242 



ON THE CHEMICAL CONSTITUENTS OF SOILS. 



Carbonate of magnesia 



Potash, principally combined with silica 



Soda .... 



Phosphoric acid 



Sulphuric acid . . 



Chlorine . . . 



Humus .... 



10-361 

 0-100 

 0013 

 1-221 

 0009 

 003 

 0-447 



100-000 



ENGLAND. 



39. Surface-soil of a very fertile sandy field from 

 the vicinity of Tunbridge, Kent, according to Davy. 

 100 parts consisted of: — 



100-000 



The great Davy, who was convinced of the impor- 

 tance of the inorganic constituents of soils, has 

 omitted to detect the phosphoric acid, potash, soda, 

 and manganese. All these must have been present 

 in the soil, for we are informed that it produced 

 good hops, for which these ingredients are indis- 

 pensable. 



40. A good turnip soil from Holkham, Norfolk, 

 yielded to Davy : — 



Siliceous sand 



Silica 



Alumina 



Peroxide of iron 



Carbonate of lime 



Vegetable and saline matter 



Moisture . ^ . 



88-888 

 1-666 

 1222 

 0-334 

 7-000 

 0-556 

 0-334 



100000 



