
 clination of the ground, and let E be a porous bed from which the water 
 finds a ready escape somewhere towards the right. Then if a boring 
 be sunk through C and D in any part of this tract of country, the wa- 
 ter will descend, and will be absorbed by the bed E. Such dry, porous 
 or absorbent beds exist in many localities, and the skilful drainer may 
 occasionally avail himself of their aid in easily and effectually freeing 
 land from water, which could not without great cost be permanently 
 drained by any other method. Where water collects on a surface rest- 
 ing upon chalk, or upon the loose sands beneath it, this method of boring 
 is frequently had recourse to in some of our southern counties. One dan- 
 ger, however, is to be guarded against in trying this method, that the 
 bore-rod, namely, may enter a bed which is full of water, and from 
 which, as in Artesian wells, it may readily, and in considerable quantity, 
 ascend. Such a boring it is obvious would only add to the evil^ and 
 might render necessary a larger outlay in establishing an efficient sys- 
 
318 
 
 PLOUGHING AND SUBSOILING. 
 
 tern of drainage by the ordinary method, than would otherwise have been 
 required.* 
 
 I do not enter into any further details in regard to the application of 
 these principles to the practice of draining, being satisfied- that when you 
 have once mastered the principles themselves, the applications will 
 readily suggest themselves to your own minds when circumstances re- 
 quire it. 
 
 § 4. Of ploughing and suhsoiling. 
 
 I. Ploughing. — Apart from the obvious effect of ploughing the land, 
 in destroying weeds and insects, the immediate advantage sought for 
 by the farmer is the reduction of his soil to a state of minute division. 
 In this state it is not only more pervious to the roots of his corn, but it 
 also gives a more ready admission to the air and to water. 
 
 Of the good effects produced by the easy descent and escape of water 
 from the surface, I have already spoken (p. 306), but the permeability 
 of the soil to air is no less useful in developing its natural powers of pro- 
 duction. How important the presence of the air is both to the mainten- 
 ance of animal and to the support of vegetable life, we have had fre- 
 quent occasion to observe. By its oxygen the breathing of animals is 
 sustained, and by its carbonic acid the living plant is fed. On tlie earthy 
 particles, of which the soil consists also, the influence of these gaseous 
 substances, though not so visible and striking, is of almost equal conse- 
 quence in the economy of nature. Among other immediate benefits 
 derived from the free access of air into the soil, we may enumerate the 
 following : — 
 
 1°. The presence of oxygen in the soil is necessary to the healthy 
 germination of all seeds (page 132), and it is chiefly because they are 
 placed beyond its reach, that those of many plants remain buried for 
 years without signs of life, though they freely sprout when again brought 
 to the surface and exposed to the air. We have also seen reason to be- 
 lieve (page 77), that the roots of living plants require a supply of 
 oxygen in-order that they may be maintained in a healthy condition. 
 Such a supply can only be obtained where the soil is sufficiently open 
 to permit the free circulation of the air among its pores. 
 
 * It sometimes happens that in sinking an old well deeper 
 for the purpose of obtaining a better supply of water, the 
 original springs disappear altogether. This is owing lo the 
 occuiTGnce at this greater depth, of an absorbent bed, in 
 which the water disappears. By descending still further, a 
 second supply of water may often be found, but which will 
 naturally ascend no further than the absorbent bed, by which 
 the whole supply will be drunk up, if not prevented by the 
 insertion of a metal pipe. Advantage is sometimes taken of 
 the known existence of such absorbent strata, not only for the 
 purposes of draining, but also for removing waste water of 
 various kinds. An interesting example of such application is 
 to be seen at St. Denis, in the Place aux Gueldres, where the 
 water from the bed/at the depth of 200 feet ascends through 
 the inner tube a — from another bed c, at 160 feet, through the 
 titbe ^— while between it and the outermost tube, through the 
 space c, it is sent down again after it has been employed in 
 washing the square, and disappears in the absorbent stra- 
 tum <2. 
 
DECOMPOSITION OF ROCKY MOUNTAINS. 319 
 
 2°. In the presence of air the decomposition of the vegetable matter 
 of the soil proceeds more rapidly — it is more speedily resolved into those 
 simpler forms of matter, carbonic acid and water chiefly (page 152), 
 which are fitted to minister to the growth of new vegetable races. In 
 the absence of the air also, not only does this decomposition proceed 
 more slowly, but the substances immediately produced by it are fre- 
 quently unwholesome to the plant, and therefore fitted to injure, or ma- 
 terially to retard, its growth. 
 
 3°. When the oxygen of the air is more or less excluded, the vege- 
 table matter of the soil takes tjiis element from such of the earthy sub- 
 stances as it is capable of decomposing, and reduces them to a lower 
 state of oxidation. Thus it converts the red or per-oxide of iron into 
 the ])rot-oxide (p. 211), and it acts in a similar manner upon the oxides 
 of manganese (p. 213). It also takes their oxygen from the sulphates (as 
 from gypsum), and converts them into sulphurets. These lower oxides 
 of iron and manganese are injurious to vegetation, and it is one of the 
 beneficial purposes served by turning up the soil in ploughing, or by 
 otherwise loosening it so as to allow the free admission of atmospheric 
 air, that the natural production of these oxides is either in a great mea- 
 sure prevented, or that when produced they speedily become harmless 
 again by the absorption of an additional dose of oxygen. 
 
 4°. Further, there are few soils which do not contain, in some quan- 
 tit}'-, fragments of one or other of those compound mineral substances of 
 which, in a previous lecture, (xii., p. 257,) we have seen the crystalline 
 rocks to consist — of hornblende, of mica, of felspar, &c., in a decom- 
 posing state. From these minerals, as they decompose, the soil, and 
 therefore the plants that grow in it, derive new supplies of several of 
 those inorganic substances which are necessary to the healthy nourish- 
 ment of cultivated crops. The continued decomposition of these mine- 
 ral fragments is aided by the access of air, and near its surface, in an es- 
 pecial manner, by the carbonic acid which the air contains. A state of 
 porosity, therefore, or a frequent exposure to the air, is favourable to the 
 growth of the plant, by presenting to its roots a larger abundance not only 
 of organic but also of inorganic food. 
 
 5°. Again, that production of ammonia and of nitric acid in the soil, 
 to which I drew your especial attention on a former occasion (pages 157 
 and 160), as apparently of so much consequence to vegetable life, takes 
 place more rapidly, and in larger quantity, the more frequently the land 
 is turned by the plough, broken by the clod-crusher, or stirred up bj^ the 
 harrow. Whatever amount of either of these compounds, also, the sur- 
 face soil is capable of extracting from the atmosphere, the entire quan- 
 tity thus absorbed will evidently be greater, and its distribution more 
 uniform, the more completely the whole soil has been exposed to its in- 
 fluence. It is for this, among other reasons, that, as every farmer knows, 
 the better he can plough and pulverise his land, the more abundant in 
 general are the crops he is likely to reap. 
 
 6°. Nor lastly, though in great part a mechanical benefit, is it one of 
 little moment that when thus every where pervious to the air, the roots 
 also can penetrate the soil in every direction. None of the food around 
 them is shut up from the approach of their numerous fibres, nor are they 
 prevented, by the presence of noxious substances, from throwing out 
 
320 EFFECT OF THE SUBSOIL-PLOUGH. 
 
 branches in every direction. A deep soil is not absolutely necessary fo 
 the production of valuable crops. A well-pulverised and mellow soil, 
 to which the air and the roots have every where ready access, will, 
 though shallow, less frequently disappoint the hopes of the husbandman, 
 — than where a greater depth prevails, less permeable to the air, and 
 therefore less wholesome to the growing roots. 
 
 II. Subsoil Ploughing. — And yet, as a general rule, it cannot be de- 
 nied that a deep soil is greatly superior in value to a shallow soil of the 
 same nature. It is so both to the owner and to the occupier, though in 
 too many cases the available qualities of deep soils have hitherto been 
 more or less overlooked and neglected. 
 
 The general theoretical principle on this subject — that the deeper the 
 soil the longer it may be cropped without the risk of exhaustion, and the 
 greater the variety of crops, deep as well as shallow-rooted, which may 
 be grown upon it — is so reasonable in itself, as to command a ready ac- 
 quiescence. But a soil is virtually shallow where a few inches of porous 
 earth, often turned by the plough, rest upon a subsoil, hard, stiff" and al- 
 most impervious, — and the practical farmer will rarely be willing to 
 allow the depth of the latter to influence his opinion in regard to the gene- 
 ral value of the land. And in this he is so far correct, that a subsoil 
 must be dried, opened up, mellowed by the air, and rendered at once 
 pervious and wholesome to the roots of plants, before it can be made 
 available for the growth of corn. This may be effected, after draining, 
 by the use of the subsoil plough, an instrument at present, I believe, 
 imequalled for giving a real, practical, and money-value to stiflT and 
 hitherto almost worthless clayey subsoils. It is an auxiliary both to the 
 surface plough and to the drain, and the source of its efficacy will appear 
 from the following eonsiderations : 
 
 1°. The surface plough turns over and loosens the soil to the depth of 
 6 to 10 inches — the subsoil plough tears open and loosens it to a further 
 depth of 8 or 10 inches. Thus the water obtains a more easy descent, 
 and the air penetrates, and roots more readily make their way among 
 the particlea-of the under-soil. So far it is an auxiliary to the common 
 plough, and assists it in aerating and mellowing the soil. 
 
 2°. But though it opens up the soil for a time to a greater depth, the 
 subsoil plough will in most cases afford no permanent cure for the defi- 
 ciencies of the subsoil, if unaided hy the drain. If the soil rest upon 
 an indurated substratum — upon a calcareous or ochrey j[7an — this plough 
 may tear it up, may thus allow the surface water to sink, and may great- 
 ly benefit the land ; but the same petrifying action will again recur, and 
 the benefit of the subsoiling will slowly disappear. Or, if the subsoil 
 contain some noxious ingredients, such as salts of iron, which the ad- 
 mission of air is fitted to render harmless, then the use of this plough 
 may afford a partial amelioration. But in this case, also, the effect will 
 be only temporary ; since the source of the evil has not been removed, 
 the same noxious compounds will again be naturally produced, or will 
 again, in fresh supplies, be convej^ed into the soil by springs. Or, if the 
 subsoil be a stiff" clay, containing no noxious ingredient, it maybe cut, or 
 for the time torn asunder, but scarcely will the plough have passed over 
 it till the particles will be again cemented together, and probably, by the 
 
PREVIOUS divYn;:ss of tiik subsoil kecessary. 321 
 
 end of a single season at the furthest, the under-soil may be as solid and 
 impermeable as ever. 
 
 It is as the follower of the drain, therefore, in the course of improve- 
 ment, that the subsoil plough finds its most beneficial and most economi- 
 cal use. After land has been drained, the water may still too slowly 
 pass away, or the air may have too imperfect an entrance into the sub- 
 soil from which the drains have removed the water. In the former case, 
 the subsoil plough must be employed, in order that the drains may be- 
 come fully efficient ; in the latter, that the under-layers may be opened 
 up to all the beneficial influences which the atmosphere is fitted to exert 
 upon them. In this respect it is an auxiliary to the drain. But as the 
 full eff^ect which the subsoil plough is capable of producing upon stifl[' 
 and clayey subsoils, can only be obtained after they have been brought to 
 such a state of dryness that the sides of the cut or tear, which the plough 
 has made, will not again readily cohere, it is of importance that the 
 drains should be allowed a considerable time to operate before the use of 
 this plough is attempted. The expense of the process is comparatively 
 great, and this expense will be in a great measure thrown away upon 
 clay lands, which are undrained, or from which the water, either through 
 defective draining, or from the want of sufficient time, has not been able 
 fully to flow away. There are few kinds of clay land on which the ju- 
 dicious use of this valuable instrument will not prove both actually and 
 economically useful, though from the neglect of the above necessary pre- 
 caution, it has been found to fail in the hands of some. Such failures, 
 however, do not justify us in ascribing tq some fancied defect in the in 
 strument, or in the theory upon which its use is recommended, what ne- 
 cessarily arose, and could have been predicted, from our own neglect of 
 an indispensable preliminary observation. The sanguine anticipations 
 of its inventor, Mr. Smith, of Deanston, may not be fully realized, yet 
 the value of the subsoil plough itself, and the benefits it is fitted to confer, 
 when rightly used, appear to me to be both theoretically and practically 
 established. 
 
 § 5. Of deep-ploughing and trenching. 
 
 Deep-ploughing and trenching differ from ordinary and subsoil plough- 
 ing in this, — that their special object is to bring to the surface and to mix 
 with the upper-soil a portion of that which has lain long at a consider- 
 able depth, and has been more or less undisturbed. 
 
 The benefit of such an admixture of fresh soil is in many localities un- 
 doubted, while in others the practical farmer is decidedly opposed to it. 
 On what principle does its beneficial action depend, and in what circum- 
 stances is it likely to be attended with disadvantage ? 
 
 1°. It is known that when a heavy shower of rain falls it sinks into 
 the soil, and carries down with it such readily soluble substances as it 
 meets with on the surface. But other substances also, which are more 
 sparingly soluble, slowly and gradually find their way into the subsoil, 
 and there more or less permanently remain. Among these may be 
 reckoned gypsum, and especially those silicates of potash and soda al- 
 ready spoken of (page 206), as apparently so useful to corn-growing 
 plants. Suoh substances as these naturally accumulate beyond the 
 reach of the ordinary plough. Insoluble substances likewise slowly 
 
322 OBJECT A:^T> Kni CT CF PKKP rLOUGIIING. 
 
 sink. This is well known to be the case with lime, when laid upon or 
 ploughed into the land. So it is with clay, when n]ixed with a surface 
 soil of sand or peat. They all descend till they get beyond the reacli of 
 the common plough — and more rapidly it is said (in Lincolnshire) 
 when laid down to grass, than when they are constantly brought to 
 the surface again in arable culture. Thus it happens that after the sur- 
 face soil becomes exhausted of one or other of those inorganic compounds 
 which the crops rec^uire, an ample supply of it may be still present in 
 the subsoil, though, until turned up, unavailable for the promotion of ve- 
 getable growth. 
 
 There can be little question, I think, that the greater success which, 
 attends the introduction of new implements in the hands of better in- 
 structed men, upon farms long held in arable culture, is to be ascribed inj 
 part to this cause. One tenant, during a long lease, has been in th< 
 Ijabit of ploughing to a depth of three, or at most, perhaps, of foul 
 inches— and from this surface the crops he has planted have derived theii 
 chief supplies of inorganic food. He has limed his land in the customary 
 manner, and has laid upon it all the manure he could raise, but his crops 
 have been usually indifferent, and he considers the land of comparative- 
 ly little value. But another tenant comes, and with better implements 
 turns up the land to a depth of 7 or 8 inches. He thus brings to the sur- 
 face the lime and the accumulated manures which have naturally sunk, 
 nnd which his predecessor had permitted year after year to bury them- 
 selves in his subsoil. He thus has a new, often a rich, and almost always 
 a virgin soil to work upon — one which, from being long buried, may re- 
 (jaire a winter's exposure and mellowing in the air, but which in most 
 cases is sure to repay him for any extra cost. The deep ploughing 
 which descends to 14 inches, or the trenching whici) brings up a new 
 soil from the depth of 20 or 30 inches, is only an extension of the same 
 practice. It is justified and recommended upon precisely ilie same 
 principle. It not only brings a new soil, containing ample nourishment, 
 to the immediate roots of plants, but it affords them also a deeper and 
 more open subsoil, through which their fibres may proceed in every di- 
 rection in seai-ch of food. The full benefits of this deepening of the soil, 
 however, can only be expected where the subsoil has previously been 
 laid dry by drains ; for it matters not how deep the loosened and perme- 
 able soils may be, if the accumulation of water prevent the roots from 
 descending. 
 
 2°. Two practical observations, however, may here be added, which 
 the intelligent farmer will always weigh well before he hastily applies 
 this theoretical principle — sound though it undoubtedly be — in a district 
 v/ith which he has no previous acquaintance. It is possible that the 
 deeper soil may contain some substance decidedly noxious to vegetation. 
 In such a case it would be improper at once to mix it with the upper 
 soil. Good drains must be established, they must be allowed some time 
 to act, and the subsoil plough will be used with advantage, before any 
 portion of such an under-soil can be safely brought to the surface. The 
 subsoil plough and the drain, indeed, as I have already mentioned, are 
 the most certain available remedies for such a state of the subsoil. In 
 many localities, however, the exposure of such an under-soil to a winter's 
 frost, or to a summer fallow, will so far improve and mellow it, as to ren- 
 
ErrECT OF INSECTS. — IMPROVEMENT OF THE SOIL. 323 
 
 der it capable of being safely mixed with the surface soil. Unless, how- 
 ever, this mellowing be effected at once, and before admixture, a long 
 time may elapse ere the entire soil attain to its most perfect condition.* 
 
 Again, it is known that some districts, for reasons perhaps not well un- 
 derstood, are more infested than others with insects that attack the corn 
 or other crops. These insects, their eggs, or their larvae, generally bury 
 themselves in the undisturbed soil, immediately beyond the ordinary 
 reach of the plough. If they remain wholly undisturbed during the 
 preparation of the soil, some species remain in a dormant state, and the 
 subsequent crop may in a great measure escape. Plough the land deep- 
 er than usual, and you bring them all to the surface. Do this in the 
 autumn, and leave your land unsown, and the frost of a severe winter 
 may kill the greater part, so that your crops may thereafter growin safety. 
 But cover them up again along with your winter corn, or let this 
 deep ploughing be done in the spring, and you bring all these insects 
 within reach of the early sun, and thus call them to life in such num- 
 bers as almost to ensure the destruction of your coming crop. It is to 
 something of this kind that I am inclined to attribute the immediate fail- 
 ures which have attended the trial of deep ploughing in certain parts of 
 England. Thus in Berkshire, certain soils which are usually ploughed 
 to a depth of only two inches, yielded almost nothing when deeper plough- 
 ing was more lately tried upon them — the crop was almost entirely de- 
 stroyed by insects. So also in the north of Yorkshire, where deep 
 ploughing has recently been attempted, the wheat crop on land so treated 
 was observed to suHer more from the worm than on any other spot. 
 Such facts as these, therefore, show the necessity of caution on the part 
 of the practical man, and especially of the land agent or steward, how- 
 ever correct may be the principles on which his general practice is 
 founded. Failures such as the above do not show th# principle on which 
 deep ploughing is recommended to be false, or the practice to be in any 
 case reprehended : but it does show that a knowledge of natural local 
 peculiarities, and some study of ancient local practice, may, in an im- 
 portarit degree, influence our mode of procedure in introducing more 
 improved methods of husbandry into any old agricultural district. 
 
 § G. Improvement of the soil hy mixing. 
 There are some soils so obviously defective in constitution, that the 
 most common observer can at once pronounce them likely to be improved 
 by mechanical admixtures of various kinds. Thus peaty soils abound 
 too much in vegetable matter; a mixture of earthy substances, there- 
 fore, of almost any common kind, is readily indicated as a means of im- 
 provement, in like manner we naturally impart consistence to a sandy 
 
 ' The Marquis of Tweedale, in his home-farm at Yestera, has raised his land in value 
 eight times (Irom 5s. to 403. per acre), by draining and deep ploughing. After draining, the 
 fields of stiff clay, with streaks of sand in the subsoil, are turned over to a depth of 12 or 14 
 inciies, by two ploughs (two horses each) following one another, the under 6 inches being 
 thrown on the top. In this state it is left to the winter's frost, when it falls to a yellow marly 
 looking soij It is now ploughed again to a depth of 9 or 10 inches, by which half the origi- 
 nal soil is Brought aa^ain to the surface. By a cross ploughing this is mixed with the new 
 soil, after which the field is prepared in the usual way for turnips. But it is observed that if 
 the ploughing has been so late that the subsoil has not had a proper exposure to the winter's 
 cold, the land on such spots does not for many years equal that which was earlier ploughed. 
 The reason is, that when once mixed up with the other soil, the air has no longer the same 
 easy access into its pores. 
 
 14* 
 
324 EFFECTS OF CLAY AND MARL. 
 
 soil by an admixture of clay, and openness and porosity to stiff' clays by 
 the addition of sand. 
 
 The first and obvious effect of such additions is to alter the physical 
 qualities of the soil — to consolidate the peats and sands, and to loosen 
 the clays. But we have already seen that the fertility of a soil, or its 
 power of producing a profitable return of this or that crop, depends in 
 the first place on its chemical constitution. It must contain in sufficient 
 abundance all the inorganic substances which that crop requires for 
 its daily food. Where this is already the case, as in a rich stiff clay, a 
 decided improvement may be produced by an admixture with siliceous 
 sand, which merely separates the particles mechanically, and renders 
 the whole more porous. But let the clay be deficient in some necessary 
 constituent of a fertile soil, and such an addition of siliceous sand would 
 not produce by any means an equal benefit. It may be proper to add 
 this sand with the view of producing the mere physical alteration, but 
 we must add some other substance also for the purpose of producing the 
 necessary chemical change. 
 
 The good effects which almost invariably follow from the addition of 
 clay to peaty or sandy soils are due to the production at one and the same 
 time of a physical and of a chemical change. They are not only ren- 
 dered firmer or more solid by the admixture of clay, but they derive 
 from this clay at the same time some of those mineral substances which 
 they previously contained in less abundance. 
 
 The addition of marl to the land acts often in a similar two-fold capa- 
 city. It renders clay lands more open and friable, and to all soils brings 
 an addition of carbonate, and generally of phosphate of lime, both of 
 which are proved by experience to be not only very influential, but to be 
 absolutely necessary to healthy vegetation. 
 
 That much benifit to the land would in many instances accrue from 
 such simple admixtures as those above adverted to, where the means 
 are available, will be readily granted. The only question on the sub- 
 ject that ought to arise in the mind of a prudent man, is that which is 
 connected with the economy of the case. Is this the most profitable way 
 in which I caiT spend my money? Can I employ the spare labour of 
 my men and horses in any other way which will yield me a larger 
 return ? It is obvious that the answer to these questions will be modi- 
 fied by the circumstances of the district in which he lives. It may be 
 more profitable to drain, — or labour may be in great request and at a 
 high premium, — or a larger return may be obtained by the investment 
 of money in purchasing new than in improving old lands. It is quite 
 true that the country at large is no gainer by the mere transfer of land 
 from the hands of A to those of B, and that he is undoubtedly the most 
 meritorious citizen who, by expending his money in improving the soil, 
 virtually adds to the breadth of the land, in causing it to yield a larger 
 produce. Yet it is no less true that the employment of individual capi- 
 tal in such improvement is not to be expected generally to take place, 
 unless it be made to appear that such an investment is likely to be as 
 profitable as any other within the reach of its possessor. It seems to be 
 established beyond a doubt, that in very many districts no money is more 
 profitably invested, or yields a quicker return, than that which is ex- 
 pended in draining and subspiling — and yet in reality one main obstacle 
 
CLAY AND SAND. — SPECIAL MIXTURES. 
 
 325 
 
 to a more rapid increase in the general produce of the British soil is the 
 practical difficulty which exists in convincing the owners and occupiers 
 of the soil that such is the case, or would be the case, in regard to their 
 own holdings. The more widely a kaowledge of the entire subject, in 
 all its beariogs, becomes diffused, the less it is to be hoped will this diffi- 
 culty become — for the economist, who regards the question of improve- 
 ment as a mere matter of profit and loss, cannot strike a fair balance 
 unless he knows the several items he may prudently introduce into each 
 side of his account. 
 
 Thus in reference to the special point now before us, it seems reason- 
 able to believe that, in a country such as that herd'' represented, where 
 alternate hills of sand (3), and hollows, and flats of clay (4) occur, there 
 
 may be many spots where both kinds of soil — being near each other — 
 might be improved by mutual admixture, at a cost of labour which the 
 alteration in the quality of the land might be well expected to repay. 
 In this condition is a considerable portion of the eastern half of the 
 county of Durham, and, especially, I may mention the neighbourhood 
 of Castle Eden, where a cold, stiff, at present often poor clay, rests upon 
 red, rich-looking, loamy sand, in many places easily accessible, and by 
 admixture with which its agricultural capabilities may be expected to 
 improve. In this locality, and in many others besides, those having a 
 ])ecuniary interest in the land rest satisfied that their fields are incapable 
 of such improvement, or would give no adequate return for the outlay 
 required, without troubling themselves to collect and compare all the 
 facts from which a true solution of the question can alone be drawn. 
 
 Besides such general admixtures for the improvement of land, the 
 geological formation of certain districts places within the reach of its in- 
 telligent farmers means of improvement of a special kind, of which they 
 may often profitably avail themselves. Thus both in Europe and Ame- 
 rica, the gree7i-sand soils (p. 243) are found to be very fertile, and 
 the sandy portions of this formation are often within easy distance of the 
 stiff clays of the gault, and of the poor soils of the chalk with either of 
 which they might be mixed with most beneficial effects. The soils that 
 rest on the new, and even on some parts of the old red sand-stone, are 
 in like manner often within an available distance of beds of red marl of 
 a very fertilizing character (p. 248), while in the granitic and trap 
 districts the materials of which these rocks consist, if mixed with judg- 
 ment, maybe made materially to benefit some of the neighbouring soils. 
 To this point, however, I shall draw your attention again in my next lec- 
 ture, when treating of mineral manures. 
 
LECTURE XV. 
 
 Improvement of the soil by chemical means.— Principles on which all manuring depends. 
 —Mineral, vegetable, and animal manures.— Saline manures.— Carbonates.— Pearl-ash. 
 —Sulphates.— Glauber salts.— Chlorides.— Common Salt.— Nitrates.— Nitrate of soda.— 
 Phosphates.— Phosphate of lime.— Silicates. Silicate of potash.— Saline mixtures — 
 Vegetable ashes.— Prepared granite.— Use of lime. 
 
 The mechanical methods of improving the soil, described in the pre- 
 cedino: section, are few in number and simple in theory. They are so 
 important, however, to the general fertility of the land, that were they 
 judiciously employed over the entire surface of our islands, they would 
 alone greatly increase the average produce of the British and Irish soils. 
 I may, indeed, repeat what was stated in reference to draining {p. 308), 
 that the full effect of every other means of improving the soil will be 
 obtained in those districts only where these mechanical methods have 
 already been had recourse to. 
 
 The chemical methods of improving the soil are founded upon the 
 following principles, already discussed and established : — 
 
 1°. That plants obtain from a fertile soil a variable proportion of their 
 organic food ; — of their nitrogen probably the greatest part. 
 
 2°. That they require inorganic food also of various kinds, and that 
 this they procure solely from the soil. 
 
 3°. That different species of plants require a special supply of dif- 
 ferent kinds of inorganic food, or of the same kinds, in different pro- 
 portions. 
 
 4°. That of these inorganic substances one soil may abound or be 
 deficient in one, and another soil in another ; and that, therefore, this or 
 that plant will prefer to grow on the one or the other accordingly. 
 
 On these few principles the whole art of improving the soil by che- 
 mical means — in other words, of beneficially manuring the soil — is 
 founded. 
 
 It must at the same time be borne in mind, that there are three dis- 
 tinct methods of operation by which a soil may be improved : — 
 
 1°. By remomw^ from it some noxious ingredient. The only method 
 by which this can be effected is by draining, — providing an outlet by 
 which it may escape, or by which the rains of heaven, or water applied 
 in artificial irrigation, may wash it away. 
 
 2°. By changing the nature or state of combination of some noxious 
 ingredient, which w^e cannot soonremove in this way ; or of some inert 
 ingredient which, in its existing condition, is unfit to become food lor 
 plants. These are purely chemical processes, and we put them re- 
 spectively in practice when we add lime to peaty soils, or to such as 
 abound in sulphate of iron (p. 212), when by admitting the air 
 into the subsoil we change the prot-oxide into the per-oxide of iron, 
 (p. 210,) or when by adding certain known chemical compounds we 
 produce similar beneficial chemical alterations upon other compounds 
 already existing in the soil. 
 
ACTION OF CHEMICAL SUBSTANCES IN THE SOIL. 327 
 
 3°. By adding to the soil those substances which are fitted to become 
 the food of plants. This is what we do in strictly manuring the soil — 
 though we are as yet unable in many cases to say whether that which 
 we add promotes vegetation by actually feeding the plant and entering 
 into its substance — or only by preparing food for it. There is reason to 
 believe, however, that many substances, such as potash, soda, &c., act 
 in several capacities, — now preparing food for the plant in the soil, now 
 bearing it into the living circulation, and now actually entering into the 
 perfect substance of the growing vegetable. In order to steer clear of 
 the difficulty which this circumstance throws in the way of an exact 
 classification of the chemical substances applied to the soil, 1 shall con- 
 sider generally under the name o'i manures, all iJiose substances which are 
 usually applied to the land for the purjjose of promoting vegetable growth ; 
 whether those substances be supposed to do so directly by feeding the 
 plants, or only indirectly, by preparing their food, or by conveying it into 
 their circulation. • 
 
 Manures, then, in this sense, are either simple, like common salt and 
 nitrate of soda, or they are mixed, like farm-yard manure and the nu- 
 merous artificial manures now on sale. Or, again, they consist of sub- 
 stances of mineral, of vegetable, or of animal origin. The latter is the 
 more natural, and is by far the most useful, classification. We shall, 
 therefore, consider the various substances employed in improving the 
 soil — or what is in substance die same thing, in promoting vegetation, — 
 in the following order : — 
 
 1°. Mineral manures — including those substances, whether simple or 
 mixed, which are of mineral origin, or which consist entirely of inor- 
 ganic or mineral matter. Under this head the use of lime and of the 
 ashes of plants will fall to be considered. 
 
 2°. Vegetable manures. — These are all of natural origin, and are all 
 mixtures of organic and inorganic matter. 
 
 3°. Animal manures, which are also mixtures, but, owing to their im- 
 mediate origin, ditTer remarkably in constitution from vegetable sub- 
 stances. . 
 
 § 1. Of mineral manures. 
 
 IMineral manures may be conveniently considered under the two heads 
 of saline and earthy manures. 
 
 A. SALINE MANURES. 
 
 1^. Carbonate of potash. — This substance, in the form either of crude 
 potash or of the pearl-ash of the shops, has hitherto been considered too 
 high in price to admit of its extensive application in the culture of the 
 land. 
 
 2°. Carbonate of soda. — This remark, however, does not apply to 
 the carbonate of soda (common soda of the shops), which is sufficiently 
 low in price (c£ll a ton) to allow of its being applied with advantage 
 under many circumstances. In the case of grass-lands, which are over- 
 run with moss — of such as abound largely in vegetabb matter or in 
 noxious sulphate of iron — a weak solution applied with a water-cart 
 might be expected to produce good results. It might be applied in the 
 same wa}/ to fields of sprouting corn, or in fine powder as a top-dressing 
 
328 QUANTITY OF SALINE MANURES USEFUL TO THE SOIL. 
 
 in moist weather — and generally wherever wood ashes are found useful 
 to vegetation. 
 
 Many experiments have shown that both of these substances may be 
 employed in the field with advantage to the growing crop — but further 
 trials are necessary to show how far the practical farmer may safely use 
 them with the hope of profit. In gardening, they greatly hasten the 
 growth and increase the produce of the strawberry,* and in garden cul- 
 ture, generally, where the cost of the manure emplo^^ed is of less con- 
 sequence, more extended trials would, no doubt, lead to useful results. 
 
 The quantity of these substances which ought to be applied to our 
 fields, in order to produce the beneficial effect which theory and practice 
 both lead us to expect, will depend much upon the natureof the soil in 
 each locality and on the kind of manuring to which it has previously 
 been subjected. By referring to our previous calculations (page 222,) 
 it will be seen that upwards of 800 lbs. of these carbonatesf would 
 be necessary to replace all that is extracted from the soil by the entire 
 crops during a four years' rotation. But in good husbandry every thing 
 is returned to the soil in the form of manure which is not actually 
 sent to market aud sold for money. That is — the grain only of the corn 
 crops, the dairy produce, and the live stock, are carried otf the land.J 
 Less than 40 lbs. per acre of the mixed carbonates would replace all that 
 is contained in the grain, and if we suppose as much to be present in the 
 other produce sold, we have 80 lbs. for the quantity necessary to be re- 
 stored to the land by the good husbandman every four years, in order to 
 keep his farm permanently in tlie same condition. There are, however, 
 in most soils, certain natural sources of supply (pp. 207, 208) by which 
 new portions of these alkalies are continually conveyed to them. Hence 
 it is seldom necessary to add to the land as much of these substances as 
 we carry off'; and therefore from 40 to 60 lbs. per acre, of either of 
 them, may be considered as about the largest quantity which, in a well- 
 managed farm, need be added in order to give a fair trial to their agri- 
 cultural value. Half a cwt. of the potash will cost less than 15s., and 
 of the soda less than 6s., or of a mixture, in equal quantities, less than 
 21s. at theiLp resent prices. 
 
 T^heory of the action of potash and soda. 
 
 But upon what theoretical grounds is the beneficial action of potash 
 and soda upon vegetation explained ? This question, to which I have 
 already more than once drawn your attention (pp. 83 and 187), it will 
 be proper here briefly to consider. 
 
 a. The first and most obvious purpose, served by the presence of these 
 alkalies in the soil, is that of yielding readily to the growing plant such 
 a full supply of each as may be essential to its healthy growth. If the 
 roots can collect them from the soil slowly only, and with, difficulty, the 
 growth of the plant will necessarily be retarded ; while in situations 
 
 ' Mr Fleming, of Baroclian, has informed me thaf he found this to be the case with the 
 common potash ; and Mr. Campbell, of Islay, with the common soda of the shops. Thoy 
 should be applied early in the spring, and" in the state of a very weadc solution. Woi li- 
 ashes would probably produce a similar effect, 
 
 t 390 lbs. of dry pearl ash and 440 lbs. of crystallized carbonate of soda. 
 X In bad husbandry much more is carried off the land by the waste of liquid and otiier 
 manure. — See the succeeding chapter, " On animal manures^* 
 
POTASH AND SODA PREPARE THE FOOD OF PLANTS. 329 
 
 where they naturally abound, or are artificially supplied, the crops will 
 as certainly prove both more early and more abundant — provided no 
 other essential food be deficient in the soil. 
 
 In reference to this mode of action ii will occur to you that potash is 
 the more likely of the two to be beneficial to our cultivated crops, inas- 
 much as the ash of those plants which are raised for food is generally 
 miich more rich in- potash than in soda. [See the tabular details given in 
 Lecture X., § 3-, p. 216 et seq.] But this may possibly arise from the 
 more abundant presence of potash in the soil generally, since some 
 chemists are of opinion that soda may take the place of potash in the in- 
 terior of plants, iviiliout materially affecting their growth, [Berzelius 
 Chimie, VI., p. 733, edit. 1832.] This hypothesis, whatever may be 
 its theoretical value, will prove useful to practical agriculture if it lead to 
 experiments from which the relative action of each of these carbonates, 
 in the same circumstances, may be deduced, — and the specific influ- 
 ence of each, in promoting the growth of particular plants, in some de- 
 gree determined. Potash (or wood-ashes) aids the growth of corn after 
 turnips or potatoes (Lampadius) — would soda do the same ? Carbon- 
 ate of soda assists in a remarkable manner the growth of buck-wheat 
 (Sprengel) — would the same good effects follow from the use of potash ? 
 
 b. Another purpose which these carbonates are supposed to serve, is 
 that of combining with, and rendering soluble, the vegetable matter of 
 the soil, so as to bring it into a state in which it may be readily con- 
 veyed into the roots of plants. They may in this case be said to pre- 
 pare the food of plants. That they are"^ really capable of forming 
 readily soluble compounds witli the humic acid, and with certain other 
 organic substances which exist in the soil, is certain. Those, however, 
 who maintain with Liebig that plants imbibe all their carbon in the 
 tbrm of carbonic acid, will not be willing to admit that this property of 
 the above carbonates can either render them useful to vegetation, or ac- 
 count for the beneficial action they have so often been observed to exer- 
 cise. From this opinion we have already seen reason (pp. 63 and 64,) 
 to dissent, and we are prepared, therefore, to concede that potash and 
 soda, in the form of carbonates, inay act beneficially upon vegetation—- 
 by preparing the organic matter of the soil for entering into the roots of 
 plants, and thus administering to their growth. 
 
 This preparation also may be effected either by their directly comi- 
 bining with the organic matter, as they are known to do with the humic 
 and odier acids which exist in the soil ; or by their disposing this or- 
 ganic matter, at the expense of the air and of moisture, to form new 
 chemical compounds which shall be capable of entering into the vege- 
 table circulation. This disposing influence of the alkalies, and even of 
 lime, is familiar to chemists under many other circumstances. 
 
 This mode of action of the carbonates of potash and soda can be ex 
 ercised in its fullest extent only where vegetable matter abounds inthe 
 soil. It is stated by Sprengel [Lehre vom DUnger, p. 402,] according- 
 ly, as the result of experiment, that they are most useful where vegeta- 
 ble matter is plentiful, and that they ought to be employed more spar- 
 ingly, and with some degree of hesitation, where such organic matter is 
 deficient. 
 
 c. We have already seen, during our study of the composition of the 
 
330 POTASH AND SODA RENDER SILICA SOLUBLE, ETC 
 
 ash of plants (page 216 et seq.) how very important a substance silica is, 
 especially to the grasses and the stems of our various corn-bearing plants. 
 This sihca exists very frequently in the soil in a state in which it is insol- 
 uble in pure water, and yet is more or less readily taken up by water 
 containing carbonate of potash or carbonate of soda; and as there is eve- 
 ry reason" to believe that nearly all the silica they contain is actually con- 
 veyed into the circulation of plants by the agency of potash and soda, (in 
 the state of silicates — see pp. 83 and 207,) it is not unhkely that a portion 
 of the beneficial action of these substances, especially upon the grass and 
 corn crops, may be due to the quantity of silica they are the means of 
 conveying into the interior of the growing plants. 
 
 d. Another mode in which these substances act, more obscurely, per- 
 haps, tliough not less certainly, is by disposing the organic matters con^ 
 tained in the sap of the plant to form such new combinations as may be 
 required for the production of the several parts of the living vegetable. ] 
 have on a former occasion illustrated ( pp. 112-114,) to you the very re- 
 markable changes which starch may be made to undergo, without any 
 essential alteration in its chemical composition — how gum and sugar 
 may be snccessivelv produced from it, without either loss or gain in respect 
 of Its original elementary constitution. We have seen also how the 
 presence of a comparatively minute quantity of diastase (p. 118) or of 
 sulphuric acid (p. 113) is capable of inducing such changes, first rendering 
 the starch soluble, and then converting it into gum and into sugar. Ana- 
 logous, though somewhat dilFerent changes, are induced by the presence 
 incertain solutions of small quantities of potash* or soda, as, for example, 
 in milk — the addition of carbonate of soda to which gradually causes (per- 
 suades }) the whole of tbe sugar it contains to be converted into the acid of 
 milk. Such changes also must be produced or facilitated by the presence 
 of acid and of alkaline substances in the sap of plants ; and though we 
 can as yet only guess at the precise nature of these changes, yet there 
 seems good ground for believing that to facilitate their production is one of 
 the many purposes served by the constant presence of inorganic substances 
 in the sap of plants, indeed so important is this function considered by 
 some writers upon the nourishment of plants, (see especially Hlubeck's 
 EmdhriiiigjicrPjlanzenund Statik desLandbaues,) that they are inclined 
 to ascribe to it, erroneously however, as I believe, the main influence upon 
 ve,o-etation, of nearly all the inorganic substances which are found in the 
 ash of plants, and therefore are known to enter into their circulation. 
 
 e. I only allude to one other way in which these substances maybe sup- 
 ])o^ed to have an influence upon vegetation. We have already seen (Lee. 
 Vin, § 5, 6, 7, pp.159 to 167,) how important a part the nitric acid produ- 
 ced in the atmosphere or in the soil may be supposed to perform in the gen- 
 eral vegetation of the globe. This acid is observed to be more abundantly 
 — either fixed or actually produced in the soils or com posts which contain 
 much potash or soda. It may be, therefore, that in adding cither of these 
 to our fields, we give to the soil the means of bringing within the reach 
 of the roots of our crops a more ready supply of nitric acid, and hence 
 of nitrogen, so necessary a part of their daily food. 
 
 3°. Sulphates of Potash and Soda. — It is nearly 100 years since Dr. 
 
 • It is also shown (p. 112,) that, by means of potash, woody fibre may be converted 
 into starch. 
 
EFFECTS PRODUCED BY SULPHATE OF SODA. 331 
 
 Home, of Edinburgh, observed that these salts produced a beneficial 
 effect upon vegetation. Applied to growing corn, they increased the 
 produce by one-fourth. Other experiments, since made in Germany, 
 have shown that they may be applied with manifest advantage both to 
 field crops and to fruit trees (Sprengel), but the price has hitherto been 
 considered too high to admit of their being economically used in ordinary 
 husbandry. 
 
 The manufacture of sulphate of soda in England, however, has of 
 late years become so much extended, and the price in consequence so 
 much reduced, that I was induced in the spring of the year 1841, (when 
 the publication of these lectures was commenced,) again to recommend 
 it to the attention of the practical agriculturists of the country — as likely, 
 either alone or mixed with other substances, to increase in many locali- 
 ties not only the produce but the profit also to be derived from the land. 
 (See Appendix, also published at the end of this volume, — *' Suggestions 
 for Experiments in Practical Agriculture," No. I.) Many experiments 
 were in conserjuence made in various parts of the country, the details of 
 some of which are given in the Appendix. When applied at the rate of 
 half a cwt. of the dry salt (or one cwt. of crystals) per acre, it produced 
 little effect upon the hay crop, the quantity being probably too small. 
 Applied to hay and rye, at the rate of 84 lbs. of the dry salt, and to pota- 
 toes at the rate of 100 lbs., it gave per imperial acre, with 
 
 Undressed. Dressed with Sulphate. 
 
 Hay 4480 lbs. 5288 lbs. 
 
 Winter Rve $ S^^'^"' ^'^^ ^^^' ^^^ 1^^- 
 
 winteri:tye ^^^^^^^^ 4Q96 ^^g, 4^08 j^g^ 
 
 Potatoes .... 16] tons. 18^^ tons. 
 
 The grain of the dressed rye was much heavier than that of the other, 
 and, though nitrate of soda and sal-ammoniac applied to other parts of 
 the same field caused a larger increase in the crop of rye, yet the increase 
 obtained by the use of the sulphate was cheaper per bushel than that ob- 
 tained by the use of either of the other substances. 
 
 On beans and peas also the effect produced by it (Appendix, page 23,) 
 was very striking — its action being exerted not upon the straw but upon 
 the pods, increasing their number and enlarging their size. 
 
 The results of these experiments, therefore, are such as to encourage 
 further trials. The quantity applied should not be less than one cwt. 
 of the dry salt per acre, and it should be put on either in the state of a 
 very weak solution with a water-cart, or sprinkled on the young crop 
 when the ground is moist or when rain is soon expected. 
 
 4°. Sulphate of Magnesia {Epsom Salts) was found by Dr. Home to 
 promote vegetation almost in anequaldegree with the sulphates of potash 
 and soda, but the usually high price of this compound, among other 
 causes, has hitherto prevented it from being tried upon an extensive 
 scale. The manufacture of this article also has of late years, however, 
 been so much extended and simplified, that the refined salts for medi- 
 ,cinal purposes may be purchased as low as 8s. a cwt. (at Messrs. Cook- 
 son's, Jarrow Alkali Works, near Newcastle,) and the impure salts of the 
 Yorkshire and other alum works at a much lower rate. So much capi- 
 tal indeed has now been embarked in the manufacture of the sulphates 
 and carbonates of soda and magnesia (p. 192), and it is so desirable 
 
 Increase. 
 
 
 808 
 
 lbs. 
 
 256 
 
 lbs. 
 
 512 
 
 lbs. 
 
 1 3 
 ^4 
 
 tons. 
 
332 USE OF SULPHATE OF LIME OR GYPSUM. 
 
 on many accounts to discover newoutleis for the products of these impor- 
 tant manufactories, that were there only theoretical reasons for believing 
 them likely to benefit practical agriculture, it would be desirable to make 
 trial of their etTects upon the land. But their favorable influence has 
 already been shown, and it remains, therefore, only to work out the de- 
 tails by which their application to this or that soil or crop shall be so 
 regulated as to yield a fair and constant profit to the farm.er who em- 
 ploys them. 
 
 1 have elsewhere (Appendix, p. 4,) recommended the application of 
 sulphate of soda at the rate of 1 cwt. of the dry salt, or of 2 cwt. of crys- 
 tals (cost 10s. or lis.) per acre. The Epsom salts are only sold in crys- 
 tals, and 1^ cwt. (cost 12s.) in this form should be nearly equal in effi- 
 cacy upon the land to 2 cwt. of crystallized sulphate of soda. In this 
 proportion, therefore, it would be proper to apply it to the young crops, 
 especially of wheat, clover, peas, beans, and other leguminous plants. 
 
 5°. Sulphate of Lime \Gypsum) has been long and extensively applied 
 to the land in various countries and to various crops. In Germany its influ- 
 ence has been most generally beneficial upon grass and red clover, while 
 In many parts of the United 'States it is applied with advantage to almost 
 every crop. In the former country and in England, it is usually dusted 
 over the young plants in early spring ; in America it is frequently sown 
 with the' seed, or, in the case of potatoes, put into the drills or holes 
 along with the manure. The propriety of adopting the one rather than 
 the other of these methods will depend upon the nature of the soil and 
 upon the climate. Gypsum requires much water to dissolve it, and in 
 dry soils, climates or seasons, it might readily fail to influence the crop 
 at all, if applied in the form of a top-dressing only. 
 
 It would appear that the time and mode of its application has more 
 influence upon its activity than we might suppose — since, according to 
 Professor Korte, when applied to clover at different periods in the spring, 
 the produce of different parts of the same field was in the following 
 proportions : — 
 
 Undressed, 100 lbs. 
 
 Top-dressed on the 30th of March, 132 lbs. 
 
 " " 13lh of April 140 lbs. 
 
 " 27th of April, 156 Ibs.* 
 
 The elTect of a top dressing of gypsum seems therefore to be greatest 
 when it is applied after the leaves have been pretty well developed. f 
 
 Theory of the action of these sulphates. 
 
 a. It does not seem difficult now to account for the general action of 
 these several sulphates of potash, soda, magnesia, and lime. The ex- 
 l)lanation may be deduced partly from recent chemical analyses, and 
 partly from agricultural experiments more lately made by practical men. 
 
 It has been found, for example, that sulphur is a constant and appa- 
 rently necessary constituent of the gluten and albumen of the several 
 varieties of grain, and of the legumin, which forms the largest part 
 
 t Moglinsche Jahrbucker, I, p. 85, quoted in Hlubek's Pflanzenn'dhrung. 
 
 \ Cau the result here mentioned have any connection with the fact observed by Peschier, 
 that gypsum laid upou the leaves of plants is gradually, converted into carbonate, its sulphurio 
 acid being absorbed 7 
 
THEORY OF THE ACTION OF THESE SULPHATES. 33J 
 
 of the substance of the pea, the bean, the vetch, and of the seeds of 
 Other leguminous plants. This sulphur they must obtain from the soil, 
 and one cause of the efficacy of the above sulphates is unquestionably 
 that they are fitted easily to yield to the growing plant the supply 
 of sulphur they necessarily require — while, if they are more efficacious 
 upon the leguminous than upon other kinds of plants, it is because 
 the latter produce a larger proportion of that kind of organic matter in 
 which sulphur is constantly present. 
 
 That such is really the true explanation of their general action is 
 proved by the observation — that sulphuric acid applied to the land in a 
 very diluted state exerts an influence upon the crops precisely similar to 
 that observed when gypsum or sulphate of soda is used. (See Appendix, 
 Nos. I. and II.) 
 
 In reference to this mode of action it is of consequence to know tlie 
 relative efficiency of the several salts. This\vill obviously depend upon 
 the relative proportions of sulphur or sulphuric acid they contain — sup- 
 posing the circumstances in which they are applied to be equally favour- 
 able to the introduction of each into the circulation of the plant. Their 
 relative value upon this view is as follows : — 
 
 100 lbs. of burned gypsum are equal to, or contain as much sulphuric 
 acid, as 
 
 126 lbs. of common or unburned gypsum. 
 128 lbs. of sulphate of potash. 
 104 lbs. of sulphate of soda — dry. 
 235 lbs. of sulphate of soda — crystallized. 
 180 lbs. of sulphate of magnesia — crystallized. 
 And as of all these the gypsum is by far the cheapest, it should form, in 
 reference to this general action of the above sulphates, in all cases, the 
 most economical application to the land. 
 
 6. But they have each also their special ^ciion dependent partly upon 
 their physical properties, and partly on their chemical constitution. 
 
 Thus'^it will be of little use mixing any of them with the soil, unless 
 they become capable of entering into the roots of the plants which are 
 growing upon it. The facility with which this can be effected depends 
 upon their solubility in water, which is very unlike. Thus an imperial 
 gallon of pure water at the ordinary temperature will dissolve of 
 
 Gypsum (burned,) about | lb. 
 
 Gypsum (unburned,) \ lb. 
 
 Sulphate of Potash, 1^ lbs. 
 
 Sulphate of Soda, 1%, IJ lbs. 
 
 Sulphate of Soda, crystallized, 3| lbs. 
 
 Sulphate of Magnesia, 4 lbs. 
 
 In rainy Weather, therefore, and in moist climates, it would still be 
 most economical to apply the gypsum, since, though very sparingly 
 soluble, water would be sufficiently abundant to dissolve as much as the 
 plant might reciuire. But in times of only moderate rain, and especially 
 in dry seasons, the use of the sulphates of soda and magnesia, which 
 are also low in price, is recommended by the comparative ease with 
 which they may be taken up by water and conveyed to the roots. 
 
 c. Again, the chemical constitution of these sulphates — the nature of 
 the substance with which the sulphuric acid is combined — determines in 
 
334 SPECIAL ACTION UPON GRASSES AND CLOVERS. 
 
 a still greater degree the nature and extent of their special action. If 
 the soil already abound in potash, in soda, in lime, or m magnesia, then 
 the influenee of these compounds may depend entirely upon the sul- 
 phuric acid they contain. But suppose the land to be deficient in linie, 
 then the gypsum we add will act not only in virtue of the sulphuric acid, 
 but of the lime also which it contains, and thus its apparent effect will 
 be much more striking than when the land is naturally calcareous, or 
 has been previously dressed with Hme. So if it be deficient in potash, 
 the sulphate of potash will be more efficient than it could be expected to 
 prove upon a soil in which sulphuric acid alone is wanting. And so 
 also, if lime and potash abound, and soda or magnesia be deficient, the 
 sulphates of these latter bases will exercise a special action upon the 
 soil, by supplying it at the same time with sulphuric acid and with soda 
 or magnesia also. Thus on land to which lime has been abundantly 
 added, according to the ordinary practice of husbandry, the sulphate of 
 soda has the best chance of proving useful to vegetation, not only because 
 it is more soluble, and is, therefore, more independent of the seasons, 
 but because it is capable of supplying two different substances^ — sulphuric 
 acid and soda — neither of which are directly added in the ordinary 
 manuring of the land, but both of which the plants may find difficulty 
 in obtaining. 
 
 d. Another consideration will indicate further special applications of 
 these several sulphates, independent of the sulphuric acid which tliey 
 in common contain. If we refer to the table (p. 220, ) in which is exhibit- 
 ed the constitution of the ash of the several clovers and grasses, we find 
 the constituents of our sulphates to be present in ]00 parts of the ash in 
 the following proportions : — 
 
 ^^^ulyf^ Red Clover. ^^^ Lucerne. Sainfoin. 
 
 Potash ...... 8-81 19-95 31-05 13-40 20-57 
 
 Soda 3-94 5-29 5-79 6-15 4-37 
 
 Lime 7-34 27-80 23-48 48-31 21-95 
 
 Magnesia .... 0-90 3-33 3-05 3-48 2-88 
 
 Sulphuric^cid . . . 3-53 4-47 3-53 4-04 3-41 
 
 Of the two clovers the red contains more lime and much less potash, 
 therefore the sulphate of lime is more likely to benefit the red clover, 
 and the sulphate of potash the white, which is consistent with the results 
 of experiment. A similar difference exists between lucerne and sainfoin, 
 to the former of which lime and soda are more necessary than the latter. 
 The first column under rye grass shows, on the other hand, how very 
 much smaller a proportion of all the four — potash, soda, lime, and mag- 
 nesia — is required by this green crop than by the others; and therefore 
 that the same weight of any one of these sulphates, which, when applied 
 as a top dressing to one crop (rye grass), would cause it to thrive luxuri- 
 antly, may be insufficient to supply the most necessary wants of another 
 crop (clover or sainfoin.) Not only the kind of mineral manure, there- 
 fore, which we mix with the soil, but the quantity also, must be deter- 
 mined by the kind of crop we intend to raise. (For the theoretical opinions 
 of other authors in regard to the action of gypsum, see Appendix, No. VI.) 
 
 C°. JSitrates of Potash and Soda. — The efficacy of these two substan- 
 ces as manures in certain circumstances is now generally acknowledged,- 
 
THEY AFFECT THE GROWTH OF THE STEM. 335 
 
 though the disappointinents which have ocasionally attended their use 
 naturally cause the practical farmer to hesitate still, before he applies 
 them in any quantity to his land. As these salts, especially the nitrate 
 of soda, are comparatively abundant in nature, — as they are really be- 
 neficial in many cases, and can be employed with a profit, — as their use 
 in practical agriculture has recently excited considerable interest — and 
 as many experiments have in consequence been made with them upon 
 various crops, — I shall briefly direct your attention to the most impor- 
 tant facts which have yet been established in regard to their action upon 
 the growing plant. 
 
 a. Apparent effects of the Nitrates. — The first visible effect of the ni- 
 trates upon every crop is to impart a dark green colour to the leaves and 
 stems. 2°. They then hasten, increase, and not unfrequently prolong 
 the growth of the plant. 3°. They generally cause an increase both in 
 the weight of hay or straw, and of corn — though the colour and growth 
 are occasionally affected without any sensible increase of the crop. 4°. 
 The hay or grass produced is always more greedily eaten by the cattle 
 than that which has not been dressed, even when the quantity is not 
 affected ; — but the grain is usually of inferior quality, bringing a some- 
 what less price in the market, and yielding a smaller produce of flour. 
 
 Its principal action seems to be expended in promoting the growth — 
 that is, increasing the production of woody fibre, either in the stem or the 
 ear, without so much affecting, except indirectly, the quantity of seed. 
 
 Illustrations. — 1°. Mr. Pusey observed that the increase of his wheat 
 crop, on the Oxford clay, where nitrate of soda was applied, arose from 
 there being no underling straws with short ears as in the undressed, but 
 all were of equal length and consequent fullness and ripeness. The 
 nitrate had merely promoted the growth. (See Royal Agricultural Jour- 
 nal, II., p. 120.) 
 
 2°. "It affected the tops of the potatoes, but the produce of bulbs was 
 less both by weight and measure" (Mr. Grey, of Dilston). "On peas, 
 in a thin sandy soil, subsoil gravel, it had much effect on the colour and 
 strength of the stems, and on the state of forwardness, but when ripe, 
 though the straw was stronger, there was no difference in the crop of 
 peas" (Colonel Campbell, of Rozelle). "On land in high condition it 
 did harm by forcing the straw at the expense of the ear" (Mr. Barclay). 
 " It appeared to act strongly, and there was a greater bulk of straw, but 
 the increase of grain was only 50 lbs. per acre" (Sir Robert Throckmor- 
 ton). In another experiment of Mr. Barclay's the straw was very strong, 
 and much of the wheat laid, but the undressed sold for 4s. a bushel more, 
 and there was no profit. 
 
 In all these cases the nitrate promoted chiefly the growth of the stem, 
 or the production of woody fibre. The inferior quality of the grain and 
 yield of flour was owing to this action. The grain was enveloped in a 
 thicker covering of the woody matter which forms the skin or bran. 
 
 3°. " The turnips after the nitrated wheat are decidedly better, the tops 
 are still growing and luxuriant, while on the other part they are begin- 
 ing to fall" (Hon. H. Wilson). They seem, therefore, in some cases, at 
 least, to prolong the growth. 
 
 From the above statements we seem to derive an exp^nation why the 
 effects of the nitrate should have been so universally observed upon the 
 
336 
 
 EFFECT UPON THE QUANTITY OF THE CROP. 
 
 grasses and clovers — while in regard to its application to com crops, 
 they indicate this important — 
 
 Practical Rule. — Not to apply the nitrates upon land or under cir- 
 cumstances wJiere there is already a sufficient tendency to produce 
 straw. 
 
 b. Effects of the nitrates upon the quantity of the crop. — Cases have 
 occurred where the nitrates have failed to produce any apparent efTect 
 at all — others where the color was affected and the growth promoted 
 without any ultimate increase of crop — and others again, where the ap- 
 plication of these salts was decidedly injurious. These failures are de- 
 serving of a close consideration, but let us first attend to the amount of 
 benefit derived from their use where it has been attended with success. 
 
 I. — Effect on Common and Clover Hay. 
 
 Locality. 
 
 Produce per acre. 
 
 Quantity of Nitrate of Soda applied p^racre, 
 and nature of soil. 
 
 Undressed. 
 
 Dressed. 
 
 Aske Hall, Earl of 
 Zetland 
 
 At Erskine, Lord 
 Blantyre 
 
 Barochan, Mr. 
 Fleming 
 
 Dilston, Mr. Grey. 
 
 Farnham, Suffolk, 
 Mr. Muskett 
 
 Methven Castle, 
 Mr, Bishop 
 
 tons. cwt. 
 
 i2 12 
 
 52 0^ 
 {2 1 
 
 Cl 6 
 
 J2 11 
 
 2 10 
 
 1" 
 
 tons. cwt. 
 
 3 Oi 
 2 10 
 
 2 4i 
 
 2 19^1 
 
 3 18 
 
 3 n 
 
 2 2 < 
 
 1 cwt., on a thin light soil, subsoil 
 clay upon limestone, 
 
 120 lbs,, good light soil, subsoil gravel. 
 Do. clay soil on clay subsoil. 
 
 160 lbs., stiff clay, after wheat. 
 Do. light clay loam, drained, after 
 barley. 
 
 1 cwt., meadow hay, soil not stated. 
 
 150 lbs., clover hay, soil not stated. 
 
 1 cwt, nitrate of potash and U of ni- 
 trate of soda, had each the same ef- 
 fect on a heavy damp loam, partially 
 drained. 
 
 On the other hand, Mr. Barclay says that, on his heavy clay lands 
 (plastic day), in Surrey, near the edge of the chalk, it is almost al- 
 ways a fliilure ; and the Messrs. Drewitt, of Guildford, that on their 
 chalk soils, the additional produce of hay, whether on upland or mea- 
 dow, does not repay the expense. 
 
 II. — On Barley. 
 
 Locality. 
 
 Produce. 
 
 Quantity per acre, and kind of soil. 
 
 Undressed. 
 
 Dressed. 
 
 Grain. 
 
 44i 
 [47 
 
 Straw. 
 
 Grain. 
 
 Sti aw 
 
 Surry, Mr.Barclay 
 Newton Hall, Nor- 
 thumberland, Mr. 
 Jobling 
 
 Suffolk, lion. H. 
 Wilson 
 
 cwt. 
 
 16i 
 26 
 
 bshls. 
 55i 
 
 59 
 32 
 
 cwt. 
 
 20^ 
 36 
 
 -\ 
 
 1 cwt., on light soil, with chalk subsoil. 
 
 1 cwt., on strong turnip land. 
 
 1 cwt., on a poor sandy soil, where 
 the turnips the preceding year were 
 nearjydestroyed by the land blowing. 
 
 
EFFECT ON WINTER RYE AND OATS. 
 
 337 
 
 In Berkshire, on the other hand, it failed (1839), for barley on the 
 light lands, causing them in some cases to be burned up (Mr. Pusey), 
 but the season was droughty. 
 
 III. — On Winter Rye. 
 
 per acre to rye, upon a 
 
 Mr. Fleming, of Barochan, applied 160 lbs 
 strong clay, after potatoes, and obtained — 
 
 Undressed. 
 Grain , . 14 bushels. 
 Straw . , 1 ton Ih cwt. 
 
 Dressed. 
 26 bushels. 
 3 tons, 19^ cwt. 
 
 IV. — Upon Oats. 
 
 Locality. 
 
 PRODUCE. 
 
 Gluantity per acre 
 and kind of soil. 
 
 Undressed. 
 
 Dres 
 
 sed. 
 
 grain. 
 
 straw. 
 
 grain. 
 
 straw. 
 
 Bakewell Derbyshire, 
 Mr. Greaves . . . 
 
 Court Farms, Hayes, 
 
 Mr. Newman .... 
 
 Leatherhead, Surrey, 
 
 Mr. Barclay . . . . 
 
 » 
 
 bush. 
 
 48i 
 
 46 
 40 
 
 cwt. 
 251 
 
 31 
 
 61 
 
 bush. 
 64 
 
 60f 
 
 60 
 
 bush. 
 
 38f 
 
 461 
 90 
 
 I cwt. ; heavy soil, 
 clay subsoil. 
 
 I cwt ; land satu- 
 rated with water, 
 and out of condi- 
 tion. 
 
 1 cwt. ; a loam con- 
 taining flints, on a 
 subsoil of chalk. 
 
 Mr. Everett, in Norfolk, obtained an increase of 15 bushels per acre, 
 by the use off cwt. per acre ; and Mr. Calvert, of Ockley Court, of 20 
 bushels of grain, and 9i cwt. of straw, by applying 1^ cwt. of nitrate 
 of soda. At Kirkleatham (North Yorkshire), it had an excellent effect 
 upon oats, on strong land — and on the strong clays of the Weald of Sur- 
 rey and Sussex, if is said by Mr. Dewdney, of Dorking, to be universally 
 beneficial, particularly when sown on ley ground— paying the grower 
 27s. to 30s. per acre. " When it has failed, the nitrate has been .sown 
 early, and when the land was in a dry state. In these instances the 
 crop was more or less blighted." On the other hand, Mr. Barclay 
 states that, on his strong heavy land (plastic clay), near the edge of the 
 chalk, in Surrey, it gave no profit. 
 
 In most cases, therefore, the nitrate of soda seems capable of pro- 
 ducing a large increase in the oat crop — the few failures which are noted 
 must be due'either to the state of the weather or to some peculiarities in 
 the physical condition or chemical constitution of the soils on which they 
 were observed. 
 
338 
 
 EFFECT OF THE NITRATES ON WHEAT. 
 
 V. — On Wheat. 
 
 Locality. 
 
 Farnhixm, Suffolk, i 
 Mr. Muskdt, . \ 
 
 Painswick, Glou- i 
 cester, Mr. HycU, \ 
 
 Fairford Park, do. i 
 Mr. Jiai/vi. Barker ) 
 Mr.Dugdale, . . 
 
 Undressed. Dressed. 
 
 grain straw grain straw 
 
 Do. 
 
 CourtFarm,Hayes i 
 
 Mr. Newman, . \ 
 Brandon, Suffolk, ^ 
 
 Hun. Mr. Wilson, ( 
 Surrey, Mr. Bar- I 
 
 chry, I 
 
 Faringdon, Mr. 
 
 Pusey, .... 
 
 Ockley Court, Mr. 
 
 Cnh-rr/, . . . 
 Newton Hall, Mr. 
 
 Johling, . . . 
 Cirencester, Dr. 
 
 Datibcny, . . . 
 
 Rozelle, near Ayr, 
 Col. Campbell, 
 
 busliU 
 
 26 
 42 
 
 32 
 
 IM 
 
 21h 
 
 30i 
 
 33f 
 
 31 
 
 27 
 
 2lf 
 
 20^ 
 
 33 
 
 27-^' 
 
 27 
 
 33i 
 54 
 
 3Gi 
 20 
 
 32 
 
 36 
 
 39* 
 
 33 i 
 
 39l 
 
 26 
 
 24^ 
 
 45| 
 
 36 
 31f 
 
 27' 
 
 15 
 34 
 
 18^ 
 
 20 
 
 24i 
 24i 
 2()i 
 20i 
 
 25| 
 
 30 29i 
 ' 16 
 
 3U 47 
 42 
 
 21f 
 
 381 
 
 25f 
 
 23 
 
 27| 
 
 34i 
 
 25i 
 24 i 
 
 37f 
 
 35* 
 20 
 
 m 
 
 52 
 
 76 
 
 Quantity per acre, and kind of soil. 
 
 H CWt. ; a poor spongy sandy soil. 
 
 1 CWt. ; a sfonc-hrash soil abounding 
 in carbonate of lime. 
 
 1 CWt. ; on a light stone-brash poor 
 thin soil. 
 
 1 CWt. nitr. of soda, on Vi gravelly soil ; 
 an equal weight nitrate of potash pro- 
 duced only § bushel of increase (?). 
 
 1 CWt. nit. of soda on a strong clay. 
 Both portions previously limed. 
 
 1 CWt.; on a very thin crop, inj'd by an 
 
 unfavorable autumn. Soil not stated. 
 
 1 CWt. ; on a fair light soil. 
 
 Do., loamy, better land. 
 
 I CWt. ; soil loamy, resting on chalk, 
 straw strong,and much wheat laid,* 
 
 Do. on heavy soil, resting on the Ox- 
 ford clay. But all these very different 
 results were obtained in the same JieM. 
 
 Do.; corn generally laid; soil not 
 mentioned. 
 
 1 CWt. ; soil not mentioned. 
 I CWt. nitrate of potash. 
 Do. niti-ate of soda, soil and subsoil 
 clay, resting on the corn-brash. 
 180 lbs. nitrate of soda. 
 Do. nit. of potash. Soil not stated.! 
 
 f, VI. — On Turnips. 
 
 At Rozelle the Swedes were improved several tons an acre by the 
 use of the nitrate of soda (Mr. Campbell). At Dorking it was very be- 
 neficial as a top-dressing to the Swedes and white turnips, when sown 
 broad-cast at the rate of li cw^t. per acre (Mr. Dewdney). In neither 
 of these cases is the soil described. On thin stony land upon chalk at 
 Flmshurst, Bucks, turnips manured with nitrate alone, were very su- 
 perior to tho.se to which 10 loads an acre of farm-yard manure had been 
 apj)lied (Mr. Burgess). The only numerical results with which 1 am 
 acquainted are those of Mr. Barclay on a loamy soil resting on chalk. 
 His crop of turnips wiis 
 
 * The dressed grain sold at 43. less than the undressed, and there was no profit; the nitrate 
 failed on heavy land, and on land in high condition. 
 
 t The produce of straw, especially from saltpetre, is very surprising. It is stated at 518 
 and 764 stones for the two lots reapectively. I suppose the acres to be Scotch, and the 
 stones 14 lbs. 
 
EFFECT UPON TURNIPS, AND THE QUALITY OF THE CROP. 339 
 
 30i cwt. when dressed with bones and wood ashes, each 15 bushels. 
 31 cwt. when dressed with 1 cwt. of nitrate of soda, drilled in. 
 35 cwt. when seed and nitrate were both broad-cast. 
 38 cwt. when the seed was drilled and the nitrate broad-cast. 
 
 On the other hand, Lord Zetland thought it did no good to turnips ; 
 Mr. Vansittart, that on strong land well dunged it did harm ; and the 
 Messrs. Drewitt, that on their dry rubbly chalk it had no effect on this 
 crop, though it improved in a remarkable degree the succeeding crop 
 of barley. 
 
 We are obviously in want of more numerous and better observations, 
 especially in regard to turnips. The above discordancies will either 
 vanish when we obtain a 2 larger collection of results, or they will find an 
 explanation in the more accurate observations we may expect to obtain 
 in regard to the climate, soil, and geological position of the locality in 
 which each experiment is made. Those practical men who arc really 
 desirous of aiding the progress of scientific agriculture, — by which pro- 
 gress not only the national welfare, but their own individual interests 
 also are likely to be promoted, — will do more towards this end by one 
 single experiment in which weights and measures are carefully deter- 
 mined, and the soil, the climate, the geological position and the lie of 
 the land, accurately described, than by any number oC mere general 
 statements, such as those I have here laid before you in regard to the 
 effect of the nitrates upon the turnip crop. 
 
 c. Effect of the nitrates on the quality of the crop. — This I have 
 already in some measure alluded to. It so affects the grass and clover 
 as to make it more relished by the cattle. This is usually expressed 
 by saying that the crop is siveeter, but since cattle are known to be fond 
 of saline substances, it may be that the grasses are, by these salts, only 
 rendered more savoury. It generally also gives a grain (of wheat) 
 of an inferior quality — which has a thicker skin, and yields more bran. 
 This may possibly arise from its having been generally allowed to ripen 
 too long. [See Mr. John Hannam's valuable experiments on the 
 oi;er- ripening of corn in the Quarterly Journal of Agriculture.] A 
 question still undetermined is, whether the flour of nitrated corn is more 
 nutritive than that obtained from corn which has been undressed. 
 
 It is generally supposed that those samples of flour which contain the 
 most gluten are also the most nutritive. But hitherto the only experi- 
 ments which have been made with the view of determining the relative 
 quantities of gluten in samples of grain from the same field, one por- 
 tion of which had been nitrated, and the other not, are, one made by 
 Mr. Daubeny, and one reported by Mr. Hyett, to the latter of which I 
 have already had occasion, for another purpose, to direct your attention. 
 [See note, p. 167.] 
 
 In these experiments the flour of the several wheats gave — 
 
 In Dr. Daubeny's In Mr. Hyett's 
 
 Experiment. Experiment. 
 
 Nitrated 15 per cent, of gluten 23^ per cent. 
 
 Unnitrated 13 per cent, of gluten 19 per cent. 
 
 Excess of gluten in the nitrated, 2 per cent. 4^ per cent. 
 
 15 
 
340 AFTER-EFFECTS OF THE NITRATES. 
 
 both of which results favour the supposition that one eflfect of the ni- 
 trates upon the quality of the grain is to increase the proportion of gluten, 
 and thus to render them, as is generally believed, more nutritive. This 
 is a result which theoretically we might be led to anticipate, were there 
 no large increase in the quantity of the produce — for then we migfit 
 naturally expect the nitrogen of the nitric acid to be expended solely in 
 enriching the grain with gluten. But the increase of crop contains in 
 many cases more nitrogen than we add to the soil when we dress it with 
 one cwt. of nitrate of soda per acre ; there is, therefore, no excess of ni- 
 trogen which we can suppose to go to such an enriching of the more 
 abundant crop of grain. For this reason, among others, I am inclined 
 to doubt whether further careful examination will prove the flour from 
 nitrated grain to be always richer in gluten, and, therefore, more nutri- 
 tious. At all events increased experiments are to be wished for. 
 
 d. After-effects of these nitrates. — It is comparatively seldom that 
 any good effects have been observed upon the crop which succeeds that 
 to which the nitrate of soda has been applied. Where ihey have been 
 noticed it has been chiefly in cases where from some cause (drought or 
 dryness of soil chiefly) the salt has been prevented from exerting its full 
 and legitimate action upon its first application. Thus, 
 
 1°. Failing to improve turnips on a rubbly chalk soil, it greatly be- 
 nefitted the succeeding crop of barley (Mr. Drewitt, Guildford, Surrey), 
 ' Producing little effect on tares (upon a clay soil ?) it improved very 
 much the turnip crop which followed (Mr. Barclay,Leatherhead, Surrey.) 
 
 2°. In the following instances the benefit was seen on successive 
 crops : — 
 
 After producing an increase of one-sixth in the wheat crop, both 
 grain and straw, on a hght sandy soil (subsoil?), the turnips of the fol- 
 lowing year were decidedly better where the nitrate had been sown (Hon. 
 H. Wilson, Brandon, Suffolk.) 
 
 After improving the crop of wheat, the after-crop of hay was also 
 better (M.r. Grey, of Dilston.) 
 
 At Upleatham, the second cut of clover was nearly as much im- 
 proved as-the first (Mr. Vansittart), and at Dilston the aftermath hay 
 was greater in quantity, and better relished by the cattle (Mr. Grey). 
 
 3°. A curious effect is noted by Mr. Rod well, of Alderton, Wood- 
 bridge — the white clover failed after barley on which nitrate had been 
 used ! 
 
 The solubility of these nitrates is so great, that in our climate, in sea- 
 sons of ordinary rain, and on lands having a moderate degree of incli- 
 nation, we should expect that they would be in a great measure washed 
 out of the land in a single year. Hence one reason — even supposing 
 little of the salt to have entered into the roots of the growing crop — why 
 we are not entitled generally to expect any marked effect from it upon 
 a second crop. But let the season be so dry, or the soil so retentive, 
 and the land so level, as to prevent its being all taken up by the roots, 
 or washed away by the rains during one year, and we may then look 
 for after-effects, such as those above described. 
 
 e. Circumstances necessary to ensure the success of these saline ma- 
 nures.— This explanation will appear more satisfactory if we glance for 
 
THEIR ACTION AFFECTED BY CIRCUMSTANCES. 341 
 
 a moment at the general conditions which are necessary to ensure the 
 success of these or any other saline manures. 
 
 1°. They must contain one or more substances which are necessary 
 to the growth of the plant. 
 
 2°. The soil must be more or less deficient in these substances. 
 3°. The weather must prove so moist or the soil be so springy as to 
 admit of their being dissolved, and conveyed to the roots. 
 
 4°. The}'' must not be applied in too large a quantity, or allowed to 
 come in contact with the young shoots in too concentrated a form — the 
 water that reaches the roots or young leaves must never be too strongly 
 impregnated with the salt, or if the weather be dry, the plant will be 
 blighted or burned up. 
 
 5°. The soil must be sufficiently light to permit the salt easily to 
 penetrate to the roots, and yet not so open as to allow it to be readily 
 washed away by the rains. In reference to this point the nature of the 
 subsoil is of much importance. A retentive subsoil will prevent the 
 total escape of that which readily passes through a sandy or gravelly 
 soil, while an open subsoil again will retain nothing that has once made 
 its way through the surface. 
 
 /. Cases in which, the nitrates have failed. — A knowledge »f the 
 above conditions will enable us in many cases to explain why the ni- 
 trates, and other generally useful substances, have failed to exhibit any 
 beneficial eflfect. 
 
 1°. Thus on the light soils of Berkshire the nitrate of soda failed for 
 barley, causing it often to be blighted or burned up. This, no doubt, 
 arose from the drought which may act in one or other of several ways. 
 Either it may prevent the salt from being dissolved at all, and thus hin- 
 der its action altogether for the time, — or it may retard the solution till 
 the planthas attained such a state of maturity, that it is no longer ca- 
 pable of being equally benefitted by the introduction of the salt into its 
 roots — or after being dissolved, and having partially descended into the 
 soil, the drought may cause it to ascend again with the water which 
 rises to the surface in consequence of the evaporation, and may thus 
 present it to the plant in so concentrated a form as to injure the young 
 shoots — or, finally, the action of the sun upon the green leaf, into which 
 a portion of the salt has already been conveyed by the roots, may be so 
 powerful as to concentrate the saline solution, or to increase its decom- 
 position to such an extent as to cause injury, and consequent blight to 
 the leaf itself. 
 
 2°. Again, a* Cheadale, in Cheshire, (Mr. Austin), the nitrate of soda 
 is said to have had a good effect on wheat and grass where the subsoil 
 was clay, but none where the subsoil was gravel, or the soil light and 
 sandy. Here the supply of water in the soil may have been such as to 
 fit it for entering readily into the roots in a proper state of dilution, when 
 the retentive subsoil kept it within reach of the roots, — and yet sufficient, 
 at the same time, to wash it away altogether where the soil and sub- 
 soil were too open to be able to retard its passage. 
 
 3°. But the occasional occurrence of droughts or the mere physical 
 distinctions of lands as light or heavy, are not sufficient to account for all 
 the recorded differences in the effect of the nitrates. Thus on the clays 
 
342 WHEN THE USE OF NITRATES 19 BENEFICIAL. 
 
 of the Weald in Sussex (Mr. Dewdney), and on the Oxford clay in 
 Berkshire (Mr. Pusey), the use of the nitrate has been attended with 
 general benefit upon oats and wheat, while on the plastic clay in Sur- 
 rey (Mr. Barclay), it has been uniformly unsuccessful. The cause of 
 these differences is to be sought for, most probably, in the chemical con- 
 stitution of the several clays, which are known to be very unlike. The 
 Weald clay is a fresh-water formation, contains much fine grained 
 siliceous matter (page 244), and is, therefore, comparatively per- 
 vious to water. The Oxford clay soils in Berkshire abound in lime, 
 and must, therefore, be in some degree pervious, while the plastic clay 
 of Surrey, where they are stiffest, contain little lime and partake more 
 of the impervious character of pipe clays. It may possibly be in such 
 differences as these that we are to find an explanation of the discordant 
 results of different experimenters, but much further observation is still 
 wanting before we can speak with any degree of confidence upon the 
 subject. 
 
 To some an explanation may appear to be most easily given by sup- 
 posing the one soil to have been rich in soda, while the other was de- 
 fective in this substance. I shall advert to this point in explaining the 
 theor^^of the action of the nitrates of potash and soda. 
 
 g. Circumstances in which the employmeyit of the nitrates is most hene- 
 ficial. — 1°. It appears to succeed most invariably in lands which are 
 poor — or out of condition — or on which the corn is thin. Every farmer 
 knows that the most critical time with his crop, as with his cattle, is 
 during the earliest stage of its growth. If it come away quickly and 
 strong during the first few weeks, his hopes are justly high, but if it 
 droop and linger after it is above the ground, his fears are as justly ex- 
 cited. It is in this latter condition of things that an addition of nitrate 
 comes to the aid of the feeble plant, re-animating the pining shoots, and 
 making the thin corn tiller. On rich lands and thickly growing crops it 
 only causes an over-growth of already abundant straw. According to 
 the experiments of Mr. Barclay, it is most advantageous when sown 
 Droad-cast.* 
 
 2°. Whatever may be the chemical nature of the surface soil, the 
 success of the nitrate seems to be most sure where the land is not wholly 
 destitute of water, where the soil is open enough to allow it readily to 
 descend, and yet the subsoil sufficiently retentive to prevent it from 
 being readily waslied away. 
 
 3°. I throw it out as a suggestion which has occurred to me from a 
 com])arison of the results contained in the above tables, with the kind 
 of soils on which the experiments were made — that probably the pre- 
 sence of lime in the soil may tend to insure the success of the^ nitrate. 
 In many of the instances of large crops obtained by its aid the land was 
 either naturally rich in lime, or it had, in the ordinary course of hus- 
 bandry, been previously marled or limed. 
 
 h. Theory of the action of the nitrates. — The nitric acid of these salts 
 
 ' A valuable prerent also is, to proceed cautiously in the use of these expensive sub- 
 sf^nces — makin? small trials at first, and increasing tlic quantities employed as success 
 may warrant. By thia mode of procedure, large losses, of which I have heard, would 
 have been avoided. 
 
THEORY OF THE ACTION OF THE NITRATES. 343 
 
 contains 26 per cent, of its weight of nitrogen — or one cwt. of pure dry 
 nitrate of soda contains about 19 lbs. of nitrogen. This nitrogen we 
 know to be a necessary constituent of plants — one which they obtain 
 almost wholly from the soil — but which nevertheless is generally pre- 
 sent in the soil in small quantity only. We have already seen reason 
 (Lee. VIII., p. 159,) to believe that nitric acid exists naturally in the 
 soil, and is the form in which a large portion of tiieir nitrogen is con- 
 veyed into the roots of plants ; — when we add it to our fields, therefore, 
 we only aid nature in supplying a compound by which vegetables are 
 usually sustained. And as the young plant will necessarily languish 
 in the absence of one essential kind of food, although every other kind 
 it may require be present in abundance, it is easy to see how the 
 growth of a crop — languidly proceeding upon a soil deficient in nitrogen 
 — may be suddenly re-animated by an application of nitrate of soda to 
 its roots. That this is the true way in which the nitrates generally act 
 is supported by the obseivation that it is in the poorest soils that they 
 are most useful to the husbandman. 
 
 We have already seen, also, that one function of the leaf in the pre- 
 sence of the sun is to decompose carbonic acid, and give off its oxygen 
 (Lee. v., sec. 5.) It exerts a similar action upon the nitric acid of the 
 nitrates, and upon the sulphuric acid of the sulphates, discharging their 
 oxygen into the air, and thus leaving the nitrogen and sulphur at liberty 
 to unite with the other elementary substances contained in the sap — for 
 the jiroduction of the several compounds of which the parts of the 
 growing plant consist. 
 
 Nor, as shown in a previous lecture, (VIII., sec. 8,) is the good effect 
 of these nitrates upon the crop limited to the supply of that quantity of 
 nitrogen only which they themselves contain. The excess of crop 
 raised by their aid often contains very much more nitrogen than they 
 have been the means of conveying to the roots, even supposing it all 
 to have been absorbed and appropriated by the plant. This arises from 
 the circumstance that the more the plant is made to thrive, the more 
 numerous and extended become its roots also, and these roots are thus 
 enabled to gather from the deeper and more distant soil those supplies 
 of nitrogenous and other necessary food, which would have remained 
 beyond their reach had the plant been allowed to remain in its pre- 
 viously feeble or more languid condition. This has been called the 
 stimulating effect of manures, and some substances have been said to 
 act only'iu this way upon vegetation. This, however, appears to me to 
 be a mistake. The supposed stimulating is always a secondary effect, 
 and necessarily follows from the use of every kind of manure, which by 
 feeding the plant gives it greater strength, and thus enables it to appro- 
 priate other supplies of food which were previously beyond its reach, or 
 which from the absence of one necessary constituent it could not render 
 available to its natural growth. 
 
 In this way the nitrates act as such — in contra-distinction to the sul- 
 phates and other salts of potash and soda. But there is every reason to 
 believe that the potash and soda themselves often aid the effect of the 
 nitric acid with which they are associated. In soils deficient in these 
 alkalies the nitrates would act beneficially, even though nitric acid 
 
344 COMPARATIVE EFFECTS OF THESE TWO NITRATES. 
 
 were already present in abundance, — while, on the other hand, a field 
 that is defective in both constituenis of the salt (nitric acid and potash 
 or soda), will be more grateful for the same addition of it than one in 
 which either of them already abounds. In this way, it is not unlikely 
 that the discordant results of experiments, even on the same tanii, and 
 especially when the soils are different, may occasionally be explained. 
 
 i. Special effects of the nitrates of potash and soda. — On this alka- 
 line consihuent of the two nitrates will depend the special action of each 
 when applied to the same soil under the same circumstances. It has 
 not yet been clearly mode out that any definite special action can be 
 ascribed to them, yet some experiments bearing upon this point fiave 
 already been published, to which it will be proper to advert. From 
 the study of the special action of given manures upon given crops, 
 practical agriculture has much good to expect. 
 
 1°. At Rozelle, near Ayr (1840), nitrate of potash caused oats to 
 come away darker and stronger, and give a heavy crop,' while in the 
 same field nitrate of soda produced no benefit. The soil was inferior, 
 light, and sandy, with a red irony subsoil (Capt. Hamilton). It is add- 
 ed that the crop was injured by the early drought, from which it never 
 recovered. This fact renders the special effect of the nitrate of potash 
 in this case doubtful. 
 
 2°. In the experiments upon wheat, made by the same gentleman 
 on the same farm, — it is to be presumed upon a similar soil, — 
 
 Nitrate of soda gave . . 46 bush, grain, and 52 cwt. straw ; 
 
 Nitrate of potash gave . . 42 bush, grain, and 76 cwt. straw; 
 
 the produce of straw being here also greatly in favourof the potash salt. 
 
 3°. Dr. Daubeny also, in the experiment upon wheat above detailed, 
 found the nitrate of potash to increase the produce considerabl3% while 
 the nitrate of soda caused no increase whatever. The soil was stiff clay 
 upon the corn-brash. 
 
 These superior effects of the potash salt may certainly be ascribed to 
 the greater deficiency of the several soils in potash than in soda, a sup- 
 position which in the case of the Rozelle experiment is consistent with 
 the fact, thirr common salt, when tried upon the same land, produced 
 no good effect. If however, as some suppose, (p. 328), potash and soda 
 are capable of re-placing each other in the living vegetable without ma- 
 terially affecting its growth, this explanation cannot be the true one. 
 Further experiments, however, if carefully conducted, will not fail to 
 clear up this question. 
 
 4°. On a gravelly soil Mr. Dugdale obtained an increase of 12 bush- 
 els of wheat by the use of nitrate of soda, while nitrate of potash in- 
 creased the crop by only half a bushel. 
 
 This result 7nay be explained after the same manner as the preceding 
 — the soil may have already abounded in potash. 
 
 6°. In Perthshire, upon a moist loam, Mr. Bishop obtained an equal 
 increase of hay from the use of both nitrates ; each having caused the 
 production of a double crop. 
 
 The equality in this case may have risen from the effects being 
 wholly due to the nitric acid, both potash and soda being already abun- 
 dant in the soil. This is consistent with the situation of the locality in 
 
USE OF COMMON SALT AS A MANURE. 
 
 345 
 
 a granite country, and is further supported by the fact, that on the same 
 soil and field, ammoniacal liquor, which contains no alkali, produced a 
 still larger increase of produce. 
 
 You will understand, however, that all these attempted explanations 
 proceed upon the supposition that the experiments have been both 
 carefully made and faithfully recorded. 
 
 7°. Chloride of Sodium or Common Salt. — The use of common salt 
 as a manure has been long recommended. In some districts it has been 
 highly esteemed, and is still extensively and profitably applied to the 
 land. It has, like many other subs;^nces, however, suffered in gene- 
 ral estimation from the unqualified terms in which its merits have been 
 occasionally extolled. About a century ago (1748J, Brownrigg* main- 
 tained that the whole kingdom might be enriched by the application of 
 common salt to the soil, and since his time its use has been at intervals 
 recommended in terms of almost equal praise. But these warm re- 
 commendations have led sanguine men to make large trials, whicii 
 have occasionally ended in disappointment, and hence the. use of salt 
 hns repeatedly fallen into undeserved neglect. 
 
 It is certain that common salt has in very many cases been advanta- 
 geous to the growing crop. Some of the more carefully observed re- 
 sults which have hitherto been published, are contained in the follow- 
 in.: table : 
 
 
 Produce 
 
 per acre. 
 
 
 Locality. 
 
 
 
 Quantity applied per acre, and kind of soil. 
 
 
 
 
 Unsalted. 
 
 Salted. 
 
 
 UPON WHEAT. 
 
 bushels. 
 
 bushels. 
 
 
 ' 
 
 I6i 
 
 22i 
 
 11 bushels, after barley. 
 
 
 lU 
 
 21 
 
 6| do., after beans. 
 
 
 16 
 
 I7f 
 
 Do. sown with the seed, ) after 
 Do. dug in with the seed, \ peas. 
 
 Mr. G. Sinclair j 
 
 — 
 
 23i 
 
 
 12 
 
 28i 
 
 b\ do. ) appied before sowing, after 
 11 do. \ turnips. 
 
 
 — 
 
 28| 
 
 Great Totham, Essex, ) 
 Mr. Cuth. Johnson . ) 
 
 13J 
 
 26i 
 
 5 bushels, light gravelly soil. 
 
 Barochan, Paisley, ) 
 Mr. Fleming 5 
 
 25 
 
 32 
 
 160 lbs., heavy loam, after potatoes. 
 
 ON BARLEY. 
 
 
 
 
 Suffolk, Mr. Ransom. . . 
 
 30 
 
 5] 
 
 16 bushels. 
 
 ON HAY. 
 
 tons. cwt. 
 
 tons. cwt. 
 
 
 At Aske Hall, near ) 
 Richmond \ 
 
 2 10 
 
 3 12 
 
 6 bushels, thin light soil, clay subsoil. 
 
 At Erskine, near Ren- K 
 frew \ 
 
 2 
 
 2 12 
 
 5 bushels, light soil on gravel. 
 
 2 1 
 
 2 8 
 
 Do., clay soil on clay. 
 
 But it is as certain that in many cases, when applied to the land, 
 common salt has failed to produce any sensible improvement of the 
 growing crop. And as failures are long remembered, and more gene- 
 rally made known than successful experiments, the fact of their fre- 
 quent occurrence has prevented the use of salt in many cases where it 
 might have been the means of much good. 
 
 * On the art of making common acdc, p. 158 (London, 1748). 
 
346 CADRES OF THK FAILURE OF COMMON SALT. 
 
 Cause of these failures.— 'li is not, indeed, to be wondered ^t, that 
 amid conflicting statements as to its value, the practical farmer should 
 have hesitated to incur the trouble and expense of applying it — so long 
 as no principle was made known to him by which its application to this 
 soil rather than to that, and in this rather than the other locality, was to 
 be regulated. 
 
 1°. We know that plants require for their sustenance and growth a 
 certain supply of each of the constituents of common salt, which supply, 
 in general, they must obtain from the soil. If the soil in any field 
 contain naturally a sufficient quantity of common salt — or of chlorins 
 and soda, in any other state of combination — it will be unnecessary to 
 add this substance, or, if added, it will produce no beneficial effect. If, 
 on the other hand, the soil contain little, and has no natural source of 
 supply, the addition of salt may cause a considerable increase in the crop. 
 
 Now there are certain localities in which we can say beforehand that 
 common salt is likely to be abundant in the soil. Such are the lands 
 that lie along the sea coast, or which are exposed to the action of pre- 
 vailing sea winds. Over such districts the spray of the sea is constantly 
 borne by the winds and strewed upon the land, or is lifted high in the 
 air, from which it descends afterwards in the rains.* This considera- 
 tion, therefore, affords us the important practical rule in regard to the 
 application of common salt — that it is most likely to be beneficial in 
 spots luhich are remote from the sea or are sheltered from the prevailing 
 sea winds. 
 
 It is an inferesting confirmation of this practical rule, that nearly nil 
 the successful experiments above detailed were made in localities more 
 or less remote from the sea, while most of the failures on record were 
 experienced near the coast. This consideration, it may be hoped, will 
 induce many practical men to proceed with more confidence in making 
 trial of its effects on inland situations. It is very desirable that the 
 value of this practical rule, which I suggested to you in a former lec- 
 ture (see p. 190), should be put to a rigorous test.f 
 
 2°. But some plants are more likely to be benefitted by the applica- 
 tion of common salt than others. This may be inferred from the fact 
 that certain species are known to flourish by the sea-shore, and where 
 they grow inland to select such soils only as are naturally impregnated 
 with much saline matter. Observations are still wanting to show which 
 of our cultivated crops is most favoured by common salt. It is known, 
 however, that the gas of salt marshes is peculiarly nourishing, and is 
 much relished by cattle, and that the grass lands along various parts of 
 our coast produce a herbage which possesses similar properties. It is 
 also said that the long tussaclc grass wh.\c\\co\ers,i\\e, Falkland Islands, 
 
 * Dr. Madden has calculated that the quantity of rain which falls at Penicuick in a y^^ar, 
 brings down upon each acre of land in that neighborhood more than GOO lbs. weight of com- 
 mon salt. Tliis would be an enormous dressing were it all to remain upon the land. 
 Heavy rains, however, probably carry oti" more from the soil than they impart to it. It is 
 the gentle showers that most enrich the fields with the saline and other matters they con- 
 tain. 
 
 t A number of failures are described in the sixth volume of the " Transact'wiis of the 
 Highland and Agricultural Society." Dr. Madden has recently shown that to nearly all 
 these cases the above principle applies — the farms on which they were tried being more or 
 less freely e.xposed to the winds from the east or west sea. — Quarterly Journal of Agri- 
 culture^ Sept. 1842, p. 574, 
 
WHEN APPLIED AS A MANURE. 347 
 
 luxuriates most when it is within the immediate reach of the driving 
 spray of the southern sea. It may well be, therefore, that among our 
 cultivated crops one may delight more in common salt than another, — 
 and if we consider how much alkaline matter is contained in the tops 
 and bulbs of the turnip and the potatoe, we are almost justified in con- 
 cluding that generally common salt will benefit green crops more than 
 crops of corn, and that it will promote more the developement of the 
 leaf and stem than the filling of the ear. 
 
 If this be so, we can readily understand how a soil may already con- 
 tain abundance of salt to supply with ease the wants of one crop, and 
 yet too little to meet readily the demands of another crop. The appli- 
 cation of salt to such a soil will prove a failure or otherwise, according 
 to the kind of crop we wish to raise. 
 
 3°. Failures have sometimes been experienced also on repeating the 
 application of salt to fields on which its first etfects were very favour- 
 able. In such cases it may be presumed that the land has been already 
 suppHed with salt, sufficient perhaps for many years' censumption, — 
 and that it now requires the application of some other substance. 
 
 If it be desired, experimentally, to ascertain whether the land already 
 contains a sufficient supply of common salt, the readiest method is to 
 collect half a pound of the soil in dry weather, to wash it well with a 
 pint or two of cold distilled water, and then to filter through paper, or 
 carefully to pour off the clear liquid after the whole of the soil has been 
 allowed to subside. A solution of nitrate of silver (common lunar-caus- 
 tic of the shops) will throw down a white precipitate, becoming purple 
 in the sun, which will be more or less copious according to the quantity 
 of salt in the soil. If this precipitate be collected, dried in an oven, 
 and weighed, every ]0 grains will indicate very nearly the presence of 
 4 grains of common salt. The quantity of this precipitate to be expect- 
 ed, even from a soil rich in common salt, is, however, very small. If 
 half a pound of the dry soil yield a single grain of salt, an acre should 
 contain about 1000 lbs. of salt where the soil is 12 inches deep — where 
 it has depth of only 6 inches, it will contain nearly 500 lbs. in every 
 acre. 
 
 8°. Chlorides of Calcium, and Magnesium. — These compounds are 
 rejected in large quantities as a refuse in some of our chemical manu- 
 factories — and they are contained, especially the latter, in considerable 
 abundance in the refuse liquor of our salt pans. They have both been 
 shown to be useful to vegetation (see Appendix), and where they are 
 easily to be obtained, they are deserving of further trials. Like com- 
 mon salt, it is generally in inland situations that they are fitted to be 
 the most useful. Where salt springs are found in the interior of Ger- 
 many, the refuse obtained by boiling down the mother liquors after the 
 separation of the salt has been often applied with advantage to the land. 
 
 Theory of the action of these chlorides. — Common salt and the chlo- 
 riiiles of calcium are not unfre(|uenily found in the sap of ])lants — they 
 may be supposed, therefore, to enter into the roots without necessarily 
 undergoing any previous decomposition. But we have already seen 
 (Lee. v., § 5), that the green leaves under the influence of the sun, 
 have the power of decomposing common salt — and no doubt the other 
 15* 
 
348 PHOSPHATE OF LIME AND EARTH OF BOKES. 
 
 chlorides also — and of giving ofT their chlorine into the surrounding air. 
 When they have been introduced into the sap therefore, by the roots, the 
 plant first appropriates so much of the chlorine they contain as is neces- 
 sary for the supply of its natural wants, and evolves the rest. When 
 common salt is tlius decomposed, soda remains behind in the sap, and 
 this is either worked up into the substance of the plant, or performs one 
 or other of those indirect functions 1 have already explained to you 
 (p. 328) when illustrating the probable action of potash and soda upon 
 the vegetable economy. When the other chlorides (of calcium or mag- 
 nesium) are decomposed, lime or magnesia remains in the sap, and is 
 in like manner either used up directly in the formation of the young 
 stem and seed, or is employed indirectly in promoting the chemical 
 changes that are continually going on in tlie sap. The living plant, 
 when in a healthy state, is probably endowed with the power of admit- 
 ting into its circulation, and of then decomposing and retaining, so much 
 only of these several chlorides, or of their constituents, as is fitted to 
 enable its several organs to perform their functions in the most perfect 
 manner. 
 
 In the soil itself, in the presence of organic matter of animal and 
 vegetable origin, common salt is fitted to promote certain chemical 
 changes, such as the production of alkaline nitrates — and probably sili- 
 cates — by which the growth of various kinds of plants is in a greater 
 or less degree increased. In the soil, also, from thek tendencj^ to deli- 
 quesce, or run into a liquid, all these chlorides attract water from the 
 air, and thus help to keep the soil in a moister state. When applied in 
 sufficient quantity they destroy both animal and vegetable life, and 
 have, in consequence, been often used with advantage for the extirpa- 
 tion of weeds, and for the destruction of grubs and other vermin that 
 infest the land. 
 
 9°. Phosphate of Lime and Earth of Bones. — The cattle that graze 
 in our fields derive, as you know, all the earthy materials of which cer- 
 tain parts of their bodies consist from the vegetables on which they feed. 
 These vegetables again must derive them from the soil. Thus the 
 earth of bones, or the phosphoric acid and lime of which it consists 
 (p. 196), must exist in the soil on which nutritive plants grow, and it 
 must occasionally occur that a soil will be deficient in these substances, 
 and will, therefore, supply them with difficulty to the crops it rears. 
 The benefit which in this country is so often experienced from the use 
 of bones as a manure, has been ascribed, in part, to the supply of bone- 
 earth, with which it enriches the land. (See Appendix, No. I.) It 
 is not, however, to be inferred from this, that wherever bones are use- 
 ful, the application of bone-earth alone — in the form of burned bones, 
 or of the native phosphate of lime, (p. 199,) will necessarily prove 
 advantageous also. Burned bones were formerly employed in Eng- 
 land, but the practice has gradually fallen into disuse, and the same is, 
 I believe, the case in Germany. This is no proof, however, that the 
 native phosphate of Estremadura — already, it is said, imported into 
 Ireland for agricultural purposes, — would not benefit many soils if ap- 
 plied in the state of a sufficiently fine powder. Until carefully con- 
 ducted experiments, however, shall have been made, and the numerical 
 
USE OF SULPHATE OF AMMONIA. 349 
 
 results precisely ascertained, it would be improper to incur much risk 
 either in bringing this substance to our shores or in applying it to our 
 fields. 
 
 10°. Silicates of Potash and Soda. — These compounds, which have 
 been already described (p. 206), are supposed to act an important 
 part in the growth of the grasses, and of the corn-bearing plants, by 
 supplying, in a soluble state to the roots, the silica which is so necessary 
 to the strength of their stems. This supposition has been strengthened 
 by the results of some experiments made by Lampadius, who found a 
 solution of silicate of potash to produce remarkable effects upon Indian 
 corn and upon rye. {Lehre von den mineralischen Dungmitteln, p. 25, 
 1833.) It is possible to manufacture them at a cheap rate, and it would 
 be desirable to ascertain by further trials how far tlie employment of 
 these compounds, as artificial manures, can be safely recommended or 
 adopted with the hope of remuneration.* 
 
 11°. Salts of Ammonia. — There is reason tobelieve that ammonia in 
 every state of combination is fitted, in a greater or less degree, to pro- 
 mote the growth of cultivated plants. None of its compounds, how- 
 ever, are known to occur anywhere in nature in such quantity as to be 
 directly available in practical agriculture, and only a very few can be 
 ])roduced by art at so low a price as to admit of their being used with 
 profit. 
 
 a. Sulphate of Ammonia. — An impure sulphate is manufactured by 
 adding sulphuric acid to fermented urine, or to the ammoniacal liquor 
 of the gas works, and evaporating to dryness. When prepared from 
 urine, it contains a mixture of those phosphates which exist in urine, 
 '?fl*id which ought to render it more valuable as a manure. The gas 
 liquor yields a sulphate which is blackened by coal tar — a substance 
 which, while not injurious to vegetation, is said to be noxious to the 
 insecis that infest our corn fields. In any of these economical forms this 
 salt has been found to promote vegetation ; but accurate experiments 
 are yet wanting to show in what way it acts — whether in promoting the 
 growth of the green parts or in filling the ear, or in both — to what kind 
 of crops it may be applied with the greatest advantage — and what 
 amount of increase may be expected from the application of a given 
 weight of the salt. It is from the rigorous determination of such points 
 (hat the practical farmer will be able to deduce the soundest practical 
 precepts, and at the same time to assist most in the advancement of 
 theoretical agriculture. 
 
 The crystallized sulphate of ammonia is soluble in its own weight of 
 water. 100 lbs. contain about 35 lbs. of ammonia, 53 lbs. of acid, and 
 1 2 lbs. of water. It may be applied at the rate of from 30 lbs. to 60 lbs. 
 per acre. 
 
 b. Sal- Ammoniac or Muriate of Ammonia. — This salt, in the pure 
 state in which it is sold in the shops, is too high in price to be economi- 
 cally employed by the practical farmer. An impure salt might, how- 
 ever, be prepared from the gas liquor, which could be sold at a sufficiently 
 
 * I have been informed by Dr. Playfair that a number of experiments with a soluble 
 silicate of soda, manufactured at Manchester, have this summer (1842) been made at hia 
 suggestion, the results of which will, no doubt, prove very interesting. 
 
350 SAL-AMMONIAC AND CARBONATE OF AMMONIA. 
 
 cheap rate to admit of an extensive application to the land.* The only 
 numerical results trora the use of this salt with which I am acquainted, 
 are those given by Mr. Fleming, who applied it at the rate of 20 lbs. 
 per acre to wheat on a heavy loam, and to winter rye, on a tilly clay, 
 both after potatoes, and obtained the following increase of produce per 
 
 acre 
 
 Grain. Straw. 
 
 Rye, undressed . 14 bushels 36^ cwt. 
 
 Do. dressed . . 19 do. 43|- do. 
 
 Increase . . ' . 5 bushels. 7 cwt. 
 
 Wheat, undressed 25 bushels, each 61 lbs. 
 Do. dressed . 264 bushels, each 62 lbs. 
 
 Increase - . . If bushels. 
 
 The increase of these experiments was not very large, but the quan- 
 tity of sal-ammoniac eraploj'ed was probably not great enough to pro- 
 duce a decided effect. It is a valuable fact for the farmer, however, and 
 not uninteresting in a theoretical point of view, that a part of the same 
 wheat field, dressed with li cwt. of common salt per acre, gave a pro- 
 duce of 40 bushels of grain (see Appendix, p. 19.) 
 
 c. Carbonate of Ammonia — is obtained in an impure form by the dis- 
 tillation of horns, hoofs, an I even bones. In this impure form it is not 
 generally brought into the market, but in this state it might possibly be 
 aff()rded at so low a price as to place it within the reach of the practical 
 farmer. It is supposed by some that this carbonate is too volatile — or 
 rises too readily in the form of vapour — to be economically applied to 
 the land. In the form of a weak solution, however, put on by a water 
 cart, or in moist showery weather simply as a top-dressing, especially 
 to grass lands and on light soils, it may be safely recommended where 
 it can be cheaply procured. 
 
 d. Ammoniacal Liquor. — This is proved by the success which has in 
 many localities been found to attend the application of the ammoniacal 
 liquor of tlw-gas works. This liquid holds in solution a variable quan- 
 tity of sulphate of ammonia and sal-ammoniac, f but in general it is 
 richest in the carbonate of ammonia. 
 
 The strength of the liquor varies in different gas works; chiefly ac- 
 cording to the kind of coal employed for the manufacture of the gas. 
 One hundred gallons may contain from 20 lbs. to 40 lbs. of ammonia, 
 in one or other of the above states of combination. No precise rule, 
 therefore, can be given for the quantity which ought to be applied to the 
 acre of land, but as the application of a larger quantity can do no harm, 
 provided it be sufficiently diluted with water, one hundred gallons may 
 be safely put on at first, and more if experience should afterwards prove 
 it to be useful. 
 
 On grass and clover, upon a heavy moist loam, Mr. Bishop applied 
 
 * By mixing, for example, the waste muriatic acid, or the waste chloride of calcium, 
 with gas liquor, and evaporating the mixture to dryness. 
 
 t Each gallon of the ammoniacal liquor of the Manchester gas-works is said to contain 
 S ounces of SdL Ammoniac. In these works the Canael coal of Wigan ia employed. 
 
SPECIAL ACTION OF THE SULPHATE AND NITRATE. 351 
 
 105 gallons an acre, diluted with 500 gallons of water, and obtained, of 
 hay, from the 
 
 Undressed ... | lb. per square yard, or 20^ cwt. per acre. 
 
 Dressed .... li lb. do. or 61i cwt. do. 
 
 Increase ... 1 lb. do. or 41 cwt.* do. 
 
 The increase herh is so very great that further trials with this liquor — 
 hitherto, in most country towns at least, allowed to run to waste — can- 
 not be too strongly recommended. On the dressed part, according to 
 Mr. Bishop, tlie Timothy grass was particularly luxuriant. 
 
 These experiments with the gas liquor show, as I have said, that im- 
 pure carbonate of ammonia may be safely applied to the land without 
 any previous i)reparation. If it is wished, however, to fix it or to ren- 
 der it less volatile — which in warm and dry seasons may sometimes be 
 desirable — this may be effected by mixing it with powdered gypsum, in 
 the proportion of 1 lb. to each gallon of the ammoniacal liquor, or by 
 adding directly sulphuric acid, or the waste of muriatic acid of the al- 
 kali works. + 
 
 e. Nitrate of Ammqnia. — If it be correct that those substances act 
 most powerfully as manures which are capable of yielding the largest 
 quantity of nitrogen to plants, the nitrate of ammonia ougiit to promote 
 vegetation in a greater degree than almost any other saline substance we 
 could employ. According to the experiments of Sir H. Davy, (Davy's 
 Agricultural Chemistry^ Lecture VII.) however, this does not appear 
 to be the case, though Sprengel has found it more efficacious than the 
 nitrates either of potash or of soda. This question as to the relative 
 action of the nitrate of ammonia is very interesting theoretically, but it 
 directly concerns practical agriculture very little, since the high price 
 of this salt is likely to prevent its being ever employed in the ordinary 
 operations of husbandry. 
 
 /. Special action of the different Salts of Ammonia. — The theory of 
 the action of ammonia itself upon vegetation I have in a former lecture 
 (p. 164) endeavoured to explain to you. But the special action of the 
 several saline compounds of ammonia above described will depend upon 
 the qualities of the acid with which it may be in combination. 
 
 The sulphate will partake of the action of the sulphates of potash, 
 soda, or lime (gypsum), — in so far as it may be expected to exhibit a 
 more marked effect upon the leguminous than upon the corn crops, and 
 upon the produce of grain than on the growth- of the leaves and the 
 stem. This special action may be anticipated from the sulphuric acid 
 it contains. And if this reasoning from analogy be correct, we should 
 expect the sulphate of ammonia to rank among the most useful of ma- 
 nures — since ihe one constituent (ammonia) will promote the general 
 growth of the plant, while the other will expend its influence more in 
 the filling of the ear. 
 
 The nitrate again has been found to act more upon the crops of corn 
 than upon the leguminous plants and clovers (Sprengel) — a result which 
 
 ' Prize Essays of the Highland Society, xiv., p. 359. 
 
 t 100 gallons thus saturated with acid will convey to the soil about 100 Iba. of sulphate of 
 ammonia or of sal-ammoniac. 
 
352 MIXTURE OF NITRATE WITH SULPHATE OF SODA. 
 
 is to be explained by the absence of sulphuric acid, which appears to 
 aid especially in the development of the latter class of plants. 
 
 On this subject, however, experiments are too limited in number, in 
 general too inaccurately made, and our information in consequence too 
 scanty, to enable us as yet to arrive at satisfactory conclusions. 
 
 12°. Mixed Saline Manures. — The principle already so frequently 
 illustrated, that plants require for their rapid and perfect development 
 a sufficient supply of a considerable number of different inorganic sub- 
 stances, will naturally suggest to yon that in our endeavours to render 
 a soil productive, or to increase its fertility, we are more likely to suc- 
 ceed if we add to it a mixture of several of those substances, than if we 
 dress it or mix it up with one of them only. This theoretical conclu- 
 sion is confirmed b^' universal experience. 
 
 Nearly all the natural manures, whether animal or vegetable, which 
 are applied to the land, contain a mixture of saline substances, each of 
 which exercises its special effect upon the after-crop — so that the final 
 increase of produce obtained by the aid of these manures, must be as- 
 cribed not to the single action of one of their constituents, but to the 
 joint action of all. An important practical problem, therefore, pro- 
 pounded by scientific agriculture in its present state, is — what mixtures 
 of saline substances are most likely to be srencrally useful, what others 
 specially useful, to this or to that crop? The complete solution of this 
 problem will require the joint aid of chemical theory and of agricultu- 
 ral experiment, — of experiments often varied and probably long con- 
 tinued. But that we may finally expect to solve it, will appear from 
 what has already been accurately observed in regard to the effect of 
 certain artificial mixtures upon some of our cultivated crops. Thus — 
 
 a. Mixture of Nitrate ivith Sulphate of Soda. — If, instead of dressing 
 young potatoes with nitrate or with sulphate of soda alone (page 331), 
 we employ a mixture of the two, the growth of the plant is much more 
 promoted and the crop of potatoes much more largely increased. Thus 
 Mr. Fleming (in 1841) ap])lied to his potatoe crop a mixture of equal 
 weights of nitrate and of dry sulphate of soda, in the proportion of 200 
 lbs. of the^ixture to the imperial acre, with the following remarkable 
 result : — 
 
 Undressed, ... 66 bolls, each 5 cwt., per acre. 
 Dressed, .... 107 bolls. 
 
 Increase, ... 41 bolls,* or 10 tons per acre ! 
 The stems also were six and seven feet high. The addition of nitrate 
 of soda to a portion of the same field gave a produce of only 80 bolls. 
 Similar effects, of which, hov/ever, I have not yet obtained the numeri- 
 cal results, have been observed on the same crop in various localities 
 during the present season (1842). 
 
 The effect of this one artificial mixture holds out the promise of 
 mucii good hereafter to be obtained by the judicious trial of other mix- 
 tures — probably of a greater number of substances — upon all the crops 
 we are in the habit of raising for food. 
 
 h. Wood ashes. — This opinion is strengthened by the effects which 
 * See Appendix, p. 20. 
 # 
 
COMPOSITION OF WOOD ASHES, AND USE AS A MANURE. 353 
 
 have almost universally been found to follow the use of wood ashes and 
 of the ash of other vegetables in the cultivation of the land. 
 
 The quahty of the ash left by plants when burned varies, as we have 
 already had oncasion to remark (p. 216), with a variety of circum- 
 stances. It always consists, however, of a mixture in variable propor- 
 tions of carbonates, silicates, sulphates, and phosphates of potash, soda, 
 lime, and magnesia, with certain other substances present in smaller 
 quantity, yet more or less necessary, it may be presumed, to vegetable 
 growth. Thus, according to Sprengel, the ash of the red beech, the oak 
 and the Scotch fir ( pinus syhestris), consists of 
 
 ■D A -D^ V. rk V Scotch Pitch Pine. 
 
 Red Beech. Oak. p^^ (Berthier.) 
 
 Silica 5-52 2G 95 659 750 
 
 Akmtiina 2'33 
 
 Oxide of Iron. . . . 377 8-14 1703 IMO 
 
 Oxide of Manganese . 3.85 — — 2 75 
 
 Lime 2500 1738 2318 1360 
 
 Magnesia 500 1-44 5-02 4-35 
 
 Potash 2211 16 20 2-20 14-10 
 
 Soda 3-32 6-73 2 22 20-75 
 
 Sulphuric Acid ... 7-64 336 2-23 3-45 
 
 Phosphoric Acid. . . 5-62 1-92 2-75 0-90 
 
 Chlorine 1-84 241 230 
 
 Carbonic Acid . . . 1400 15-17 3648 17-50 
 
 100 100 100 960 
 
 The composition of these different kinds of ash is very unlike — that 
 of the pitch pine, for example, being greatly richer in potash and soda, 
 arid poorer in lime and phosphoric acid, than that of the Scotch fir — 
 while the beech is richer than any of the others in potash and lime and 
 in the sulphuric and phosphoric acids. The several effects of diflTerent 
 kinds of wood ashes when applied to the land will therefore be diflTerent 
 also. 
 
 In England, wood ashes are largely employed in many districts, 
 mixed widi bone dust, as a manure for turnips, and often with great 
 success. As much as 15 bushels (7^ cwi.) of ashes are drilled in per 
 acre w^ith 15 bushels (6 cwt.) of bones. The large quantity of alkali 
 present in the turnip crop (p. 219) may be supposed to explain the 
 good effects which wood ashes have upon it, and may lead us to expect 
 that they would in a similar degree increase the produce of the carrot 
 and of the potatoe.* 
 
 The immediate benefit of wood ash is said to be most perceptible upon 
 leguminous plants (Sprengel), such as lucerne, clover, peas, beans, and 
 vetches. As a top-dressing to grass lands it roots out the moss and pro- 
 motes the growth of white clover. Upon red clover it^ effects will be 
 more certain if previously mixed with one fourth of its weight of gyp- 
 sum. In small doses of two or three hundred weight (4 to 6 bushels) 
 it may be safely applied even to poor and thin soils, but in large and 
 repeated doses its effects will be too exhausting, unless the soil be either 
 
 * This inference has been verified by Mr. Wharton, of Dryburn, who has obtained an 
 excellent crop of potatoes from newly ploughed-out land by manuring with wood ashes 
 only. 
 
354 SPONTANEOUS COMBUSTION OF WOOD ASHES. 
 
 naturally rich in vegetable matter, or be mixed from year to year with a 
 sufficient quantity of animal or vegetable manure. 
 
 In so far as the immediate effect of wood ashes is dependent upon the 
 soluble saline matter they contain, their effect maj'- be imitated by a 
 mixture of crude potash with carbonate and sulphate of soda, and a lit- 
 tle common salt. The wood ash of this country contains only about 
 one-fifteenth of its weiglit of soluble matter (Bishop Watson), so that 
 the following quantity of such a mixture would be nearly equal in effi- 
 cacy to the saline matter of one ton of wood ash. 
 
 Crude of Potash 60 lbs. at a cost of 15s. 
 
 Crsytallized Carbonate of Soda . . 60 " " " 7s. 
 
 Sulphate of Soda 20 " > „ 
 
 Common Salt 20 " J 
 
 2s. 
 
 160 24s. 
 
 Where the wood ash costs only a shilling a bushel (or c€2 a ton), it 
 would obviously be more economical to employ this mixture, were the 
 efficacy of wood ashes dependent solely upon the soluble saline matter 
 they are capable of yielding on the first washing with water. But they 
 contain also a greater or less quantity of imperfectly burned carbonace- 
 ous matter, the effect of which upon vegetation cannot be precisely 
 estimated, and a large proportion — nine-tenths, perhaps, of their whole 
 weight — of insoluble carbonates, silicates, and phosphates of yiotash, 
 lime, and magnesia, which are known more permanently to influence 
 the fertility of the land to which they are applied.* 
 
 c. Washed or lixiviated wood-ashes. — In countries where wood ashes 
 
 are washed for the manufacture of the pot and pearl ash of commerce 
 
 • 
 ' Some discussion has lately arisen in America (Siltimmi's Journal^ xlii. p. 165, and 
 xliii. p. 80), in regard to the fact, in itself sufficiently interesting, that wood ashes, when 
 thrown together in heap^, not unfrequently take fire, becoming red hot throughout their 
 whole mass, and sometimes occasioning serious accidents. Such ash^s always contain a 
 quantity of minutely divided carbonaceous matter, which, like the impalpable charcoal 
 powder of the gunpowder manufactories, may have the property of absorbing much air 
 info its pores, and of thus undergoing a spontaneous elevation of temperature. I tlirow it 
 out, however, as a more probable conjecture, that during the combustion of the wood a 
 portion of flTe^btash has been decomposed by the charcoal, and converted info potassium 
 (potash consisting of potassium and oxygen, p. 187. When exposed to the air and to 
 moisture this potassium gradually absorbs oxygen and spontaneously burns, again form- 
 ing potash. That such a decomposition may take place where wood or other vegetable 
 mntter is burned with little access of air will, readily be granted, but it is not so obvious 
 (hat it can take place in an open fire. But even in an open fire, or in an open capsule, par- 
 ticles of potassium may remain in the pores of the imburned charcoal, or more frequently 
 may be covered over with a glaze of melted potash, by which further combustion will be 
 prevented. That this really does happen, any one must have satisfied him.'^elf who has 
 been in the habit of burning vegetable substances for the purpose of determining the pro- 
 portion of ash they leave. The glaze of melted alkaline matter often renders the com- 
 plete combustion a very difficult and tedious matter. That potassium is formed during this 
 process is rendered further probable by the observation that the quantify of potash ob- 
 tained from wood or other vegetable ash is less when the wood has been burned at a high 
 than a low temperature. The potassium, which is volatile, may have been dissipated in 
 vapour. 
 
 It is probable that a spontaneous combustion similar to that observed in America may 
 occasionally take place in the heaps of ashes left to stand upon our fields after paring and 
 burning— and hence probably has arisen the prnctical rule, fo spread (he ashes as soon as 
 possible after the burning is i^nished. If allowed to remain, tliey are said "?o take hold of 
 the land," and when it is of clay, to burn it into brick. An instance of such combustion is 
 mentioned as having occurred at Chatteris, in the Isle of Ely, where an entire common 
 was burned 16 or 18 inches deep, down to the very gravel.— See British Husbandry, II., 
 p. 350. 
 
COMPOSITION OF LIXIVIATED WOOD ASHES. 355 
 
 (p. 187), this insoluble portion collects in large quantities. It is also 
 present in the refuse of the soap maimers, where wood ash is em- 
 ployed for the manufacture of soft soap. The composition of this inso- 
 luble matter varies very much, not only with the kind of wood from 
 which the ash is made, but also with the temperature it is allowed to 
 attain in burning. The former fact is illustrated by the following analy- 
 sis made by Berthier, of the insoluble matter left by the ash of five dif- 
 ferent species of wood carefully burned by himself: — 
 
 Oak. Lime. Birch. Pitch Pine. Scotch Fir. Beech. 
 
 Silica ..... 3-8 
 
 20 
 
 5-5 
 
 130 
 
 4-6 
 
 5-8 
 
 Lime 548 
 
 51-8 
 
 52-2 
 
 27-2 
 
 423 
 
 426 
 
 Magnesia .... 0-6 
 
 2-2 
 
 30 
 
 87 
 
 10-5 
 
 70 
 
 Oxide of Iron . . — 
 
 01 
 
 05 
 
 22-3 
 
 01 
 
 1-5 
 
 Oxide of Manganese — 
 
 0-6 
 
 35 
 
 5-5 
 
 0-4 
 
 4-5 
 
 Phosphoric Acid . 08 
 
 2-8 
 
 4-3 
 
 1-8 
 
 10 
 
 5-7 
 
 Carbonic Acid . . 396 
 
 39-8 
 
 310 
 
 215 
 
 360 
 
 32-9 
 
 Carbon .... — 
 
 — 
 
 — 
 
 — 
 
 4-8 
 
 — 
 
 99-6 
 
 100 
 
 100 
 
 100 
 
 99 7 
 
 100 
 
 The numbers in these several columns differ very much from each 
 otlier, but the constitution of the insoluble part of the ash he obtained 
 probably differed in every case from that which would have been left 
 by the use of the same wood burned on the large scale, and in the open 
 air. This is to be inferred from the total absence of potash and soda in 
 the lixiviated ash — while it is well known that common lixiviated wood 
 ash contains a notable quantity of both. This arises from the high tem- 
 perature at which wood is commonly burned, causing a greater or less 
 portion of the potash and soda to combine with the silica, and to form 
 insoluble silicates, which remain behind along with the lime and other 
 earthy matter, when the ash is washed with water. It is to these sili- 
 cates, as well as to the large quantity of lime, magnesia, and phosphoric 
 acid it contains, that common wood ash owes the more permanent effects 
 upon the land, which it is known to have produced. When the rains 
 have washed out or the crops carried off" the more soluble part from the 
 soil, these insoluble compounds still remain to exercise a more slow and 
 enduring influence upon the after- produce. 
 
 Still from the absence of this soluble portion, the action of lixiviated 
 wood ash is not so apparent and energetic, and it may therefore be safely 
 added to the land in much larger quantity. Applied at the rate of two 
 tons an acre, its effects have been observed to continue for 15 or 20 
 years. It is most beneficial upon clay soils, and it is said especially to 
 promote the growth of oats. 
 
 I am not aware that in any part of the British Islands this refuse ash 
 is to be obtained in large quantity, but in North America much of it is 
 thrown away in waste, which might be advantageously restored to the 
 land on which the wood had grown. 
 
 d. Kelp is the name given in this country* to the ash left by marine 
 plants when burned. It used to be extensively prepared in the Western 
 
 • In Brittany and Normandy it is called varec, while that of Spain is known by the name 
 of barilla. 
 
356 
 
 COMPOSITION AND USE OF KELP. 
 
 Islands, but the low price at which carbonate of soda can now be man- 
 ufactured has so reduced the price and the demand for kelp as almost 
 to drive it from the market. As a natural mixture, however, which 
 can now be obtained at a cheap rate (about c£3 a ton), and which has 
 been proved to be useful to vegetation in a high degree, (Prize Essays 
 of the Highland Society, vols. 1 and 4,) it is very desirable that accu- 
 rate experiments should l)e instituted with the view of determining the 
 precise extent of its action, as well as the crops and soils to which it can 
 be most advantageously and most economically applied. 
 
 Like wood ashes, kelp varies in composition with the species and age 
 of the marine plants (sea weeds) from which it is prepared, and like 
 them also it consists of a soluble and insoluble portion. Two samples 
 from different locaUties in the Isle of Skye, analyzed by Dr. Ure, (Dic- 
 tionary of Arts and Manufactures, p. 726), consisted of — 
 
 Soluble Portion. 
 Carbonate of Soda with Sulphuret of Sodium 
 
 Sulphate of vSoda 
 
 Common Salt 
 
 Chloride of Potassium .... 
 
 
 
 Normandy, 
 
 Jeisker. 
 
 Rona. 
 
 Gay-Lussac. 
 
 8-5 
 
 5-5 
 
 — 
 
 80 
 
 190 
 
 — 
 
 ^36-5 
 
 37-5 
 
 5 560 
 {25 
 
 530 
 
 620 
 
 
 240 
 
 100 
 
 
 
 8-0 
 
 — 
 
 — 
 
 90 
 
 100 
 
 — 
 
 — 
 
 95 
 
 — 
 
 60 
 
 8-5 
 
 — 
 
 100 
 
 100 
 
 
 Insoluble Portion 
 Carbonate of Lime . 
 Silica .... 
 Alumina and Oxide of Iron 
 Gypsum .... 
 Sulphur and loss 
 
 Besides these constituents, however, the .soluble portion contains 
 iodide of potasium or sodium in variable quantity, and the insoluble 
 more or less of potash and soda in the state of silicates. 
 
 Kelp may be applied to the land in nearly the same circumstances as 
 wood-ash — but for this purpose it would probably be better to burn the 
 sea weed at a lower temperature than is usually employed. By this 
 means, being prevented from melting, it would be obtained at once in 
 the state of a fine powder, and would be richer in potash and soda. 
 
 It might lead to important results of a practical nature, were a series 
 ai" precise experiments made with this finely divided kelp as a manure* 
 — especially in inland situations — for though the variable proportion of 
 its constituents will always cause a degree of uncertainty in regard to 
 the action of the ash of marine plants — yet if the quantity of chloride 
 of potassium it contains to be on an average nearly as great as is stated 
 above in the analysis of Gay-Lussac — kelp will really be the cheapest 
 form in which we can at present apply potash to the land. 
 
 e. Straw ashes. — The ashes obtained by burning the straw of oats, 
 barley, wheat, and rye, contain a natural mixture of saline substances, 
 which is exceedingly valuable as a manure to almost every crop. The 
 
 * For some other suggestions on this subject, I beg to refer the reader to the Prize Es- 
 says and Transactions of the Highland and Agricultural Society^ xiv., p. 508. 
 
SOILS ON WHICH STRAW ASH MAT BE USED. 357 
 
 proportion of the several constituents of this mixture, however, is differ- 
 ent, according as the one or the other kind of straw is burned. Thus, 
 100 parts of each variety of ash — in the samples analyzed by Sprengel 
 {Chcmie, II.) — consisted of — 
 
 
 Oats. 
 
 Barley. 
 
 Wheat. 
 
 Rye. 
 
 Rape. 
 
 Potash . 
 
 . 15-2 
 
 34 
 
 06 
 
 12 
 
 18-8 
 
 Soda 
 
 . trace. 
 
 09 
 
 0-8 
 
 04 
 
 11-2 
 
 Lime 
 
 . 26 
 
 10-5 
 
 6-8 
 
 6-4 
 
 16-9 
 
 Magnesia 
 
 . 04 
 
 1-4 
 
 09 
 
 0-4 
 
 31 
 
 Silica 
 
 . 800 
 
 73-5 
 
 81-6 
 
 82-2 
 
 21 
 
 Alumina 
 
 01 
 
 2-8) 
 
 
 
 
 Oxide of Iron . 
 
 . trace. 
 
 02 V 
 
 26 
 
 0.9 
 
 2-3 
 
 Oxide of Manganese 
 
 . trace. 
 
 0-3 S 
 
 
 
 
 P!iosi)lioric Acid 
 
 . 0-2 
 
 35 
 
 4-8 
 
 1-8 
 
 99 
 
 Sulphiu-ic Acid 
 
 14 
 
 2 2 
 
 10 
 
 61 
 
 133 
 
 Chlorine . 
 
 01 
 
 1-3 
 
 09 
 
 0-6 
 
 11-4 
 
 Carbonic Acid 
 
 — 
 
 — 
 
 — 
 
 — 
 
 110 
 
 100 100 100 100 100 
 
 The most striking diflTerences in the above table are the comparatively 
 InriiP quantity of potash in the oat straw — of lirne in that of barley — 
 of phosphoric acid in that of wheat — of sulf)huric acid in that of rye — 
 and of all the saline substances in rape straw. These differences are 
 not lo be considered as constant, nor will the numbers in any of the 
 above columns represent correctly the composition of the ash of any 
 variety of straw we may happen to burn (see p. 183), but they may 
 be safely depended upon as showing the general comj)osition of such 
 ashes, as well as the general differences which may be expected to pre- 
 vail among them. 
 
 That such ashes should prove useful to vegetation might be inferred 
 not only from their containing many saline substances which are known 
 to act beneiiciaily when applied to the land, but from the fact that they 
 have actually been obtained from vegetable substances, i^ inorganic 
 matter be necessary to the growth of wheat, then surely the mixture of 
 such matters contained in the ash of wheat straw is more likely than 
 any other we can apply to promote the growth of the young wheat 
 plant. A question might even be raised, whether or not in some soils, 
 rich in vegetable matter, the ash alone would not produce as \isible an 
 effect upon the coming crop, as the direct application of the straw, either 
 in the dry state or in the form of rotted farm-yard manure. And this 
 ([uestion would seem to be answered in the aflfirmalive, by the result 
 of many trials of straw ashes which have been made in Lincolnshire. 
 In this county the ash of five tons of straw has been found superior in 
 efficacy to ten tons farm-yard manure, (Survey of Lincolnshire, p. 
 304, quoted in British Husbandry, II., p. 334.) This is perfectly con- 
 sistent with theory, yet as veeetable matter appears really essential to a 
 fertile soil, and as the quantity of this vegetable matter is lessened in 
 some degree by every corn crop we raise, it cannot be good husbandry 
 to manure for a succession of rotations with saline substances only. 
 The richest soil by this procedure must ultimately be exhausted. On 
 the other hand, where much vegetable matter exists, and especially 
 what is usually called inert vegetable matter, it may be an evidence of 
 
358 COMPARATIVE EFFECTS OF STRAW AND STRAW ASH. 
 
 great skill in the practical farmer to apply for a time the ashes only of 
 his straw — or some other saline mixture to his land. 
 
 The practice of burning the stubble on a windy day has been found 
 in the East Riding of Yorkshire to produce better clover, and to cause 
 a larger return of wheat, (British Husbandry, ii., p. 333) — for this 
 purpose, however, the stubble must be left of considerable length. la 
 Germany, rape straw — which the above table shows to be rich in saline 
 and earthy matter, and, therefore, exhausting to the land — is spread 
 over the field and burned in a similar manner. The destruction of 
 weeds and insects which attends this practice, is mentioned as one of its 
 collateral advantages, (Sprengel, Lehre vom Diinger, p. 355.) 
 
 In l1ie United States, where, according to Captain Barclay, the st^aw 
 is burned merely in order that it may be got rid of, (Agricultural Tour 
 in the United States, pp. 42 and 54,) it would cost little labour to apply 
 the ash to the soil from which the straw was reaped, while it would 
 certainly enlarge the future produce — and in Little Russia, where front 
 the absence of wood the straw is universally burned for fuel, and the 
 ashes afterwards consigned to the nearest river, the same practice 
 might bo beneficially adopted. However fertile, and apparently inex- 
 haustible, the soils in this country may appear, the time must come 
 when the present mode of treatment will have more or less exhausted 
 their productive powers. 
 
 It is not advisable, as I have already said, wholly to substitute the 
 ash for the straw in ordinary soils, or in any soils for a length of time, 
 yet that it may be partially so substituted with good effect — or that straw 
 ashes will alone give a large increase of the corn crop, and therefore 
 should never be wasted — is shown by the following comparative experi- 
 ments, conducted as such experiments should be, during an entire rota- 
 tion of four years. The quantity of manure applied, and the produce 
 per imperial acre, were as follows : 
 
 15 cwt. barley 3 tons stable dung 2 tons of rotten 
 No manure. straw burned in the straw dung eight 
 
 on the ground. state. months old. 
 
 1°. Turnips, 22 lbs. 8* cwt. I8f cwt. \&% CMrt. 
 
 2°. Barley, U% bush. 30^ bush. 30i bush. 30f bush. 
 
 3<^. Clover, 8 cwt. 18 cwt. 20 cwt. 21 cwt. 
 
 4°. Oats, 32 bush. 18 bush. 38 bush. 40 bush. 
 
 The kind of soil on which this experiment was made is not slated, 
 (British Husbandry, ii., p. 248,) but it appears to show, as we should 
 Expect, that the effects of straw ash are particularly exerted in promot- 
 ing the growth of the corn plants and grasses which contain much sili- 
 ceous matter in their stems — in short, of plants similar to those from 
 which the ash has been derived. 
 
 Theory of the action of straw ash. — That it should especially pro- 
 mote the growth of such plants appears most natural, if we consider 
 only the source from which it has been obtained, but it is fully ex- 
 plained by a further chemical examination of the ash itself. The so- 
 luble matter of wood ash in general contains but a small quantity of 
 silica — while that part of the straw ash which is taken up by water 
 contains very much. Thus a wheat ash analyzed by Berthier contained 
 of— 
 
COMPOSITION AND USE OF DUTCH ASHES. 
 
 359 
 
 Soluble salts 
 Insoluble matter 
 
 19 per cent. 
 
 81 " 
 
 100 
 
 and that which was dissolved by water consisted of 
 
 Silica 
 
 Chlorine . 
 Potash and soda 
 Sulphuric acid ■. 
 
 35 per cent. 
 13 " 
 50 " 
 2 « 
 
 100 
 
 so that it was a mixture of soluble silicates and chlorides with a little 
 sulpiiale of potash and soda. These soluble silicates will find an easy 
 admission into the roots of plants, and will readily supply to the young 
 stems of the corn" plants and grasses the silica which is indispensable to 
 their healthy growth. 
 
 /. Turf or peat ashes, obtained by the burning of peat of various 
 qualities, are also applied with advantage to the land in many districts. 
 They consist of a mixture in which gypsum is usually the predominat- 
 ing useful ingredient — the alkaline salts being present in very small 
 proportion. Of ashes of this kind those made in Holland, and 
 generally distinguished by the name of Dutch ashes, are best known, 
 and have been most frequently analyzed. The following table exhi- 
 bits the composition of some varieties of ashes from the peat of Hol- 
 land and from the heath of Luueburg, examined by Sprengel : — 
 
 Dutch Ashes (grey). 
 
 Best 
 quality. 
 Silica 471 
 
 Alumina ... 
 Oxide of Iron . 
 Do. of Manganese 
 Lime .... 
 Magnesia . . . 
 Potash ... 
 Soda , . . . , 
 
 4-5 
 66 
 10 
 136 
 4-9 
 02 
 10 
 
 Sulphuric Acid 7*2 
 
 Phosphoric Acid .... 2-0 
 
 Chlorine 1-2 
 
 Carbonic Acid 4*1 
 
 Charred Turf 66 
 
 Inferior 
 quality. 
 55-9 
 35 
 5-4 
 4-3 
 8-6 
 1-6 
 0-2 
 3-9 
 
 6-4 
 
 0-8 
 
 30 
 6.4 
 
 Worst 
 quality. 
 70-4 
 41 
 41 
 0-2 
 6.1 
 3-9 
 01 
 0-4 
 
 3-4 
 
 1-3 
 
 0-5 
 5-5 
 
 Luneburg Ashes (reddish). 
 
 6-2 
 
 Gypsum 
 0-2 
 
 Phosph. of Lime 
 1-2 0-2 
 
 Common Salt 
 01 01 
 
 4-4 120 
 
 1000 1000 100-0 1000 1000* 
 
 In the most useful varieties of these ashes it appears, from the above 
 analyses, that lime abounds — partly in combination with sulphuric and 
 phosphoric acids, forming gypsum and phosphate of lime — and partly 
 with carbonic acid, forming carbonate. These compounds of lime, 
 therefore, may be regarded as the active ingredients of peat ashes. 
 
 • Sprengel Lehre vom Danger, p. 363 et seq. 
 
360 COMPOSITION AND USE OF COAL ASHES. 
 
 \el the small quantity of saline matter they contain is not to be con- 
 sidered as wholly without effect. For the Dutch ashes are often ap- 
 plied to the land to the extent of two tons an acre — a quantity which, 
 eren when the proportion of alkali does not exceed one per cent., will 
 contain 45 lbs. of potash or soda, equal to twice that weight of sulphates 
 or of common salt. To the minute quantity of saline matters present in 
 them, therefore, peat ashes may owe a portion of their beneficial in- 
 fluence, and to the almost total absence of such compounds from the 
 less valuable sorts, their inferior estimation may have in part arisen. 
 
 In tlolland, when applied to the corn crops, they are either ploughed 
 in, drilled in with the seed, or applied as a top dressing to the young 
 shoots in autumn or spring. Lucerne, clover, and meadow grass are 
 dressed with it in spring at the rale of 15 to 18 cwt. per acre, and the 
 latter a second time with an equal quantity after the first cutting. In 
 Belgium the Dutch ashes are applied to clover, rape, potatoes, flax, 
 and peas — but never to barley. In Luneburg the turf ash which 
 abounds in oxide of iron is applied at the rate of 3 or 4 tons per acre, 
 and by this means the physical character of the clay soils, as well as 
 their chemical constitution, is altered and improved. 
 
 In England peat is in many places burned for the sake of the ashes 
 it yields. Among the most celebrated for their fertilizing qualities are 
 the reddish turf ashes of Newbury, in Berkshire. The soil from be- 
 neath which the turf is taken abounds in lime, and the ashes are said to 
 contain from one-fourth to one-third of their weight of gypsum, [Bri- 
 tish Husbandry, ii., p. 334.] They are used largely both in Berkshire 
 and Hampshire, and are chiefly applied to green crops, and especially 
 to clover.* 
 
 g. Coal ashes are a mixture of which the composition is very varia- 
 ble. They consist, however, in general, of lime often in the state of 
 gypsum, of silica, and of alumina mixed with a quantity of bulky and 
 porous cinders or half burnt coal» The ash of a coal from St. Etienne, 
 in France, after all the carbonaceous matter had been burned away, 
 was found by Berthier to consist of 
 
 Akimiiia, insoluble in acids 
 Alumina, soluble 
 Lime .... 
 
 Magnesia .... 
 Oxide of Manganese 
 Oxide and Sulphuret of Iron 
 
 100 
 
 Such a mixture as this would no doubt benefit many soils by the 
 alumina as well as by the lime and magnesia it contains; but in the 
 English and Scotch coal ashes a small quantity of alkaline matter, 
 chiefly soda,f is generally present. The constitution of the ash of our 
 best coals, therefore, may be considered as very nearly resembling that 
 of peat ash, and as susceptible of similar applications. When well 
 
 * 50 bushels per acre (at 3d. a bushel, or 12s. 6d. an acre) increase the clover crop fully 
 one fifth Morton " On Soils," p. 170. 
 
 t From the common salt with which our coal is so often impregnated. 
 
 62 
 
 per 
 
 cent. 
 
 5 
 
 
 
 6 
 
 
 
 8 
 
 
 
 3 
 
 
 
 16 
 
 
 
CATfE ASHES. — CRUSHED AND DECAYED TRAPS AND LAVAS. 361 
 
 burned, it can in many cases be applied with good effects as atop-dress- 
 ing to grass lands which are overgrown with moss ; while the admix- 
 ture of cinders in the ash of the less perfectly burned coal produces a 
 favourable physical change upon strong clay soils. 
 
 h. Cane Ashes. — I may allude here to the advantage which in sugar- 
 growing countries may be obtained from the restoration of the cane ash 
 to the fields in which the canes have grown. After the canes have been 
 crushed in the mill they are usually employed as fuel in boiling down 
 the syrup; and the ash, which is not unfrequenily more or less melted, 
 is, I believe, almost uniformly neglected — at all events, is seldom aj)- 
 plied again to the land. According to the principles I have so often 
 illustrated in the present Lectures, such procedure must sooner or later 
 exhaust the soil of those saline substances which are most essential to 
 the growth of the cane plant. If the ash were applied as a top-dressing 
 to the young canes, or put into the cane holes near the roots — having 
 been previously mixed with a quantity of wood-ash, and crushed if it 
 happen to have been melted — this exhaustion would necessarily take 
 place much more slowly. 
 
 i. Crushed Granite. — We have already seen that the felspar existing 
 in granite contains much silicate of potash and alumina. It is, in fact, 
 a natural mixture, which in many instances may be beneficially applied, 
 especially to soils which abound in lime. It is many years since Fuchs 
 proposed to manufacture potash from felspar and mica by mixing them 
 with quicklime, calcining in a furnace, and then washing with wafer. 
 By this means he said felspar might be made to yield one- fifth of iis 
 weight of potash. (Journal of the Royal Institution, I., p. 184.) Mr. 
 Prideaux has lately proposed to mix up crushed granite and quicklime, 
 to slake them together, and to allow the mixture to stand in covered 
 heaps for some months, when it may be applied as a top-dressing, and 
 will readily give out potash to the soil. Fragments of granite are easi- 
 ly crushed when they have been previously heated to redness, and there 
 can be little doubt, I think, that such a mixture as that recommended 
 by Mr. Prideaux would unite many of the good effects of wood ashes 
 and of lime. 
 
 k. Crushed Trap. — I need not again remind you of the natural fer- 
 tility of decayed trap soils (Lee. XII., §4,) and of the improvement which 
 in many districts may be effected by applying them to I he land. When 
 granite decays, the potash of the felspar is washed out by the rains, and 
 an unproductive soil remains — when trap decays, on the other hand, the 
 lime by which it is characterised is not soon dissolved out, so that the 
 soil which is produced is not only fertile in itself, but is capable of being 
 employed as a fertilizing mixture for other soils. Thus when it is much 
 decayed it is dug out from pits both in Cornwall and in Scotland, and 
 is applied like marl to the land. 
 
 I. Crushed Lavas. — Of the fertile and fertilizing nature of the crushed 
 or decayed lavas I have also already spoken to you (Lee. XII., § 4). 
 In St. Michael's, one of the Azores, the natives pound the volcanic mat- 
 ter and spread it on the ground, where it speedily becomes a rich mould 
 capable of bearing luxuriant crops. At the foot of Mount Etna, when- 
 ever a crevice appears in the old lavas, a branch or joint of an Opuntia 
 
362 EXPERIMENTS WITH MIXED MANURES. 
 
 {Cactus Opuntia, — European Indian-Fig) is stuck in, when the rootsin- 
 sinuate themselves into every fissure, expand, and finally break up the 
 lava into fi-agments. These plants are thus not only the means of pro- 
 ducing a soil, but they yield also much fruit, which is sold as a refresh- 
 ing food throughout all the towns of Sicily. (Decandolle, quoted in the 
 Quart. Journ. of Agr., IV. p. 737.) 
 
 These are all so many natural mineral mixtures of which we may 
 either directly avail ourselves, or which we may imitate by art. 
 
 Experiments with mixed manures. 
 
 Note. — As a valuable appendix to the preceding observations on 
 mixed manures, I am permitted to insert the following very interesting 
 results obtained during the present season, 1842, from experiments made 
 on the estate of Mr. Burnet, of Gadgirth, near Ayr. The crop to which 
 the several manures were applied was wheat of the eclipse variety, sown 
 on the 29th of October, ]841, and reaped on the 15th of August last. 
 The soil is a loam with subsoil of clay, tile drained and trenched plough- 
 ed. It had been in beans the previous year, and gave six quarters per 
 acre, which were sold at 46s. a quarter. No manure had been applied 
 with the bean crop, and except a good dose of lime before sowing the 
 wheat, nothing but the saline mixtures mentioned below was applied 
 with this latter crop. 
 
 Application per imperial acre. 
 
 PRODUCE. 
 
 Weight per 
 bushel. 
 
 100 lbs. grain 
 
 produced of 
 
 fine flour. 
 
 Straw. Grain. 
 
 cwt. bush. lbs. 
 
 lbs. 
 
 lbs. 
 
 351 39 54 
 
 60 
 
 66i 
 
 441 49 6 
 
 60 
 
 631 
 
 Sulphate of Ammonia, 2 cwt.* ) 
 
 Wood-ashes, 4 cwt \ 
 
 vSulphate of Ammonia, 2 cwt. 
 Sulphate of Soda, 2 cwt. . . 
 
 Wood-ashes, 4 cwt 
 
 Sulphate of Ammonia, 2 cwt. ) »■ 
 
 Common Salt, 2 cwt. ... ^ 45 49 60 , 65j 
 
 Wood-ashes^ 4 cwt. . . . ) 
 
 Sulphate of Ammonia, 2 cwt. ) 
 
 Nitrate of Soda. 1 cwt. - • ( 44i 48 20 59 54| 
 
 Wood-ashes, 4 cwt. . . . j 
 
 No Application 29 » 31 38 GU 76§ 
 
 The reader will observe here that though the first mixture produced 
 a large increase both of straw and grain, a still larger additional increase 
 was caused by mixing with the substances of which it consisted either com- 
 mon salt or sulphate of soda or nitrate of soda. Each of these three sub- 
 stances produced nearly the same effect. The soda, therefore, more 
 than the acid with which it was combined, must in these cases have act- 
 ed beneficially. The comparatively small proportion of fine flour yield- 
 ed by the nitrated wheat, and the comparatively large proportion ob- 
 
 *Thc sulphate of ammonia was prepared from urine, and, therefore, contained other ad- 
 mixtures (pa);e 349). The straw was strongest, coarsest, and longest in ripening, where 
 this sulpliaie was applied. The two guanos produced little luxuriance, but the lots to which 
 they were applied were soonest ripe. 
 
IMPORTANCE OF SUCH EXPERIMENTS. 363 
 
 tained from that to which no application was made, are also highly de- 
 serving of notice. 
 
 Mr. Burnet has transmitted to me samples of the flour from these 
 several growths of wheat, with the view of determining the relative 
 proportions of gluten they contain. The result of this examination, 
 which cannot fail to be interesting, will be given in a succeeding Lec- 
 ture — before which, however, I hope the whole of Mr. Burnet's experi- 
 ments will be laid before the public. 
 
 It will be observed that Mr. Burnet has exercised a sound discretion 
 in making and trying mixtures not hitherto specifically recommended. 
 It is by the result of such varied experimental trials, made by intelli- 
 gent practical men, on different soils and crops, and with mixtures of 
 which the constitution is exactly known, that we shall be able hereafter to 
 correct our theoretical principles — as well as to simplify and render 
 more sure cur general practice. 
 
 [Since writing the above, I am informed that the silicate ofpotash^ re- 
 ferred to at p. 349, is manufactured by Messrs. Dymond, of London, and 
 may be obtained from the London dealers at 56s. a cwt. I expect also, 
 that a silicate of soda will soon be brought into the market by the Messrs. 
 CooUsons, of the Jarrow Alkali Works, at a much lower price. The 
 probable efficacy of these substances, as manures, has, no doubt, been 
 extolled too highly by some — their real efficacy, however, is well de- 
 serving of investigation. I insert in the Appendix No. VII, therefore, 
 some suggestions for experiments with these substances, in the hope that 
 during the spring of 1843, some experiments on the subject may be 
 made. 
 
LECTURE XVll. 
 
 Use of lime as a manure. — Value of lime in improving the soil. — Of the composition of 
 common and magnesian lime-stones. — Burning and slaking of lime. — Changes which 
 slaked lime undergoes by exposure to the air. — Various natural states in which carbonate 
 of Jime is applied to the land. — Marl — shell and coral sand, — limestone sand and gravel, 
 — crushed lime-stone. — Chemical composition of various marls, and shell and lime-stone 
 sands. — Their effects on the soil. —Use of chalk. — Is lime necessary to the soil? — Ex- 
 hausting effect of lime.— Analogy between this action of lime and that of wood-ashes. 
 Quantity of lime to be applied. — Effects of an overdose. — Form in which it may be most 
 prudently used. — When it ought to be applied in reference to the season — to the rotation 
 — and to the application of manure.— Its general and special effects on different soils and 
 crops.—Circumstances which influence its action. — Length of time during which its ef- 
 fects are perceptible. — Theory of the action of lime. — Necessity and nature of tlie ex- 
 haustion which it sometimes produces. — Sinking of lime into the soil. — Why the a|>|ili- 
 cation of lime must be repeated. — Action of lime on living animals and vegetables. 
 Suggestions of theory. — Use of silicate of lime. 
 
 Having explained to you the action of the most important sahne 
 and mixed mineral substances which are or may be beneficially ap- 
 plied to the soil, I have now to draw your attention to the use of lime 
 — the most valuable and the most extensively used of all the mineral 
 substances that have ever been made available in practical agricul- 
 ture. It has, and with much reason, been called " the basis of all 
 good husbandry" — it well deserves, therefore, your most serious atten- 
 tion as practical men, and on my part the application of every chem- 
 ical light by which its usefulness may be explained and your practice 
 guided. This consideration also will justify me in dwelling upon it 
 with some detail, and in illustrating separately the various points, 
 both of theory and practice, which present themselves to us, when 
 we study the history of its almost universal application to the soil. 
 
 § 1. Of the composition of common and magnesian lime-stones. 
 
 1°. Common lime-stones. — Lime is never met with in nature except 
 in a state of chemical combination (Lee. L, § 5,) with some other 
 substance. That which is usually employed in agriculture is met 
 with in the state of carbonate. 
 
 Carbonate of lime, or common lime-stone, consists of lime and car- 
 bonic acid, and when perfectly pure and dry, in the following propor- 
 tions : — 
 
 per cent. 
 
 Carbonic acid 43-7 
 
 Lime 56-3 ( 
 
 j lime contains Hi cwts. of lime. 
 
 '. or one ton of pure dry carbonate of 
 ( lime contains Hi cwts. of lime. 
 100 J 
 
 Limestones, however, are seldom pure. . They always contain a sen- 
 sible quantity of other earthy matter, chiefly silica, alumina, and oxide 
 of iron, with a trace of phosphate of lime, sometimes of potash and soda, 
 and often of animal and other organic matter. In lime-stones of the 
 best quality the foreign earthy matter or impurity does not exceed 5 per 
 cent, of the whole — while it is often very much less. The chalks and 
 
COMMON AND MAGNESIAN LIME-STONES. 365 
 
 mountain lime-stones are generally of this kind. In those of inferior 
 quality it may amount to 12 or 20 per cent., while many calcareous beds 
 are met with in which the proportion of lime is so small that they will 
 not burn into agricultural or ordinary building lime — refusing to slake 
 or to fall to powder when moistened with water. Of this kind is the 
 Irish calp and the lime-stone nodules which are burned for the man- 
 ufacture of hydraulic limes or cements.* It is easy to ascertain the 
 quantity of earthy matter contained in lime-stone, by simply intro- 
 ducing a known weight of it into cold diluted muriatic acid, and ob- 
 serving or weighing the part which, after 12 hours, refuses to dis- 
 solve or to exhibit any effervescence. It is to the presence of these 
 insoluble impurities that hme-stones in general owe their color, pure 
 carbonate of lime being perfectly white. 
 
 2^. Magnesian lime-stone. — Though often nearly white, the mag=^ 
 nesian lime-stones of our island are generally of a yellow color. They 
 cannot by the eye be distinguished from common lime-stones of a simi- 
 lar color, but they are characterised by containing a greater or less 
 proportion of carbonate of magnesia, which is more or less easily de- 
 tected by analysis. Pure carbonate of magnesia consists of 
 per cent. 
 
 Carbonic acid. .51-7 "| 
 
 Magnesia 4S;3 ( or one ton of pure dry carbonate of magnesia 
 
 ( contains 9| cwts. of magnesia. 
 
 100 J 
 
 It contains, therefore, a considerably larger proportion of carbonic 
 acid than is present in carbonate of lime. 
 
 Magnesian lime-stone is very abundant, is indeed the prevaihng 
 rock in many parts of England (Lee. XL, sec. 4,) but the proportion 
 of carbonate of magnesia it contains is very various in different lo- 
 calities. Even in the same quarry different beds contain very unlike 
 proportions of magnesia, and are therefore more or less fitted for 
 agricultural purposes. Thus several varieties of this lime-stone, ex- 
 amined by myself, from different parts of the county of Durham, 
 contained the two carbonates in the following proportions : 
 
 
 g ^ " O..^ 3 ii 
 
 Garmondsway 97-5 25 trace trace Hard compact gi-ey. 
 
 Stony-gate 980 161 0-27 0-12 Crystallinefine grained yellow 
 
 m , 1, nn n o 1 n 'J o-fi 5 Honey-combed crystalline 
 
 Fulwell 95 21 03 26 J yellow. 
 
 Seaham (A) 96-5 23 0-2 1-0 Hard fine-grained compact. 
 
 " (B) 950 1-3 0-2 3-5 Hard porous brown. 
 
 Hartlepool 54.5 44-93 0-33 024 Oolitic yellow. 
 
 HumbledonHill(A)57-9 41-8 1 028 Perfect encrinal columns. 
 
 " " (B) 60-41 3878 1 081 Consistingin part encrinal col. 
 
 FeiTy Hill 54-1 44-72 1-58 4-6 Yellowish compact. 
 
 Some of these varieties, as we see, contain very little carbonate of 
 
 * Thus that of Aberthaw contains about 86 of carbonate of lime and 11 of clay, &c. ; 
 that of Yorkshire 62 of carbonate of lime and 34 of clay ; of Sheppy 66 of carbonate of 
 lime and 32 of clay. These lime-stones are burned, and then crushed to an impalpable 
 powder, which sets almost immediately when mixed up with water. 
 
 ^. ^.aC 
 
366 OF THE BURNING AND SLAKING OF LIME. 
 
 magnesia, and therefore, are found to produce excellent lime for agri- 
 cultual purposes — while in others this substance forms nearly one- 
 half of the whole weight of the rock. Similar differences are found 
 to prevail in almost every locality. / 
 
 This admixture of magnesia in greater or less quantity is not con- 
 fined to the lime-stones of the magnesian lime-stone formation pro- 
 perly so called. It is found in sensible quantity in certain beds of 
 lime-stone in nearly every geological formation, and there are few 
 natural lime-stones of any land in which traces of it may not be dis- 
 covered by a carefully conducted chemical examination. 
 
 The simplest method of detecting magnesia in a lime-stone is to dis- 
 solve it in diluted muriatic acid, and then to pour clear lime water into 
 the filtered solution. If a light white powder fall, it is magnesia. The 
 relative proportions in two lime-stones maybe estimated pretty nearly 
 by dissolving an equal weight of each, pouring the filtered solutions 
 into bottles which can be corked, and then filling up both with lime 
 water. On subsiding, the relative bulks of the precipitates will indi- 
 cate the respective richness of the twt) varieties in magnesia. 
 
 § 2. Of the burning and slaking of lime. 
 
 Burning. — When carbonate of lime or carbonate of magnesia is 
 heated to a high temperature in the open air the carbonic acid they 
 severally contain is driven off, and the lime or magnesia remains in 
 the caustic state. When thus heated the carbonate of magnesia 
 parts with its carbonic acid more speedily and at a lower temperature 
 than carbonate of lime. 
 
 On the large scale this burning is conducted in lime kilns, one ton 
 good lime-stone yielding about 11 cwts. of burned^ shelly quick, or 
 caustic lime. 
 
 Slaking. — When this shell or quick-lime, as it is taken from the kiln, 
 is plunged into water for a short time and then withdra^vn, or when a 
 quantity of water is poured upon it, heat is developed, the lime swells, 
 cracks, gives off much watery vapor, and finally falls to a fine, bulky, 
 more or^less white powder. These appearances are more or less rapid 
 and striking according to the quality of the lime, and the time that has 
 been allowed to elapse after the burning, before the water was applied. 
 All lime becomes difficult to slake when it has been for some time ex- 
 posed to the air. When the slacking is rapid as in the rich limes, the 
 heat produced is sufficient to kindle gunpowder strewed upon it, and 
 the increase of bulk is from 2 to 3 J times that of the original lime 
 sliells. If the water be thrown on so rapidly or in such quantity as 
 to chill the lime or any part of it, the powder will be gritty, will con- 
 tain many little lumps which refuse to slake, will also be less bulky 
 and less minutely divided, and therefore will be less fitted cither for 
 agricultural or for building purposes. 
 
 When quick-lime is left in the open air, or is covered over with sods 
 ill a shallow pit, it gradually absorbs water from the air and from the 
 soil, and falls, though much more slowly, and with little sensible deve- 
 lopment of heat, into a similar fine powder. In the rich limes the in- 
 crease of bulk may be 3 or 3i times ; in the poorer, or such as contain 
 much earthy matter, it may be less than iwice. 
 
FURTHER CHANGES UNDERGONE BY SLAKED LKVIE. 367 
 
 Hydrate of lime. — When quick-lime is thus slaked it combines with 
 the water which is added to it, and becomes converted into a milder or 
 less caustic compound, which among chemists is known by the name of 
 hydrate of lime. This hydrate consists of 
 
 Lime . . 76 percent. \ or one ton of pure burned lime becomes 
 Water . . 24 " ^ nearly 25 cwt. of slaked lime. 
 
 100 
 
 It is rare, however, that lime is so pure or so skilfully and perfectly 
 slaked as to take up the whole of this proportion of water, or to increase 
 quite so much as one-fourth part in weight. 
 
 Hydrate of Magnesia. — When calcined or caustic magnesia is 
 slaked, it also combines with water, but without becoming so sensibly 
 hot as quick-lime does, and forms a hydrate, which consists of 
 
 Magnesia . 69*7 per cent. \ or one ton of pure burned magnesia be- 
 
 Waler . . 30-0 *' \ comes 28| cwt. of hydrate. 
 
 100 
 
 When magnesian lime is slaked, the fine powder which is obtained 
 consists of a mixture of these two hydrates, in proportions which depend 
 of course upon the composition of the original lime-stone. 
 
 A.n important difference between these two hydrates is, that the hy- 
 drate of magnesia will harden under water or in a wet soil in about 8 
 days — forming a hydraulic cement. Hydrate of lime will not so 
 harden, but a mixture of the two in the proportions in which they exist 
 in the Hartlepool, Humbledon, and Ferryhill lime-stones (page 365), 
 will harden under water, and form a solid mass. In the minute state 
 of division in which lime is applied to the soil, the particles, if it be a 
 magnesian lime, will, in wet soils, or in the event of rainy weather 
 ensuing immediately after its application, become granular and gritty, 
 and cohere occasionally into lumps, on which the air will have little 
 effect. Tfiis property is of considerable importance in connection with 
 the further chemical changes which slaked Times undergo when exposed 
 to the air or buried in the soil. 
 
 § 3. Changes ivhich the hydrates of lime and magnesia undergo by 
 prolonged exposure to the air. 
 
 When the hydrates of lime or magnesia obtained by slaking are ex- 
 posed to the open air, they gradually absorb carbonic acid from the at- 
 mosphere, and tend to return to the state of carbonate in which they ex- 
 isted previous to burning. By mere exposure to the air, however, they 
 do not attain to this state within any assignable time. In some walls 
 600 years old, the lime has been found to have absorbed only one-fourth 
 of the carbonic acid necessary to convert the whole info carbonate; in 
 others, built by the Romans 1800 years ago, the proportion absorbed 
 has not exceeded three fourths of the quantity contained in natural lime- 
 stones. In damp situations the absorption of carbonic acid proceeds 
 most slowly. 
 
 1°. Change undergone by pure lime during spontaneous slaking. — 
 In consequence, however, of the strong tendency of caustic lime to ab- 
 sorb carbonic acid, a considerable quantity of the hydrate of lime first 
 
368 OP CALCINED AND SLAKED MAGNESIA. 
 
 formed, during spontaneous slaking, becomes changed into carbonate 
 
 during the slaking of the rest. But, when it has all completely fallen, 
 
 the rapidity of the absorption ceases, and the fine slaked lime consists of 
 
 Carbonate of lime 57*4 
 
 Hydrate of lime I ^;^j^g^; ; ; ^'^ 42-6 
 
 100 
 or, a ton of lime, left in the open air till it has completely fallen to 
 powder, contains about 8^ cwt. in the state of hydrate. If left to slake 
 in large heaps, the lime m the interior of those heaps will not absorb so 
 much carbonic acid till after the lapse of a very considerable time. 
 More caustic lime (hydrate) also will be present if it be left to slake, as 
 is often done for agricultural purposes, in shallow pits covered with sods, 
 to defend it from the air and the rains. 
 
 After the lime has attained the state above described, and which is a 
 chemical compound* of carbonate with hydrate of lime, the further ab- 
 sorption of carbonate acid from the air proceeds very slowly, and is only 
 completely etTected after a very long period. 
 
 2°. When slaked in the ordinary way lime falls to powder, without 
 having absorbed any notable quantity of carbonic acid. Numerous 
 small lumps also remain, which, though covered with a coating of hy- 
 drate, have not themselves absorbed any water. Tlie absorption of 
 carbonic acid by this slaked lime is at first very rapid, — so that where 
 the full effect of caustic lime upon the soil is required, it ought to be 
 ploughed in as early as possible, — but it gradually becomes more slow, 
 a variable proportion of the compound of carbonate and hydrate above 
 described is formed, and even when thinly scattered over a grass-field, 
 an entire year may pass over without eflfecting the complete conversion 
 of the whole into carbonate. 
 
 3°. Calcined or burned magnesia, whether in the pure state or mixed 
 with quick-lime, as in the magnesian limes, absorbs carbonic acid more 
 slowly—and by mere exposure to the air will probably never return to 
 its original condition of carbonate. 
 
 When allowed to slake spontaneously, three-fourths of it become 
 ultimately changed into carbonate, and form a compound of hydrate 
 and carbonate which is identified with the common uncalcined magne- 
 sia of the shops. This compoundf consists of 
 
 Carbonate of magnesia 69-37 
 
 Hydrate of magnesia 16'03 ^ 
 
 Water 14-60 
 
 100 
 and it undergoes no further change by continued exposure to the air. 
 Bui if slaked by the direct application of water, magnesia, like lime, 
 
 * This compound consists of one atom of carbonate of lime (Ca O 4* CO2) combined with 
 one of hydrate (Ca O -\- HO,) and is represented shortly by Ca C + Ca H— in which Ca 
 denotes calcium (Lee. IX., § 4,) Ca O or (Ja oxide of calcium or lime, CO2 or C carbonic 
 acid (Lee. III., § 1,) and H O or H water (Lee. II. § 6.) 
 
 t It is represented by the formula 3 (Mg C + H) + Mg H. 
 
STATES 11? WHICH LIME IS APPLIED. 369 
 
 forms a hydrate only, without absorbing any sensible quantity of car- 
 bonic acid. The hydrate thus produced is met with in the form of 
 mineral deposits on various parts of the earth's surface, and this mineral 
 is not known to undergo any change or to absorb carbonic acid though 
 exposed for a great length of time to the air. When magnesian limes 
 are slaked by water, therefore, (he magnesia they contain may remain 
 in whole or in part in the caustic state (of hydrate), which will change 
 but slowly even when exposed to the air. When it is left to sponta- 
 neous slaking, one-fourth of it at least will always remain in the caustic 
 state, however long it may be exposed to the air. 
 
 Should a lime be naturally of such a kind, or be so mixed with the 
 ingredients of the soil as to form a hydraulic cement or an ordinary- 
 mortar, which will solidify when rains come upon it, or when the natu- 
 ral moisture of the soil reaches it — the absorption of carbonic acid will 
 in a great measure cease as it becomes soUd, and a large proportion of 
 the lime will remain caustic for an indefinite period. 
 
 § 4. Slates of chemical combination in which lime may he applied to 
 
 the land. 
 
 There are, therefore, four distinct states of chemical combination, in 
 wliif;li pure lime may be artificially applied to the land. 
 
 ] ^ . Quick-lime or lime-shells, in which the lime as it comes from the 
 kiln is uncombined either with water or with carbonic acid. 
 
 2°. Slaked lime or hydrate of lime, in which by the direct application 
 of water it has been made to combine with about one-fourth of its 
 weight of water. 
 
 In both these states the lime is caustic, and may be properly spoken 
 of as caustic lime. 
 
 3°. Spontaneously slaked lime, in which one-half of the lime is com- 
 bined with water and the other half with carbonic acid. In this state 
 it is only half caustic. 
 
 ' 4°. Carbonate of lime — the state in which it occurs in nature, and to 
 which burned lime, after long exposure to the air, more or less perfectly 
 arrives. In this state lime possesses no caustic or alkaline (p. 48, § 5, 
 note) properties, but is properly called mild lime. 
 
 5°. ^i-carbonate of lime may be adverted to as a fifth state of com- 
 bination, in which, as I have previously explained to you (pp. 45-6, 
 § 1), nature usually applies lime to the land. In this state it is combined 
 with a double proportion of carbonic acid, and is to a certain extent 
 readily soluble in water. Hence, springs are often impregnated with 
 it, and the waters that gush from fissures in the lime-stone rocks spread 
 it through the soil in their neighbourhood, and sweeten the land. 
 
 I shall hereafter speak of these several states under the names of 
 quick-Wme, hydrate of lime, spontaneously slaked lime, carbonate of 
 lime, and Bi-carbonate of lime. By adhering to these strictly correct 
 names, we shall avoid some of that confusion into which those who 
 have hitherto treated of the use of lime as a manure have unavoidably 
 fallen. The term mild, you will understand, applies onlyto that which 
 is entirely in the state of carbonate. 
 
 Magnesia, in the magnesian linies, may in like manner be either in 
 the state o^ calcined magnesia^ oi hydrate of magnesia^ o^ spontaneously 
 
370 
 
 VARIOUS NATURAL FORMS OF CARBONATE OF LIME. 
 
 slaked — meaning by this the compound of hydrate with carbonate — of 
 carboiiate, or of Bi-carbonate of magnesia, the latter of which is so- 
 luble in water to a very considerable extent. (It dissolves in 48 times 
 its weight of water — or a gallon of water will dissolve 5 ounces of 
 the Bi-carbonate containing I'j ounces of magnesia.) ^tjLl 
 
 § 5. Of the various natural forms in which carbonate of lime is " 
 applied to the land. 
 
 In the unburned or natural state, lime is met with on the earth's - 
 surface in numerous forms — in many of which it can be applied * 
 largely, easily, and with economy to the land. 
 
 1°. Marl. — Of these forms that of marl occurs most abundantly, 
 and is most extensively used in almost every country of Europe. By 
 the term marl, is understood, as I explained to you, when treating of 
 soils (Lee. XL, § 3,) an earthy mixture, which contains carbonate of 
 lime, and eflervesces more or less sensibly when an acid (vinegar or 
 diluted muriatic acid — spirit of salt) is poured upon it. Generally, 
 also, the tenacious marls, when introduced into water, lose their co- 
 herence, and gradually fall to powder. This test is often employed 
 to distinguish between marly and other clays, yet the falling asunder, 
 though it afford a presumption, is not an infallible proof that the sub- 
 stance tried is really a marl. 
 
