228 



ON THE CHEMICAL CONSTITUENTS OF SOILS. 



(B) Analysis of the subsoil taken from a depth of 

 1| foot. 100 parts contain : — 



Silica and siliceous sand 



Alumina ..... 



Peroxide of iron with a little phosphoric acid 



Peroxide of manganese 



Lime, principally combined with silica 



Magnesia, idem .... 



Potash ..... 



Soda . . . . . 



Sulphuric acid .... 



Chlorine 



Humus ..... 



Both the surface and the sub-soil contain only 

 traces of sulphuric acid. Hence the application of 

 gypsum is attended with great benefit. Without 

 doubt, marl and lime will be found of essential 

 service. 



17. Soil from the environs of Brunswick, consisting 

 principally of sand, and eminently remarked for its 

 sterility. It was, however, much improved by ma- 

 nuring it with marl which contained 24 per cent, of 

 lime, together with magnesia, manganese, potash, 

 soda, gypsum, and common salt. 100 parts of the 

 soil contained : — 



100 000 



Here another proof is presented, that a soil may 

 be very rich in humus and yet be very poor as re- 

 gards fertility. By means of the marl, the inorganic 

 ingredients of the plants are furnished to the soil, 

 which contains them in very small quantity. 



