24» CHYMISTRY APPLIED TO AGRICULTURE. 



ARTICLE IV. 



Of the Composition of Arable Lands. 



It would be easy to ascertain the nature of any portion 

 of arable land, if we had to consider only the character of 

 the rock from which it was produced ; but vegetation, 

 time, and the labor of man, have wrought so many changes 

 in it, that the primitive character has nearly disappeared; 

 and it is necessary to judge of, and appreciate it in its 

 actual state. Still, the lands devoted to agriculture are 

 generally composed of silex, lime, and alumina ; with 

 these are intermixed pebbles or sand of different natures, 

 and in vsCrious proportions, and the remains of animal and 

 vegetable matter, more or less thoroughly decomposed. 

 The other substances which, by analysis, are found in 

 these soils, are not in sufficient quantities to be classed 

 amongst their elements; when these are too abundant, 

 as is the case in certain localities with magnesia and the 

 oxide of iron, the soil becomes less fit for vegetation. 



The best basis for good lands is a mixture of lime, 

 silica, and alumina ; but, in order that they may possess 

 all the desirable qualities, it is necessary that certain pro- 

 portions, which an analysis of the best lands has made 

 known, should be observed in the mixture. 



I propose, in the first place, to examine in what propor- 

 tions the constituent principles enter into those lands, 

 which are the most favorable to vegetation, and afterwards 

 to ascertain the properties peculiar to each kind of soil ; 

 and to enlighten the agriculturist as to the best methods 

 of correcting the faults of one, by the qualities of another. 

 I shall then treat of the effect produced upon the fertility 

 of soils, by the accidental deposits of animal and vegeta- 

 ble matter, which are mingled with them ; and I shall 

 conclude by a short exposition of the means which can be 

 employed by the agriculturist, for becoming acquainted 

 with the nature of his lands. 



In order to know the earthy composition of those soils, 

 which have been considered the most fertile in various 

 climates, I shall have recourse to the analyses of them 

 which have been made by men worthy of the utmost con- 

 fidence^. 