 Marls are of various colors, white, grey, yellow, blue, and of various 
 degrees of coherence, some occurring in the form of a more or less fine, 
 loose, sandy powder, others being tenacious and clayey, and others, 
 again, hard and stony. These differences arise in part from the kind 
 and proportion of the earthy matters they contain, and in part, also, from 
 the nature of the locality, moist or dry, in which they are found. The 
 hard and stony varieties are usually laid upon the land, and exposed to 
 the pulverising influence of a winter's frost before they are either spread 
 over the pasture or ploughed into the arable land. Some rich marls 
 consist in part or in whole of broken and comminuted shells, which 
 clearly indicate the source of the calcareous matter they contain. 
 
 COMPOSITION OP MARLS FROM 
 
 Luneburg. Osnabruck Magdeburg. Erunswick. "Wesermarbh. Brunswick. 
 
 powdery. stuny. clayey. loamy. powdery. stony. 
 
 auartz-Sandfe Silica.. 56 2:v0 584 734 789 711 
 
 Alumina . 0-4 lO-O 8-4 1-9 31 4 
 
 Oxides of Iron 4 2 1-9 67 3 2 38 65 
 
 Do. of Magnesia trace trace 0-3 03 0-3 M 
 
 Carbonateof Lime.... 85-5 35-0 18-2 181 8-2 13-3 
 
 Do. of Magnesia 1-25 09 38 1-5 3-0 2-6 
 
 Sulphuret of Iron — 7-3 — — — — 
 
 Potash & Soda, com- 1 r\ nK. * ^ n no An Art 
 
 bined with Silica..! ""^ ^'^ ^'^ ^ 
 
 Common Salt 0-03 trace trace trace 01 trace 
 
 Gypsum 0-06 0'9 2-1 01 05 trace 
 
 7bi"Ll^.'"^.| 3-3 0-5 0-5 07 1-2 1-3 
 
 Nitrate of Lime 001 _ _ _ _ — 
 
 carbon 
 
 Organic Matter 06 205 _ _ _ _ 
 
 100 100 100 100 100 100 
 
 ^^" 
 
UNLIKE EFFECTS OF DIFFERENT MARLS. 371 
 
 The characteristic property of true marls of every variety is, I have 
 Baid, the presence of a considerable per centage of carbonate of lime in 
 the state of a fine powder, and, in general, ditfused uniformly through 
 the entire mass. To this calcareous matter the chief efficacy of these 
 marls is no doubt to be ascribed, yet as they always contain other chem- 
 ical compounds to which the special efficacy of certain varieties has 
 sometimes been ascribed, it may not be improper to direct your attention 
 to the preceding table, in which the constitution of several marls, from 
 different localities, is represented, after the analyses ot Sprengel. 
 
 Several reflections will occur to you on looking at these tables — such 
 as. 
 
 First — that marls differ very much in composition, and therefore 
 must differ very much also in the effects which they are capable of pro- 
 ducing when apphed in the same quantity to the same kinds of land. 
 
 Second — that, among other differences, the proportion of carbonate 
 of lime is very unlike — in some varieties amounting to 85 lbs. out of 
 every hundred, while in others as little as 5 lbs. are present in the same 
 weight. You will understand, therefore, how very different the quan- 
 tity applied to the land must be, if these several varieties are to produce 
 an equal liming or to add equal quantities of lime to the soil. You 
 will see that each of three persons may be adopting the best practice 
 with his own marl — though the one add only 12 to 20 tons per acre, 
 while the second adds 50 to GO, and the third 100 to 120 tons. 
 
 Third — that the proportion of phosphate of lime (bone-earth) is in 
 some marls considerably greater than in others. Thus with every ton 
 of the first of the above marls you would lay on the soil 52 lbs. of bone 
 earth — about as much as is contained in a cwt. of bone dust — while 
 with the second you would only add 11 lbs. In so far as their effects 
 upon the land depend, or are influenced by the presence of this sub- 
 stance, therefore, they must also be very different. And, 
 
 FourUi — that the mechanical effects of these marls upon the soil to 
 which they are added must be very unlike, since some contain 70 or 
 80 lbs. of sand in every hundred — while others contain a considerable 
 quantity of clay. The opening effects of the one marl, and the stiff- 
 ening effects of the other, when they are laid on in large quantities, 
 cannot fail to produce very different alierations in the physical cha- 
 racters of the soil. 
 
 2^. Shell Sand. — The sands that skirt the shores of the sea are 
 found in many localities to be composed, in large proportion, of the 
 fragments of broken and comminuted shells. These form a calcare- 
 ous sand, mixed occasionally with portions of animal matter, and, 
 when taken fresh from the sea-shore, with some saline matter derived 
 from the sea. 
 
 Such is the case in many places on the coast of Cornwall. From 
 these spots the sand is transported to a distance of many miles into 
 the interior for the purpose of being laid upon the land. It has been 
 estimated (De la Beche's Geological Report on Cornwall^ ^c, p. 480) 
 that seven millions of cubic feet are at present employed every year 
 in that county for this purpose. 
 
 On the western coast of Scotland also, and on the shores of the island 
 of Arran and of the Western Isles, this shell sand abounds, and i3 
 16* 
 
372 COMPOSITION OF SHELL AND CORAL LANDS. 
 
 applied extensively, and with remarkably beneficial effects, both to the 
 pasture lands and to the peaty soils that cover so large an area in this 
 remote part of Scotland. It is chiefly along the coasts that it has hith- 
 erto been extensively employed, and it is transported by sea to a dis- 
 tance of 80 or 100 miles. " In the island of Barray alone, there are four 
 square miles of shells and shell sand of the finest quality and of an 
 indefinite depth" (Macdonald's Agricultural Survey of the Hebrides, 
 p. 401.) When covered with a dressing of this shell sand the peaty 
 surface becomes covered with a sward of delicate grass — and the 
 border of green herbage that skirts the shores of these islands in so 
 many places is to be ascribed either to the artificial apphcations of 
 such dressing or to the natural action of the sea winds in strewing 
 the fine sand over them, when seasons of storm occur. 
 
 The coast of Ireland is no less rich in sach sand in many parts both 
 of its northern and southern coasts. A century and a half ago, it is 
 known to have been used for agricultural purposes in the north of Ire- 
 land — and nearly as long ago to have been brought over to the oppo- 
 site (Galloway) coast of Scotland with a view of being applied to the 
 land (Macdonald.) In the south, according to Mrs. Hall, (Mrs. Hall's 
 Ireland^) the coral sand raised in Bantry Bay alone produces £4000 
 or £5000 a-year to the boatmen who procure it and to the peasants 
 who convey it up the country. 
 
 On the coast of France, and especially in Brittany, opposite to Corn- 
 wall, on the other side of the English channel, it is obtained in large 
 quantity, and is in great demand (Payen and Boussingault, Annales de 
 Chim. et de Phys., third series, iii., p. 92.) It is applied to the clay soils 
 and to marshy grass lands with much advantage, and is carried far 
 inland for this purpose. It is there called trez, and is laid on the land at 
 the rate of 10 to 15 tons per acre. On the southern coasts of France, 
 where shell sand is met with, it is known by the name of tanque or 
 tangue. 
 
 The shell sand of Cornwall contains from 40 to 70 per cent, of car- 
 bonate of lime, with an equally variable small admixture of animal 
 matter and-of sea salt. The rest is chiefly siliceous sand. Other va- 
 rieties have a similar composition. Two specimens oHangue from the 
 south of France, analysed by Vitalis, and one of shell sand from the 
 island of Isla, partially examined by myself, consisted of 
 
 Tannue from the Shell Sand 
 
 Soul h of France. from Isla. 
 
 Sand, chiefly siliceous 20-3 40 i^.-, ^-„ 
 
 Alumina and Oxide of Iron 4-6 4-6 \ 
 
 Carbonate of Lime 66-0 47.5 28 to 34 
 
 Phosphate of Lime ? ? 0-3 
 
 Water, and loss 9-1 7-9 — 
 
 100 100 100 
 
 3°. Coral sand is similar in its nature to the shell sand with which 
 it is often intermixed on the sea-shore. It is collected in considerable 
 quantities, however, by the aid of the drag — being torn up by the fish- 
 ermen in a living state — on the coasts of Ireland (Bantry Bay and 
 elsewhere,) and on the shores of Brittany, especially near the mouths of 
 the rivers. In this fresh state it is preferred by the farmer, probably be- 
 
USE OF LIME-STONE SAND AND GRAVEL. 373 
 
 cause it contains both more saline and more animal matter. This ani- 
 mal matter enables it to unite in some measure the beneficial effects 
 which follow from the application of marl and of a small dressing of 
 farm-yard or other valuable mixed manure. 
 
 Payen and Boussingault ascribe the principal efficacy of the shell 
 and coral sands to the small quantity of animal matter which is present 
 in them. These chemists estimate the relative manuring powers of 
 different substances applied to the land by the quantities of nitrogen 
 which they severally contain, and thus, compared with farm-yard 
 manure, attribute to the shell and coral sands the following relative 
 values: — 
 
 Contain of Relative 
 
 Nitrogen. value. 
 
 100 lbs. of Farm-yard Manure . . . 0-40 lbs. 100' 
 
 do. of Coral Sand [Merl) . . . 0-512 lbs. 128 
 
 do. of Shell Sand (Trez) . . . 0-13 lbs. 32^* 
 
 Tliat is to say, that, in so far as the action of these substances is de- 
 pendent upon the nitrogen they contain, fresh coral sand is nearly one- 
 third more valuable than farm-yard manure, while fresh shell sand is 
 only equal in virtue to one-third of its weight of the same substance. 
 
 Though, as I have already had frequent occasion to observe to you, 
 j:!iuch weight is not to be attached to such methods of estimating the re- 
 lative values of manuring substances by the proportions of any one of 
 the ingredientS'they happen to contain — yet the fact, that so much ani- 
 mal matter is occasionally present in the living corals, accounts in a 
 satisfactory manner for the immediate effects of this form of calcareous 
 application. This animal matter acts directly and during the first year; 
 the carbonate of lime begins to show its beneficial influence most dis- 
 tinctly when two or tiiree years have passed. 
 
 4°. Lime-stone Sand and Gravel. — In countries which abound in 
 lime-stones, there are found scattered here and there, in the hollows and 
 on tlie hill-sides, banks and heaps of sand and gravel, in which rounded 
 particles of lime-stone abound. These are distinguished by the names 
 of lime-stone sand and gravel, and are derived from the decay or wear- 
 ing down of the lime-sLone and other rocks by the action of water. 
 Such accumulations are frequent in Ireland. They are indeed exten- 
 sively diffused over the surface of that island, as we might expect in a 
 country abounding so much in rocks of mountain lime-stone. In the 
 neighbourhood of peat bogs these sands and gravels are a real blessing. 
 They are a ready, most useful, and largely employed means of im- 
 provement, producing, upon arable land, the ordinary effects of liming, 
 and, when spread upon boggy soils, alone enabling it to grow sweet 
 herbage and to afford a nourishing pasture. The proportion of carbon- 
 ate of lime these sands and gravels contain is very variable. I have 
 examined two varieties from Kilfinane, in the county of Cork (?). The 
 one, a yellow sand, contained 26 per cent, of carbonate of lime — the re- 
 sidue, being a fine red sand, chiefly siliceous ; the other, a fine gravel 
 of a grey colour, contained 40 per cent, of carbonate of lime in the 
 form chiefly of rounded fragments of blue lime-stone, the residue con- 
 sisting of fragments of sand-stone, of quartz, and of granite. 
 
 * Annales de Chim. et de Phys., third series, iii., p. 103. 
 
374 CRUSHED LIME-STONES. — EFFECTS OF MARLS. 
 
 The application of such mixtures must not only improve the physi- 
 cal characters of the soil, but the presence of the fragments of granite, 
 containing undecomposed felspar and mica (Lee. XII., § 1), must con- 
 tribute materially to aid the fertilizing action of the lime-stone with 
 which they are mixed. 
 
 5°. Crushed Lime-stone. — The good efTects of calcareous marls and 
 of lime-stone gravels naturally suggest the crushing of lime-stones as a 
 means of obtaining carbonate of lime in so minute a state of division 
 that it may be usefully applied to the soil. Lord Kames was, I be- 
 lieve, the first who in this country endeavoured to bring this suggestion 
 into practical operation. He is said to have caused machinery to 
 be erected for the purpose in one of the remotest districts of Scotland, 
 but from some cause the plan seems never to have obtained a proper 
 trial. 
 
 One of the resSults which, as we have already seen, follows from the 
 burning of rich lime is this, that it naturally falls to a very fine powder 
 as it slakes. Where coal or other combustible is cheap, therefore, it 
 may possibly be reduced to a fine powder by burning, at a less cost 
 than it could be crushed. 
 
 Yet there are two cases or conditions in which crushing might be re- 
 sorted to with equal advantage and economy : 
 
 First, where coal is dear or remote, while lime-stones and water 
 power are abundant. There are many inland districts in each of the 
 three kingdoms where these conditions exist, and in which, therefore, 
 the erection of cheap, machinery might afford the means of greatly fer- 
 tilizing the land ; and. 
 
 Second, there are in many localities rocks rich in calcareous mat- 
 ter, which are nevertheless so impure, or contain so much other earthy 
 matter, that they cannot be burned into lime. Yet, if crushed, these 
 same masses of rock would form a valuable dressing for the land. 
 Many lime-stones of this impure character, which are really useless for 
 buildino; purposes — which do not fall to powder when burned, and 
 which have, therefore, been hitherto neglected as useless — might, by 
 crushing, be made extensively available for agricultural purposes. The 
 siliceous lime-stones (corn-stones) of the old red sand-stone, the earthy 
 beds of the mountain lime-stone, and many of the calcareous strata of 
 the Silurian system might thus be made to improve more extensively 
 the localities in which they are severally met with. The richer limes 
 now brought from a great distance, and at much expense — as on the 
 Scottish borders — might be in a great measure superseded by the native 
 produce of the district. 
 
 § 6. Effects of marl and of the coral, shell, and lime-stone sands, 
 
 upon the soil. 
 
 The effects which result from the application of the above natural 
 forms of carbonate of lime are of two kinds. 
 
 1°. Their physical effect in altering the natural texture of the soils to 
 which they are added. This effect will necessarily vary with the na- 
 ture of the earthy matter associated with the lime. Thus the clay 
 marls will improve, by stiffening, such soils as are light and sandy — 
 the shell sands and lime-stone gravels, by opening and rendering more 
 
' OBSERVED EFFECTS OF MARLS. 375 
 
 free and easier worked such soils as are stiff, intractable, and more or 
 less impervious — while either will impart solidity and substance to 
 such as are of a peaty nature or over-bound with other forms of vege- 
 table matter. 
 
 2°. Their chemical effect in actually rendering the soil productive of 
 larger crops. This effect is altogether independent of any alteration in 
 the physical properties of the soil, and is nearly the same in kind^ what- 
 ever be the variety of marl, &c., we apply. It differs in degree, chiefly 
 according to the proportion of calcareous matter which each variety 
 contains. This action of the pure carbonate of lime they contain is 
 supposed to be modified in some cases by the proportion of phosphate of 
 lime, &c. (p. 370,) with which it maybe mixed — it is certainly modified 
 by the animal and saline matters which are present in the recent cor- 
 als and shell sands. 
 
 The several effects of marls and calcareous sands being dependent 
 upon circumstances so different, it is not surprising that the opinions of 
 practical men should, in former times, have been divided in regard to 
 the action of this or that marl upon their respective soils. In no two 
 localities was the substance applied to the land exactly alike, and 
 hence unlike results must necessarily have followed, and disappoint- 
 ment been occasionally experienced from their ^use. And yet the im- 
 portance of rightly understanding the kind and degree of effect which 
 these manuring substances ought to produce may be estimated from 
 the fact, that a larger surface of the cropped land in Europe is improved 
 by the assistance of calcareous marls and sands — than by the aid of 
 burned lime and farm-yard manure put together. 
 
 It is not easy in any case to estimate with precision what portion of 
 the effect caused by a given marl is due to its chemical and what to its 
 physical action. Even the pure limes, when applied in large doses, 
 produce a change in the texture of the soil, which on stiff" lands is ben- 
 eficial, and on light or sandy fields often injurious. In all cases, there- 
 fore, the action of lime applied in any form may be considered as part- 
 ly physical and partly cliemical — the extent of the chemical action in 
 general increasing with the proportion of lime which the kind of cal- 
 careous matter employed is known to contain. 
 
 The observed effects of marls and shell sands, in so far as they are 
 chemical, are very analogous to those produced by lime as it is gener- 
 ally applied in the quick or slaked state in so many parts of our islands. 
 
 They alter the nature and quality of the grasses when applied to 
 pasture — they cover even the undrained bog with a short rich grass — 
 they extirpate heath, and bent, and useless moss — they exterminate 
 the weeds which infest the unlimed corn fields — they increase the 
 quantity and enable the land to grow a better quality of corn — they ma- 
 nifest a continued action for many years after they have been applied — 
 like the purer limes they act more energetically if aided by the occa- 
 sional addition of other manure — and like them they finally exhaust* 
 a soil from which the successive crops are reaped, without the requisite 
 return of decaying animal or vegetable matter. 
 
 * Of shell marl the same quantity exhausts sooner than clay marl (Kames). This i3 
 owing chiefly to the larger proportion of lime contained in the former. 
 
376 OF THE USE OF CHALK AS A MANURE. 
 
 But to these and other effects I shall have occasion to draw your at- 
 tention more particularly in a subsequent part of the present lecture. 
 
 § 7. Of the use of chalk as a manure. 
 
 Chalk is another form of carbonate of lime which occurs very abun- 
 dantly in nature, and which, from its softness, has in many parts of 
 England been extensively applied to the land in an unburned stale. 
 
 The practice of chalking prevails more or less extensively in all 
 thai part of England (Lee. XL, § 8,) over which the chalk formation 
 extends. It is usually dug up from pits towards the close of the au- 
 tumn or beginning of winter, when full of water, and laid upon the 
 land in heaps. During the winter's frost the lumps of chalk fall to 
 pieces, and are readily spread over the fields in spring. The quantity 
 laid on varies with the quality of the soil and of the chalk itself, and 
 with the more or less perfect crumbling it undergoes during the season 
 of winter, and with tlie purpose it is intended to serve. It gives tena- 
 city and closeness to gravelly soils,* opens and imparts freeness to stiff 
 clays, and adds firmness to such as are of a sandy nature. 
 
 If a physical improvement of this kind be required, it is laid on at 
 the rate of from 400 to 1000 bushels an acre. But some chalks con- 
 tain much more clay than others, and are employed, therefore, in small- 
 er proportions. 
 
 For the improvement of coarse, sour, marshy pasture, it is applied at 
 the rate of 150 to 250 bushels an acre, and speedily brings up a sweet 
 and delicate herbage. It is also said to root out sorrel from lands that 
 are infested with this plant. 
 
 These effects are precisely such as usually follow from the ap^^jlica- 
 tion of marl, and, like marl, the repetition of chalk exhausts the land, if 
 manure be not afterwards added to it in sufficient quantity. 
 
 But the chalking of the Southern Downs and of the Wolds of Lin- 
 colnshire and Yorkshire would appear to differ in some respects from 
 ordinary marling. On the thin soils immediately resting upon the 
 clialk, exjperience has shown that repeated dressings of chalk recently 
 dug up, may be applied with much benefit. To a stranger, also, it ap- 
 pears singular that an admixture of that chalk which lies immediately 
 beneath the soil is not productive of the same advantage. Even the 
 clialk of an entire district is, in some cases, rejected by the farmer, 
 and he will rather bring another variety from a considerable distance, 
 than incur the less expense of laying on his land that which is met 
 with on his own or on his neighbors' farms. Thus the Suffolk farmers 
 [)refer the chalk of Kent to lay on their lands, and are at the cost of 
 bringing it across the estuary of the Thames, though chalk rocks lie al- 
 fnost everywhere around and beneath them. 
 
 The cause of the diversities which thus present themselves in the 
 practice of experienced agriculturists, partly at least, is to be sought for 
 in the qualities of the different varieties of chalk employed. Careful 
 analyses have not yet shown in wliat respects these chalks differ in che- 
 mical constitution, and until this is ascertained we must remain in 
 
 • Mr. Gfavvler, North Hampshire, stales that'a gravel thus stiffened, instead of 12 to 16 
 bushel^of wheat, yielded afterwards 24 to 30 XiMshels.— British Husbandry, i., p. 280. 
 
EFFECTS OF CHALK ON THE WOLDS. 377 
 
 some measure in the dark, both as to the way in which a dressing of 
 chalk acts in improving a soil already rich in chalk, and why chalk 
 from one locality should act so much more beneficially than another. 
 
 With one thing, however, we are familiar, that the upper beds of 
 chalk abound in flint, and where they form the surface support a thin 
 and scanty herbage — while the under chalks are more tenacious and 
 apparently more rich in clay, and support generally a soil which yields 
 valuable crops of corn. An admixture of the lower, therefore, ought to 
 improve the soils of the upper; and as the chalks of Kent consist of 
 iliese lower beds, we can understand why the practical farmer in Suf- 
 folk should prefer ihem to the upper chalks of his own neighbourhood. 
 Still we cannot, as yet, give the scientific reasons why the one chalk 
 sliould be better than the other. A rigorous chemical analysis can 
 alone determine with certainty why the one should produce a differ- 
 ent effect from the other. 
 
 Chalks may difler in the proportion of clay or of organic matter with 
 which they are associated — in the quantity of silica (the substance of 
 flints) or of silicates they contain, — in the amount of magnesia or of 
 jihosphate of lime which can be detected in them — or of saline matter 
 v\l)ich a careful examination will discover, — and they may even differ 
 jihysically in the fineness of the ultimate particles of which the sub- 
 stance of the chalk is composed.* All such differences may modify 
 I he action of the several varieties in such a way as, when accurately 
 investigated, to enable us to account for the remarkable preference 
 manifested by practical men for the one over the other. Until such 
 an investigation has been carefully made, it is unfair hastily to class 
 among local prejudices what may prove to be the results of long prac- 
 tical experience. 
 
 On the chalk Wolds of Lincolnshire and Yorkshire the practice of 
 chalking even the thin soils is now comparatively old in date. The 
 lowest chalks are there also much preferred, — they are laid on at the 
 rate of 60 to 80 cubic yards per acre, and they cause a great improve- 
 ment, especially upon the deep lands, as they are called, where the 
 soil is deepest. Corn does not yield so well, nor ripen so early, on 
 these deep soils, as where a thinner covering rests upon the chalk. It 
 is naturally also unfit for barley or turnips, the latter plant being espe- 
 ciall}^ infested with the disease called fingers and toes [British Hus- 
 bandry, iii., p. 124] (Strickland). But a heavy chalking removes all 
 the above defects of these deep soils, and for a long period of time. 
 The corn ripens sooner, is larger in quantity, and better in quality, 
 and the turnips grow perfectly free from disease. 
 
 These, however, are to be regarded as only the usual effects of a large 
 addition of lime to a soil in which previously little existed. It is a 
 fact which will naturally strike you as remarkable, that soils which rest 
 ui)()n chalk, as well as upon other lime-stone rocks, even at the depth 
 of a few inches only, are often, and especially when in a state of nature, 
 so destitute of lime that not a particle can be detected in them. That 
 linie in any form should benefit such soils is consistent with uniform 
 
 ' Ehrenberg has discovered that chalk i? in a great measure composed of the skeletons, 
 shells, or other exuvial (spoils) of marine microscopic animals. 
 
378 LIME ALWAYS PRESENT IN FERTILE SOILS. 
 
 experience. I shall presently have an opportunity of directing your 
 attention to the two concurring causes hy the joint operation of which 
 lime is sooner or later wholly removed from the soil, even where, as in 
 tlie Wolds, it rests immediately upon the chalk. 
 
 § 8. Is lime in dispensable to the fertility of the soil? 
 It is the result of universal experience vvherever agriculture has been 
 advanced to the state of an art, thai the presence of lime is useful to 
 the soil. 
 
 Not only is this fact deduced from the result of innumerable applica- 
 tions of this substance to lands of every quality, but it is established 
 also 1)}^ a consideration of the known chemical constitution of soils 
 which are naturally possessed of unlike degrees of fertility. 
 
 Thus sandy or siliceous soils are more or less barren if lime be ab- 
 sent — while the addition of this substance in the form of marl or other- 
 wise renders them susceptible of cultivation. So clay soils, in which 
 no lime can be detected, are often at once changed in character by a 
 sufficient liming. Felspar soils contain no lime, and they are barren — 
 and the same is true of such as are derived immediately from the de- 
 gradatioji of the serpentine rocks. 
 
 Traj) soils, on the other hand — such as are derived from decayed 
 basalts or green-stones — are poor in proportion as felspar abounds in 
 them. Where augites and zeolites are present in large proportion in 
 the trap from which they are formed, the soils are rich, and may even 
 be used as marl. The only difference in this latter case is, that lime is 
 not dcHcient (Lee. XII., § 4), — and to this ditference the greater fertility 
 may fairly be ascribed. 
 
 But let it be conceded that lime is useful to or benefits the soil in 
 which it exists, yon may still ask — is lime indisptnsahle to the soil ? — 
 is it impossible for even an average fertility to be manifested where 
 lime is entirely absent 1 
 
 There arc two different considerations, from each of which we may 
 deduce a^nore or less satisfactory answer to this question. 
 
 1°. The result of all the analyses hitherto made of soils naturally 
 fertile show that lime is universally present. The per-centage of lime 
 in a soil may be very small, yet it can always be detected when valua- 
 ble and healthy crops will grow upon it. Thus the fertile soil of the 
 Marsli lands in Holstein contains 0-2 per cent, of carbonate of lime. 
 Salt marsh in East Friesland 0-6 " " 
 
 Rich pasture near Durham . 1'31 " " 
 
 But though the per centage of lime in these cases appears small, the 
 absolute quantity of lime present in the land is still large. Thus sup- 
 pose the first of these soils, which contains the least, to be only six 
 inches in depth, and each cubic foot to weigh only 80 lbs. — it would 
 contain about 3500 lbs. of carbonate of lime, upwards of a ton and a 
 half, in every acre. Arid this lime would be intimately mixed with the 
 whole soil, in which state it is always most eflfective in itsoperation. It 
 may also be inferred with safety, that if the upper six inches contained 
 this pro})ortion of lime, the under soil would probably be richer still, 
 since lime tends not so much to dillus'e itself through, as to sink down- 
 wards into the soil. 
 
STATE IN WHICH LIME EXISTS IN THE SOIL. 379 
 
 2°. The results of all the chemical examinations hitherto made in 
 regard to the nature of the inorganic matter contained in the sap and 
 substance of plants indicate, — if not the absolute necessity of lime to the 
 growtli of plants, — at least that in nature all cultivated plants do ab- 
 sorb it by their roots from the soil, and make use of it in some way in 
 aid of their growth. In so far as our practice is concerned, this is very 
 much the same as if we could prove lime to be absolutely indispensable. 
 
 The ash of the leaf and bulb of the turnip or potatoe, of the grain 
 and straw of our corn-bearing plants, and of the stems and seeds of our 
 grasses, all contain lime whenever and wherever they are grown. And 
 most of them attain high health and luxuriance only where lime is 
 easily attained. 
 
 Grant, then, that lime appears to be, perhaps virtually is, a necessary 
 food of plants, without which their natural health cannot be maintained, 
 nor functions discharged, — still the quantity which must be present in 
 the soil to supply this food is not necessarily large. Even in favor- 
 able circumstances we have seen (Lee. X., § 3,) that the average crops 
 during an entire rotation of four years may not carry off more than 250 
 lbs. of lime from the acre of land, a quantity which even the marsh 
 soils of HolsJ:ein would be able to supply for half a century, could the 
 roots readily make their way into every part of the soil. 
 
 Still we may safely hold, I think, that this quantity of lime at least 
 is indispensable — if cultivated plants are to flourish and ripen. So 
 much, at least, must in practice be every year added to cultivated land 
 in one form or another, where the crops are in whole or in part carried 
 off the land. Where it is not added either artificially or by some natu- 
 ral i)rocess, infertility must gradually ensue. We shall presently see 
 tliMt lime has other functions to perform in the soil, and that there are 
 natural causes in constant operation in our climate which render a 
 larger addition than this desirable at least, if not indispensable to con- 
 tinued fertility. 
 
 § 9. State of combination in which lime exists in the soil. 
 
 This lime, which we have concluded to be an indispensable constitu- 
 ent of fertile soils, may be present in several distinct states of combi- 
 nation. 
 
 1°. In that of chloride of calcium. — This compound, as we have al- 
 ready seen (Lee. IX., § 4,) is very soluble in water, and is not unfre- 
 quenily to be detected in the sap, especially of the roots of plants. Its 
 solubility, however, exposes it to be readily washed out of the soil by 
 the rains, and perhaps for this reason it is not one of those forms of com- 
 bination in which lime is recognised as a uniform or necessary consti- 
 tuent of the soil. Its presence may be detected by boiling half a pound 
 of the soil in distilled water, filtering and evaporating the solution to 
 dryness. If the dry mass become moist on exposure to the air, and if, 
 after being dissolved in water, it give a white precipitate with oxalate 
 of ammonia, and after being rendered sour by a few drops of nitric acid, 
 a white precipitate again with nitrate of silver, it may be inferred to 
 contain chloride of calcium. 
 
 2°. In that of sulphate of lime or gypsum. — In this state also it is not 
 a constant, and in a few cases only an abundant, constituent of the soil. 
 
380 iiumat:-: or j.\:.\i. is 'viiv. potl. 
 
 Its presence may be detected by tbe dejjosition of minute crystals on tbe 
 sides of the vessel during the evaporation of the solution obtained by 
 boiling the soil in distilled water. Or, its presence may be inferred if, 
 after observing that oxalate of ammonia causes a precipitate in one 
 small portion of the solution, it be found that nitrate of baryta also 
 throws down a white precipitate from another small portion. 
 
 3°. In the state of phosphate. — This compound is probably present, 
 though always in small proportion, in every soil which is capable of 
 raising a nutritious vegetation. It may be readily detected by treating 
 500 grains of the dry soil for 12 hours with dilute muriatic acid, and oc- 
 casionally stirring. If to the filtered solution caustic ammonia be add- 
 ed, a brownish precipitate will usually fall. If this precipitate be se- 
 parated, and treated with acetic acid (vinegar), it will all dissolve if no 
 phosphoric acid be present. If this experiment be carefully performed, 
 and a residue remain undissolved, the presence of phosphoric acid in 
 tlie solution, and of phosphate of lime in the soil, may be safely inferred. 
 
 4°. In the state of silicate, lime rarely exists in the soil in any con- 
 siderable quantity. It is chiefly in such as are derived from the decay 
 of the trap rocks or of some varieties of granite (sienite), that silicate 
 of lime is to be expected to occur. 
 
 If, after being treated with dilute sulphuric acid, as above described, 
 the soil be digested for some hours at a gentle heat with concentrated 
 uiuriatic acid— a solution will be obtained from which ammonia will 
 ngain throw down a brown precipitate. If oxalate of ammonia now 
 cause a white precipitate of oxalate of lime, and if, on evaporating to 
 dryness, the solution leave a portion of silica insoluble in acids, we may 
 infer that the soil most probably contains some lime in the state of sili- 
 cate. 
 
 5°. In the state of carbonate, lime is generally supposed most usually 
 to exist, and most abundantly in all soils. If on pouring dilute muri- 
 anc acid upon a soil, a visible effervescence or escape of minute bubbles 
 of gas manifest itself, or if, when the experiment is made in a tube 
 closed atj)ne end, and inverted over water or mercury, bubbles of gas 
 collect in the upper end of the tube — the soil contains so7ne carbonate. 
 If after ammonia has been added to the solution, oxalate of ammonia 
 til rows down a white precipitate of oxalate of lime — the soil contains 
 carbonate o^lime. 
 
 6°. In the state of humate. — In combination with humic acid (Lee. 
 XIII., § 1,) lime exists most frequently in soils which abound in vege- 
 table matter — in peaty soils, for example, to which quick-lime or marl 
 of any kind has been added for the purpose of agricultural improve- 
 ment. The presence of lime in the state of humate is only to be detect- 
 ed by carefully determining the relative weights of the carbonic acid 
 given off" during the action of dilute muriatic acid upon the soil, and of 
 the lime contained in the solution thus obtained, (see Appendix.) If for 
 every 100 grains of carbonic acid there be more than 77'24 grains of 
 lime, the remainder or excess has existed in the soil in combination with 
 humic or some analogous organic acid.* 
 
 * To such analogous acids belong the crenic and apocrenic acids (Leo. XIII., § 1.) The 
 existence of these acids in the soil is by no means problematical. According to Professor 
 Hermann, of Moscow, they exist in the rich black soil (Tchornoi Zem.) of Little Russia, 
 to the amount of 4 per cent. 
 
QUANTITY OF LIME TO BE APPLIED TO THE SOIL. 381 
 
 Few investigations have as yet been made in regard to the proportion 
 of lime which exists in the soil in the state of humate. It has gene- 
 rally been taken for granted — either that a soil was destitute of Hme if 
 it exhibited no sensible effervescence with dilute muriatic acid, — or 
 when further research was made, and the quantity of hme taken up by 
 this acid rigorously determined, that the whole of this lime must have 
 existed in the soil in tne state of carbonate. That this is not necessarily 
 the case, however, appears to be proved by some recent examinations 
 of certain soils in Normandy, which contain as much as 14 to 15 per 
 cent, of lime, and yet exhibit no effervescence, and contain no carbo- 
 nate. The whole of the lime is said to be in the state of humate. 
 
 M. Dubuc, who has published the analyses of these soils, attributes 
 much of their fertility to tl^e presence of tlie humate of lime. Thus he 
 
 says that the soils of 
 
 Containing per cent. 
 Of Carbonate. Of Humate. Yields of Wheat. 
 
 Liouvin, Neubourg, and Sistot, 18 t(^0 12 to 15 fold. 
 
 PaviUi 5 ^' 8 to 10 ♦' 
 
 BieviUe 24 8 to 10 " 
 
 ClayofOuche 1 4 to 5 " 
 
 The first two yielding a wheat crop every second year, the third only at 
 longer intervals. 
 
 Wliatever degree of influence on the fertility of the soil it may ap- 
 pear proper to attribute to the existence of lime in the soil in the state 
 of humate, it is manifestly of some importance that its presence in this 
 state of combination should be more frequently and more carefully 
 sought after. 
 
 Tiie only one of the above compounds which is usually added to the 
 land, for the purpose of producing the ordinary effects of lime, is the 
 carbonate. Gypsum is applied only in small quantity for certain spe- 
 cial purposes, and does not always produce a sensible effect. It is in- 
 capable, therefore, of performing those purposes in the soil which are 
 served either by quick-lime or by the carbonate. The humate of lime 
 is probably formed in our lime composts, especially when much vege- 
 table matter is contained in them, and may thus be not unfrequeutly 
 applied directly to the land. 
 
 § 10. Of the quantity of lime which ought to he added to the soil. 
 
 The quantity of lime which ought to be added to the soil is dependent 
 upon so many circumstances, that it is impossible to state any general 
 rule by which, in all cases, the practical man can safely regulate his 
 procedure. 
 
 1°. To soils which contain no lime, or to which it is added for the 
 first time, a larger dose must be given. 
 
 Wo have seen that a certain minimum portion of lime is indispensa- 
 ble to a productive soil. If we suppose this smallest quantity to be no 
 greater than in the surface of the marsh lands of Holstein (p. 378) — 
 then with a soil six inches in depth, which contains no lime, we ought 
 to mix a ton and a half, say 40 bushels of slaked lime, and by succes- 
 sive yearly additions to supply the annual waste. 
 
 But to mix this feeble dose of lime intimately with the soil to a depth 
 of six inches would obviously require an expenditure of labor which 
 
382 MORE OUGHT TO BE LAID ON CLAY, WET, AND MARSHY SOILS, 
 
 the practical farmer could rarely afford. It would be greater economy, 
 therefore, in most cases to add a dose several times larger, and this not 
 only because the same amount of labor would diffuse it more general- 
 ly through the whole soil, but because this larger liming would render 
 less necessary the immediate addition of new supplies to repair the un- 
 avoidable waste. 
 
 But there is reason to believe that the proportion of lime which the 
 soil ought to contain, if it is to be successfully subjected to arable cul- 
 ture, ought to be much larger than is above assumed as the smallest 
 or minimum quantity. If we suppose one per cent, to be necessary, 
 then eight tons of lime-shells, or upwards of 300 bushels of slaked lime, 
 must be mixed with a soil six inches in depth, to impart to it this pro- 
 portion — or half the quantity, if it be kept within three inches of the sur- 
 face. Even a very large dose of lime, therefore, does not, if it be well 
 mixed, materially alter the constitution of the soil. 
 
 2°. But experience has proved that the quantity of lime which a 
 skilful farmer will adato his land will vary with many other circum- 
 stances besides the depth of his soil, and the proportion of lime it al- 
 ready contains. Thus — 
 
 a. On clay lands more lime is necessary than on light and sandy 
 soils. This may bs partly ascribed to the physical effect of the lime 
 in opening and loosening the stiff* clay — but independent of this action 
 the particles of lime are liable to be coated over and enveloped by the 
 fine clay, and thus shut out from the access of the air. These parti- 
 cles, therefore, must be more numerous in such a soil, if as many of 
 them are to be exposed to the air as in lighter land, through which the 
 atmospheric air continually permeates. 
 
 h. On wet and marshy soils, a larger application still may be made 
 with safely, and partly for the same reason. 
 
 The moisture surrounding the lime shuts out the air, without the 
 ready access of which lime cannot perform its important functions. The 
 same moisture tends to carry down the lime and lodge it more speedily 
 in the subsoil. The continued evaporation also keeps such soils too 
 cold (Lee. II., § 7), to allow the chemical changes, which lime in fa- 
 vorable circumstances produces, to proceed with the requisite degree 
 of rapidity. The soluble compounds which are formed as the conse- 
 quence of these changes are, in wet and marshy soils, dissolved by the 
 moisture, and so diluted as to enter in smaller quantity into the roots of 
 plants. And lastly, in certain cases, new compounds of the lime with 
 the earthy and stony matters of the soil are formed, which may either 
 harden into visible lumps of mortar and cement, or into smaller parti- 
 cles of indurated matter, in which the lime is no longer in such a state 
 as to be able to act in an equal degree as an improver of the soil. 
 
 In cold and wet clays, in which all these evil conditions occasionally 
 meet, it is not surprising, therefore, that large doses of lime should 
 sometimes have been added without producing any sensible benefit 
 whatever. (" An instance is mentioned in the Nottingham Report of 
 720 bushels having been laid on an acre of clod clay land without any 
 benefit whatever." — British Husbandry, i., p. 296.)" 
 
 c. Again, when the soil is also rich in vegetable matter, lime may 
 be still more abundantly applied. Thus, when a field is at once wet 
 
AND SUCH AS ARE RICH IN VEGETABLE MATTER. 383 
 
 or marshy, and full of vegetable matter, as our peat bogs are, lime may 
 be laid on more unsparingly than under any other circumstances. 
 For in this case, besides the action of the access of water, as above ex- 
 plained, the vegetable matter combines with and masks the ordinary 
 action of a considerable quantity of the lime. By this combination, no 
 part of the ultimate influence of the whole lime upon the soil is neces- 
 sarily lost ; in most cases the immediate effect only is lessened, which 
 the same quantity applied to other soils would have been seen to pro- 
 duce. In favorable circun}stances its action is retarded and prolonged, 
 the compounds it forms with vegetable matter decomposing slowly, and, 
 therefore, remaining long in the soil. 
 
 To the exact chemical constitution of the compounds thus formed, 
 as soon as lime is mixed up with a soil rich in vegetable matter, and to 
 the chemical changes which these compounds gradually undergo, it will 
 be necessary to direct our attention when we come to study the theory 
 of the action of lime, as an improverof the soil. 
 
 d. Not only the natural depth of the soil, as already stated, but also 
 the depth to which it is usually ploughed, and to which it is customary 
 to bury the lime, will materially affect the quantity which can be safely 
 applied. A dose of lime which would materally injure a soil into 
 which the plough rarely descends beyond two or three inches, might be 
 too small an application where six or eight inches are usually turned 
 over by the plough. When new soil, also, is to be brought up, which 
 may be supposed to contain no lime, or in which noxiotis substances are 
 present, a heavier dose of lime must necessarily be laid upon the land. 
 
 3°. Such are the circumstances in which large applications of lime 
 may be usefully applied to the land. In soils of an opposite character, 
 not only will smaller quantities of lime produce an equally beneficial 
 effect, but serious injury would often be inflicted by spreading it too lav- 
 ishly upon your fields. 
 
 The more dry and shallow the soil, the more light and sandy, the 
 less abundant in vegetahle matter, the more naturally mild its locality, 
 and the drier and warmer the climate in which it is situated — the less 
 the quantity of lime which the prudent farmer will venture to mix with 
 it. It is to the neglect of these natural indications that the exhaustion 
 and barrenness that have occasionally followed the application of lime 
 are to be ascribed. It is only in rare cases, such as the presence of 
 much noxious mineral matter in the soil, that these indications can be 
 safely neglected. 
 
 § 11. Ought lime to he applied in large doses at distant intervals^ or in 
 smaller quantities more frequently repeated 7 
 
 The quantity of lime which ought to be applied to the land must, as 
 we have seen, vary with its quality, and with the conditions in which it 
 is placed. Hence the practice in this respect necessarily varies in every 
 coiuny and in almost every district. 
 
 But a difference of opinion also prevails among practical men, as to 
 whether that quantity of lime which land of a given kind may require 
 ought to be applied in large doses at long intervals, or in small quantities 
 frequently repeated. The indications of theory in reference to this point 
 are clear and simple. 
 
384 OUGHT LIME TO BE APPLIED IN LARGE OR SMALL DOSES. 
 
 A certain proportion of lime is indispensable in our climate to the 
 production of the greatest possible fertility. Let us suppose a soil to be 
 wholly destitute of lime — the first step of the improver would be to add 
 to this indispensable proportion. This would necessarily be a large 
 quantity, and, therefore, to land limed for the first time theory indicates 
 the jJropriety of adding a large dose. 
 
 Every year, however, a certain variable proportion of the lime is re- 
 moved from the soil by natural causes. The effect of this removal in a 
 few years becomes sensibly apparent in the diminished productiveness 
 of the land. After the lapse of five or six years, during which it has 
 been gradually mixing with the soil, the beneficial effects of the lime is 
 generally the most striking — after this they gradually lessen, till at the 
 end of a longer or shorter period, the land reverts to its original condition. 
 To keep land in its best possible state, therefore, the natural waste ought 
 from Lime to time to be supplied by the addition of smaller doses of lime 
 at shorter intervals. 
 
 Such is obviously the most natural course of procedure, and he who 
 farms his own estate, and has therefore no strong inducement to do oth- 
 erwise, will, on the first breaking up of new land, give it a heavy 
 liming, and whether he afterwards retain it in arable culture or lay it 
 down to grass, will at intervals of 4 to 6 years give it a new doseof one- 
 fourth to one-eighth of the original quantity. But local circumstances 
 and customs interfere in many well-farmed districts with this most na- 
 tural treatment of the soil. In the county of Roxburgh, for example, 
 on entering upon his farm, which holds on a lease of 19 or 21 years, the 
 tenant begins by liming that portion of his land which is in fallow, or 
 in preparation for turnips, at the rate of 240 to 300 bushels of quick-lime 
 per acre. A similar liming is given to the other portions as they come 
 into fallow, so that at the end of his first rotation (4 or 5 years) the whole 
 of his land has been limed at the same rate. He now continues crop- 
 ping for three or four rotations (14 to 16 years), when if he is sure of re- 
 maining on his farm he begins to lime again with the same quantity as 
 before. IfLhe is to quit, however, he takes the best crops he can get, 
 but incurs no further outlay in the addition of lime. His successor fol- 
 lows the same course — begins by expending perhaps d£lOOO in lime, 
 and before he leaves at the end of his lease, has, by continued cropping, 
 brought back his land nearly to the same state in which he found it. 
 
 In the district of Kyle and other parts of Ayrshire, again, lime is laid 
 on — often when preparing for the wheat crop, either by ploughing in the 
 second furrow, or by harrowing in with the seed — at the rate of 40 bush- 
 els of shells an acre, and this dose is of course repeated every 4 or 6 years, 
 according to the length of the rotation. If we consider the probable dif- 
 ference in the soil and climate, the proportion of lime added in the two 
 districts does not materially differ. In Ayrshire from 8 to 10 bushels, and 
 in Roxburgh from 10 to 12 bushels, are added for each year.* In both 
 counties, however, many farms may be met with in which the treatment 
 of the land in this respect differs from that which is generally followed. 
 
 * According to General Beatson (^Ncw System of Cultivation, 1820), upwards 100 bushels 
 an acre, at a cost of jE7. 16s., used to be applied to the clay lands of Sussex^ — on the fallow, 
 before wheat— every foui years. This was 25 bushels per acre for each year. In such 
 lands as these the saving in the article of lime alone, which would follow a judicious drain* 
 age, would be very great. 
 
COMPARATIVE ECONOMY OF THE TWO METHODS. 385 
 
 in Flanders a similar difference in the practice prevails in different 
 districts. In some the land is limed only once in 12 yearg^in others 
 every third, fourth, or sixth year, according to the length of the rotation. 
 In the former case from 40 to 50 bushels are applied per acre, in the lat- 
 ter from 10 to 12 bushels every third year. In both modes of procedure 
 the quantity of lime applied by the year is nearly the same — between 
 3i and 4 bushels per acre. These quantities are very much less than 
 those employed in our island, but the soils are also greatly lighter, and 
 the climate, as well as the general treatment of the land, very different. 
 
 We may consider it, therefore, as a principle recognized or involved 
 in the agricultural practice both of our own and of foreign countries, 
 that nearly the same annual addition of lime ought to be made to the 
 land, whether it be applied at long intervals or at the recurrence of each 
 rotation. There is, therefore, on the whole, no saving in the cost of lime, 
 whichever method you adopt. A slight consideration of the subject, 
 however, may satisfy us that there is a real difference in the compara- 
 tive economy or profit of the two methods. 
 
 Let us suppose two acres of the same clay land to be limed respec- 
 tively with 200 bushels each, and that the one is cropped for twenty 
 years afterwards without further liming, while the other at the end of 
 every five years is dressed with an additional dose of 40 to 50 bushels. 
 In both cases the land would have attained the most productive con- 
 dition in five or six years. Let us suppose that in this condition it pro- 
 duced annually a crop of (or equivalent in nutritive value to) 30 bushels 
 of wheat, and that on neither acre did a sensible diminution appear be- 
 fore the end often years. Then during the second ten the crops would 
 gradually lessen in the one acre, while, in consequence of the re- 
 addition of the lime as it disappears, the amount of produce would re- 
 main sensibly the same in the other acre. Suppose the produce of 
 the former gradually to diminish from 30 to 20 bushels during these ten 
 years, — or that while the one has continued to yield 30 bushels during 
 the whole period, the other has, on an average, yielded only 25 bushels 
 during the latter ten years. If now the second large dose of 200 bushels 
 be added to this latter acre, the cost of liming both will have become 
 sensibly the same, but the amount of produce or of profit from the two 
 acres during the second ten years will stand thus — 
 
 10 crops, of 30 bushels each, amount to 300 bushels. 
 10 crops, of 25 bushels each, amount to 250 bushels. 
 
 Difference in favour of frequent liming, 50 bushels per acre, 
 or nearbj two ivhole crops every lease of twenty years. 
 
 Thus it appears 
 
 1°. That, according to the practice of different countries, the quantity 
 of lime which ought to be added, and consequently the cost of adding it, 
 is very nearly the same, whether it be applied in larger doses at longer 
 intervals, or in smaller doses more frequently repeated. 
 
 2°. That, after the first heavy liming, the frequent application of small 
 doses is the more natural method — and 
 
 3'^. That it is also the most economical or profitable method. 
 
 It is possible that other considerations, such as the tenure by which 
 your land is held, may appear sufficient to induce you to depart from 
 
386 MANURE MUST BE ADDED WHERE LIME ABOUNDS. 
 
 this method ; but there seems every reason to believe that it will best 
 reward those who feel themselves at liberty to follow the indications at 
 once of sound theory and of enlightened practice. 
 
 One thing, however, must be borne in mind by those who, in adopt- 
 ing the best system of liming, do not wish both to injure their land and 
 to meet with ultimate disappointment. Organic matter — in the form of 
 farm-yard manure, of bone or rape dust, of green crops ploughed in, or 
 of peat, and other composts — must be abundantly and systematically 
 added, if at the end of 20 or 40 years the land in which the full supply 
 of lime is kept up is to retain its original fertility. High farming is the 
 most profitable — for the soil is ever grateful for skilful treatment — but 
 he who farms high in the sense of keeping uj) the supply of lime, must 
 also farm high in the sense of keeping up the supply of organic and 
 other manures in the soil — otherwise present fertility and gain will be 
 followed by future barrenness and loss. If this is not to be done, it 
 were better to add lime at long intervals, since as the quantity of lime 
 diminishes, the land begins to enjoy a little respite, and has had time in 
 some measure to recover itself — the cropping in both instances being the 
 same — before the new dose is laid upon its surface.* 
 
 § 12. Form and state of combination in which lime ought to he 
 applied to the land. 
 
 The form and state of combination in which lime ought to be applied 
 to the land depend upon the nature of the soil, on the kind of cropping 
 to which it is subjected, and on the special purpose which the lime is 
 intended to effect. The soil may be heavy or light, in arable culture, 
 or laid down to grass, and eaclr of these conditions indicates a different 
 mode of procedure in the application of lime. So the lime itself may 
 he intended either to act more immediately or to be more permanent in 
 its action — or it may be applied for the purpose of destroying unwhole- 
 some herbage, of quickening inert vegetable matter, of generally sweet- 
 ening the soil, or simply of adding to the land a substance which is in- 
 dispensable to its fertility. The skilful agriculturist will modify the 
 form and mode of application according as it is intended to serve one or 
 other of tliese^ purposes. 
 
 From the considerations already presented to you (§ 3 ) in regard to 
 the changes which quick-lime undergoes in the air, it appears to be ex- 
 pedient, 
 
 1°. To slake lime quickly, and to apply it immediately upon clay, 
 boggy, marshy, or peaty lands — upon such also as contain much inert 
 or generally which abound in other forms of vegetable matter. 
 
 2°. To bents and heaths which it is desirable to extirpate, it should 
 be applied in the same caustic state, or to unwholesome subsoils which 
 contain much iron (sulphate of iron), as soon as they are turned up by 
 the plough. In both these cases the unslaked lime-dust from the kilns 
 might be laid on with advantage. 
 
 * " In the neighbourhood of Taunton, in Somersetshire, and over all the soil of the new 
 red sand-stone, the farmers lime their land every time it comes in course of fallow for tur- 
 nips, and this produces excellent crops, even without dung."— Morton on Soils, third edition, 
 p. 181. Ttie practical reader must not consider this custom of the Somersetshire farmers 
 as at all at variance with what is stated in the text; he must conclude, rather,— if the sen- 
 tence here quoted is meant to apply that they lime their arable land so repeatedly, and ye 
 add no organic manure— that they will, sooner or later, cease to boast of its fertility. 
 
COMPARATIVE ECONOMY OF LIME AND MARL. 387 
 
 3°. Where it is to be spread over grass lands without destroying the 
 herbage, it is in most cases safer to allow the lime to slake spontaneous- 
 ly, and in the open air rather than in a covered pit. It is thus obtained 
 in an exceedingly fine powder, which can be easily spread, and, while 
 it is sufficiently mild to leave the tender grasses unharmed, it contains 
 a sufficient quantity of caustjc lime (p. 368) to produce those chemical 
 changes in the soil on which the efficacy of quick-lime depends. 
 
 4°. Where lime is applied to the fallow, is ploughed in, well har- 
 rowed or otherwise mixed with the soil, it is generally of little conse- 
 quence in which of the above states it is laid on. The chief condition 
 is, that it be in the state of a fine powder, and that it be well spread 
 and intimately mixed with the soil. Before ihese operations are con- 
 cluded the lime will be very nearly in the state of combination in 
 which it exists in si)ontaneously slaked lime — whatever may have 
 been the state of causticity in which it has been applied. 
 
 You will understand that tlie above remarks apply only to localities 
 where burned lime is usually or alone used for agricultural purposes. 
 There may be localities where marl also exists, or shell or lime-stone 
 sand, in greater or less abundance, and in such places it may be a ques- 
 tion of some importance to determine which it would be better or more 
 economical to apply. In such a case you may safely proceed upon 
 the principle that the lime in the marls, &c., will ultimately produce 
 precisely the same effects upon your land as the lime from the kiln, 
 provided you lay on an equal quantity, and in an equally minute state 
 of division. The effect will only be a little more slow, and the full 
 fertility of the land a year or two longer in being brought out. You 
 would therefore consider, 
 
 1°. How much of the marl or sand must I add to be equal to a ton 
 of lime-shells ? This will depend on the per-centage of lime which 
 the marl contains. Suppose it to contain 20 per cent., or one-fifth of its 
 weight of lime, (not carbonate o^ lime, but of lime in the state in which 
 it comes from the kiln, 100 lbs. of carbonate containing 56 lbs. quick 
 lime, p. 364,) then five tons of the marl will be equal to one ton of lime 
 shells. But as the lime in the marls and sands is never in so minute 
 a state of division as in the slaked lime, the same quantity of lime in 
 the former cannot be so equally diffused through the soil as in the lat- 
 ter state. An allowance must therefore be made on this account, and 
 an additional quantity equal to one-fourth or one-fifth of the whole add- 
 ed, for the purpose of equalizing the effect. 
 
 2°. Which of the two, the quick-lime or its equivalent of marl, can 
 I obtain and apply at the less cost 1 This will not be difficult to calcu- 
 late, the proportion of lime contained in the marl being once ascertained. 
 
 3°. This question of economy being' decided, it is necessary to con- 
 sider the kind and quantity of the earthy matter with which the lime 
 in the marl is mixed. If it be a lime-sand or sandy marl, it may be un- 
 fit to apply to light and sandy soils ; if it be a stiff" unctuous clay marl, it 
 may only render stiff^er and more difficult to work the clay lands on 
 which you may propose to spread it. In such cases as these, however 
 economical the use of marls or lime-stone sands may be, the intelligent 
 farmer will prefer the addition of quick-lime wherever it is readily ac- 
 cessible. 
 
 17 
 
388 USE AVD ADVANTAGE OF THE COMPOST FORM. 
 
 Sussex is one of those districts in which the ancient use of marl has 
 given place to the employment of burned lime, (Beatson,) — chiefly, I 
 believe, from the nature of the local marl being less adapted to the stiff 
 clay lands of that county. 
 
 § 13. Of the use ana advantage of the compost form. 
 
 As there are many cases in wliich lime ought to be applied unmixed 
 and In the caustic state, so there are others in which it is best and most 
 beneficially laid upon the land in a mild state and in the form of com post. 
 
 1°. When lime is required only in small quantities, it can be more 
 evenly spread when previously well mixed with from 3 to 8 times its 
 bulk of soil. 
 
 2°. On light, sandy, and gravelly soils, when of a dry character, un- 
 mixed lime will bring up much cow-wheat {melampyrum) and red 
 poppy. If they are moist soils, or if rainy weather ensue, the lime is 
 apt to run into mortar, and thus to form either an impervious subsoil, 
 or lumps of a hard conglomerate, which are brought up by the plough, 
 but do not readily yield their lime to the soil. These bad consequences 
 are all avoided by adding the lime in the form of compost. 
 
 3°. Applied to grass lands — unless the soil be stiff clay — or much 
 coarse grass is to be extirpated, — it is generally better and safer to apply 
 it in the compost form. The action of the lime on the tender herbage 
 is by this means moderated, and its exhausting effect lessened upon 
 soils which contain little vegetable matter. 
 
 4°. In the compost form the same quantity of lime acts more imme- 
 diately. While lying in a state of mixture, those chemical changes 
 which lime either induces or promotes have already to a certain extent 
 taken place, and thus the sensible effect of the lime becomes apparent 
 in a shorter time after it has been laid upon the land. 
 
 5°. This is still more distinctly the case when, besides earthy mat- 
 ter, decayed vegetable substances, ditch scourings, and other refuse, are 
 mixed with the lime. The experience of every practical man has long 
 proved how very much more enriching such composts are, and more 
 obvious iaJiieir effects upon the soil, than the simple application of 
 lime alone. 
 
 6°. It is stated as the result of extended trial in Flanders and in parts 
 of France, that a much smaller quantity of lime laid on in this form 
 will produce an equal effect. For this, one cause may be, that the rains 
 are prevented from acting upon the mass of compost as they would do 
 upon the open soil — in washing out either the lime itself or the saline 
 substances which are produced during its contact with the earthy and 
 vegetable matter with which it is mixed. 
 
 7°. The older the compost the more fertilizing is its action. This 
 fact is of the same kind with that generally admitted in respect to the 
 action of marls and unmixed lime — that it is more sensible in the se- 
 cond year, or in the second rotation, than in the first. 
 
 In conclusion, it may be stated that this form of application is especi- 
 ally adapted to the lightest and driest soils, and to such as are poorest in 
 vegetable matter. In this form, lime has imparted an unexpected fertility 
 even to the white and barren sands of the Landes (Puvis,) and upon 
 the dry hills of Derbyshire it has produced an almost equal benefit. 
 
PERIOD FOR THE APPLICATION OF LIME. 389 
 
 § 14. When ought lime to he applied ? 
 
 This question may refer either to the period in the lease, in the rota- 
 lion, or of the year in which lime ma}' most beneficially be laid upon 
 the land. We have already considered this point in so far as it refers 
 to the lease, while discussing the propriety of applying lime in large or 
 small doses. 
 
 In regard to the period of the year and of the rotation, there are three 
 principles by which the procedure of the practical man ought chiefly to 
 be directed. 
 
 1°. That lime takes some time to p>foduce its known effects upon the 
 soil. — It ought, therefore, to be applied as long as possible before the 
 crop is sown. That is, in the early autumn, where either winter or 
 spring corn is about to be sown, — on the naked fallow where the land 
 is allowed to be at rest for a year, — or on the grass fields before break- 
 ing up, where the pasture is to be immediately succeeded by corn. 
 
 2°. That quick-lime expels ammonia from decomposed and fermenting 
 manure. 
 
 When such manure, therefore, is applied to the land, as it is in all 
 our well-farmed districts, quick-lime should not be so laid upon the 
 land as to come into immediate contact with it. If both must be ap- 
 plied in the same year, they should be laid on at periods as distant from 
 each other as may be convenient, or if this necessity does not exist, the 
 lime should be spread eitfier a year before or a year after the period in 
 the rotation at which the manure is usually applied. 
 
 It is for this reason, as well as for the other already stated, (1°.) that 
 lime is applied to the naked fallow, to the grass before breaking up, or 
 along with the winter wheat after a green crop which has been aided 
 by fermented manure. When ploughed into the fallow, or spread upon 
 the grass, it has had time to be almost completely converted into the 
 mild state (that of carbonate,) before the manure is laid on. In this 
 mild state it has no sensible effect in expelling the ammonia of decom- 
 posing manure. Again, when it is applied in autumn along with, or 
 immediately before the seed, the volatile or ammoniacal part of the 
 manure has already been expended in nourishing the green crop, so that 
 loss can rarely accrue from the admixture of the two at this period of 
 the rotation. 
 
 The excellent elementary work of Professor Lowe, (Elements of 
 Practical Agriculture, third edition, p. 63,) contains the following re- 
 mark : — " It is not opposed to theory that lime should be applied to the 
 soil at the same time with dung and other animal and vegetable sul)- 
 stances, as is frequent in the practice of farmers." This is strictly cor- 
 rect only in regard to marls, lime-sand, (tec, or to perfectly miki lime, 
 any of which may be mixed, without loss, with manure in any state. 
 Of quick or caustic lime it is correct only when the animal or vegetable 
 matter has not yet begun to ferment. With recent animal or vegetable 
 matter, quick-lime may be mixed up along with earth into a compost, 
 not only without the risk of much loss, but with the prospect of mani- 
 fest advantage. 
 
 3°. That quick-lime hastens or revives the decomposition of inert or- 
 ganic matter. — This fact also indicates the propriety of allowing the 
 
390 LIME HASTENS ORGANIC DECOMPOSITION. 
 
 lime as much time as possible to operate before a crop is taken from 
 land in which organic matter already abounds. Or where fermenting 
 manure is added," it advises the farmer to wait till spontaneous decom- 
 position becomes languid, when the addition of lime will bring it again 
 into action and thus maintain a more equable fertility. 
 
 In a work upon soils, which I have frequently commended to your 
 notice, (Morton "On 5^oiZ5," third edition, p. 181,) you will find the 
 following observations : — " Writers on agriculture have stated that lime 
 hastens the decay of vegetable matter, whereas the fact is, that it retards 
 the process of the decomposition of vegetable matter. If straw or long 
 dung be mixed with slaked lime, it will be preserved; while if mixed 
 with an equal portion of earth, the earth will hasten its decay." The 
 two facts stated in this last sentence are, I believe, correct, yet it is 
 nevertheless consistent both with theory and universal observation, that 
 lime in the soil promotes the decomposition of organic matters, both 
 animal and vegetable. This will appear more clearly when we come 
 to study the precise nature of the action of lime upon organic substan- 
 ces in general. 
 
 The above remarks, in regard to the best time for appl3ang lime, re- 
 fer chiefly to quick-lime, the state in which, in England, it is so exten- 
 sively used. Marls and shell-sands can cause no loss when mixed 
 with the manure, and therefore may with safety be laid on at any |)e- 
 riod of ihe rotation. The same remark applies with greater force to the 
 lime composts. Tiiese may be used precisely in the same way as, and 
 even instead of, the richer manures — may be laid, without risk, upon 
 grass lands of any quality, and at any period — or as a top dressing on 
 the young corn in spring, when the grass and clover seeds are sown by 
 which the corn crop is to be succeeded. And as the compost acts 
 more speedily than lime in any other form, it is especially adapted for 
 immediate application to the crop it is intended to benefit. To wet 
 lands also, it is well suited, and to such as are subject to much rain, by 
 which, while the surface is naked, ihe soluble matters produced in the 
 soil are likely to be very much washed away. 
 
 § 15. Of the effects produced by lime. 
 
 The effects of pure lime upon the land, and upon vegetation, are ul- 
 timately the same, whetiier it be laid on in a state of hydrate or of car- 
 bonate. If different varieties produce unlike etrecls, the quantity of 
 lime applied being the same, it is because in nature lime is always 
 more or less mixed with other substances which are capable of modi- 
 fying the effects which pure lime would alone produce. The special 
 effects of marls, &c., when they differ from those of burned lime, are 
 to be ascribed to the presence of such admixtures. -In general, how-* 
 ever, llie chemical action of the marls and calcareous sands is precisely 
 the same in kind as that of lime in the burned and slaked state, and so 
 far the effects which we have already seen to be produced by maris, 
 (p. 374,) represent also the general effects of lime in any form. 
 
 These general effects may be considered in reference to the land on 
 which it is laid, and to the crops which are, or may bc^ made to grow 
 upon it. 
 
EFFECTS or LIME UPON T.IE LAND AND CROPS. 391 
 I. EFFECTS OF LIME UPON THE LAND. 
 
 Pure lime, like the marls, produces both a mechanical and a chemi- 
 cal etfect upon the soil. The former is constant with all varieties of 
 tolerably pure lime, and is easily understood. It opens and renders freer 
 such soils as are stiliand clayey, while it increases the porosity of such 
 as are already light and sandy. To the former its mechanical action is 
 almost always favourable, to the latter not unfrequently the reverse. 
 
 From its chemical action the benefits which follow the use of lime 
 are chiefly derived. These benefits are principally the following: — 
 
 1°. It increases the fertility of all soils in which lime does not already 
 abound, and especially adds to the productiveness of such as are moist 
 or contain nmch inert vegetable matter. 
 
 2°. It enables the same soils to produce crops of a superior quality 
 also. Land which, un limed, will produce only a scanty crop, (3 or 4 
 fold,) of rye, by the addition of lime alone, will yield a 6 or 7 fold re 
 turn of wheat. From some clays, also, apparently unfit to grow corn 
 it brings up luxuriant crops. 
 
 3°. It increases the eiiect of a given application of manure; calls 
 into action that which, having been previously added, appears to lie 
 dormant ; and though, as we have already seen, (p. 386,) manure must 
 be plentifully laid upon the land, after it has been well-limed, yet the 
 same degree of productiveness can still be maintained at a less cost of 
 manure than where no lime has been applied. 
 
 4°. As a necessary result of these important changes, the money 
 value and annual return of the land is increased, so that tracts of coun- 
 try which had let with difficulty for 5s. an acre, have in many locali- 
 ties been rendered worth 30s. or 40s. by the application of lime alone, 
 (Sir J. Sinclair.) 
 
 II. — EFFECTS OF LIME ON THE PRODUCTIONS OF THE SOIL. 
 
 1°. It alters the natural produce of the land, by killing some kinds 
 of plants and favouring the growth of others, the seeds of which had 
 before^ lain dormant. Thus it destroys the plants which are natural to 
 siliceous soils and to moist and marshy places. From the corn-field it 
 extirpates the corn-marigold, {chrysanthemum segetum, [Bonninghau- 
 sen,]) while, if added in excess, it encourages the red poppy, the yel- 
 low cow-wheat, {melamjyyruyn pratense,) and the yellow rattle, {rhinan- 
 Ihus crista galli,) and when it has sunk, favours the growth of the trou- 
 blesome and deep-rooted coltsfoot. 
 
 Similar effects are produced upon the natural grasses. It kills heath, 
 moss, and sour and benty* (agrostis) grasses, and brings up a sweet 
 and tender herbage, mixed with white and red clovers, more greedily 
 eaten and more nourishing to the cattle. Indeed, all fodder, whether 
 natural or artificial, is said to be sounder and more nourishing when 
 grown upon land to which lime has been abundantly applied. On 
 benty grass the richest animal manure often produces little improvement 
 until a dressing of lime has been laid on. 
 
 ' In Liddisdale, on the Scottish border, is a large tract of land In what is there called 
 Jiying bent, not worth more than 3s. an acre. If surface-drained and limed at a ccst of 
 £2 to £3 an acre, this becomes worth I2s. an acre for sheep pasture. An intelligent and 
 experienced border farmer assures me that such land would never forget 40 to 60 bushela 
 of lime per acre. 
 
392 LIME IMPROVES THE QUALITY OF THE CROP. 
 
 It Is partly in consequence of the change which it thus produces in 
 the nature of the herbage, that the appHcation of quick-lime to old grass- 
 lands, some time before breaking up, is found to be so useful a practice. 
 The coarse grasses being destroyed, tough grass land is opened and 
 softened, and is afterwards more easily worked, while, when turned 
 over by the plough, the sod sooner decays and enriches the soil. It is 
 another advantage of this practice, however, that the lime has time* to 
 difTuse itself through the soil, and to induce some of those chemical 
 changes by which the succeeding crops of corn are so greatly benefitted. 
 
 2°. It improves the quality of almost every cultivated crop. Thus, 
 upon limed land, 
 
 a. The grain of the corn crops has a thinner skin, is heavier, and 
 yields more flour, while this flour is said also to be richer in gluten. 
 On the other hand, these crops, after lime, run less to straw, and are 
 more seldom laid. En wet seasons, (in Ayrshire,) wheat preserves its 
 healthy appearance, while on unlimed land, of equal quality, it is yel- 
 low and sickly. A more marked improvement is said also to be pro- 
 duced both in the quantity and in the quality of the spring-sown than of 
 the winter-sown crops, (Puvis.) 
 
 h. Potatoes grown upon all soils are more agreeable to the taste and 
 mpre mealy after lime has been applied, and this is especially the case 
 on heavy and wet lands, which lie still undrained. 
 
 c. Turnips are often improved both in quantity and in quality when 
 it is laid on in preparing the ground for the seed. It is most etficient, 
 and causes the greatest saving of farm-yard manure where it is applied 
 in the compost form, and where the land is already rich in organic mat- 
 ter of various kinds. 
 
 d. Peas are grown more pleasant to the taste, and are said to be 
 more easily boiled, soft. Both beans and peas also yield more grain. 
 
 e. Rape, after a half-Wramg and manuring, gives extraordinary crops, 
 and the same is the case with the colsa, the seed of which is largely 
 raised in France for the oil which it yields. 
 
 f On flax alone it is said to be injurious, diminishing the strenj;th of 
 the fibre oflTie stem. Hence, in Belgium, flax is not grown on limed 
 land till seven years after the lime has been applied. 
 
 3°. // hastens the maturity of the crop. — It is true of nearly all our 
 cultivated crops, but especially of those of corn, that their full growth 
 is attained more speedily when the land is limed, and that they are 
 ready for the harvest from 10 to 14 days earlier. This is the case even 
 with buck-wheat, which becomes sooner ripe, though it yields no larger 
 a return, when lime is applied to the land on which it is grown. 
 
 4°. The liming of the land is the harbinger of health as well as of 
 abundance. It salubrifies no less than it enriches the well cultivated 
 district. I have already drawn your attention (p. 310) to this as one 
 of the incidental results which follow tlie skilful introduction of the 
 drain over large tracts of country. Where the use of lime and of the 
 drain go together, it is diflficult to say how much of the increased 
 healthiness of the district is due to the one improvement, and how much 
 
 * A comparatively long period is sometimes permitted to elapse before the grass land is 
 broken up after liming. Thus at Nelherby, " lime or compost is always applied to the 
 third year's pasture, wliich is renovated by it, and in two or three years breah:s up admi- 
 rably for oats." 
 
LIME SHOULD BE KEPT NEAR THE SURFACE. 393 
 
 to the other. The lime arrests the noxious effluvia which tend to rise 
 more or less from every soil at certain seasons of the year, and decom- 
 poses them or causes their elements to assume new forms of chemical 
 combination, in which they no longer exert the same injurious influ- 
 ence upon animal life. How beautiful a consequence of skilful agri- 
 culture, that the health of the community should be promoted by the 
 same methods which most largely increase the produce of the land ! 
 Can you doubt that the All-benevolent places this consequence so 
 plainly before you, as a stimulus to further and more general improve- 
 ment — to the application of other knowledge still to the amelioration of 
 the soil ? 
 
 § 16. Circumstances hy which the effects of lime are modified. 
 
 These effects of lime are modified by various circumstances. We 
 have already seen that the quantity which must be applied to produce 
 a given effect, and the form in which it will prove mast advantageous, 
 arc, in a great measure, dependent upon the dryness of the soil, upon 
 the quantity of vegetable matter it contains, and on its stiff" or open tex- 
 ture. There are several other circumstances, however, to which it is 
 ])ro|)er still to advert. Thus, 
 
 1°. Its effects are greatest when well mixed with the soil, and kept 
 near the surface within easy reach of the atmosphere. The reason of 
 this will hereafter appear. 
 
 2°. On arable soils of the same kind and quality, the effects are 
 greatest upon such as are newly ploughed out, or upon subsoils just 
 brought to day. In the case of subsoils, this is owing partly to their 
 containing naturally very little lime, and partly to the presence of nox- 
 ious ingredients, which lime has the power of neutralizing. In the case 
 of surface soils newly ploughed out, the greater effect, in addition to these 
 two causes, is due also to the large amount of vegetable and other or- 
 ganic matter which has gradually accumulated within them. It is tne 
 presence of this organic matter which has led to the establishment of 
 the excellent practical rule — " thai lime ought alivays to precede putres- 
 cent manures when old leys are broken up for cultivation.''^ 
 
 3°. Its effects are greater on certain geological formations than on 
 others. Thus it produces much effect on drifted (diluvial) sands and 
 clays— on the soils of the plastic and wealden clays (Lee. XL, § 8) — 
 on those of the new and old red sand-stones, of the granites, and of 
 many slate-rocks — and, generally, on the soils formed from all rocks 
 which contain little lime, or from which the lime may have been washed 
 out during their gradual degradation. 
 
 On the other hand, it is often applied in vain to the soils of the oolites 
 (Lee. XL, § 8), and other calcareous formations, because of the abund- 
 ance of lime already present in them. The advantage derived from 
 chalking thin clay soils resting immediately upon the chalk rock (Lee. 
 XL, § 8, and page 376), is explained by the almost entire absence ot 
 lime from these soils. The clay covering of the chalk wolds has pro 
 bably been formed, not from the ruins of the chalk rock itself, but 
 from the deposit of muddy waters, which rested upon it for some time 
 before those localities became dry land. 
 
 4°. Lime produces a greater proportional improvement upon poor soils 
 
394 LAND MAY BE SATUR ATF.D VvlTH LIMK. 
 
 than on such as are richer (Dr. Anderson.) This is also easily under- 
 Btood, It is of poor soils in their natural state of which Dr. Anderson 
 speaks.* In this state they contain a greater or less quantity of organic 
 matter, but are nearly destitute of lime, and hence are in the most favour- 
 able condition for being benefitted by a copious liming. Experience 
 has proved that by this one operation such land may be raised in money 
 value eight times, or from 5s. to 40s. per acre ; but no practical man 
 would expect that arable land already worth £2 per acre, could, by 
 liming or any other single operation, become worth c£l6 per acre of an- 
 nual rent. The greater proportional improvement produced upon poor 
 lands by lime is only an illustration, therefore, of the general truth — 
 that on poor soils the eflforts of the skilful improver are always crowned 
 with the earliest and most apparent success. 
 
 5°. In certain cases, the addition of lime, even to land in good culti- 
 vation, and according to the ordinary and approved practiceof the district, 
 produces no effect whatever. This is sometimes observed where the 
 custom prevails, as in some parts of Ayrsliire and elsev^-here, to apply 
 lime along with every wheat crop (p. 384,) and on such farms especially 
 where the land is of a lighter quality. Where from 40 to 60 bushels 
 of lime are added at the end of each rotation of 4 or 5 years, the land 
 may soon become so saturated with lime that a fresh addition will pro- 
 duce no sensible effect. Thus Mr. Campbell, of Craigie, informs me 
 of a trial made by an intelligent farmer in his neighbourhood, where al- 
 ternate ridges only were limed without any sensible difference being ob- 
 served. No result could show more clearly than this — that for one ro- 
 tation at least the ex|)ense of lime might be saved, while at the same time 
 the land would run the less risk pf exhaustion. Another fact mentioned 
 by Mr. Campbell proves the soundness of this conclusion. The lime 
 never fails to produce obvious benefit where the land is allowed to be 4 
 or 5 years in grass — where it is" applied, that is, only once in 8 or 9 
 years. The fair inference is, therefore, that in this district as well as 
 in others where similar effects are observed, too much lime is habitually 
 added to the land, whereby not only is a needless expense incurred, but 
 a sj)eedier exhaustion of the soil is insured. Good husbandry, therefore, 
 indicates either the application of a smallerdose at the recurrence of the 
 wheat crop — or the occasional omission of lime altogether for an entire 
 rotation. The practical farmer cannot have a better mode of ascer- 
 taining when his land is thus fully supplied wdth lime — than by mak- 
 mg the trial upon alternate ridges, and niarking the effect. 
 
 6°. On poor arable lands, which are not naturally so, but which are 
 worn out or exhausted by repeated liming and cropping, lime produces 
 no good whatever! (Anderson, Brown, Morton.) Such soils, if they do 
 not already abound in lime, are, at least, equally destitute of numerous 
 other kinds of food, organic and inorganic, by which healthy plants are 
 nourished, — and they are only to be restored to a fertile condition by a 
 
 ' " I never met," he says, " with a poor soil in its natural state, which was not benefitted 
 in a very great degree by calcareous matter when administered in proi)er quantities. But 
 I have met witli several rich soils, whicli are fully impregnated with dung, on which lime 
 applied in any quantity produced not the smallest sensible effect." 
 
 t " It is scarcely practicable to restore fertility to land, even of the best natural quality, 
 which has Leen tlms abused ; and thin nioorisli soils, after being exhausted bv Hme, are 
 aot to be restored." (IJrown.) 
 
LIME DOES KOT BENEFIT EXHAUSTED LANDS. 395 
 
 judicious admixture of all This truth is confirmed by the practical 
 observation, that on soils so exhausted farm yard manuie along with 
 the lime does not produce the same good results as in other cases. All 
 that the soil requires is not supplied in sufficient abundance by these 
 two substances laid on alone. 
 
 " 7°. On lands of this kind, and on all in which vegetable matter is 
 wanting, lime may even do harm to the immediate crop. It is apt to 
 singe or burn the corn sown upon them (Brown) — an effect which is 
 probably chemical, but which may in part be owing to its rendering 
 more open and friable soils already, by long arable culture, too open. 
 (Morton.) 
 
 8°. A consideration of the circumstances above adverted to explains 
 why, in some districts, and even in some whole provinces, the use of 
 lime in any form should be condemned and even entirely given up. 
 The soil has been impoverished through its unskilful application — or, 
 by large admixtures of lime or marl for a series of years, the soil has 
 been so changed as to yield no adequate return for new additions. Thus 
 for a generation or two the practices of liming and marling are abandoned, 
 to be slowly and reluctantly resuined again, when natural causes have 
 removed the lime from the soil, and produced an accumulation of tRose 
 other substances which, when associated with it, contribute to the pro- 
 ductiveness of the land. 
 
 § 17. Effects of an overdose of lime. 
 
 There are several effects which are familiar to the practical man as 
 more or less o])servable when lime in any form is laid too lavishly upon 
 the land. Thus 
 
 1°. It is rendered so loose by an overdose as to be capable of hold- 
 ing no water (Karnes). Upon stiff' clays a very large quantity indeed 
 will be required to produce this effect. 
 
 2°. By an overdose of quick-lime the land is hardened to such a degree 
 as to be impervious to water or to the roots of plants. Several parts of 
 the Carse of Govvrie are thus rendered so hard as to be unfit tor vegeta- 
 tion — (Lord Kames' Gentleman Farmer, edit. 1802). This effect will 
 be observed only in soils which are naturally wet and undrained, or 
 where much rain has fallen and lingered on the land after the lime 
 has been apj)lied (p. 388). 
 
 3°. But the most injurious effect of an over-liming, whether it be 
 laid on at one or at successive periods, is the exhaustion by which it is 
 succeeded. " An overdose of shell-marl," says Lord Kames, "laid per- 
 haps an inch thick, produces for a time large crops, but at last renders 
 the soil capable of bearing neither corn nor grass, of which there are 
 many examples in Scotland." The same is true of lime in any form. 
 The increased fertility continues as long as there remains an adequate 
 supply of organic (animal and vegetable) matter in the soil, but as that 
 disappears the crops every year diminish both in quantity and in quality. 
 
 An interesting illustration of this exhausting power of lime is afforded 
 
 by the observed effects of long-continued marling upon certain poor soils 
 
 in the province of Isere, in France. The marl there employed is a 
 
 aaady marl, containing from 30 to 60 per cent, of carbonate of lime. — 
 
 17* 
 
396 LENGTH OF TIME DURING WHICH LIME ACTS. 
 
 very much like the Hme-sand of Ireland or the shell-sand of the West- 
 ern Islands already described (p. 371). A layer of this marl one-third 
 of an inch thick, applied at intervals to a soil producing in its natural 
 state only a three-fold return of rye every other year, causes it to yield 
 for the first 10 or 12 years an eightfold i^eturn ofwhear. But after 40 
 years' marling, the farmers now complain that the land will give only a 
 four-fold return of wheat. But the cause of this reduction is to be 
 found in the constant cropping with corn, in the growing of no green 
 crops, and in the addition of no manure. Yet even with this treat- 
 ment the land is still more productive than before the marling was com- 
 menced. It produces four returns instead of three, and it grows wheat 
 where before only rye would thrive and ripen. 
 
 From the possession of this exhausting property has arisen the al- 
 most universally diffused proverb, that lime enriches the fathers hut 
 im,poverishes.the sons. The fault, however, is not in the lime, but in 
 the improvident fathers, who in this case, as in so many others^ exhaust 
 and inconsiderately squander the inheritance of their sons. If care 
 be taken to keep up the supply of organic matter in the soil^by copi- 
 ous additions of manure or otherwise (p. 380) — lime may be added 
 freely and a system of high farming kept up, by which both the pres- 
 ent holder of the land and his successors will be equally benefitted. 
 
 The opinion expressed by some of the highest authorities among 
 practical men, that too much lime cannot be added, provided the soil 
 abound sufficiently in vegetable matter, may perhaps be rather over- 
 stated ; but it undoubtedly embodies the result of long-continued gen- 
 eral observation — that the exhausting effect of lime may be postponed 
 indefinitely by a liberal management of the land.* 
 
 § 18. Length of time during which lim£ acts. 
 
 It is the fate of nearly all the superficial improvements of the soil, 
 that they are only temporary in their duration. The action of lime 
 ceases after a time, and the land returns to its original condition. The 
 length of time which must elapse before this takes place will depend, 
 amongotlier circumstances, upon the quantity of lime added to, or ori- 
 ginally contained in, the soil — upon the kind of cropping to which it is 
 subjected — on the nature of the soil itself — on the slope and exposure 
 and natural moisture of the land, and on the climate in which it is 
 situated. 
 
 We have seen that on the arable lands of the south of Scotland 20 
 years is the longest period during which the doses there applied act 
 beneficially upon the crops — while in other parts of the country re- 
 newed applications are considered necessary at much shorter intervals. 
 Mr. Dawson, of Frogden, who introduced the practice of liming into the 
 Border counties of Scotland, observed that, when harrowed in with the 
 grass seeds, its effect in improving the subsequent pasture was sensible 
 for 30 years after. A heavy marling or chalking* in the southern and 
 
 • In Germany the necessary union of manure and marl is in the mouth of every peasant— 
 
 Ohne mist 
 
 1st das Geld fiir mergeln verqulst. 
 
 t Applied at a cost of 30s. lo 50s. per acre, according to the locality.— Mr. Pusey, Roj/mt 
 Agricultural Journal, iii., p. 185. 
 
 •-I 
 
LIME NATURALLY SINKS INTO THE SOIL. 397 
 
 Midland counties of England is said also to last for 30 yeare, and the 
 same period is assigned to the sensible effect of the ordinary doses of 
 lime-sand in Ireland, and of shell-sands and marls in several parts of 
 France. 
 
 The effect ff the lime lessens gradually, and though at the end of an 
 assignable number of years it becomes almost insensible, yet it does not 
 altogether cease till a much later period. This period is in some cases 
 so protracted that intelligent practical men are in many districts to be 
 met with who believe — that certain grass lands would never forget a 
 good dose of lime (p. 391, note). 
 
 § 19. Of the sinking of lime into the soil. 
 
 One of the causes of this gradual diminution of the action of lime is to 
 be found in the singular property it possesses of slowly sinking into the 
 land, until it almost entirely disappears from the surface soil. It has 
 been long familiar to practical men, that when grass lands, which have 
 been hmed on the sward, are after a time broken up, a white layer or 
 band of lime is seen at a greater or less depth beneath the surface, but 
 lodging, generally, where it has attained its greatest depth between the 
 upper, loose and fertile, and the lower, more or less impervious and un- 
 productive soil. In arable lands the action of the plough counteracts 
 t.liis tendency in some measure, bringing up the lime again from be- 
 neath, and keeping it mixed with the surface mould. Yet, through 
 ploughed land it sinks at length, especially where the ploughing is 
 shallow, and even the industry of the gardener can scarcely prevent it 
 from descending beyond the reach of his spade. 
 
 The chief cause of this sinking is to be found in the extreme minute- 
 ness of the particles into which slaked lime naturally falls. If a por- 
 tion of slaked lime be mixed with water it forms a milky mixture, in 
 which some lime is dissolved, but much more is held in suspension in 
 an extremely divided state. When this milk is allowed to stand undis- 
 turbed, the fine particles subside very slowly, and are easily again dis- 
 'tarbed, but if thrown upon a filter they are arrested immediately, and 
 the lime-water passes through clear. Suppose these fine particles to 
 be mixed with the soil, and the rain to fall upon them, it will carry 
 them downwards through the pores of the soil till the close subsoil acts 
 thn part of a filter, and arrests them. This tendency to be washed 
 down is common not only to lime, but to all minutely divided earthy 
 matter of a sufficiently incoherent nature. Hence the formation of that 
 more or less impervious layer of finely divided matter which so often 
 forms the subsoil beneath free and open surface soils. And that lime 
 should appear alone or chiefly to sink on any cultivated field, may arise 
 from this circumstance — that the continued action of the rains had long 
 before carried downwards the finer incoherent particles of other kinds 
 wliich existed naturally in the soil, and therefore could find little else 
 but the lime on which this action could be exercised. 
 
 This explanation is satisfactory enough in the case of light and open 
 soils, wliich are full of pores, but it appears less so in regard to stift 
 clays and to loamy soils, which are not only close and apparently void 
 of pores, but seem themselves to consist of particles in a sufficiently 
 niinute state of division to admit of their being carried down by the 
 
398 EFFECTS OF SINKING, AND REMEDIES FOR IT. 
 
 rains in an equal degree with lime itself. This difficulty induced Lord 
 Dundonald to suspect the agency of some chemical principle in produ- 
 cing the above effect.* As the lime, however, is unchanged after it has 
 descended, is still in a powdery state, and exhibits no appearance of 
 having been dissolved; it is difficult to imagine any chemical action by 
 which such a sinking could have been brought about. 
 
 It is possible tliat in grass lands the earth-worms, which contribute so 
 much to the gradual production of a fine mould, may, by bringing up 
 the other earthy matters only, contribute to the apparent sinking of the 
 lime, as well as of certain other top-dressings.f 
 
 The effects of this sinking are to remove the lime from the surface 
 soil, and to form a layer of calcareous matter which in wet or imper- 
 vious bottoms will harden and form a more or less solid bed or pan, 
 through which the rains and roots refuse to penetrate, and which the 
 subsoil plough in some districts can tear up with difficulty. On our 
 stitfer soils it encourages the growth of the troublesome coltsfoot, and in 
 tJie open ditches of the wholesome water-cress. 
 
 The practical remedies for this sinking are of two kinds : 
 
 1°. The ploughing of a deeper furrow, and hence one of the benefits 
 which in many localities follow the use of the trench plough (p. 322). 
 
 2°. The sowing of deep-rooted and lime-loving crops, such as lucerne 
 and sainfoin, which in such soils not only thrive, but bring up in their 
 stems, and restore to the surface, a portion of the lime which had pre- 
 viously descended, and thus make it available to the after-crops. 
 
 § 20. Why liming- must be repeated. 
 
 Lime which sinks, as above described, does not wholly escape from 
 the soil, but may by judicious management be again brought to the 
 surface. Such a sinking; therefore, does not necessarily call tor the ad- 
 dition of a fresh dose of lime, nor does it explain the reason why in prac- 
 tice the application of lime to the land must at certain intervals be every 
 where repeated. 
 
 We have already seen that the influence of the lime we have laid 
 upon our fields after a time gradually diminishes — the grass becomes 
 sensibly lessiich year by year, the crops of corn less abundant, the kind 
 of grain it will ripen less valuable. Does the lime, you might ask, ac- 
 tually disappear from the soil, or does it merely cease to act ? This 
 question has been most distinctly answered by an experiment of Lam- 
 padius. He mingled lime with the soil of a piece of ground till it was 
 in the proportion of 1-19 per cent, of the whole, and he determined sub- 
 sequently, by analysis, the quantity of lime it contained in each of the 
 three succeeding years. 
 
 The first year it contained . 1-19 per cent, carbonate of lime. 
 The second year .... 0-89 " « 
 
 The third year 0-52 " « 
 
 The fourth year 0-24 « " % 
 
 * "In clay pjr and loamy soils, which are (T) equally ditfusible with lime, and nearly of the 
 same specific gravity, t^.e tendency which lime has to sink cannot be accounted for simply 
 on mechanical prinoipies " — Lord Dundonald's Agricultural Chemistry, p. 45. 
 
 fSee in a subsequent lecture the remarks on laying doxim to grass; also the Author's 
 Elements of Agricultural Chemistry, p. 212. 
 
 X Schiibler, Agricultural Chemie, ii,, p. 141. 
 
WHY LIMING MUST BE REPEATED. 399 
 
 There can be no question, therefore, that the lime gradually disappears 
 or is removed from th'fe soil. 
 
 The agencies by which this removal is effected are of several kinds. 
 
 1°. In some cases it sinks, as we have already seen, and escapes into 
 the subsoil beyond the reach of the plough or of the roots of our culti- 
 vated crops. 
 
 2°. A considerable quantity of lime is annually removed from the 
 soil by the crops which are reaped from it. We have already seen 
 (Lcc. X., § 4,) that in a four years' rotation of alternate green and corn 
 crops the quantity of lime contained in the average produce of good 
 land amounts to 248 lbs. This is equal to 60 lbs. of quick-lime or 
 107 lbs. of carbonate of lime every year. The whole of this, however, 
 is not usually lost to the land. Part at least is restored to it in the ma- 
 nure into which a large proportion of the produce is usually converted. 
 Yet a considerable quantity is always lost — escaping chiefly in the 
 liquid manure and in the drainings of the dung-heaps — and this loss 
 must be repaired by the renewed addition of lime to the land. 
 
 3°. But the rains and natural springs of water percolating tlirough 
 the soil remove, in general, a still greater proportion. While in the 
 quick or caustic state, lime is soluble in pure water. Seven hundred 
 and fifty pounds of water will dissolve about one pound of lime. 'The 
 rains that fall, therefore, cannot fail, as they sink through the soil, to 
 dissolve and carry away a portion of the hme so long as it remains in 
 the caustic state. 
 
 Again, quick-lime, when mixed with the soil, speedily attracts car- 
 bonic acid, and becomes, after a time, converted into carbonate, which 
 is nearly insoluble in pure water. But this carbonate, as we have 
 already seen (Lee. HI., § 1), is soluble in water impregnated with car- 
 bonic acid — and as the drops of rain in falling absorb this acid from the 
 air, they become capable, when they reach the soil, of dissolving an 
 appreciable quantity of the finely divided carbonate which they meet 
 with upon our cultivated lands. Hence the water that flows from 
 the drains upon such lands is always impregnated with lime, and 
 sometimes to so great a degree as to form calcareous deposits in the in- 
 terior of the drains themselves, where the fall is so gentle as to allow the 
 water to linger a sufficient length of time in the soil. 
 
 It is impossible to estimate the quantity of lime which this dissolving 
 action of the rains must gradually remove. It will vary with the 
 amount of rain which falls in each locality, and with the slope or inclina- 
 tion of the land ; but the cause is at once universal and constantly oper- 
 ating, and would alone, therefore, render necessary, after the lapse of 
 years, the application of new doses of lime both to our pastures and to 
 our arable fields. 
 
 4°. During the decay of vegetable matter, and the decomposition of 
 mineral compounds, which take place in the soil where hme is present, 
 new combinations are formed in variable quantities which are more so- 
 luble than the carbonate, and which therefore hasten and facilitate this 
 washing out of the lime by the action of the rains. Thus chloride of 
 calcium, nitrate of lime, and gypsum, are all produced — of which the 
 IW'"* former are eminently soluble in water — while organic acids also re- 
 sult from the decay of the organic matter, with some of which the lime 
 ic»-m3 readily soluble compounds (salts) easily removed by water. 
 
400 ACTION OF LIME UPON THE SOIL, AND AS THE FOOD OF PLANTS. 
 
 The ultimate resolution of all vegetable matter in the soil into carbo- 
 nic acid and water (Lee. VIIL, § 3,) Hkewise aids the removal of the 
 lime. For if the soil be everywhere impregnated with carbonic acid, 
 the rain and spring waters that flow through it will also become charg- 
 ed with this gas, and thus be enabled to dissolve a larger portion of the 
 carbonate of lime than they could otherwise do. Thus theory indi- 
 cates, what I believe experience confirms, that a given quantity of lime 
 will disappear the sooner from a field, the more abundant the animal 
 and vegetable matter it contains. 
 
 §21. Theory of the action of lime. 
 
 Lime acts in two ways upon the soil. It produces a mechanical al- 
 teration which is simple and easily understood, and is the cause of a 
 series of chemical changes, which are really obscure, and are as yet 
 susceptible of only partial explanation. 
 
 In the finely divided state of quick-lime, of slaked lime, or of soft 
 and crumbling chalk, it stiffens very loose soils, and opens the stiffer 
 clays, — while in the form of limestone gravel or of shell-sand, it may 
 be employed cither for opening a clay soil or for giving body and firm- 
 ness to boggy land. These effects, and their explanation, are so obvi- 
 ous to you, that it is unnecessary to dwell upon them. 
 
 The purposes served by lime as a chemical constituent of the soil are 
 at least of four distinct kinds. 
 
 1°. It supplies a kind of inorganic food which appears to be necessa- 
 ry to the healthy growth of all our cultivated plants. 
 
 2^. It neutralizes acid substances which are naturally formed in the 
 soil, and decomposes or renders harmless other noxious compounds 
 which are not unfrequently within reach of the roots of plants. 
 
 3°. It changes the inert vegetable matter in the soil, so as gradual- 
 ly to render it useful to vegetation. 
 
 4"^. It causes, facihtates, or enables other useful compounds, both 
 organic and inorganic, to be produced in the soil, — or so promotes 
 the decomposition of existing compounds as to prepare them more 
 speedily for^ntering into the circulation of plants. 
 
 These several modes of action it will be necessary to illustrate in 
 some detail. 
 
 § 22. Of lime as the food of plants. 
 
 In considering the chemical nature of the ash of plants (Lee. X., 
 § 3 and 4), we have seen that lime in all cases forms a considerable 
 proportion of its v/hole weight. Hence the reason why lime is re- 
 garded as a necessary food of plants, and hence also one cause of its 
 benefi ^ial influence in general agricultural practice. 
 
 The quantity of pure lime contained in the crops produced upon one 
 acre during a four years' rotation amounts, on an average, to 242 lbs. 
 which are equal to about 430 lbs. (say 4 cwt. ) of carbonate of lime, m 
 the state of marl, shell-sand, or lime-stone gravel. (See Lee. X., § 3.) 
 It is obvious, therefore, that one of the most intelligible purposes served 
 by lime, as a chemical constituent of the soil, is to supply this compara- 
 tively large quantity of lime, which in some form or other must enter 
 into the roots of plants. 
 
ACTS CHIEFLY UPON THE ORGANIC MATTER OF THE SOIL. 401 
 
 But the different crops which we grow contain hme in unlike propor- 
 tions. Thus the average produce of an acre of land under the follow- 
 ing crops contains of lime — 
 
 Grain or roots. Straw or tops. Total. 
 
 Wheat, 25 bushels. ... 1-5 7-2 8-7 lbs. 
 
 Barley, 38 bushels,' ... 2-1 12-9 15-0 lbs. ^ 
 
 Oats, 50 bushels, .... 2-5 5-7 8-2 lbs. 
 
 Turnips, 25 tons 45-8 93-0 138-8 lbs. 
 
 Potatoes, 9 tons,' .... 6-6 259-4 266-0 lbs. 
 
 Red clover, 2 tons, ... — 126-0 126-0 lbs. 
 
 Rye grass, 2 tons, ... — 33-0 33-0 lbs. 
 
 These quantities are not constant, and wheat especially contains 
 much more lime than is above stated, when it is grown upon land to 
 which lime has been copiously applied. But the very different quanti- 
 ties contained in the several crops, as above exhibited, shew that one 
 reason why lime favours the growth of some crops more than others is, 
 that some actually take up a larger quantity of lime as food. These 
 crops, therefore; require the presence of lime in greater proportion in the 
 soil, in order that they may be able to obtain it so readily that no delay 
 may occur in the performance of those functions or in the growth of those 
 parts to which lime is indispensable. 
 
 § 23, The chemical action of lime is exerted chiefly upon the organic 
 
 matter of the soil. 
 
 There are four circumstances of great practical importance in regard 
 to the action of lime, which cannot be too carefully considered in refe- 
 rence also to the theory of its operation. These are — 
 
 1°. That lime has little or no effect upon soils in which organic mat- 
 ter is deficient. 
 
 2°. That its apparent effect is inconsiderable during the first year 
 after its application, compared with that which it produces in the second 
 and third years. 
 
 3°. That its effect is most sensible when it is kept near the surface of 
 the soil, and gradually becomes less as it sinks towards the subsoil. 
 And, 
 
 4°. That under the influence of lime the organic matter of the soil 
 disappears more rapidly than it otherwise would do, and that after it 
 has thus disappeared fresh additions of hme produce no further good 
 effect. 
 
 It is obvious from these facts, that wi general the main beneficial pur- 
 pose served by lime is to be sought for in the nature of its chemical ac- 
 tion upon the organic matter of the soil — an action which takes place 
 slowly, which is hastened by the access of air, and which causes the 
 organic matter itself ultimately to disappear. 
 
 § 24. Of the forms in which organic matter usually exists in the soil, 
 and circumstances vnder which its decomposition may take place. 
 
 I. — The organic matter which lime thus causes to disappear is pre- 
 sented to it in one or other of five different forms : 
 
 1°. In that of recent, often green, moist, and undecomposed roots, 
 leaves, and stems of plants. 
 
402 UPON THE DECOMPOSITION OF ORGANIC MATTER. 
 
 2°. In that of dry, and still undecomposed, vegetable matter, such 
 as straw. 
 
 3°. In a more or less decayed or decaying state, generally black or 
 brown in colour — and often in some degree soluble in water. 
 
 4°. in what is called the ineti state, when spontaneous decay ceases 
 to be sensibly observed. And 
 
 5°. In the state of chemical combination with the earthy substances 
 — with the alumina for example, and with the lime or magnesia — al- 
 ready existing in the soil. 
 
 Upon these several varieties of organic matter lime acts with differ- 
 ent degrees of rapidity. 
 
 II. — The final result of the decomposition of these several forms of 
 organic matter, when they contain no nitrogen, is their conversion into 
 carbonic acid and water only (Lee. VIIL, §3). They pass, however, 
 through several intermediate stages before they reach this point — the 
 number and rapidity of which, and the kind of changes they undergo 
 at each stage, depend upon the circumstances under which the decom- 
 position is ellected. Thus the substance may decompose — 
 
 1°. Alone, in which case the changes that occur proceed slowly, and 
 arise solely from a new arrangement of its own particles. This kind of 
 decomposition rarely occurs to any extent in the soil. 
 
 2°. Ill ilie 'presence of water onhj. — This also seldom takes place in 
 the soil. Trees long buried in moist clays impervious to air exhibit the 
 kind of slow alteration which results from the presence of water alone. 
 In the bottoms of lakes, ditches, and boggy places also, from which in- 
 flammable gases arise, water is the prmcipal cause ofthe more rapid 
 decomposition. 
 
 3°. In the presence of air only. — In nature organic matter is never 
 placed in this condition, the air of our atmosphere being always largely 
 mixed with moisture. In dry air decomposition is exceedingly slow, 
 and the changes which dry organic substances undergo in it are often 
 scarcely perceptible. 
 
 4°. In the presence of both water and air. — This is the almost uni- 
 versal conditioii of the organic matter in our fields and farm-yards. 
 The joint action of air and water, and the tendency of the elements of 
 the organic matter to enter into new combinations, cause new chem- 
 ical changes to succeed each other with much rapidity. It will of 
 course be understood that moderate warmth is necessary to the pro- 
 duction of these effects.* 
 
 b°. In the presence of lime, or of some other alkaline substance (pot- 
 ash, soda, or magnesia). — Organic matter is often found in the soil in 
 such a state that the conjoined action of both air and water are unable 
 to hasten on its decomposition. A new chemical agency must then be 
 
 ' A familiar illustration of the conjoined efficacy of air and water in producinj? oxidation is 
 exhibited in their action upon iron. If a piece of polished iron be kept in perfectly dry air 
 it will not rust. Or if it be completely covered over with pure water in a vrellsloi>pered 
 bi'tile, from which air is excluded, it will remain bright and untarnished. But if a polished 
 rod of iron tie put into an open vessel half full of water, so tlwU one part of its Icn^jih only 
 is under water— then the rod will begin very soon to rust at ihe surface of the water, and a 
 brown ochrey rin^ of oxide will foriii around it, exactly wliere the air and \vatcr meet 
 From this point the rust will gradually spread upwards and downwards. So it is with the 
 organic matter of the soil. Wherever the air and water meet, their decomposing action 
 upon it, in ordinary temperatures, soon becomes perceptible. 
 
INFLUENCE OF ALKALINE SUBSTANCES. 403 
 
 introduced, by which the elements ofthe organic matter may again be 
 set in motion. Lime is the agent which for this purpose is ihost large- 
 ly employed in practical agriculture. 
 
 § 25. General action of alkaline substances upon organic matter. 
 
 It is this action of alkaline matters upon the organic substances ofthe 
 soil in the presence of air and water that we are principally to investigate. 
 
 When organic matter undergoes decay in the presence of air and 
 water only, it first rots, as it is called, and blackens, giving off water 
 or its elements chiefly, and forming humus — a mixture of humic, ulmic, 
 and some other acids, (Lee. XIII., § 1,) with decaying vegetable fibre. 
 It then commences, at the expense of the oxygen of the air and of 
 water, to form other more soluble acids (malic, acetic, lactic, crenic, 
 madesic, &c.,) among which is a portion of carbonic — and, by the aid 
 of the hydrogen of the water which it decomposes, one or more of 
 tho many compounds of carbon and hydrogen, which often rise up, 
 a« the marsh-gas does, and escape into the air, (Lee. VIII., § 3.) 
 
 Tlius there is a tendency towards the accumulation of acid substances 
 of vegetable origin in the soil, and this is more especially the case when 
 the soil is moist, and where much vegetable matter abounds. The effect 
 of tills super-abundance of acid matter is, on the one hand, to arrest the 
 farther natural decay of the organic matter, and, on the other, to render 
 the soil unfavorable to the healthy growth of young or tender plants. 
 
 The general effect of the presence of alkaline substances in the soil 
 i.-; to counteract these two evils. They combine with and thus remove 
 t!io sourness of the acid bodies as they are formed. In consequence of 
 this the soil becomes sweeter or more propitious to vegetation, while the 
 natural tendency ofthe vegetable matter to decay is no longer arrested. 
 
 it is thus clear that an immediate good effect upon the land must fol- 
 io vv either from the artificial application or from the natural presence of 
 alkaline matter in the soil — while at the same time it Avill cause the 
 vt\^^ctable matter to disappear more rapidly than would otherwise be 
 the case. But the effect of such substances does not end here. They 
 actually dispose or provoke — pre-dispose, chemists call it — the vegeta- 
 ble matter to continue forming acid substances, in order that they may 
 combine with them, and thus cause the organic matters to disappear 
 more rapidly than they otherwise would do — in other words, they 
 hasten forward the exhaustion of the vegetable matter of the soil. 
 
 Such is the general action of all alkaline substances. This action 
 they exhibit even in close vessels. Thus a solution of grape sugar, 
 mixed with potash, and left in a warm place, slowly forms melassic 
 acid — while in cold lime-water the same sugar is gradually converted 
 into another acid called the glucic. But in the air other acids are 
 formed in the same mixtures, and the changes proceed more rapidly. 
 Such is the case also in the soil, where the elements of the air and 
 of water are generally at hand to favor the decomposition. 
 
 But the nature of the alkaline matter which is present determines 
 also the rapidity with which such changes are produced. The most 
 powerful alkaline substances—potash and soda — produce all the above 
 effects most quickly; lime and magnesia are next in order; and the 
 alumina of the clay soils, though much inferior to all of these, is far 
 from being without an important influence. 
 
404 ACTION OF CAUSTIC LIME UPON ORGANIC MATTER 
 
 Hence one of the benefits which result from the use of wood-ashes 
 containing carbonate of potash, when employed in small quantities, 
 and along with vegetable and animal manures, as they are in this coun- 
 try ; but hence also the evil effects which are found to follow from the 
 application of them in too large doses. Thus in countries where wood 
 abounds, and where it is usual, as in Sweden and Northern Russia, 
 to burn the forests and to lay on their ashes as manure, the tillage 
 can be continued for a few years only. After one or two crops the 
 land is exhausted, and must again be left to its natural produce. 
 
 § 26. Special effects of caustic lime upon the several varieties of 
 organic matter in the soil. 
 
 The effects of lime upon organic matter are precisely the same 
 in kind as those of the alkalies in general. They are only less in de- 
 gree, or take place more slowly, than when soda or potash is em- 
 ployed. Hence, the greater adaptation of lime to the purposes of 
 practical agriculture. 
 
 1^. Action of caustic lime alone upon vegetable mutter. — If the fresh 
 leaves and twigs of plants, or blades and roots of grass, be introduced 
 into a bottle, surrounded with slaked lime, and corked, they will slowly 
 undergo a certain change of color, but they may be preserved, it is 
 said, for years, without exhibiting any striking change of texture (Mr. 
 Garden.) If dry straw be so mixed with slaked lime, it will exhibit 
 still less alteration. In either case also the changes will be even less 
 perceptible, iC instead of hydrate of lime, the carbonate (or mikl lime,) 
 in any of its forms, be mixed with these varieties of vegetable matter. 
 On some other varieties of vegetable matter, — such, for example, as are 
 undergoing rapid decay, or have aiready reached an advanced stage of 
 decomposition, — an admixture of slaked lime produces certain percepti- 
 ble changes immediately, and mild lime more slowly, but these changes 
 being completed, the tendency of lime alone is to arrest rather than to 
 promote farther rapid alterations. Hence, the following opinions of 
 experienced practical observers must be admitted to be theoretically 
 correct — in so far as they refer to the action of lime alone. 
 
 " If strawTjf long dung be mixed with slaked lime, it will be pre- 
 served." (Morton, >On Soils, 3d edition, p. 181.) 
 
 " Lime mixed in a mass of earth containing the live roots and seeds 
 of plants, will 7iot destroy them." (Morton.) 
 
 " Sir H. Davy's theory, that lime dissolves vegetable matter, is 
 given up ; in fact, it hardens vegetable matter. (Mr. Pusey, Royal 
 AgricidturalJournal, iii., p. 212. 
 
 These opinions, I have said, are probably correct in so far as re- 
 gards the unaided action of lime. They even express, with an ap- 
 E roach to accuracy, what will take place in the interior of compost 
 caps of a certain kind, or in some dry soils ; but that they cannot 
 apply to the ordinary action of lime upon the soil is proved by the 
 other result of universal observation, that lime, so far from preserv- 
 i7ig the organic matter of the land to which it is applied, in reality 
 wastes it — causes, that is, or disposes it to disappear. 
 
 2^. Action of caustic lime on orgastic matter in the presence of air 
 and water. — In the presence of air and water, when assisted by a 
 
IN THE PRESENCE OF AIR AND WATER. 405 
 
 favoring temperature, vegetable matter, as we have already seen, 
 undergoes spontaneous decomposition. In the same circumstances 
 hme promotes and sensibly hastens this decomposition, — altering the 
 forms or stages through which the organic matter must pass — but 
 bringing about more speedily the final conversion into carbonic acid 
 and water. During its natural decay in a moist and open soil, organic 
 matter gives off a portion of carbonic acid gas, which escapes, and 
 ibrms certain other acids which remain in the dark mould of the soil 
 itself When quick or slaked lime is added to the land, its first effect 
 is to combine with these acids — to form carbonate, humate, &c., of 
 lime — till the whole of the acid matter existing at the time is taken 
 up. That portion of the lime which rem^ains uiicombined, either slowly 
 absorbs carbonic acid from the air or unites with the carbonate already 
 formed, to produce the known compound of hydrate with carbonate 
 of lime, — (that compound, namely, which is produced when quick-lime 
 slakes spontaneously in the air — see p. 368.) — waiting in this state in 
 the soil till some fresh portions of acid matter are formed v/ith which 
 it may combine. But it does not inactively wait ; it persuades and 
 influences the organic matter to combine with the oxygen of the air 
 and Vv-ater with which it is surrounded, for the production of such acid 
 substances — till finally the whole of the lime becomes combined either 
 with carbonic or with some other acid of organic origin. 
 
 Nor at this stage are the action and influence of lime observed to 
 cease. On the contrary, this result will, in most soils, be arrived at in 
 the course of one or two years, while the beneficial action of the lime 
 if self' may be perceptible for 20 or 30 years. Hence there is much ap- 
 })arent ground for the opinion of Lord Kames, " that lime is as effica- 
 cious in its (so called) effete as in its caustic state." Even the more 
 strongly expressed opinion of the same acute observer, " that lime pro- 
 duces^little effect upon vegetables till it becomes effete" — derives much 
 support from experience — since lime is known to have comparatively 
 little eflTect upon the productiveness of the land till one or tvv^o years 
 idler its application ; and this period, as I have said, is in most locali- 
 ties sufficient to deprive even slaked lime of all its caustic properties. 
 
 Of the sahne compounds, (saline compounds or salts are always 
 formed when hme, magnesia, potash, soda, &c.; combine with acids,) 
 which caustic lime thus forms, either immediately or ultimately, some, 
 like the carbonate and humate, being very sparingly soluble in water, 
 remain more or less permanently in the soil ; others, like the acetate 
 of lime, being readily soluble, are either washed out by the rains or 
 are sucked up by the roots of the growing plants. In the former case 
 they cause the removal of both organic matter and of lime from the 
 land ; in the latter they supply the plant with a portion of organic food, 
 and at the same time with lime — without which, as we have frequent- 
 ly before remarked, plants cannot be maintained in their most healthy 
 condition. 
 
 § 27. Action of mild (or carbonate of) lime upon the vegetable matter 
 
 of the soil. 
 
 The main utility of lime, therefore, depends upon its prolonged 
 a/iJer-action upon the vegetable matter of the soil. What is this ac- 
 tion, and in what consist the benefits to which it gives rise ? 
 
406 ACTION OF CARBONATE OF LIME UPON VEGETABLE MATTER. 
 
 In answering this question, it is of importance to observe that ail 
 the effects produced by alkaline matter in general — whetJier by lime 
 or by potash — in the caustic state, are produced in kind also by the 
 same substances in the state of carbonate. The carbonic acid with 
 which they are united is retained by a comparatively feeble affinity^ 
 and is displaced with greater or less ease by almost every other acid 
 compound which is produced in the soil. With this displacement is 
 connected an interesting series of beautiful reactions, which it is of 
 consequence to understand. 
 
 You will recollect that the great end which nature, so to speak, has 
 in view, in all the changes to which she subjects organic matter in the 
 soil, is to convert it — with the exception of its nitrogen — into carbonic 
 acid and water. For this purpose it combines at one time, with the 
 oxygen of the air, while at another it decomposes water and unites with 
 the oxygen or the hydrogen which are liberated, or with both, to form 
 new chemical combinations. Each of these new combinations is either 
 immediately preliminary to or is attended by the conversion of a por- 
 tion to the elements of the organic matter into one or other of those 
 simpler forms of matter on which plants live. Now during these pre- 
 liminary or preparatory steps, acid substances, as I have already ex- 
 plained, are among others constantly produced. With these acids, the 
 carbonate of lime, when present in the soil, is ever ready to combine. 
 But in so combining, it gives off the carbonic acid with which it is al- 
 ready united, and thus a continual, slow evolution of carbonic acid is 
 kept up as long as any undecomposed carbonate remains in the soil. 
 
 I do not attempt to specify by name the various acid substances 
 wliich are thus formed during the oxidation of the organic matter, and 
 which successively unite with the lime, because the entire series of 
 interesting and highly important changes, which organic substances 
 undergo in the soil, has as yet been too little investigated, to permit 
 us to do more than speak in general terms of the nature of the che- 
 mical compounds which are most abundantly produced. Of two facts, 
 however, in regard to them, we are certain — that they are simpler in 
 their constitution than the original organic matter itself, from which 
 they are derived — and that they have a tendency to assume still 
 simpler forms, if they continue to be exposed to the same united action 
 of air, water, and alkaline substances. 
 
 Hence the compounds which lime has formed with the acid sub- 
 stances of the soil, themselves hasten forward to new decompositions, 
 — unite with more oxygen, liberate slowly portion after portion of 
 their carbon in the form of carbonic acid, and of their hydrogen in the 
 form of water, till at length the lime itself is left again in the state 
 of carbonate, or in union with carbonic acid only. This residual car- 
 bonate begins again the same round of changes through which it had 
 previously passed. It gives up its carbonic acid at the bidding of 
 some more powerful organic acid produced in its neighborhood, while 
 this acid, by exposure to the due influences, undergoes new altera- 
 tions till it also is finally resolved into carbonic acid and water. 
 
 Two circumstances are deserving to be borne in mind in reference 
 to these successive decompositions— ^rsi, that in the course of them 
 more soluble compounds of lime are now and then formed, some of 
 
SUMMARY OF THE CHANGES PRODUCED BY LIME. 407 
 
 which are washed out by the rains, and escape from the soil, while 
 others minister to the growth of plants ; — and second^ that very much 
 carbonic acid is produced as their final result — of which also part is 
 taken up by the roots of plants, and part escapes into the air. Thus 
 at every successive stage a portion of organic matter is lost to the 
 soil. If this quantity be greater than that which is yearly gained in 
 the form of roots or decayed leaves and stems of plants, or of manure 
 artificially added, the soil will be gradually exhausted — if less, it will 
 every year become more rich in vegetable matter. 
 
 It is also to be borne in mind, that although, for the purpose of il- 
 lustration, I have supposea the carbonate of lime first formed in the 
 soil to be subsequently combined with other acids, which gradually 
 decompose and leave it again in the state of carbonate, — yet it will 
 rarely happen that the whole of the carbonate of lime in the soil 
 will be in any of these new states of combination. In general, a part 
 of it only is thus at any one time employed in working up the acid 
 substances produced. But it is necessary that it should be univer- 
 sally diffused through the soil in order that it may be everywhere at 
 hand to perform the important part of its functions above explained. 
 It is only where little lime is present, or where decaying vegetable 
 matter is in exceeding abundance, that the whole of the carbonate 
 can at one and the same time disappear (p. 380.) 
 
 The changes, therefore, which lime and organic matter, supposed 
 to be free from nitrogen, respectively undergo, and their mutual ac- 
 tion in the soil, may be summed up as follows : — 
 
 1°. The organic matter, under the influence of air and moisture, 
 spontaneously decomposes, and besides carbonic acid which escapes, 
 forms also other acid substances which linger in the soil. 
 
 2°. With these acids the quick-lime combines, and, either by its 
 union with them or with carbonic acid from the air, soon (compara- 
 ratively) loses its caustic state. 
 
 3 '. The production of acid substances by the oxidation of the organ- 
 ic matter — goes on more rapidly under the disposing influence of the 
 lime, whether caustic or carbonated. These acids combine with the 
 lime, liberating from it, when in the state of carbonate, a slow but 
 constant current of carbonic acid, upon which plants at least partly 
 live. 
 
 4°. The organic acid matter which thus unites with the lime con- 
 tinues itself to be acted upon by the air and water, aided by heat and 
 light — itself passes through a succession of stages of decomposition, 
 at each of which it gives off water or carbonic acid, retaining still 
 its hold of the lime, tiU at last being" wholly decomposed it leaves the 
 lime again in the state of carbonate, ready to begin anew the same 
 round of change. 
 
 Durmg this series of progressive decompositions, certain more so- 
 luble compounds of hme are formed, by which plants are in part at 
 leas!; supplied with this earth, and which with the aid of the rains 
 carry off both lime and organic matter from the soil. 
 
 And, again, the more rapid the production of the acid substances 
 
408 COMPARATIVE UTILITY OF BURNED AND UNBURNED LIME. 
 
 which result I'rom the union of the organic matter with oxygen, the 
 more abundant in general also the production of those gaseous and 
 volatile compounds which they form by uniting with hydrogen, so 
 that in promoting the formation of the one class of bodies, lime also 
 favors the evolution of the other in greater abundance, and thus in 
 a double measure contributes to the exhaustion of the soil. 
 
 The disposing- action of lime to this twin form of decomposition, few 
 varieties of organic matter can resist, — and hence arises the well 
 known efficacy of lime in resolving and rendering useful the appa- 
 rently inert vegetable substances that not unfrequently exist in the 
 soil. 
 
 § 28. Of the comparative utility of burned and unbumed lime. 
 
 Is there no advantage, then, you may ask, in using caustic or burned 
 rather than carbonated or unburned lime? If the ultimate effects of 
 both upon the land be the same, why be at the expense of burning ? 
 Among other benefits may be enumerated the following : — 
 
 1°. By burning and slaking^ the lime is reduced to the state of an im- 
 palpable powder, finer than could be obtained by any available method 
 3f crushing. It can in consequence be diffused more uniformly tlirough 
 .he soil, and hence a smaller quantity will produce an equal effect. 
 This minute state of division also promotes in a wonderful degree the 
 chemical action of the lime. In all cases chemical action takes place 
 between exceedingly minute particles of matter, and among solid sub- 
 stances the more rapidly, the finer the powder to which they can be re- 
 duced. Thus a mass of iron or lead slowly rusts or tarnishes in the air, 
 but if the mass of either metal be reduced to the state of an impalpable 
 powder — Avhich can be done by certain chemical means — it will take 
 fire when simply exposed to tlte air at the ordinary temperature, and 
 will burn till it is entirely converted into oxide. By mere mechanical 
 division the apparent action of the oxygen of the air upon metals is aug- 
 mented and hastened in this extraordinary degree — and a similar re- 
 sult follows when lime in an impalpable state is brought into contact 
 with the vegetable matter upon which it is intended to act. 
 
 2^. The_effect of burned lime is more powerful and more immediate 
 than that of unburned lime in the form of chalk, marl, or shell sand. 
 Hence it sooner neutralizes the acids which exist in the soil, and 
 sooner causes the decomposition of vegetable matter of every kind to 
 commence, upon Avhich its efficacy, in a greater degree, depends. 
 Hence, Avhen it can easily be procured, it is better fitted for sour grass 
 or arable lands, for such as contain an excess of vegetable matter, and 
 especially for such as abounds in that dead or inert form of organic mat- 
 ter which requires a stronger stimulus — the presence of more power- 
 ful chemical affinities, that is — to bring it into active decomposition. 
 In such cases, the lime has already done much good before it has been 
 brought into the mild state — and remaining afterwards in this state in 
 the soil, it still serves, in a great measure, the same slower after-pur- 
 poses as the original addition of carbonate would have done. 
 
 3°. Besides, if any portion of it, after the lapse of two or three 
 years, still linger in the caustic state, (p. 368,) it will continue to pro- 
 voke more rapid changes among the organic substances in the soi., 
 than mild lime alone could have done. 
 
ORGANIC MATTER OF THE SOIL CONTAINS NITROGEN. 409 
 
 4°. Farther, quick-lime is soluble in water, and hence every shower 
 that falls and sinks mto the soil carries with it a portion of lime, so 
 long as any of it remains in the caustic state. It thus reaches acid 
 matters that lie beneath the surface, and alters and ameliorates even 
 the subsoil itself 
 
 5°. It is not a small additional recommendation of quick-lime, that 
 by burning it loses about 44 per cent, of its weight, thus enabling 
 nearly twice the quantity to be conveyed from place to place at the 
 same cost of transport. This not only causes a direct saving of 
 money, — as when the burned chalk of Antrim is carried by sea to 
 the Ayrshire coasts — but an additional saving of labor also upon the 
 farm, — where the number of hands and horses is often barely suffici- 
 ent for the necessary work. 
 
 § 29. Action of lime on orgmiic substances which contain nitrogen. 
 
 I have hitherto, for the sake of simplicity, directed your attention 
 solely to the action, whether immediate or remote, which is exercised 
 by lime upon organic matter supposed to contain no nitrogen. Its action 
 upon compounds in which nitrogen exists is no less beautiful and simple, 
 perhaps even more inteUigible and more obviously useful to vegetation. 
 
 There are several well known facts which it is here of importance 
 for us to consider — 
 
 1°. That the black vegetable matter of the soil always contains ni- 
 trogen. Even that which is most inert retains a sensible proportion of 
 it. It exists in dry peat to the amount of about 2 per cent, of its weight, 
 and still clings to the other elements of the organic matter, even after it 
 has undergone those prolonged changes by which it is finally converted 
 into coal. Since nitrogen, therefore, is so important an element in all 
 vegetable food, and so necessary in some form or other to»the healthy 
 growth and maturity of plants, it must be of consequence to awaken 
 this element of decaying vegetable matter, when it is lying dormant, 
 and to cause it to assume a form in which it can enter into and be- 
 come useful to our cultivated plants. 
 
 2°. That if vegetable matter of any kind be heated with slaked lime, 
 the whole of the nitrogen it may contain, in whatever state of combina- 
 tion it may previously exist, will be given off in the form of ammonia. 
 The same takes place still more easily if a quantity of hydrate of potash 
 or of hydrate of soda be mixed with the hydrate of lime. Though it 
 has not as yet been proved by direct experiment — yet I consider it to be 
 exceedingly probable, that what takes place quickly in our laboratories^ 
 at a comparatively high temperature, may take place more slowly also 
 in the soil, and at the ordinary temperature of the atmosphere. 
 
 3'^. That when animal and vegetable substances are mixed with 
 earth, lime, and other alkaline matters, in the so-called nitre beds, (Lee. 
 VIII., § 5.) ammonia and nitric acid are both produced, the quantity of 
 nitrogen contained in the weight of these compounds extracted being 
 much greater than was originally present in the animal and vegetable 
 matter employed (Dumas.) Under the influence of alkaline substances, 
 therefore, even when not in a caustic state, the decay of animal and ve- 
 getable matter in the presence of air and moisture causes some of the 
 nitrogen of the atmosphere to become fixed in the soil in the form of 
 
410 ANALOGOUS DECOMPOSITION OF ALL ORGANIC SUBSTANCES. 
 
 ammonia or of nitric acid. What takes place on the confined area of a 
 nitre bed, may take place to some extent also in the wider area of a 
 well-limed and well-manured field. 
 
 In the action of alkalies in the nitre bed, disposing to the produc- 
 tion of nitric acid, we observe the same kind of agency, which we 
 have already attributed to lime, in regard to the more abundant ele- 
 ments which exist in the vegetable matter of the soil. It gently per- 
 suades all the elements — nitrogen and carbon alike — to unite with 
 the oxygen of air and water, and thus ultimately to form acid com- 
 pounds with which it may itself combine. 
 
 The action of lime upon such organic matters containing nitrogen as 
 usually exist in the soil, may, therefore, be briefly stated as follows : — 
 
 1°. These substances, like all other organic matter, undergo in moist 
 air — and, therefore, in the soil — a spontaneous decomposition, the ge- 
 neral result of which is the production of ammonia, and of an acid 
 substance with which the ammonia may combine. This change is 
 precisely analogous to that which takes place in such substances as 
 starch and woody fibre, which contains no nitrogen. In each case, 
 one portion of the elements unites with oxygen to produce an acid, 
 the other with hydrogen to form a compound possessed of alkaline or 
 indiflerent properties. Thus, — 
 
 With oxygen. — vegetable matter produces carbonic, ulmic, and other 
 acids. 
 " animal matter produces carbonic, nitric, ulmic, and 
 
 other acids. 
 With hydrogen, — -vegetable matter produces marsh gas or other 
 carburetted hydrogens. 
 " animal matter produces ammonia. 
 
 If the ammonia happen to be produced in larger relative quantity 
 than the acids v.'ith which it is to combine, or if the carbonic be the 
 only acid with which it unites, a portion of it may escape into the air. 
 This rarely happens, however, in the soil, the absorbent properties of 
 the earthy matters of which it consists being in most cases sufficient 
 to retain the ammonia, till it can be made available to the purposes 
 of vegetable life. 
 
 When caustic (hydrate of) lime is added to a soil in which ammonia 
 exists in this state of combination with acid matter, it seizes upon the 
 acid and sets the ammonia free. This it does with comparative slow- 
 ness, however — for it docs not at once come in contact with it all — 
 and by degrees, so as to store it up in the pores of the soil till the roots 
 of plants can reach it or till it can itself undergo a further change 
 by which its nitrogen may be rendered more fixed (p. 411.) 
 
 Carbonate of lime, on the other hand, still more slowly persuades 
 the ammonia to leave the acid substances (ulmic, nitric ? &c.,) with 
 which it is combined, and yielding to it in return its own carbonic 
 acid, enables it in the state of soluble carbonate of ammonia to be- 
 come more immediately useful to vegetation. 
 
 2°. But in undergoing this spontaneous decay, even substances con- 
 taining nitrogen reach at length a point at which decomposition appears 
 to stop — an inert condition in which, though nitrogen be present as in 
 peat, they cease sensibly to give it off in such a form or quantity as to 
 
AMMONIA AND NITRIC ACID FORMED. 411 
 
 be capable of ministering to vegetable growth. Here caustic lime steps 
 in more quickly, and mild lime by slower degrees, to promote the fur- 
 ther decay. It induces the carbonaceous matter to take oxygen from 
 the air and from water and to form acids, and the nitrogen to unite with 
 the hydrogen of the water for the production of arnmonia — thus help- 
 ing forward the organic matter in its natural course of decay, and 
 enabling it to fulfil its destined purposes in reference to vegetable life. 
 
 3°. But the ammonia which is thus disengaged in the soil by decay- 
 ing organic matter, though not immediately worked up, so to speak, by 
 living plants, is not permitted to escape in any large quantity into the 
 air. The soil, as I have already stated, is usually absorbent enough to 
 retain it in its pores for an indefinite period of time. And as in nature 
 and upon the eartli's surface the elements of matter are rarely permitted 
 to remain in a state of repose, the ammonia, though retained apparently 
 inactive in the soil, is yet slowly uniting with a portion of the surround- 
 ing oxygen and forming nitric acid (Lee. VIII., § 5, note.) When no 
 other base is present, this nitric acid, as it is produced, unites with some 
 of the ammonia itself which still remains, forming nitrate of ammonia 
 — but if potash or lime be present within its reach, it tmites with them 
 in preference, and forms the nitrate of potash or of lime. 
 
 But lime, if present, is not an inactive spectator, so to speak, of 
 this slow oxidation of ammonia. On the contrary, it promotes this 
 final change, and by being ready to unite^ with the nitric acid as it 
 forms, increases and accelerates its production, at the expense of the 
 ammonia which it had previously been instrumental in evolving. 
 
 4°. One other important action of lime, by which the same com- 
 pounds of nitrogen are produced in the soil, may in this place be most 
 properly noticed. It is a chemical law of apparently extensive applica- 
 tion, that when one elementary substance is undergoing a direct chemi- 
 cal union with a second in the presence of a third, a tendency is impart- 
 ed to the third to unite also with one of with both of the other two, al- 
 though in the same circumstances it would not unite with either, if pre- 
 sent alone. Thus, when the carbonaceous matter of the soil is under- 
 going oxidation in the air — that is, combinmg with, the oxygen of the 
 atmosphere — it ^mparts a tendency to the nitrogen also to unite with 
 oxygen, which when mixed with that gas alone, (the atmosphere con- 
 sisting, as you will recollect, of nitrogen and oxygen — Lee. II., § 4,) — 
 it has no known disposition to do. The result of this is the production of 
 a small and always a variable, proportion of nitric acid during the de- 
 composition in the soil, of organic matter even, which itself contains no 
 nitrogen. 
 
 Again, it is an equally remarkable chemical law, that elementary 
 bodies which refuse to combine, however long we may keep them to- 
 gether in a state of mixture, will yet unite readily when presented to 
 each other in what is called by chemists the nascent state— that is, at 
 the moment when one or other of them is produced or is separated 
 from a previous state of combination. 
 
 Thus when the organic matter of the soil decomposes water in the 
 presence of atmospheric air, its carbon unites with the greater part 
 of the oxygen and hydrogen which are set at liberty, and at the same 
 time with more or less of the oxygen of the atmosphere — but at the 
 
 IB 
 
412 HOW THESE CHEMICAL CHANGES BENEFIT VEGETATION. 
 
 eame instant the nitrogen of the atmosphere, which is everywhere 
 present, seizes a portion of the hydrogen and forms ammonia. Thus 
 a variaijle, and in any one hmited spot a minute, but over the entire 
 surface oi' the globe, a large quantity of ammonia is produced during 
 the oxidation even of the purely carbonaceous portion of the organic 
 matter of the soil. 
 
 Now in proportion as the presence of lime promotes this decay of 
 vegetable and other organic matter in the soil — in the same propor- 
 tion does it promote the production of ammonia and nitric acid, at the 
 expense of the free nitrogen of the atmosphere, and this may be re- 
 garded as one of the valuable and constant purposes served by the 
 presence of calcareous matter in the soil. 
 
 § 30. How these chemical changes directly benefit vegetation. 
 
 You will scarcely, I think, inquire how all these interesting chemical 
 changes which attend upon the presence of lime in the soil are di- 
 rectly useful to vegetation, and yet it may be useful shortly to answer 
 the question. 
 
 1°, Lime combines with the acid substances already existing in the 
 soil, and thus promotes the decomposition of vegetable matter which 
 those acid substances arrest. The further decompositions which en- 
 sue are attended at every step by the production either of gaseous 
 compounds — such as carbonic acid and light carburetted hydrogen — 
 which are more or less abundantly absorbed by the roots and leaves 
 of plants, and thus help to feed them — or of acid and other compounds, 
 soluble in water, which, entering by the roots, bear into the circula- 
 tion of the plant not only organic food, but that supply of lime also 
 which healthy plants require. 
 
 2°. The changes it induces upon substances in which nitrogen is 
 present are still more obviously useful to vegetation. It eliminates am - 
 monia from the compounds in which it exists already formed, and pro- 
 motes its slow conversion into nitric acid, by which the nitrogen is 
 rendered more fixed in the soil. It disposes the nitrogen of more or 
 less inert organic .matter to assume the form of ammonia and nitric 
 acid, in whieh state experience has long shown that this element is 
 directly favorable to the growth of plants. 
 
 3"^. It influences in an unknown degree, the nitrogen of the atmos- 
 phere to become fixed in larger proportion in the soil, in the form of nitric 
 acid and ammonia, than would otherwise be the case, and this it does 
 both by the greater amount of decay or oxidation which it brings 
 about in a given time, and by the kind of compounds which, under its 
 influence, the organic matter is persuaded to form. The amount of 
 nitrogenouK food placed within reach of plants by this agency of lime 
 will vary with the climate, with the nature of the soil, with its con- 
 dition as to drainage, and with the more or less liberal and skilful 
 manner in which it is farmed. 
 
 § 31. Why lime must he kept near the surface. 
 
 Nor will you fail to see the important reasons why lime ought to 
 be kept near the surface of the soil — since 
 1°. The action of lime upon organic matter is almost nothing in 
 
ACTION OF LIME UPON SALINE SUBSTANCES. 413 
 
 the absence of air and moisture. If the Hme sink, therefore, beyond 
 the constant reach of fresh air, its efficacy is in a great degree lost. 
 
 2°. But the agency of the hght and heat of the sun, though I have 
 not hitherto insisted upon their action — are scarcely less necessary to 
 the full experience of the benefits which lime is capable of conferring. 
 The light of the sun accelerates nearly all the chemical decompositions 
 that take place in the soil — while some it appears especially to promote. 
 The warmth of the sun's rays may penetrate to some depth, but their 
 light can only act upon the immediate surface of the soil. Hence the 
 skilful agriculturist will endeavor, if possible, to keep some of his lime 
 at least upon the very surface of his arable land. Perhaps this in- 
 fluence of light might even be adduced as an argument in favor of the 
 frequent application of lime in small doses, as a means of keeping a 
 portion of it always within reach of the sun's rays; and this more es- 
 pecially on grass lands, to which no mechanical means can be applied 
 for the purpose of bringing again to the surface the lime that has sunk. 
 
 There ai*e, at the same time, as you will recollect, good reason also 
 why a portion of the lime should be diffused through the body of the 
 soil, both for the purpose of combining with organic acids, already 
 existing there, and with the view of acting upon certain inorganic or 
 mineral substances, which are either decidedly injurious, or by the ac- 
 tion of lime may be rendered more wholesome to vegetation. 
 
 In order that this diffusion may be effected, and especially that lime 
 may not be unnecessarily wasted where pains are taken by mechanical 
 means to keep it near the surface, an efficient system of under-drainage 
 should be carefully kept up. Where the rains that fall are allowed 
 to flow off the surface of the land, they wash more lime away the more 
 carefully it is kept among the upper soil — but where a free outlet is af- 
 forded to the waters beneath, they carry the lime with them as they 
 sink towards the subsoil, and have been robbed again of the greater 
 part of it before they escape into the drains. Thus on drained land 
 the rains that fall aid lime in producing its beneficial effects, while in 
 undrained land they in a greater or less degree counteract it. 
 
 § 32. Action of lime upon the inorganic or mineral matter of the soil. 
 
 Though the main general agency of lime is exerted, as we have 
 seen, upon the organic matter it meets with, yet it often also produces 
 direct chemical changes upon the mineral compounds existing in the 
 soil, which are of great importance to vegetation. Thus 
 
 P. Lime, either in the mild or in the caustic state, possesses the 
 property of decomposing the sulphate of iron, which especially abounds 
 in peaty soils, and in many localities so saturates the subsoil as to 
 make it destructive to the roots of plants. Sprengel mentions a case 
 where the first year's clover always grew well, while in the second 
 year it always died away. This, upon examination, was found to be 
 owing to the ferruginous nature of the subsoil, which caused the death 
 of the plant as soon as the roots began to penetrate it. 
 
 When salts of iron exist in the soil, a dressing with lime will bring 
 the land into a wholesome state without other aid. The lime will 
 combine with the acid, and form gypsum, if it is the sulphate of iron 
 that is present, while the first oxide of iron which is set free will, by 
 
414 LIME DECOMPOSES SULPHATES AND SILICATES, SETS TREE 
 
 exposure to the air, be converted into the second or red oxide, in 
 which state this metal is no longer hurtful to vegetation. 
 
 When these salts are to be decomposed and removed from the sub- 
 soil, lime must be aided by the subsoil plough and the drain. Unless 
 an outlet beneath be provided for the surface water, by which the 
 rains may be enabled to wash away slowly the noxious substances 
 from the subsoil, even the addition of a copious dose of lime will only 
 produce a temporary improvement. 
 
 2°. Lime decomposes also the sulphates of magnesia and of alumi- 
 na, both of which are occasionally found in the soil, and, being very so- 
 luble salts, are liable to be taken up by the roots in such quantity as to 
 be hurtful to the growing plants. When soils which contain any of 
 the three salts I have mentioned have once been limed or marled^ it 
 is in vain to add gypsum in the hope of favoring the clover crop, since 
 the lime, in decomposing the sulphates, has already formed an abun- 
 dant supply of this compound for all the purposes of vegetation. 
 . 3°. Among the earthy constituents of the soil, we have already seen 
 that there often exist fragments of felspar and of other minerals derived 
 from the granitic and trap rocks, which contain potash or soda in the 
 state oi^ silicates. These silicates we know to be slowly decomposed 
 by the agency of the carbonic acid of the air, (Lee. X., § 1,) and 
 their alkali set free in a soluble state. This decomposition is said to 
 be prompted by the presence of lime (p. 361.) 
 
 Again, the stalks of the grasses and the straw of the corn-bearing 
 plants contain much silica in combination with potash and soda. In 
 farm-yard manure, therefore, much of these silicates is present, and 
 when mixed with the soil, there appears little reason to doubt that 
 they are of much benefit to the growing crops. On these silicates, 
 in the presence of carbonic acid and moisture, the lime acts as it does 
 upon the mineral silicates. It aids in the liberation of the potash and 
 soda, and thus promotes the performance of those important functions 
 which these alkalies are destined to exercise in reference to vegetable 
 growth (p. 328.) 
 
 While the alkali is set free the lime itself combines with the silica, 
 and hence_one source of the silicate of lime which, as I have already 
 mentioned to you, (p. 380,) usually exists in sensible quantity in our 
 cultivated soils. It has been stated by Sprengel (Lehre vom Diinger, 
 p. 310,) as one reason why the addition of lime must be repeated so 
 frequently upon some soils in which silica abounds, that an insoluble 
 silicate of lime is found, which is of no use to vegetation. But the 
 silicates of lime are slowly decomposed by the agency of the carbonic 
 acid of the air and of decaying vegetation, and to this cause in a pre- 
 vious lecture (Lee. XII., § 4,) I have ascribed much of the fertile 
 character of the trap and syenitic soils, and of their beneficial action 
 when laid on as a manure. 
 
 - 4°. Potash and soda' exist to some extent in clay soils in combina- 
 tion with their alumina. The presence of lime has a similar influence 
 in setting the alkalies free from this state of combination also. 
 
 5°. Alumina has the property of comdnning readily with many vege- 
 table acids, and in the clay soils exercises a constant influence, similar 
 m kind to that of lime and other alkaline substances, in persuading the 
 
ALKALINE SUBSTANCES, AND DECOMPOSES COMMON SALT. 415 
 
 organic matter to those forms of decay in which acid compounds are 
 more abundantly produced. Hence, clay soils almost always contain a 
 portion of alumina in combination with organic matter. This organic 
 matter is readily given up to lime, and by the more energetic action of 
 this substance is sooner made available to the wants of new races of 
 plants. 
 
 6°. I shall bring uniier yoar notice only one other, but a highly im- 
 portant, decomposing action, which lime exercises in soils that abound 
 in vegetable matter. In the presence of decaying organic substances 
 the carbonate of lime is capable of slowly decomposing common salt, 
 producing carbonate of soda and chloride of calcium. I^ exercises also 
 a similar decomposing effect, even upon the sulphate of soda, and, ac- 
 cording to BerthoUet, (Dumas Traite de Chemie, ii., p. 334.) incrus- 
 tations of carbonate of soda (of Trona or Natron, which is a sesqid 
 carbonate of soda,) are observed on the surface of the soil, wherever 
 carbonate of hme and common salt are in contact with each other. 
 If we consider that along all our coasts common salt may be said 
 to abound in the soil, being yearly sprinkled over it by the salt sea 
 winds — that generally, along the same coasts, the application of 
 sulphates produces little sensible effect upon the crops, ancl that, there- 
 fore, in all probability they abound in the soil, derived, it may be, from 
 the same sea spray — we may safely conclude, I think, that the decom- 
 position now explained must take place extensively in all those parts of 
 our island which are so situated, if lime in any of its forms either exists 
 naturally or has been artificially added to the land. The same must be 
 the case also in those districts where salt springs occur, and generally 
 over the new red sand-stone formation, in which sea salt more especially 
 occurs. 
 
 And if we further consider the important purposes which the carbo- 
 nate of soda thus produced may serve in reference to vegetation — that 
 it may dissolve vegetable matter and carry it into the roots— that it may 
 form soluble silicates, and thus supply the necessary siliceous matter to 
 the stems ofthe grasses and other plants — and that rising, as it naturally 
 does, to the surface ofthe soil, it there, in the presence of vegetable mat- 
 ter, provokes to the formation of nitrates, so wholesome to vegetable 
 lit'e — we may regard the decomposing action of lime by which this car- 
 bonate is produced as among the most valuable of its properties to the 
 practical farmer, wherever circumstances are favorable for its exercise. 
 
 § 33. Action of lime on animal and vegetable life. 
 
 It is only necessary to allude, in conclusion, to one or two other 
 useful purposes which lime is said to serve in reference to animal and 
 vegetable life. Thus 
 
 1°. It is said to prove fatal, especially in the caustic state, to worms, 
 to slugs,* and to many insects injurious to the farmer, and to destroy 
 their eggs and larvae. In Scotland it has been found in some instances 
 to check the ravages of the fly. On the other hand, in the state of car- 
 bonate,^ it is propitious to the growth of the land snail and similar crea- 
 
 • When the wheat crop is attacked by slugs above ground, nothino; will do so much goo*" 
 as slaked lime, sown over the crop before sunrise. — Hillyard, Royal Agricultural Journa 
 iii., p. 302. 
 
416 LIME KILLS INSECTS AND SEEDS. 
 
 ■hires which bear shells. In highly limed land the former may be seen 
 crowded at the roots of the hedges, from which they make frequent in- 
 cursions upon the young crops, and are, I believe, especially hurtful 
 to the turnips. 
 
 2°. It is found to prevent sm.iit in wheat. For this purpose the 
 seed is steeped in lime, and afterwards dried with slaked lime, or lime 
 water is poured upi^n the heap of corn, which is turned over, and left 
 for 24 hours (Hillyard.) 
 
 3"'. It is also said to prevent the rot and foot-rot in sheep fed upon 
 pastures on which, before liming, the stock was liable to be affected 
 by these diseases (Prideaux.) 
 
 4°. In regard to its action upon living plants, it is certain that it ex- 
 tirpates certain of the coarser grasses from sour pastures and brings up 
 a tenderer herbage ; but practical men appear to differ in regard to its ef- 
 fects upon the roots and seeds of the more troublesome weeds. Accord- 
 ing to some, the addition of lime to a compost, or to the soil, will kill 
 the roots of weeds and render unproductive such noxious seeds as may 
 happen to be present. According to others (p. 405,) this is a mistake. 
 I believe the truth to be, that lime will lead to their destruction and 
 decay, if the circumstances are favorable or if proper pains be taken 
 to effect it. But air and moisture are necessary to insure this, as they 
 are to effect the rapid decay of dead organic matter. If the ingre- 
 dients of the compost be duly proportioned, or if the dose of lime 
 added to the land be sufficiently large, and if in each case the mix- 
 ture be frequently turned, the final destruction of roots and seeds may 
 in general be safely calculated upon. 
 
 § 34. Use of silicate of lime. 
 
 There is one compound of lime which, though occurring occasionally 
 in all soils, has not hitherto been applied to the improvement of the land 
 even in localities where it most abounds. This compound is the silicate 
 of lime. I have already directed your attention to the presence of this 
 compound in the trap rocks, and to the fertile character which it imparts 
 to the soilswhich are formed by the natural degradation of these rocks. 
 
 In those districts where the smelting of iron is carried on, the first 
 slag that Ts^btained consists in great part of silicate of lime. This 
 slag accumulates in large quantities, and is employed in some dis- 
 tricts for mending the roads. It is not unworthy the attention of the 
 practical farmer — as an improver of his fields — especially where caus- 
 tic lime is distant and expensive, or where boggy and peaty soils are 
 "met with in which vegetable matter abounds. On such land it may 
 be laid in large quantity. It will decompose slowly, aitd while it im- 
 parts to the soil solidity and firmness, will supply both lime and silica 
 to the growing crops, for a long period of time. 
 
 I have thus dra\vn your attention to the most important topics connected witli the use of 
 lime, so efficacious an instrument in the hands of the siiilfal and improvioL' farmer for ame- 
 lioratin;: the condition and increasing the productiveness of his land. If I have appeared 
 to dwell long upon this subject, it is because of ihe value which I know to be attached by 
 practical men to a correct exposition of the virtues of lime and of the theory by which its 
 effects are to be explained. I believe that in the theoretical part I have been able to point 
 out to you the leading chemical principles upon which its influence depends — if any thing 
 is still darK, it is because our knowledge is not yet complete. A few years more, and we 
 may hope to have the mists which hang over this, as over many other branches of agricul- 
 tural chemistry, in a great measure cleared away. 
 
 I 
 
LECTURE XVII. 
 
 Of organic manures.— Vegetable and animal manures.— Green manuring ; ploughing in of 
 spurry, the white lupin, the vetch, buck-wheat, rape, rye, borage. — Natural green manu- 
 ring. — Improvemeni: of the soil by laying down to grass and by planting. — Use of sea- 
 weed. — Dry vegetable manures : ilry straw, chaff, rape-dust, malt-dust, saw-dust, cotton 
 seeds, dry leaves.— Decayed vegetable matter: use of peat, tanners' bark, and composts 
 of vegetable matter. — Charcoal powder, soot.— Relative value, theoretical, and practical, 
 of different vegetable manures. 
 
 By organic manures are understood all those substances either of 
 vegetable or of animal origin, which are applied to the land for the 
 purpose of increasing its fertility. It will be convenient to consider 
 these two classes of organic substances separately. 
 
 The parts of vegetables may be applied to the soil in three dif- 
 ferent forms — in the green, in the dry, and in the more or less natu- 
 rally decayed, fermented, or artificially decomposed state. 
 
 ^ I. Of green manitring, or the application of vegetable matter in 
 
 the green state. 
 
 By green manuring is meant the ploughing in of green crops in 
 their living state — or of green vegetables left or spread upon the 
 land for the purpose. 
 
 1°. We have seen in the preceding lecture how important air and 
 water are to the decomposition of organic matter. Now green ve- 
 getable substances contain within themselves much water, undergo 
 decomposition more readily, therefore, than such as have been dried, 
 and are more immediately serviceable when mixed with the soil. 
 
 2°. In the sap of plants also there generally exist certain compounds 
 containing nitrogen, which not only decompose very readily themselves, 
 but have the property of persuading or inducing the elements of the 
 other organic matters, with which they are in contact, to assume new 
 forms or to enter into new chemical combinations. Hence, the sap of 
 plants almost invariably undergoes more or less rapid decomposition 
 even when preserved from the contact of both air and water. When 
 this decomposition has once commenced in the sap it is gradually propa- 
 gated to the woody fibre and to the other substances of which the mass 
 of the stems and roots of plants is composed. Hence, recent vege- 
 table matter will undergo a comparatively rapid decomposition, even 
 when buried to some depth beneath the soil— and the elements of which 
 it consists will form new compounds more or less useful to living plants, 
 in circumstances where dry and where many forms even of partially 
 decomposed vegetable matter would undergo no change whatever. 
 
 3°. Further — when green vegetable m.atter is allowed to decay in 
 the open air, it is gradually resolved more or less completely into car- 
 bonic acid, which escapes into the air and is so far lost. But when 
 buried beneath the surface, this formation of carbonic acid proceeds 
 less rapidly, and other compounds— preparatory to the final resolution 
 mto carbonic acid and water— are produced in greater quantity and 
 
418 GREEN VEGETABLES READILY DECAY, AND ENRICH THE SOIL. 
 
 linger in the soil. Thus by burying vegetable substances in his land 
 in their green state, the practical man actually saves a portion of the 
 organic tbod of plants, which would otherwise so far run to waste. 
 
 4°. Finally: Green vegetable substances, by exposure to the air, 
 gradually give up a portion of the sahne matter they contain to the 
 showers of rain that fall. This more or less escapes and is lost. But if 
 buried beneath the soil this sahne matter is restored to the land, and 
 where the green matter thus buried is in the state of a growing crop, 
 both the organic and inorganic substances it contains are more equally 
 diffused through the soil than they could be by any other known process. 
 
 On one or other of these principles depend nearly all the special ad- 
 vantages which are known to follow from green manuring and from the 
 employment of green vegetable matter in the preparation of composts. 
 
 § 2. Important practical results obtained by green manuring. 
 
 But this explanation of the principles on which the efficacy of g-reen 
 manuring depends, does not fully illustrate the important practical re- 
 sults by which, in many localities, it is uniformly followed. 
 
 Let us glance at these results. 
 
 1°. The ploughing in of green vegetables on the spot where they 
 have grown may be followed as a method of manuring and enriching 
 all land, wliere other manures are less abundant. Growing plants 
 bring up from beneath, as far as their roots extend, those substances 
 which are useful to vegetation — and retain them in their leaves and 
 stems. By ploughing in the whole plant we restore to the surface 
 what had previously sunk to a greater or less depth, and thus make 
 it more fertile than before the green crop was sown. 
 
 2°. This manuring is performed with the least loss by the use of 
 vegetables in the green state. By allowing them to decay in the open 
 air7 there is, as above stated, a loss both of organic and of inorganic 
 matter — if they be converted into fermented (form-yard) manure, there 
 is also a large loss, as we shall hereafter see ; and the same is the 
 case, if they are employed in feeding stock, with a view to their con- 
 version into manure. In no other form can the same crop convey to 
 the soil aiT~Equal amount of enriching matter as in that of green 
 Leaves and stems. Where the first object, therefore, in the farmei-'s 
 practice, is so to use his crops as to enrich his land — he will soonest 
 effect it by ploughing them in in the green state. 
 
 3°. Another import-ant result is, that the beneficial action is almost 
 immediate. Green vegetables decompose rapidly, and thus the first 
 crop which follows a green manuring is benefitted^ and increased by 
 it. But partly for this reason also the green manuring — of corn crop- 
 ped land — if aided by no other manure, must generally be repeated 
 every second year. 
 
 4°. It is said that grain crops which succeed a green manuring are 
 never laid — and that the produce in grain is greater in proportion to 
 the straw, than when manured with fermented dung. 
 
 5°. But it is deserving of separate consideration, that green manu- 
 ring is especially adapted for improving and enriching soils which are 
 poor in vegetable matter. The principles on which living plants draw 
 a part — sometimes a large part — of their sustenance from the air, 
 
GREEN MANURE MOST USEFUL TO POOR AND SANDY SOIL. 419 
 
 have already been discussed, and I may presume that you sufficiently 
 understand the principles and admit the fact. Living plants, then, 
 contain in their substance not only all they have drawn up from the 
 soil, but also a great part of what they have drawn from the air. 
 Plough in these hving plants, and you necessarily add to the soil 
 more than was taken from it — in other words, you make it richer in 
 organic matter. Repeat the process with a second crop and it be- 
 comes richer still — and it would be difficult to define the limit beyond 
 which the process could no further be carried. 
 
 Is there any soil then, in the ordinary climates of Europe, which is be- 
 yond the reach of this improving process ? Those only are so on which 
 plants refuse to grow at all, or on which they grow so languidly as to 
 extract from the air no more tlian is restored to it again by the natur 
 ral decay of the organic matter which the soils already contain. 
 
 But for those plants which grow naturally upon the soil, agricultural 
 slcill may substitute others, which will increase more rapidly, and pro- 
 duce a larger quantity of green leaves and stems for the purpose of being 
 buried in the soil. Hence, the selection of particular crops for the pur- 
 pose of giving manuring — those being obviously the fittest which in the 
 given soil and climate grow most rapidly^ or which p?^odiice ike largest 
 qnaniity of vegetable matter in the shortest time and at the smallest cost. 
 
 § 3. Of the plants which in different soils and climates are employed 
 
 for green manuring. 
 
 On this prmciple is founded the selection o^ different ^loxiXii in different 
 soils and climates for the purpose of green manuring. That which ' 
 in Italy will yield the largest produce of leaves and stems, at the least 
 cost, and in the shortest time,^may not do so in the North of" England or 
 of Germany — and that wliich will enrich a poor clay or an exhausted 
 loam may refuse even to grow, in a healthy manner, upon a drifting sand. 
 
 1°. Spurry (Spergula Arvensis.) — It is to poor dry sandy soils that 
 green manuring has been found most signally beneficial, and for such 
 soils no plant has been more lauded than spurry. It may either be 
 sown in autumn on the corn stubble or after early potatoes, and 
 ploughed in in spring preparatory to the annual crop, or it may be 
 used to replace the naked fallow, which is often hurtful to lands of so 
 light a character. In the latter case, the first sowing may take place 
 in March, the second in May, and the third in July — each crop being 
 ploughed in to the depth of three or four inches, and the new seed 
 then sown and harrowed. When the third crop is ploughed in, the 
 land is ready for a crop of v*/^inter corn. 
 
 Von Voght (Vorthelle der griinen Bedungung) states that by such 
 treatment the worst shifting sands may be made to yield remunerative 
 crops of rye — that the most worthless sands are more improved by it 
 than those of a better natural quality^that the green manuring every 
 other year not only nourishes sufficiently the alternate crops of rye, 
 but gradually enriches the soil — and that it increases the effect of any 
 other manure that may subsequently be put on. He adds, also, that 
 spurry produces often as much improvement if eaten off by cattle as 
 if ploughed in, and that when fed upon this plant, either green or in • 
 the state of hay, cows not only give more milk, but of a richer quality. 
 
 18* 
 
420 USE OF THE VETCH, BUCKWHEAT, ETC. 
 
 2°. White Lupins. — In Italy, and in the south of France, the white 
 lupin is extensively cultivated as a green manure. In Germany, also, 
 it has been found to be one of those plants by which unfruitful sandy 
 soils may be most speedily brought into a productive state. The supe- 
 riority of this plant for the purpose of enriching the soil depends upon 
 its deep roots, which descend more than two feet beneath the surface 
 — upon its being little injured by drought, and little liable to be at- 
 tacked by insects — on its rapid growth — and upon its large produce 
 in leaves and stems. Even in the North of Germany it is said to 
 yieldy in three and'a half to four months, 10 to 12 tons of green herb- 
 age. It grows ift all soils except such as are marly and calcareous, 
 is especially partial to such as have a ferruginous subsoil, and besides 
 enriching, also opens stiff clays by its strong stems and roots. 
 
 3^. 7%e Vetc/i is inferior in many of its qualities to the white lu- 
 pin — yet in Southern Germany it is often sown on the stubble, and 
 ploughed in after it has been touched with the frost, and has begun 
 to decay. In England also the winter tare ploughed in early in spring- 
 has been found highly advantageous (British Husbandry, I., p. 407.) It 
 is a more precarious, however, and a more expensive crop than either 
 of tlie former, and requires a better soil for its successful growth. 
 
 4°. Buck- Wheat is also too uncertain a crop, and the high price of 
 its seed renders it inferior in value to spurry on sandy soils. It is su- 
 perior to this latter plant, however, on poor heaths. In Southern 
 Germany it is sown on the stubble, and ploughed in when it is 18 or 
 20 inches high. ^ 
 
 5^. Rape can only be sown upon a soil which is already in some 
 measure ricli, but it has the advantage of continuing to grow very late 
 in the autumn, and of beginning again very early in spring. It sends 
 down deep roots also, and loosens clayey soils by its thick stems. In 
 the light soils of Alsace it is sown after early peas and potatoes, and 
 manures the land for the succeeding crop of wheat or rye. 
 
 5°. Rye is pronounced by Von Voght to be the best of all green 
 manures for sandy soils, but it is also the most expensive. It is a 
 very sure crop and begins to grow very early in the spring, but it is 
 not'deep rooted. It has been used with advantage in Northern Italy 
 and in Germany. 
 
 6°. Turnips have been sown in Sussex with good effect as a stub- 
 ble crop for ploughing in in spring, and in Norfolk and elsewhere the 
 portions of the turnip bulbs which are left when they are eaten off 
 by sheep contribute, when ploughed in, to enrich the land for the 
 barley that is to follow. Turnip tops are in many places ploughed 
 in with much benefit to the land.* Potatoe tops also might be dug 
 or ploughed in with equal advantage. 
 
 7^. Boras^e has been strongly recommended in Germany, and es- 
 pecially by Lampadius. It is stated by this experimenter that borage 
 draws from the air ten times as much of the elements of its organic 
 matter as it does from the soil, and that therefore it is admirably fitted 
 for enriching the land on which it grows. 
 
 8°. Red Clover is often ploughed in as a manure. On the Rhine it 
 
 • " I find no better way of manuring for wheat after turnips, than ploughing in the tops 
 while etill^een, as soon as the turnips are taken oflf the land" — Mr. Campbell, of Graigie. 
 
GREEN MANURING SUITABLE FOR AFTER-CROPS OF CORN. 421 
 
 IS sown for this purpose, being ploughed in before it begins to flower. 
 In French Flanders two crops of clover are cut- and the third ploughed 
 m, and in some parts of the United States of North America the clover 
 which alternates with the wheat crop is ploughed in as the only ma- 
 nure (Barclay's '* Agricultural Tour in the United States.") White 
 Clover is not so valuable for this purpose, for neither is it so deep 
 rooted nor does it yield so large a crop of stems and leaves. 
 ■ 9^. Old Grass. — Perhaps the most common form of green manur- 
 ing practised in this country is that of ploughing up grass lands of 
 various ages. The green matter of the sods serves to manure the 
 after-crop, and renders the soil capable of yielding a richer return at 
 a smaller .expense of manure artificially added. 
 
 In regard to all these forms of green manuring it is to be observed 
 that they enrich the soil generally, and are therefore well fitted to 
 prepare it for after-crops of corn ; they will not fit it, however, for a 
 special crop, such as turnips, which requires to be unnaturally forced 
 or pushed forward at a particular period of its growth. 
 
 § 4. Will green manuring alone prevent land from becoming exhausted! 
 
 If by green manuring is meant the growing of vegetable matter upon 
 one field, and ploughing it in green into another, as is sometimes done, 
 it may be safely said that, when judiciously j)ra.ctised, land may by 
 this single process be secured for an indefinite period against ex- 
 haustion. But if we plough in only what the land itself produces, 
 and carry off occasional crops of corn, the time will ultimately come 
 when any soil thus treated will cease to yield remunerating crops. A 
 brief consideration of the subject will satisfy you of this. 
 
 Suppose a loose sand to be improved by repeatedly sowing and 
 ploughing in crops of spurry or white lupins, the green leaves and stems 
 fix the floating elements of the atmosphere, and enrich the soil with or- 
 ganic matter, while the roots, more or less deep, bring up saline matters 
 to the surface, and thus supply to the plant what is no less necessary to 
 its healthy growth. But the rams yearly wash away from the surface, 
 and the corn crops remove, a portion of this saline matter. This portion 
 the crops grown for the purpose of green manuring yearly renew by 
 fresh supplies from beneath. But no subsoil contains an inexhaustible 
 store of those saline substances which plants require. Hence, though by 
 skilful green manuring waste land may be brought to a remunerative 
 state of fertility, it will finally relapse again into a state of nature, if no 
 other methods are subsequently adopted for maintaining its productive- 
 ness. The process maybe a slow one, and practical men may be un- 
 willing to believe in the possibihty of a result which does not exhibit it- 
 self within the currency of a single lease, or during a single life-time — 
 yet few thiags arc more certain than that in general the soil must sooner 
 or later receive supplies of saline manure in one form or another, or 
 else must ultimately become unproductive. It may be considered as 
 a proof of this fact that, in all densely peopled countries in which 
 agriculture has been skilfully prosecuted, the manufacturing of such 
 manures has become an important branch of business, giving em- 
 ployment to many hands, and affording an investment to much capital. 
 
 The following table, in addition to other particulars, exhibits the 
 
422 
 
 OF THE PRACTICE OF GREEN MANURING. 
 
 relative proportions of dry organic and saline matter, capable of be- 
 ing added to the surface soil by a few of those plants which are em- 
 ployed for the purposes of remanuring : — 
 
 Kind of Plant. 
 
 Average 
 
 produce 
 
 per imp. 
 
 acre. 
 
 Spurry 
 
 White Lupin. 
 
 Vetch 
 
 Buck- wheat.. 
 Rape 
 
 1000 lbs. contain 
 in the green state 
 Organic Saline 
 Matter. Matter. 
 
 lbs 
 
 6,500 
 25,000 
 
 11,000 
 
 8,000 
 
 16,000 
 
 lbs. 
 
 199 
 
 188 
 
 233 
 170 
 214 
 
 Depth of 
 Roots. 
 
 lbs. 
 21 
 12 
 
 17 
 10 
 16 
 
 inches 
 12 to 15 
 
 Crops 
 
 in a 
 
 year. 
 
 2 or 3 
 
 24 to 26 I or U 
 
 15 to 20 
 12 to 15 
 
 1 
 
 2 
 
 2 
 
 1 or U 
 
 Soil for which they are 
 fitted. 
 
 Dry, loose, sandy. 
 Any except marly or 
 
 calcareous. 
 Strong soil. . 
 Dry, sandy, or moorish 
 Rich soil. 
 
 § 5. Of the practice of green manuring. 
 
 In the practical adoption of green, manuring it is of importance to 
 bear in mind — 
 
 1°. That a sufficient quantity of seed must be sown to keep the 
 ground well covered, one of the attendant advantages of stubble 
 crops being that they keep the land clean and prevent it from becom- 
 ing a prey to weeds. 
 
 2°. That the plants ought to be mown or harrowed, and at once 
 ploughed in before they come into full flower. The flower-leaves 
 give otf nitrogen into the air, and as this element is supposed especi- 
 ally to promote the growth of plants, it is desirable to retain as much 
 of it in the plant and soil as possible. Another reason is that, if al- 
 lowed to ripen, some of the seed may be shed and afterwards infest 
 the land with weeds. 
 
 3°. That they should be ploughed in to the depth of 3 or 4 inches 
 only, that they may be covered sufficiently to prevent waste, and yet be 
 within reach of the air, and of the early roots of the succeeding crop. 
 
 § 6. O/" natural manuring with recent vegetable matter. 
 
 Besides the^ method of ploughing in, which maybe distinguished as 
 artificial green manuring, — there is another mode in which recent ve- 
 getable matter is employed in nature for the purpose of enriching the 
 soil. The natural grasses grow and die upon a meadow or pasture field, 
 and though that which is above the surface may be mowed for hay, or 
 cropped by cattle, yet the roots remain and gradually add to the quantity 
 of vegetable matter beneath. The same is the case to a greater or less 
 extent with all the artificial corn, grass, and leguminous crops we grow. 
 They all leave their roots in the soil, and if ihe quantity of organic mat- 
 ter which these roots contain be greater than that %vhich the crop we car- 
 ry off has derived from the soil, then, instead of exhausting, the growth 
 of this crop will actually enrich the soil in so far as the presence of or- 
 ganic matter is concerned. No crops, perhaps, the whole prodiice of 
 which is carried of the field, leave a sufficient mass of roots behind them 
 to effect this end, but many plants, when in whole or in part eaten upon 
 the field, leave enough in the soil materially to improve the condition of 
 the land — while in all cases those are considered as the least exhaust- 
 
WEIGHT OF ROOTS LEFT IN THE SOIL. 423 
 
 ing, to which are naturally attached the largest weight of roots. Hence, 
 the main reason why poor lands are so much benefitted by being laid 
 down to grass, and why an intermediate crop of clover is often as benefi- 
 cial to the after-crop of corn as if the land had lain in naked fallow. (If 
 the third crop be ploughed in, the land is actually enriched.-Schwertz.) 
 ' An interesting series of exf)eriments on the relative weights of the 
 roots and of the green leaves and stems of various grasses, made by 
 Hlubek, (Ernahrung der Pflanzen, p. 466,) throws considerable light 
 upon their relative efficacy in enriching the soil by the vegetable mat- 
 ter they diffuse through it in the form of roots. The grasses were 
 grown in beds of equal size (180 square feet) in the agricultural gar- 
 den at Laybach, and mown on the fourth year after sowing, just as 
 they were coming into flower. The roots were then carefidly taken 
 up, washed, and dried. The results were as follows : 
 
 Weij:ht of 
 Produce in Produce in Roots, dry Roots 
 
 Kind of Grass. , * > > * > to 100 lbs. 
 
 Grass. Hay. Fresh. Dry. of Hay. 
 
 1. Festuca Elatior— TaZZ Fescue-grass.. 124 lbs. 3Glbs. 5Glbs. 22 lbs. 61 lbs. 
 
 2. Festuca Ov'ina— Sheep's Fescue-grass. 90 30 — 80 2G6 
 
 3. Fh\eum Piatensc—Tmothy-grass... 90 25 5fi 17 GO 
 
 4. Dactylis Glomerata — Rough Cock's- 
 
 faot 202 67 — 221 33 
 
 5. Lolium Perenne — Perennial Rye- 
 
 grass 50 17 — 50 300 
 
 6. Alopecurus Vxsii^nsi^- Meadow Fox- 
 
 tail 106 35 — 24 70 
 
 7. Tridcum Repens — Creeping Couch 
 
 or Quicken- grass 120 60 — 70 116 
 
 8. Poa Annua — Annual Meadow-grass. — — — — HI 
 
 9. Bromus Mollis and Racemosus — 
 
 Soft and smooth Brovie-grass — — — — 105 
 
 10. Anthoxanthum Odoratum — Sweet- 
 scented Vernal grass — — — — 93 
 
 A mixture of white clover, of ribwort, of hoary plantain, and of 
 couch-grass, in an old pasture field, gave 400 lbs. of dry roots to 100 
 lbs. of hay — and in a clover field, at the end of the second year, the 
 fresh roots were equal to one-third of the whole weight of green clo- 
 ver obtained at three cuttings— one in the first, and two in the second 
 year — while in the dry state there were 56 lbs. of dry roots to every 
 100 lbs. of clover hay which had been carried off. 
 
