ON THE CHEMICAL CONSTITUENTS OF SOILS. 231 



By comparing this analysis with that of the three 

 soils which have preceded, it will be observed that 

 this subsoil is fitted to impart to them those mineral 

 ingredients in which they are deficient. 



22. Surface soil of a barren heath in the vicinity 

 of Walsrode in Luneberg. 100 parts by weight 

 contain : — 



Silica and siliceous sand .... 92-216 



Alumina ..... 0*266 



Peroxide of iron . • . . . 0*942 



Protoxide of iron .... 0*394 



Peroxide of manganese .... a trace 



Lime, in combination with silica, sulphuric acid, 



and humus ..... 1*653 



Magnesia, in combination with silica . . 0*036 



Potash, principally in combination with silica 0038 



Soda . . . . . .a trace 



Phosphoric acid . ... .a trace 



Sulphuric acid ..... 0051 



Chlorine . . . . .a trace 



Humus, soluble in alkaline carbonates . . 2 084 



Humus ...... 1*900 



Resinous matter ..... 0*420 



100*000 



This soil contains a large quantity of protoxide of 

 iron, which, together with a deficiency of phosphoric 

 acid, is the cause of its sterility. But when this 

 land was manured with the ashes of peat, it was 

 rendered much more fertile. The ashes used for this 

 purpose were found to contain in 100 parts : — 



Silica, with siliceous sand . . . 96*352 



Alumina ..... 1-859 



Peroxide and protoxide of iron, with a little phos- 

 phoric acid ..... 1120 



Peroxide of manganese . . . 0*160 



Lime . . . . . .0112 



Magnesia ..... 0*141 



Potash . . . . . . 0-093 



Soda . . . . . . 0007 



Sulphuric acid . ' . . . . 0*152 



Chlorine ..... 0*004 



100000 



The ashes, on exposure to the air, absorbed am- 



monia. 



23. Analysis of a very fertile loamy soil from Got- 

 tingen. It is very rich in humus, and produces beau- 



