ON THE CHEMICAL CONSTITUENTS OF SOILS. 229 



18. The soil of a very fertile loam from the vicin- 

 ity of Walkenried. 100 parts contain: — 



Silica, with coarse-grained siliceous sand . 88-456 



Alumina . . . . . . 0650 



Peroxide and protoxide of iron, accompanied by much 



magnetic iron sand .... 5-608 



• Peroxide of manganese . . . . 0-560 



Carbonate of lime . . . . . 1-063 



Carbonate of magnesia .... 1*688 



Potash combined with silica . . . 0*040 



Soda combined with silica . . . 0-012 



Phosphate of lime . . . . . 0035 



Sulphate of lime . . . . . a trace 



Common salt , . . . .0 005 



Humus soluble in alkalies . . . 0-550 



Humus with several azotized organic remains . 1-333 



100-000 



Gypsum acts most excellently upon this land. 

 The soils in the southern range of the Harz moun- 

 tains are particularly remarked for containing more 

 magnesia than lime. Even the different varieties 

 of marl contain a considerable quantity of magnesia. 

 Thus in a specimen of marl obtained from the vi- 

 cinity of Walkenried, I obtained 55^ per cent, car- 

 bonate of lime, and 30^ per cent, carbonate of mag- 

 nesia ; in another 41 per cent, lime, and 11 per cent, 

 magnesia; and in a third, 47| per cent, lime, and 

 13J per cent, magnesia. Most of these soils contain 

 also J, — 1 per cent, of gypsum, and |, — 1 per cent, 

 phosphate of lime, and are, therefore, well fitted for 

 manuring other lands. 



19. Subsoil of a loam from a depth of IJ foot. It 

 occurs in the vicinity of Brunswick. The surface- 

 soil is remarkable on account of producing beautiful 

 red clover on being manured with gypsum ; although 

 the soil itself contains only traces of lime, magnesia, 

 potash, and phosphoric acid. 100 parts of the sub- 

 soil contained : — 



Silica and coarse siliceous sand . . . 88-980 



Alumina . . . . . 2-SMO 



Protoxide and peroxide of iron . . . 3-840 



Peroxide of manganese ... a trace 



Carbonate of lime .... 2720 



Carbonate of magnesia . . • 0*600 



Potash and soda ..... 0*095 



20 