 The 'fourth column of the above table shows how large a quantity of 
 vegetable matter some of the grasses impart to the soil, and yet how un- 
 like the different grasses are in this respect. The sheep's-fescue and 
 the perennial rye-grass — besides the dead roots, which detach them- 
 selves from time to time— leave, at the end of the fourth year, a weight 
 of living roots in the soil which is equal to three times the produce of 
 that year in hay. If v/e take the mean of all the above grasses as an 
 average of what we may fairly expect in a grass field — then the amount 
 of living roots left in the soil when afour-year-old grass field is plough- 
 ed up., vnll be equal to one-sixth 7nore than the weight of that yearns crop. 
 
 In an old pasture or meadow field again, when ploughed up, the 
 living roots left are epual to four times the weight of that yearns hay 
 
424 MANURING BY THE ROOTS OF CLOVER, AND BY 
 
 crop. If a ton and a half of hay have been i:eaped — then about six 
 tons of dry vegetable matter remain in the soil in the form of roots. 
 
 In the case of clover, at the end of the second year the quantity of 
 dry vegetable matter left in the form of roots is equal to upwards oi 
 one-half the weight of the whole hay which the clover has yielded. 
 Suppose there be three cuttings, yielding 4 tons of hay, then 2 tons 
 of dry vegetable matter arc added to the soil in the form of roots, 
 lohen the clover stubble is plong-Jied up. 
 
 But the quantity of roots, like that of green produce, is dependent 
 upon a variety of circumstances. It will sometimes, therefore, be 
 greater and sometimes less than is above stated. It may be received 
 as a rule — not without exceptions perhaps, yet stiU as a general rule 
 — that whatever causes an increased produce above ground, will 
 cause a corresponding increase in the growth of roots. Thus nitrate 
 of soda, which gives us a larger yield of hay, makes the roots also 
 stronger and deeper, and the sward tougher and more difficult to 
 j)lough [Appendix^ No. III.) Hence it is that the farmer is anxious 
 tliut his clover crop should succeed, not merely for the increased 
 amount of green food or of hay it will give him, but because it will 
 secure liim also a better after-crop of corn. 
 
 This burying of recent vegetable matter in the soil, in the form of 
 living and dead roots of plants, is one of those important ameliorating 
 operations of nature which is always to some extent going on, where- 
 ever vegetation proceeds. It is one by which the practical man is 
 often benefitted unawares, and ol' which — too often without imder- 
 etandiiig the source from whence the advantage comes — he syste- 
 matically avails himself in some of the most skilful steps he takes 
 with a view to the improvement of his land. 
 
 § 7. Improvement of the sail by laying down to gi^ass. 
 
 One of the most common of these methods of improvement is that 
 of laying down to grass. This may be done for two, three or four 
 years only, or for an indefinite period of time. In the latter case, the 
 land is said_to be laid down permanently, or to permanent pasture. 
 
 1°. l^emporary pasture or meadow. — If the land be sown with 
 grass and clover-seeds, only as an alternate crop between two sow- 
 ings of corn, the eftect is fully explained by what has been already 
 stated (§ C.) The roots which are left in the soil enrich the surface 
 with both organic and inorganic matter, and thus fit it for bearing a 
 better after-crop of corn. 
 
 If, again, it be left to grass for three or five years, the same effect is 
 produced more fully, and therefore this longer rest from corn is better 
 fitted for soils which are poor in vegetable matter. The quantity of 
 organic matter which has accunnilated b(H^omes greater every year, in 
 conscquenc(> of the annual death of stems and roots, and of the soil being 
 more closely covered, but this increase is probably never in any one 
 after-year equal to that which takes place during the first. The quan- 
 tity of roots which is produced during the first year of the young plants' 
 gl'owth must, we may reasonably suppose, be greater than can ever 
 afterwards be necessary in an equal space of time. Hence, one good 
 year of grass or clover will enrich the soil more in proportion to the 
 
LAYING DOWN TO GRASS. — PERMANENT PASTURE. 425 
 
 time expended^ than a rest of two or three years in grass, if annually 
 mowed. 
 
 Or if, instead of being mown, the produce in each case be eaten off 
 by stock, the result will be the same. That which lies longest will be 
 tlie richest when broken up, but not in an equal proportion to the time 
 it has lain. The produce of green parts, as well as of roots, in the ar- 
 tificial grasses, is generally greatest during the first year after they are 
 sown, and therefore the manuring derived from the droppings of the 
 stock, as well as from the roots, will be greatest in proportion during the 
 first year. That farming, therefore, is most economical — where the 
 land will admit oi'it — which permits the clover or grass seeds to occupy 
 the land ior one year only. 
 
 But if, after the first year's hay is removed, the land be pastured for 
 two or three years more, it is possible that each succeeding year may 
 enrich the surface soil as much as the roots and stubble of the first 
 yrar's hay had done ; so that if it lay three years it might obtain 
 three times the amount of improvement. This is owing to the cir- 
 cumstance that the whole produce of the field remains upon it, ex- 
 cept what is carried off by the stock when removed — but very ifiuch^ 
 it is obvious, will depend upon the nature of the soil, and upon the 
 selection of the seeds being such as to secure a tolerable produce of 
 green food during the second and third years. 
 
 2°. Permanent pasture or meadow. — But when land is laid down 
 to permanent grass it undergoes a series of further changes, which 
 have frequently arrested attention, and which, though not difficult to 
 be understoodj have often appeared mysterious and perplexing to 
 practical men. Let us consider these changes. 
 
 a. When grass seeds are sown for the purpose of forming a per- 
 manent sward, a rich crop of grass is obtained during the first, and 
 perhaps also the second year, but the produce after three or four 
 years lessens, and the value of the pasture diminishes. The plants 
 generally die and leave blank spaces, and these again are slowly 
 filled up by the sprouting of seeds of other species, which have either 
 lain long buried in the soil or have been brought thither by the winds. 
 
 This first change, which is almost universally observed in fields of 
 artificial grass, arises in part from the change which the soil itself has 
 undergone during the few years that have elapsed since the grass 
 seeds were sown, and in part from the species of grass selected not 
 being svich as the soil, at any time, could permanently sustain. 
 
 h. When this deterioration, arising from the dying out of the sown 
 grasses, has reached its utmost point, the sward begins gradually to 
 improve, natural grasses suited to the soil spring up in the blank places, 
 and from year to year the produce becomes greater and greater, and 
 the land yields a more valuable pasture. Practical men often say 
 that to this improvement there are no bounds, and that the older the 
 pasture the more valuable it becomes. 
 
 But this is true only within certain limits. It may prove true for 
 tlie entire currency of a lease, or even for the lifetime of a single ob- 
 server, but it is not generally true. Even if pastured by stock only and 
 never mown, the improvement will at length reach its limit or highest 
 point, and from this time the value of the sward will begin to diminish. 
 
426 THE SOIL AND GRASSES CONTINUALLY CHANGE. 
 
 c. This, agairi; is owing to a new change -which has come over the 
 soil. It has become, in some degree, exhausted of those substances 
 which are necessary to the growth of the more vakiable grasses — 
 less nutritive species, therefore, and such as are less willingly eaten 
 by cattle, take their place. 
 
 Such is the almost universal process of change which old grass fields 
 undergo, whether they be regularly mown or constantly pastured only 
 — provided they are left entirely to themselves. If mown they begin 
 to fail the sooner, but even when pastured they can be kept in a state 
 of full productiveness only by repeated top-dressings, especially of sa- 
 line manure — that is, by adding to the soil those substances which are 
 necessary to the growth of the valuable grasses, and of which it suf- 
 fers a yearly and unavoidable loss. Hence, the rich grass lands of 
 our fathers are found now in too many cases to yield a herbage of 
 little value. Hence, also, in nearly all countries, one of the first steps 
 of an improving agriculture is to plough out the old and failing pas- 
 tures, and either to convert them permanently into arable fields, or after 
 a few years' cropping and manuring, again to lay them down to grass. 
 
 Bitt when thus ploughed out, the surface soil upon old grass land is 
 found to have undergone a remarkable alteration. When sown with 
 grass seeds, it may have been a stiff, more or less grey, blue, or yellow 
 clay — v>dien ploughed out it is a rich, brown, generally light and fria- 
 ble vegetable mould. Or when laid down it may have been a pale- 
 colored, red, or yellow sand or loam. In this case the surface soil 
 is still, when turned up, of a rich brown colour — it is lighter only and 
 more sandy than in the former case, and rests upon a subsoil of sand 
 or loam instead of one of clay. It is from the production of this change 
 that the improvement caused by laying down to grass principally re- 
 sults. In what does this change consist ? and hov/ is it effected ? 
 
 If the surface soil upon stiff clay lands, which have lain long in grass, 
 be chemically examined, it will be found to be not only much richer 
 in orga^nic matter, but often also poorer in alumina than the soil which 
 formed the surface when the grass seeds were first sown upon it. 
 The brownjnould which forms on lighter lands will exhibit similar 
 differences when compared with the soil on which it rests ; but the 
 proportion of alumina in the latter being originally small, the diffe- 
 rence in respect to this constituent will not be so perceptible. 
 
 The effect of this change on the surface soil is in all cases to make 
 it more rich in those substances which cultivated plants require, and 
 therefore more fertile in corn. But strong clay lands derive the fur- 
 ther important benefit of being rendered more loose and friable, and 
 thus more easily and more economically cultivated. 
 
 The mode in Avhich this change is brought about- is as follows : — 
 
 1°. The roots, in penetrating, open and loosen the subjacent stiff clay. 
 Diffusing themselves every where, they gradually raise, by increasing 
 the bulk of, the surface soil. The latter is thus converted into a mix- 
 ture of clay and decayed roots, which is of a dark colour, and is necessa- 
 rily more loose and friable than the original or subjacent unmixed clay. 
 
 2°. But this admixture of roots effects the chemical composition as 
 well as the state of aggregation of the soil. The roots and stems of 
 the grasses contain much inorganic — earthy and saline — matter (Lee. 
 
AGENCY OF THE RAINS AND WINDS. 427 
 
 IX., § 1), which is gathered from beneath, wherever the roots pene- 
 trate, and is by them sent upwards to the surface. A ton of hay con- 
 tains about 170 lbs. of this inorganic matter (Lee. X., § 3). Suppose 
 the roots to contain as much, and that the total animal produce of 
 grass and roots together amounts to four tons, then about 680 lbs. of 
 saline and earthy matters are every year worked up by the living 
 plants, and in a great measure permanently mixed with the surface 
 soil. Some of this, no doubt, is carried off by the cattle that feed, 
 and by the rains that fall, upon the land — some remains in the deeper 
 roots, and some is again, year after year, employed in feeding the 
 new growth of grass — still a sufficient quantity is every season 
 brought up from beneath, gradually to enrich the surface with valua- 
 ble inorganic matter at the expense of the soil below. 
 
 8^. Nor are mechanical agencies wanting to increase this natural 
 difference between the surface and the under soils. The loosening 
 and opening of the clay lands by the roots of the grasses allow the 
 rains more easy access. The rains gradually wash out the fine par- 
 ticles of clay that are mixed with the roots, and carry them down- 
 wards, as they sink towards the subsoil. Hence the brown mould, as 
 it forms, is slowly robbed of a portion of its alumina, and is rendered 
 more open, while the under soil becomes even stiffer than before. 
 This sinking of the alumina is in a great measure arrested when the 
 soil becomes covered with so thick a sward of grass as to break the 
 force of the rain-drops or of the streams of water by which the land 
 is periodically visited. Hence the soil of some rich pastures contains 
 as much as 10 or 12, of others as little as 2 or 3 per cent, of alumina. 
 
 4-. The winds also here lend their aid. From the naked arable 
 lands, when the weather is dry, every blast of wind carries off a portion 
 of the dust. This it suffers to fall again as it sweeps along the surface 
 of the grass fields — the thick sward arresting the particles and sifting 
 the air as it passes through them. Everywhere, even to remote dis- 
 tricts, and to great elevations, the winds bear a constant small burden 
 of earthy matter ;* but there are few practical agriculturists who, du- 
 ring our high winds, have not occasionally seen the soil carried off in 
 large quantities from their naked fields. Upon the neighbouring grass 
 lands this soil falls as a natural top-dressing, by which the texture of 
 the surface is gradually changed and its chemical constitution altered. 
 
 5"^. Another important agency also must not be overlooked. In grass 
 lands insects, and especially earth-worms, abound. These almost 
 nightly ascend to the surface, and throw out portions of finely-divided 
 earthy matter. On a close shaven lawn the quantity thus spread over 
 the surface in a single night often appears surprising. In the lapse of 
 years the accumulation of the soil from this cause must, on old pasture 
 fields, be very great. It has often attracted the attention of practical 
 men,t and so striking has it appeared to some, that they have been in- 
 
 ' It. lia^ been observed that on spots purposely sheltered from the wind and rain on every 
 side, the quantity of dust that is collected, when pressed down^ is ia 3 years equal to one line, 
 or in 36 years to one inch in thickness. — Sprengel, Lehre vom Diinger, p. 443. 
 
 t The permanence cf a fine carpeting of rich sweet grass upon a portion of his farm is 
 ascribed (by Mr. Purdie) to " the spewings of worms, apparently immensely numerous, 
 which incessantly act as a rich top-dressing." — Prize Essays of the Highland Society, L 
 p. 191. 
 
428 WHY ARTIFICIAL PASTURES DETERIORATE. 
 
 clined to attribute to the slow but constant labour of these insects, the 
 entire formation of the fertile surface soils over large tracts of country. 
 ('• Geological Transactions.") 
 
 I have^ directed your attention to these causes chiefly in explana- 
 tion of the changes which by long lying in grass the surface of our 
 stiif clay lands is found to undergo. But they apply equally to other 
 soils also — tlie only difference being that, in the case of such as are 
 already light and open, the change of texture is not so great, and 
 therefore docs not so generally arrest the attention. 
 
 Upon this subject I may trouble you further with two practical re- 
 marks : 
 
 P. That the richest old grass lands — those which have remained 
 longest in a fertile condition — are generally upon our strongest clay 
 soill (the Oxford and Lias clays, Lee. XL, § 8). This is owing to 
 the fact that such soils naturally contain, and by their comparative 
 impermeability re-tain, a larger store of those inorganic substances on 
 which the valuable grasses live. When the surface soil becomes de- 
 ficient in any of these, the roots descend further into the subsoil and 
 bring up a fresh supply. But these grass lands are not on this account 
 exem])t from the law above explained, in obedience to which all pas- 
 tured lands, when left to nature, must ultimately become exhausted. 
 Tliey must eventually become poorer ; but in their case the deterio- 
 ration will be slower and more distant, g,nd by judicious top-dressings 
 may be still longer protracted. 
 
 2\ The natural clianges which the surface soil undergoes, and es- 
 pecially upon clay lands when laid down to grass, explain why it is so 
 difficult to procure, by means of artifical grasses, a sward equal to that 
 v.'Iiich grows naturally upon old pasture lands. As the soil changes 
 upon our artificial pastures, it becomes better fitted to nourish other spe- 
 cies of grass than those which we have sown. These naturally spring 
 up, therefore, and cover the soil. But these intruders are themselves 
 not destined to be permanent possessors of the land. The soil under- 
 goes a further change, and new species again appear upon it. We can- 
 not tell how often different kinds of grass thus succeed each other upon 
 the soil, bufwe know that the final rich sward which covers a grass field 
 when it has reached its most valuable condition, is the result of along 
 series of natural changes which time only can bring about. 
 
 The soil of an old pasture field, which has been ploughed up, is made 
 to undergo an important change both in texture and in chemical con- 
 stitution, before it is again laid down to grass. The 'same grasses, 
 therefore, which previously covered it will no longer flourish, even 
 when they are sown. Hence the unwiflingness felt by practical men 
 to plougli up their old pastures — but hence, also, the benefit which 
 results from the breaking up of such as are old, worn out, or covered 
 with unwholesome grasses. When again converted into pasture land, 
 new races appear, and a more nourishing sward is produced.* 
 
 ' For an excellent article on the superior feedins qualities of recent artificial grasses 
 over many ojd pasture lands, by Mr. BosweU, of Kingcaussie, see the Qftarlerly Journal 
 of Agriculture, N., p. 783. 
 
IMPROVEMENT OF THE SOIL BY PLANTINa OF TREES. 429 
 
 § 8. Improvement of the soil by the planting of trees. 
 
 It has long been observed by practical men, tliat when poor, thin, 
 unproductive soils have been for some time covered with wood, their 
 quality materially improves. In the intervals of the open foref::t, they 
 will produce a valuable herbage — or when cleared of trees they may 
 for some time be made to yield profitable crops of corn. 
 
 This fact has been observed in almostevery country of Europe, bat 
 the most precise observations upon the subject with which I am ac- 
 qauiuted are those which have been made in the extensive plantations 
 of the late Duke of Atliol. These plantations consist chiefly of white 
 larch (^Larix Europoia^) and grow upon a poor hilly soil, resting on 
 gneiss, mica-slate, and clay-slate (Lee. XL, § 8.) In six or seven 
 years the lower branches spread out, become interlaced, and com- 
 })letely overshadow the ground. Nothing, therefore, grows upon it 
 till the trees are 24 years old, when the spines of the lower branches 
 beginning to fall, the first considerable thinning takes place. Air and 
 light being thus re-admitted, grasses (chiefly holcus moUis and lana- 
 tiis) spring up, and a fine sward is gradually produced. The ground, 
 which previously was worth only 9d. or Is. per acre as a sheep pas- 
 tart;, at the end of 30 years becomes worth from 7s. to 10s. per acre. 
 
 The soil on this part of the Duke's estate is especially propitious to 
 the larch — and. therefore, this tree both thrives best and in the great- 
 est degree improves the soil. Thus in oak copses, cut every 24 years, 
 the soil becomes worth only 5s. or 6s. per acre, and this during the last 
 six years only. Under an ash plantation, the improvement amounts 
 to 2s. or 3s. per acre ; under Scotch fir, it does not exceed 6d. an acre 
 — while under spruce and beech the land is worth less than before. 
 (Mr. Stephens, in the Transactions of the Highland Society, xi., p. 
 189; also Loudon's Encylopaidia of Agricidture, p. 1346.) 
 
 The main cause of this improvement, as of that which is produced 
 by laying down to grass, is to be found in the natural manuring with 
 recent vegetable matter, to which the soil year by year is so long 
 pubjected. Trees differ from grasses only in this, that while the lat- 
 ter enrich the soil both by their roots and by their leaves, the former 
 manure its surface only by the leaves which they shed. 
 
 The leaves of trees, like those of grasses, contain much inorganic mat- 
 ter, and this when annually spread upon the ground slowly adds to the 
 depth as well as to the richness of the soil. Thus the leaves of the fol- 
 lowing trees, when dried in the air, contain respectively of inorganic 
 matter ((Sprengel, Chemiefur Landwirthe, ii., passim) : — 
 
 April. Aui^ust. November. 
 
 Oak — 5 per cent. 4^ per cent. 
 
 Ash — 6i « — " 
 
 Beech — 7 " 6^ « 
 
 Birch — 5 " _ u 
 
 Elm — 111 " — " 
 
 Willow — Sh " — " 
 
 White Larch 6 J. per cent. — " — " 
 
 Scotch Fir — 1| " — " 
 
 In looking at the differences among these numbers — especially in 
 
430 RELATIVE EFFECTS OF DIFFERENT KINDS OF TREES. 
 
 the case of the elm and of the Scotch fir — one would naturally sup- 
 pose that the diversity of their effects in improving the land is in some 
 measure to be ascribed to the quantity and kind of the inorganic mat- 
 ter which the leaves of these several trees contain. And to this 
 cause, no doubt, some effect is to be ascribed, in localities where all 
 the trees thrive equally. 
 
 But upon the quantity of leaves produced, as much in general will 
 depend, as upon the relative proportions of organic and inorganic 
 matter which these leaves may respectively contain. And as the 
 quantity of leaves is always greatest where the tree flourishes best or 
 finds a most propitious soil — the improvement of the soil itself, by 
 any particular tree, will be always in a great measure determined by 
 its fitness to promote the growth of that kind of tree. 
 
 On the soil planted by the Duke of Athol, the larch shot up luxu- 
 riantly, while the Scotch fir lingered and languished in its growth. 
 Thus the quantity of leaves produced and annually shed by the 
 former was vastly greater than by the latter tree. Had the Scotch 
 fir thriven better than the larch, the reverse might have been the 
 case, and the value of the soil might have been increased in a great- 
 er proportion by plantations of the former tree. 
 
 Other special circumstances also will account for the relative de- 
 grees of improvement produced by the larch and by some of the 
 other trees — for example, the oak. In the oak copse the soil in 16 
 years become worth 6s. or 8s. an acre. If, therefore, instead of being 
 cut down for their bark at the end of 24 years, the trees had been al- 
 lowed to grow up into an oak forest, the permanent improvement of 
 the pasture, even on this soil, would probably have been at least as 
 great as under the larch. The above experiments, therefore, are in 
 reality not so decisive in regard to the relative improving 'power of 
 the several species of trees as they at first sight appear. The most 
 rational natural rule by which our practice should be guided seems 
 to be contained in these three propositions — 
 
 1". That the soil will be most improved by those trees which thrive 
 best upon it. 
 
 2°. Among those which thrive equally, by such as yield the 
 largest produce of leaves, and — 
 
 3°. Among such as yield an equal weight of leaves, by those whose 
 leaves contain the largest proportion of inorganic matter — which 
 bring up from beneath, that is, and spread over the surface in largest 
 quantity, the materials of a fertile soil. 
 
 The mode in which the lower branches of the larch spread out and 
 overshadow the surface is not without its influence upon the ultimate 
 improvement which the soil exhibits. All vegetation being prevented, 
 the land, besides receiving a yearly manure of vegetable mould, is 
 made to lie for upwards of 20 years in uninterrupted naked fallow. 
 It is sheltered also from the beating of the rain drops, which descend 
 slowly and gently upon it, bearing principles of fertility instead of 
 washing out the valuable saline substances it may contain. 
 
 Beneath the overshadowing branches of a forest, the soil is also pro- 
 tected from the wind, and to this protection Sprengel attributes much 
 of that rapid improvement so generally experienced where lands are 
 
MANURING WITH SEA-WEED. " 431 
 
 covered with wood. The winds bear along particles of earthy mat- 
 ter (see note, p. 427,) which they deposit again in the still forests ; and 
 thus gradually form a soil even on the most naked places. This slow 
 general cause of accumulation may not be without its effect, and 
 should not be forgotten, but it evidently affords no explanation why, 
 in the same range of country, the soil which is covered by forests of 
 one kind should improve more rapidly than those which are shelterea 
 by trees of another species. 
 
 § 9. Of the use of sea-weed as a manure. 
 
 Among green manures of great value and extensive application 
 there remains to be noticed the sea-weed or sea-ware of our coasts. 
 The marine plants of which it consists differ from the green vege- 
 tables grown upon land, — , 
 
 1°. By the greater rapidity with which they undergo decay. When 
 laid as top-dressings upon the land they melt down, as it were, and in 
 a short time almost entirely disappear. Mixed with soil into a com- 
 post or with quick-lime, they speedily crumble down into a black earth, 
 in which little or no trace of the plant can be perceived. 
 
 2°. By the greater proportion of saline or other inorganic matter 
 which these plants, in their dry state, contain. It is these substances 
 which are obtained in the form of kelp when dry sea-weeds are burn- 
 ed in the air. 
 
 We have seen (Lee. X., § 3,) that the quantity of ash left by 1000 
 lbs. of our more usually cultivated grasses, in the dry state, varies 
 from 5 to nearly 10 per cent., but the ficcus vesicidosus, which is 
 reckoned the most valuable for the manufacture of kelp, gives up- 
 wards of 160 lbs. of ash from 100 lbs. of the dry plant. This ash, 
 according to Fagerstrom, consists of — 
 
 Gypsum 63-4 lbs. 
 
 Carbonate of Lime 34-1 " 
 
 Iodide of Sodium 2-7 " 
 
 Other Salts of Soda •. 29-9 " 
 
 Sihca, Oxide of Iron, and earthy Phosphates.31-1 " 
 
 161-2* 
 
 This ash contains less potash, but more soda and gypsum, than 
 those of the grasses, (Lee. X., § 3,) and hence, as you will readily 
 
 * Berzelius Arsber'dttelse, 1824, p. 225. — If we compare the composition of lliis ash with 
 thut of the several varieties of kclp,°\ven in page 356, it will be seen to differ from them 
 very considerably. But kelp is always manufactured from a mixture of different plants 
 in varying proportions, and hence one cause of the diversity of composition among differ- 
 ent samples of this substance. 
 
 Sprengel states (Lekre vom Dilnger, p. 277,) that the fucus vesiculosus contains only 16 
 per cent, of water. I do not know whether this is the result of experiments of his own, 
 but I have not introduced it into the text, because it appears to me inconsistent with the 
 remarkable manner in which sea-weed shrivels up when dried, and with its little perma- 
 nence as a manure. " If an acre of land is completely covered with it, after a few days 
 of dry weather, the whole would not weigh 500 lbs. The fibrous parts reduced to mere 
 threads alone remain — so that it is like manuring land icith cobwebs" (Dr. Walker.) This 
 would seem to imply the presence of a larger quantity of water in fresh sea-weed than in 
 green grass, and consequently a less efficacy as a manure when applied in equal weights. 
 According to Boussingault, the fucus digitatus contains 40 per cent, of water, and the 
 fucus saccliarinus 76 per cent, when newly taken from Uie sea, and 40 per cent, after being 
 dried in the air. 
 
432 MODE IN WHICH SEA-WEED IS APPLIED. 
 
 understand, may be expected to- exercise a somewhat dififerent influ- 
 ence upon vegetation. 
 
 It is of importance, however, to bear .in mind tliat the sahne and 
 other inorganic matters whicli are contained in tlie sea-weed we lay 
 upon our fields, form a positive addition to tJie land. If we plough in a 
 green crop where it grew, we restore to the soil the same saline matter 
 only which the plants have already taken from it during their growth, 
 while the addition of sea-weed imparts to it an entirely new supply. It 
 brings back from the sea a portion of that which the rivers are con- 
 stantly carrying into it, and is thus valuable in restoring, in some mea- 
 sure, what rains and crops are constantly removing from the land. 
 
 Sea- weed is collected along most of our rocky coasts — and is 
 seldom neglected by the farmers on the borders of the sea. In the Isle 
 of Thanet, it is spmetimes cast ashore by one tide and carried off by 
 the next ;— so that after a storm the teams of the farmers may be seen 
 at work even during the night in collecting the weed, and carrying it 
 beyond the reach of the sea (British Husbandry, II., p. 418.) In that 
 locality, it is said to have doubled or tripled the produce of the land. 
 On the Lothian coasts, a right of way to the sea for the collection of 
 sea-Avare increases the value of the land from 25s. to 30s. an acre 
 (Kerr's Berwickshire, p. 377.) In the Western Isles it is extensively 
 collected and employed as a nianure — (" sea-w^eeds constitute one- 
 half of Hebridean manures, and nine-tenths of those of the remoter 
 Islands," Macdonald's Agricidture of the Hebrides, p. 401,) — and 
 on the north-east coast of Ireland, the farming fishermen go out in 
 their boats and hook it up from considerable depths in the sea (Mrs. 
 Hall's Ireland.) 
 
 It is appUedeitherimmediately as a top-dressing, especially to grass 
 lands — or it is previously made into a compost with earth, with hme, 
 or with shell-sand. Thus mixed with lime, it has been used with ad- 
 vantage as a top-dressing for the young wheat crop, (British Hus- 
 bandry, IL, p. 419 ;) and with shell-sand, it is the general manure for 
 the potatoe crop among the Western Islanders ("Transactions of the 
 Highland Society, 1842-3, p. 766.) It may also be mixed with farm- 
 yard manure or even with peat moss, both of which it brings into a 
 more rapid fermentation. In some of the Western Isles, and in Jer- 
 sey, it is burned to a light, more or less coaly powder, and in this 
 form is applied successfully as a top-dressing to various crops. There 
 is no reason to doubt that the most economical method is to make it 
 into a compost with absorbent earth and lime, or to plough it in at 
 once in the fresh state. 
 
 In the Western Islands one cart load of farm-yard manure is con- 
 sidered equal in immediate effect — upon the first crop, that is — to 2i 
 of fresh sea-weed, or to If after it has stood two months in a heap. 
 The sea-weed, however, rarely exhibits any considerable action upon 
 the second crop. 
 
 Sea-Aveed is said to be less suited to clay soils, while barren sand 
 has been brought into the state of a fine loam by the constant appli- 
 cation of sea-weed alone, for a long series of years (Macdonald's 
 Hebrides, p. 407.) 
 
 Conflicting opinions are given by different practical men m regard 
 
USE OF STRAW AS A MANURE. 433 
 
 to the crops to which it is best suited. But the explanation of most 
 of these and similar discordances is to be found in the answers to the 
 three following questions — what substances does the crop specially 
 require ? — how many of these abound in the soil ? — can the manure we 
 are about to use supply all or any of the remainder ? If it can, it maybe 
 expected to do good. Thus simply and closely are the kind of crop, the 
 kind of soil, and the kind of manure, in most cases, connected together. 
 
 § 10. Of manuring with dry vegetable substances. 
 
 The main general difference between vegetable matter of the same 
 kind, and cut at the same age, when applied as a manure in the green 
 and in the dry state, consists in this — that in the former it decomposes 
 more rapidly, and, therefore, acts more speedily. The total effect upon 
 vegetation will probably in either case be very nearly the same. 
 
 Bat if the dry vegetable matter have been cut at a more advanced 
 age of the plant or have been exposed to the vicissitudes of the weather 
 while drying, it will no longer exhibit an equal efficacy. A ton of dry 
 straw, when unripe, will manure more richly than a ton of the sam.e 
 straio in its ripe state — not only because the sap of the green plant 
 contains the materials from which the substance of the grain is after- 
 wards formed — but, because, as the plant ripens, the stem restores to the 
 soil a portion of the saline, especially of the alkaline, matter it previous- 
 ly contained (Lee. X., § 5.) After it is cut, also, every shower of rain 
 that falls upon the sheaves of corn or upon the new hay, washes out 
 some of the saline substances which are lodged in its pores, and thus 
 diminishes its value as a fertiUzer of the land. These facts place in 
 a still stronger light the advantages which necessarily follow from 
 the use of vegetable matter in the recent state, for manuring the soil. 
 
 1°. Dry straw. — It is in the form of straw that dry vegetable mat- 
 ter is most abundantly employed as a manure. It is only, however, 
 when already in the ground in the state of stubble, that it is usually 
 ploughed in without some previous preparation. When buried in the 
 soil in the dry state, it decomposes slowly, and produces a less sensi- 
 ble effect upon the succeeding crop ; it is usually fermented, there- 
 fore, more or less completely, by an admixture of animal manure in 
 the farm-yard before it is laid upon the land. During this fermenta- 
 tion a certain unavoidable loss of organic, and generally a large loss ol 
 saline matter, also takes place (see in the succeeding lecture the sec- 
 tion upon mixed animal and vegetable manures.) It is, therefore, the- 
 oretically true of dry, as it is of green, vegetable matter, that it will add 
 most to the soil, if it be ploughed in without any previous preparation. 
 
 Yet this is not the only consideration by which the practical man 
 must be guided. Instead of a slow and prolonged action upon his 
 crops, he may require an immediate and more powerful action for a 
 shorter time, and to obtain this he may be justified in fermenting his 
 straw with the certainty even of an unavoidable loss. Thus the dis- 
 puted use of short and long dung becomes altogether a question of 
 expediency or of practical economy. But to this point I sliall again 
 recur when treating of farm-yard manure in the succeeding lecture. 
 
 2°. Chaff partakes of the nature of straw, but it decomposes more 
 slowly when buried in the soil in Hie dry state. It is also difficult to 
 
434 ACTION OF RAPE-DUST ON WHEAT AND BEANS. 
 
 bring into a state of fermentation, even when mixed with the liquid 
 manure of the farm-yard, 
 
 3°. Rape-dust. — When rape seed is exhausted of its oil, it comes 
 from the press in the form of hard (rape) cakes, which, when crushed 
 to powder, form the rape-dust of late years so extensively employed as 
 a manure. It is occasionally mixed with farm-yard dung, and applied 
 to the turnip crop, but its principal employment has hitherto been, I 
 beheve, as a top-dressing for the wheat crop, either harrowed in with 
 the seed in October, or applied to the young corn in spring. 
 
 Rape-dust requires rtioisture to bring out its full fertilizing virtues ; 
 hence it is chiefly adapted to clay soils or to such as rest upon a stiff 
 subsoil. It is seldom applied, therefore, to the barley crop, and even 
 upon wheat it will fail to produce any decidedly good ei^'ect in a very 
 dry season. Several interesting circumstances have been experi- 
 mentally ascertained in regard to the action of rape-dust, to which it 
 is proper to advert : — 
 
 a. That in very dry seasons it may produce little benefit upon tur- 
 nips, potatoes, and other crops, while in the same circumstances the 
 efiect of guano may be strikingly beneficial. Thus in one experi- 
 ment, made in 1842, upon unmanured land sown with turnips — 
 
 16 cwt. of rape-dust gave 3| tons of bulbs per acre, 
 
 2 cwt. of guano gave 5 do. 
 Unmanured gave 3 J do. 
 
 And in another, in the same season, upon unmanured land — 
 1 ton of rape-dust gave 14i tons of bulbs per acre. 
 
 3 cwt. of guano gave 23^ do. 
 Unmanured gave 121* do. 
 
 Again^ upon potatoes, planted without other manure, in three ex- 
 periments the produce per acre, in tons, was as follows : — 
 
 Unmanured. 1 ton Rape-dust. 3 cwt. Guano. 4 cwt. Guano. 
 
 White Don Potatoes — 12i 18^ — 
 
 Red Don Potatoes 6| 10 — 14i 
 
 Connaught Cups 5f ' 13 . — 13| 
 
 In none^flthe above experiments did the action of the large quaa- 
 tity of rape-dust equal that of the comparatively small quantity of 
 guano — though, from being buried in the soil, the difference was less 
 striking in the case of the potatoe crops. 
 
 b. Rape-dust may actually cause the crop to be less than the land 
 alone would naturally produce — if in a dry season it be laid on in 
 any considerable quantity. 
 
 Thus in 1842, in an experiment upon Oots, made at Lennox Love — 
 16 cwt. of rape-dust gave 45 bushels. 
 2 cwt. of guano gave 68 do. 
 Unmanured soil gave 49 do. 
 In this property of injuring the crop, when rain does not happen to 
 fall, rape-dust resembles very much those saline substances which, as 
 we have seen, may often be applied with much advantage to the land. 
 
 c. Yet it would appear to exercise less of this evil influence upon 
 wheat and beans, and in similar circumstances. Thus in the same 
 
 • See Appendix, No. VIII. 
 
THE aUANTITY MUST NOT BE TOO GREAT. 435 
 
 Beason, 1842, and in the same locality, Lennox Love, a crop of wheat, 
 with — 
 
 16 cwt. of rape-dust gave 51 bushels per acre. 
 2 cwt. of guano gave 43 do. 
 
 Unmanured gave 47| do. 
 
 And a crop of beans, with — 
 
 16 cwt. of rape-dust gave 38 bushels. 
 2 cwt. of guano gave S5h do. 
 Unmanured gave 30 do. 
 
 In both of these cases, notwithstanding the drought, the rape-dust 
 improved the crop, and though not sufficiently so to pay the cost of the 
 application, yet to a greater extent than the same quantity of guano. 
 It is deserving of investigation, therefore, whether rape-dust be more 
 especially adapted to wheat and beans. Even in favorable seasons 
 it may possibly prove more economical than guano as a manure for 
 these two crops (see Appendix, No. VIII.) 
 
 d. But even in favorable seasons, and to the wheat crop, there is 
 reason to believe that rape-dust cannot be economically applied in more 
 than a certain, perhaps variable, quantity per acre. Thus four equal 
 plots of ground (nearly half an acre each,) sown with wheat, were top- 
 dressed with rape-dust in different proportions with the following results: 
 
 With 7 cwt. the produce was 26 bushels of market corn. 
 
 With 10 cwt. the produce was 28 do. 
 
 With 15 cwt. the produce was 29i do. 
 
 With 26 cwt. the produce was 27f do. 
 
 Unmanured the produce was 22i* do. 
 
 In this experiment not only was the crop diminished when more 
 than 15 cwt. was added, but the increased produce was not sufficient 
 to defro.y the additional cost of the application, when more than 7 
 cwt. of rape-dust was put on. 
 
 e. It may be noticed as another curious fact, that the action of 
 rape-dust is dependent upon the presence or absence of certain other 
 substances in the soil. Common salt and sulphate of soda, when 
 mixed with it under certain circumstances, lessen the effect which it 
 would produce alone, and the same will probably happen when it is 
 applied, without admixture, to soils in which these saline compounds 
 happen to be already present. Some remarks upon this interesting 
 point will be found in the Appendix, No. VIII. 
 
 4°. Lintseed, poppy-seed, cotton-seed, and cocoa-nut cakes. — The 
 cake which is left when other oils are extracted from the seeds or fruits 
 in which they exist is, also, in almost every case, useful as a manure. 
 Thus the seeds of the cotton plant yield an oil and leave a cake which is 
 now used as a manure in the United States, though little known as yet, I 
 believe, in England. The cocoa-nut cake is employed in Southern In- 
 dia partly in feeding cattle and partly as a manure for the cocoa-nut tree 
 itself Some trials have recently been made with it among ourselves, 
 but I am ignorant of the precise results. In this country Hntseed cake 
 is made in large quantity, but as it is relished by cattle, is fattening, and 
 enriches the droppings of the stock fed upon it, it is seldom applied di- 
 
 " British Husbandry, I,, p. 412. 
 
 19 
 
436 USE OF MALT-DUSTj DRY LEAVES, AND PEAT, AS MANURES. 
 
 rectly to the land. In France and some parts of Belgium, where the 
 poppy is largely cultivated for the oil yielded by its seeds, the cake 
 which these seeds leave is highly esteemed as a manure. 
 
 5°. Malt-dust. — When barley is made to sprout by the malster, and 
 is afterwards dried, the small shoots and rootlets drop off, and form 
 the substance known by the name of malt-dust. One hundred bushels 
 of barley yield 4 or 5 bushels of this dust. It is sold at the rate of 
 from 5s. to 8s. a quarter, and has been applied with success as a top- 
 dressing to the barley and wheat crops. It may also be drilled in 
 with turnips or dusted over the young grass in spring. 
 
 6°. Saw-dust is usually rejected by the agriculturist, in consequence 
 of the difficulty which is generally experienced in bringing it into a state 
 of fermentation. It decomposes slowly when ploughed into the soil in 
 its dry state, but it nevertheless gradually benefits the land, and should 
 not, theretbre, be permitted in any case to run to waste. It forms an 
 excellent absorbent also for liquid manures of any kind, which it pre- 
 serves from sinking too rapidly when they are to be applied to porous, 
 sandy, or chalky soils, while these liquids again hasten the decomposi- 
 tion of the saw-dust and augment its immediate effect upon the land. In 
 localities favorable for the collection of sea-weed, it may also be more 
 rapidly fermented by an admixture with this substance. Saw-dust 
 forms an ingredient in some of the mixed manures which have re- 
 cently come into use (see Appendix, No. VIII., Exp. B.) 
 
 7°. Dry leaves may either be dug into the land at once, or maybe 
 laid up in heaps, when they will gradually decay, and form, in most 
 cases, an enriching manure. They gradually improve the soil (as 
 we have already seen, p. 429,) on which they annually fall, but the 
 same quantity of leaves will do more good if collected and immedi- 
 ately dug in, or if made into a compost heap, than if left to undergo 
 a slow natural decay on the surface of the land. 
 
 § 12. Of the use of decayed vegetable matter as a manure. 
 
 The most abundant forms of partially decayed vegetable matter 
 which come within the reach of the practical farmer, are peat and 
 tanner's barkr 
 
 1°. Peat. — To soils which are deficient in vegetable matter, it is 
 clear that a judicious admixture of peat must prove advantageous, be- 
 cauae it will supply some at least of those substances which are neces- 
 sary to the production of a higher degree of fertility. But peat decays 
 very slowly in the air, and hence its apparent effect when mixed with 
 the soil is very small. It may gradually ameliorate its quality, espe- 
 cially if the soil be calcareous, but it will not immediately prepare the 
 land for th(^- growth of any particular crop. But if the obstacles to 
 its further decomposition be removed — that is, if by artificial means 
 its decay be promoted — then its immediate and apparent effect upon 
 the soil is increased, and it becomes an acknowledged fertilizing ma- 
 nure. Different methods have been successfully practised for bring- 
 ing it into this more rapid state of decay or fermentation. 
 
 a. The half-dried peat may be mixed with from one-fourth to one- 
 half of its weight of fermenting farm-yard manure — the whole heap 
 
FERMENTATION OF PEAT AND TANNER's BARK. 437 
 
 being carefully covered over with a layer of peat to prevent the es- 
 cape of fertilizing vapors. By this method — ifirst introduced to pub- 
 lic notice by the late J^ord Meadowbank — the entire mixture is gra- 
 dually brought into an equable state of heat and fermentation, and 
 as a manure for the turnip crop, is said to be as efficacious as an 
 equal weight of unmixed farm-yard manure. 
 
 b. Or the liquid manure of the farm-yard may be employed fbrthe 
 same purpose, either in v/liole or in part. If the heap of mixed peat 
 and dung be watered occasionally with the liquid manure, the fer- 
 mentation will be more speedily effected, and at a less expense of 
 common farm-yard dung. Or the half-dried peat may be used un- 
 mixed, as an absorbent for the liquid of the farm-yard, by which, 
 without other aid, it will be brought into a state of fermentation with 
 comparative rapidity. 
 
 c. Or instead of the liquid manure, the ammoniacal liquor of the 
 gas-works may be employed, with less prominent benefit certainly, 
 but still with great advantage. 
 
 d. Or the peat may be mixed with from one-sixth to one-fourth of its 
 bulk of fresh sea-weed, the rapid decay of which will gradually reduce 
 the entire heap into a fertilizing mass (British Husbandry, II., p. 417.) 
 
 e. Or rape-dust in the proportion of 1 ton to 30 cubic yards may 
 be mixed with the half-dried peat from two to six weeks before the 
 time of sowing tlie turnip crop. The fermentation of the rape-dust 
 takes place so quickly, that this short time is usually sufficient to con- 
 vert the whole into a uniform and rapidly decaying mass. 
 
 In short, it is only necessary to mix half-dried peat with any sub- 
 stance which undergoes rapid spontaneous decomposition — when it 
 will more or less speedily become infected with the same tendency to 
 decay, and will thus be rendered capable of ministering to the growth 
 of cultivated plants. 
 
 2°. Tanner^s hark is still more difficult to reduce or to bring into a 
 rapid state of decomposition. Any of the methods above recommended 
 for peat, however, will to a certain extent succeed also with the spent 
 bark of the tan pits. But in the case of substances so solid and refrac- 
 tory as the lumps of bark are, the admixture of a quantity of lime and 
 earth, so as to form a compost heap, is perhaps the most advisable 
 mode of procedure. The way in which lime promotes the decay of 
 woody fibre in such heaps has already been explained (see p. 382.) 
 
 § 13. Use of charred vegetable matters as a manure. 
 
 Soot and charcoal are the principal substances of this class which 
 have been more or less extensively employed for the purpose of in- 
 creasing the productiveness of the land. 
 
 1°. Soot is a complicated and variable mixture of substances pro- 
 duced during the combustion of coal. Its composition, and consequent- 
 ly its effects as a manure, vary with the quality of the coal, with the 
 way in which the coal is burned, and with the height of the chimney 
 in which it is collected. 
 
 Soot has not been analyzed since the year 1826, when a variety ex 
 amined by Braconnot was found by him to consist in a thousand parts ot 
 
438 COMPOSITION OF SOOT — ITS EFFECTS UPON RYE-GRASS. 
 
 Ulmic acid? (a substance resembling that portion of the 
 vegetable matter of the soil which is soluble in caustic 
 
 potash— (see Lee. XIII., § 1) 302-0 
 
 A reddish brown soluble substance, containing nitrogen, and 
 
 yielding ammonia when heated 200-0 
 
 A sboline 5-0 
 
 Carbonate of lime, with a trace of magnesia (probably de- 
 rived in part from the sides of the chimney) 146-6 
 
 Acetate of lime 56-5 
 
 Sulphate of lime (gypsum) 50-0 
 
 Acetate of magnesia 5-3 
 
 Phosphate of lime, with a trace of iron 15-0 
 
 Chloride of potassium 3-6 
 
 Acetate of potash 41-6 
 
 Acetate of ammonia 2-0 
 
 Silica (sand) 9-5 
 
 Charcoal powder 38-5 
 
 Water 125-0 
 
 1000^ 
 
 The earthy substances which the soot contains are chiefly derived 
 from the walls of the chimney, and from the ash of the coal, part of 
 which is carried up the chimney by the draught. These, therefore, 
 must be variable, being largest in quantity where the draught is strong- 
 est and where the earthy matter or ash in the coal is the greatest. The 
 quantity of gypsum present depends upon the sulphur contained in the 
 coal, — that which is freest from sulphur will give a soot containing the 
 least gypsum. The ammonia and the soluble substances containing ni- 
 trogen will vary with the quantity of nitrogen contained in the coal ami 
 with certain other causes — so that the composition of different samples 
 of soot may be very unlike, and their influence upon vegetation there- 
 fore very unequal. The consequence of this must be, that the results 
 obtained in one spot, or upon one crop, are not to be depended upon, as 
 indicativej)f_the precise effect which another specimen of soot will 
 produce in another locality, and upon another crop even of the same 
 kind. And thus it happens that the use of soot is more general, and 
 is attended with more beneficial effects, in some districts than in others. 
 
 a. In general it may be assumed that where ammonia or its salts 
 will benefit the crop, soot also will be of use, and hence its successful 
 application to grass lands. From its containing gypsum it should also 
 especially benefit the clover crops. Yet Dr. Anderson says, " I have 
 used soot as a top-dressing for clover and rye-grass in all proportions, 
 from one hundred bushels per acre to six hundred, and I cannot say 
 that ever I could perceive the clover in the least degree more luxuri- 
 ant than in the places where no soot had been applied. But upon 
 rye-grass its eff*ects are amazing, and increase in proportion to the 
 quantity so, far as my trials have gone." (Dr. Anderson's Essays^ 
 edit. 1800, ii., p. 304.) And his general conclusion is, that soot does 
 not affect the growth, of clover in any loay, ictiile it wonderfully jyromotes 
 
 ' Annoies de Chemie et de Physique, xxxi., p. 37. 
 
ACTION OF SOOT UPON WHEAT AND OATS. 439 
 
 that of rye-grass. Will any of you, by experiment, ascertain if such 
 be really the case with the s»ot of your own neighborhood ? 
 
 h. The presence of ammonia in soot causes it, when laid in heaps, 
 to destroy all the plants upon the spot ; and Dr. Anderson adds the in- 
 teresting observation, " that the first plant which appears afterwards 
 is constantly the common couch-grass (triticum repens). (Dr. Ander- 
 son's Essays, edit. 1800, ii., p. 305.) 
 
 c. This ammonia also causes soot to injure and diminish the crop in 
 very dry seasons. Thus the produce of a crop of beans, after oats, in 
 1842, upon an 
 
 Unmanured part of the field was 29| bushels. 
 
 Dressed with 4 bushels of soot 28 bushels.* 
 
 It also diminished, in a small degree,' the potatoe crop in the same 
 year in the experiments of Lord Blantyre, at Erskine (Appendix, No. 
 IX.) — 
 
 With manure alone, the produce was 11 tons 17 cwt. 
 
 With 30 bushels of soot sprinkled over the dung. 11 tons 4 cwt. 
 
 Like rape-dust (p. 434) and saline substances, therefore, soot seems 
 to require moist weather, or a naturally moist soil, to bring out all its 
 virtues. 
 
 cL Yet even in the dry season of 1842, its effect upon wheat and oats 
 in the same locality (Erskine) was very beneficial. Thus the com- 
 parative produce of tliese crops, when undressed and when top-dress- 
 ed with 10 bushels of soot per acre, was as follows : — 
 
 Unmanured Wheat 44 Oats 49. 
 
 Top-dressed with soot Wheat 54 Oats 55. 
 
 But the dressed wheat was inferior in quafityto the undressed — the 
 former weighing only 58, the latter 62 lbs. a bushel. In the oats there 
 was no difference. Are we to infer from these results that, even in 
 dry seasons, soot may be safely applied to crops of corn, while to pulse 
 and roots it is sure to do no good ? Further precise observations, no 
 doubt, are still necessary — and the more especially as the experiments 
 upon oats and wheat, made in the still drier locality of Lennox Love 
 (Appendix, No. VIII.), gave a decrease in the produce of grain — while 
 in Mr. Fleming's experiments upon turnips (Appendix, No. VIII.), 50 
 bushels of soot, applied alone, gave an increase of 4 tons in the crop. 
 
 e. An experiment of Lord Blantyre's (Appendix, No. IX.), enables 
 us to judge of the efficacy of soot in a dry season, compared with that 
 of nitrate of soda and of guano upon the produce of hay. Thus the 
 crop of hay, per imperial acre, from the 
 
 Cost, 
 tons. cwts. £ s. d. 
 
 Undressed portion, weighed 1 8 
 
 Dressed with 40 bushels of soot 1 15 11 8 
 
 160 lbs. nitrate of soda 1 19 1 15 9 
 
 160 lbs. guano 2 2 1 15 9 
 
 In this experiment the soot proved a more profitable application than 
 either of the other manures. 
 /. In regard to this substance, I shall only advert to one other obser- 
 
 • See Appendix, No. VIII. 
 
440 USE OF CHARCOAL-DUSTj AND OF COAL-TAR. 
 
 vation — but it is an important one — made by Mr. Morton, when des- 
 cribing the management of a well conducted farm in Gloucestershire, 
 (that of Mr. Dimmery, described in the Journal of the Royal Agri- 
 cultural Society^ I., p. 400.) " The quantity of soot used upon this 
 farm amounts to 3000 bushels a-year, one-half of which is applied to the 
 potatoe, the other half to the wheat crop." All the straw grown upon 
 this farm is sold for thatch^ and for the last 30 years the only manure 
 that has been purchased to replace this straw is the soot, which is 
 brought from Gloucester, Bristol,* and Cheltenham. Soot no doubt 
 contains many things useful to vegetation, yet where all the produce is 
 carried off, and soot only added in its stea.d — even the rich soils of the 
 vale of Gloucester cannot be expected to retain a perpetual fertility. 
 The slow changes which theory indicates may altogether escape the 
 observation of the practical man, who makes no record of the history 
 of his land, and yet may be ever slowly proceeding. 
 
 2^. Charcoal. — Wood-charcoal, from its porous nature, and its tend- 
 ency to absorb animal odors and other unpleasant eifluvia (Lee. I.. § 2), 
 has beeu found, when reduced to fine powder, to be an excellent admix- 
 ture for night soil, for liquid manure, and for other substances which 
 undergo putrescent decay. It is therefore employed to a considerable 
 extent by the manufacturers of artificial manures. It is also applied 
 with advantage in some cases as a top-dressing to various cropsj — its 
 efficacy being probably due in part to its power of absorbing from the 
 air, or of retaining in the soil, those gaseous substances which plants re- 
 quire, and in part to the slow decay which it is itself capable of under- 
 going. In moist charcoal powder seeds are said to germinate with 
 great ease and certainty. 
 
 3°. Coal-tar. — Another product of coal, the tar of the gas-works, has 
 recently been recommended as an admixture for peat and similiar com- 
 posts, and it is one of the substances with which Mr. Daniel impreg- 
 nates his saw-dust in the manufacture of his patent manure. It is im- 
 possible to say how much of the good effect derived from the use of 
 such mixtures as that described in the Appendix, No. VIII., is due to 
 the coal-tar they contain, — and as no experiments have hitherto been 
 made from^which the true action of coal-tar can be inferred, it may 
 still be considered as a matter of doubt whether it can at all add direct- 
 ly to the fertility of the soil. 
 
 § 14. Of the theoretical value of different vegetable substances 
 
 as manures. 
 
 Vegetable manures are known to differ in fertilizing virtue. Thus, 
 1 ton of rape-dust is said to be equal to 16 of sea-weed or to 20 of farm- 
 yard manure. On what principles do these unlike fertilizing virtues 
 depend ? 
 
 1°. According to Boussingault and other French authorities, the re- 
 lative efficacy of all manures depends upon the proportions of nitrogen 
 
 ' At Bristol the price of soot is 9d. a bnshel, at Gloucester only 6d., yet the former is pre- 
 ferred even at the higher price. It is of better quality, owing, it is said, to the greater length 
 of the chimnies— it may be also to the quality of the coal and to the way it is burned. 
 
 t See Mr. FieminK's experiment upon Swedes (Appendix No. VIII.), in which 50 bush- 
 els of charcoal powder increased the crop by three tons an acre. 
 
THEORETICAL VALUE OF VEGETABLE MANURES. 441 
 
 they severally contain, {Annales cle Ckemieet de Phys., 3d series, III,, 
 p. 76. ) And taking farm-yard manure — consisting of the mixed drop- 
 pings and litter of cattle — as a standard, they arrange vegetable sub- 
 stances, as manures, in the following order of value : — 
 
 Equal effects are produced by 
 
 Farm-yard manure 1000 lbs. 
 
 Potatoe and turnip (?) tops 750 " 
 
 Carrot tops 470 " 
 
 Natural grass 760 " 
 
 Clover roots 250 " 
 
 Fresh sea-weed 450 to 750 " 
 
 Sea-weed dried in the air 300 " 
 
 Pea straw 220 « 
 
 Wheat straw 750 to 1700 " 
 
 Oat straw , 1400 « 
 
 Barley straw 1750 " 
 
 Rye straw 1000 to 2400 «* 
 
 Buck-wheat straw 850 " 
 
 Wheat chaff 470 " 
 
 Fir saw-duyt 1700 to 2500 « 
 
 Oak do 750 « 
 
 Soot, from coal 300 " 
 
 Lint and rape-dust 80 " 
 
 The numbers in this table agree with the results of experiment in 
 so far as they indicate that green substances generally, when ploughed 
 in as manures, should enrich the soil more tnan an equal weight of 
 farm-yard manure — that the roots of clover should be more enriching 
 still — and that sea-weed is likewise a very valuable manure. They 
 agree also with practical observation in placing pea, and probably 
 bean straw, far above the straws of wheat, oats, &c., in fertilizing 
 power, and in representing soot and rape-dust as more powerful than 
 any of the other substances in the table. So far, therefore, a certain 
 general reliance may be placed upon the fertilizing value of a sub- 
 stance as represented by the proportion of nitrogen it contains. 
 
 But if we bear in mind that plants, as we have frequently had occa- 
 sion to mention, require inorganic as well as organic^oocZ, it is quite 
 clear that the mere presence of nitrogen in a substance is not sufficient 
 to render it highly nutritive to growing plants. Otherwise the salts 
 of ammonia would be the richest manures of all, and would best nourish 
 and bring to perfection every crop and in all circumstances — which ex- 
 perience has proved to be by no means the case. Hence 
 
 2°. The value of vegetable substances as manures must depend in 
 some degree upon the quantity and kind of inorganic matter they 
 contain. In reference to the quantity of inorganic matter which they 
 respectively impart to the soil, their relative values are represented 
 by the following numbers : — 
 
442 
 
 INFLUENCE OF THE CARBONACEOUS MATTER. 
 
 Potato tops, 
 Turnip tops, 
 Carrot tops. 
 Rye-grass, 
 Vetch, 
 
 One ton contains of inorganic 
 matter about 
 
 green 26 lbs. 
 
 do 48 
 
 do 45 
 
 do 30 
 
 do 38 
 
 Green sea-weed, do 22 
 
 Hay 90 to 180 
 
 Pea straw 100 
 
 Bean straw 60 to 80 
 
 Wlieat straw 70 to 360 
 
 Oat straw 100 to 180 
 
 Barley straw 100 to 120 
 
 Rye straw 50 to 70 
 
 Fir saw-dust 6 
 
 Oak saw-dust 5 
 
 Soot 500 
 
 Rape-dust 120 
 
 This table places the several vegetable substances in an order of 
 efficacy considerably different from the former, in which they are 
 arranged according to the quantity of nitrogen they respectively con- 
 tain. We knov: that wood-ashes (p. 353), kelp, and the ashes of straw 
 (p. 356), do promote the fertility of the land, and therefore the abso- 
 lute as well as the relative efficacy of the above vegetable substances 
 must depend in some degree upon the quantity of inorganic matter 
 they contain. But we should be wrong were we to ascribe the total 
 effect of any of them to the inorganic matter alone. 
 
 3°. Even the carbonaceous matter of plants contributes its aid in 
 increasing the produce of the soil, by supplying, either directly or in- 
 directly, a portion of the necessary food of plants. This has already 
 been shown in various parts of the preceding lectures. 
 
 It is the property of substances which contain a larger proportion 
 of nitrogen, to undergo rapid decay in the presence of air and moisture, 
 and thus to produce a more immediate and sensible action upon grow- 
 ing plants. But the carbon changes more slowly, and the inorganic 
 matter also separates slowly from decaying vegetables in the soil — 
 and hence the apparent effects of these constituents are less striking. 
 Thus the immediate and visible effect of different vegetable substances, 
 in the same state, is measured by the relative quantities of nitrogen 
 they contain — their permanent effects by the relative quantities of in- 
 organic and of carbonaceous matters. In the case of rape-dust, for ex- 
 ample, the immediate effect is determined chiefly by its nitrogen — the 
 permanent effects, by the ash it leaves when burned, or when caused 
 to undergo complete decay in the air. 
 
LECTURE XVIIl. 
 
 Animal manures— Flesh, blood, and skin.— Wool, woollen rags, hair, horn, and bones.-On 
 what does the fertilizing action of bones depend 7— Animal charcoal and the refuse ol the 
 sugar refineries.-Fish and fish-refuse, whale blubber and oil.— Relative fertilizing value 
 of the substances previously described.— Pigeon dung.— Dung of sea-fowl : guano.— 
 Liquid manures : the urine of various animals.— Mixed animal and vegetal)le manures.— 
 Ni^ht soil, the droppings of the horse, the cow, the pig.-Effects of digestion upon vege- 
 table food.— Why equal weiiilits of vegetable matter, and the droppings of ^nimals fed 
 upon it, possess different fertilizing powers.-Farm-yard dung.— Weight of dung pro- 
 (iuced from a given weight of grass, straw, and other produce.-Loss undergone bjr 
 farm-yard manure during fermentation.— Improvement of the soil by irrigation. 
 
 Animal substances have always been considered as more fertilizing 
 to the land than such as are of vegetable origin. Their action is in 
 general more immediate and apparent, and it takes place within such a 
 Innited period of time that the farmer can calculate upon its being^ ex- 
 ercised in benefitting the crop to which it is apphed. The reason ot this 
 more immediate action will presently appear. 
 
 § 1. Of Jlesh, blood, and skin. 
 '1°. Flesh.— The flesh of animals is not only a rich manure in itself, 
 but the rapidity with which it undergoes decay in our climate enables 
 it speedily to brincr other organic substances with which it may be mixed 
 into a state of active fermentation. It is only the flesh of sucli dead 
 animals, however, as are unfit for food, that can be economically ap- 
 plied to the land as a manure. , ci. 
 
 The flesh of animals consists of a lean part, called the muscular fibre, 
 or by chemists fibrin, and r fatty part, intermixed with the lean in 
 greater or less proportion, according to the condition of the animaJ. 
 Of these two it is the lean part which acts most immediately and most 
 enercretically in the promotion of vegetation. Lean beet, in the recent 
 stateTcontains 77 per cent, of its weight of water, so that 100 lbs. consists 
 of 77 lbs. of water and 23 lbs. of dry animal matter. 
 
 2^ Blood.— The blood of animals is more extensively employed as 
 a man^ ire. It is carried offin large quantities from the slaughter-houses 
 ofthe butchers, and makes rich and fertUizing composts. ^^^ ^ome 
 parts of Europe it is dried, and in the state of dry powder is applied with 
 much effect as a top-dressing to many crops. ^rnlhn 
 
 Liquid blood consists offibrin-the substance of lean meat, of a Ibu- 
 menlthe same as the white of eggs-of a red colormg matter and of 
 certain saUne substances dissolved in a considerable quanity of water. 
 When blood cools it gradually congeals, and separates into two parts, 
 a gelatinous red portion, called the clot, and a liquid, nearly co orks , 
 part called the sern7n. The clot contains most ot the fibrin and color- 
 Fnc^ matter, and a portion ofthe albumen ; the serum, the greater par 
 ofihe albumen aiid ofthe soluble saline substances which are present 
 
 '"^ The^rdative composition of fresh muscular fibre and of liquid blood 
 is thus represented in 100 parts : — 
 
444 COMPOSITION OF BLOOD, AND OF SKIN. 
 
 , , , „. Water. Dry animal matter 
 
 Muscular fibre 77 23 
 
 Blood 79 21* 
 
 It appears singular that the solid muscle of animals should contain 
 so nearly the same quantity of water as their liquid blood does. 
 
 But it is no less striking that the dry animal matter which remains, 
 when lean muscular fibre and when blood are fully dried, has nearly the 
 same apparent composition. Thus, according to the analyses of Play- 
 fair and Boeckman, dry flesh and dry blood consist respectively of— 
 
 ,, , Dry bee Dry ox blood. 
 
 Carbon 51-83 51-96 
 
 Hydrogen 7-57 7-25 
 
 Nitrogen 15-01 15-07 
 
 Oxygen 21-37 21-30 
 
 Ashes 4-23 4-42 
 
 100 loot 
 
 The organic part, therefore, of blood and of flesh is nearly identical 
 in ultimate composition, and the final result of equal weights of each 
 when applied as manures, should be nearly the same. The ashes, how- 
 ever, or inorganic part, though present in each nearly in the same pro- 
 portion (4-23 and 4-42 per cent.), are somewhat different in composition 
 and therefore the action of blood and flesh will be a little unlike in so 
 far as it depends upon the saline substances they are respectively capa- 
 ble of conveying to the roots of plants. 
 
 3°. Skin.—T\\Q skins of nearly all animals find their way ultimately 
 into the soil as manure, in a more or less changed state. " 
 
 The refuse parings from the tan-yards, and from the curriers' shops 
 though usually employed for the manufacture of glue, are sometimes 
 used as a manure, and with great advantage. They may either be 
 ploughed in sufficiently deep to prevent the escape of volatile matter 
 when they begin to decay, or they may be made into a compost by 
 which their entire virtues will be more effectually retained. 
 
 Skin differs considerably in its constitution from flesh and blood. It 
 contains, inJJie recent state, about 58 per cent, of water, and leaves 
 when burned, only 1 per cent, of ash. The combustible or oro-anic part 
 consists of— '^ -^ 
 
 Carbon 50-99 
 
 Hydrogen 7-07 
 
 Nitrogen 18-72 
 
 Oxygen 23-22 
 
 100 
 It contains, therefore, 3^ per cent, more nitrogen than flesh or blood, 
 bo iar as the fertilizing action of these substances depends upon the 
 proportion of this constituent— glue, the parings of skins, and all gelati- 
 nous substances, will consequently exhibit a greater efficacy than flesh 
 or blood. ^ 
 
 ' Thomson's Animal Chemistry, pp. 285 and 367. 
 
 T Liebig's Organic Oienustry applied to Physiology, p. 314. 
 
USE AND COMPOSITION OF WOOL. HAIR, AND HORN. 445 
 
 § 2. Wool, woollen rags, hair, horn, and bones. 
 
 ' 1°. Wool, in the form of the waste of the Bpinning-mills, and espe- 
 cially in that of woollen rags, acts very efficaciously as a manure. 
 The rags are usied with good effect upon light chalks and gravels, in 
 which they retain the water. They are sometimes ploughed in for 
 wheat along with the clover stubble, in the winter with the corn stub- 
 ble, when the land is intended for turnips, and are sometimes applied 
 as a top dressing to clover and grass lands (British Husbandry, I., p. 
 425.) They are used most extensively, however, in the hop-grounds, 
 being dug in round the roots, to which they continue for a long time to 
 supply much nourishment. The estimation in which they are held may 
 be judged of by the price they bring, which is from £5 to £10 a ton. 
 
 2°. Hair also is fitted to produce effects similar to those which fol- 
 low the use of wool. It can seldom, however, be obtained by the 
 farmer at so economical a rate as to enable him to trust to it as an 
 available resource when other manures become scarce. 
 
 3-. Horn, in the form of horn shavings, parings, and turnings, is just- 
 ly considered as a very powerful manure. Even in the state of shav- 
 ings, however, it undergoes decay still more slowly than woollen rags ; 
 and, therefore, like them, will always be most safely and economically 
 employed when previously rotted, by being made into a compost. 
 
 Wool, hair, and horn, differ from flesh, blood, and skin, by contain- 
 ing very much less water in their natural state, and by undergoing, 
 in consequence, a much slower decay, and exhibiting a much less 
 immediate action upon any crop to which they may be applied. The 
 intelligent farmer, therefore, will bear this important distinction in 
 mind, in any opinion he may form as to the relative efficacy of these 
 several substances as general fertilizers of the land. 
 
 In chemical composition, these three substances are nearly identi- 
 cal, and they do not differ widely from the lean of beef or from dried 
 blood. When burned they leave only a small quantity of ash • — 
 
 Wool leaves 2-0 per cent, of ash. 
 
 Hair 0-72 " " 
 
 Horn 0-7 « " 
 
 And the part which burns away — the organic part — consists of— 
 
 Wool. Hair. Horn. 
 
 Carbon 50-65 51-53 51-99 
 
 Hydrogen 7-03 6-69 6-72 
 
 Nitrogen 17-71 17-94 17-28 
 
 Oxygen and Sulphur .24-61 23-84 24-01 
 
 100 100 100 
 
 The organic part of these three substances, therefore, is nearly 
 identical in composition, and hence, when equally decomposed, they 
 ought to produce the same effects upon the young crops. They con- 
 tain a little more nitrogen than dried flesh and blood, and a httle less 
 than dried skin, and therefore in so far as their fertilizing action de- 
 pends upon this element, they ought to occupy an intermediate place 
 between these several substances. 
 
440 THE INORGANIC MATTER CONTAINED IN BONES. 
 
 § 3. O/" the composition of bones. 
 
 Few substances have of late years done so much to increase the 
 agricultural produce of various parts of England as the use of crushed 
 bones for manuring the land. 
 
 1°. Recent bones contain a variable quantity of water and fat. 
 The proportion of fat depends upon the position of the bone in the 
 body, and upon the condition of the animal. The proportion of water 
 depends partly upon the solidity of the bone and partly upon its age. 
 According to Uenis, the radius of a female, 
 
 Aged 3 years, contained 33-3 per cent, water, with a little fat. 
 
 ■ Aged 20 years, « 13-0 « " 
 
 Aged 78 years, " 15-4 " " 
 
 The quantity of water thus present in bones performs an important 
 part in determining the action which bone-dust is known to exercise 
 upon the land. The oil is sometimes extracted by boiling the bones. 
 During this boiling they absorb more water, and thus, when laid upon 
 the land, undergo a more rapid decomposition, and exercise, in conse- 
 quence, a more immediate and apparent, and therefore, as some may 
 think, a more powerful and fertilizing action. 
 
 2°. But bones differ from the other animal substances already de- 
 scribed chiefly by containing a much larger proportion of inorganic 
 matter, or by leaving, when burned, a greater percentage of ash. 
 The quantity of inorganic matter, however, contained in bones is not 
 constant. It is less in the young than in the full-grown animal — less 
 m the spongy than in the compact or more solid bones — and less in 
 those of some animals than in those of others. Thus, when freed 
 from fat and perfectly dried — 
 
 Of inorganic matter. 
 
 The lower jaw-bone of an adult left 68-0 per cent. 
 
 a child of 3 years. — 62-8 " 
 
 A compact human bone — 58-7 "• 
 
 A spongy human bone — 50-2 " 
 
 ^ The tibfa of a sheep — 48-03 " 
 
 The vertebrae of a haddock — 60-51 " 
 
 It is obvious that the relative efficacy of equal weights of bones 
 must be affected by such differences in the relative productions of 
 organic and inorganic matter which they severally contain. 
 
 3°. This inorganic matter or ash consists in great part of phosphate 
 of lime (Lee. IX., § 4.) but it contains also a considerable though 
 variable proportion of carbonate of lime, with smaller quantities 
 of several other ingredients. The proportion of carbonate of lime 
 appears to be smallest in carnivorous animals. 
 
 Thus, for every 100 parts of phosphate of lime there exists in— 
 
 Human bones about 20-7 carbonate of lime. 
 
 Bones of the sheep 24-1 " 
 
 Do. ox 13-5 " 
 
 Do. fowl 11-7 « 
 
 Do. haddock 6-2 « 
 
 Do. frog 5-8 « 
 
 Do. lion 2-6 " 
 
COMPOSITION OF BURNED BONES. 447 
 
 These proportions are not to be considered as constant, because it 
 varies not only in the different bones of the same animal but also in 
 bones from the same part of the body of different animals of the same 
 species. (Thomson's Animal Chemistry^ p. 242.) But the existence of 
 such differences must render unhke the fertilizing action of the 
 bones of different animals — if, as many think, this action depends in 
 any great degree upon the quantity of phosphate of lime which they 
 respectively contain, 
 
 4°. Besides the phosphate and carbonate of lime, I have stated that 
 bones contain certain other inorganic substances, which are found in 
 small quantity in the ash. What these substances are Avill appear 
 in the following table, which represents the constitution of the bones 
 of some animals, as analysed by Dr. Thompson : 
 
 Ileum Ileum Vertrhra. 
 
 of a shf-ep. of an ox. of a haddock. 
 
 Organic or combustible matter 43-3 48-5 39-5 
 
 Phosphate of hme 50-6 45-2 56-1 
 
 Carbonate of lime 4-5 6-1 3-6 
 
 Magnesia 0-9 0-2 0-8 
 
 Soda 0-3 0-2 0-8 
 
 Potash 0-2 0-1 — 
 
 99-8 100-3 100-8 
 The soda exists in bones probably in the state of common salt, and 
 the magnesia in that of phosphate. An appreciable quantity of fluor- 
 ide of calcium, with traces of iron and magnesia, are also generally 
 found in bones, in addition to the substances indicated in the pre- 
 ceding analyses. 
 
 5^. When bones are heated to redness in the open air the organic 
 part burns away, and leaves the white earthy matter in the form, and 
 nearly of the bulk, of the original bone. But if a dry bone be cover- 
 ed with dilute muriatic acid, the earthy or inorganic part is slowly dis- 
 solved out, and the organic part — the cartilage or gelatine — will alone 
 remain, retaining also the form and size of the organic bone. In this 
 state it is flexible and somewhat soft, and by prolonged boiling may 
 be dissolved in water, and manufactured into glue. 
 
 This organic or combustible part of bones is identical in chemi- 
 cal composition with skin and glue, and is nearly the same as wool, 
 hair, and horn, of which the analysis has already been given. In 
 so far, therefore, as their efficacy depends upon the organic consti- 
 tuent, dry bones must be greatly inferior to an equal weight of any 
 of the other animal substances above described, because of the much 
 greater proportion ofearthy matter they contain. 
 
 § 4. On what does the fertilizing action of bones depend 7 
 
 Bones contain, as we have seen, a large proportion both of organic 
 and of inorganic matter ; — on which of these two constituents does 
 their fertilizing action most depend ? Some regard the phosphate of 
 lime or bone earth, as the only source of the benefits so extensively 
 derived from them — and it is by supposing the soil to be already suf- 
 ficiently impregnated with this phosphate, that Sprengel accounts for 
 
448 EFFECT OF BOILING UPON BONES. 
 
 the little success which has attended the use of bones in Mecklenburg 
 and North Germany. Others, again, attribute the whole of their in- 
 fluence to the organic part — the gelatine — which bones contain. 
 Neither of these views is strictly correct. Plants, as we have seen, 
 require a certain quantity of phosphoric acid, lime^ and magnesia, 
 which are present in the inorganic part of bones, and so far, therefore, 
 are capable of deriving inorganic food from bone-dust. But the or- 
 ganic part of bones will decompose, and therefore will act nearly in 
 the same way as skin, wool, hair, and horn do — which substances it 
 resembles in ultimate composition.* It cannot be doubted, therefore, 
 that a considerable part of the effect of bones upon all crops must be 
 due to the gelatine which they contain. 
 
 The principal facts, now known in regard to the action of bones, 
 may be thus stated : — 
 
 1°. The organic matter of bones acts like that of skin, woollen rags, 
 horn shavings, &c., but as bone-dust contains only about one-third of 
 the organic matter which is present in an equal weight of either of the 
 above substances, its total effect, in so far as it depends upon the or- 
 ganic matter, will be less in an equal proportion. 
 
 2°. Bat as the organic matter of bones contains more water than 
 horn or wool, (p. 446,) it will decay more rapidly than these substan- 
 ces when mixed with the soil, and will therefore be more immediate in 
 its action. Hence the reason why woollen rags and horn shavings must 
 be ploughed in in the preceding winter, if they are to benefit the subse- 
 quent wheat or turnip crops, while bone-dust can be beneficially ap- 
 plied at the sowing of the seed. 
 
 3°. When bones are boiled the oil will be separated, and a portion of 
 the gelatine will at the same time be dissolved out.j The bones, 
 tiierefou, will be in reality rendered less rich as a manure. But as 
 they at the same time take up a considerable quantity of water, boiled 
 hones will decompose more rapidly when mixed with the soil, and 
 thus will appear to act as beneficially as unboiled bones. Hence the 
 reason why in Cheshire, where boiled bones are used to a considerable 
 extent, m^ny practical men are of opinion that their action upon the 
 crops is not inferior to that of bones from which the oil has not been 
 extracted by boiling. The immediate effect may indeed be equal, or 
 even greater, than that of unboiled bones, but the total effect must 
 be less in proportion to the quantity of organic matter wliich has 
 been removed by boiling. Cases, however, may occur in which the 
 
 ' The main difference in, in the quantity of sulphur contained in hair. An analysis of 
 human hair, by Van Laer {Annaleyi der Pharmacie, xiv., p. 168.) which has reached me 
 Rlnre the preceding sheet went to press, shows the proportion of sulphur more accurately 
 than that which is given at page 445. He found human hair of various colors to leave froih 
 one-third to nearly two per cent, of ash when burned, and to consist besides of Carbon, 
 60-65— Hydrogen, 6 36— Nitrogen, 1714— Oxygen, 20-85- Sulphur, 500— Total, 100— and 
 nearly half a per cent, of Phosphorus. 
 
 t The prolonged boiling of bones, so as to dissolve a portion of the gelatine, is practised 
 to a considerable extent as a mode of manufacturing size or glue. In the large dyeing es- 
 tablishments in Manchester, the bones are boiled in open pans for 24 hours, the fat skim- 
 med off and sold to the candle-makers, and the size afterwards boiled down in another 
 vessel till it is of sufficient strength for stiffening the thick goods for which it is intended. 
 The size liquor, when exhausted, or no longer of sufficient strength for stiffening, is applied 
 with much benefit as a manure to the adjacent pasture and artificial grass lands, and the 
 bones are readily bought up by the Lancashire and Cheshire farmers. The boiled bones 
 must evidently lose all the fertilizing virtue which the size liquor acquire.s. 
 
COMPOSITION OF LONG-BURIED BONES. 449 
 
 skilful man will prefer to use boiled bones because they are fitted to 
 produce more immediate effect where — as in the pushing forward of 
 the young turnip plant — such an effect is particularly required. 
 
 4°. When bones are buried in a more or less entire state, as they oc- 
 casionally are about the roots of vines and fruit trees, they gradually 
 decay, and sensibly promote the growth of the trees to which they are 
 applied. Yet after the lapse of years these same bones may be dug up 
 nearly unaltered either in form or in size. The bones of a bear and of a 
 stag, after being long buried, were found by Marchand to consist of — 
 
 Bones of the bear buried 
 
 deep. shallow. Femur of a stag. 
 
 Animal matter 16-2 4-2 7-3 
 
 Phosphate of lime 56-0 62-1 54-1 
 
 Carbonate of lime 13-1 13-3 19-3 
 
 Sulphate of lime 7-1 12-3 12-2 
 
 Phosphate of magnesia 0-3 0-5 2-1 
 
 Fluoride of calcium 2-0 2-1 2-1 
 
 Oxide of iron and manganese. 2-0 24 2-9 
 
 Soda.. M 1-3 — 
 
 Silica 2-2 2-1 — 
 
 100 100 100 
 
 The most striking change undergone by these bones was the large 
 loss of organic or animal matter they had suffered. The relative 
 proportions of the phosphate and carbonate of lime had been com- 
 paratively little altered. The main effect, therefore, produced by 
 bones when buried at the roots of trees, and their first effect in all 
 cases, must be owing to the animal matter they contain — the ele- 
 ments of this animal matter, as it decomposes, being absorbed by the 
 roots with which the bones are in contact. 
 
 Such facts as this prove, I think, the incorrectness of the one-sided 
 opinion too hastily advanced by Sprengel, and after him reiterated 
 by Liebig and his followers — that the principal efficacy of bones is, 
 in all cases, to be ascribed to their earthy ingredients, and especially 
 to the phosphate of lime. 
 
 This opinion of Sprengel rests mainly on two facts put forward by 
 himself (Lehre vom Diinger, p. 153.) Bones, he says, have failed to 
 produce in North- Western Germany the good effects for which they 
 are so noted in England, yet in the same districts, farm -yard and other 
 animal manures exhibit their usual fertilizing action. It cannot, there- 
 fore, he concludes, be the animal matter of bones to which their benefi- 
 cial influence is to be ascribed. But to this conclusion we may fairly 
 demur, when we know how often on heavy and undrained lands bone- 
 dust fails even among ourselves. Let bones be tried for the turnip 
 crop — a crop still almost unknown in Northern Germany — and upon 
 well drained soils similar to those of our best turnip lands, and I ven- 
 ture to predict, in opposition to SprengePs experience, that bones will 
 no longer fail even in Mecklenburg. 
 
 Again, having drawn his conclusion in regard to the inutility of the 
 animal matter, Sprengel states that the marl which is applied to the 
 land in Holstein and the neighboring provinces, contains phosphate 
 
450 CAUSE OF THE PROLONGED EFFECT OF BONES. 
 
 of lime (p. 371,) and hence the reason why the earthy matter of the 
 bones applied does not improve the land. In so far as the efficacy of 
 bones really depends upon their earthy constituents, the use of a marl 
 containing phosphate of lime* will, no doubt, greatly supersede tliem ; 
 — but in so far as it depends upon the animal matter they contain, 
 bones will exhibit their natural fertilizing action, however rich the 
 soil may already be in those compounds of which their earthy or in- 
 combustible part consists. 
 
 5°. Yet there is reason to believe — nay, it maybe assumed as cer- 
 tain — that the phosphate and carbonate of lime which bones contain so 
 largely, are not without effect in promoting vegetation. All our culti- 
 vated plants require and contain both phosphoric acid and lime, (see 
 Lee. X., § 3,) and from the vegetables on which they feed, all animals 
 derive the entire substance of their bones. This same phosphoric 
 acid and lime, therefore, must exist in the soil on which the plants 
 grow, or they will neither thrive themselves nor be able properly to 
 nourish the animals they are destined to feed. If a soil, then, be de- 
 ficient in phosphate of lime or its constituents, it is clear that the ad- 
 dition of bones will benefit the after-crops not only by the animal, but 
 by the earthy matter also which they contain. And that such is the 
 case, in many instances, there is good reason for believing. But that 
 this can by no means account for the whole effect of bones, even sup- 
 posing the soil to which they are applied to be, in every instance, defi- 
 cient in phosphates, is clear from the fact (see Lee. X., § 4.) that 260 
 lbs. — less than 6 bushels — of bone-dust per acre are sufficient to sup- 
 ply all the phosphates contained in the crops which are reaped during 
 an entire fourshift rotation of turnips, barley, clover, and wheat. Yet 
 the quantity of bones actually applied to the land is from three to five 
 times the above weight, repeated every time the turnip crop comes 
 round. 
 
 6*^. Still, granting that the chief effect of bones upon the immedi- 
 ately succeeding crops is due to their organic part, upon what does 
 their pi^oJonged good effect depend ? Some lands remember a single 
 dressing ^f^ones for 16 or 20 years, and some after the application 
 of 2 or 2i tons of bones have yielded 10 to 15 successive crops of 
 oats, and have been sensibly benefitted for as many as sixty years 
 after the bones were applied. (See Appendix, No. I., and British 
 Husbandry, I., p. 398.) 
 
 This prolonged effect is also due in part to both constituents. When 
 not crushed to powder, the organic matter of bones is always slow in 
 disappearing; and slower the deeper they are buried. In some soils, 
 also, the process is more slow than in others. The long-buried bones of 
 the bear and of the stag, of which the analysis is given above (p. 449,) 
 had lain in the soil for an unknown period, and yet they still contained 
 a sensible proportion of animal matter. So it is with the bones used for 
 manure, Avhen they are not crushed too fine. They long retain a por- 
 tion of their organic matter, which they give out more slowly, and 
 
 * Most lime-stones and shell-sands contain an appreciable quantity of this phosphate, and 
 will, therefore, to the same extent, supersede the use of the earihy matter of bones. Much 
 of the marl of Holstein consists of the detritus of chalk rocks, anciently broken up and 
 carried oflf— by the waters of the sea with which that part of Europe was covered at no 
 very remote geological epoch. 
 
FERTILITY OF ANCIENT BATTLE-FIELDS. 451 
 
 in smaller quantity, every year that passes, yet still in such abun- 
 dance as to contribute sensibly to the nourishment, and in some de- 
 gree to promote the growth of the crops which the land is made to 
 bear.* So it would be with the horns and hoofs of cattle,- if laid on in 
 equal quantity, for they also decay with exceeding slowness. 
 
 Still the inorganic part is not without its use. If the soil be defici- 
 ent in phosphates or in lime^ the earthy matter of the bones will sup- 
 ply these substances. 1 only wish to guard you against the conclu- 
 sion, that because bones often act for so long a period, that therefore 
 the organic matter can have no share in the influence they exercise 
 after a limited period of years. 
 
 He who candidly weighs the considerations abov* presented will, I 
 think, conclude that the whole effect of bones cannot in any case be 
 ascribed exclusively either to the one or to the other of their principal 
 constituents. He will believe, indeed, that in the turnip husbandry the 
 organic part performs the most prominent and most immediately useful 
 office, but that the earthy part, nevertheless, affords a ready supply ot 
 certain organic kinds of food, which in many soils the plants would 
 not otherwise easily obtain. He will assign to each constituent its 
 separate and important function, being constrained, at the same time, 
 to confess that while in very many cases the earthy part of hones ap- 
 plied alone would fail to benefit the land, there are few cultivated 
 fields in which the organic part applied alone would not materially 
 promote the growth of most of our artificial crops. 
 
 § 5. Of the application of hone-dust to pasture lands. 
 
 If the soil be deficient in phosphate of lime, bone-earth alone, or the 
 mineral phosphate (Lee. IX., § 4,) maybe advantageously applied to 
 increase its fertility. In a four-years' rotation of turnips, barley, clover, 
 and wheat, if bones be used for the turnip crop, the land will every ro- 
 tation become richer in bone-earth, (see preceding page,) and there- 
 fore the application of earthy phosphates cannot — after a few rota- 
 tions — be expected materially to affect its productiveness. But pas- 
 ture lands are treated differently, and it is not unlikely that in some 
 instances the earth of bones, even applied alone, may to such lands 
 be productive of considerable benefit. 
 
 The application of bone-dust to permanent pasture has of late 
 years been practised with great success in Cheshire. Laid on at the 
 rate of 30 to 35 cwt, or at a cost of £10 per acre, it has increased 
 the value of old pastures from 10s. or 15s. to 30s. or 40s. per acre : 
 and after a lapse of 20 years, though sensibly becoming less valu- 
 able, land has remained still worth two or three times the rent it paid 
 before the bones were laid on. 
 
 It is this lengthened good effect of bone-dust that affords the strongest 
 ground for believing that the earthy phosphate has a large share in the 
 
 * This opinion derives a singularly interesting; confirmation from the fact that a portion 
 of the soil of an arable district in Sweden, "which from time immemorial had grown ex- 
 cellent wheat without manure," was found by Berzelius to contain minute fragments of 
 bone capable upon boiling with water of yielding a weak solution of gelatine. It was 
 concluded, therefore, that the spot had been an ancient battle-field, and that its prolonged 
 fertility was due to the bones of old time buried in it, and still to some extent undecom- 
 poscd (Marchand) 
 
452 PHOSPHATE OF LIME YEARLY CARRIED OFF. 
 
 effect. I have already shown that this prolonged action is not conclu- 
 sive upon the point — since the organic matter lingers long, even in buri- 
 ed bones — but a consideration of the necessary effect of long continu- 
 ed pasturage upon soils to which nothing is artificially added, lends a 
 singular support to the view that the bone-earth may act an important 
 and beneficial part upon old meadow and other grass lands. Take 
 the instance of a dairy farm in the neighborhood of a large town, — 
 
 1°. The milk is all carried off the farm, either directly or in the shape 
 of butter cheese, &c., and every 40 gallons of milk contain 1 lb. of 
 bone-earth, besides other phosphates. Estimate the average yield of a 
 good cow at 3000 quarts, or 750 gallons a-year, its milk will contain 19 
 lbs. of earthy phosphate — as much as is present in 30 lbs. of bone-dust. 
 
 2^. Again, the urine of a inilk cow, taken at 700 gallon.s a-year, 
 contains about 11 lbs. of the same phosphate. (A cow, not in milk, 
 gives on an average about 1300 gallons of urme — see page 460.) 
 Suppose only a third of this to run to waste, and the farm will lose for 
 every cow in this way about 4 lbs. — equal to about 6 lbs. of bone-dust. 
 
 3°. But for every cow an annual calf is reared and sold off. Let this 
 calf contain but 20 lbs. of bone — then for every cow it maintains, a dairy 
 farm, will lose of earthy phosphates npon the whole as mnck as is 
 contained in 56 lbs. of bone-dust. Suppose a farm to be pastured 
 for centuries, as those of Cheshire have been, and the produce to be 
 carried off in the form of milk, butter, and veal — we may reasonably 
 suppose that it will at length begin to feel the want of those phos- 
 phates which year by year have been drawn from its surface. It is 
 reasonable also to suppose that the addition of these deficient phos- 
 phates would impart new vigor to the soil, would cause new grasses 
 to sprout, and a more milk-yielding herbage to spring up. 
 
 Such is the reasoning upon wdiich I some years ago attempted to 
 found an explanation of the singularly striking effects produced by bone- 
 dust on the grass lands of Cheshire, while it failed materially to im- 
 prove those of other districts on which it had been tried. I still consider 
 it as by no means witho at its weight, though I cannot concur Avith the 
 extreme views which some have since adopted — that either in the case 
 of Cheshire, or in any other case with which I am acquainted, the benefi- 
 cial action of bone-dust is to be ascribed solely to its earthy constituents. 
 
 § 6. Of animal charcoal, the refuse of the sugar refineries, and 
 animalized carbon. 
 
 P. Animal charcoal, (bone black.) — AVhen bones are charred or 
 distilled at a red heat in close vessels, they leave behind a coaly re- 
 siduum to Avhich the name of animal charcoal is usually given. By 
 Jthis calcination the animal matter is almost entirely decomposed. 
 The charcoal still retains, however, a little nitrogen, and though it is 
 seldom employed as a manure, yet it is not wholly without effect in 
 promoting the growth of our cultiva^ted crops. Thus in 1842, when 
 applied to Swedish turnips, Mr. Fleming obtained from the unma- 
 nured soil 12 tons 5 cwt. per acre ; but when manured with 10 cwt. 
 of animal charcoal, 21 tons 2 cwt. (see Appendix, No. VIII.) 
 
 2°. Refuse charcoal of the sugar refiners. — The animal charcoal 
 above described is chiefly employed for the purpose of removing the 
 
REFUSE CHARCOAL OF THE SUGAR-REFINERS. 453 
 
 color from solutions of raw sugar. Blood is also used for clarifying 
 the same solutions, and quick-lime for neutralizing the acid matter 
 they contain — thus rendering the syrups more capable of easy crys- 
 tallization. Hence the animal charcoal, the blood, the lime, and the 
 coloring and other matters separated from the sugar, become mixed 
 together, and form the refuse of the sugar refiners. This refuse often 
 contains from one-fifth to one-fourth of its weight of blood, and hence 
 is in general — and especially in France, where it is extensively em- 
 ployed as a manure — considered from four to six times more power- 
 ful than tlie pure animal charcoal alone. In the western parts of 
 France this mixture has for some years been in great repute among 
 agriculturists, and in addition to that which is produced at home, has 
 been largely imported from other countries. Into the ports upon the 
 river Loire alone there were entered, in 1839, upwards of ten thousand 
 tons (Boussingault, A?i. de Chim.et de P/iys., 3d series, iii., p. 96.) 
 It sells at about five pounds a ton. 
 
 The value of this substance depends very much upon the propor- 
 tion of blood which it contains, and as this is in some measure vari- 
 able, its fertilizing qualities must be va,riable also. In England blood 
 is used much more sparingly in the refining of sugar than it used to 
 be, and hence the refuse of our refineries is probably less valuable 
 as a manure now than it was in former years.* This is probably one 
 reason why Mr. Fleming obtained from the use of it a somewhat 
 smaller crop of turnips than from an equal quantity of the unused 
 animal charcoal. Upon Swedish turnips 10 cwt. of unused animal 
 charcoal gave him 21 tons 2 cwt. ; while 10 cwt. of the refuse gave 
 10 tons 7 cwt. (Appendix, No. VIII.) 
 
 Still this result is sufficiently favorable to recommend the refuse or 
 exhausted animal charcoal to the practical agriculturist where more 
 economical manures cannot readily be obtained. 
 
 3\ Animalized carbon. — The estimation in which the refuse char- 
 coal of the sugar works was held, has led to the manufacture of very 
 useful imitations of it under the name of animalized carbon. A cal- 
 careous soil, rich in vegetable matter, (an intimate mixture of peat 
 and marl or shell-sand would answer well,) is charred in close ves- 
 sels, and is then mixed at intervals with repeated portions of night 
 soil as long as it disinfects it or removes its smell — and to this mixture 
 is added 4 or 5 per cent, of clotted and partially dried blood. This 
 animalized carbon is said to be of much value as a manure. The 
 main objections to it are its liability to adulteration and the uncertain- 
 ty to which, even when skilfully and conscientiously prepared, its 
 composition must be in some measure liable. 
 
 § 7. Of fish, fish refuse, whale bhcbber, and oil. 
 
 1°. Pish. — In some parts of the world, and occasionally on the shores 
 of England, fish are met with in such abundance that they can be econo- 
 mically employed as a manure for the land. They are either spread over 
 
 * The refining " consists in puttins; the suzar into a large sqtiare copper cistern along with 
 some lime water, a little bullock's blood, and from 5 to 20 per cent, of bone black, and in- 
 jecting steam through the mixture. Instead of the blood many refiners employ a mixture 
 of gelatinous alumina and gypsum, called finings, prepared by adding lime water to a so- 
 lution of alum, and collecting the precipitate" (Ure.) Hence the reason why, in England 
 at least, tlie refuse charcoal of the sugar works Is not always rich in blood. 
 
454 OP risH, PISH refuse, and oil ; and the relative 
 
 it in a recent state, or — which is more economical, — are made into a com- 
 post chiefly with earth, which after a time proves rich and fertihzing. 
 
 The bones of fish are similar in composition to those of terrestrial 
 animals (p. 447), and their muscular parts are nearly identical in ele- 
 mentary constitution with the lean part of beef and the clot of blood. 
 As fertilizing agents, therefore, the parts of fishes will act nearly in 
 the same way as the blood and bodies of animals. 
 
 2°. Fish refuse. — The pilchards of Cornwall and the herrings, cod, 
 and ling of our northern coasts, when cleaned for salting, yield a 
 large quantity of refuse, (fourteen barrels of herrings yield one of 
 refuse,) which is peculiarly valuable to the farmers in the neighbor- 
 hood of the principal fishing stations. 
 
 In the North, a compost prepared from this fish refuse, is generally 
 esteemed as a manure for barley and green crops, but when exten- 
 sively used, " is said to render the soil unfit for the production of oats." 
 Such soil is said to be poisoned (Sinclair's Statistical Account of 
 Scotland, vii., p. 201, quoted in British Husbandry, I., p. 421.) 
 
 3^. Whale blubber. — When the oil is expressed from whale blub- 
 ber, a skinny or membraneous refuse remains, which has hitherto 
 been employed only as a manure. It is made into a compost with 
 earth, which is several times turned, and the mixture is most usefully 
 employed after it has lain not less than 9 or 12 months. It may be 
 applied either to grass or to arable land. 
 
 4°. Whale oil^ and that of other fish, when made into a compost with 
 earth and a little lime or wood ashes, yields a manure which was much 
 recommended by the late Dr. Hunter of York (see his Georgical Es- 
 says, vols. 1, 2, and 5.) Merely mixed with absorbent earth, and ap- 
 plied at the end of one month, impure whale oil, at the rate of 40 gallons 
 per acre, gave the late Mr. Mason, of Chilton, near Durham, a crop of 
 23i tons of turnips, while 40 bushels of bones gave him only 22 tons. 
 More recently, also, it has been found that the mixture of a few gallons 
 of oil with the usual quantity of bone-dust increased to a considerable 
 degree the turnip crop to which it was applied. In a theoretical point 
 of view, it4vould be interesting to establish the fact, that piire oil is 
 capable of promoting in a large degree the growth and produce of 
 our cultivated crops — though, as a resource, of which farmers in gene- 
 ral can avail themselves where other manure is scarce, its high price 
 will probably prevent it from ever becoming extensively useful. 
 
 § 8. Relative fertilizing value of the animal manures already 
 
 described. 
 
 No sufficiently decisive experiments are yet upon record, from 
 which the relative value of the several animal manures above des- 
 cribed can be satisfactorily deduced. That they differ in fertilizing 
 power every farmer is aware, but it is not yet decided by actual trial, 
 in what proportion one of them exceeds the other. 
 
 I have already stated to you (p. 440) the theoretical opinion enter- 
 tained by many, that the efficacy of all manures is in proportion to the 
 quantity of nitrogen they contain. Adopting this principle as true, it 
 is easy to assign to each substance its proper place in an artificial table. 
 The last column in the following table shows the quantity of each 
 
FERTILIZING VALUE OF VARIOUS ANIMAL MANURES. 455 
 
 substance in its ordinary state of dryness, which will be necessary to 
 produce the same effect as 100 lbs. of common farm-yard manure, 
 supposing this effect to be determined by the nitrogen alone. 
 
 Equal effects 
 Water per cent. Ash per cent. Nitrogen per cent, produced by 
 
 Farm-yard manure.. 80 ? j 100 lbs. 
 
 Flesh 77 1 3^ 14 "' 
 
 Fish 80 2 2^ 20 « 
 
 Blood 79 to 83 1 3 16 " 
 
 Blood dried* 12 to 20 3i 12 to 13 8 « 
 
 Skin 58 i 8 12 " 
 
 Wool,hair, and horn. 9 to 11 1 to 2 16 6 " 
 
 Bones 14 40 to 60 5 to 9 11 to 20 " 
 
 Refuse charcoal of 
 
 the Sugar-works . . 48 ? 1 50 " 
 
 Animalized carbon . . 45 ? 1 50 " 
 
 I have already had occasion to remark, however, that this mode of 
 classifying manures is not altogether to be depended upon. Since — 
 
 1°. It does not take into account the quantity of inorganic matter 
 they severally contain, which as shewn in the third column is parti- 
 cularly large in bones, and is by some considered as the (most?) im- 
 portant and influential constituent of this manure. Nor is any effect 
 ascribed to such substances as the sulphur, which in hair and wool 
 forms nearly 5 per cent, ol' their whole weight, and which cannot be 
 wholly without influence upon the plants, by which, as they decay, 
 the elements of these manures may happen to be absorbed. 
 
 2^. It passes by the practical influence of the quantity of water 
 which the several substances contain. Flesh, fish, blood, and skin, in 
 their recent state, contain so much water that they begin almost im- 
 mediately to decompose, and thus expend most of their fertilizing 
 virtue upon the first crop to which they are applied. Hair and wool, on 
 the other hand, retain so little water that they decay with great slowness. 
 Hence, the true amount of the action of these latter substances cannot 
 be estimated in a single year, and must therefore be altogether a mat- 
 ter of theory until a series of careful observations, made in consecu- 
 tive years, shall afford some decisive facts upon which to reason. 
 
 3°. This is confirmed by the statement of Boussingauit and Payen, 
 {Annates de Chim. et de Phys., 3d series, iii., p. 94,) that the effect 
 of the animal charcoal of the sugar refiners and of the animalized 
 carbon is, by experience, five times greater than the proportion of ni- 
 trogen they« contain would indicate ; and — 
 
 4°. If pure oil, which contains no nitrogen at all, will yet produce 
 an enriching manure by mere mixture with the soil (v- 454), or will 
 increase greatly the effect of bones — we must obviously seek for 
 some other principle upon which to account for the eflfect of manures, 
 besides or in addition to the proportion of nitrogen they contain. It 
 is true that the impure or refuse whale oil used for composts may 
 contain some nitrogen, but we can scarcely suppose 250 or 300 lbs. 
 of such oil to hold so much of this element as to account for all the 
 effects which the oil is said to have produced. 
 
 * As it is sold for manure at Paris and elsewhere, p. 443. 
 
456 OF THE DROPPINGS OF BIRDS. 
 
 While, then, we put so much faith in theory as to believe that suo- 
 stances which contain much nitrogen are very likely to prove valua- 
 ble manures, — we must not allow ourselves to be so carried away by 
 the simplicity of the principle as to believe either that their relative 
 effects upon our crops may be always estimated by the proportion of 
 nitrogen they contain, or that a substance may not largely increase 
 the produce of our fields in which no nitrogen is present at all. In- 
 deed, the effects of saline substances alone are sufficient to satisfy us 
 how untrue to nature this latter opinion would be. 
 
 § 9. Of the droppings of Jowls — pigeons^ dung^ and guano. 
 
 The droppings of birds form one of the most powerful of known ma- 
 nures. This arises in part from the circumstances that in the econo- 
 my of birds there is no final separation between the liquid and solid 
 excretions. Both escape mixed together from the same aperture. 
 
 1°. Pigeons'' dAing is much prized as a manure wherever it can be 
 obtained in any considerable quantity. In Belgium it is esteemed as 
 a top-dressing for the young flax, and the yearly produce of 100 
 pigeons is sold for about 20s. Its immediate effect depends upon the 
 quantity of soluble matter it contains, and this varies much accord- 
 ing to its age and the circumstances under which it has been pre- 
 served. Thus Davy (Davy's Agricultural Chemistry, Lecture VI.,) 
 and Sprengel obtained respectively of 
 
 Recent. Six months' old. After fermentation. 
 
 (Davy.) (Sprengel.) (Davy.) 
 
 Soluble matter in > ^3 ^^^^^ ^g ^^^^^ g ^^^^^ 
 
 pigeons' dung. . ^ ^ ^ ^ 
 
 The soluble matter consists of uric acid in small quantity, of urate, 
 sulphate, and especially of carbonate of ammonia, common salt, and 
 sulphate of potash ; — the insoluble chiefly of phosphate of lime, with 
 a little phosphate of magnesia, and a variable admixture of sand and 
 other earthy matters (Sprengel's Lehre vom Dunger^ p. 140.) When 
 exposed to moisture, the pigeons' dung, especially if recent, undergoes 
 fermentation, loses a portion of its ammoniacal salts, and thus be- 
 comes less valuable. When it is intended to be kept it should be 
 mixed withra dry vegetable soil, or made into a compost with earth 
 and saw dust, with a portion of pulverized or charred peat, or with 
 such a disinfecting charcoal as that which is employed in the manu- 
 facture of the animalized carbon above described. 
 
 2°. Hens'' dung often accumulates, decomposes, and runs to waste 
 in poultry yards, when, with a little care, it might be collected in 
 considerable quantities. 
 
 3°. Goose dung is less rich than that of hens or pigeons, because 
 this bird feeds less upon grain, and derives a considerable portion of 
 its nourishment from the grass which it crops, when allowed to go at 
 liberty over the fields. Its known injurious effects upon the grass 
 upon which it falls arise from its being in too concentrated a state. 
 In moist weather, or where rain soon succeeds, it does no injury, and 
 even when in dry weather it kills the blades on which it drops, it 
 brings up the succeeding shoots with increased luxuriance. 
 
 4°. Rooks'' dung unites with the leaves of the trees among which 
 they live, in enriching the pasture beneath them. In old rookeries the 
 soil is observed also to be slowly elevated above the surrounding land. 
 
COMPOSITION OF GUANO. 
 
 457 
 
 This surface soil I have found to be especially rich in phosphate of lime, 
 which has gradually accumulated and remained in it while the volatile 
 and soluble parts of the droppings of the birds have slowly disappeared. 
 
 5°. Guano is the name given to the accumulated dung chiefly of 
 sea birds, which is found upon the rocky promontories, and on the isl- 
 ands that skirt the coast of South America, from the 13th to the 21st 
 degree of south latitude. In that part of America, the climate being 
 very dry, the droppings of the birds have decomposed with exceeding 
 slowness, and upon some spots have continued to accumulate for many 
 centuries, forming layers, more or less extensive, of 10, 20, and at cer- 
 tain places it is said even 60 (?) feet in thickness. In some places 
 the more ancient of these deposites are covered bv layers of drift 
 sand, which tend further to preserve them from decay. In our moist 
 climate the dung of the sea fowl is readily washed away by the rains, 
 so that even where sea birds most abound no considerable quantity 
 of guano can ever be expected to collect. 
 
 The solid part of the droppings of birds in general, when recent, con- 
 sists chiefly of uric acid, with alittle urate of ammonia, and a variable 
 per-centage of phosphate of lime and other saline compounds. The 
 liquid part, like the urine of other animals, contains much urea, with 
 some phosphates, sulphates, and chlorides. The uric acid and urea, 
 however, gradually undergo decomposition, and are changed into car- 
 bonate and other salts of ammonia. If applied to the land when this 
 stage of decomposition is attained, they form an active, powerful, and 
 immediately operating manure ; but if allowed to remain exposed to 
 the air for a lengthened period of time, the salts of ammonia gradually 
 volatilize, and the efficacy of what remains becomes greatly dimin- 
 ished. Hence, the guano which is imported into this country is very 
 variable in quality, some samples being capable of yielding only 7 
 per cent, of ammonia, while others are said to give as much as 25 
 per cent. Of two portions taken by myself from the same box, the 
 one contained 8 per cent, and the other only 1} per cent, of sand, 
 while their other constituents were as follows : — 
 
 Water, salts of ammonia, 
 and organic matter ex- 
 pelled by a red heat 
 
 Sulphate of soda 
 
 Common salt, with a little 
 phosphate of soda 
 
 Phosphate of lime, with alit- 
 tle phosphate of magnesia 
 and carbonate of lime .... 
 
 percent- 
 
 23-5 
 1-8 
 
 30-3 
 44-4 
 
 100 
 
 -^ • percent. 
 
 Ammonia 7-0 
 
 Uric acid 0-8 
 
 Water and carbonic and ox- 
 alic acids, &c., expelled 
 
 by a red heat 51-5 
 
 Common salt, with a little 
 sulphate and phosphate 
 
 of soda ... 
 
 Phosphate of lime, &c 
 
 11-4 
 
 29-3 
 
 100 
 
 On the other hand. Dr. Ure gives the following as the average re- 
 sult of his analyses of genuine guano : — 
 
 percent. 
 Organic matter containing nitrogen, including urate of ammo- 
 nia, and capable of affording from 8 to 17 per cent, of am- 
 
 ' monia by slow decomposition in the soil 50 
 
 Water 11 
 
458 VALUE OP GUANO AS A MANURE. 
 
 •per cent. 
 
 Phosphate of Ume 25 
 
 Ammonia, phosphate of magnesiaj phosphate of ammonia, & ox- 
 alate of ammonia, containing from 4 to 9 per cent, of ammonia. 13 
 Siliceous matter from the crops of the birds 1 
 
 100* 
 Others have found sand in much larger proportion than was pre- 
 sent in the samples examined by myself — while it may, I think, be 
 taken for granted that very little of Avhat comes to this country is so 
 rich in soluble matter, containing ammonia or its elements, as is re- 
 presented by the analyses of Dr. Ure.t 
 
 Variable as its composition is, however, there is now no doubt that 
 any of the samples yet brought into the English market may be ad- 
 vantageously applied as a manure to almost any crop. From the 
 most remote period guano has been the chief manure applied to the 
 land on the parched shores of Peru — and at the present day it is not 
 only employed for the same purpose in the provinces which lie along 
 the coast, but it is also carried across the desert of Atacama many 
 leagues inland, " on the backs of mules over rough mountain paths, 
 and at a great expense, for the use of the agricultural districts of 
 Peru and Bolivia" (Silliman's Journal, xliv., p. 10.) It has been 
 estimated that a hundred thousand quintals (the quintal is equal to 
 lOU lbs. avoirdupois) are, at the present day, annually sold in Peru. 
 There also the quantity and the price vary — the recent white guano 
 selling usually at 3s. 6d., the more recent red and grey varieties at 
 2s. 3d. per cwt. (Winterfeldt.)J In this country, the latter — the only 
 variety yet imported — sells at present (1843) at about 10s. a cwt. 
 
 In regard to the effects of guano upon various crops, many import- 
 ant experimental results, obtained in 1842, will be found in the Ap- 
 pendix. I here insert a few of the more important of these, along 
 with some others made in the more southern counties, which appear 
 to be highly deservmg of consideration. 
 
 Swedish Turnips. 
 
 Produce per acre. 
 Top-dressed with tons. cwt. Locality. 
 
 P. Farm-yard dung.20 tons. 18 ^U Barochan neir P-iislev 
 Guano 3 cwt. 23 8 \ ^^rocnan, near rai^iey . 
 
 2°. Farm-yard dung.20 tons. 16 18 ^ 
 
 Guano§ 2\ cwt. 17 4 > Parish of Wraxal, Somerset. 
 
 Bones 32 bush. 15 17 ) 
 
 • By way of comparison, 1 insert here the approximate composition of the solid part of 
 the excrements of four different varieties of eagle, as determined by Coindet : — 
 
 American American Grand Duke 
 
 Senepal Eagle. Hunting Eagle. Fishing Eagle. of Virginia. 
 
 Uric acid 89-79 9037 84 65 8871 
 
 Ammonia 785 6-87 9 20 8-55 
 
 Phosphate of hme 2-36 076 6 15 274 
 
 100 100 100 100(a) 
 
 (o) Gmelin TIandbuchder Chemie, II., p. 1456. 
 
 ■f The presence of ammonia in guano is readily ascertained by mixing it with a little 
 slaked lime — when the odour of ammonia will be- immediately perceived, and will be 
 strong in proportion to the quantity contained in the guano. 
 
 t For further particulars regarding guano the reader js referred to a paper ia tiieJouTTiai 
 of the Royal Agricultural Society, II. , p. 301. 
 
 § Mixed with I cwt. of charcoal powder. 
 
ITS ACTION UPON TURNIPS, POTATOES, WHEAT, ETC. 
 
 459 
 
 Top-dressed with 
 
 Guanot 5 
 
 Rape-dust 15 
 
 Bone-dust 30 
 
 Yellow Turnips. 
 
 Produce per acre. 
 
 tons. cwt. Locality. 
 
 cwt. 32 2) 
 
 cwt. 24 11 vBarochan, near Paisley. 
 
 bush. 17 2 S 
 
 Potatoes, 
 
 18 
 
 9-^ 
 
 12 
 
 6 
 
 14 
 
 6 
 
 10 
 
 
 
 1. 9 
 
 15 
 
 13 
 
 14 
 
 13 
 
 
 
 1. 13 
 
 14 
 
 Barochan. In all these cases 
 the manures were put in 
 alone with the potatoe cut- 
 tings, no other manure be- 
 ing afterwards added. 
 
 P. Guano 3 cwt. 
 
 Rape-dust 1 ton. 
 
 2°. Guano 4 cwt. 
 
 Rape-dust 1 ton. 
 
 Bone-dust 45 bush. 
 
 3''. Guano 4 cwt. 
 
 Rape-dust 1 ton. 
 
 Bone-dust 45 bush. 13 
 
 As a top-dressing to the young potatoe crop at Erskine, in 1842, one 
 cwt. of guano per acre produced no important increase. This might, 
 however, be owing to the extreme dryness of the season (Appendix, 
 No. IX.) 
 
 Wheat, 
 
 Produce per acre. 
 Top-dressed with bush, lbs 
 
 1°. Guano 1 cwt. 48 
 
 Rape-dust 16 cwt. 51 
 
 Undressed 47i 
 
 2°. Guano 3 cwt. 30 
 
 Undressed 24 
 
 3°. Guano 2 cwt. 32 
 
 Undressed J 31 
 
 4°. Guano 1 cwt. 46 
 
 Nitrateof Soda. . 1 cwt. 51 
 
 Undressed 44 
 
 5°. Guano H cwt. 45 
 
 Nitrate of Soda., li cwt. 41 
 
 Undressed 39 
 
 Locality. 
 
 ^ Lennox Love, near Had- 
 
 > dington — 
 
 ) drought very great 
 
 r-n i Barochan. 
 55 i 
 
 oV > Gadgirth, near Ayr. 
 
 15) 
 
 18 > Erskine. Renfrewshire.il 
 
 4) 
 
 0) 
 
 > Seisdon, Worcestershire. § 
 
 0) 
 
 . K i Barochan. 
 
 Barley. 
 
 Guano 3 cwt. 64 
 
 Undressed 47 
 
 Oats. 
 
 1<3. Guano 2 cwt. 70 > Lennox 
 
 Undressed 52 
 
 2°. Guano 1 cwt. 48 
 
 Nitrate of Soda.. 1 cwt. 50 
 Undressed 49 
 
 
 
 1.. 
 
 Love, 
 dington. 
 
 near Had- 
 
 } Erskine, Renfrewshire. 
 0) 
 
 t Mixed with 20 bushels of wood-ashes. 
 
 t The undressed grain was of supprior qualify, yielding 76J per cent, of fine flour, while 
 that dressed with guano gave only 68f per cent. 
 
 II The grain dressed with guano weighed half a pound per bushel less than the others, i 
 
 § The guano gave 4 cwt. more straw than the nitrate, and II cwt. more than the undressed. 
 The undressed grain also weighed half a pound less per bushel than either of the other two. 
 20 
 
 f^ 
 
460 SOLID MATTER IN THE URINE OF DIFFERENT ANIMALS. 
 
 Beans. 
 
 Produce per acre. 
 Top-dressed with bush. Locality. 
 
 Guano 2 cwt. 33i "j 
 
 Rape-dust 16 cwt, 35 (Lennox Love, near 
 
 Nitrate of soda. . 1 cwt. 33 [ Haddington. 
 
 Undressed 29| J 
 
 Hay. 
 
 tons. cwt. ' 
 
 1°. Guano li cwt. 1 18 ^ 
 
 Nitrate of Soda. . 1^ cwt, 2 10 > Barochan, near Paisley. 
 
 Undressed 1 8) 
 
 2°. Guano 1^ cwt. 2 2^ 
 
 Nitrate of Soda. . li cwt. 1 17 > Erskine, Renfrewshire. 
 
 Undressed 1 10 ; 
 
 An inspection of the above results appears to indicate that guano 
 is more uniformly successful with root crops, than when applied as a 
 top-dressing to corn and grass. The unusual drought which pre- 
 vailed in 1842 no doubt materially diminished its action, when used 
 as atop-dressing — and the results upon the corn crops in a more moist 
 season may probably prove more generally favorable to its use as an 
 economical manure. 
 
 Some experiments seem already to indicate that the favorable in- 
 fluence of guano does not cease with the first season. If the phos- 
 phate of lime which they contain operates in any way in prolonging 
 the fertilizing operation of bones, the large, though variable, quanti- 
 ty of this phosphate contained in guano should , render this latter 
 substance also capable of permanently improving the soil. 
 
 By exposure to the air, guano gradually gives off a portion of its 
 volatile constituents ; it ought, therefore, to be kept in covered ves- 
 sels or casks. It also in our climate absorbs moisture from the air, 
 and therefore should be purchased as soon as possible after importa- 
 tion. When applied as a top-dressing it may be conveniently mixed 
 with an equal weight of gypsum or wood ashes — with charcoal pow- 
 der, or with-€ne dry soil. 
 
 § 10. Of liquid animal manures — the urine of man, of the coiv, 
 the horse, the sheep, and the pig. 
 
 The following table exhibits the average proportions of water, and 
 of the solid*organic and inorganic matters contained in the urine of 
 man and some other animals in their healthy state — and the average 
 quantity voided by each in a day : — 
 
 Water. Solid matter in 1000 parts. Average quan- 
 
 Urine in , —^ . ^ tity voided ia 
 
 of a 1000 parts. Orffanic. Inorj-'anic. Total. 21 hours. 
 
 Man 969* 23-4 7-6 31 3 lbs. 
 
 Horse ...940 27 33 60 3 " 
 
 Cow 930 50 20 70 40t-" 
 
 Pig 926 56 18 74 ? 
 
 Sheep... 960 28 12 40. ? 
 
 ' Alfred Becquerel. See Thomson's Animal Chemistry^ p. 477. It is to be observed that 
 the proportions of water and of solid matter in urine vary with the food, and with a great 
 variety of circumstances. 
 
 ; t A milk cow voids less than this in a proportion which varies with the quantity of milk 
 
COMPOSITION OF HUMAN URINE. 461 
 
 Of natural liquid manures, the most important and valuable, though 
 the most neglected and the most wasted also, consists of the urine*of 
 man and of the animals he has domesticated. 
 
 The efficacy of urine as a manure depends upon the quantity of 
 solid matter which it holds in solution, upon the nature of this solid 
 matter, and especially upon the rapid changes which the organic 
 part of it is known to undergo. 
 
 The numbers in the above table show that the urine of the cow, 
 estimated by the quantity of solid matter it contains, is more valu- 
 able than that of any other of our domestic animals, with the excep- 
 tion of the pig. But the quantity voided by the cow must be so 
 much greater than by the pig, that in annual value the urine of one 
 cow must greatly exceed that of many pigs. 
 
 It might be supposed at first that in all animals the quantity of 
 urine voided would have a close connection with the quantity of water 
 which each was in the habit of drinking. But this is by no means the 
 case. Thas it is the result of experiment that in man the drink ex- 
 ceeds the urine voided by about one-tenth part only — while 
 
 Of wafer in 24 hour?. Of urine in 24 hours. 
 
 A horse, which drank 35 lbs. gave only 3 lbs. 
 A cow, which drank 132 lbs. gave 18 lbs., and 
 
 19 lbs. of milk (Boussingault). 
 How very large a quantity of the liquid they drink must escape 
 from the horse and the cow in the form of insensible perspiration ! 
 That this should be very much greater indeed than in man, we are 
 prepared to expect from the greater extent of surface which the bo- 
 dies of these animals present. 
 
 Let us now examine more closely the composition of urine, the 
 changes which by decomposition it readily undergoes, and the effect 
 of these changes upon its value as a manure. 
 
 1°. Human 2irine — The exact composition of the urine of a healthy 
 individual in its usual state was found by Berzelius to be as follows ; 
 
 Water 933-0 
 
 Urea 30-1 
 
 Uric acid 1-0 
 
 Free lactic acid, lactate of 
 ammonia , and animal 
 
 matter not separable... 17-1 
 
 Mucus of the bladder 0-3 
 
 Sulphate of potash 3-7 
 
 Sulphate of soda 3-2 
 
 Phosphate of soda 2-9 
 
 Phosphate of ammonia. ... 1-6 
 
 Common salt 4-5 
 
 Sal-ammoniac 1-5 
 
 Phosphates of lime and mag- 
 nesia, with a trace of silica 
 
 and of fluoride of calcium, 1 • 1 
 
 1000 
 
 From what I have already had occasion to state in regard to the ac- 
 tion upon living plants of the several sulphates, phosphates, and other 
 saline compounds, mentioned in the above analysis, you will see that 
 the fertilizing action of urine would be considerable, did it contain no 
 other solid constituents. But it is to the urea which exists in it in very 
 much larger quantity than any other substance, that its immediate 
 and marked action in promoting vegetation is chiefly to be ascribed. 
 This urea, which is a white salt-like substance, consists of^ — 
 
 she gives. Boussingault found a milk cow to yield daily 18 lbs. of urine and 19 lbs. of 
 milk,— ilnn. de Chim. et de Phys., Ixxi., pp. 123, 124. 
 
462 URINE OP THE COW — ITS VALUE. 
 
 Carbon 20-0 per cent. 
 
 Hydrogen 6-6 " 
 
 Nitrogen 46-7 per cent. 
 
 Oxygen 26-7 " 
 
 100 
 
 It is, therefore, far richer in nitrogen than flesh, blood, or any of 
 those other richly fertilizing substances, of which the main efficacy is 
 supposed to depend upon the large proportion of nitrogen they contain. 
 
 But urea possesses this further remarkable property, that when 
 urine begins to ferment, — as it is known to do in a few days after it is 
 voided — it changes entirely into carbonate of ammonia.* Of the am- 
 monia thus formed a portion soon begins to escape into the air, and 
 hence the strong ammoniacal odour of fermenting urine. This escape 
 of ammonia continues for a long period, the liquid becoming weaker 
 and weaker, and consequently less valuable as a manure every day 
 that passes. Experience has shown that recent urine exercises in gen- 
 eral an unfavorable action upon growing plants, and that it acts 
 most beneficially after fermentation has freely begun, but the longer 
 time we suffer to elapse after it has reached the ripe state, the great- 
 er the quantity of valuable manure we permit to go to waste. 
 
 2°. The urine of the cow hOiS been analysed in several states by 
 Sprengel, with the following results in 1000 parts : — 
 
 Allowed to ferment for four weeks 
 Fresh. 
 
 Water. 926-2 
 
 Urea 40-0 
 
 Mucus 2-0 
 
 Hippuric and lactic acids. .. 6-1 
 
 Carbonic acid 2-1 
 
 Ammonia 2-1 
 
 Potash 6-6 
 
 Soda 5-5 
 
 Sulphuric acid 4-0 
 
 Phosphoric acid 0-7 
 
 Chlorine 2-7 
 
 Lime ..__, 06 
 
 Magnesia 0*4 
 
 Alumina, oxide of iron, and 
 
 oxide of manganese 0-1 
 
 Silica -. . 0-4 
 
 in the open 
 
 air. 
 
 A. 
 
 B. 
 
 954-4 
 
 934-8 
 
 10-0 
 
 6-0 
 
 0-4 
 
 0-3 
 
 7-5 
 
 6-2 
 
 1-7 
 
 15-3 
 
 4-9 
 
 16-2 
 
 •6-6 
 
 6-6 
 
 5-5 
 
 5-6 
 
 3-9 
 
 3-3 
 
 0-3 
 
 1-5 
 
 2-7 
 
 2-7 
 
 trace 
 
 trace 
 
 0-3 
 
 0-4 
 
 trace 
 
 
 
 0.1 
 
 0-1 
 
 1000 998-2 999'Ot 
 
 The first variety of fermented urine (A.), had stood four weeks in 
 the air in its natural state of dilution ; the second (B.), had been mix- 
 ed while recent with an equal bulk of water — which is again deducted 
 
 * This takes place by the decomposilion at the same time of two atoms of the water in 
 which it is dissolved. Thus urea is represented by Ca Il4 N2 O2 ; two of water by 2H O : 
 and carbonate of ammonia by N H3 + C O2 ; and the change is thus shown— 
 
 2 of 2of " 
 
 Urea. Water. Carbonate of Ammonia. 
 
 C2 H4 N2 O2 + 2 H O = 2 (N H3 + C O2) 
 tThe small quantity necessary to make up the 1000 parts in the two latter analyses con- 
 sisted of a deposit of carbonate and phosphate of lime and other earthy matters which 
 had gradually been formed, and of a trace of vinegar and of sulphuretted hydrogen.— Sea 
 Sprengel, Lehre votn Biinger, pp. 107 to 110. 
 
URINE OF THE HORSE, SHEEP, AND PIG. 463 
 
 from it in the analysis — with the view of ascertaining how far such 
 an admixture would tend to retain the volatile ammonia produced by 
 the natural decomposition of the urea. 
 
 An inspection of these tables shows three facts of importance to 
 ihe agriculturist — 
 
 1°. That the quantity of urea in the urine of the cow is considerably 
 greater than in that of man ; 2^. That as the urine ferments, the quan- 
 tity of urea diminishes, while that of ammonia increases — owing, as I 
 have aheady stated, to the gradual decomposition of the urea and its 
 conversion into carbonate of ammonia; and 3°. That by dilution with 
 an equal bulk of water the loss of this carbonate of ammonia, which 
 would otherwise naturally take place, is in a considerable degree pre- 
 vented. The quantity of ammonia retained by the urine^ after dilu- 
 tion^ was in the same circumstances nearly three times as great as when 
 it was allowed to ferment in the state in lohich it came from, the cow. 
 
 But even by this dilution the whole of the ammonia is not saved. 
 One hundred parts of urea form by their decomposition 56i parts of 
 ammonia, and as 36 parts of the urea in the urine B. had disappear- 
 ed, there ought to liave been in its stead 19 parts of ammonia in ad- 
 dition to that which the urine contained in its recent state, or 21 parts 
 in all — whereas the table shows it to have contained only 16 parts. 
 Even when diluted with its own bulk of water, therefore, the urine 
 had lost by fermentation in the open air upwards of one-fourth of 
 the ammonia produced in it during that period. This shows the ne- 
 cessity of causing our liquid manures to ferment in covered cisterns, 
 or of adopting some other means by which the above serious loss of 
 the most valuable constituents may be prevented. 
 
 3^. The urine of the horse, sheep, and jng, have not been so care- 
 fully analysed as that of the cow. They consist essentially of the 
 same constituents, and the specimens which have been examined 
 were found to contain the three most important of these in the follow- 
 ing proportions : 
 
 Horse. Sheep. Pig. 
 
 Water 940 960 926 
 
 Urea 7? 28 56 
 
 Saline substances . . 53 12 18 
 
 1000 1000 1000 
 
 Some of the saline substances present in the urine, as above stated, 
 contain nitrogen. This is especially the case in the urine of the horse, 
 so that the quantity of urea above given is not to be considered as re- 
 presenting the true ammonia-producingpower of the urine of this ani- 
 mal. The urine of the pig, if the above analysis is to be rehed upon as 
 any thing like an average result, is capable of producing more ammonia 
 from the same quantity than that of any other of our domestic animals. 
 
 § 11. Of the waste of liquid manure — of urate, and ofsulphated urine. 
 1°. Waste of human urine. — The quantity of solid matter contain- 
 ed in the recent urine voided in a year by a man, a horse, and a cow, 
 and the weight of ammonia they are respectively capable of yielding, 
 may be represented as follows : 
 
464 CRATE, AND SULPHATED URINE. 
 
 Quantity of urine. Solid matter. Containing: of urea. And yielding of ammonia. 
 
 Man 1000 lbs. 67 lbs. 30 lbs. 17 lbs. 
 
 Horse 1000 " 60 " ? ? 
 
 Cow 13000 « 900 " 400 " 230* " 
 
 How much of all this enriching matter is permitted to run to waste ? 
 The solid substances contained in urine, if all added to the land, would 
 be more fertilizing than guano, which now sells at £10 a ton. If we 
 estimate the urine of each individual on an average at only 600 lbs., 
 then there are carried into the common sewers of a city of 15,000 in- 
 habitants, a yearly weight of 600,000 pounds, or 270 tons, of manure, 
 which, at the present price of guano, is worth £2700, — which would no 
 doubt prove more fertilizing than its own weight of guano, and might be 
 expected to raise an increased produce of not less than 1000 qrs. of grain. 
 
 The saving of all this manure would be a great national benefit, 
 though it is not easy to see by what means it could be effectually ac- 
 complished. What is thus carried off by the sewers and conveyed 
 ultimately to the sea, is drawn from and lost by the land, which must, 
 therefore, to a certain extent be impoverished. Can we believe that 
 in the forpi of fish, of sea tangle, or of spray, the sea ever delivers 
 back a tithe of the enriching matter it daily receives from the land ? 
 
 2°. Urate. — In order to prevent a portion of this waste, the practice 
 has been introduced into some large cities of collecting the urine, add- 
 ing to it one-seventh of its weight of powdered gypsum, pjlowing 
 the whole to stand for some days, pouring off the liquid and drying 
 the powder. Under the name of urate this dry powder has been high- 
 ly extolled, but it can contain only a small portion of what is really 
 valuable in urine. The liquid portion poured off must contain most 
 of the soluble ammoniacal and other salts, and even were the whole 
 evaporated to dryness, the gypsum does not act so rapidly in fixing 
 the ammonia as to prevent a considerable escape of this compound 
 as the fermentation of the urine proceeds. 
 
 3°. Sulphated urine A method of more apparent promise is that 
 
 now practised by the Messrs. Turnbull of Glasgow, of adding diluted 
 sulphuric acid to the urine as the ammonia is formed in it, and subse- 
 quently evaporating the whole to dryness. From the use of this sub- 
 stance very favorable results may be anticipated.! Still none of these 
 preparations will ever equal the urine itself, part of the efficacy of 
 which depends upon the perfect state of solution in which all the sub- 
 stances it contains exist, and upon the readiness with which in this 
 state they make their way into the roots of plants, 
 
 4°. Loss ofcow'^s iirine. — When left to ferment for five or six weeks 
 
 'The numbers {riven above, and in p. 460, are calculated from the analysis of the urine 
 of the horse by Fourcruy and Vauquelin, ami of that of the cow by Sprerigel. Boussingault, 
 however, obtained very different results. Thus a cow and a horse, on which his experi- 
 ments were ma(!e, yielded a quantity of urine which in a year would have amounted tc, 
 and would have contained, 171 pounds — 
 
 Containins of Capable of yield- 
 
 Quantity. Solid matter (total). Inorganic matter. Nitrogen, ing of ammonia. 
 Cow 6570 773 309 29 35 
 
 Horse 1100 243 B9 30 36 
 
 The cow yielded at the same time 19 lbs. of milk each day, which accounts for the 
 smaller proportion of urine voided, than is given in the text. It is remarjcable, however, 
 that the quantity of nitrogen contained in an equal weight of the urine of the horse was in 
 this case so much greater than that of the cow— and in that the whole amount which would 
 have been yielded by that of a cow in a year should be so very much less than in the re« 
 
LOSS OF LiaUID MANURE IN THE FARM-YARD, 465 
 
 alonej and with the addition of an equal bulk of water, the urine of 
 the cow loses, as we have seen, a considerable proportion of volatile 
 matter, and in these several states will yield in a year — 
 
 Solid matter. Yielding of ammonia. 
 
 Recent urine 900 lbs. 226 lbs. 
 
 Mixed with water, after 6 weeks. . 850 " 200 " 
 
 Unmixed, after 6 weeks 550 " 30 " 
 
 Those who scrupulously collect in tanks and preserve the liquid ma- 
 nure of their stables, cow-houses, and fold-yards, will see, from the 
 great loss which it undergoes by natural fermentation, the propriety 
 of occasionally washing out their cow-houses with water, and, by thus 
 dilating the liquid of their tanks, of preserving the immediately 
 operating constituents of their liquid manure from escaping into the 
 air. Even when thus diluted it is desirable to convey it on to the 
 land without much loss of time, since even in this state there is a con- 
 stant slow escape, by which its value is daily diminished. Gypsum, 
 sulphate of iron, and sulphuric acid, are, by some, added for the pur- 
 pose o^ Jixing the ammonia, but in addition to diluting it, an admix- 
 ture of rich vegetable soil, and especially of peat, will be much more 
 economical, and — except in so far as the gypsum or sulphuric acid 
 themselves act as manures — nearly as effectual. 
 
 But these remarks apply only to the liquid manure when collected. 
 How much larger a waste is incurred by those who make no effort to 
 collect the urine of their cow-houses or stables ! The recent urine of 
 one cow is valued in Flanders — where liquid manures are highly es- 
 teemed — at 40s. a year. It contains on an average, as we have seen, 
 900 lbs. of solid matter, and this estimated at the price of guano only, 
 is worth at present £4 sterling. Multiply this by 8 millions, the num- 
 ber of cattle said to exist in the United Kingdom, and we have 32 mil- 
 lions of pounds sterling, as the value of the urine, supposing it to be 
 worth no more than the foreign g^ano. It is impossible to estimate 
 how much of this runs to waste, but 1-lOth of it will amount to nearly 
 as much as the whole income-tax recently laid upon the country. The 
 practical farmer who uses every effort to collect and preserve the ma- 
 nure which nature puts within his reach, is deserving of praise when 
 he expends his money in the purchase of manures brought from a dis- 
 tance, of whatever kind they may be ; but he, on the other hand, is 
 only open to censure who puts forward the purchase of foreign ma- 
 nures as an excuse for the neglect of those which are running to 
 waste around him. Let every stock farmer, with the help of the 
 facts above stated, make a feir calculation of what is lost to himself 
 and to the country by the hitherto unheeded waste of the urine of 
 his cattle, and he will be able clearly to appreciate the importance of 
 taking some steps for preserving it in future. 
 
 suit obtaineil by Sprengel. The milk did not contain nitrogen sufficient to yield more than 
 45 lbs. of ammonia, and this, added to the 35 lbs. makes only 80 lbs. in all — whereas 
 Sprenuel givps 230 lbs. as the qiiantity which recent urine is capable of yielding. This re- 
 markable difference must be ascribed either to an actual loss of volatile matter by the urine 
 analysed by BoussinJault, or— which is more probable — to a difference in the quality of the 
 food on which the two animals were fed. 
 
 "The Messr.o. TurnbuU inform me that with this sulphated urine, tmder the incorrect 
 name of sulphate of ammonia, the experiments of Mr. Burnet were made (p. 362), as well 
 as those of Mr. Fleming and Mr. Alexander, detailed in the Appendix. 
 
466 NIGHT SOIL READILY DECOMPOSES — ITS COMPOSITION. 
 
 § 12. Of solid animal manures — night soil, the dung of tJie covj, the 
 horse, the sheep, and the pig. 
 
 1°. Night soil is in general an exceedingly rich and valuable ma- 
 nure, but°its disagreeable odour has in most countries rendered its 
 use unpopular among practical men. This unpleasant smell may be 
 in a great measure removed by mixing it with powdered charcoal or 
 with half-charred peat, — a method which is adopted in the manufac- 
 ture of certain artificial manures. Q,uick-lime is in some places em- 
 ployed for the same purpose, but though the smell is thus got rid of, 
 a large portion of the volatile ammonia produced during the decom- 
 position of the manure is at the same time driven off by the hme. 
 
 In general, night soil contains about three-fourths of its weight of 
 water, and when exposed to the air undergoes a very rapid decompo- 
 sition, gives off much volatile matter — consisting of ammonia, of car- 
 bonic acid, and of sulphuretted and phosphuretted hydrogen gases — 
 and finally loses its smell. In the neighborhood of many large cities, the 
 collected night soil is allowed thus naturally to ferment and lose its smell, 
 and is then dried and sold for manure, under the name of poudrette. 
 
 But by this fermentation a very large proportion of valuable matter 
 is permitted to escape into the air. To retain this, gypsum or dilute 
 sulphuric acid may be added to the night soil, but the more economi- 
 cal and generally practicable method is to mix it with earth rich in ve- 
 getable matter, with partially dried peat, with saw-dust, or with some 
 other readily accessible absorbent substance. In this way a rich and 
 fertilizing compost will be obtained, which will have little smell, and 
 yet will retain most of the virtues of the original manure. 
 
 In China the fresh night soil is mixed up with clay and formed into 
 cakes, which when dried are sold under the name of Taffo, and form 
 an extensive article of commerce in the neighborhood of the larger cities. 
 
 The composition of night soil, and consequently its value as a ma- 
 nure, varies with the food, and with many other circumstances (p. 470). 
 The excrements of a healthy man were found by Berzelius to consist of: 
 
 Mucilage, fat, and other ani- 
 mal matters 167 
 
 Undecomposed food 70 
 
 looo 
 
 Of the excrement when freed from water 1000 parts left 132 of ash, viz. 
 
 Water ^733 
 
 Albumen ^_^_^ 9 
 
 Bile 9 
 
 Saline matter 12 
 
 Carbonate of soda 
 
 Sulphate of soda, with a little 
 sulphate of potash, and phos- 
 phate of soda S 
 
 Phosphate of lime and magne- 
 sia, and a trace of gypsum . . 100 
 Silica 16 
 
 132 
 
 2°. Cow dung forms by far the largest proportion of the animal ma- 
 nure which in modern agriculture is at the disposal of the practical 
 farmer. It ferments more slowly than night soil, or than the dung of 
 the horse and the sheep. In fermenting it does not heat much, and it 
 gives off little of an unpleasant or ammoniacal odour. Hence it acts 
 more slowly, though for a longer period, when applied to the soil. 
 
 The slowness of the fermentation arises chiefly from the smaller 
 quantity of nitrogen, or of substances containing nitrogen, which are 
 present in cow dung, but in part also from the food swallowed by the 
 cow being less perfectly masticated than that of man or of the horse. It 
 
L 
 
 HORSE DUNG SPEEDILY FERMENTS, AND LOSES WEIGHT. 467 
 
 is a consequence of this^ slower fermentation, that the same evolution 
 ofammoniacal vapours is not perceived from the droppings of the cow- 
 as from night soil and from horse dung. Yet by exposure to the air, it 
 undergoes a sensible loss, which in 40 days has been found to amount 
 to 5 per cent, or nearly one-fifth of the whole solid matter which re- 
 cent cow dung contains.* (Gazzeri.) Although, therefore, the compa- 
 ratively slow fermentation as well as the softness of cow dung fits it 
 better for treading among the straw in the open farm-yard, yet the 
 serious loss which it ultimately undergoes will satisfy the economical' 
 farmer that the more effectually he can keep it covered up, or the 
 sooner he can gather his mixed dung and straw into heaps, the great- 
 er proportion of this valuable manure will he retain for the future en- 
 riching of his fields. 
 
 3°. Horse dung is of a warmer nature than that of the cow. It 
 heats sooner, and evolves much ammonia, not merely because it con- 
 tains less water than cow dung, but because it is generally also rich- 
 er in those organic compounds of which nitrogen forms a constituent 
 part. Even when fed upon the same food the dung of the horse will 
 be richer than that of the cow, because of the greater proportion of 
 the food of the latter which is discharged in the large quantity of urine 
 it is in the habit of voiding (p. 470). 
 
 In the short period of 24 hours, horse dung heats and begins to suf- 
 fer loss by fermentation. If let\ in a heap for two or three weeks, scarce- 
 ly seven-tenths of its original weight will remain. Hence the propriety 
 of early removing it from the stable, and of mixing it as soon as possi- 
 ble with some other material by which the volatile substances given 
 off may be absorbed and arrested. The colder and wetter cow or pig's 
 dung will answer v/ell for this purpose, or soil rich in vegetable matter, 
 or peat or saw-dust, or powdered charcoal, or any other absorbent sub- 
 stance which can readily be obtained — or if a chemical agent be pre- 
 ferred, moistened gypsum maybe sprinkled among it, or diluted sulphu- 
 ric acid. There is undoubtedly great loss experienced from the general 
 neglect of night soil, but in most cases the dung of the horse might also 
 be rendered a source of much greater profit than it has hitherto been. 
 
 The warmth of horse dung fits it admirably for bringing other sub- 
 stances into fermentation. With peat or saw-dust it will form a rich 
 compost, and to soils which contain much inert vegetable matter it can 
 be applied with great advantage. Horse and cow dung, in the dry 
 state, have been subjected to ultimate analysis by Boussingaultf, 
 (Ann. de Chim., Ixv., pp. 122, 134,) with the following results: — 
 
 Dung of the Horse. Dung of a Milk Co\y. 
 
 Carbon 38-7 42-8 
 
 Hydrogen 5-1 5-2 
 
 Oxygen 37*7 37-7 
 
 Nitrogen 2-2 2-3 
 
 Ashes 16-3 12-0 
 
 loo" 100 
 
 Watert 300 5 66 
 
 ^00" 666~ 
 
 • Cow dung consisting of 75 of water and 25 of dry solid matter, of which latter 3 disappear, 
 t Recent horse dung losing 75 per cent, of water bj' drying, of cow dung 75 per cent. 
 
 20* 
 
468 THE DUNG OF THE PIG AND THE SHEEP. 
 
 The proportion of nitrogen contained in the two njanures, according 
 to these results, is so nearly alike — being in reahty greater in the cow 
 dung— that were we to consider the above numbers to represent the 
 average constitution of the droppings of the horse and cow, we should 
 be compelled to ascribe the difference in their qualities solely to the 
 different states in which the elements exist in the two, and to the pro- 
 portions of water they respectively contain. But the nature of the 
 food and other circumstances affect the quality of these manures so 
 much (p. 470), that we cannot as yet draw any general conclusion 
 from the results obtained in one special case. 
 
 4°. Pig'^s dung is still colder and less fermentable than that of the 
 cow. It is characterized by an exceedingly unpleasant odour, which 
 when applied to the land alone it imparts to the crops, and especially 
 to the root crops which are manured with it. Even tobacco, when 
 manured with pig's dung, is said to be so much tainted that the leaves 
 subsequently collected are unfit for smoking [Sprengel, Lehre vom 
 Dunger, p. 38.] It is a good manure for hemp and other crops not 
 intended for food, but is best employed in a state of mixture with the 
 other manures of" the farm-yard. 
 
 5°. Sheep's dung is a rich dry manure, which ferments more readi- 
 ly than that of the cow, but less so than that of the horse. A speci- 
 men examined by Zierl consisted of — 
 
 Water 68*0 per cent. 
 
 Animal and vegetable matter 19-3 " 
 
 Saline matter, or ash 12-7 " 
 
 100 
 
 The food of the sheep is more finely masticated than that of the cow, 
 and its dung contains a little less water, and is probably richer in nitro- 
 gen ; hence its more rapid fermentation. When -crops are eaten off 
 by sheep, their manure is more evenly spread over the field, and is, at 
 the same time, trodden in. When thus spread it decomposes more 
 slowly than when it is collected into heaps, and the ammonia and other 
 useful prodjicts of the decomposition are absorbed in great part by the 
 soil as they are produced. Those soils in which a considerable quan- 
 tity of vegetable matter is already present, are said to be most bene- 
 fitted by sheep's dung, because of the readiness with which they ab- 
 sorb the volatile matters it so soon begins to give off. 
 
 Sheep's dung is said to lengthen the straw of the corn crops, and 
 to produce a grain rich in gluten — and unfit therefore for seed, for the 
 manufacture of starch, or for the purposes of the brewer and the dis- 
 tiller (Sprengel.) It may be doubted, however, whether these can as 
 yet be safely considered as the universal effects of sheep's dung upon 
 every soil, and when the animals are fed upon every kind of food. 
 
 § 13. Of the quantity of manure produced from the same kinds of 
 food by the horse, the cow, and the sheep. 
 
 The carefully conducted experiments of Block give the following 
 as the total quantities of manure, solid and liquid, produced from 100 
 lbs. of the different kinds of food by the cow, the horse, and the sheep. 
 
MANURE PRODUCED BY DIFFERENT ANIMALS. 469 
 
 Quantity of manure in lbs., produced by 
 
 , . , Water in 
 
 From 100 lb3. of the cow. the horse. the sheep, the manure, 
 
 fresh, dried, fresh, dried, fresh, dried. per cent. 
 
 Rye — — 212 53 — — 75 
 
 Oats — — 204 51 — — 75 
 
 Rye and other straws(chopped)2fi8 43 168 42 117 40 66 to 84 
 
 Hay 275 44 172 43 123 42 do. do. 
 
 Potatoes (containing 72 pci- ct. 
 
 of water) 87^ 1 4 — — 38 13 do. do. 
 
 Turnips (containing 75 percent. 
 
 of water) 37^ 6 — — — — 84 
 
 Carrots (87 per cent, of water) 37j 6 — — — — 84 
 
 Green Clover (79 per ct. watei') 65 j 9;^ — — — — 86 
 
 After 8 days. After 3 weeks. After 8 weeks. 
 
 Rye Straw (used for bedding) 238 96 269 97 206 95 54 to 64 
 
 One important theoretical result is presented in this table — that 
 the manure voided by an animal contains very much less solid matter 
 than the food it has coivsumed. We shall presently see how this fact 
 is to be explained (p. 472), and, at the same time, what light it throws 
 upon the quality of the manure produced. 
 The most valuable practical results from the above experiments are — 
 
 1°. That for 100 lbs. of dry fodder the horse or cow will give on 
 an average 216 lbs. of fresh or 46 lbs. of dry manure — the sheep 128 
 lbs. moist or 43 lbs. dry. 
 
 2°. That root crops, on an average, give about half their weight 
 of fresh or one-twelfth of dry manure — the potatoe giving more and 
 the turnip less. 
 
 3^. That green crops give about half their weight of fresh or one- 
 eighth of dry manure. 
 § 14. Of the relative fertilizing values ofdiferent animal excretions. 
 
 1°. The theoretical value of different animal excretions calculated 
 solely from the quantity of nitrogen which the specimens examined 
 were found respectively to contain, is thus given by Payen and Bous- 
 singault. The numbers opposite to each substance indicate the weights 
 of that substance which ought to produce an equal effect with 100 lbs. 
 of farm-yard manure in the recent and in the dry states : — 
 
 Equal effects ought to be produced by 
 in the dry state. artificially^ dried. 
 
 Farm -yard dung 100 lbs 
 
 Cow.._ 125 " 
 
 Do. urine 91 
 
 Horse ^ ^^ 
 
 Mixed excrements of the — Pig 63 
 
 Horse 54 
 
 Sheep 36 
 
 Pigeon. ...... 5 
 
 Poudrette...-. . 10^ 
 
 Another variety 26 
 Too much reliance is not in any case to be placed upon the princi- 
 ple of classifying manures solely by the proportion of nitrogen they 
 contain (pp.441 & 454)— much less can we depend upon the order of 
 value it assigns to substances - the composition of which is liable to 
 
 bs. 
 
 100 lbs. 
 
 a 
 
 84 " 
 
 (( 
 
 51 " 
 
 (C 
 
 88 « 
 
 u 
 
 58 " 
 
 u 
 
 64 " 
 
 a 
 
 65 « 
 
 a 
 
 22 " 
 
 a 
 
 44 « 
 
 a 
 
 73 " 
 
470 FERTILIZING VALUES OF ANIMAL EXCRETIONS. 
 
 constant change from the escape of those volatile compounds in which 
 the nitrogen principally exists. 
 
 2°. A series of experiments made by Hermbstadt upon tlie quantity 
 of grain of different kinds, raised in the same circumstances by equal 
 weights of different manures, gave thejbllowing results : 
 
 Number of seeds reaped from 
 Manure applied. Wheat. Barley. Oats. Rye. 
 
 Ox blood 14 16 121 14 
 
 Nightsoil — 13 141 l3i 
 
 Sheep's dung 12 16 14 13 ' 
 
 Human urine — 131 13 13 
 
 Horse dung 10 13 14 11 
 
 Pigeon dung — 10 12 9 
 
 Cow dung 7 11 16 9 
 
 Vegetable matter 3 7 13 6 
 
 Unmanured — 4 5 4 
 
 If the results contained in this table were to be depended upon, it 
 would appear that, in so far as the quantity of the produce is concern- 
 ed, these manures severally exercise a special action upon certain 
 crops — that night-soil, for example, is most propitious to rye, cow 
 dung to oats, and sheep's dung to barley and wheat. And the latter 
 fact would seem at once to justify and to recommend the eating off 
 with sheep preparatory to either of the latter crops. 
 
 None of these kinds of m.anure. however, is constant in composition, 
 and the following observations will satisfy you that implicit reliance 
 ought not to be placed either upon the relative practical values of the 
 different animal manures as they appear in the latter table, nor on 
 their theoretical values as exhibited in the former. 
 
 § 15. Influence of circumstances on the quality of aniw.al manures. 
 
 The quality of the droppings of animals considered as manures is 
 affected by a great variety of circumstances — such as 
 
 1°. By the kind of food upon which the animal is fed. — Thus night 
 soil is more valuable in those countries and districts in v^^hic;! much 
 flesh meatls^consumed, than where vegetable food forms the principal 
 diet of the people. It is even said by Sprengel, that in the neighborhood 
 of Hildesheim the farmers give a higher price for the house manure 
 of the Lutheran than for that of the Roman Catholic families, because 
 of the numerous fasts which the latter are required to observe. (Lehre 
 vom Danger, p. 142.) Every keeper of stock also knows that tiie ma- 
 nure in his farm-yard is richer when he is feeding his cattle upon oil- 
 cake, than when he gives them only the ordinary produce of his farm. — 
 [12 loads of the dung of animals fed (while fattening) chiefly upon oil- 
 cake was found to give a greater produce than 24 loads from store stock 
 fed in the straw yard. — Cowplete Grazier. 6th edit, p. 103.] 
 
 2°. By the quantity of urine voided by the animal. — Upon the unlike 
 quantities of urine they produce appears mainly to depend the unlilce 
 richness of the dung of the horse and of the cow. The latter animal, 
 when full grown and not in milk, voids nearly 13 times as much urine 
 as the former (p. 460), and though an equal bulk of this urine is poorer 
 in soUd matter, yet the whole quantity contains several times as much 
 
ANIMAL MANURES AFFECTED BY MANY CIRCUMSTANCES. 471 
 
 as is present, in that of the horse. But if the cow discharges more in 
 its urine it must void less in its sohd excretions. Hence, supposing the 
 food of a full-grown horse and of a cow to be very nearly the same, 
 the dung of the former — the less urine-giving animal — must be the 
 richer, the warmer, and the more valuable— as it is really known to be. 
 
 3°. By the amount of exercise or labor tovjJiich the animal is sub- 
 jected. — The greater the fatigue to which an animal is subjected the 
 richer the urine is found to be in those compounds (tirea chiefly) which 
 yield ammonia by their decomposition (Front). The food of two 
 animals, therefore, being the same — other things also being equal — 
 the solid excretions willbe richer and more fertilizing in that which 
 is kept in the stall or fold-yard, the urine in that which is worked in 
 the open air or pastured in the field. 
 
 4°. By the state of growth to which the animal has arrived. — A 
 full-grown animal has only to keep up its weight and condition by the 
 foodlt eats. Every thing which is not necessary for this purpose, 
 therefore, it rejects cither in its sohd or in its liquid excretions. A young 
 animal, on the other hand, adds to and increases its bone and muscle 
 at the expense of its food. It rejects, therefore, a smaller proportion 
 of what it eats. Hence the manure in fold-yards, where young cattle 
 are kept, is always less rich than where full-grown animals are fed. 
 
 5°. By the purpose for which the animal is fed. — Is it to be im- 
 proved in condition ? Then the food must supply it with the mate- 
 rials for increasing the size and strength of its muscles— with albu- 
 men, or fibrin, or other substances containing nitrogen. In such sub- 
 stances, therefore, or in nitrogen derived from them, the droppings 
 must be poorer, and as a manure, less valuable. 
 
 Is the animal to be fattened ? Then its food must supply fatty mat- 
 ters, or their elements, of which nitrogen forms no part. All the ni- 
 trogen of the food, therefore, will pass off in the excretions, and hence 
 the'richest manure yielded at any time by the same species of ani- 
 mal is that which is obtained when it is full-grown, and, being large- 
 ly fed, is rapidly fattening. 
 
 Is the cow kept for its milk? Then the milk it yields is a daily 
 drain upon the food it eats. Whatever passes into the udder is lost 
 to the dung, and hence, other things being equal, the dung of a milk 
 cow will be less valuable to the farmer than that of a full-grown ani- 
 mal from which no milk is expected, or than that of the same animal 
 when it is only laying-on fat, 
 
 6°. By the length of time during which the manure has been kept. — 
 In 24 hours, as we have seen, the dung of the horse begins to fer- 
 ment and to lessen in weight. AU rich manures in like manner— the 
 dung of all animals especially — decompose more or less rapidly and 
 part'^with their volatile constituents. The value we assign to them, 
 to-day, therefore, will not apply to them to-morrow, and hence the 
 droppings of the same animal at the same age, and fed in the same 
 way, will be more or less valuable to the farmer according to the 
 length of time during which they have been permitted to ferment. 
 
 7°. Lastly. By the way in which the manure has been preserved. — 
 The mixed dung of the farm-yard must necessarily be less valuable 
 where the liquid manure is allowed to run oif— or where it is permitted 
 
472 CHANGES PRODUCED UPON THE FOOD 
 
 to stand in pools and ferment. Twenty cart-loads of such dung may 
 hasten the growth of the turnip crop in a less degree than half the 
 weight will do, where the liquid manure has been carefully collected 
 and returned upon the heaps — to hasten and complete their fermenta- 
 tion, and to saturate them with enriching matter. 
 
 Since, then, the quality or richness of the dung of the same animal is 
 liable to be affected by so many circumstances — it is obvious that no 
 accurate general conclusions can be drawn in regard to its precise 
 fertilizing virtue when applied to this or to that crop, or to its relative 
 fertilizing value when compared with equal weights of the dung of 
 other animals. The results obtained in one set of analyses, as in that 
 of Boussingault, or in one series of practical experiments, as in that 
 of Hermbstadt (p. 470), will not agree with those obtained in any 
 other — because the substances themselves with which our differeni 
 experiments are made, though called by the same name, are yet very 
 unlike in their chemical properties and composition. 
 
 § 16. Of the c flanges which the food undergoes in 'passing through 
 the bodies of animals. 
 
 it is the result of long experience that vegetable matter is more 
 sensibly active as a manure, after it has passed through the body of an 
 animal, than if applied to the land in its unmasticated and undigested 
 state. In becoming animalized, therefore — as it has been called — 
 vegetable substances have been supposed to undergo some mysteri- 
 ous, because not very obvious or intelligible, internal change, by which 
 this new virtue is imparted to them. Yet the change is very simple, 
 and when explained is not more satisfactory than it is beautiful. 
 
 You will recollect, as I have already stated to you (p. 469), that 
 the weight of dry manure voided by an animal is always considerably 
 less than that of the dry food eaten by it. Upon the nature and 
 amount of this loss which the food undergoes depends the quality of 
 the manure obtained. 
 
 This you^will readily comprehend from the following statement : 
 
 1°. Every thing which enters into the body in the form of food must 
 escape from the body in one or other of three different forms. It must 
 be breathed out from the lungs, perspired by the skin, or rejected in the 
 solid or liquid excretions. We have already seen (Lee. VIII., §3), 
 that the function of the lungs is to give off carbon in the form of car- 
 bonic acid, while they drink in oxygen from the air — and that the quan- 
 tity of carbon thus given off by a healthy man varies from 5 to 13 or 
 more ounces in the 24 hours. From the skin also carbon escapes along 
 with a small and variable proportion of saline matter. The weight 
 of carbon given off by the skin has not been accurately ascertained. 
 Let us leave it out of view for a moment, and consider solely the ef- 
 fect of respiration upon the nature of the solid and liquid excretions. 
 
 Suppose a healthy mari, taking a moderate degree of exercise, to 
 give off from his lungs 6 ounces of carbon in 24 hours, and to eat 
 during the same time 2 lbs. of potatoes, half a pound of beef, and 
 half a pound of bread. Then he has taken in his food — 
 
BY PASSING THROUGH THE BODIES OF ANIMALS. 473 
 
 Carbon. Nitrogen. Saline matter. 
 
 In the potatoes 1716 grs. 47 grs. 196 grs. 
 
 In the bread 1004 " 34 " 22 " 
 
 Inthebeef. 790 " 120 " 35" 
 
 3510 grs. 201 grs. "253 grs. 
 
 And he has given off in respiration 2625 " 
 
 Leaving to be rejected sooner or 
 
 later in the excretions 885 " 201 " 253 " 
 
 In this supposed case, therefore, the carbon, nitrogen, and saline 
 
 matter were to each other nearly as the numbers 
 
 Carbon. Nitrogen. Saline matter. 
 
 35 2 2h in the food, 
 
 and as 9 2 2^ in the excretions : 
 
 Orj in oiher words, the carbon being in great part sifted out of the 
 food by the lungs, the excretions are necessarily much richer in ni- 
 trogen and in saline matter, weight for weighty than the mixed vege- 
 table and animal matters on which the man has lived. 
 
 But the immediate and most sensible action of animal and vegetable 
 substances, as manures, depends upon the proportion of nitrogen and sa- 
 line matters they contain. This proportion, then, being greater in the ex- 
 cretions than in the crude vegetables, the cause of the higher estimation 
 in which the former are held by the practical farmer is sufficiently clear. 
 
 2°. In the above case I have supposed the allowance of food to be 
 such only as a person of sedentary habits would consume, and the 
 quantity of carbon given off from the lungs to be such as his habits 
 would occasion. But if the weight of carbon given off from the lungs 
 and skin together amount, as it often does, to 15 ounces,* the quantity 
 of food must be greatly increased beyond the quantity I have stated, 
 if the health and strength are to be sustained. By such an increase 
 of food — the carbon being removed by respiration — the proportion of 
 nitrogen and of saline matters in the excretions may be still further 
 increased, or as manvires they may become still richer and more im- 
 tnediately fertilizing. 
 
 3°. Let me present to you the results of an actual experiment made 
 by Boussingault upon a horse fed with hay and oats — and of which 
 both the food and the excretions were carefully analysed. 
 
 In 24 hours the horse consumed — 
 
 Carbon. Nitrogen. Saline matter. 
 
 Hay, 16i lbs..t containing 45,500 grs. 1,500 grs. 8,960 grs. 
 
 Oats, 5 "lbs..' 15,000 " 650 " i;i80 " 
 
 Total in the food "60,500" « ~2,150 " To^lio"" " 
 
 And gave off from the lungs & skin 37,960 " 
 
 Leaving to be rejected in the ex- 
 cretions 22,540 " 2,150 " 10,140 " 
 
 While there was actually found in 
 the mixed dung 22,540 " 1,770 " 10,540 " 
 
 * Liebig estimates tlie qnantily of carbon which escapes from the lungs and skin of a 
 healthy man, taking moderate exercise, at 1393 ounces (Hessian), or I5]i ounces avoirdu- 
 pois, in 24 hours. 
 
 t Each containing about 14 per -cent, of water. — Annates de Chim. ei de Phys., lxxi..p. 136. 
 
474 STATE IN WHICH FARM-YARD MANURE CAN BE 
 
 In this case, then, the carbon, nitrogen, and saline matter were con- 
 tained in the proportion of — 
 
 Carbon. Nitrogen. Saline matter. 
 
 28 1 5 in the food, 
 
 and of 10^ 1 5 in the dung ; 
 
 The analysis of the dung itself proving that in passing through the 
 body of an animal, the ibod — 
 
 a diminishes very considerably in weight ; 
 
 b losing a large but variable proportion of its carbon, 
 
 c but parting with scarcely any of its nitrogen and saline matter — 
 and therefore 
 
 d that the fertilizing virtues of the dung above that of the food of 
 animals — weight for weight — depends mainly upon the larger pro- 
 portion of these two constituents (the nitrogen and the saline matter) 
 which the dung contains. 
 
 I have only further to remind you upon this subject, that the state 
 of combination also in which the nitrogen exists in the excretions has 
 a material influence in rendering their action more immediate and 
 sensible than that of unchanged vegetable matter. It passes off for 
 tlie most part in the form of urea, which is resolved into ammonia and 
 its compounds more rapidly than the albumen of the dried or even of 
 the recent plant, and is thus enabled sooner to exert an appreciable 
 influence upon the growing crop. 
 
 § 17. Of farm-yard manure^ and of the state in which it ought 
 to be applied to the land. 
 
 The manure of the farm-yard consists, for the most part, of cow- 
 dung and straw mixed and trodden together, in order that the latter 
 may be brought into a state of decomposition. In the improved hus- 
 bandry, where green crops are extensively grown and many cattle 
 are kept, the horse-dung forms only a small proportion of the whole 
 manure of the farm-yard. 
 
 On an average, the quantity of recent manure obtained in the farm- 
 yard amounts to a little more than twice the weight of the dry food of 
 the cattle and of the straw spread in the farm-yard or in the stables 
 (p. 469). That is to say, for every 10 cwt. of dry fodder and bedding, 
 20 to 23 cwt. of fresh dung may be calculated upon. But if green 
 clover or turnips (every 100 lbs. of which contain from 70 to 90 lbs. 
 of water) be given to the cattle, an allowance must be made for the 
 water they contain — the quantity of mixed manure to be expected 
 being from 2 to 2l times the weight of the drij food and fodder only. 
 
 But the recent manure loses weight by lying in the farm-yard. The 
 moisture evaporates and volatile matters escape by fermentation. By 
 the time that the straw is half rotten this loss amounts to one fourth of 
 the whole weight, while the bulk is diminished one-half If allowed to 
 lie still longer the loss increases, till at length it may approach to one- 
 half of the whole, leaving a weight of dung little greater than that of 
 the food and straw which have been consumed. The weight of com- 
 mon mixed farm-yard dung, therefore, obtained from 10 cwt. of dry food 
 and straw, at different periods, may be thus stated approximately — 
 
MOST ECONOMICALLY APPLIED TO THE LAND. 475 
 
 10 cwt. of dry food, and straw yield of recent dung 23 to 25 cwt. 
 
 At the end of six weeks 21 cwt. 
 
 After eight weeks 20 cwt. 
 
 When half-rotten 15 to 17 cwt. 
 
 When fully-rotten .-. .10 to 13 cwt. * 
 
 These quantities, you will observe, are supposed to be obtained in 
 the common open farm-yards, with the ordinary slow process of fer- 
 mentation. An improved, quicker, or more economical mode of fer- 
 menting the mixed dung and straw may be attended with less loss 
 and may give a larger return of rich and fully-rotten dung. 
 
 A knowledge of these facts shows clearly what is the most eco- 
 nomical form in which farm-yard manure can be applied to the land. 
 
 P. The more recent the manure from a given quantity of food and 
 straw is ploughed in, the greater the quantity of organic matter we 
 add to the land. When the only object to be regarded, therefore, 
 is the general enriching of the soil, this is the most economical and 
 the most expedient form of employing farm-yard manure. 
 
 2°. But where the soil is already very light and open, the plough- 
 ing in of recent manure may make it still more so, and may thus ma- 
 terially injure its mechanical condition. In such a case the least of 
 two evils must be chosen. It may be better husbandry — that is, more 
 economical — to allow the manure to ferment and consolidate in the 
 farm-yard with the certainty of a considerable loss, than to diminish 
 the sohdity of the land by ploughing it in in a recent state. 
 
 3°. Again — in the soil, a fermentation and decay similar to that 
 which takes place in the farm-yard will slowly ensue. The benefit 
 which generally follows from causing this fermentation to take place in 
 the field rather than in the open yard is, that the products of the decom- 
 position are taken up by the soil, and thus waste is in a great measure • 
 prevented. But in very fight and open soils, tliis absorption of the pro- 
 ducts of decay does not take place so completely. The rains wash out 
 some portions, while others escape into the air, and thus by burying the 
 recent manure in such soils, less of that waste is prevented which when 
 left in the open air it is sure to undergo. It may even happen, in some 
 cases, that the waste in such a soil will not be greatly inferior to that 
 which necessarily takes place in the farm-yard. The practical man, 
 therefore, may question whether, as a general rule, it would not be safer 
 in farming very light arable lands, to keep his manure in heaps till it is 
 well fermented, and to adopt those means for preventing waste in the 
 heaps themselves which science and practical skill point out to him. 
 
 It may be regarded indeed as a prudent and general opinion to hold 
 — one, however, which must not be maintained in regard to any par- 
 ticular tract of land in opposition to the results of enlightened expe- 
 rience — that recent farm-yard manure {long dung) is not suited to 
 very light soils, because it will render them still fighter, and because 
 m them the manure may suffer almost as much waste as in the farm- 
 
 * In an excellent little practical work printed for private circulation, under the title of 
 "Notes on the Culture and Cropping of Arable Land," by the late Dr. Coventry, of Edin- 
 burgh, the reader will find a valuable section upon manures. The most complete work 
 now in existence upon the general subject of agricultural statics, is that of Hlubek, DieEr- 
 n'dhrung der PJianzcn une die Statik des Landbaues. 
 
476 AFFECTED BY THE PURPOSE IT IS TO SERVE. 
 
 yard ; — and, therefore, that into such soils it should be ploughed in 
 the compact state (short dung-)^ and as short a time as possible be- 
 fore the f?owing of the crop which it is intended to benefit. 
 
 4°. But upon loamy and clay soils the contrary practice is recom- 
 mended. Such soils will not be injured, they may even be benefitted 
 by the opening tendency of the unfermented straw, while at the same 
 time the products of its decomposition will be more completely re- 
 tained — the land consequently more enriched, and the future crops 
 more improved by it. On such soils, the recent dung ploughed in, in 
 the autumn, has been found greatly more influential upon the crops 
 of corn which followed it, either in winter or in spring, than a propor- 
 tional quantity of well fermented manure. By such treatment, in- 
 deed, the whole surface soil is converted into a layer of compost, in 
 which a slow fermentation proceeds, and which reaches its most fer- 
 tilizing condition when the early spring causes the young corn to seek 
 for larger supplies of food. 
 
 5^. But the nature of the crop he is about to raise will also influ- 
 ence the skilful farmer in his application of long or short dung to his 
 land. If the crop is one which quickly springs up, runs through a 
 shoit life, and attains an early maturity, he'will apply his manure in 
 such an advanced state of fermentation as may enable it immediately 
 to benefit the rapidly growing plant. In this case, also, it may be 
 better to lose a portion by fermenting it in the farm-yapd, than, by ap- 
 plying his manure fresh, to allow his crop to reach nearly to maturity 
 before any benefit begins to be derived from it. 
 
 6°. So also the purpose for which he applies his manure will regu- 
 late his procedure. In manuring his turnips the farmer has two dis- 
 tinct objects in view. He wishes, first, to force the young plants for- 
 Vv^ard so rapidly that they may get into the second leaf soon enough 
 to preserve them from the ravages of the fly — and afterwards to fur- 
 nish them with such supplies of food as shall keep them growing till 
 they have attained the most profitable size. For the former purpose 
 fermented manure appears to be almost indispensable — if that of the 
 farm-yard is employed at all — for the latter, manure, in the act of slow 
 and prolonged decomposition, is the most suitable and expedient. 
 
 It is because bone-dust is admirably adapted for both purposes, that 
 it has become so favourite a manure in many districts for the turnip 
 crop. The gelatine of the outer portion of the bones soon heats, fer- 
 ments, and gives off" those substances by which the young plant is 
 benefitted — while the gelatine in the interior of the bone decays, lit- 
 tle by little, and during the entire season continues to feed the ma- 
 turing bulb. Rape-dufet, when drilled in, acts in a similar manner, if 
 the soil be sufficiently moist. It may be doubted, however, whether 
 its effects are so permanent as those of bones. 
 
 The considerations I have now presented will satisfy you that the 
 disputes which have prevailed in regard to the use of long and short 
 dung have arisen from not keeping sufficiently distinct the two ques- 
 tions — what is theoretically the best form in which farm-yard dung 
 can be applied in general 7 — and what is theoretically and practical- 
 ly the best form in which it can be applied to this or to that crop^ or 
 for this or for that special object 7 
 
TOP-DRESSING WITH FERMENTING MANURES. 477 
 
 § 18. Of top-dressing with fermenting manures. 
 
 ■ If so large a waste occur in the farm-yard where the manure is 
 left long to ferment — can it be good husbandry to spread fermenting 
 manure as a permanent top-dressing over the surface of the fields 1 
 This, also, is a question in regard to which different opinions are 
 entertained by practical men. 
 
 That a considerable waste must attend this mode of application there 
 can be no doubt. Volatile matters will escape into the air and. saline 
 substances may be washed away by the rains, and yet there are many 
 good practical farmers who consider this mode of applying such manure 
 to be in certain cases as profitable as any that can be adopted. Thus — 
 
 1^. It is common in spring to apply such a top-dressing to old pas- 
 ture or meadow lands, and the increased produce of food in the form of 
 grass or hay is beheved to be equal, at least, to what would have been 
 obtained from the same quantity of manure employed in the raising 
 of turnips. Where such is really the case, experience decides the 
 question, and pronounces that notwithstanding the loss which must 
 occur, this mode of applying the manure is consistent with good 
 husbandry. But if the qi'iantity or market value of the food raised by 
 a ton of manure applied in this way is not equal to what it would 
 have raised in turnips and corn, then it may as safely be said that 
 the most economical method of employing it has not been adopted. 
 
