680 



FARMERS' REGISTER 



[No. 11 



it is altered by, or combined with, principles derived 

 from the atmosphere. The influence of the soil, 

 of water, and of air, will therefore he the next 

 subject of consideration. Soils in ail cases consist 

 of a mi.xture of diflerent finely divided earthy 

 matters; with animal or vejietable substances in a 

 state of decomposition, and certain saline infjre- 

 dients. The earthy matters are the true basis of 

 the soil; the other parts, whether natural, or arti- 

 ficially introduced, operate in the same manner as 

 manures. Four earths rrenerally abound in soils; 

 the aluminous, the silicious, the calcareous, and 

 the magnesian. These earths, as I have disco- 

 vered, consist of hitrhly inflammable metals united 

 lo pure air, or oxyy;en; and they are not, as far 

 as we know, decomposed or altered in vegetation. 



The great use of the soil is to afford support to 

 the plant, to enable it to fix its roots, and to derive 

 nourifehmeni l\v its tubes slowly and gradually, 

 from the soluble and dissolved substances mixed 

 with the earths. 



That a particular mixture of the earths is con- 

 nected with fertility, cannot be doubted: and al- 

 most all steril soils are capable of being im- 

 proved, by a modification of their earthy constitu- 

 ent parts. 1 shall describe the simplest method 

 as yet discovered of analysing soils, and of ascer- 

 taining the constitution and chemical ingredients 

 which appear to be connected with fertility; and 

 on this subject many of the former difficulties of 

 investigation will be found to be removed byjecent 

 inquiries. 



The necessity of water to vegetation, and the 

 luxuriancy of the growth of plants connected with 

 the presence of moisture in the southern countries 

 of the old continent, led to the opinion so preva- 

 lent in the early schools of philosophy, that water 

 was the great productive element, the substance 

 from which all things were capable of being com- 

 posed, and into which they were finally resolved. 

 The ^' nriston men hydnr " of the poet, " water is 

 the noblest," seems to have been an expression of 

 this opinion, adopted by the Greeks from the 

 Egyptians, taught by Thnles, and revived by the 

 alchemists in late times. Van Helmont, in 1610, 

 conceived that he had proved, by a decisive ex- 

 periment, that ull the products of vegetables were 

 capable of being generated from water. His re- 

 sults were shown lo be fallacious by Woodward 

 in 1691; but the true use of water in vegetation 

 was unknown till 1785; when Mr. Cavendish 

 made the discovery, that it was composed of two 

 elastic fluids or gases, inflammable gas or hydro- 

 gen, and vital gas or oxvgen. 



Air, like water, was regarded as a pure element 

 by most of the ancient philosophers: a few of the 

 chemical inquirers in the sixteenth and seven- 

 teenth centuries, formed some happy conjectures 

 respecting its real nature. Sir Kenelm Digbv, in 

 1660, supposed that it contained some saline mat- 

 ter, which was an essentud food of plants. Boyle, 

 JHook, and Mayow, between 1665 and 1680, 

 stated, that a small part of it only was consumed 

 in the respiration of animals, and in the combus- 

 tion of inflammable bodies; but the true statical 

 analysis of the atmosphere is comparatively a re- 

 cent labor, achieved towards the end of the last 

 century by Scheele, Priestley, and Lavoisier. 

 These celebrated men showed that its principal 

 elements are two gases, oxygen and azote, of 

 which the first is essential to flame, and to the life 



of animals and that it likewise contains small 

 quantities of aqueous vapor, and of carbonic acid 

 gas; and Lavoisier proved that this last body is it- 

 self a compound elastic fluid, consisting of char- 

 coal dissolved in oxygen. 



Jethro Toll, in his Treatise on Horse-hoeing, 

 published in 1733, advanced the opinion, that mi- 

 nute earthy particles supplied the whole nourish- 

 ment of the vegetable world; that air and water 

 were chiefly useful in producing these particles 

 from the land; and (hat manures acted in no other 

 way than in ameliorating the texliu'e of the soil, 

 in short, that their agency was mechanical. This 

 ingenious autlior of the new system of agriculture 

 having observed the excellent effects produced in 

 farmin<r, by a minute division of the soil, and the 

 pulverization of it by exposure to dew and air, 

 was misled, by carrying his principles too far. 

 Duhamel, in a work printed in 1754, adopted the 

 opinion of Tull; and stated, that by finely dividing 

 the soil, any number of crops might be raised in 

 succession from the same land. He attempted 

 also to prove, by direct experiments, that vegeta- 

 bles of every kind were capable of being raised 

 without manure. This celebrated horticulturist 

 lived, however, sufficiently long to alter his opi- 

 nion. The results of his later and most refined 

 observations led him to the conclusion, that nn 

 single material aflbrded the food of plants. The 

 general experience of farmers had long before 

 convinced the unprejudiced of the truth of the 

 same opinion, and that manures were absolutely 

 consumetl in the process of vegetation. The ex- 

 haustion of soils, by carrying off corn crops from 

 them, and the effects of feeding cattle on lands, 

 and of preserving their manure, ofl'er familiar il- 

 lustrations of the principle; and several philoso- 

 phical inquirers, particularly Hassenfratz and 

 Saussure, have shown, by satisfactory experi- 

 ments, that animal and vegetable matters de- 

 posited in soils are absorbed by plants, and be- 

 come a part of their organized matter. But though 

 neither water, nor air, nor earth, supplies the 

 whole of the food of planta, yet they all operate in 

 the process of vegetation. The soil is the labora- 

 tory in which the food is prepared. No manure 

 can be taken up by the roots of plants, unless 

 water is present; and water, or its elements, exist 

 in all the products of vegetation. The germina- 

 tion of seeds doas not take place without the pre- 

 sence of air or oxygen gas: and in the sunshine, 

 vegetables decompose the carbonic acid gas of the 

 atmosphere, the carbon of which is absorbed, and 

 becomes a part of their organized matter, and the 

 oxywen gas, the othej constituent, is given off;* 

 and. in consequence of a variety of agencies, the 

 economy of vegetation is made subservient to the 

 general order of the system of nature. 



It is shown by various researches, that the con- 

 stitution of the atmosphere has been always the 

 same since the time that it was first accurately 

 analyzed; and this must, in a great measure, de- 



* The great accumulation of carbon in forests and 

 in peat mosses, not to lay stress on beds of mineral 

 coal, which there is good reason to consider of vegeta- 

 ble orig-in, affords demonstrative proof, as it appears to 

 me, of the truth in the text, that plants, in active vege- 

 tation and growth, either mediately or immediately 

 derive from the atmosphere carbon, by the decomposi- 

 tion of carbonic acid and the hberation of its q«y- 

 gen. J- D. 



