6 



On Agricultural Chemistry. 



growing plant in relation to the soil and atmosphere ; and in con- 

 nexion with each of these subjects much laboratory labour has 

 constantly been in progress. 



The scope and object of our investigation has been therefore to 

 examine, in the field, the feeding-shed, and the laboratory, into 

 the chemical circumstances connected with the agriculture of 

 Great Britain in its four main features ; namely — 



First, the production of the Cereal grain crops ; 

 Secondly, that of Root crops ; 



Thirdly, that of the Leguminous corn and Fodder crops ; and 

 Fourthly, and lastly, that of the consumption of food on the 

 farm for its double produce of Meat and Manure. 



So much then for the rationale and general plan of the experi- 

 ments themselves, and we now propose to call attention to some 

 of the results which they have alforded us. 



Hitherto only part of the results of the wheat experiments of 

 the harvests of 1844, 1845, and 1846, and of these seasons only, 

 have been published ; those on turnips, only for the seasons 

 1843, 1844, and 1845 ; those on the leguminous crops not at all 

 as yet ; and those on feeding, only as far as sheep are concerned, 

 and chiefly too in relation to the one point only of the increase 

 of live weight obtained from a given quantity of food, or its con- 

 stituents. Of the laboratory results but few have been given 

 in relation to any one of these branches up to the present time. 

 The vast accumulation of results, indeed, will necessarily still 

 further postpone the publication of them in any extended form ; 

 and hence it seems the more desirable to take advantage of the 

 present opportunity to attempt to bring together into one view 

 some of the general indications which have been arrived at in 

 relation to a few of the more important points. 



With this view, it is to the field experiments on wheat that we 

 shall chiefly confine our attention on this occasion ; for wheat, 

 which constitutes the principal food of our population, is with the 

 farmer the most important crop in his rotation, all others being 

 considered more or less subservient to it ; and it is, too, in refer- 

 ence to the production of this crop in agricultural quantity that 

 the mineral theory of Baron Liebig is perhaps more promi- 

 nently at fault than in that of any other. 



It is true that, in the case of vegetation in a native soil, un- 

 aided by art, the mineral constituents of the plants being fur- 

 nished from the soil, the atmosphere is found to be a sufficient 

 source of the nitrogen and carbon ; and it is the supposition 

 that these circumstances of natural vegetation apply equally 

 to the various crops when grown under cultivation that has 

 led Baron Liebig to suggest that, if by artificial means we 