 But theory also throws some mteresting light upon this question. 
 
 Old grass lands can only be manured by top-dressings. And if 
 they cannot continue, and especially such as are mead owed, to yield 
 an average produce, unless there be now and then added to the soil 
 some of those sa7ne substances which are carried off in the crop, it 
 appears to be almost necessary that farm-yard dung should now and 
 then be applied in some form or other. It is true that hay or straw 
 or h7ig dims- contains all the elements which the growing grass re- 
 quires, but if spread on the surface of the field and then allowed to 
 ferment and decay, the loss would probably be still greater than when, 
 for this purpose, ii is collected into heaps or strewed in the farm-yard. 
 Thus the usual practice of laying on the manure in a highly fer- 
 mented state may be the most economical. 
 
 2°. Again, where the turnip crop is raised in whole or in part by 
 means of bones only, of rape dust, or of other artificial manures, as they 
 are called; it is usual to expend a large proportion of the farm-yard dung 
 in top-dressing the succeeding crop of clover. Thus the land obtains 
 two manurings in the course of the four years' rotation — bones or rape- 
 dust Avith the turnips — and fermented dung with the clover. This 
 second appliceition increases the clover crop in some districts one-fourth 
 and the after-crop of wheat or barley very considerably also. [Such 
 is the case upon some of the farms in the Vale of the Tame (Stafford- 
 shire,) where the turnips are raised with rape-dust, and wheat follows 
 the clover.] 
 
 Here, also, it is clear, that if manure be necessary to the clover, it 
 can only be applied in the form of a top-dressing. But why is it ne- 
 cessary, as experience says, and why should farm-yard manure, which 
 is known to suffer waste, be applied as a top-dressing rather than 
 
478 EATING OFF COMPARED WITH GREEN MANURING. 
 
 rape-dust, which in ordinary seasons is not so likely to suffer loss ? 
 1 offer you the following explanation : — 
 
 If you raise your turnip crop by the aid of the bones or rape-dust alone 
 you add to the soil what, in most cases, may be sufficient to supply near- 
 ly all the wants of that crop, but you do 7iot add all whick the succeed- 
 ing crops of corn and clover require. Hence if these crops are to be 
 grown continuously, and for a length of time, some other kind of ma- 
 nure must be added — in which those necessary substances or kinds 
 of food are present which the bones and rape-dust cannot supply. 
 Farm-yard manure contains them all. This is within the reach of 
 every farmer. It is, in fact, his natural resource in every such diffi- 
 culty. He has tried it upon his clover crop in the circumstances we 
 are considering, and has necessarily found it to answer. 
 
 Thus to explain the results at which he has arrived in this special 
 case, chemical theory only refers the practical man to the general prin- 
 ciple upon which all scientific manuring depends — that he must add to 
 the soil sufficient supplies of every thing he carries off in his crops — and, 
 therefore, without some such dressing as he actually applies to his 
 clover crop, he could not long continue to grow good crops of any kind 
 upon his land, if he raise his turnips with bones or rape-dust only. 
 
 It might, I think, be worthy of trial, whether thfe use of the fer- 
 mented dung for the turnips, and of the rape-dust for top-dressing the 
 after-crops, would not, in the entire rotation, yield a larger and more 
 remunerating return. 
 
 § 19. Of eating off witti sheep. 
 
 The practical advantages derived from eating off turnips and clover 
 crops with sheep are mainly of two kinds. Light lands are trodden 
 down and solidified, and they are at the same time equably and more 
 or less richly manured. With this latter effect, that of manuring, 
 some interesting practical facts and theoretical considerations are 
 connected. Thus — 
 
 1°. In the preceding lecture (p. 419) I mentioned to you that in some 
 parts of Germany, spurry, among other plants, is extensively grown, 
 and with much profit, for ploughing in as a green manure. Now it is 
 mentioned that the crops of rye which follow a crop of spurry are some- 
 times quite as great when it has been eaten off with sheep or cattle as 
 when it has been ploughed in (Von Voght, Uher Manche Vortheile 
 der gr liner dungung.') 
 
 2°. In accordance with this statement is the opinion of many skil- 
 ful practical men among ourselves, that a crop of clover or of tares 
 will cause a larger after-growth of corn, if it be eaten off with sheep, 
 than if it be ploughed in in the green state. 
 
 The correctness of these practical observations appears from a 
 brief consideration of one of those interesting theoretical questions 
 we have recently been discussing. 
 
 When a crop is eaten off by full-grown animals, it returns again to 
 the soil, deprived of a portion of its carbon only (p. 473.) The manure 
 contains all the nitrogen and saline matter of the green vegetables, and 
 in a state in which they are more immediately available to the uses of 
 the young plant. Thus far, then, we can understand that in certain 
 
IMPROVEMENT OF THE SOIL BY IRRIGATION. 479 
 
 cases a crop may appear to fertilize the land more after it has been eaten 
 and digested, than if it had been ploughed in green, and we can recog- 
 nize the correctness of the opinion at which practical men have arrived. 
 But theory does not forsake us here. As in all other cases in which 
 it furnishes a true explanation of known facts, it points to new facts also, 
 which more or less modify our received opinions, and define the limits 
 within which their truth'can be rigorously maintained. Thus — 
 
 1°. Theory says that if the animals fed upon the green crop be in a 
 growing state — if they be increasing in muscle or in bone — they will 
 not only dissipate through their lungs and skin a portion of its carbon, 
 but will retain also a part of its nitrogen and saline matter, and will 
 thus return to the soil, in their excretions, a smaller quantity of these 
 substances than the crop would have given to it if ploughed in green. 
 If, therefore, a maximum fertilizing effect is to be produced upon a 
 field by eating off a green crop, it is not altogether a matter of indif- 
 
 ^ ference what kind of animals we employ as digesters. 
 
 |, 2°. Again, the practice of green manuring is resorted to chiefly 
 upon soils which are poor in organic matter — to which the carbon of 
 the green crop is of consequence, as well as the nitrogen and saline 
 matter it contains. But when eaten off, much carbon is lost to the 
 soil, and thus the supply of organic matter which it ultimately gets is 
 considerably less than if the crop it bore had been ploughed in in the 
 green state. Such soils, then, cannot be equally enriched by the 
 former as by the latter method. 
 
 This case presents a very interesting illustration, and one which you 
 can readily appreciate, of the kind of useful information which theoreti- 
 cal chemistry is capable of imparting upon almost every branch of prac- 
 tical agriculture. It says to the farmer — yes, you may in some cases, 
 certainly, eat off the crop with advantage — but if you wish to do most 
 good to your land you must eat it off with fattening, not with growing 
 sheep — and you must do so upon soils which are not very poor in 
 vegetable matter. And that explains to me also, says the practical 
 man, in reply, why I have always found sheep-folding to be most be- 
 neficial on soils which are rich in vegetable matter* (p. 468.) 
 
 § 20. Of the improvement of the soil by irrigation. 
 
 Irrigation, as it is practised in our climate, is only a more refined 
 method of manuring the soil. In warm climates, where the parched 
 plant would wither and die unless a constant supply of water were 
 artificially afforded to it, irrigation may act beneficially by merely 
 yielding this supply to the growing crops ; but in our latitudes only 
 a small part of its beneficial effects can be ascribed to this cause. It 
 is to pasture and meadow land almost solely that irrigation is applied 
 by British farmers, and the good effect it produces is to be explained 
 oy a reference to various and natural causes. 
 
 1°. If the water be more or less muddy, bearing with it solid matter 
 which deposites itself in still places, the good effects which follow its 
 
 • Sprengel explains this fdct by alleging that the humic acid of the vegetable matter re- 
 tains more effectually the ammonia of the decomposing dung. There may be something 
 in this, but more, in most cases, I think, in the fact that digestion separates much of the 
 carbon in which the soils abound, but returns the nitrogen and saline matter almost en- 
 tirely and in a more active state. 
 
480 ^ THE WATER SHOULD NOT BE STAGNANT. 
 
 diffusion over the soil may be ascribed to the layer of visible manure 
 which it leaves everywhere behind it. Thus the Nile and the Ganges 
 fertilize the lands over which their annual floods extend, and partly 
 m this way do some of our smaller streams improve the fields over 
 which they either naturally flow or are artificially led. 
 
 2°. Or if the water hold in solution, as the liquid manures of the 
 farm-yard do, substances on which plants are known to feed, then to 
 diffuse them over the surface is a simple act of liquid manuring, from 
 which the usual benefits follow. Such is the irrigation which is prac- 
 tised in the neighborhood of our large towns, where the contents of 
 the common sewers are discharged into the waters which subsequent- 
 ly spread themselves over the fields. (For an interesting account of 
 the effects of such irrigation in the neighborhood of Edinburgh, see 
 Stephens, On hTigatio7i and Draining^ p. 75.) In so far also as any 
 streams can be supposed to hold in solution the washings of towns or 
 of higher lands — and there are few w^hich are not more or less im- 
 pregnated in this manner — so far may their beneficial action, when 
 employed for purposes of irrigation, be ascribed to the same cause. 
 
 3°. But spring waters which have run only a short way from their 
 source are occasionally found to be valuable irrigators. In such cases, 
 also, the good effect may be due in whole or in part to substances held 
 in solution by the water. Thus, in lime-stone districts, and especially 
 those of the -mountain lime-stone formation (Lee. XL, § 8,) — in which 
 copious springs are not unfrequently met with — the water is generally 
 impregnated with much carbonate of lime, which it slowly deposites as 
 it flows away from its source. To irrigate with such water is, in a re- 
 fined sense, to lime the land, and at the same time to place within the 
 reach of the growing plants an abundant supply of this substance, in a 
 form in which it-can readily enter into their roots. (Some of the water 
 used in the well-known scientific irrigations at Closeburn Hall, in 
 Dumfries-shire, appears to have been impregnated with lime. See 
 Stephens, p. 43.) 
 
 In other districts, again, the springs contain gypsum and common 
 salt, ani-sulphate of soda and sulphate of magnesia, and thus are ca- 
 pable of imparting to plants many of those inorganic forms of matter, 
 without which, as we have seen, they cannot exhibit a healthy growth. 
 
 4°. Again, it is observed that the good effects of irrigation are pro- 
 duced only by running watei — coarse grasses and marsh plants spring- 
 ing up when the water is allowed to stagnate (Low's Elements of 
 Agriculture, 3d edition, p. 472.) This is explamed in part by the 
 fiict that a given quantity of water will soon be deprived of that por- 
 tion of matter held in solution, of which the plants can readily avail 
 themselves, and that when this is the case it can no longer contribute 
 to their growth in an equal degree. 
 
 But there is another virtue in running water, which makes it more 
 wholesome in the living plant It comes upon the field charged with 
 gaseous matter, with oxygen and nitrogen and carbonic acid, in propor- 
 tions very different from those in which these gases are mixed together 
 in the air (Lee. II., § 6.) To the root, and to the leaf also, it carries 
 these gaseous substances. The oxygen is worked up in aiding the 
 decomposition of decaying vegetable matter. The carbonic acid is 
 
A GOOD DRAINAGE NECESSARY. 48^ 
 
 absorbed by and feeds the plant. Let the same water remain on the 
 same spot, and its supply of these gaseous substances is soon ex- 
 hausted. In its state of rest it re-absorbs new portions from the air 
 with comparative slowness. But let it flow along the surface of the 
 field, exposing every moment new particles to the moving air, and it 
 takes in the carbonic acid especially with much rapidity — and as it 
 takes it from the air, almost as readily again gives it up to the leaf or 
 root with which it first, comes in contact. This is no doubt one of the 
 more important of the several purposes which we can understand 
 running water to serve when used for irrigation. 
 
 But further, if water be allowed to stagnate over the finer grasses, 
 they soon find themselves in circumstances in which it is not consist- 
 ent with their nature to exhibit a healthy growth. They droop, 
 therefore, and die, and are succeeded by new races, to which the wet 
 land is more congenial. 
 
 5°. It is known also, that even running water, if kept flowing with- 
 out intermission for too long a period, will injure the pasture. This 
 is because a long immersion in water induces a decay of vegetable 
 matter in the soil which is unfavorable to the growth of the grasses — 
 producing chemical compounds which are not naturally formed in 
 those situations in which the grasses delight to grow, and which are 
 unwholesome to them. Although, therefore, the water continues to 
 support those various kinds of food by which the grasses are benefit- 
 ted, yet it becomes necessary to withdraw it for a time, in order that 
 other injurious consequences may be avoided. 
 
 6*^. Lastly. — Irrigation is most beneficial where the land is well 
 drained beneath — where the water, after the irrigation is stopped, can 
 sink and find a ready outlet. The same benefits indeed flow from the 
 draining of irrigated as from that of arable lands. The soil and sub- 
 soil are at once washed free of any noxious substances they may 
 naturally contain, or may have derived from the crops they have 
 grown, and are manured and opened by the water which passes 
 through them. As the water descends also, the air follows it, to 
 change and mellow the under-soil itself 
 
 Such are the main principles upon which the beneficial action of 
 irrigation depends, and they appear to me satisfactorily to account 
 for all tlie facts upon the subject wfth which I am acquainted. I 
 pass over the alleged beneficial action of water in keeping the tem- 
 perature of irrigated fields from sinking too low. As irrigation is 
 practised in our islands, little of the good done to watered meadows 
 can be properly attributed to this cause. 
 
 1 have now drawn your attention to the most important and readily 
 available mea,ns, mechanical and chemical, for improving the soil. 
 Let us next study the products of the soil — their composition, their 
 diflferences, and the purposes they are intended to serve in the feed- 
 ing and nourishment of animals. 
 
LECTURES 
 
 ON THE 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 ON THE PRODUCTS OF THE SOIL, AND THEIR 
 USE IN THE FEEDING OF ANIMALS. 
 
 21 
 
LECTURE XIX. 
 
 Of the produce of the soil. — Average produce of England and Scotland. — Circumstances by 
 which the produce of the land is affected.— Influence of climate, of season, of soil, of the 
 kind and variety of crop, of the method of culture, and of the course of cropping. — ^Theory 
 of the rotation of crops. — Why lands become tired of clover (clover-sick) and other special 
 crops. — Theory of fallows.— Composition of wheat, oats, barley, rye, and Indian com. — In- 
 fluence of climate, soil, manure, variety of seed, mode of cul{ure, and time of cutting, upon 
 the composition ofLhese grains. — Effect of baking upon bread.— Supposed relation between 
 the weight of bread and the proportion of gluten.— Effect of germination (malting) upon 
 barley.— Composition of peas, beans, and vetches.— Effects of soil, «fec., upon the boiling 
 quality of pea.s —Composition of the turnip, the carrot, the beet, and the potatoe. — Effect; 
 of soil, age, size, rapidity of growth, &c.,upon their composition. — Relative proportions of 
 nutritiv'e mitter produced by different crops on the same extent of ground.— Composition 
 of the grasses and clovers. — Elfoct of soils, manures, time of cutting, mode of drying, &c., 
 upon their composition and nutritive value. 
 
 Having now considered the most important of those mean.s by which 
 the .soil may be improved, it will be proper to direct our attention to that 
 which the land produces — to the chemical nature of the crops you raise, 
 to the differences which exist among them, and to the purposes they are 
 fitted to serve in the feeding of man and other animals. 
 
 Agricultural products are of three distinct kinds : 
 
 1'^. Such as are directly reaped from the .soil in the form of corn, pota- 
 toes, hay, &c. 
 
 2°. Such as are the result of a kind of natural process of manufacture, 
 by which the direct produce of the soil is more economically converted 
 into the beef and mutton of the feeder of stock. 
 
 3°. Such as are the results of a further conversion at the hands of the 
 dairy farmer, and are sent to market in the form of butter and cheese. 
 
 Thus three di.stinct topics of consideration present themselves in con- 
 nection with the produce of the soil, — the nature of the immediate pro- 
 ducts themselves — the economy of the feeding of stock — and the prepara- 
 tion of butter and cheese. We shall study these several topics in their 
 natural order. 
 
 § 1. Of the maximum or greatest possible., and the average or actual^ 
 produce of the land. 
 
 There is a wide difference in most countries between the actual 
 amount of food produced by the land, and that which, in the most fa- 
 vourable circumstances, it would delight to yield. 
 
 An imperial acre of land in our island has been known to yield of 
 wheat 70 bushels,* barley 80 bushels, oats 100 bushels, potatoes 30 
 tons,f and turnips 60 tons.J 
 
 The .average produce of the land, however, is far below these quanti- 
 ties. It is not easy to arrive at a tolerable approximation even to the 
 
 * In the county of Middlesex the produce of wheat varies from 12 to 68 bushels — of bar- 
 ley from 15 to 75 — and of oats from 32 to 96 bushels. — Middlelon's View of the Agricul- 
 ture of Middlesex, 1798, pp. 176, 183, and 188. 
 
 t See Mr. Fleming's experiments upon potatoes in the Appendix. 
 
 t Perhaps this is not the maximum. — In the Second Report of (he Royal Agricultural Im- 
 provement Society of Ireland, p. 57, a crop of turnips is mentioned, which weighed 56 tons — 
 tops and bulbs amounting together to 76 tons. 
 
488 PRODUCE OF THE LAND IN GREAT BRITAIN, 
 
 true average produce of the island. Mr. Maccu-lloch estimates that of 
 wheat at 26 bushels an acre, barley at 32, and oats at 36. 
 
 Sir Charles Lemon gives for the average produce of all England, and 
 for the highest and lowest county averages, the following numbers; — 
 
 Wheat - • 
 
 Average for 
 all England 
 in bushels. 
 ■ - 21 
 
 Highest 
 
 county average 
 
 in bushels. 
 
 26 Nottinghamshire. 
 
 Lowest 
 
 county average 
 
 in bushels. 
 
 16 Dorset. 
 
 Barley - • 
 
 - - 321 
 
 40 Huntingdon. 
 
 24 Devon. 
 
 Oats - - ■ 
 
 ■ - 351 
 
 48 Lincolnshire. 
 
 20 Gloucester. 
 
 Potatoes - ■ 
 
 ■ - 241 
 
 360 Cheshire. 
 
 100 Durham. 
 
 While in Scotland, according to Mr. Dudgeon, the average produce 
 
 of corn is — 
 
 Good land. Lighter land. 
 
 Wheat - - - - 30 to 32 bushels. 22 to 26 bushels. 
 Barley - - - - 40 to 44 do. 34 to 38 do. 
 
 Oats 46 to 50 do. 36 to 43 do. 
 
 If these numbers of Sir Charles Lemon and of Mr. Dudgeon are to be 
 depended upon, the averages for the whole island cannot be far from 
 wheat 24 bushels, barley 34 bushels, oats 37 bushels, potatoes 6 tons, 
 and turnips 10 tons. 
 
 Though even these, especially in regard to the root crops, must be 
 considered as in a considerable degree hypothetical.* 
 
 What is the cause of the striking diflerences above exhibited between 
 the maximum produce of certain parts of the island and the average pro- 
 duce of the whole ? Are such ditferences necessary and unavoidable ? 
 Can the less productive lands not be made to yield a larger return ? 
 Can the large crops of the richer districts not be further increased, and 
 their amount kept up for an indefinite succession of seasons ? 
 
 These interesting questions lie at the foundation of all agricultural im- 
 provement — and skill and science answer that, though differences to 
 a certain amount are unavoidable, yet that means are already known 
 by which tlie fertility of the richer lands may be maintained, and the 
 crops of the less productive indefinitely enlarged. 
 
 § 2. Of the circumstances by which the 'produce of food is affected — 
 climate, season, soil, Si^'c 
 
 The quantity of food produced by a given extent of land is aff^ected by 
 the climate, by the season, by the soil, by the nature of the crop, by the 
 variety sown or planted, by the general method of culture, and by the ro- 
 tation or course of crojjping that is adopted. 
 
 1°. Climate. — That the warmth of the climate, the length of the sum- 
 mer, and the quantity of rain that falls, influence in a remarkable degree 
 the amount of food which a district of country is fitted to raise, is fa- 
 miliar to every one. The warmth of the equatorial regions maintains a 
 perpetual verdure, while the short northern summers afford only a few 
 months of pasture to the stunted cattle. The difference of latitude be- 
 tween the extreme ends of our island produces a similar difference, though 
 in a less degree. The almost perennial verdure of the southern counties 
 
 " In 1821, Mr. Wakefirld estimated the average produce of wheat in all England at 17 
 bushels only — Devonshire producing an average of 20, and the lands near the coast of Kent, 
 Norfolk, Suffolk, and Essex, 40 bushels per acre. 
 
INFLITENCE OF CLIMATE, SEASON, ANl SOIL. 489 
 
 cannot be hoped for in the north of Scotland, and yet it is said that in 
 parts of Ross-shire the com and turnip crops are equal to those of the 
 most favoured districts of Britain. Is tliis to be regarded solely as the 
 triumph of skill and industry over the difficulties presented by nature ? 
 
 2°. Season. — The influence of the seasons, wet or dry, warm or cold, 
 has been observed by the farmer in all ages, and it cannot be entirely 
 overcome. The heavy crop of this year may not be reaped again on 
 the next, because an unusual cold may arrest its growth. And 
 yet good husbandry will do much even here — since the higher the farm- 
 ing the fewer the number of failures which the intelligent man will 
 have occasion to lament. 
 
 3°. Soil. — Diversity of soil is held to be a sufficient reason for differ- 
 ence both in kind and in weight of crop. A poor sand is not expected to 
 give the same return as a rich clay. Yet in regard to the capabilities of 
 soils under skilful management, practical agriculture appears as yet to 
 have much to learn. Is there any method hitherto little tried by which 
 soils of known poverty may be compendiously and cheaply doctored, so 
 as to produce a greatly larger return ? Science seems to say that there is, 
 and points to a wide field of experimental research, by the diligent cul- 
 ture of which we may hope that this great result will hereafter be at- 
 tained. The principles upon which this hope rests have been explained, 
 for the most part, in the preceding Lectures. 
 
 4°. Kind of crop. — The amount of food, either for man or beast, 
 which a given field mil produce, depends considerably upon the kind 
 of crop which is raised. Thus a crop of 30 bushels of wheat will yield 
 only about 1400 lbs. of fine flour, while a crop of 6 tons of potatoes will 
 give about 4400 lbs. of an agreeable, dry, and mealy food. Thus the 
 gross weight of food for man is in the one case three times what it is in 
 the other. So it is said, on the authority of the Board of Agriculture, 
 that a crop of clover, of tares, of rape, of potatoes, turnips, or cabbages, 
 will furnish at least thrice as much food for cattle as one of pasture grass 
 of medium quality.* 
 
 5°. Variety of seed soion. — The variety of seed sown has also an im- 
 portant influence on the amount of produce reaped. I need not refer to 
 the well known necessity of changing the seed if the same laud is to 
 continue to yield good crops — but of strange seeds of the same species 
 two varieties will often yield very unlike weights of ^orn, of turnips, or 
 of potatoes. I may quote as an illustration the experiinents of Colonel 
 Le Couteur upon wheat. He found, on the same soil and under the 
 same treatment, that the varieties known by the name of the White 
 Downy and the J ersey Dantzic yielded respectively : 
 
 Grain. Weight pr bush. Straw. Fine flour. Fine do. pr.ct. 
 
 White Downy - 48 bush. 62 lbs. 4557 lbs. 2402 lbs. 80| lbs. 
 Jersey Dantzic - 43^ bush. 63 lbs. 46811bs. 2161 lbs. 79|lbs. 
 while on a different soil and treated differently from the above, two other 
 
 varieties yielded — 
 
 Grain. Weight pr bush. Straw. Fine flour. Fine do. pr.cL 
 Whittington, - - - 33 bush. 61 lbs. 7786 lbs. 1454 lbs. 72|lbs. 
 BelleVue Talavera, -52 bush. 61 lbs. 5480 lbs- 24851b8.t 78^1ba. 
 
 • Loudon's Encyclopobdia of Agriculture^ p. 910. 
 
 t Journal of the Royal Agricultural Society of England^ L, p. 123. 
 
490 INFLUENCE OF THE METHOD OF CULTURE, 
 
 In each of tliese cases, therefore, and especially in the last, a striking 
 difference presented itself both in the absolute and in the relative weights 
 of grain and of straw reaped under precisely similar circumstances, by 
 the use of different varieties of the same species of seed. Nor are the 
 above by any means extreme cases. In the same field I have known 
 the Golden Kent and the Flanders Red varieties, sown in the same 
 spring, to thrive so differently, that, while the former was an excellent 
 crop, tiie latter was almost a total failure. It will require a very refined 
 chemistry to explain the cause of such diversities as tliese. 
 
 § 3. Influence of the method of culture upon the produce of food. 
 
 In addition to the circumstances abovfe alluded to, the quantity of food 
 that is raised depends very much upon the method of culture which is 
 adopted. Thus, in land of medium quality, our opinion in regard to the 
 quantity of food it is likely to yield would be greatly affected by the 
 answers we should obtain to the following questions ; — 
 
 1°. 7s the land in permanent pasture^ or is it under the plough? — 
 With the exception of rich pasture, it is said that land, under clover or 
 turnips, will produce three times as much for cattle as when under grass. 
 If such a green crop then alternate with one of corn, the land would 
 every two years produce as much food for stock as it would during three 
 years if lying in grass, besides the crop of corn as food for man, and 
 of straw for the production of manure. 
 
 This statement may possibly be a little exaggerated, or may represent tru- 
 ly the comparative produce of food in special cases only — yet there seems 
 sufficient reason for believing, as a general rule, that a very much larger 
 amount of food may be reaped from land under arable culture, than 
 when laid away to permanent pasture. 
 
 2°. What kind and quality of manure is applied ? — Every practical 
 man knows the importance of -manuring his land, and how much the 
 abundance of every crop he sows depends both upon the quantity and upon 
 the kind of manure he is able to add to it. 
 
 3°. In whatriDay is it aj^j^Hed ? — But much depends also upon the 
 manner in which the manure is expended, or the kind of crop to which 
 it is applied. 
 
 I have already (p. 477) directed your attention to the loss which must 
 necessarily be sustained by top-dressing with fann-yard manure, and yet 
 how in certain modes of cropping and manuring the land, it may be 
 not only advisable but necessary to do so. Yet the comparative return 
 of food obtained from the use of such manure, when applied as a top- 
 dressing to grass land for instance, and when buried with the turnip crop 
 in the usual manner, is very unlike. 
 
 Thus, suppose an acre of grass land, of such a quality as to produce 
 annually without manure 1| tons of hay, to be top-dressed every spring 
 or autumn with 5 tons of farm-yard manure per acre — and suppose 
 another acre of the same land in arable culture to be manured for turnips 
 with 20 tons of fann-yard manure at once. Then the grass land, by 
 the aid of the manure, would not produce more than double its natural 
 crop, or 2i tons an acre, that is, 10 tons of hay in the four years. This, I 
 believe, is making a large allowance for the effect of the manure. 
 
 But the arable land, in the four years, if of the same quality, may be 
 
— ~ 
 
 ^£20 
 
 £2 
 
 10 
 
 1 
 
 16 
 
 2 
 
 9 
 
 
 fi 1 <! n 
 
 
 
 AND OF THE MOEE OF API'i.fING THE MANURE. 491 
 
 expected to produce — turnips 20 tons, barley 36 bushels, clover 2| tons, 
 wheat 28 bushels ; besides upwards of 4 tons of straw. 
 
 In all these taken together there must be much more food than in the 
 ten tons of hay. 
 
 If we consider the money profit, however, to the farmer, the result 
 may be different. The cost of raising the ten tons of hay, exclusive of 
 rent, may be reckoned at one-half the produce, and of the several crops 
 in the four years' rotation at three-quarters of the produce: we thus 
 have for the clear return — 
 
 In the one case, half the produce — 5 tons of hay ; 
 In the other case, a fourth of the produce — 5 tons of turnips, 9 bushels 
 of barley, ^ ton of clover, 7 bushels of wheat, and 1 ton of straw. 
 
 Let the clover and the straw together equal in value only one ton of 
 the hay, and the money value in the two cases will stand as follows ;— 
 Hay, 4 tons, at <£5, 
 Turnips, 5 tons, at 10s. = ^£2 
 Barley, 9 bush., at 4s. = 
 Wheat, 7 bush., at 7s. — 
 
 Leaving a gain upon the grass land of ^£1.3 5 
 Or, <£3. 6s. an acre every year. 
 
 Thus, though more food is raised by converting the land to arable 
 purposes, and more people niay be sustained by it, yet more money 
 may be made by meadowing the land — ivhere a ready market exists 
 for the hay, cohere it is allowed to he sold off the farm, and where abun- 
 dance of manure can he obtained for the ijuri^ose of top-dressing the grass 
 every year. It is only in the neighbourhood of large towns, however, 
 that all these circumstances usually co-exist, and hence one cause of the 
 value of grass land in such localities. 
 
 The farmer, however, is never prohibited from selling his corn off the 
 farm, or his fat stock, or his dairy produce, and thus at a distance from 
 large towns he must turn his attention solely to the raising of one or other 
 of these kinds of produce. 
 
 Of the two ways of employing his grass or green crops — in rearing 
 and fattening cattle, namely, and in the production of butter and cheese 
 — we shall hereafter see reason to believe that theoretically the latter 
 ought both to be the most profitable in money to the farmer, and at the 
 same time to produce the greatest amount of food for man; 
 
 3°. What rotation or course of cropjnng is adopted ? — If the land be 
 cropped with corn, year after year, the produce of food will not only be 
 less than if an alternate husbandry were introduced — but the yearly return 
 of corn, even on the richest land, must sooner or later diminish, till at 
 length the crop will not be sufficient to defray the expense of cultivation. 
 The tillage of such land must then be abandoned, and it must be left to 
 a slow process of natural restoration. No arable land will produce so 
 much food if year by year it be made to raise the same crop, as if the 
 crop be varied — and especially as if corn, root, and leguminous crops be 
 made to succeed each other in a skilful alternation. 
 
 Upon the introduction of the alternate husbandry, it was found that 
 upon lands formerly in pasture, not only could one-third more stock be 
 
492 THEORY OF THE ROTATION OF CROPS. 
 
 kept continuously than before, but that in addition a crop of corn could be 
 reaped every second year. On the other hand, those which had been 
 cropped with corn alone, or which after two white crops had usually been 
 left to naked fallow, yielded more corn in a given number of years than 
 before, while a green crop every second year was raised on them besides. 
 It cannot be doubted, therefore, that a change of cropping influences, in 
 a great degree, the amount of food which the same piece of land is fitted 
 to produce. 
 
 § 4. Of the theory of the rotation of crops. 
 
 Upon what principles do the beneficial effects of this change of crop- 
 ping depend ? What is the true theory of a rotation of crops ? 
 
 It was supposed by Decandolle — 
 
 1°. That the roots of all plants gave out or excreted certain substan- 
 ces peculiar to themselves — and, 
 
 2°. That these substances were unfavourable to the growth of those 
 plants from the roots of which they came, but were capable of promo- 
 ting the growth of plants of other species — that the excretions of one 
 species were poisonous to itself, but nutritive to other species. 
 
 Upon these suppositions he explained in a beautiful and apparently 
 simple and convincing manner the beneficial effects of a rotation or al- 
 ternation of different crops. If wheat refused to grow after wheat, it was 
 because the first crop had poisoned the land to plants of its own kind. 
 If after an intervening naked fallow a second wheat crop could be safely 
 grown, it was because during the year of rest the poisonous matter had 
 time to decompose and become again fitted to feed the new crop. And 
 if, after beans or turnips, wheat grew well, it was because the excretions of 
 these plants were agreeable to the young wheat, and fitted to promote 
 its growth. 
 
 Thus easily explained were the benefits both of a rotation of crops 
 and of naked and other fallows — and supported at once by its own beauty 
 and by the great name of Decandolle, this explanation obtained for 
 many years an almost universal reception. 
 
 But thoughrthere seems reason enough for believing (p. 82) that the 
 roots of plants really do give out certain substances into the soil — there is 
 no evidence that tliese excretions take place to the extent which the 
 theory of Decandolle would imply — none of a satisfactory kind that 
 they are noxious to the plants from which they are excreted* — and none 
 that they are especially nutritive to plants of other species. Being un- 
 supported by decisive facts and observations therefore, the hypothesis of 
 Decandolle must, for the present, be in a great measure laid aside, and we 
 must look to some other quarter for a more satisfactory theory of rotation. 
 
 The true general reason why a second or third crop of the same kind 
 will not grow well, is — not that the soil contains too much of any, but that 
 it contains too little of one or more kinds of matter. If, after manuring, 
 turnips grow luxuriantly, it is because the soil has been enriched mth 
 all that the crop requires. If a healthy barley crop follow the turnips, 
 it is because the soil still contains all the food of this new plant. If 
 clover thrive after this, it is because it naturally requires certain other 
 kinds of nourishment which neither of the former crops has exhausted. 
 If, again, luxuriant wheat succeeds, it is because the soil abounds still in 
 
 ' See page 81, note. 
 
PRACTICAL RULES SUGGESTED BY THEORY. 493 
 
 all that the wheat crop needs — the failing vegetable and other matters of 
 the surface being increased and renewed by the enriching roots of the 
 preceding clover. And if now, turnips refuse again to give a fair re- 
 turn, it is because you have not added to the soil a fresh supply of that 
 manure without which they cannot thrive. Add the manure, and the 
 same rotation of crops may again ensue. 
 
 We have already had frequent occasion, in studying the inorganic 
 constituents of plants, to observe that different species require very un- 
 like proportions of the several kinds of inorganic food which they derive 
 from the soil. Some require a large proportion of one kind, some of 
 another kind. If a soil, therefore, abound especially in one of these va- 
 rieties of inorganic food, one kind of plant will especially flourish upon 
 it — while, if it be greatly deficient in another substance, a second plant 
 will remarkably languish upon it. If it abound in both substances, then 
 either crop will succeed which we may choose to sow, or they may be 
 alternately cultivated with a fair return from each. 
 
 Upon this principle the true general explanation of the benefit of a 
 rotation of crops appears to depend. There may be special cases in 
 which peculiar qualities of soil or climate may intervene and give rise 
 to appearances, or cause results to which this principle does not apply, 
 but for the general practice it seems to afford a satisfactory explanation. 
 
 It may be said that this explanation seems to im ply that the same 
 kind of crop maybe reaped from the same soil for an indefinite number of 
 years, by simply adding to it what the crop carries off. This is certain- 
 ly implied in the principle — and if we knew exactly what to add for each 
 crop, we might possibly attain this result, except in cases where the soil 
 undergoes some gradual chemical alteration within itself, which it may 
 require a change of treatment to counteract. At all events it does not 
 seem impossible to obtain crop after crop of the same kind — and we may 
 hope hereafter not only to be able to effect this, but to do it in a suffi- 
 ciently economical manner. 
 
 Two practical rules are suggested by the fact that different plants require 
 different substances to abound in a soil in which they shall be capable of 
 flourishing. 
 
 1°. To grow alternately as many different classes or fajnilies of plants 
 as possible — repeating each class at the greatest convenient distance of time. 
 
 In this country we grow chiefly root crops, — corn plants ripened for 
 seed, — leguminous plants sometimes for seed (peas and beans), and 
 sometimes for hay or fodder (clover and tares), — and grasses, and these 
 in alternate years. Every four, five, or six years, therefore, the culture 
 of the same class of plants comes round again, and a demand is made 
 upon the soil for the same kinds of food in the same proportion. 
 
 In other countries — tobacco — flax— rape, poppy or madia, cultivated for 
 their oily seeds — or beet for its sugar, can be cultivated with profit, and 
 being interposed among the other crops, they make the Return of each 
 class of plants more distant. A perfect rotation would include all those 
 classes of plants which the soil, climate, and otlier circumstances allow 
 to be cultivated with a profit. 
 
 2°. A second rule is to repeat the same species of plant at the greatest 
 convenient distance of time. In corn crops there is not much choice, 
 since in a four years' course two corn crops, out of the three (barley, 
 21* 
 
494 WHY LAND BECOMES CLOVER-SICK. 
 
 wheat, oats) usually grown, must be raised. But of the leguminous 
 crops we have the choice of beans, peas, vetches, and clover — of root 
 crops, turnips, carrots, beets, and potatoes — while of grasses, there is a 
 great variety. Instead, therefore, of a constant repetition of the turnip 
 every four years, theory says — make the carrot or the potatoe take its 
 place now and then, and instead of perpetual clover, let tares or beans, 
 or peas, occasionally succeed to your crops of corn. The land loves a 
 change of crop, because it is better prepared with that food which the 
 new crop will relish, than with such as the plant it has long fed before 
 continues to require. 
 
 It is for this reason that new species of crop, or new varieties, when 
 first introduced, succeed remarkably for a time, and give great and en- 
 couraging returns. But they are continued too long — till the soil has 
 been exhausted in some degree of those substances in which the new 
 crops delighted. They cease in consequence to yield as before, and fall 
 into undeserved disrepute. Give them a proper place in a long rotation, 
 and they will not disappoint you. 
 
 It is constant variety of crops, which, with rich manuring, makes our 
 market gardens so productive — and it is the possibiUty of growing in the 
 fields many different crops in succession, that gives the fertihty of a gar- 
 den to parts of Italy, Flanders, and Cliina.* 
 
 § 5. Why land becomes tired of clover {clover-sick). 
 
 What I have said of the general principle might be supposed to 
 explain fully wliy crops fail at one time and succeed at another — why 
 the soil will nourish one plant well, while it is unable adequately to sus- 
 tain another. But a brief reference to the case of the clover plant will 
 enable us to see how modes of culture, apparently skilful and generous, 
 may yet be of such a kind as to lead, sooner or later, to the inevitable 
 failure of a particular crop. 
 
 It is known that upon many well cultivated farms the lands become 
 now and then tired or sick of clover, and this crop failing, the wheat 
 which succeeds it in a great measure fails also. It may be said that the 
 soil in such arrrase is in want of sojnething, and so it is, — but how does 
 this deficiency of supply arise ? The land is skilfully managed and 
 has been well manured, and the failure of the clover crop is, therefore, a 
 matter of surprise. 
 
 If farm-yard manure be copiously applied previous to the root crop, 
 the land has received a certain more or less abundant return of all those 
 substances lohich the last rotation of crops had carried off from it, — and 
 which the new rotation will require for food. When the clover comes 
 round, therefore, a supply of proper food is ready for it, as well as for 
 the wheat which is to follow. 
 
 But if the turnip crop be raised by means of bones only, the lime 
 
 A method of superseding in some measure the necessity of a rotation of crops is de- 
 ecribed by Mr. James Wilson as lon^ practised in Slietland, in the neis?hbourhood of Ler- 
 wick. " It is known that bear has been grown in the same patch for perhaps 100 years suc- 
 cessively, and this they managed by scarifying other part.s of the ground (the out-field por- 
 tion), and renovating the arable patch by sjireading it over the surface." This was varying 
 the soil instead of the crop. A five years' rotation, however, is now getting into favour, and 
 the average produce, after liming, is found to be increased by it four-fold. In this district 
 much herring refuse is employed as a manure, and the improved land lets at 20s. an acre. 
 —Wilson's Voyage round the Coast of Scotland, II., p. 268. 
 
RESULT OF FREQUENT MANURING WITH BONES. 495 
 
 and phosphoric acid which the earth of bones contains are almost the only 
 kinds of inorganic f)od required by plants that are returned to the soil. 
 By the aid of the animal matter and the small supply of other substances 
 in the bones,* good crops — and especially the turnips and the corn which 
 immediately follows them — may be raised for a few rotations, but at 
 every return the clover and wheat will become more unhealthy, till they 
 at length appear to sicken upon the land. Neither bones nor rape-dust 
 nor any such single substance can replace farm-yard manure for an in- 
 definite period, because it does not contain all the substances which the 
 entire rotation of crops requires. 
 
 If wood-ashes be used along with the bones, the bad effects I have des- 
 cribed will be much longer delayed — they may even be delayed indefi- 
 nitely, since wood-ashes are said to be especially favourable to the growth 
 of clover and other leguminous plants, (p. 353), and this because they 
 contain those substances which the clovers require. 
 
 It thus appears, therefore, that while the failure, upon a given spot, of 
 a crop which formerly grew well there, is explained generally upon the 
 principle that the soil has become deficient in something which the crop 
 requires — tlie cause of this deficiency may not unfrequently be found in 
 the mode of culture, or in the species of manuring which the land has 
 received. The cause being discovered, the remedy is easy. Cease to 
 employ exclusively the manure with which your land has hitherto been 
 dressed. Mix your bones or rape-dust with wood-ashes, with gypsum, 
 or with other portable manures in which the necessary food of your 
 crops is present — or employ farm-yard manure now and then in their 
 stead, and you will apply the most likely remedy. Unless tliis be done, 
 it will be of comparatively little service to vary the species, — to substi- 
 tute tares or beans for the clover, — since these also will refuse to grow 
 while the same incorrect system of manuring is persisted in. 
 
 I have already drawn your attention (p. 477) to the falling of the 
 clover crops in certain parts of Staffordshire, where the turnips are 
 raised by means of rape-dust — and of the mode of improving them by a 
 top-dressing of farm-yard manure. Were this manure laid in with the 
 turnips, the after top-dressing would most probably not be required. 
 
 § 6. Of the theory of fallows. 
 
 By fallowing, it has been known in all ages that the produce of the 
 land was capaljle of being increased. How is tViis increase to be ac- 
 counted for? We speak of leaving the land to rest, but it can never 
 really become wearied of bearing crops. It cannot, through fatigue, lie 
 in need of repose. In what, then, does the efficacy of naked fallowing 
 consist 1 
 
 1°. In strong clay lands one great benefit derived from a naked fallow 
 is the opportunity it affords for keeping the land clean. In such soils it 
 is believed by many that weeds cannot possibly be extirpated without an 
 occasional fallow. It is certain that naked fallows are had recourse to 
 in many places for the purpose of cleaning the land, where if it could 
 easily have been kept so by other means they would not have been 
 adopted. Is it not the case on some farms that a neglect of other avail- 
 able methods of extirpating weeds has rendered necessary the assistance 
 * For the composition of bones, see page 416. 
 
496 FALLOWS MAT REPLACE DEEP PLOUGHING AND DRAINING. 
 
 of a naked fallow, while on similar farms in the same neighbourhood 
 they can easily be dispensed with ? 
 
 2°. In a naked fallow, where the seeds are allowed to sprout, and 
 young plants to shoot up, which are afterwards ploughed in, the land is 
 enriched by a green manuring of greater or less extent. If weeds abound, 
 the enriching is the greater — if they are more scanty, it is less — but in 
 almost every instance where land hes without an artificial crop during 
 the whole summer, a crop of natural herbage springs up, the burying of 
 which in the soil must be productive of considerable good. 
 
 3°. When land is assiduously cropped, the surface in which the roots 
 chiefly extend themselves becomes especially exhausted. In indiffer- 
 ently worked land some parts of this surface may be more exhausted than 
 others. By leaving such soils to themselves, the rains that fall and more 
 or less circulate through them ecjualize the condition of the whole sur- 
 face soil — in so far as the soluble substances ii contains are concerned. 
 The water also, which in dry weather ascends from beneath, brings 
 with it saline and other soluble compounds, and imparts them to the up- 
 per layers of the soil. Thus, by lying fallow, the land, becomes eqiia- 
 bly furnished over its whole surface with all those substances required by 
 plants which are anywhere to be found in it. The roots of die crop, 
 therefore, can more readily procure them, and thus the plants more 
 readily and more quickly grow. In some cases, this beneficial action of 
 the naked fallow will, to a certain extent, make up for shallow- ploughing^ 
 and for insufficient working of the land. 
 
 4°. It is known that the subsoil in many places is of such a nature 
 that it must be turned up to the surface, and exposed for a considerable 
 period to the action of the air, before it can be safely mixed with the sur- 
 face soil. To a less degree stiff clay lands acquire this noxious quality 
 during the ordinary course of cropping. Air and water do not find their 
 way through them in sufficient quantity to retain them in a healthy 
 condition, and thus they require an occasional fallow with repeated 
 ploughings, that the air and the rains may have access to their inner- 
 most parts. I do not detail the specific chemical changes which are in- 
 duced by this^exposure to the air and rain ; it is sufficient that they are 
 of a kind Jo render the soil more propitious to the growth of crops, to 
 satisfy us that, upon very stiff lands, one of the benefits of fallowing is to 
 be thus accounted for. 
 
 -* We have seen that one of the important benefits of draining is the 
 permeability it imparts to the soil. The surface water is permitted to 
 escape downwards, and as it sinks to the drain the air follows it, so that 
 the very deepest part of the soil from which the water runs off, is ren- 
 dered wholesome by the frequent admission of new supplies of atmos- 
 pheric air. 
 
 It thus appears that in a certain sense draining and fallowing may 
 take the place of each other — that where there is no drainage, fallowing 
 is more necessary and will partially supply its place, and that where a 
 good drainage exists, the use of naked fallows even upon stiff clay lands 
 becomes less necessary. 
 
 5°. I have already had occasion to speak of the existence of organic 
 (animal and vegetable) matter in the soil, in a so-called inert state — a 
 state iu which it undergoes decay very slowly, and thus only in a small 
 
THE SOIL IS MANURED BY THE SEA AND THE AIR. 497 
 
 degree discharges those functions for which vegetable matter in the soil is 
 specially destined. In stiff clays also, the roots of plants, without actu- 
 ally attaining this inert state, yet decay with extreme slowness in conse- 
 quence of their being so completely sealed up from the access of the air. 
 In both cases the frequent and prolonged exposure which a naked fallow 
 occasions, induces a more rapid decay of this vegetable matter, or brings 
 it into a state in which its elements more readily assume those new 
 forms of combination which are capable of ministering to the sustenance 
 and growth of plants. 
 
 Among the other compounds which are produced (p. 161) during this 
 prolonged exposure and more rapid decay of the organic matter of the 
 soil, nitric acid is one which appears to exercise a considerable in- 
 fluence upon the future fertility of the land. The favourable action of 
 the nitrates in promoting vegetable growth is now well known, and 
 the more rapid formation of these compounds, when the land lies na- 
 ked to the action of the sun and air, must not be neglected among the 
 fertilizing influences of the summer fallow. 
 
 6°. The soil, besides the clay, (quartz) sand and lime of which it 
 chiefly consists, contains also fragments of mineral substances of a com- 
 pound nature — of felspar, of mica, of hornblende — of those minerals 
 which constitute or which occur in the granitic and trap rocks. These 
 slowly decompose in the soil — more rapidly also the more freely they 
 are exposed to the air — and the substances (potash, soda, lime, magne- 
 sia, silica, &c.*) which they contain, are by this decomposition diffused 
 more equably and brought within the more easy reach of the roots of 
 plants. Wlien these minerals, therefore, exist in the soil, and when 
 their constituents are of such a kind as to favour the growth of any given 
 plant, the effect of a naked fallow being to produce an accumulation of 
 their constituent substances in the soil, it will be so far favourable in pre- 
 paring the land for an after-crop of that particular species of plant. 
 You are not to be misled, however, by any broad and unguarded state- 
 ments of scientific men, so as to imagine for a moment that the benefi- 
 cial effects of fallowing in any case are to be solely ascribed to the oper- 
 ation of this one cause. f 
 
 7°. The rains bring down upon every soil periodical supplies of ad 
 those saline substances — common salt, gypsum, salts of lime, of mag- 
 nesia, and of potash in minute quantity — which exist in the sea, and of 
 nitrate of ammonia, produced or present in the air. If any soil be defi- 
 cient in these, then a year's rest from cropping, by allowing them to ac- 
 cumulate, may cause the succeeding herbage to exhibit a more luxuriant 
 growth. 
 
 8°. The same remark applies to soils into which springs from beneath 
 bring up variable quantities of hme and other substances which the wa- 
 ters, hold in solution. Such springs are, no doubt, of much benefit in 
 some districts, and when the supply they convey is scanty, a year's 
 accumulation may impart additional fertility to the fallowed land. 
 
 9°. Besides that beneficial action of tlie air to which I have already 
 adverted (4° and 5°), and which is to be ascribed mainly to the influ- 
 
 ' For the constitution of these mineral substances, see pp. 257 to 260. 
 t Fallow is the term applied to land left at rest for further disintegration.— I Aebig^s Organic 
 Chemistry applied to Agriculture, p. 149. 
 
498 OF GREEN OR FALLOW CROPS. 
 
 ence of the oxygen it contains — the exposure of the naked soil to the at- 
 mosphere for a length of time is said by some to be productive of another 
 good effect. The atmosphere contains a small and variable portion of 
 ammonia (p. 156). Of this ammonia, a ])ortion is brought down by the 
 rains and a portion is probably absorbed by the leaves of plants as they 
 spread themselves through the air. But the clay, the oxide of iron, and 
 the organic matter of the soil are supposed also to have the power of 
 extracting this ammonia from the atmosphere and retaining it in their 
 pores. If so, the more the soil is exposed, and for the longer period 
 to the air, the more of this substance will it extract and absorb. If 
 turned over by frequent ploughing, it will be able to drink it in more 
 abundantly, from the greater surface it can present to the passing winds; 
 and if, besides, it be kept naked for an entire year, a still larger accumu- 
 lation must take place. And as this ammonia is known in many cases 
 to be favourable in a high degree to the growth of plants, it is not un- 
 reasonable to believe thcit if thus absorhedin quantity from the air, it should 
 be one source at least of the augmented fertility of fallowed land. 
 
 To one or other — or to all of these causes combined — the acknowledged 
 benefit of naked fallows is in a great degree to be ascribed. 
 
 O^ green or fallow crops little need be said in addition to what I have 
 already laid before you in reference to the rotation of crops. The green 
 crop demands a comparatively small supply only of those inorganic sub- 
 stances which the corn crops specially require. During its growth, 
 therefore, these latter accumulate in the same way, though in a some- 
 what less degree than during a naked fallow. But the additional vege- 
 table matter and manure which the green crops introduce into the soil, 
 and the large supplies of inorganic matter which such of them as are 
 deep-rooted bring up from beneath, amply compensate for any diminu- 
 tion they may cause in the benefits which are usually derived from the 
 naked fallow. 
 
 § 7. Of loheat and tvlieaten flour. 
 The grain of wheat in the hands of the miller is readily separated into 
 two portions-^^the husk, which forms the bran, and the greater portion 
 of the pollard — and the kernel, which, when ground, forms the wheaten 
 flour. The relative weights of these two parts vary very much. Some 
 varieties of grain are much smoother, more transparent, and thinner 
 skinned than others, and yield in consequence a larger return of the 
 finest flour. In good wheat the husk amounts to 14 or 16 percent, of 
 the whole weight* — though the quantity separated by the miller is 
 sometimes not more than ith (or 11 per cent.) of the weight of the 
 wheat. In making the fine white flour of the metropolis and other 
 large towns, about ^th of the whole is separated in the form of pollard 
 and bran. The proportion of the husk that can be sifted out at the mill 
 
 * Boussingaulf, found as much as 38'a perrenf. of husk on a winter wheat grown in the 
 botanic garden of Paris. Three lots of good English wheat, ground at Mr, Robson's mill ia 
 Durham, gave per cent, respectively — 
 
 Fine flour 74 2 751 77 9 
 
 Boxings 9 8 3 61 
 
 Sharps 5 8 6-6 56 
 
 Bran 7 8 7 6 9 
 
 Waste 3-2 30 3-5 
 
 100 100 100 
 
N RELATIVE WEIGHTS OF FLOUR AND BRAN. 499 
 
 depends considerably upon the hardness of the grain. From such as is 
 soft it peels off in flakes under the stones, whereas, when the grain and 
 nusk are flinty, much of the latter is crushed and ground — adding to the 
 weight of the flour, but giving it a darker colour, and lowering its quality. 
 
 The country millers generally separate their wheaten flour by sifting 
 into four parts only — fine flour, boxings, sharps or pollard, and bran. 
 In London and Paris no less than six or seven qualities are manufac- 
 tured and sold by the millers.* The value of the wheat to ^e miller 
 depends very much upon the quantity of fine flour it will yield, though 
 he cannot always judge accurately of this point by simple inspection. 
 
 The experimental wheats of Mr. Burnet, of Gadgirth,f raised all from 
 the same seed differently manured, gave respectively 54|, 63 J, 65|, 
 66^, 68f, and 76^ lbs. of fine flour from 100 of wheat, so that the kind 
 of manure applied to the land appears materially to affect the relative 
 })roportions of flour and bran. 
 
 Again, Colonel le Couteur's samples of wheat (p.489) of different va- 
 rieties, grown under the same circumstances, gave from one field 80 1 
 and 79| lbs., and from another 72| and 78^ lbs. from 100 of wheat — so 
 that upon the variety of seed soion also^ though in a less degree, the quan- 
 tity of fine flour is dependent. 
 
 § 8. Of the composition of wheaten flour. 
 
 1°. Water. — When wheat is kept for ayear it loses a little water, be- 
 coming one or two pounds a bushel lieavier than before. When put into 
 the mill and ground it becomes very hot, and gives off so much watery 
 vapour, that the flour and bran, though together nearly twice as bulky, 
 are nearly 3 per cent, lighter tlian the grain before it was ground. A 
 further loss of weight is said to take place when the flour is kept long in 
 the sack. If fine flour be slowly heated to a temperature not higher 
 than 220 for several hours, it loses a quantity of water, which, in up- 
 wards of 20 samples of English flour which I have examined, has varied 
 from 15 to 17 per cent, of the whole weight. It may, therefore, be as- 
 sumed, that English flour contains nearly a sixth part of its weight of 
 water — or every six pounds of fine flour contain nearly one pound of 
 water. 
 
 2°. Gluten, albumen, caseine, starch, gum, and sugar. — When the 
 flour of wheat is made into dough, and is then washed carefully with 
 successive portions of water upon a fine gauze or hair sieve, as long as 
 the liquid passes through milky, the flour is separated into two portions — 
 the starch, which subsides from the water, and the ^^M^e», which remains 
 in the sieve (p. 116). If the water be poured off^ after the starch has 
 subsided, and be heated nearly to boiling, it becomes troubled, and flakes 
 of vegetable albumen (p. 117) are seen to float in it. On setting aside to 
 
 • These are called respectively in London and Paris — 
 
 London. Paris. Called. 
 
 Fine flour. White flours, 1st quality, de ble. 
 
 Seconds. do. 2d do. de le gruau. 
 
 Fine middling'S. do. 3d do. de 2e gruau. 
 
 Coarse middlings. Brown meals, 4th do. de3e gruau. 
 
 Pollard. do. 5th do. de4e gruau. 
 
 Twentypenny. Bran, fine and coarse. 
 
 Bran W^aste, &c., Remoulage and Recoupe. 
 
 Page 362, and Appendix, pp. 51 and 70. 
 
SO^ STARCH, SU6AR, GUM, AND OIL, IN WHEAT. 
 
 cool, the flaky powder falls to the bottom, and may he collected, dried, 
 and weighed. If the water, after filtration, be evaporated to dryness on 
 the water bath, a residue will be obtained, Avhich consists chiefly of solu- 
 ble sugar, gum, and saline matter, with a little fatty matter, and sparingly 
 soluble caseine* (p. 117). 
 
 3°. Glutine and oil. — If, further, the crude gluten be boiled in alco- 
 hol, a solution is obtained which, on cooling, deposits a wbite flocky sub- 
 stance, having much resemblance to caseine. When the clear solution is 
 concentrated by evaporation, water separates from it an adhesive mass, 
 which consists of a substance to which the name of glutine is given, 
 mixed with a little oil. By digesting the mixed mass in ether the oil is 
 dissolved out from the glutine, and may be obtained in a pure state by 
 evaporating the ethereal solution. This oil possesses the general pro- 
 perties of the fatty oils, or of butter. As it is partly washed out, how- 
 ever, along with the starch, the whole of the fatty matter of the flour is 
 best obtained by boiling it in a considerable quantity of ether. 
 
 4°. Vegetable fibrine. — The crude gluten, after boiling in alcohol, lias 
 much resemblance to the fibre of lean beef, and has therefore been named 
 vegetable tibrine. When burned, it leaves behind an ash, containing, 
 among other substances, the phosphates of lime and magnesia, which 
 are to be considered also as among the usual constituents of wheaten 
 flour, f 
 
 Thus, fine wheaten flour, in addition to the water it contains, and to 
 the small quantity of bran which is ground up along with it, consists of 
 vegetable fibrine, albumen, caseine, glutine, starch, sugar, gum, oil or 
 fat, besides the saline substances, chiefly phosphates, which remain in 
 the form of ash, when the flour is burned. All these substances vary in 
 quantity in different samples of flour, — their relative proportions appear- 
 ing to depend upon a variety of circumstances as yet little understood. 
 In the various analyses of flour that have hitherto been published, little 
 attention has been paid to the per-centageof oil, of glutine, or of caseine, 
 which the specimens examined have severally contained. In general, 
 the weight of 4he crude gluten only lias been estimated, without extract- 
 ing from it either the oil or the glutine. 
 
 The following table exhibits the approximate composition of some 
 varieties of French and Odessa flour as determined many years ago by 
 VauquelinJ : — 
 
 * This caseine begins to form a pellicle on the surface, when the liquid is concentrated by 
 evapbralioii, and though it is generally present only in a small proportion 0-i to 1 per cent.), 
 yet the comparative quantities present in two samples of flour may be judged of by the 
 abundance in which tlie pellicle is formed. 
 
 t The saline and other inorganic matter of grain resides chiefly in the husk, as may be 
 seen by the relative quantities of ash left by the flour, bran, «fcc., of several samples of Eng- 
 lish and Foreign wlieat as determined in my laboratory — 
 
 ,„„„„„ ppnvvK ^^^ ^^^'^ ^'^'^ C-E.nr. BY DRY. 
 
 WKERE GROWN. Fine Flour. Boxings. Sharps. Bran. 
 
 1°. Sunderland Bridge, near } ■, r,A a n ro en 
 
 Durham \ :\ ^ ^^ ^'^ ""'^ ^'^ 
 
 2°. Kimblesworth, do 115 38 49 6-7 
 
 3°. Iloughall, do 0% 30 CC 71 
 
 4°. Piawsworth, do 093 27 5-5 7-6 
 
 5°. Stettin II 45 62 , f)-9 
 
 6°. Odessa 11 49 6-6 Ff) 
 
 X Dumas' Traite de Chimie, vi. p. 388. 
 
ON THE COMPOSITION OF WHEATEN FLOUR. 
 
 501 
 
 COMPOSITION OP THE FLOUR OP 
 
 French Wheat. Odessa Wheat. 
 
 ^, ^d ^^^£ "flinty ^{l^J^^^i^-' 
 
 quality, quality. B|j^-; Wheat. ^ ^licy. 
 
 Water 10 120 100 120 100 80 
 
 Gluten 110 73 101 14-6 120 120 
 
 Starch 715 720 728 565 620 70-8 
 
 Sugar 4-7 54 4-2 8-5 74 49 
 
 Gum 33 3-3 2-8 4-9 5-8 4-6 
 
 Bran _ _ _ 2-3 1-2 — 
 
 100-5 100 100 98-8 984 1003 
 
 § 9. Of the influence of soil and climate on the composition of 
 wheaten flour. 
 
 1°. The nature of the soil has a sensible influence upon the composi- 
 tion of the grain that is reaped from it. The proportion of gluten, for 
 example, is said to be generally greater in grain which is reaped from 
 calcareous soils, or from such as abound in organic matter. In the north 
 of Ireland, this flict has been observed in regard to the wheat grown in 
 the limestone districts ; and the millers of the midland counties of Eng- 
 land (on the new red sandstone) are accustomed to mix, with their native 
 com, that of the chalk districts to the east and south, for the purpose of 
 giving additional strength to their flour. 
 
 Climate. — The wheat of warm climates also is supposed usually to 
 contain more gluten. Thus flour, prepared from some Eastern wheats, 
 compared with that from others of French growth, was found to contain 
 water and dry gluten in the following proportions : 
 
 French, Saissette 
 Roche] le 
 
 Brie .... 
 Tuzelle 
 Odessa . . . . . 
 
 Taganrog* ..... 
 The quantity of gluten contained in English flour has generally been 
 stated much too high. Thus, Sir Humphrey Davyf says that he ob- 
 tained from the flour of — 
 
 Gluten, Gluten, 
 
 per cent. per cent. 
 
 English winter wheat 19 Barbary wheat 23 
 
 English spring wheat 24 Sicilian wheat 21 
 
 — and others have given numbers nearly as high. But the gluten is 
 very difficult to dry, and I believe that the large per-centage of this sub- 
 stance assigned by previous experimenters has arisen from the water not 
 being sufficiently expelled from it by prolonged heating to 220° F. I 
 select the follov^dng from a greater number of determinations, carefully 
 made in my laboratory : — 
 
 Water, 
 
 Gluten, 
 
 per cent. 
 
 per cent. 
 
 . . 15-1 
 
 12-7 
 
 . . 12-9 
 
 11-2 
 
 . . 13-5 
 
 10-7 
 
 . . 13-0 
 
 8-3 
 
 . . 13-0 
 
 15.0 
 
 . 12-6 
 
 22*7 
 
 * Taganrog, at the head of the sea of Asoph, exports the produce of the banks of the 
 Don. 
 ' Agricultural Chemistry^ Lecture III. 
 
502 INFLUENCE OF CLIMATE, VARIETY OF SEED, 
 
 Weight Water 
 per in Gluten. 
 
 KINP OF WHEAT. bushcI. Fiour. -WHERE GROVirN. 
 
 lbs. perct. perct. 
 
 Red English.. .. 62^ 17-5 81 At Sunderland Bridge, near Durham. 
 
 " " .... 62| 16-4 9-5 At Kimblesworth, near Durham. 
 
 " « 63 150 8-5 At Houghall, near Durham. 
 
 " «• .... 62| 16-8 9-9 Near North Deighton, Yorkshire. 
 
 White " .... 63 155 75 At Plavvsworth, near Durham. 
 
 " Scotch.. 61^ I6-3 9-4 At Gadgirth, near Ayr (Appendix, p. 59.) 
 
 Red Stettin 63 14 6 8 6 
 
 *' Odessa.... 61 159 US 
 
 In all these cases the quantity of gluten falls far short of that assigned to 
 English flour by Davy ; yet we may safely, I think, conclude from them 
 that English flour seldom contains more than 10 per cent, of dry gluten. 
 The flour from North Deighton, which gave 9-9 per cent, was grown 
 upon a thin limestone soil, and may perhaps owe its larger per-centage 
 to this circumstance. 
 
 But these numbers do not indicate the exact quantity of nitrogen-hold- 
 ing food which these flours contained. For in the gluten there is al- 
 ways present a variable quantity of fatty matter which contains no nitrogen, 
 and which, if extracted, would lessen considerably the weight of the glu- 
 ten in some of the flours. On the other hand, however, the water em- 
 ployed in washing out the starch holds in solution -some albumen and 
 casein, which, having the same composition, might be added to the glu- 
 ten, and would sensibly increase its weight. Thus in a sample of flour* 
 grown in Ayrshire I found — 
 
 Gluten .... 9*3 per cent. 
 
 Albumen .... 0*45 per cent. 
 
 Casein .... 0*40 per cent. 
 
 ' Making in all . . . 10-15 of substances which contain 
 
 nitrogen in nearly equal proportions. 
 
 We probably, therefore, do not greatly err in general in estimating 
 the nutritive value of wheaten flour — in so far as it depends upon these 
 nitrogenous compounds — ^by the per centage of dry gluten which a care- 
 ful washing enables us to separate from it. Further researches, how- 
 ever, which are now in progress, will throw much additional light upon 
 tliis subject. 
 
 § 10. Influence of variety of seed, of mode of culture, of time of culling, 
 and of special manures, on the composition of wheat. 
 
 1°. Variety of seed and mode of culture. — The influence of these two 
 circumstances upon the relative proportions of bran and gluten are shown 
 by the following results of the examination by Boussingaultf of several 
 varieties of wheat grown in the Botanic Garden at Paris — 
 
 liusk or Bran Flour Water Gluten, &c. 
 
 in the Grain, in tlie Grain, in the Flour, in the Flour. 
 
 per cent. per cent- per cent. per cent. 
 
 Cape wheat 19 81 70 20-6 
 
 Russian wheat '. 18 82 64 24 8 
 
 Dantzic wheat 24 76 73 25-8 
 
 Red Foix wheat 18 5 815 93 26-1 
 
 Barrel wheat 22 78 8-8 277 
 
 Winter wheat 38 62 141 33 
 
 • No. 2. Appendix, p. 171. ^ 
 
 t Annates de Chim. et de Phys. Ixv., p. 311. 
 
TIME OF CUTTING, AND SPECIAL MANURES. 503 
 
 In all the samples the bran and gluten are both very high, but they 
 vary much in the several varieties. 
 
 The gluten includes the albumen and casein and other substances con- 
 taining nitrogen, but even though grown in the rich soil of a botanic gar- 
 den, I fear the sum of these has been estimated much too high.* The 
 same variety of wheat grown in the open fields in Alsace gave 17'3 of 
 gluten, and in the Botanic Garden of Paris, 26-7 of gluten. 
 
 2°. The time of cutting affects the weight of produce, as well as the 
 relative proportions of flour, bran, and gluten. Thus from 3 equal patch- 
 es of the same field of wheat upon thin limestone soil at North Deighton, 
 in Yorkshire, cut respectively 20 daj'^s before the crop was fully ripe, 10 
 days before ripeness, and when fully ripe, the produce was in grain — 
 20 days before. 10 days before. Fully ripe. 
 
 166 lbs. 220 lbs. 209 lbs. 
 
 and the per-ccntage of flour, sharps, and bran, yielded by each, and of 
 water and gluten in the flour, was as follows : — 
 
 IN THE GRAIN PER CENT. IN THE FLOUR PER CENT. 
 WHEN CUT. , " ^-v , • ^ 
 
 Flour. Sharps. Bran. Water. Gluten. 
 
 20 days before it was ripe 747 72 17-5 157 9-3 
 
 10 days before 791 55 132 155 99 
 
 Fully ripe 72-2 110 160 15 9 96 
 
 When cut a fortnight before it is ripe, therefore, the entire produce o^ 
 grain is greater, the yield of flour is larger, and of bran considerably less, 
 while the proportion of gluten contained in the flour appears also to be 
 in favour of that which was reaped before the corn was fully ripe.f 
 
 3°. Special ynanures. — It is said that the employment of manures 
 which are rich in nitrogen not only causes a larger crop, but also produ- 
 ces a grain which is much richer in gluten. The experiments which 
 have hitherto been chiefly relied upon in proof of this result are those of 
 Hermbstadt. On ten patches, each 100 square feet, of the same soil (a 
 sandy loam) manured with equal weights of different manures in the dry 
 state, he sowed equal quantities (J^ lb.) of the same wheat — collected, 
 weighed, and analysed the produce. His results are represented in the 
 following table : — 
 
 ™ a .IB 
 
 _: ^ G.. ». re- <o . g. .iSb<«T3 
 
 "O ^. Oibc ^bo aaj Mtij gbD feho ujajg j-qj 
 
 X _o — o -S3 "^d u °a -—3 <23 I'S 33 
 
 Ojd "(Cm w^ O-a K 3 ffi-a Pht3 Ot3 > a ^a 
 
 Keturn 14 fold. 14 fold. 1-2 fold. 12 fold. 12 fold. 10 fold. 9fold. 7 fold. 5 fold. 3 fold. 
 
 Water 4-3 4-2 4-2 4-3 4-2 4-3 4-3 4-2 4-2 4-2 
 
 •9 32-9 35-1 137 12-2 12-0 96 9-2 
 
 ■3 1-3 1-4 l-I 0-9 1-0 0-8 07 
 
 •8 42-4 39-9 61-6 632 62-3 65-9 666 
 
 •5 1-5 1-4 1-6 1-9 1-9 1-9 1-9 
 
 •5 1-5 1-6 1-6 1-9 1-9 1-6 IB 
 
 •0 09 1-0 1-0 0-9 ro 1-0 1-0 
 
 •7 07 0-9 0-6 0-5 05 0-5 0-3 
 •8 14-2 14-2 14-0 14-0 14-9 14-0 14-0 
 
 Gluten 34-2 339 32 
 
 Albumen l-O 1-3 ! 
 
 Starch 41-3 41-4 42 
 
 Sugar 1-9 1-6 1 
 
 Gum 1-8 1-6 1 
 
 FattyOil 09 M 1 
 
 SolublePhosphates,&c. 0-5 0-6 
 
 Husk and bran 13-9 14-0 13 
 
 99-8 997 997 997 997 99-6 99-8 997 99-8 997 
 The large per-centage of gluten obtained by the use of the first five 
 
 * In these flours the gluten was not determined by washing out the starch, but by a more 
 refined method of ultimate analysis, as it is called, by which the per-centage of nitrogen is 
 determined, and the proportion of gluten, &c., calculated from this. When the per-centage 
 of nitrogen is small, as in wheaten flour, this method is open to many sources of error. 
 
 ' See a paper by Mr. John Hannam, Quarterly Journal of Agriculture, Iviii., p. 173. 
 
604 EFFECTS OF GERMINATION AND BAKING 
 
 manures is very striking, if the determinations are really to be depended 
 upon. They are certainly interesting in a theoretical point of view, and 
 are deserving of careful repetition. In reference to their bearing upon 
 practical farming, however, it must not be forgotten, that the results of 
 small experiments are never fully borne out when they are repeated on 
 the large scale — that the relative value of different animal manures is 
 materially affected by the kind of food on which the animal has lived — 
 that independent of manures, there are circumstances not yet made out 
 which materially affect the produce of single patches* — and that it will 
 rarely be in the power of the practical farmer to apply at pleasure to his 
 fields the relative proportions of the several manures used by Hermb- 
 stadt. Thus, if instead of 20 tons of farm-yard manure he wished to 
 try blood or urine alone, he must apply 24 tons of the former, and 70 
 tons of the latter — quantities which it might be both difficult to procure 
 and inconvenient to apply. 
 
 The most practically useful results yet published in regard to the ac- 
 tion of the different manures upon the weight of the crop, the proportion 
 of flour yielded by it, and of gluten in the flour, are those of Mr. Burnet, 
 to which I have already had occasion to draw your attention. f These 
 results were as follow : — 
 
 i^TMT^ nr. TiTAviTTTJi:. Produce Fine Flour Gluten 
 
 KIND OP MANURE. p^^. ^^^^ ^^^^ ^j^^ ^^^.^ .^ ^j^^ ^^^^^ 
 
 Nothing . . . . ; • , . . 31| bshls. 76| lbs. 9-4 per cent. 
 
 Snlphated urine and wood ashes. 40 " 66^ '* 10-5 " 
 
 Do. and sulphate of soda. 49 " 63^" ■ 9-7 " 
 
 Do. and common salt. . 49 " 65| " 9-6 " 
 
 Do. and nitrate of soda. . 48^ " 54| *' lO'O " 
 
 We perceive here a slight increase in the per-centage of gluten when 
 the manures were applied, but nothing which at all resembles the great 
 differences given by Hermbsatdt, or which renders it probable that by 
 skilful management, as some have supposed, we may hereafter be 
 able to raise in our fields whole crops of corn -which shall yield a flour 
 containing 20 or 30 per cent, of gluten. 
 
 § 11. Of the effecfs of germination, and of baking, ujjon the jiour of wheat. 
 
 The effects of germination and of baking upon the flour of wheat are 
 very analogous to each other. In both cases, a portion of the starch is 
 changed into gum and sugar. 
 
 1°. Germination. — I have already described to you (p. 118), the very 
 beautiful change which takes place during the sprouting of the seeds of 
 plants — how a portion of their gluten is changed into diastase, and how, 
 by the agency of this diastase, the starch of the seed is changed into gum 
 and sugar. In an experiment made by De Saussure, 100 parts of the 
 farina of wheat had by germination lost 6 parts of starch, and in their 
 stead had acquired 3i of gum and 2i of sugar. The effect of this 
 change — which proceeds as the plant continues to grow — is to make the 
 starch soluble, and thus capable of entering into the circulation of the 
 young plant. 
 
 2°. Baking. — It is the larger proportion of gluten usually contained 
 in the flour of wheat that renders it so much better fitted for the bakin? of 
 
 • See Appendix, pp. 59 and 79. T See p. 362 and Appendix pp. 49 and 71. 
 
UPON THE TLOUR OF WHEAT* 505 
 
 bread than the flour of any other grain. If the gluten be washed out of 
 the flour, and put alone into the oven, it will swell up, become full of 
 pores, and assume a large size. The comparative baking qualities 
 of different samples of flour may be judged of by the height to jvhich, in 
 similar vessels, the gluten of equal weights of flour is thus observed to rise. 
 
 We have already seen that by heating in an oven, dry starch is gra- 
 dually changed into gum {British gum, p. 113), and into a species of 
 sugar — becoming completely soluble in water. Such a change is pro- 
 duced upon a portion of the starch of wheaten flour when it is baked in 
 the oven. Thus in 100 parts of the flour, and of the bread of the same 
 wheat, Vogel found respectively — 
 
 Starch. Sugar. Gum. 
 
 Flour ... 68 5 — 
 
 Bread . . .53^ 3^ 18 
 
 So that a very considerable portion of gum had been produced at the ex- 
 pense of the starch. 
 
 The yeast which is added to the dough in baking, acts in the same 
 way as when it is added to the sweet wort of the brewer. It induces a 
 fermentation by which the sugar of the flour is changed into carbonic 
 acid and alcohol. The carbonic acid is liberated in the form of minute 
 bubbles of gas throughout the whole substance of the dough and causes 
 it to rise, the alcohol is distilled off" in the oven. If too much water 
 have been added to the dough — or if it have not been sufficiently knead- 
 ed — or if the flour be too finely ground — or if the paste be not sufficiently 
 tenacious in its nature, these minute bubbles will run into each other, 
 will form large air holes in the heart of the bread, and will give it that 
 open irregularly porous appearance so much disliked by the skilful 
 baker. Good bread should be full of small pores and uniformly light. 
 Such bread is produced by a. strong flour ; that is, one which will rise well, 
 will retain its bulk, and will bear the largest quantity of water. 
 
 The quantity of water which wheaten flour retains when baked into 
 bread depends in some degree upon the quality of the flour. In the 
 Acts of Parliament relating to the assize of bread, it is assumed that a 
 sack of flour (280 lbs.) will produce 80 quartern loaves, or 320 lbs. of 
 bread. According to this calculation the flour should take up and retain 
 when baked one-seventh of its weight of water. But the quantity of water 
 retained by the flour now in use is very much greater, and the profit to 
 the baker, therefore, very much more than this calculation supposes. 
 
 This is shown by the quantity of water v^hich is lost by wheaten 
 bread, whether of first or second quality, when it is dried by prolonging 
 heating, 'at a temperature not exceeding 220° F. The home-made 
 bread (white and brown) baked in my own house, and in two other 
 private houses in Durham, lost of water by drying in this way — 
 
 How lopg baked. Water per sent. 
 
 1°. White . . . 24 hours. 43-3 
 
 Brown* 
 
 2°. Brown 
 
 White 
 
 3°. White 
 
 24 do. 44-0 
 
 42 do. 44-1 
 
 36 do. 42-9 
 
 9 do. 44-1 
 
 " The brown bread is made from the whole grain of the wheat as it comes from the 
 miUstones— nothing being separated by sifting. 
 
506 WATER TAKEN UP BY FLOUR IN BAKING. 
 
 So that wheaten bread one day old contains about 44, and two days old, 
 about 43 per cent, of water. Something, however, will depend upon 
 the size of the loaves. 
 
 This proportion is almost exactly the same as that contained in the 
 white bread of Paris. According to Dumas, the water in tho conixiion 
 white bread of Paris amounts to — 
 
 Hours baked. Water per cent. 
 
 2 45-7 
 
 4i 45-3 
 
 10 43-0 
 
 24 . 43-5 
 
 We m.ay assume, therefore, 44 per cent, as very nearly the average 
 quantity of water contained in good white bread both in England and in 
 France. Bread baked for public establishments contains more water,; — 
 not being generally so well fired, or being baked in tlie form of miany 
 loaves stuck together, instead of in separate tins, as is done- with home- 
 made bread. Such is the case with the soldiers' bread of our own 
 country, and the barrack bread of Paris (pain de munition) which con- 
 tains about 51 per cent, of water. 
 
 We have already seen (p. 499) that English wheaten flour contains, on 
 an average,- about 16 per cent, of water. If, therefore, tlie bread baked 
 from it, as it comes from the mill, contain 44 per cent., every hundred 
 pounds consist of — 
 
 Dry flour . . . . • . 56 ) ^^^ 
 
 Water in the flour (naturally) . lOJ J 2 
 
 Water added by the baker . .'" . . 33i 
 
 100 
 Or^ the flour, in baking, takes up half its iveight of water. A hundred 
 pounds of flour, therefore, as it comes from the mill, will give very 
 nearly 150 pounds of bread. Thus — 
 
 Flour contains Bread contains 
 
 Dry flour .... 84 84 
 
 Natural water ... 16 16 
 
 Water added . . 50 
 
 100 
 
 Weight of bread 150 
 A sack of flour, therefore, or 280 lbs., ought to give about 420 lbs. of 
 well baked bread. Something must be deducted from this for the loss 
 by fermentation, and for the dryness of the crusts. Allowing 5 per cent, 
 far these, a sack of flour should give 400 lbs. of bread of the best quality,* 
 or 100 quartern loaves. The cost of fine white bread, therefore, com- 
 pared with that of corn and flour,'^ought to be very nearly as follows : — 
 
 Cost of Flour, Cost of Bread, Market price of 
 
 per sack. per stone. ' per quartern loaf. Grain per qr.f 
 
 35s. Is. 9d. 4]d. 47s. 
 
 40s. 2s. Od. 4|d. 62s. 
 
 * Unmixed with potatoes, which are employed by many bakers in considerable quantity . 
 Mixed with the yeast tliey are said to make the bread lighter. 
 
 t This column has been calculated for me, from the price of the flour, by my friend Mr. 
 John Robson, miller, in Durham. The practical rule is, that 6 bushels ol corn should give 
 one sack of flour, and that the miller should have the offal for his trouble. 
 
RELATIVE COST OF CORN, FLOUR, AND BREAD. 507 
 
 Cost of Flour, 
 er sack. per stone. 
 45s. 2s. 3d. 
 
 Cost of Bread, 
 
 per quartern loaf. 
 
 5fd. 
 
 Market price of 
 Grain per qr. 
 60s. 
 
 50s. 
 
 2s. 6d. 
 
 6d. 
 
 
 67s. 
 
 55s. 
 
 2s. 9d, 
 
 6id. 
 
 
 72s. 
 
 60s. 
 
 3s. Od. 
 
 7id. 
 
 
 80s. 
 
 The economy of baking at home, therefore, at the usual prices of 
 bread, seems to be very considerable. 
 
 § 12. Of the supposed relation between the per-centage of gluten in 
 Jlour, and the iveight of bread obtained from it. 
 It has been assumed by recent chemical writers that the quantity of 
 water absorbed by flour, and consequently the weight of bread obtained 
 from it, depends, in whole or in great part, upon the proportion of gluten 
 which the flour contains. The following facts, however, do not accord 
 with this supposition. 
 
 1°. Household bread, made respectively from the flour of a French 
 wheat and of a wheat from Taganrog, retained nearly the same per- 
 centage of water, though the one sample contained upwards of twice as 
 much gluten as the other. Thus — 
 
 Gluten per cent. Water per cent, 
 
 in the Flour. in the Bread. 
 
 Flour of Brie . . . 10-7 47-4 
 
 Flour of Taganrog . . 22-7 47-0 
 
 This one fact might be supposed to settle the question, but I shall 
 mention others. 
 
 2°. The flour from Odessa wheat contains about jth more gluten than 
 French flour in general, and yet it absorbs very little more water (Du- 
 mas). This Dumas accounts for by the fact that the starch of tlie 
 Odessa wheat forms hard transparent horny particles, which take less 
 water to moisten them than the impalj)able powder yielded by the softer 
 French wheats — so that the gluten does not appear to produce its full 
 efTect. I do not know how far this explanation is consistent with the 
 fact that the hard flinty wheats give the best biscuit flour — what the 
 baker calls the strongest, which rises best, and absorbs the most water.* 
 
 3°. Rice is said to contain very little gluten — not estimated by any to 
 amount to more than 6 or 7 per cent. — and yet it is stated as the result of 
 numerous trials, that an admixture of a seventh part of rice flour causes 
 wheaten flour to absorb more water. f 
 
 4°. If the hard wheats be ground too fine they lose a part of their ap- 
 parent strength, th*e flour becomes dead, as it is sometimes called, and 
 refuses to rise as it would do if sent to the baker in a more gritty and less 
 impalpable state. 
 
 5°. Lastly, the admixture of very minute quantities of foreign matter, 
 by way of adulteratioa, is said to have a remarkable influence upon the 
 quantity of water which the flour will absorb. In some parts of Belgium 
 it appears to have been the practice to adulterate the bread with a small 
 quantity of sulphate of copper.J This salt is dissolved in water, and 
 
 * That such is the case also in foreign countries, see a letter from the British ConBul at 
 Lisbon, in Davy's Agriculturcd Chemistry, Lecture IIL 
 t Dumas' Traite de Chimie, vi., p. 396. 
 X Blue vitriol — ^a violent poison. 
 
508 COMPOSITION OF BARLEY. 
 
 the solution added to the water with which the dough is to he made, i:i 
 the proportion of about one grain to two pounds of flour. It gives the 
 bread a fairer colour, and thus permits the use of inferior flour, and it causes 
 the bread to retain about six per cent, more water without appearing moist- 
 er. Even in the small proportion of one grain of the sulphate to 6, or 
 7 lbs. of flour, it produces a very sensible effect (Kuhlman). 
 
 Other adulterations also exercise a similar influence. Alum improves 
 the colour of the bread, raises it well, and causes it to keep water, but it 
 requires to be added in larger quantity than the more poisonous sulphate 
 of copper. Common salt likewise makes the paste stronger, and 
 causes it to retain more water, so tliat the addition of salt is a real gain 
 to the baker. 
 
 From all these facts, therefore, we may infer that, independent of the 
 relative proportions of gluten, very slight differences in composition — 
 such as have not yet been sought for or appreciated — may materially 
 affect the relative weights of bread obtained by the baker from diflerent 
 samples of wheaten flour. 
 
 § 13. Of the composition of barley, and the influence of different manures 
 upon the relative proportions of its several constituents. 
 
 The grain of barley consists of nearly the same substances as that of 
 wheat, but in proportions somewhat different. These proportions, how- 
 ever, are affected both by the kind of manure with which the land is 
 dressed, and by the nature of the soil on which the seed is sown. 
 
 1°. Manure. — The effect of manure appears from the following table, 
 containing the results of Hermbstadt, obtained in the same way as those 
 with wheat already described (p. 503) : — 
 
 KIND OP 2 ■^ S a a 2 ^ B aS^ ^^"^ 
 
 MANURE. ^ l-alfs ^= = -ii^O^^S 
 
 OxBlood 10-4 13-6 5-7 0-4 599 4-6 4-4 04 0-4 16 
 
 Night-soil 10-2 13-6 5-8 0-5 59-6 4-5 4-3 0-5 0-6 13 
 
 Sheep's dnng... 10-3 13-5 5-7 0-4 59-9 4-6 4-4 0-4 0-3 16 
 
 Goat'sdung^... 10-4 135 5-7 0-4 59-9 4-6 4-5 0-4 0-3 15 
 
 Human urine... 10-3 13-6 5-9 0-5 59-6 4-4 4-4 0-4 0-7 13V 
 
 Horsedung 10-4 13-5 5-7 0-4 59-7 4-6 4*5 0-4 0-4 13" 
 
 Pigeon's dung.. 10-4 13-5 5-6 0-4 59-8 4-6 4-5 0-4 0-4 10 
 
 Cow'sdung 10-8 13-6 3-3 0-2 61-9 4-8 4-6 0-3 0-3 11 
 
 Veget. manure.. 10-8 13-6 2-9 0-2 62-2 4*9 4-8 0-2 0-1 7 
 
 No manure 10 8 13-6 2-9 01 62-5 5*0 4'7 0-1 0-1 4 
 
 In SO far as reliance is to be placed upon the numbers in the above 
 table, as indicative of the general.effect of the several manures men- 
 tioned, it would appear that the relative proportions of gluten, albumen, 
 and starch do not vary very much until we come to cow-dung, when the 
 former two substances sensibly diminish. Further experiments, how- 
 ever, are required upon this subject (see page 514). 
 
 2°. Soil. — The effect of soil upon the barley crop is known to all 
 practical farmers — so that the terms barley-land and wheat-land are the 
 usual designations for light and heavy soils adapted especially to the 
 growth of these several crops. On clay lands the produce of barley is 
 greater, but it is of a coarser quality, and does not malt so well — on 
 loams it is plump and full of meal — and on light chalk soils the crop is 
 light, but the grain is thin in the skin, of a rich colour, and well adapted 
 
EFFECT OF MALTING UPON BARLEY. 509 
 
 for malting.* The barley of the light lands in Norfolk is celebrated in the 
 North of England fpr its malting properties — and the brewers refuse tlie 
 barley of the county of Durham, even at a lower price, when Norfolk 
 barley is in the market. Wlien unfit for malting, barley affords a fat- 
 tening food for pigs and for some other kinds of stock. 
 
 § 14. Effect of malting upon barley. 
 
 During the germination good barley increases in bulk one-half. In 
 order that it may do so, it must be uniforfnly ripe — a quality of great 
 value to the maltster. This maximum bulk is generally acquired in 24 
 hours after it has been moistened and laid in heaps. In drying, how- 
 ever, the barley again diminishes in bulk, so that the dried malt rarely 
 exceeds bj'- more than ^-^th or f^th the bulk of the grain as it came from 
 the market. The well-dried malt, however, is lighter by |th tnan the 
 barley from wliich it is made — 100 lbs. of barley yielding about 80 lbs. 
 of malt. This is not all loss of substance, since by a similar drying the 
 barley itself before malting would lose about 12 per cent of water. The 
 loss of substance, therefore, is only about 8 per cent. This diminution 
 of solid matter arises in part from the loss of the little roots which form 
 the malt-dust {cummins), of which I have already spoken (p. 436) as 
 being a valuable manure, and of which 4 or 5 bushels are obtained from 
 100 bushels of barley. 
 
 The colour of the malt varies with the temperature at which it is dried. 
 If the heat does not exceed 100° F. a very pale malt is obtained, which 
 gives a very white beer. A heat not rising above 180° gives an amber 
 coloured malt — while for brown malt the temperature may rise as high 
 as 260° F. By mixing these varieties beer of any colour may be made. 
 But in the porter breweries it is usual to prepare a quantity of malt of a 
 brownish black colour [burned malt), by adding a portion of which any 
 required shade of colour is imparted to the liquor. 
 
 During gemiination a variable quantity of the gluten is converted into 
 diastase (p. 119), and about two-fifths (40 per cent.) of its starch into 
 sugar or gum (dextrine). The quantity of diastase produced depends 
 upon the extent to which the germination has proceeded. It is greatest 
 at the moment when the gemmule is about to burst from the seed, and to 
 form the young shoot. 
 
 I have already explained the beautiful purpose served by this diastase 
 in converting the insoluble starch of the grain into soluble sugar and 
 gum. When the beer is to be made wholly from malt, it is unnecessary 
 to continue the germination till the largest quantity of diastase is pro- 
 duced. It is sufficient if the gemmule, on holding up a grain of the 
 barley, be seen within the skin to have attained one-half or two-thirds of 
 the length of the seed. The diastase then produced is more than enough 
 to convert the who4e of the starch of the grain into sugar (p. 120). But 
 if raw grain, as in some of our distilleries, is to be added to the malt, 
 then the malting should be prolonged till the bud is about to burst through 
 the husk, so that the largest possible supply of diastase may be contain- 
 ed in it. In this way also malt is prepared when it is to be employed 
 
 • *' The barley on the compact clays (in Hants) is of a coarser quality, but produce greater — 
 pn the light chalk soils it is well calculated for malting— the skin is thin, and colour rich but 
 light — in fullness of meal and plumpness of appoai-ance it never equals I he barleys grown ia 
 Staffordshire, and upon loamy lands." — Mr. Gawler in British Htisbandry, iii. p. 12. 
 
 oo 
 
510 COMPOSITION OF OATS AND RYE. 
 
 in the manufacture of syrup {glucose) from potatoe flour — a branch of in- 
 dustry which has become of some 'mportance in certain parts of Fraace. 
 
 § 15. Composition of oats, and effect of manures in modifying that composition. 
 
 The relative proportions of husk and meal in the several varieties of 
 the oat differ in a greater degree, probably, than in any other grain. 
 Thus, the potatoe-oat is known to be richer in meal, the Tartary-oat in 
 husk. The round grain of the former is chiefly grown in Scotland, for 
 grinding into meal, the latter in England, for feeding horses. 
 
 But even the round potatoe-oat varies much in the produce of meal 
 which it gives. Many samples yield only half their weight of oatmeal, 
 others 9 stones out of 16, while some give as much as 12 stones from the 
 same quantity, or three-fourths of their weight. In one variety of oat 
 Vogel found 66 per cent, of meal and 34 of husk, which is equal to 10^ 
 stones of meal from 16 of grain. He also extracted from the meal 2 per 
 cent, of oil, and 59 of starch, and observed it to lose by drying upwards 
 of 20 per cent, of water. 
 
 Soil, season, climate, variety of seed sown, and the kind and quantity 
 of manure applied — all affect the amount of produce and the chemical 
 composition of the oats that are reaped. According to Hermbstadt, the 
 effect of different manures in modifying the composition of the produce 
 
 of the same seed are represented by the numbers in the following table : 
 
 • • a> .^ p- *^^ 
 
 KIND OP S. -^Saripcae ■SmSs^'o 
 
 MANURE. ^ 3 =£■" ca g' 3 — "S^^^s^^S 
 
 !? KC5<5S»JtBOO acP-i'5,«a PS<Sm 
 
 OxBlood 120 19-3 5-0 0-4 53-1 3-8 5-5 0-3 . 0-4 12^ 
 
 Night-soil 12-1 19-2 4-6 0*4 53-3 3-8 5-4 0-3 0-5 14| 
 
 Sheep's dung... 12-6 13-3 4-0 0-5 540 5-2 5-5 0-3 0-4 14 
 
 Goat'sdiing 12-9 170 4-3 0-4 53-2 5-4 5-7 0-3 0-4 15 
 
 Human urine... 130 17-0 44 05 53-1 50 5-7 0-4 06 13 
 
 Horsedung 131 160 40 05 545 52 5-6 03 0-5 14 
 
 Pigeon's dung .. 12-3 18-3 3-2 0-3 53-2 5-0 6-8 0-3 0-3 12 
 
 Cowdung 11-6 150 3-1 0-3 55-0 6-8 73 03 0-3 16 
 
 Veget. manure.. 10-8 13-0 20 0-2 599 6-4 70 0-2 0-2 13 
 
 Unmanured 10 8 120 1-9 02 600 64 70 03 0-1 5 
 
 The differences in this table are very striliing [see p. 515]. 
 
 § 16. Composition of rye, and effect of different manures upon its composition. 
 The grain of rye approaches nearest to that of wheat in the quantity 
 of gluten it contains, and in the consequent fitness of its flour for baking 
 into bread. It sometimes also contains much sugar — recent rye-bread 
 having almost invariably a sweet taste — but the proportion of sugar ap- 
 pears to be by no means constant. Thus Einhof and Greif exhibit the 
 composition of a sample of rye-flour, examined by each of them, re- 
 spectively as follows : — 
 
 Einhof, per cent. Grief, per cent. 
 
 12-8 
 
 3-0 
 
 58-8 
 
 10-4 
 
 7-2 
 
 7-8 
 
 100 100 
 
 Husk . 
 
 . 6-4 
 
 Gluten (not dried) 
 
 9-5 
 
 Albumen 
 
 3-3 
 
 Starch . . 
 
 61-1 
 
 Sugar . . 
 
 3-3 
 
 Gum . . 
 
 IM 
 
 Loss ... 
 
 5-3 
 
COMPOSITION or RICE. ^ 511 
 
 Perhaps no great degree of faith is to be placed in these analyses. If 
 they are to be depended upon, they show that very remarkable differ- 
 ences indeed may exist in the relative proportions of some of the consti- 
 tuents of rye flour. The flour of rye is said to be more absorbent of 
 moisture from the air than that of any other grain.* 
 
 Rye delights in a sandy soil, and is cultivated in general in such as 
 are poor in vegetable matter, and to which manure is not very abun- 
 dantly added. The experiments of Hermbstadt, whose results are ex- 
 hibited in the following table, do not show any very striking difference 
 to have been produced upon the composition of the grain by the use of 
 the different animal manures : — 
 
 j-.c Si ti —OTCo 
 
 KIND OP S M S3fl2 rtS aS- s-H-a 
 
 MANURE. ^ 3 2 S <" S 3 3 ^ 'o S ^ O V u Z 
 
 OxBlood 10 1 10-4 120 36 52-2 3 
 
 Night-soil 100 10-7 11-9 3-2 524 3 
 
 Sheep's dung... 100 10-8 11-9 3-4 523 3 
 
 Goat'sdung. ... 10-0 108 II 9 34 52-2 3 
 
 Human urine... 101 10-8 120 3-5 50-2 3 
 
 Horsedung 100 107 11-9 28 51-2 4 
 
 Pigeon's dung .. 101 10-5 11-6 3-7 52-2 3 
 
 Cowdung 10-0 10-4 10-8 2-0 54-3 3 
 
 Veget. manure,. 10 10-7 88 2-6 551 4 
 
 Unmanured 10 101 8-6 2-6 563 4 
 
 6 6-2 1-0 0-8 14 
 
 5 6-3 0-9 0-9 13i 
 
 6 61 1-1 0-6 13 
 5 6-0 10 0-9 12| 
 3 4-6 1-1 4-2 13 
 4-6 1-0 3-6 11 
 
 7 4-7 0-9 2-3 9 
 9 5-7 09 1-8 9 
 
 8 5-2 0-9 1-7 6 
 7 5-4 0-9 1-3 4 
 
 The above table exhibits a larger increase in the return or produce 
 from some of the animal manures than from others, but we do not see 
 any of those reinarkable differences in the composition of the flour, which 
 are observable in the results obtained by the application of different 
 manures to the wheat crop. 
 
 The substance extracted from rye, and called gluten by Hermbstadt, is 
 different from the gluten of wheat, and is more like the gbitine extracted 
 from the latter grain. When dough made of rye flour is washed in 
 water, it nearly all diffuses itself through the liquid, leaving little more 
 than the husk or bran behind. The starch deposits itself from the milky 
 liquid, or may be separated by the filter. When the liquid is evaporated 
 to dryness, and the dry mass boiled in alcohol, the so-called gluten is 
 dissolved out, and may be separated from the alcohol by distillation. It 
 must then be washed with water to free it from sugar. Like the gluten 
 of wheat, it is now insoluble in water, and is less cohesive than gluten. 
 Both of these forms of gluten are supposed to have the same composi- 
 tion as vegetable fibrin and albumen, and as the curd of milk. 
 
 § 17. Composition of rice, maize {Indian corri), and buck-wheat. 
 
 1°. Rice is usually supposed to differ from other kinds of grain by the 
 larger proportion of starch which it contains. 
 
 The large quantities of rice consumed by the native inhabitants of 
 India, and of other warm countries, has often appeared surprizing to 
 foreigners. Chemists have explained this alleged fact by supposing the 
 small per-centage of gluten contained in rice, as shown by the following 
 analyses, to be insufficient for the sustenance of the body — when no 
 other food is used — unless this grain be eaten in exceedingly large quan- 
 
 * A sample of rye meal, dried in my laboratory, lost only 14>^ per cent, of water, and of 
 rye bread leavened 44, and yeasted 46 per cent This rye meal may possibly have been 
 mixed. 
 
il2 
 
 OP MAIZE OR INDIAN CORN. 
 
 titles. It is probable, however, that the nitrogenous constituents of rice 
 are stated too low in the analyses of Braconnot, and that it contains albu- 
 men or casein, or some analogous substance, which has been passed over 
 by this chemist. A series of carefully repeated analyses of different 
 varieties of rice, if it did not modify, would at least fix our present opin- 
 ions in regard to its theoretical value as food for man.* 
 
 Two samples of rice examined by Braconnot, were found by him to 
 
 be composed of — 
 
 Carolina. Piedmont. 
 
 Water .... 5-0 7-0 
 
 Husk .... 4-8 • 4-8 
 
 Gluten .... 3-6 3-6 
 
 Starch .... 85-07 83-8 
 
 Sugar .... 0-3 0-05 
 
 Gum .... 0-7 0-1 
 
 on 0-13 0-25 
 
 Phosphates . . 0-4 0-4 
 
 100 100 
 
 2°. Maize or Indian corn is celebrated for the large return of food 
 which it yields from a given extent of land, and for its remarkably fat- 
 tening qualities when given to poultry, pigs, and cattle. Buckwheat 
 is also a very nourishing grain. They consist respectively of — 
 
 
 Dry maize (Pay en). 
 
 Buckwheat (Zenneck). 
 
 Husk . . . 
 
 5-0 
 
 26-9 
 
 Gluten, &c. 
 
 1-2 
 
 10-7 
 
 Starch 
 
 7-1 
 
 52-3 
 
 Sugar and gum 
 
 . ■ 0-5 
 
 8-3 
 
 Fatty matter 
 
 8-9 
 
 0-4 
 
 Colouring matter 
 
 . 5-05 
 
 — 
 
 Salts 
 
 1-8 
 
 7 
 
 24-53f 98-6 
 
 The above-analysis of maize must be incorrect, as it supposes the fatty 
 matter to amount to nearly 36 per cent, of the weight of the corn. 
 Dumas has lately stated it at 8-9 per cent. — instead of 8-9 in 24-65 parts, 
 as found by Pay en — and Liebig denies that Indian corn contains more 
 than 5 per cent, of fatty matter. New analyses, therefore, are required 
 of this grain also. Indeed it may be said in general of all the substances 
 used, especially in feeding animals, that we have not yet the requisite 
 knowledge to enable us to reason accurately in regard to the special ope- 
 ration of each in sustaining the body or in promoting the growth of fat.J 
 
 * Five varieties of rice, as it is sold in the shops, examined in my laboratory, lost of water 
 and gave of ash per cent, respectively — 
 
 Water. Ash. Water. Ash. 
 
 Madras rice .... 135 058 Carolina rice . . . 130 0-33 
 
 Bengal rice .... 131 0-45 Do. flour . . 146 035 
 
 Patna rice .... 131 0-36 
 
 The water in these samples is very much greater than in those examined by Braconnot. By 
 exposure to the air the rice in a few days re-absorbed nearly all it had lost by drying. The 
 ash of rice contains more alkaline matter than that of wheat, and is very difficult to burn white. 
 
 t Dumas, Traite de Chimie, vi., p. 394. 
 
 t A sample of Indian corn examined in my laboratory, lost of water 13-6 per cent, and 
 left of white earthy ash 1-3 per cent. 
 
GENERAL EFFECT OF MANURES. 513 
 
 § 18. On the alleged general effect of different manures in modifying the 
 amount of gluten and albumen in wheat, barley, oats, and rye. 
 
 Among the general deductions in regard to the special influence of 
 manures upon the quality of the grain we reap, that which has been re- 
 ceived with the greatest confidence is this — that the richer in nitrogen the 
 manure we apply, the richer in gluten the grain we reap. 
 
 The only experiments, having any pretensions to accuracy, by which 
 this opinion has hitherto been supported, are those of Hermbstadt. The 
 results of these experiments are contained in the four tables to which I 
 have directed your attention under the heads of wheat, barley, oats, and 
 rye. As the opinion founded upon them is one which, if correct, is of 
 great practical value, — it will be proper to examine the experiments them- 
 selves a little more narrowly. Are they really deserving of implicit 
 credit ? Do they justify the conclusion that has been drawn from them ? 
 
 Turn first to the experiments upon wheat, of wliich the results are 
 embodied in the following table, repeated from page 503 : — 
 
 OS 
 
 Return 14 fold. 
 
 Water 4-3 
 
 Gluten 34-2 
 
 Albumen 1*0 
 
 Starch 41-3 
 
 Sugar 1-9 
 
 Gum 1-8 
 
 Fatty Oil 0-9 
 
 SoUiblePhosphates,&c. 0*5 
 Husk and bran 13-9 
 
 99-8 99-7 99-7 997 99-7 99-6 99-8 99-7 99-8 99-7 
 1°. Water present. — The water in each of these 10 specimens of grain 
 was nearly the same, about A\ per cent. I have already stated the quan- 
 tity of water in English flour to amount to about 16 per cent, on an ave- 
 rage. Many samples of wheat also have been dried in my laboratory. 
 From the results I extract the following, showing the water lost by corn 
 grown in four different parts of the world : — 
 
 EngUsh, Lammas red 15-1 per cent. 
 
 Seminoff wheat . 13-2 " 
 
 St. Petersburg . . 16-1 «' 
 
 Btirletta wheat 13-1 " 
 
 This weight of water is lost when the grain, as it is sold in the market, 
 is crushed and then heated to a temperature not exceeding 220° as long 
 - as it loses weight. 
 
 The above quantities of water are very much greater than those found 
 in the wheats of Hermbstadt. I cannot offer these results, however, as a 
 _proq/' of inaccuracy on the part of this experimenter, as I have not had 
 access to his original memoir. It is only fair towards him, therefore, to 
 conclude that, before they were subjected to analysis, his wheats had been 
 artificially dried in a very considerable degree. 
 
 2°. oil in the different samples. — Again, it appears remarkable that 
 the quantity of oil in all the samples of wheat in the above table is nearly 
 identical, and is also very small. I have examined the fine flour yielded 
 by several samples of the same wheat, grown by Mr. Burnet, of Gad- 
 
 ►? o 
 
 0; be 
 
 s: 3 
 02 -a 
 
 O 3 
 
 CO ■ 
 
 
 2f 
 
 
 '"-3 S 
 
 > s 
 
 P a 
 
 14 fold. 
 
 12 fold. 
 
 12 fold. 
 
 12 fold. 
 
 10 fold. 
 
 9 fold. 
 
 7 fold. 
 
 5 fold. 
 
 3 fold. 
 
 4-2 
 
 4-2 
 
 4-3 
 
 4-2 
 
 4-3 
 
 4-3 
 
 4 
 
 2 
 
 4-2 
 
 4-2 
 
 33-9 
 
 32-9 
 
 32-9 
 
 35-1 
 
 13-7 
 
 12-2 
 
 12 
 
 
 
 9-6 
 
 9-2 
 
 V3 
 
 1-3 
 
 1-3 
 
 1-4 
 
 M 
 
 0-9 
 
 1 
 
 
 
 0-8 
 
 0-7 
 
 41-4 
 
 42-8 
 
 42-4 
 
 39-9 
 
 61-6 
 
 63-2 
 
 62 
 
 3 
 
 65-9 
 
 66-6 
 
 1-6 
 
 1-5 
 
 1-5 
 
 1-4 
 
 1-6 
 
 1-9 
 
 1 
 
 9 
 
 1-9 
 
 1-9 
 
 l-f) 
 
 1-5 
 
 1-5 
 
 1-6 
 
 1-6 
 
 1-9 
 
 1 
 
 9 
 
 1-6 
 
 1-8 
 
 11 
 
 1-0 
 
 0-9 
 
 Ifi 
 
 1-0 
 
 0-9 
 
 1 
 
 
 
 ro 
 
 1-n 
 
 0-6 
 
 0-7 
 
 0-7 
 
 0-9 
 
 0-6 
 
 0-5 
 
 
 
 5 
 
 0-5 
 
 0-3 
 
 14-0 
 
 13-8 
 
 14-2 
 
 14-2 
 
 14-0 
 
 14-0 
 
 14 
 
 9 
 
 140 
 
 14-0 
 
514 
 
 OIL IN DIFFERENT SAMPLES OF WHEAT. 
 
 1°. 
 
 2°. 
 3°. 
 
 4°. 
 5°. 
 6°. 
 
 7°. 
 
 girth, upon the same field, but dressed with different manures, [Appen- 
 dix, pp. 55 and 71,] and the proportions of oil which they yielded in 
 the state in which they came from the mill, were as follows : — 
 
 Per cent. 
 
 From the undressed soil • • ] '4 
 
 Dressed with guano and wood-ash 1"9 
 
 With artificial guano and wood-ash 2*2 
 
 Sulphated urine and wood-ash 2*2 
 
 Do. do. and sulphate of soda 2*0 
 
 Do. do. and common salt 2*7 
 
 Do. do. and nitrate of soda 2-3 
 
 The two facts — that the quantity of oil in nearly all the above sam- 
 ples is so much greater than was found by Hermbstadt in any of his 
 specimens, and that the proportion varied with the kind of manure with 
 which the wheat had been dressed — these two facts, I think, show that 
 the analyses of Hermbstadt have not been made with such a degree of 
 accuracy as to justify us in relying with confidence upon the general de- 
 ductions to which they seem to lead. 
 
 3°. Relative effects of these manures upon different crops. — If we com- 
 pare together the relative proportions of gluten and albumen contained in 
 the several samples of wheat, barley, oats, and rye, examined by 
 Hermbstadt, and exhibited in his tab'es, we shall find that the effects of 
 his manures were by no means unifo' m upon the several crops. Thus, 
 when manured with — 
 
 The gluten and albumen per cent, 
 taken together were in the 
 Barley. ' ~ 
 
 61 
 6'3 
 61 
 6-4 
 61 
 60 
 3-5 
 30 
 
 the following remarks : — 
 a. Upon the wheat, the effect of the Jiorse and pigeon's dung, in in- 
 creasing the amount of gluten and albumen, was little more than one- 
 fifth of that produced by the sheep's dung. Thus the wheat contained 
 of gluten and albumen, — 
 
 Per cent. Increase of gluten. 
 
 9-9 — 
 
 34-1 24-2 per cent. 
 
 14-7 4-8 
 
 13-1 3-2 
 
 But we have seen (p. 470) that in so far as the nitrogen is concerned^ 
 dry horse and sheep'' s dung ought to produce equal effects, while pigeon's 
 dung should have three times the effect of either.* Whatever be the 
 cause of the increased proportion of gluten in the experimental wheats 
 of Hermbstadt, it cannot, therefore, have been owing solely to the pro- 
 portion of nitrogen in the manures he applied. 
 
 * 22 of dry pigeon's dung axe equal to 65 of sheep's, or 64 of horse's dung. 
 
 Kind of Manure 
 
 
 Wheat 
 
 Ox blood .... 35-2 
 
 Night soil . 
 
 
 
 352 
 
 Sheep's dung 
 
 
 
 342 
 
 Human urine 
 
 
 
 36 5 
 
 Horse dung 
 
 
 
 14-8 
 
 Pigeon's dung 
 
 
 
 131 
 
 Cow dung . 
 
 
 
 130 
 
 Nothing 
 
 
 
 9-9 
 
 Upon the numbers in 
 
 this 1 
 
 table 
 
 I offer y< 
 
 Oats. 
 
 Rye. 
 
 5-4 
 
 156 
 
 50 
 
 151 
 
 45 
 
 15-3 
 
 4-9 
 
 155 
 
 45 
 
 14-7 
 
 35 
 
 153 
 
 34 
 
 12-8 
 
 21 
 
 11-2 
 
 Undressed . . . 
 With sheep's dung 
 With horse dung , 
 With pigeon's dung 
 
DIFFERENT PROPORTIONS OF GLUTEN. 615 
 
 5. Again, upon the barley, oats, and rye, the sheep's dung produced 
 little more effect than the horse's dung. It might be said that this was 
 because these two manures contain nearly the same proportions of nitro- 
 gen. But if so, why did they not produce like effects also upon the 
 wheat ? — and why did pigeon's dung impart less gluten than either, to 
 all these varieties of grain ? 
 
 c. The unsatisfactory nature of these experiments is still more clearly 
 seen when we compare the relative proportions of nitrogen, contained in 
 the several manures applied, with the proportions of the same element 
 contained in the several crops to which these manures had been added. 
 
 This comparison is made in the following table — the quantity of nitro- 
 gen in sheep's dung and in the crops manured with it being called 
 100 :— 
 
 Proportions of Proportions of nitrogen added to the 
 
 Manure applied. "he manure. crop by each manure.- 
 
 Wheat. Barley. Oats. Rye. 
 
 Sheep's dung ... 100 100 100 100 100 
 
 Horse dung ... 102 16 75 100 66 
 
 Pigeon's dung . . 300 9 48 43 55 
 
 Cow dung ... 97 6 1 6G 22 
 
 The relation which exists among the numbers in the first of the above 
 columns, is totally unlike that which exists among those in any of the 
 others. In none of the crops does the quantity of nitrogen in the manure 
 hear a perceptible relation to that contained in the grain that was reaped. 
 
 The theory, therefore, that the quantity of gluten in the crop is always 
 determined by that in the manure, and that the amount of gluten in the 
 grain we reap may at pleasure be increased by the use of manures 
 which are rich in nitrogen — this theory derives in reality no solid support 
 from the experiments of Hermhstadt. The theory may indeed be correct, 
 but it is not sustained by any rigorous experiraent.s hitherto made — and 
 the prudent man will place little reliance upon it, until its correctness 
 shall have been proved by future and more rigorously conducted investi- 
 gations. 
 
 § 19. Composition of peas, beans, and vetches. 
 
 The seeds of leguminous plants in general contain a large quantity of 
 a substance — very analogous to the gluten of wheat — to which the name 
 of legumin has been given. 
 
 To extract this legumin, bruised beans, peas, or vetches, are steeped 
 in tepid water for some hours, then rubbed to a pulp in a mortar with 
 their own weight of warm water, and, after an hour, strained through 
 linen. The strained liquid deposits, at first, a quantity of starch, but is 
 obtained nearly clear by filtration. To the filtered solution diluted 
 acetic acid (vinegar) or sulphuric acid is added in small quantity, when 
 the legumin coagulates and falls in the form of nearly insoluble flocks, 
 
 * These columns are calculated by multiplying together the increase of crop and the in- 
 crease in the per centage of gluten and albumen. Thus in the case of wheat — 
 
 Increase of crop. Increase of gluten. Product. Proportions; 
 
 Sheep's dung 9 fold X 24-3 per cent. = 218-7 = 100 ' 
 
 Horse dung 7 fold X 4 9 per cent. = 34-3 = 16 
 
 Pigeon's dung 6 fold X 3-2 per cent. = 19-2 = 9 
 
 Cow dung 4 fold X 31 per cent. = 124 = 6 
 
516 COMPOSITION OF PEAS, BEANS AND LENTILS. 
 
 which are easily collected on a filter. The addition of an excess t)f acid 
 will re-dissolve the coagulated legumin, which is again thrown down by 
 a few drops of a solution of carbonate of soda or of ammonia ; a slight 
 excess of either of the latter, however, will cause the precipitate a second 
 time to disappear. The legumin of the pea and bean, therefore, differs 
 from the gluten of wheat, in being soluble in water (Dumas), and in very 
 dilute acid or alcaline solutions. 
 
 The solution of legumin in water is coagulated when heated nearly to 
 boiling, in which respect it resembles albumen (white of egg), and it is also 
 coagulated by rennet, in which, and in its relations to acids and alcalies, 
 it resembles casein, the curd of milk. Legumin has, indeed, by Liebig, 
 been called vegetable casein, from an impression that it is identical in 
 composition and properties with the pure curd of milk. 
 
 The semi-transparent solution of legumin in water, obtained directly 
 from beans or peas, gradually becomes opaque, and slowly deposits the 
 legumin in an insoluble state. This is owing to the production of a 
 small quantity of acid by the decomposition of the sugar or other sub- 
 stances present in the liquid. This acid slowly coagulates the legumin 
 in the same way as when dilute acids are artificially added to the solu- 
 tion. It is proper to mention that other chemists consider legumin, like 
 casein, [see the following lecture,] to be nearly insoluble in water, and 
 that in the solutions from the bean and the pea it is rendered soluble by 
 the presence of a little potash, soda, or lime — the liquid becoming turbid 
 as soon as a quantity of acid is formed to combine with these alcaline 
 substances. According to Dumas, pure legumin dried in vacuo at 284° 
 F. consists of — 
 
 Fibrin 
 Legumin. of 
 
 Whe,, 
 
 ■ Carbon 504 53-23 
 
 Hydrogen .... 69 701 
 
 Nitrogen .... 18-2 16-41 
 Oxygen, sulphur, <5c 
 phosph. .... 24-5 23-35 
 
 Albumen 
 
 Glutine 
 
 Cajsein 
 
 of 
 
 of 
 
 of 
 
 Wheat. 
 
 Wheat. 
 
 Wheat. 
 
 53-74 
 
 53 05 
 
 53-46 
 
 711 
 
 7-17 
 
 713 
 
 15-65 
 
 15-94 
 
 1604 
 
 23-50 
 
 23-84 
 
 23-37 
 
 100 100 100 100 100 
 
 For the purj)ose of comparison, I have inserted the composition, ac- 
 cording to the same chemist, of the several nitrogenous compounds ex- 
 isting in wheat. 
 
 _ If these analyses be correct, legumin contains more nitrogen than the 
 fibrin, the albumen, the glutine, or the casein of wheat, and is almost 
 identical with tlie gelatine of bones. The important consequence deduced 
 from this fact, by Dumas, in reference to the feeding of animals, we shall 
 consider in a subsequent lecture. 
 
 Above, I have given the composition of legumin, the nitrogenous 
 principles contained in peas and beans, as found by Dumas, from whicli 
 it would appear to contain more nitrogen than any of the other vegetable 
 principles hitherto found in cultivated grains. The legumin analysed by 
 Dumas was extracted from siDcet almonds. 
 
 Since the preceding sheet was pre])ared for press, a further analysis of 
 legumin, extracted from leans, has been published by Rochleder,* which 
 
 * Annalen der Cfiem. et Pharmacie, xlvi., p. 155. 
 
 I 
 
ANALYSIS OF LEGUMIN. 517 
 
 does not agree with that of Dumas, but represents this legumin as iden- 
 tical with casein, the curd of milk (see the following lecture), and as dif- 
 fering in properties as well as in composition from that of the almond. 
 
 The legumin of beans and peas is soluble in cold water, and the solu- 
 tion, upon evaporation, forms a skin on the surface which is renewed as 
 often as it is removed. It is not coagulated by boiling, but is immediately 
 thrown down in fine flocks by acetic acid, which, when added in excess, 
 does not redissolve it (Liebig). 
 
 The legumin from sweet almonds is also soluble in cold water, but, 
 like albumen, falls in flocks when the solution is heated nearly to boil- 
 ing. It is precipitated also by diluted acetic acid, and is again dissolved 
 when an excess of this acid is added (Dumas). 
 
 The two substances, therefore, are different in their properties. Their 
 constitution is represented respectively by — 
 
 LEGUMIN FROM 
 
 Beans Sweet almonds 
 
 (Rochleder). (Dumas). 
 
 Carbon .... 54-5 50-4 
 
 Hydrogen . . . . 7'4 6-9 
 
 Nitrogen .... 14-8 18-2 
 
 Oxygen .... 23-3 24-5 
 
 100 100 
 
 When we come to consider the feeding of animals, we shall find that 
 this difference in the composition of the two varieties will inalerially af- 
 fect the view we must take in regard to the action of each in contributing 
 to the support of the various parts of the animal body. 
 
 The approximate composition of the entire peas and beans is thus 
 stated by Einhof. [Zierl Ency clop (^ die, ii., p. 52]. 
 
 Composition of the grain. Composition of the meal. 
 
 Water. Husk. Meal. Starch. Legumin. Gum,&c. 
 
 Peas 140 10 5 755 65 23 12 
 
 Field Beans . . . 155 16-2 G8 3 690 19 12 
 
 A series of rigorous analyses of the seeds of leguminous plants is at 
 present much to be desired. According to those of Braconnot and Einhof, 
 certain species examined by them consisted of — 
 
 Kidney Field beans, Lentils, 
 Peas. beans. (Einhof.) dried* 
 
 (Einhof.) 
 
 Water • 125 230 156 
 
 Husk ...... 83 70 100 18-7 
 
 Leffumin, albumen, (fee. . 26-4 23-6 11-7 38-5 
 
 Starch 43-6 430 50-1 328 
 
 Sugur 20 2 o^ 3-1 
 
 Gimi, &c 40 1-5 ^^ 60 
 
 Oil and fat 1-2 0-7 7 '? 
 
 Salts and loss .... 2-0 1-0 4-4 0-9 
 
 1000 1000 1000 lOOOt 
 
 These analyses agree in showing that the seeds of leguminous plants 
 
 " By drying, the lentils lost 14 per cent, of water. 
 
 t Dumas Traite de Ckiniie, vi. p. 307, comparad with Thomson's Vegetable Chemistry, 
 p. 884, Schiibler's AgricuUur Chemie, ii., p. 194, and Sprengel's Chemie fiir LandwirthCy ii.^ 
 p. 358. 
 
 22* 
 
618 EFFECT OF SOILS AND MANURES UPON PEAS. 
 
 are especially rich in substances containing nitrogen (legumin and albu- 
 men), and are therefore fitted to contribute much to the nourishment of 
 those animals which, in consequence of the state of their growth and 
 health, or the purposes for which they are reared and maintained, require 
 a large supply of this important element. 
 
 § 20. Effect of soils and manures upon the quality of peas and beans. 
 
 The quality of the seeds of leguminous plants is also affected by the 
 mode of culture to which they are subjected, and by the kind of soil in 
 which they are raised. 
 
 1°. Effect of animal manures. — The dung ♦' of sheep or horses has 
 been found to impart a better flavour to the pea, and to render the husk 
 thinner than when that of hogs or oxen has been used." [British Hus- 
 bandry, ii., p. 217.] 
 
 2°. Effect of mineral manures. — The effect of gypsum and of other 
 sulphates upon leguminous plants is universally known (p. 482.) The 
 beneficial influence of a mixture of gypsum and common salt upon 
 sickly crops of beans and peas is very strikingly displayed in the inter- 
 esting experiments of Mr. Alexander, of Southbar, to the details of which 
 I have already had occasion to draw your attention. [See Appendix, p. 
 217.] 
 
 3°. Effect of lime. — Dr. Anderson says, " that the pea cannot be 
 reared to perfection in any field which has not been either naturally or 
 artificially impregnated with some calcareous matter," but that " a soil 
 which could hardly have brought a single pea to perfection, although 
 richly manured with dung, if once limed, will be capable of producing 
 abundant crops of peas ever (?) afterwards, if duly prepared in other re- 
 spects." [Essays, ii., p. 302.] 
 
 4°. Boiling or melting quality of peas. — But the most singular cir- 
 cumstance in connection with this class of seeds, to which the agricul- 
 tural chemist has hitherto been directed, is the property possessed by 
 peas and beans of boiling soft or mouldering into a pulp more or less 
 easily, according to the kind of land in which they are raised or to the 
 species of manure with which they are dressed. The observations, 
 however, which I have found upon record in reference to this point are 
 of a contradictory character. Thus — 
 
 a. Sprengel says "that peas which are raised after liming or marling 
 boil sojt more easily, and are more agreeable to the taste than when raised 
 after manure." [Die Lehre vom Diinger, p. 297.] 
 
 b. A French authority, on the other hand, quoted by Loudon, [Ency- 
 clopaedia of Agriculture, p. 837,] says, that " stiff* land or sandy land 
 that has been limed or marled, or to which gypsum has been applied, 
 produces peas that ivill not melt in boiling, no matter what the variety 
 may be. The same effect is produced on the seeds and pods of beans 
 and of all leguminous plants. To counteract this fault in the boiling, it 
 is only necessary to throw into the water a small quantity of the com- 
 mon soda of the shops." 
 
 c. The author of the British Husbandry, [ii., p. 217,] says, " that 
 shell marl or lime is found to forvVard this crop more than any other 
 mineral manure, though it is said to communicate a degree of hardness 
 tp the grain which renders it unfit for boiling." 
 
SOME PS.VS REFUSE TO BOIL SOFT. 519 
 
 Independently of all applications to the soil, I believe it is generally 
 observed that good boilers are produced upon light, sandy, and gravelly 
 soils ; while heavy, wet, undrained (and newly broken up ?) land usually 
 produces bad boiling peas and beans. Thus melting peas {sidder peas, 
 as they are locally called) for the Birmingham market are grown on the 
 slopes of the gravelly hill of Hopwas, two miles from Tamworth, on 
 the Lichfield road— the red clay lands of the vale of the Tame produc- 
 ing in general pig'^ peas or beans only. It is on similar soils that melt- 
 ing barley and mealy potatoes are produced, and the effect upon the 
 three crops may probably be due to a common cause. 
 
 At all events it is probable — 
 
 a. That the boiling quality of the pea crop is not owing to the qual- 
 ity of the seed — since peas of both varieties have been raised from the 
 same seed.f 
 
 b. That it is not generally owing to the seasons, since some land pro- 
 duces hard peas every yea/. If the wetness of the soil indeed have any 
 influence, a rainy season may cause the production of bad boilers upon 
 land from which soft peas are usually reaped. 
 
 4°. Chemical difference between the two varieties of pea. — Why does 
 one of these varieties of pea melt more readily than the other ? For 
 the same reason very nearly that one potatoe boils mealy, and another 
 waxy, and that one sample of barley melts better in the mash-tub than 
 another. Melting peas and barley and mealy potatoes contain a larger 
 proportion of starch than samples which are possessed of an opposite 
 quality. 
 
 The pea, as we have seen, consists essentially of legumin and starch. 
 The former coagulates and contracts, or runs together into a mass by 
 boiling,— the latter, on the contrary, expands, becomes more bulky, tends 
 to burst the busk, and to separate into single grains. If the tendency to 
 contract and cohere be greater than the disposition to expand and sepa- 
 rate — in other words, if the legumin predominate — the pea does not melt, 
 while if the starch be abundant the pea boils well. It is possible that 
 the addition of a little soda may cause hard peas to melt, since legumm 
 is soluble in a solution of soda,^but in waters impregnated with lime all 
 peas are said to boil soft much less readily than in such as are free from, 
 that ingredient. [Dumas, Traite de Chimie, vi.] 
 
 It is only when peas and beans are raised for the food of man that the 
 possession of the melting property becomes a matter of importance. It 
 is rather because they are more agreeable to the palate than because they 
 are ascertained to be more nutritive, that they are preferred in this state. 
 When we come to consider the feeding of stock, we shall see that, ac- 
 cording to the present state of our knowledge, the opinion may rea- 
 sonably be entertained that insoluble peas are really better adapted for the 
 feeding and fattening pigs and other stock— the purpose for which they 
 are employed— than those which are possessed of the melting quality. ^ 
 
 It is a difference in the chemical composition of the seeds of legumi- 
 nous plants that makes them melt more or less easily— but by what 
 
 • Much used for the feeding of pigs. 
 
 t Some however suppose it to depend upon the age of the seed, or the time of sowing. 
 —British Husbandry, ii., p. 217. 
 
620 COMPOSITION or potatoes. 
 
 quality in the soil or manure is this clifTerence in composition produced ? 
 In regard to lime the evidence is contradictory. Gypsum may render 
 them harder since legumin contains sulphur, and a portion of the effect 
 of gypsum upon leguminous crops is supposed to arise from its yielding 
 sulphur to the growing plants, and thus promoting the production of le- 
 gumin. Wet and clay lands also favour the production of legumin 
 more than that of starch — hut in what way, we are not yet in possession 
 of experimental results of sufficient accuracy to enable us to say. 
 
 § 21. Of the composition of potatoes^ and the effect of circumstances in 
 modifying their composition. 
 
 1°. Composition of potatoes. — Potatoes, in addition to much water, 
 consist of starch, gum, woody fibre, and albumen. The proportions of 
 llicse several constituents are very variable. Thus, according to 
 Einhof and Lampadius, the following kinds of potatoe consisted in 100 
 parts of — 
 
 2°. Influence of the state of ripeness. — According to Korte the quan- 
 tity of dry solid matter contained in the potatoe depends very much upon 
 the state of rijieness to which it has attained. The ripest leave 30 to 32 
 per cent, of dry matter, the least ripe only 24 per cent. The per 
 centage of starch varies from 8 to 16 per cent. The mean result of his 
 examination of 55 varieties of potatoe gave him for the solid matter 24*9, 
 and for the starch 11-85 per cent. [Schiibler, Agricultur Chemie, ii., p. 
 213.] 
 
 3°. Influence of variety. — Much appears also to depend upon the 
 variety of potatoe. Thus the following varieties of potatoe grown at 
 Barrochan in Renfrewshire, in 1842, yielded respectively — 
 
 Connaught cups .... 21 per cent, of starch. 
 
 Irish blacks 
 
 White dons 
 
 Red dons 
 — while, according to a starch manufactur 
 per cent, has been the average quantity obtained from the common 
 rough red of good quality during the last four years. 
 
 The difference in the quantity of starch yielded by the above-named 
 varieties is the more striking wlien taken in connection with the weight 
 of each per acre, raised from the same land, treated in the same way. 
 These weights were as follows : — 
 
 Manure. 
 Cups^ with 4 cwt. of guano 
 
 Red Dons, with 4 cwt. of guano 
 White Dons, witli 3 cwt. of guano 
 
 So that, of these three crops, that of cups, which weighed the least, 
 gave the largest produce of starch. It yielded nearly twice as much as 
 the red dons, whicli were half a ton heavier, and one-fifth more than 
 even the ichite dons, th^ crop of which was greater by five tons an acre. 
 Such differences as these, in the relative quantities of starch, which may 
 be obtained from an acre of the same land by the growth of diff^erent va- 
 rieties of potatoe are deserving of the attentive consideration of the prac- 
 tical man. 
 
 See Appendix, p. 61. 
 
 16^- 
 
 13 " 
 
 er in the neighbourhood, 11^ 
 
 
 Containing of 
 
 Produce per acre. 
 
 starch. 
 
 I3f tons 
 
 2-9 tons. 
 
 I4i " 
 
 1-5 " 
 
 m- « 
 
 24 " 
 
THE PROPORTION OF STARCH VARIES VERY MUCH. 521 
 
 Larger quantities of starch than any of those above stated have been 
 obtained from potatoes by some experimenters. Thus from the 
 
 Per cent, of starch. 
 Kidney potatoe, Dr. Pearson obtained . . . 28 to 32 
 
 Apple do. Sir H. Davy 18 to 20 
 
 Shaw do. Vauquehn ..... 18-8 
 
 L'OrpheUne do. . . ... . . 24-4 
 
 The first and last of these proportions are probably very rare in oui 
 climate. 
 
 4°. Effect of keeping. — Those potatoes are said to keep best in which 
 the starch is most abundant, but in general keeping has an efiect — 
 
 a. On the proportion of starch. — ^By keeping till the spring, potatoes 
 lose from 4 to 7 per cent, of their weight, and the quantity of starch they 
 are capable of yielding suffers a considerable diminution. Thus, ac- 
 cording to Payen, the same variety of potatoe yielded of starch in 
 
 October, 17*2 per cent. January, 15-5 per cent. 
 
 November, 16-8 " February, 15-2 " 
 
 December, 15-6 " March, 15-0 " 
 
 April, 14-5 " 
 
 This diminution is probably owing to the conversion of a portion of the 
 starch into sugar and gum. When potatoes are rendered unfit for food 
 by being frozen and suddenly thawed, the quantity of starch which they 
 are capable of yielding is said to have undergone no diminution. 
 
 b. On the proportion of gluten. — The proportion of gluten also ap- 
 pears to become less when potatoes are kept. Thus, in new potatoes 
 Boussingault found the gluten amount to 2]- per cent., but in old potatoes 
 to only li per cent, of their weight. To this natural diminution of the 
 proportion of starch and gluten, is probably to be ascribed the smaller 
 value in the feeding of stock, which experience has shown very old po- 
 tatoes to possess. 
 
 5°. Effect of soils and manures. — The potatoe thrives best on a light 
 loamy soil — neither too dry, nor too moist. The most agreeably flavour- 
 ed table potatoes are almost always produced from newly broken up 
 pasture ground, not manured, or from any new soil. [Loudon's Ency- 
 clopaedia of Agriculture, p. 847.] When the soil is suitable, they delight 
 in much rain, and hence the large crops of potatoes obtained in Ireland, 
 in Lancashire, and in the west of Scotland. No skill will enable 
 the farmer to produce crops of equal weight on the east coast where 
 rains are less abundant. It has not been shown, however, that the weighs 
 of starch produced in the less rainy districts is defective in an equal de- 
 gree. Warm climates and dry seasons, as well as dry soils, appear to 
 increase the per-centage of starch. 
 
 Potatoes are considered by the farmer to be an exhausting crop, and 
 they require a plentiful supply of manure. .By abundantly manuring, 
 however, the land in the neighbourhood of some of our large towns, 
 where this crop is valuable, have been made to produce potatoes and 
 corn every other year, for a very long period. 
 
 6°. Influence of saline manures. — I have already drawn your attention 
 to the remarkable influence of certain saline substances in promoting the 
 growth of the potatoe crop in some localities. The most striking effects 
 of this kind hitherto observed in our island have been produced by mix- 
 
522 OCCASIONAL FAILURE OF SEED POTATOES. 
 
 tures of the nitrate of soda with the sulphate of soda or with the sulphate 
 of magnesia.* The effect of such mixtures affords a beautifal illustration 
 of the principle I have frequently before had occasion to press upon your 
 attention — that plants require for their healthy growth a constant suppl}^ 
 of a considerable number of different organic and inorganic substances. 
 Thus upon a field of potatoes, the whole of which was manured alike 
 with 40 cart loads of dung, the addition of — 
 
 a. Nitrate of soda alone gave an increase of 3]- tons. 
 Sulphate of soda alone gave ... " 
 While one half of each gave ... 5^ " 
 
 h. Sulphate of ammmiia alone gave . . 1^ " 
 
 Sulphate of soda " 
 
 But one half of each gave .... 6| " 
 
 c. Nitrate of soda alone gave .... 3r " 
 Sulphate of magnesia alone gave . . a " 
 And one half of each gave .... 9f " 
 
 These results are very interesting, and when confirmed by future re- 
 petitions of such experiments — and followed up by an examination of 
 the quality and composition of the several samples of potatoes produced— 
 cannot fail to lead to very important practical conclusions. ' 
 
 7°. Occasional failure of seed potatoes. — The seeds of all cultivated 
 plants are known at times to fail, and the necessity of an occasional 
 change of seed is recognised in almost every district. In the Lowland.? 
 of Scotland potatoes brought from the Highlands are generally pre 
 ferred for seed, and on the banks of the Tyne Scottish potatoes bring a 
 higher price for seed than those of native growth. This superior quality 
 is supposed by some to arise from the less perfect ripening of the wp- land 
 potatoes, and in conformity with this view the extensive failures which 
 have taken place during the present summer (1643) have been ascribeo 
 to the unusual degree of ripeness attained by the potatoes during the 
 warm dry autunm of the past year. 
 
 This may in part be a true explanation of the fact, if — as is said — the 
 ripest potatoes always contain the largest proportion of starch — since 
 some very interesting observations of Mr. Stirrat, of Paisley, would 
 seem to indicate that whatever increases the per-centage of starch, in- 
 creases also the risk of failure in potatoes that are to be used for seed.\ 
 This subject is highly deserving of further investigation. 
 
 ' For the particulars of these experiments see the Appendix. 
 
 t I insert Mr. Stirral's letter upon this subject, not only because his observations are in- 
 tereplingr in themselves, but because they are really deserving of the careful attention of 
 practical men : — 
 
 "Sir, — The foliowinjr experiment wilh potatoes was tried with the view of discovering the 
 cause of so many failures in the crops of late years, from the seed not vegetating, and rotting 
 In the ground. I bad an idea thai the vegetalive principle of the plant might become weak 
 In con.fequpnce of being grown on land that had been a long time subjected to cropping, and 
 not allowed any length of lime to lie at rest. 1, therefore, raised a few bolls on land that had 
 lain lea for 70 years (being part of my bleach green), and found that these on being planted 
 again the following year were remarkably strong and healthy, and not a plant gave way, and 
 I have continued the same method for the last six years, and the result has, in every instance, 
 been equally favourable. Four years ago, one boll of my seed potatoes was planted along 
 with some others in a field of about an acre, the other seed was grown on the farm, and the 
 seed all gavo way excepting that got from me. They were all planted at the same time and 
 
EFFECT OF SALINE SUBSTANCES 523 
 
 8°. Effect of saline top-dressings on the quality of the seed. — It may 
 be doubted, however, whether the relative proportions of starch are to be 
 considered as the cause of the relative values of different samples of seed 
 potatoes. This proportion may prove a valuable test of the probable 
 success of two samples when planted, without being itself the reason of 
 the greater or less amount of failures. With the increase of the starch 
 it is probable that both the albumen and the saline matter of the potatoe 
 will in some degree diminish, and both of these are necessary to its fruit 
 fulness when used for seed. 
 
 The value of the saline matter is beautifully illustrated by the obser- 
 vation of Mr. Fleming, that the potatoes top-dressed with sulphate and 
 nitrate of soda in 1841, and used for seed in 1842, "presented a remark- 
 able contrast to the same variety of potatoe, planted alongside of them, 
 but which had not been so top-dressed in the previous season. These 
 last came away weak, and of a yellowish colour, and under the same 
 treatment in every respect did not produce so good a crop by fifteen bolls 
 (3f tons) an acre." This observation, made in 1842, is confirmed by the 
 appearance of the crops now growing (July, 1843) upon Mr. Fleming's 
 experimental fields. The prosecution of the enquiry opened up by his 
 experiments promises to lead to the most valuable practical results.* They 
 may teach us how to secure at all times a fruitful seed, and thus to dis- 
 pense with supplies of imported produce. 
 
 § 22. The composition of the turnip, the carrot, the beet, and the parsnip. 
 
 1°. Composition. — The potatoe is characterised by containing a large 
 proportion of starch in connection with a small quantity of albumen — the 
 turnip and carrot by containing, in place of the starch, a variable pro- 
 
 with the same manure. From these circumstances, I am of opinion, that if farmers were 
 careful in raising their own seed potatoes from land that has lain long in a stateof rest(a)— or 
 where that cannot be had, the same object can be obtained by bringing ne# soil to the sur- 
 face by trenching as much as is necessary, or by the use of the subsoil-plough— failures of 
 the potatoe crop from the seed not being good, would become much less frequent. I am 
 somewhat confirmed in this opinion by the fact, that it has been found for the last dozen of 
 years that generally the best seed potatoes have been got from farms in the moors or high 
 lands of the country. The reason of this may be that these high lands have been but of late 
 brought under crops of any kind, and many of them but newly brought from a stateof nature, 
 and the superiority of seed potatoes from these high lands may not at all arise (as is gene- 
 rally supposed) from a change of soil or climate. 
 
 " Potatoes raised on new soil, or on ground that has been long lying lea, are not so good 
 for the table as the others, being mostly very soft, and, by the following experiment, it would 
 appear that they contain a much less quantity of farina than those which are raised from 
 land that has been some lime under crop, and, perhaps, this is the reason why they arc belter 
 for seed. From one peck of potatoes, grown on land near Paisley, which has been almost 
 constantly under crop for the last 30 years, I obtained nearly 7 lbs. of flour or starch ; and 
 from the other peck, grown on my bleach green, the quantity obtained was under 4 lbs., from 
 which it would sef m that as the vegetative principle of the plant is strengthened, the farina- 
 ceous principle is weakened, and vice versa. Jas. Stikrat." 
 
 Paisley, 22d November, 1842. 
 
 (a) Mr. Finnie, of Swansfone, informs me that the growins of potatoes intended for seed upon 
 new land, has long been practised by good farmers. Mr. Little, of Carle.sgill, near Langholm, 
 writes me that in Dumfriesshire, they obtain the best change of potatoe seed from mossy 
 land— of oats and barley from the warmer and drier climate of Uoxbuj-ghshirc. The grains, 
 he adds, degenerate by once sowing, still looking plump when dry, but having a thicker husk, 
 and weighing two or three pounds less per bushel. The deterioration of seeds, in general, 
 is a cA<?m/(o-physiological subject of great interest and importance, and will doubtlee.? soon 
 be taken up and investigated. 
 
 • In the Appendix, p, 47, the experiments are recorded, and in p. 66 I have more fully ad- 
 verted to the iateresting results likely to be derived from the continuance of such experiment*. 
 
524 COMPOSITION OF THE TURNIP, CARROT, AND BEET. 
 
 portion of sugar, and of a gelatinous gummy-like substance, to which 
 the name o^ pectin has been given. In the Swedish turnip and in beet- 
 root the sugar predominates, in the white turnip and in the carrot the 
 pectin is usually present in the larger quantity. 
 
 The composition of the turnip, the carrot, and the beet varies very much, 
 and is influenced by a great variety of circumstances. We are not in 
 possession of any recent detailed analyses of these roots. The following 
 table exhibits the component parts of several varieties, as they have been 
 given cliiefly by Hermbstadt, [Schiibler, Ag. Chem., ii., p. 207] : — 
 
 
 Variety of Turnips. 
 
 
 Sugar 
 
 
 
 ,— 
 
 ' ^ 
 
 Common 
 
 beet 
 
 Parsnip 
 
 
 White. 
 
 Swedish. Cabbage. 
 
 Carrof. 
 
 (Payen). 
 
 (Crome). 
 
 Water . . . 
 
 . 79-0 
 
 800 78-0 
 
 800 
 
 85-0 
 
 79-4 
 
 Starch and fibre 
 
 . 7-2 
 
 5-3 60 
 
 90 
 
 30 
 
 69 
 
 Gum {pectin ?) 
 
 . 2-5 
 
 30 35 
 
 1-75 
 
 20 
 
 61 
 
 Sugar . . . 
 
 . 8-0 
 
 90 90 
 
 7-8 
 
 100 
 
 5-5 
 
 Albumen . . 
 
 . 2-5 
 
 20 2.5 
 
 11 
 
 7 
 
 21 
 
 Salts .... 
 
 . 0-5 
 
 0-5 0-5 
 
 — 
 
 a 
 
 1 
 
 Loss .... 
 
 . 0-3 
 
 09 5 
 
 oil 35 
 
 — 
 
 — 
 
 
 100 
 
 100 100 
 
 100 
 
 100 
 
 100 
 
 These analyses are very defective, and apply with any degree of cor- 
 rectness only to the specimens actually operated upon. Any rea.sonings, 
 therefore, which are founded upon them can only lead to probable or ap- 
 proximate conclusions. 
 
 2°. The proportion of sugar contained in the sap of these roots is 
 greatest when they are young, and diminishes as they ripen. In the 
 beet, it has been observed that the nitrates of potash and ammonia are 
 present in considerable quantity, and that in the old beet these nitrates 
 become more abundant as the sugar diminishes. In the beet, also, when 
 raised by the aid of rich manure, the production of nitrates is increased 
 more than that of sugar.* The same may possibly be the case with the 
 common cultivated turnips. It would not be without interest, both theo- 
 retically and practically, to ascertain by experiment, the relative com- 
 position of the~same variety of turnip, grown on the same soil, by the 
 aid of rich farm-yard manure, and by the aid of bones or of rape-dust. 
 The one may produce more sugar, the other more albumen or nitrates. 
 Such ditferences may materially affect the value of the crop, either in 
 the feeding of stock or in the production of an enriching manure. It is 
 in suggesting and carrying on enquiries of this kind that the joint labours 
 of the practical farmer and of the theoretical chemist are likely, among 
 other ways, to promote the advancement of a rational and scientific agri- 
 culture. 
 
 3°. Effect of soils and manures. — These roots delight in a rich, open, 
 and loamy soil — and the weight of produce varies much with the kind 
 of manure that may have been applied to them. [See, for many in- 
 structive illustrations of this fact, the experiments upon turnips, detailed 
 in the Appendix,' pp. 43 et seq.] No experiments, however, have yet 
 been made to determine the relative proportions of water and of their 
 other constituents which the same turnips contain, when raised by the 
 
 * According to Payen, the boot, when raised with street manure, contains 20 times as 
 much saltpetre as when raised in the ordinoi-y manner. 
 
WATER PER CENT. 
 
 DRY MATTER PER CENT. 
 
 Einhof. Playfair. ^^t 
 
 Einhof. Playfair. 
 
 Hermb- 
 stadt. 
 
 92 89 79 
 
 8 
 
 11 
 
 21 
 
 871 85 80 
 
 12| 
 
 15 
 
 20 
 
 86 — 78 
 
 14 
 
 — 
 
 22 
 
 white. 
 
 
 
 
 86 87 80 
 
 14 
 
 13 
 
 20 
 
 WATER IN DIFFERENT VARIETIES OF TURNIP. 525 
 
 aid of different manures, nor, consequently, the tnie effect of these 
 manures upon the relative values of the several crops." 
 
 4°. Quantity of water in different varieties of turnip — The same re- 
 mark may be made in regard to the several varieties of turnip. All 
 those examined by Hermbstadt, as appears from the above tables, con- 
 tained 20 to 22 per cent, of solid matter (78 to 80 of water), while other 
 experimenters have found as little as from 8 to 15 of solid matter in tur- 
 nips, and generally less in the white and large globe turnip than in the 
 yellow and more solid Swede. 
 
 Thus, four varieties of the above roots contain of water and solid mat- 
 ter, according to three different experimenters : — 
 
 White turnip 
 Swedish do. 
 Cabbage do. 
 
 Carrot . . 
 
 The above differences are very great, especially when we look to the 
 relative proportions of dry matter in which the nutritive power resides. 
 They are of much importance, therefore, to the feeding of stock, and 
 the circumstances under which they occur, are deserving of a careful in- 
 vestigation. 
 
 5°. Relative nutritive properties of the potatoe and the turnip. — The 
 potatoe is usually considered more nutritive than the turnip, weight for 
 weight, and no doubt it generally is so. But if we compare together the 
 ][uantities of solid matter which the two roots may contain, we shall see 
 how very far wrong our estimate may be in any special case. Thus — 
 
 The turnip contains of solid matter from 8 to 22 per cent. 
 
 The potatoe do. do. 24 to 32 " 
 
 — so that, while the driest turnips may contain four times as much solid 
 matter as the most watery potatoes, very dry potatoes may contain 
 nearly as much as very juicy turnips. It is impossible, therefore, with- 
 out an actual examination of the samples, to pronounce upon the relative 
 amount of food which is likely to be contained in any equal weights of 
 turnips and potatoes. The very discordant estimates which different 
 feeders of stock have formed in regard to the relative value of these 
 crops in the production of beef or mutton is partly owing to this cause. 
 [Other causes for these discordant estimates will be stated in Lecture 
 XXL] Until the efftcts of equal weights of the different kinds of food, 
 estimated in the dry state., are carefully ascertained, it will be impossible 
 to obtain results of a general kind or upon which any real confidence 
 can be placed. 
 
 § 23. Of die composition of the green stems of peas, vetches, clover, spurry, 
 
 and huck-wheat. 
 
 The stems and leaves of plants which are given as green food to 
 animals differ much in composition, according to the age they have at- 
 tained, to the rapidity of their growth, to the nature of the soil, the 
 season, and the mode of culture. They are generally supposed to be 
 richest in nutritive matter when the plant has just come into flower: 
 
526 COMPOSITION OF THE GREEN STEMS OP PEAS, ETC 
 
 The following table exhibits the approximate composition of the 
 
 feen stems of some clovers and vetches, as they have been given by 
 inhof and Crome : — 
 
 
 O..S 
 o 
 
 ■a 
 
 Pi 
 
 
 S 
 
 3 
 1^ 
 
 o 
 
 D 
 02 
 
 Green stalks o 
 Buckwheat 
 (.Crome.) 
 
 "J 
 U 
 
 o 
 
 o 
 
 c ^ 
 
 V 
 kl 
 
 b7 
 1 ■ 
 
 Water 
 
 800 
 
 760 
 
 800 
 
 750 
 
 770 
 
 82-5 
 
 77-5 
 
 79-5 
 
 86-0 
 
 Starch 
 
 3-40 
 
 14 
 
 10 
 
 2-2 
 
 2-3 
 
 4-7 
 
 2G 
 
 3-8 
 
 1-3 
 
 Woody fibre . 
 
 1031 
 
 13-9 
 
 11-5 
 
 143 
 
 120 
 
 100 
 
 10-4 
 
 11-5 
 
 70 
 
 Sugar 
 
 455 
 
 21 
 
 1-5 
 
 0-8 
 
 — 
 
 — 
 
 — 
 
 — 
 
 — 
 
 Albumen 
 
 090 
 
 20 
 
 15 
 
 19 
 
 2-3 
 
 0-2 
 
 1-9 
 
 0-7 
 
 1-8 
 
 Extractive matter and 
 
 
 
 
 
 
 
 
 
 
 gum 
 
 0-65 
 
 3-5 
 
 34 
 
 44 
 
 52 
 
 2-6 
 
 76 
 
 3-6 
 
 2-9 
 
 Phosphate of lime . 
 
 019 
 
 10 
 
 0-8 
 
 0-8 
 
 0-8 
 
 1 
 
 — 
 
 — 
 
 — 
 
 Wax and Resin 
 
 — 
 
 01 
 
 0-2 
 
 0-6. 
 
 1 
 
 1 
 
 1 
 
 0-9 
 
 10 
 
 100 100 991) 100 99-6 100 100 100 100 
 
 § 24. Of the composition of the grasses when made into hay. 
 
 1°. An elaborate examination of the grasses of this country, in the 
 dry state, with the view of determining their relative nutritive proper- 
 ties, was made by the late Mr. Sinclair, gardener to the Duke of Bed- 
 ford. His method was to boil in water equal weights of each species of 
 liay till every thing soluble was taken up, and to evaporate the solution 
 to dryness. The weights of the dry matter thus obtained he considered 
 to represent the nutritive values of the grasses from which the several 
 samples of hay were made. 
 
 The results of Mr. Sinclair, liowever, have lost much of their value, 
 since it has been satisfactorily ascertained — * 
 
 a. That the proportion of soluble matter yielded by any species of 
 grass, when made into hay, varies not only with the age of the grass, 
 when cut, buf^ith the soil, the climate, the season, the rapidity of 
 growtli, the variety of seed sown, and with many other circumstances 
 wliich are susceptible of constant variation. 
 
 h. That animals have the power of digesting a greater or less propor- 
 tion of that part of their food whicli is insoluble in water. Even the 
 woody fibre of the hay is not entirely useless as an article of nourish- 
 ijient — experiment having shown that the manure often contains less 
 ('f this insoluble matter than was present in the food consumed.* (Spren- 
 
 (*. That some of the substances which are of the greatest importance 
 in (lie nutrition of animals — such as vegetable fibrin, albumen, casein, 
 :in.l legumin — are either wholly insoluble in water or are more or less 
 perf<x'tly coagulated and rendered insoluble by boiling with water. Mr. 
 Sinclair, therefore, must have left behind, among the insoluble parts of 
 
 * This will not appear surprising when it is recollected that, by prolonged dieestion in 
 ili!utt>d sulphuric acid, insoluble woody fibre may be slowly changed into soluble gum or 
 sii>;ar (see p. 112). The proportion of the woody fibre which will be thus worked up in the 
 stomach of an animal will depend, among other circumstances, upon the constitution of the 
 animal itself, upon the abundance of food supplied to it, and upon the more or less perfect 
 Diasiication to which ttie food is subjected. 
 
WOODY FIBRE AND GLUTEN IN THE GRASSES. 527 
 
 nls hay, the greater proportion of these important substances. Hence, 
 the nature and weight of the dry extracts he obtained could not fairly re- 
 present either the kind or quantity of the nutritive matters which the 
 hay was likely to yield when introduced into the stomach of an animal. 
 
 For these reasons I do not think it necessary lo dwell upon the results 
 of his experiments.* 
 
 2°. Woody fibre in the grasses. — In the stems of the grasses (in. hay 
 and straw), woody fibre is the predominating ingredient. They are not 
 destitute of starch, gum, and sugar, but they are distinguished from all 
 the other usual forms of animal food, by the large quantity of woody 
 fibre, and of saline or earthy matter wbicli ttiey contain. The propor- 
 tion of woody fibre in the more common grasses, in their usual state of 
 dryness when made into hay and straw, is thus given by Sprengel (see 
 
 p. 106) :— 
 
 Per cent. Per cent. 
 
 Wheat straw, ripe .... 52 
 
 Barley straw, do 50 
 
 Oat straw, do 40 
 
 Rye straw, do 48 
 
 Indian corn, do 24 
 
 Pea straw, ripe 30 
 
 Bean straw, do 51 
 
 Vetch hay, do 42 
 
 Red clover, do 28 
 
 Rye grass, do 35 
 
 The proportions of woody fibre here given, however, can be considered 
 only as approximations. The riper the straw or grass, the less soluble 
 matter does it contain, and every farmer knows how much soil, season, 
 and manure, affect the quality of liis artificial grasses. One field will 
 grow a hard wiry rye-grass, while another will produce a soft and flexi- 
 ble plant, and a highly nutritious hay. 
 
 3°. Gluten in the grasses. — Boussingault, who considers the relative 
 nutritive value of the vegetable substances employed for fodder to be in- 
 dicatedi)y the proportions of nitrogen they severally contain, has arranged 
 grass and clover hays and the straws of the corn plants, in their usual 
 state of dryness, in the following order : — 
 
 
 Or cluten, 
 
 
 Equal effects 
 
 
 Nitrogen 
 
 &c., 
 
 
 should be 
 
 
 per cent. 
 
 per cent. 
 
 
 produced by 
 
 
 115 
 104 
 
 71 
 6-4 
 
 \ 
 
 100 lbs. 
 
 
 i-54 
 
 9-3 
 
 
 75t " 
 
 
 1-5 , 
 
 9-3 
 
 
 75 " 
 
 
 1-95 
 
 12-3 
 
 
 64X " 
 
 
 101 
 
 6-4 
 
 
 114 " 
 
 
 054 
 
 3-4 
 
 
 ^0 " 
 
 
 — 
 
 — 
 
 
 520 " 
 
 
 
 
 
 
 
 520 " 
 
 
 — 
 
 — 
 
 
 550 " 
 
 
 omnare 
 
 the above 
 
 theoretical 
 
 values 
 
 Hay from mixed grasses 
 
 Do. aftermath . 
 
 Do. from clover in flower 
 Pea straw .... 
 Lentil straw 
 Indian corn straw 
 Wheat straw 
 Barley straw 
 Oat straw .... 
 
 We shall have occasion to compare 
 (equivalents) assigned to the several kinds of fodder, with the results of 
 
 • They will be found at length in the Appendix to Davy's Agricultural Chemistry, or in a 
 tabulated form in Schiibler's Agricultur Chemie, U., p. 208. 
 
 t It is usually supposed that the aftermath is not so valuable as Uie first produce. Schwertz, 
 however, considers it more nourishing by one-tenth part. 
 
 X "The value of all straw for fodder must depend on the mode in which it is harvested. 
 In Scotland, the order in which the farmer places his straw for fodder is — 1st, pea ; 2nd, 
 bean ; 3d, oat ; 4th, wheat ; 5th, barley. While in England, where the bean is quite withered 
 before it is cut, it stands last in the scale."— Mr. Hyett, Roj/cU Agricultural Journal, iv., p. 148. 
 
628 COMPOSITION OF HEMP AND LINT SEEDS. 
 
 practical experience, when we come to direct our attention more parti- 
 cularly to the feeding of stock. 
 
 4°. Fatty matter in the grasses.— Besides woody fibre, starch, gum, 
 and gluten, dry hay and straw contain also a variable proportion of fatty 
 matter. According to Liebig, it does not exceed 1*56 per cent, in hay, 
 while, according to Dumas and Boussingault, as much as 3, 4, or even 5 
 per cent, of fat can be extracted from it. To this fact we shall also re 
 turn when considering the methods of fattening stock. 
 
 5°. Inorganic matter in the grasses. — The proportion of saline and 
 earthy matter contained in the grasses is an important feature in their 
 composition. This, as I have already said, is much larger than in any 
 of the other kinds of food usually given to animals, being seldom less 
 than 5, and occasionally amounting to as much as 10 per cent, of their 
 weight when in the state of hay or straw. A large proportion of the ash 
 left by the stems of the corn plants, and by many grasses, consists of 
 silica. The straw of the bean, pea, and vetch, and the ditTerent kinds 
 of clover hay, contain little silica, its place in these plants being supplied 
 by a large (juantity of lime and magnesia. 
 
 § 25. Ofhonp, line, rape, and other oil-bearing seeds. 
 
 The oily seeds are important to the agriculturist from their long ac- 
 knowledged value in the feeding and fattening of cattle. Lintseed is ex- 
 tensively used for the latter purpose, both in its entire state and in the 
 form of cake — when the greater part of the oil has already been expressed 
 from it. All these seeds, however, are not ecjually palatable to cattle. 
 Some varieties they even refuse to eat. Among these is the rape-seed, 
 from which so mucb oil is expressed, and the cake left by which is now 
 so extensively employed as a manure. 
 
 These seeds are distinguished from those of the corn plants, by con- 
 taining, instead of starch or sugar, a predominating proportion of oil ; and 
 instead of their gluten a substance soluble in water, which possesses many 
 of the properties of the curd of cheese {casein). 
 
 We are in possession of a somewhat imperfect analysis of hemp seed 
 and of the seed of the common lint, accordmg to which the varieties ex- 
 amined consisted in 100 parts of — 
 
 Hemp seed Lime seed 
 
 (Bucholz). (Leo Meier). 
 
 Oil 19-1 11-3 
 
 Husk, &:c 38-3 44-4 
 
 Woody fibre and starch . .5-0 1*5 
 
 Sugar, &c 1-6 10-8 
 
 Gum 9-0 7-1 
 
 Soluble albumen (Casein ?) . 24-7 15-1 
 
 Insoluble do — 3*7 
 
 Wax and resin .... 1-6 3*1 
 
 Loss 0-7 3-0 
 
 100 100 
 
 These analyses show that, besides the oil, these seeds contain consi- 
 derable proportions of gum and sugar and a large quantity of a substance 
 here called soluble albumen^ of which nitrogen is a constituent part, but 
 

 Oil per cent. 
 
 Sun-flower seed . 
 
 . 15 
 
 Walnut kernels . . 
 
 . 40 to 70 
 
 Hazel-nut do. 
 
 . . 60 
 
 Beech-nut do. 
 
 . . 15 to 17 
 
 Plum stone do. . 
 
 . . 33 
 
 Sweet almond do. 
 
 . . 40 to 54 
 
 Bitter do. do. 
 
 . . 28 to 46 
 
 PROPORTION OF OIL IN DIFFERENT SEEDS. 529 
 
 which differs in its properties from the gluten and albumen of the seeds 
 of the corn-bearing i)lants, and has much resemblance to the curd of, 
 milk. Besides tlieir fattening projjerties, therefore — which these seeds 
 probably owe in a great measure to tlie oil they contain — this peculiar 
 albuminous matter ought to render them very nourishing also ; — capable 
 of promoting the growth of the growing, and of sustaining the stiength 
 of the matured, animal. 
 
 The quantity of oil contained in different seeds of this class, and even 
 in the same species of seed when raised in different circumstances, is 
 very variable. These facts will appear from the following table, which 
 represents the proportions of oil that have been found in 100 lbs. of some 
 of the more common seeds : — 
 
 Oil per cent. 
 
 Line seed 11 to 22 
 
 Hemp seed 14 to 25 
 
 Rape seed 40 to 70 
 
 Poppy seed . . . . 36 to 53 
 "White mustard do. . . 36 to 38 
 Black do. do. . . 15 
 Swedish turnip do. . . 34 
 
 It seems to be a provision of nature, that the seeds of nearly all plants 
 should contain a greater or less ])roportion of oil, which is lodged for the 
 most part in, or immediately beneath, the husk, and, among other pur- 
 poses, may be intended to aid in preserving the seed. We shall here- 
 after see that this oily constituent is of much importance also to the prac- 
 tical agriculturist. 
 
 § 26. General differences in composition among the different lands of 
 
 vegetable food. 
 
 It may be useful shortly to recapitulate the leading differences in 
 chemical constitution which exist among the different kinds of vegetable 
 food to which I have directed your attention in the present lecture. 
 
 We have seen that each of the varieties of food contains a greater or 
 less proportion of three different classes of chemical substances — an 
 organic substance containing nitrogen, an organic substance containing 
 no nitrogen, and an in-organic substance. But it is interesting to mark 
 how in each class of those vegetable products which we gather from the 
 earth for our sustenance, the organic substances vary either in composition 
 or in chemical characters, while the inorganic matter alters also eitlier in 
 kind or quantity. Thus — *■ 
 
 1°. In the seeds of the corn 'plants — wheat, oats, &c. — the predomi- 
 nating ingredient is starchy m connection with a considerable pro[)ortioii 
 of gluten^ and a small quantity of saline matter consisting chiefly of the 
 phosphates of potash and of magnesia, and in the case of barley of a 
 considerable proportion of lime. 
 
 2°. In the seeds of leguminous plants — the pea, the bean, the vetch, 
 &c. — starch is still the predominating ingredient, but it is connected with 
 a large quantity of legumin, and with a greater proportion of inorganic 
 matter — in which phosphate of lime also is more abundant. 
 
 3°. In the oil-bearing seeds — tliose of hemp, lint, &c. — oil is often the 
 
530 SPECIAL DIFFERENCES AMONG SEEDS AND ROOTS. 
 
 predominating ingredient, and it is connected with a large proportion of a 
 nitrogenous substance, resembling the curd of milk [casein), and with a 
 quantity of ash about equal to that in the pea, but in which the phos- 
 phate of lime is said to be still more abundant. 
 
 4°. In the potatoe — starch is the greatly predominating ingredient, .but 
 it is united with albumen nearly in the same proportion as it is with 
 gluten in wheat. The inorganic matter is nearly in the same proportion 
 to the dry organic matter, as in the pea and the bean, but is much 
 more rich in potash and soda. Still it is more rich in the earthy phos- 
 phates than the ash left by wheat and oats, and is inferior in this respect 
 only to that of barley. 
 
 5°. In the turnip — sugar and pectin take the place of the starch, and 
 these are associated with albumen, and with a proportion of inorganic 
 matter about equal to that of the potatoe, abounding like it in potash and 
 soda, but more rich in the phosphates of lime and of magnesia. 
 
 6°. In the stems of the grasses and clovers — woody fibre becomes the 
 predominating ingredient, associated apparently with albumen, and with 
 a larger proportion of inorganic matter than in any of the other crops. 
 In the straws and in some of the grasses which are cut for hay, silica 
 forms a large portion of this inorganic matter. In the clovers, lime and 
 magnesia take its place. 
 
 The natural differences above described not only exercise an important 
 influence upon the mode of culture by which the different crops may be 
 most successfully and most abundantly raised, but also upon the way 
 in which they can be most skilfully and economically employed in the 
 feeding of stock. To this latter point we shall return hereafter. 
 
 § 27. Average composition and produce of nutritive matter per acre, by 
 each of the usually cultivated crops. 
 
 1°. Average composition. — The relative proportions of the several most 
 important constituents contained in our cultivated crops vary, as we have 
 seen, with a great number of circumstances. The following table exhi- 
 bits the average composition of ] 00 parts of the more common grains, 
 roots, and grasses, as nearly as the present state of our knowledge upon 
 the subject enables us to represent it. (See table at top of next page.) 
 
 In drawing up this table, I have adopted the proportions of gluten, for 
 the most part, from Boussingault. Some of them, however, appear to 
 be very doubtful. The proportions of fatty matter are also very uncer- 
 tain. With a few exceptions, those above given have been taken from 
 Sprengel, and they are, in general, stated considerably too low. 
 
 It is an interesting fact, that the proportion of fatty matter in and im- 
 mediately under the husk of the grains of corn, is generally much greater 
 than in the substance of the corn itself. Thus I have found the pollard 
 of wheat to yield more than twice as much oil as the fine flour obtained 
 from the same sample of grain ;* and Dumas states that the husk of oats 
 sometimes yields as much as 5 or 6 per cent, of oil. We shall perceive 
 the practical value of this fact when we come to consider the use of bran 
 and pollard in the fattening of pigs and other kinds of stock. 
 
 • Thus the four portions separated by the miller from a superior sample of wheat grown 
 in the neighbourhood of Durham, gave of oil respectively :— fine flour, 1-5 per cent. ; pollard, 
 2*4 ; boxings, 36; and bran, 3-3 per cent. 
 
AVERAGE COMPOSITION OP THE DIFFERENT CROPS. 
 
 531 
 
 Wheat . 
 Barley 
 Oats . . 
 Rye . . 
 
 Indian corn 
 Buckwheat 
 Beans . . 
 Peas . . 
 
 Potatoes . 
 Turnips . 
 Carrots 
 
 Meadow hay 
 Clover hay 
 Pea straw 
 Oat do. . 
 Wheat do. 
 Barley do. 
 Rye do. . 
 Indian corn do 
 
 Water. 
 
 16 
 
 15 
 
 16 
 
 12 
 
 14 
 
 161 
 
 16 
 
 13 
 
 151 
 
 85 
 85 
 
 14 
 
 14 
 10tol5 
 
 12 
 12tol5 
 
 do. 
 
 do. 
 
 12 
 
 Husk or 
 woody 
 fibre. 
 
 15 
 15 
 
 20 
 10 
 151 
 
 25'? 
 
 10 
 
 8 
 
 57 
 
 3 
 
 3 
 
 30 
 25 
 25 
 45 
 50 
 50 
 45 
 25 
 
 Starch, 
 
 gum, and 
 
 sugar. 
 
 55 
 
 60 
 50 
 60 
 50 
 50 
 40 
 50 
 
 12? 
 
 10 
 
 10 
 
 40 
 40 
 45 
 35 
 30 
 30 
 38 
 52 
 
 Gluten, al- 
 bumen, le- 
 gumin,&c. 
 
 10tol5 
 12 7 
 14-57 
 14-5 
 120 
 145 
 28-0 
 24-0 
 
 2-25 
 
 1-2 
 
 20 
 
 71 
 93 
 123 
 1-3 
 1-3 
 1-3 
 1-3 
 30 
 
 Fatty 
 matter. 
 
 2 to 4 J 
 
 25 J 
 
 56 J 
 
 30 
 
 5 to 9 D. 
 
 0-4 7 
 
 2 + 
 
 2-8 7 
 
 0-3 
 
 1 
 
 0*4 
 
 2to5D. 
 30 
 1-5 
 0-8 
 0-5 
 0-8 
 05 
 1-7 
 
 Saline 
 mattec 
 
 20 
 20 
 3-5 
 10 
 1-5 
 15 
 30 
 2-8 
 
 0-8 to 1 
 
 0-8 to 1 
 
 10 
 
 5 to 10 
 9 
 5 
 6 
 5 
 5 
 3 
 4 
 
 2°. Gross produce per acre. — The gross produce, per acre, of the dif- 
 ferent crops varies as we have already seen (p. 487) in different districts 
 
 of the country. The weight of each crop in pounds, however, will, in 
 general, approach to one or other of the quantities represented by the num- 
 bers in the following table : — 
 
 Produce Weight Total weight 
 
 per acre. per bushel. in pounds. 
 
 Wheat 25 bush. 60 lbs. 1500 
 
 — 30 ♦' 1800 
 
 Barley 35 " 63 lbs. 1855 
 
 — 40 " 2120 
 
 Gats 40 " 42 lbs. 1680 
 
 — 50 " 2100 
 
 Rye 25 " 54 lbs. 1350 
 
 — 30 " 1620 
 
 Indian corn .... 30 " 60 lbs. 1800 
 
 Buckwheat .... 30 " 46 lbs. 1380 
 
 Beans 25 " 64 lbs. 1600 
 
 — 30 *' 1920 
 
 Peas 25 " 66 lbs. 1650 
 
 Potatoes . 
 Turnips . 
 
 Weight of produce. 
 
 . 6 tons. 
 
 12 tons. 
 
 . 20 tons. 
 
 30 tons. 
 
