208 ON THE CHEMICAL CONSTITUENTS OF SOILS. 



Ingenhouss proposed dilute sulphuric acid as a 

 means of increasing the fertility of a soil. Now, 

 when this acid is sprinkled on calcareous soils, gyp- 

 sum (sulphate of lime) is immediately formed, which 

 of course prevents the necessity of manuring the 

 soils with this material. 100 parts of concentrated 

 sulphuric acid diluted with from 800 to 1000 parts 

 of water, are equivalent to 176 parts of gypsum. 



SUPPLEMENTARY CHAPTER. 



ON THE CHEMICAL CONSTITUENTS OF SOILS. 



The fertility of a soil is much influenced by its 

 physical properties, such as its porosity, color, attrac- 

 tion for moisture, or state of disintegration. But 

 independently of these conditions, the fertility de- 

 pends upon the chemical constituents of which the 

 soil is composed. 



We have already shown, at considerable length, 

 that those alkalies, earths, and phosphates, which 

 constitute the ashes of plants, are perfectly indis- 

 pensable for their development ; and that plants 

 cannot flourish upon soils from which these com- 

 pounds are absent. The necessity of alkalies for 

 the vital processes of plants will be obvious, when 

 we consider that almost all the difl*erent families of 

 plants are distinguished by containing certain acids, 

 differing very much in composition ; and further, 

 that these acids do not exist in the juice in an 

 isolated state, but generally in combination with 

 certain alkaline or earthy bases. The juice of the 

 vine contains tartaric acid, that of the sorrel oxalic 

 acid. It is quite obvious, that a peculiar action must 

 be in operation in the organism of the vine and 

 sorrel, by means of which the generation of tartaric 

 and oxalic acid is effected ; and also that the same 

 action must exist in all plants of the same genus. 



