ON THE CHEMICAL CONSTITUENTS OF SOILS. 243 



In this case also, phosphoric acid, manganese, 

 potash, magnesia, &c., have escaped detection by 

 this acute chemist; yet doubtless they must be 

 present in the soil, for we are informed that it pro- 

 duces good turnips. 



41. An excellent wheat soil from the neighborhood 

 of West Drayton, Middlesex, according to Davy. 

 100 parts contained: — 



Sand and silica .... 72*800 



Alumina ..... 11 '600 



Carbonate of lime .... 11-200 



Humus and moisture . . . 4*400 



100*000 



This analysis has been executed so imperfectly, 

 that it only conveys a very feeble representation of 

 the nature of the soil. A soil which bears good 

 wheat must contain phosphate of potash, soda, chlo- 

 rine, and sulphuric acid ; yet none of these are exhib- 

 ited by the analysis. 



42. Surface-soil of a fertile field in the neighbor- 

 hood of Bristol. 100 parts contained : — 



Silica and siliceous sand . . . 60*000 



Alumina ..... 12000 



Peroxide of iron . . . . 3*500 



Lime (carbonate) . . . . 7*500 



Mag-nesia ..... 0*500 



Humus ...... 1*250 



Saline and extractive matter . . 0*750 



Water ...... 14*500 



100000 



Davy has made several analyses of various fertile 

 soils, and since his time numerous other analyses 

 have been published ; but they are all so superficial, 

 and in most cases so inaccurate, that we possess no 

 means of ascertaining the composition or nature of 

 English arable land. 



SWEDEN. 



43. Surface-soil of a field which produces the most 

 abundant crops, and has never been manured. (Ber- 

 zelius.) 100 parts consist of: — 