 Carrots . 
 Meadow hay 
 Clover hay 
 
 Weight of produce. 
 . 25 tons. 
 . 1^ tons. 
 . 2 tons. 
 
532 
 
 PRODUCE PER ACRE. 
 
 
 Weight of produce. 
 
 
 Weight of produce. 
 
 Wheat straw 
 
 . 3000 ]bs. 
 
 Rye straw 
 
 . 
 
 4000 lbs. 
 
 
 3600 " 
 
 
 
 4800 " 
 
 Barley straw- 
 
 . 2100 " 
 2500 " 
 
 Bean straw . 
 
 • 
 
 2700 "? 
 3200 " 
 
 Oat straw . . 
 
 . 2700 " 
 
 Pea straw 
 
 . 
 
 2700 " ? 
 
 
 . 3500 " 
 
 
 
 
 3°. Average produce of nutritive matter per acre. — In the gross pro- 
 duce above given, there are contained, according to the first table, the fol- 
 lowing average proportions of nutritive matter of various kinds : — 
 
 AVERAGE PRODUCE OF NUTRITIVE MATTER OF DIFFERENT KINDS FROM 
 AN ACRE OF THE USUALLY CULTIVATED CROPS. 
 
 Gross produce. 
 
 H^J^,'"^ Starch, 
 
 Wheat 
 
 Barley 
 
 Oats 
 
 Rye 
 
 Indian corn 
 Buck wheat 
 Beans . . 
 
 Peas 
 
 Potatoes 
 
 Turnips 
 
 Carrots 
 Meadow hay 
 Clover hay 
 Pea straw . 
 Wheat straw 
 
 bush. 
 25 
 30 
 35 
 40 
 40 
 50 
 25 
 30 
 30 
 30 
 25 
 30 
 25 
 
 tons. 
 
 6 
 
 12 
 
 20 
 
 ~30 
 
 25 
 
 n 
 
 2 
 
 Oat straw . — 
 
 Barley straw — 
 Rye straw . — 
 
 lbs. 
 1,.500 
 1,800 
 1,800 
 2,100 
 1,700 
 2,100 
 1,300 
 1,600 
 1,800 
 1,300 
 1,600 
 1,900 
 1,600 
 
 13,500 
 
 27,000 
 
 45,000 
 
 67,000 
 
 56,000 
 
 3,400 
 
 4,500 
 
 2,700 
 
 3,000 
 
 3,600 
 
 2,700 
 
 3,500 
 
 2,100 
 
 2,500 
 
 4,000 
 
 4,800 
 
 lbs. 
 
 225 
 
 270 
 
 270 
 
 315 
 
 340 
 
 420 
 
 130 
 
 160 
 
 270 
 
 320^ 
 
 160 
 
 190 
 
 130 
 
 675 
 1350 
 1350 
 2010 
 1680 
 1020 
 1120 
 
 675 
 1500 
 1800 
 1210 
 1570 
 1050 
 1250 
 1800 
 2200 
 
 lbs. 
 
 825 
 
 990 
 
 1080 
 
 1260 
 
 850 
 
 1050 
 
 780 
 
 960 
 
 900 
 
 650 
 
 640 
 
 760 
 
 600 
 
 1620 
 3240 
 4500 
 6700 
 5600 
 1360 
 1800 
 1200 
 
 900 
 1080 
 
 950 
 1200 
 
 630 
 
 750 
 1500 
 1800 
 
 Gluten, 
 
 &.C. 
 
 lbs. 
 150 to 220 
 180 to 260 
 
 216 
 
 252 
 
 2301 
 
 2901 
 
 190 
 
 230 
 
 216 
 
 180 
 
 450 
 
 530 
 
 380 
 
 300 
 
 600 
 
 5401 
 
 8001 
 
 11201 
 
 240 
 
 420 
 
 330 
 
 40 
 
 48 
 
 36 
 
 48 
 
 28 
 
 33 
 
 53 
 
 64 
 
 Oil or fat. 
 
 lbs. 
 30 to 60 
 36 to 72 
 
 45 + 
 
 52-^ 
 
 95 
 118 
 
 40 
 
 48 
 90 to 170 
 5 + 
 
 32 + 
 
 36 + 
 
 45 
 
 45 
 90 
 
 7 
 
 200 
 70 to 170 
 135 to 225 
 
 40 
 
 15 
 
 18 
 
 20 
 
 28 
 
 16 
 
 20 
 
 20 
 
 24 
 
 Saline 
 matter. 
 
 lbs. 
 30 
 36 
 36 
 42 
 60 
 75 
 13 
 16 
 27 
 21 
 48 
 57 
 45 
 
 120 
 240 
 400 
 600 
 560 
 220 
 400 
 135 
 150 
 180 
 135 
 175 
 105 
 125 
 120 
 144 
 
 The most uncertain column in this table is that which represents the 
 quantity of oil or fat contained in the several kinds of produce. The 
 importance ot the whole table to the practical man will appear more 
 clearly when we come to treat of the feeding of stock. 
 
LECTURE XX. 
 
 Of milk and its products. — Properties and composition of the milk of different animals.— 
 Circumstances which affect the quality and quantity of milk— species, size, variety, age, 
 health, and constitution of the animal, time of milking, kind of food, &c. — Mode of sepa- 
 rating and estimating the several constituents of milk. — Sugar of milk, and acid of milk 
 (Lactic acid), their composition and properties. — Souring of milk, cause of. — Cream- 
 composition and variable proportions of— mode of estimating ils quantity — the galactome- 
 ter. — Churning of milk and cream. — Composition of butter. — 13iillcr-milk. — The solid and 
 liquid fats contained in butter — margarin and butter-oil — their separation and properties.— 
 Rancidity and preservation of butter. — Composition and propertiis of the curd (caserne- 
 Curdling of milk, natural and artificial — by acids and by animal membranes. — Making and 
 action of rennet — how explained. — Manufacture of cheese. — Varieties of cheese. — Aver- 
 age produce of butter and cheese. — Colouring of butter and cheese. — The whey. — Saline 
 matter in the whey. — Nature of the saline constituents of milk. — Fermentation of milk. — 
 Intoxicating liquor from milk.— Milk vinegar. — Purposes served by milk in the economy 
 of nature. 
 
 Of the indirect products of agriculture, milk, and the butter and 
 cheese manufactured from it, are among the most important. In our 
 large towns these substances may almost be considered as necessaries of 
 life, and many extensive agricultural districts are entirely devoted to the 
 • production of them. The branch of dairy husbandry also presents many 
 curious and interesting questions to the scientific enquirer, and upon 
 these questions modern chemistry has thrown much light. To the con- 
 sideration of this subject, therefore, it is my intention to devote the pre- 
 sent lecture. 
 
 § 1. Of the properties and composition of milk. 
 1°. Properties of milk. — The milk of most animals is a white opaque 
 liquid, having a slight but peculiar odour — which becomes more distinct 
 when the milk is warmed — and an agreeable sweetish taste. It is 
 heavier than water — usually in the proportion of about 103 'to 100.* 
 When newly taken from the animal, cow's milk is almost always 
 slightly alcaline. It speedily loses this character, however, when ex- 
 posed to the air, and hence even new milk often exhibits a slight degi-ee 
 of acidity, f When left at rest for a number of hours, it separates into 
 two portions, throwing up the lighter part to the surface in the form of 
 cream. If the whole milk, or the cream alone, be agitated in a proper 
 vessel (a churn), the temperature of the liquid undergoes a sUght increase, 
 it becomes distinctly sour, and the fatty matter separates in the form of 
 butter. If a little acid, such as vinegar or diluted muriatic acid, be add- 
 ed to milk warmed to about 100° F., it immediately coagulates and se- 
 parates into a solid and a liquid part — the curd and the whey. The 
 same effect is produced by the addition of rennet or of sour milk — and 
 it takes place naturally when milk is left to itself until it becomes sour. 
 At a very low temperature, or when kept in a cool place, milk remains 
 sweet for a considerable time. At the temperature of 60° F. it soon 
 
 * Or it has a specific gravity of 1020 in woman's milk, to 1041 in sheep's milk : water being 
 1000. 
 
 t It is said that if the animal remain long unmilked, the milk will begin to sour in the 
 udder, and that hence it is sometimes slightly acid*when fresh drawn from the cow. 
 
 23 
 
534 PROPERTIES AND COMPOSITION OF MILK. 
 
 turns or acquires a sour taste, and at 70° or 80° it sours with stiU greater 
 rapidity. If sour milk be gently warmed it undergoes fermentation, and 
 may^be made to yield an intoxicating liquor. By longer exposure to the 
 air it gradually begins to putrify, becomes disagreeable to the taste, 
 emits an unpleasant odour, and ceases to be a wholesome article of 
 food. 
 
 The milk of each species of animal is distinguished by some charac- 
 ters peculiar to itself. 
 
 Ewe's milk does not differ in appearance from that of the cow, but it 
 is generally more dense and thicker, and gives a pale yellow butter, 
 which is soft, and soon becomes rancid. The curd is separated from 
 this milk with greater difficulty than from that of the cow. 
 
 Goafs milk generally possesses a characteristic unpleasant odour and 
 taste, which is said to be less marked in animals of a white colour or 
 that are destitute of horns. The butter is always white and hard, and 
 keeps long fresh. The milk is considered to be very wholesome, and is 
 often recommended to invalids. 
 
 Ass's milk has much resemblance to that of the woman. It yields 
 little cream, and the butter is white and light, and soon becomes rancid. 
 It contains much sugar, and hence soon passes to the state of fermenta- 
 tion. 
 
 2°. Composition of milk. — Milk, like the numerous vegetable products, 
 we have had occasion to consider, consists, besides water, of organic sub- 
 stances destitute of nitrogen — sugar and butter ; of an organic substance 
 containing nitrogen in considerable (juantity — the curd or casein ; and 
 of inorganic or saline matter, partly soluble and partly insoluble in pure 
 water. 
 
 The proportions of these several constituents vary in diflferent animals. 
 This appears in the following table, which exhibits the composition of 
 the milk of several animals in its ordinary state, as found by Henry and 
 Chevallier : — 
 
 Woman. 
 
 Casein (cheese) . . 1-52 
 
 Butter 3-55 
 
 Milk sugar . . . 6-50 
 
 Saline matter . . . 0*45 
 
 Water 87-98 
 
 Cow. 
 
 Ass. 
 
 Goat. 
 
 Ewe. 
 
 4-48 
 
 1.82 
 
 4-08 
 
 4-50 
 
 3-13 
 
 0-11 
 
 3-32 
 
 4 20 
 
 4-77 
 
 6-08 
 
 5-28 
 
 5-00 
 
 0-60 
 
 0-34 
 
 0-58 
 
 0-68 
 
 87-02 
 
 91-65 
 
 86-80 
 
 88-62 
 
 100 100 100 100 100 
 
 From the numbers in the above table, it appears that the milk of the 
 cow, the goat, and the ewe, contains much more cheesy matter than that 
 of the woman or the ass. It is probably this similarity of asses' milk to 
 that of the human species, together with its deficiency in butter, which, 
 from the most remote times, has recommended it to invalids, as a light 
 and easily digested drink. 
 
 § 2. Of the circumstances by which the composition or quality of the milk 
 
 is modified. 
 
 But the composition or quality of milK varies with a great variety of 
 circumstances. Let me direct your attention to a few of these. 
 
 1°. Distance from the time of calving. — The most remarkable depar- 
 
INrLUENCE OF THE HEALTH OF THE ANIMAL. 535 
 
 ture from the ordinary composition of milk is observed in the leistingSf 
 colostrum or first milk, yielded by the animal after the birdi of its young. 
 This milk is thicker and yellower than ordinary milk, coagulates by 
 heating, and contains an unusually large quantity of casein or cheesy 
 matter. Thus the first milk of the cow, the ass, and the goat, consisted, 
 in some specimens examined by Henry and Chevallier, of — ' 
 
 Cow. Ass. Goat. 
 
 Casein » . 15-1 11-6 24-5 
 
 Butter . . 2-6 0-6 5-2 
 
 Milk sugar . — 4-3 3-2 
 
 Mucus . . 2-0 0-7 3-0 
 
 Water . . 80-3 82-8 64-] 
 
 100 100 100 
 
 The increase in the proportion of cheese is peculiarly great in the first 
 milk of the ass and the goat. 
 
 This state of the milk, however, does not long continue. It gradually 
 assumes its ordinary qualities. After ten or twelve days from the time 
 of calving, its peculiarities disappear, though in the celebrated dairy dis-. 
 tricts of Italy it is considered that the milk does not reacli perfection until 
 about eight months after calving. [Cataneo, 11 latte e i suoi prodotiL p. 
 27.] 
 
 2°. Age of the animal. — It is observed that milk of the best quality is 
 given only by cows which have been already three or four times in calf. 
 Such animals continue to give excellent milk till they are ten or twelve 
 years of age, and have had seven or eight calves, when they are 
 generally fattened for the butcher. 
 
 3°. Climate and season of the year. — Moist and temperate climates 
 are favourable to the production of milk in large quantity. In hot coun- 
 tries, and in dry seasons, the quantity is less, but the average quality is 
 richer. Cool weather favours the production of cheese and sugar in the 
 inilk, while hot weather increases the yield of butter, [Sprengel, Che- 
 mie fiir Landwirthe, ii., p. 620.] 
 
 In spring the milk is more abundant and of finer flavour. In autumn 
 and winter, other things being equal, it yields less cheese, but a larger 
 return of butter.* Where cattle are fed upon pasture grass only, this 
 observed difference may be derived from a natural ditference in the 
 quality of the herbage upon which the cow is fed. 
 
 4°. Health and general state of the atiimal. — It is obvious that the 
 quality of the milk must be affected by almost every change in the health 
 of the animal. It is sensibly less rich in cream also, as soon as the cow 
 becomes pregnant, and the same is observed to be the case when it shows 
 a tendency to fatten. The poorer the apparent condition of the cow, 
 good food being given, the richer in general is the milk. 
 
 5°. Ti?ne and frequency of milking. — If the cow be milked only once 
 a day, the milk will yield a seventh jiart more butter than an equal 
 quantity of that which is obtained by two milkings in the day. When 
 the milk is drawn three times a day, it is more abundant but still less 
 
 • British Husbandry, ii., p. 404. This opinion seems to contradict that of Sprengel in the 
 preceding paragraph. Does this difference ai'ise from the locality and other, unlike circum 
 stances in which the observations of the two writers were severally made — or are there no 
 accurate experiments upon the subject from which a correct result can be drawn 1 
 
636 INFLUENCE OF THE BREED ON THE QUALITY OF MILK. 
 
 rich. It is also universally remarked, that the morning's milk is of bet- 
 ter quality than that obtained in the evening. 
 
 6°. Period at whichit is taken, during the milking. — The milk in the 
 udder of the cow is not uniform in quality. That which is first drawn 
 off is thin and poor, and gives little cream. That which is last drawn — 
 the stroakings, strippings, or afterings — is rich in quality, and yields 
 much cream. Compared with the first milk, the same measure of the 
 last will give at least eight and often sixteen times as much cream (An- 
 derson). The quality of the cream also, and of the milk when skimmed, 
 is much better in the later than in the earlier drawn portions of the milk. 
 
 7°. Treatment and moral state of the animal. — A state of comparative 
 repose is favourable to the performance of all the important functions in 
 a healthy animal. Any thing which frets, disturbs, torments, or renders 
 it uneasy, affects these functions,* and, among other results, lessens the 
 quantity or changes the quaUty of the milk. Such is observed to be the 
 case when the cow has been newly deprived of her calf — when she is 
 taken from her companions in the pasture field — when her usual place 
 in the cow-house is changed — when she is kept long in the house after 
 the spring has arrived — when she is hunted in the field or tormented by 
 insects — or when any other circumstance occurs by which irritation or 
 restlessness is caused, either of a temporary or of a permanent kind. I 
 do not enquire at present into the physiological nature of the changes 
 which ensue — to the dairy farmer it is of importance chiefly to be familiar 
 with the facts. 
 
 8°. Theracc or breed and size of the animal. — The quality of the milk 
 depends much upon the race and size of the cow. As a general 
 rule, small races, or small individuals of the larger races, give the richest 
 milk from the same kind of food. Thus the small Highland cow gives 
 a richer milk than the Ayrshire. The small Alderneys give a richer 
 cream than any other breed in common use in this country.* The small 
 Kerry cow is said to equal the Alderney in this respect, while the small 
 Shetlander has been found in the north of Scotland to give from the same 
 food a more profitable return of rich milk than any of the larger races. 
 All these breeds are hardy, and will pick up a subsistence from pastures 
 on which other breeds would starve. 
 
 The old Yorkshire stock, a cross between the short-horn and the 
 Holderness, is preferred by the London cow-keepers as giving the ^ar^e*i 
 quantity of milk, though poor in quality. 
 
 The long-horns are preferred in Cheshire and Lancashire because of 
 their producing a greater quantity of cheese. The Ayrshire kyloe, on 
 ordinary pasture, is said to be unrivalled for abundant produce"(Ayton) 
 — though the milk is not so rich as that of the small breeds. Various 
 crosses have been tried in different parts of the island — and in almost 
 every district it has been found that the produce of some particular stock 
 is best adapted to the chmate, the soil, the natural grasses, the prevailing 
 husbandry, or to the kind of dairy produce which it is the interest of the 
 farmer to raise in his own peculiar neighbourhood. 
 
 • A very sfrikiiiK illustration of the difference in the quality of the milk of two breeds, in 
 the same circvimslances, is given by Mr. Malcolm, in his Cumpendmm of Modern Hus- 
 bandry. He kept an Alderney and a SufTolk cow, the latter the best he ever saw. During 
 seven years, the milk and butter being kept separate, it was found, year after year, that the 
 value of the Alderney exceeded that of the Suffolk, though the latter gave more than 
 double the quantity of milk at a meal — British Husbandry^ ii.. p. 397. 
 
EXPERIMENTS WITH DIFFERENT KINDS OP FOOD. 537 
 
 In the South of Europe, the Swiss breeds are considered the best for 
 dairy purposes, and of these that of the Canton of Schweitz, which, in 
 size, is intermediate between the large cattle of Fribourg and Berne, and 
 the small breed of Hasti. They have enormous udders and give much 
 milk, but like that of the Suffolk cows it is less rich in butter and clieesc. 
 
 The influence of breed alone upon the quality of the milk is well il- 
 lustrated by the result of a series of trials made at Bradley Hall, in 
 Derbyshire. During the height of the season, and when fed upon tUa 
 same pasture, cows of four ditlerent breeds gave per day — 
 
 Or 1 lb. of butter was 
 Breed. Milk. Butter. yiejded by 
 
 Holderness . . 29 quarts, and 38| oz. 12 quarts of milk. 
 
 Aldemey ... 19 " 25"" " 12 " 
 
 Devon ... 17 " 28 " 9| " 
 
 Ayrshire ... 20 *' 34 " 9^ " 
 
 The Ayrshire cows gave the richest milk and a larger quantity of both 
 milk and butter than the Alderneys or Devons, but the Holderness breed 
 surpassed them all. It gave ^ lb. more butter than the Ayrshire, and 
 nearly one-half more milk. It would appear, therefore, to be admirably 
 adapted to the purposes of the town dairyman, whose profit arises from 
 milk and cream only. It does not appear what is the relative value of 
 this breed in the production of cheese. 
 
 9°. The kind of food. — But the kind of food has probably more in- 
 fluence upon the quality of the milk than any other circumstance. It is 
 familiar to every dairy farmer that the taste and colour of his milk and 
 cream are affected by the plants on which his cows feed, and by the food 
 he gives them in the stall. The taste of the wild onion and of the turnip, 
 when eaten by the cow, are often perceptible both in the milk and in the 
 butter. If madder be given to cows the milk is red, if they eat saffron 
 it becomes yellow. It has also been observed from the most remote 
 times, that when fed upon one pasture a cow will yield more cheese, 
 upon another more butter. From this has arisen the practice more or 
 less observed in all dairy districts of varying the food of the cattle — of 
 giving some artificial food in addition to that obtained in the natural pas- 
 tures — of leaving the animal at liberty to roam over wide pastures and 
 thus to seek out for itself, as the sheep does on extensive sheep-walks, 
 those diflTerent kinds of herbage which are necessary to the production 
 of a rich and valuable milk — or in more inclosed districts, and where 
 different soils exist on the same farm, of turning them during the former 
 part of the day into one field, and during the latter part into another. 
 
 Various sets of experiments have been made with the view of deter- 
 mining the relative quantities of butter and cheese produced by the same 
 animals, when fed upon different kinds of food. Much, however, re- 
 mains yet to be done both by the practical dairy farmer and by the an- 
 alytical chemist, before this subject can be fully cleared up. According 
 to theory, as I shall more fully explain in my next lecture, the legumi- 
 nous plants — clover, tares, &c., and the cultivated seeds of such plants- 
 peas and beans, ought to promote the production of cheese ; while oil- 
 calie, oats, and other kinds of food which contain much oily matter, 
 ought to favour the yield of butter. The most recent experiments we 
 possess, however, do not lend ciny decided confirmation to these theoreti- 
 
538 EXPERIMENTS WITH DIFFERENT KINDS OF FOOD. 
 
 cal views. The most extensive series of trials lately published is that 
 of Boussingault, [Annales de Chim. et de Phys., Ixxi., p. 79,] from 
 which I select the following : — 
 
 FIRST SERIES MADE ON A FRENCH COW. 
 
 T\^„„ „f,^^ Quarts Composition of the milk per cent. 
 
 Svine Kind of food. of . ^ i . 
 
 ^**^"^" milk. Casein. Butter. Sugar. Salts. Water. 
 
 200 Hay .... 5 30 45 47 01 877 
 
 207 Turnips ... 5^ 3-0 42 50 0-2 87-6 
 
 215 Beet .... 5 34 40 53 02 871 
 
 229 Potatoes ... 4f 34 40 5-9 02 86-5 
 
 302 Kay and oil-cake 2h 3-4 36 60 02 86-8 
 
 SECOND SERIES MADE ON A SWISS COW. 
 
 176 Potatoes and hay 8'- 3-3 48 51 03 86-5 
 
 182 Hay and clover 7§ 40 4-5 40 03 87-2 
 
 193 Clover ... 8f 4-0 22 4-7 0-3 88-8 
 
 204 Do. in flower . 6^ 3-7 3-5 52 0-2 87*4 
 
 In the first series of experiments the proportion of cheesy matter and 
 of sugar was greatest when beets, potatoes, and oil-cake were given, 
 while the largest proportion of butter was obtained from the use of hay 
 and the least from oil-cake. 
 
 In the second series the proportion both of cheese nnd of butter de- 
 creased by the use of clover, while the quantity of milk was not per- 
 manently increased. 
 
 These two series of experiments may appear to be deserving of less 
 
 reliance because they were not made on successive days, but at varjdng 
 
 intervals of time. But some recent experiments, made in Lancashire 
 
 by Dr. Playfair, are little more satisfactory. These Avere made upon a 
 
 short-horned cow, which was fed one day in the field on after-grass, and 
 
 during the four succeeding days in the stall, upon weighed quantities of 
 
 tlifferent kinds of food. [Memoirs of the Chemical Societ}^, i., p. 174.] 
 
 Composition of the milk. 
 
 Day's Food. Qts. . ^ , 
 
 Casein. Butter. Sugar. Salts. Water. 
 
 lo AftPrjrm^ 5 Evening's milk.. 4 5-4 3-7 38 06 86-5 
 
 1 . Auer grass ^Morning's do.. 4^ 3-9 5-6 30 0-5 87-0 
 
 2°. 281bs.nay ^Evening's do.. 3i 4-9 5-1 3-8 0-5 85-7 
 
 2i lbs. Oatmeal S Morning's do.. 4" 5-4 3-9 4 '8 0-5 85-4 
 
 '"•fxSl^oZtm^aV^ Evening's do.. 4 - - _ - - 
 
 8lbs Bean ?lour::^ Morning's do.. 4^ 3-9 4-6 4-5 0-7 86-3 
 
 *°u\bs^Hlfr'""" Evening's do.. 5 3-9 6-7 4-6 0-6 &i-2 
 8 lb?Bea.TFiour::^ Morning's do.. 4 27 4-9 5-0 0-5 86-9 
 
 5°. Wlbs.Hay P Evening's do.. 5i 3-9 4-6 3-9 0-5 87-1 
 
 SOlbs. Potatoes... S Morning's do.. 4f 3*5 4*9 3*8 0-5 87*3 
 
 In these experiments there appears an increase in the proportion of but- 
 ter and sugar, and in the quantity of milk on the fourth day, when the 
 potatoes, hay, and bean flour were given together. On the fifth, when 
 potatoes and hay only were given, the quantity of milk went on increas- 
 ing, but it was poorer in quality. Could we infer any thing, then, from 
 a single day's trial, it would be that the bean meal had aided in the pro- 
 duction of butter and sugar — instead of cheese, as theory Avould indicate 
 — while the steamed potatoes had added to the quantity of the milk. 
 But no sensible results can justly be expected in regaxd to the influence 
 
INFLUENCE OF THE STATE OF PREGNANCY. 639 
 
 of this or that food, except by a much more prolonged series of careful 
 
 observations. , • j • i 
 
 If we compare the quantity of albumen and casem contamed m the 
 food, with that yielded in the milk during the four days' experiments of 
 Dr. Playfair, we shall -find no perceptible relation between the two quan- 
 tities. Thus, the cow on the — . 
 
 Albumen Of Casein 
 
 2d day eat 2 i- lbs., and yielded 0-93 lbs. 
 
 3d " 5 » " 1-0 " 
 
 4th " 4 " " 0-75 " 
 
 5tl^ a 1-7 «' «' 0-94 " 
 
 So that, whether, as on the third day double the quantity was eaten, or, 
 as on the fifth, little more than half as much as was consumed on the 
 second day, the produce of cbeesy matter in the milk was sensibly the 
 same, on each of the three days. i i • j r 
 
 We must not, however, from these experiments, mfer that the kmdot 
 food really has no influence upon the quality of the milk— for this con- 
 clusion is contradicted by general experience. We must wait rather for 
 renewed and more extended practical researches, by which both our 
 theory and practice may probably be amended, and by which the con- 
 clusions may be reconciled to which they respectively lead us. [See the 
 following Lecture " On the feeding of stock:'] 
 
 ■ 10°. State of 'pregnancy.— -I have already stated (p. 535), that the 
 richness in cream diminishes as soon as the cow becomes pregnant. The 
 same is no doubt true also of the amount of cheese which the same 
 volume of milk will be capable of yielding. It must become poorer in 
 every respect, or else considerably less in quantity (p. 541), as soon as the 
 cow is with calf, since a portion of the food which might otherwise have 
 been employed in the production of milk, must now be directed to the 
 nourishment of the young animal in the womb of the mother. In the 
 experiments to which I have just directed your attention in regard to the 
 effect of the kind of food upon the quality of the milk, the state of preg- 
 nancy of the animal was not taken into consideration, though, as I have 
 already said, this must necessarily exercise an important influence upon 
 the quality of the milk, whatever be the kind of food upon which the 
 animal may have been fed.* To this the want of accordance between 
 theory and experiment is probably in part to be ascribed. ^ _ 
 
 11°. Individual form and constitution of the animal— Bnt it is well 
 known that animals of the same breed, fed on the same food, will yield 
 milk not only in different quantities, but also of very different quality. 
 In regard to the form, Mr. Youatt states that the '' Milch cow should 
 haveli long thin head, with a brisk but placid eye,— should be thin and 
 hollow in the neck, narrow in the breast and point of the shoulder, and 
 altof^ether li^ht in the forequarter— but wide in the loins, with little dew- 
 lap,°and neither too full fleshed along the chine, nor shewing in any part 
 an inclination to put on mucli fat. The udder should especially be 
 large, round, and full, with the milk veins protruding, yet thm skmned, 
 but not hanging loose or tending far behind. The teats should also stand 
 square, all pointing out at equal distances and of the same size, and al- 
 
 • Both of the cows experimented upon by BoussingauU were with calf, Dr Playfair does 
 not mention whether his was so or not. 
 
540 EFFECT OF l>'r>IVlDUAL FORM AND CONSTITUTION. 
 
 though neither very large nor thick towards the udder, yet long and 
 tapering towards a point. A cow with a large head, a high backbone, a 
 small udder and teats, and drawn up in the belly, will, beyond all doubt, 
 be found a bad milker." [Youatt's Cattle, p. 244, quoted in British Hus- 
 bandry, ii., p. 397.] Thus, while much depends upon the breed, the 
 form of the individucd also has much influence upon its value as a 
 milker. 
 
 But independent of form, the quality of the milk is greatl}'' affected by 
 the individual constitution of every cow we feed. Thus in a report of 
 the produce of butter yielded by each cow of a drove of 22, chiefly of the 
 Ayrshire breed — all of which we may presume to have been selected 
 for dairy purposes with equal regard to their forms — and which were 
 all fed upon tlie same pastures in Lanarkshire, the yield of milk and 
 butter by four of the cows in the same week is given as follows : — 
 Milk. Butter. 
 
 A yielded ... 84 quarts, which gave .... 3^ lbs. 
 
 F and R each . 86 " u "it 5| ibg, 
 
 G yielded ... 88 " " " 7 lbs.* 
 
 Showing that, though the breed, the food, and the yield of milk was 
 nearly the same, the cow G produced twice as much butter as the cow 
 A — or its milk was twice as rich. This result would have been still 
 more interestiag had we known the relative quantities of grass consumed 
 by these two cows respectively. 
 
 I will not insist upon other causes by which the quality of the milk is 
 more or less materially affected. It is said that when stall fed the same 
 cow will yield more butter than when pastured in the field — that the age 
 of the pasture also influences the yield of butter — ani that salt mingled 
 with the food improves botli the quantity and the quality of the milk 
 There are, probably, few circumstances which are capable in any way 
 of affecting the comfort of the animal which will not also modify the 
 quality of the milk it yields. 
 
 § 3. Of tJie fiircumstances which affect the quantity of the milk. 
 
 The epithet good-milker applied to a cow has very different significa- 
 tions in different districts and countries. Thus the experiments of 
 Boussingault upon the effect of different kinds of food on the quality of 
 the milk (p. 538) were made upon a French cow which was considered 
 a good milker, and yet when in best condition never gave more than 11 
 quarts a day. Two, or even two and a half, times that quantity is not 
 considered extraordinary in the height of the season in many parts of our 
 island. 
 
 There are three circumstances which principally affect the quantity of 
 milk— -namely, the breed, the kind of food or pasture, and the distance 
 from the time of calving. 
 
 1°. The breed. — The smaller breeds of cattle yield, as is to be ex- 
 pected, a smaller daily produce of milk — though from the same weight 
 of food they occasionally give even a greater volume of milk than the 
 larger breeds. 
 
 Good ordinary cows in this country yield, on an average, from 8 to 12 
 
 * Prize Essays of the Higkiand Society, New Series, ii., p. 258. ^ 
 
CIRCUMSTANCES ArFECT THE QUANTITY Or MILK. 541 
 
 quarts a day. The county surveys state the average daily produce Df 
 dairy cows to be, in — 
 
 Devonshire ... 12 qts. I Lancashire . . . 8 to 9 qts. 
 
 Cheshire .... 8 " | Ayrshire 8 " 
 
 But the best Ayrshire kyloes will yield an average of 12| quarts daily, 
 during 10 months of the year (Ayton). 
 The yearly produce of the best Ayrshire kyloes is stated by Mr. 
 
 Ayton at 4000 qts 
 
 Of average Ayrshire stock ....... 2400 " 
 
 Good short-horns, grazed in suinmer, and fed on hay and tur- 
 nips in winter (Dickson) ....... 4000 " 
 
 Mixed breeds in Lancashire (Dickson) ..... 3500 " 
 
 Large dairy of mixed long and short-horns, at Workington 
 
 Hall, taking an average of 4 years (Mr. Curwen) . .^5700 " 
 Crossed breeds in many localities are found more productive in milk 
 than pure stock of any of the native races of cattle. 
 
 2°. Food and pasture. — Li the same animal the quantity of milk is 
 known to be greatly influenced by the kind of food. This is best under- 
 stood in the neighbourhood of large towns where the profit of the dairy- 
 man is dependent upon the quantity* rather than upon the quality of his 
 milk. Hence the value of highly succulent foods — of the grass (/f irri- 
 gated meadows — of mashed and steained food — of brewers' grains — ot 
 turnips, potatoes and beets — and of other similar vegetable productions 
 which contain much water intimately mixed with nutritive matter, and 
 thus tend both to aid in the production of milk and to increase its quan- 
 tity. 
 
 3°. Distance from the time of calving. — It is a well-known fact that 
 cows in general after the first two inonths from the time of calving, 
 though fed upon the same food in equal quantity, begin gradually to give 
 less milk, till at the end of about 10 months they become altogether, or 
 nearly, dry. In the best Ayrshire kyloes, the rate of this decrease is thus 
 represented by Mr. Ayton : — 
 
 First fifty days, 24 qts. per day,— ^or in all, 1200 qts. 
 '■ ' - u u 1000 " 
 
 " " 400 " 
 
 " " 400 " 
 
 " u 300 " 
 
 Some cows indeed do not run dry throughout the whole 3^ear, but these 
 may be considered as exceptions to the general rule. By feeding them 
 upon brewer's grains, mashes, and succulent grass, the milk-sellers near 
 our large towns occasionally keep the same cow in profitable milking 
 condition for three years and upwards. f Such cows are generally fat- 
 tened after they have become dry — indeed as they cease to give milk, 
 they generally lay on fat in its stead — and, as soon as they arc consider- 
 ed ripe, are sold off to the butcher. 
 
 * It is quoted, even by foreign writers, as a fair joke against the dairy establishments of 
 our large towns, that among the advantages possessed by one which was advertised for sale, 
 much stress was laid upon a never-failing pu7np. — See II lalte e i suoi produtii.^ p. 67. 
 
 t Even on shipboard I have heard of a cow being kept in milk during the whole of a three 
 years' cruise — the food being principally a kind of pease soup. After the first year, how- 
 ever, the milk is said to become thinner and more watery. 
 23* 
 
 -fadfib*^ 
 
 Second 
 
 do. 
 
 20 
 
 Third 
 
 do. 
 
 14 
 
 Fourth 
 
 do. 
 
 8 
 
 Fifth 
 
 do. 
 
 8 
 
 Sixth 
 
 do. 
 
 6 
 
542 MODE OF SEPARATING THE CONSTITUENTS OF MILK. 
 
 § 4. Of the mode of separating and estimating the several constituents 
 
 of milk. 
 
 1°. If a weighed quantity of milk be allowed to stand for a sufficient 
 length of time, the cream will rise to the top, and may be easily skim- 
 med off. If this cream be gently heated the butter in an oily form will 
 collect upon the surface, and when cold may be separated from the 
 water beneath, and its weight determined. 
 
 2°. If the skimmed milk be gently warmed, and a little vinegar or 
 rennet then added to it, the curd will separate, and may be collected in a 
 cloth, pressed, dried, and weighed. 
 
 3°. If a second equal portion of the milk be weighed and then evap- 
 orated to dryness by a gentle heat and again weighed, the loss will be 
 the quantity of water which the milk contained. 
 
 4^. If now the dried milk be burned in the air till all the combustible 
 matter disappears, and the residue be weighed, the quantity of inorganic 
 saline matter will be determined. 
 
 5°. Supposing those processes to be performed with tolerable accuracy, 
 the difference between the sum of the weight of the water, butter, curd, 
 and ash, and the weight of the milk employed, will nearly represent 
 that of the sugar contained in the given quantity of milk. 
 
 For many purposes a rude examination of milk after this manner may 
 be sufficient, but where any thing like an accurate analysis is required, 
 more refined methods must be adopted. In such cases, the following 
 appears to be the best which has hitherto been recommended. [Haid- 
 len, Annal. der Chera. & Phar,, xlv., p. 263.] 
 
 a. The butter. — The weighed quantity of milk is mixed with one- 
 sixth of its weight of common unburnt gypsum previously reduced to a 
 very fine powder. The whole is then evaporated to dryness with fre- 
 quent stirring at the heat of boiling water (212° F.) A brittle mass is 
 obtained, which is reduced to fine powder. By digesting this powder in 
 ether, the whole of the butter is dissolved out, and by evaporating the 
 ether, may be obtained in a pure state and weighed. Or the powder 
 itself, after being treated with ether, may be dried and weighed. The 
 butter is thelTestimated by the loss. 
 
 b. The sugar. — After the removal of the butter, alcohol is poured upon 
 the powder and digested with it. This takes up the sugar with a little 
 saline matter soluble in alcohol. By evaporating this solution and 
 weighing the dry residue, the quantity of sugar is determined. Or, as 
 before, the powder itself may be dried and weighed and the sugar esti- 
 mated by the loss. If we wish to estimate the small quantity of inor- 
 ganic saline matter which has been taken up along with the sugar, it 
 maybe done by burning the latter in the air, and weighing-the residue. 
 
 c. The saline matter. — A second weighed portion of milk is now evap- 
 orated carefully to dryness and again weighed. The loss is the water. 
 The dried milk is then burned in the air. The weight of the incombus- 
 tible ash indicates the proportion of inorganic saline matter contained in 
 the milk. 
 
 d. The casein. — The weight of the butter, sugar, saline matter and 
 water being thus known and added together, the deficiency is the weight 
 of the casein. 
 
 I 
 
PROPERTIES OF THE SUGAR OF MILK. • 543 
 
 § 5. Of the sugar of milk, and of the acid of milk or lactic acid. 
 Before I can hope to make you understand the nature of the changes 
 which take place during the souring, the churning, and the curdling of 
 milk, it will be necessary to make you acquainted with the sugar of 
 milk, and with lactic acid or the acid of milk. 
 
 1°. Sugar of milk. — When the curd is separated from milk, the raw 
 whey afterwards boiled—with or without the addition of new and butter 
 2nilk— and the floating churd skimmed off or separated by straining 
 through a cloth, the whey is obtained nearly free from butter and cheese. 
 By mixing it while hot with well beat white of egg, the remainder of the 
 curd is coagulated, and may be removed by again straining through 
 cloth. If the clear whey, thus obtained, be boiled down in a pan to one 
 fourth of its bulk, then poured into an earthen dish, and set aside for a 
 few days in a cool place, minute hard white crystals gradually de- 
 posit themselves upon the sides and bottom of the vessel. These crystals 
 are sugar of milk. A second portion may be obtained by evaporating 
 the remaining whey still further, and again setting aside. Ifthewhey 
 be at once evaporated to dryness a white mass of impure sugar is pre- 
 pared, which in many places is used as an article of food. Of the purer 
 variety large quantities are extracted from milk by the Swiss shepherds, 
 and in their country it forms an important article of commerce. 
 
 The sugar of milk is less sweet than that of the grape, or of the sugar 
 cane. It Is harder also, and much less soluble in water, and is gritty 
 between the teeth. This sugar undergoes no change when exposed to 
 the air, either in the dry state or when dissolved in water. But if a little 
 of the curd of milk (casein) be introduced into the solution it gradually be- 
 comes sour, lactic acid is formed, and the liquid begins to ferment. Car- 
 bonic acid is given off— as is the case during the fermentation of other 
 liquids— and alcohol is produced. In milk the two substances are na- 
 turally intermixed, and it is the presence of the cheesy matter, as we 
 shall hereafter see, which at favourable temperatures always causes milk 
 of every kind first to become sour and then to ferment. 
 
 The gluten of wheat and animal membranes of various kinds produce 
 a similar effect upon solutions of sugar of milk. A piece of bladder, or 
 of the gut or stomach of an animal, immersed into a solution of the sugar, 
 changes it by degrees into lactic acid, and upon this influence depends 
 the effect of the calf s stomach, in the form of rennet, in the curdling of 
 milk. The effect of such membranes is more speedy after they have 
 been some time taken from the body o*f the animal, a fact which also ac- 
 cords with the long experience of the dairy districts in the preparation of 
 
 rennet. r -u 
 
 When a litde sulphuric or muriatic acid is added to a solution ot milk 
 sugar, it is slowly converted into grape sugar. This change is hastened 
 very much by boiling it with the acid. It is supposed that previous to 
 the fermentation of milk the sugar it contains undergoes a similar change 
 into the sugar of grapes. , . 
 
 Milk sugar has not hitherto been formed by art. It exists in the niilK 
 of all mammiferous animals, and from this source alone have we hith- 
 erto been able to obtain it. j i, • 
 2°. The acid of milk—lactic aci^.— When milk is exposed to the air 
 for a length of time it acquires a sour taste, which gradually increases in 
 
544 
 
 THE ACID OF MILK, OR LACTIC ACID. 
 
 intensity till at lengtli the whole begins to ferment. This sour taste is 
 owing to tlie production of a peculiar acid, to which the name of acid 
 of milk or lactic acid has been given. The same acid is formed during 
 the fermentation of the juices of the beet, and of the turnip, in sour cab- 
 bage {sauer kraut), and sour malt, in brewers' grains which have become 
 sour, in the sour vegetable mixtures with which cattle are often fed, in 
 the waste liquor of the tanners, in the fermented extract of rice, and in 
 large quantity during tlie fermentation of the gluten in the manufacture 
 of starch from wlieaten flour, or of a mixture of oat-meal or bean- 
 meal with water, which is allowed to stand and become sour. 
 
 The acid, therefore, differs from the sugar of milk in so far that it can 
 readily be formed, and in any quantity, by artificial means. As it is 
 not employed for an}'- economical purposes, I shall not trouble you with 
 the methods by which this acid is obtained in a state of purity. 
 
 It is rarely found in milk Avhen first drawn from the cow, but it very 
 soon begins to be formed in it. It is produced from the sugar, through 
 the influence of the cheesy matter of the milk. The pure acid may be 
 mixed with cold milk without causing it to curdle, but if the mixture be 
 heated, the curd forms and speedily separates. It is for the same reason 
 that milk may be distinctly sour to the taste, and yet may not coagulate. 
 But if such milk be heated it will curdle immediately. So cream when 
 sour may not appear so, till it is poured into hot tea, when it will break 
 and leave its cheesy matter floating on the surface. 
 
 § 6. Of the mutual relations which exist hetiveen lactic acid and the cane^ 
 grape, and milk sugars. 
 
 It is important, and I think it will prove interesting to you, to under- 
 stand the beautifully simple relation which exists between the sugar of 
 milk and this lactic acid, which plays so important a part in nearly all 
 your daily operations. 
 
 Cane sugai", grape sugar, milk sugar, and lactic acid, as they exist in 
 solution in water or in milk, may all be represented as compounds of car- 
 bon loith water — or of carbon with hydrogen and oxygen in the propor- 
 tions in whichlhey exist in water. Thus they consist respectively of — 
 
 12Carbon + 12 Water 
 
 or 
 
 Cane sugar . . . 
 
 Grape sugar . . 
 
 Milk sugar . . . 
 
 Lactic acid . . . 
 
 Acetic acid (vinegar) 
 
 I have added acetic acid to this list, to show you that the lactic acid 
 bears a similar relation to the sugars as this acid does. You will recol- 
 lect that starch, gum, and woody fibre, have also a similar relation to 
 the sugars — and that by certain apparently simple transformations these 
 
 12C + 
 
 12H + 
 
 120 
 
 12C + 
 
 14H -f 
 
 140 
 
 24C -f 
 
 24H + 
 
 240 
 
 6C + 
 
 6H 4- 
 
 CO 
 
 4C + 
 
 3H + 
 
 30 
 
 or 
 
 or 
 
 or 
 
 or 
 
 12C -f 12HO* 
 
 12 Carbon + 14 Water 
 12C + 14HO 
 24 Cai-bon -j- 24 Water 
 
 24C -f 24HO 
 6 Carbon -\- 6 Water 
 
 6C -f 6HO 
 
 4 Carbon + 3 Water 
 4C 4- 3HO 
 
 • C, H, and O, as in our former lectures, representing respectively carbon, bydroisen, and 
 oxygen, and HO water— a compound of hydrogen with oxygen. 
 
CHANGE OF MILK SUGAR INTO LACTIC ACID. 645 
 
 several substances are capable of being converted into grape sugar. In 
 like manner all these sugars by a similar simple transformation are 
 readily converted into one or other of the two acids above named. Starch, 
 gum, and woody fibre in favourable circumstances are transformed intc 
 sugar, (see Lecture VI., p. Ill) — the sugars, in favourable circum- 
 stances, are further transformed into the lactic or the acetic acids. 
 
 We have seen that animal membranes or the curd of milk liave the 
 property of changing these sugars into lactic acid. This they do, though 
 cxchided from the action of the air, and without the escape of any gas. 
 The above formulas show with what apparent simplicity this may be 
 accomplished. 
 
 In fact, cane sugar, milk sugar, and lactic acid, as above represented, 
 consist of the same elements united together m the same proportions. It 
 is easy to conceive therefore in what way the one may be transtbrmed 
 into the other. 
 
 1°. Two of lactic acid are represented by 12C + 12H + 120, whicli 
 is the formula for cane sugar. The transforming action of the animal 
 membrane, or of the casein in its state of incipient decay, is therefore 
 simply to cause the elements of the sugar to assume a new arrangement 
 — in which instead of cane sugar they form a substance having the very 
 ditferent ])roperties of lactic acid. 
 
 2°. Again, milk sugar is represented by 24C + 24H + 240, and 4 
 of lactic acid are also equal to 24C -}- 24H + 240 ; the change which 
 takes place when milk becomes sour, therefore, is easily understood 
 Under the influence of the casein the elements of a portion of the milk 
 sugar are made to assume a new arrangement, and the sour lactic acid 
 is the result. There is no loss of matter, no new elements are called into 
 play, nothing is absorbed from the air or given off into it — but a simple 
 transposition of the elements of the sugar takes place, and the new acid 
 compound is produced. 
 
 These changes appear very simple, and yet how difficult it is to con- 
 ceive by what mysterious influence the mere contact of this decaying 
 membrane or of the casein of the milk, can cause the elements of the 
 sugar to break up their old connexion, and to arrange themselves anew 
 in another prescribed order, so as to form a compound endowed Avith 
 properties so very diflferent as those of lactic acid. It is beautiful to see 
 the simple means by which in nature so many important ends are ac- 
 complished — to observe how they are all veiled to the uninstructed — and 
 how every slight accession to our knowledge opens up new wonders to 
 us even in those ordinary operations with which during our whole lives 
 we have been most familiar. 
 
 From these intellectual, in addition to other rewards, which constantly 
 follow the study of nature, you will with me draw the conclusion — 
 which is ever pressing itself upon our attention — that it is the will and 
 intention of the Deity, that all his works shall be thoroughly studied and 
 investigated. But you will, I think, agree with me in drawing this con- 
 clusion, because of the further and higher moral effect also which such 
 investigations tend to produce upon the mind. Every fresh discovery, 
 as it opens up new fields of knowledge, forces upon us more distinctly the 
 sense pf our own ignorance. In the case before us we are delighted by 
 the apparent simplicity which the several transformations of starch intc 
 
546 SOURING AND PRESERVING OF MILK. 
 
 sugar, and of the latter into lactic acid, may be brought about, and seem 
 almost to understand how it is done, since it can be effected by a simple 
 transposition of their elements. But the after-thought occurs — by what 
 kind of power is this change effected ? The materials are certainly pre- 
 sent, but how are they made to shift their relative positions, and move 
 into their new places ? We have conquered one intellectual difficulty 
 only to encounter another apparently still harder to overcome. 
 
 It was said first, I believe by Priestley, [Experiments and Obser- 
 vations, ii., p. ix., edition 1781,] " that the greater the circle of light, 
 the greater is the boundary of darkness by which it is confined." Thus 
 they who know the most are the most strongly impressed with the sense 
 of their own want of knowledge. What a fine result this is of large 
 acquirements ! And how touchingly it was expressed by Sir Isaac New- 
 ton, when he likened his great discoveries to the gathering of a few peb- 
 bles along the sea-shore — the vast ocean of natural knowledge lying still 
 unexplored before, him ! 
 
 § 7. Of the souring and preserving of milk. 
 
 The natural souring of milk requires now little explanation. It arises 
 from the gradual conversion of the sugar into the acid of milk by the 
 action of the casein. There are, however, one or two circumstances con- 
 nected with it to which it may be proper to advert. 
 
 1°. If milk be kept at a low temperature, it may. be preserved for se- 
 veral days without becoming sensibly sour. This is effected in Switzer- 
 land by immersing the milk vessels in a shallow trough of cool water, 
 which, by means of a running stream, can at any time be renewed. In 
 such circumstances the action of the cheesy matter in converting the 
 sugar into lactic acid is very slow. 
 
 2°. But if the milk be kept at the temperature of 65° or 70° F. it be- 
 comes sour with great rapidity, and if afterwards raised to the boiling 
 point curdles immediately. An easy way of preserving milk or cream 
 sweet for a longer time, or of removing the sourness when it has alre^Idy 
 coine on, is to add to it a small quantity of the common soda, pearl ash, 
 or magnesianof the shops. Enough is added, when a little of the milk 
 poured into boiling water no longer throws up any curd. As the small 
 quantity of soda or magnesia thus added is not unwholesome, cream 
 may in this way be kept sweet for a considerable time, or may have its 
 sweetness restored when it has already become sour. 
 
 3°. I have already observed to you that animal membrane, the curd of 
 milk, or any of those substances which possess the power of changing sugar 
 into lactic acid, loose that power if the solution in which they are present 
 be raised to the boiling temperature. Hence if milk be introduced into 
 bottles, be then well corked, put into a pan with cold water, and gradually 
 raised to the boiling point, and after being allowed to cool be taken out 
 and set away in a cool place, the milk may be preserved perfectly 
 sweet for upwards of half a-year. 
 
 1 mentioned also th&t if the solution containing the sugar and cheesy 
 matter be again exposed to the air after boiling, it will gradually resume 
 the property of transforming the sugar into lactic acid. Hence, if milk 
 be boiled, it is preserved sweet for a longer period of time, but the 
 casein gradually resumes its trajisforming property, and at the end of a 
 
SEPARATION OF CREAM FROM THE MILK. 547 
 
 few days turns it sour. If, however, the milk be boiled every morning 
 or every second morning, the souring property of the casein is at every 
 boiling destroyed again, and the milk may thus be kept fresh for two 
 months or more. 
 
 4°. Another mode of preserving milk is to evaporate it to dryness by 
 a gentle heat, and under constant stirring. By this means a dry mass is 
 obtained which may be preserved for a length of time, and which when 
 dissolved in water is said to possess all the properties of the most excel- 
 lent milk. It is known in.Italy by the name of latteina. [II latte e i 
 suoi prodotti, p. 19.] 
 
 § 8. Of the separation and measurement of cream, the galactometer, the 
 composition of cream, and the prejmration of cream-cheese. 
 
 1°. Separation of cream. — The fatty part of the milk which exists in 
 the cream, and which forms the butter, is merely mixed with and held in 
 suspension by -the water of which the milk chiefly consists. In the 
 udder of the cow it is in some measure separated from, and floats on, the 
 surface of the milk, the later drawn portions being always the richest in 
 cream. During the milking, the rich and poor portions are usually 
 mixed intimately together again, and thus the after-separation is render- 
 ed slower, more difficult, and less complete. That this is really so, is 
 proved by two facts — first, that if niilk be well shaken or stirred, so 
 as to mix its parts intimately together before it is set aside, the cream 
 will be considerably longer in rising to the surface — and second, that 
 more cream is obtained by keeping the milk in separate portions as it is 
 drawn, and setting these aside to throw up their cream in separate ves- 
 sels, than when the whole milking is mixed together. When the collec- 
 tion of cream, therefore, is the principal object, economy suggests that 
 the first, second, third, and last drawn portions of the milk should be 
 kept apart from each other. Even in large dairies this could easily be 
 effected by having three or four pails, in one of which the first, in 
 another the second milk, and so on, might be collected. 
 
 Cream does not readily rise through any considerable depth of milk ; 
 it is usual, therefore, to set it aside in broad shallow vessels in which the 
 milk stands at a depth of not more than two or three inches. By this 
 means the cream can be more effectually separated within a given time. 
 
 But the temperature of the surrounding air materially affects the 
 quantity of cream which milk will yield, or the rapidity with which it 
 rises to the surface and can be separated. Thus it is said that from the 
 same milk an equal quantity of cream may be extracted in a much 
 sViorter time during warm than during cold weather — that, for example, 
 milk may be perfectly creamed in — 
 
 .36 hours, when the temperature of the air is 
 
 nA (( (t (( (( 
 
 18 to 20 hours " '• " 
 
 10 to 12 " " " 
 
 — while, at a temperature of 34° to 37° F., milk may be kept for three 
 weeks,» without throwing up any notable quantity of cream (Sprengel). 
 
 The reason of this is that the fatty matter of the rtiilk becomes partially 
 solidified in cold weather, and is thus unable to rise to the surface of the 
 milk so readily as it does when in a warm and perfectly fluid state. 
 
 50° 
 
 F. 
 
 55° 
 
 F. 
 
 68° 
 
 F. 
 
 77° 
 
 F. 
 
548 COMPOSITION OF CREAM. 
 
 The above remarks apply to milk of ordinary quality and consistency. 
 In very thin or poor milk, in which little cheesy matter is contained, the 
 cream will rise more quickly. 
 
 2°. Measurement of cream — the galactometer. — The richness of milk 
 is very generally estimated by the bulk of cream which rises to its 
 surface in a given time. For the purpose of testing this richness, a 
 simple instrmnent, dignified by the learned name of a s;alactometer 
 (milk-gauge), has been recommended and may often be useful. It con- 
 sists of a narrow cylindrical vessel or long tube of glass, divided or gra- 
 duated into 100 equal parts. This vessel is filled up to 100 with the 
 milk to be tested, and at the end of 24 or 36 hours, the quantity of cream 
 which has risen is estimated by the number of degrees of space which it 
 occupies at the top of the milk. If it cover 3 degrees the milk yields 
 3 per cent., if 7 degrees 7 per cent, of cream. This instrument, how- 
 ever, will give a result which will be generally less than the truth, be- 
 cause the cream will always rise slowly through 5 or 6 inches of milk — 
 the smallest length which the instrument can conveniently be — and most 
 slowly in the richest and thickest milk. Unless considerable care be 
 taken, therefore, this milk-gauge may easily lead to erroneous con- 
 clusions in regard to the relative degrees of richness of different samples 
 of milk. 
 
 3°. Composition of cream. — Cream does not consist wholly of fatty 
 matter (butter), but the globules of fat as they rise bring up with them a 
 variable proportion of the casein or curd of the milk, and also some of the 
 milk sugar. It is owing to the presence of sugar that cream is capable 
 of becoming sour, while the casein gives it the property of curdling when 
 mixed with acid liquids or with acid fruits. 
 
 The proportion of cheesy matter present in cream depends upon the 
 richness of the milk and upon the temperature at which the milk is kept 
 during the rising of the cream. In cool weather the fatty matter will 
 bring up with it a lai'ger quantity of the curd, and form a thicker cream, 
 containing a greater propoidon of cheesy matter. The composition of 
 cream, therefore, is very variable — much more so than that of milk — 
 and depends very much upon the mode in which it is collected. 
 
 A specimen of cream, examined by Berzelius, which had a density 
 (specific gravity) of 1'0244, consisted of — 
 
 Batter, separated by agitation 4*5 per cent. 
 
 Cheesy matter, separated by coagulating the butter- 
 milk 3-5 " 
 
 Whey 92-0 « 
 
 100 
 Some of the butter remained, as is usually the case, in the butter- 
 milk, and added a little to the weight of the curd which was afterwards 
 separated, but the result of this analysis is sufficient to show that cream 
 in general contains a very considerable proportion of cheesy matter — 
 sometimes almost as much cheese as butter.* 
 
 ' The clouted cream of Devonshire and other Western counties, as well as the butter pre- 
 pared from it, probably contains an unusually large (inantity of cheese. It is prepared by 
 straining the warm m.ilk into large shallow pans into which a little water has previously been 
 put, allowing these to stand from 6 to 12 hours, and then carefully heatin , them over a slow 
 fire, or on a hot plate, till the milli approaches the boiling point. The n Jlk, however, must 
 
CREAM-CHEESE AND MASCARPONI. 549 
 
 I would remark, however, that this cream examined by Berzelius 
 must have been of an exceedingly poor quality — little richer, indeed, 
 than common milk, since 100 lbs. of it would only have yielded 4^ lbs. 
 of butter. CreaTU of good quality in this country, when skilfully 
 churned, will yield about one-fourth of its weight of butter, or one wine 
 gallon of cream, weighing 8} lbs., will give nearly 2 lbs of butter.* 
 
 4°. Cream-cheese. — You will now readily understand the nature of 
 what is called cream-cheese — how it differs from ordinary cheese and 
 from butter, and why it so soon becomes first sour, and then rancid. 
 
 In preparing this cheese the cream in this country is generally, I be- 
 lieve, either tied up in a cloth or put into a shallow cheese vat, and al- 
 lowed to curdle and drain without any addition. The cheesy matter and 
 butter remain thus intimately intermixed, and it is more or less rich, ac- 
 cording as the proportion of butter to the cheesy matter in the cream is 
 greater or less. This cheese becomes soon rancid and unpleasant to the 
 taste, because the moist curd, after a certain length of exposure to the 
 air, not only decomposes and becomes unpleasant of itself, but acquires 
 the property of changing the butter also and of imparting to it a dis- 
 agreeable taste and smell. 
 
 In Italy, cream-cheeses, called mascarponi, are made by heating the 
 cream nearly to boiling, and adding a little sour whey as the oily matter 
 begins to separate. The whole then coagulates, and the curd is taken 
 out and set ta drain in shapes. As the sour whey is apt to give this 
 cheese an unpleasant flavour or a yellow colour, it is said to be better to 
 take 20 grains of Tartaric acid for each quart of cream, to dissolve it in 
 a little water, and to add this, instead of the sour whey, to the hot cream. 
 The acid runs off in the whey of the cream, and the cheese is colour- 
 less and free from foreign flavour. The mascarponi, like the Knglish 
 cream-cheeses, are covered with leaves or straw, are littled pressed or 
 handled, and must be eaten fresh. 
 
 § 9. Of the separation of butter by churning or otherivise. 
 
 Milk is a kind of natural emulsion in which the fatty matter exists in 
 the state of very minute globules, suspended in a solution of casein and 
 sugar. Cream is a similar emulsion, differing from milk chiefly in con- 
 taining a greater number of oily globules and a much smaller proportion 
 of water. In milk and cream these globules appear to be surrounded 
 with a thin white shell or covering, probably of casein, by which they 
 are prevented from running into one another, and collecting into larger 
 oily drops. 
 
 But when cream is heated for a length of time, these globules, by their 
 lightness, rise to the surface, press nearer to each other, break through 
 
 not actually boil, nor must the skin of the cream be broken. The dishes are now removed 
 into the dairy, and allowed to cool. In summer the cream should be churned on tht; fol- 
 lowing day— in winter it may stand over two days. The quantity of cream obtained is said 
 to be one-fourih greater by this method, and the milk which is left is proportionably poor. 
 When milk on which no cream floats is heated nearly to boiling in the air, apelUcleof 
 cheesy matter forms on its surface. Such a pellicle may form in a less degree in the scald- 
 ding process of Devonshire, and may thus increase the bulk of the cream. The Corstor- 
 phine cream of Mid-Lothian resembles the clouted cream very much, and is made in a very 
 similar way. 
 
 * A series of analyses of cream, collected under different circumstances, might throw some 
 useful light upon the manufacture and preservation of butter. 
 
550 OF THE SEPARATION OF BUTTER. 
 
 their coverings, and unite into a film of melted fat. In like manner, 
 when milk and cream are strongly agitated by any mechanical means, 
 the temperature is found to rise, the coverings of the globules are broken 
 or separated, and the fatty matter unites into small grains, and finally 
 into lumps, which form our ordinary butter. This union of the globules 
 appears to be greatly promoted by the presence of a small quantity of 
 acid — since in the practice of churning it never takes place until the 
 milk or cream has become somewhat sour. 
 
 These two facts afford an explanation of the various methods which 
 are in different places adopted for the preparation of butter. 
 
 1°. By heating the cream. — When rich cream is heated nearly to boil- 
 ing, and is kept tor some time at that temperature, the butter gradually 
 rises and collects on the surface in the form of a fluid oil. On cooling, this 
 oil becomes solid, and may be readily removed from the water and curd 
 beneath. The fatty matter of the milk is thus obtained in a. purer form 
 than when butter is prepared in the usual way. It may, therefore, be 
 kept for a longer period without salt and without becoming rancid, but it 
 has neither the agreeable flavour nor the consistence of churned butter, 
 and is, therefore, scarcely known in our climate as an article of food.* 
 
 The same oily kind of butter may also be obtained by melting the 
 churned butter and pouring off the transparent liquid part which floats 
 upon the top. .This is the only form in which sweet butter is known in 
 many parts of Russia. In warm weather it has the consistence of a 
 thick oil, is used instead of oil for many culinary purposes, and is de- 
 noted, indeed, by the same Russian word. It may be kept for a consi- 
 derable time without salt. 
 
 2°. By churning the cream — a. Sour cream. — Cream for the purpose 
 of churning is usually allowed to become sour. It ought to be at least 
 one day old, but may with advantage be kept several days in cool 
 weather — if it be previously well freed from milk and be frequently 
 stirred to keep it from curdling. 
 
 This sour cream is put into the churn and worked in the usual way 
 till the butter-separates. This is collected into lumps, well beat and 
 squeezed free from the milk, and in some dairies is washed with pure 
 cold water as long as the water is rendered milky. In other localities 
 the butter is not washed, but, after being well beat, is carefully freed 
 from the remaining milk by repeated squeezings and dryings with a clean 
 cloth. Both metliods, no doubt, have their advantages. In the same 
 circumstances the washed butter ma}'' be more easily preserved in the 
 fresh state, while the unwashed butter will probably possess a higher 
 flavour. 
 
 b. Sweet cream. — If sweet cream be put into the churn the butter may 
 be obtained, but in most cases it requires more labour and longer time, 
 widiout, in the opinion of good judges, affording in general a finer 
 quality of butter. In all cases the cream becomes sour during the agi- 
 tation and before the butter begins distinctly to form (see p. 554.) 
 
 c. Clouted cream. — The churning of the clouted cream of this and 
 other countries forms an exception to the general rule just stated, that 
 more time is required in the churning of sweet creams. Clouted cream 
 
 ' It is said, that when melted butter is poured into very cold water, it acquires the consis* 
 tency and appearance of common butter. 
 
CHURNING THE WHOLE MILK. 551 
 
 may be churneil in tlie morning after it is made, that is, within 24 hours 
 of the time when the milk was taken from the cow — and from such 
 creara.it is well known that the butter separates with very great ease. But 
 in this case the heating of the cream has already disposed the oily matter 
 to cohere, an incipient running together of the globules has probably taken 
 place before the cream is removed from the milk, and hence the com- 
 parative ease with which the churning is effected. I suppose there is 
 something peculiar in butter prepared in this way, as it is known in 
 other counties by the name of Bohemian butter. It is said to be very 
 agreeable in flavour, but it must contain more cheesy matter than the 
 butter from ordinary cream. 
 
 3°. Ckurning the whole milk. — Butter m very many districts is pre- 
 pared from the whole milk. This is a much more laborions method — 
 from the difficulty of keeping in motion such large quantities of fluid. 
 It has the advantage, however, it is said, of giving a larger quantity of 
 butter ; and in the neighbourhood of the towns in Scotland and Ireland 
 the ready sale obtained for the butter-milk is another inducement for the 
 continuance of the practice. 
 
 At Rennes, in Brittany, the milk of the previous evening is poured 
 into the churn along with the warm morning's milk, and the mixture is 
 allowed to stand for some hours, when the whole is churned. In this 
 way it is said that a larger quantity of butter is obtained, and of a more 
 delicate flavour. [II latte e i suoi prodotti, p. 112.] 
 
 In the neighbourhood of Glasgow, according to Mr. Ayton,* the milk 
 is allowed to :stand 6, 12, or 24 hours in the dairy till the whole has 
 cooled, and the cream has risen to the surface. Two or three milkings, 
 still sweet, are then poured, together with their cream, into a large ves- 
 sel, and are left undisturbed till the whole has become distinctly sour, 
 and is completely coagulated. The proper sourness is indicated by the 
 formation of a stiff' fera^ upon the surface luhicli has become uneven (Bal- 
 lantyne). Great care must be taken, however, to keep the brat and 
 curd unbroken until the milk is about to be churned, for if any of the 
 whey be separated the air gains admission to it and to the curd, and 
 fermentation is induced. By this fermentation the quality of the butter 
 may or may not be affected, but that of the butter-milk is almost sure to 
 be injured. 
 
 In Holland the practice is a little different. The cream is not allow 
 ed to rise to the surface at all, but the milk is stirred two or diree times a 
 day, till it gets sour, and so thick that a wooden spoon will stand in it. 
 It is then 'put into the churn, and the working or the separation of tha 
 butter is assisted by the addition of a quantity of cold water. 
 
 By churning the sour milk in one or other of these ways, the butter 
 js said to be " rich, sound, and well-flavoured." If it be greater in 
 quantity — which appears to be the opinion of those who practise it in 
 this country, in Germany, and in Holland — it is, according to Sprengel, 
 because the fatty matter carries with it from the milk a larger quantity of 
 casein than it does in most cases from the cream alone ( ?). 
 
 § 10. Of the composition of butler. 
 Butter prepared by any of the usual methods contains more or less of 
 * In his Dairy Husbandry, a work much praised, and which I regret that I have never seen. 
 
552 COMPOSITION OF BUTTER. 
 
 all the ingredients which exist in milk. It consists, however, essentially 
 of the fat of milk intimately mixed with a more or less considerable 
 proportion of casein and water, and with a small quantity of sugar of 
 milk. Fresh butter is said to contain about one-sixth of its weight (16 
 per cent.) of these latter substances, and five-sixths of pure fat (Chev- 
 reul). How much of the 16 per cent, usually consists of cheesy matter 
 has not yet been determined.* 
 
 It is probable, however, that the proportion of cheesy matter contained 
 in butter varies very much. The thickness and richness of the milk— 
 the mode of preparing the butter, whether from the whole milk or from 
 the cream — the way in which the cream is separated from the milk, 
 whether by clouting or otherwise — and the nature of the food and pas- 
 ture, must all affect in a very considerable degree the relative pro- 
 portions of the fatty and cheesy matters of which our domestic butter 
 consists. 
 
 Besides the casein and sugar, butter also usually contains some colour- 
 ing substance derived fz-om the plants on which the cow has fed, and 
 some aromatic or other similar ingredients to which its peculiar flavour 
 is owing, and which are also derived from the food on which the animal 
 lives. 
 
 The fat of butter may be readily separated from all these substances, 
 and obtained in a nearly pure state. Fresh newly-churned butter is 
 melted in a cylindrical jar at a temperature of 140° to 180° F., the 
 fluid oil poured off* into water heated to the same temperature, and re- 
 peatedly shaken with fresh portions as long as any thing soluble is taken 
 up. When left at rest in a warm place, the melted fat rises to the sur- 
 face in the form of a nearly colourless transparent oil, which, on cooling, 
 hardens into a colourless mass. 
 
 This pure fat may be preserved for a much longer time without be- 
 coming rancid (Thenard). It is the various substances with which its 
 fatty matter is mixed that give to common butter its tendency to become 
 so speedily rancid and to acquire an unpleasant taste. To the nume- 
 rous precaiotious which have been adopted with the view of counteract- 
 ing this tendency, and of preserving the sweet taste of butter, I shall pre- 
 sently direct your attention. 
 
 § 11. Of the average quantity of butter yielded hy milk and cream, and 
 of the yearly produce of a cow. 
 
 l^have already made you acquainted with some of those numerous 
 circumstances by which the quality of milk is affected. These same 
 circumstances will necessarily more or less affect the quantity of butter 
 also, which a given weight or measure of milk can be made to yield. 
 
 Thus in the King William's town dairy (County Kerry), the average 
 quantity of milk and butter yielded by the Kerry and Ayrshire breeds 
 respectively was, in a whole year — 
 
 Ayrshire cow, 1328 quarts, of which 9|to 9,^ quarts gave 1 lb. of but- 
 ter. 
 
 * Since the above was written, two samples of fresh butter, from cream, examined in my 
 laboratory, have yielded only 05 and 07 per cent, respectively of cheesy matter. This is 
 certainly a much smaller quantity than I had expected. Does butter from the whole milk 
 contain more 1 A series of such examinations would prove not iminteresting. 
 
QUANTITY OF BUTTER YIELDED BY MILK. 553 
 
 Kerry coiv, 1264 quarts, of which from 8 quarts to 8} gave 1 lb. of 
 butter. » 
 
 Showing, as I have before stated, (p. 536), that the small Kerry cow, 
 upon the same pasture, will give a richer milk even than the Ayrshire. 
 
 In Holstein and Lunenburg again, it is considered, on an average, 
 that 15 quarts of milk will yield 1 lb. of butter. The milk in that 
 country, therefore, must be very much poorer in butter. [Journal of the 
 Royal Agricultural Society, I. p. 386.] 
 
 The result of numerous trials, however, made upon the milk and 
 cream of cows considered as good butter-givers, in this country, has 
 established the following average relation between milk, cream, and but- 
 ter : — 
 
 Milk. Cream. Butter. 
 
 18 to 21 lbs. I . n S 4 lbs. ? , „ 
 
 9tollqts.$ y^^^^ J2qts.*^ ^'■llb- 
 
 The cow, therefore, that yields 3000 quarts of milk should produce, 
 where butter is the principal object of the farmer, about 300 lbs. of but- 
 ter, or 1 lb. a day for 300 days in the year. 
 
 This is not a large daily produce, since some cows have been known 
 to give for a limited time as much as two or even three pounds of butter 
 in a single day. It is a large quantity however, taken as the average of 
 a lengthened period of time, and hence such cases as that of Mr. Cramp's 
 cow, which for four years continuously yielded nearly a pound and a 
 half of butterf every day, are naturally quoted as extraordinary. 
 
 In most districts the average of the whole year is much less than a 
 pound a day, even for ten months only. lo Devon, for the first twenty 
 weeks after calving, a good cow will yield 12 quarts of milk a day, from 
 which, by the method of scalding, a pound and a quarter of butter can be 
 extracted. 
 
 In South Holland, [Loudon's Encyclopgedia,] a good cow will pro- 
 duce during the summer months about 76 lbs. of butter. In the high 
 pastures of Scaria in Switzerland, a cow v/ill yield during the ninety 
 days of summer about 40 lbs. of butter, or less than half a pound a day. 
 In Holstein and Lunenburg it is considered a fair return if a cow yields 
 100 lbs. of butter, and even in England, [British Husbandry, II., p. 
 404,] 160 to 180 lbs. is reckoned a fair annual produce for a cow, or from 
 8 to 9 ounces a day for ten months in the year. 
 
 § 12. Of the circumstances which affect the quality of butter. 
 It is known that the butter produced in one district of the country, dif- 
 fers often in quality from that produced in another, even though the same 
 method of manufacture be adopted. In different seasons also the same 
 farm will produce different qualities of butter — thus it is said that cows 
 which are pastured yield the most pleasant butter in May, when the first 
 green fodder comes in — that the finest flavoured is given by cows fed upon 
 spurrey (Sprengel) — that it is generally the hardest when the animal 
 lives upon dry food — and that autumn butter is best for long keeping. 
 
 ' The quarts spoken of in this lecture are old wine quarts, of which 5 make an iinperial 
 gallon. A wine gallon of milk or cream weighs about 8 lbs. 4 oz., an imperial gallon about 
 10 lbs. 5 oz. About two imperial gallons, therefore, should yield a pound of butter. 
 
 t It gave in four years 2132 lbs. of butter from 23,559 quarts of milk, or 16 quarts a da7, of 
 which 11 quarts gave a pound of butter. 
 
554 FIRST AND SECOND MILX AND CREAM. 
 
 These differences may all be ascribed lo varieties or natural differe^ices 
 in the pasture^or fodder upon wliich the cow is fed.* The constitution oi 
 the animal also is known to affect the quality of the butter — since there 
 are some animals which with the best food will never give first-rate but- 
 ter. 
 
 In all such cases as these, however, the quality of the butter is almost 
 entirely dependent upon that of the milk from which it is made, so that 
 whatever affects the quality of the milk must influence also that of the 
 butter prepared from it. But as I have already considered the circum- 
 stances by which the quality of the milk is principally modified (p. 
 534), I shall not further advert to this subject at present. 
 
 But from the same milk, and even from the same cream, by different 
 modes of procedure, very different qualities of butter may be obtained. 
 The mode of making or extracting butter, therefore, is highly worthy of 
 your attention. Let us consider a few of the more important circum- 
 stances under which different qualities of butter may be extracted from 
 the same quality of milk or cream. 
 
 1°. First and second drawn milk. — If the milk be collected in two or 
 three successive portions, as it comes from the cow, Ave have already 
 seen (p. 536), that the last drawn portion v/ill be much richer than that 
 which has been taken first. The cream yielded by it will also be richer, 
 and of a finer and higher flavour. Whether, therefore, the butter be ex- 
 tracted directly from the whole milk, or from the cream, the butter ob- 
 tained from the three successive portions will differ in quality almost as 
 much as the several portions of milk themselves. 
 
 A practical application of this fact is made in some of the Highland 
 counties of Scotland, and in other districts, where the calves are allowed 
 to suck, or are fed with, the first half of the milk as it comes from the 
 cow — the latter and richest half only being reserved for dairy purposes. 
 This second milk is found to afford an exquisite butter. 
 
 2°. First and second cream.— In like manner the first cream that rises 
 upon any milk is always the richest, and gives the finest flavoured but- 
 ter. The after-creamings are not only poorer in butter, but yield it of a 
 whiter colour and of inferior (juality. 
 
 This fact again is well understood, and has been long practically ap- 
 plied in the neighbourhood of Epping, which is celebrated for the excel- 
 lence of its butter. The cream of the first 24 hours is set aside and 
 churned by itself. The second and third creams produce a pale, less 
 pleasant butter, which always sells for an inferior price. Any admix- 
 ture of the after-creamings causes a corresponding diminution in the value 
 of the butter produced. To produce the most exquisite butter the cream 
 of the first eight hours only ought to be taken. 
 
 3°. Mode of creaming. — The rapidity with which cream rises to the 
 surface, either naturally or when influenced by art, affects the quality of 
 the cream, and consequently that of the butter made from it. In warm 
 weather it rises more quickly than in cold, and more quickly still when 
 the milk is heated, as in the preparation of clouted cream. The butter 
 
 * The influence of the food given in the stall and of the plants eaten in the pasture, upon 
 the colour and flavour of the butter, is familiar to all practical men. The turnipy taste of 
 the butter in winter— the garlic taste in summer, where the wild onion grows in the pastures 
 —and the alleged effect of raw potatoes in winter, in giving a rich colour to the butter, are 
 eommoa examples of this kind. 
 
TOO RAPID OR OVER-CHURNING. 555 
 
 (Bohemian butter) obtained from such cream — from cream thus rapidly 
 brought to the surface — may be expected to differ both in flavour, in con- 
 sistency, and in composition, from that yielded by the cream of the same 
 milk when allowed to rise in the usual manner. 
 
 4°. Sourness of the cream. — For the production of the best butter it is 
 necessary that the cream should be sufficiently sour before it is put into 
 the churn. Butter made from sweet cream (not clouted), is neither good 
 in quality nor large in quantity, and longer time is required in churning. 
 It is an unprofitable method (Ballantyne). 
 
 5°. Quickness in churning. — The more quickly milk or cream is 
 churned, the paler, the softer, and the less rich the butter. Cream, ac- 
 cording to Mr. Ayton, may be safely churned in an hour and a half, 
 while milk ought to obtain from two to three hours. The churning 
 ought also to be regular, slower in warm weather that the butter may 
 not be soft and white, and quicker in winter that the proper temperature 
 may be kept up. 
 
 Mr. Blacker has lately introduced into this country a barrel-churn in- 
 vented by a Mr. Valcourt, which, being placed in a trough of water of 
 the proper temperature, readily imparts the degree of heat required by 
 the milk or cream without the necessity of adding warm water to the 
 milk, and churns the whole i!h ten or twelve minutes. It is said also to 
 give a larger weight of butter from the same quantity of milk. If the 
 quality be really as good by this quick churning, the alleged inferiority 
 in the quality of butter churned quickly in the common churn can not 
 be due to the mere rapidity of churning alone. 
 
 6°. Over- churning. — When the process of churning is continued after 
 the full separation of the butter, it loses its fine yellowish, waxy ap- 
 pearance, and becomes soft and light coloured. The weight of the butter, 
 however, is said to be considerably increased ; and hence that in Lan- 
 cashire over-churning is frequently practised in the manufacture of fresh 
 butter for immediate sale (Dr. Traill.) 
 
 7°. Temperature of the milk or cream.— Much also depends upon the 
 temperature of the milk or cream when the churning is commenced. 
 Cream when put into the churn should never be warmer than 53° to 55° 
 F. It rises during the churning from 4° to 10° F. above its original 
 temperature. When the whole milk is churned, tne temperature should 
 be raised to 65° F., which is best done by pouring in hot water into the 
 churn ivhile the milk is kept in motion.* 
 
 The importance of attending to the temperature and to the quickness 
 of churning, when the best quality of butter is required, is shown by the 
 two following series of results obtained in the churning of cream at dif- 
 ferent temperatures and with different degrees of rapidity. 
 
 The first series was obtained in the August and September of 1823,.by 
 Dr. Barclay and Mr. Allan. The quantity of cream churned in each 
 experiment was 15 wine gallons, weighing from 8 lbs. to 8^ lbs. per gal- 
 lon. 
 
 Ballantyne, Transactions of the Highland Society, New Series, I., p. 24. Some object to 
 this method of adding hot water, saying that it renders the butter pale and less valuable in the 
 market. This is by no means universally the case, and the keeping the milk in motion, 
 while the water is added, may possibly, in some cases, make the difference. lu other cases. 
 maybe owing to natural differences in the quality of the milks operated upon. 
 
556 TEMPERATURE OF THE MILK OR CREAM. 
 
 Temperature. Quantity of 
 
 ,. -^ X Time in Butler 
 
 No. Begin- ^^-i Churning, per gallon. Quality of the Butter, 
 
 ning. *'"''• Hours. lb. oz. 
 
 1 50° 60° 4 1 15A Very best, rich, firm, well tasted. 
 
 2 55° 65° 3} 1 154 Not sensibly superior to the former. 
 
 3 58° 67° 3 1 14 Good, but softer. 
 
 4 60° 68° 3 1 121 Soft and spongy. 
 
 5 66° 75° 2i 1 10| Inferior in every respect. 
 
 The results of these experiments prescribe the temperature of 50 to 55° 
 F. for the cream when put into the churn, and from 3^ to 4 hours as the 
 most eligible for producing butter, both in the largest quantity and of the 
 finest quality. Something, however, appears to depend upon the quality 
 of the cream ; since the indications of the next series of experiments dif- 
 fer considerably from the above, in so far at least as regards the length 
 of time expended in churning. 
 
 The following experiments were made in Edinburgh, by Mr. Ballan- 
 tyne, between June and August, 1825. The quantity of cream he used 
 at each churning was 8 wine gallons — weighing 8 lbs. to the gallon, ex- 
 tcept hat of the fourth experiment, which weighed 4 ounces less. 
 
 
 Temperature. Time in 
 
 Quantity of 
 
 
 
 ,,/>>. Chum- 
 
 Butter 
 per gallon. 
 
 io. 
 
 Of the 
 
 When but- ing. 
 
 
 cream. 
 
 ter came. Hours. 
 
 lbs. oz. 
 
 1 
 
 56°F. 
 
 60°F. n 
 
 2 1 
 
 2 
 
 52° 
 
 56° 2 
 
 2 0) 
 
 3 
 
 52° 
 
 56 2 
 
 2 0\ 
 
 4 
 
 65° 
 
 67° i 
 
 1 15 
 
 5 
 
 50° 
 
 53i° 3 
 
 1 15i 
 
 Quality of the butter. 
 
 Inferior; white and softer than No. 2. 
 
 The flavour and quality of these two 
 butters could not be surpassed. 
 
 Soft, white, and milky. 
 
 Good — evidently injured by long churn- 
 ing. 
 
 6 53i° 57^° li 2 Of Most excellent. High in flavour and 
 
 colour, and solid as wax. 
 
 To obtain butter from cream, therefore, both finest in quality and 
 largest in quantity, these two series of experiments prescribe the follow- 
 ing temperatures of the cream, and times in the churning — 
 
 ' Temperature. Time. 
 
 First ... 50° to 55° 3| to 4 hours 
 
 Second . . 53^° li to 1| " 
 
 In the temperature both agree. It is probable that the nature of the 
 (jream obtained at different seasons or in different localities may render 
 a longer time necessary in the churning on some occasions or in some 
 places than in others. It is certain that the sourer the cream, the sooner 
 generally will the butter come.* 
 
 8°. Churnwg the entire milk. — It is in connection with the tempera- 
 ture at which milk and cream may respectively be best and most eco- 
 nomically churned, that the chances of obtaining a butter of good quality 
 at every season of the year appear to be greater when the whole milk is 
 used, than when the cream only is put into the churn. 
 
 Cream, when the churning commences, sliould not be warmer than 
 55° F. — milk ought to be raised to 65° F. In winter, either of these tem- 
 peratures may be easily attained. In cold weather it is often necessary 
 
 * In sweet cream, when the butter is long in coming, the addition of a little vinegar, brandy, 
 or whiskey, will hasten the churning. 
 
ADVANTAGE OF CHURNING THE WHOLE MILK. 557 
 
 I.) add hot water to the cream to raise it even to 55°. But in summer, 
 and '".specially in hot vv^eather, it is difficult, even in cool and well or- 
 dered dairies, to keep the cream down to this comparatively low temper- 
 ature. Hence if the cream he then churned, a second rate butter, at best, 
 is all that can be obtained. 
 
 Milk, on the other hand, requires a temperature of 65° — ten degrees 
 higher than cream — and therefore neither summer nor winter weather 
 materially affects the ease of churning it. In winter, its temperature is 
 raised by hot water, as that of cream is, and even in summer there can 
 be few days in our climate — where the milk is kept in a well contrived 
 dairy — in which it will not be necessary to add more or less hot water in 
 order to raise the milk to 65° F. Thus, where the entire milk is churned, 
 the same regular method or system of churning can be carried on through- 
 out the whole year. No difficulty is to be apprehended from the state 
 of the weather, nor, so long as the quality of the milk remains the same, 
 is there reason to appreliend any change in the quality of the butter. 
 The winter butter and the summer butter may be alike firm, finely fla 
 voured, and rich in colour. 
 
 The alleged advantages of churning the entire milk rather than the 
 cream may be thus stated : — 
 
 a. The proper temperature can be readily obtained both in winter and 
 in summer. 
 
 •- 6. A hundred gallons of entire milk will give in summer five per cent, 
 more butter than the cream from the same quantity of milk will give 
 (Ballantyne). 
 
 c. Butter of the best quality can be obtained without difficulty both 
 in winter and in summer. 
 
 d. No special attention to circumstances or change of method is at 
 any time required. The churning in winter and summer is alike simple 
 and easy. 
 
 e. The butter is not only of the best quality while fresh, but is also 
 best for long keeping, when properly cured or salted (Ballantyne). 
 
 To these advantages it is set oflf, that except in the neighbourhood of 
 large towns, the butter-milk is of little value — while from the skimmed- 
 milk, a marketable cheese can always be manufactured. But this ought 
 to be no objection, where churning the whole milk would otherwise be 
 preferred, since it is litde more difficult to make cheese frorii the sour 
 butter-milk than from the sweet skimmed-milk. To this point I shall 
 direct your attention hereafter. 
 
 9°. Cleanliness. — It seems almost unnecessary for me to allude to 
 cleanliness as peculiarly necessary to the manufacture of good butter. 
 But I do so to bring under your notice the fact, that cream is remarkable 
 for the rapidity with which it absorbs and becomes tainted by any un- 
 pleasant odours. It is very necessary thai the air of the dairy should be 
 sweet, that it should be often renewed, and that it should be open in no 
 direction from which bad odours can come. 
 
 § 13. Of the fatty substances of which butter consists, and of the acid of 
 butter {butyric acid,) and the capric and caproic acids. 
 1*. Butter fat. — I have already mentioned to you that if the butter as 
 it is taken from the churn be melted in water of a temperature not ex- 
 24 
 
558 THE FATTY SUBSTANCES IN BUTTER. 
 
 ceeding 180° F., and be then washed with repeated portions of warm 
 water, a nearly colourless fluid oil is obtained, which, if not transpar- 
 ent, becomes so when filtered through paper, and when cool congeals into 
 a more or less pure white solid fat. If this fat be put into a linen cloth 
 and be submitted to a strong pressure in a hydraulic or other press at the 
 temperature of 60° F., a slightly yellow, transparent oil will flow out, 
 and a solid white fat will remain behind in the linen cloth. The solid 
 fat is known to chemists by the name oi^ margarine. The liquid oil is 
 peculiar to butter, at least it has not hitherto been found in any other sub- 
 stance ; it is therefore called the oleine of butter, or simply butter-oil. 
 
 The pure fat of butter consists almost entirely of these two substances, 
 there being generally present in it only a small quantity of certain fatiy 
 acids, which I shall presently introduce to your notice. Thus a speci- 
 men of butter made in the month of May gave a fat which was found 
 by Bromeis to consist of about — 
 
 Margarine 68 per cent. 
 
 Butter oil 30 " 
 
 Butyric, caproic, and capric acids .... 2 " 
 
 100* 
 But the proportion of the solid and fluid fats in butter varies very much. 
 It is familiar in every dairy that the butter is harder and firmer at 
 one time and with one mode of churning than with another, — and this 
 greater firmness depends mainly upon the presence of the solid fat {jnar- 
 garine) in larger proportion. According to Braconnot, summer butter 
 contains much more of the butter-oil than winter butter does ; and he 
 states their relative proportions in these two seasons, in the butter of the 
 Vosges, which he examined, to be as follows : — 
 
 Summer. Winter. 
 
 Margarine 40 65 
 
 Butter oil 60 35 
 
 100 100 
 
 Of courselhese proportions are not to be considered as constant. In- 
 deed, the proportion of oil here given for summer butter is much greater 
 than in the butter examined by Bromeis. It is probable, therefore, that 
 the relative proportions of the two fats are affected by climate, by sea- 
 son, by the race, the food, and the constitution of the animal; by the way 
 in which the butter is made, by the manner in which it is kept, and by 
 other circumstances not hitherto investigated. 
 
 2°. Margarine. — This soUd fat, which exists so largely in butter, is 
 also the solid ingredient in olive oil, and in goose and human fat. But- 
 ter, therefore, appears to be a most natural food for the human race, since 
 it contains so large a proportion of one of those substances which enter 
 directly into the constitution of the human frame. 
 
 Margarine is white, hard, and brittle, and melts at 118° F. In the 
 pure state it may be kept for a length of time without undergoing any 
 sensible change, but in the state of mixture in which it exists in milk and 
 butter it is apt to absorb oxygen from the atmosphere, and to be partially 
 
 ' Antud, der Chem. und Phar., xlii., p. 70. 
 
PROPERTIES OF THE SUGAR OF MILK. 55^ 
 
 changed into butter oil, and into one or other of those fatty acids which 
 are present in butter in smaller quantity. 
 
 3°. Margaric acid. — When this fat (Margarine) is introduced into a 
 hot solution of caustic potash, it readily dissolves and forms a soap. If 
 the solution of this soap in water be decomposed by the addition of diluted 
 sulphuric acid a white fatty substance separates, which, after being col- 
 lected, dried, and dissolved in hot alcohol, crystallizes as the solution 
 cools, in the form of pearly scales. This substance is known by the 
 name of the margaric (or pearly) acid. Margarine consists of this acid 
 in combination with a sweet substance known by the name of glycerine, 
 or oil sugar.* 
 
 Margaric acid is represented by the formula 34 C + 34 H + 4 O, or 
 C34 H34 O4. To this formula it will be necessary in a few minutes to 
 revert. 
 
 Butter oil. — The liquid fat expressed from butter has the appearance 
 of an oil, sometimes colourless, but often tinged of a yellow colour. It 
 has the taste and smell of butter — mixes readily with alcohol, and be- 
 comes solid when cooled down to 32° F. — the freezing point of water. 
 It dissolves without difficulty in a solution of caustic potash, and forms 
 a soap. 
 
 Acid of butter-oil — oleic acid of butter. — When the solution of the oil 
 in caustic potash is diluted with much water, and decomposed by the ad- 
 dition of diluted sulphuric acid, an oily substance is separated, which is 
 different from the original oil of butter, possesses acid properties, and is 
 known by the name of the oleic acid of butter. This fatty acid has 
 never hitherto been obtained from any other substance than the oil of 
 butter, and the oil consists of the acid in combination with oil-sugar. 
 You will recollect that margarine consists of margaric acid in combination 
 with the same sugar (p. 558.) 
 
 * Such is the apparent composition of the two fatty substances, margarine and butter-oil, 
 inasmuch as when they are dissolved in a solution of caustic potash, and their solutions 
 afterwards decomposed by an acid, they are resolved respectively — 
 Margarine — into margaric acid and oil-sugar ; 
 Butter-oil— mlo butter oleic acid and oil-sugar. 
 
 But, for the benefit of my chemical readers (my other readers will please to pass over 
 this note), it is necessary to state — 
 
 1°. That a compound is supposed to exist, consisting of 3 atoms of carbon united to 2 of 
 hydrogen— C3 Hi, to which the name oflipyk is given. 
 
 2°. That this radical Cs H2 unites with an atom of oxygen, forming C3 H2 O, or oxide of 
 lipyle. 
 
 30. That in neutral fatty bodies, such as margarine., this oxide exists in combination 
 with a fatty acid. Thus, for example, that— 
 
 ,S1 of margaric acid = C34 H34 O4 
 
 Margarine consists ofji ^j- ^^^^^ ^j- jjpyig = C3 H2 O 
 
 Forming, together, 1 of margarine = C37 H36 05 
 
 And r „ •, f S 1 of oleic acid of butter = C34 H3l 05 
 
 butter-oil of J ^ ^^ ^^jjg ^j- lipyig = C3 H2 O 
 
 Forming, together, 1 of butter-oil = C37 H33 Oe 
 
 4°. And that when this oxide of lipyle is separated from its combination with the fatty 
 acids it unites with a quantity of water, and forms glycerine or oil-sugar. Thus— 
 
 2 of oxide of lipyle = C6 H4 O2 united to 
 
 3 of water = H3 O3 give 
 
 1 of glycerine (oil-sugar) ..-....=: Ce H7 05 
 50. The above is the view of Berzelius, but Redtenbacher has recently suggested, [Annal. 
 der Chem. und Phar, XLVII., p. 141,] that a known substance called acrolein exists in the 
 
560 CHANGE OF MARGARINE INTO OLEIC ACID. 
 
 When pure, ihis oilv ncid is colourless and transparent, and is re- 
 markable for the rapidi y icilh which it absorbs oxygen from the atmos- 
 phere, and becomes converted into new chemical compounds. It is re- 
 presented by the formula 34C + 3lH + 50, or C34 Hsi O5. 
 Let us compare this formula with that of the margaric acid : 
 
 Margaric acid = C34 H34 O4 
 
 Butter oleic acid . . . . = C34 Hu O5 
 
 Difference +H3 — Oi 
 
 or, if 3 of hydrogen be taken from the margaric acid and 1 of oxygen 
 added to it, it will be converted info the oleic acid. 
 
 Now this may be el leered by simply supposing one atom of margaric 
 acid to absorb four atoms of oxygen from the atmosphere. Thus — 
 
 1 of margaric acid = C34 H34 O4 
 
 4 of oxygen . . = Oi 
 
 • 1 of oleic acid + ^ of water. 
 
 C34 H34 Oa , or C34 H31 O5 -f 3HO. 
 
 So that either in the body of the animal, in the milk while it remains 
 in the udder, or when it is exposed to the air after being drawn from the 
 cow, or even in the churn itself, it may happen that a portion of the 
 margaric acid may absorb oxygen and become changed into the oleic 
 acid. It may also be that this change, this absorption of oxygen, is pro- 
 moted by warm and retarded by cold weather, and that thus the butter 
 is rendered generally softer in the summer and harder in the winter sea- 
 son. B ut these are as yet only conjectures ; for, after all, the relative pro- 
 portions of the soft and hard fat in butter at different times of the year 
 may depend upon natural differences in the herbage at the several 
 seasons, or upon some other causes which have not as yet been in 
 vestigated. 
 
 5°. Butyric, capric, and caproic acids. — These substances, as I have 
 already stated to you, exist in butter only in small quantity — to the 
 amount of 2 or 3 per cent. To these acids, and especially to the capric 
 and caproic, butter owes its disagreeable smell when it becomes rancid. 
 They do not^xist, naturally, to any unpleasant extent in perfectly fresh 
 butter — they are gradually formed in it, however, when fresh butter 
 is exposed to the air. I do not enter into any detail of their proper- 
 ties, or of the mode of extracting them from butter, because these points 
 
 fats in combination witli the fatty acid. Tliis acrolein is represented by C6 H4 O2, which 
 is exactly the constitution of 2 of lipyle. So that according to this view the solid fat of but- 
 ter would consist of— 
 
 2 of marsaric acid . . . . = CG8 H63 08 
 
 1 of acrolein = C6 H4 O2 
 
 2 of margaric acid . . . . = C74 1172 Oio 
 
 and, by a like substitution of acrolein for oxide of lipyle, may the constitution of butter-oil 
 be represented. 
 
 The principal known fact in favour of this view of Rcdtenbachcr is, that when glycerine is 
 distilled with anhydrous phosphoric acid, acrolein is produced. He supposes that the acid 
 takes the elements of 3 atoms of water from glycerine, forming acrolein : since if from — 
 
 1 of glycerine = Co H7 05 we take 
 
 3 of water = Hi Oi 
 
 Acrolein remains = Ce H4 O2 
 
 The conversion of acrolein into glycerine, when it is separated from the fatty acids, is sup- 
 posed to proceed, as in the case of lipyle, from its combination with tlie water at the moment 
 of extrication. Further researches are yet required to clear up this subject. 
 
PROPERTIES OF THE CURD OF MILK. 561 
 
 are of less interest or importance to you. It is necessary only, to a 
 clear understanding of the kind of changes which take place when butter 
 becomes rancid, that I should exhibit to you the formulae by which these 
 acid bodies are severally represented : — 
 
 Butyric acid = Cg Hs O4 
 
 Caproic acid = C12 Hg O3 
 
 Capric acid = C18 H14 O3 
 We shall see how these substances are produced from the solid and 
 fluid fats of butter, when we come to treat of the preservation of butter. 
 
 § 14. Of casein or the curd of rnilk and its properties. 
 
 The casein or cheesy matter of milk may be obtained nearly pure by 
 the following process : — Heat a quantity of milk which has stood for 5 
 or 6 hours, as if you intended to prepare clouted cream (p. 548), let it 
 cool, and separate the cream completely. Add now to the milk a little 
 vinegar and heat it gently. The whole will coagulate, and the curd will 
 separate. Pour off" the whey, and wash the curd well by kneading it 
 with repeated portions of water. When pressed and dried, this will be 
 casein sufficiently pure for ordinary purposes. It may be made still 
 more pure by dissolving it in a weak solution of carbonate of soda, al- 
 lowing the solution to stand for 12 hours in a shallow vessel, separating 
 any cream that may rise to the surface, again throwing down the curd 
 by vinegar, washing it frequently, and occasionally boiling it with pure 
 water. By repeating this process two or three times, it may be obtained 
 almost entirely free from the fatty and saline matters of the milk. 
 
 Casein thus prepared reddens vegetable blues, and is therefore a 
 slightly acid substance. It is very sparingly soluble in water — 400 lbs. 
 of cold water dissolving only 1 lb. of pure casein (Rochleder). It dis- 
 solves readily, however, and in large quantity, in a weak solution of the 
 carbonate of potash or of soda, and to some extent even in lime-water. 
 These solutions are coagulated by the addition of an acid — of sulphuric 
 acid, of vinegar, or of lactic acid — and the curd readily separates on the 
 application of a gentle heat. If a large quantity of acid be added, a por- 
 tion of the casein is re-dissolved. This property of dissolving in weak 
 alcaline (potash or soda) solutions, Scitisfactorily explains what takes 
 place during the curdling of milk, as we shall hereafter see (p. 567). 
 
 The casein of milk is identical in chemical constitution with the fibrm 
 of wheat, the legumin of the pea and bean,* and the albumen of the 
 egg or of vegetable substances. Hence the opinion has naturally arisen 
 among chemists, that the cheesy matter contained in an animal's milk is 
 derived directly, and without change, from the food on which it lives. 
 The probability of this opinion will come naturally under our considera- 
 tion in the following lecture. (See next lecture, " On the feeding of 
 stock.'') 
 
 Casein possesses still one property more remarkable than any of its 
 
 * In page 394 it is staterl. on the authority of Dumas, that the legumin of the pea and bean 
 tliifers in composition from fibrin and alhnnven Since tliat sheet was published, it appears, 
 from the experiments of Rochleder (Annal. der Chem. und Pharm., xlvi., p. 1G2), that the 
 legumin which Dumas extracted from the almond, analysed, and supposed to be identical 
 with the legumin of the bean and pea, is not so, but is in reality a different substance ; and 
 tliat the legumin of peas does agree in composition with the casein of milk. 
 
562 ACTION OF CASEIN UPON SUGAR. 
 
 Others, and exceedingly interesting to the practical agriculturist. Let 
 me explain this property a little more in detail. 
 
 § 15. Of the relations of casein to the sugars and the fats. 
 
 1°. Relation to the sugars. — a. Production of lactic acid. — I have 
 already adverted (p. 543) to the remarkable property which casein pos- 
 sesses of gradually converting milk or other sugars into lactic acid. If 
 a small quantity of this substance, either in the state of fresh curd or in 
 the purer form just described, be introduced into a solution of cane-sugar, 
 or of sugar of milk, lactic acid begins very soon to be formed. Thus 
 the casein it contains is the cause of the souring of milk. In like man- 
 ner it is the casein contained in bean or pea-meal v^hich makes it so 
 soon become sour when mixed with water. 
 
 h. Production of butyric acid. — But the transforming action of casein 
 doos not end when this cliarige is produced. After a longer time a 
 further alteration is effected by its means. A fermentation commences, 
 during which carbonic acid and pure hydrogen gases are given off, and 
 butyric acid is produced (Pelouze and Gelis). Let us consider the 
 nature of this new cliange. 
 
 Butyric acid is represented by Cs Hs O4 ; and lactic acid, as we have 
 seen, by Ce Hg Oe ; therefore — 
 
 4 of lactic acid = C04 H24 O24 and 
 
 3 of butyric acid = C24 H24 O12 
 
 Difference O12 
 
 That is to say, that 4 of lactic acid, in order to be converted into 3 of 
 butyric acid, must give off* 12 of oxygen. But during the fermentation 
 which accompanies the change no oxygen is given off". The gases 
 which escape are carbonic acid and hydrogen. The oxygen given off 
 by one portion of the lactic acid, therefore, must combme with the ele- 
 ments of another portion, and convert it into these gases. Thus to — 
 1| of lactic acid . . == Cg Hg O9 
 Add 12 of oxygen . . = O12 
 
 9 of carbo- , 6 of liy- , 3 of 
 nic aciil ' drogen ' water. 
 
 And we have . . . Cg Hg O21 = 9 C O2 -f CH -j- 3 HO ; 
 or, while 4 atoms of lactic acid are converted into 3 of butyric acid, I5 
 of lactic acid are at the same lime converted into 9 of carbonic acid gas, 
 G of hydrogen gas, and 3 of water. The gases escape and cause the fer- 
 mentation, while the water remains in the solution.* 
 
 * I have taken in the text the smallest numbers by which the general change could be re- 
 presented in the simplest way. Acconlinj: to Pelouze and Gelis, however, the hydrogen 
 given off is sensibly one-third of the bulk of the carbonic acid when the butyric fermenta- 
 tion is in its vigour. To satisfy this condition, therefore, much higher numbers must be 
 taken ; such as the following: — 
 
 20 of lactic acid = Ci'20 H120 O120 are converted into 
 
 15 of butyric acid = CVM HiLO Oeo 
 
 Giving off = Oeo 
 
 And these 60 of oxygen decompose 6 of lactic acid, as above described. Thus to — 
 
 6 of lactic C36 H.56 ()36 
 
 Add 60 of oxygen , . Oeo 
 
 6 of carbonic acid -4- 12 hydrogen + 24 water. 
 
 And we have . . C36 H36 096 = 36C02 + ]2H + 24HO, 
 
 where the carbonic acid gas is exactly three times the bulk of the hydrogen gas produced. 
 
OF THE RANCIDITY OF BUTTER. 663 
 
 The oulyric acid thus produced is a colourless transparent volatile 
 liquid, which emits a mingled odour of vinegar and of rancid butter. 
 To the production and presence of this acid, therefore, in the milk or 
 cream or in the manufactured butter, the rancidity of this important 
 dairy product is partly to be ascribed. 
 
 2°. Relation to the fatty bodies. — It is probable that in certain cir- 
 cumstances the casein of milk is capable of inducing chemical changes 
 in the fatty bodies as well as in the sugars, but tlais conjecture has not, 
 as yet, been verified by rigorous experimental investigation. 
 
 3°. Relation to fats and sugars 7iiixed. — It is know'n, however, to act 
 upon fatty bodies when mixed with sugar. Thus, if a small quantity 
 of casein be added to a solution of sugar, lactic acid is produced for a 
 certain length of time, but it ceases to be sensibly formed before the 
 whole of the sugar is transformed into this acid. If now a quantity of 
 oily matter be added to the mixture, the production of lactic acid will re- 
 commence, and may continue till all the sugar is changed. If more 
 sugar be added by degrees, the formation of acid will go on again, and, 
 after a while, will cease. The introduction of a little more oil will again 
 give rise to the production of acid, and, at length, the acid will cease to 
 be formed, while both sugar and oil are present. The casein originally 
 added has now produced its full effect (Lelimann). 
 
 It appears, therefore, that in the presence of sugar, casein is capable 
 of changing or decomposing the fatty bodies also, and of giving birth to 
 oily acids of various kinds. Now, in milk, in cream, and in butter, the 
 casein is mixed with the sugar of the milk and the fats of the butter, and 
 thus is in a condition for changing at one and the same time both the 
 sugar into lactic or butyric acid, and the butter into other acids of a 
 fatty kind. Among those latter into which the butter-oil is convertible 
 may probably be reckoned the ca])ric and (;a])roic acids, which are still 
 more unpleasant to the smell and taste than the butyric acid, and which 
 are known to be present in rancid butter. 
 
 § 16. Of the rancidity and preservation of butter. 
 " We are now prepared, in some measure, to understand the changes 
 that take place when butter becomes rancid — and the way in which those 
 substances act which are usually employed for preserving it in a sweet 
 and natural state. 
 
 1°. When butter becomes rancid, there are two substances which 
 change — the fatty matters and the milk sugar with which they are mixed. 
 There are also two agencies by which these changes are induced — the 
 casein present in butter, and the oxygen of the atmosphere. The quantity 
 of casein or cheesy matter which butter usually contains is very small, 
 but, as we have seen, it is the singular property of this substance to in- 
 duce chemical changes of a very remarkable kind, upon other compound 
 bodies, even when mixed with them in very minute quantity. 
 
 2°. As it comes from the cow, this substance, casein, produces no 
 change on the sugar or on the fatty matters of the milk. But after a 
 
 Every chemist is aware, however, that in decompositions of this kind, it is seldom 
 that one single product is obtained alone. Though the above formula, therefore, represents 
 truly how butyric acid may be produced from lactic acid under the circumstances, yet 
 other substances are not unfrequenlly formed during the actual experiment, by which the 
 result is more or less complicated. 
 
564 INFLUENCE OF THE CHEESY MATTER. 
 
 short exposure to the air it alters in some degree, and acquires the power 
 of transforming milk sugar into lactic acid. Hence, as we have seen, the 
 milk begins speedily to become sour. Further changes follow, and, 
 among other substances, butyric acid is formed. 
 
 In butter the same changes take place. The casein alters the suga? 
 and the fatty matters, producing the butyric and other acids, to which its 
 rancid taste and smell are to be ascribed. 
 
 In the manufacture of butter, therefore, it is of consequence to free it as 
 completely as possible from the curd and sugar of milk. This is done 
 in some dairies by kneading and pressing only ; in others, by washing 
 with cold water as long as the latter comes off' milky. The washing 
 must be the most effective method, and is very generally recommended 
 for butter that is to be eaten fresh. In some dairies, however, it is care- 
 fully abstained from, in the case of butter which is to be salted for long 
 keeping. 
 
 There are two circumstances which, in the case of butter that is to be 
 kept for a length of time, may render it inexpedient to adopt the method 
 of wasliing. The water may not be of the purest kind, and thus may 
 be fitted to promote the future decomposition of the butter. Sprengel 
 says that the water ought to contain as little liuje as j)ossible, because 
 the butter retains the lime and acquires a bad taste from it. 
 
 But the water may also contain organic substances in solution — vege- 
 table or animal matters not visible perhaps, yet usually present even in 
 spring water. These the butter is sure to extract, and tliey may mate- 
 rially contribute to its after-decay, and to the difficulty of preserving it 
 from rancidity. 
 
 Again, the washing with water exposes the particles of the butter to 
 the action of the oxygen of the atmosphere much more than when the 
 butter is merely well squeezed. The effect of this oxygen, in altering 
 either the fatty matters themselves oi" the small quantity of casein which 
 remains mixed with them, may, no doubt, contribute to render some but- 
 ters more susceptible of decay. 
 
 3°. But the casein, af'er it has been a still longer time or more fully 
 exposed to the-air, undergoes a second alteration, by which its tendency 
 to transform the substances with which it may be in contact, is consi- 
 derably increased. It acquires the property also of inducing chemical 
 changes of another kind, and it is not improbable that the more un- 
 pleasant smelling capric and caproic acids may be produced during this 
 period of its action. 
 
 In llie preservation of butter, therefore, for a length of time, it is of 
 indispensable necessity that the air should be excluded from it as com- 
 pletely as possible. In butter that is to be salted also, it is obvious that 
 the sooner the salt is applied and the whole packed close, the better and 
 sweeter the butter is likely to remain. 
 
 4°. The action of this cheesy matter, and its tendency to decay, are 
 arrested or greatly retarded by the presence o^ saturated solutions of cer- 
 tain saline and other substances. Of this kind is common salt, which is 
 most usually employed for the purpose of preserving butter. Saltpetre, 
 also, possesses this property in a less degree, and is said to impart to the 
 butter an agreeable flavour. A syrup or strong solution of sugar will 
 likewise prevent both meat and butter from becoming rancid. Like salt- 
 
HOW TO PURIFY SALT FOR BUTTER. 565 
 
 petre, however, it is sekloin used alone, but it is not uncommon to em- 
 ploy a mixture fjf common salt, saltpetre, and sugar, for the preservation 
 of butter. Where the butter has been washed, this admixture of cane- 
 sugar may supply the place of the milk-sugar which the butter originally 
 contained, and may impart to it a sweeter taste* 
 
 The salt should be as pure as possible, as free, at least, from lime and 
 magnesia as it can be obtained, since these substances are apt to give 
 it a bitter or other disagreeable taste. It is easy, however, to purify the 
 common salt of the shops from these impurities by pouring a couple of 
 quarts of boiling water upon a stone or two of salt, stirring the whole 
 well about, now and dien, for a couple of hours, and afterwards straining 
 it through a clean cloUi. The water which runs through is a saturated 
 solution of salt, and contains all the impmities, but may be used for com- 
 mon culinary purposes or may be mixed with the food of the cattle. 
 The salt which remains on the cloth is free from the soluble salts of lime 
 and magnesia, and may be hung up in the cloth till it is dry enough to 
 be used for mixing with the butter or with cheese. 
 
 Tlie quantity of salt usually employed is from ^V^h to /gth part of the 
 weight of the butter — with which it ought to be well and thoroughly in- 
 corporated. The first sensible eflect of die salt is to make the butter 
 shrink and diminish in bulk. It becomes more solid and squeezes out a 
 portion of tlie water — with which part of die salt also flows away. It is 
 not known that the casein actually combines widi the salt, nor, if it did, 
 considering the very small quantity of this substance which is present in 
 butter, could much salt be required for this purpose. But the points to 
 attend to in the saldng of butter are to take care that all the water which 
 remains in the butter shall be fully saturated with salt — that is to say, 
 shall liave dissolved as much as it can possibly take up — and that in no 
 part of the butter shall there be a particle of cheesy matter which is not 
 also in contact with salt. If you exclude the air, the presence of a sat- 
 urated solution of salt will not only preserve this cheesy matter from it- 
 self undergoing decay, but will render it unable also to induce decay in 
 the sugar and fat whicli are in contact with it.* 
 
 It is really extraordinary that such rigid precautions should be neces- 
 sary to prevent tlie evil intluenc-e of half a pound of cheesy matter, or less, 
 in a hundred pounds of butter (p. 551). 
 
 5°. Though the curd or casein appears to be the enemy against whose 
 secret machinations the dairy farmer has chiefly to guard, yet the oxygen 
 of the atmosphere is a second agent by which die fatty matters of butter 
 are liable to be brought into a state of decomposition, and the jjresencc 
 of which, dierefore, should be excluded as carefully as possible. 
 
 "We have seen that by the acdon of oxygen the solid margaric acid of 
 butter may be changed into the oleic or liquid acid of butter (p. 560.) 
 
 ' Mr. Ballantyne thus describes tlie method of saltiiig butter practised at. his dairy farm of 
 30 cows, near Edinburgli :— "The butter is drawn warm from tiie churn, and it is an invari- 
 able rule never tu wash it or dip il into tenter, v^hen intended to be salted. Tiie dairymaid 
 puts it into a clean tub, which is previously well rinsed with cold water, and then worlds it 
 with cool liands till all the milk is tliorou^iily squeezed out. Half the allowed (luanliiy of 
 salt is then added, and well mixed up with the butter, and in this state it is allowed to stand 
 till next morning, when it is a«ain wrouglit up, any brine squeezed out, and the remauider 
 of the salt added. It is then paclted into kits, which, when full, should bo well coverecl up, 
 and placed in a cool dry store— a small quantity of salt is usually sprinkled on the surface. 
 The proportion of salt used at this dairy is halfapound to fourteen pounds of butter. — 
 Journal of Agriculture, New S'eries, vol. I., p. 26. 
 
 24* 
 
566 EVIL EFFECT OF THE AIR UPON BUTTER. 
 
 This is the first stage in the (Jecomposiiion, which, when, once begun, 
 generally spreads or extends with increasing rapidity.* 
 
 Again, I have also stated that this fluid (oleic) acid of butter absorbs 
 oxygen with great rapidity from the air (p. 560), and changes rapidly into 
 otlier compounds. This is the second stage, and is succeeded by others, 
 which it is unnecessary to enumerate. 
 
 To this action of the air is partly to be ascribed that peculiar kind of 
 rancidity, which, without penetrating into the interior of well packed 
 butter, is yet perceptible on its external surface, wherever the air has 
 come in contact with it. A knowledge of this action of the atmosphere, 
 therefore, urges strongly the necessity of closely incorporating and knead- 
 ing together the butter in the cask or firkin — that no air holes or openings 
 for air be left — that the cask itself be not only water-tight but air-tight — 
 and that it should never be finally closed till the butter has shrunk in as 
 far as it is likely to do, and until the vacancies, which may have 
 arisen between the butter and the cask, have been carefully filled up 
 again. 
 
 § 17. Of the natural and artificial curdling of milk. 
 
 Wiien milk is left to itself for a certain length of time it becomes sour 
 and curdles. The curd and whey, however, do not readily separate un- 
 less a gentle heat be applied, when the curd contracts in bulk, and either 
 squeezes out and floats upon the whey, or, when cut into pieces or placed 
 in a perforated cheese-vat, allows the whey freely to flow from it. If 
 the mixed curd and whey from the entire milk be allowed to simmer for 
 a length of time at a slow fire, tlie buttery part will separate from the 
 cheese, and will float on the top in the form of a fluid oil. 
 
 1°. Natural curdling. — The natural curdling of inilk is produced by 
 the lactic acid, which, as we have seen (p. 544), is always formed from 
 the milk-sugar when milk is allowed to stand for any length of time in 
 the air. It does not curdle immediately upon becoming sour, for a reason 
 which I shall presently explain. 
 
 2°. Artificial curdling. — But it is not usual in the manufacture of 
 cheese to attow the milk to sour and curdle of its own accord. The pro- 
 cess is generally hastened by the artificial addition of acid, or of some 
 substance, such as rennet, by which the natural production of acid is ac- 
 celerated. Almost any acid substance will have the eflect of curdling 
 milk. Muriatic acid (spirit of salt), diluted with water, is said to be ex- 
 tensively, though not universally, employed in Holland for this pur- 
 pose. In other countries vinegar, f tartaric acid, lemon juice, cream of 
 
 * I do not know whether a converse change is ever observed in butter by long keeping in 
 contact with brine — whether it ever becomes very sensibly harder. Tallow, as is well 
 known to candle-makers, and especially to the manufacturers of stearin candles, becomes 
 harder by keeping, indeed sometimes is unfit for use until it is a year old — candles in a damp 
 place become harder by keeping — and in tallow that has lain long in a wet mine tlie oily part 
 lias been found entirely changed into the solid fat of tallow (Beetz). A similar change, 
 therefore, is not impossible nor inexplicable in butter also — only if it ever do take place, we 
 should expect the changed butter to be less solid and dense than before. 
 
 t " To coagulate a cotyla of milk we add a cyathus of sweet vinegar" (Dioscorides). Milk 
 is also curdled by ardent spirits, by the juice of the fig, and by a decoction of the flowers of 
 the artichoke, of the white and yellow bed-straw (galium), and of the crowfoot (ranunculics 
 Jlammula and liiigula). The Tuscan ewe-cheese is curdled with the juice of the fresh, or 
 v/ith a decoction of the dried flowers of the wild thistle, or with the flowers of the artichoke, 
 which gives a cheese of finer colour and less pungent taste. 
 
NATURAL AND ARTIFICIAL CURDLING OF MILK. 567 
 
 tartar, and salt cf sorrel have been occasionally used, and in Switzerland 
 — especially in the manufacture of the schabzieger cheese — it is cus- 
 tomary to add merely a little sour milk for the purpose of producing the 
 curd. 
 
 3°. Chemical action of the acid. — But how does the acid act in causing 
 the milk to curdle, and why is it necessary to allow a little time to 
 elapse and to apply also a gentle heat before the curd will completely 
 separate ? 
 
 In regard to casein or the cheesy matter of milk, we have seen (p. 
 561)— 
 
 a. That though nearly insoluble in pure water, it dissolves readily in 
 Water containing in solution a small quantity of potash or soda, either in 
 the caustic or carbonated state. In other words the casein, which is an 
 acid substance, unites chemically with the potash or the soda, and fonns 
 a compound which is soluble in water. 
 
 b. That when an acid is added to this solution, it takes the potash or 
 soda from the casein and combines with it, leaving the curd again in its 
 original insoluble state, and causing it, therefore, to separate from the 
 water. 
 
 Now in milk, as it comes from the cow, the casein is in chemical 
 combination with a small quantity of soda, by which it is rendered so- 
 luble in the water of which the milk chiefly consists. When the milk 
 stands for a time in the air, the sugar of milk, as we have seen, is trans- 
 formed into lactic acid — this acid takes the soda from the casein, and 
 forms lactate of soda, and the cheesy matter, in consequence, being itself 
 insoluble in water, separates in the form of curd. The application of a 
 gentle heat acts in two ways. It aids the acid in more completely taking 
 the soda from the casein, and causes the latter at the same time to 
 shrink in, to become less bulky, and thus to separate readily from the 
 whey. 
 
 If we add an acid artificially to milk, the effect is exactly the same. 
 Either muriatic acid, or tartaric acid, or vinegar, or sour milk, will, in the 
 same way, take the soda from the casein, and render it insoluble. And 
 that this is the true action is readily proved by adding a little soda to 
 curdled milk, when the curd will be re-dissolved, and the milk will be- 
 come sweet. Add acid to it now, or let it sour naturally a second time, 
 and the curd will again be separated. 
 
 The action of rennet is in some degree different, though no less simple 
 and beautiful. Let us first, however, consider what rennet is, and how 
 it is prepared. 
 
 § 18. Of the preparation of rennet. 
 
 Rennet is prepared from the salted stomach or intestines of the suck- 
 ling calf, the unweaned lamb, the young kid, or the young pig.* In 
 general, however, the stomach of the calf is preferred, and there are 
 various ways of curing and preserving it. 
 
 1°. Preparing the stomach. — The stomach of the newly killed animal 
 contains a quantity of curd derived from the milk on which it has been 
 fed. In most districts (Switzerland, Gloucester, Cheshire) it is usual to 
 
 * Dried pig's bladder ih often employed instead of the dried kid's stomach for curdling the 
 goat's milk on Mont Dor. 
 
568 METHODS OF MAKING THE RENNET. 
 
 remove hy a gentle washing the curd and slimy matters which are pre- 
 sent in the stomach, as they are supposed to impart a strong taste to the 
 cheese. In Cheshire the curd is frequently salted separately for imme- 
 diate use. In Ayrshire and Limhurg, on the other hand, the curd is 
 always left in the stomach and salted along with it. Some even give 
 the calf a copious draught of milk shortly before it is lulled, in order that 
 the stomach may contain a larger quantity of the valuable curd. 
 
 2°. Salting the stomach. — In the mode of salting the stomach similar 
 differences prevail. Some merely put a few handfuls of salt into and 
 around it, then roll it together, and hang it near the chimney to dry. 
 Others salt it in a pickle for a few days, and then hang it up to dry 
 (Gloucester), while others again (Cheshire) pack several of them 4n 
 layers with much salt both within and without, and preserve them in a 
 cool place till the cheese-making season of the following year. They 
 are then taken out, drained from the brine, spread upon a table, sprinkled 
 with salt which is rolled in with a wooden roller, and then hung up to 
 dry. In some foreign countries, again, the recent stomach is minced very 
 fine, mixed with some spoonfuls of salt and bread-crumb into a paste, 
 put into a bladder, and then dried. In Lombardy the stomach, after 
 being salted and dried, is minced and mixed up with salt, pepper, and a 
 little whey or water into a paste, which is preserved for use. [Cattaneo, 
 II latte e i suoi prodotti, p. 204.] 
 
 In whatever way the stomach or intestine of the calf is prepared and 
 preserved, the almost universal opinion seems to be, that it should be 
 kept for 10 or 12 months before it is capable of yielding the best and 
 strongest rennet. If newer than 12 months, the rennet is thought in 
 Gloucestershire " to make the cheeses heave or swell, and become full 
 of eyes or holes." [British Husbandry, ii., p. 420.] 
 
 3°. Making the rennet, — In making the rennet different customs also 
 prevail. In some districts, as in Cheshire, a bit of the dried stomach is 
 put into half a pint of lukewarm water with as much salt as will lie 
 upon a shilling, is allowed to stand over night, and in the morning the 
 infusion is poured into ihe milk. For a cheese of 601bs. weight, a piece 
 of the size ofLhalf-a-crown will often be sufficient, though of some skins 
 as much as 10 square inches are required to produce the same effect [Dr. 
 Holland.] 
 
 It is perhaps more common, however, to take the entire stomach 
 {dried-maws^ veils, reeds, or yirning* they are often called), and to pour 
 upon them from one to three quarts of water for each stomach, and to 
 allow them to infuse for several days. If only one has been infused, and 
 the rennet is intended for immediate use, the infusion requires only to be 
 skimmed and strained. But if several maw-skins be infused — ^or, as is 
 the custom in Cheshire, as many as have been provided for the whole 
 season — about two quarts of water are taken for each, and, after stand- 
 ing not more than two days, the infusion is poured off", and is completely 
 saturated with salt. During the summer it is constantly skimmed, and 
 fresh salt added from time to time. Or a strong brine may at once 
 
 ' In Northumberland the di-ied stomach is sometimes called the keslap, which is evidently 
 the German kdse-lab, cheese-rennet. Loppert and lappert, applied in Northumberland and 
 the West of Scotland respectively to sour, curdled milk, is derived from the same German 
 iab, rennet, or laber, to coagulate. 
 
THEORY OF THE ACTION OF RENNET. 569 
 
 be poured upon the skins, and the infusion, when the skins are taken 
 out, may be kept for a length of time. Some even recommend that 
 the liquid rennet should not be used until it is at least two months old. 
 When thus kept, however, it is indispensable that the water should be 
 fully saturated with salt. 
 
 In Ayrshire, gj^d in some other counties, it is customary to cut the 
 dried stomach into small pieces, and to put it, with a handful or two of 
 salt and one or two quarts of water, into a jar, to allow it to stand for two 
 or three days, afterwards to pour upon it another pint for a couple of days, 
 to mix the two decoctions, and, when strained, to bottle, the whole for 
 future use. In this state it may be kept for many months.* 
 
 In all the methods above described, the exhausted skins are thrown 
 away. Where they are cut into pieces, as in Cheshire and Ayrshire, 
 they cannot of course be put to any second use, but where they are steeped 
 whole, there is every reason to believe that they might be used with al- 
 most equal advantage a second or even a third time. Accordingly, it 
 has long been the custom in the north of England to re-salt the stomach 
 after it has been once steeped, and when long dried, as before, to use it 
 a second and even a third time for the preparation of rennet. When we 
 explain the mode in which rennet acts, you will see that the same skin 
 may, with good reason, be expected to yield a good rennet, after being 
 s'alted again and again for an indefinite number of times. 
 
 In making rennet, some use pure water only, others prefer clear whey, 
 others a decoction of leaves — such as those of the sweetbriar, the dog- 
 rose, and the bramble — or of aromatic herbs and flowers, while others, 
 again, put in lemons, cloves, mace, or brandy. These various practices 
 are adopted for the purpose of making the rennet keep better, of lessen- 
 ing its unpleasant smell, of preventing any unpleasant taste it might 
 give to the curd, or finally of directly improving the flavour of the cheese. 
 -The acidity of the lemon will, no doubt, increase also the coagulating 
 power of any rennet to which it may be added. 
 
 4°. How the rennet is used. — The rennet thus prepared is poured into 
 the milk previously raised to the temperature of 90° or 95° F., and is 
 intimately mixed with it. The quantity which it is necessary to add 
 varies with the quality of the rennet — ^irom a table-spoonful to half a 
 pint for 30 or 40 gallons of milk. The time necessary for the complete 
 fixing of the curd varies also from 15 minutes to an hour or even an hour 
 and a half. The chief causes of this variation are the temperature of the 
 milk, and the quality and quantity of the rennet employed. 
 
 But how does the rennet act in causing this coagulation? Before 
 we can answer this question it is necessary to enquire what rennet 
 really is. 
 
 § 19. Theory of the action of rennet. 
 
 It has been stated, and hitherto almost generally received, that the only 
 effective substance contained in rennet is the gastric juice derived from 
 the stomach of the calf. To this persuasion is, no doubt, to be ascribed 
 
 * A table-spoonful of this rennet, according to Mr. Aif.on, will coagulate 30 gallons of milk, 
 and will curdle it in five or ten minutes, whereas tlie English rennet requires from one to 
 three hours. This superiority he ascribes to the custom of leaving the curdled milk in the 
 dtomach. He denies also that this milk gives any harsh taste to the cheese. 
 
570 THE SUBSTANCE OF THE STOMACH CHANGES 
 
 the custom both of preserving the natural contents of the stomach — and 
 of generally throwing away the bag after being once salted, dried, and 
 extracted. The gastric juice which exudes from the interior surface of 
 the stomachs of all animals is l^nown to curdle milk readily, and, there- 
 fore, it was natural to ascribe the action of rennet to the presence of this 
 substance, and to infer that, jeing once extracted, it .was in vain to ex- 
 pect much advantage from salting and infusing the membrane a second 
 time. But the three facts — 
 
 a. That in most places it is customary to wash the interior of the 
 stomach before salting it, and thus to remove the greater part Of the gas- 
 tric juice it may contain ; 
 
 h. That besides, in many places, the hags are laid up in brine for 
 weeks and months, and are then drained out of this brine before they are 
 dried — by which any gastric juice remaining must be almost entirely re- 
 moved, — and 
 
 c. That after being (hied and steeped once for the preparation of ren- 
 net, experience has proved that they may again be salted and used over 
 again ; 
 
 — these three facts, I think, shew that the efficacy of rennet does not de- 
 pend upon any thing originally contained in the stomach, hut upon 
 something derived from the suhstance of the stomach itself. 
 
 Now when considering the properties of milk-sugar and of lactic acid, 
 I have stated that if a piece of the fresh membrane of the stomach or in- 
 testine, or even of the bladder of an animal, be exposed to the air for a 
 few days, and be then immersed into a solution of milk-sugar, it will 
 gradually transform the sugar into lactic acid. In milk this membrane 
 would produce a similar effect, aiding and hastening the natural souring 
 and curdling effect of the casein. By exposure to the air, the surface of 
 the membrane has undergone such a degree of change or decomposition, 
 as enables it to induce the elements of the sugar to alter their mutual 
 arrangement, and to unite together in such a way as to form lactic acid. 
 
 If the moist membrane be exposed for a longer time to the air this 
 change of its surface will penetrate deeper, and it will become more ef- 
 fective in inducing the transformation of the sugar into lactic acid. But, 
 at the same time, a portion of its surface may run into a state of putre- 
 faction, and besides acquiring a disagreeable odour may become capable 
 also of bringing on fermentation and putrefactive decay in the solutions 
 upon which it may be made to act. It is not expedient, therefore, to at- 
 tempt to heighten the transforming effect of animal membranes by 
 exposing them for a greater length of time to the air in a moist and fresh 
 state. 
 
 But if the membrane be salted, and thus preserved from the rapid 
 action of the air, it will be protected from putrefaction in a great degree, 
 while, at the same time, it will undergo that gradual change upon its 
 surface to which its power of transforming solutions of sugar is ascribed. 
 And this change will be materially hastened and increased and made to 
 penetrate deeper, if the salted membrane be subsequently dried slowly 
 in the air by a gentle heat, and be afterwards kept for a length of time 
 where the air has more or less ready access to it. Such is the mode of 
 treatment to which the calf's stomach is subjected for the preparation of 
 rennet, and it is an important practical observation that the membrane 
 
WHEN EXPOSED A SHORT TIME TO THE AIR. 671 
 
 should be kept at least 12 months, if it is to acquire very powerful 
 coagulating properties. 
 
 It is necessary further to remind you that when malt is steeped in 
 water for a few minutes, a substance, named diastase., is extracted from 
 it, which possesses the remarkable property of changing starch into 
 sugar in a very short time, and in large quantity ^p. 119). Now if this 
 diastase be exposed to the air for a length of time, it undergoes a change 
 similar to that experienced by the surface of animal membranes, and 
 acquires the property of transforming sugar into lactic acid. After un- 
 dergoing this change it still dissolves readily in water, and if a solution 
 of it be poured into one of sugar, the transformation of the latter into lactic 
 acid gradually proceeds. There exist, therefore, substances soluble in 
 zoater, which possess tlie same power as slightly decayed but insoluble 
 animal membrane, of converting sugar into lactic acid. 
 
 During the protracted drying and decay of the salted stomach, the 
 change undergone at length by the surface of the membrane is such as to 
 produce a quantity of 7natter capable of dissolving in water, and which 
 also possesses the property of quickly converting the sugar into the acid 
 of milk. This matter, water extracts from the dried skin, and it forms 
 the active ingredient in rennet. 
 
 I need not further explain to you upon what this activity depends — 
 since as you already know any thing which will rapidly change sugar 
 into lactic acid, will also, if gently warmed, rapidly curdle milk (p. 
 567). 
 
 Thus the action of rennet resolves itself simply into a curdling of milk 
 by the action of its own acid. It is the same thing as when sour milk 
 in Switzerland is at once mixed with that from which the cheese is to be 
 made ; or it is only a more speedy way of bringing about the curdling 
 that takes place when milk sours naturally and is then gently warmed 
 till the curd separates. 
 
 But how, it may be asked, is the coagulation effected so much more 
 rapidly by the action of rennet than when the milk is left to sour of its 
 own accord ? It is because the whole of the animal matter in the rennet 
 is already in the state in which it easily transforms the sugar into acid, 
 and being intimately mixed with the whole milk in a warm state, it pro- 
 duces acid near every particle of the cheesy matter. From this 
 cheesy matter the acid formed takes away the soda that holds it in solu- 
 tion, and thus renders it insoluble or curdles the milk. In milk, on the 
 dlher hand, which is left to sour and curdle of itself, the casein must first 
 be changed by the action of the air before it can transform the sugar and 
 produce acid. This change takes place more or less slowly, and chiefly 
 at the surface of the milk where it is in contact with the air. The sour- 
 ing, therefore, must also proceed slowly, and the curdling of which it is 
 the cause. 
 
 It is no objection to this explanation of the action of rennet, that neither 
 the milk nor the whey become sensibly sour during the separation of ihe 
 curd. The acid, as it is produced, combines directly with the soda pre- 
 viously united to the curd, and renders the latter insoluble — while, if 
 any excess of acid do happen to be formed, it is in great part taken up 
 and retained mechanically by the curd, and thus is not afterwards sen- 
 sibly perceived in the whey. 
 
572 USE OF THE CURD FOUND IN THE CALF's STOMACH. 
 
 Using the same skin a second time. — If tliis then be a true explanation 
 of the action of rennet — if the coagulating ingredient in it be merely a 
 portion of the changed membrane of the stomach itself — it is obvious that 
 the bag, after being once used, may be again salted and dried with ad- 
 vantage. The slow decay may, after a second salting, become still 
 slower, and thus it may reepire to be longer kept after the second than 
 after the first salting, before it will give a rennet as powerful as that 
 which was first extracted from it. But cculess it be merely the inner 
 membrane of the stomach and intestines which is capable of undergoing 
 that kind of change upon which the coagulating power depends, there is 
 no apparent reason, as I have already staged to you, why the same 
 maw- skin may not be salted, dried, and steeped many times over. 
 
 Use of whey. — Again, in the making of rennet there seems some pro- 
 priety in the use of whey rather than of water. The whey may contain 
 a portion of the rennet which had been added to the milk from which 
 it was extracted, and may tlius be able of itself to curdle milk. It is 
 sure also to contain some milk-sugar, which, being changed into acid 
 when the whey is poured upon the dried stomach, will add to the coag- 
 ulating power of the rennet obtained. 
 
 Use of the curdled milk contairied in the stomach. — Does the view we 
 have taken of the action of rennet throw any light upon the use of the 
 curdled milk found in the stomach? Is it of any service, or ought it to 
 be rejected? 
 
 We are certain that it must be of service m coagulating milk, since in 
 Cheshire, according to Dr. Holland, it is frequently taken out and salted 
 by itself for immediate use. But a slight consideration of the properties 
 of casein, as I have already stated them to you (p. 562), will explain 
 why this curdy matter should be serviceable for such a purpose. 
 
 You will recollect that casein, after being exposed to the air for a short 
 time, ac(]uires, like anim,al membranes, the property of converting sugar 
 into lactic acid (p. 562), and of curdling milk. Now the curdy matter 
 taken from the stomach of the calf, after being exposed to the air, ac- 
 quires this property as completely as a more pure curd will do. If salted 
 and kept, it^will be changed still further, and will acquire this property 
 in a greater degree. In short, keeping will affect the curd precisely in 
 the same way as it does the membrane of the stomach itself, and will 
 render it alike fit to be employed in the preparation of rennet. Nor is 
 it unlikely that fresh well-squeezed curd, if mixed with much salt and 
 kept in slightly covered jars for 10 or 12 months, might yield a rennet 
 possessed of good coagulating properties. 
 
 It thus appears that, so far as economy is concerned, the curdy matter 
 contained in the calPs stomach ought to be preserved and salted for use. 
 If in any district this curd be suspected to impart an unpleasant flavour 
 to the cheese, this bad eff^ect may probably be remedied by taking it out 
 of the stomach, washing it well with water — as is done in some dairy 
 districts — mixing it mth salt, and then returning it into the stomach 
 again. 
 
 Another practical conclusion may also be drawn from tins explanation 
 of the action of the stomach. Since it is the membrane alone that acts, 
 there can no loss accrue b}'- carefully washing the stomach, as well as 
 the curd it contains. On the contrary, by so doing we may remove 
 
CHEESE OF DIFFERENT QUALITIES HOW OBTAINED. 573 
 
 from its inner surface some substances which, if allowed to remain, might 
 afterwards act injuriously upon the flavour or upon the other qualities of 
 the cheese. 
 
 § 20. Of the circumstances by which the quality of cheese is affected. 
 
 All cheese consists essentially of the curd mixed with a certain por- 
 tion of the fatty matter and of the sugar of milk. But differences in the 
 quality of the milk, in the proportions in which the several constituents 
 of milk are mixed together, or in the general mode of dairy manage- 
 ment, give rise to varieties of cheese almost without number. Nearly 
 every dairy district produces one or more qualities of cheese peculiar to 
 itself. It will not be without interest to attend briefly to some of these 
 causes of diversity. 
 
 1°. Natural differences in the milk. — It is obvious that whatever gives 
 rise to natural differences in the quality of the milk must affect also that 
 of the cheese prepared from it. If the milk be poor in butter, so must 
 the cheese be. If the pasture be such as to give a milk rich in cream, 
 the cheese will partake of the same quality. If the herbage or other food 
 affect the taste of the milk or cream, it will also modify the flavour of the 
 cheese. 
 
 2°. Milk of different animals. — So the milk of different animals 
 will give cheese of unlike qualities. The ewe-milk cheeses of Tuscany, 
 Naples, and Languedoc, and those of goat's milk made on Mont Dor 
 and elsewhere, are celebrated for qualities which are not possessed by 
 cheeses prepared from cow's milk in a similar way. Buffalo milk also 
 gives a cheese of peculiar (jualities, which is manufactured in some parts 
 of the Neapolitan territory. 
 
 Other kinds of cheese agam are made from mixtures of the milk of dif- 
 ferent animals. Thus the strong tasted cheese of Lecca and the cele- 
 brated Roquefort cheese are prepared from mixtures of goat with ewe- 
 milk, and the cheese of Mont Cenis* from both of these mixed with the 
 milk of the cow.f 
 
 3°. Creamed or uncreamed milk. — Still further differences are pro- 
 duced according to the proportion of cream which is left in or is added to 
 the milk. Thus if cream only be employed, we have the rich cream- 
 cheese which must be eaten in a comparatively recent state. Or, if the 
 cream, of the previous night's milking be added to the new inilk of the 
 morning, we may have such cheese as the Stilton of England, or the 
 small, soft, and rich Brie cheeses, so much esteemed in France. If the 
 entire milk only be used, we have such cheeses as the Cheshire, the 
 Double Gloucester, the Cheddar, the Wiltshire, and the Dunlop cheeses 
 of Britain, the Kinnegad cheese, I believe, of Ireland, and the Goudaand 
 Edam cheeses of Holland. Even here, however, it makes a difference 
 whether the warm milk from the cow is curdled alone, as at Gouda and 
 Edam, or whether it is mixed with the milk of the evening before, as is 
 generally done in Cheshire and Ayrshire. Many persons are of opin- 
 ion that cream, which has once been separated, can never be so well 
 
 ' Lecca is a province in the Eastern pait of the Neapolitan territory ; Roquefort, a town 
 in the pastoral department of Aveiron, in the South of France, famed for its sheep; and 
 Mont Cenis, a naountain in Savoy. 
 
 t The milk of 2 goats is mixed with that of 20 sheep and 5 cows. 
 
574 BUTTER-MILK, WHET, AND VEGETABLE CHEESES. 
 
 ■i 
 
 mixed again with the milk, that a portion of the fatty matter shall no*" 
 flow out with the whey and render the cheese less rich. 
 
 If, again, the cream of the evening's milk be removed, and the skim- 
 med milk added to the new milk of the next morning, such cheeses as 
 the Single Gloucester are obtained. If the cream be taken once from 
 all the milk, the better kinds of skimmed-milk cheese, such as the Dutch 
 cheese of Leyden, are prepared — while if tlie milk be twice skimmed, 
 we have the poorer cheeses of Friesland and Groningen. If skimmed 
 for three or four days in succession, we get the hard and horny cheeses 
 of Essex and Sussex, which often require the axe to break them up. 
 
 4°. Butter-?nilk cheese. — But poor or butterless cheese will also differ 
 in quality according to the state of the milk from which it is extracted. 
 If the new milk be allowed to stand to throw up its cream, and this be 
 then removed in the usual way, the ordinary skimmed-milk cheese will 
 be obtained by adding rennet to die milk. But if, instead of skimming, 
 we allow the milk to stand till it begins to sour, and then remove the 
 butter by churning the whole, we obtain tlie milk in a sour state {butter- 
 viilk). From this milk the curd separates naturally by gentle heating. 
 But being tlius prepared from sour milk and without the use of rennet, 
 butter-milk cheese differs more or less in quality from that which is made 
 from sweet skimmed milk. 
 
 The acid in the butter-milk, especially after it has stood a day or two, 
 is caj)able of coagulating new milk also, and thus, by mixing more or 
 less sweet milk with the butter-milk before it is warmed, several other 
 qualities of mixed butter and sweet milk cheese may readily be manu- 
 factured. 
 
 If, as is stated by Mr. Ballantync, the churning of the whole milk 
 gives butter in larger quantity, of better quality, and more uniformly 
 throughout the whole year (p. 558), the manufacture of these butter-milk 
 cheeses is deserving of the attention of dairy farmers, especially in those 
 districts where butter is considered as the most important produce. 
 
 5°. Whey-cheese. — The whey which separates from the curd, and 
 especially the white whey, which is pressed out towards the last, contains 
 a portion of curd, and not unfrccjuently a considerable quantity of butter 
 also. When the whey is heated, the curd and butter rise to the surface, 
 and are readily skimmed ofi". This curd alone will often yield a cheese 
 of excellent quality, and so rich in butter, that a very good imitation of 
 Stilton cheeee may sometimes be made with alternate layers of new 
 milk-curd and this curd of whey. 
 
 6°. Mixtures of vegetable substances ivith the milk. — New varieties 
 of cheese are formed by mixing vegetable substances with the curd. A 
 green decoction of two parts of sage-leaves, one of marigold, and a Uttle 
 parsley, gives its colour to the green cheese of Wiltshire ; some even mix 
 up the entire leaves with the curd. The celebrated Schabzieger cheese 
 of Switzerland is made by crushing the skim-milk cheese after it is se- 
 veral rnontbs old to fine powder in a mill, mixing it then witli one-tenth 
 of its weight of fine salt and one-twentieth of tlie powdered leaves of the 
 mellilot trefoil {trifolium melilotus cerulea), and afterwards with oil or 
 butter — working the whole mto a paste, which is pressed and carefuUy 
 dried. 
 
 Potato cheeses, as they are called, are made in various ways. One 
 
TEMPERATURE AND HEATING OF THE MILK. 575 
 
 pound of sour milk is mixed with five pounds of boiled potatoes and a 
 little salt, and the whole is beat into a pulp, which, after standing five or 
 six days, is worked u}) again, and then dried in the usual way. Others 
 mix three parts of dried boiled potatoes with two of fresh curd, or equal 
 weights, or more curd than potato according to the quality required. 
 Such cheeses are made in Thuringia, in Saxony, and in other parts of 
 Germany. In Savoy, an excellent cheese is made by mixing one of the 
 pulp of potatoes with three of ewe milk curd, and in Westphalia a po- 
 tato cheese is made with skimmed milk. This Westphalian cheese, 
 while in the pasty state, is allowed to undergo a certain extent of fer- 
 mentation before it is finally worked up with butter and salt, made into 
 shapes and dried. The extent to which this fermentation is- permitted to 
 go determines the flavour of the cheese. 
 
 § 21. Circumstances under lohich cheese of different qualities may he 
 obtained fj'om the same milk. 
 
 Bnt from the same milk, in the same state, ditTe rent kinds or qualities 
 of cheese may be prepared according to the way in which the milk or 
 the curd is treated. Let us consider also a few of the circumstances by 
 which this result may be brought about. 
 
 1°. Temperature to luhich tJie milk is heated. — The temperature of new 
 or entire milk, when the rennet is added, should be raised to about 95° F. 
 — that of skimmed milk need not be quite so high. If the milk be 
 warmer the curd is hard and tough, if colder, it is soft and difficult to ob- 
 tain free from the whey. When the former hap[)ens to be the case, a 
 portion of the first whey that separates may be taken out into another 
 vessel, allowed to cool, and then poured in again. If it prove to have 
 been too cold, hot milk or water may be acliled to it — or a vessel contain- 
 ing hot water may be put iaito it before the curdling commences — or the 
 first portion of whey that separates may be heated and poured again 
 upon the curd. The quality of the cheese, however, will always be 
 more or less affected when it happens to be necessary to adopt any of 
 these remedies. To make the best cheese, the true temperature should 
 always be attained as nearly as possible, before the rennet is added. 
 
 2°. Mode in which the milk is warmed. — If, as is the case in some 
 dairies, the milk be warmed in an iron pot upon the naked fire, great care 
 must be taken that it is not singed or jire-fanged. A very slight inat- 
 tention may cause this to he the case, and the taste of the cheese is sure 
 to be more or less affected by it. In Cheshire the milk is put into a large 
 tin pail, which is plunged into a boiler of hot water, and frequently stir- 
 red till it is raised to the proper temperature. In large dairy establish- 
 ments, however, the safest method is to have a pot wiih a double bottom, 
 consisting of one pot within another-^after the manner of a glue-pot — the 
 space between the two being filled with water. The fire applied be- 
 neath thus acts only upon the water, and can never, by any ordinary 
 neglect, do injury to the milk. It is desirable in this heating, not to raise 
 the temperature higher than is necessary, as a great heat is apt to give 
 an oiliness to the fatty matter of the milk. 
 
 3°. The time during ivhich the curd stands is also of importance. It 
 shot. Id be broken up as soon as the milk is fully coagulated. The longer 
 it stands after this the harder and tougher it will become. 
 
576 QUALITY AND QUANTITY OF THE RENNET. 
 
 4°. The quality of the rennet is of much importance not only in regard 
 to tlie certainty of the coagulation, hut also to the flavour of the cheese. 
 In some parts of Cheshire, as we have seen, it is usual to take a piece 
 of the dried membrane and steep it overnight with a little salt for the 
 ensuing morning's milk. It is thus sure to be fresh and sweet if the 
 dried maw be in good preservation. But where it is customary to steep 
 several skins at a time, and to bottle the rennet for aft&r-use, it is very 
 necessary to saturate the solution completely with salt and "to season it 
 with spices, in order that it may be preserved in a sweet and wholesome 
 state. In some parts of Scotland the rennet is said to be frequently kept 
 in bottles till it is almost putrid, and in this state is still put into the milk. 
 Such rennet may not only impart a bad taste to the cheese, but is likely 
 also to render it more difficult to cure and to bring on putrefaction after- 
 wards and a premature decay. 
 
 5°. The quantity of rennet added ought to be regulated as carefully 
 as the temperature of the milk. Too much renders the curd tough ; too 
 little causes the loss of much time, and may permit a larger portion of 
 the butter to separate itself from the curd. It is to be expected also that 
 when rennet is used in great excess, a portion of it will remain in the 
 curd, and will naturally affect the kind and rapidity of the changes it 
 afterwards undergoes. Thus it is said to cause the cheese to heave or 
 swell out from fermentation. It is probable also that it will affect the 
 flavour which the cheese acquires by keeping. Thus it may be that the 
 agreeable or unpleasant taste of the cheeses of certain districts or dairies 
 may be less "'due to the quality of the pastures or of the milk itself, than 
 to the quantity of rennet with Vv^hich it has there been customary to co- 
 agulate the milk. 
 
 6°. The way in which the rennet is made, no less than its state of pre- 
 servation and the quantity employed, may also influence the* flavour or 
 other qualities of the cheese. For instance, in the manufacture of a 
 celebrated French cheese — that of Epoisse — the rennet is prepared as fol- 
 lows : — Four fresh calf-skins, with the curd they contain, ai^e well 
 washed in "water, chopped into small pieces, and digested in a mixture 
 of 5 quarts of brandy with 15 of water, adding at the same time 2^ lbs. 
 of salt, half an ounce of black pepper, and a quarter of an ounce each 
 of cloves and fennel seeds. At the end of six weeks the liquor is filtered 
 and preserved in well corked bottles, while the inembrane is put into salt- 
 water to form a new portion of rennet. For makmg rich cheeses, the 
 rennet should always be filtered clear. [II latte e i suoi prodotti, p. 274.] 
 
 Again, on Mont Dor, the rennet is made with white wine and vinegar. 
 An ounce of common salt is dissolved in a mixture of half a pint of 
 vinegar with 2i pints of white wine, and in this solution a prepared 
 goat's stomach or a piece of dried pig's bladder is steeped for a length of 
 time. A single spoonful of this rennet is said to be sufficient for 45 or 
 50 quarts of milk. No doubt the acid of the idnegar and of the wine aid 
 the coagulating power derived from the membrane. 
 
 Rennets prepared in the above ways must affect the flavour of the 
 cheese differently from such as are obtained by the several more or less 
 careful methods usually adopted in this country. 
 
 7°. Wlien acids are used alone — as vinegar, tartaric acid, and muria- 
 tic acid sometimes are — for coagulating tlie milk, the flavour of the 
 
now THE WHEY IS SEPARATED. 577 
 
 cheese can scarcely fail to be in some measure different from that which 
 is prepared with ordinary rennet. 
 
 8°. The way in which the curd is treated. — It is usual in our best 
 cheese districts carefully and slowly to separate tlie curd from the whey — 
 not to hasten the separation, lest a larger portion of the fatty matter should 
 be squeezed out of the curd and the cheese should thus be rendered poorer 
 than usual. But in some places the practice prevails of washing the 
 curd with hot water after the whey has been partially separated from it. 
 
 Thus at Gouda in Holland, after the greater part of the whey has been 
 gradually removed, a quantity of hot water is added, and allowed to re- 
 main upon it for at least a quarter of an hour. The heat makes the 
 cheese more solid and causes it to keep better. 
 
 In Italy, again, the so-called pear-shaped caccio-cavallo cheeses and 
 the round palloni cheeses of Gravina, in the Neapolitan territory, arc 
 made from curd, which, after being scalded with boiling whey, is cut into 
 slices, kneaded in boiling water, worked with the hand till it is perfectly 
 tenacious and elastic, and then made into shapes. The water in which 
 the curd is washed, after standing*24 hours, throws up much oily mat- 
 fter, which is skimmed off and made into butter. 
 
 The varieties of cheese prepared by these methods no doubt derive the 
 peculiar characters upon whicli their reputation depends from the treat- 
 ment to which the curd is subjected — but it is obvious that none of them 
 can be so rich as a cheese from the same milk would be, if manufactured 
 in a Cheshire, a Wiltshire, or an Ayrshire dairy. 
 
 9°. The separation of the whey is a part of the process upon which the 
 quality of the cheese in a considerable degree depends. In Cheshire 
 more time and attention is devoted to the perfect extraction of the whey 
 than in almost any other district. Indeed, when it is considered that the 
 whey contains sugar and lactic acid, which may undergo decomposition, 
 and a quantity of rennet which may bring on fermentation — by both of 
 which processes the flavour of the cheeses must be considerably affected 
 — it will appear of great importance that the whey should be as com- 
 pletely removed from the curd as it can possibl}'^ be. To aid in effecting 
 this a curd-mill, for chopping it fine after the whey is strained off, is in 
 use in many of the large English dairies, and a very ingenious, and I 
 believe effectual, pneumatic cheese-press for sucking out the whey was 
 invented by the late Sir John Robinson, of Edinburgh. [Transactions 
 and Prize Essays of the Highland Society, vol. x., p. 204.] 
 
 But the way in which the whey is separated is not a matter of indif- 
 ference, and has much influence upon the quality of the cheese. Thus 
 in Norfolk, according to Marshall, when the curd is fairly set, the dairy- 
 maid bares her arm, plunges it into the curd, and with the help of her 
 wooden ladle breaks up minutely and intimately mixes the curd with tlic 
 whey. This she does for 10 or 15 minutes, after which the curd is al- 
 lowed to subside, and the whey is drawn off. By this agitation 
 the whey must carry off more of the butter and the cheese must be 
 poorer. 
 
 In Cheshire and Ayrshire, again, the curd is cut with a knife, but is 
 gently used and slowly pressed till it is dry enough to be chopped fine, and 
 thus more of the oily matter is retained. On the same principle, in making 
 the Stilton cheese, the curd is not cut or broken at all? but is pressed 
 
578 KIND OF SALT, AND HOW IT IS APPLIED. 
 
 gently and with care till the whey gradually drains out. Thus the butter 
 and the curd remain intermixed, and the rich cheese of Siilton is the result. 
 
 Thus you will see that M'hile it is of importance that all the whey 
 should be extracted from the curd, yet tliat the quickest v/ay may not he 
 the best. More time and care must be bestowed in order to effect this 
 object, the richer the cheese we wish to obtain. You will see, also, how 
 the quality of the milk or of the pastures may often be blamed for de- 
 ficiencies in the richness or other qualities of our cheese, which are 
 in reality due to slight but material differences in our mode of manufac- 
 turing it. 
 
 10°. The kind of salt used is considered by many to have some effect 
 upon the taste of the cheese. Thus the cheese of Gerome, in the Vos- 
 ges, is supposed to derive a peculiar taste from the Lorena salt with 
 which it is cured. In Holland, also, the etficacy of one kind of salt 
 over another for the curing of cheese is generally acknowledged, [British 
 Husbandry, ii., p. 424.] It is indeed not unlikely that the more or less 
 impure salts of different localities may affect the flavour of the cheese, 
 but wherever the salt may be manufactured, it is easy to obtain it in a 
 uniform and tolerably pure state, by the simple process of purification, 
 which I have already described to you (p. 565.) 
 
 11°. The mode in which the salt is applied. — In making the large 
 Cheshire cheeses the dried curd, for a single cheese of 60 lbs., is broken 
 down fine and divided into three equal portions. One of these is 
 mingled with double the quantity of salt added to the others, and tliis 
 is so put into the cheese-vat as to form the central part of the cheese. 
 By this precaution the after-salting on the surface is sure to penetrate 
 deep enough to cure effectually the less salted parts. In the counties of 
 Gloucester and Somerset the curd is pressed without salt, and the cheese, 
 when formed, is made to absorb the whole of the salt afterwards through 
 its surface. This is found to answer well with the small and thin 
 cheeses made in these counties, but were it adopted for the large cheeses 
 of Cheshire and Dunlop, or even for the pine-apple cheeses of Wiltshire, 
 there can be no doubt that their quality would frequently be injured. It 
 may not beTmpossible to cause salt to penetrate into the very heart of a 
 large cheese, but it cannot be easy in this way to salt the whole cheese 
 e(pially, while the care and attention required must be greatly increased. 
 
 12°. Addition of cream or butter to the curd. — Another mode of im- 
 proving the quality of cheese is by the addition of cream or butter to the 
 dried and crumbled curd. Much diligence, however, is required fully 
 to incorporate these, so that the cheese may be uniform throughout. Still 
 this practice gives a peculiar character to the cheeses of certain districts. 
 In Italy they make a cheese after the manner of the English, [II latte e i 
 suoi prodotti, p. 277], into which a considerable quantity of butter is 
 worked; and the Reckem cheese of Belgium is made by adding half an 
 ounce of butter and the yoke of an egg to every pound of pressed curd. 
 
 13°. The colouring matter added to the cheese is thought by many to 
 affect its quality. In foreign countries saffron is very generally used to 
 give a colour to the milk before it is coagulated. In Holland and in 
 Cheshire annatto is most commonly employed, while in other dis- 
 tricts the marigold or the carrot, boiled in milk, are the usual colouring 
 matters. 
 
MODE OF CURING THE CHEESE. 579*: 
 
 The quantity of annatto employed is comparatively small — ^less than 
 naif an ounce to a cheese of 60 lbs. — but even this quantity is considered 
 by many to be an injurious admixture. Flence a native of Cheshire 
 prefers the uncoloured cheese, the annatto being added to such only as 
 are intended for the London or other distant markets. 
 
 14°. Size of the cheese. — From the same milk it is obvious that cheeses 
 of different sizes, if treated in the same way, will at the end of a given 
 number of months possess qualities in a considerable degree different. 
 Hence, without supposing any inferiority, either in the milk or in the ge- 
 neral mode of treatment, the size usually adopted for the cheeses of a 
 particular district or dairy, may be the cause of a recognized inferiority 
 in some quality which it is desirable that they should possess in a high 
 degree. 
 
 15°. The. method of curing has very much influence upon the after- 
 qualities of the cheese. The care with which they are salted — the 
 warmth of the place in which they are kept during the first two or three 
 weeks — the temperature and closeness of the cheese-room in wliich they 
 are afterwards preserved — the frequency of turning, of cleaning from 
 mould, and of rubbing with butter — all these circumstances exercise a 
 remarkable influence upon the after-qualities of the cheese. Indeed, in 
 very many instances the high reputation of a particular dairy district or 
 dairy farm is derived from some special attention to one or other or to all 
 of the apparently minor points to which I have just adverted. 
 
 In Tuscany, the cheeses, after being hung up for some time at a proper 
 distance from the fire, are put to ripen in an underground cool and damp 
 cellar; an 1 the celebrated French cheeses of Roquefort are supposed to 
 owe much of the peculiar estimation in which they are held, to the cool 
 and unif)rm temperature of the subterranean caverns in which the 
 inhabitants of the village have long been accustomed to preserve them. 
 
 In Rosshire it is said to be the custom with some proprietors to bury 
 their cheeses under the sea sand at low water, and that the action of 
 the sea-water in this situation renders them more juicy and of an exquisite 
 flavour. 
 
 16°. Ammoniacal cheese. — The influence of the mode of curing upon 
 the quality is shown very strikingly in the small ammoniacal cheeses of 
 Brie, which are very much esteemed in Paris. They are soft unpressed 
 cheeses, which are allowed to ripen in a room the temperature of which 
 is kept between 60° and 70° F. till they begin to undergo the putrefac- 
 tive fermentation and emit an ammoniacal odour. They are ge- 
 nerally unctuous, and sometimes so small as not to weigh more than an 
 ounce. 
 
 A little consideration, indeed, will satisfy you, that by varying the 
 mode of curing, and especially the temperature at which they are kept, 
 you may produce an almost endless diversity in the quality of tJie cheeses 
 you bring into the market. 
 
 17°. Inoculating cheese. — It is said that a cheese, possessed of no 
 very striking taste of its own, may be inoculated with any flavour we 
 approve of, by putting into it with a scoop a small portion of the cheese 
 which we are desirous that it should be made to resemble. Of course 
 this can apply only to cheeses otherwise of equal richness, for we could 
 scarcely expect to give a single Gloucester the flavour of a Stilton, 
 
580 AVERAGE QUANTITY OF CHEESE YIELDED. 
 
 by merely putting into it a small portion of a rich and esteemed Stilton 
 cheese. 
 
 § 22. Of the average quantity of cheese yielded by different varieties of 
 miik, and of the produce of a single cow. 
 There appear to be very great difTerences in the proportions of cheese 
 yielded by milk at different seasons and in different localities. 
 
 In milJv, of an average quality, there are contained from 4 to 5 percent, 
 of casein or dry cheesy matter (p. 534),which, if all extracted, would give — 
 6 lbs. to 7 lbs. of shimmed milk cheese, or ? from 100 lbs. of 
 9 lbs. to 10 lbs. of entire milk cheese, \ milk. 
 
 This is very nearly the proportion actually obtained in some of the 
 best dairy districts in the swmner season. Thus — 
 
 In Ayrshire — 10 lbs. of milk, or } gave 1 lb. of whole milk 
 1 imperial gallon, ^ cheese ; 
 
 or 136 wine quarts gave l27i lbs. of cheese three months old.* 
 
 In Gloucester — 7 lbs. of milk, or ? gave 1 lb. of double 
 3^ wine quarts, ^ Gloucester ; 
 
 this is a much larger proportion, and is probably much above the average 
 of the county. 
 
 In Holstein, it is said that 100 lbs. of milk will give about — 
 
 Neiv skimnied milk cheese 6 lbs. 
 
 Butter 3^ " 
 
 Butter-milk 14 
 
 h 
 
 Whey 76f " 
 
 100 lbs. 
 
 But this statement is so far indefinite that it affords us lio means of 
 judging how much curd is left in tlie butter-milk, nor how much water 
 was present in the new cheese. Indeed, most of the statements on record 
 are deficient in this respect, that the dryness of the cheese is not accu- 
 rately expressed. 
 
 In Cheshire, the average produce of a cow is reckoned at 360 lbs. of 
 whole milk-cheese, or about 1 lb. per day for the whole year. Taking 
 8 wine quarts of milk as the average daily yield of a cow in that county, 
 we have as the average produce of the milk the whole year through — 
 1 lb. of cheese from 8 wine quarts, or 16 lbs. of milk. 
 
 It is indeed undoubted, that the proportion of cheese varies very 
 much with the season of the year and with the drytiess of the weather. 
 Though, therefore, in summer 7 or 8 lbs. of milk may sometimes yield 
 a pound of cheese, it is possible that as much as 20 lbs. of milk may at 
 other seasons be required to give the same quantity. Thus in — 
 
 South Holland, the summer produce of a cow is reckoned at about 200 
 lbs. of skimmed milk cheese, and 80 lbs. of butter ; or in a week 10 lbs. 
 of ski;iimed milk cheese, and 4 to 7 lbs. of butter. Of whole milk 
 cheese sotne expect as much as 3 or A lbs. a day. 
 
 * Mr. Alexander, of Southbar, informs me that the result of his experience with a dairy 
 of 40 cows in the higher part of Ayrshire, near Muirkirk, is, that — 
 
 90 imperial quarts of sweet milk give an Ayrshire stone of 24 lbs. of full milk cheese, 
 while tlie same quantity of skim milk gives only 16 lbs. of skimmed milk cheese. That is 
 very nearly — 
 
 9 lbs. of new milk give 1 lb. of full milk cheese. 
 
 14 lbs. of skim-milk give 1 lb. of skim-milk cheese (see p. 685). 
 
MILK SPIRIT AND MILK VINEGAR. 581 
 
 In Switzerland, generally, a cow, giving 12 quarts of milk a day will, 
 during the summer, yield a daily produce of 1^ lbs. of whole or full milk 
 cheese — or 10| quarts of milk, about 21 lbs., will give a pound of cheese. 
 
 In the high pastures of Scaria, again, in the same country, one cow 
 will give fir the 90 days of summer about 60 lbs. of skimmed-milk 
 cheese and 40 lbs. of butter — or 11 ounces of cheese per day. 
 
 It appears, therefore, as we should otherwise expect, that the average 
 produce of cheese is aflfected by many circumstances — but that in this 
 country 8 to 10 lbs. of good milk, in the summer season, will yield one 
 pound of whole milk cheese. 
 
 § 23. Of the fermented liquor from milk, and of milk vinegar. 
 
 Milk is capable of undergoing what is called the vinous fermentation, 
 and of yielding an intoxicating liquor. The Tartars prepare such a 
 liquor from mare's milk, to which the name o^ kou7niss is given. When 
 made from cow's milk it is called airen, and is less esteemed because 
 generally of a weaker quality. The Arabians and Turks prepare a si- 
 milar licjuor, which the former call leban, and the latter yaourt. In the 
 Orkney Islands, and in some parts of the north of Scodand and Ireland, 
 butter-milk is sometimes kept till it undergoes the vinous fermentation, 
 and acquires intoxicating qualities. 
 
 It is the sugar contained in milk which, by the fermentation, is changed 
 into alcohol. As mare's milk, like that of the ass, contains more sugar 
 (p. 534) than that of the cow, it gives a stronger licjuor, and is therefore 
 naturally preferred by the Tartars. By distillation ardent spirits are ob- 
 tained from koumiss, and when carefully made in close vessels, a pint of 
 the liquor will yield half an ounce of spirit. The koumiss is prepared In 
 the following manner : 
 
 To the new milk, diluted with a sixth of its bulk of water, a quantity 
 of rennet, or what is better, of sour koumiss, is added, and the whole is 
 covered up in a warm place for 24 hours. It is then stirred or churned 
 together till the curd and whey are intimately mixed, and is again left 
 at rest for 24 hours. At the end of this time it is put into a tall vessel, 
 and agitated till it becomes perfectly homogeneous. It has now an agree- 
 able sourish taste, and in a cool place may be preserved for several 
 months in close vessels. It is always shakeJ up before it is drunk. This 
 liquor, from the cheese and butter it contains, is a nourishing as well as 
 an exhilarating diink, and is not followed by the usual bad efTects of in- 
 toxicating liquors. It is even recommended as a wholesome article of 
 diet in cases of dyspepsia or of general debility. 
 
 Milk vinegar. — If the koumiss be kept in a warm place the spirit dis- 
 appears and vinegar is formed. In some parts of Italy a rnilk vinegar 
 of pleasant quality is prepared by adding honey, sugar, spirit, and a lit- 
 tle yeast to the boiled whey, and setting'the mixture aside to ferment in 
 a warm place. [II latte e i suoi prodotti, pp. 415 and 450.] 
 
 § 24. Of the composition of the saline constituents of milk 
 
 When milk is boiled down to dryness, and the dry residue burned, a 
 
 small quantity of ash remains behind. The proportion which the 
 
 weight of this ash bears to that of the whole milk is variable — as the 
 
 qualities of the milk itself are — so that 1000 lbs. will leave sometimea 
 
 25 
 
582 USE OF MILK IN THE ANIMAL ECONOMY. 
 
 only 2 lbs., at others as much as 7 lbs. of ash. This ash consists of a 
 mixture of common salt and chloride of potassium (p. 188), with the 
 phosphates of lime, magnesia, and iron. The relative proportions of 
 these several substances yielded by 1000 lbs. of the milk of two dif- 
 ferent cows, were as follows [Haidlen, Annal. der Chem. und Phar., 
 xiv., p. 273] : 
 
 I. II. 
 
 Phosphate of lime 2-31 lbs. 3-44 lbs. 
 
 Phosphate of magnesia . . . 0*42 " 0*64 '* 
 
 Phosphate of peroxide of iron . 0-07 " 0-07 " 
 
 Chloride of potassium .... 1-44 " 1-83 " 
 
 Chloride of sodium 0-24 " 0-34 " 
 
 Free soda ........ 0-42 " 0-45 "- 
 
 4-90 " 6-77 '' 
 
 It is probable that the phosphates and chlorides existed as such in the 
 milk as it came from the cow, the free soda is believed to have been in 
 combination with the casein, and to have held it in solution in the milk. 
 You will recollect that the explanation I have given of the curdling of 
 milk is, that the acid produced in, or added to, the milk, takes this soda 
 from the casein, and renders it insoluble in water, and that in conse- 
 quence it separates in the form of curd (see p. 566). 
 
 § 25. Purposes served by milk in the animal economy. 
 
 Milk is the food provided for the young animal, at a period when it is 
 unable to seek food for itself. It consists, as we have seen, of — 
 
 1°. The casein- or curd. — This being almost identical in constitution 
 Avith the lean part or fibrin of the muscles serves to promote the growth 
 of the flesh of the animal. 
 
 2°. The fat or butter., which is mainly expended in supplying fat to 
 those parts of the body in which fat is usually deposited. 
 
 3°. The sugar, which is probably consumed by the lungs during re- 
 spiration. 
 
 4°. The~sdline inatter, from which come the salts contained in the 
 blood, and the earthy part of the bones of young and growing animals 
 fed upon milk. 
 
 These several purposes served by milk will come again under our 
 consideration in the following lecture. 
 
