234 ON THE CHEMICAL CONSTITUENTS OF SOILS. 



reaches the soil, and manures it with these ingredi- 

 ents. It is only in this manner that we are enabled 

 to explain the fertility of this soil ; for, reasoning 

 from its chemical composition, we should be induced, 

 a priori, to suppose that it would be barren. At the 

 base of this hill, certain portions of the land are 

 covered with calcareous tuff, containing the above 

 salts : a fact which proves that the water which pen- 

 etrates through the soil must also contain them in 

 solution. The large proportion of humus exhibited 

 by the analysis depends upon the nature of the ma- 

 nure with which it was treated. 



26. Analysis of a heavy alluvial soil, from Norden. 

 100 parts contain: — 



Silica, and very fine siliceous sand . . 84*543 



Alumina 



Peroxide of iron 



Peroxide of manganese 



Lime 



Magnesia . 



Potash .... 



Soda, in combination with silica 



Phosphoric acid, in combination with lime 



Sulphuric acid ... 



Chlorine . . . 



Humus, soluble in alkalies 



3-458 

 3-488 

 0-560 

 0-319 

 0-740 

 a trace 

 6-004 

 0-260 

 0-008 

 0-008 

 0-416 



Hulnus ajid nitrogenous matter . . 0-196 



100000 



The portion of the soil subjected to analysis was 

 taken at a depth of 10 inches, from a field which 

 had received no manure for several years. It had 

 previously produced in succession barley, beans, 

 wheat, and grass, the latter for two years. The soil 

 is remarkable, in a chemical point of view, from the 

 large quantity of soda which it contains. Although 

 the sulphuric acid, chlorine, and potash, are present 

 in small quantity, yet this does not present any bar- 

 rier to the development of the plants, as the surface- 

 soil is 18 inches in depth. 



27. Analysis of a heavy alluvial soil in the vicinity 

 of Norden. 100 parts contain; — 



Silica, and very fine siliceous sand . . 79*174 



Alumina ..... 3016 



