T8 Power of Soils to Absorb Moisture. 
100 grains of this dry matter gave, of 
Silica, 88-810 
Peroxide of iron and alumina, - 10*760 
Lime, magnesia, potash and loss, - 0'430 
100 000 
The white Oneida sand, used in the manufacture of glass, boiled 
it in hydrochloric acid for half an hour, washed with pure water 
and dried. — 100 grains saturated with moisture gave, of 
Water, 21-73 
Dry matter, .... 78-27 
100-00 
This dry sand ground to an almost impalpable powder, and 
saturated with moisture, gave, of 
Water, 19-725 
Dry matter, - - - , - 80275 
100-000 
The grinding seems to have reduced the saturating point 2 per 
cent. 
We could give the results of more experiments, but as they all 
go to confirm what has been given, we do not think it necessary. 
It may be stated here, that the water driven off below 212° is 
considered as held by cohesive attraction; that which requires a 
higher temperature to expel it, is said to be chemically combined. 
Soils often contain water in both these states. In general, that 
only which is held by cohesive attraction is yielded up to plants. 
Sir H. Davy says: " The water chemically combined amongst 
the elements of soils, unless in the case of the decomposition of 
animal and vegetable substances" — and we would include mine- 
ral — "cannot be absorbed by the roots of plants; but that adhering 
to the parts of the soil is in constant use in vegetation." Hence, 
in determining the power of soils to withstand a drought, that 
water only which is held mechanically, or adheres to their parts, 
should be taken into account. 
The best soils — those that contain from 8-20 per cent, and up- 