 NOTES. 
 1°. On the churning of butter in the French churn. 
 Mr. Burnett, of Gadgirth, has favoured me with the following intbr- 
 mation regarding the merits of the French churn mentioned in page 
 555:— 
 
 " I see you make mention, in page 555 of your Lectures, of a churn 
 lately introduced by Mr. Blacker from France. I got one of these from 
 Mr. Blacker about tv/o years ago, and have proved its merits to be very 
 great. I use none else, and have been the means of distributing it over 
 
CHURNING IN THE FRENCH CHURN. 583 
 
 different parts of England and Scotland. It is made of tin, of a barrel 
 shape, and is placed in a trough of water, heated or otherwise, to convey 
 the proper temperature to the cream. I have tried many experi- 
 ments to ascertain the proper temperature for churning cream in 
 this churn, and have found that 58° F. produces the best quality of but- 
 ter in the shortest time — the time occupied being from ten to twenty 
 minutes. At 60° it was often done in five to seven minutes, and although 
 a little soft at first, produced butter of a good colour and quality — on no 
 occasion was it ever white. I also tried 56° F. It took generally one 
 hour, was harder, but no better in quality than that of 58°. 
 
 " With regard to the quantity of butter from a given quantity of cream, 
 I found that in July, when the cows were on good pasture, and occasion- 
 ally house-fed on clover — 
 
 16 quarts of cream produced . 12 lbs. 8 oz. 
 
 24 do. do. do. .16 lbs. 12 oz. 
 
 30 do. do. do. . 20 lbs. 8 oz. 
 
 Or, 70 quarts produced . . . . . 49 lbs. 12 oz. 
 
 When fed on cabbage — 
 
 50 quarts of cream produced . . 32 lbs. 
 Again — 
 
 50 quarts of cream produced . . 32 lbs. 4 oz. 
 60 do. do. do. . . 40 lbs. 
 
 Or the whole six quarts of cream in July gave 4 lbs. of butter. 
 
 " On churning the ivhoie milk in this churn, 100 quarts of milk at 60° 
 produced 8 lbs. of butter of excellent quality in one hour and a half — 8 
 quarts of hot water were put into the churn according to the old system. 
 
 " 100 quarts of milk from the sa7ne cows at 64° produced only 7 lbs. 
 of butter of a soft and inferior qi^ality, and took two hours to churn, 16 
 quarts of hot water being put into the churn on this occasion. 
 
 " The whole milk was sometimes churned in less than one hour, but 
 from that to one hour and a half was the general time occupied, whereas 
 three to four hours is the time occupied in churning in ihe common churn. 
 
 " To ascertain whether the whole milk or the cream produced the 
 greatest quantity of butter in this churn, I toDk the milk of five cows 
 (Ayrshire breed) for one week in July last, amounting to 508 quarts — 
 the yield of butter was 36 lbs. 11 oz. I then took the same quantity of 
 milk from the same cows for the same period of time, and let it stand for 
 cream — the butter produced was 37 lbs. 4 oz. The food and other cir- 
 cumstances were quite the same. 
 
 " To test the quality of my butter, I sent it last summer to a show at 
 Ayr, and obtained the* second premium both for fresh and salt ; the heat 
 at which it was churned was 58°, and the time not exceeding half an 
 hour." 
 
 On these observations of Mr. Burnett, I must in fairness remark, that 
 several other persons who have used this churn, have not reported by any 
 means so favourably of its merits. Perhaps they have not known how 
 to manage it so skilfully. 
 
 2°. Quantity of milk and butter yielded by Ayrshire cows. 
 Mr. Alexander, of Southbar, has furnished me with the following pro- 
 
584 COMPARATIVE PROFIT OF 
 
 portions of cream and butter yielded by his dairy of 38 cows, at Well- 
 wood, in the higher part of Ayrshire, near Muirkirk, during six several 
 
 days in November and December, 1843 : — 
 
 Cream Butter 
 
 Date. in imp. galls. in pounds. 
 
 November 1 ...... 16 43i 
 
 " 7 191 47^ 
 
 14 18| 43 
 
 *' 21 2]| 47 
 
 " 29 18 39 
 
 December 7 19 43| 
 
 i 
 
 In all . . . . .1121 galls, gave 263^ 
 
 or, seven quarts of cream in November gave four pounds of butter 
 
 The cream appears from the table to have become gradually less rich, 
 though the whole quantity did not diminish. 
 
 Mr. Alexander remarks, that " the proportion of cream varies in his 
 dairy from ^^th to y^^th of the bulk of the milk, and that the Guernsey or 
 Highland, or any black or black-marked cow, gives more cream from the 
 same quantity of milk." That is, they give a richer milk. 
 
 This is a curious physiological fact, and is probably related to an ob- 
 servation made in the fattening of these races, that the same quantity of 
 food goes further in fattening a black or black-marked than a dun or white 
 beast. I do not suppose that any thing of this kind has been observed in the 
 Durham breed — as white animals, of pure blood, are often great favour- 
 ites with the breeders of Tees- Water stock. 
 
 3*^. Profit of making butter and cheese compared with that of 
 selling the milk. 
 
 For the following particulars I am *also indebted to Mr. Alexander. 
 The produce of cheese and butter is the average of his experience at 
 Wellwood, in Ayrshire. 
 
 There are three ways in which the milk is usually disposed of. It is 
 sold in the^ate of new milk, or it is made into full milk cheese, and the 
 whey given to pigs — or it is made into butter, and the skim -milk sold, or 
 made into cheese, or given to pigs. The profit of each of these three 
 methods, at the Ayrshire prices, is as follows approximately : — 
 
 5. d. 
 a. — 90 quarts of new milk, at 2d. a quart, are sold for . 15 
 b. — 90 quarts of new milk give 24 lbs. of full milk cheese, 
 
 which, at 4 ^d., per lb. are sold for . . . .90 
 The whey is worth, at least 6 
 
 9 6 
 
 c. — 90 quarts of milk, churned altogether, give 9 lbs. of butter, 
 
 at 9d 6 9 
 
 90 quarts of butter-milk, at ^d. per quart . . . .3.9 
 
 10 6 
 In the country, where the butter-milk cannot be sold, it is given to the 
 pigs, and does not yield so large a return. 
 
6 
 
 9 
 
 
 
 9 
 
 o 
 
 11 
 
 MAKING BUTTER AlfD CHEESE. 585 
 
 S. d. 
 d. 90 quarts of new milk give 18 quarts of cream, yielding 
 9 lbs. of butter at 9d., as before ..... 
 18 quarts of butter-milk, at ^d. . . 
 70 quarts of skim-milk, at ^d. 
 
 10 5 
 
 When the skim-milk cannot be sold, it may be given to the pigs, or 
 it may be made into skim-iniik cheese. In the latter case the profit is 
 as follows : — 
 
 s. d. 
 
 e. — Butter and butter-milk, as before . . . . .76 
 70 quarts of skim-milk give 16 lbs. of cheese, which, at 3d. 
 
 per lb . . ■ . .40 
 
 Thus we have 90 quarts of milk — 
 
 a — sold as new milk, worth .... 
 
 h — made into full-milk cheese .... 
 
 c — made into butter and butter-milk, where the latter 
 can be sold ...... 
 
 d — made into butter and skim-milk, where the latter 
 can be sold . . . . " . 
 
 e — made into butter and skim-milk cheese 
 In the country, therefore, according to these calculations,. the most pro- 
 fitable way is to make butter and skim-milk cheese. The farmer is thus 
 in a great measure independent of an adjoining population. The small 
 quantity of butter-milk he thus obtains he will easily be able to dispose 
 of, or otherwise to employ to advantage. 
 
 According to Mr. Ayton, it is still more profitable to feed calves with 
 the milk, but I find many people differ from him on this point. At all 
 events, a good and ready market is required for the veal. 
 
 
 11 
 
 6 
 
 s. 
 
 d. 
 
 
 15 
 
 
 
 
 9 
 
 6 
 
 
 10 
 
 6 
 
 
 10 
 
 5 
 
 
 11 
 
 6 
 
 
LECTURE XXI. 
 
 Of the feeding of animals, and the purposes served by fheir food.— Substances of which the 
 parts of animal bodies consist. — Whence do the animals derive these substances— are 
 they all present in the food! — Use of the starch, gum, and sugar contained in vegetable 
 food. — Functions of a full-growrn animal. — Of the respiration of animals. — General origin 
 and purposes served by the fat in carnivorous and herbivorous animals.— Of the digestive 
 process in animals— Purposes served by food and digestion. — The food sustains the full- 
 grown animal. — Necessity of a mixed food. — It sustains and increases the fattening ani- 
 mal. — Relative fattening powers of different kinds of fond. — How circumstances affect this 
 fattening property. — Purposes served by food in the pregnant — in the young and growing 
 animals, such as the call'^and in tiie milk cow. — Effect of different kinds of food on thu 
 quality of the milk. — Fattening of the cow as the milk lessens in quantity — Experimental, 
 economical, and theoretical value of different kinds of food for these several purposes. — 
 Circumstances which affect these values. — Soil, manure, form in which "the food is given, 
 ventilation, light, warmth, exeicise, activity, salt and other condiments. 
 
 Having in the preceding lectures considered the composition of the 
 direct products of the soil — grains, roots, and grasses — and of the most 
 important indirect products — milk, butter, and cheese — t)ie only part of 
 our subject which now remains to be discussed is tlie relative values of 
 these several products in the feeding of animals. 
 
 Under this head it will be necessary to enquire how far these values 
 are affected by the age, the growtli, the constitution, and race of the ani- 
 mal — by the purposes for which it is fed — and by the circumstances 
 under which it is placed while the food is hdrainistered to it. 
 
 § 1. Of the suhstance of which the parts of animals consist. 
 
 The bodies of animals consist of solid and fluid parts. 
 1°. The solid parts are chiefly made up of the muscles, the fat, and 
 the bones. 
 
 a. The muscles, in their natural state, as I have already had occasion 
 to mention (p. 444), consist in 100 parts of about — 
 
 ' Dry matter 23 
 
 Water 77 
 
 100 
 so that, to add 100 lbs. to the weight of an animal in the form of muscle, 
 only 23 lbs. of solid matter require to be incorporated with its system. 
 
 When the muscular or lean part of beef, mutton, &c., is washed 
 in a current of water for a length of time — the blood, to which the red 
 colour is owing, and all the soluble substances, gradually disappear, and 
 the muscle becomes perfectly white. In this state, with the exception 
 of some fatty and other matters which still remain intermixed with it, the 
 white mass forms what is known to chemists by the name of fibrin. 
 This name is given to it because it forms the fibres which run along the 
 muscles and constitute the greater portion of their substance. 
 
 The following table exhibits the relative proportions of muscular fibre 
 and other substances contained in the flesh of several different animals in 
 its natural state, [Schlossberger, Annalen der Pharmacie, December, 
 1842, p. 344] :— 
 
 I 
 
COMPOSITION or RECENT MUSCLE. 587 
 
 o 
 
 Muscular fibre, vessels. nerves 
 and cellular substance . . 17*5 
 
 Soluble albumen and colour- 
 ing matter of blood {Jiema^ 
 tosin) 2-2 
 
 Alcoholic. extractjContaining ^ , c i i ^ a t 'y \ 
 saUne matter \ '■'^ ^'^ ^'^ (24^ 
 
 Watery extract, containing i ^.3 ^ ^.^ ^^.g C 1 ^^ ^ ^^ q.^ 
 saline matter ) -^ ^ 
 
 Phosphate of lime, with a lit- 
 tle albumen* trace 01 trace trace 0*4 — 0'6 — 2-2 
 
 Water and loss 77-5 79-7 78-2 783 76-9 76-0 77-3 80-1 80-5 
 
 Calf. 
 
 'A 
 
 
 
 PS 
 
 c 
 
 
 0) 
 
 be 
 
 s 
 
 M 
 
 
 
 6 
 
 i 
 
 *2 
 
 a 
 
 1°. 
 
 2°. 
 
 1 
 
 150 
 
 16-2 
 
 16-8 
 
 18-0 
 
 170 
 
 16-5 
 
 12-0 
 
 111 
 
 3-2 
 
 2-6 
 
 2-4 
 
 2-3 
 
 4-5 
 
 3-0 
 
 52 
 
 4-4 
 
 11 
 
 1-4 
 
 1-7 
 
 i 
 
 (10 
 
 14 
 
 10 
 
 1-6 
 
 100 100 100 100 100 100 100 100 100 
 
 The proportions in the above table are not to be regarded as constant ; 
 they seem, however, to shew what we should otherwise expect, that the 
 muscular part of fishes contains a less proportion of fibrin than that of 
 land animals in general. 
 
 When dried beef is burned it leaves about 4^ per cent, of incombus- 
 tible ash — or 100 lbs. of the mu.scle of a living animal in its natural 
 state contain about one pound of saline or inorganic matter. 
 
 Of this inorganic matter, it is of importance to know that about two- 
 thirds consist of phosphate of lime. Thus to add 100 lbs. to the muscular 
 part of a full grown animal, there must be incorporated with its substance 
 about — 
 
 Water 77 lbs. 
 
 Fibrin, with a little fat . . 22 " 
 Phosphate of lime ... f " 
 
 Other saline matters . . i " 
 
 100 
 
 b. The fat of animals consists, like the fat of butter, of a solid and 
 fluid portion. The fluid fat is in great part squeezed out when the whole 
 is submitted to powerful pressure. 
 
 The^Zm^ portion of tlie fat, called by chemists oleine, so far as it has 
 yet beeu examined, appears to be identical in all animals. It is also the 
 same thing exactly as the fluid part of olive oil, of the oil of almonds, 
 and of the oils of many other fruits. It exists in larger quantity in the 
 fat of the pig than in that of the sheep, and hence pork fat is softer than 
 beef or mutton suet. From lard it is now expressed on a great scale in 
 the United States of America, for burning in lamps and for other uses. 
 The manufacturers of stearine candles express it from beef and mutton 
 fat, but chiefly for the purpose of obtaining the solid part in a harder 
 state, that it may make a more beautiful and less fusible candle. The 
 fluid oil of animal fats, however, is known to differ from the liquid part 
 of butter (butter-oil) described in the preceding Lecture (p. 559), and 
 from the fluid part of linseed and other similar oils which dry, and form 
 
 * Thie phosphate of lime is over and above that which exists naturally in, and is insepar* 
 able from, the muscular fibre itself afid from the albumen. 
 
5BS OF FAT, AND OF WHAT BONES CONSIST. ^^| 
 
 a kmd of varnish when exposed to the air. These latter facts are not 
 without their importance, as we shall hereafter see. 
 
 The solid part of the fat of animals is known to vary to a certain ex- 
 tent among different races. Thus the solid fat of man is the same with^ 
 that of the goose, and with that which exists in olive oil and in butter. ' 
 To this the name of margarine is given. But the solid fat of the cow, 
 the sheep, the horse, and the pig, differs from that of m.an, and is 
 known by the name of stearine. 
 
 The solid and fluid parts are mixed together in different proportions in 
 the fat, not only of different animals, but of the same animal at differ- 
 ent periods, and in different parts of its body. Hence the greater hard- 
 ness observed in the suet than in other portions of the fat of beef and mut- 
 ton, and hence also the different quality and appearance of the fat of an 
 ox according to the kind of food upon which it has been fed or fattened. 
 
 c. The hones, like the muscles, consist of a combustible and an incom- 
 bustible portion, but in the bones the inorganic or incombustible part is 
 by much the greater. To the organic matter of'bones the name of gel- 
 atine or glue is. given, and it can be partly extracted from them by boil- 
 ing. The proportion of gelatine which exists in l)ones varies with the 
 kind of animal — with the part of the body from which the bone is taken 
 — and very often with the age and state of health of the animal, and with 
 the way in which it has been accustomed to be fed. It is greater in spongy 
 bones, in the bones of young animals, and probably also in the bones of ^ 
 such as are in high condition, in perfectly dry bone It rarely exceeds 
 from 35 to 40 per cent, of the whole weight. 
 
 The incombustible portion consists for the most part of phosphate and 
 carbonate of lime. The relative proportions of these two earthy com- 
 pounds also vary with the kind of animal, with its age, its condition, its 
 food, and its state of health. To form 100 lbs. of bone the animal will 
 usually require to incorporate with its own substance aho-ut — 
 35 pounds of gelatine, 
 55 pounds of phosphate of lime, 
 
 4 pounds of carbonate of lime, 
 
 3 pounds of phosphate of magnesia, 
 
 3 pounds of soda, potash, and common salt. 
 
 100 
 
 d. Hair, horn, and wool, are distinguished from the muscular parts of 
 the animal body by the large proportion — about five per cent. — of sul- 
 phur which they contain. They consist of a substance which in other 
 respects closely resembles gluten and gelatine in its chemical composi- 
 tion (page 445). When burned, they leave from one to two per cent, of 
 ash, which in the case of a variety of human hair, which left 1*1 per cent. 
 of ash, was found by Van Laer to consist of — 
 
 Per cent. 
 
 Soluble chlorides and sulphates 0-51 
 
 Oxide of iron 0-39 
 
 Phosphate and sulphate of lime, phosphate of magnesia and silica . 020 
 
 1-10 
 The inorganic matter contained in hair is therefore, generally speak- 
 
OF HAIR, HORN, AND WOOL, AND OF BLOOD. 689 
 
 ing, the same in kind as that which exists in the muscular fibre and in 
 the bone. It contains the same phosphate of hme and magnesia — the 
 same sulphates and the same chlorides, among which latter common salt 
 is the most abundant. The absolute quantity of ash or inorganic matter 
 varies, as well as the relative proportions in which the several substances 
 are mixed together in the different solid parts of tiie body, but the sub- 
 stances themselves of which the inorganic matter is composed are nearly 
 the same, whether they be obtained from the bones, from the muscles, or 
 from the hair. 
 
 2°. Of the fluid parts of the body, the blood is the most important, 
 and by far the most abundant. The body of a full grown man, of mo- 
 derate dimensions, contains about 12 lbs. of blood, [Lehmann, Physi- 
 ologische Chemie, I., pp. 113 and 338,] that of a full grown ox, six 
 times as heavy, cannot contain less than 70 or 80 lbs. Blood consists of 
 about — 
 
 Per cent. 
 
 Water 80 
 
 Organic matter 19 , 
 
 Saline matter 1 
 
 100 
 The organic matter consists chiefly of fibrin, wliich, when the blood 
 coagulates, forms the greater part of the clot — and of albumen, which re- 
 mains dissolved in the serum or fluid part of clotted blood, but which, 
 like the white of egg, runs together into insoluble clots when the serum 
 is heated. 
 
 The saline matter remains dissolved in the serum after the albumen 
 has been separated by heating, and consists chiefly of phosphates, sul- 
 phates, and clilorides — nearly the same compounds as exist in the soluble 
 part of the asli left by the solid parts of the body. 
 
 Besides this soluble saline matter which remains in the serum, a por- 
 tion of phosphate of lime and a small quantity of phosphate of magnesia 
 exist also in the fibrin and in the albumen of the blood. Thus in the dry 
 state these substances contain respectively of the mixed phosphates — 
 
 Albumen of ox blood .... 1-8 per cent. ? /r> y ^ 
 Fibrin of human blood .... 0-7 per cent. ^ ^ ' ' 
 
 Thus the same saline and earthy compounds, which form so large a 
 portion of the bones, are distributed every where in sensible proportions 
 throughout all the more important solids and fluids of the body 
 
 § 2. Whence does the body obtain these substances ? Are they contained 
 
 in the food ? 
 
 Whence does the body derive all the substances of which its several 
 parts consist ? 
 
 The answer to this question appears at first sight to be easy. They 
 must be obtained from the food. But when the enquiry is further con- 
 sidered, a reply to it is not so readily given. 
 
 It is true, indeed, that the organic part of the food contains carbon, 
 hydrogen, oxygen, and nitrogen — the elements of which the organic parts 
 of the body are composed. The in-organic matter also which exists in 
 26* 
 
590 WHENCE THE TAT AND BONES OF ANIMALS. 
 
 the food contains the lime, the magnesia, the potash, the soda, the sul- 
 phur, the phosphorus, and the iron, which exist in the inorganic parts of 
 the animal body — so that the question seems already resolved. The 
 body obtains from the food all the elements of which it consists, and 
 if these be not present in the food, the body of the animal cannot be 
 properly built up and supported. 
 
 But to the chemist and physiologist the more important part of the 
 question still remains. In what state do these elements enter into the 
 body 1 Are the substances of which the food consists decomposed after 
 they are taken into the stomach ? Are their parts first torn asunder, and ' 
 then re-united in a different way, so as to form the chemical compounds 
 of which the muscles, bones, and blood consist? Are the vital powers 
 bound to labour, as it were, for the existence and support of the body ? 
 Do they compound or build up out of their ultimate elements the various 
 substances of which the body is composed — or do they obtain these sub- 
 stances ready prepared from the vegetable food on which animals, in 
 general, are fed ? The answer which recent chemical researches give to 
 this second question forms one of the most beautiful contributions which 
 have been made to animal physiology in our time. 
 
 1°. We have seen that the flour of wheat and of our other cultivated 
 grains consists in part of gluten, of albumen, or of casein. These sub- 
 stances all contain nitrogen, and are identical in constitution with each 
 other, and with the fibrin of which the muscles of animals chiefly con- 
 sist.* The substance of the muscles exists ready formed, therefore, in the 
 food which the animal eats. The labour of- the stomach is in conse- 
 quence restricted to that of merely selecting these substances from the 
 food and dispatching them to the several parts of the body, where they 
 are required. The plant compounds and prepares the materials of the 
 muscles — the stomach only picks out the bricks, as it were, from the other 
 building materials, and sends them forward to be placed where they 
 happen to be wanted. 
 
 2°. Again, we have seen that in all our crops, so far as they have 
 been examijied, there exists a sensible proportion of fatty or oily matter 
 more or less analogous to the several kinds of fat which exist in the bo lies 
 of animals. In regard to this portion, therefore, of the body, the vege- 
 table performs also the larger part of the labour. It builds up fatty sub- 
 stances out of their elements — carbon, hydrogen, and nitrogen. These 
 substances the stomach extracts from the food, and the body appropriates 
 them, after they have been more or less slightly changed, in order to 
 adapt them to their several purposes. There may ]Kxssibly be other 
 sources of fat, as we shall hereafter see, but the simplest, the most na- 
 tural — and probably, where a sufficient supply exists, the only one Iiad 
 recourse to by the healthy animal — is the fat which is found, ready 
 formed, in the vegetable food it eats. 
 
 3°. Further, the bones, the muscles, and the blood, contain phosphate 
 
 ' The chemical reader, who is aware of the exact state of our knowledge upon this sub- 
 ject, will perceive that I speak here of the identity of these substances only in so far as the 
 proportions of carbon, iiydrojien, oxygen, and nitrogen are concerned, li is unnecessary to 
 allude in this place to the different proportions of sulphur and phosphorus they are known 
 to contain — as the more popular nature of this work will not permit me to discuss the re- 
 fined, though singularly beautiful, physiological questions with which tliese differences are 
 coQinected. 
 
T3E FUNCTION OF RESPIRATION. 591 
 
 of lime, phosphate of magnesia, common salt, and other saline com- 
 pounds. These same compounds exist, ready formed, in the vegetable 
 food, associated generally with the gluten, the albumen, or the casein, 
 it contains. The materials of the harder parts of the body, therefore — 
 (the phosphates) as well as the inorganic saline substances which are 
 found in the blood, and in the other fluids of the body — are all formed in 
 or by the plant, or are by it extracted from the soil and incorporated with 
 the food on which the animal is to live. 
 
 Not only, therefore, do the mere elements of which the parts of the 
 bodies of animals are formed, exist in the food — but they occur in it, put 
 together and combined, nearly in the state in which they are wanted, in 
 order to form the several solids and fluids of the body. The plant, in 
 short, is the compounder of the raw materials of living bodies. The ani- 
 mal uses up these raw materials — cutting them into shape when neces- 
 sary, and fitting them to the several places into which they are intended 
 to be built. 
 
 This is a very simple, and yet a very beautiful view of one of the 
 many forms of chemical connection which exist between the processes 
 and purposes of animal and vegetable hfe. Nature seems to divide the 
 burden of building up living bodies between the vegetable and the animal 
 kingdoms — the lower appearing to exist and to labour only for the good 
 of the higher race of beings. 
 
 § 3. Of the respiration of animals, and of the purposes served hy the starch, 
 gum, and sugar, contained in vegetable food. 
 But, besides the gluten of plants and seeds, which supplies the mate- 
 rials from which the muscular parts of animals are formed, the oil which 
 is converted into the fat of animals, and the saline and earthy matters 
 of plants which supply the salts of the blood and the earth of the bones — 
 vegetable food in general contains a large proportion of starch, sugar, 
 gum, and other substances which consist of carbon and the elements of 
 water only (p. 111). What purpose is served by this part of the food? 
 Is it merely taken into the stomach and again rejected, or is it decom- 
 l)osed and made to serve some vital purpose in the economy of the 
 living animal ? From the fact that so large a part of all vegetable food 
 consists of these substances, we might infer that they were destined to 
 serve some important purpose in the animal economy. To the herbiv- 
 orous animal they are, in fact, almost necessary for the support of a 
 healthy life. 
 
 In order to understand this fact, it will be necessary briefly to advert to 
 the respiration of animals — the chemical changes produced by it, and 
 the purposes it is supposed to serve in the animal economy. 
 
 1°. Of the function of respiration. — All animals possessed of lungs al- 
 ternately inhale and exhale the atmospheric air. They breathe, that is, 
 or respire. The air they draw into their lungs, supposing it to be dry, 
 consisljs by volume (pp. 32 and 148) very nearly of — 
 
 Nitrogen 79-16 
 
 Oxygen 20-80 
 
 Carbonic acid 0-04 
 
 100 
 
592 FAT SUPPORTS RESPIRATION? IN SOME, 
 
 — the proportion of carbonic acid being very small. But as it is breathed 
 
 out again it consists of about— 
 
 Nitrogen 79-16 
 
 Oxygen 16-84 to 12 
 
 Carbonic acid 4-00 to 8 
 
 I' 
 
 100 
 — ^the proportion of oxygen being considerably less, that of carbonic acid 
 very much greater, than before. On an average the natural proportion 
 of carbonic acid in the air is found to be increased 100 times after it is 
 expelled by breathing from the lungs. 
 
 Now carbonic acid consists, as we have previously seen, of carbon and '"^ 
 oxygen. In breathing, therefore, the animal throws off" into the air a 
 quantity of carbon — in the form of carbonic acid — which varies at dif- 
 ferent times, in different species of animals, and in different individuals of 
 the same species. By a heahhy man the quantity of carbon thus 
 thrown off varies from 5 to 13 ounces, and by a cow or a horse from 3 to 
 5 pounds, in 24 hours. All this carbon must be derived from the food. 
 The animal eats, therefore, not merely to support or to add weight to its 
 body, but to supply the carbon also which is wasted by respiration. 
 
 2°. How the respiration is fed. — What part of the food supphes the 
 waste caused by respiration ? How is the respiration fed ? 
 
 In animals which live upon flesh — carnivorous animals — it is the fat 
 of their food from which the carbon given off by their lungs is derived. 
 It is only when the fat fails in quantity that the lean or muscular part 
 of the flesh they eat is decomposed for the purpose of supplying carbon 
 to their lungs. 
 
 In an animal to which no food is given for a time, the lungs are fed, 
 so to speak, from fat also. But in this case it is the living fat of the 
 animal's own body. When digestion is fully performed and hunger is 
 keenly experienced, the body begins to feed upon itself — the lungs still 
 play, respiration continues for many days after food has ceased to be ad- 
 ministered, Jiut the carbon given off is derived from the substance of the 
 body itself. The fat first disappears — escapes with the breath — and af- 
 terwards the muscular part is attacked. Hence the emaciation which 
 follows a prolonged abstinence from food. 
 
 In animals which live upon vegetable food again — herbivorous ani- 
 mals — it is the starch, gum, and sugar, of the food which supply the 
 carbon for respiration. It is only when the food does not contain a suf- 
 ficient supply of these compounds that the oil first, and then the gluten, 
 are decomposed, and made to yield their carbon to the lungs. 
 
 In man, who lives on both kinds of food, and in the domestic dog, and 
 the pig, which also eat indifferently both animal and vegetable food, the 
 carbon of respiration may be derived in part from the fat, and in part 
 from the starch and sugar which they eat — according as they are chiefly 
 supported by the one cr by the other kind of food. 
 
 It may be asked how we know that such are the parts of the food, to 
 which the duty of supplying the demands of the lungs is especially com- 
 mitted. There are several considerations which lend force to this opin- 
 ion. Of these I will draw your attention to one or two. 
 
 a. Why is the fat rather tlian the lean part of the food of carnivorous 
 
STARCH AND 5UGAR IN OTHER RACES. 593 
 
 animals devoted to the service of the lungs, and why do starving ani- 
 mals lose their fat first ? Because the chemical decomposition by which 
 carbon can be derived from the fat is simpler and more easily effected 
 than that by which it can be ob airieJ from muscular fibre. By combi- 
 nation with oxygen, fat can be converted into carbonic acid and water 
 only, of which the former will pass off by the lungs and the latter in the 
 urine. The muscular fibre, on the other hand, contains much nitrogen 
 (p. 444), and, if deprived of its carbon for the uses of respiration, miLSt 
 undergo very complicated decompositions, and form a series of com- 
 pounds, the use of which, in the animal economy, it is not easy to perceive. 
 
 Besides, in producing the carbonic acid of the 1 ui^'^ from the fat of the 
 animal food or of the living body, there is less waste of material. Fat 
 consists wholly of the three elements, carbon, hydrogen, and oxygen. 
 These all disappear entirely in the form of carbonic acid and water — both 
 of which are used up. Muscle, on the other hand, besides nitrogen, con- 
 tains a constant proportion of sulphur and phosphorus. If the muscle, 
 then, be decomposed for the purpose of supplying carbon to the lungs, 
 not only the large quantity of nitrogen, but the sulphate and phosphorus 
 also, would go to waste, and would pass off in the urine. In nature, 
 however, such waste is rarely seen to take place ; and, therefore, as a 
 general rule, the respiration will be supported by the muscular fibre only 
 when other kinds of food are deficient. 
 
 b. But in the stomachs oi^ herbivorous animals, why are the starch and 
 sugar especially appropriated to the use of the lungs ? The food of ani- 
 mals which live upon vegetable substances contains fat as well as starch 
 — why then is the starch in this case dissipated by the process of respira- 
 tion, while the fat is applied as it is supposed to another use ? The 
 answer to this question is both beautiful and satisfactory. 
 
 Starch, gum, and sugar, consist of carbon and water only, and we can 
 conceive them in their passage through tlie body to be actuafly separated 
 into these two substances — in which case the carbon has only to combine 
 with oxygen and form carbonic acid, to be ready to pass off by the lungs. 
 Here, therefore, only one chemical combination is required — the union 
 of carbon with oxygen. It is the simplest way in which we can con- 
 ceive carbon to bo supplied for the use, or for the purposes of the lungs.* 
 
 But it is otherwise with fat. Though nearly all kinds of fat consist en- 
 tirely of carbon, hydrogen, and oxygen-^yet they cannot be supposed to 
 consist only of carbon and water. They contain much more hydrogen than 
 is necessary to form water with the oxygen which is present in them. If, 
 then, the carbon of these fats be separated, this excess of hydrogen will 
 also be set free, and if the former be made to combine with oxygen to 
 form carbonic acid, the latter must also combine with hydrogen to form 
 water.. Thus two chemical changes must go on simultaneously, for 
 which more oxygen will be required, and which involve more labour in 
 the system than when the carbon alone is to be combined with oxygen. 
 It is natural, therefore, that where both starch and oil are present to- 
 gether, the former should be first converted to the uses of the lungs, the 
 latter only when the supply of starch or sugar has been exhausted. 
 
 ' The chemical reader will understand that lam here only giving a popular view of the 
 final result of the several changes through which the carbon no doubt passes before it 
 escapes in the form of carbonic acid. 
 
694 PURPOSES SERVED BY RESPIRATION. 
 
 There appears, therefore, to he a beautiful adaptation to the wants and 
 convenience of animals in the large proportion of starch, gum, and sugar, 
 which the more abundant varieties of vegetable food contains. In obtaining 
 carbon from these, the least possible labour, so to speak, is imposed upon 
 the digestive organs of the herbivorous races. The starch and sugar 
 abound because much carbon is required, while fatty matter or oil is 
 present in smaller quantity, because comparatively little of this is neces- 
 sary to the performance of the usual healthy functions of the animal 
 body. And it is another adaptation of the living body to the circum- 
 stances in which it may be placed, that when starch or sugar cannot be 
 obtained, the oil of the food is consumed for the supply of carbon to the 
 lungs — and failing this also, the gluten and albumen of the vegetable food 
 or the muscular fibre of the animal food, or even of the living animal it- 
 self. 
 
 3°. Purposes served hy respiration. — But for what purpose essential to 
 life do animals respire ? If the starch and sugar be so necessary to feed 
 the respiration — the breathing itself must be of vital importance to the 
 living animal. 
 
 Some doubts still exist upon this point. It is generally believed, 
 however, that carbon is consumed or given off from the lungs for the pur- 
 pose of sustaining the heat of the living body. When starch, or sugar, 
 or gum, are burned in the open air, they are changed into carbonic acid 
 and water, and at the same time produce much heat. It is supposed that 
 in the body the same change — the conversion of starch and sugar into 
 carbonic acid and water — taking place, heat must in like manner be pro- 
 duced. A slow combustion, in short, is su[)posed to be going on in the 
 interior of the animal — the heaf of the body being greater, in proportion 
 to the quantity of carbonic acid given off from the lungs. In favour of 
 this view many strong reasons have been advanced, but there are also 
 objections against it of considerable weight, which cannot as yet be satis- 
 factorily removed. 
 
 Were we to adopt this opinion in regard to the main purpose served by 
 respiration^asthe true one, it would afford a very distinct reason for the 
 large amount of starch existing in all our cultivated crops. Respiration, 
 according to this view, is necessary to supply heat to the animal, and 
 this respiration is most simply and easily fed by the starch contained in 
 the vegetable food. The life and labours of the plant again minister to 
 the life and labours of the animal. 
 
 § 4. Of the origin, and the purjjoses served by the fat of animals. 
 
 1°. The immediate oriffin or source of the fat of animals depends upon 
 the kind of food with which the animal is fed. Carnivorous animals 
 obtain or extract it ready formed from the flesh they eat — herbivorous 
 animals from the vegetable food on which they live. 
 
 It has only been lately shown that the corn, hay, roots, and herbage, 
 on wliich cattle are fed, contaiii a suflicient quantity of oily matter ready 
 formed to supply all the fat which accumulates in their bodies — or which, 
 by the milk cow, is yielded in the form of butter. Before the different 
 kinds of food had been analyzed, with the view of determining the quan- 
 tity of oil and fat they severally contain, it was supposed that the fat of 
 animals was derived almost solely from the starch and sugar or gum, of 
 
ORIGIN or THE FAT Or ANIMALS. 595 
 
 which so large a proportion of vegetable food consists. This opinion, 
 however, has given way before the advance of analytical research. 
 Animals fatten quickest upon Indian corn, or oil cake, or oil mixed with 
 chopped straw, or upon oily seeds and nuts — or, as in the case of poultry, 
 on a mixture of meal or suet — because these kinds of food contain a large 
 proportion of fatty matter ready formed which the animal can easily ex- 
 tract, and after a slight chemical change can convert into a portion of its 
 own substance. 
 
 The conversion of starch or sugar into fat in the animal body implies 
 a chemical change of a less simple nature — one which seems to impose 
 upon the vital principle a greater amount of labour than is implied in the 
 simple appropriation of the fat which exists ready formed in the food. If, 
 then, there be in the food as much fat as is necessary to supply all that 
 the animal appropriates to itself, and if it is observed to lay on or appro- 
 priate more when the food is richer in fatty oils, we are led to believe 
 that the natural purpose served by the oil in the vegetable food is to supply 
 the fat of the animal body. In other words, the vegetable ministers to the 
 animal and lessens its labour by preparing beforehand the materials out 
 of which the animal is to build up the fatty parts of its body. 
 
 But though this is the general source of the fat of animals, circum- 
 stances may occur in which the. only vegetable food which the animal can 
 procure does not contain a sufficient proportion of fat to supply all the 
 wants of its body — or to enable it to perform the several natural functions 
 ^it is destined to fulfil. Thus wax is a kind of fat, and it has been shown 
 %Milne Edwards) that, when fed upon pure sugar, the bee is capable of 
 forming wax from its food. When fed upon such sugar, it not only lays 
 up a store of honey, but it continues to build its cells of wax. Now the 
 starch of the food is readily changed into sugar. It may be so changed 
 in the stomach of man and of other animals. That power which the bee 
 possesses they also may in cases of emergency be able to exercise. 
 Where a sufficient supply of oil for the necessary uses of the animal is 
 not contained in the food it eats, it may form an additional portion from 
 the starch or sugar in which its food abounds. 
 
 According to the present state of our knowledge, therefore, the most 
 probable opinion in regard to the origin of the fat of animals seems to be 
 expressed in these two proposition. 
 
 a. That the fat of animals is contained ready formed, and is usually 
 derived from the vegetable or other food on which they live — and that 
 when the food abounds largely in fat, the animal lays it more quickly 
 and abundantly upon its own body. 
 
 6. That when the food does not contain a sufficient proportion of fat to 
 enable the animal comfortably to perform the various functions of its 
 body, it has the power to form an additional quantity from the starch or 
 sugar it eats — but that it will not readily fatten or lay on large additions 
 of "fat upon its body when fed upon farinaceous, saccharine, or other food 
 in which oil is not naturally contained.* 
 
 * For the sake of the chemical reader I may be pcrmitteil here to show by what kind of 
 chemical changes— 1°, the fat of animals in general may be derived from the starch or sugar 
 of their food ; and 2°, how the peculiar kinds of fat contained in the body of any given ani- 
 mal may be formed from the peculiar kinds of fat contained in its food. 
 
 1°. Haw fat may be formed from starch or sugar .—These two substances, as we have 
 already seen, may be represented by carbon and water only— 
 
CHAIfGES OF OX FAT INTO HUMAN FAT. 596 
 
 2°. The purposes served by the fat. — In all healthy animals which 
 take a sufficient quantity of exercise to maintain them in a healthy con- 
 Carbon. Water. 
 
 Slarck, consisting of 12 + 10) represented by Ci2 Hio Oio 
 
 Cane sugar, consisting of 12 + 1^ represented by C12 Hii On 
 Pc^ again, margarine for example, the solid fat of the human body, is represented (p. 
 559, TWte,) by Cj7 H.iC O5 Compare this with 4 of starch, and we have — 
 4 of starch = Cis K40 O40 
 
 1 of margarine = C37 H36 O5. 
 
 Difference = Cii'Hi O35 
 
 This difference is equal to, or may be represented by, 
 
 11 of carbonic acid -{- 4 of water + 9 of oxygen 
 11 COi + 4UO + 90 
 
 So that by the separation of carbonic acid, which may be given otf from the lungs — of 
 water, which may or may not remain in the system, — and of a portion of oxygen, which 
 may be used up in various ways in the blood, the starch or sugar of the food may be con- 
 verted into fat. 
 
 That in some such way these substances may be changed into the fat of animals was first 
 insisted upon and explained by Liebig; and it is probable, as I have said in the text, that in 
 cases of emergency I'ai is really formed in the animal body from such kinds of food. But 
 when Liebig put forth his views on this subject, it was not known that vegetable substances 
 naturally contained so large a proportion of fat as has since been found in them. The ne- 
 cessity for the constant production or formation of fat in the body itself, therefore, is not now 
 so apparent, and the soundest opinion, according to our present knowledge, seems to be 
 that, while the vegetable food usually supplies all the fat ready formed which the animal re- 
 quires, yet that a conversion of a certain part of the starch, gum, sugar, and even of the cel- 
 lular fibre of the food, into fat, may take place, when all the wants of the body are not sup- 
 plie<l by the fat which the food naturally contains." Of course this opinion apphes only to 
 animals in perfect health. In certain diseased states of the body a larger and more con- 
 stant production of fat from the food may take place, as appears to be the case in animals 
 which no diminution of food seems to prevent from laying on fat. 
 
 2^. How the peculiar kinds of fat in the body maxj bed'^ivcdfrom the peculiar kinds of fat 
 in the food. 
 
 a. We have already seen (p. 553) that the solid part of butler, of olive oil, and of the goose, 
 is identical with the solid fat of the human body. When eaten by man, therefore, these se- 
 vered kinds of fat may be at once conveyed, without change, from the stomach to the several 
 parts of the body wliere they are required. From this circumstance these kinds of fat seem 
 remarkably fitted for the food of man. 
 
 b. The solid fat of the ox and the sheep is called stearine. Upon this man lives much 
 and converts it into the solid fat (margarine) of his own body. This may take place after 
 the following manner : — 
 
 2 of margarine = C74 H72 Oio 
 
 1 of stearine = C74 Hog O7 
 
 Difference . . . ". . . = C3 H3 O3 
 
 If we double this difference, we have Ce H6 Os ; which is the formula for lactic acid. 
 Recent researches, however, have failed in detecting this acid in the blood — if it be formed 
 at all, therefore, it must exist only in a transition state, and must be speedily converted into 
 other compounds. The final result may poa.gibly be the evolution oi the 3 of carbon (Cs ) 
 by the lungs in the form of carbonic acid. 
 
 c. That the body or its parts possess the power of easily transforming these different kinds 
 of fat one into the other, we know, also, from other facts. Thus the calf Uves upon milk, 
 and from the two kinds of fat contained in the cream of the milk, it forms the solid and liquid 
 fats of its own body. The stearine of the animal in this case may be formed from the mar- 
 garine of the butter, being exactly the converse of the previous case, while the butter oil may 
 be changed into the Liquid fat of the tallow. 
 
 This latter is more difficult to explain, since the composition of elaine — the liquid fat of 
 the ox, c df, and sheep—compEured with that of butter oil, presents a considerable difference. 
 Thus— 
 
 Elaine . . " z= C47 H42 Os 
 
 Butter oil = C37 H33 06 
 
 Difference . . . . =Cio 119 
 What becomes of this difference, Cio H9, we are unable as yet precisely to explain. By 
 the intervention of a little oxygen it might readily s^ve rise to a'iittle more fat. 
 
 d. The cow and calf toj^cther, however, illustriifc very clearly the existence of this trans- 
 forming power of the animal body. We are unacquainted, as yet. with the composition of 
 the several kinds of fat which occur in vegetables— but we know that out of these the cow 
 can form the two kinds of fat— the stearine and the elaine— which exist in its own tallow, 
 and at the same time the two kinds of fat — margarine and butter-oil — which are found in its 
 milk. The calf, again, can change these two latter fats into those which its own body, as 
 
PURPOSES SERVED BY THE EAT. 597 
 
 dition, the principal purposes served by the fat are simple and the same. 
 It lubricates the joints — covers and protects the internal viscera — keeps 
 the muscles separate, and enables them to play freely among each other 
 — makes the hair and skin soft and flexible, — and, by filling up hollows, 
 contributes to the roundness and plumpness of the parts, and defends the 
 extremities of the bones from external injur3^ When exercise is taken, 
 a portion of the fat of the body appears to be more or less changed and 
 removed, and is afterwards found in the perspiration, or in the dung. It 
 is to make up for this natural waste that all animals, even when the fat 
 of their body undergoes no increase, recjuire a certain supply to be daily 
 given to them in their food. 
 
 The accumulation of fat in animals seems to be an effort of nature to 
 lay in a store of food in time of plenty, which may be made available in 
 the performance of the usual functions of the animal when a time of 
 scarcity comes. If the food contain too little oil^ to lubricate the joints 
 and to supply the natural waste of this kind of matter, then the store of 
 fat which has been accumulated in time of plenty is drawn upon, a por- 
 tion of it is worked up, so to speak, and the fat of the body diminishes in 
 quantity. We have seen also that the respiration of carnivorous animals 
 is supported at the expense of the fat which they eat — and that the lean- 
 ness which attends upon starvation is owing to the fat of the living body 
 beingconsumed in supplying thecarbon given off from the lungs. Another 
 purpose, therefore, for which animals seem to be invested with the power 
 of laying on fat, is, that a store of food for the purposes of respiration 
 may be carried about in the body itself, to meet any unusual demand 
 which the food may not be able wholly to supply. 
 
 § 5. O/" the natural waste of the parts of the body in a full grown animal. 
 
 We have seen that, if the food of the animal be unable to supply the 
 carbon given off from the lungs, and the fat which the movements of the 
 limbs require, the parts of the body themselves are laid under contribu- 
 tion in order to supply these substances. Thus, when the food is stinted, 
 the body necessarily undergoes a waste from this cause. 
 
 But this is not a constant waste.. -It is prevented by the use of a larger 
 quantity of food. The parts of the body, however, do undergo a con- 
 stant and natural waste, to make up for which is one of the main pur- 
 poses served by the food. 
 
 It has been ascertained by physiologists, that all the parts of the body 
 undergo a slow and insensible process of renewal. The hair and the nails 
 we can see to be constantly renewed. They grow, or are thrust out- 
 wards. But the muscles and even the bones are by little and little re- 
 well as that of ItB mother, requires. And, lastly, man by eating the fat of the calf can re 
 convert it into margarine and those other fatty substances which are found in the various 
 parts of his body. Substances which can thus so frequently and so readily be changed, the 
 one into the other, must be very cloeely connected, and the mode in which their mutual 
 transformations are eflfected will, no doubt, prove to be simple when these are rightly im- 
 derstood. 
 
 The chemical reader will understand that it is for the sake of simplicity only that I have 
 in this note compared together the entire fats stearine, margarine, &;c., instead of the fatty 
 acids only which they are known to contain. 
 
 The reader will consult with much advantage and satisfaction upon this subject, a work 
 upon Chemical Physiology, by Professor Mulder, of Utrechi (Procve eener Algemeene Phy- 
 siolo ffische Scheikunde, p. 260, et seq.) of which I am happy to say that a translation from 
 the Dutch is now in progress by my assistant, Mr. Fromberg, and will speedily be published 
 by the Messrs. Blackwood. 
 
598 FOOD REQUISITE FOR THE NATURAL WASTE. 
 
 moved inwardly and rejected in the excretions — the place of that which 
 IS removed being supplied by new portions of matter derived from the 
 food. 
 
 This removal, though unfelt by us, goes on so rapidly that in a space 
 of time, which varies from one to five years, the whole body of the ani- 
 mal is renewed. There does not remain, it is said, in any of our bodies, 
 a single particle of the same matter which formed their substance three 
 or five years ago. It is just as if we were to take a single old brick every 
 day out of the corner of a house, and put in a new one — the fomi and 
 dimensions of the house would remain unaltered, and yet in the course 
 of a few years its walls would be entirely renewed. 
 
 In full grown animals, some parts of the body are renewed more ra- 
 pidly than others — the muscles, for example, more frequently and rapidly 
 than the bones and the brain. In young animals, again, the whole body 
 is oilener renewed than in such as are advanced in years, but all the 
 parts of all animals are believed to be more or less quickly removed and 
 replaced. 
 
 The new materials "which arc conveyed to the different parts of the 
 body are derived directly from tlie food. The fibrin of the muscles is 
 replaced from the gluten which the food contains — the fat from its oil — 
 and the earthy matter of the bones and the salts of the blood, from the 
 phosphates and saline substances wliich are naturally present in it. On 
 the other hand, those parts which are extracted from the muscles and 
 bones, and carried off in the excretions, are decomposed during their re- 
 moval. New chemical compounds are produced from tliem, which are 
 found in the urine and dung of the animal, and which give to these ex- 
 cretions their richness and value in the manuring of the soil. 
 
 § 6. Of the kind and quantity of food necessary to maJce up for the natural 
 waste in the body of a full grown animal. 
 
 The substances which constantly disappear from the body in conse- 
 quence of the natural waste above described, are of three kinds — ihe fibrin 
 and other analogous organic compounds, which form the muscles and the 
 cartilage of the bones — the earthy ■jjhosphates (of lime and magnesia), 
 which form so large a proportion of the bones, and exist in small quan- 
 tity in the muscles also — and the soluble saline substances, which abound 
 in the blood and in the other fluids of the living animal. In the solid and 
 liquid excretions, a larger quantity of each of these three classes of com- 
 pounds is carried out of the body. How much of each must be contained 
 in the daily food of a full-grown animal in order that it may be kept in 
 its actual condition ? 
 
 1°. Qriantity of fibrin or other analogous compounds [albumen or 
 casein) which the daily food must contain. — The most accurate experi- 
 ments that have yet been made upon this subject (Lecanu) appear to 
 show that a full grown man rejects in his urine alone about half an ounce 
 of nitrogen (230 grs.) every 24 hours. This quantity of nitrogen is con- 
 tained in about tliree ounces of dr}^ muscular fibre, which must, therefore, 
 every day be decomposed or removed in order to yield it. 
 
 But if the body is kept in condition, this quantity of fibrin must be 
 daily restored again by the food. Now, to supply three ounces of dry 
 fibrin, there must be eaten about — 
 
IN THE BODY OF A FULL-GROWN ANIMAL. 599 
 
 30 ounces of wheaten flour ; or 
 45 " of wheaten bread ; or 
 14 " of fresh beef or mutton ; or 
 12 *' of pease or bean meal; or, 
 4 " of cheese ;* 
 Or, if we live wholly upon potatoes or milk, we must eat no less than 
 six or seven pounds of the former daily, or drink three or four imperial 
 pints of the latter — if we would restore to the body as much of the sub- 
 stance of its muscles and cartilage as is daily removed from it by the 
 urine. 
 
 But t]i& urine is not the only channel through which nitrogen is given 
 OiT from tlie animal body. A considerable, though, of course, a variable 
 pro])ortion is found in the solid excretions or dung, which has also been 
 (icrived from the substance of the body itself. A small quantity of ni- 
 trogen is believed to be given olf from the lungs also in breathing, and 
 from the skin in the perspiration, v\^hich nitrogen must have been either 
 directly or indirectly derived from the food. And, lastly, of the fibrin or 
 other food containing nitrogen which may be introduced into the stomach, 
 a portion must pass the mouths of the al)Sorbcnt vessels as it descends 
 througli the intestines and thus escape with the dung, without having 
 perf^jrmed its part in the ordinary nourishment of the body. 
 
 It is impossible to maKe any correct estimate of the amount of nitrogen 
 which escapes from the animal in the several ways just noticed — in the 
 solid excretions from the lungs and from the skin— or of the quantity of 
 food which is necessary to supply its place. If we .suppose the loss 
 through all these sources taken together to be equal to one-half or two- 
 thirds of that which is found in the urine, then the whole (juantity of dry 
 fibrin which the food ought to contain would amount to four and a half or 
 five ounces in the day. To supply this, we must eat of bread, beef, 
 cheese, potatoes, or milk, one half more than the quantities already 
 specified. 
 
 No experiments have hitherto oeen published from which we can de- 
 termine the average quantity of nitrogen rejected in the excretions of the 
 horse, the cow, or the sheep, and, consequently, the amount of waste 
 which takes place in ordinary circumstances in the muscles and cartilage 
 of these animals. If we suppose that in the horse or cow it is in direct 
 proportion to their weights, compared with that of a full grown man — or 
 five times greater than in a man — then the loss of dry fibrin would 
 amount to 20 or 2b. ounces in the 24 hours. To supply this, the animal 
 must eat the following quantities of one or other of the kinds of food here 
 mentioned : — 
 
 120 lbs. of turnips. 17 lbs. of clover hay. 
 
 115 " of wheat straw. 12 " of pea straw. 
 
 75 " of carrots. 12 " of barley. 
 
 67 " of potatoes. 10 " of oats. 
 
 20 " of meadow hay. 5 " of beans, f 
 
 Or instead of the whole quantity of any one of these, a half or quarter or 
 any other proportion of each may be taken, and the animal will pro- 
 
 • Supposing the wheaten flour to contain 10 per cent, of gluten, and the cheese one half 
 its weight of dry curd (see also pp. 506 and 531.) 
 T These numbers are calculated from the table given in p. 531. 
 
600 A mix:ed food necessary to animals. 
 
 bably be found to thrive better on the mixture than if fed upon any one 
 of tliese kinds of food alone. 
 
 2°. Quantity of fixed saline matter and of earthy phosphates which 
 the food ought to contain. — A full grown animal rejects in its dung, its 
 urine, and its perspiration, as much saline and earthy matter as its 
 food contains. If its body is merely maintained in its existing condition, 
 only that which is removed from it by the daily waste is restored to it by 
 the daily food. Thus whatever quantity of saline and earthy matter is 
 present in the food, an equal quantity is found in the excretions of the 
 living animal. 
 
 But how much of that which is found in the excretions has actually 
 formed part of the living body, and been removed from it in consequence 
 of the natural waste ? This we have no means as yet of determining. 
 It must be considerable, but it varies with many circumstances, and the 
 experiments which have hitherto been made and published do not enable 
 us to say how much the average waste really is, and how much of the 
 several more common kinds of food ought to be consumed by a full 
 grown animal, in order to supply it with the necessary daily proportion 
 of saline and earthy substances. 
 
 The benefits so often derived from the use of salt in the feeding of 
 stock show how a judicious admixture of saline matter with the food 
 may render its other constituents more available than they would other- 
 wise be, to the support and mcrease of the animal body. 
 
 § 7. The health of the animal can he sustained only by a mixed food. 
 
 From what I have already stated, you see that the vegetable food eaten 
 by a full grown animal for the purpose of keeping up its condition should 
 contain — 
 
 1°. Starch or sugar, to supply the carbon given off in respiration. 
 
 2°. Fat or fatty oil, to supply the fatty matter which exists more or 
 less abundantly in the bodies of all animals. 
 
 3°. Gluten or fibrin, to make up for the natural waste of the muscles 
 and cartilage^ 
 
 4°. jEar thy phosphates, to supply what is removed from the bones of 
 tlie full grown .animal by the daily waste ; and — 
 
 5°. Saline substances- — sulphates and chlorides — to replace what is 
 daily rejected in the excretions. 
 
 Hence the food upon which any animal can be fed with the hope of 
 maintaining it in a healthy state must be a mixed food. Starch, or sugar 
 alone, or pure fibrin or gelatine alone, wUl not sustain the animal body, 
 because these substances do not contain what is necessary to build up all 
 its parts, or to supply what is daily given off during respiration and in 
 the excretions. The skilful feeder, therefore, will not attempt to main- 
 tain his stock on any kind of food which does not contain a sufficient 
 supply of every one of the kinds of matter which the body requires. 
 
 Two other points he will also attend to. First, he will occasionally 
 change the kind of food, or will vary the proportions in which he gives 
 the different kinds of fodder to his feeding stock. This practice is founded 
 on the fact that, although every crop he raises contains a certain propor- 
 tion of all the substances which the animal requires, yet some contain 
 one of tliese in larger quantity than others do, and by an occasional 
 
ADDITIONAL FOOD REQUIRED TOR FATTENING. 601 
 
 change or variation he may hope more fully to supply to the animal the 
 necessary quantity of each. 
 
 Second, he will adapt the kind and quantity of food to the age of the 
 animal, and to the other purposes for which it is fed. This rule depends 
 partly upon the same fact, that different vegetables contain the several 
 kinds of necessary food in different proportions, but in a great degree also 
 upon the further fact, that the animal requires these substances in differ- 
 ent proportions, according to its age and to the special purpose for which 
 it is fed. Let me direct your attention to this latter fact a littler more 
 at length. 
 
 § 8. O/* the kind and quantity of additional food required by the 
 fattening animal. 
 
 In the animal which is increasing in size or in weight, the food has a 
 double function to perform. It must sustain and it must increase the 
 body. To increase the body, an additional quantity of food must be con- 
 sumed, but the kind or nature of this additional food will depend upon 
 the kind of increase which the animal is making or is intended to make. 
 
 One of the important objects of the stock farmer is to make his full 
 grown animals lay on fat, so that they may as quickly as possible, and 
 at the least cost, be made ready for the butcher. To effect tliis object, 
 he adjusts the kind and quantity of the food he gives, to the practical ob- 
 ject he wishes to attain. 
 
 We have already seen reason to believe, that the natural and imme- 
 diate source of the fat of animals is in the oily matter which the food 
 contciins. If we wish only, or chiefly, to lay on fat, therefore, we 
 ought to give some kind of food which contains a larger proportion of "* 
 fatty matter than that upon which the animal has. been accustomed to 
 live. This is what the practical man has actually learned to do. To 
 his sheep and oxen he gives oil-cake or linseed oil mixed with chopped 
 straw, to his dogs cracklings,* to his geese and turkeys Indian corn, 
 which contains much oil, and to his poultry beef or mutton suet. 
 
 Many experiments are yet wanting to determine with accuracy the 
 proportion of fat contained in all the different kinds of food usually con- 
 sumed by animals. Nearly all we yet know upon this subject is ex- 
 hibited in the tabular view of their composition to which I have already 
 directed your attention (p. 531.) 
 
 One thing, however, of considerable practical value has been recently 
 ascertained — that the oily matter of seeds exists chiefly near their outer 
 surface, — in or immediately under the skin or husk. This fact is shown 
 in the case of wheat, by the following results of the examination of two 
 varieties of this grain, one grown near Durham, the other in France. 
 The result as to the French grain is given by Dumas : — 
 
 PER CKNTAaS OF FATTY OIL. 
 
 English. French, 
 
 Fine flour ... 1-5 1*4 
 
 Pollard .... 2-4 4-8 
 
 Boxings .... 3'6 — 
 
 Bran 3-3 5-2 
 
 " Cracklings are the skinny parts of the suet from which the tallow has been for the most 
 part squeezed out by the tallow chandlers. Might cattle not be fattened upon cracklings 
 crushed auid mixed with their other food? Might not some cAeap varieties of oil also be 
 mixed wi^ (heir food for the purpose of fattening. 
 
602 PATTY MATTER IN THE HTJSKS OF SEEDS. 
 
 This fact of the existence of more fat in the husk than in the inner 
 part of the grain, explains what often seems inexplicable to the practical 
 man — why bran, namely, which appears to contain little or no nourish- 
 ing substance, should yet fatten pigs and other full grown animals, when 
 given to them in sufficient quantity along with their other food. It also 
 explains why rice dust should be found to fatten stock,* though the 
 cleaned and prepared rice contains but little oil, and is believed, there- 
 fore, to be unfitted for laying on fat upon animals with any degree of 
 rapidity. No doubt the dust from pearl-barley and from oats, as well as 
 the husk of these grains, might be economically employed by the stock 
 feeder where they can readily be obtained. 
 
 § 9. Kind and quantity of additional food required hy a groioing 
 
 animal. 
 
 The young and growing animal requires also that its food should be 
 adjusted to its peculiar wants. In infancy the muscles and bones in- 
 crease rapidly in size when the food is of a proper kind. This food, 
 therefore, should contain a large supply of the phosphates, from which 
 bone is formed, and of gluten or fibrin, by which the muscles are en- 
 larged. Some kinds of fodder contain a larger proportion of these phos- 
 phates. Such are corn seeds in general, and the red clover among grass- 
 es. Some again contain more of the materials of muscles. Such are 
 beans and peas among our usually cultivated seeds, and tares and other 
 leguminous plants among our green crops. 
 
 Hence the skilful feeder or rearer of stock can often select with judg- 
 ment that kind of food which will specially supply that which the ani- 
 mal, on account of its age or rapid growth, specially requires — or which, 
 with a view to some special object, he wishes his animal specially to lay 
 on. Does he admire the fine bone of the Ayrshire breed? — he will try 
 to stint it while young of that kind of fooi in which the phosphates 
 abound. Does he wish to strengthen his stock, and to enlarge their 
 bones ? — he will supply the phosphates liberally while the animal is 
 rapidly growing. 
 
 An intere^ng application of these principles is seen in the mode of 
 feeding calves adopted in different districts. Where they are to be reared 
 for fattening stocli, to be sold to the butcher at two or three years old, 
 they are well fed with good and abundant food from the first, that they 
 may grow rapidly, attain a great size, and carry much flesh. If starved 
 and stunted while young, they often fatten rapidly when put at last upon 
 a generous diet, but they never attain to their full natural size and weight. 
 
 When they are reared for breeding stock or for milkers, similar care is 
 taken of them in the best dairy countries from the first, though in some 
 the allowance of milk is stinted, and substitutes for milk are early given 
 to the young animals. 
 
 But it is in rearing calves for the butcher that the greatest skill in 
 feeding is displayed, where long practice has made the farmers expert in 
 this branch of husbandry. To the man who has a calf and a milk cow, 
 the principal question is, how can I, in the locality in which I am placed, 
 make the most money of my calf and my milk ? Had I better give 
 my calf a little of the milk, and sell the remainder in the form of new 
 
 * Rice dust is very good food for fattening pigs, makes excellent pork, and is very proflt> 
 able when given along with whey. 
 
TEEDING OF YOUNG CALVES. 603 
 
 milk^-or had I better make butter and give the skimmed milk to my 
 calves — or will the veal, if I give my calf all the milk, pay me a bet- 
 ter price in the end ? The result of many trials has shown, that in some 
 districts tlie high price obtained for well fed veal gives a greater profit 
 than can be derived from the milk in any other way. 
 
 While the calf is very young — during the first two or three weeks — 
 Its bones and muscles chiefly grow. It requires the materials of these, 
 therefore, more than fat, and hence half the milk it gets, at first, may be 
 skimmed, and a little bean meal may be mixed with it to add more of 
 the casein or curd out of which the muscles are to be formed. The cos- 
 tive eflfect of the bean meal must be guarded against by occasional me- 
 dicine, if required. 
 
 In the next stage, more fat is necessary, and in the third week at 
 latest, full milk, with all its cream, should be given, and more milk than 
 the mother supplies if the calf requires it. Or, instead of the cream, a 
 less costly kind of fat may be used. Oil-cake, finely crushed, or lin- 
 seed meal, may supply at a cheap rate tlie fat which, in the foiTn of 
 cream, sells for much money. And, instead of the additional milk, bean 
 meal in larger quantity may be tried, and if cautiously and skilfully used, 
 the best effects on the size of the calf and the firmness of the veal may 
 be anticipated. 
 
 In the third or fattening stage, the custom is, with the same quantity 
 of milk, to give double its natural quantity of cream — that is, to supply 
 in this way the fat which the animal is wished chiefly to lay on. This 
 cream may either be mixed directly with the mother's milk, or, what is 
 better, the afterings of several cows may be given to the calf along 
 with its food. For the expensive cream there might no doubt be sub- 
 stituted many cheaper kinds of fat which the young animal might be 
 expected to appropriate as readily as it does the fat of the milk. Lin- 
 seed meal is given with economy. Might not vegetable oils and even 
 animal fats be made up into emulsions which the calf would readily 
 swallow, and which would increase his weight at an equally low cost ? 
 A fat pease-soup has been found to keep a cow long in milk ; might it 
 not be made profitable also to a fattening calf? 
 
 The selection of articles of food wliich will specially increase the size 
 of the bones in the growing animal, by supplying a large quantity 
 of the phosphates, is at present limited in a considerable degree. The 
 grain of wheat, barley, and oats is the source from which these phos- 
 phates are most certainly and most abundantly suj)plied to the animals 
 that feed upon them. But in many cases corn is too expensive a food, 
 and those kinds of corn which contain the largest proportion of the phos- 
 phates supply only a comparatively small quantity in a given time to the 
 growing animal. Why should not bone-dust or bone-meal be introduced 
 as an article of general food for growing animals '( There is no reason 
 to believe that animals would dislike it — none that they would be unable 
 to digest it. With this kind of food at our command, we might hope to 
 minister directly to the weak limbs of our growing stock, and at pleasure 
 to provide the spare-boned animal with the materials out of which a 
 limb of great strength might be built up. 
 
 Chemical analysis comes further to our aid in pointing out the kind 
 of food we ought to give for the purpose of increasing this or that part 
 
004 FOOD REQUIRED DURING PREGNANCY. 
 
 of tne animal body. Thus in regard to the same growth of bone, it ap- 
 pears that, while linseed and other oil cakes are mainly used with the 
 view of adding to the fat, some varieties are more fitted at the same time 
 to minister to the growth of bone than others are. Thus, four varieties 
 of oil-cake examined in my laboratory, contained respectively of earthy 
 phosphates and of other inorganic matter in 100 lbs. the following quan- 
 tities : — ^j 
 
 PER CENTAGE OF "S 
 
 Earthy phosphates. Other inorganic matter. 
 
 British liriseed cake . . 2-86 2-86 
 
 Dutch do. . . 2-70 2-54 
 
 Poppy cake .... 5-22 1-24 
 
 Dodder cake . . . . 6-67 3-37 
 
 The numbers in the first column, opposite to poppy and dodder cake, 
 show that these varieties of oil-cake contained a much larger proportion 
 of the phosphates than the others did, and consequently that an equal 
 weight of them would yield to growing stock more of those substances 
 which are specially required to build up their increasing bones. 
 
 § 10. Kind and quantity of additional food required by a 
 pregnant animal. 
 
 The food of the pregnant animal must sustain the full-grown mother, 
 and must add at the same time to the substance of her unborn young. 
 The quantity of food which is necessary to sustain the mother — if herself 
 full-grown, which is often far from being the case — varies with many 
 circumstances. • 
 
 It is said that in the stall an ox or a cow will eat one-fifth of its weight 
 of turnips in a day, or one-fiftieth of dry food, such as hay and straw. 
 With this allowance of food the animal would probably increase in 
 weight in some degree, — but according to Riedesel one-sixtieth of its 
 weight of dry ha}'' is necessary merel}'' to sustain it. From what we 
 have already seen of the composition of the difTerent grasses, it is obvi- 
 ous that the^quantity required will be much affected by the kind of hay 
 with which the animal is fed. 
 
 To nourish the young calf in the womb of its mother, an additional 
 quantity of food must be given, and this quantity must be increased as 
 the state of pregnancy advances. And though the kind of additional 
 food which is given must readily supply the materials of the growing 
 bones and muscles of the foetus, yet it must contain also a larger cj^uan- 
 tity of starch or sugar also than the mother in her ordinary slate would 
 require. This is owing to the circumstance that the mother must now 
 breathe for two animals, for herself and her young. The quantity of 
 blood is increased, more oxygen is taken in by the lungs, and more carbon 
 is given off in the form of carbonic acid. To supply this carbon, more 
 of farinaceous or saccharine food must be eaten from the time when 
 pregnancy takes place, and it must increase as the young animal en- 
 larges in size. 
 
 Except in the way of feeding the mother, in all respects well, I am 
 not aware that any experiments have been made with the view of spe- 
 cially affecting the condition of the futiure calf by the kind of food given 
 to the mother. A certain proportion of bone aad muscle no doubt muat 
 
FOOD REQUIRED BY A COW IN MILK. 605 
 
 be supplied to the young animal by the food given to the mother, or the 
 bones and muscles of the mother herself will be laid under contribution to 
 supply it — but it does not appear impossible to affect the size of the bona 
 by the quantity of phosphates which are given in the food, or the growth 
 and development of the muscles by that of the gluten, fibrin, or casein 
 with which the mother is fed. Might not an addition of bone-meal to the 
 food of the pregnant cow give a calf of larger bone ? Would not bean- 
 meal or skim-milk add to the size of its muscles ? 
 
 § 11. Kind and quantity of additional food required by a 
 milking animal. 
 
 After the young animal is born, the mother has still to feed it with her 
 milk. And as the calf grows rapidly, the food it requires increases daily 
 with its bulk, and the demands upon the mother therefore every day be- 
 come greater. At this period, therefore, the cow must obtain larger sup- 
 plies of food to sustain herself and to produce a sufficient quantity of 
 milk for her calf than at any other period. If these adequate supplies 
 are not given, a portion is daily taken from her own substance — her body 
 becomes leaner, and her limbs more feeble, while her young also is 
 stinted and puny in its growth. 
 
 By-and-bye, however, the calf begins to pick up food for itself. It 
 begins to live partly upon vegetables. The mother is in consequence 
 relieved of a part of her burden — her udders are less drawn upon — the 
 quantity of milk secreted becomes less — she begins again to lay muscle 
 and fat upon herself — her udders at length become dry, and she slowly 
 recovers her original plump condition. She has, indeed, at this period a 
 tendency to fatten if the same supply of food is continued to her, and 
 in many districts it is customary to feed her off' at this time for the 
 butcher. 
 
 What I have already said of the artifices by which the food given to 
 the cow may possibly be made to affect the bodily character of the future 
 calf, applies equally to the means of more or less effectually promoting 
 the growth of the young animul while it is fed solely upon milk. The 
 kind of food given to the mother may make the milk richer in curd, 
 which will promote the growth of muscle — or richer in phosphates, by 
 which the enlargement of the bones of the calf will be assisted. Scarcely 
 any two samples of milk, indeed, are found, upon analysis, to contain 
 the same proportion of phosphates and of other saline substances, and 
 there is little reason to doubt that if an unusual quantity of these be given 
 in the food of the mother, an unusual quantity will be found also in the 
 milk she produces. 
 
 For the production of milk the mother requires an adequate additional 
 supply of all the substances which we have seen to be necessary to the 
 support of the unborn foetus — of the starch as well as of the gluten and 
 saline substances of the food. But it is interesting to mark the very dif- 
 ferent purposes to which the additional supply of starch in her food is 
 now applied. 
 
 The pregnant mother requires this starch to supply the carbon given 
 off" more abundantly during her increased respiration. She breathes, as 
 I have already said, for her young and for herself, and therefore gives 
 off" more carbon from her lungs. 
 26 
 
606 USES or milk in the economy of nature. 
 
 But when the young animal is born it breathes for itself. It must, 
 therefore, be supplied with that kind of food which seems specially in- 
 tended to meet the wants of respiration. 
 
 The additional starch eaten by the mother, therefore, instead of being 
 breathed away in her own lungs, is conveyed in the form of sugar into 
 the food of the young animal. It is changed into the sugar of the milk, 
 and the natural function of this sugar is to supply the carbon which the 
 young animal gives off when it begins to breathe for itself. 
 
 It is not difficult to understand the kind of process by which the 
 Btarch of the mother's food is converted into the sugar of her milk. If to 
 
 2 of starch = 24C + 20H + 20O, 
 we add 4 of water = 4H + 40, 
 
 we have 24C -{- 24H -{- 240, which is the formula for 
 
 milk sugar. In passing through the digestive organs of the cow, there- 
 fore, the elements of the 2 of starch require only to be combined with 
 those of 4 of water to be converted into the sugar of milk. 
 
 But though it is not difficult to understand in what way this change 
 may be effected, yet it is exceedingly interesting to find that such a 
 chemical change as this should he made to commence at a certain special 
 epoch with a vieiv to a certain special end. 
 
 Milk is a perfect food for a growing animal, containing the curd which 
 is to form the muscles, the butter which is to supply the fat, the phos- 
 phates which are to build up the bones, and the sugar which is to feed 
 the respiration. Nothing is wanting in it. The mother selects all the 
 ingredients of this perfect food from among the useless substances which 
 are mingled in her own stomach with the food she eats — she changes 
 these ingredients chemically in such a degree as to present them to the 
 young animal in a state in which it can most easily and with least labour 
 employ them for sustaining its body — and all this she begins to do at a 
 given and appointed moment of time. How beautiful, how wonderful, 
 how kindly provident is aU this ! 
 
 But apart from its natural use in the economy of nature, milk may be 
 regarded as an article of manufacture — an important article of agricul- 
 tural husbandry. As a mere producer of milk for otlier purposes than 
 the feeding of calves, the cow will be differently fed according to the pur- 
 pose for which her milk is intended to be employed, or the form in which 
 it is to be carried to market. 
 
 a. The town dairyman., who sells his new milk to daily customers, 
 requires quantity rather than quality. He gives his cattle, therefore, 
 succulent food in which water abounds — green grass — forced rapidly for- 
 ward by irrigation or otherwise — green clover, young rye, brewers' 
 grains, or hay tea.* In this way, without the actual addition of water, 
 he can make his milk thin, and "increase its bulk. 
 
 h. Those, again, who desire much rich cream, or who grow milk for 
 
 A mixed hay tea and pease soup, which ig excellent for making cows give milk, is pre. 
 pared by putting hay into a pot in alternate layers, sprinkling between each a handful of 
 pease-meal, adding water and bringing to a boil. 
 
TO PRODUCE MILK FOR CHEESE OR BUTTER. 607 
 
 t 
 
 the manufacture of butter, pay less attention to the bulk of the milk 
 itself than to that of the cream they can collect from its surface. The 
 proportion of butter is increased by the use of food which contains much 
 fatty matter — of any of those kinds of food, indeed, by which an ox can 
 be made rapidly to lay on fat. Oil-cake has by some been objected to 
 as likely to give a taste to the milk, but it may be safely used ia small 
 quantity, and gives an abundant and good flavoured cream. 
 
 c. In cheese countries, again, it is the curd that is chiefly in request. 
 No doubt the value of a cheese depends much upon the proportion of 
 butter it contains diffused throughout its substance, but the weight of 
 cheese produced upon a farm depends mainly upon the quantity of curd 
 which the milk of the dairy yields. Where skim-milk cheese is made, 
 the weight of produce obtained depends almost solely upon the richness 
 of the milk in curdy matter. Clovers, vetches, and pea straw abound in 
 casein or vegetable curd, and thus give a rich and productive milk to the 
 cheese maker, while bean-meal and pease-meal, in so far as they can be 
 given to the cow with safety, may with advantage be employed to pro- 
 duce the same etFect. As every thing which tends to lay on fat on the 
 animal is likely also to increase the proportion of butter in its milk, so 
 every thing which promotes the growth of muscle will also add to the 
 richness of the milk in curd or cheese. 
 
 § 12. Influence of size, condition, warmth, exercise, and light, on the 
 quantity of food necessary to make up for the natural waste. 
 
 But the quantity of food of any kind which an animal will require is 
 affected by many circumstances. Thus — 
 
 1°. The size and condition of the animal will regulate very much the 
 quantity of food which is necessary to sustain it. The larger the mus- 
 cles and bones the greater will be the daily waste, and the greater the 
 quantity, therefore, of the food necessary to replace it. If an animal re- 
 quire a 50th or a 60th of its weight of dry food daily, of course his size 
 and weight will regulate almost entirely the quantity of food he ought to 
 eat. 
 
 A knowledge of this circumstance is occasionally of economical value 
 to the stock feeder or dairy farmer, and will modify very much the line 
 of conduct he may be inclined to adopt as the most profitable. 
 
 A large animal requires more food to keep it in its actual condition — 
 to make up, that is, for the natural waste. If you wish to convert much 
 produce into much rich dung, therefore, keep large animals. They will 
 convert a large quantity of vegetable matter into manure without adding 
 any thing to their own substance. If one-fiftieth of its weight of dry 
 food be necessary to sustain it, then an animal of 100 stones weight will 
 convert two stones of hay daily into dung. Whatever it eats beyond the 
 two stones, will go to the increase of its weight. 
 
 But a small animal, of 50 stones, requires only one stone a day to sus- 
 tain its body, or converts one stone wholly into dung. Whatever it eats 
 beyond this quantity, therefore, will go to the production of increased 
 beef and bone. Hence, if I have a given quantity of vegetable produce, 
 [ ought to be able to manufacture more beef from it by the use of small 
 cattle than of large, provided my large and small stock are equally pure 
 in breed, are equally quiet, and are as kindly feeders. 
 
60^ ' INFLUENCE OF EXERCISE AND WARMTH. 
 
 The same reasoning applies to dairy cows of different breeds. If t 
 give two stones of hay to a smad Shetland cow, she may not convert 
 more than one of them into dung, the other she may consume for the 
 production of milk. But if I give the same quantity to a cow of double 
 the size, nearly the whole two stones may be converted into dung — may 
 be employed in sustaining the animal — and if she yield any milk at all, 
 it will be poor and thin. 
 
 This reasoning accounts for the fact which has been long observed, 
 that small breeds of cattle give the richest milk, and that such as the 
 small Orkney breed yield the largest produce of butter and cheese from 
 the same quantity of food. They waste less of their food in sustaining 
 their own bodies. Lean, spare cows also require less to sustain them ; 
 and hence the skin-and-bone appearance of thebest milkers among ihe 
 Ayrshire and Alderney breeds. 
 
 2°. The quantity of exercise which an animal takes, or of fatigue it 
 is made to undergo, requires a proportionate adjustment in the quantity 
 of food. The more it is exercised the more frequently it breathes, the 
 more carbon it throws off from its lungs, the more starch or sugar con- 
 sequently its food must contain. If more is not given to it, the fat or 
 other parts of the body will be drawn upon, and the animal will become 
 leaner. 
 
 Again, the natural waste of the muscles and bones is said to be caused 
 by, or at least to be in proportion to, the degree of motion to which the 
 several parts of the body are subjected. Take more exercise, therefore, 
 move one or more limbs oftener than usual, and a larger part of the sub- 
 stance of these limbs will be decomposed, removed, and rejected in the 
 excretions. Hence the reason why hard work reciuires good food, and 
 why the strength of all animals is diminished, if they be subjected to 
 great fatigue and are not in an equal degree supplied with nourishing 
 food, by which the wasting parts of the body may be again built up. 
 
 3°. The degree of warmth in which the animal is kept, or the tem- 
 perature of the atmosphere in which it lives, affects also the quantity of 
 food which-the animal requires to eat. The beat of the animal is inse- 
 parably connected with its respiration. The more frequently it breathes, 
 the warmer it becomes, and the more carbon it throws off from its lungs. 
 It is believed, indeed, by many, that the main purpose of respiration is to 
 keep up the heat of the body, and that this heat is produced very much 
 in the same way as in a common fire, by a slow combustion of that car- 
 bon which escapes in the form of carbonic acid from the lungs. Place a 
 man in a cold situation, and he will either starve or he will adopt some 
 means of warming himsell". He will probably take exercise, and by tiiis 
 means cauSe himself to breathe quicker. But to do this for a length of 
 time, he must be supplied with more food. For not only does he give 
 off juore carbon from his lungs, but the exercise he takes causes a greater 
 natural waste also of the substance of his body. 
 
 So it is with all animals. The greater the difference between the tem- 
 perature of the body and that of the atmosphere in which they live, the 
 more food they require to " feed the lamp of life" — to keep them warm, 
 that is, and to supply the natural waste. 'Hence the importance of plan- 
 tations as a shelter from cold winds to grazing stock — of open sheds to 
 protect fattening stock from the nightly dews and colds — and even of 
 
EFFECT OF ABSEXCE OF LIGHT. 609 
 
 closer covering to quiet and gentle breeds of cattle or slieep, which feed 
 without restlessness and quickly fatten. 
 
 A proper attention to the warmth of his cattle or sheep, therefore, is of 
 great practical conscvquence to the feeder of stock. By keeping them, 
 warm he diminishes the quantity of food which is necessary to sustain 
 them, and leaves a larger proportion for the production of beef or 
 mutton. 
 
 Various experiments have been lately published, which confirm the 
 opinions above deduced from theoretical considerations. Of these I shall 
 only mention one by Mr. Childers, in which 20 sheep were folded in 
 the open field, and 20 of nearly equal weight were placed under a shed 
 in a yard. Both lots were fed for three months — January, February, 
 and March — upon turnips, as many as they chose to eat, half a pound 
 of linseed cake, and half a pint of barley eacli sheep per day, with a 
 little hay and salt. The sheep in the field consumed the same quantity 
 of food, all the barley and oil-cake, and about 19 lbs. of turnips per day, 
 from first to last, and increased on the whole 36 stones 8 lbs. Those 
 under the shed consumed at first as much food as the others, but after 
 the third week they eat 2 lbs. of turnips each less in the day, and in the 
 ninth week, again 2 lbs. less, or only 15 lbs. a day. Of the linseed-cake 
 they also eat about one-third less than the other lot, and yet they in- 
 creased in weight 56 stones 6 lbs., or 20 stones more than the others. 
 
 Thus the cold and exercise in the field caused the one lot to convert 
 more of their food into dung, the other more of it into mutton. 
 
 But why did the sheltered sheep also consume less food ? Why did 
 they not eat the rest of the food offered them, and convert it also into 
 mutton? Because the stomach of an animal will not do more than a 
 certain limited amount of work in the way of digesting, after the wants 
 of the body are fully supplied. When circumstances cause the sustain- 
 ing quantity of food to increase, the digestive powers are stimulated into 
 unusual activity, and though plenty of food he placed before the animal 
 it may be unable to consume and digest more than is barely sufficient to 
 keep it in condition. If the sustaining portion be lessened, by placing 
 the animal in new circumstances, more food may be digested than is ab- 
 solutely necessary to supply the daily waste — that is to say, the animal 
 may increase in weight. But the unusual stimulus being removed, it 
 may not now be inclined, perhaps not be able, to digest so large a quan- 
 tity as it did before when that large quantity was necessary to sustain its 
 body — that is to say, that while it increases in weight it will also con- 
 sume less food. 
 
 4°. The absence of light has also a material influence upon the effects 
 of food in increasing the size of animals. Whatever excites attention in 
 an animal, awakens, disturbs, or makes it restless, appears to increase 
 the natural waste, and to diminish the effect of food in rapidly enlarging 
 the body. The rapidity with which fowls are fattened in the dark is 
 well known to rearers of poultry.* In India, the habit prevails of sew- 
 ing up the eyelids of the wild hog-deer, the spotted deer, and other wild 
 
 * It is astonishing with what rapidity fowls (dorkings) increase when well fed, kept in con- 
 fined cribs, and in a darkened room. Fed on a mixture of 4 lbs. of oatmeal, 1 lb. of suet, 
 and § lb. of sugar, with milk for drink five or sixlimes a day in summer, a dorkiag wiU add 
 to its weight 2 lbs. in a week, sometimes 1^ lbs. in four days, A young turkey will lay on 6 
 .Ds. a week, under the same treatmeut. 
 
610 VENTILATION AND CLEANLINESS. 
 
 animals when netted in the jungles, with the view of taming and speedily 
 fattening them. The absence of light indeed, however produced, seems 
 to soothe and quiet all animals, to dispose them to rest, to make less food 
 necessary, and to induce them to store up more of what they eat in the 
 form of fat and muscle. 
 
 An experiment made by Mr. Morton, on the feeding of sheep, shows 
 the effect at once of shelter, of (juict, and of the absence of light upon 
 the quantity of food eaten and of mutton produced from it. 
 
 Five sheep, of nearly equal weights, were fed each with a pound of 
 oats a-day and as much turnips as they chose to eat. One was fed in 
 the open air, two in an oi^en shed — one of them being confined in a crib — 
 two more were fed in a close shed in the dark — and one of these also was 
 confined in a crib, so as to lessen as much as possible the quantity of ex- 
 ercise it should take. The increase of live weight in each of the five, 
 and the quantity of turnips they respectively consumed, appear in the 
 following table : — 
 
 
 
 
 
 
 Increase 
 
 
 LIVE WEIGHT. 
 
 
 
 for each 
 
 
 
 
 Increase. 
 
 Turnips 
 eaten. 
 
 100 lbs. of 
 turnips. 
 
 
 Nov. 18. 
 
 March 9. 
 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 Unsheltered 
 
 108 
 
 131-7 
 
 23-7 
 
 1912 
 
 1-2 
 
 In open sheds .... 
 
 102 
 
 129-8 
 
 27-8 
 
 1394 
 
 2-0 
 
 Do., but confined in cribs 
 
 108 
 
 130-2 
 
 22-2 
 
 12:38 
 
 1-8 
 
 In a close shed in the dark 
 
 104 
 
 132-4 
 
 28-4 
 
 886 
 
 3-1 
 
 Do., but confined in cribs 
 
 111 
 
 131-3 
 
 20-3 
 
 886 
 
 2-4 
 
 From this table it appears, as we should have expected — 
 
 a. That much less — one -third less — turnips was eaten by the animal 
 which was sheltered by the open shed, than by that which was without 
 shelter, while in live weight it gained four pounds more. 
 
 b. That in the dark the quantity of turnips eaten was one-half less, 
 and the increase of weight a little greater still. 
 
 c. But that when confined in cribs — though the food eaten might be a 
 little less-^the increase in weight was not so great. The animal, in 
 fact, was fretful and restless in confinement, and whatever produces this 
 effect upon an animal prevents or retards its fattening. 
 
 d. That the most profitable return of mutton from the food consumed, 
 is when the animal is kept under shelter and in the dark. 
 
 Such a mode of keeping animals, however, must not be entered upon 
 hastily or without due consideration. The habits of the breed must be 
 taken into account, the effect of the confinement upon their health must 
 be frequently attended to, and, above all, the ready admission of fresh air 
 and a good ventilation must not be forgotten. By a neglect of the pro- 
 per precautions, unfortunate results have frequently been obtained and a 
 sound practice brought into disrepute. 
 
 5°. Ventilation and cleanliness indeed are important helps to economy 
 in the feeding of all animals. Shelter and warmth will do harm, if free 
 and pure air is not admitted to the fattening stock. The same is true of 
 cleanliness, so favourable to the health of all animals. The cleaner 
 their houses and skins are kept, the more they thrive under any given 
 form of treatment in other respects. 
 
ErFECT OF THE SOURING OF FOOD. 611 
 
 § 13. Influence of the form or state in which the food is given on the 
 quantity required by an animal. 
 The state in which the food is given to his stock has often an important 
 influence upon the profits of the feeder. Thus — 
 
 1°. The souring of the food, in some cases, makes its use more econo- 
 mical. Arthur Young details several series of experiments on the fat- 
 tening of pigs, in which bean meal was given mixed with water in the 
 sweet state, and after it had been allowed to stand several days to sour. 
 In every case in which it was given sour, the pork obtained gave a profit 
 upon the price of the meal, while in every case in which the same meal 
 was given sweet and in equal quantity, the price obtained for the pork 
 was less than that which was paid for the meal. 
 
 Upon sour food, indeed, pigs are universally observed to fatten best. 
 In Holstein, it is customary to collect waste green herbage of every kind, 
 and to let it sour in water. It then fattens pigs which would scarcely 
 thrive on it before. During this souring of vegetable matter in water, it 
 is lactic acid — the acid of milk — which is chiefly produced. This acid, 
 therefore, would appear to favour the increase of size in the pig, and to 
 this cause may be owing the profitable use of sour whey in feeding this 
 kind of stock in cheese-making districts. 
 
 1 have been told by some cow-feeders who use brewers' grains, that 
 the dry cows, when fattening off, relish the grains most when slightly 
 sour, and fatten most quickly upon them. From others, however, I 
 have obtained a contrary opinion, and have been assured that fattening 
 stock of all kinds like the grains best, and thrive best upon them, when 
 perfectly sweet and fresh. It is a matter of doubt, therefore, whether or 
 not the souring of food generally, of all kinds and for all kinds of stock, 
 can be safely tried or recommended. 
 
 2°. The boiling or steaming of dry food, and even of potatoes and tur- 
 nips, is recommended by many as an economical practice. I beheve 
 that the general result of the numerous experiments which have been 
 made upon this subject in various parts of the country is in favour of 
 this opinion in so far as regards fattening and growing stock. It seems a 
 more doubtful practice in the case of horses which are intended for heavy 
 and especially for fast work — though even for these animals the use of 
 steamed food is beginning to be adopted by some of the most extensive 
 coach contractors. [Stephens' Book of the Farm.] 
 
 3°. It is a curious fact not less worthy of tlie attention of the chemist 
 than it is of the practical man, that the age of the food singularly affects 
 its value in the nourishment of animals. Thus new oats are not con- 
 sidered fit for hunters before the months of February or March. They 
 affect the heels and limbs with something like grease, and make the 
 horse unfit for fast work. Nor is it merely water which the grain loses 
 by the five or six months' keeping — for if it be dried in the kiln it is still 
 unfit for use, from its stimulating in an extraordinary degree the action 
 of the kidneys. Some chemical change takes place in the interior of the 
 oat which has not yet been investigated. 
 
 The potato, on the other hand, by keeping, loses much of its nutritive 
 value, even before it has begun to sprout — and every feeder knows that 
 turnips which have shot in(o flower, add much less than before to the 
 weight of his fattening stock. 
 
612 INFLUENCE OF SOIL AND CULTURE ON THE 
 
 § 14. InjlueThce of soil^and culture on the nutritive value of agricultural 
 
 liroduce. — 
 
 I have on several former occasions, (pages 500 to 528), directed your"' 
 attention to the remarkable influence which soil, culture, and climate 
 have upon the chemical composition of the different corn and green crops 
 usually raised for food. Every such change of composition alters also 
 the nutritive value of any given crop. If the wheat or barley be richer 
 in gluten, it will build up more muscle — if it abound more in starch, a 
 smaller weight of it will supply the carbon of respiration — if it be richer 
 in fatty matter, it will round off the edges of the bones, and fill up the in- 
 equalities in an animal's body more quickly with fat. Such differences 
 as these I have already shown you do really exist among samples of the 
 same kind of grain grown upon soils either of different quality, or of the 
 same quality when differently cultivated or manured. 
 
 But this different culture or manuring affects the relative proportions 
 of the several kinds of inorganic matter also — the phosphates and other 
 saline substances — which are known to exist necessarily in all vegetable 
 productions. In illustration of this, I would direct your attention to the 
 following analyses — ^made in my laboratory by Mr. Fromberg — of the 
 ash of two samples of the same kind of turnip (red topped yellow) 
 raised by Lord Blantyre, on the same field, the one with guano alone, 
 the other with farm-yard dung alone. The quantity of ash left by the 
 tw^o varieties of turnip was 0-68 and 0*7 per cent, respectively, and this 
 ash was composed as follows : — 
 
 Composition of the ash of turnips raised with guano, and with farm-yard dung. 
 
 GUANO. DUNG. 
 
 Chloride of Potassium 
 Sulphate of Potash 
 Carbonate of Potash . 
 Phosphate of Potash , 
 
 Lime . 
 
 Magnesia 
 
 » — Alumina 
 
 Carbonate of Lime 
 
 Alumina 
 
 Oxide of Manganese . 
 SiUca 
 
 /-■■ ■ ' — ■- 
 
 Interior. 
 
 Exterior. 
 
 Interior. 
 
 Exterior. 
 
 556 
 
 503 
 
 5-40 
 
 10-71 
 
 30-85 
 
 37 04 
 
 3120 
 
 35-47 
 
 11-38 
 
 903 
 
 3674 
 
 17-63 
 
 20-93 
 
 1017 
 
 5-51 
 
 3-65 
 
 4-55 
 
 4-49 
 
 1-58 
 
 2-02 
 
 0-34 
 
 1-62 
 
 263 
 
 3-13 
 
 4-87 
 
 9.94 
 
 0-92 
 
 2-76 
 
 9-52 
 
 9-73 
 
 11-56 
 
 14-82 
 
 509 
 
 2-79 
 
 0-94 
 
 0-46 
 
 3-21 
 
 5-90 
 
 2-60 
 
 5.33 
 
 1-65 
 
 343 
 
 — 
 
 3-04 
 
 ^ 97-95 99-16 9908 99-02 
 
 The most striking difference between the two varieties of ash is in the 
 proportion of phosphates they respectively contain. The ash of the 
 guano turnips contained from 25 to 30 per cent, of phosphates, that of 
 the dung turnips only from 9 to 11 per cent. This could not fail to 
 make an important difference in their relative values for the feeding of 
 stock whose bones are growing, and which require, tlierefore, a larger 
 supply of phosphates in their food. 
 
 The phosphates of lime and magnesia form, as w^e know, one of the 
 valuable constituents of guano, but we could scarcely have inferred that 
 this manure would have caused so much larger a proportion of these 
 phosphates to enter into the constituents of the turnips raised with them. 
 
NUTRITIVE VALUE OF AGRICULTURAL PRODUCE. 613 
 
 It is not unlikely that turnips, raised from bones, will also abound more 
 largely in phosphates than turnips raised from dung or rape dust, and 
 may therefore be better fitted for growing stock. 
 
 § 15. Can we correctly estimate the relative feeding properties of different 
 kinds of produce under all circumstances. 
 
 Since the several nutritive effects of different kinds of food are de- 
 pendent upon so many circumstances — upon the state of the animal 
 itself — the purpose for which it is fed — the mode in which it is housed 
 and protected — the form and period at which it is given— can it be pos- 
 sible to classify them in an order which will indicate their relative feed- 
 mg values in all cases and for all purposes ? This is obviously impos- 
 sible. We may easily arrange them in tlie order of their relative values 
 in reference to some one of the several purposes for which food is given. 
 We may shew in as many different tables the order of their relative 
 values in laying on fat — in increasing the muscles — or in promoting the 
 growth of bone ; but we cannot arrange theoretically, nor can experi- 
 ment ever practically classify, all our common vegetable productions in 
 one invariable order which shall truly represent their relative values in 
 reference to each of these three different points : — 
 
 1°. Experimental values. — This, however, practical writers have often 
 attempted to do. Making their experiments in different circumstances, 
 with different varieties of the same produce, upon different kinds of 
 stock, or upon animals fed for different purposes, they have obtained re- 
 sults of the most diversified kind, and have classified the several kinds of 
 fodder in the most unlike order. I select a few of these results for the sake 
 of illustration. Taking 10 lbs. of meadow hay as a standard, — then, to 
 produce an equal nutritive effect, the different quantities of each of the 
 other kinds of fodder represented by the numbers in the following table 
 ought to be used — according to the several authors whose names are 
 given. 
 
 Experimental quantities of fodder lohich must be used to produce an 
 equal nutritive effect, according to — 
 
 Sch 
 
 Lwertz. 
 
 Block. 
 
 Petri. 
 
 Thaer. 
 
 Pabst. 
 
 Meyer. 
 
 Middleton. 
 
 Meadow hay . . 
 
 10 
 
 10 
 
 10 
 
 10 
 
 10 
 
 10 
 
 10 
 
 Aftermath hay 
 
 11 
 
 — 
 
 10 
 
 — 
 
 — 
 
 
 
 __ 
 
 Clover hay . . . 
 
 10 
 
 10 
 
 9 
 
 5 
 
 10 
 
 
 
 __ 
 
 Green clover in- flow- 
 
 
 
 
 
 
 
 
 er and lucerne . 
 
 — 
 
 43 
 
 — 
 
 45 
 
 42 
 
 
 
 -_ 
 
 Lucerne hay . . 
 
 9 
 
 — 
 
 9 
 
 9 
 
 10 
 
 
 
 _«. 
 
 Wheat straw . . 
 
 — 
 
 20 
 
 36 
 
 45 
 
 30 
 
 15 
 
 _ 
 
 Barley straw . . 
 
 40 
 
 19 
 
 18 
 
 40 
 
 20 
 
 15 
 
 — 
 
 Oat straw . . . 
 
 40 
 
 20 
 
 20 
 
 40 
 
 20 
 
 15 
 
 __ 
 
 Pea straw . . . 
 
 — 
 
 16 
 
 20 
 
 13 
 
 15 
 
 15 
 
 ___ 
 
 Potatoes . . . 
 
 20 
 
 22 
 
 20 
 
 20 
 
 20 
 
 15 
 
 _ 
 
 Old potatoes . . 
 
 — 
 
 40 
 
 — 
 
 — 
 
 — 
 
 — 
 
 — 
 
 Carrots .... 
 
 27 
 
 37 
 
 25 
 
 30 
 
 25 
 
 23 
 
 34 
 
 Turnips .... 
 
 45 
 
 53 
 
 60 
 
 52 
 
 45 
 
 29 
 
 80 
 
 Wheat .... 
 
 4 
 
 3 
 
 6 
 
 6 
 
 
 
 
 
 -« 
 
 Barley .... 
 
 — 
 
 3 
 
 6 
 
 — 
 
 5 
 
 5 
 
 
 Oats 
 
 — 
 
 4 
 
 7 
 
 — 
 
 6 
 
 — 
 
 — 
 
 From an inspection of this table, we should naturally conclude eitner 
 26* 
 
614 THEORETICAL NUTRITIVE VALUES. 
 
 that the different kinds of fodder vary very much in quality, or that those 
 who determined their relative values by experiment must have tried 
 their effects upon very different kinds of stock, fed probably also for dif- 
 ferent purposes. Both of these conclusions are no doubt true. We 
 know that the same kind of produce does vary very much in chemical 
 constitution, but it is not likely that different samples of the same kind of 
 turnip are so unlike each other that 29 lbs. of the one will go as far in 
 feeding the same animal as 80 lbs. of another. These great differences 
 in the table, therefore, seem to show that different kinds or varieties of 
 fodder have been used, or under different circumstances, or results so dis- 
 cordant could scarcely have been obtained. 
 
 A certain value, it is true, attaches to the numbers in the table when 
 those given by the different authors nearly agree. Thus, about 20 of 
 potatoes and 30 of carrots appear to be equal in nutritive value to 10 of 
 hay. It must be confessed, however, that this subject of the experimental 
 value of different kinds of farm produce in feeding stock of the same 
 kind for the same purposes is still almost wholly uninvestigated. Will 
 none of the skilful stock feeders, of whom so many are now springing 
 up, turn their attention to this interesting field of experimental inquiry ? 
 
 2°. Theoretical values. — But the theoretical values of different kinds 
 of food in reference to a particular object, can be determined by analyti- 
 cal investigations made in the laboratory. This has been done in a 
 very able manner by Boussingault, in reference to the value of different 
 lands of fodder in the production of muscle. These values, according to 
 his analyses, are as follow, 10 of hay being again taken as a standard: — 
 
 Theoretical quantities of different Mnds of vegetable produce ivhich ivill 
 produce equal effects in the growth of muscle {Boussingault): — 
 
 Hay 10 
 
 Clover hay, cut in flower . . 8 
 
 Lucerne do 8 
 
 Aftermath do 8 
 
 Green clover, in flower ... 34 
 
 Green lucerne 35 
 
 Wheat straw^i 52 
 
 Rye straw 61 
 
 Barley straw 52 
 
 Oat straw 55 
 
 Pea straw 6 
 
 Vetch straw 7 
 
 Potato leaves 36 
 
 Carrot leaves 13 
 
 Oak leaves 13 
 
 This table possesses much value. 
 
 Potatoes 28 
 
 Old potatoes 41 
 
 Carrots 35 
 
 Turnips 61 
 
 White cabbage 37 
 
 Vetches 2 
 
 Peas 3 
 
 Indian corn 6 
 
 Wheat 5 
 
 Rye 5 
 
 Barley 6 
 
 Oats 5 
 
 Bran 9 
 
 Oil-cake 2 
 
 It cannot, however, be relied upon 
 
 as a safe guide in all cases by the feeder, because of the differences in 
 the composition of our crops, which arise from the mode of culture and 
 the kind jf manure employed. It possesses, however, a higher value 
 froni this circumstance — that as muscle in most animals forms the larger 
 portion of their bulk, the order in which different kinds of vegetable food 
 promote the growth of this part of the body, may in most cases be adopted 
 as the order also of their relative values in sustaining animals and keep- 
 ing them in ordinary condition. The same remark, however, will not 
 
EFFECT OF MODE OF FEEDING ON THE MANURE. 615 
 
 apply to animal food, since we may have a kind of animal food, such as 
 gelatine, which would greatly promote the growth of muscle, but which, 
 from its composition, is capable of ministering so little to the wants of 
 the other parts of the body that it will not even support life for any length 
 of time. 
 
 § 16. Effect of different modes of feeding on the manure and on the soil. 
 
 There remains still one practical point in connection with the feeding 
 of stock, to which I think you will feel some interest in attending. 
 
 The production of manure is an object with the European farmer of 
 almost equal importance with the production of milk or the fattening of 
 stock. What influence has the mode of feeding or the purpose for 
 which tho animal is fsd, upon the quantity and quality of the manure 
 obtained ? 
 
 1°. The quantity of the manure depends upon the quantity of food 
 which is necessary to sustain the animal. With the exception of the 
 carbon, which escapes from the lungs in the form of carbonic acid, and 
 a comparatively small quantity of matter which forms the perspiration, 
 the whole of the food which sustains the body is rejected again in the 
 form of dung. 
 
 Now the sustaining food increases with the size of the animal, with 
 the coldness of the temperature in which it is kept, and with the quantity 
 of exercise it is compelled to take. Large, hardly worked, much driven, 
 and coldly housed animals, therefore, if ample food is given them, will 
 produce the largest quantity of manure. It might be possible, indeed, to 
 keep large animals for no other purpose but to manufacture manure — by 
 giving them an unlimited supply of food, using means to persuade them 
 to eat it, and causing them at the same time to take so much exercise as 
 to prevent them from ever increasing in weight. 
 
 2°. Quality of the manure. — The quality of the manure depends al- 
 most entirely upon the kind of food given to an animal, and upon the 
 purpose for which it is fed. 
 
 a. The full-grown animal, which does not increase in weight, returns 
 in its excretions, all that it eats. The manure that it forms is richer in 
 saline matter and in nitrogen than the food, because, as I have already 
 explained to you in detail (p. 472), a portion of the carbon of the latter 
 is sifted out as it were by the lungs, and diffused through the air during 
 respiration. In other respects, whatever be the nature of the food — the 
 quantity of saline matter or of gluten it contains — the dung will contain 
 nearly the same quantities of both or of their elements. 
 
 b. The case of the fattening animal again is different. Besides the 
 sustaining food, ihere is given to the animal some other fodder which 
 will supply an additional quantity of fat If this additional food be only 
 oil, then the dung will be little aflected by it. It will be little richer than 
 the dung of the full-grown animal to which the same sustaining food is 
 given. 
 
 But if the additional food contain other substances besides fat — saline 
 substances, namely, and gluten — then these will all pass into the dung 
 and make it richer in precise proportion to the quantity of this additional 
 food which is given. Thus if oil-cake be given for the purpose of laying 
 on fat — the usual sustaining food at the same time being supplied— the 
 
616 WHY OLD PASTURES CONTINUE RICH. 
 
 dung will be enriched by all those other fertilizing constituents present in 
 the oil-cake which are not required or worked up by the fattening animal. 
 
 Hence it is that the dung of fattening stock is usually richer than that 
 of stock of other kinds. Oil-cake would be a rich manure were it put 
 into the soil at once ; it is not surprising, therefore, that after it has 
 parted with a portion of its oil it should still add much to the richness of 
 common dung. 
 
 A knowledge of the kind of material, so to speak, which the animal 
 requires to fatten it, explains in a considerable degree another practical 
 fact of some consequence through which it is not easy at first sight to see 
 one's way. There are in various parts of the island certain old pastures 
 which, from time immemorial, have been celebrated for their fattening 
 qualities. Full-grown stock are turned upon them year after year in the 
 lean state, and after a few months are driven off again fat and plump and 
 fit for the butcher. This, I have been told when on the spot, has gone 
 on time out of mind, and yet the land, though no manure is artificially 
 added, never becomes less valuable or the pasture less rich. Hence the 
 practical man concludes that the addition of manure to the soil is un- 
 necessary, if the produce be eaten off by stock — that the droppings of 
 the animals which are fed upon the land are alone sufficient to maintain 
 its fertility. 
 
 But the reason of this continued richness of such old pastures is 
 chiefly this-^that the cattle, .when put upon them, are usually full-grown 
 —they have already obtained their full supply of bone and nearly as 
 much muscle as they require. While on the fields they chiefly select 
 fat from the grasses they eat, returning to the soil the phosphates, saline 
 substances, and most of the nitrogen which the grasses contain. Their 
 bodies are no doubt constantly fed or renewed by new portions of these 
 substances extracted from the food they eat, but they return to the soil an 
 equal quantity from the daily waste of their own bodies — and thus are 
 indebted to, and carry off the land, little more than the fat in which 
 they are observed daily to increase. 
 
 But as the materials of the fat may be, and no doubt originally are, 
 derived wholly — perhaps indirectly, yet wholly — from -the atmosphere, 
 the land is robbed of nothing in order to supply it, and thus may con- 
 tinue for many generations to exhibit an equal degree of fertility. 
 
 I give this only as a general explanation, by which the difficulty 
 may be solved, where no other more likely explanation can be found 
 in the local circumstances of the spot, or of the district in which such 
 rich old pastures exist. 
 
 c. The growing animal, again, does not return to the soil all it re- 
 ceives. It not only discharges carbon from its lungs, but it also extracts 
 phosphates from its food to increase the size of its bones, gluten to swell 
 out its muscles, and saline substances to mingle with the growing bulk 
 of its blood. The ^ung of the growing animal, therefore, will not be so 
 rich as that of the full-grown animal fed upon the same kind and quan- 
 tity of food. Hence from the fold-yard, where young stock are reared, 
 the manure will not be so fertilizing, weight for weight, as from a yard 
 in which full-grown or fattening animals only are fed. 
 
 d. The milk cow exhausts stUl further the food it eats. In the lean 
 
THE GROWING ANIMAL AND THE MILK COW. 617 
 
 milk cow, which has little muscle or fat to waste away, and, therefore, 
 little to repair, the sustaining food is reduced to the smallest possible 
 quantity. This small portion of food is all that is returned to the /lus- 
 bandman in her dung. The phosphates, salts and gluten, and even the 
 starch, of the remainder of the food she eats, are transformed in her 
 system, and appear again in the form of milk. The dung of the milk 
 cow must be very much poorer, and less valuable, compared with the 
 food she eats, than that of any other kind of stock. 
 
 It is true that the bulk of her dung may not be very much less than 
 that of a full-grown animal which is yielding no milk, but this bulk is 
 made up chiefly of the indigestible woody fibre and other comparatively 
 useless substances which her bulky food contains. The ingredients of 
 the milk have been separated from these other substances as the food 
 passed through her body, and hence, though bulky, the dung of the milk 
 cow is colder and less to be esteemed than that of the dry cow or of the 
 full-grown ox. 
 
 Nothing can more strikingly illustrate the difference between the effect 
 of the digestive organs of the fattening ox and those of the milk cow 
 upon the food they consume, than the well-known and remarkable dif- 
 ference in quality which exists between distillery dung, obtained from 
 fattening cattle fed upon the refuse of the distilleries, and cow-feeders* 
 dung, voided by milk cows fed upon nearly the same kind of food — 
 namely, the refuse of the breweries. 
 
 § 17. Summary of the views illustrated in the present Lecture. 
 
 The topics discussed in this Lecture are of so interesting a kind, and so 
 beautifully connected together, that you will permit me, I am sure, 
 briefly to draw your attention again to the most important and leading 
 points. 
 
 1°. It appears that all vegetables contain ready formed — that is, 
 form during their growth from the food on which they live — those sub- 
 stances of which the parts of animals are composed. 
 
 2°. That from the vegetable food it eats, the animal draws directly 
 and ready-formed the materials of its own body — phosphates to form the 
 bones — gluten, &:c., to build up its muscles — and oil to lay on in the 
 form of fat. 
 
 3°. That during the process of respiration a full grown man throws 
 off from his lungs about 8 oz. — a cow or horse five times as much — of 
 carbon every 24 hours ; and that the main office of the starch, gum, and 
 sugar of vegetable food is to supply this carbon. In carnivorous animals 
 it is supplied by the fat of their food — in starving animals, by the fat of 
 their own bodies — and in young animals, which live upon milk, by the 
 milk sugar it contains. 
 
 4°. That muscles, bone, skin, and hair undergo a certain necessary 
 daily waste of substance — a portion of each being removed every day 
 and carried out of the body in the excretions. The main function of the 
 gluten, the phosphates, and the saline substances in the food of the full 
 grown animal, is to replace the portions of the body which are thus re- 
 moved, and to sustain its original condition. Exercise increases this na- 
 tural waste and accelerates the breathing also, so as to render necessary 
 
618 SUMMARY OF THE VIEWS ILLUSTRATED. 
 
 a larger sustaining supply of food — a larger daily quantity to keep the 
 animal in condition. 
 
 5°. That the fat of the body is generally derived from the fat of the 
 vegetable food — which fat undergoes during digestion a change or trans- 
 formation by which it is converted into the peculiar kinds of fat which 
 are specially fitted to the body of the animal that eats it. In carnivor- 
 ous animals, the fat is also derived directly from the fat of their food — 
 which is, in like manner, changed in order to adapt it to the constitution 
 of their own bodies. In cases of emergency, it is probable that fat may 
 be formed in the animal from the starch or sugar of the food. 
 
 6°. In the growing animal, the food has a double function to perform, 
 it must sustain and it must increase the body. Hence, if tlie animal be 
 merely increasing in fat, the food, besides what is necessary to make up 
 for the daily waste of various kinds, must also supply an additional pro- 
 portion of oil or fat. To the growing animal, on the other hand, it must 
 supply also an additional quantity of gluten for the muscles, and of phos- 
 phates for the bones. If to each of a number of animals, equal quantities 
 of the same kind of food be given, then those which require the smallest 
 quantity of food to sustain them will have the largest proportion to con 
 vert into parts of their own substance. Hence, whatever tends to in- 
 crease the sustaining quantity — and cold, exercise, and uneasiness do so 
 — will tend, in an equal degree, to lessen the value of a given weight of 
 food, in adding to the weight of the animal's body. To the pregnant 
 and to the milk cow the same remarks apply. The food is partly ex- 
 pended in the production of milk, and the smaller and leaner the cow is, 
 less food being required to sustain the body, the more will remain for the 
 production of milk. 
 
 7°. Lastly, that the quantity and (juality of the dung — while they de- 
 pend in part upon the kind of food with which the animal is fed — yet 
 even when the same kind of food is given, are materially affected by the 
 purpose for which the animal is fed. If it be full-grown and merely 
 kept in condition, the dung contains all that was present in the food, ex- 
 cept the carbon that has escaped from the lungs. If it be a growing 
 animal, then_a portion of the phosphates and gluten of the food are re- 
 tained to add to its bones and muscles, and hence the dung is something 
 less in quantity and considerably inferior in quality to that of the full- 
 grown animal. 
 
 So it is in the case of the milk cow, which consumes comparatively 
 little in sustaining her own body, but exhausts all the food that passes 
 through her digestive organs, for the production of the milk which is to 
 feed her young. 
 
 The reverse takes place with the fattening ox. He takes little else 
 from the rich additional food he eats but the oil with which it is intended 
 that he should invest his own body. Its other constituents are for the most 
 part rejected in his excretions, and hence the richness and high price of 
 his dung. 
 
 Such are the main points I have endeavoured to illustrate to you in 
 this Lecture — they involve so many interesting considerations, both of a 
 
COxNCLUDING SECTION. 619 
 
 theoretical and of a practical kind, that had my limits permitted 1 could 
 have wished to dwell upon them at still greater length. 
 
 § 18. Concluding Section. 
 
 I have now brought the subject of these Lectures to a close. I have 
 gone over the whole ground which in the outset I proposed to tread. It 
 is the first time, I believe, that much of it has been trodden by scientific 
 men, and I have endeavoured in every part of our journey to lay before 
 you, as clearly as I could, everything we knew of the country we passed 
 over, in so far as it had a practical bearing or was likely to be suscepti- 
 ble hereafter of a practical application. 
 
 In the first Part, I directed your attention to the organic portion of 
 plants — showed you of what substances it consisted — on what kind of 
 organic food plants live — and by what chemical changes the peculiar 
 organic compounds of which they consist are formed out of the organic 
 food on which they live. 
 
 In the second Part, I explained in a similar way the nature, composi- 
 tion, and origin of the inorganic portion of plants. I dwelt, also, upon 
 the nature, origin, and natural differences which exist among the soils on 
 which our crops are grown, and from which the inorganic constituents of 
 plants are altogether derived. This led me to explain the connection 
 which exists between Agriculture and Geology, and the kind of light 
 which this interesting science is fitted to throw upon the means of prac- 
 tically improving the soil. 
 
 In the third Part, I dwelt upon the various means which may be 
 adopted for increasing the general productiveness of the land — whether 
 these means be of a mechanical or chemical nature. The whole doc- 
 trine of manures was here discussed and many suggestions offered to 
 your notice, which have already led to interesting practical results. 
 
 In the fourth Part, I have explained the chemical composition of the 
 several kinds of vegetable produce which are usually raised for food — 
 showed upon what constituents their nutritive values depend — and how 
 soil, climate, and manure affect their composition and their value as 
 food. The nature and composition of milk and of its products — butter 
 and cheese — the theory of their manufacture, and the circumstances upon 
 which their respective quantities and qualities depend — and, lastly, the 
 way in which food acts upon and supports the animal body, and how the 
 value of the manures they make is dependent upon the purpose for 
 which the animal is fed — these subjects have also been considered and 
 discussed in this fourth Part. 
 
 In discussing new topics I have had occasion to bring before you many- 
 new views. This, however, I have not done lightly or without consi- 
 deration, and I feel it to have been one of the greatest advantages which 
 have attended die periodical form in which these Lectures have been 
 brought before the public, that it has allowed me leisure to think, to in- 
 quire, and to make experiments in regard to points upon which it was 
 difficult at first to throw any satisfactory light. It is gratifying to me to 
 know that the general diffusion which these Lectures have obtained, baa 
 already done some service to the agriculture of the country. 
 
 FINIS. 
 
APPENDIX: 
 
 CONTAININQ 
 
 eUGGESTIONS FOR EXPERIMENTS IN PRACTICAL AGRI- 
 CULTURE, WITH RESULTS OF EXPERIMENTS 
 MADE IN 1841, 1842, AND 1843, 
 
APPENDIX. 
 
 No. I. 
 
 STTSGESTIONS FOR EXPERIMENTS IN PRACTICAL AGRICULTURB 
 DURING THE ENSUING SPRING AND SUMMER. 
 
 One of the most important objects which chemistry is at present desirous of 
 attaining for the improvement of practical agriculture, is the discovery and ap- 
 plication of specific or special manures. 
 
 We know that certain substances, such as fold-yard manure, are capable of 
 fertilizing to a considerable extent almost any land, and of causing it to yield 
 a better return of almost any crop. But we know also that manvu-es or fertili- 
 zers of nearly every kind are more efficacious on one soil than on another, and 
 that some answer better also for one species of crop than tor another. The 
 case of gypsum will serve to illustrate both these positions. 
 
 The effects of gypsum in the United States, in Prussia, and other parts of 
 Germany, and in some districts of England, are said to be absolutely astonish- 
 ing ; while in many other parts of our Island, of Germany, and even of the 
 United States, the benefit derived from it has not repaid the trouble and expense 
 incurred in applying it. Gypsum, therefore, \s especially adapted for use in cer- 
 tain soils only. 
 
 Again, the remarkable effects of gypsum have been observed most distinctly 
 on clover* and certain kinds of grass. The same benefits have not followed, 
 to any thing like an equal extent, from its use on barley, oats, wheat, or other 
 kind of grain. Therefore, while specially adapted to certain soils, it is also 
 specially adapted to certain crops. It is a kind of specific manure for clover 
 and some of the grasses. 
 
 Now, neither of these subjects which it is so important to investigate, — 
 neither that of the manures which are especially fitted for each soil, nor of those 
 which are specially fitted for each crop,— can be determined either from theory 
 or from experiments devised and executed in the laboratory of a chemist. The 
 aid of the practical farmer, of many practical farmers, must be called in. Nu- 
 merous experiments, or trials, must be made in various localities, and by differ- 
 ent individuals, — all, however, according to the same rigorous and accurate 
 method, — in order that, from the comparison of many results, something like a 
 general principle may be deduced. 
 
 It is pardy with a view to determine the mode of action of certain fertilizers, 
 and partly in the hope of obtaining some additional light on the subject of 
 manures specifically adapted to particular crops, that I venture to suggest to you 
 the propriety of making one or more of the following sets of experiments, 
 during the spring and summer of the present year. I could have much enlarged 
 
 * In regard to its use in Germany, Lampadius says, — " It may with certainty, be stated, 
 that by the use of gypsum the produce of clover and the consequent amount of live stock 
 have been increased at least one-third." — Die Lehrk von dbn Mineralischen Dungmit- 
 
 TELM, p. 34. 
 
2 or GRASS AND CLOVEH. [Appendix, 
 
 the list of suggestions, but I neither wish to fatigue your attention, nor to place 
 ' before you more work of the kind than can be readily accomphshed, wil/i little 
 expense of time, labour, or money. Another season will, I hope, afford us an 
 opportunity of interrogating nature by further, and perhaps more refined, modes 
 of experimenting, 
 
 1. OP GRASS AND CLOVER. 
 
 1°. It is beyond dispute, that on /certain soils, gypsum causes a largely in- 
 creased growth of grass and clover, but experiment alone appears capable of 
 determining on wkqt soils it is likely to be thus beneficial. Such experiments, 
 therefore, ought to be made on every farm, on a small scale at first, and at little 
 cost,* but made with care and accuracy, and with a minute attention to weights 
 and measures, 
 
 2°. The action of gypsum appears to be entirely chemical, but the only ex- 
 planation of this action yet attempted is far from being satisfactory. It is desi- 
 rable therefore, that experiments with other substances should be made, which 
 are likely to throw light on the theory. Important practical results may at the 
 same time be obtained — they are sure, indeed, to follow from a right under- 
 standing of the theory. 
 
 In the neighbourhood of Lyons, it has been found that very dilute sulphuric 
 acidt (oil of vitrol) exhibits the same beneficial effect upon clover, that has else- 
 where attended the use of gypsum. It is desirable, therefore, that a compara- 
 tive experiment should be made with this acid on a portion of the same field to 
 which the gypsum is applied. Where the one fails the other may act, 
 
 3°. It was observed by Dr. Home, of Edinburgh, so early as the year 1756, 
 that sulphate of sodat had a remarkable effect in promoting the growth of plants 
 — its action being nearly equal to that of saltpetre or nitrate of soda. This fact, 
 though mentioned by Lord Dundonald, has been lost sight of by practical men, 
 the sulphate of soda being generally represented as too high in price to be avail- 
 able as a fertilizer.§ The use of saltpetre, however, and of nitrate of soda, both 
 of which are more than double the price of sulphate of soda, show that the cost 
 of this latter article should not stand in the way of an accurate trial of its value 
 as a fertilizer on various crops. Dry sulphate of soda can be readily obtained 
 from any of the alkali works on the Tyne,ll and being an article of domestic 
 manufacture, it is proper that its merits should be ascertained, and, if it can be 
 available, that its use should be encouraged. 
 
 From the circumstance of its containing sulphuric acid, therefore, I would 
 recommend jliat it should be tried on clover and grass, in comparison with 
 gypsum and sulphuric acid, and on a portion of the same field. It may suc- 
 ceed where the others fail. 
 
 4°, Nitri;ite of soda also, as a top-dressing on grass land, has been often used 
 with great benefit, I have seen grassland in Dumfriesshire, which, after being 
 long let for pasture at 30s. an acre, had been sprinkled with an annual top- 
 dressing of nitrate of soda at the rate of 20s, an acre, and had since readily let 
 at £4: an acre, yielding thus an annual profit of 30s, an acre to the landlord. 
 
 In other districts, again, it has been found to answer better for corn. Thus, 
 after a discussion on this subject in the Gloucester Farmers' Club, it was agreed, 
 that nitrate of soda " was a very valuable manure for white straw crops, but 
 
 * The price of gypsum in London is about 2s. 6d. per cwt. ; in Newcastle, 3s. 
 
 t Gypsum consists of sulphuric acid and lime. 
 
 X Qlauber salts — consisting of sulphuric acid and soda. 
 
 § Lord Dundonald says — " From experiments it has been proved to promote vegetation in 
 a very high degree. The high price at present of this article precludes the use of it, but 
 could it be made and sold at a cheap rate, it would prove a most valuable acquisition to agri- 
 culture." Since the time of Lord Dundonald some trials made in Germany have shown it 
 to have a beneficial action on rye, potatoes, and fruit trees. 
 
 I Messrs. Allan & Co., of the Hewonh Alkali Works, deliver it in Newcastle and the neigh 
 bouring towns, at 9s. or 10s. per cwt. 
 
No. /.] OF GRASS AND CLOVER. 3 
 
 when applied to green crops the benefit was not sufficiently great to counter-bal- 
 ance the expense." In Northumberland, where it has been tried in a skilful 
 manner by Mr. Gray, of Dilston, it was found to yield a most profitable return 
 on both hay and barley. 
 
 These results show the necessity of further trials, not only for the purpose of 
 illustrating the cause of the beneficial action of this saline substance, but also 
 with the view of arriving at some general rule by which the practical man may 
 be guided in determining on what fields^ and for what crops on those fields, the 
 nitrate of soda may be beneficially applied 
 
 This experiment, like the others above-mentioned,'will be much more valua- 
 ble, if made in such a way that the result can be compared with that obtained 
 by the use of other chemical agents. I would, therefore, propose that in the 
 same field of grass or clover, a portion should be measured off, to be top- 
 dressed with nitrate of soda, that thus not only the absolute, but also the com- 
 parative, weight of the produce may at the same time be ascertained, 
 
 5°. There are other trials also, from which this general subject is capable of 
 receiving illustration. The fertilizing power of gypsum has been explained by 
 its supposed action on the ammonia which is presumed to exist in the atmos- 
 phere. If this be the true explanation, a substance containing ammonia should 
 act at least as energetically. At all events, the action of fold-yard manure and 
 of putrid urine is supposed to depend chiefly on the ammonia they contain or 
 give off. Now, among the substances containing ammonia in large quantity, 
 which in most towns are allowed to run to waste, the ammoniacal liquor of 
 the gas works is one which can easily be obtained, and can be applied in a li- 
 quid state at very little cost. It must be previously diluted with water till its 
 taste and smell become scarcely perceptible. 
 
 I would propose, therefore, as a further experiment, that along with one or 
 more of the substances above-mentioned, the ammoniacal liquor of the gas 
 works should be also tried, on a measured portion of ground, and, if possible, 
 in the same field. 
 
 6°. Soot, as a manure, is supposed to act pArtly, if not chiefly, in conse- 
 quence of the ammonia it contains. In Gloucestershlx-e it is applied to pota- 
 toes and to wheat, chiefly to the latter, and with great success. In the Wolds 
 of Yorkshire it is also applied largely to the wheat crop, at the rate of about 24 
 bushels to the acre.* In this county it is frequently used on grass land, to the 
 amount of 20 bushels an acre, and though I am not aware that it is extensively 
 employed upon clover, I am inclined to anticipate that the sulphur it contains,t 
 in addition to the ammonia, would render it useful to this plant. At all events, 
 comptirative experiments in the same field with the gypsum and the ammonia- 
 cal liquor, are likely to lead to interesting results. 
 
 7°. Common salt, highly recommended as a manure by some, has been as 
 much depreciated by others, and hence, when directly applied, is considered as 
 a doubtful fertilizer by almost all. The obscurity in regard to its use, however, 
 rests chiefly on the quantity which ought to be employed. The result of com- 
 parative experiments made in Germany, showed that a very few pounds per 
 acre were sufficient to produce a largely increased return of grass— while in 
 England it has been beneficially applied within the wide limits of from five to 
 twenty bushels per acre, and, when used for cleaning the land for autumn, of 
 thirty bushels an acre. 
 
 Among the comparative experiments upon grass and clover here suggested, 
 the eff'ect of salt might also be tried with the prospect of practical benefit. It 
 would give an additional interest to the experiments and supply an additional 
 term of comparison. 
 
 * The price is from 6d. to Is. a bushel. In this county the soot is said to be often of an 
 inferior quality, and brings therefore a less price. 
 
 t The gypsum. I might also say, for much of our soot contains gypsum, the lime being 
 derived chiefly from the sides of the flue. 
 
OF GRASS AND CLOVER. 
 
 [AppendiXf 
 
 The entire series of experiments, therefore, which I would recommend, would 
 occupy eight patches on a clover or grass field, one of which would be left un- 
 dressed for the purpose of comparison. Thus, each plot being half an acre • 
 
 Gypsum. 
 
 Sulphate of 
 Soda. 
 
 Ammoniacal 
 Liquor. 
 
 
 Sulphuric 
 Acid. 
 
 Nitrate of 
 Soda. 
 
 Common 
 
 Salt. 
 
 Soot 
 
 The ammoniacal liquor and the soot are placed as far as possible from the 
 gypsum and sulphuric acid, that they may not interfere with each other's action. 
 In a large field they might be placed still farther apart, and other trials might be 
 made in one or two of tlie vacant places. 
 
 The appearance of each patch should be entered, with the date, in an experi- 
 ment book, at weekly intervals, and the final produce both of hay and of after- 
 math carefully noted, both as to weight and quality. 
 
 Nor will the experiment be completed when the crop for the year is gathered 
 in; but, where it is possible, two further points should be ascertained, — 
 
 1°. The relative feeding or nourishing properties of the produce. To those 
 who rear and fatten cattle, this is a matter of great importance, and it is one 
 which they could easily determine, at least very approximately. 
 
 2°. What has been the permanent effect of the several substances on the soil, 
 as indicated by the compai'ative quantity and quality of the crop obtained from 
 each half acre, on the succeeding or during the titjo following years. The result of 
 these further observations may materially modify the conclusion we should draw 
 from the comparative weight and quality of the produce of the first year. 
 
 I shall only observe, in conclusion, on this head, that the result of a simulta- 
 neous trial of all these substances in the saaie field would not only throw much 
 light on the specific action of each on the grass or clover in general, but would 
 be of permanent utility to that farm or locality in which the experiments were 
 made. It would indicate the kind of fertilizer which was best adapted to the 
 farm or neighbourhood, in the existing condition of its general culture. It would 
 form a local record, useful not only to the tenant who made the experiment (if 
 well made) and by whom the farm at the time was tenanted, but more useful 
 by far, and more permanently so, to the owner of the land, whose interest in it 
 is supposedrto be not only greater, but much more lasting. 
 
 In regard to the quantities of the several substances above-mentioned, which 
 are to be applied to each acre, they may probably be varied according to cir- 
 cumstances, but the following may be recommended in the comparative experi- 
 ments: 
 
 1°. Gypsum 2 to 3 cwt. per acre. 
 
 2°. Sulphate of Soda 1 cwt. per acre. 
 
 3°. Nitrate of Soda 1 cwt. per acre. 
 
 4°. Soot 20 bushels per acre — this in different districts may be varied accord- 
 ing to the known quality of the soot. 
 
 5°. Of Sulphuric Acid from 30 to 40 lbs. per acre, applied at three or four 
 several intervals — and diluted with at least 200 times its weight of water. Or 
 so much water may be added as to make it perfectly tasteless, or so weak as 
 not sensibly to injure the texture of a plant left in it during the previous night.* 
 
 6°. Of Ammoniacal Liquor 100 to 200 gallons per acre, according to its 
 strength, for this is constantly vaiying. It must also be diluted with so large a 
 quantity of water as will render it perfectly tasteless, and is likely to prove most 
 beneficied if laid on at several successive periods. 
 
 ' The quantity above-mentioned amounts to about two gallons of the acid of the shops, and 
 it should be diluted with three or four hundred gallons of water. 
 
No. /.] or WHEAT, BARLEY, AND OATS. -5 
 
 7°. Of common salt it will be safer to apply not more than four to six bushels 
 an acre ; though, where time and circumstances permit, compai'ative trials might 
 also be made on the efficacy of salt when applied in different proportions, to the 
 same land on which the other experiments are made. 
 
 As to the time when these several dressings ought to be applied, some varia- 
 tion may be made according to the state of the young crop. They need not, in 
 general, be used before the lOth of April, and they should rarely be later 
 than the middle of May. 
 
 It will be desirable that in the detail of every set of experiments, the kind and 
 quality of the soil (and subsoil) should be stated — with its drainage and expo- 
 sure — and the kind of grass or clover which had been sown upon it. 
 
 II, OF WHEAT, BARLEY, AND OATS. 
 
 It is known that saltpetre and nitrate of soda produce highly beneficial effects 
 on all these varieties of grain. Thei'e remains much to be done, however, be- 
 fore the principle of their operation, or the circumstances on which their most 
 useful application depends, can be clearly understood. Their relative effects on 
 the same kind of grain must be made the subject of more frequent, more precise, 
 and more carefully conducted experiments — and these effects must be compared 
 with those of other fertilizing substances, in order that we may arrive ultimate- 
 ly at some comparative estimate of the practical value of each, in increasing the 
 growth and produce of those crops which are the staples of animal food. 
 
 A.— Of Wheat. 
 
 It is confidently stated by some, as a general rule, that saltpetre is more ad- 
 vantageous than nitrate of soda, when applied to wheat. On the other hand, it 
 is beyond question that the apphcation of nitrate of soda to wheat has been 
 found productive of remarkable benefit. 
 
 Is saltpetre especially adapted for wheat of all varieties, on all soils, and under 
 every variety of 7nanagement, and is nitrate of soda, in like manner, especially 
 fitted for barley and oats 1 
 
 These are questions to which the experiments hitherto made do not enable us 
 to give a reply. New data must be obtained before we can have the means of 
 reasoning usefully in regard to any of them. I would propose, therefore, — 
 
 \°. That where two varieties of wheat are sown on the same field, or on dif- 
 ferent fields of precisely the same kind of land and in the same condition, that 
 two half acres of each variety should be measured off, and that one half acre of 
 each should be dressed with saltpetre, and the other with nitrate of soda, at the 
 rate of 1 cwt. per acre. If three vai'ieties could be so treated, the experiment 
 would be the more valuable. 
 
 It would thus be determined how far the effect of each of these nitrates was 
 dependent upon the variety of wheat sown — and what was the relative action of 
 each nitrate upon any of the varieties. 
 
 2°. That when the same varieties of wheat are sown upon two or more dif- 
 ferent soils— in different parts of a farm— that one portion of the wheat on every 
 different soil should be dressed with nitrate of soda, and another with nitrate ot 
 potash (saltpetre). By this experiment, it would be shown how far the effect 
 of these substances is dependent on the nature of the soil, and how far the action 
 of the one, compared with that of the other, is modified by diversity of soil. 
 
 In these diflferent experiments, the management is presumed to be the same. 
 If the experiments be repeated by several persons in different parts of the coun- 
 try, the effects of difference of management will, in a great measure, be shown 
 in the diversity of the resvilts. 
 
 3°. With the view of ascertaining the comparative effect of the sulphate of 
 soda on this crop, I would suggest that in each case above specified, an equal 
 area should be set aside to be dressed with this salt, in the proportion of 1 cwt. 
 per acre. 
 
 Of each variety of wheat, therefore, and on each variety of soil, four patches 
 
OP WHEAT, BARLEY, AND OATS. 
 
 [AppendiXf 
 
 Nitrate of 
 Soda. 
 
 Saltpetre. 
 
 y 
 
 Sulphate of 
 Soda. 
 
 of equal area, say half an acre, should be measured off— one of which should be 
 undressed for the purpose of comparison : thus — 
 
 As before, the nature of the soil and the kind of 
 grain must be recorded — the appearance of each patch 
 noted week by week — with the time of ripening and 
 reaping — and the respective quaUties and weights of 
 the grain and straw collected from each half acre. 
 
 The quantity of gluten contained in the wheat 
 should also be determined, or a sample of the flour 
 transmitted for the purpose to the writer of these sug- 
 gestions, accompanied by a detail of the experiments they are intended to 
 illustrate. 
 
 B. — Of Barley and Oats. 
 To barley and oats the above remarks all apply, with this difference, that to 
 these crops saltpetre is said to be less beneficial than the nitrate of soda. In 
 connection with these crops, however, I would make the following additional 
 observation. 
 
 According to any theory of the action of the nitrates of potash and soda 
 which readily presents itself, their effect on any crop which they are equally 
 capable of benefitting ought to be nearly equal, weight for weight. The nitrate 
 of soda ought to have a decidedly more powerful action, were it not that the 
 state of moisture in which it is generally sold, increases its weight so much as 
 in a great measure to deprive it, in equal weights, of this superiority. 
 
 But while 1 cwt. of saltpetre (nitrate of potash) is recommended as a suffi- 
 cient dressing for an acre, 1| to IJ cwt. of nitrate of soda is recommended for 
 an equal area. It would, therefore, be desirable where nitrate of soda is applied 
 to any large extent of land, either with oats Or barley, to make a comparative 
 trial on three equal portions of the same field, with 1, li, and 1 J cwt. per acre, 
 respectively. 
 
 In addition, therefore, to the experiments suggested in regard to wheat, with 
 the view of determining — 
 
 1°. The absolute and relative efficacy of saltpetre and nitrate of soda on dif- 
 ferent varieties of the grain; 
 
 2°. The same on different varieties of soil ; 
 
 3°. And under diversities of management, — as in the previous treatment of 
 the land, &c. ; 
 
 There mayj)e added, in regard to oats and barley, another series of trial to 
 , determine — 
 
 4°. The relative effects of the different proportions of tlie nitrate of soda, 
 which is at present svpposed to be specially beneficial to these kinds of gi'ain. 
 If any one be desirous of uniting this latter series with the fonner, it may be 
 done thus — 
 
 The vacant half-acre being as before left 
 for the purpose of comparison. Such an 
 entire series might be made at the same 
 time on a field of Tartary and of potatoe 
 oats, and on two or more varieties of bar- 
 ley. 
 
 These top-dressings may all be sown 
 broad-cast — on the wheat most convenient- 
 ly when the seeds are sown in April or May, and on the barley and oats when 
 the fields have become distinctly green. 
 
 I may be pemaitted to add, as inducements to practical men, to try one or 
 more of these experiments in the accurate manner above described: 
 
 1°. That the result will be directly available and of immediate practical value 
 on his own farm, to the person by whom they are carefully made. That they 
 
 Sulphate of 
 Soda. 
 
 Nitrate of 
 
 Soda, 1 cwt. 
 
 per acre. 
 
 Saltpetre. 
 
 Nitrate of 
 Soda, 
 H cwt. 
 
 
 Nitrate of 
 Soda, 
 IJ cwt. 
 
No. /.] OF TURNIPS. 7 
 
 will be permanently useful to his landlord (if carefully recorded), ought to be 
 an inducement to the latter to give every facility and encouragement to his ten- 
 ant in making them. 
 
 '2P. That, instead of involving expense and outlay, which in many instances 
 rriay ill be spared, they are sure in almost every case to do more than repay the cost 
 of making them, by the increased quantity or value of the produce obtained. 
 Any of the series of experiments, on the scale suggested, may be made for five 
 pounds, so that were the outlay all to be lost, the accurate knowledge obtained 
 in reference to the general tillage of his lemd, would be worth more money to 
 the holder of a farm of a hundred acres. 
 
 3°. I need scarcely add, as a further inducement, the additional interest which 
 such experiments give to the practice of farming — and the means they afford 
 of calling forth the intelligence of the agricultural population. The moment a 
 man begins to make experiments under the guidance of an understood principle, 
 from that moment he begins to think. To obtain materials for thought he will 
 have recourse to books — and thus every new experiment he makes, will further 
 stimulate and awaken his intellect, and lead him to the acquisition of further 
 knowledge. Does it require anything more than this general awakening of the 
 minds of the agricultural class, to advance the science of agriculture as surely 
 and as rapidly as any of the other sciences, the practical application of which 
 have led to those extraordinary developments of natural resources which are 
 the characteristic and the pride of our time 1 
 
 III. OF TURNIPS. 
 
 The raising of turnips is of such vast importance in the prevailing system 
 of husbandry, that any improvement in the mode of culture must be of exten- 
 sive and immediate benefit. Experiments so numerous and so varied have been 
 made with this view, that it may almost seem superfluous in*me now to make 
 any further suggestions on the subject. But when experiments have been 
 made with a view to one subject only, it often happens in all departments of na- 
 tural science, that as new views are advanced or more precise methods pointed 
 out, it becomes necessary to repeat all our former experiments, — either for the 
 purpose of testing the results they gave us, or of observing new phenomena to 
 which our attention had not previously been directed. 
 
 I. Numerous experiments, for example, have been made upon the use of bones 
 in the raising of turnips, but they have been chiefly directed to economical ends, 
 and so far with the most satisfactory results. But among fifty intelligent and 
 thinking practical men, and who all agree in regard to the profit to be derived 
 from the use of bones with the turnip crop, how many will agree in regard to 
 the mode in which they act — how few will be able to give a satisfactory reason 
 for the opinion they entertain ! The same is true of theoretical chemists, some 
 attributing their effect more especially to the earthy matter, others to the gelatine 
 they contain. Dry bones contain about two-thirds of their weight of earthy 
 matter, the other third. consisting chiefly of animal matter resembling glue. Of 
 the earthy matter five-sixths consist of phosphate of lime and magnesia, and 
 the rest chiefly of carbonate of lime. Thus a ton of bone dust will contain — 
 
 Animal matter 746 lbs. 
 
 Phospate of lime, &c 1245 
 
 Carbonate of lime, &c 249 
 
 - 2240 
 
 On which of these constituents does the efficacy of bones chiefly depend 1 
 Does it depend upon the animal matter 1 This opinion is in accordance with the 
 following facts : — 
 
 1°. That in the Doncaster repoit it is said to be most effectual on calcareous 
 soils, — for in the presence of lime all organic matter more rapidly decomposes. 
 
 27 
 
8 OP TURNIPS. [Appendix- 
 
 2°. That horn shavings are a more powerful manure than bones, — since 
 horn contains only one or two per cent, of earlhy matter.* 
 
 3°. That before the introduction of cru.slied bones, the ashes of burned bones 
 had been long employed to a small extent in agriculture, but have since fallen 
 almost entirely into disuse. 
 
 4°, That old sheep skins cut up and laid in the drills, have been found to 
 yield as good a crop of turnips and after-crop of corn, as the remainder of the 
 field which was manured with bones. 
 
 5°, That "40 lbs. of bone dust are sufficient to supply tliree crops of wheat, 
 clover, potatoes, turnips, &c., with phosphates,"! while one to two-thirds of a 
 ton of bones, containing from 400 to 800 lbs. of phosphates, is the quantity usu- 
 ally applied to the land. 
 
 On the other hand, the quantity of animal matter present in a ton of bones 
 (746 lbs.) is so small, and its decomposition so rapid during the growth of the 
 turnips — while at the same time the efi'ccts of the bones are so lasting and so 
 beneficial to the after-crop of corn — that many persons hesitate in considering 
 the great excess of phosphates applied to the land, as really without any share 
 of influence in tlie production of the crops. 
 
 Thus Sprengel, an avithority of the very highest character, both in theoretical 
 and practical agriculture, is persuaded that the phosphates are the sole fertilizing 
 ingredients in bones, and he explains the want of success from the use of crush- 
 ed bones in Mechlenburg and North Germany, on the supposition that the 
 soils in those countries already contain a sufficient supply of phosphates, while 
 in England generally they are deficient in these compounds. 
 
 Further, if the animal matter be the fertilizing agent in bones, why are not 
 they of equal efficacy on grass land as upon turnips 7 
 
 With the view, therefore, of leading to some rational explanation of the rela- 
 tive effects of the sevea-al constituents of bones, it would be desirable to institute 
 comparative experiments of the following kind — 
 
 1°. With half a ton of bones per acre. 
 
 2°. With three or four cwt. of horn shavings or glue per acre, 
 
 3°, With two cwt. of burned bones per acre, 
 
 4°, With six or seven cwt. of burned bones per acre. 
 
 The quantity of burned bones in No. 4 is that which is yielded by a ton of 
 fresh bones; that in No. 3 is upwards of five times what should be talcen up by 
 the crops — as great part of what is added must be supposed to remain in the 
 soil, while some must be dissolved and carried, off by the rains. 
 
 The result^xif^such experiments as these, if made accurately on different soils, 
 will lead us sooner to the truth than whole volumes of theoretical discussion. 
 
 II. Nitrate of soda has also been applied with great benefit in the culture of 
 turnips. Some experiments, exceedingly favourable in an economical point of 
 view, have been made by Mr. Barclay, of Eastwick Park, Surrey,? who found 
 that one cwt. per acre, drilled in with the seed, gave as great a return of Swedes 
 as 15 bushels of bones with 15 of wood ashes per acre, and when the nitrate of 
 soda was sown broadcast, from 20 to 25 per cent. more. In eveiy part of the 
 country, therefore, this substance ought to be tried. And as this nitrate is very 
 soluble in water, and may therefore be readily carried off by the rain, and as 
 that only which is within reach of the plant is of any avail, I would suggest 
 that not more than one-fourth of the whole should be drilled in with the seed, 
 for the pui7)0se of bringing away the plant; and that after the thinning by the 
 hoe, the rest should be strewed along the rows by the hand or by the drill. In 
 
 • This, I believe, is rather a matter of opinion than the result of a sufficient number of ac- 
 tual trials. Some trials made by Mr. Hawden (British Husbandry, I. p. 395) gave results 
 very unfavourable to horn shavings. 
 
 t Liebigy p. 84. The acre here spoken of is the Hessian, about three-fifths of the English 
 acre. The English, therefore, will require 66 lbs. 
 
 ; I lournal of the English Agricultural Society, I. p. 428. 
 
Ne. /.] 
 
 OF TURNIPS. 
 
 9 
 
 this way the whole energy of the salt being expended where it is required, the 
 greatest possible effect will be produced. 
 
 III. I have already stated the reasons which lead me to anticipate highly be- 
 neficial effects to vegetation from the use of sulphate of soda ; I would suo-o-est 
 therefore, a trial of this salt on the turnips also, at the same rate of 1 cwt. per 
 acre, and applied in the way above recommended for the nitrate of soda. Of 
 course tlie intelligent farmer will vary the proportions and mode of application 
 of these substances, as his leisure or convenience permit, or as his better judg- 
 ment may suggest to him. 
 
 The entire series of experiments on turnips, above suggested, may be repre- 
 sented as follows, adding two plots for different proportions of the nitrate and 
 Bulphate of soda :- 
 
 Burned Bones, 
 2 cwt. per acre. 
 
 Nitrate of Soda, 
 U cwt. per acre. 
 
 Bone Dust, or 
 
 Crushed Bones, 
 
 1 ton per acre. 
 
 Burned Bones, 
 
 6 or 7 cwt. per 
 
 aero. 
 
 Sulphate of 
 
 Soda, 
 
 1 cwt. per acre. 
 
 Horn Shavings, 
 or Glue, 7 or 8 
 cwt. per acre. 
 
 Unmanured. 
 
 Sulphate of 
 
 Soda, 
 
 U cwt. per acre. 
 
 Nitrate of 
 
 Soda, 
 
 1 cwt. per aero. 
 
 Some of these experiments most of you may easily try. Those with the 
 burned bones and horn shavings, which in this part of the countiy are less easy 
 to be obtained, it is not to be expected that many of you will think of undertak- 
 ing. I hope, however, that they will not be lost sight of by those who possess fa- 
 cilities for obtaining them in sufficient quantity to make a satisfactory experiment. 
 
 In many parts of the United States, gypsum is the universal fertilizer for 
 every crop, and among the rest it is said tt) benefit turnips. The same opinion 
 is entertained in Germany. I am not aware how far, in what way, or with 
 what results, it has been applied to the turnip crop in this countiy. A simple 
 mode of testing its efficacy, however, would be to strew it over the plants when 
 in the rough leaf, on part of a field, the whole of which had been already ma- 
 nured in the ordinary way with fold-yard manure. The difference of produce 
 would thus show its efficacy, in the given circumstances ; and the experiment 
 could be made effectually at the cost of a single cwt. of gypsum, 
 
 I have not included rape dusl among the trials above suggested, though it is 
 undoubtedly, under certain modes of management, a beneficial manure both to 
 corn and turnip crops. There is also a diversity of opinion as to the cause of 
 its fertilizing action, as well as a manifest difference in the effect of different 
 samples of the dust on the same soil. Though, therefore, certain experiments 
 which I may on a future occasion suggest, would undoubtedly throw light on 
 the cause of the good qualities of this manure, yet as its action (taking different 
 samples) is not constant on the same soil, results obtained with it cannot pos- 
 sess the same importance, either theoretical or practical, as those which are ob- 
 served to follow from the use of bones' and of saline substances, the composi- 
 tion of which is nearly invariable. 
 
 Many farmers, however, are in the habit of constantly vising rape dust. If 
 any of these could conveniently make experiments on the effect of different sam- 
 ples of the cake, from different kinds of seed, and from different oil mills, and 
 would accurately note the results, they would perform an important service in 
 preparing the way for that clear explanation of the cause of its fertilizing action, 
 which is at present wanted,* and which experiment alone can discover to us. 
 
 ' Its good effects are generally attributed to the oil which is left in the seed, and its vary- 
 ing action to the ditferent quantities of oil left in it by different crushers. I doubt, however, 
 if the oil ought to be considered as more than a secondary cause of its beneficial action. 
 
10 OP POTATOES. [AppendtXf 
 
 IV. OP POTATOES. 
 
 1°. Nitrate of soda has been applied with great benefit to potatoes also. Af- 
 ter the potatoes have been harrowed down and (hand) hoed, and the plants are 
 four to six inches above the ground, it is applied by the hand round the stem 
 of the plants, and the earth then set up by the plough. Mr. Tumbull, in Dum- 
 bartonshire, last year used it in this way at the rate of 1^ to 2 cwt. per Scotch 
 acre, (1^ English acres,) and the produce exceeded that of the land to which no 
 nitrate was applied, by 20 Scotch bolls to the Scotch acre. 
 
 2°. Applied in the same way there is every reason to believe that the sul- 
 phate of soda would have a highly beneficial effect also. I repeat my recom- 
 mendation that this substance should be fairly tried with every crop, because it 
 is a product of our own manufactories, which can be supplied in unlimited, 
 quantity, and without the chance of any material increase of cost: while the 
 nitrate of soda is already in the hands of speculators, and within a short period 
 has risen in the market to the extent of nearly one-third of its former price. 
 
 In plastering their potatoes, the Americans generally put in a spoonful of 
 gypsum with every cutting — a similar method, if preferred, might be adopted 
 with the nitrate and sulphate of soda, though the chance of loss by percolation 
 through the soil, would, by this method, be in some degi-ee increased. In Flan- 
 ders, wood ashes and rape dust are frequently thrown in by the hand, when each 
 cutting is introduced. 
 
 3°. 1 shall have occasion hereafter to recommend to the attention of the prac- 
 tical farmer, many waste materials of various kinds, thrown outfrom our manu- 
 factories, the application of which to useful purposes would be a great national 
 benefit. In reference to the culture of potatoes, I will here bring under your no- 
 tice the chloride of calcium, which is said to have been beneficially applied to 
 various crops, but to potatoes especially, with sui-prising effect. Under the in- 
 fluence of this substance the sunflower and maize have grown to the height of 
 l4'to 18 feet, and potatoes have attained the weight of 2 to 3 lbs.* In Germany, 
 Sprengel also found it useful to potatoes. — {Chemic fur Landioirthe, I. p. 635.) 
 
 Thousands of tons of chloride of calcium may eveiy year be prepared from the 
 waste materials which flow into the river Tyne, from the alkali works upon its 
 banks. Thousands of gallons of the solution of tliis substance yearly run off 
 from the works of Messrs. Allan & Co at Heworth, and might be procured for 
 little more than the expense of collecting. It is also contained largely, though 
 mixed with other substances, in the mother liquor of the salt pans ; and from the 
 numerous salt works on the coast might readily be obtained for trial. When 
 prepared in thedry state, this substance rapidly deliquesces and runs into a liquid. 
 The most convenient way of applying it, therefore, would be in the state of so- 
 lution — so largely diluted as to have only a slight taste — and by means of a wa- 
 tering cart so contrived as to allow it to flow on the tops of the ridges and young 
 plants, by which unnecessary waste would be prevented. 
 
 Without knowing the sti-ength of the solution likely to be obtained from the 
 works, it is impossible to give any idea of the quantity of the chloride of calcium 
 which ought to be employed ; but .500 gallons per acre may safely be used, if 
 the solution be so far diluted as to have only a decided taste of the substance. 
 The experiments here suggested, ther^ore, require four patches, as follows: — 
 These ex}:)eriments are supposed to be made in ground 
 already prepared for the potatoe crop, by the usual quan- 
 tity of manure. I think it not unlikely, however, that 
 by planting the potatoe in the midst of nitrate or sul- 
 phate (sprinkled over with diy soil) at the rate of \ cwt. 
 per acre, and afterwards applying 1 cwt. per acre, when 
 the plants are hoed, a crop might be obtained without 
 the use of manure. Of course, such an experiment as 
 
 * The Rohan, a French variety of potatoe lately introduced into the United Statesy-by the 
 ordixiary mode of culture— yields tubers, very many of which weigh 3 lbs. and many attain to 
 
 Nitrate of 
 Soda, 1 to IX 
 cwt. pr acre. 
 
 Sulphate of 
 Soda, 1 to i;^ 
 cwt. pr acre. 
 
 Chloride of 
 Calcium, 500 
 gals, pr acre. 
 
 Manure 
 only. 
 
No. /.] OF MIXED MANURES. H 
 
 this, though important to be made, should be tried cautiously, and on such a 
 scale as to secure the experimenter from any serious loss. 
 
 In the above suggestions I have introduced nothing in regard to mixed ma- 
 nures — though where plants require for the supply of all their wants nine or 
 ten different ingredients, of which the soil they gi-ow in can perhaps yield in 
 sufficient quantity only three or four, it is obvious that the very best conse- 
 quences may follow from the employment of mixed manures. To this class 
 belong common night-soil, urine, animalised carbon, poudrette (night-soil mixed 
 with lime and gypsum), the foudre vegetatif (a mixture of soot and saltpetx-e), 
 the xorate (now manufactured in London), and many others. 
 
 The mode of preparing, and the special uses of these and other mixed ma- 
 nures, will be explained in the third part of these lectures, which will be devoted 
 to the consideration of the nature and uses, and to the theory of the action of 
 natural and artificial fertilizers. In the mean time it is desirable, in the first 
 place, to obtain results from which the special action of each, when used alone, 
 can be fairly deduced. 
 
 That these experiments may have their full value, it is indispensable that a 
 measured portion of each field should be left without manure or dressing of any 
 kind, in order that a true idea may be formed of the exact effect of each sub- 
 stance employed. Experiments are valuable to the practical man if they mere- 
 ly show the superiority of one species of manure over another, but they are in- 
 sufficient to show how much each of them tends to increase the produce — or to 
 enable us to arrive at a satisfactory explanation of the mode in which they 
 severally act in promoting vegetation. 
 
 Among other important experiments lately published, to which the above ob- 
 servation is applicable, may be mentioned those of Mr. T. Waite of Doncaster. 
 The effects of nitrate of soda on his land were very striking, showing a remarkable 
 increase of produce over bone dust, rape-dust, or rotten fold-yard manure — but 
 he does not seem to have determined the produce of the same land during the 
 same season and vnlhout manure. We have, therefore, no term of comparison, 
 by means of which we can ascertain the absolute or even the exact comparative 
 effect of the different substances employed. 
 
 It has been well observed by Sir Humphry Davy, "that nothing is more 
 wanting in agriculture than experiments in which all the cimmistanccs are mi- 
 nutely and scientifically detailed, and that this art will advance in proportion as 
 it becomes exact in its methods."* The above suggestions are submitted to 
 practical men in the hope that they may assist in introducing such exact meth- 
 ods into oiu- agricultural operations, and at the same time promote the theoreti- 
 cal advancement of the most important art of life. 
 
 Exact methods lead to theoretical discoveries, while these are no less certain- 
 ly followed by important practical improvements. 
 
 No. II. 
 
 {^See Lecture IL, p. 37.) 
 
 -fej illustration of the effect of sudden alternations of temperature on vegetable 
 substances, explained in a note subjoined to page 37, I quote with pleasure the 
 
 the weight of 5 lbs. When perfectly ripe, it is said to be an excellent table potatoe, and to be 
 best in the spring. — Albany Cultivator, for March, 1841. 
 
 • Agricultural Chemistry, Lecture L 
 
12 ON SUDDEN ALTERNATIONS OP TEMPERATURE. [AppeTldtX^ 
 
 following instructive letter from an ably conducted monthly journal published 
 at Albany, in the State of JNevv-York, under the title of the Cultivator. It is 
 extracted from the Number for March last : — 
 
 *' In regard to Irish potatoes, a still thinner covering of earth than the one 
 just mentioned suffices with us to presei-ve them from rotting. Indeed, it would 
 seem as if they could freeze and thaw several times, during winter, without 
 being destroyed, provided they are covered with earth all the time ; for we often 
 find them near the surface and peifectly sound, in the spring, when spading up 
 the ground in which the crop had grown during the previous season. There 
 they must have undergone freezing and thawing whenever the earth was in 
 either state, as it often is to a much greater depth than the potatoe roots ever 
 extend. Why should those roots always be destroyed when they freeze above 
 ground, and not suffer equally when frozen tender ground ? 
 
 *' The reason why potatoes, apples, &c. become soft, and rot when frozen 
 and then thawed suddenly, uncovered and in open air, is the sudden thawing. 
 You may put a heap of apples on the floor of a room, or other dry place, where 
 they will freeze perfectly hard, and if covered close with any thing that will ex- 
 clude the air, when the weather becomes warm enough to thaw, the apples will 
 remain sound and uninjured, after they are thus closely thawed. The cover 
 may be of the coarse tow of flax, or any article that will cover them close and 
 exclude the air. So apples may be packed in a tight barrel, if full and headed 
 up so as to exclude the air. They may be suffered to remain so in a garret, or 
 any dry place where it freezes hard, and they will be found sound and free from 
 injury, if the baiTel remains tight till they are thoroughly thawed. It is the sud- 
 den thawing that causes the apples or other vegetables to become soft and rot. 
 
 " So if the fingers on your hand be frozen, and you expose them to sudden 
 heat by warming them at the fire and they suddenly thaw, the flesh will morti- 
 fy and slough off. But, if you freeze your fingers or other limbs, and put them 
 in snow, and rub gently till they thaw, — or if put into a pail of water just drawn 
 from the well, which will be less cold than your frozen fingers, — they will thaw 
 slowly, and suffer but little injury. 
 
 " So during the early autunmal frosts in September, if the morning after the 
 frost is cloudy, the frost will be slowly drawn from the frozen vegetables, and 
 they will be uninjured ; but if they receive the rays of the early and clear sun, 
 they thaw so suddenly, that they will hang their heads and perish. If wet with 
 water from the well, long enough to exti'act the frost before the sun shines on 
 them, they dojiot suffer. 
 
 " Onions are a difficult root to keep in winter. If they are put in a cellar 
 warm enough to save them from frost, they will vegetate and be deteriorated. I 
 put them in the warehouse, where they freeze as hard as if out of doors. If in 
 a heap, I cover them close with some old clothes, or any thing that covers close, 
 to exclude the air. The same if in boxes or casks. They freeze hard, but it 
 does not appear to injure them for present use, if thawed by putting them into 
 a pail of fresh-drawn water, to draw out the frost just before cooking them. 
 Onions, thus kept, will be in good condition in the spring, after thawing under 
 cover from the air. 
 
 " I put parsneps, carrots, beets, &c., in boxes or casks, and then cover them 
 with potatoes, which preserves them from drying." 
 
 In farther illustration of this subject I need only recall to the recollection of 
 the gardener the well known fact, that, when the winter frosts begin to set in, 
 and his finest flowers to be nipped, those continue to blow the longest, on which 
 the sun's rays fall latest in the day. Dahlias protected in this way, will bloom 
 occasionally for weeks, after those which regard the eastern sky are completely 
 withered. 
 
 Professor Lindley has published a series of valuable observations on the effects 
 of extreme cold upon plants. The general results of these observations are 
 stated in his ^'■Theory of Horticulture,'' p. 88. But the conclusions at which 
 
No. II.] ON SUDDEN ALTERNATIONS OP TEMPERATURE. 13 
 
 he has arrived are deduced from the appearance presented by the plant after it 
 was thawed. He found the tissue more or less lacerated, the contents of the air 
 and sap vessels intermingled, and the colouring matter and other secretions de- 
 composed. He attributes the laceration to the freezing and consequent expan- 
 sion of tlie juices, but this cannot be the necessary consequence of that freezing, 
 since it does not appear, if the whole tuber or leaf be slowly thawed. I would 
 explain the phenomena as follows: — 
 
 1°. When the leaf, fruit, or tuber freezes, the fluid portions slightly expand 
 in becoming solid, but the air in the air vessels contracts in at least an equal de- 
 gree, and thus allows a lateral expansion of the sap vessels sufficient to prevent 
 lesion. When the temperature is slightly raised, the air expands but slightly, 
 and ice is melted long before the gaseous substances reach their original bulk. 
 
 2°. But if the rays of the sun strike suddenly upon the leaf or fruit, the sur- 
 face may at once be raised in temperature 3(1° or 40° F. The air will conse- 
 quently expand suddenly, and before the sap is thawed may have distended and 
 torn the vessels, and caused sap and air to be mutually intermingled. 
 
 3°. But the moment the sun's rays strike upon the green leaf, its chemical 
 functions commence. It begins to absorb and decompose carbonic acid : and 
 as in the frozen part of the leaf the circulation is not, and in consequence of the 
 lesion cannot be, established, the cliemical action of the sun's rays must be ex- 
 pended upon the stagnant sap ; and hence those changes not only in the sap 
 itself, but even in the solid parts which are seen to take place in the withered 
 leaf 
 
 4°. Though not in a state of growth, the tuber of the potatoc contains the 
 living principle, and there must be such a circulation going on in its interior as 
 to maintain an approximate equilibrium of temperature throughout its sub- 
 stance. A sudden thawing of the exterior, will, as in the leaf, expand the air 
 before the circulation can be established throughout the frozen mass. The solid, 
 fluid, and aeriform substances which nature has separated and set apart from 
 each other, will thus all be intermingled, and from their mutual action, those 
 chemical changes of which we know tliestarcli of the potatoe to be susceptible, 
 will speedily ensue ; — in other words, the potatoe will rot. 
 
 The practical applications of these views are numerous. If a sudden frost 
 come on, — protect your delicate flowers in the early morning from the rays of 
 the approaching sun, and cover with straw or earth the potatoes which have 
 been left overnight in the field. 
 
 No. III. 
 
 RESULTS OF EXPERIMENTS ON PRACTICAL AGRICULTURE DURING 
 THE SPRING AND SUMMER OF 1841. 
 
 (^See Appendix, No. 1., and Lectures VIII. and IX.') 
 
 In a previous article inserted in this Appendix, and which was published 
 early in the present spring (April, 1841,) I ventured to offer to the practical ag- 
 riculturist some suggestions in regard to the experimental use of certain un- 
 mixed manures. From the results of these experiments, which I was quite sure 
 some of the many zealous agriculturists of the day would be induced to under- 
 take after the manner, and with the precautions, I had pointed out, I anticipated 
 
14 
 
 RESULTS OF EXPERIMENTS ON PRACTICAL AGRICULTURE, [AppeudtXf 
 
 n two-fold advantage. In the first place, that important practical benefits to 
 the agriculture of certain districts would be derived from tliem, and secondly, 
 that interesting and important light would be thrown by them on many parts 
 of agricultural theory. It is by experiment that all the remarkable results — 
 theoretical as well as practical — of modern cliemistry have been arrived at ; 
 but by experiments cautiously made, frequently repeated, and logically reason- 
 ed from. The proceedings of the practical farmer are a continued course of ex- 
 perimental trials, and to convert liim into an experimental philosopher, and to 
 lead him to philosophical results, it is necessary only that his experiments 
 should be made vsi/k a constant reference to weifiiit and 7Hcasiire, and should be 
 repeated nnder varied and carefully noted conditions — and that he should be 
 taught to draw fz'om them no conclusions more general than they really 
 justify. , ■ 
 
 The following results of experiments made duj'ing the past summer confirm 
 all my anticipations. Though necessarily somevvhat limited, and local in their 
 nature, they, nevertheless, present on the whole a beautiful illustration of what 
 we have yet to expect from a continuation of such experimental researches, con- 
 ducted in so skilful a manner. I need not especially commend the experiments 
 of Mr. Fleming : for I can scarcely, I think, render a better service to practical 
 agriculture than by jjlacing all of them in the hands of -practical men, tind ear- 
 nestly commending them to their careful consideration and imitation. 
 
 I. Experiments made near Aske Hall, on the property of the Earl of Zet- 
 land, on lots of half an acre each. 
 
 3. Salt — jnd on May 24 — 3 bushels-cost Q>s. 6d. 
 Weight of grass when mown, 3 tons 19 cwt. 
 Weight when made into hay, 1 " 16 " 
 
 1. Soot — p^/t on May 24 — 10 bushels cost 6s. 6d. 
 Weight of grass when mown. 3 tons IG cwt. 
 Weight when made into hay, 1 " 15 " 
 
 3, No Manure . 
 
 Weight of grass when mown, 3 tons 12 cwt. 
 
 Weight when made into hay, 1 " 6 " 
 
 ;o 00 CQ to o I 
 
 ot-h O O O O I 
 
 y >^ 
 
 4. Nitrate of Soda — fvt on May 24 — 4 stones 
 
 cost \\s. 
 
 Weight of grass when mown, 4 tons 10 cwt. 
 Weight when made into hay, I " 12 " 
 
 Sulphate of Soda (in crystals) — put on May 
 24 — 4 stones cost 10s. 
 Weight of grass when mown, 3 tons 3 cwt. 
 Weight when made into hay, 1 " f) " 
 
 Sulphuric Add— ^ put on May 26, ^ p^tt on 
 June 7, A put on June 1 1 — l6lbs: cost 5s. 
 
 Weight of grass when mown, 3 tons 4 cwt. 
 
 Weight when made into hay, 1 " 6 " 
 
 ;i5 
 
 
 CQ CO O ?£ O -O 
 kO lO CO T^ T^ 1^3 
 
 •g C? O rf 00 CQ CQ 
 
 oCCCC CO CTC^ CQ 
 
 soo C^ O O OC "* 
 
 gl— I I-H 
 
 ct^ Jr-cTs o en t^ 
 
 S Cl- 
 ef ca 
 
 W OT K OT CC 
 CO CO I?} O O I 
 rH ,-1 CI CN II 
 
 CO O OQ c^ o 
 
 Ol ^ — CO 
 
 C CO ii • 
 
 C/2 t^ <q CD 
 
 U-. <=> O B 
 
 C OL^'5 3 ° 
 
 03 
 
 c 
 o 
 
 S 
 
 N. B. The cost of the manure does not include the expense of laying it on. 
 
No. IIL] RESULTS OP EXPERIMENTS ON PRACTICAL AGRICULTURE. 15 
 
 Mr. Turner, his lord&liip's agent, thus writes : — 
 
 " The plan I followed in putting on the different manures, and the quantities 
 used, accorded as nearly as 1 could manage it, with the directions given in your 
 published lectures. 
 
 " The field on which the experiments were tried is situate in a high, bleak 
 climate, and consists of a thin light soil, upon a bad subsoil of barren clay 
 resting upon limestone. It had been completely exhausted by a succession of 
 white crops, and was full of weeds and quickens. I had it well ploughed, and 
 took a crop of drilled turnips fairly, but not extravagantly, manured. The crop 
 was a poor one. I ploughed the Land as soon as the turnips could be got off. 
 Drained it ; and in the spring worked it very fine. The following August I 
 sowed it away with grass seeds without a crop. The seeds came up beautiful- 
 ly, and were the admiration of all who saw them, keeping a deep green through 
 the winter, and beginning to grow early in the spring; and it was on this crop 
 that the experiment was tried early in the succeeding summer. 
 
 " I need scarcely remark, that the crop of grass for such land was enormous, 
 and has fully repaid the money expended upon it, with the exception of drain- 
 ing, and in two or three years I have no doubt but it will repay this also." 
 
 Remarks. — On compai'ing the effect of these several top-dressings as indi- 
 cated by the results above stated, tlie reader will be struck with the extraordi- 
 nary increase caused by the addition of common salt. 1 have in the text 
 (Lecture IX., p. 190,) indicated a principle which may serve to explain in some 
 measure both the localities in which the use of common salt may be expected 
 to be beneficial, and the reason why in many parts of our island the employ- 
 ment of this substance has not been attended by any large measure of success. 
 The position of the land experimented upon by Mr. Turner, is such as to lead 
 us to expect it to be improved by common salt, according to the views there 
 stated. 
 
 The nitrate of soda produced less effect than either the common salt or the 
 soot, but it gave an increase which was double of that yielded by the sulphate 
 of soda. The latter salt, however, was. applied in the state of crystals, which 
 contain 53 per cent, of water, so that less than one half of that weight of drij 
 salt was used, which was recommended in the suggestions I offered for the 
 employment of this substance in practical agriculture. At the same time, the 
 price paid by Mr. Turner for this salt was four times as great as it ought to 
 have been. Any c[uantity of the rfrT/ sulphate of soda may be procured at lOs. 
 a cwt., at which price it is forvv^arded in casks to all parts of the country by 
 Messrs. Allan & Co., Heworth Alkali Works, Newcastle. 
 
