GARDENING FoR ALL. II 
And some granites contain 
from 44°50 to 73°70 per cent. of Silica. 
12°27 to 17°35 Ps Alumina. 
0750 to 984 re Lime. 
o'21 to 3°99 a Magnesia. 
2°02 to 7°24 a. Potash. 
264 to 4°21 a Soda. 
It will thus readily be understood how a mixed soil is so 
fertile, possessing, as it does, a per centage of all the chemical 
matter that goes to build up a plant. 
A perfect soil for general cultural purposes would consist 
of about—- 
60 per cent. (by weight) of Sand. 
25 ” 7 Clay. 
Te on " Humus. 
Te oo. i Lime. 
This soil would be warm, retentive of moisture, but not 
too retentive, contain sufficient lime and organic matter, and 
generally be most conducive to a healthy growth of vegetation. 
(2) The mechanical nature of soils. Soils generally may 
be formed into eight classes, viz :— 
Pure Clay (Pipe Clay). 
Strongest Clay Soil (Tile Clay), 5—15 per cent. Sand. 
Clay Loam, 15—30 i ” 
Loamy Soil, 30—60 a " 
Sandy Soil, 60—90 i ” 
The above five are supposed to contain less than 5 per 
cent. of lime. 
Marly Soil, containing 5—2o per cent. of Lime. 
Calcareous Soil, containing more than 20 per cent. of Lime, 
Peaty Soil, containing 2o—7o0 per cent. organic matter. 
The three latter may be either clayey, loamy, or sandy. 
The water-holding power of soils is said to be—~ 
Clay Soil, 40 per cent. of Water. 
Loam, 51 ' ” 
Heavy Clay 61 i " 
Fine Carbonate of Lime, 85 
” ” 
