ON THE CHEMICAL CONSTITUENTS OF SOILS. 



233 



100 parts by weight left, after ignition, 10 parts 

 \ of ashes. 100 parts of these ashes consisted of: — 



Silica and siliceous sand .... 79*600 



Alumina 



Peroxide of iron 



Peroxide of manganese 



Carbonate of lime . 



Carbonate of magnesia . 



Potash 



Soda 



Phosphoric acid 



Sulphate of lime (gypsum) 



Chlorine 



100000 



Soils such as this, after having been burned seve- 

 ral times, and made to produce buckwheat, are com- 

 pletely deprived of their potash and soda ; and in 

 consequence of this are rendered quite barren. Hence 

 it is that ashes of wood exert such an astonishing 

 effect upon them. 



25. Analysis of a very fertile loamy sand, from 

 Osnabruck, near Rotherfeld. It is remarkable for 

 being manured only once every 10 or 12 years, and 

 bears beautiful wheat as the last crop. 100 parts 

 contain : — 



100-000 



The soil in question lies on the southern exposure 

 of a hill, which consists of layers of limestone and 

 marl. The rain-water penetrates through these lay- 

 ers, and becomes saturated with the soluble salts 

 contained in them, such as potash, gypsum, common 

 salt, lime, magnesia, and saltpetre. It afterwards 



20* 



