161 
PARTS. 
Silica - 54 
Alumina - - - 28 
Carbonate of lime - 3 
Oxide of iron - - 5 
Decomposing vegetable matter - 4 
Moisture and loss - - 6 
An excellent wheat-soil from the neighbourhood 
of West Drayton, Middlesex, gave 3 parts in 5 of 
siliceous sand ; and the finely divided matter con- 
sisted of 
Carbonate of lime - - 28 
Silica - - - 32 
Alumina - - - - 29 
Animal or vegetable matter and 
moisture - - 1 1 
Of these soils the last was by far the most, and 
the first the least, coherent in texture. In all 
cases the constituent parts of the soil which give 
tenacity and coherence are the finely divided 
matters ; and they possess the power of giving 
those qualities in the highest degree when they 
contain much alumina. A small quantity of finely 
divided matter is sufficient to fit a soil for the 
production of turnips and barley ; and I have 
seen a tolerable crop of turnips on a soil contain- 
ing 11 parts out of 12 sand. A much greater 
proportion of sand, however, always produces 
absolute sterility. The soil of Bagshot heath, 
which is entirely devoid of vegetable covering, 
contains less than of finely divided matter. 400 
parts of it which had been heated red, afforded 
me 380 parts of coarse siliceous sand ; 9 parts of 
M 