 The most valuable practical suggestion to be derived from these experiments 
 is certainly this — that a liberal use of common salt is likely to increase in a great 
 degree the produce of grass in the locality where they were made, and on the 
 same kind of soil. This valuable discovery will far more than repay the ex- 
 pense and trouble of the entire series of experiments. INo application can be 
 so cheap as this, so long as tt succeeds. At the same time a mixture of the other 
 substances — the nitrate and the sulphate, which were partially successful — might 
 possibly prove still more efiicacious on the grass, and might be expected even 
 to ameliorate the condition of the land for the further production of white crops. 
 In a future part of this Appendix I intend to offer some suggestions in regard to 
 the kind and quantify of the ingredients which may, with probable advantage, 
 enter into the constitution of these viixed, rtiannrcs. 
 
 I have calculated and introduced into Mr. Turner's table an additional col- 
 ' umn, exhibiting the weight of hay yielded by 100 lbs. of grass, with the view 
 of showing the relative succulence of the several crops when cut. As a gen- 
 eral rule, the weight of dry hay does not exceed one-fourth of the weight of the 
 grass when cut. In the experiments of Mr. Turner, however, the weight of 
 hay in every case was much beyond this quantity — the most succulent crop, 
 that to which no dressing was applied, yielding 36 per cent, of hay. This gen- 
 27* 
 
16 RESULTS OP EXPERIMENTS ON PRACTICAL AGRICULTURE. [Appendix, 
 
 eral result may have been partly due to the state of- ripeness in which all the 
 grasses were cut, while the greater produce of hay from the dressed portions 
 may indicate the relative ripeness, and therefore dryness, of each when cut down. 
 It is evident, therefore, that the relative values of crops of grass or clover are 
 not to be judged of by the several weights when green, but by the weights of 
 the diy hay. This is further confirmed by the results of an experiment with 
 nitrate of soda, communicated to me by Mr. Carmthers, of Warmonbie, near 
 Annan, in which the relative weights of hay obtained vvei-e muck riiore in favour 
 of the use of the nitrate than the several weights of gi'ass yielded by the dressed 
 and undressed portions of the field. On the contrary, from a field on Oliver 
 Farm, near Richmond, Mr. Sivers informs me, that the weight of hay was viuch 
 kss in favour"*- of the use of the nitrate of soda than the relative weights of 
 grass. In all cases, therefore, the weight of the dry crops obtained by different 
 methods should be compared with each other, as the safest test of the relative 
 merits of the several modes of procedure by which they have respectively been 
 raised. 
 
 II. Experiments made at Erskine, on the property of Lord Blantyre. 
 
 I insert the clear and well-digested statement of his Lordship's agent without 
 alteration: — 
 
 " Freeland, Ersliirie, by Old KUpairid\ Glasgovj, 29 fh July, 1841. 
 
 " Sir — Agreeably to Lord Blantyre's instructions I send you a copy of the re- 
 sults of some experiments with manures on young gx-ass for hay, undertaJcen 
 on two separate pieces of land — the one a very good light soil (subsoil gi-avel) ; 
 the other stiff clay soil with a clay subsoil. The manures were applied on 1st 
 May, the hay cut on the 1st and weighed on the 19th July current; the extent 
 of each plot one-twentieth of an imperial acre. From the small extent of each plot 
 it will be evident that the results cannot be exactly depended on, farther than as 
 a general result ; because in so small a portion of land the least variation in the 
 soil or crop naturally will affect the results very materially ; still, on the whole, 
 I am of opinion that the experiment gives the compaj'ative view of the value of 
 the different manures used pretty nearly. 
 
 " One thing has astonished us with regard to soda (nitrate). On all the fields 
 I have observed it sown on, the part dressed has a much greater vigour of after- 
 math than where no nitrate of soda was given: showing that this manure is not 
 so evanescent as was generally supposed. 
 
 " I am, Sir, your most obedient servant, 
 
 " Jas. Wilson," 
 
 Experirttentsrwith Manures as a top-dreBsing for Hay, at ErsJcine, 1841. 
 
 Remarks. — It will be observed in these experiments, that the saltpetre and 
 nitrate of soda produced neojly an equal increase on botlr kinds of soil, the ni- 
 trate of soda having the greater effect on the light, the nitrate of potash on the 
 heavy soil. Next to these on the light soil are the common salt and sulphate of 
 soda, though on the heavy soil the common salt had the better effect of the two. 
 It is to be observed, however, that in Uiis case the sulphate was used in ciystals, 
 and therefore only in half the quantity reconiuiended. Had twice the quantity 
 been employed upon the ligkt soil the produce might have equalled that from the 
 nitrates. 
 
 It is a singular illustration, however, of the necessity of applying different 
 substances to chfferent soils— that so far as this experiment is to be depended 
 upon, the sulphate of soda almost entirely failed on the heavy land. 
 
 The most valuable practical deduction from these experiments also, is, that 
 on both the soils in question, the grass land, in its present condition, may be salted 
 to advantage. At the same time, it appears probable that on the light soil the 
 increased produce would amply repay the cost of applying either niti'ate or sul- 
 
 ' In Mr. Sivers' experiments, 100 square yards, nitrated, gave 68 stones of hay, unnitrated 
 52 stones, but when dry they were reduced to 12 stones each. How very much more suc- 
 culent these grasses were than those of Mr. Turner ! 
 
No. Ill] 
 
 ON MANURE AS A TOP-DRESSING FOR HAT. 
 
 17 
 
 phate of soda at the rate of 120 lbs. per acre — the latter being in its dry or un- 
 
 crystallized state. 
 
 The effect, generally, of all the dressings is strikingly greater on the light 
 soil — a fact which speaks strongly in favour of the adoption of any of those 
 methods by which the openness and friability of the land has been found to be 
 permanently promoted. On the stiff soil, even the ammonia, by some deemed 
 so vitally necessary to vegetation, appears to have produced iio sensible alter- 
 ation. 
 
 j 
 
 ^ 
 
 0^ . 
 
 
 
 
 
 1 
 
 ,;. Manures used, and quantities applied, to 
 
 Ml» 
 
 
 Total produce 
 
 Total additionall 
 
 o 
 
 each plot of l-20th of an aore. 
 
 •ss 
 
 b"s 
 
 
 per 
 
 weight per 
 
 Oi 
 
 
 ~ 
 
 271 
 
 £^ 
 
 Imperial Acre. 
 
 Imperial Acre. 
 
 1 
 
 Exp. I. Good light soil, subsoil gravel. 
 
 1 lb. sulphuric acid, diluted in 47 ) 
 galls, water . . . ) 
 
 44 
 
 ts. 
 2 
 
 cwt. 
 8 
 
 qrs. lbs. 
 1 16 
 
 ts. cwt. 
 
 - 7 
 
 qrs. lbs. 
 3 12 
 
 2 
 
 6 lbs. saltpetre (nitrate of potash) 
 
 322 
 
 95 
 
 2 17 
 
 2 
 
 - 16 
 
 3 24 
 
 3 
 
 6 lbs. nitrate of soda . 
 
 339 
 
 112 
 
 3 
 
 
 
 2 4 
 
 1 
 
 
 
 4 
 
 Gibs, sulphate of soda (in crystals) 
 
 292 
 
 65 
 
 2 
 
 12 
 
 16 
 
 - 11 
 
 2 12 
 
 5 
 
 17 lbs. gypsum 
 
 254 
 
 27 
 
 2 
 
 5 
 
 1 12 
 
 - 4 
 
 3 8 
 
 6 
 
 1 bush, wood charcoal (pounded) 
 
 277 
 
 50 
 
 2 
 
 9 
 
 1 24 
 
 - 8 
 
 3 20 
 
 7 
 
 i bush, common salt, 25 galls, water 
 
 294 
 
 67 
 
 2 
 
 12 
 
 2 
 
 - 11 
 
 3 24 
 
 8 
 
 1 gal. ammoniacal liquor, 47 gls. water 
 
 277 
 
 50 
 
 2 
 
 9 
 
 1 24 
 
 - 8 
 
 3 20 
 
 9 No application .... 
 
 227 
 
 — 
 
 2 
 
 
 
 2 4 
 
 - - 
 
 - - 
 
 1 Exp. II. Clay soil, subsoil day. 
 
 
 
 
 
 
 
 
 1 
 
 1 lb. sulphuric acid, diluted in 47 } 
 galls, water . . . ) 
 
 256 
 
 26 
 
 2 
 
 5 
 
 2 21 
 
 - 4 
 
 2 16 
 
 o 
 
 6 lbs. saltpetre (nitrate of potash) 
 
 286 
 
 56 
 
 2 
 
 11 
 
 8 
 
 - 10 
 
 
 
 3 
 
 G lbs. nitrate of soda . 
 
 282 
 
 52 
 
 1 
 
 10 
 
 1 12 
 
 - 9 
 
 1 4 
 
 4 
 
 6 lbs. sulphate of soda (in crystals) 
 
 232 
 
 2 
 
 2 
 
 1 
 
 1 20 
 
 - 
 
 1 12 
 
 5 
 
 nibs, gypsum .... 
 
 240 
 
 10 
 
 2 
 
 2 
 
 3 12 
 
 - 1 
 
 3 4 
 
 G 
 
 1 bush, wood charcoal (pounded) 
 
 257 
 
 27 
 
 2 
 
 5 
 
 3 16 
 
 - 4 
 
 3 8 
 
 7 
 
 i bush, common salt, 25 galls, water 
 
 269 
 
 39 
 
 2 
 
 8 
 
 4 
 
 - 6 
 
 3 24 
 
 8 
 
 1 gal. ammoniacal liquor, 47 gls. water 
 
 201 
 
 — 
 
 1 
 
 15 
 
 3 16 
 
 — — 
 
 - — 
 
 9 
 
 No application .... 
 
 230 
 
 — 
 
 2 
 
 1 
 
 8 
 
 - - 
 
 - - 
 
 The Dressings were applied 1st May, the Grass cut 1st July, and the Hay 
 weighed 19th July. 
 
 III. Expeinments made under the immediate superintendence of W. Fleming, 
 Esq., of Barochan, near Paisley, and on his own property. The statement is 
 drawn up by Mr. Fleming himself 
 
 1, — Experiments on Hay with Nitrate and Sulphate of Soda and with Gypsum^ 
 
 
 
 Description of 
 
 Rate per 
 
 Weight per 
 
 Weight 
 
 No. 
 
 Field. 
 
 Dressins. 
 
 imp. Rood 
 
 Rood, green. 
 
 when stack'd 
 
 1 
 
 Covenlea. 
 
 Nothing. 
 
 
 3361 lbs. 
 
 1120 lbs. 
 
 2 
 
 Do. 
 
 Nitrate of Soda. 
 
 40 lbs. 
 
 4907 " 
 
 1636 " 
 
 3 
 
 Do. 
 
 Sulphate of Soda. 
 
 40 lbs. 
 
 3966 " 
 
 1322 " 
 
 4 
 
 Do. 
 
 Gypsum. 
 
 10 lbs. 
 
 3831 " 
 
 1277 " 
 
 1 
 
 Crook's High 
 
 Nothing. 
 
 — 
 
 4436 " 
 
 1.478 ." 
 
 2 
 
 Do. 
 
 Nitrate of Soda, 
 
 40 lbs. 
 
 4999 " 
 
 1666 " 
 
 1 
 
 Crook's Low. 
 
 Nothing. 
 
 — 
 
 2185 " 
 
 728 " 
 
 2 
 
 Do. 
 
 Nitrate of Soda. 
 
 40 lbs. 
 
 3764 " 
 
 1254 « 
 
 3 
 
 Do. 
 
 Gypsum. 
 
 80 lbs. 
 
 3110 « 
 
 1036 " 
 
18 
 
 EXPERIMENTS ON WINTER RYE. 
 
 [Appendix, 
 
 Character of the Soil — Nos. 1, 2, 3, and 4 were good sharp soil, on rotteu 
 rock, (decayed trap,) all as near as possible the same description of land, 
 drained, and lying together. Nos. 1 and 2, Crook's High, stiflF clay, drained; 
 the hay was after wheat. Nos. 1, 2, and 3, Crook's Low, light clay-loam, 
 drained ; the hay was after barley. 
 
 On Covenlea the dressings were applied on the 22nd of April, and the hay cut 
 on the 2nd of July ; on the other fields the nitrate and gypsum were applied on 
 the 12th of April, and the hay cut on the 9th of July. 
 
 N. B. The above is the average of tx'ials in three parts of the Covenlea field; 
 a small portion of moss was also sown with nitrate of soda, in the low part of 
 the same field, but no benefit was observable, beyond the usual dark green 
 colour which appeared about ten days after the application. The sulphate of 
 soda, although evidently beneficial, does not produce the dark green colour. -In 
 the Crook's fields the effect of nitrate of soda in producing the dark green colour 
 was as remarkable as in the Covenlea field. The gypsum on both fields seems 
 to have had a good effect, particularly on the aftermath clover. 
 
 - Remarks. — In these experiments also the sulphate of soda was used in only 
 half the quantity recommended. By referring to the prices paid by Mr. Fleming, 
 it will appear that the use of sulphate of soda gave an increase of 200 lbs. of 
 hay for Is. 9d. (or 500 lbs. for 4s. 5d.), while the nitrate of soda gave an increase 
 of 516 lbs. for 7s. lOd. ; so that, though the actual increase of hay per rood was 
 considerably less by the use of the sulphate, yet that increase was obtained at 
 little more than half the cost of the same weight of increase derived from the ni- 
 trate. A similar remark applies to the gypsum, so that these experiments give 
 ample encouragement for the application of both these substances in somewhat 
 large quantity to succeeding crops, on the same land. 
 
 2. — Experiments 071 Winter Rije, dressed with Nitrate of Soda, Lime inth Potash, 
 Sulphate of Soda, and Muriate of Avimonia {Sal Ammoniac.^ 
 
 
 
 
 Rate per 
 
 Weight of 
 
 Weight of 
 
 Bushels 
 
 No. 
 
 Field. 
 
 Description of 
 
 rood 
 
 Grain. 
 
 Straw 
 
 per 
 
 
 
 Dressing. 
 
 imperial. 
 
 per rood. 
 
 per rood. 
 
 rood. 
 
 1 
 
 Garden Plot. 
 
 Nothing. 
 
 
 
 160 lbs. 
 
 1024 lbs. 
 
 3i 
 
 2 
 
 Do. 
 
 Nitrate of Soda. 
 
 40 lbs. 
 
 336 " 
 
 1664 " 
 
 6i 
 
 3 
 
 Do. 
 
 Lime and Potash. 
 
 40 " 
 
 272 " 
 
 1344 " 
 
 5i 
 
 4 
 
 Do. 
 
 Sulphate of Soda. 
 
 40 " 
 
 224 " 
 
 1152 '' 
 
 4i 
 
 5 
 
 Do. 
 
 Mur. of Ammonia 
 
 5 " 
 
 232 " 
 
 1216 " 
 
 4f 
 
 Character of the Soil. — Tilly clay, which had been trenched, and in potatoes 
 the year before. The Rye was sown on their being lifted in October, 1840. 
 
 The applications were made on the 14th of April, the grain was cut on the 
 9th of August, and thrashed on the 25th. 
 
 N. B, As early as the end of April the effects of the nitrate of soda were very 
 apparent from the dark green colour produced, and broad leaves, and after it was 
 ripe the heads were longer than any of the others ; but it was so strong that it 
 was laid a month before it was cut ; none of the others were laid. Every ap- 
 plication seems to have done good, by increasing the produce. The pT)tash and 
 lime was made by slaking quick-lime and sand with a solution of potash, and 
 allowing them to lie together for a month. As much was used as contained 1 
 lb. of carbonate of potash to the pole. 
 
 Remarks. — From these experiments, it appears that, besides the proportionate 
 increase of straw, that of grain was 
 
 From nitrate of soda, 
 " lime and potash, 
 " sulphate of soda, 
 " sal-ammoniac, 
 
 12 bushels for 31s, Od., or 2s. 9d. per bush. ; 
 7 " for 33s. 6d., or 4s. 9d. " 
 3 " for 7s, Od., or 2s. 4d. « 
 5 «' for lOs. 9d., or 2s. 2d. " 
 
1^0. Ill] 
 
 EXPERIMENTS ON WHEAT FIELD. 
 
 19 
 
 Although, therefore, the total increase by the employment of sulphate of soda 
 and muriate of ammonia, in the proportions actually put on, was not so gi-eat as 
 by the use of the other two dressings, yet this increase was obtained at a con- 
 siderably less cost per bushel. The lime and potash, thovigh producing an im- 
 portant effect, will probably not yield a remunerating return wjtli this crop on 
 this soil, while the results hold out a fair inducement for the trial of the last two 
 dressings in larger and varied proportions. 
 
 The five samples weighed respectively, — 4.5 3-5, 513-4, 514-5, 52 3-5, and 
 48 4-5 lbs. per bushel, so that, while on all the dressed plots tlie gnun was 
 heavier than on the undressed, that which was dressed with sulphate of soda 
 was considerably the heaviest. 
 
 3. — Experiments on Wheat field, Crook's (crop, 1841.) 
 
 No. 
 
 1 
 
 2 
 
 3 
 4 
 5 
 
 6 
 
 7 
 
 Description 
 of Top-dressing. 
 
 Nitrate of Soda. 
 
 Potash 
 
 and Lime. 
 
 Common Salt. 
 
 Mur. Ammonia, 
 
 Nitrate of Soda 
 
 and Gypsum. 
 
 Nitrate of Soda 
 
 and Rape-dust. 
 
 Mur. Ammonia 
 
 and Lime. 
 Common Salt 
 and Lime. 
 Nothins:. 
 
 Rate per 
 Scotch acre. 
 
 .1 
 
 IGO lbs. 
 
 160 lbs. 
 40 bush 
 
 160 lbs. 
 20 lbs. 
 80 lbs. ) 
 
 160 bush. S 
 80 lbs. ) 
 5 cwt. \ 
 20 lbs. \ 
 40 bush, f 
 28 lbs. ) 
 80 bush. ( 
 
 Weight of Weight 
 
 produce of 
 
 Grain of 
 
 jeth acre. 
 
 of 
 
 Grain 
 
 pr. bshl. 
 
 209 lbs. 63 lbs. 
 
 210 " 02 " 
 
 249 
 
 208 
 
 214 
 
 240 
 
 230 
 
 200 
 190 
 
 62 ' 
 62 ' 
 
 62 ' 
 62i' 
 
 63 ' 
 
 63r 
 61 ' 
 
 Weight of to- 
 tal produce, 
 when cut, of 
 >i; til an acre. 
 
 9,500 lbs. 
 
 8,930 " 
 
 12,.540 " 
 
 8,300 " 
 
 8,620 " 
 
 11,970 " 
 
 9,500 " 
 
 8,740 " 
 8,050 " 
 
 Character of the Soil— The land was a heavy loam, and of as nearly as pos- 
 sible the same quality. It had been in potatoes, and the wheat was sown when 
 they were lifted in October, 1840. 
 
 The applications were all made on the 13th of April, and the crop was reaped 
 on the 2d of September. 
 
 The produce of ith of a Scotch acre, thrashed and weighed and well cleaned, 
 gave an average of from 32 to 33 bushels of 61 lbs. each per Scotch acre of grain. 
 
 Remarks. — This table presents us with two remarkaWe results, — that ob- 
 tained by the use of common salt, and that from a mixture of soda and rape- 
 dust. Thus, exclusive of the straw, — 
 
 Nitrate of soda alone gave 152 lbs. of wheat for 31s., or 12s. 2d. per bushel ; 
 
 Nitrate with rape-dust gave 400 lbs. of wheat for 43s. 6d., or 6s. 9d. per bushel ; 
 
 Common salt gave 472 lbs. of wheat for 3s. 6d., or 6d. per bushel. 
 
 The increased produce, by the use of common salt, is by far the most valua- 
 ble result to Mr. Fleming in an economical point of view, and plainly indicates 
 the kind of application he can most profitably make— to his wheat crops at least— 
 on land similar to the above, and in the district where he resides. 
 
 Neither the nitrate of soda nor the mixture of this salt with rape-dust, gave 
 such an increase as to repay their own cost, unless when corn is very high. It 
 is interesting, however, to observe that the mixture with rape-dust gave so large 
 an increase, though the value of tliis particular experiment is lessened by the ab- 
 sence of any trial with rape-dust alone, by which the effect of each of the ingre- 
 dients ought to be judged of I have reckoned the rape-dust at £1 a ton, so that 
 5 cwt. would cost 28.S., and we know tliat a top-dressing of this substance alone, 
 in a somewhat larger quantity, gives a remunerating return in many of our wheat 
 lands. 
 
90 
 
 EXPERIMENTS ON EARLY POTATOES. 
 
 [AppendiZf 
 
 Mr. Outhwaite, of Banesse, in the North Riding of Yorkshire, a skilful and 
 enterprising practical farmer, who has for some years been using rape-dust over 
 a great breadth of his wheat crop, has favoured me with the result of one of his 
 more accurate trials on spring wheat, made during the past season. The wheat 
 was sown after turnips taken off in April, and part of the field was dressed with 
 rape-dust at the rate of 5| cwt. (or at £l a ton, of 40s.) per acre. The produce 
 of the dusted portion was 39 bushels, and of the undusted 29 bushels per acre, 
 and the increase of straw was one-fifth of the whole. Both samples were of 
 equal weight, and sold at the same price, — 8s. 3d. per bushel. In this experi- 
 ment the increased 10 bushels cost 40s., or 4s. per bushel, giving, on a large 
 breadth of land, a handsome remuneration. 
 
 These results will, I trust, encourage others to make trials similar to those of 
 Mr. Fleming and Mr. Outhwaite ; while these gentlemen will, doubtless, be in- 
 duced each to try that application which has succeeded so well in the other's 
 hands. It might be useful as well as interesting to compare the produce of four 
 plots arranged and dressed as follows : — 
 
 Common Salt. 
 
 Rape- dust. 
 
 Common Salt 
 and Rape-dust. 
 
 Nothing. 
 
 4. — Experiments on Early Potatoes, 1841. 
 All were dunged in the usual manner with farm-yard manure, at the rate of 
 about 30 cubic yards per acre. The potatoes were all planted on the 25th of 
 Maixh, on the same heavy black soil. The several dressings were applied on 
 the 20th of May, and the potatoes were all lifted on the 28th of September. 
 
 Description 
 
 of 
 Top-dressing. 
 
 Rate 
 per imp. 
 
 Nothing. 
 Nitrate of Soda. 1 GO lbs. 
 Sulphate of Soda. i2(K) " 
 Do.&;Nitr.ofSoda200 " 
 
 Produce 
 per imp. 
 
 6fi bolls. 
 80 " 
 73 " 
 107 " 
 
 Weight of 
 
 Produce of 
 
 18 yards (iriU. 
 
 77 lbs. 
 93 " 
 86 " 
 124 '' 
 
 Nolrj.—The 
 peck is 35 lbs. 
 weight, and 16 
 make a boll 
 or 5 cwt. 
 
 This break of ground consists of a piece of poor clay mixed with moss, about 
 9 inches deep ; subsoil a very stiff blue till. The dung was old from the farm-yard, 
 about the ordinary quantity (30 cubic yards per acre) spread upon the land, and 
 dug in. Thej)otatoes were drilled in with the hoe; as the ground was wet the 
 plants came up but weak. The nitrate of soda was sown before the other top- 
 dressings, and had temarkably quick effect, as it showed the third night after 
 being sown. The sulphate of soda does not occasion the dark green colour 
 which is seen upon the potatoes after the dressing of the nitrate, but there is not 
 the smallest doubt of its beneficial effects, although not in so great a degree as 
 the nitrate. The mixture, which is composed of fds of sulphate of soda and |d 
 of nitrate, has a wonderful effect in strengthening the growth (which it keeps 
 longer than with nitrate alone), and the mixture has the same effect in producing 
 the dark green colour as the nitrate alone. 
 
 Remarks. — That a mixture of substances is likely to be more efficacious as a 
 dressing, than the application of one substance alone, except in peculiar circum- 
 stances, is consistent not only with long practical experience — for how many 
 substances are mixed together in ferm-yard manure 1 — but also with the theore- 
 tical principles laid down in the text. [See Lectures IX. and X.] These experi- 
 ments upon potatoes show that this crop upon Mr. Fleming's land was benefitted 
 by both nitrate and sulphate of soda, but in a vastly greater degree by a mixture 
 of the two. And I might consider my suggestion in regard to the employment 
 of sulphate of soda as a manure, to have been of no mean use in practical agri- 
 culture, had it led to nothing else than to this happy mixture of Mr. Fleming. 
 
 I have received also from Mr. Fleming's gardener'(Mr. Alexander Gai"diner) 
 
No. III.] EXPERIMENTS ON EARLY POTATOES. 31 
 
 a very well digested and well drawn up paper, detailing numerous experiments 
 made by himself during the past summer. Among these is one upon the use of 
 this same mixture upon thepotatoe crop, which I shall quote in his own words: 
 
 " April 26th. — Planted potatoes of the red Don variety, soil a mellow loam 
 two feet deep, subsoil yellow till. Farm-yard dung was trenched in some days 
 before planting, at the rate of 40 cubic yards per acre ; sets drilled in with the 
 hoe. Plants came up very regular, and were top-dressed with a mixture of § 
 sulphate and ^ nitrate of soda on June 2nd, at the rate of 2 cwt. per acre. They 
 grew very strong after this application. Stevis six or seven feet in kngtk, dark 
 gi'een, and the produce, when lifted in October, was 16 Renfrewshire pecks of 35 
 lbs. each per Scotch fall of potatoes fit for market." 
 
 This produce is equal, 1 believe, to about 26 tons per Scotch, or 21 tons per 
 imperial acre, about equal to that of Mr. Fleming with the same mixture. And 
 what an amazing luxuriance of vegetation, to yield at once stems seven feet in 
 length and upwards of 20 tons of tubers per acre ! 
 
 Those who are the most sceptical in regard to the benefits to be derived from 
 agricultural experiments, when well conducted, will scarcely question the impor- 
 tance of this result — the most backward in making experiments will be anxious 
 to repeat this upon his oum potatoes. The cost of the mixture to be applied in 
 the quantity used by Mr. Fleming is as follows : — 
 
 s. d. 
 
 c< 1 u t CQ} A S 75 lbs. rZr?/ at 10s. per cwt, or ^ a n 
 Sulphate of Soda <,rAii • , i »x i ^ 9 
 
 ^ { 150 lbs. in crystals at 5s, . J 
 
 Nitrate of Soda . . 75 lbs. at 22s 14 9 
 
 21 6 
 
 The return for this 21s. 6d. was in each of the above cases upwards of 8 tons 
 of potatoes, 
 
 I may here mention also two other interesting experiments of Mr, Gardiner, 
 in which he tried the effect of sal-ammoniac upon his potatoe crop, — 
 
 1°. In the one he mixed sal-ammoniac, previously dissolved in water, in the 
 proportion of 1 lb. to each cubic yard of a compost formed from the refuse of the 
 garden, and planted eai-ly potatoes with it at the rate of 35 cubic yards per acre. 
 The produce was one-sixth more than when no ammonia was used. The va- 
 riety of potatoe was Taylor's forty-fold, the soil moss and clay. The cost of 
 this application was 19s. per acre. 
 
 2^. Sal-ammoniac, dissolved in water, was sprinkled on moss or peat earth, 
 at the rate of 20 lbs. to a ton of earth, and, after strewing a little lime at the bot- 
 tom of the drills, this mixture was put in at the rate of 2 tons per acre. The po- 
 tatoes were 14 days later in coming through the ground than the same variety 
 planted with farm-yard manure. They were strong in the stem, of a dark green 
 colour, and equal, in point of produce, to the others. The variety of potatoe 
 was the Irish apple, the soil a veiy light brown loam, of that description locally 
 named deaf. 
 
 I may observe on this latter experiment, that the application is not so simple 
 as it appears. The lime would decompose the sal-ammoniac, and form chloride 
 of calciuvi, while ammonia would be liberated. The effect, therefore, may be 
 partially due to both. It will be recollected that in a previous part of this Ap- 
 pendix I suggested the trial of this chloride of calcium as a top-dressing for va- 
 rious crops. 
 
 5. — Experiments on Moss Oats, soimi about \sl May, 1841, top-dressed 25th June. 
 " These top-dressings were applied on the 5th of June, and by the 24th there 
 was a striking improvement, especially on No. 2 and No. 7. It was quite visi- 
 ble in gi-eater strength and evenness of crop. One or two of the others also 
 showed improvement, but not so visibly as to merit particular notice, I exam- 
 ined them from time to time, and at different dates : the appearances much the 
 same as noticed upon June 24th. I again examined them a few days before 
 
^ 
 
 EXPERIMENTS ON OATS. 
 
 [Appendix, 
 
 they were cut, when I was much satisfied with No. 2; the straw appeared to me 
 as stiff and shining, and the ear as well filled, as if it had been grown upon stiff 
 loam, and 1 consider the same dressing, applied lo grain crops upon moss, will in- 
 sure a good crop of ivell-fdled oats. No. 7 was nearly as good, but the want of the 
 bones being dissolved was a drawback. However, I consider the two merit 
 the expense of another trial." 
 
 No. 
 
 Top-dressing per pole (imperial). 
 
 Nothing. 
 
 Bones dissolved in sulphuric acid and nitrate of soda | lb, 
 
 Sulphate of soda \ lb., bone dust \ peck. 
 
 Potash 1 lb., lime and bone dust \ peck. 
 
 Chloride of calcium 1 lb., bones \ peck. 
 
 Lime, potash, and chloride of calcium, \ lb. each. 
 
 Potash and lime, nitrate, and bones, \ lb. each. 
 
 Cliaracter of the Soil. — Moss 4 feet to clay. No. 2 the best crop and heaviest 
 grain (not thrashed). Nos. 3, 4, and 5 not so good as No. 2, but all much 
 better than Nos. 1 or G. No. 6 the worst — not better than No. 1. No. 7 very 
 good — next to No, 2, 
 
 Rkmarks. — These experiments of Mr. Fleming on moss oats may be con- 
 sidered as affording another illustration of the benefits which are yet to accrue 
 to practical agriculture from the suggestions of natural science. It is well known 
 to those who have directed their attention to the reclaiming of peat lands, that 
 the crops of oats raised on such land yield abundance of straw, but that the ear 
 is small and badly filled. It is also well known that claying such lands is an al- 
 most unfailing remedy for this defect in the ear, as well as for the less important 
 one which is also observed in the straw. My friend, Mr. Alexander, of South 
 Bar, a neighbour of Mr. Fleming, and, like him, extensively engaged in the im- 
 provement of peat lands, finding, as most other persons have, that in some lo- 
 calities the claying of his land was very expensive,* conceived the idea that 
 some chemical application might be made to this soil, which would supply 
 what the defective oat plants required, and thus supersede the necessity of 
 claying. He was pleased to communicate this opinion to me — stating the de- 
 fect in the crop, and asking a chemical remedy. Looking chiefly to what was 
 evidently required by the ear, I suggested a trial of various mixtures, in all of 
 which, — from an idea that phosphates, among other substances, might be ne- 
 cessary to convplete the eai:, — bone-dust formed a necessary part. The result of 
 these suggestions is seen in the above experiments of Mr. Fleming. They have 
 been varied and improved upon, as Mr. Fleming's united chemical knowledge 
 and practical skill enabled him to do, and as first results on a new field of re- 
 search, Nos. 2 and 7 may be considered as highly encouraging, if not, indeed, 
 eminently successful. Too much confidence, however, must not be placed on 
 the effects observed in one or two instances; yet I hope those above stated are 
 such as will induce others to repeat the experiments with equal care, in order 
 that another year, affording us more numerous results, may enable us to base 
 our conclusions upon a larger experience. 
 
 6. — Experiments upon Oats top-dressed with Sulphate and Nitrate of Soda (lower 
 
 end of Barn Park.) 
 "The first was sown on the 11th May, viz., 3 ridges with sulphate of soda, 
 at the rate of 1^ cwt. per acre. This was examined from time to time, but there 
 
 * Mr. Garden, of Glenae House, near Dumfries, a gcnlleman to wliom, though personally 
 unknown, I am indebted for many valuable communications, informs me that, in improving 
 his porous peat lands, lie has found it necessary to lay on a coaling of'clay six inches thicic, 
 at an e.xpeiise of j615 an acre. A coating of two or three inches on their peat, he says, sinks 
 down, and in a few years descends beyond the reach of the plough, and hence it] is more 
 economical to lay on at once an entire soil of six inches. 
 
; -. ///,] EFFECTS OF SULPHATE AND NITRATE OF SODA. 23 
 
 appeared to be little, if any, difference from the general crop (it has not yet been 
 thrashed.) Next, 3 ridges were sown with nitrate of soda, at the rate of 80 lbs. 
 per acre. This made a little alteration both in colour and strengtli, but it was 
 too little to make a very decided difference. Also, alongside of the last-men- 
 tioned, a piece was dressed with a mixture of suiphate and nitrate of soda, in the 
 proportion of frds of the former to ^rd of the latter. This immediately took the 
 lead of the others both in colour and strength, so much so, that by May 27th it 
 could be seen from a distance. Many examinations were made of them all 
 during the season, and this always appeared the best. A few days before it was 
 cut, it showed the largest and best filled ear. There was a piece of yellow-col- 
 oured earth at the bottom of the field, showing the presence of iron, upon which 
 was sown potash and lime. The plant was yellow and sickly-looking, but im- 
 mediately after the application it acquired a d<^i'k green colour, and became vi- 
 gorous, and yielded a crop at least equal to any in the field. There were some 
 other dressings put on other ridges of this field, but it was dry weather directly 
 after they were sown, and the crop was too far forward before they began to take 
 effect to say any thing decided about them. By mistake there were two varie- 
 ties of oats sown upon the field, which prevented the experiments being so de- 
 cided, as the dressings were put on indiscriminately upon the land before it was 
 known." 
 
 Remarks. — The only remark I need make upon these experiments is, to sug- 
 gest to my readers that, by repeating the above trials upon oats with Mr. Flem- 
 ing's mixtures, they may not only benefit their own crops, but may also aid 
 materially in the advancement of practical agricultural knowledge. 
 
 7. — Oil the effect of Sulphate of Soda applied as a top-dressing to Beans and Peas. 
 
 " The first dressing was applied the 4th of. May, on some beans on a border 
 in the garden ; the drills that wei*e dressed quickly took the lead of the others. 
 There was no alteration of colour, but greater strength, and it tillered, wondcr- 
 fvlly. There were five or six stems from every seed sown, and the pods were 
 larger and more numerous, and the beans in the pods a great deal larger than 
 the same variety undressed. It was also put upon some of the ridges of the 
 beans in the field, and with the same effect, and gave a very large crop (not yet 
 thi-ashed.) 
 
 " Upon peas in the garden it appeared to add little, if any thing, to the strength 
 of straw, but those that were dressed had a far greater number of pods, and those 
 better filled', and the peas of a better flavour, and it seems a valuable dressing for 
 all leguminous crops. When sown in the drills along with the peas, it nearly 
 killed every one of them, while the same quantity, put on as a top-dressing to 
 some drills next to them (where the peas were two inches high,) did no injuiy. 
 
 Remark.s. — The testimony of Mr. Fleming to the value of sulphate of soda 
 as a dressing for leguminous crops, is very valuable and satisfactory. We may 
 hope that next year will furnish us with experiments, all the_ results of which 
 shall have been so carefully ascertained, as to enable us to decide upon the eco- 
 nomical value of this sulphate as a manure, by a comparison of the amount of 
 increase in the crop, with the cost of the application. 
 
 8. — On Nitrate of Soda as a top-dressing to Gooseberry and Currant bushes. 
 
 " It was applied April 14th, at about the rate of J cwt. per acre, or \ lb. per 
 bush.* It had the effect, in the course of a week, of producing on the bushes a 
 dark green colour and broader leaves, and the fruit set better and more plentiful- 
 ly, especially on some red currants that had borne little for two years. These 
 set their fruit well, and yielded double their former produce. The dressed bushes 
 kept the lead in strength and vigour all the season, and now, when the undressed 
 bushes. have lost their leaves, the others are quite green." 
 
 9. — " Many experiments were tried in the garden on turnips, by top-dressing 
 with nitrate of soda, but with no perceptible effect. However, the Swedish, and 
 
24 ON EXPERIMENTS WITH GUANO. [AppmdtX 
 
 red-top yellow, in a field of rather stiff soil, were benefitted, the former vieldine 
 i more produce in weight, and the latter ^ more weight. Wm. Fleming 
 
 '' Baroc/ian,2Glh October, iSil." xvi. r^tMiNG. 
 
 <5..SrT''^ •""'"''• "^^''^ ^y ^^'■- Fleming were as follow :-Bone dust, (fine) Is. 9d. per bushel • 
 sulphate of ammonia (in crystals)28s. per cwt. ; potash (very impure) 24s per cwt-sulDhate 
 of «oda (m crystals) 5s. per cwt. ; nitrate of soda hs. ; and sll-ammoLc 60^^ cwt ^^^'^ 
 
 ^ No. IV. 
 
 SUGGESTIONS FOR COMPARATIVE EXPEKIMENTS WITH GUANO 
 AND OTHER MANURES. 
 
 Giiano is the name given in South A merica to the dung of the sea fowl which 
 hover in countless ilocks along the sliores of thr. Pacific.and which, from time 
 immenioria , have deposited tlieir droppings on the rocks and the islands which 
 are met with along the coast o. Peru. 
 
 Besides the fresh white guano which is deposited year by year in these locali- 
 ties, there exist m some spots, large accumulations more or less buried beneath 
 a covering of drifted sand, winch liave been tints buried and partially preserved 
 from an unknown antiquity. This ancient guano is of a brown colour, more or 
 ess dark, and forms layers or heaps of limited extent, but which are said some- 
 tunes to exceed even GO feet in thickness. 
 
 In the time of the Incas this substance" was known and hi^^hly valuedasama- 
 nure.-the country along the coast for a length of 200 leagues was entirely ma- 
 nured by it,--the islands on which it was formed were carefully watch4 and 
 preserved,— and it was declared to be a capital offence to kill any of the sea fowl 
 by winch It was deposited. Ever since that time it has been more or less em- 
 ployed for the same purpose, and much of the culture now practised on this 
 thmy-peopled coast is entirely dependent for its success, if not for its existence 
 on he stores of manure which the sea fowl thus place within reach of those parts 
 ot the country which are susceptible of cultivation. 
 
 In modenr times, however, the access of foreign shipping, and the want of 
 careful protection, have driven away many of the sea fowl, and lessened toa vei-v 
 great degree the production of the recent guano. Thus the countri^ is more de- 
 pendent than in former times on the more ancient deposits, which are now assi- 
 duously sought for, and when discovered beneath the sand, are carefully exca- 
 vated and tran.sported to the sea-ports for sale. 
 
 The dun- of bh-ds of all kinds, when exposed to the air. gradually underffoes 
 decomposition, gives off" ammonia, and acquires a brown 'colour. As this am- 
 monia IS one of the most fertilizing substances it contains, it will be readily un- 
 derstood that the old brown guano is much less valuable as a manure than that 
 which IS recent and white ; hence the care of the ancient Peruvians in collect- 
 ing the fresh, and their comparative neglect of the ancient guano. 
 70 ner'cent''nrrj'' fT^'-'T' \"^^^^'^S'' ^ ^^'S^ ^"'^"tity of it-sometimes 
 pZ I «^ 1 1 '''•^^^r'" "^'f ''^''^''' ^^"'^^' '^ i«' b^^^^"^« the climate of 
 
 Feiu IS so dry and and that in the plains rain scarcely ever falls, that the guano 
 can accumulate as it is found to do. North and south of this line of coast 
 where rains are less unfrequent, such accumulations are not met with, though 
 Uie birds appear equally plentiful, and it may be safely stated that, had the cli- 
 n-ate of Peru been like that of England, the rains would have washed the guano 
 from the rocks almost as rapidly as it was deposited ^ 
 
 Of the brown guano several cargoes have lately been brought to England by 
 
No. IV.] ON EXPERIMENTS WITH GUANO. 25 
 
 an enterprising merchant in Liverpool, and it has been deservedly recommend- 
 ed to the attention of British agricuUurists. It has ah-eady been tried upon va- 
 rious crops, both of huy and corn, upon turnips also, and upon hops, and there 
 can be no doubt whatever that in our climate, as well as in that of Peru, it is 
 fitted to promote vegetation to a very remarkable degree. 
 
 This brown guano varies much in quality, according probably to the degree 
 of exposure to the air to which it lias been subjected, or to its position in the de- 
 posit from which it has been dug. Two different portions, taken at random 
 from the same box, gave me the following very different results : — 
 1°. — Water, salts of ammonia, and organic matter, expelled 
 
 by a red heat, , . . ' . . . . 23-5 per ct. 
 
 Sulphate of soda, . . . . . . . 1-8 " 
 
 Common salt, with a little phosphate of soda, . . 30-3 " 
 Phosphate of lime, with a little phosphate of magnesia 
 
 and carbonate of lime, 44*4 " 
 
 100* 
 
 2°. — Ammonia, — 70 ^ 
 
 Uric acid, =. 08 [^(jq 
 
 Water, carbonic and oxalic acids, &c., expelled [ "**^ P*^"* 
 
 by a red heat, . . . . . =515 J 
 Common salt, with a little sulphate & phosphate of soda, 11-4 " 
 Phosphate of lime, &c 293 " 
 
 100 
 
 According to M. Wiuterfeldt, this brown guano is sold at the ports near 
 which it is oljtained at about 3s. a cwt. It might, therefore, if this be correct, 
 De imported into the country, and sold at loss than lOs. per cwt. The price at 
 present asked, however, is 25s. per cwt., a cost at which it is doubtful if the 
 English agriculturist can afford to use it. 
 
 In any case it seems improbable that the guano can continue to be imported 
 into this country for any length of time. It is absolutely necessary to the cul- 
 tivation of the land in Peru,— and it is also diminishing in quantity, — the first 
 settled government, therefore, which is formed in that country, must prohibit 
 the further exportation of a substance so important to the national interests. It 
 is a matter not unworthy of the attention of chemists, therefore, to consider 
 whether a mixture similar to the guano, and of equal efficacy, cannot be form- 
 ed by art — not only at a cost so reasonable as at once to make the British 
 farmer independent of the importer, — but also in such abundance as at the same 
 time to place so valuable a manure within the reach of all. 
 
 The following mixture contains the several ingredients found in guano in 
 nearly the average proportions ; and I believe it is likely to be at least as effica- 
 cious as the natural guano, for all the crops to which the latter has hitherto been 
 applied in this country : — 
 
 315 lbs. [7 bushels] of bone dust at 2s. 9d. per bushel 
 100 lbs, of sulphate of ammonia,t containing 35 lbs. of ammo- 
 nia at 20s. a cwt , 
 
 5 lbs, of pearl-ash ... .... 
 
 100 lbs. of common salt ....... 
 
 11 lbs. of dry sulphate of soda . , . . . 
 
 531 Ihs. of artificial guaTho cost ..... 2 1 
 
 • The first contained also 8 per cent, and the second Ih per cent, of sand, which has been 
 left out of the true composition of the guano considered as free from sand. 
 
 t Sulphate of ammoaia is now manufactured largely at Glasgow, and may be had for less 
 than 20s, a cwt. 
 
 £. 
 
 s. 
 
 d. 
 
 
 
 19 
 
 
 
 
 
 18 
 
 
 
 
 
 1 
 
 
 
 
 
 2 
 
 
 
 
 
 1 
 
 
 
S6 
 
 ON EXPERIMENTS WITH GUANO. 
 
 [Appendix^ 
 
 The quantity here indicated may be intimately mixed with 100 lbs. of chalk, 
 and will be fully equal in efficacy, I believe, to 4 cwt. of guano, now selling 
 at £5. 
 
 At the same time it is desirable that the relative efficacy both of this mixture 
 (artificial guano), and of the American guano, should be tried by actual experi- 
 ment in comparison with other substances of known value, and which are 
 supposed to act in a way somewhat similar. The substances with which I 
 would suggest that such compai'ative experiments should, in the first place, be 
 made, are farm-yard manure, bone dust, and rape dust, and the following 
 scheme exhibits the proportions in which they may be added to the diffei-ent 
 plots of land on which the experiments are intended to be made : — 
 
 20 tons of 
 farm-yard manure. 
 
 20 bushels of 
 
 bones 
 with ashes. 
 
 6 cwt. of guano, 
 
 mixed with 
 chalk or gypsum. 
 
 ■ 
 
 6 cwt. of 
 
 artificial guano. 
 
 10 tons do. 
 
 with 10 bushels of 
 
 bone dust. 
 
 20 cwt. of 
 rape with ashes. 
 
 10 Ions of farm- 
 yard manure with 
 3 cwt. of guano. 
 
 10 tons of farm-yard 
 manure with 3 cwt. 
 of artificial guano. 
 
 10 tons do. 
 
 wtth 10 cwt. of 
 
 rape dust. 
 
 fo cwt. of 
 
 rape with 3 cwt. 
 
 of guano. 
 
 10 tons do. with 
 2 cwt. of guano. 
 
 10 tons do. with 2 
 
 cwt. of artificial 
 
 guano. 
 
 The practical farmer need not be deterred by the formidable array of experi- 
 ments above suggested. He may try any two or three of them, and his i-esults 
 will be valuable in proportion to the accuracy with which his land is measured 
 and his manures and crops weighed. I have taken 20 tons of farm-yard manure 
 as a standard, though in many highly farmed parts of the country no more than 
 15 tons are usually applied. Twenty bushels of bones are recommended by the 
 Doncaster report, and I have lately found that in the Lothians 1 cwt. of rape 
 dust is considered to replace 1 ton of form-yard manure. This proportion of 
 course will vary with the quality of the latter manure ; but whatever quantity 
 of this latter we take as the standard of comparison, it is easy to adjust the 
 proportions of the other substances accordingly. I have not recommended any 
 trial to be made with more than 6 cwt. of guano, because, where farm-yard 
 manure is valued only at 6s. or 7s. per ton, 5 cwt. of the former would cost as 
 much as 20 tons of the latter.* 
 
 The above experiments are intended to be made with the green crop, and to 
 be continueilrduring an entire rotation :t any pair of them, however, may be 
 tried on single crops, whether of corn or of turnips and potatoes. In this way 
 guano ought also to be tried against nitrate of soda and against bones, upon 
 seeds and upon old grass-lands. The mode in which such experiments may 
 be made will speedily suggest themselves to the intelligent farmer. In all 
 cases tke results should be accurately recorded, and, if possible, published. 
 
 ,^!«^^^" *^'^ paragraph waa written, the price of guano was 25s. a cwt. : it is now (May, 
 1842) reduced to 15s. 
 
 t By this I mean that the effect of these several manures, applied once for all to the green 
 crop at the commencement of the rotation, should be traced on each successive crop through 
 the entire course of cropping. 
 
No. v.} OF THE PHYSICAL PROPERTIES OP THE SOIL. 27 
 
 No. V. 
 
 OF THE EXAMINATION AND ANALYSIS OP SOILS. 
 
 1°. Selection of specimens of soils. — In the same field different varieties of soil 
 often occur, and some recommend that in collecting a specimen for analysis, 
 
 Cortious should be taken from different parts of the field and mixed together, 
 y which an average quality of soil would be obtained. But this is bad advice, 
 when the soils in different parts of the field are really unlike. Suppose one 
 part of a field to be clay, and another sandy, as is often the case in this county, 
 and that an average mixture of theai is submitted to analysis, the result you 
 get will apply neither to the one part of the field nor to the other — that is, it 
 will be of little o.r no value. In selecting a specimen of soil, therefore, one or 
 two pounds should be taken from each of four or five parts of the field where 
 the soil appears nearly alike, these should be well-mixed together and dried in 
 the open air or before the fire. Two separate pounds should then be taken 
 from the whole for the purpose of analysis, or if it is to be sent to a distance 
 should be tied up in clean strong paper, or what is much better, should be en- 
 closed in clean well-corked bottles. 
 
 I. — OF THE PHYSICAL PROPERTIES Of THE SOIL. 
 
 2'-\ Determinati-on of the density of the soil. — In order to determine the den- 
 sity of the soil, a portion of it must be dried at the temperature of boiling 
 water (Sl^o), till it ceases to lose weight, or upon a piece of white paper in an 
 oven at a heat not great enough to render the paper brown. A common phial 
 or other small bottle perfectly clean and dry may then be taken and filled up 
 to a mark made with a file on the neck, with distilled or pure rain water, and 
 then carefully weighed. Part of the water may then be poured out of the 
 bottle, and 1000 grains of the dry soil introduced in its stead, the bottle must 
 then be well shaken to allow the air to escape from the pores of the soil, filled 
 up again with water to the mark on the neck, and again weighed. The weight 
 of the soil, divided by the difference between the weight of the bottle with soil 
 and water and the sum of the weights of the soil and the bottle of water to- 
 gether, gives the specific gravity. 
 
 Thus, let the bottle with water weigh 2000 grains, and with water and soil 
 2G00, then- 
 Grain?. 
 
 The weight of the bottle with water alone = 2000 
 
 The weight of the dry soil 1000 
 
 Sum, being the weight which the bottle with the soil and water ) 
 
 would luive had could the soil have been introduced without > 3000 
 displacing any of the water * 
 
 But the weight of the bottle with soil and water was .... 2600 
 
 Difference, being the weight of water talcen out to admit 1000 ) ^qq 
 grains of dry soil > 
 
 Therefore, 1000 grains of soil have the same hulk as 400 gi-ains of water, or 
 the soil is 2i times heavier than water, since 10004-400=2-5 its .specific 
 gravity. 
 
 3°. Determination of the absolute weight. — The absolute weight of a cubic 
 foot of solid rock is obtained in pounds by multiplying its specific gravity by 
 G3^ — the weight in pounds of a cubic foot of water. But soils are porous, and 
 contain more or less air in their interstices according as their particles are more 
 or less fine, or as they contain more or less sand or vegetable matter. Fine 
 sands are heaviest, clays next in order, and peaty soils the lightest. The 
 simplest mode of determining their absolute weight, therefore, is to weigh an 
 exact imperial half pint of the soil in any state of dryness, when this weight 
 
98 OP THE PHYSICAL PROPERTIES OP THE SOIL. [AppmdtX, 
 
 multiplied by 150, will give very nearly the weight of a cubic foot of the soil in 
 that state. 
 
 4°. Determinatian of the relative proportio7is of gravel, sajid, and clay. — Five 
 hundred grains of the diy soil maybe boiled in a flask half full of water till the 
 particles are thoroughly separated from each other. Being allowed to stand 
 for a couple of minutes, the water with the fine matter floating in it may be 
 poured off into another vessel. This may be repeated several times till it ap- 
 pears that nothing but sand or gravel remains. This sand and gravel is then 
 to be washed completely out of the flask, dried, and weighed. Suppose the 
 weight to be 300 grains, then 60 per cent.* of the soil is sand and ^avel. The 
 sand and gravel are now to be sifted through a gauze sieve more or less fine, 
 when the gravel and coarse sand are separated, and may be weighed and their 
 proportions estimated. 
 
 These separate portions of gravel and sand should now be moistened with 
 water and examined carefully with the aid of a microscope, with the view of 
 ascertaining if they are wholly silicious, or if they contain also fragments of 
 different kinds of rock — sand-stones, slates, granites, traps, lime-stones, or iron- 
 stones. A few drops of strong muriatic acid (spirit of salt) should also be 
 added — when the presence of lime-stone is showh more distinctly by an effer- 
 vescence, which can be readily perceived by the aid of the glass, — of per-oxide 
 of iron by the brown colour which the acid speedily assumes, — and of black 
 oxide of manganese by a distinct smell of chlorine which is easily recognised. 
 In the subsequent description of the soil, these points should be carefully noted. 
 
 Suppose the sand and gravel to contain half its weight of fine sand, then 
 our soil would consist of coarse sand and small stones 30 per cent., fine sand 
 30 per cent., clay and other lighter matters 40 per cent. 
 
 5°. Adsorbing poiaer of the soil. — A thousand grains of the perfectly dry soil, 
 crushed to powder, should be spread over a sheet of paper and exposed to the 
 air for tv/elve or twenty-four hours, and then weighed. The increase of weight 
 shows its power of absorbing moisture from the aix\ If it amount to 15 or 20 
 grains, it is so far an indication of great agricultural capabilities. 
 
 6°. Its power of holding iixiter. — This same portion of soil may now be put 
 into -a funnel upon a douhlef filter and cold water poured upon it, drop by drop, 
 till the whole is wet and the water begins to trickle down the neck of the filter. 
 It may now be covered with a piece of glass and allowed to stand for a few 
 hours, occasionally adding a few drops of water, until there remains no doubt 
 of the whole soil being perfectly soaked. The two filters and the soil are then 
 to be removed from the funnel, the filters opened and spread for a few minutes 
 upon a linen cloth to' remove the drops of water which adliere to the paper. 
 The wet soil and inner filter being now put into one scale, and the outer filter 
 in the other, and the whole carefully balanced, the true weight of the wet soil 
 is obtained. Suppose the original thousand grains now to weigh 1400, then 
 the soil is capable of holding 40 per cent, of water.t 
 
 7°. Rapidity nnth which the soil dries. — The wet soil with its filter may now 
 be spread out upon a plate and exposed to the air, in what may be considered 
 ordinary circumstances of temperature and moisture, for 4, 13, or 24 hours, and 
 the loss of weight then ascei-tained. This will indicate the comparative ra- 
 pidity with which such a soil would dry, and the consequent urgent demand 
 for draining, or the contrary. As great a proportion of the water is said to 
 evaporate from a given weight of sand saturated with water, in 4 hours, as 
 from an equal weight of pure clay in 11, and of peat in 17 hours — when placed 
 in the same circumstances. 
 
 8^. Power of absorbing heat f?-om the sun. — In the preceding experiment a por- 
 tion of pure quartz sand or of pipe clay may be employed for the purpose of 
 
 • As 500 : 300 :: 100 to 60 per cent, 
 t That is, one filter within another. 
 t 1000 : 400, the increase of weight as 100 : 40i 
 
No. F.] OP THE PHYSICAL PROPERTIES OF THE SOIL. 29 
 
 obtaining a comparative result as to the rapidity of drying. The same method 
 may be adopted in regard to the power of the soil to become wai-m under the 
 influence of the sun's rays. Two small wooden boxes, containing each a 
 layer of one of the kinds of soil, two inches in depth, may be exposed to the 
 same sunsliine for the same length of time, and the heat they severally acquire 
 determined by a tliermometer, buried about a quarter of an inch beneath the 
 surface. Soils are not fovmd to differ so much in the actual temperature they 
 are capable of attaining under such circumstances — most soils becoming 20° 
 or 30° warmer than the surrounding air in the time of summer — as in the re- 
 lative degree of rapidity with which they acquire this maximum temperature — 
 and this, as stated in the text, appears to depend chiefly upon the darkness of 
 their colour. The determination of this quality, therefore, except as a matter 
 of curiosity, may, at the option of the experimenter, be dispensed with. 
 
 II. OF THE ORGANIC MATTER PRESENT IN THE SOIL, 
 
 9°, Deteryninatioji of the pcr-ccntage of oriimiic matter. — The soil must be 
 thoroughly dried in an oven or otlierwise, at a temperature not higher than be- 
 tween 250° to 300° F. Humic and ulmic acids will bear this latter tempera- 
 ture without change. An accurately weighed portion (100 to 200 grains) must 
 then be burned in the open air, till all the blackness disappears. This is best 
 done in a small platinum capsule over an argand spirit or gas lamp. The loss 
 indicates the total weight of organic matter present. It is scarcely ever pos- 
 sible, however, to render soils absolutely dry without raising them to a tem- 
 perature so high as to char the organic matter present, and hence its weight, as 
 above determined, will always somewhat exceed the truth, the remaining water 
 being driven off along with the organic matter when the soil is heated to red- 
 ness. This excess, also, will in general be greater in proportion to the quantity 
 of clay in the soil, since this is the ingredient of most soils from which the 
 water is expelled with the greatest difficulty. 
 
 10°. Detcnninal'wn of the huridc acid. — 'rhisacid, whether merely mixed with 
 the soil, or combined with some of the lime and alumina it contains, is extracted by 
 boiling with a solution of the common soda of the shops. Into about two ounces 
 by measure of a saturated solution of this salt, contained in a flask, 200 or 300 
 grains of soil, previously reduced to coarse powder, are introduced, an equal 
 bulk of water added, and the whole boiled or digested on the sand bath with 
 occasional shaking for an hour. The flask is then removed from the fire, filled up 
 with water, well shaken, and the particles of soil afterwards allowed to subside. 
 The clear liquid is then poured off. If it has a brown colour it has taken up 
 some humic acid. In this case, the process must be repeated once or twice 
 with fresh portions of the soda solution, till the whole of the soluble organic 
 matter appears by the pale colour of the solution to be taken up. These coloured 
 solutions are then to be mixed and filtered. The filtering generally occupies 
 considerable time, the humic and ulmic acids clogging up the pores of the filter 
 in a remarkaV)le manner, and permitting the liquid to pass through sometimes 
 \vith extreme slowness. 
 
 When filtered, muriatic acid is to be slowly added to the coloured liquid — 
 which should be kept in motion by a glass rod — till effervescence ceases, and 
 the whole has become dictinctly sour. "On being set aside the humic acid falls 
 in brown flocks. A filter is now to be dried and carefully weighed,* the liquid 
 filtered through it, and the humic acid thus collected. It must be washed in the 
 filter with pure water — rendered slightly sour by muriatic acidt — till all the soda is 
 
 * This is best effected by putting the filter into a covererl porcelain crucible of known 
 weight, and heating it for ten minutes over a lamp or otherwise, at a temperature which 
 just, does not discolour the paper, allowing then the crucible to cool under cover, and when 
 cold weighing it. The increase above tlie known weight of the crucible is that of the filter, 
 which, besides being recorded in the experiment book, should also be marked in several 
 places on the edge of the filter with a black lead pencil. 
 
 t This is to prevent in some measure the humic acid from passing through the filter, 
 which it is very apt to do, when the saline matter is nearly washed out of it. 
 
30 OP THE ORGANIC MATTER PRESENT IN THE SOIL. [AppendlXj 
 
 separated from it,* when it is to be dried at 250° F., till it ceases to lose weight. 
 The final weight, minus that of the filter, gives the quantity of humic acid con- 
 tained in the portion of soil submitted to examination. As it is rarely possible to 
 wash the humic acid perfectly upon the filter, rigorous accuracy requires that the 
 filter and acid should be burned after being weighed, and the weight of ash left, 
 minus the known weight of ash left by the filter,t deducted from that of the 
 acid as previously determined. It is to be observed here that by this, which 
 is really the only available method we possess of estimating the humic acid, a 
 certain amount of loss arises from its not being wholly insoluble, the acid 
 liquid which passes through the filter being always more or less of a brown 
 colour.j 
 
 11°. Determination of the insoluble kumus. — Many soils after this treatment 
 with carbonate of soda are still more or less of a brown colour, evidently due 
 to the presence of other organic matter. To separate this, Sprengel recom- 
 mends to boil the soil, which has been treated with carbonate of soda, and 
 which we suppose still to remain in the flask, with a solution of caustic potash, 
 repeated, if necessary, as in the case of the soda solution. By this boiling, 
 the vegetable mattei, which was insoluble in the carbonate of soda, is changed 
 in constitution and dissolves in the caustic potash, giving a brown solution, 
 from which it may be separated in brown flocks by the addition of muriatic 
 acid, and then collected and weighed as above described. 
 
 In some soils, also, distinct portions of vegetable fibre, such as portions of 
 roots, &c., are present, and may be separated, mechanically dried, and weighed. 
 
 1'2°. Of other ors,nnic substances present in the soil. — The sum of the weights 
 of the above substances deducted from the whole weight of organic matter, as 
 determined by burning, gives that of other organic substances present in the 
 soil. The quantity of these is in general comparatively small, and, unless they 
 are soluble in water, there is no easy method of separating them, and determin- 
 ing their weight. The following two methods, however, may be resorted to: — 
 
 1°. Half a pound or more of the moist soil may be boiled with two separate 
 pints of distilled water, the liquid filtered and evaporated to a small bulk. From 
 clay soils, when thus boiled with water, the fine particles do not readily subside. 
 Sometimes, after standing for several days, the water is still muddy, and passes 
 muddy through the filter, but, after being evaporated, as above recommended, to 
 a small bulk, most of the fine clayey matter remains on the paper when it is 
 again filtered. As soon as it has thus passed through clear, the liquid may be 
 evaporated to perfect dryness at 250° F., and weighed. Being now treated 
 with water — a portion will be dissolved — this must be poured off", and the inso- 
 luble remainder again perfectly dried and weighed. If this remainder be now 
 heated to redness in the air, any organic matter it contains will be burned off", 
 and its weight ascertained by the loss on again weighing. This loss may be 
 considered as humic acid rendered insoluble by drying.§ It does not require to 
 be added to the weight of humic acid already determined (10°), because in 
 that experiment a portion of soil was employed which had not been boiled in 
 vwJer., and from which therefore the carbonate of soda would at once extraoj, 
 all the humic acid. The present experiment need only "be made when it is de- 
 
 * This is ascertained by collectinjr a few drops of what is passing throush upon a piece of 
 cle*n glass or platinum, and drying them over the lamp, when, ifa perceptible stain or spot is 
 left, the substance is not sufficiently washed. 
 
 t The ash left by the paper employed for filters should always be known. This is ascer- 
 tained, once for all, by drying a quantity of it in the way described in the previous note, 
 weighmg It m this dry state, burning it, and again weighing the ash that is left. In good 
 filtering paper, the ash ought not to exceed one per cent. 
 
 X The portion which thus remains in the solution may be precipitated by adding a small 
 quantity of a solution of alum, and afterwards pouring in ammonia in excess. The alumina 
 falls coloured by the organic matter, and after being collected on a filter, washed, and dried, 
 the weight of organic matter in the precipitate may be determined approximately as des- 
 cribed under 12° (2°). r v j rv j 
 
 § See Lecture xiii., §1. 
 
No. v.] OF THE ORGANIC MATTER PRESENT IN THE SOIL. 31 
 
 slrable to ascertain how much humic acid a soil contains in a state in which it 
 is soluble in water. Where ammonia, potash, or soda is present in the soil, 
 some chemists consider this quantity to be very considerable, and to exercise 
 an important influence upon vegetation. 
 
 That which was taken up by water from the dried residuum is again to be 
 evaporated to dryness, dried at 150°, weighed, and burned at a loio red heat. 
 The loss is organic matter, and may have been crenic or apocrenic, or some 
 other of the organic acids formed in soils, the compounds of v/hich, with lime, 
 alumina, and prot-oxide of iron, are soluble in water. If any little sparkling or 
 burning like match-paper be observed during this heating to redness, it may be 
 considered as an indication of the presence of nitric acid — in the form of ni- 
 trate of potash, soda, or lime. In this case the loss by burning will slightly ex- 
 ceed the true amount of organic matter present, owing to the decomposition and 
 escape of the nitric acid also. The mode of estimating the quantity of this acid, 
 when it is present in any sensible proportion, will be hereafter described. 
 
 2^. The caustic potash employed to dissolve the insoluble humus (11") takes 
 up also any alumina which may have been in combination with the humic 
 acid or may still remain united to the mudesous* or other organic acids. When 
 the solution is filtered and the humic acid separated by the addition of muriatic 
 acid till the liquid has a distinctly sour taste, this alumina, and the acids with 
 which it is in combination, still remain in solution. After the brown flocks of 
 humic acid, however, arejcoUected on the filter, the alumina may be thrown down 
 from the filtered solution by adding caustic ammonia to the sour liquid, until 
 it has a distinctly ammoniacal smell. The light precipitate which falls must 
 be collected on a filter and washed with hot water till the potash is as completely 
 separated as possible. It is then to be dried at 300° F., weighed and heated 
 for some time in a close crucible over the lamp, at a temperature which begins 
 to discolour it, and again weighed. Being now burned in the air till it is quite 
 white, and weighed, the last loss may be considered as mudesous or some simi- 
 lar acid. 
 
 The reason why this second method of drying over the lamp is here re- 
 commended, is, that alumina and nearly all its compounds part with their 
 water with great difficulty, and even with the precautions above indicated, it is 
 not unlikely that a larger per-centage of organic matter may thus be indicated, 
 than in reality exists in the soil. The check which tlie accurate experimenter has 
 upon all these determinations is this, that the sum of the several weights of the 
 humic acid, the insoluble humus, the vegetable fibre, and of the crenic and mu- 
 desous acids, if present, should be somewhat less than that of the whole com- 
 bustible organic matter, as determined by burning the dry soil in the open air 
 (9"). This quantity we have seen to be in most cases greater tlian the truth, 
 because any remaining water or any nitric acid the soil may contain, are at the 
 same time driven off. 
 
 I may further remark upon this subject that the quantity of alumina thus 
 dissolved by the caustic potash is in most soils very small, and the quantity of 
 organic matter by which it is accompanied in many cases so minute, that the 
 determination of it may be considered as a matter of curiosity, rather than one 
 of practical impoi'tance. 
 
 III. — or THE SOLUBLE SALINE MATTER IN THE SOIL. 
 
 13°, With a view to determine the 7iaiure of the soluble saline matter in the 
 soil, a preliminary experiment must be made. An unweighed portion must be 
 introduced into five or six ounces of boiling distilled water in a flask, and kept 
 at a boiling temperature, with occasional shaking for a quarter of an hour. It 
 may then be allowed to subside, after which the liquid is to be filtered till it 
 passes through clear. It is then to be tested in the following manner. Small 
 
 * Except where gypsum is present in the insohible portion, which is not unfrequently the 
 case, when the loss will be partly water— since gypsum, after being dried at 250°, loses stiU 
 about 208 per cent, of water when heated to redness. 
 
 28 
 
32 OP THE SOLUBLE SiiLINE MATTER IN THE SOIL. [AppcndtX, 
 
 separate portions are to be put into so many clean wine glasses, and the effect 
 produced upon these by different chemical substances carefully noted. 
 If with a few drops of — 
 
 a. Nitrate of Baryta, it gives a white powdery precipitate, which does not 
 disappear on the addition of nitric or muriatic acid, the solution contains sulphu- 
 ric acid. If the precipitate does appear, it contains carbonic acid. In this lat- 
 ter case, the liquid will also effei-vesce on the addition of either of the acids 
 above mentioned. 
 
 b. If with oxalaie of ammonia, it gives, either immediately or after a time, a 
 white cloud, it contains lime,* and the greater the milkiness, the larger the 
 quantity of lime may be presumed to be. 
 
 c. If with nitrate of silver, it gives a white curdy precipitate, insoluble in pure 
 nitric acid, and speedily becoming purple in the sun, it may be presumed to 
 contain chlorine. 
 
 d. If with caustic ammonia, it gives a pure white gelatinous precipitate, it 
 contains either alumina, m' magnesia, or both. In this case, muriatic acid must 
 be added till the precipitate disappears, and the solution is distinctly acid. If 
 on the addition of ammonia in excess, the precipitate reappears undiminished 
 in quanlfty, it contains alumina only. If it be distinctly kss in quantity, we 
 may infer the presence of both magnesia and alumina ; and if no precipitate now 
 appears, that it contains magnesia only. If a large quantity of magnesia be present, 
 it may be necessaiy to re-dissolve and acidify the soUition a second time be- 
 fore, on the 7-^-addition of ammonia, the precipitate would entirely disappear. 
 
 If the precipitate, by ammonia, have more or less of a brown colour, the pre- 
 sence of iron, and perhaps nianganesp., may be inferred. If, on the second 
 addition of ammonia, the colour of the precipitate has disappeared, it has been 
 due to the manganese only— if it still continue brown, it is owing chiefly or 
 altogether to the presence of oxide of iron. If the colour of the precipitate, by 
 ammonia, be very dark, it consists almost entirely of oxide of iron, and may 
 contain little or no alumma, — when it is only more or less brown, the px-esence 
 of both alumina and oxide of iron may with certainty be inferred. 
 
 e. If, after the first addition of ammonia, the solution be filtered to separate 
 the alumina, the oxides of iron and manganese, and the magnesia that may be 
 thrown down — if .oxalate of ammonia be then added till all the lime falls, and 
 the liquid be again filtered, evaporated to dryness, and then heated to incipient 
 redness in the air, till the excess of oxalate of ammonia is destroyed and driven 
 off — and if a soluble residue then remain, t it is probable that fotash or soda, or 
 both, are present If, on dissolving this residue in a little water, the addition of 
 a few drops of a solution of tartaric acid to it produce a deposite of small 
 colourless crystals (of cream of tartar), or if a drop of a solution of bi-chlo- 
 ride of platinum produce in a short time a yellow powdery j^recipitate, it con- 
 tains potash. If no precipitate is produced by cither of these — re-agents as they 
 are called — the presence of soda may be inferred. If the yellow precipitate, 
 containing potash and platinum, be si^parated by the filter, and the solution, after 
 being treated with sulphuretted hydrogen and filtered to separate the excess of 
 bi-chioridc of platinum, be evaporated to dryness — if, then, a soluble saline 
 residue still remain, the solution contains soda as well as potash. 
 
 It is to be observed that some magnesia, if present, may accompany the pot- 
 ash and soda through these sevei-al processes. After the separation of the potash, 
 a httle caustic ammonia will detect the presence of magnesia, but it will rarely 
 be found so far to interfere with i\\\s preliminary examination as to prevent the 
 experimenter from arriving at correct results (see p. 35, /). 
 
 ' The learned reader will under.sfand why, for the sake of simplicity, I take no notice of 
 substances not likely to be present in the soil — as, for example, baryta, which would here be 
 thrown down alonfi with the lime, or of oxilic acid, which, eqaally with the sulphuric or car- 
 bonic (a), wouldgive a white precipitate with nitrate of baryta. 
 
 t Not precipitated from its solution by ammonia, for if precipitated it is partly at least 
 chloride of magnesium. 
 
No. v.] OP THE SOLUBLE SALINE MATTER IN THE SOIL. 33 
 
 /. If the addition of bi-chloride of platinum to the sokition directly filtered 
 from the soil give a yellow precipitate, it contains either potask or amvionia. 
 If, when collected on the filter, dried, and heated to bright redness in the air, 
 white fumes are given off by this yellow precipitate, and only a spongy mass 
 of metallic platinum remains behind, the solution contains ariiriionia only. If, 
 with the platinum, be mixed a portion of a sokxble substance having a taste 
 like that of common salt, and giving again a yellow precipitate with bi-chloride 
 of platinum, it contains pofash — and if the spongy platinum contained in the 
 burned mass, after prolonged heating, amount to more dian 57 per cent, of 
 its weight, or if it be to the soluble matter in a higher proportion than that of 
 4 to 3, the solution contains both polasli and avivionia. 
 
 The presence o{ am nwma in the saline substance, or in the concentrated solu- 
 tion, is more readily detected by adding'^ few drops of a solution of caustic 
 potash, when the smell of ammonia becomes perceptible, or if in too small 
 qviantity to be detected by the smell, it will, if present, restore the blue colour 
 to reddened litmus paper. This e.\periment is best made in a small tube. 
 
 g. If, when the solution, obtained directly from the soil, is evaporated to dry- 
 ness, and the residue heated to redness in the air, a deflagration or burning like 
 match-paper be observed, nitric ii.cid is present. Or, if the dry mass, when put 
 into a test tube with a little muriatic acid, evolves distinct i-ed fumes on bemg 
 heated, or enables the muriatic acid to dissolve gold-dust, and form a yellow 
 solution ; or, if to a colourless . solution of green vitriol (sulphate of iron), 
 introduced into the tube along with the muriatic acid, it imparts more or less of a 
 brown colour — in any of these cases the presence of nitric acid may with cer- 
 tainty be inferred. It will be only on rare occasions, however, that salts, so 
 soluble as the nitrates, will be found in sensible quantity in the small portion 
 of a soil likely to be employed in these preliminary experiments. 
 
 //. If ammonia throw down nothing (see under (t) from the solution, and if 
 no precipitate appear when chloride of calcium or magnesium is afterwards 
 added, the solution contains no phosphoric add. But if ammonia cause a pre- 
 cipitate, and after this is separated by the filter, nothing further falls on adding 
 either of the above chlorides, the phosphoric acid, if any is present, will be con- 
 tained in the precipitate which is upon the filter. Let this, after being well 
 washed with distilled water, be dissolved off with a little pure nitric acid 
 diluted with water, and then neutralized as exactly as possible with ammonia. 
 If a solution of acetate (sugar) of lead now throw down a white precipitate, phos- 
 phoric acid is present. The phosphate of lead — the white precipitate which 
 falls — melts readily before the blow-pipe, and, on cooling, crystallizes mto a bead 
 with beautiful crystalline facets. 
 
 Or — if the precipitate thrown down by ammonia be wholly or in part insolu- 
 ble in pure acetic acid (vinegar), that which is undissolved contains phosphoric 
 acid. If acetic acid dissolve the whole, it may be inferred that no phosphoric 
 acid is present in the soil. 
 
 But if no precipitate be' thrown down by ammonia, instead of the chloride of 
 calcium above recommended, a few drops of a dilute solution of akmi may ba 
 mixed with the solution, after adding the ammonia, and the whole well shaken. 
 If the white precipitate, which now falls, dissolve wholly in acetic acid, no phos- 
 phoric acid is present, and vice versa. 
 
 These preliminaiy trials being made, notes should be kept of all the appear- 
 ances presented, as the method to be adopted for separating and detennining 
 the weight of each substance will depend upon the number and nature of those 
 which are actually found to be present. 
 
 14'^. Deterrtiinotion of tlte quantities of the several constituents of the soluble 
 saline matter. — The quantity of soluble saline matter extracted from a mode- 
 rate quantity of any of our soils is rarely so great as to admit of a rigorous 
 analysis, and the preceding determination of the kind of substances it contains 
 will be in most cases sufficient. Cases may occur, however, in which much 
 
34 
 
 OF THE SOLUBLE SALINE MATTER IN THE SOIL. 
 
 [Appendix, 
 
 saline matter may be obtained;* it will be proper, therefore, briefly to state 
 the methods by which the respective quantities of each constituent may be ac- 
 curately determined. 
 
 a. Eslimation of the SidpJiuric Add. — The solution being gently warmed, a 
 few drops of nitric acid are to be added until the solution is slightly acid, and 
 any carbonic acid that may be present is expelled, after wloich nitrate of baryta 
 is to be added to the solution as long as any thing falls. The white precipi- 
 tate (sulphate of baryta) is then to be collected on a weighed filter, well washed 
 with distilled water, dried over boiling water as long as it loses weight, and 
 then weighed. The weight of the filter being deducted, t every 100 grains of 
 the dry powder are equal to 3437 grains of sulphuric acid. 
 
 b. Estimation of the Chlorine. — The solution of nitrate of silver must be add- 
 ed as long as any precipitate falls, the precipitate then washed, dried at 212° F., 
 and weighed as before. Evei-y 100 grs. of chloride of silver indicate 24'67 grs. 
 of chlorine, or 40-88 gi's. of common salt. 
 
 c. Estimatw?i of the JLivie. — A little diluted muriatic acid being added to throw 
 down the excess of silver, and a little sulphuric acid to separate the excess of 
 baryta, added in the former operations, and the precipitates separated by fil- 
 tration — caustic ammonia is to be poured in^ til^the solution is distinctly alcaline. 
 
 * This is the case with the rich soils of India and Egypt, and of other warm climates. 
 This will appear from the following analyses of some Indian soils, made on the spot by Mr. 
 Fleming, of Barochan, during the hours of leisure left him by his more important duties : — 
 
 Analysis of soils in North and South Bchar, Bengal Presidency — (200 ^rams of 
 
 each being analysed.) 
 
 ■1) 
 
 12 
 
 14 
 
 15 
 
 10 
 
 o o 
 
 O O 
 
 7 12 
 
 8 13 
 
 4 20 
 
 14 
 
 20 
 
 16 
 
 12 
 
 12C 
 
 115 
 
 110 
 
 130 
 
 140 
 
 -^2 
 
 REMARKS. 
 
 9^ 
 
 7 7 
 
 14 
 
 1°. Near G ya, South Behar. — Of a dark colour, soapy 
 to the touch when moist, hard and cracks when dry ; 
 yields a crop of rice and one of wheat every year. Ne- 
 ver lies fallow, but is covered with water during part of 
 the rainy season, and is productive — from 30 to 50 
 bushels of wheat per acre. 
 
 2°. Soil from the same district. — Also soapy when 
 moist and cracks when dry — rather more productive 
 than No. 1. 
 
 3°. From the same district.— Heavy red clay soil, 
 producing wheat, pea.se, cotton, or poppy in the dry 
 season, and Indian corn and millet in the wet season ; 
 not inundated in the rains, and sometimes manured 
 with ashes of wood and cow dung. 
 
 4°. Soil from North Behar, Tirhoot. — A deep loam, 
 yielding two crops yearly; not inundated, producing 
 wheat, bailey, Indian corn, indigo, poppy, &c. From 
 25 to 35 bushels of wheat per acre ; is not usually 
 manured. 
 
 5°. Tirhoot.— Soil light coloured ; producing nearly 
 the same crops, but not so productive as No. 4. Saline 
 efflorescence in patches. 
 
 6°. Tirhoot. — Not so productive as No. 5, and some 
 patclies nearly .sterile from the saline efflorescence, 
 except in the rainy season, when it produces good 
 crops of Indian corn. Soil light coloured. 
 
 I have already alluded (Lecture VIII., p. 159) to the influence which this large proportion 
 of saline matter exercises upon the luxuriance of the vegetation. 
 
 t Or the whole may be heated to redness in the air, and the filter burned away. In this 
 case the weight of ash left by the paper must be ascertained by previous trials, and the du« 
 proportion deducted from the weight of the sulphate. 
 
No. F.] OP THE SOLUBLE SALINE MATTER IN THE SOIL. 35 
 
 If no precipitate fall, oxalate of ammonia is to be added as long as any white 
 powder appears to be pro-luced. The solution must then be left to stand over 
 night — that the whole of the lime may separate,— th^ white powder afterwards 
 collected on a filter, washed, dried, and burned with the filter^ at a low red heat. 
 The s,^^^ powder obtained is carbonate of lime, every 100 grs. of which con- 
 tain 43'7l grs. of lime. 
 
 d. Es! i ination of the O.riJe of Iron and of the Alumina. — But if a precipitate 
 fall on tlie addition of ammonia, as above prescribed — the solution may con- 
 tain magnesia, alumina, and the oxides of iron, and manganese. In this case 
 the precipitate is to be x-e-dissolved by the addition of muriatic acid till it is dis- 
 tinctly acid, and ammonia again added in slight excess. If any precipitate now 
 fall, it will consist only of alumina and oxide of iron, unless magnesia and 
 oxide of manganese be present in large proportion, when a minute quantity of 
 each may fell at the same time. 
 
 The precipitate is to be collected on the filter as quickly as possible, — the fun- 
 nel being at the same time covered with a plate of glass to prevent as much as 
 possible the access of the air, — washed with distilled water, and then re-dissolved 
 in muriatic acid. This is best effected by spreading out the filter in a small 
 porcelain dish, adding dilute acid till all is dissolved, and then washing the pa- 
 per well with distilled water. A few drops of nitric acid are then to be added, 
 and the solution heated, to pcroxidize the iron. A solution of caustic potash 
 added in excess will at first tlirow down both the oxide of iron and alumina, but 
 will afterwards re-dissolve the alumina, and leave only the oxide of iron. This 
 is to be collected on a filter, washed, dried, heated lo redness, and weighed. 
 Every 100 grains of this peroxide of iron are equal to 89'78 grains of protoxide, 
 in which state it had most probably existed in the original solution. 
 
 To the potash solution muriatic acid is added till the alkali is saturated, or till 
 the solution I'eddens litmus faper* when the addition of ammonia precipitates 
 the alumina. As it is difficult to wash this precipitate perfectly free from potash, it 
 is better to dissolve it again in muriatic acid, and to re-precipitate it by caustic 
 ammonia. When well washed, dried, and weighed, this precipitate gives the true 
 quantity of alumina present in the portion of salt submitted to analysis. 
 
 e. Estim.alioii of the Manganese. — To the ammoniacal solutions from which 
 the oxalate of lime has been precipitated (c), a solution of hydro-sulphuret of 
 ammonia is to be added. The manganese will fall in the form of a flesh red 
 sulphuret. When this precipitate has fully subsided, it must be collected on the 
 filter and washed with water containing a very little hydro-sulphuret of ammo- 
 nia. The filter is then put into a glass or porcelain basin, the precipitate dis- 
 solved off by dilute muriatic acid, and the solution filtered, if necessary. A so- 
 lution of carbonate of potash then throws down carbonate of manganese, which 
 is collected, dried, and heated to redness in the air. Of the brown powder ob- 
 tained 100 grains indicate the presence of 93-84 grains of protoxide of manganese 
 in the salt or solution under examination. 
 
 /. Estimation of the Magnesia. — If no potash or soda be present in the residual 
 solution, the determination of the magnesia is easy. A few drops of muriatic 
 acid are added, and the whole gently heated,* and afterwards filtered, to separate 
 the sulphur of the excess of hydro-sulphuret of ammonia previously added. The 
 solution is then evaporated to dryness, and the dry mass heated to redness to 
 drive off all the ammoniacal salts previously added. A few drops of diluted sul- 
 phuric acid are added to what remains, to change the whole of the magnesia 
 into sulphate, the mass again heated to redness and weighed. One hundred 
 grains of this sulphate indicate the presence of 3401 grs. of pure magnesia. 
 
 But if potash or soda be present — the weight of which it is desirable to deter- 
 mine—the simplest method is to take a fresh portion, 15 to 20 grains, of the 
 
 ' Litmus paper is paper stained by dipping it into a solution of litmus, a vegetable blue cq 
 lour, prepared and sold for the purpose of detecting the presence of free acids, by which it 
 is reddened. 
 
3G OF THE SOLUBLE SALINE MATTER IN THE SOIL. [AppcndtX, 
 
 saline matter under examination. If any sulphuric acid be present in it add ni- 
 trate of baryta drop by drop to the solution till the whole of the acid is exactly 
 thrown down — if possible, no excess of baryta being left in the solution — then 
 precipitate the alumina and oxides of iron and manganese, and the lime, if any 
 of these be present, and, finally evaporate to diyness, and heat to redness as be- 
 fore. The dry mass is now to be dissolved in water, adding, if necessary to 
 complete the sotntion, a few drops of muriatic acid. A quantity of red oxide of 
 mercury is then to be added to the concentrated solution, and the whole boiled 
 down to dryness. Water now- dissolves out the potash and soda only, and 
 leaves the magnesia mixed with oxide of mercury. This is to be collected on 
 a filter, washed — not with too much water — and heated to redness, when the 
 magnesia remains pure, and may be weighed, 
 
 g. Esliynation of the Polish and Soda. — The solution containing the potash 
 and soda, is to be evaporated to dryness, and heated to redness to drive off any 
 mercury it may contain. The weight of the mass which consists of a mixture 
 of chloride of potassium with chloride of sodium (common salt) is accurately 
 determined, it is then dissolved in a small quantity of water, and a solution of 
 bi-chloride of platinum added to it in sufficient quantity. Being evaporated by 
 a very g ntle heat nearly to dryness, weak alcohol is added, which dissolves the 
 chloride of sodium and any excess of salt of platinum which may be present. 
 The yellow powder is collected on a weighed filter, washed well with spirits, 
 dried by a gentle heat and weighed on the filter. Every 100 grains indicate 
 the presence of 19'33 grains of potash, or 30'56 grains of chloride of potassium. 
 The quantity of chloride of sodium is estimated from the loss. The weight 
 of the chloride of potassium above found, is deducted from that of the mixed 
 chlorides previously ascertained, the remainder is the weight of the chloride of 
 sodium. Every 100 grains of chloride of sodium (common salt) are equiva- 
 lent to 53-29 of soda. 
 
 h. Estimation of the Ammonia. — If ammonia be present in the solution along 
 with potash and other substances, the method by which it can be most easily 
 estimated is to introduce the solution into a large tubulated retort, to add water 
 until the solution amounts to nearly an li^nglish pint — then to introduce a quan- 
 tity of caustic potash or caustic baryta, and to distil by a gentle heat into a 
 close receiver, containing a little dilute muriatic acid, until fully one half has 
 passed over. Bi-chloride of platinum is then to be added to the solution, 
 which has come over, previously rendered slightly acid by muriatic acid, and 
 the whole is evaporated nearly to dryness by a veiy gentle heat. Dilute alco- 
 hol is then added to wash out the excess of the salt of platinum, and the yellow 
 powder is cortected on a filter, washed with spirit, dried by a very gentle heat, 
 and weighed. One hundred grains indicate the presence of 7*69 grains of 
 ammonia. 
 
 Or the yellow powder, without being so carefully dried, may be heated to red- 
 ness, when only metallic platinum will remain. One hundred grains of this 
 metallic platinum indicate the presence of 1739 grains of ammonia. 
 
 i. Estimation of the Phosphoric Acid. — If phosphoric acid be present in the 
 solution, it will be contained in the precipitate thrown down by ammonia (^d). 
 As it will never be found but in very small quantity, the rigorous determination 
 of its amount is a matter of considerable difficulty. The following method 
 already described (13°, A,) may be adopted. The precipitated alumina, oxide 
 of iron, &c., thrown down by ammonia, after being di-ied, are to be mixed with 
 three times their weight of pure dry carbonate of soda, and fused together in a 
 platinum crucible. The fused mass is then to be treated with cold distilled 
 water till every thing soluble is taken up. The filtered solution is next to be 
 gently heated and exactly neutralized with nitric acid, when a solution of ni- 
 trate of silver will throw down a lohite pi-ecipitate of phosphate of silver, which 
 is to be collected, dried, and weighed. Every hundred grains of it are equal to 
 23-51 of phosphoric acid, or 48-50 of bone earth, ^ 
 
No. v.] OP THE SOLUBLE SALINE , MATTER IN THE SOIL. 37 
 
 Or the filtered solution may be treated with muriatic acid, ammonia added in 
 excess, and tlien a solution of chloride of calcium. Bo?ic cartli will fall, which 
 is to be collected, washed, heated to redness, and weighed. One hundred 
 grains of it contain 48'45 of phosphoric acid. The former mediod is probably 
 the better, but neither of them will give more thtm an approximation to the truth. 
 
 That portion of the fused mass which cold water has refused to take up is to 
 be dissolved in muriatic acid, and again precipitated by ammonia. The clear 
 solution which peisses through is to be added to the first ammoniacal solu- 
 tion (c), from which the lime is not yet thrown down, as when little alumina 
 and oxide of iron are present, a small portion of lime and magnesia, if con- 
 tained in the salt under examination, may have fallen along with them in com- 
 bination with phosphoric acid. 
 
 The alumina and oxide of iron which rest on the filter are to be separated 
 and estimated as already described (^'). 
 
 /'. Estivudion of the Ciirhonic A id. — The lime and magnesia di.ssolved by 
 cold diluted muriatic acid are pardy in combination with carbonic acid and 
 partly with the humic, ulmic, and other vegetable acids. To determine the 
 carbonic acid, 100 grains of tlie soil dried tit 212'^, are to be introduced into a 
 small weighed fiask, ami then just covered l)y a weighed quantity of cold di- 
 luted muriatic acid. After 12 hours, when the action has ceased, a small tube 
 is to 1)6 introduced into the flask and air sucked through it till the whole of the 
 carbonic acid is drawn out of the flask. The loss of weight will indicate the 
 amount of cai'bonic acid very nearly. It would be more rigorously ascertained 
 by fitting into the mouth of the flask a tube containing chloride of calcium, 
 and then heating the solution to expel the carbonic acid. 
 
 Eveiy hundred grains of carbonic acid indicate the presence of 7724 grains 
 of lime in the state of carbonate. The weight of lime in this state, deducted 
 from the whole weight obtained as above (t), gives the quantity which is it 
 combination with other organic acids. 
 
 IV. OF THE INSOLUBLE EARTHY MATTER OF THE SOIL. 
 
 IS''. When the soil has been washed with distilled water as above directed — 
 it is to be treated in the cold with diluted muriatic acid — and allowed to stand 
 with occasional stirring for 12 hours. By this means the carbonates of lime, 
 magnesia, and iron, and the phosphates of lime, and alumina, are dissolved— 
 with any lime, magnesia, oxide of iron, or alumina, which may have been in 
 combination with organic acids. The iron, alumina, and phosphoric acid are 
 to be precipitated by ammonia, the lime by oxalate of ammonia, and such other 
 steps taken as may be necessary, according to the methods already described. 
 
 l(P. The undissolved portion may now be treated with hot concentrated 
 muriatic, kept warm and occasionally stirred for two or three hours, and the 
 solution afterwards evaporated to dryness. The dry matter is then to be 
 moistened with a few drops of muriatic acid, and subsequently treated with 
 water. What remains undissolved is silica, which must be collected on a 
 filter, dried, heated to redness, and weighed. 
 
 The solution may contain oxide of iron, alumina, lime, magnesia, potash, 
 and soda. Any of the four last substances, which may be detected in it, have 
 most probably existed in the soil, in combination with silica^n the state of 
 silicates. 
 
 17°. But the soil may still contain alumina, not soluble in hot niuriatic acid. 
 To ascertain if this be the case, and to separate and detennine this portion of 
 the alumina, if present, either of two methods may be adopted. 
 
 a. The residual soil may be drenched with concentrated sulphuric acid and 
 heated for a considerable time till the sulphuric acid is nearly all driven off. 
 On treating with water, and adding ammonia to the filtered solution, alumina, 
 and oxide of iron, if any have been present, will be thrown down. If any 
 alumina be thus separated, the treatment with sulphuric acid must be repeat- 
 
38 
 
 OF THE SOLUBLE SALINE MATTER IN THE SOIL. 
 
 [Appendix, 
 
 o 
 
 
 
 ^ 
 
 
 
 
 
 
 
 15 o" 
 
 C 
 
 
 01 
 
 c 
 
 
 
 
 
 
 
 
 O M 
 
 J3 
 
 
 S o 
 
 O 
 
 
 "o f^ 
 
 "2 
 
 
 M 
 
 p 
 
 
 o cT 
 
 fcJO 
 
 
 J~ CO 
 
 
 
 :3 o 
 
 o 
 
 
 
 a 
 
 
 "" 
 
 
 ;li fcO 
 
 2 
 
 
 
 o 
 
 
 "c 7i 
 
 > 
 
 
 C ==! 
 
 
 
 «5^ 
 
 1 
 
 c; 
 
 TS 
 
 -^■^ 
 
 -2 
 
 1— c 
 
 o 
 
 
 ^§ 
 
 (t 
 
 • t, G a 
 
 .Eg 
 
 c 
 
 o 2; 
 
 o •.- :x ^ 
 ^ = ^ 5 X^ X 
 
 ..II ^ 
 
 . c 5 -- = 2 = 
 
 — — (SOS.>.OaJOO 
 
 .2 £ O <D 
 p C 2 "3 
 
No. F.J OF THE SOLUBLE SALINE MATTER IN THE SOIL, 39 
 
 ed, till on treating with water and ammonia, as before, no more alumina ap- 
 pears. 
 
 b. Or that portion of the soil on which hot muriatic acid refuses to act may 
 be mixed with twice its weight of carbonate of soda, and heated in a platinum 
 crucilDle till the whole is completely fused. The mass is then to be treated with 
 diluted muriatic acid till every thing soluble is taken up, the filtered solution 
 evaporated to dryness, the diy mass moistened with muriatic acid, and again 
 treated with water. If any thing is left undissolved it will be silica, and if any 
 alumina be contained in the solution, it will be precipitated by ammonia, and 
 may be collected, waslied, dried, and weighed, as already described. The so- 
 lution may also be tested for magnesia, and if any be present it may be sepa- 
 rated hy the process already explained. 
 
 The former of these two methods is to be preferred as the simpler, though it 
 will also require considerable care and attention. That which the sulphuric acid 
 leaves behind must be washed, dried, heated to redness, and weighed. It will be 
 found to consist chiefly of quartz sand, and finsly divided siliceous matter. 
 
 The 'accuracy and care with which the whole of tliese processes have been 
 conducted is tested by adding together the weights of the several substances 
 that have been separately obtained. If this sum does not differ more than one 
 per cent, from the weight of the soil employed, the results may be considered 
 as deserving of confidence. One of the points in which a beginner is most 
 likely to err, is in the washing of the several precipitates he collects upon his 
 filters. As this is a tedious operation, he is veiy likely to wash them, at first, 
 only imperfectly, and thus to have an excess of weight when his quantities are 
 added together — whereas a small loss is almost unavoidable. The precipitates 
 should always be washed with distilled water, and the washing continued until 
 a drop of what passes through leaves no stain when dried upon a bit of glass. 
 
 No. VI. 
 
 ACTION OF GYPSUM. — (»S^ee jjflg-cs 333-34.) 
 
 In the text I have stated what appear to me the most pi'obable effects which 
 gypsum is fitted to produce upon the soil. Some of the numerous opinions that 
 have been entertained vipon this point are thus summed up by Hlubeck : — 
 
 " According to Kb/Z?icr, the action ofgypsmn depends upon the power pos- 
 sessed by lime to form with the oxygen and carboii-of the atmosphere compounds 
 which are favourable to vegetation ; according to Ruckcrl, it acts like any other 
 food ; according to Mayer and Broivn, it merely improves the physical proper- 
 ties of the soil ; while, according to Reil, it is an essential constituent of the plant. 
 Her/i^;/^ called gypsum the saliva and gastric juice of plants ; Humboldt, Gir- 
 tancr, and Albert T'.iaer considered it as a stimulant by which the circulation 
 of plants is promoted ; and Ckoptnl ascribed its action to a supposed power of 
 supplying water and carbonic acid to plants. Davy regarded it as an essential 
 constituent of plants, because it acts only where gypsum is wanting in the soil, 
 while other English agriculturists have supposed it to promote fermentation in 
 the soil. According to Lauhender, it acts as an exciting power without mixing 
 itself with the sap of the plant; according to Llebii^, it fixes the ammonia of the 
 atmosphex-e ; and, according to B raconnot and Sprmgel, it supplies sulphur 
 for the formation of the legvimin of the leguminous plants (the most probable 
 view)." — Erndkrung der PJianzen, p. 70, note. 
 
 To the above extract I may add, tiiat Mr. Cuthbert Johnson, so long known 
 for his many valuable writings upon agriculture, in following out the above idea 
 of Roil and Davy in a recent paper on the use of gypsum (Jour, of the Royal 
 28° 
 
40 ACTION OP GYPSUM. [Appeudix, 
 
 Agr. Society, ii., p. 108,) has stated that a crop of clover or sainfoin contains IJ 
 to 2 cwt. of gypsum per acre, exactly the quantity which the farmers of Kent and 
 Hampshire find it useful to apply to their grass lands every year. This state- 
 ment affords a very simple explanation of the use of gypsum, and one which 
 at first sight leaves nothing to be desired. But it proves too much, for it 
 supposes the whole of the gypsum which is laid upon the grass or clover 
 field to be removed year by year in the crop, and makes no allowance either for 
 the quantity v^rhich must necessarily be carried off by the rains, or for that 
 which must be sometimes at least laid on in the form of farm-yard or other 
 similar manure. Nor does the result rf analysis confirm the above statement 
 as to the quantity of gypsum contained in the crop of clover or sainfoin. By 
 referring to page 230, it will be seen that 1000 lbs. of dry hay do not con- 
 tain, on on average, more than 4 lbs. of sulphuric acid— equal, supposing it all 
 to be in combination with lime, to 8| lbs. of gypsum. Or a crop of li tons of 
 hay contains the elements of about 30 lbs. of gypsum— only about a sixth 
 part of what is usually added as a top-dressing to the land. 
 
 No. VII. 
 
 SUGGESTIONS FOR EXPERIMENTS WITH THE SOLUBLE SILICATES 
 OF POTASH AND SODA, 
 
 In the text (pp. 207 and 349,) I have had frequent occasions to refer to the pre- 
 sence in the soil of the silicates of potash and soda, and to their supposed action 
 in supplying silica to the stems of the grasses and of the corn-bearing plants 
 It would be interesting in a theoretical point of view, to ascertain by experi- 
 ment, more fully than has hitherto been done, how fai- the application of these 
 substances to the growing crops would, as a general rule, imijrove or otherwise 
 aliect their growth. But as those experiments which have already been made 
 (page 349), afford a strong presumption in favour of their economical value 
 It becomes a matter of practical interest also to investigate their apparent effects 
 upon each of our cultivated crops. 
 
 These experiments are placed within the reach of the practical farmer durinff 
 the ensuing season, by the introduction of the above compounds into the 
 market at a reasonable rate (page 3G3). I therefore subjoin a few suff-es- 
 tions for experiments with these silicates, in the hope that some of the many 
 zealous and intelhgent practical men, wiio are now directing their attention to 
 the applications of chemical science to agriculture, may be induced to enter 
 upon this field of inquiry during the ensuing spring. 
 
 1°. In order to convey silica into the plant, it appears to be chemically indif- 
 ferent whether the silicate of potash or that of soda be placed within reach of 
 Its roots. But as the silicate of soda can be manufactured very much cheaper 
 than that of potash, it is desirable above all to try the effects of this compound 
 —upon the grasses and corn-bearing plants especially. 
 
 2°. But as in the ashes of most plants potash is found in larger quantity than 
 
 soda, it IS possiMe that the effect of the silicate of potash upon soitie soils may 
 
 be so much greater than that of the salt of soda as to counterbalance the dif- 
 
 oun^also''''^'^"^''' ""''"''® ^^'^ propriety of extended trials with tliis com- 
 
 3°. But as in the ashes of all our cultivated plants both potash and soda are 
 tound, It may be that a piixture of the two silicates may act better than either 
 alone. It will be proper, therefore, to apply such a mixture in different pro- 
 portions and to compare it effects with those of each of the silicates laid 
 
 O J* 
 
No. VIII.] OF THE SOLUBLE SILICATES OF POTASH ANT) SODA. 
 
 41 
 
 The first series of comparative experiments, therefore, would be as follo\rs: 
 
 The application may be from 1 cwt. to 1 J 
 cwt. per acre, laid on as a top-dressing in 
 moist weather early in the spring. Or it 
 may be mixed with a large quantity of wa- 
 ter, and applied with a water-cart. In either 
 
 Silicate of 
 Soda- 
 
 Silicate of 
 Potash. 
 
 }^ Silicate of 
 Potash, 
 
 ^ Silicate of 
 So<la. 
 
 % Silicate of 
 Potash, 
 
 >3 Silicate of 
 Soda. 
 
 Nothing. 
 
 case it ought to be in the state of a fine powder. 
 
 But although the above applications produce a bene- 
 ficial effect upon the crops, it will not necessarily follow 
 that the silica, which the silicates contain, has had any 
 share in bringing about the good result. By mere expo- 
 sure to the air for a lengtli of time the potash or soda of those silicates will absorb 
 carbonic acid from the atmosphere, and be converted into carbonates. The 
 same will take place more rapidly still in the soil, where carbonic acid abounds 
 This conversion of the alkali into carbonate will set free a large part of the 
 silica — in a state it is true in which it is in some degree soluble in water (page 
 206,) — but in whicn, nevertheless, it will find its way into the plant with 
 much more difficulty than if it had remained in the state of a soluble silicate. 
 
 Now as the carbonates of potash and soda are known to promote vegetation 
 (page 328), — though even with these, sufficient trials have not yet been made 
 — it is possible, as I have remarked above, that a good effect may follow the 
 application of the silicates, and yet it maybe altogether due to the action of the 
 carbonates which are formed by their decomposition. It is of consequence to 
 ascertain if this really be the case, because the quantity of carbonates which 
 would be 'formed by the decomposition of the silicates could be laid on directly 
 at one half of the price at which the silicates can as yet be sold. 
 
 The second series of comparative experiments, therefore, which it would be 
 interesting to try, would be such as the following : — 
 
 The quantities here indicated are by the acre — thai 
 of carbonate of soda is- given so great, because this salt 
 contains upwards of thi-ee-fifths its weight of water (see 
 p. 215.) 
 
 Another consideration ought not here to be omitted. 
 Nature, as has been frequently illustrated in the text, 
 feeds her plants with a mixture of many different sub- 
 stances, and by the aid of such mixtures they always 
 thrive the best. The full benefit of the silicates, when 
 applied alone, will be experienced only when every oth- 
 er ingredient which the plant requires is already present in the soil, and in suf- 
 ficient abundance. But this can rarely be the case. Its success will be more 
 sure, therefore, if it be applied in a state of mixture with other saline substances 
 which are known to be more or less useful to vegetation, and which will not, 
 upon admixture, decompose these silicates. Such are common salt and the 
 sulphate and nitrate of soda. 
 
 A third series of comparative experiments, therefore, might be made, in which 
 from 1 to U cwt. per acre of the following mixtures might be applied : — 1°. 
 Equal weights of common salt, of dry sulphate of soda, of nitrate of soda, and 
 of silicate oi potash; 2°. Equal weights of the same substances, omitting the 
 silicate of potash ; 3°. Equal weights of common salt, oi dry sulphate of soda, 
 of nitrate of potash, and of silicate of soda; and 4". Equal weights of the sanie 
 substances, omitting the silicate of soda, or substituting carbonate of soda in 
 its stead. 
 
 The sulphate of magnesia (Epsom salts) or of lime (gypsum) can not be 
 safely used along with the silicates, as the magnesia or lime they contain may 
 decompose the silicates — forming sulphate of potash or soda and silicate of 
 magnesia or lime, in which the silica is insoluble, and could not, therefore, until 
 a further chemical change took place, find its way into the roots of the plant. 
 
 Silicate of 
 Potash, 
 1 cwt. 
 
 Crude 
 Potash or 
 Pearlash, 
 
 75 lbs. 
 
 Silicate of 
 Soda, 
 1 cwt. 
 
 Crystallized 
 
 Carbonate 
 
 of Soda, 
 
 150 lbs. 
 
4S 
 
 EXPERIMENTS ON TURNIPS. 
 
 [AppendtXf 
 
 No. VIII. 
 
 RESULTS OF EXPERIMENTS IN PRACTICAL AGRICULTURE, 
 MADE IN 1842. 
 
 I have much gratification in laying before my readers the results of a second 
 year's series of experiments undertaken in consequence of suggestions thrown 
 out in previous parts of this Appendix, or of opinions expressed in the body of 
 the work. It is one of the numerous good results which have followed from the 
 issue of these Lectures in a periodical form that I have the pleasure of incoi*po- 
 rating in the same volume the results of experiments made during two succes- 
 sive years. No one who studies with care the experiments which follow, and 
 the few remai'ks I have appended to them, will hesitate in pronouncing them to 
 be as a whole the most valuable contributions to accurate experimental agricul- 
 ture ever hitherto published. The results are not all equally important, nor all 
 equally instructive, but they are the first fruits of a new line of research, which 
 will lead us hereafter to the discovery of important general truths. They show 
 that practical men are now on the right road, and — spreading as scientific know- 
 ledge now is among the agricultural body — I trust there is no fear of their here- 
 after being prevented from pm-suing it. 
 
 A.— EXPERIMENTS ON TURNIPS. 
 
 I. The first series of experiments was made with the view of obtaining an- 
 swers to these two questions : 
 1°. W7iat arc the relative effects of different saline substances iipo7i the turnip crop 
 
 under the same circumstances ? and 
 2°. Hoiv far may these substances be employed. alo7ie to supersede farm-yard manure 
 
 in the culture of turnips 7 
 
 Turnips grown in Salter's Bog.^Field furrow-drained and subsoil ploughed. Manures ap- 
 plied partly in drills before sowing on 1st .June, and partly as top-dressing on 28th July, 
 1842. The salt and nitrate of soda last applied were dissolved in water; the others applied 
 dry. The quantity of land in each plot was one-thirteenth of an acre. 
 
 No. 
 
 11 
 
 DescnpITon of 
 Dressing. 
 
 1st June. 28thJuly Total 
 
 Nothing 
 
 Common Salt.... 
 Common Salt.... 
 
 Rape-dust 
 
 Nitrate of Soda. 
 Nitrate of Soda.. 
 
 Rape-dust 
 
 Nitrate of Soda.. 
 Sulphate of Soda. 
 Sulphate of Soda. 
 Sulphate of Soda. 
 
 Rape-dust 
 
 Rape-dust 
 
 Guano 
 
 Soot 
 
 Manure appUed. 
 
 lbs 
 
 67 
 2 
 
 67 
 
 5j 
 
 67 
 
 67 
 
 8 
 
 bush. 
 
 U 
 
 lbs. 
 
 67 
 
 9 
 
 bush. 
 
 1 
 
 Produce 
 
 weight 
 
 of bulbs. 
 
 lbs. 
 
 8 
 
 67!; 
 
 ? 4^ 
 8 
 
 4P 
 
 67 S 
 
 134 
 
 17 
 
 bush. 
 
 2i 
 
 sts. lbs. 
 43 11 
 23 
 
 66 
 
 10 
 
 36 
 
 6 
 
 45 
 
 8 
 
 35 
 
 12 
 
 29 
 
 7 
 
 39 
 
 12 
 
 Remarks. 
 The rest of the field, 
 grown with farm-yard 
 inanure, was a fair ave- 
 rage ci'op. Those expe 
 rimented upon were i 
 complete failure, owing 
 partly, no doubt, to the 
 severe drought of the sea 
 son, but chiefly to the 
 want of farm-yard dung. 
 The seeds brairded bad- 
 ly, and the drills were 
 blanky throughout. Few 
 of the plants reached any 
 size, and the best of them 
 were inferiorto the plants 
 immediately adjoining 
 sown at the same time. & 
 similarly treated, except 
 as respects the manuring 
 
 The foregoing experiments were made at the suggestion of Lord Blantyre on 
 the home farm, at Lennox Love, near Haddington, and have been reported to 
 me, at his Lordship's request, by Mr. William Goodlet, under whose immedi- 
 diate superintendence the whole were conducted. 
 
 The reader will not suppose, because they proved what are commonly called 
 
No. F///,] EXPERIMENTS ON TURNIPS. 43 
 
 failures, that therefore they are of no value. On the contrary, they so far satis- 
 factorily answer the questions they were intended to solve. They show 
 
 1°. That saline manures in that locality cannot economically take the place 
 of farm-yard manure, even for a single season. 
 
 2°. That saline manures are even hurtful in the present condition of the land, 
 when employed alone — producing a smaller crop than if no manure had been 
 applied at all, and some of them in a remarkable degree. This appears to be 
 especially the case with common salt, which at the rate of 1 cwt. an acre reduced 
 the crop of bulbs nearly to one-half of what was yielded by the unmanured por- 
 tion of the field. It is still more striking that nitrate of soda applied at the same 
 rate should diminish the crop though in a less degree than common salt — and 
 that soot should almost kill it entirely, and that 15 cwt. of rape-dust per acre 
 should produce scarcely any effect. In regard to guano, it was applied in too 
 small quantity to do all the good of which it was capable had it been laid on 
 more largely. If G or 8 cwt. instead of H cwt per acre had been used, the crop 
 would probably have equalled that obtained by the use of farm-yard manure. 
 
 There is no doubt that to the extreme drought of the season, as Mr. Goodlet 
 observes, must be ascribed the injury or actual lessening of the crop, in this case, 
 by the use of saline manures. The drought brings up the saline matters to the 
 surface, and thus enables it to encrust, and weaken, or entirely kill, the growing 
 plants. The want of rain in 1843 was much more felt in the Eastern part of 
 Scotland than in the West, where the greater part of the succeeding experi- 
 ments were made, and where occasional showers refreshed the land. 
 
 One other observation I may make. Had the saline matters been mixed 
 with a fair proportion of farm-yard manure, it is probable that even on this field 
 the effects would have been very different. One reason for this expectation is, • 
 that the plants being kept in a rapidly growing state — partly use up, and even 
 eagerly appropriate, a large portion of the saline matter as it rises to the surface 
 — and by their strength are enabled to resist the injurious action of any excess, 
 which in ordinary circumstances is likely to remain. The reader, however, 
 will not ask why the experiments were not so made — for he has already seen 
 that their object was to ascertain the effect of saline manures applied alone. 
 From their results, however, he will draw for himself the important practical 
 rule, that in ordinary circumstances it is unsafe to trust his turnip crop to saline 
 manures alone — that they may assist the action of farm-yard or other similar 
 mixed manures, but cannot supply their place. But upon this point the suc- 
 ceeding series of experiments thi'ow much further light. 
 
 II. The special object of the following four series of experiments was to as 
 certain — 
 
 1°. The relative effects chiejly of various mixed manures upon several varieties 
 of turnips ; and 
 
 2°. Whether any of these mixtures could ahne be economically used to supersede 
 farnv-yard manure. 
 
 They were made at the home-farm at Barochan, near Paisley, under the 
 direction and superintendence of Mr. Fleming, whose excellent experiments, 
 made in 1841, are recorded in a previous part of this Appendix (pp. 17 to 24). 
 Mr. Fleming describes himself as much indebted to his overseer, Mr. Gardiner, 
 without the aid of whose zeal, intelligence, and careful superintendence, so 
 numerous a body of experiments could neither have been made, nor the results 
 accurately ascertained. 
 
 1°. Comparative Experiments with various substances used as manures, for growing 
 Swedish Turnips : seed sown 6th June, bulbs hfted 25th Nov., 1842. 
 Remarks.— The land is alight loam, loose in texture, and of alight brown colour. Sub- 
 soil hard, and full of small stones : it is of as nearly as possible the same quality. The tur- 
 nip seed was all sown upon the same day. Rain came on the night after sowing, and in 
 consequence the crops brairded well, and came away strong. Those which show the great- 
 est weight in the Table kept the lead of the others all the season. The numbers of the 
 plots in the Table are placed in the order in which they followed each other on the ground. 
 The crop would probaWy have been larger had there been more rain. 
 
44 
 
 EXPERIMENTS ON TURNIPS. 
 
 [AppeTidtx, 
 
 No. 
 
 1 
 
 ORCHARD FIELD. 
 
 Description of Manures used. 
 
 Quantity 
 applied 
 
 per 
 imperial 
 
 Acre. 
 
 • 
 
 Produce 
 
 of Bulbs, 
 
 topped & 
 
 tailed, per 
 
 imp. Acre. 
 
 Produce of 
 
 Bulbs, topped 
 
 and tailed, per 
 
 imperial 
 
 acre. 
 
 Cost of Manure 
 per imperial 
 
 Acre,including 
 
 carriage and 
 
 putting on. 
 
 1 
 2 
 
 3j 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 10 
 11 
 12 
 13 
 
 "1 
 
 17 
 
 18 
 19 
 20 
 21 
 
 9'^ 
 
 Peat and Night-soil, mixed. . . . 
 Gypsum 
 
 20 tons. 
 
 5 cwt. 
 20 bush. 
 
 1 cwt. 
 20 bush. 
 20 bush. 
 
 lbs. 
 .50 bush. 
 50 bush. 
 10 cwt. 
 10 cwt. 
 50 bush. 
 10 cwt. 
 
 3 cwt. 
 3 cwt. 
 3 cwt. 
 
 50 bush. 
 
 50 bush. 
 
 50 bush. 
 
 50 bush. 
 50 bush. 
 40 bush. 
 
 1 ton. 
 1 ton, 
 
 20 Ions. 
 
 lbs. 
 
 4800 
 4080 
 4640 
 
 i 4320 
 
 3980 
 44U0 
 4240 
 5920 
 5560 
 4800 
 5200 
 4960 
 4080 
 6560 
 
 4240 
 
 4480 
 
 4400 
 
 3200 
 3600 
 4160 
 4000 
 3920 
 5200 
 3440 
 
 tons 
 17 
 14 
 16 
 
 15 
 
 14 
 15 
 15 
 21 
 19 
 17 
 18 
 17 
 14 
 23 
 
 15 
 
 16 
 
 15 
 
 11 
 
 12 
 14 
 14 
 14 
 18 
 12 
 
 cwt 
 
 2 
 
 11 
 
 11 
 
 8 
 
 13 
 14 
 
 2 
 
 2 
 17 
 
 2 
 11 
 14 
 U 
 
 8 
 
 2 
 
 
 14 
 
 8 
 17 
 17 
 
 5 
 
 
 11 
 
 5 
 
 T 
 
 2 
 2 
 
 2 
 
 1 
 1 
 3 
 3 
 1 
 3 
 3 
 1 
 2 
 2 
 
 3 
 
 
 
 1 
 
 2 
 1 
 1 
 3 
 
 2 
 3 
 
 jE. 
 6 
 
 
 
 1 
 
 
 
 2 
 2 
 2 
 2 
 3 
 I 
 1 
 3 
 
 
 
 1 
 
 1 
 
 
 1 
 
 5 
 
 8 
 
 9 
 
 10 
 
 s. 
 12 
 12 
 3 
 
 12 
 
 2 
 15 
 10 
 10 
 
 
 10 
 
 
 10 
 
 4 
 15 
 
 15 
 
 
 
 17 
 
 9 
 5 
 
 10 
 
 10 
 
 9 
 
 10 
 
 d. 
 
 6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 9 
 
 
 
 6 
 
 9 
 
 
 10 
 
 : 
 
 
 
 Carbonate of Lime 
 
 Sulphate of Ammonia 
 
 Quick-lime 
 
 Soot 
 
 Sulphur 
 
 Imitation of Daniel's mixture.. 
 
 Wood Charcoal Powder 
 
 Fresh Animal Charcoal 
 
 Exhausted Animal Charcoal. . . 
 Turnbull's Humus 
 
 Bones diss, in Muriatic Acid., , 
 
 Barochan Artificial Guano 
 
 Turnbull's do. do 
 
 Natural Guano 
 
 Salt and Quick-lime, mixed, ) 
 
 3 months old < 
 
 Soot 
 
 Potash and Lime mixed, 14 ) 
 months old \ 
 
 Quick-lime 
 
 Wood-ashes 
 
 Bone dust 
 
 Rape- dust 
 
 Woollen Rags 
 
 Farm-yard dung 
 
 23 
 
 Notliing 
 
 2°. Results of Experiments with various Substances used as manures for gi'owing i^ar/i/ 
 Liverpool Yellow Turnips, sown 9tli June, and lifted 2d December, 1842. TTie quantity of 
 land in each plot was one eighth of an imperial acre. 
 
 No. 
 
 BERRIE KNOWES FIELD. 
 Description of Manures used. 
 
 Natural Guano at 25s 
 
 Wood-ashes 
 
 Barochan Artificial Guano 
 
 Wood-ashes 
 
 Rape-dust 
 
 Turnbull's Artificial Guano 
 
 Wood ashes 
 
 Soil simple 
 
 Turnbull's Humus , 
 
 Bone-dust , 
 
 Potash <fe Lime mixed, 14 mos. old. , 
 
 Salt & Lime mixed, 3 mos. old , 
 
 Sulphate of Magnesia 
 
 Sulphate of Ammonia , 
 
 Nitrate of Soda , 
 
 Sulphate of Ammonia 
 
 Wood-ashes 
 
 Nitrate of Soda 
 
 Sulphate of Magnesia 
 
 Woodashcs.. . 
 
 Sulphate of Ammonia 
 
 Sulphate of Magnesia 
 
 Lime and Potash 
 
 Turnbull's Artificial Guano 
 
 Barochan Artificial Guano 
 
 Soil simple 
 
 Quantity of 
 Manure ap- 
 plied per im- 
 {5erial Acre. 
 
 cwt. 
 
 bush. 
 
 cwt. 
 
 bush. 
 
 cwt. 
 
 cwt. 
 
 bush. 
 
 bush. 
 
 bush. 
 
 bush. 
 
 bush. 
 
 cwt. 
 
 cwt. 
 
 cwt. 
 
 lbs. 
 
 bush. 
 
 lbs. 
 
 lbs. 
 
 bush. 
 
 lbs. 
 
 lbs. 
 
 bush. 
 
 cwt. 
 
 cwt. 
 
 Cost per Acre 
 
 including 
 carriage and 
 putting on. 
 
 Produce of 
 Bulbs, topped 
 and tailed, per 
 
 imperial Acre. 
 
 tons, cwt 
 
 qrs. 
 
 32 2 
 
 2 
 
 21 2 
 
 3 
 
 24 11 
 
 2 
 
 18 5 
 
 3 
 
 11 8 
 
 13 14 
 
 17 2 
 
 14 5 
 
 18 17 
 14 17 
 24 11 
 27 2 
 
 2 
 1 
 3 
 3 
 1 
 1 
 2 
 3 
 
 20 17 
 
 2 
 
 \ 
 
 
 11 11 
 
 2 
 
 16 14 
 
 1 
 
 21 4 
 24 2 
 12 17 
 
 I 
 1 
 1 
 
No. VIIL] 
 
 EXPERIMENTS ON TURNIPS, 
 
 45 
 
 Remarks. — The soil is a light hazel loam incumbent upon sand-stone rock. It was 
 trenched with the spade, in the spring of 1842, out of pasture grassj to the depth of 16 inches, 
 and the rock quarried out when it came nearer the surface than that depth, it was again 
 pointed over before sowing, after which the drills were made upon the flat surface with the 
 hoe, at the distance of 27 inches between them, the vianure soicn in by the hand, and co- 
 vered up, the seed sown and rolled in. The vveather was very dry at the time they were 
 sown, and continued so till about the 20th June, accompanied with east winds and bright 
 sunshine. They brairded moderately well, and most of them came away strong and 
 healthy. In examining them, and in the working them, which was done by the hand-hoe, 
 many of them showed a remarkable difference from the others ; parlioularly No. 1 was pre- 
 eirmient above the others for size of bulbs and strength of foliage. Many of the bulbs were 
 11 lbs. in weight; those with the saline and alkaline manures, such as Nos. 8, 9, 10, and 12, 
 were much smaller in bulbs and leaves than No. \, but were remarkable for firmness and 
 solidity of bulbs. No. 11 was larger in size boih of bulbs and leaves, but soft and light in 
 weight. No. 7 iiad very firm solid bulbs, as had also Nos. 2 and 4. The numbers of the 
 plots given in the Table indicate the order in which they were grown in the field. 
 The Uarochan Artificial Guxino consisted of 
 
 Bones dissolved in Muriatic Acid 2 cwt. 1 Nitrate of Soda 28 lbs. 
 
 Charcoal powder 2 cwt. | Sulphate of Soda and ,^ „„„. ^(\\\.a 
 
 Sulphate of Ammonia 1 cwt. I Sulphate of Magnesia \ ^^^^ °^' 
 
 Common Salt and Gypsum, each 1 cwt. | 
 
 Wood-ashes 5 cwt. | 12 cwt. I qr. 20 lbs. 
 
 See note to page 47. 
 
 3°. Experiments with various Manures on nine Acres of Turnips on the Farm 
 
 at Crooks, 1842. 
 
 6 
 
 Date of 
 Sowing. 
 
 Quantity 
 
 ofLaud 
 
 per Scotch 
 
 acre. 
 
 Manures, and quantities applied to 
 the land sown, per Scotch acre. 
 
 Produce 
 
 in Tons 
 
 per Scotch 
 
 acre. 
 
 Kinds 
 
 of 
 
 Turnip. 
 
 Value 
 of ma- 
 nures 
 applied. 
 
 1 
 
 May 28. 
 
 A. 
 
 1 
 
 1 
 
 1 
 
 
 
 1 
 
 1 
 
 1 
 1 
 
 R. 
 
 1 
 
 
 
 2 
 
 3 
 
 
 
 1 
 
 I 
 1 
 
 Rape-dust 5 cwt., Ilumus 25 bushels, 
 Bone-dust 12 bushels, Peat ashes 5 
 carts 
 
 22 
 
 20 
 
 24 
 
 19 
 
 20 
 
 IS 
 14 
 12^ 
 
 Swedes. 
 
 Do. 
 Yellow. 
 
 Do. 
 
 Do. 
 
 Do. 
 
 Do. 
 
 White. 
 
 £. 
 
 4 
 
 4 
 
 10 
 
 10 
 
 3 
 
 2 
 4 
 5 
 
 s. 
 
 15 
 
 10 
 
 15 
 
 
 
 5 
 
 15 
 
 2 
 
 12 
 
 2 May 30. 
 
 3 June 6. 
 
 4 June 11. 
 
 5 June 15. 
 
 6 June 17. 
 
 Rape-dust 5 cwt.. Bones 10 bushels. 
 Humus 25 bush., Ashes 5 carts 
 
 Johnstone town-dung 30 tons at Cs., 
 Bones 14 bush, at 2s. 6d 
 
 Farm-yard dung 25 tons at 7s., Bones 
 
 Artificial Guano (No. 1., p. 50) 2 cwt., 
 Humus 40 bush., Peat ashes 5 carts. 
 
 Natural Guano 1 cwt , Humus 40 
 busliels 
 
 7 
 
 8 
 
 June 28. 
 July 4. 
 
 Humus 57 bush., Bones 10 bush 
 
 Artificial Guano mix., (No. 11., p. 50.) 
 
 Remarks.— No. 1. Soil a stiff loam, moist, and in good order ; when the seed was sown 
 It brairded well, and came away at once. 
 
 No. 2. Soil rather lighter than the former; seed brairded well, and came away at once. 
 
 No. 3. Soil the same as above ; brairded quickly in consequence of a shower of rain. 
 
 No. 4. Soil lighter than No. 3; a bad braird, and turnips long of springing for want of rain. 
 
 No. 5. Soil as above ; long of brairding in consequence of want of rain. 
 
 No. 6. Soil as above ; and like No. 5, still very dry for want of rain ; a late braird. 
 
 No. 7. Soil lighter, mixed with peat ; no rain— bad braird. 
 
 No. R. Soil heavy clay loam ; no rain, and a bad braird. 
 
 The two latter, from drought and late sowing, did not grow much till the end of Sep- 
 tember ; and when checked by frost in the beginning of November, were still growing 
 vigorously. 
 
 N. B — The land was of different qualities, the seed also sown at different times, and in 
 very different states of the atmosphere, with respect to moisture, yet the average produce 
 was good ; and although it is not easy to say which of the artificial manures, under such 
 circumstances, was actually the beet, the general result shows that any of these used will 
 produce on my land a good average crop of turnips, and at a less expense than farm-yard 
 manure, and tends to confirm the correctness of various experiments tried by me on a 
 smaller scale. The measurements having been made by the Scotch chain, I have not al- 
 tered them. No. 8 would probably have been the best turnips, had they been sown earlier, 
 and been assisted by a fall of rain. 
 
4b 
 
 EXPERIMENTS ON TURNIPS. 
 
 [Appendix^ 
 
 4°. Results of Experiments with different mixed manures, in growing TV/iile Globe Tur- 
 nips, on new trenched land, Bucklather Field. Sown 13lh July, and lifted 16th December, 
 1842. 
 
 Description of Manure used. 
 
 Turnbull's Humus 
 
 TurnbuU's improved Bones 
 Barochan artificial Guano.. . . 
 Natural Guano 
 
 Quantity 
 
 per 
 
 imperial 
 
 Acre. 
 
 60 bush. 
 5 cwt. 
 5 cwt. 
 5 cwt. 
 
 Price of 
 
 Manure 
 
 per 
 
 Acre. 
 
 £. s. d. 
 
 3 
 
 1 10 
 
 2 10 
 6 5 
 
 Weight in 
 
 imperial 
 
 pounds pr. 
 
 >8th Acre. 
 
 Weight in 
 Tont5, &c. 
 per impe- 
 rial Acre. 
 
 lbs. 
 
 5950 
 
 4900 
 
 6300 
 
 9170 
 
 tons. cwt. 
 
 21 5 
 17 10 
 
 22 10 
 39 15 
 
 The Natural Guano was purchased December, 1S41, when the price was JE25 per ton. It 
 can now be had for £12. 
 
 Remarks. — The land was trenched 18 inches deep, and completely drained at the dis- 
 tance of 18 feef, with tile drains laid 30 inches deep, in Feb. 1842. Previous to this it was in 
 a wef, sour state. It was again pointed over with the spade, and the drills made for the 
 manures with the hoe upon the level surface. The manures were then sown in the bottom 
 of the drills with the hand, and a little earth being put over them, the seed was sown, 
 covered, and rolled. The weather had been dry for some time before sowing, but rain 
 came on that day , they brairded quickly, and continued to grow till lifted — the field being 
 well sheltered. The tops of Nos. 2, 3, and 4 were of a dark green colour, and remarkably 
 luxuriant, many of the bulbs weighing from 5 to Ribs. No. 1 was of a lighter green, but 
 strong and healtliy, and many of the bulbs of this lot were 5 and 6 lbs. The bulbs of all of 
 them were finely shaped. 
 
 in. The object of the two following scries of experiments was the same as in 
 those of Mr. I'leming. 
 
 1°, Results of comparative experiments upon Swedes rxwA. other Turnips made 
 on the home farm of Mr. Alexander, of Southbar, near Paisleyj in 1842. 
 
 The soil of the field was a deep loam, with a slight admixture of peat — tlie 
 subsoil was partly a hght clay and partly a sandy gravel. It was thoroughly 
 tile-drained and subsoiled to the depth of fourteen inches. 
 
 No. 
 
 Kind of Manures. 
 
 Swedes, sown 8th May. 
 
 Botte-dust , 
 
 Bones 
 
 Ash-dung 
 
 Farm-yard dung 
 
 Mixture of Yellow Sf White, soion 20th July. 
 
 Guano 
 
 Guano 
 
 Farm-yard manure 
 
 Quantity 
 
 per 
 
 imperial 
 
 Acre. 
 
 32 bush. 
 16 bush. 
 12 tons. 
 32 tons. 
 
 3J cwt. 
 2 cwt. 
 8 tons. 
 
 Cost per 
 
 imperial 
 
 Acre. 
 
 £. s. 
 
 4 8 
 
 5 8 
 11 4 
 
 3 10 
 ' 4 16 
 
 Produce 
 
 in bulbs 
 
 per imp. 
 
 Acre. 
 
 24 tons. 
 28 tons. 
 30| tons. 
 
 20 tons. 
 j24 tons. 
 
 Mr. Alexander adds, I must here notice particularly the result of the last two experi- 
 ments. The seed sown was a mixture of yellow and white, and llie period of sowing as 
 late as the 10th .Inly. The weather at the time being favourable, they brairded quickly, 
 grew with great vigour, and when all the other turnips in the field became affected with 
 mildew they stood as green as ever. This (viz., the non-mildewing) I attribute greatly to 
 the guano, as well as to the late sowing, never before having seen such a weight of turnips 
 produced, sown so late in the season. I applied other artificial manures on both of these 
 fields with a due proportion of dung, varying the quantities and modes of application, as ap- 
 peared to me best to test their qualities, but as the comparative effect is so difficult to decide 
 upon, I can only here observe, with any certainty, that though the turnips brairded quicker 
 when the dung was assisted with these manures, particularly where Turnbull's humus was 
 applied, the crops afterwards did not appear tome to be materially aided. 
 
 2°. Result of experiments upon Yclloio Turnips made by Mr. Alexander, of 
 Southbar, at Wellwood Farm, Muirkirk, Ayrshire, 1842. 
 
 T))e nature of the soil on which the experiments were made was reclaimed moss 
 (then about 2 feet deep), having a clayey subsoil, but which had been thoroughly 
 drained with tiles at fifteen feet apart. The field had produced white and hay 
 
No. VIII.] 
 
 EXPERTMENTS ON TURNIPS. 
 
 47 
 
 crops, but, as far as known, had never been previously green-cropped. The whole 
 of it received the same labour, preparatory to sowing, and the weather during the 
 operation (-whicli lasted four days) was tiie same, thus giving to each experiment 
 an equal chance. The period of sowing was from the 15th to 19th of May ; the 
 turnip seed used was Skirving's improved purple-topped yellow ; the dung used 
 was the produce of the farm, and, with the exception of the foreign guano, all the 
 other manures applied were those manufactured and sold by Mr. TurnbuU, of 
 Glasgow. T/ie extent of ground for each experiment laas one acre, Scotch measiire. 
 
 No. 
 
 Kind of Manure. 
 
 Farm-yard Dung. . 
 Humus 
 
 Farm-yard Dung. . 
 
 Humus' 
 
 Artificial Guano. . . 
 Farm-yard Dung. . 
 Prepared Bones*.. 
 Farm-yard Dung. . 
 
 Humus 
 
 improved Bones.. 
 Artificial Guano... 
 Ammoniacal Salts. 
 Artificial Guano... 
 Guano 
 
 Quantity 
 
 per 
 
 imperial 
 
 Acre. 
 
 12 tons. 
 
 2 cwt. 
 12 tons. 
 
 If cwt. 
 
 1- " 
 12 tons. 
 
 2^ cwt. 
 12 tons. 
 90 lbs. 
 90 " 
 90 " 
 45 " 
 
 3i cwf. 
 
 3| " 
 
 Cost of 
 Manure 
 
 Produce 
 in Bulbs 
 
 per impe- [per impe- 
 rial Acre, rial Acre. 
 
 £. 
 
 4 
 
 
 
 4 
 
 
 
 
 
 4 
 
 15 
 
 4 4 
 
 
 
 
 
 
 
 
 
 1 
 
 3 
 
 s. d. 
 4 O; 
 8 0< 
 
 4 o; 
 
 7 0} 
 
 c oS 
 
 4 O; 
 OS 
 
 "1 
 
 3 9 1 
 
 4 10 
 
 5 6 
 
 8 
 3 
 5 
 
 28 tons. 
 
 24 
 
 20 
 
 16 
 
 28 " 
 
 Cost for 
 Manure 
 per ton. 
 
 3§ 
 1 
 
 IV. Ejj'ect of Gypsum on the T-urnip Crop. 
 
 In 1841, Mr. Burnet of Gadgirth, near Ayr, applied a top-dressing of gypsum 
 to part of a field of turnips, and found that it nearly doubled, the crop. 
 
 In 1842, Mr. Canapbell, of Craigie, in the same neighbourhood, "dressed a 
 six acre field, with the exception of a few rows, with two cwt. of unburned 
 gypsum per acre. The crop over the v/hole was excellent, but there was no 
 perceptible difference between the dressed and the undressed part." 
 
 How are these discordant results to be reconciled 7 The following questions 
 suggest themselves as worthy of investigation — 
 
 1°. Is gypsum really propitious to the turnip crop, — and to every variety alike? 
 
 2°. Are the unlike results above obtained to be ascribed to the abundant pre- 
 sence, in the one case, of gypsum in the soil, or in the manure ploughed in, 
 and its absence in the other — or to the variety of turnip cultivated 1 — or 
 
 3°. Can the sea-spray supply gypsum to Mr. Campbell's estate, which is 
 within two miles of the coast, while it is less bountiful to that of Mr. Burnet, 
 which is six miles inland 1 
 
 B.— EXPERIMENTS ON POTATOES. 
 
 I. Results obtained by Mr. Campbell, of Craigie. 
 
 Four equal drills of potatoes were treated as follows : — . 
 
 J °. Guano, 3 cwt. per acre produce 5 pecKS. 
 
 2°. Farm-yard dung, 40 cubic yards per acre . . . produce 6 do. 
 3°. Do., top-dressed afterwards with 60 lbs. of nitrate of soda, produce 6 do. 
 4°. Do., top-dressed with 160 lbs. sulphate and nitrate, mixed, produce 6 do. 
 
 * TurnlndVs Humus is formed from urine and night-soil mixed with gypsum and char- 
 coal and then dried. 
 
 TurnbuW 8 prepared Bones are hones and flesh dissolved in muriatic acid, and mixed 
 with about an equal quantity of charcoal in powder. 
 
 TurnbuWs Artificial Guano is, I believe, prepared bones, with a little salt and sulphate of 
 ammonia prepared from urine, and dried with a stove-heat. 
 
4b 
 
 EXPERIMENTS ON TURNIPS. 
 
 [Appendix, 
 
 The above result is favourable to guano, considering that it was applied in 
 such small quantity ; but why did the saline manures produce no effect — was 
 it "because of the drought of the season, or was it because Mr. Campbell's land 
 is already amply supplied with salts of soda from its vicinity to the sea'? (see 
 Lectures, pp. 344 and 346). These experiments are not unworthy of repetition 
 on a larger scale. 
 
 II. Some very striking results, obtained by top-dressing potatoes with saline 
 manures on a small scale, were described by Mr. Fleming, of Barochan, in 
 1841, and are recorded in the preceding part of this Appendix (p. 20). The 
 following three series of experiments, made under the direction and superin- 
 tendence of the same gentleman, have been made upon a larger scale, and with 
 the view of throwing light upon a greater number of interesting points — 
 
 The object of the first series was to ascertain the effect — 
 
 1°. Of (lijjerent mixed mrmures, 2ohen applied alone to the potato crop. 
 
 2°. 1'^heir relative effects on different varieties of potato. 
 
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No. VIII.] 
 
 EXPERIMENTS ON POTATOES. 
 
 2°. The object of the two following series of experiments was to ascertain — 
 1°. The relative effect of different sali7i£ snbstances applied along wUh farmyyard 
 manure; and — 2°. Whether the effects were gresiter when mixed with the ma- 
 nure at the time of planting, or when subsequently applied, as a top-dressing, to 
 the growing plants. 
 
 1°. Result of Experiments with satitie substances in top-dressing Early American 
 Potatoes. Planted 18th April, top-dressed 1st June, and lifted 28th Sep- 
 tember, 1842. Low Field, Barochan. The quantity of land in each plot 
 was one-eighth of an imperial acre. 
 
 No. 
 
 Description of 
 Top-dreesing. 
 
 Quantity IProduce 
 of dressing in pecks 
 
 applied i of 35 
 per j pounds 
 imp. acre. each. 
 
 Produce in 
 bollis of 5 
 cwt. each 
 
 per imperial 
 acre. 
 
 Produce in 
 
 tons, (fee, 
 
 per imperial 
 
 acre. 
 
 Cost of 
 
 dressings pr. 
 
 imp. acre, 
 
 including 
 
 caiTiage and 
 
 putting on. 
 
 Nitrate of Soda 
 
 Sulphate of Ammonia. 
 Sulphate of Magnesia . 
 
 Nitrate of Potash 
 
 Nothing but Dung 
 
 Sulphate of Soda 
 
 Nitrate of Soda 
 
 Sulphate of Soda 
 
 Sulphate of Soda 
 
 Sulphate of Ammonia. 
 Sulphate of Magnesia. . 
 I Nitrate of Soda 
 
 cwt. 
 U 
 
 10 cubic yds. 
 
 H 
 
 pecks. 
 128 
 110 
 106 
 148 
 98 
 
 144 
 
 GO 
 
 151 
 
 180 
 
 bolls. 
 64 
 58 
 53 
 74 
 49 
 
 72 
 
 49 
 
 75^ 
 
 90 
 
 tns. cwt. qrs. 
 
 16 — — 
 
 10 — 
 
 5 — 
 
 10 — 
 
 15 — 
 
 £. 8. d. 
 
 1 11 
 
 1 11 
 12 6 
 
 2 3 
 
 
 18 — — 
 
 12 15 — 
 
 18 17 2 
 
 [22 10 — 
 
 1 4 9 
 
 e 15 
 
 14 9 
 
 1 9 
 
 Remarks. — The soil is a light loam of good quality, subsoil hard, stoney fill, and retentive 
 of water. The potatoes were planted with the spade at the distance of 26 inches between 
 drills. The manure, farm-yard dung at the rate of 40 cubic yards per acre, spread in the 
 bottom of the drills — cut sets laid on this and covered up. (The cut tubers planted were 
 the produce of those top-dressed last season (see Appendix, page 20). Came away strong 
 and healthy, of a dark green colour, and were very remarkable from the contrast which 
 they presented to the same variety of Potato— planted alongside this experimental ground 
 — that had not been dressed last season. These last came away weak, and of a yellowish 
 green colour, and, under the some treatment in every respect, did not produce so good a 
 crop by 15 bolls per acre). Nos. 1, 2, 4, 6, S, and 9, had all the same effect in altering the 
 colour of the stems and leaves to a darker green. Nos 3 and 7 had not that effect, but No. 
 3 added greatly to the produce. No. 7 made no visible altGration, but burned the tops se- 
 verely at the time of dressing, as did most of tJie others this dry season ; this burning was in 
 most cases only temporary. 
 
 2°. Results of Experiments witli different saline subsr'anccs, -mixed xiyilh farm- 
 yard dung at the time of planting, in growing Early American Potatoes. 
 Planted 29th April, and lifted 31st August, 1842. The quantity of land in 
 each plot loas one-eighth of an imperial acre. 
 
 
 
 
 
 
 
 Cost of Salts 
 
 
 
 Quantity 
 
 Produce 
 
 Produce 
 
 Produce 
 
 used, per 
 
 
 Description 
 
 apphcd per 
 
 in pecks 
 
 in bolls, of 
 
 in tons, 
 
 acre, inclu- 
 
 No. 
 
 of Manure and Salts. 
 
 imperial 
 
 of 35 lbs. 
 
 5 cwt. 
 
 &c., per 
 
 ding patting 
 
 
 
 acre. 
 
 each. 
 
 each, per 
 acre. 
 
 acre. 
 
 on,excluBive 
 of Dung.' 
 
 
 
 
 Pecks. 
 
 Bolls. 
 
 tns. cwt. qrs. 
 
 £. s. d. 
 
 1 
 
 Farm-yard Dung alone. . 
 
 35 cubic yds. 
 
 71 
 
 35i 
 
 8 17 2 
 
 
 2 Com Salt, added to Dung 
 
 2 cwt. 
 
 70 
 
 3b 
 
 8 15 
 
 4 
 
 3 Nitrate of Soda, do. 
 
 li » 
 
 99 
 
 49i 
 45t 
 
 12 7 2 
 
 1 12 
 
 4 Sulph. of Magnesia, do. 
 
 2 « 
 
 91 
 
 11 7 2 
 
 17 
 
 5 Sulph. of Ammonia, do. 
 
 H" 
 
 107 
 
 53| 
 
 13 7 2 
 
 1 12 
 
 6 Sulph. of Soda, do. 
 
 2 " 
 
 64 
 
 32 
 
 8 
 
 17 
 
 7 Silicate of Potasht do. 
 
 1 « 
 
 120 
 
 60 
 
 15 
 
 
 * Dung 5s. 6d. per cubic yard, exclusive of cartage and spreading, 
 t The sUicate of potash or soluble glass was directly prepared from caustic potash and 
 sand, or silex fu$iQd together. 
 
50 
 
 EXPERIMENTS ON POTATOES. 
 
 [Appendix, 
 
 Remarks. — The soil upon which the above were grown was a subsoil, the upper soil 
 having been taken off at diflferent times. It was trenched two feet deep in tlie Spring of 
 1841, and which had to be done with tlie mattoclt, it being too hard for the spade alone, it 
 was cropped that season with potatoes, manured with 40 cubic yards of compost of weeds, 
 cut grass, and half-rotten leaves. It was again trenched to the same depth after the crop of 
 potatoes was lifted ; and was again planted in the Spring of 1842 with potatoes, manured 
 witti 35 cubic yards of farm-yard dung, mixed in the proportions stated with the above salts. 
 The potatoes were planted with the spade, at the distance of two feet between the drills, the 
 manure being put in the bottom of the drills, the salts sown by the hand above it, and then 
 all mixed together with a dang fork. The cut sets were laid upon the mixture, and covered 
 up. As was remarked in 1841, the potatoes with No. 3 were eight to ten days brairded before 
 the others ; also Nus. 5 and 7 were earlier than the others., those three being all fairly up in 
 drills before the others trwde their appearance through the ground. Nos. 2, 4, and 6 were la- 
 test, and very irregular in coming up, and upon examining the drills a few of the sets ap- 
 peared to have been burned. There was a marked dissimilarity in the stems and leaves of 
 these potatoes through the summer. Nos. 3, 5, and 7, were al\ of a darker green colour and 
 stronger than the others. No. 7 was remarkable' for intenseness of colour and length of 
 stems, so much so that it appeared to be a different variety of potato. No. 4 was fully bet- 
 ter in appearance thun Nos. 2 and 6, which were of a yellowish green colour and had a 
 stunted appearance all the season. — When this ground was first broken up, a pound of it 
 was boiled in pure rain water and filtered, which was then evaporated, the residue weighed 
 4^ grains, mostly soluble salts, but hardly a trace of common salt. 
 
 3°. The followmg experiments were made with the view of determining koio 
 far e:miomical mixtures might be made to supersede farm-yard manure in the 
 groivth of potatoes : — 
 
 1°. Account of an Experiment in growing Potatoes (Irish Pink Eyes) with the following 
 mixture of substances, instead of farm-yard dung, planted a3th April, 1842. 
 
 No. 1 
 
 Ingredients. 
 
 Rape-dust 
 
 Bones dissolved in Muriatic Acid 
 
 Sulphate of Magnesia 
 
 Carbonate of Lime 
 
 Nitrate of Soda 
 
 Common Salt 
 
 Sulphate of Soda 
 
 Sulphate of Ammonia 
 
 Sulphur 
 
 Dry Moss-Earth 
 
 Quantity in- 
 tended to ma- 
 nure four 
 acres. 
 
 cwts. qrs. lbs. 
 5 
 
 20 26 
 
 Cost of 
 Substances 
 
 for 
 four acres. 
 
 £. s. 
 
 1 10 
 
 12 
 
 6 
 
 1 
 
 10 
 
 2 
 
 9 
 
 10 
 
 1 
 
 1 
 
 Remarks. — The above mixture was sown in the drills at the rate of about 5 cwts. per im- 
 perial acre, at a cost of little more than .£1. sterling, and produced a fair crop of potatoes of 
 a remarkably fine quahty, 43 bolls per acre of imperial Renfrewshire measure, weighing 5 
 cwt. each, upon a poor and light, although new soil, but not worth more than 25s. per acre. 
 Great caution is required in using this mixture, as it is very apt to bum the cut sets if laid 
 directly upon them. A httle earth should be put between the cut potato and the manure. 
 
 2°. The following mixture was made, and lay together for five weeks, when it was sown in 
 the bottoms of potato drills upon a poor tilly soil, and White Don Potatoes planted with it 
 80th April, 1842. 
 
 No. 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 
 Ingredients. 
 
 Quantity mixed 
 
 to manure one 
 
 acre. 
 
 Cost of Sub- 
 stances for 
 one acre. 
 
 Saw-dust, mostly from Alder. . . . 
 Potash <fe Lime mixed, 14 mos. old 
 Common Salt 
 
 cwta. qrs. 
 
 1 2 
 1 
 2 
 2 
 
 bush. 
 40 
 10 
 
 £. s. d. 
 
 7 6 
 2 3 
 10 
 3 6 
 4 
 10 
 
 Sulohaf e of Ammonia 
 
 Sulphate of Soda 
 
 Sulphate of Magnesia 
 
 
 
 
 3 2 
 
 50 
 
 2 7 3 
 
No. F/7/.] EXPERIMENTS ON POTATOES. 51 
 
 Remarks. — The potatoes planted with the above mixture came quickly through the 
 ground, and were very luxuriant in foliage. They were lifted 15th October, after being cut 
 down by frost whilst still unripe and growing. On being taken up, they were found to yield 
 a produce of 56 bolls of Renfrewshire measure, weighing 5 cwts. each, per acre, of very 
 fine potatoes, many of which weighed from 24 to 30 oz. each. 
 
 N. B — This mixture, after being put together, fermented, and was frequently turned, but 
 kept dry. 
 
 The several series of experiments made upon potatoes by Mr. Fleming are 
 deserving of careful consideration, and many of them of judicious repetition. 
 They are all well contrived or devised, and each series skilfuUy arranged. 
 
 In agricultural experiments it is of the greatest possible consequence that the 
 practical man should have a clear and definite object distinctly in view. If so, 
 his experiments may be signally successful in his own estimation, while, eco- 
 nomically considered, they may be total failures. This, as we have seen, was, 
 to a certciin extent, the case with the first series of experiments made upon Lord 
 Blantyrc's farm, as above detailed (p. 42). The applications in some instances 
 lessened the crop, but the result, nevertheless, threw considerable light upon the 
 questions which the trials were intended to solve. 
 
 In making an experiment, the practical farmer asks a question of nature ; — in 
 arranging the form and details of his experiment, he is putting together the 
 words by which his question is to be expressed. If his question be clearly put, 
 nature will give him, sooner or later, a clear and distinct answer — if he have 
 skill enough in nature's language to understand what she has said to him. I 
 say, sooner or later, for it may be sometimes necessary to repeat the question, 
 either because something has intervened to prevent nature, so to speak, from 
 hearing his question, — because it has not been accurately expressed — or because 
 something in the seasons, or otherwise, has prevented her answer from being 
 clearly understood — perhaps from being; heard or read at all. Circumstances 
 may even prevent the answer from being given until a second summer come 
 round, when, if we are not on the alert, it may never be received at all. 
 
 The above experiments, as well as those which follow, form an excellent 
 study for the practical farmer in reference to this matter. Eveiy series is plan- 
 ned with a view to a given end, the circumstances are carefully noted before, 
 durmg, and at the close of each of the several trials, and the answers are re- 
 corded with a very praiseworthy degree of accuracy. I shall place together, in 
 one view, the most important of the deductions to which the experiments of 
 1842 appear to have led, when I shall have laid before the reader the whole of 
 the tables which have as yet been placed in my hands. 
 
 C— EXPERIMENTS UPON BARLEY. 
 
 The object of the following experiments, also made by Mr. Fleming, was to 
 ascertain the relative effect of different saline stdistances, when applied, as tap- 
 dressings, to a crop of vJhite barley. 
 
 The results, as shown in the last column, are sufficiently interesting. 
 
 Results of Experiments witli various substances used as top-dressings upon 
 Barley (common white). The Barley sown i4th April, top-dressed 6th 
 May, and cut down 25tli August, thrashed, cleaned, measured, and weighed 
 5th October, 1842. T/ie qtiantity of land in each plot was one-eighth of an 
 imperial acre. 
 
 Remarks.— The soil of this field is a light loam, as nearly as possible uniform in quality, 
 and had lain about ten years in pasture previous to the spring of 1842, when it was all 
 trenched with the spade twelve inches deep. It had been thorough-drained with tiles some 
 years before breaking up. After being trenched, it was dressed over, except where the ex- 
 periments were, with two chaldrons of lime per acre, slaked with water, in which commoa 
 salt had been dissolved, and before sowing the barley, with the exception of the experiment 
 ground, it v/as top-dressed over with two and a half cwts. of TurnbuU's artificial guano per 
 acre, harrowed in, as was also the top-dressing No. 3 in the table of experiments. The bar- 
 ley was sown broadcast, 2| bushels per acre. Owing to the extraordinary drought at time 
 of sowing, it did not braird well till rain came ; after which it made rapid progress. Advan- 
 tage vras taken of heavy rains to put on the top-dressings, all of which were .sown at the 
 time above stated, viz., 6th May, except No. 4, which was not sown till the 17tb, at which 
 
52 
 
 EXPERIMENTS UPON BARLEY. 
 
 [Appendix 
 
 No. 
 
 RoDEN Hill Field. 
 
 Description 
 of Top-Dressings. 
 
 Nitrate of Soda 
 
 Common Salt 
 
 Sulphate of Soda 
 
 Sulphate of Magnesia 
 
 Natural Guano, at 25s 
 
 Nitrate of Potash 
 
 Common Salt 
 
 Nothing 
 
 Turnbull's Artificial Guano.. 
 
 CO bi 
 
 s c 
 
 lbs. 
 10^ 
 14 S 
 2W 
 
 42 
 14 
 42 
 
 42 
 
 _ » nj 
 
 .5 "C HI 
 
 cx: 
 ■^ 3 ca 
 
 lbs. 
 1821 
 
 1638 
 
 2192 
 1665 
 1735 
 1620 
 1925 
 
 be s m ■ 
 V. o Bi "n 
 
 i 5 = 
 
 C ex o;< 
 
 lbs. 
 364 
 
 378 
 
 432 
 255 
 378 
 325 
 334 
 
 1^' 
 
 
 
 lbs. 
 500 
 
 491 
 
 589 
 590 
 495 
 425 
 480 
 
 lbs. 
 56 
 
 55 
 
 54 
 54 
 57 
 55 
 54 
 
 O.S 
 
 C i-i 
 
 CftcS 
 
 s. 
 2 
 
 1 
 
 9 
 3 
 6f 
 
 3 
 
 7 
 6 
 
 bush. lbs. 
 
 52 
 
 54 54 
 
 64 
 
 37 42 
 
 53 3 
 47 15 
 49 26 
 
 time there tras little rain, and, in conserjueyice, it burned theplatits, of which they did not re- 
 cover all the season, and the ground got full of weeds. No. 5 burned the plants also, but 
 they recovered quickly, and gave a good return. As was remarked be/ore, wherever common 
 salt was put on as a top dressing on grain crops, either of wheat, bar lei/, or oats, and on what- 
 ever description of soil upon this estate, the grain was invariably heavier per bushel, and had 
 fewer weaks or tails in proportion to the quantity of grai7i per acre, than any of the other 
 dressings applied here. From the frequent mention of spade culture in these experiments, 
 many may consider that they were upon a very small scale, which is not the case, the 
 greater proportion of them being very extensive. Mr. Fleming, to give employment to the 
 destitute labourers, having dug and trenched about thirty acres of land instead of ploughing 
 it, which accounts for the frequent mention of spade culture, which, when it can be got ex- 
 ecuted at a moderate rate (particularly trenching at £1. per acre), is very advantageous, 
 and seems superior to trench ploughing. • A. F. Gardiner. 
 
 D.— EXPERIMENTS UPON OATS. 
 
 The first of the following series of experiinents was made at Lennox-Love, 
 at the request of Lord Blantyre, the second at Baroch an, under the direction 
 of Mr. Fleming. The general object of both was the same — to ascertain the 
 relative effect of different saline substances applied as top-dressings upon young 
 oats ; but those of Mr. Fleming have, besides, the special object of ascertaining the 
 effect of certain viixtures upo7i oats when grown upon mossy land. 
 1°. Oats, second crop, after old lea. Soil sharp loam ; subsoil clay resting on sand-stone 
 rock. Oats sown 14th March ; top-dressings applied 13th May ; crop cut 27th Aug. ; and 
 thrashed 9th Sept., 1842. TTwquantityof land in each plot was one-eighth of an imperial acre. 
 
 No. 
 
 Quarry Park, 
 Lennox-Liove. 
 
 Description of 
 Dressing. 
 
 Nothing 
 
 Common Salt 
 
 Common Salt 
 
 Rape-dust 
 
 Nitrate of Soda. . . . 
 Nitrate of Soda,.,. 
 
 Rape-dust 
 
 Nitrate of Soda. . 
 Sulphate of Soda, . 
 Sulphate of Soda. . 
 Sulphate of Soda . 
 
 Rape-dust 
 
 Rape-dust 
 
 Guano 
 
 Soot 
 
 Waste water from gas 
 work diluted with 4 
 times itsbulk of water 
 
 Cf 
 
 lbs. 
 
 6galls. 
 
 s. d 
 
 4 
 
 7 
 
 3 1 
 
 8 7 
 
 2 
 
 1 
 
 7 5 
 
 14 
 5 
 
 4 
 
 Weight taken from 
 Thrashing Mill of 
 
 
 •SPrt. 
 
 C3<C O 
 
 lbs. 
 672 
 
 588 
 
 644 
 588 
 616 
 
 504 
 
 504 
 
 672 
 
 616 
 938 
 532 
 
 lbs. 
 264 
 239 
 
 236 
 
 205 
 
 231 
 
 187 
 
 188 
 
 263 
 
 224 
 351 
 193 
 
 700 I 273 
 
 CD o 
 
 lbs. 
 
 8 
 
 13 
 
 24 
 
 2'x 
 
 17 
 
 12§ 
 
 11 
 
 20 
 
 26 
 30 
 11 
 
 15 
 
 lbs 
 3G2 
 323 
 
 328 
 
 276 
 
 296 
 
 266 
 
 249 
 
 355 
 
 324 
 496 
 269 
 
 390 
 
 6§ 
 
 lbs. 
 38 
 13 
 
 56 
 
 86 
 
 72 
 
 38i 
 
 56 
 
 34 
 
 42 
 61 
 59 
 
 22 
 
 be !.> 
 
 lbs. 
 39^ 
 40 
 
 40 
 
 39| 
 
 40 
 
 39 
 
 39i 
 
 40i 
 
 40 
 40 
 37| 
 
 39i 
 
 '^ •- 
 
 3j 
 
 bushs. 
 6-75 
 6-00 
 
 5-95 
 
 519 
 
 5-56 
 
 4-81 
 
 4-82 
 
 6-56 
 
 5-62 
 8-75 
 512 
 
 7 00 
 
 £ 
 
 Q. 
 
 -a 
 
 CO 
 
 m 
 
 
 
 Oi 
 
 
 O 
 
 a 
 
 
 (U 
 
 
 
 frt 
 
 .5 
 
 
 Sh 
 
 -J 
 
 ® 
 
 
 r3 
 
 2 
 
 £t30!c^0 
 
 bush. 
 
 2 00 
 •26 
 
 ,bush. ' 
 
 •75 I 
 
 •80 ! 
 
 1-56 ! 
 
 119 i 
 
 I 
 
 1-94 I 
 
 1-93 i 
 •19 J 
 113 
 
 163 
 
No. VIIL] 
 
 EXPERIMENTS UPON OATS. 
 
 53 
 
 2°. Results of Experiments with various substances used as top-dressings upon Oats (Sandy 
 Oats), sown 16th April, upon drainedpeat moss. Nos. 2, 3, and 5 top-dressed on the same 
 day ; No. 1 dressed Cth May, cut down 14th September, and thrashed, cleaned, and 
 weighed 6th Oct,. 1842. The quantity of land in cachplot icas one-eighth of an imperial acre. 
 
 No. 
 
 SHAW PARK FIELD, BAROCHAN, 
 
 Description of Dressing. 
 
 Cf 
 
 "5.S 
 
 is 
 
 J3 >, . 
 
 Sulphate of Ammonia 112^ lbs. 
 
 Water 20 galls. 
 
 Sulphate of Soda 21 lbs. 
 
 Nitrate of Soda 9^ lbs. 
 
 Bones dissolved in Muriatic' 
 Acid )421bs. 
 
 Nothing I 
 
 Sulphate of Ammonia 7 lbs. 
 
 Silicate of Potash 14 lbs. 
 
 ■j ISulphate of Soda 14 lbs. 
 
 { '.Bones dissolved in Muriatic 
 
 [{ Acid |141bs. 
 
 lbs. 
 ! 1105 
 
 !l220 
 
 1340 
 <J60 
 
 1600 
 
 et > <v 
 
 -G 'C .G 
 
 lbs. 
 270 
 
 305 
 
 320 
 210 
 
 350 
 
 
 hU C 
 
 OP C 
 
 O) -^ 
 Q.<C 
 
 ■S-§ 
 
 ><~ a; 
 
 > o Ja! 
 
 Jbs. 
 420 
 
 450 
 
 4S0 
 320 
 
 620 
 
 lbs. 
 41 
 
 40 
 
 42 
 39 
 
 43 
 
 s. d. 
 
 2 6 
 
 3 6 
 
 2 I 
 1 2^ 
 
 U 2, 
 
 o'C^ 
 
 Of; 
 
 bush. lbs 
 52 18 
 
 61 
 
 60 40 
 43 3 
 
 65 5 
 
 Remarks. — The soil upon which the above were grown is moss, rather deeper in some 
 parts than others, incumbent upon gravel of a stiff retentive quality. It had been partly 
 drained some years ago, but owing to the nature of the soil the drains did not act well. In 
 the spring of 1842, it was again drained with tiles, and trenched over with the spade to tlie 
 depth of 16 inches, and some of the gravel subsoil brought up among the moss. The ground 
 being divided into lots for the purpose, the top-dressings Nos. 2, 3, and 5 were sown on the 
 16th April, and slightly harrowed in ; the oats were then sown and harrowed in- No. I was 
 made from 160 Iba. sulphate of ammonia dissolved in 100 galls, of water (proportions for an 
 imperial acre), and sprinkled upon the oats during the time of rain on Gth May. No. 5 was 
 sown upon a lot where the moss was fully the deepest. They all brairded well ; Nos. 2 and 
 5 coming rather earlier than the others, and of a darker colour, parlicularly No. 2. No. 1, 
 after being watered with the solution, became also of a darker green, but neither Nos. 1 nor 
 2 were so strong in the straw as Nos. 3 and 5, both uftohich xc ere remarkable for strength and 
 luxuriance, especially No. 5, lohich kept the lead of the others all the season. 
 
 E.— EXPERIMENTS UPON WHEAT. 
 The following three Experiments upon wheat exhibit very interesting results : 
 1°. The first series was made on the home farm of Lord Blantyre at Lennox 
 Love, and was intended to ascertain the relative effects in that hcality of differ- 
 ent, chiejk/ saline, manures ap^Med as top-dressings to spring wheat. 
 
 iNo. 
 
 1 
 2 
 
 3^ 
 
 4 
 
 5^ 
 
 6 j 
 7 
 
 \^ 
 
 10 
 U . 
 
 Lennox-Love. 
 
 Description of 
 Dressing. 
 
 Nothing 
 
 Common Salt. ... 
 
 Common Salt 
 
 Rape-dust 
 
 Nitrate of Soda. . . 
 Nitrate of Soda... 
 
 Rape-dust 
 
 Nitrate of Soda. 
 Sulphate of Soda. 
 Sulphate of Soda. 
 Sulphate of Soda 
 
 Rape-dust 
 
 Rape-dust 
 
 Guano 
 
 Soot 
 
 MANURES. 1 
 
 
 <-; 
 
 
 o 
 
 
 0) 
 
 
 Si 
 
 t^ . 
 
 »J 
 
 .-T3 
 
 ^ 
 
 
 
 C •- 
 
 <3 ea 
 
 o 
 
 lbs. 
 
 s. d. 
 
 14 
 
 4 
 
 112 5 
 
 7 
 
 14 
 
 3 1 
 
 7? 
 112 S 
 
 8 7 
 
 7S 
 
 2 
 
 14 
 
 1 
 
 7? 
 112 S 
 
 7 5 
 
 224 
 
 14 
 
 28 
 
 5 
 
 4 bush. 
 
 4 
 
 ~> .S- •^ . 
 
 rftC 
 
 lbs. 
 1036 
 1003 
 
 1148 
 
 1120 
 
 1176 
 
 1078 
 
 896 
 
 980 
 
 1106 
 1092 
 1036 
 
 Weight taken from 
 
 Thr 
 
 ashing Mi 
 
 11 of 
 
 .G = 
 
 rt 
 
 
 
 
 -o 
 
 
 
 
 d'S 
 
 
 -o 
 
 •^ 
 
 
 >(-c 
 
 
 lU 
 
 ° -A 
 
 
 
 
 CO 
 
 <l> 
 
 Si 
 
 2 = 
 
 
 in 5 
 
 > •— 
 
 « 
 
 O o 
 
 72 
 
 ^ 3 
 
 -> o 
 
 lbs. 
 
 lbs. 
 
 lbs 
 
 lbs. 
 
 lbs. 
 
 865 
 
 10 
 
 507 
 
 1.54 
 
 61i 
 
 349 
 
 20 
 
 547 
 
 92 
 
 61i 
 
 386 
 
 171 
 
 610 
 
 134J 
 
 61* 
 
 363i 
 
 20i 
 
 598 
 
 138§ 
 
 60f 
 
 394 
 
 17| 
 
 648 
 
 H6i 
 
 61i 
 
 364 
 
 12 
 
 595 
 
 107 
 
 60f 
 
 286i 
 
 11 
 
 483 
 
 115i 
 
 60 
 
 339i 
 
 lOi 
 
 514 
 
 116i 
 
 61 
 
 399 
 
 14 
 
 575 
 
 116 
 
 62i 
 
 367 
 
 14 
 
 .566 
 
 145 
 
 6H 
 
 361 
 
 14 
 
 564 
 
 97 
 
 60| 
 
 •2 '=5 
 
 ■pi "-■ 
 
 (§"§• 
 
 bushs. 
 5-9% 
 5-750 
 
 6-250 
 
 5 970 
 6-375 
 
 6 000 
 
 4-750 
 
 5-562 
 
 6-381 
 6 000 
 5-939 
 
 6V 
 
 §1 
 
 £ '^ 
 
 
 "•ai 
 
 . "^ 
 
 — S" 
 
 °fi 
 
 "O 
 
 
 
 M a 
 
 
 (0 — " 
 
 !- (U.S 
 
 3 o t« 
 
 Hod 
 
 - 3 "r 
 
 
 ii-aO 
 
 C-oCU 
 
 bush. 
 
 bush. 
 
 — 
 
 •206 
 
 ■29 
 
 — 
 
 •014 
 
 — 
 
 419 
 
 — 
 
 -044 
 
 — 
 
 — 
 
 1^206 
 
 — 
 
 •394 
 
 •425 
 
 
 
 •044 
 
 — 
 
 — 
 
 •017 
 
54 
 
 EXPERIMENTS UPON WHEAT. 
 
 [Appendix 
 
 Remarks. — Spring Wheat after Turnips, South-Lawn. Soil loamy clay ; subsoil clay 
 Drained every furrow before breaking up from old grass in the autumn of 1839; ploughed 
 deep and subsuiled in spring of 1841. Wheat sown 5th February, 1842 ; manures applied 13th 
 May; crop cut 24th August; and thrashed 10th September, 1842. The quantity of land in 
 each plot was one-eighth of an imperial acre, 
 
 2°. The object of the second series, made at Barochan, was to ascertain the 
 relative effect of certain mixed, chiejly saline, manures applied as top-dressings to 
 lointer icheat. 
 
 Results of Experiments with various substances used as top-dressings, upon Winter Wheat. 
 Dressed 9th May, and cut 7th September, 1842. TTie quantity of land in each plot was one- 
 sixteenth of an i7nperial acre. 
 
 No. 
 
 crook's farm, 
 barochan. 
 
 Description of 
 Top Dressings. 
 
 P 
 
 S 60 
 
 Nothing < .... 
 
 Natural Guano. . . . 
 Turnbull's Artificial 
 
 Guano 
 
 Common Salt.... 
 Sulphate of Soda. . 
 Nitrate of Soda... 
 
 Common Salt 
 
 Dissolved Bones.. 
 
 Rape-dust 
 
 Sulphate of Magnesia 
 
 D.02 
 
 ^1 
 
 O Et- 
 w O O) 
 
 .HP . M 
 
 ^.3| 
 
 5.S 
 
 lo 
 
 lbs. 
 400 
 540 
 
 420 
 360 
 
 480 
 
 510 
 
 lbs. 
 
 95 
 
 115 
 
 95 
 80 
 
 101 
 
 4601 90 
 
 110 
 
 lbs. 
 160 
 230 
 
 175 
 150 
 
 190 
 170 
 200 
 
 be 
 
 lbs. 
 
 61 
 
 60 
 
 6U 
 
 62^ 
 
 61 
 63 
 62 
 
 d. 
 
 
 4i 
 
 nii 
 
 n 
 
 C c „; 
 
 cc! .- p 
 
 3 2 O 
 C? fco ca 
 
 ISS. 
 'I' ? Si 
 
 bush. 
 24 
 30 
 
 24 
 21 
 
 26 
 
 22 
 28 
 
 lbs. 
 
 56 
 
 40 
 
 56 
 27 
 
 30 
 54 
 24 
 
 lbs. 
 
 2560 
 
 3680 
 
 2800 
 2400 
 
 3040 
 2720 
 3200 
 
 Remarks. — The soil is a heavy loam, incumbent upon a deep clay. The wheat was sown 
 at the end of November, 1841, after a crop of yellow turnips. The turnips were manured 
 with 20 tons of town dung per acre. Owing to the severity of the winter of 1S41 and spring 
 of 1842, the plants were very thin upon the ground. In April, 1842, it was sown down with 
 grass seeds, harrowed and rolled, after which it tillered and gradually recovered. At the 
 time the dressings were put on there was rain, but in general it was dry iceather after, and 
 in consequence the top-dressings did not produce such great results as they did m 1841. The 
 field was examined from time to time, and the appearance of each experiment as noted 
 down is fully borne out by the results given in the table, viz. : — No. 1 was taller in the straw, 
 longer in the ear, and of a darker green colour than any of the others ; No. 6 was next, and 
 No. 4 was third. In point of appearance there was in the others no perceptible difference 
 from the general crop, except No. 3, which appeared to have checked the growth of the 
 plants, and from this check they scarcely recovered all the season. It is however remarka- 
 ble that wherever common salt was applied the grain was heavier per bushel. // will be 
 observed, with reference to the experiment upon wheat grown on this land last year, that the 
 a:p]Mcation of comnu/n salt had a very great effect, and would probably have also benefitted tht> 
 general crop this year, had it not been for the extraordinary drought of the season (see Appen- 
 dix, p. 17.) 
 
