462 EUROPEAN AGRICULTURE. 



quite remarkable in respect to them ; the one is the different 

 qualities of grain grown with manures of the greatest efficacy, 

 and that grown without any manure, being a difference of nine 

 and thirty-five ; and the comparatively low result of pigeon s 

 dung, which is generally rated very highly, and supposed to take 

 its place with guano. The manner in which the animals whose 

 manure was used for these experiments were fed, is a circumstance 

 which may. have materially affected the results ; for the qualities 

 of the manure of the same animals, under different courses of 

 feeding, may be expected to be composed of different elements, 

 and so to give different results ; so complicated necessarily are all 

 experiments of this kind. 



The farmers in France are behind no others in what may be 

 called, technically, agricultural science ; and some of those emi 

 nent men, who are sometimes called farmers of the closet, have 

 gone into the most exact and minute mathematical calculations 

 as to the actual amount of certain mineral elements, which are 

 supposed essential to the growth of the crop, or of any particular 

 crop ; and next, as to the amount of these mineral substances, 

 which any particular crop carries off in the straw, and in the 

 grain. They then proceed to determine the exact amount of 

 these substances, which must be restored to the soil in order to 

 keep up its fertility. The first point is determined by analyzing 

 with great chemical exactness a portion of the soil ; the second, 

 by analyzing a portion of the crop, of the straw, and the grain ; 

 and these premises being obtained, the third is of course matter 

 of plain inference. These calculations are curious and ingenious, 

 and if vegetation or the growth of plants were as simple an affair, 

 and as well and as easily understood as many pretend that it is, 

 these facts would have a most direct and immediately practical 

 bearing. One of the most eminent of these calculators, however, 

 himself admits that the application of these facts, or rather the 

 rules deduced from them, is an operation difficult, delicate, and 

 which only the most skilful persons can undertake.* 



In the present very imperfect state of our knowledge of vege 

 tation, I am free to express my conviction, that they will answer 

 no other purpose than that of mere curiosity and amusement. In 

 the analysis of a soil, for example, if we suppose that a cubic 



* Gasparin s Course of Agriculture, vol. iii. p. 405. 



