92 M. De Gaspai-in on the Classif cation of Soils. 



drawn from improvement, and no longer with that of tenacity ; 

 for, in these two classes of lands, we find that, according to 

 the proportion of the mineral principles which they contain, 

 the soils possess a different degree of tenacity. 



Other kinds of culture confirm this view. Fruit-trees thrive 

 admirably in siliceous and clayey lands, and these are gene- 

 rally the soils of forests ; leguminous plants prefer soils in 

 which there is a carbonate, and then they appear naturally ; 

 and it is only in the same circumstances that dye-plants afford 

 vivid colours. 



We have already remarked, that we cannot avail ourselves 

 of the characters which are drawn from the tenacity of the 

 soil, without destroying the groups which we had previously 

 formed. We can, however, reserve them for the formation 

 of secondary groups, which will subdivide the primary classes. 

 It will be the same thing with those which are derived from the 

 property which gypsum possesses of rendering certain soils emi- 

 nently productive of vegetables ; but \\'e have seen that it is 

 the geological position of soils, more than their composition, 

 which has hitherto contributed to designate them. But each 

 of our groups contains earths of different geological forma- 

 tions, so that we should run the risk of breaking them up if 

 we were to introduce this consideration into the formation of 

 our primary groups ; and, upon the principle above insisted 

 upon, this character will rank after the one derived from 

 tenacity. 



These principles being allowed, we now proceed to the ex- 

 position of the classification of soils, which they supply. 



FIRST DIVISION.— SOILS HAVING A MINERAL BASIS. 

 Character. — These soils do not lose a fourth of their weight upon heat- 

 ing them till they emit no more vapour. 



FIRST CLASS.-SALIFEROUS SOILS. 



Character. — Soils with a salt or styptic taste, containing at least 0,006 

 parts of hydrochlorate of soda, or sulphate of iron. 



1st, Saline Soils. — Water digested with these soils, gives a precipitate 

 with nitrate of silver. 



2d, Vitriolic Soils. — Hydrocyanate of potass gives a white precipitate 

 with the ferruginous salt which is contained in the water digested with 

 this soil. 