 3°. The object of the third series, made by Mr, Burnet, of Gadgirth, nea 
 Ayr, was the same as those of Mr. Fleming. The mixtures employed, how- 
 ever, were different, and tlie tabulated results are at least equally interesting, 
 and satisfactory. 
 
 Results of Experiments with mixed Manures used as top-dressings upon Winter Whea 
 (Eclipse variety), sown 29th October, 1841, and reaped 15th August, 1842. The quantity 
 of land in each plot was one fourth of an imperial acre. 
 The soil a loam, with subsoil of clay ; tile-drained and trench-ploughed. Had been in 
 
 beans the year previous, and had no manure with that crop nor with the wheat, except the 
 
 above applications, harrowed in in spring. No. 6, at a cost of £2. 4s., has produced an in> 
 
 crease over No. 1 of jB6. 19s. 3d. being a gain of J64. 15s. 3d. 
 
No. VIIL] 
 
 EXPERIMENTS UPON WHEAT. 
 
 55 
 
 
 
 ^ 
 
 d 
 
 c" 
 
 M 
 
 
 o 
 
 
 a> 
 
 
 o 
 
 
 
 GADGIRTH, 
 NEAR AYR. 
 
 2 
 
 3} 
 
 O 
 
 2 
 
 D 
 
 .a 
 
 c 
 
 05 
 Si 
 
 
 3 
 > 
 
 _3 
 
 > 
 
 u 
 
 ■ « 
 
 .S <u 
 
 
 Manures applied 
 
 o 
 
 o 
 
 o^ 
 
 0) 
 
 
 
 rt^ 
 
 ■a 
 
 »! • 
 
 ■a 
 
 
 "S 
 
 
 16th April. 
 
 .ST 
 
 
 i-S 
 
 
 
 
 (D.C 
 3 « 
 
 i'5 
 
 
 O 05 
 
 
 6 
 
 
 '53 
 
 'S 
 
 'S a 
 
 
 "be 
 lbs. 
 
 2 = 
 
 PL,- 
 bshl. lbs 
 
 rtx! 
 
 |5 
 
 o- 
 
 c* 
 
 CO 5 
 
 O Q. 
 
 lbs. 1 
 
 
 cwtqrslbs 
 
 cwtqrs lbs 
 
 cwt qrs lbs- 
 
 lbs. 
 
 L. 8. 
 
 L. s. 
 
 s. d. 
 
 L. s. 
 
 1 
 
 No application.. 
 
 7 1 18i 
 
 4 3 23| 
 
 4 16 
 
 61i 
 
 9 
 
 31 38 
 
 11 1 
 
 — 
 
 — 
 
 — 
 
 9£ 1 
 
 2 
 
 Guano ^ cwt & 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 Wood-ashes.. .. 
 
 7 2 18 
 
 5 24 
 
 4 1 9 
 
 61i 
 
 10 
 
 32 20 
 
 11 6 
 
 6 
 
 — 
 
 2 
 
 88 
 
 3 
 
 Artificial Guano 
 1 cwt. & Wood- 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 ashes 1 cwt . . . . 
 
 6 3 25 
 
 5 17 
 
 4 1 10 
 
 591 
 
 9 
 
 32 24 
 
 11 6 
 
 5 
 
 — 
 
 1 12 
 
 88 
 
 4 
 
 Sulph. of Ammo- 
 nia-5CWt.,Wood- 
 
 
 
 
 
 
 
 
 
 
 ■ 
 
 
 
 ashes 1 cwt 
 
 8 3 21 
 
 6 2 7 
 
 5 1 lOi 
 
 60 
 
 17 
 
 39 54 
 
 14 
 
 2 19 
 
 63 
 
 2 
 
 85 
 
 5 
 
 Sulph. of Ammo- 
 Ilia^ cwt.. Sulph. 
 of Soda § cwt., 
 & Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 
 G 
 
 cwt 
 
 11 18| 
 
 7 9i 
 
 6 2 8i 
 
 60 
 
 13 
 
 49 6 
 
 17 4 
 
 6 3 
 
 16 9 
 
 2 16 
 
 81. 
 
 Sulph. of Ammo- 
 
 
 nia 5 cwt., Com- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 mon Salt 5 cwt , 
 
 
 
 
 
 
 
 
 
 
 
 
 
 <fc Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 cwt 
 
 11 1 4 
 
 7 1 24 
 
 6 2 6i 
 
 60 
 
 9 
 
 49 
 
 17 3 
 
 6 2 
 
 17 3 
 
 2 4 
 
 84 
 
 7 
 
 Sulph. of Ammo- 
 nia scwt., Nitrate 
 of Soda 5 cwt., 
 <& Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 ' 
 
 
 1 
 
 8 
 
 cwt 
 
 11 5 
 
 7 23 
 
 6 1 25 59 
 
 11 
 
 43 20 
 
 J6 18 
 
 5 ]7 
 
 16 U 
 
 3 4 
 
 70 
 
 Tunibull's Gua- 
 
 
 
 
 no 1 cwt., Sulph. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 of Lime 1 cwt., 
 
 
 
 
 
 
 
 
 
 
 
 
 
 & Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 cwt . . 
 
 8 6 
 
 5 2 8 
 
 4 2 2 
 
 60 23 1 
 
 33 44 11 16| 
 
 15 
 
 2 3 
 
 1 16 
 
 81 
 
 F.— EXPERIMENTS UPON PASTURE AND OTHER GRASSES. 
 
 I. Experiments made by Mr. Alexander, at Wellwood, in 1843. 
 
 A. On crops of meadow and njc grass hay. 
 
 ■ 1°. One Scots acre of well-drained mossy meadow, and full of timothy grass, 
 
 was top-dressed during the last week of April, with 1 cwt. improved bones, i 
 
 cwt glauber salts, h cwt of charcoal, all well mixed with ashes. Result. — 
 
 Crop much improved, and came to 180 Ayrshire stones (of 24 lbs.) per acre. 
 
 I may mention that this meadow suffered generally much from the severe 
 
 drought ; the above kept its growth best. 
 
 2°. One Scots acre of well-drained mossy meadow, full of timothy grass, was 
 top-dressed during the last week of April, with 1 cwt. of aitificial guano, 12 
 bushels of humus, well mixed with a quantity of ashes. Result.— Not so 
 good; more affected by drought; crop 160 stones per acre ; the rest of the un- 
 dressed meadow land, on an average, 140 stones per acre. 
 
 3°. Three acres of rye grass hay, upon a vcnj light sharp soil, was top-dressed 
 during the last week of April, with 3 cwt. of artificial guano, 2^ cwt. of improved 
 bones, 1 cwt. of charcoal, all mixed with a quantity of ashes. Result.— I can- 
 not pronounce that the hay on the three acres was increased in bulk ; the crop 
 was a light one on the whole field, owing to the severe drought, and the veiy 
 diy nature of the soil this season, therefore, gave this experiment no fair trial. 
 I would say, however, that I have rarely seen such an appearance of white 
 clover since the hay was cut, and particularly on the dressed land, 
 
 29 
 
56 
 
 EXPERIMENTS UPON PASTURE GRASS. 
 
 [Appendix, 
 
 B, On pasture grass. 
 
 Three years' old lea. The extent 2 acres 3 roods Scots measure, divided into 
 three equal parts, and the manures applied during the last week of April. 
 
 No. 1. Dressed with J cwt. of aramoniacal salts, 1 csvt. of sulphate of soda 
 (glauber salts). 
 
 No. 2. Dressed with f cwt of ammoniacal salts, ^ cwt. of glauber salts, ^ cwt. 
 of common salt. 
 
 No. 3. Dressed with | cwt. of ammoniacal salts, f cwt. of glauber salts, J cwt. 
 of nitrate of soda. 
 
 Rksults. — Nos. I, 2, and 3 were much alike ; in all the three cases the vege- 
 tation was quickened and improved ; but, as is always the case with experi- 
 ments on pasture, unless the cattle were kept off for the whole season, and the 
 produce cut, it is not easy to say how far tlie above application went to improve 
 the grass ; but certainly the small field did wonders — for it pastured fifteen early 
 calves nearly all the season, 
 
 II. The following carefully conducted series of experiments were made by 
 Mr. Fleming, of Barochan, with the view of determining the relative effect of 
 saline substances vpon the v)eight of the hay crop, on the field v/here the experi- 
 mental wheat of 1841 was grown: — 
 
 Result of E.xperimenls tried upon sown Grass, cut for Hay on 30th June, 1842, Crook's 
 Farm, where the Wheat grew in 1841. (See preceding part of this Appendix, p. 19.) 
 The quantity of land in each plot icas one-sixleeyith of an imperial acre. 
 
 No. 
 
 crook's farm, barochan. 
 Description of Dressing. 
 
 Nothing 
 
 Sulphate of Soda 
 
 Common Salt 
 
 Nitraie of Soda 
 
 Sulpliate of Soda 
 
 Nitrate of Soda, mixed 
 
 Natural Guano 
 
 SilicaLeaifLJ'otash 
 
 Gypsum 
 
 Sulphate of Ammonia 
 
 TurnbuU's Guailo 
 
 Common Salt 
 
 Soot 
 
 Hay of Barley Land, ma- 
 nured with Bone-dust, 1841. 
 
 lbs. 
 
 21 
 
 21 
 
 lOi 
 7" 
 3^ 
 
 lOi 
 
 21 
 
 7 
 
 14 
 
 14 
 
 I 
 
 1 bushel S 
 I 
 
 II 
 
 H is 
 
 iperial 
 ut, per 
 e. 
 
 6 
 
 2 
 
 dried 
 ;d by 
 h cut. 
 
 ns,<kc. 
 green. 
 0th of 
 
 - CO 
 
 = ■0 
 
 .•±<^z 
 
 
 
 °2 2. 
 
 O CO 
 
 
 
 
 * 3 
 
 
 
 » 3 
 " 2 
 
 1^'^ 
 
 
 
 ~ " 2 
 
 w "^ 
 
 
 ^ rt 
 
 bCo 
 
 
 ct C "* „: 
 
 Pro( 
 
 rial 
 
 cut. 
 
 
 1? 
 
 0) — 
 
 =! CO O 
 
 OfSS 
 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs 
 
 lbs. 
 
 tns.cwt.qrs. 
 
 710 
 
 11,-360 
 
 — 
 
 105 
 
 275 
 
 5 1 2 
 
 434 
 
 7,740 
 
 — 
 
 163 
 
 337 
 
 3 9 
 
 G72i 
 
 10.960 
 
 — 
 
 176 
 
 262 
 
 4 17 3 
 
 1125 
 
 18,100 
 
 6640 
 
 351 
 
 312 
 
 8 3 
 
 515 
 
 8,240 
 
 — 
 
 186 
 
 362 
 
 3 13 2 
 
 9321 
 
 14,920 
 
 3560 256* 
 
 275 
 
 6 13 1 
 
 757 i 
 
 12,120 
 
 760 198 
 
 262 
 
 5 8 1 
 
 S20 
 
 13.120 
 
 1760 225 
 
 275 
 
 5 17 
 
 595 
 
 9,520 
 
 — 186 
 
 312 
 
 4 5 
 
 795 
 
 12,720 
 
 1360^228 
 
 287 
 
 5 13 2 
 
 940 
 
 15,840 
 
 3680 305 
 
 324i 
 
 6 14 1 
 
 Remarks.— Nos. i,2, 3, 4, 5, and 8, were all ■Iressed on the "Oth of April, the weather be- 
 ing very dry at the time, and llioir clTccts were hardly perceptible ; but in the last week of 
 April Nos. 3 and 4 showed an improvement over the others. We had heavy rains the first 
 week of May, and by the 7lh of May the nitraie of .^oda (No. 3) could be seen at a distance by 
 the alteration of ihe colour to dark ureen, and its heii^lU above the otliers ; upon that day 
 Nos. 1 and 2 showed no vi.=;ible alteration from the untlresscd. No. 3 was the best of any : 
 taller, and of a dark frreen colour, and thicker swarded. No. 4 shmred lillle or ito alteration 
 in colour, but reus fully longer than th^genrral crop, and presented Ihe remarkable apjwurance, 
 as did No. 1, m being nearly all Festuca Rubra, ui/h h/irdly any rye grass, although of this 
 grass, viz. (Fosluca Rubra), 7ume teas soir7i ; the field haring b^-en soicn rcith rye gi'ass, tim- 
 othy, artd red clover. No. 5 darker than No. 4 in tlie colour, and good ; but No. 8 hardly im- 
 proved. Nos. 6, 7, 9, and 10, were dressed upon Ihe 7th of May. The men in ploughing up 
 the stubble of 1S41 found that the ridges whicli were top dressed tliat season \yith nitrate of 
 soda, were more difficult to plougli, from tlic strength and depth of the grass roots, than the 
 ridges undressed, each alternate ridge only liaving been dressed. 
 
 Prtces o/'jlfartMr/Es.— Sulphate of soda, 7s. per cwt. ; Nitrate of soda, jEl. per cwt. ; Natu- 
 ral Guano, 25s. per cwt. ; Artificial Guano, 8s. per cwt. ; Silicate of Potash or Sol«ble Glass, 
 16s. per cwt. • Sulphate of Ammonia, jEl. per cwt. 
 
No. VIII.] EXPERIMENTS UPON MIXED CROPS. 57 
 
 a— EXPERIMENTS UPON MIXED CROPS. 
 
 The following interesting experiment was made by Mr. Alexander, for the 
 pui-pose of ascertaining the eject of a vdxture of gypsum and common salt upon a 
 viixcd crop of oafs, beans, and peas : — 
 
 Result of an experiment upon the effect of gypsum and common salt, applied 
 as a top-dressing at Wellwood, Muirkirk, 1842. 
 
 Four Scotch acres of strong soil, bordering on clay, broken up from two-year- 
 old pasture, were sown with oats, beans, and peas (which is called in Scotland 
 7Has/dem, and is a first-rate fodder for dairy stock). 'They all came well up, but 
 worming and other causes injured the crop so much that 1 had serious intention 
 of ploughing it up, and sowing turnips. Instead of doing so, 1 top-dressed the 
 whole four acres with the following substances, well-pounded and mixed to- 
 gether, and this being done immediately before copious I'ains, the mixture was 
 washed into the soil : — 13 cwt. gypsum (from Turnbull), which, with carriage, 
 cost 8s. ; 4 cwt, common salt, which, with carriage, cost 8s. ; — this and the 
 gypsum, I6s. Cost of top-dressing, 4s. per acre. 
 
 The effect was like magic ; the plants immediately assumed a deeper green 
 colour, and grew wonderfully, and this field took the lead of all my other oats, 
 and when reaped the field generally was the best I had. Oats, beans, and peas 
 wei-e all particularly well filled. 1 may state further, that after the dressing it 
 stood the severe drought better than any of my other crops. Wellwood is 23 
 miles from the sea, and 550 feet above it. 
 
 From other experiments which I had before made, but which I shall not fur- 
 ther enter on here. I am convinced that common salt is a great auxiliary in that 
 locality (if not to most others distant from the sea), and it ought to be far more 
 extensively used. 
 
 H.— EXPERIMENTS UPON BEANS. 
 
 The following experiments were made by Mr. Alexander, of Southbar, at his 
 farm of Wellwood, in Ayrshire, with the view of ascertaining the relative appa- 
 rent effects of different saline top-dressings upon beans at different periods oj 
 their grotofh : — 
 
 Experiments made at Wellwood upon a crop of beans (1842). 
 
 The gi-ound was manured, previous to sowing, with 15 tons of farm-yard 
 dung per Scotch acre, and the other manures applied when the beans were about 
 two inches high (they were sown in broad-cast). The extent of ground was 2^ 
 acres Scots measure, divided into four equal proportions. 
 
 No. 1. Dressed with | cwt. of sulphate of soda, \ cwt. of nitrate of soda. 
 Result. — The effect of the dressing was seen soon after application, by deep- 
 ening the colour of the plants. The beans were deficient in straw, but remark- 
 ably well podded and filled. 
 
 No. 3. Dressed with i cwt. of sulphate of soda, 1 cwt. of gypsum. Result. 
 — More straw than the foregoing, and rather better crop. 
 
 No. 3. Dressed with i cwt. improved bones, \ cwt. artificial guano, 3 bushels 
 TurnbuU's humus. Result. — About the same as No. I. 
 
 No. 4. At first not dressed ; but, in consequence of being weakly, was after- 
 wards top-dressed with 3 cwt. of gypsum, and 1 cwt. of common salt, done in 
 consequence of the highly beneficial effect produced on the four acres of mashlam 
 crop above alluded to. Result. — Though done so late that the beans were already 
 coming into jlowcr, it helped them much, and they ended as well as any of the 
 above. It may here be remarked, that all the beans were, particularly for that 
 liigh district, heavy, being on trial soon after mowing 65 to ^Q) lbs. per bushel. 
 
 r> Observations upon the effect of the top-dressings applied m 1841 upon the crop 
 
 of 1842. 
 
 The following remarks are quite as interesting as any thing contained in the 
 numerous experiments made tliis year at Barochan by Mr. Fleming's skilful 
 
58 EXPERIMENTS UPON MIXED CROPS. [Appmdix, 
 
 overseer. They are, I believe, the first systematic series of observations of the 
 Kind yet published. They are valuable, therefore, as the first steps in the line 
 oi prolonged observations upon the same land made during successive seasons, 
 by which prolonged observations only can we hope to eliminate the effect of 
 our variable seasons, and to arrive at true deductions in regard to the kind and 
 amount of effect which this or that manure is fitted to produce. 
 
 I do hope that Mr, Gardiner, who is capable of observing so well, and of 
 experimenting so accurately, will not lose the opportunity which the present 
 year will afford him of continuing these important observations: — 
 
 1°. Top-dressings upon hay, Covenlea field (see Appendix, p. 17). On 
 looking over this field at different times, and particularly early last spring, the 
 square on which nitrate of soda and bones mixed" had been sown was earlier, 
 and of a darker green colour, than any of the rest of the field, and when stocked 
 with cattle, the portion top-dressed was more relished, and consequently always 
 eaten quite bare. 
 
 2°. Upon part of the pleasure-ground — soil a very stiff blue clay — nitrate of 
 soda was sown at the rate of 160 lbs. per acre. After this application white 
 clover came up very thick and strong, and it was cut three different times with 
 the scythe, and each time it came up stronger and thicker than the surrounding 
 grass, whilst, before dressing, it was the weakest, and this season, 1842, it is 
 better, and the portion dressed still easily distinguished. 
 
 3°. The field at Crook's farm (see Appendix, p. 17), which had been top- 
 dressed with nitrate of soda applied on each alternate ridge, on being ploughed up 
 from hay stubble was found tougher upon the dressed ridges, the grass roots 
 being stronger and deeper in the soil of those ridges which had been dressed. 
 
 4°. At p. 21 of this Appendix an experiment upon moss-oats is recorded. 
 This was sown down with a mixture of grass and clover seeds, and cut for hay 
 this season, 1842. In examining the hay crop some of the dressings on the oats 
 of last year seemed to have had a good effect on the hay crop of this ji-ear. Nos. 
 1 and 2 were the worst of any; No. 3 very little better, rather more clover ; No. 
 4 excellent, very thick of red and white clovers and rye-grass, and the hay was 
 of a good quality ; No. 5 a little better than No. 3, but far from being equal to 
 No. 4 ; No. 6 the best of any, full of red and white clovers and rye-grass, and 
 had three-fourths more hay upon it than all the others, except No. 4 ; No. 7 not 
 better than the undressed ; Nos. 6 and 4 presented a most remarkable appearance 
 compared with the others, and any person seeing them, and not knowing the 
 circumstances of the case, would have said that these two portions only had 
 been cultivaled, whilst the rest had been left in a state of nature. After being 
 cut for hay, the aftermath of these two portions still presented the same difference 
 of appearance in the sward, and they continue of a better colour. 
 
 A. F. Gardiner. 
 
 GENERAL REMARKS ON THE ABOVE EXPERIMENTS OF 1842. 
 
 However valuable the above experiments may be, and however interesting 
 the results to which some of them may appear to lead, it is of importance to 
 bear in mind — 
 
 1°. That they are the results only of a single season, and that a remarkably 
 dry one. 
 
 2°. That they show the effect of the substances employed in certain localities 
 only — the localities differing in the nature of their soil — in their distance from, 
 and height above, the sea — and in the average fall of rain to which they are 
 subject. 
 
 3*^. That the results are obtained by trials upon certain varieties of each crop 
 only, and may not be obtained even on the same spots with other varieties — of 
 turnips for example, of potatoes, oats, wheat, or barley. 
 
 4°. And that other causes, not yet noted, may have existed of sufficient in« 
 
No. VIII.] EXPERIMENTS UPON TURNIPS, 69 
 
 fluence to prevent the exact results from being obtained upon a repetition of the 
 experiaient. 
 
 5°. Above all, it must be borne in mind that we are yet in the first infancy of 
 accurate experimental agriculture — that it will take many careful repetitions of 
 our experiments before we can eliminate the effects of the seasons — of the alti- 
 tude of our farms, their distance from the sea, the falls of rain to which they 
 are subject, and the kind of soil of which they consist. In the mean time our 
 most careful deductions must be considered as partial only, and as open to doubt 
 — as facts by the combination and comparison of which wc are hereafter to ar- 
 rive at more general truths. 
 
 With these preliminary observations, I turn to the experiments themselves — 
 
 A. — The experiments upon turnips. 
 
 The first series, those of Lord Blantyre — except the general answer that saline 
 substances carmot replace farm-yard vtanure — afford no very satisfactory results. 
 They exhibit, indeed, some striking circumstances — such as 
 
 1°. That 100 lbs. of salt per acre may, in a dry season, reduce the natural or 
 unaided produce of turnips one-half — and that the same weight of nitrate of soda 
 may reduce it one-fourth. 
 
 2^, That in such a season as much as 16 cwt. of rape-dust per acre may be 
 applied, one-half drilled in, and one half as atop-dressing, wlthtnd producing any 
 sensible benefit. 
 
 '6°. That the same may be the case, if eight cwt. of rape-dust be drilled in, 
 and half a cwt. of nitrate of soda be afterwards applied as a top-dressing — 
 while if the same weight of common salt be used as a top-dressing instead, 
 the crop will be increased one-half. 
 
 These results are too anomalous to beconsidered for the present as more tha>* 
 accidental. They may possibly be explained either by the different degrees (ft 
 moisture of the several parts of the field in which the mixtures were applied— 
 or on the supposition, which is very probable, that in the concentrated state 
 $oyne of these saline substances are more hurtful to the grmvi?ig plavt than others. 
 It is to be regretted that the season was so unpropitious to this series of experi- 
 ments, for though the following experiments of Mr. Fleming afford some valuable 
 information, further knowledge still is wanted in i-egard to the relative effects of 
 different saline substances upon the growth of turnifs^ where no fermentible ma- 
 nure is applied, 
 
 4°. In these experiments, a striking contrast is presented between the effects 
 of rape-dust and those of guano, IG cwt. per acre of the former gave only 3f 
 tons of turnip bulbs, while 2 cwt. per acre of the latter gave 5 tons. It appears, 
 therefore, that rape-dust requires moist weather or occasioned rain, while guario, 
 even in very dry seasons, will produce a considerable effect. This is consistent with 
 what we know of the employment of tlie latter substance as a manure on the 
 arid plains of Peru, 
 
 II. The next four series of experiments, those of Mr. Fleming, are rich in re- 
 sults and suggestions, 
 
 1°. Limits of error. — The first observation which a careful examination of 
 them will lead the reader, to make — and it appears to me to be a very important 
 one in reference to all future experiments of this kind — is suggested by the se- 
 cond series — those upon early yellow turnips, p. 44. 
 
 In this series there are included two plots (Nos. 5 and 18), upon which no 
 manure was used. Upon one of these the produce amounted to 12 tons 17 cwt., 
 upon the other to 11 tons 8 cwt. only — being a difference of U tons, or one- 
 eighth of the whole. This diffei-ence between two equal portions of the same 
 field, apparently similar in soil, could scarcely, I think, have been anticipated, 
 and it shews that — where the produce obtained by the application of two unlike 
 manures, to this turnip crop, does not differ more than 1 ^ tons per acre, the effects 
 
60 EXPERIMENTS UPON TURNIPS. [Appendtx, 
 
 « 
 
 of the two manures may he considered as practically equal — since this amount of 
 difference may have arisen from the unlike quaUties of the two plots of land, to 
 which the manures were respectively applied. 
 
 This is an important practical rule for enabling us to judge accurately in 
 regard to the true effect of the several manures employed in the series of experi- 
 ments (p. 44) referred to, but the fact itself suggests also an important modifi- 
 cation in the mode of conducting all similar comparative experiments in future. 
 
 In my previously published Suggestions, I have recommended the setting 
 apart o^ on-e undressed portion only of the field on which the trials were made — 
 considering that the produce of this portion would represent the average fertiUty 
 of the whole undressed part of the field. But these experiments of JNlr. Flem- 
 ing seem to shew that this opinion cannot safely be entertained. It appears to 
 be necessary, therefore, in all future experiments from which accurate deduc- 
 tions are intended to be drawn — that two undressed plots, at least, should, in ccdi 
 case, be measured out, and their relative pro ditce ascertained, in order to afford a 
 trust-worthy average of the unaided fertility of the land. 
 
 Suggestion I. — For the clearing up of this point, however, it would be very 
 desirable to institute a series of weighings of the produce of equal portions of 
 land, in several different parts of the same field, the whole of whicli iias been 
 tilled and manured in the same way. This would throw some certain and sat- 
 isfactory light upon the amount of variation which, from natural causes, may 
 take place in the same -crop, grown upon different parts of the same field, and 
 under the same circumstances. We should thus be enabled to allow for the 
 influence of natural causes upon the results of such experiments as are made, 
 with the view of determining the true action of the different manures we apply. 
 
 Suggestion II. — But if some slight difference in tlie soil, which die eye cannot 
 detect, be capable of materially affecting the natural produce of the unmanured 
 parts of a field, it may also be sufficient to modify — that is, to increase or to 
 lessen — the effects produced by the saline and other manures we apply to the 
 different parts of the same field. It suggests itself, therefore, as the more pru- 
 dent and wary course of experiment to dress two plots at least with each of the 
 manures whose relative virtues we are desirous of testing, and these in different 
 parts of the piece of land upon which our trials are made. The mean produce 
 of the two or more plots we thus dress, compared with the mean produce of 
 those to which no dressing has been given, will indicate more nearly the aver- 
 age effect of the manure we have been trying, upon the given soil and crop. 
 
 The reader will perceive in the new precautions thus indicated, one of those 
 practical results which year by year will necessarily flow from the continuation 
 of the train of inductive experimental research, now, I hope, fiiirly entered upon 
 by the practical agriculture of our country. 
 
 2°. Guano. — Among the other experiments upon turnips here stated, those 
 upon guano are the most practically successful. Thus, per acre, without any 
 farm-yard manure 
 
 3 cwt. of guano alone gave 23 tons S cwt. o^ Swedes . . (p. 44)- 
 
 20 SiefsTwooTa^shes I ^^ *°"^ 2 cwt. of Early Yellow . (p. 44). 
 
 5 cwt. of guano alone 32 tons 15 cwt. of White Globes . (p. 46). 
 
 3^ cwt. do. 20 tons Q cvn. oi Yellow <^' White mixed {y>- ^(>). 
 
 3i cwt. do. 28 tons cwL of Purple-topped Yellow (p 47). 
 
 ■'These results are very gratifying, since they seem to shew that for the turnip 
 crop this light and portalale manure may be substituted with safety for farm- 
 yard dung. But they are more gratifying in connection with the large reduction 
 which has lately taken place in the price of this substance. In none of the 
 cases above mentioned did the quantity applied exceed 5 tons per acre. This 
 quantity may now be pm'chased for three guineas, though when these experi- 
 ments were undertaken it cost .£6 5s. 
 
 It is no small matter of congratulation, that this important reduction has been 
 
No VIIl.] EXPERIMENTS UPON TURNIPS. 61 
 
 mainly brought about by the expression of scientific opinion, and by the readi- 
 ness with which various persons, manure-manufacturers and others, have put 
 in practice the suggestions contained in the preceding part of this Appendix 
 (p. 26), for the formation of an artificial mixture in imitation of the natural 
 guano. The fear of competition produced its natural effect upon the market, 
 and led the importers of this substance to content themselves with a smaller 
 profit. It is to be hoped that the more extended sale which has followed the 
 redviction, will leave the spirited merchants who first brought it into the country 
 no reason to regret the diminution in price. The benefits which the practical 
 agriculturist derives from one such reduction as this are not all at first 
 sight pei'ceptible. The demand for guano has so greatly lessened the call for 
 rape-dust, that it has also fallen in price from .£8 to £5 10s. per ton. Thus 
 ramified and extended are the results of a single chemical investigation — or the 
 publication of a single well-founded scientific opinion. 
 
 3'^. Artificial Gunno. — In connection with this subject it is important to as- 
 certain to what extent the attempts to manufacture a substitute for the natural 
 guano have been attended with success — in so far as the turnip crop is concern- 
 ed. The only comparative results which the above experiments present, are the 
 following — those upon Swedes being obtained by the use of 3 cwt. of each 
 mixture, those upon the yellow and wdaite turnips by the use of 5 cwt. of each: — 
 
 Swedes. Early Yellow. White Globe. 
 
 1°. Nothing . . . 12 tons 5 cwt. 12 tons 17 cwt. — tons — cwt. 
 
 2^. Natural guano . . 23 " 8 " 32 " 2 " 32 " 15 " 
 3^. Barochan artificial guano 17 "14 " 24 '' 2 " 22 " 10 « 
 4^. TurnbuU's artificial guano 14 "11 " 21 " 4 " — « — « 
 
 These results show that, when equal quantities are employed, equal results 
 are not obtained from the natural guano and from the artificial mixtures. 
 It also appears that Mr. Fleming's mixture is much more efiicacious than thf\ 
 of Mr. TurnbuU. They are made up, with some modifications, after the recipf. 
 given in the preceding part of this Appendix (p. 25), 6ut are, no doubt, suscep- 
 tible of improvement. It is, indeed, one of the indirect benefits which will re- 
 sult from the introduction of this foreign manure, that it will stimulate to expe- 
 riments, by which we shall, no doubt, at last successfully imitate it — and wili 
 lead, at the same time, to a more general and thorough understanding of the 
 principles upon which mixed manures ought to be compounded, and of the 
 mode of preparing them with the greatest possible economy. Many crude mix- 
 tures may be made at first, by dealers in manure and others, and many instan- 
 ces of want of success may occur, but now that we have adopted (he system of 
 recording: results, whether apparently successful or the contrary, there is little fear 
 of our arrivins; at satisfactory and economical trilths at last. 
 
 Suggestion III. — In experiments made for the purpose of aiding the real ad- 
 vance of scientific agriculture, I would suggest that no mixture should be used of 
 which the composition is not exactly knoicvi — which, therefore, has not been either 
 made by the experimenter himself or by some dealer upon whose honor perfect 
 reliance is to be placed. The use of the random mixtures now sold under so 
 many diflferent names, however successful they may be in this or that case, can 
 never lead to the discovery of useful agricultural principles, and, therefore, are 
 unworthy of the attention of the cultivator of inductive experimental agriculture. 
 
 4°. Sulphate of ammonia. — These remarks lead me to notice the effect ascrib- 
 ed in Mr. Fleming's second table (p. 44), to sulphate of ammonia — one cwt. 
 of which nearly doubled the crop. Thus — 
 
 The unmanured soil gave . . 12 tons 17 cwt. 
 With 1 cwt. of sulphate of ammonia 24 " 11 " 
 
 This is exactly equal to the effect produced by 15 cwt. of rape-dust at a cost of 
 £() 10s. But the sulphate of ammonia here employed was that prepared by 
 the Messrs. Turnbull, of Glasgow— which is not merely sulphate of ammonia, 
 but a variable and undetermined mixture. It is prepared from urine, and I be- 
 
62 EXPERIMENTS UPON TURNIPS, [AppcnaiX 
 
 lieve is contaminated also with a considerable proportion of saline substances 
 artificially added to it. That it contains many substances useful to plants there 
 can be no doubt, and that it may prove a valuable manure is exceedingly pro- 
 bable, but under its present name it can only lead to false deductions in expe- 
 rimental agriculture — and the use of it, therefore, in compeu^ative trials such as 
 these we are now discussing, ought to be avoided. It is only, as I have already 
 said, from the use of pure substances mixed in known proportions, that valua- 
 ble, because undoubted, conclusions can be drawn. It is in vain cq attempt to 
 eliminate the effects iof diversity of soil and climate, if new causes of diversity 
 are introduced by the very substances with whicli our experiments are made. 
 
 5°. Bones dissolved in mvriatic acid. — The action of bones is not in general 
 exhausted in a single season. If they are in the state of fine dust, tliey decom- 
 pose more quickly and cease to act in a shorter space of time. By dividing 
 tlrem still more minutely, or by solution in an acid, it has been thought that 
 their apparent efficacy might be increased. Mr. Fleming, in 1841, made some 
 experiments which seemed to justify this conclusion. In the present tables 
 other results are exhibited, which favour the same opinion. I place togetlier 
 here the results upon potatoes, as well as upon turnips, for the pui'pose of 
 comparison : — 
 
 Bo7ie-d2isi . Bones in muriatic a/yid. 
 
 IGCWT. J8 CWT. 3 CWT. 10 CWT. 
 
 tons. cwt. Ions. cwf. tons. cwt. tons. cw(. 
 Swede Turnips . . . 14 17 — — — — 18 11 
 
 White Don Potatoes . . — _ 915 12 15 — — 
 
 These results, the only ones contained in our tables which can be compared 
 together, are both greatly in favour of the dissolved bones, in so far as the action 
 upon the first crop is concerned. It will require longer observation to deter- 
 mine in which form the same weight of bones will produce the more lasting 
 effects — and will be the more economical on the whole. 
 
 6°. Nitrate of soda. — The effect of 1 cwt. of this salt per acre upon the early 
 yellow turnip is very remarkable (p. 44), having given upwards of 27 tons of 
 bulbs, at a cost of 25s. It is to be regretted that no similar experiment is re- 
 corded upon the other varieties of turnip, either by Mr. Fleming or by Mr. Al- 
 exander. In the text (Lecture XV., p. 335 to p. 342) an abstract of all the pub- 
 lished results hitherto obtained by the use of nitrate of soda will be found in a 
 tabulated form. 
 
 7°. Lime. — An interesting result in Mr. Fleming's first table may hereafter 
 lead to some satisfactory experiviental determinations of the points considered 
 still doubtfulTTT regard to the form in which, and the time when, lime may 
 be most efficaciously applied, in reference to the culture of particular crops. He 
 caused carbonate of lime and caustic (newly slaked '?) lime to be sown in the 
 drills without manure, and the effect upon the crop of Swedes was as follows: 
 Soil unmanured ..... 12 tons 5 cwt. 
 Carbonate of lime, 20 bushels . . 16 " 11 " 
 
 Caustic lime, 50 bush els . . 11 " 8 " 
 
 The immediate effects of lime applied in these two forms was very different — 
 the caustic lime lessened the turnip crop, while the cai'bonate. increased it by 
 4^ tons. This effect most probably arose from the lime, in its caustic state, 
 taking from the soil the carbonic and other organic acids from which the roots 
 in the early infancy of the plant would have derived a portion of their nourish- 
 ment, and thus retarding and stunting their growth. At all events the experi- 
 ment seems to indicate that lime ought to be in the state of carbonate— the rnild 
 state — ^^inore or less entirely, if it is intended to benefit the crop to which it is 
 immediately applied. When mixed with manure, however, where vegetable 
 matter abounds in the soil, or where the lime is merely harrowed into the sur- 
 face — in all which cases it will readily become, in a great measure, saturated 
 with carbonic acid — the skilful farmer will understand that the deduction drawn 
 fi'om the preceding experiment will not apply. 
 
No, VIIL] EXPERIMENTS UPON TURNIPS. G3 
 
 8°. Rape-dust. -^The results exhibited in this year's experiments, generally, 
 are not so favourable to the employment of this substance as was to be expect- 
 ed. The reason, however, is, probably, that which has already been suggested 
 in discussing the results obtained at Lennox Love — that rapc-chist requires a 
 moist soil or occasional shoioers. But this itself is an important probable deduction. 
 The reader will find a comparative view of the whole of the results with this 
 substance in the text (see Lecture XVII.) 
 
 9^^. Animal Charcoal. — The effect of animal charcoal upon Swedes in Mr. 
 Fleming's experiments is only inferior to that of guano. It is certainly deserv- 
 ing of further trials, and especially in comparison with what is called exhausted 
 animal charcoal — that which has already been used in the refining of sugar. 
 In France, the latter is said to be prefen-ed to the former, and to be sold by the 
 sugar refiners at a higher price than they pay for it in the recently prepared 
 state. 
 
 10°. Olher mixed manures. — In regard to other mixed manures, the reader 
 will find much practical information by the study especially of No. 3 of Mr. 
 Fleming's tables, p. 45 ; and of Nos. 1 and 2 of those of Mr. Alexander, p. 4G. 
 These are the more worthy of the attention of the practical man, since Mr. Flem- 
 ing considers himself justified iii remarking as the general result of the experi- 
 ments in p. 45, tkat any of tlic mixtures used will in his kind produce an ave- 
 rage crop of tnirnips a', a kss exp3nss than farm-yard manure. This is the kind 
 of result which it ought to be the ambition of every practical man to work out 
 for himself upon his own land. 
 
 11°. Size and loeight of bulbs. — There remains only one other topic in con- 
 nection with these experiments to wliich space will permit me at present to ad- 
 vert. In the remarks upon the table inserted in p. 44, it is stated tliat the tur- 
 nips on the plots dressed with — 
 
 Guano and wood-ashes — were pre-eminent for size of bidbs. 
 
 Sulphate of ammonia — large in bti'b, hut soft., and, light in tve>ght. 
 
 Potash and lime, salt and lime, sulphate of magnesia, nitrate of soda.-^smaU 
 in bulb, but firm and solid. 
 
 Bone-dust and the artificial guanos — both containing bones — the bulbs firm 
 and solii, but not remarkable in size. 
 
 Now upon the solidity of the bulb — other things being equal — it may be pre- 
 sumed that the relative nourishing properties of different specfes of turnijD will 
 materially depend. The quantity of water which different specimens of the 
 same variety of turnip contain varies from 79 to 91 per cent. — that is, some tur- 
 nips of the same species contain only four-fifths, uviile others contain ujnvrirds of 
 nine-tenths of their ^weight of water. In other words, the same variety of turnip 
 may contain such unlike quantities of water, that 2 tons grown on one spot 
 may not contain moi'e than 1 ton grown in another. Theiceight of bulbs, there- 
 fore, is no safe criterion of the quantity of food raised on different parts of the 
 same field— wiiere the general treatment, or the substances applied to aid the 
 growth, have been different. 
 
 Now in the above experiments the guano gave 32 tons of very large, the sul- 
 phate of ammonia 24 of soft, and the nitrate of soda 27 of snail and solid bulbs. 
 It is probable, therefore, that the actual quantity of food raised by the aid of the 
 nitrate of soda was much greater than even by the natural guano. It may also 
 have been that the l4i tons of solid bulbs given by the sulphate of magnesia, 
 or the I2i raised from the land without manure at all, may have contained as 
 much nutriment as the -M tons of soft bulbs raised by the sulphate of ammonia. 
 
 Suggestion IV. — The bare jiossibility of sucji a circumstance as the last, 
 shows how little absolute confidence we can place in the numerical results as 
 yet obtained, considered as evidences of the greater or less amount of food, which 
 the use of this or that kind of manure will enable us to raise from a given ex- 
 tent of land. It suggests, also, the necessity of a further determination of the 
 relative quantity of water contained in our experimental turnip crops. This 
 will, without difficulty, be effected by selecting three or four turnips of different 
 ' 29* 
 
White Don. 
 
 Red Don. 
 
 Coniiaught Cups. 
 
 7 tons 1 cwt. 
 
 6 tons 15 cwt. 
 
 5 tons 15 cwt. 
 
 18 " 9 " 
 
 (( t£ 
 
 u u 
 
 (E ___ (( 
 
 14 " 6 " 
 
 13 " 14 " 
 
 12 " 6 " 
 
 10 '= " 
 
 13 " " 
 
 64 EXPERIMENTS UPON POTATOES. [Appendix^ 
 
 sizes from each sample — cutting a slice from either side, and one from the mid- 
 dle of each turnip — weighing the whole — drying them then, first in the air, 
 afterwards before a gentle fire, and lastly in an oven so hot as not to brown white 
 paper or dry flour, and then weighing. The loss being the weight of the water 
 in tlie turnips, will enable the experimenter to determine the relative quantities 
 of food raised upon his different plots, and therefore the relative value of his 
 different applications or methods of culture. 
 
 In this suggestion the reader will perceive another of those precautions which 
 the prosecution of our experimental inquiries renders necessaiy — future years 
 will suggest others — but the increase of trouble will not deter the zealous la- 
 bourer in this important field — for the more precautions and difficulties multiply, 
 the greater the honour will be to those who by perseverance shall successfully 
 overcome them. 
 
 B. — The Experiments upon Potatoes. 
 
 Nearly all the experiments in the first table of results (p. 48) were made with 
 mixed manures. 
 
 1°* Chiano and rape-dnst. — Among these the effect of guano is again striking, 
 and upon two of the varieties gi-eatly exceeds that of rape-dust. Thus, the pro- 
 duce of the tliree varieties tried was — 
 
 Unaided soil . 
 "With 3 cwt. guano . 
 With 4 cwt. guano . 
 With 1 ton of rape-dust 
 
 We are not enabled, by the experiments before us, to compare its effect with 
 that of farm-yard manure. 
 
 A curious question suggests itself upon the inspection of the above numbers 
 — one which could scarcely have arisen in our minds, had not differences such 
 as the above presented themselves among the results of our experiments. 
 Nothing is more common than to ask which of several varieties of potato is the 
 more prolific — and a practical man who has made the trial has no difficulty in 
 giving an immediate answer to the question. But the experiments of Mr. Flem- 
 ing seem to say that tke relative ineiiiht of crop yielded by eaeh of hvo or more va- 
 rieties of potato, depends upon the uay in vhich you treat or manure theju. With 
 one treatment a variety (A), with another a variety (B), will give the heaviest 
 crop. Thus, our three varieties gave with — 
 
 Vvhite Don. Red Don. Connaught Cups. 
 
 Natural guano . 18 tons 9 cwt. 14 tons G cwt. 13 tons 14 cwt. 
 
 Rape-dust . . 12 " 6 " 10 " " 13 " " 
 
 Both substances agree in saying that the white is considerably more prolific 
 than the red Don. But while the guano adds that both Dons are more prolific 
 than the C»/«, the rape-dust pronounces the latter variety to be superior to either 
 of the former. Now it may have happened that in the last case of the three, the 
 rape-dust, from some circumstance not noticed, may have acted better than in 
 the other two cases, and that in this way the discordance may have arisen. Un- 
 fortunately, however, there are upon record no other experiments made upon 
 any two of the varieties of potato with other substances used in like proportion 
 — oy which this question might have been in some measure solved. But the 
 interesting, and as it may hereafter prove, important inquiry suggests itself — 
 what is the order of relative productiveness of the several varieties of the savie culti- 
 vated plant, when they are severally dressed or manured with this or with that sub- 
 stance? This question will, no doubt, hereafter lead to extended series of veiy 
 refined experimental inquijies, from which not only much knowledge but much 
 practical benefit may be derived. 
 
 Suggestion V. — It may be, for instance, that a given variety of potato, turnip, 
 oat, laeurley, &c., is more valuable as food, more agreeable to the taste, or brings 
 
No. F//J.] EXPERIMENTS UPON P0TAT0K3. 65 
 
 a better price in the market — ^but by the ordinary modes of culture is the least 
 productive of those generally cultivated. It vsrould then be not only an interest- 
 ing, but an important economical question to ask — could this variety be render- 
 ed more productive by a different mode of treatment — one especially adapted to 
 its own nature 1 Would the practical man not rejoice to think that such a result 
 could be brought about by the aid and suggestions of science 1 Yet this is tlie 
 result to which the refined series of experiments suggested by the question 
 abov^e proposed may possibly lead. 
 
 May I venture to hope that some of my more zealous readers will be induced, 
 during the present or succeeding summer, to make trials of the relative effects 
 of the same saline or other known substances and mixtures, upon different varie- 
 ties of the same crop — of potatoes, turnips, wheat, &c., in circumstances other- 
 wise equal, in some such form as the following : 
 
 Varicly A. Variety B. Variety C. Variety D. Variety E. 
 
 Substances. Substances. Substances. Substances. Substances. 
 
 A. I B. I C. A. 1 B. I C. A. I B, I C. A. | B. | C. A. | B, | C. 
 
 The results if carefully ascertained are sure to lead to good, if they should 
 not be successful at once in solving the problem above proposed. 
 
 3°. Solidity and size of the potatoes. — Nothing is said in the observation of 
 Mr. Fleming, or his overseer, in regard to the size or solidity of the .different 
 varieties of potato, or of the different samples of the same variety on which the 
 experiments were made. Yet in connection with the remarks 1 have already 
 offered upon these qualities of the turnip, it is proper to add that the potato is» 
 subject to similar variations in the proportion of water it contains — and, there- 
 fore, in the relative amount of nourishment capable of being afforded by equal 
 weights of its different varieties. 
 
 Some potatoes contain less than 70, others upwards of 80 per cent, of water, 
 so that while 100 tons of one sample will give only 20 tons of nourishment, the 
 same weight of another will give 30 tons, or one half more. In general, such 
 as grow on heavy or clay soils, or such as are less ripe, contain the most, while 
 those which have been planted upon sandy spots, or are fully ripe, contain the 
 least water. But the effect produced by different soils we begin now to 
 see may be produced by different methods of dressing or medicating our crops 
 also. 
 
 Suggestion VJ. —It would be interesting to determine, therefore, by actual 
 experiment, the relative proportions of water contained in the produce of the 
 several experimental patches of potato ground upon the same field, when 
 equally ripe, or when dug up on the same day. This would afford us the 
 means of approximating still more closely to the true ecorwmical action of our 
 different manures upon the potato crop. It may turn out that in certain cases 
 the increase of produce, as indicated by a greater weight, is only apparent, 
 while the increased amount of food raised may in other cases be considerable, 
 though the balance indicates no increase of weight. 
 
 Did we know the relative proportions of water in the several samples of the 
 three varieties of potato raised by Mr. Fleming by the aid of guano, and of 
 rape-dust, already compared together, our conclusion in regard to their relative 
 productiveness, when treated by either substance, might be materially altered. 
 I hope, therefore, that this point also will hereafter arrest the attention of some 
 of our experimentalists. 
 
 4°. Pe?-manent effects of saline manures on the future jrroductiveness of the 
 seed. — Recommending to' my practical readers a careful consideration of tlie 
 effects of an admixture of wood-ashes with the several dressings applied to the 
 turnip and potato crop, I pass on to the two following series of experiments 
 with saline manures upon the potato crop, as given on p. 49. These two series 
 are well conceived, and the results veiy instructive. Of these results the one 
 which seems to me most deserving of the attention of the practical man is cdn- 
 
66 EXPERTMENTS UPON POTATOES, [Appeildix, 
 
 tained in a few words, tlu-ust in as it were, among the remarks appended to the 
 table (1°, p. 49.) In the later printed copies I have caused them to be put in 
 italics, with the view of bringing them into notice. If the reader will turn to p. 
 20 of this Appendix, he will find a remarkable experiment recorded, in which, 
 by top-dressing well -manured potatoes, with a mixture of ^ of nitrate and ^ of 
 sulphate of soda, the enormous crop of 30 tons an acre was obtained from tlae 
 small plot experimented upon. Some of these potatoes were kept for seed, and 
 planted alongside of others of the same variety, which had not been so dressed, 
 and the result is stated in the few words above referred to — " These Inst, under 
 the sajue treatment in every respect, did not produce so good a crop by 15 bolls (3| 
 tons) per acre.'' 
 
 In so far, therefore, as this experiment is to be relied upon — for we must not 
 be hasty in drawing general conclusions — it appears that the benefit to be de- 
 rived from a skilful treatment of the potato plant does not terminate with the 
 greater immediate crop we reap, but extends also into future years, improving 
 the seed and rendering its after-culture more productive. 
 
 Suggestion VII. — This idea is worth pursuing, were it only for the purpose 
 of making out the possible existence of so important a physiological law — kow 
 much more when it appears so pregnant with important practical results. But 
 thus it is in all cases, that the prosecution of experimental research, witli im- 
 mediate reference either to purely scientific or to purely practical results, ends 
 in improving and benefitting both abstract science and economical practice. 
 
 I am unwilling to follow out or to reason upon this possible law, as if it 
 were really established ; but the possibility of its ti-uth appears to throw light 
 upon such questions as this — why the seed must occasionally be changed if 
 large, crops are to-be continually reaped. One soil may be adapted to give the 
 plant a large supply of this or that substance in which the other soil is com- 
 paratively deficient; and it may be possible to medicate our seed-corn, while 
 growing, so as to give it the qualities which at present it can acquire only by a 
 change of soil. 
 
 All this, however, can be only determined by experiment, emd the intelligent 
 reader will net fail to be struck Avitli the remarkable richness of these first trials, 
 in suggestions for future carefully conducted experimental researches. 
 
 5°. Hoiv should saline vianures he applied to the potato cro/; ?— Ought they to 
 be mixed with the manure, or to be applied as a top-dressing 1 Mr. Fleming's 
 experiments do wot fully solve this question ; because the soil on his two fields 
 was very unlike in quality. Thus with manure alone the one field produced 
 12 tons 15 c wt., the other only 8 tons 17 cwt per acre, j* perfectly satisfactory 
 solution of the question can be obtained only by experiments with the same sub- 
 stances, upon the same soil, and with the same variety of potato. Yet the experi- 
 ments now before us add considerably to our knowledge upon this point, and 
 such of them as are capable of being compared together are much in favour 
 of mixing the saline sicbstanccs vAth the manure. Thus applied in nearly 
 equal proportions by both methods, nitrate of soda, sulphate of magnesia, and 
 sulphate of ammonia, gave the following results : — 
 
 FIRST FIELD. 
 
 Top-di 
 tons. 
 
 Manure alone 12 
 
 Nitrate of soda IG 
 
 Sulphate of magnesia .... 13 
 
 Sulphate of ammonia .... 14 
 ThQ proportionate increase, therefore, in these three cases, is greatly in favour 
 of mixing with the manure, but something may depend upon the soil and 
 season ; and, therefore, other experiments are necessary before we can draw a 
 general conclusion. It may prove tliat some act better when applied in the one 
 way, and some in tlie other. 
 6*^. Sulphaie of soda. — With this substance applied in either way, the singu- 
 
 ELD. 
 
 SECOND FIELD. 
 
 sed. 
 
 Mixed with manure. 
 
 vvt. 
 
 tons, cwt 
 
 15 
 
 8 17 
 
 
 
 12 7 
 
 5 
 
 11 7 
 
 10 
 
 13 7 
 
No. VIII] EXPERIMENTS UPON POTATOES, BARLEY AND OATS. 9f 
 
 lar and consistent result was obtained that 2 cwt. per acre caused no alteration 
 whatever in the weight of the produce upon either of the two on which tlie trials 
 were made. Of the respective qualities of the crops nothing is stated. 
 
 7°. Stdp^iate with filtrate of soda. — The above result with sulphate of soda 
 alone, is the more remarkable from the known effect produced by this and other 
 sulphates when mixed with nitrate of soda. Tliis year, also, the mixture of 
 nitrate with sulphate of soda added one-half (G tons per acre) to the crop, a 
 greater proportionate increase even than in the experiment of 1841, which gave 
 an increase of 8 tons out of a total produce of 30 tons per acre. But this 
 season Mr. Fleming has tried, with still greater success, a mixture of 1 cwt, 
 each of sulphate of magnesia and nitrate of soda, the produce rising by the use 
 of this top-dressing to 22i tons. The relative effects of the two sulphates 
 would have been more clearly proved, had the proportions of nitrate of soda 
 applied per acre in the two mixtures been the same. 
 
 8°. Nitrates of soda and potash. — Another interesting fact to add to those 
 alrerdy registered upon the relative efficiency of these two saline substances, is 
 presented in page 49. One hundred weight and ahalf of — 
 
 Nitrate of soda gave IG tons. 
 
 Nitrate of potash gave I8i tons. 
 
 This difference may have been due to accidental causes — or the 18^ tons of 
 the one result may have contained no more food than the 1(5 tons of the other; 
 but the multiplication of accurate experiments will eventually lead us to the 
 truth. Apparent failures and discordant results must not discourage the prac- 
 tical man. By recording all trust- worthy results, the light will almost sponta- 
 neously spring up at last. 
 
 9''^. Silicate of potash. — The results obtained by the use of this substance, and 
 the remarks appended to them (p. 50), are deserving of much attention. In re- 
 ference to this compound, and to the silicate of soda, I beg the reader to turn to 
 the suggestions contained in this Appendix, p, 40. 
 
 10°. Mixed maiiures. — The mixtures in page 50 will no doubt be imitated, 
 and by those who can obtaia them oi known composition, comparative experi- 
 ments may be tried with advantage both to theory and to practice. 
 
 C. — The Experiments upon Barley, 
 
 The true practical value of the experiments upon barley will be shown by 
 placing them in the following fonn : — 
 
 Increase. £ s. d. Cost per bush. 
 
 Nitrate of soda with common salt, gave 5 bush, for 17 6 — 3s. 8d. 
 
 Sulphate of soda with sulphate of magnesia, 7i bush, for 15 6 — •2s. Id. 
 Guano (at 25s.), .... 17" bush, for 3 18 — 4s. 7d. 
 
 Common salt, 6 bush, for 4 — Os. 9d. 
 
 Turnbull's artificial guano, . . 2 bush, for 1 4 — 12s. Od. 
 
 The cheapest application, without doubt, upon this soil, is common salt. 
 At half the above price guano would produce the barley at 2s. 3d. per bushel, 
 and the larger quantity reaped, together with the value of the straw in the pre- 
 paration of manure, may satisfy many that either guano or the mixture of sul- 
 phates may be used with profit. It is a further recommendation of the common 
 salt, however, that it produced the heaviest, wliile guano produced the lightest 
 grain. 
 
 From the experiment with nitrate of potash no result can fairly be drawn, in 
 consequence of the great drought of the season (see Mr. Gardiner's remarks). 
 
 D, — The Experiments upon Oats. 
 1°. Negative effect of saline manures. — The first of the two series of experi- 
 ments above recorded being made at Lennox Love — like those made at the same 
 place upon turnips — derive their principal interest from the illustration they 
 afford of the negative effect of saline manures upon the oat crop, under the in- 
 
68 EXPERIMENTS UPON OATS AND WHEAT. [Appendix^ 
 
 fluence of great heat and drought. I select the more simple and stiiking cases 
 of diminution. The undressed part of the field produced 54 bushels per acre 
 Common salt diminished this produce by 6 bushels. 
 
 Nitrate of soda 12^ " 
 
 Sulphate of soda 15* " 
 
 Rape-dust 9" " 
 
 Soot I2i " 
 
 while 2 cwt. of guano raised the produce to 70 bushels, being an increase of 16 
 bushels. 
 
 These results not only confirm the deductions which we have already drawn 
 from the preceding experiments upon potatoes and turnips — that guano will act 
 even in our driest seasons, while rape-dust requires at least occasional rain — but 
 they go further in showing that, like the saline suhstancesy rape-dust, and even soot, 
 imll inaterially diminish the oat crop, if the season be distinguished by remarkable 
 drought. 
 
 2°. Moss oats. — The experiments upon moss oats (p. 53) are a continuation 
 and extension of those of 1841 with greater attention to accuracy in the determi- 
 nation of the produce. The last column in the table speaks for itself The 
 general produce of the field being 43 bushels per acre. 
 
 Increa.se. Cost per bush. 
 
 Sulphate of ammonia gave ... 9 bushels 2s. 3d. 
 
 Sulphate of soda with nitrate of soda gave 18 bushels Is. 7d. 
 
 Bones in muriatic acid gave , . . 18 bushels Is. 6d. 
 
 Silicate of potash, mixed with the above, gave 22 bushels 2s. Od. 
 
 In the last two cases the straw, which is usually imperfect in oats grown upon 
 moss land, was strong and healthy. It is obvious, therefore, that all these exper- 
 iments deserve repetition, though, as here set forth, the increase of grain by Nos. 
 2 and 3 was obtained at the least cost, and, therefore, to the economist will ap- 
 pear most important. 
 
 E. — The Experiments upon WJieat. 
 I. Effect of drought. — The first series, those made at Lennox Love, aflford in- 
 teresting illustrations of the eftect of great drought in modifying the action of sa- 
 line manures and of rape dust, upon the wheat crop. The more prominent 
 results are distinctly brougtit out when thrown into the following form. The 
 produce of the undressed part of the field being 47i bushels an acre, this produce 
 was affected by the several substances employed in the following manner: — 
 
 Decrease per acre. Increase per acre. 
 
 Common salt, 1 cwt \h bush. — 
 
 Sulphate of soda, 1 cwt. . . . 9 J bush. — 
 
 Soot, .32 bush slight. — 
 
 Nitrate of soda, 1 cwt. ... — slight. 
 
 Rape-dust, IG cwt — 3^ bush. 
 
 Guano, 2 cwt. ..... — \ bush. 
 
 Thus, the nitrate of soda and the soot did no harm, though the drought did 
 not peniiit them to do any good. Common salt slightly, and sulphate of soda 
 largely diminished the crop ofgrain— while of these four substances the sulphate 
 was the only one which diminished the yield of straw. Nitrate of soda and 
 soot largely increased it. 
 
 On the other hand, guano slightly increased the yield ofgrain, and rape-dust 
 added 3^ bushels to the natural produce, both also augmenting the weight of 
 the straw by about one-tenth of the whole. 
 
 In this case, then, the rajie-dust surpassed in beneficial effect the natural 
 guano, though, as we have already seen, it proved gi*eatly inferior to the latter 
 when applied in similar proportions to oats, potatoes, and turnips. 
 
 2°. Snggest'ion VIII. — This fact suggests an interesting hiquiry. It is known 
 that one of the most lucrative modes in which rape-dust has been hitherto 
 
No. VIII.] EXPERIMENTS UPON OATS AND WHEAT. 69 
 
 employed as a manure has been in top-dressing the wheat crop (see the prece- 
 ding part of this Appendix, p. 19). Has it, therefore, some s;»t?daZ adaptation to 
 the wheat crop — which will account at once for its comparative failure upon oats 
 turnips, and potatoes, and for its superior efficacy to guano upon the wheat crop 
 — in the proportions stated, and even in a very dry summer 1 The comparative 
 efficacy of the two substances applied in various proportions is certainly deserv- 
 ing of further investigation. It will be a gain not only to practical but to theo- 
 retical agriculture, should it be established that rape-dust can be profitably 
 applied to the wheat crop, in circumstances when it would be thrown away upon 
 oats or turnips. By turning to the next series, that of Mr. Fleming (p. 54), it 
 will be seen that the last result tliere stated is also favourable to the action of 
 rape-dust upon the wheat crop.* 
 
 3°. MiUuallij counteracting influence of differe^it mmiures. — But another curi- 
 ous observation presents itself in the table of Lord Blantyre's results. It is in 
 the apparent struggle between the good and evil influences of the rape-dust on 
 the one hand, and of the saline substances on the other, when they were applied 
 together to the same plot of wheat (see Appendix, p. 19). Thus, when applied 
 in the proportions above stated — 
 
 Increaae. Decrease. 
 
 Common salt gave .... — \\ bush. 
 
 Rape-dust gave 3j bush. — 
 
 One-half of each gave ... 2^ bush. — 
 
 Or the natural effect of the ra'pe-dust was lessened one-third when mixed vnth 
 the given weight of common salt. So, also — 
 
 Increase. Decrease. 
 
 Sulphate of soda gave ... — 9^ bush. 
 
 Rape-dust gave 3| bush. — 
 
 One-half of each gave ... — 3 bush. 
 
 Or the influence of 1 cwt. of sulphate of soda for evil was one-third greater than 
 that of I'G cicL. of rape-dust for good — in the given circumstances of soil, climate, 
 and crop. This result, which at present seems only curious, may hereafter lead 
 to the establishment of interesting truths capable of practical application. 
 
 Suppose, for instance, that upon two fields rape-dust were applied to the 
 wheat crop at the rate of 16 cwt. per acre, and that the one field contained na- 
 turally in Its surface soil the proportion of sulphate of soda employed in Lord 
 Blantyre's experiment, while the other contained none — then in the one case 
 the rape-dust would not only expend all its influence in overcoming the tenden- 
 cy of the sulphate to lessen the crop, — but would even seem to do harm if the- 
 produce were compared with that of another field, of apparently similar soil, 
 near the surface of which this abundance of sulphate did not exist ; while, in the 
 other case, the rape-dust, having no counteracting influence to overcome, would 
 spend itself entirely in increasing the-growth of the plant and the final yield of 
 grain. 
 
 Or suppose an artificial guano or other mixed manure artificially prepared, 
 to contain two or more substances which, in the soil they are applied to, have 
 a tendency to produce opposite effects— the one to increase, the other to 
 diminish, the amount of produce— the effect of this conflicting action of its 
 component substances would be such as to render the mixture of less efficacy, 
 perhaps of no efficacy at all— it might be even injurious to the crops, — although 
 it contained substances which, if applied alone, would have exhibited a power- 
 ful fertilizing action. 
 
 These two illustrations are sufficient to show the kind of light which obser- 
 vations, such as the one above adverted to, may hereafter throw upon practical 
 agriculture. , 
 
 II. The substance of Mr. Fleming's table (p. 54), may be thus presented. 
 
 • See also the subsequent observations on the experiments upon beans. 
 
70 EXPERIMENTS UPON "WHEAT. [Appendix^ 
 
 The unaided produce of the soil was 25 bushels an acre, and the effect of the 
 
 dressings as follows : — 
 
 Increase. Decrease. 
 
 Guano, 3 cwt 6 bush. — 
 
 Rape-dust, 5 cwt., sulphate of magnesia, | cwt. . 3h bush. — 
 
 Sulphate of soda, 1| cwt,, nitrate of soda, f cwt. Ih bush. 
 
 Common salt, 3 cwt. ...... — 3^ bush. 
 
 Common salt, 3 cwt., dissolved bones, 1 cwt. . — 2 bush. 
 
 Turnbull's artificial guano produced no sensible effect. 
 
 Under the circumstances, besides being favourable to guano, tlie above re- 
 sult is also in favour of the mixed sulphate and nitrate of soda, which we have 
 seen to operate beneficially upon so many other cultivated plants. The entire 
 crop appears to have been injured, not only by the summer's drought, but by 
 the severity of the preceding winter. 
 
 In regard to common salt, it is worthy of remark, that the grain dressed by 
 it, whether oats, barley, or wheat, in Mr. Fleming's experiments of this year, 
 has been always heavier per bushel than any of tlie other samples tried. This 
 accords with the previous results of some other experimenters; but it does not 
 agree with Mr. Fleming's observations upon the wheat of 1841, nor with those 
 of Mr. Burnet for 1842, and therefore cannot yet be considered as a universal 
 consequence of the application of t]us>.substance as a top-dressing. 
 
 III. The experiments of Mr. Burnet, of Gadgirth, have already been paitiallj 
 detailed in the text (Lecture XV f., p. 3G2), and their value explained. The} 
 are important, chiefly, as showing — ■ 
 
 1°. Ecoiwviical mixtures. — That mixtures can be prepared which, upon somi 
 soils, surpass guano in efficacy and in economical value, at its former price. 
 The price being now I'educed, other experiments are required, yet still the less 
 effect of guano upon the wheat crop is in acconlance with the results of Lord 
 Blantyrc. A wet season, however, may alter the numerical relation which 
 these results exhibit. It will be observed that here also Turnbull's guano pro- 
 duced no sensible effect. 
 
 2°. Effect of soda. — The efficacy of the salts of soda, whether the sulphate, 
 tlie niti'ate, or common salt, upon Mr. Burnet's laiid, are also very striking — 
 half a hundred weight per acre of either producing an additional increase of 
 about 10 bushels of grain. 
 
 3°. Yield of Jiour. — Into his tabulated results, Mr. Burnet has introduced a 
 new element, and, as it seems to me, an important one in an economical point 
 of view, namely, the quanfitij of fine flour yielded by equal weights of the several 
 samples of grain. The differences presented in this column are very stiiking. 
 Thus 100 lbs. of the grain reaped from the plot which was — 
 
 Undressed, gave 76| lbs. of fine flour. 
 
 Dressed with guano . 68f lbs. " 
 
 With sulphate of ammonia ^h lbs. " 
 
 With sulphate of ammonia and niti-ate of soda . . . 54| lbs. " 
 
 It would be interesting to learn from an experienced miller to what extent 
 such differences affect the money value of the greun to the manufacturer of 
 flour. 
 
 4°. Amount of gluten. — Through the anxiety of Mr. Burnet to di-aw as much 
 information as possible from his excellent experiments, I am able to present 
 another feature in regard to the action of these saline and other substances upon 
 the quality of the produce. 
 
 It is known that the quantity of gluten contained in different samples of 
 flour is very unlike, and that the nutritive property of the flour depends, to a cer- 
 tain extent, upon this qua)itity of gluten. It has also been stated, as the result 
 of experiment, that the grai,n which is raised by means of manure containing 
 the largest quantity of nitrogen, is also the richest in gluten. With a view to 
 these questions, Mr. Burnet transmitted to me a poun^ of each of the samples 
 
No. VIIL] EXPERIMENTS UPON WHEAT. 71 
 
 of flour (sec Appendix, p. 5), and upon examination I found them to contain 
 
 the following proportions of gluten : — 
 
 Water per cent. Gluten per cent. 
 
 No. 1. No application 16-3 9-4 
 
 2. Guano and wood-ashes 16-15 9-3 
 
 3. Artificial guano and do. ...... . 16*8 9-6 
 
 4. Sulphate of ammonia and do 164 10-5 
 
 5. Do., do., and sulphate of soda 15-7 91 
 
 6. Do., do., and common salt 15'7 9*6 
 
 7. Do., do., and nitrate of soda 16-4 10-0 
 
 8. Turnbull's guano, gypsum, and wood-ashes . 15-2 9-1 
 These results are not without their interest, for though they do not show any 
 
 siri/L-mo- difference in the per-centage of gluten, yet upon the whole the result is 
 in favour of those samples to which the sulphate of ammonia* had been ap- 
 plied. One of these, No, 4, exceeded the undressed grain by about one per 
 cent., or one-ninth of the whole gluten it contained. Were the amount of this 
 gluten alone therefore to determine the feeding quality of the grain, this sample 
 might be considered as considerably the most nutritious. But besides the re- 
 lative proportions of fine flour which they severally yielded, there are other im- 
 portant considerations which bear upon this question, and must influence our 
 judgment. These considerations it would be out of place to present among the 
 present observations. They will be found stated in the text of the Lectures, 
 (XIX., p. 498 ct seq.) where we treat of the composition of wheat and other 
 varieties of grain — and of their respective values in the feeding of man and other 
 animals. 
 
 F. — The Experiments upon Grass. 
 
 I. The experiments of Mr. Alexander are not very remarkable or conclusive. 
 The meadow, which was drained moss full of timothy grass, gave naturally 1 
 ton 4 cwt. of hay, whereas the one dressing raised the produce to 1 ton 8 cwt., 
 the other to 1 ton 11 cwt., per imperial acre. The cost is not stated. 
 
 II. But those of Mr. Fleming are very interesting. By referring to page 17 
 of this Appendix, it will be seen that in 1841 Mr. Fleming obtained a greatly 
 increased produce of hay by the use of nitrate of soda. He informs me that 
 in making the present experiments he was desirous of again testing the efiicacy 
 of this salt upon grass, on the same kind of land, and of comparing it with that 
 produced by other saline substances. He selected also a portion of the same 
 field, on anotiier part of which the trials upon wheat had been made in 1841 
 (see Appendix, p. 19), with the view of ascertaining if any analogy could be 
 traced or difference detected, between their action in 1841 upon lohcat, and their 
 effect in 1842 on sown grasses — rye-grass, timothy, and red clover. Both objects 
 have been in some measure attained. I shall first present a summary of the 
 results. 
 
 OP HAY. INCREASE. DECREASE. 
 
 tons cwt. tons cwt. tons cwt. 
 
 The undressed soil produced ..18 5 
 
 Sulphate of soda, 3 cwt. ... 1 3 
 
 Nitrate of soda, l^ cwt 2 10 12 
 
 Sulphate of soda, 1 cwt i . « ^ - 
 
 Nitrate of soda, J cwt S 
 
 Common salt, 3 cwt 1 6 2 
 
 Common salt, 2 cwt ^112 fl 4 
 
 Soot, 16 bushels ) 
 
 Sulphate of ammonia, 1 cwt. . . 1 13 5 
 
 Guano, 1^ cwt 1 18 10 
 
 * It will be borne in mind that this is Turnbull's sulphate of ammonia, already adverted 
 to in page 61 of this Appendix. 
 
72 EXPERIMENTS UPON GRASS. [Appendix^ 
 
 A mixture of silicate of potash with gypsum produced no sensible effect, 
 neither did TurnbuU's artificial guano. 
 
 1°. In this repetition of his experiment, therefore, the nitrate of soda on si- 
 milar land again increased greatly the produce of hay — giving, at the first cut- 
 ting, an excess of upwards of 1 ton, at a cost of 30s. 
 
 2°. But on comparing this action of the nitrate upon grass with its action in 
 the same field the previous year upon wheat — we find that though it considera- 
 bly increased the crop of wheat, yet every additional bushel raised cost 12s. 6d. 
 as the price of the nitrate added to the land (Appendix, p. 19). It appears, 
 therefore, that upon soils tohere the nitrate will not iniy when applied to wkeat^ it 
 viay yet pay locll when applied to grass. 
 
 3°. Again, we find above that 3 cv/t. of common salt lessened in a slight de- 
 gree the crop of ha)', while, in 1841, Ih cwt. increased considerably the produce 
 of wheat in the same field — the additional grain reaped from the sailed portion cost- 
 ing only Gd. a bushel (p. 19). It would appear, therefore, that on soils where 
 aimmoii salt can be projiuibiy used, npon wheat it viay do injury upon hay. The 
 only circumstance that renders this deduction less safe is that 3 cwt. of salt per 
 acre were applied to the grass, which may have been too much considering the 
 dryness of the season. 
 
 4°. The latter remark applies also to the sulphate of soda which was laid on 
 at the rate of 3 cwt. per acre. A less addition might possibly have aided the 
 crop. Yet the negative influence of this salt seems great, since U cwt. of nitrate 
 — itself tending to increase the crop — was unable entirely to overcome the dimin- 
 ishing influence of 1 cwt. of sulphate. 
 
 Rut the reason of this apparent inefficiency of the niti-ate, when mixed with the 
 sulphate, is in some measure explained by the remarkable fact, that on botkof ths 
 patches to which the sulphate of soda ivas applied^ the grass that came up consisted 
 almost eniirdy of red fescue (Festuca Rubra), though rye grass, timothy, and red 
 clover locre the only grasses soion. The sulphate, therefore, must first have checked 
 or entirely destroyed the grasses which had already sprung up, and then have 
 incited the dormant seeds of fescue to germinate, before the fertilizing agency of 
 the nitrate could come into play. 
 
 This effect of the sulphate, should it be confirmed by later experiments, will 
 establish the important theoretical principle, that those substances which, when 
 present in the soil, will destroy some of our cultivated grasses, will encourage the 
 growth of others ; and the no less important practical truth, that saline substan- 
 ces exercise such a special action on the several crops we grow that we may 
 hope to discover^ the means of aiding the growth of the one or the other at plea- 
 sure, and it may be at little cost. 
 
 Suiigesfion IX. — It is to be recollected that in the case of Mr. Fleming's 
 field it may have accidentally happened that the seeds of the fescue particularly 
 abounded m those plots to which the sulphate was applied. With every dis- 
 position, therefore, to advance as rapidly as we possibly can, 1 think it better 
 to suspend our judgment upon this point — until the following two series of ex- 
 periments shall have been made in two or three different localities : — 
 
 a. By top-dressing any of the ordinary grasses sown — excluding the fescues 
 — on four or more plots, with h cwt., 1 cwt., 2 cwt., and 3 cwt. of sulphate 
 of soda respectively, and marking the kind of grasses that most abundantly 
 spring. 
 
 b. By sowing half an acre of one or more of the fescues, and especially the 
 Ridna, and noting the effect of the sulphate applied in similar proportions upon 
 as many patches as before. 
 
 These experiments, it is obvious, would be rendered more interesting were 
 nitrate of soda, alone and mixed with the sulphate, tried on other plots, and on 
 both varieties of grass. I trust Mr. Fleming, whose educated eye enabled him 
 to detect the interesting fact in question, may be induced himself to prosecute 
 the subject by further experiments. 
 
 6°. Suggestion X. — We have already seen in the above joint action of the 
 
No. Vin.'\ EXPERIMENTS UPON GRASS AND MIXED CROPS. 73 
 
 nitrate and sulphate, another illustration of the kind of struggle we may suppose 
 to go on between substances tending respectively, the one to increase, the other 
 to diminish, the produce. In the joint action of the common salt and the soot, 
 when applied together, we have a further instance of the same kind — an increase 
 of 4 cwt. only being caused by the application of 16 bushels of soot, when coun- 
 teracted by an admixture of 2 cwt. of common salt. Applied alone, the increase 
 of produce would probably liave been greater. Will any one undertake exper- 
 iments with the view of further bringing out this interesting mutually-counter- 
 acting influence of different applications! 
 
 6°. I can only call attention to the large yield of hay naturally obtained from 
 that part of the field on which barley dressed with bone-dust in 1841 had previ- 
 ously grown : Mr. Fleming informs me that no sensible diflference in the produce 
 of hay was observed between the undressed part of the field and that upon which 
 the dressed wheat had grown in 1841, tliough the crop was not set apart or 
 weighed, as we might wish it to have been. 
 
 ill. Since the preceding experiments went to press I have received the fol- 
 lowing short notice of trials upon hay made by jNdr. Campbell, of Islay : — 
 
 " It is very difficult to get the tenants in our wild part of the world to expend 
 money in the purchase of foreign substances, however beneficial ; and for this 
 reason I have been induced to try the substances mentioned below, because, 
 with the exception of sulphuric acid, the others are to be got in abundance 
 in the island — the pigeons' dung may be got in large quantities in the caves, 
 sea-ware on tlie shore, and lime is abundant and excellent m quality. The ex- 
 periment was made thus — 
 
 WEIGHT IN POUNDS. 
 
 Fresh cut. Dry. 
 
 1. Nothing 240 199 
 
 2. Pigeon Dung 318 275 
 
 3. Sea-ware, Lime, and Sulphuric Acid . , . 306 269 
 
 4. Lime and Sulphuric Acid . . .., 293 25G 
 
 1. A field of about ten acres, lately improved from heather, was chosen; the 
 field was well drained and deep ploughed, so as to raise the subsoil (red loam) 
 with the moss. On its surface the grass was sown down with oats — ^8 cwt. of 
 each substance was used to the acre. Eight yards square carefully measured 
 from the centre of each variety, and weighed the day they were cut, and again 
 on the day they were put into stack. The hay was fully ripe when cut. 
 
 2. The pigeon dung, which looks like peat-dust, was laid on exactly as it 
 was taken from the cave. 
 
 3 One ton of lime-shells was mixed with 12 tons fresh sea-ware; after being 
 twice turned, the whole of the sea- ware was consumed, leaving only small black 
 particles mixed with the lime: the bulk was reduced to five large carts (not 
 weighed) ; 4 galls, sulphuric acid, mixed with 400 galls, of water, were added to 
 the powder — a violent fermentation took place, and the bulk was further re- 
 duced about an eighth. 
 
 4. A ton of lime-shells was prepared according to your recommendation 
 slaking the lime with the dilute acid. 
 
 N. B. One measure of this lime in shells gives three and a half in powder," 
 
 G. — The Experiments upon Mixed Crops. 
 Mr. Alexander's experiment upon a field of mixed oats, beans, and peas, is 
 very deserving of notice, and will, I have no doubt, be repeated. Not only did 
 the mixture of gypsum and common salt increase the ultimate produce — but, as 
 Mr. Alexander says, it acted like viagic — imparting life and vigour to an appa- 
 rently dying and worthless crop. 
 
 H. — The Experiments upon Beans. 
 I. The principal fact of importance in the experiments of Mr. Alexander is 
 the effect he found his niixture of gypsum and common salt to produce upon the 
 
74 
 
 EXPERIMENTS UPON BEANS. 
 
 [AppendiXf 
 
 beans even ivhen already injlower.. This is another of those new and practical- 
 ly valuable observations which, year by year, are sure to present themselves to 
 our observing experimenters as their inductive researches are continued, 
 
 II. I am happy in being able to introduce here, though it reached me too late for 
 insertion among the other tables, the following digest of results upon beans, ob- 
 tained upon Lord Blantyre's farm at Lennox Love. The object of them was 
 to ascertain the relative effect of certain saline manures, and of rape-dust, and 
 guano, upon beans, after a crop of oats. 
 
 Experiments upon Beans, after a crop of Oats. The. quantity of land in each 
 plot was one-eighth of an imperial acre. Seeds sown 125th February ; manures 
 applied l3th May; crop cut 8th August; stacked 1st September, J842; and 
 thrashed 6th February, 1843. 
 
 
 
 MANURES, j"^ 
 
 Weight taken from 
 
 tc 
 
 S 
 
 
 
 
 
 
 
 T H >-o cii ; .,, ,T Mill «f 
 
 
 
 Increase 
 of 
 
 De- , 
 
 crease of 
 
 
 FORDHILL 
 
 
 
 
 
 
 ""o 
 
 
 
 CD 
 J2 
 
 
 
 FIELD, 
 
 
 o 
 
 .5P 
 
 
 
 
 
 
 ^ . 
 
 c c 
 
 produce 
 
 produce 
 
 
 LENNOX LOVE. 
 
 
 S-i 
 
 '^6 
 u 
 
 
 
 
 
 
 O OJ 
 
 
 in gram. 
 
 lu gram. 
 
 No. 
 
 Description of 
 Dressing. 
 
 3 
 
 <3 
 
 6 
 
 C 
 
 03 
 
 w 
 
 a 
 
 73 
 1 
 
 1 
 
 ■t: a. 
 
 > <^ 
 
 c§.5 
 
 
 
 75 
 B 
 
 CS 
 
 cq 
 
 
 in 
 
 a 
 
 <D 
 
 33 
 
 m 
 
 a. 
 
 
 
 lbs. 
 
 s. d. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 bushs. 
 
 bsh. 
 
 lbs. 
 
 bsh. 
 
 lbs. 
 
 1 
 
 Common Salt. 
 
 14 
 
 U 4 
 
 588 
 
 231 
 
 54 
 
 285 
 
 225 
 
 78 
 
 6.54 
 
 3'538 
 
 — 
 
 
 •182 
 
 31 
 
 2j 
 
 Common Salt. 
 Rape-dust 
 
 7? 
 112 < 
 
 7 
 
 630 
 
 265 
 
 53 
 
 318 
 
 230 
 
 82 
 
 66i 
 
 4-000 
 
 •282 
 
 — 
 
 
 32 
 
 3 
 
 Nitrate of Soda 
 
 14 
 
 3 1 
 
 672 
 
 276 
 
 63 
 
 339 
 
 254 
 
 79 
 
 66f 
 
 4134 
 
 -414 
 
 
 
 
 
 22 
 
 4 j 
 
 Ni.*rateofSoda 
 Rape-dust 
 
 112 ( 
 
 8 7 
 
 644 
 
 2&0 
 
 59 
 
 339 
 
 253 
 
 52 
 
 66i 
 
 4-210 
 
 -490 
 
 — 
 
 — 
 
 26 
 
 5 j 
 
 Nitrate ofSoda 
 Sulpli. of Soda 
 
 ?! 
 
 2 
 
 6.% 
 
 282 
 
 60 
 
 342 
 
 258 
 
 86 
 
 66i 
 
 4-256 
 
 -536 
 
 — 
 
 — 
 
 25 
 
 6 
 
 Sulph. of Soda 
 
 14 
 
 1 
 
 700 
 
 282 
 
 73 
 
 355 
 
 261 
 
 84 
 
 66i 
 
 4-240 
 
 -.520 
 
 
 
 
 
 12 
 
 7\ 
 
 Sulph. of Soda 
 Rape-dust . . . 
 
 7? 
 112^ 
 
 7 5 
 
 700 
 
 289 
 
 65 
 
 354. 
 
 261 
 
 85 
 
 67 
 
 4 313 
 
 593 
 
 — 
 
 — 
 
 20 
 
 8 
 
 Rape-dust .... 
 
 224 
 
 14 
 
 700 
 
 292 
 
 61 
 
 353 
 
 260 
 
 87 
 
 66| 
 
 4-374 
 
 -654 
 
 
 
 
 
 24 
 
 9 
 
 Guano 
 
 28' 
 
 5 
 
 728 
 
 2S0 
 
 68 
 
 348 
 
 263 
 
 117 
 
 66^ 
 
 4-210 
 
 •490 
 
 
 
 — 
 
 17 
 
 lU 
 
 Nothing 
 
 — 
 
 — 
 
 672 
 
 248 
 
 85 
 
 333 
 
 265 
 
 74 
 
 66S 
 
 3-720 
 
 — 
 
 
 
 
 
 
 II 
 
 Soot 
 
 4 b=:h 
 
 4 n 
 
 {'&) 
 
 234 
 
 87 
 
 321 
 
 281 
 
 84 
 
 66 
 
 3 545 
 
 — 
 
 2 
 
 •175 
 
 — 
 
 
 
 
 
 
 Remarks. — The soil of Fordhill, on which they grew, is light and of inferior quality — the 
 subsoil is of indurated clay, intersperised with boulders and small stones, and occasionally 
 beds of gravel. The field was drained every furrow previous to its being broken up from 
 old lea in the winter of 1840— ploughed deep and subsoiled in the autumn of 1841, and ma- 
 nured with farm:xaJ"<J dung in the drill before sowing the beans in the spring of 1842. Owing 
 to the dryness of the season, the beans were rather short in the straw; the specific manures 
 wei-e applied after the plants had attained some inches in height. TTie sulphate of soda (dry, 
 not in crystals) blackened and destroyed the under leaves, wherever il came in contact with 
 them., but fresh shoots soon apj^eared, and it did not seem permanently to injure or retard the 
 growth of the plants. They did not, after the application, sliewany marked change of colour ; 
 and at no period did they seem to differ much from the rest of the field. A few peas were 
 sown among the beans ; and in dressing the grain, an attempt, partially successful, was made 
 to separate them — each experiment underwent the same process in the dressing. Grain 
 column 1st represents the produce in beans — grain column 2nd represents that in peas. 
 The separation, however, not being completely effected, there were left peas among the beans, 
 and some of the smaller and inferior beans among the peas. I thought a distinction of this 
 kind worth making in the Tables, as I observed that some of the lots contained much more 
 peas than others, and conceived that the relative value of the manure, as applied to either, 
 might thereby in soi.ie measure be shown, as well as their effects on the beans alone more 
 truly exhibited. The gross weights were taken, as those of the other experiments, at the 
 town of Haddington's weighing-machine, before thrashing — the detailed weights and mea- 
 surements by myself. Wm. Goodlet. 
 
 The produce of the undressed part amounted in the above experiment to 29^ 
 bushels, and it is remarkable — 
 
 1°. That the soot alone caused a sensible diminution of the gross produce, 
 and alone did not lessen the proportion of peas. 
 
 2"^. Although the season was so dry the sulphate of soda gave a larger increase 
 than was obtained by the addition of twice its own weight of guano. 
 
 3°. That an admixture of half its weight of nitrate with the sulphate (^soda 
 
./ 
 
 No. Vin.'\ EXPERIMENTS UPON BEANS. 75 
 
 did not increase the produce beyond that of an equal weight of sulphate alone. 
 This is different from the action of the latter salt in the case of the other grain 
 crops and of potatoes. 
 
 4*^ . That 1 cwt. of sulphate of soda produce as great an effect as 16 cwt. of rape- 
 dust — the quantity of grain reaped from both applications being very nearly the 
 same. 
 
 Suggestion XI. — These striking effects of the sulphate ultimately took place, 
 although when first applied to the young plants it burned and blackened their 
 leaves. I trust that these results will also be tested by repetitions in other years 
 — less droughty, it is to be hoped — and in other parts of the country. For the 
 sulphate of soda, Mr. Alexander's experiment seems to say that gypsum, which 
 is still cheaper, may be economically substituted. 
 
 5°. It will be seen that guano upon this crop, as upon the wheat already noticed 
 (p. 68), was less successful than some of the other substances employed. 
 
 Conclusion. — Upon the observations of Mr. Gardiner in regard to the effect 
 of the dressings of 1841 upon the crop of 1842, I have nothing to add to the re- 
 marks I have already made (p. 57) upon their importance, and upon the good 
 that must follow from continuing them. But in concluding these observations, 
 the reader will please to recollect that I have adverted to those points only, in the 
 above tables of results, which appeared to myself most important. There are 
 many other points to which by a careful study of the tables his attention will 
 naturally be drawn. He will consider the observations themselves also, as 
 only so many gropings after ti'uth. The present state of our experimental inqui- 
 ries can scarcely be supposed as yet to give us more than a glimpse here and 
 there of the true light. Like a man who finds himself in a dark dungeon, we 
 are peering thi'ough the comparative gloom of our prison-house, in the hope of 
 finding some mode of escape into the upper day. Like him we may be long in 
 discovering the true outlet, and the passage upwards may be narrow and in- 
 tricate ; — but the same conviction which will give him safety, will ultimately 
 lead us also to the light — that he who persists in trying — marking and recollect- 
 ing every turning he has explored — may at length escape; but that he who sits 
 still, in indifference, or gives up his quest in despair, is sure to die in darkness. 
 
 No. IX. 
 
 ADDITIONAL EXPERIMENTS IN PRACTICAL AGRICULTURE, 
 MADE IN 1842. 
 
 The following experiments were made at Erskine, in Renfrewshire, upon the 
 Home Farm of Lord Blantyre : — 
 
 Experiment I. — Potato Oats, after old Grass. 
 
 The soil was variable, chiefly good loam, resting on a subsoil partly gravel 
 and partly sand. The field, having been long in pasture, in many places very 
 wet, was drained in November and December, 1841 ; ploughed soon after, and 
 sown with oats on the 8th of April. The manures were applied on the 15th 
 of April, and harrowed in with a single stroke of the harrows. One-fourth of 
 an iviperial acre being previotisly measured off for each plot. 
 
 According to notes taken of the appearance of the crop from time to time — 
 
 May 23. — The nitrate of soda (No. 1) looking darker in colour than any of 
 
 the other plots; next to it, in point of colour, the foreign guano (No. 5) seems 
 
 best; then the soot (No. 9); then the sulphate of ammonia (No. 2); cannot^ 
 
 however, discern any very decided difference in the appearance of tlie othera, 
 
76 
 
 EXPERIMENTS UPON OATS AND GRASS. 
 
 [Appendix, 
 
 May 30. — There appears a slight diflferencein favour of all the applications 
 in the order above staled, the sulphate of soda (No. 3) pale in colour. 
 
 June 28. — Appearance same as on 30th May. 
 
 The crop was cut 19th and 20th of August, and thrashed from the stock on 
 the 7th of September ; the results carefully ascertained, the grain by weight and 
 measure ; the straw by weight, as it came from the thrashing-machine ; no ac- 
 count taken of the chaff. . 
 
 RESULTS OF EXPERIMENT I. OATS, 
 
 No. 
 
 Applications. 
 
 Nitrate of Soda, 28 lbs 
 
 Sulphate of Ammonia, 28 lbs... 
 
 Sulphate of Soda, 56 lbs 
 
 Nothing 
 
 Foreign Guano, 28 lbs 
 
 TurnbuU's BritishGuano,56 lbs. 
 TurnbuU'sImpr'd Bones, 56 lbs. 
 TurnbuU's Humus, lU bush. . . . 
 Soot, 10 bush 
 
 Good grain. 
 
 -C to 
 
 bsh. lbs. 
 
 12 21 
 
 12 22 
 
 12 — 
 
 12 10 
 
 12 4 
 
 12 17A 
 11 2" 
 11 8i 
 
 13 30i 
 
 lbs. 
 
 42i 
 40" 
 40 
 41 
 
 41;^ 
 
 4U 
 41" 
 41 
 41 
 
 Light grain. 
 
 lbs. 
 
 8 
 10 
 14i 
 10| 
 
 6i 
 lOi 
 
 lo; 
 
 lU 
 9| 
 
 
 lbs. 
 29i 
 
 cc 
 
 lbs. 
 908 
 770 
 762 
 717 
 768 
 788 
 675 
 644 
 8Su 
 
 Increase + 
 or 
 
 Decrease — . 
 
 Grain. 
 
 Straw. 
 
 lbs. 
 +26i 
 
 —18 
 
 lbs. 
 +191 
 + 53 
 + 45 
 
 + 6 
 --I4 
 —49 
 +41 
 -60 
 
 + 51 
 + 71 
 -42 
 — 73 
 +163 
 
 Experiment II. — On Old Pasture Grass to be cut for Hay. 
 
 The soil was of medium quality, on stony clay subsoil. The part of the 
 field experimented on was originally very wet, "producing scarcely any better 
 herbage than rushes and other semi-aquatic plants, was drained in 1835, has 
 been three years pastured after a crop of hay from young grass in 1838; the 
 soil is of a blackish friable texture, the subsoil veiy retentive. The specific 
 manures were applied on 15th April, with the exception of the soot, which was 
 sown on the plot in the experiment at the same time that the other parts of the 
 field were dressed with soot, being about the middle of March, and by the 
 15th of April were shewing a greener shade than the portion left for experiment. 
 
 April 25. — Observed the ridge or plot No. 5 (sulphate of ammonia) looking 
 dark in the shade, and that the salt has burned the leaves of daisies and other 
 broad-leaved plants ; the moss or fog seems also to be burned, it looks black 
 and unhealthy. 
 
 May 7. — The ridges or plots Nos. 2, 5, and 7, look decidedly better than the 
 rest ; No. 3 also seems farther advanced than where no applications were made. 
 
 May 23. — No. 2 getting on very fast, and now looks as well as No. 1, which 
 has always had the advantage (to appearance) of the other plots. , The grass 
 on No. 3 pale in colour, but taller than where no manure was applied. 
 
 The hay was cut on the 3d of July, and the grass weighed soon, i. e., in a 
 few hours after being cut down, but being very sunny weather it was somewhat 
 faded when weighed. The made hay weighed and put into stack on . 
 
 Each plot consisted of one-fourth of an imperial acre. 
 
 
 RESULTS OF EXPERIMENT 
 
 II. — HAY. 
 
 
 No. 
 
 Applications. 
 
 Cost of 
 applica- 
 tion. 
 
 PRODUCE. 
 
 Increase 
 in Hay. 
 
 Grass. 
 
 Hay. 
 
 1 
 
 2 
 3 
 4 
 5 
 6 
 ■ 7 
 8 
 
 Soot, 10 bushels 
 
 s. d. 
 2 11 
 8 lU 
 
 4 3| 
 
 7 H 
 
 8 lU 
 
 5 8| 
 
 lbs. 
 2331 
 2536^ 
 1936 
 1760 
 2516^ 
 2374 
 3024 
 2841 
 
 lbs, 
 
 970 
 
 1026i 
 
 841 
 
 726 
 
 935 
 
 8:38 
 
 1190 
 
 1044 
 
 lbs. 
 188 
 2441 
 59^ 
 
 153 
 
 408 
 262 
 
 Nitrate of Soda, 40 lbs 
 
 Sulphate of Soda, 80 lbs 
 
 Nothing 
 
 Sulphate of Ammonia, 40 lbs. . . . 
 Nothing 
 
 Foreign Gnano, 40- lbs 
 
 TurnbuU's British Guano, 80 lbs. 
 
No. IX.] 
 
 EXPERIMENTS UPON WHEAT AND POTATOES. 
 
 77 
 
 N. B. — I take the average of the two plots which had no manure, as the sum 
 to deduct for finding the increased produce. The second column from the 
 right is made hay, the third is green grass, weighed soon after being cut. 
 
 Experiment III. — Upon Wheat. 
 
 Soil, a good sti'ong loam, resting on a heavy subsoil composed of clay and 
 small stones, called till. The wheat was sown in November, 1841, after a crop 
 of potatoes. The field had been long in grass previous to 1840 — when it was 
 drained, and ploughed for oats in the spring of 1840 — was well dunged with 
 good farm-yard manure, and was also limed for the potato crop of 1841, so that 
 the field was in very good condition for wheat. 
 
 The manures were applied 14th April, 1842, and harrowed in with a stroke 
 of the harrows. 
 
 May 10. — The portion No. 1 seems darker in shade than No. 9 and No. 8. 
 
 June 28. — A calm day, with gentle rain — many of the lots much bent down, 
 as follows: — No. 1 much bent down. No. 2 partly swirled and bent at the 
 end next a planting. No. 1 swayed at east end next the planting, not so bad as 
 No. 2. No. 4 less bent down than No. 3. No. 5 much bent down and swirled. 
 Nos. 6 and 7 all standing. No. 8 partly laid down. No. 9 very much swirled 
 and laid. All the laid wheat came up again in a few days after the rain. 
 
 The wheat was reaped with the sickle, and in due course stacked, in good 
 condition. It was thrashed on the 8th February, 1843. 
 
 RESULTS OP EXPERIMENT III. WHEAT. 
 
 No. 
 1 
 2 
 3 
 4 
 
 Applications. 
 
 Soot, 10 bushels 
 
 TurnhuU's Humus, 10 bushels 
 
 Improved Bones 
 
 TiirnbuU's Biilish Guano 
 
 Foreign Guano , 
 
 Nofhinjj 
 
 Sulphate of Soda 
 
 Siiljihate of Ammonia. 
 
 Nitrate of Soda 
 
 STRAW. 
 
 
 GRAIN 
 
 
 Total 
 
 Increase -4- 
 
 Total 
 
 Weisht 
 
 
 quan- 
 
 or 
 
 quantity. 
 
 per 
 
 Increase. 
 
 tity. 
 
 Decrease — . 
 
 bushel. 
 
 
 lbs. 
 
 lbs. 
 
 bush. lbs. 
 
 lbs. 
 
 bush. lbs. 
 
 1213 
 
 4- 20.5 
 
 13 33 
 
 58 
 
 2 32 
 
 105.5 
 
 -1- 47 
 
 12 48 
 
 60 
 
 1 47 
 
 973 
 
 - 35 
 
 11 53 
 
 62 
 
 57 
 
 1193 
 
 + ISb 
 
 14 43 
 
 01 
 
 3 42' 
 
 1049 
 
 + 41 
 
 11 34i 
 
 61i 
 
 33i 
 
 1008 
 
 
 11 1 
 
 62 
 
 
 1073 
 
 + 65 
 
 13 7 
 
 62 
 
 2 6 
 
 113S 
 
 + 130 
 
 13 38 
 
 62 
 
 2 37 
 
 1 lo9 
 
 + 151 
 
 13 38 
 
 62 
 
 2 37 
 
 * Experiment IV. — On Potatoes. 
 
 Soil, a medium loam, resting on gravel and sand. The, field was ploughed 
 from old grass, and sown with oats in 1841 ; was drained (where wet) and deep 
 ploughed in the autumn of 1841 ; prepared for potatoes in the spring of 1842, 
 and well dunged at the rate of about 45 tons of very good dung from Glasgow, 
 per acre. The manures were applied in addition to the dung, hy being sprinkled 
 above the (iung in the drilh before placins; the sets, then covered by reversing the 
 drills, on the 2ist and 22d of April, 1842. 
 
 During the season could discover little or no difference in the appearance of 
 the portions dressed with the specific manures, from where no applications 
 were made ; the crop was a very equal good one over all the field. One-fourth 
 of an imperial acre in each plot. 
 
 • I can ill reconcile the great produce from No. 4 with the appearances when growing, 
 and have been suspicious, that notwithstanding every precaution being taken to avoid mix- 
 ing, some sheaves of No. 5 plot, have been taken to No. 4, while the crop was in stook, as it 
 was sometimes necessary (during the time the stocks were in the field) to have them re- 
 paired, they being blown down once or twice. 
 
 The cost of the applications, as also '.he quantities applied, of the different materials, were 
 the same as in Experiment No. I., on Oats. The light grain is not here taken into account, 
 as it was too trifling in quantity and quality to be of any importance, and nearly the same in 
 every case. 
 
78 
 
 EXPERIMENTS UPON POTATOES. 
 
 [AppendtZf 
 
 RESULTS OP EXPERIMENT IV. — ON POTATOES, 
 
 iNo. 
 
 Manures. 
 
 Cost. 
 
 .Nitrate of Soda 14 lbs. ) 
 
 ' Sulphate of Soda 28 lbs. \ 
 
 Sulphate of Soda 28 lbs. ^ 
 
 Sulphate of Ammonia 14 lbs. I 
 
 Foreign Guano 28 lbs. 
 
 TurnbuU's British Guano 56 lbs. 
 
 Soot, 7J bushels 
 
 Improved Bones, TurnbuU's, 56 lbs. 
 
 Gypsum, 1 bushel 
 
 Nothing 
 
 s. 
 
 d. 
 
 4 
 
 7i 
 
 4 
 
 
 
 6 
 4 
 2 
 3 
 
 3 
 
 
 
 6i 
 
 
 
 
 
 
 tons. cwt. qrs. lbs 
 3 1 24| 
 
 2 19 241 
 
 
 21 
 21 
 21 
 21 
 
 7 
 
 The gypsum used turned out to be genuine on analysis.* 
 
 REMARKS UPON THE PRECEDING EXPERIMENTS. 
 
 1°. Effect of the drought. — It is to be observed, in the first place, that the 
 great drought of the season exercised an unfavourable influence upon the re- 
 sults of these experiments also. It is necessary, therefore, to suspend our judg- 
 ment in some measure regarding them — until future experiments in other sea- 
 sons shall confirm or modify them. 
 
 2°. Inferences to be drawn from the colour of the crop. — A new feature m- 
 troduced by Mr. Wilson in the account of these experiments, is the appearance 
 presented by the several crops at diflferent specified periods after the dressings 
 were applied. 
 
 It is a common thing for practical men to estimate the relative produce of 
 different fields or parts of the same field by their appearance, and especially by 
 the colour of the growing crops. Yet that this is not to be depended upon in 
 a corn crop, is proved by the observation that up to the end of June appearances 
 in the oat field were most in favour of the nitrate of soda, the guano being se- 
 cond, and the soot third in order. Yet, when reaped, the — 
 
 Nitrate gave an increase of only 2i bushels per acre. 
 
 Guano 24 lbs. per acre. 
 
 Soot 6 bushels per acre. , 
 
 The nitratejdid give a little more straw than either of the other two, but that 
 the colour is not an unfailing criterion even as to the produce of straw or of 
 hay is shewn by the experiments upon oats and upon hay. In both of these 
 
 * Li.st of prices paid for the manures used in the foregoing experiments : — 
 
 1. Foreign Guano 25s. per cwt. 
 
 2. TurnbuU's Guano 8s. " 
 
 3. TurnbuU's Improved Bones 6s. " 
 
 4. TurnbuU's Humus • Is. per bushel. 
 
 5. Nitrate of Soda 25s. per cwt. 
 
 6. Sulpliate of Soda (dry) 6s. " 
 
 7. Sulphate of Ammonia 20s. " 
 
 8. Soot ....." 3§d. per bushel. 
 
 Nos. 2, 3, 4, and 7, wore manufactured and furnished by Tumbull and Company, Chem- 
 ists, Glasgow. The British (Guano No. 2) is said to be made up as follows : — 
 
 2 cwt. of Sulphate of Soda. 
 2 cwt. of Sulphate of Ammonia. 
 1 cwt. of Common Carbonate of Soda. 
 15 cwt. of Improved Bones, manufactured by Tumbull & Co. 
 
 20 xwt., or 1 ton. 
 
 The Improved Bones are said to be half dissolved bones and half wood-charcoal. I be- 
 lieve the bones include animal matter, as I am informed the carcases of old horses, «fec., 
 are all used in the manufacture. James Wilson. 
 
 FYeeland, Erskine, 20fA February^ 1843. 
 
No. IX.\ REMARKS UPON PRECEDING EXPERIMENTS. 79 
 
 crops the portions dressed with sulphate of soda are described as pale in coloui^ 
 and yet the excess of produce over the undressed parts was as follows : — 
 In the oats . . li cwt. straw. } ^xr, ^i i i . ,. , 
 
 In the hay . . 2"cwt. per acre. \ ^^^^"^^ ^^^ ^"'^l^^^^ ^^« ^PPl^^d. 
 The increase in neither case would be desei-ving of much attention — except 
 as showing satisfactorily that wrong conclusions may be drawn in regard to 
 the efficacy of manures and top-dressings by those who judge only by the eye 
 — and that safe reliance can be placed on those comparative results onlij lohich have 
 been tested by weight and measure. I know, indeed, that practical farmers who 
 have applied nitrate of soda to grass land, and have been delighted by the beauti- 
 ful green colour which followed, have occasionally been disappointed by find- 
 ing that after all this promise the weight of hay obtained was no greater than 
 upon the undressed parts of their fields. As to the feeding qualities of the two 
 kinds of hay no experiments have yet been made, though it is known that cat- 
 tle prefer that which has been dressed. 
 
 Suggestion XI. — I put down, therefore, as a distinct suggestion for the pur- 
 pose of drawing attention to the subject, that this plan of specially noting the 
 appeai'ance of the crops at stated, say monthly periods, should be adopted in all 
 future experiments. This will serve, not merely to show us more clearly what 
 kind of appearances are to be trusted, and how far, as indications of an increase 
 of crop — but may hereafter prove of further importance when experiments shall 
 begin to be instituted upon the feeding properties of crops reaped under dif- 
 ferent circumstances, and raised under diffei-ent kinds of management. 
 
 3°. Importance of Iiaving tvjo or more experimental plots similarly treated. — 
 The experiments upon hay above-mentioned exhibit another illustration of the 
 fact adverted to in page 59 of this Appendix under the head of limits of error. 
 I there drew the attention of experimenters to the difference in the produce ob- 
 tained on two equal patches of the same field of turnips, to neither of which 
 any dressing had been applied. At Erskine two equal plots of grass in the 
 same field gave a similar difference of produce. I present both results here for 
 the sake of clearness. The produce per imperial acre was — 
 
 Hay at Erskine. Turnips at Barochan. 
 
 tons, cwt tons. cwt. 
 
 1st plot 4 5 12 17 
 
 2d plot 3 3 11 8 
 
 Difference 12 19 
 
 In my remarks upon the difference between the two plots of turnips (Appen- 
 dix, p. 59), I expressed an opinion that differences equally great, depending not 
 at all upon the substance applied, might be expected on equal portions of those 
 fields upon which our different saline manures may have been applied ; — and 
 that very erroneous conclusions might thence be drawn in regard to the abso- 
 lute and comparative effects of the substances with which our experiments are 
 made upon the crops to which they are applied. 
 
 I have since met with a confirmation of this view in a record of two pairs of 
 experiments made with equal quantities of rape cake upon equal plots of red 
 wheat, in the same season, and upon adjoining parts of the same field, ^British 
 Husbandry, I., p. 112.) The results of two experiments with different quan- 
 tities of rape dust were as follows : — 
 
 Produce of Light 
 
 Rape dust applied, market com. Weight per bushel. corn. 
 
 stones. bush. lbs. oz. lbs. 
 
 1st plot 59i . . . 26 . *. . 52 10 . . . 46 
 
 2nd plot 59i ... 21 ... 50 8 ... 67 
 
 1st plot 86 ... 28 ... 53 4 ... 35 
 
 2nd plot 86 ... 22 ... 51 2 ... 91 
 
 The differences both in the quantity and in the weight of the grain reaped, ii* 
 
 30 
 
80 REMARKS UPON PRECEDING EXPEKIMENT». [AppCUdiXf 
 
 each of these pairs of experiments, are so great that had they been ohtained from 
 plots of ground dressed with different manures we should readily have ascribed 
 them to the unlike action of the substances we had applied. Doubts may natu- 
 rally arise, therefore, when we look at the sevei'al tables of results contained in 
 this Appendix, how f^r the differences presented in them are really due to the un- 
 like action of the manures employed, and how far to natural causes not hitherto 
 investigated. Can all the experiments made during these last two years with so 
 much care really be vitiated by this source t)f error'? The point must be eluci- 
 dated by further experiment. Should it prove that we have here a general 
 source of error, it is satisfactory at least that we have discovered it at the threshold 
 as it were of our accurate experimental inquiries, and that we can devise means 
 of avoiding it in future. 
 
 I therefore repeat the Suggestions I. and II., which I ventured to offer in page 
 CO (Appendix), that some of my readers, of whom I believe many are interested 
 in this subject, would in the ensuing season ascertain accurately the produce of 
 equal measured quantities of the same field, under whatever crop it may be, 
 and publish or transmit the result to me — and that in all future experiments 
 made with the view of ascertaining the effect of different manures upon any crop, 
 two plots at least, and not adjoining to each other, should be treated alike in each 
 field, and the mean of the several results obtained with each substance taken as 
 the average produce from which their comparative effects are to be estimated. 
 
 These pomts appear to me to be of primary importance, and to lie at the 
 foundation of the structure 1 hope we are now beginning to rear with the results 
 of inductive experimental agriculture. 
 
 4. Action of soot. — In these experiments a top-dressing of soot increased con- 
 siderably the produce of oats and wheat, while it diminished the produce of po- 
 tatoes when mixed loith the manure. Thus the produce ^r acre on the dressed 
 and undressed parts was — 
 
 Oats. Wheat. Potatoes. 
 
 Undressed . . 49 bush. . . 44 bush. . . 11 tons 16 cwt. 
 Dressed ... 55 bush. . . 54 bush. . . 11 tons 3 cwt. 
 The unfavourable effect upon the potato crop may probably be due to the 
 mode in which it was applied, as in other districts it is very useful to potatoes, 
 and gave, as we have seen, when applied alone to turnips, an increase of4tons 
 per acre. (See Mr. Fleming's Experiments, Appendix, p. 43: also, Lecture 
 XVII. p. 438). 
 
 5. Comparative aciioji of soot and of nitrate of soda. — The immediate effect 
 of both these— substances is to darken the colour and to increase the growth 
 of hay and straw. In this respect the advantage is rather on the side of the ni- 
 trate, while the soot in some cases gives a little more grain. Thus the increase 
 of produce per imperial acre of the three crops of hay, wheat, and oats, dressed 
 with each of the three, was nearly as follows: — 
 
 Hay. Wheat. Oats. 
 
 Grain. Straw. 
 
 Soot .... 7 cwt. . . 10 bush. . . 6 bush. 6 cwt. 
 Nitrate of soda . 9 cwt. . . 10^ bush. . . 6^ bush. 7 cwt. 
 
 In both cases, however, the sooted grass was lighter per bushel. Thus their 
 comparative vR^ights were — 
 
 Wheat. Oats. 
 
 Sooted ... 58 lbs. . . 41 lbs. 
 Nitrated ... 02 lbs. . . 42^ lbs. 
 Nevertheless, the advantage to the practical man is decidedly on the side of 
 the soot, since the cost of 40 bushels of soot per acre was only 12s., while that 
 of 1 cwt. of nitrate of soda was 25s. It is only to be regretted that soot is so 
 variable in its constitution that firm reliance cannot be placed upon the uniform- 
 ity of its effects. 
 
 6°. Action ofgnano. — In the text, p. 460, 1 have stated the apparent conclusion 
 to which the Erskine experiments, taken in connection with all the others I have 
 
No. IX.] UEMARKS UPON PRECEDING EXPEBIMENTS. 81 
 
 yet met with, seem to point — that it is more uniformly successful when applied to 
 root than to grain crops. The increase of oats in the present experiment did not 
 exceed half a bushel per acre — though that of hay amounted to 14^ cwt. 
 
 7°. Action of sulphate of soda. — I have ah-eady noticed the effect which this 
 salt has in paling the colour of the crop, even when the produce of grass or 
 straw is increased. In regard to the grain, we see in the experiment upon oats 
 that it reduced the crop, If bushels per acre — while the wheat crop was increased 
 10 bushels by a similar application. 
 
 Is this difference in its effects due to the nature of the soil, or to the special 
 action of the sulphate upon the two crops 1 
 
 We have seen in the experiments made in 1842 at Lennox Love (p. 52), that the 
 sulphate of soda diminished the oat crop 15i bushels per acre — an effect, how- 
 ever, which may be mainly ascribed to the great drought in that locality, since 
 ' even nitrate of soda caused a diminution of l2^ bushels. But it also diminished 
 the wheat crop at the same place to the extent of 9| bushels per acre, but upon 
 this crop also the drought appeared to interfere with the natural action of the sev- 
 eral top-dressings which were applied, so that no trust-worthy conclusion can 
 be drawn from the apparent results of their action. 
 
 Suggestion XII. — I have already suggested (p. 72) an interesting experiment 
 with sulphate of soda, in order to test the very curious observation of Mr. Flem- 
 ing, that when applied to land sown with artificial grasses, it brought up a crop 
 consisting almost entirely of fescue grasses, though none of these had been 
 sown. I would here suggest further that the marked difference observed at 
 Erskine between the action of this sulphate upon wheat and oats should be 
 further investigated — with the view of obtaining a satisfactory answer to this 
 question — Does sulphate of soda act less favourable upon wheat than upon 
 oats in the same soil ? Or does an unlike action manifest itself only when the 
 soils are different 1 I fear the suggestion comes too late for the present year, 
 unless, as I hope, there are experiments already in progress which will throw 
 light upon the question. But the suggestion will not, I believe, be overlooked 
 when another year comes round. 
 
 It is further worthy of remark, in regard to the action of the sulphate of soda 
 upon the wheat crop, that the straw was stronger and less laid than where any 
 of the other dressings were applied. 
 
 8°. Action of sulpliatc of ammonia. — The substance employed under the name 
 of sulphate of ammonia,' as I stated in a previous part of this Appendix (p. 61,) 
 is not what its name implies. The makers, the Messrs. Turnbull, of Glasgow, 
 inform me that it is prepared by adding sulphuric acid to fermenting urine, and 
 evaporating to dryness*. Though such a substance must vary in composition 
 with the urine from which it is prepared, and must contain more or less am- 
 monia according to the degree of fermentation which the urine has undergone, 
 yet good effects may fairly be expected from it. I here exhibit the effect of 1 to 
 1| cwt. per acre applied to different crops — 
 
 Undressed. Dressed. Made at 
 
 Wheat 44 bush. 54^ bush, Erskine. 
 
 Do 31 J bush, 40 ' bush, Gadgirth. . 
 
 Oats 49 bush. 50 bush. Ei'skine, 
 
 Turnips 12| tons, 24^ tons. Barochan. 
 
 Potatoes 12f tons, 14^ tons. do. 
 
 Do 8f tons. I3i tons. do. 
 
 These results not only recommend this substance to the practical farmer, but 
 they also enforce the remarks I have made in the text upon the value of urine 
 in general, upon the large waste of manure annually incurred by the neglect of 
 it, and upon the virtual money-loss which is suffered by those who allow it to 
 escape from their farm-yards. [See Lecture XVIII., p. 463.] 
 
 9°. Action of TitrnhuWs humus. — This humus, as it is called, is night-soil 
 
 • In the text I have deseribed it under the name of sulphated urine.— Bee p. 451. 
 
82 REMARKS UPON PRECEDING EXPERIMENTS. [AppendiXt 
 
 and urine mixed with charcoal and gypsum, and dried by a gentle heat. Its ef- 
 fects upon the wheat crop are, in the present experiments, more favourable than 
 any of those I have yet placed upon record. The following experimental re- 
 sults exhibit the nature of its action in two localities, both in the same neigh- 
 bourhood : — 
 
 Undressed. Dressed. Experiments made at 
 
 Wheat ... 44 bush. 51 bush. Erskine. 
 
 Oats .... 49 bush. 45 bush. do. 
 
 Turnips . . . I2f tons. 13| tons. Barochan. 
 
 Do. ... 12 tons. 17 tons. do. 
 
 Potatoes . . . 5f tons. lOf tons. do. 
 
 These results, especially those upon the corn crops, are not so beneficial as 
 might well be expected from a prepared night-soil, and they afford room for the 
 suspicion that the mode of manufacture has been such as to dissipate some of 
 the more valuable constituents. 
 
 10°, Experiments upon potatoes. — In the experiments upon potatoes the whole 
 crop averaged 12 tons per acre, and the parts of the field to which the artificial 
 manures were added exhibited no marked increase above thisgeneral average. 
 Even the mixture of nitrate with sulphate of soda, which in so many other 
 cases has proved beneficial to the potato crop, in this instance produced only 1 
 cwt. of increase. 
 
 It may be that the manure which was added at the rate of 45 tons per acre 
 contained a sufficient supply of all those kinds of food which were added after- 
 wards in the saline and other substances. If so, a larger crop could only have 
 been obtained by the addition of some other substance not tried, for a loam of 
 modei'ate quality ought to be able to produce more than 12 tons of potatoes per 
 acre. 
 
 Or it may be that these same artificial manures would have produced a larger 
 increase had they been put on as a top-dressing after the crop had come up, in- 
 stead of being spread upon the manure before the potatoes were planted upon 
 it. In the experiments of Mr. Fleming made with especial reference to this 
 point, [Appendix, pp. 49 and (56,] it was found that a lafrger proportionate 
 increase was obtained from the same saline substances applied in equal quanti- 
 ties to the potato crop xolien they were spread upon the manure^ than when they 
 were applied as a top-dressing after the crop had come up. Still the experiments 
 in his case being made in different fields, I stated that the point was not to be 
 considered as established, but was deserving of further investigation. This 
 opinion is strengthened by the results of these experiments of Lord Blantyre : 
 I would therefbi-e beg to offer as — 
 
 Svggestion XIII. — That the application of saline manures to the potato 
 crop — either when the trial is made for the purpose of obtaining practical infor- 
 mation, which may, hereafter, be valuable as a guide to the operations of the 
 farmer, on the land where his experiments are made, or for that of arriving at 
 results which may be theoretically useful — that the same proportions should be 
 applied to two or more plots buried with the manure, and to two or more dusted 
 on as a top-dressing. From an accumulation of results obtained in both ways, 
 we shall be able to extract something like a principle by which practical men 
 may be easily guided in that direction which is likely in the greatest number 
 of cases to lead to the greatest amount of profit, 
 
 11°. Water in the potatoes. — I will here add one other observation upon the 
 potato experiments. There was, as we have already remarked, no notable dif- 
 ference in the weight oi Q.xo\i raised upon the several patches. But the quality of 
 the crop — the weight of dry food raised upon the several patches — might really 
 be different notwithstanding. In my remarks, [Appendix, p. G5], upon the Baro- 
 chan experiments upon potatoes, made in 1842, I have drawn attention to the 
 fact that potatoes sometimes contain as much as 30 per cent, of dry food, and at 
 other times as little as 20 per cent., and therefore that a ton of potatoes of one 
 kind may contain 6 cwt., while the same weight of another contains only 4 
 
No. IX.] REMARKS UPON PRECEDING EXPERIMENTS. 83 
 
 cwt. of dry nourishment. It may be, therefore, that as by growing in unlike 
 soils or with unequal degrees of rapidity our potatoes may contain different pro- 
 portions of water, so by different kmds of dressings which act in the same way 
 as natural differences of soil, and cause the plants to develope themselves with 
 greater or less rapidity, the same effects may be produced. One kind of saline 
 substance, such as nitrate of soda, by hastening the growth, may give us a crop 
 of potatoes containing much water, while another, such as sulphate of soda, by 
 retarding the growth, may give a crop containing less water — and thus, though 
 tnere may be no difference in the weight of the two crops, they may be very 
 unlike in the relative proportions of food they contain. 
 
 If such be the case it is of great practical importance to determine the quantity 
 of water which our several experimental potato crops contain, since without 
 this we may draw very incorrect conclusions as to the value of our experimental 
 manures — placing the highest value upon that which gives the greatest weight 
 of raw material, and esteeming least, perhaps, that which produces the greatest 
 weight of dry food. 
 
 I would again, therefore, draw the attention of my readers to the subject of 
 Suggestions IV. and VI., [Appendix, pp. 63 and 65,] in reference to the deter- 
 mination of the quantity of water in their experimental root crops. The 
 method of doing this is very simple, and has already been described, [Appendix, 
 p. 64.] 
 
 Each new series of experimental results we are called upon to examine and 
 analyse, will, I hope, more and more satisfy my readers, as they do myself, 
 that this is the true line of procedure, and that though there may be much in 
 our results at first which may appear contradictory and discouraging, yet that 
 out of these crude results, when combined, compared, and frequently repeated, 
 the real substance of a rational agriculture will, slowly it may be and with dif- 
 ficulty, yet surely at last, be extracted. 
 
 No. X. 
 
 RESULTS OP EXPERIMENTS IN PRACTICAL AGRICULTURE, MADE 
 AT BAROCHAN IN 1843. 
 
 Experiment I. — Upon Potatoes. 
 
 Comparative effects of guano, farm-yard manure, gypsum, &c., by them- 
 selves and in mixture, upon Potatoes of different varieties, planted 25th, 26th, 
 and 27th April; lifted, measured, and weighed from 12th to 14th October, 
 1843, Oil one-eighth of an imperial acre. 
 
 The portion of the field upon which these potatoes were grown contams 
 about five acres ; soil — loam of medium texture, super-incumbent upon trap 
 rock. It was trenchc^d with the spade out of seven years old lea in the winter 
 of 1842 and 1843 to the depth of 16 inches, the sward being turn-sp&ded into 
 the bottom of the trench, and the subsoil a stiff yellow till brought up to the 
 top, which mouldered down to a fine mould during the winter. The drills were 
 formed for the potato cuts with the double-moulded plough, and by the 7th 
 June the plants were all brairded in the rows, and were worked in the usual 
 manner with the plough, drill, grubber, and hand-hoes. After the drills were 
 formed, where the guano was used, it was sown in the drills by the hand, on 
 the bottom and sides of the drills, the farm-yard manure being then put in and 
 30* 
 
&4 
 
 EXPERIMENTS UPON POTATOES. 
 
 lAppcTidiXf 
 
 No. 
 
 Manures 
 
 Guano 
 
 Farm yard manure 
 Guano 
 
 Farm-yard manure 
 Farm-yard manure 
 
 Guano 
 
 Farm-yard manure 
 
 Guano ^ 
 
 Farm-yard manure 
 
 Gypsum 
 
 Farm-yard manure 
 Gypsum, powdered on 
 
 sots 
 
 Farm-yard manure 
 Farm-yard manure 
 and top-dressed 7th July 
 
 with Guano 
 
 Guano 
 
 Farm yard manure 
 
 Guano 
 
 Guano 
 
 Farm-yard manure 
 Farm-yard manure 
 Guano 
 
 30 
 
 Do. 
 
 26 10 
 
 Berwks. 
 Blues. 
 
 24 
 
 Do. 
 
 21 10 
 
 Do. 
 
 spread upon the top of it. Cut sets were then laid on and covered up with 
 about three inches of soil. Pariicular aUeriiion should be paid when guano is 
 used, that it be well mixed with the soil, as this is of the greatest importance to the 
 health of the plants and the bulk of the crop, especially in the case of potatoes and 
 turnips. This conclusion has been arrived at after three years' extensive ex- 
 perience in the use of guano as a manure; as it has been found here that the 
 more minutely it is spread and worked into the soil the crop is the heavier and 
 the better matured. When it has been used in a body immediately under the 
 plant, it has always been found to induce a strong vigorous growth of stems 
 and leaves, and, in general, to ripen the plant prematurely, and both the potatoes 
 and turnips ^were in consequence deficient in tubers and bulbs. Prom these 
 circumstances it may be inferred — what is indeed known to be the case — that 
 the guano does not contain all the ingredients which are required by the plants, 
 and that the large proportion of ammoniacal salts it contains — when it is laid 
 in a mass in immediate contact with the roots of the plants — pushes on the 
 growth too quickly with small stems and delicate leaves. Numerous small 
 bulbs are the consequence, and the cultivator being disappointed is led to pro- 
 nounce the guano worthless, whilst his inferior crop may be in a great measure 
 owing to bad management. Whatever may be the reason, however, it has 
 been found in using it here that lohcn soivn broad-cost the cropsofeveiy descrip- 
 tion have been benefitted, while, on the other hand, wheji laid in a body near 
 the roots the i-everse has been the case. In cutting the potato for seed, gypsum 
 in powder was strewed upon the sets when newly cut, and it will be seen from 
 No. G of the table, with good effects in adding to the produce, as where the cuts 
 were so powdered, as in No. 6, their superiority over' No. 7 (which was not 
 done so) m point of strength and vigour was most remarkable, and when lifted 
 the produce was 1 ton 5 cwt. per acre more than No. 7. It may also in a certain 
 measure be a means of preventing failure in the potato, as there was no failure 
 in this field where the gypsum was so used on the cuts, while the same seed 
 potatoes failed upon anotlier field which was planted at the same time, but 
 
No. X.\ 
 
 EXPERIMENTS UPON POTATOES AND HAT. 
 
 85 
 
 Vjhere no gypsum was pmvdered on the sets. At all events, it is worthy of a more 
 extensive trial as a preventative, and it will in all soils, where it is deficient, 
 add to the produce. It has, at the same time, the merit of being a cheap appli- 
 cation. 
 
 There was no great alteration in point of strength or forwardness till the 1st 
 of July, when all those patches upon which the guano had been used began to 
 take the lead of those planted with farm-yard manure alone. The guano produced 
 a dark green colour and very strong stems and leaves, so much so, that it was 
 found when too late that they had been too near planted, i.e., 32 inches between 
 the drills, and 12 inches between plant and plant. There would have been a 
 far heavier crop if there had been more space, as the strong growing varieties, 
 such as the cups and blues, were nearly choked for want of air. It will be 
 seen from the tables that a mixture of guano and farm-yard manure gave a 
 greater crop than where either of them was used alone. The portion, So. 8, 
 was top-dressed with guano when the potatoes were set up for the last time. 
 It was sown broad-cast between the drills, after which the drill harrow was put 
 through them and the plough followed, it acted immediately by altering the 
 colour to a dark green, the plants putting out, at the same time, new stems and 
 leaves, but owing to its being applied so late in the season, there was a larger 
 proportion of small potatoes than at the others when lifted. After many trials 
 it has been found that the best and, most economical v:ay of using g7iano for the 
 potato crop is by adding 2 or 3 cwt. per acre to half the usual qua.ntity of farmr 
 yard dung^ which will be found to give, at least., as good a crop as double the quan- 
 tity of dung alo}ie, whilst it is much cheaper in the first cost, and saves much 
 cartage, which is of the greatest moment to the farmer in spring. From its 
 effects upon the oat crop of this season, where it was used as a manure for the 
 turnip crop of 1842, at the rate of 3 cwt. per acre, it seems permanent — as the 
 oats will bear a comparison with those which grew where the land was manured 
 witli 40 cubic yards of fai-m-yard dung, and the hay crop, at this time, looks 
 as strong and forward as any in the same field. Potatoes manured with guano, 
 or dressed with sulphate and nitrate of soda, appear also to be improved in health, 
 and the tubers so grown are less apt to fail when cut and planted the following 
 season. 
 
 Experiment II. — On Hay. 
 
 Effect of top-dressings of various substances upon three years old Grass, 
 mostly Timothy, cut for hay in 1843 ; top-dressed on the 3d of June ; cut on 
 the 5th of August ; weighed when cut, and again v/eighed when stacked on the 
 28th ot August, duantity of ground under each dressing — One-eighth of an 
 imperial acre. 
 
 
 
 ON ONE-EIGHTH 
 
 OF AN IMPERIAL ACRE. 
 
 PER. IMP. ACRE. 
 
 S 
 
 'i 
 
 bb 
 
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 s'rt 
 
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 cs rt 
 
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 to 
 
 V 
 
 
 a 
 
 e 
 
 <- 2 
 
 S3 a. 
 
 
 No. 
 
 Dressings. 
 
 e3 
 I* 
 C 
 
 a 
 Gf 
 
 o 
 
 CQ 
 
 o 
 
 
 5 
 
 O O 
 c >- 
 
 Produce of 
 hay in im 
 stones. 
 
 Increased 
 ducc of wo 
 in stones. 
 
 1! 
 
 P-.S 
 
 Value of l 
 4d. per im 
 slone. 
 
 2"" 
 
 "lis 
 
 
 
 qrs. lbs. 
 
 s. d. 
 
 lbs. 
 
 lbs. 1st. lbs. 
 
 St. lbs. 
 
 St. 
 
 £. 8. d. |lbs. 
 
 1 
 2 
 
 Nothing 
 
 1 14 
 
 5 bush. 
 
 3 10 
 2 6 
 
 1344 
 
 — 152 11 
 
 33 10 
 43 9 
 
 416 
 752 
 
 761 
 
 6 18 8 350 
 
 Guano 
 
 4660i33169l 7 
 4500|3156 96 6 
 
 12 10 8 
 12 13 8 
 
 275 
 300 
 
 Compost of saw- ? 
 dust and coal tar. \ 
 
 4 " 
 
 Muriate of ammonia. 
 
 20 
 
 3 
 
 370012356 70 
 
 17 3 
 
 560 
 
 9 6 8 
 
 26b 
 
 5J 
 
 Sulphate of urine, ) 
 Turnbull'3 \ 
 
 20 
 
 3 
 
 3780 2436 84 
 
 32 
 
 672 
 
 11 4 
 
 312 
 
 6 
 
 Nitrate of soda 
 
 20 
 
 9 
 
 2840 1496 53 
 
 1 
 
 424 
 
 7 1 4 
 
 265 
 
 'S 
 
 Muriate of ammonia. 
 Common salt 
 
 15 
 
 1 
 
 2 6 ; 
 4^^ 
 
 3760 2416 93 8 
 
 1 
 
 41 
 
 744 
 
 12 8 
 
 375 
 
 8^ 
 
 Nitrate of soda 
 
 Common salt 
 
 15 
 
 1 
 
 24 ^ 
 4i^ 
 
 3460 1 21 16 
 
 87 
 
 35 
 
 696 
 
 11 12 
 
 350 
 
86' 
 
 EXPERIMENTS UPON HAY AND OATS. 
 
 [AppendiXj 
 
 The part of the field where the above dressings were put is a stiflf clay loam 
 lying quite level upon a sandstone rock, and has a south exposure. The 
 dressings were late of being put on, and it was intended for green cutting for 
 soihng, but owing to the abundance of other feeding, the parts dressed were 
 saved for hay. All the dressings except No. 3 had the effect of altering the 
 colour to a dark green in the course of a week, and they all came away very 
 strong and vigorous. No. 3 (the compost, see note 1°, p. 88,) had the effect of td- 
 tering the colour in about three weeks after being applied, and came away so 
 rapidly that it soon gained upon the others in point of strength and luxuriance 
 of stems and leaves. It will be seen from the tables that Nos. 4 and G gave 
 less hay from 1000 lbs. green cut, when used alone, than any of the others ; but 
 with the addition of common salt 1 000 lbs. gave more than any of the other 
 dressed portions. Sulphated urine may be considered a salt of ammonia, all 
 of which salts have been found to giv-e greater bulk than almost any other ap- 
 plication of saUs applied to green produce, but they have invariably been found 
 here to give less dry hay when used by themselves. The extra produce from 
 the sulphated urine is probably owing to its compound nature. It appears from 
 the above, therefore, that the most profitable way of using these salts is by 
 mixing them with otlieis, aiul that the more covipound the mixture is the better will 
 be the crop.* 
 
 Experiment III. — 07i Oats. 
 
 Effects of guano upon Oeds (potato), sown on the 17th of April ; cut and 
 weighed on the 15th of September, Thrashed, cleaned, and weighed on the 
 24th of October. 
 
 1 
 
 .2 
 
 at 
 
 2.S 
 
 
 s -f 
 
 .3 
 
 o 
 
 03 
 
 c 1 
 
 
 
 a, 
 
 CQ 
 
 M ? v; 
 
 
 3Q J= 
 
 fcC 
 
 OJ 
 
 bfi 
 
 No. 
 
 Dressing. 
 
 a. 
 
 0) 
 
 o 
 
 
 
 "3 "5 
 ^1 
 
 IP/ a 
 
 is 
 
 Vi 
 O 
 
 m 
 
 
 
 a 
 
 o 
 
 o 
 
 
 tDG 
 
 '3 u 
 
 C CD 
 
 2; o 
 
 Si 
 o 
 
 a 
 
 
 
 qrs. 
 
 s. d. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 bush. lbs. 
 
 bush. lbs. 
 
 1 
 
 Guano 
 
 3 
 
 7 6 
 
 3300 
 
 653 
 
 1015 
 
 40 
 
 16 13 
 
 3 20 
 
 2 
 
 Nothing 
 
 — 
 
 — 
 
 2120 
 
 539 
 
 749 
 
 42 
 
 12 35 
 
 
 Note. — The above quantities were applied to and reaped from one-fourth of 
 an imperial acre. , 
 
 The portion of the field upon which the above oats were grown is a deep 
 stiff yellow clayT'super-incumbent upon sandstone rock. It has been thoroughly 
 drained for a number of years. It had been sown with wheat on the 20th of 
 Januaiy, 1843, top-dressed with guano at the same time, which was harrowed 
 in, but owing to the dampness and constant change from frost and thaw, tlie 
 greatest part of.the wheat failed, and was ploughed up on the 15th of April, and 
 potato oats sown upon it on the 17th of that month. The oats brairded all 
 alike, showing no difference in point of earliness ; but by the 9th of June a 
 most remarkable alteration had taken place, the portion which had been dressed 
 with guano for the wheat taking the lead of the undressed portion, and being 
 of a dark green colour widi broad leaves, and covering tlie ground well ; whilst 
 that which had no dressing was brown and stinted in comparison, and the 
 ground not half covered. l"he two portions continued throughout the season to 
 present the same difference in their appearance, and at tiie time of cutting there 
 was more than a foot in length of straw in favour of the dressed portion. It 
 will be seen from the table, however, that although the guano had the effect of 
 giving more bushels per acre, the bushels were lighter in weight by 2 lbs. than 
 the grain from the undressed. It may be remtuked, however, that had common 
 
 • See on this subject of mixtures the Autliior's Elements of Agricultural Chemistry and 
 Geology, p. 149. 
 
No. X.\ 
 
 EXPERIMENTS UPON OATS AND TURNIPS. 
 
 87 
 
 saJt been mixed with the guano, there is reason to believe, from other trials, 
 that the grain would not have been deficient in weight per bushel. Ammonia- 
 cal salts should at no time be dressed upon grain crops, without, at the same 
 time, adding, according to the composition of the soil upon which such crops 
 axe grown, such other inorganic ingredients as may be requii-ed. Few soils, at 
 least in this part of the countiy, appear able to supply these in sufficiency to the 
 plants — particulEurly the phosphates, which seem always deficient. At least the 
 addition of bone-dust or animal charcoal seems always to improve the crops to 
 which they are applied. 
 
 Experiment IV. — On Turnips. 
 
 Comparative effects of guano, farm-yard manure, bone-dust, and animal char- 
 coal, by themselves and in mixtures,' on Turnips of different varieties ; lifted, 
 topped, tailed, and weighed, in Nov., 1843. 
 
 No. 
 
 Variety of turnips and 
 liind of manures. 
 
 Time oi 
 Sowing. 
 
 ON AN EIGHTH OP AN IMPERIAL ACRE. 
 
 ON AN IMP. A ORE. 
 
 I Cost of 
 Quantity of manures, 
 manure exclusive of 
 applied. cartage. 
 
 Produce. 
 
 Pro- 
 duce. 
 
 Vsdue of 
 
 produce 
 
 at 15s. 
 
 per ton. 
 
 SWEDISH. 
 
 Farm-yard manure.., 
 
 Guano , 
 
 Animal ciiarcoal'.... , 
 Farm-yard manure., 
 
 Guano , 
 
 Half-incli bones 
 
 Farm-yard manure... 
 
 Guano , 
 
 Ualf-incti bones 
 
 June 
 5 to 7 
 
 PURPLE-TOP YELLOW. 
 
 Guano 
 
 Dung 
 
 Bones 
 
 Farm-yard manure... 
 
 Guano 
 
 Farm-yard manure... 
 
 Bone-dust 
 
 Farmyard manure... 
 
 Guano 
 
 Animal charcoal 
 
 13 
 
 17 
 
 JONES' YELLOW TOP. 
 
 Farm-yard manure ... 
 
 Animal charcoal ; 
 
 Farm-yard manure..., 
 
 Bone-dust , 
 
 Farm-yard manure..., 
 Sulphate of Soda, as a 
 
 top-dressing 
 
 Farm-yard manure. 
 
 Guano 
 
 Farm-yard manure.. 
 
 Guanot 
 
 Animal charcoal. . . . 
 Compost of coal-tar 
 
 and saw-dust 
 
 21 
 
 29 
 
 2h cub. yds. 
 
 42 lbs. 
 
 70 lbs. 
 
 2i cub. yds. 
 
 42 lbs. 
 
 2h bushels. 
 
 5" cub. yds. 
 
 70 lbs. 
 
 5 bushels. 
 
 56 lbs. 
 4J cub. yds. 
 ik bushels. 
 2j cub. yds. 
 28 lbs. 
 2| cub. yds. 
 Ih bushels. 
 2i yds. 
 28 lbs. 
 42 lbs. 
 
 3| yds. 
 70 lbs. 
 3f yds. 
 Ig bushels. 
 
 3|vd3. 
 20 lbs. 
 
 31 yds. 
 70 lbs. 
 2h yds. 
 42 lbs. 
 li cwt. 
 
 S bushels. 
 
 ts. cts. qrs 
 5 6 Oi 
 
 4 19 
 
 ts. cts. 
 42 9 
 
 £. s. d. 
 31 7 
 
 39 1229 19 3 
 
 10 
 
 12 
 
 2 
 
 12 
 
 3 
 
 12 
 
 2 
 
 10 
 7 
 
 33 17 
 32 
 25 14 
 
 25 7 11 
 
 6 
 
 824 
 
 IS 
 2 
 
 18 
 3 
 
 19 
 1 
 
 6 
 
 12 
 
 3 
 
 5 
 
 
 
 10 
 
 3 3 
 
 4 18 3 
 
 4 
 
 3 10 
 
 5 
 26 16 
 
 24 
 
 36 
 
 25 10 
 
 3J 10 
 
 14 2 6 
 
 13 8 
 
 12 
 
 18 
 12 15 
 
 19 15 
 
 32 016 
 24 912 4 6 
 
 28 014 
 
 3 10 
 
 5 
 5 
 
 2 
 
 13 
 
 12 
 
 0|13 
 9 
 
 17 
 10 
 14 11 
 
 The field upon which the above turnips were grown is a hght gravelly loam, 
 super-incumbent upon a deep gravelly till. The greater part of the held was 
 trenched with the spade, and all drained with tiles and soles 30 mches deep and 
 20 feet apart, in the winter of 1841 and 1842, and in the preparation for the tur- 
 
 • The animal charcoal here used is the refuse of the sugar refiners, and contains about 
 |lb. of its weight o{ bone-earth. 
 t This part of the field was trenched. 
 
g9 EXPERIMENTS UPON TURNIPS. [AppeudtX^ 
 
 nip crop in 1842 and 1843, what had not been trenched was subsoiled. The 
 turnip ci'op was sown at different times, as noticed in the tables. All the parts 
 brairded well and healthy, and continued to grow without intermission through 
 the season. The field contains about 11 acres imperial, and the crop was most 
 luxuriant, so much so, that the lightest turnips in any part of the field would 
 have been reckoned good. The field was drilled fi^r the crop with the double 
 mould plough at 30 inches apart, for swedes and purple tap-yellow, and 26 and 28 
 inches for Jones' yelloio, which variety is remarkable for very small tops, and, in 
 consequence, may be drilled nearer. The difference in the appearance of the 
 turnips, where the various manures and mixtures had been applied, was veiy 
 marked. Whei'ever guano had been applied, the tops were larger tlian any of 
 the others, except No. 3 of the table (^Jones' i/ellmo), upon which sulphate of soda 
 was top-dressed, after the plants were thinned. The crop upon this portion was 
 remarkable for luxuriance of tops and large bulbs, and gave a veiy good crop.* 
 No. 6 of the table (Jones' yellow), was upon spade-trenched land, and 
 is the only lot where a comparison can be made between trenching and subsoil- 
 ing. Where bone dust was used the tops were not so large, and where the ani- 
 TTval charcoal had been added the lops ivere least of all and the bulbs largest. Upon 
 all the varieties of soils in this farm, the application of animal charcoal or bone 
 dust has been of great benefit to all crops — to wheat, barley, oats, hay, andgi'ass 
 — the crops being bulkier and of superior quality, especially upon soils superin- 
 cumbent on trap rock, giving an evidence that all such soils upon this estate are 
 in want of phosphates. This has also been proved by the analysis of several — 
 none of them giving more than a trace of phosphates, and some of them none at 
 all. Upon all these soils animal charcoal or bones seem to be indispensable, 
 because the grain crops cannot be matured without phosphates of lime and 
 magnesia. It appears from the many experiments that have been made here, 
 that guano does not contain a sufficiency of the phosphates to supply the crops 
 to which it is usually applied, and which, from the greater luxuriance of growth 
 its application at all times induces, would be required in greater quantity accord- 
 ing to the bulk of crop. A portion of the animal charcoal of tlie sugar refiners 
 being mixed with it at the time of sowing, will supply the deficiency, and at all 
 places inland from the sea, common salt will be found a valuable addition. The 
 cultivator who is obliged from deficiency of farm-yard manure to use guano will 
 find that by taking one-half of his usual quantity of farm-yard manure per acre, 
 and making up for the other half by the addition of 2 to 4 cwts. of guano, his 
 crops will be, at least, as bulky, and his after-crops as good, as if he had used 
 40 cubic yards of good dung. Guano, however, should not be used by itself 
 upon soils that-do not contain a certain amount ofvegetable matter (i^.e. on poor 
 sharp soils), but it will in all cases be found an invaluable manure for thorough- 
 drained moss soils. 
 
 Notes. — 1^. The compost of coal-rar and saw-dust used in the preceding experiments is 
 composed of saw-dust or moss 40 bushels, coal-tar 20 gallons, bone-dust 7 bu.^jhels, sulphate 
 of soda 1 cwt., sulphate of magnesia U cwt., and common salt H cwt., put together in a 
 heap, with 20 bushels of quicklime, and allowed to ferment and heat for three weeks, when 
 it is turned, and again allowed to ferment, and is then fit for use. 
 
 2°. In using the nitrate of soda for the last four years in the garden, it has been found 
 that top-dressing the leeks- in* the month of August or September enabled them to resist the 
 eflFects of winter, whilst those that were not so dressed have invariably failed, and gone to 
 decay early in the season ; at the same time, it increases their bulk in a remarkable man- 
 ner. Knowing this etrect upon leeks, — a crop that if grown to a large size has a great 
 tendency to rot and fail in winter, — might it not have the same effect upon autumn sown 
 wheats if dressed with it after they are brairded 1 This hint is merely thrown out as worthy 
 of trial, as the salt appears to have tiie power of toughening the fibre or o'.herwise enabling 
 the plants to withstand the rigours of winter, and in this way might, perhaps, prevent the 
 wheat crop from failing in winter, which is often the case, to the great loss and disappoint- 
 ment of the farmer 
 
 Wm. Fleming. ' 
 Barockan, Feb., 1844. 
 
 * Sulphuric acid and the sulphates appear to exercise a marked action on the turnip crop.— J. 
 
No. X.] REMARKS UPON PRECEDING EXPERIMENTS/ 89 
 
 REMARKS. 
 
 I submit these experiments to the reader without any lengthened comment. 
 The experiments with guano are very seasonable, and will be of much service 
 to the thousands of practical men who are now likely to try this valuable 
 manure. 
 
 There are three interesting general observations of Mr. Fleming, to which 
 alone I would direct especial attention — 
 
 1°. That the potato sets did not fail when powdered with gypsum, and that 
 the more extensive trials of this substance which he recommends ought cer- 
 tainly to be encouraged. 
 
 2°. That potatoes dressed with guano, or with nitrate and sulphate of soda, 
 appear to be improved in health, and are less apt to fail when cut and planted 
 the following year. 
 
 3°. That his trap soils are supposed to be especially deficient in phosphates, 
 and that the use of bones, in any form, always improved his crops upon these 
 soils. 
 
 These three observations are very interesting, and a careful study of the 
 tables of results will lead the reader to make other interesting observations and 
 deductions for himself 
 
 It is very satisfactory to^e to have been able in this Appendix to incorpa- 
 rate the results of experiments performed on three successive years by one so 
 skilful and zealous as Mr. Fleming, — conducted every year also with more 
 care, and more likely therefore to lead to important conclusions. 
 
 The subject of agricultural experiments has now been taken up so warmly 
 and so successfnlly in almost every part of the country, that we may look for- 
 ward with confidence to the gradual accumulation of a body of facts, out of 
 which correct and practically useful principles may gradually be elicited. The 
 large body of experimental results, which the prize offered last year by the 
 Highland Society has brought before the public, shows how eagerly the en- 
 lightened practical fai-mers of the present day will follow the guidance of such 
 as are willing to show them how the art by which they live may be really and 
 permanently improved. 
 
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 AJLLjEN, Author of''- Compend of Jivierica>\ Agriculture," 6fC. 
 
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THE AMERICAN FARM BOOK: 
 
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 i^ontaining a concise and plainly written Exposition of Duties pertaining to tb« 
 
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 tical scienlitic piincinles. 
 
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 The clioapest and most valuaMe book for a farmer ever printed : temg a con: 
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 Besides the varied practical knowledge which this book imparts, and which is 
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 sign of the author seems to be to remove all that technical phraseology which is 
 used in medical works gei>erally, and thus simplify the practice of that science 
 which the head of every family should be acquainted with. It is generally recom- 
 mended to our professional readers as a guide in cases where it is not deemed 
 necessary te have the services of regularly educated practitioners. This book 
 should find a place in every family." — Boston Mail. 
 
 " This is a work of Family Medicine on the plan of Dr. Ewell. It is the most 
 olain- written, untechnical book of the kind we have met with ; a decided improve 
 ment on both Buchan and Ewell. It is printed in a very superior style, revised 
 from the first edition, and containing a variety of useful information not hitherto 
 laid before the vulgar eye. It treats of the passions. It has also a catalogue of 
 medicines, with their properties and doses, and the diseases and manner in which 
 they are treated ; comprising a synoptical Materia Medica, exceedingly useful in 
 families, and moie particularly to captains of vessels and planters, who cannot 
 conveniently^ procure medical advice. It is an excellent book." — New Orleans 
 True American. 
 
 " If we judge of the merits of the book by the immense number of copies already 
 sold, and the very flattering testimony of medical men of the first standing, (and 
 among the number, several of the most distinguished members of the faculty in 
 our city,) it is a valuable compendium of the modern practice of physic, and must 
 prove a valuable assistant to families, particularly in sudden emergencies, and in 
 all situations where regular professional attendance cannot be commanded." — 
 Louisville Journal. 
 
 " The great advantage it possesses over all other books of the kind is, that the 
 author has avoided all Latin terms ; this is what has brought Dr. Gunn's work 
 mto such extensive family use." — New Orleans Picayune. 
 
 " As a medical Vade Mecum, it has for years stood high ; and now, since its re- 
 vision, (Raymond's copy,) will take the lead of all similar works."— Mobile Daily 
 Advertiser. 
 
 " Its extensive sale has established .ts worth, and stamped it as a standard and 
 , tseful hook."— Kentucky Gazette. 
 
 (jy On the receipt of Three Dollars, Dr. Gunn's book will be sent, free oj 
 postage, to any part of the United States. 
 
 AH letters must be addressed, (post-paid,) to C. M. SAXTON,191F0LtonSt 
 New York. 
 
 '< Raymond'a Copy " is the only complete edition and is so marked on tb<% back 
 
THE AMERICAN BEE-KEEPER'S MANUAL. 
 
 BY T. B. MINER. 
 
 360 pp. 12m o. 35 Eagravings. Price $1. 
 
 PUBLISHED BY C. M. SAXTON, 123 FULT( N ST., N. Y, 
 
 OPINIONS OF THE PRESS. 
 
 " The most complete work on the Bee and Bee-keeping we have yet seen." — 
 N. Y. Tribune. 
 
 " Mr. Minor has handled this subject in a masterly manner." — N. Y. True Sun. 
 
 " He has written a work of the most fascinating interest." — N. Y. Suiiday Dis- 
 patch. 
 
 " It will interest the general reader. It is indeed a charming volume. — Com 
 merciul Jldverliser. 
 
 " This is a truly valuable work, and very interesting." — Morning Star. 
 
 "It is decidedly the best work we have ever seen." — Boston Daily Mail. 
 
 " Mr. Miner has performed his task with signal ability." — Scientific American. 
 
 " It does high credit to the observation and intelligence of the author." — Chris- 
 tian Intelligencer. 
 
 " This is the most comprehen.sive and valuable work on the Honey-bee that 
 hns ever come under our notice." — Journal of Commerce. 
 
 " To appreciate the value of the honey-bee one must get this book and read it 
 attentively." — Noah's Messenger. 
 
 " We like it for its independent tone, and the amount of practical information 
 that it contains." — Literary World. 
 
 " We have been greatly edified and entertained by this by>k. from which the 
 reader will collect a great deal of excellent information, — The Independent. 
 
 " This ie probably the most complete manual of the kind ever published. It will 
 richly repay the general reader, too, by the variety of interesting facts it com* 
 tains." — Boston Traveller. 
 
 " It is a most excellent and useful treatise, and happily supplies a vacuum 
 thart had long existed." — Boston Times. 
 
 " This volume has all the charm of a romance and admirably displays the 
 habits of this insect." — O^gan. 
 
 " This volume is what it pretends to be, (more than can be said of many works) 
 and all who want a full and thorough history of the nature and management ox 
 of the bee should have it in their possession." — Scientific American. 
 
 " It is neatly printed, well illustrated and clearly written and contains a great 
 deal of practical information." — Mirror. 
 
 " This work probably contains better instructions in regard to bees than any 
 which have ever appeared." — Sun, 
 
 " The practical directions are the result of evident experience, and being 
 j>laiB.ly end couoisely stated, are excellent, It is so louch better than can ba 
 obtained els'iwHoro that we commend it to favor." — N. Y. Evangelist. 
 
 ♦• It i« an eyr^Uent book and the best published on the subject." — Boston Oliv* 
 Bfanck. 
 
THE 
 
 AMERICAN POULTRY YARD; 
 
 COMPRISING THE 
 
 DRIGIN", niSTORY, AND DESCRIPTION OF THE DIFFERENT 
 
 BREEDS OF 
 
 S)om£0ttc fj3oultrj3; 
 
 WITH 
 
 Complete Directions for their Breedings Crossing, Rearing, 
 
 Fattening, and Preparation for Market ; 
 
 Including Specific Directions for Caponising Fowls, and for the 
 
 Treatment of the Principal Diseases to which they are subject. 
 
 DRAWN FROM AUTHENTIC SOURCES AND PERSONAL OBSERVATION 
 Illustrated by Numerous Engravings 
 
 By D. J. BROWNE. 
 
 With an Appendix, embracing the Comparative Merits of 
 Different Breed of Fowls. 
 
 By SAMUEL ALLEN". 
 
 Price ^\,in cloth — 75 cts. with paper covers. 
 
 Piiblislicd l>y C. M. SAXTON, 123 Fulton Street, N. V. 
 
 OPINIGlSrS OF THE PRESS. 
 
 Mr. Browne was bred and broiigbit np a practical farmer. Fi'om his intimate know 
 ledge of the liistory and habits of our domestic auiiuals, having devoted, pi-obablj;, 
 more attention to tlie subject, as a whole, by reading and obserA^ation, than any other 
 individual in the country, the task of preparing this work was assigned to him.-- 
 Salem Register. 
 
 Tlie style of the engi-avings and the mechanical execution of the work arc excellent 
 —Maine Farmer. 
 
 An extensive work on poultry, embracing every information desired. — JV. H. Tele 
 graph. 
 
 We commend the book and the subject to the thoughts of fanners. — Vt. Watchman, 
 
 Every one who may purchase a copy, upon a perusal of the same, will be fully satis- 
 
 9ed that their money was well ^T^enL— Bristol Phanix. 
 It is one of flToTjest treatises on the Domestic Fowl ever published. — JVeic-Haven 
 
 Palladium. 
 
 The details into which this book enters, on all the subjects connected with the pro- 
 fitable raising of fowls, are precisely of that minute and practical chai'acter which ia 
 needed. — J\r. Y. Kuangdist. 
 
 We are glad to see that the evident demand for information on the subject of 
 rearing Domestic Fowls has called out so valuable a work aa the one before us. — JV. Y. 
 Daily Tribune. 
 
 It contains matter to interest and instnict upon almost everything that concerns the 
 poultry yaid, and bears the impress in its pages that its editor was well qualifled to 
 fullill the tusk he undertook. — Avierican Farmer. 
 
 It is the most complete book of its class ever published, and quite indispensable lo 
 all who are interested in raising poultry.— C/iarZesion, S. C, Weekly Gazette. 
 
 No farmer among us would remain a day longer svithout the work, did he bu-t know 
 Us value. — Ralnoay Register. 
 
 It is unquestionably the cheapest and best work of the kind extant, and should have 
 A place in every farmer's library. — Ocrmnviown, Ohio, Gazette. 
 
 The volume is cnricliod by an Appendix from the the pen of Mr. Samuel Allen, an 
 experienced breeder of fowls, who luis taken micli pains to improve the stock in this 
 C-ountry.— .v. V. Weekly 'J'ri//iiv.r.. 
 
THE- 
 
 AMERICAN BIRD FANCIER; 
 
 CONSIDERED WITH REFERENCE TO THE 
 
 BREEDING, REARING, FEEDING, MANAGEMENT, AND PECULIARITIES 
 
 OF 
 
 CAGE AND HOUSE BIRDS. 
 
 Illustrated -with Engravings 
 
 BY D. J. BROWNE, 
 
 AUTHOR OF THE BYLVA AMERICANA, THE AMERICAN POULTRY YARD, ETC. 
 
 NEW YORK: 
 C. M. SAXTON, 123 FULTON STREET. 
 
 ALSO, STRINGER <fe TOWNSEND, H. LON^ & BROTHER, W. F. BURGESS, 
 
 DEWITT & DAVENPORT, "WILSON & CO., DEXTER & BROTHER. 
 
 PHILADELPHIA I W. B. ZIEBER, LINDSAY & BLAKISTON. 
 
 boston: REDDING & CO. 
 
 1850. 
 
AN 
 
 ESSAY ON MANURES, 
 
 SUBMITTED TO THE TRUSTEES OF 
 
 THE MASSACHUSETTS SOCIETY 
 
 FOR 
 
 PROMOTING A6BIGULTURE, 
 
 FOB, THEIR PREMIUM. 
 
 BY SAMUEL L. DANA. 
 
 From the New York Ohserver: 
 Essay on Manures. By Samuel L. Dana 
 
 This Essay~ebntains much useful infomation for tbe practical fanner, in a 
 small compass, in reference to the nature and management of manures imme- 
 diately under his control ; the knowledge and practice of which will amply com- 
 pensate for the expense of ascertaining its value. 
 
 NEW YORK: 
 C. M. SAXTON, 123 FULTON STREET. 
 
 ALSO, STRINGER <fe TOWNSEND, H. LONG & BROTHER, W. F. BUR- 
 GESS, DEWITT & DAVENPORT, WILSON & CO., DEXTER A 
 BROTHER. BOSTON : REDDING & CO. PHILADELPHIA : 
 W. B. ZIEBER, LINDSAY & BLAKI8TON. 
 
 1850. 
 
THE 
 
 FAMILY KITCHEN GARDENER; 
 
 CONTAINING 
 
 PLAIN AND ACCURATE DESCRIPTIONS 
 
 OF ALL THE 
 
 DIFFERENT SPECIES AND VARIETIES 
 
 OF 
 
 BY ROBERT BUIST, 
 
 AUTHOR OF THE AMKRICAN FLOWER-GARDEN DIRECTORY, ROSE MANUAL, ETC. 
 
 NEW YORK: 
 C. M. SAXTON, 123 FULTON STREET, 
 
 ALSO, STRINGER & TOWNSEND, H. LONG & BROTHER, W. F. BTJR- 
 OESS, DEWITT <& DAVENPORT, WILSON & CO., BEXTER <fc 
 BROTHER. BOSTON : REDDING 4 CO. PHILADELPHIA : 
 W. B. ZIEBER. LINDSAY & BLAKISTON. 
 
 1850. 
 
A PRACTICAL TREATISE 
 
 ON THE 
 
 CULTIVATION OF THE GRAPE VINE 
 
 ON OPEN WALLS. 
 
 WITH A DESCRIPTIVE ACCOUNT OF AN 
 IMPROVED METHOD OF PLANTING AND MANAGING 
 
 THE 
 
 EOOTS OF &RAPE VINES. 
 
 BY CLEMENT HOARE. 
 
 TO WHICH IS ADDED, 
 
 AN APPENDIX, 
 
 CONTAINING 
 
 REMARKS ON THE CULTURE OF THE GRAPE VINE IN 
 THE UNITED STATES. 
 
 NEW YORK: 
 C. M. SAXTON, 123 FULTON STREET. 
 
 1851. 
 
LIBERAL OFFER!! 
 
 TO THE 
 
 FARMERS AND AGRICULTURISTS 
 
 OF THE UNITED STATES. 
 
 *^* ANY PERSON CAN SELECT FROM THE LIST BELOW, TO BE SENT THEM BY MAIL 
 OR OTHERWISE, BY FORWARDING TO US, POST PAID, 
 
 (All of the following are boundin paper covers,) 
 
 ONE DOLLAR, 
 
 One copy of any of the 75 ct. books, and one 
 of the 50 ct. books, or one of the 75 ct. 
 and two of the 25 ct. books. 
 
 FOR TWO DOLLARS, 
 
 Two 75 ct. and two 50 ct. Books. 
 
 FOR THREE DOLLARS, 
 
 Three 75 ct. and two 60 ct. Books, and two 
 25 ct. Books. 
 
 FOR FOUR DOLLARS, 
 
 One copy Gunn's Domestic Medicine $3 00 
 
 One copy Farm Book ... '5 
 
 One copy American Poultry Yard . 75 
 
 One copy Dana's Essay on Manures . 25 
 
 FOR FIVE DOLLARS, 
 
 One set American Architect, 24 Nos., com- 
 plete, or the following : — 
 One copy Gunn's Domestic Medicine $3 
 One copy Farm Book 
 One copy Poultry Yard . 
 One copy Kitchen Gardener 
 One copy Domestic Animals . 
 One copy Dana's Essay on Manures 
 One copy Bird Fancier 
 
 FOR SIX DOLLARS, 
 
 One copy American Architect . . $5 00 
 
 One copy Farm Book ... 75 
 
 One copy Poultry Yard ... 7a 
 
 Johnston's Practical Agriculture . 50 
 
 Or the following: — 
 One copy Gunn's Domestic Medicine 
 One copy Farm Book . 
 One copy Poultry Yard 
 One copy Bee Keeper's Manual . 
 One copy Kitchen Gardener . 
 One copy Domestic Animals . . 
 Johnston's Practical Agriculture . 
 One copy Dana on Manures . 
 
 $3 00 
 75 
 75 
 75 
 50 
 50 
 50 
 25 
 
 FOR TEN DOLLARS, 
 
 Rich's American Architect, 24 Nos. . 
 Gunn's Domestic Medicine, 12 Nos. 
 Allen's American Farm Book . 
 Brown's American Poultry Yard . 
 Miner's Bee Keeper's Manual . 
 Allen's Domestic Animals 
 Buisl's Family Kitchen Gardener . 
 Browne's Bird Fancier . 
 Dana's Prize Essay on Manures 
 
 $5 00 
 3 00 
 75 
 75 
 75 
 60 
 50 
 25 
 25 
 
 ^/LIST OF BOOKS PUBLISHED BY C. M. SAXTON, 
 
 123 FULTON STREET, NEW YORK. 
 
 a 
 a 
 
 a 
 a 
 
 a 
 a 
 
 a 
 a 
 
 6i 
 
 $5 00 
 3 00 
 75 
 75 
 75 
 50 
 50 
 25 
 25 
 
 RICH'S AMERICAN ARCHITECT. 24 NOS. COMPLETE 
 
 GUNNS DOMESTIC MEDICINE. 12 NOS. PAPER COVERS 
 
 ALLEN'S AMERICAN FARM BOOK, " 
 
 BROWNE'S AMERICAN POULTRY YARD 
 
 MINER'S AMER. BEE-KEEPER'S MANUAL " 
 
 ALLEN'S DOMESTIC ANIMALS 
 
 BUIST-S FAMILY KITCHEN GARDENER 
 
 BROWNE'S BIRD FANCIER'S MANUAL 
 
 DANA'S PRIZE ESSAY ON MANURES ^^.^,. 
 
 PROFESSOR JOHNSTON'S LECTURES ON PRACTICAL 
 
 AGRICULTURE, PAPER COVER 
 
 Traveling Booksellers, Book Agents, and Pedlars, will be supplied at 
 very low prices with the above list of Books, in di^erent styles of binding^ 
 
 FOR CASH ONLY. 
 
 APPLY, POST PAID, TO 
 
 C. M. SAXTON PUBLISHER, NEW YORK. 
 
 50 
 
GREAT PREMILMS 
 
 TO SUBSCRIBERS 
 
 FOR 
 
 "THE AMERICAN AGRICULTURIST" 
 
 FOR 1851. 
 
 With the view of increasing its subscription list, and thereby its useful- 
 ness, the Publishers otFer the following Premiums, by way of encourage- 
 ment, to individuals or Clubs, who will subscribe, and remit to us the 
 money, postage free, at the time of ordering the paper : — 
 
 FOR ONE DOLLAR. — Oue co-pj of the American Agriculturist, and 
 one copy of either of the 26 ct. Books enumerated in the list below. 
 
 FOR TWO DOLLARS. — Two copies of the American Agriculturist, 
 
 and one of the 75 ct. Books in the list below. 
 
 FOR THREE DOLLARS. — Three copies of the American 
 Agriculturist, and one copy of the 75 ct. Books, and one of the 
 50 ct. Books. 
 
 FOR FOUR DOLLARS. — ^onr copies oiihe American Agricultxtrist 
 and two of the 75 ct. Books, and one 25 ct. Book. 
 
 FOR FIVE DOLLARS. — Five copies of the American Agriculturist, 
 and two of the 76 ct. Books, and one of the 50 ct, and one of the 25 
 ct Books. 
 
 FOR EIGHT DOLLARS . — Eight copies of the American Agricul- 
 turist, and three copies of the 75 ct. Books, and two 50 ct. and 
 one of the 25 ct. Books. 
 
 FOR TEN DOLLARS. — Ten copies o{ \he American Agriculturist, 
 and one copy of Rich's American Architect. 
 
 FOR TWENTY DOLLARS. — Twenty copies of the American 
 Agriculturist, and one copy of the American Architect, four copies of 
 the 75Trt Bot)ks, three copies of the 50 ct., and two of the 25 ct. Books. 
 
 The following list «f Agricultural Books are published by C. M. Saxton, 
 
 123 Fulton street, and offered as premiums to subscribers to the American 
 
 Agriculturist, for 1851 : — 
 
 ALLEN'S AMERICAN FARM BOOK $ 75 
 
 MINER'S BEE-KEEPER'S MANUAL 75 
 
 BROWN'S AMERICAN POULTRY YARD. ... 76 
 
 ALLEN'S DOMESTIC ANIMALS 50 
 
 JOHNSTON'S LECTURES ON PRACTICAL AGRI- 
 CULTURE 50 
 
 BUISrS FAMILY KITCHEN GARDENER ... 50 
 
 BROWN'S AMERICAN BIRD FANCIER .... 25 
 
 DANA'S PRIZE ESSAY ON MANURES .... 25 
 KICK'S AMERICAN ARCHITECT (24 NUMBERS, 
 
 COMPLETE) 5 00 . 
 
 The above list of books are all substantially bound in paper covers, and 
 
 can be sent by mail to all parts of the United States. 
 
NEW-YORK AGRICULTURAL WAREHOUSE 
 
 AND SEED STORE. 
 
 A. B. ALLEN & CO., 
 
 189 & 191 WATER STREET, NEW-YORK. 
 
 Farmers, Planters, and Gardeners will find in our Warehouse, the largest and 
 most complete as-sortment of Agricultural and Horticultural Implem.ents. Field 
 and Garden Seeds, Fertilizers, Fruit and Ornamental Trees. &.C.. &c., in New 
 York. A few of the articles we enumerate Delow, Our implements are mostly 
 made'up from new and highly-impkoved patterns, and are warranted to te of 
 the best matcriills. put together m the strongest manner, and of superior finish. 
 Plows -Of these wc liave upwards of FIFTY diflerent kinds, among which 
 
 are Cotton, Rice, and Sugar Pl»w$, at $'2 to 4.50 
 
 Two and Four 
 Horse Plows, of dif- 
 ferent sizes, and for 
 all kinds of soils — 
 stony, sandy, loam, 
 or clay ; also for 
 stubble and sward 
 land. Some of these 
 have patent clovies 
 attached to them, 
 thus cnaliling the 
 off-horse, in plowinjj 
 a wet meadow, to 
 
 DounLE Mold-Board Plow. 
 
 SoBSoib Plow, with Wheel, Dial-Clevis, and Draft-Rod. 
 %V»lk an the solid ground, instead Ci a mirjt Iresh-plowed furrow. Others are 
 
Neio York Agricultural Warehouse. 
 
 adapted to trench-plowing, enabling the farmer to turn up virgin earth in a deep 
 soil. These plows are strong enough to grub up roots, heavy bogs, &c. They 
 
 likewise answer for shallow ditching $5 to $20 
 
 One Horse Plows for the North, with single and Double Mold-Boards. The 
 last are admirable to work between the rows of root crops and corn, when not 
 over -Vz feet a])art. as they turn the furrow both ways, thus doing double the 
 wuik of a single mold-board $3 tojd 
 
 Cultivator with V/heel. 
 
 ^Sr^' S^ 
 
 ^-s-i^&ie^^^ 
 
 Set.d Sower. 
 fihould be without them 
 
 Some of these plows are made 
 
 expressly for light sandy soils, 
 
 others for a loam, or stiff clay, 
 
 which they work in the best 
 
 manner. Being made by patent 
 
 machinery, they are superior to 
 
 anything of the kind ever before 
 
 sold in this market. 
 
 ,5j,.,^ Rice Trenching Plow. — This does 
 
 l^^^lthe same work as the hands per- 
 
 "^^fovm. on a rice plantation with 
 
 trenching hoes, equally well, and 
 
 with much greater rapidity than a 
 
 negro can work. No Planter 
 
 $6 to 6.50 
 
 Subsoil Plows for 
 deep plowing $5.50 
 to 16.00. 
 
 Double MoliLBnnrd 
 or Fluke Plows for 
 furrowing to plant, 
 cultivate and ditch ; 
 and the largest made 
 expressly for plant 
 ing the sugar cane, 
 ^3.50 to 9.00. 
 
 Side- Hill Shifting 
 Mold- Board or Swiv- 
 el Plown, for turning 
 the furrow in either 
 direction, $5.00 to 
 16.00. 
 
 Paring Plows, for 
 shaving oft" the turf 
 preparatory to burn- 
 ing $15.00. 
 
 Harrows. — A com- 
 plet3 assortment of 
 square, triangle, and 
 double triangle fold- 
 ing, harrows, with 
 wrought iron oi 
 iteel pointed teet: 
 $6 to 16.00. 
 
 |477 
 
 /|i S^UABR Harrow^