ABSORPTIVE POWER OF THE SOIL. 300 
physical qualities that oppose disintegration are inherent 
in the soil, and constantly manifest themselves in the 
kind, if not in the degree, involved in the making of rocks. 
The fourteen elementary substances that exist in all soils 
are capable of forming and tend to form a multitude of 
combinations. In our enumeration of the minerals from 
which soils originate, we have instanced but a few, the 
more common of the many which may, in fact, contribute 
to its formation. The mineralogist counts by hundreds 
the natural compounds of these very elements, com- 
pounds which, from their capability of crystallization, 
occur in a visibly distinguishable shape. The chemist is 
able, by putting together these elements in different pro- 
portions, and under various circumstances, to identify a 
further number of their compounds, and both mineralogy 
and chemistry daily attest the discovery of new combi- 
nations of these same elements of the soil. 
We cannot examine the soil directly for many of the 
substances which most certainly exist in it, on account of 
their being indistinguishable to the eye or other senses, 
-even when assisted by the best instruments of vision. 
We have learned to infer their existence either from analo- 
gies with what is visibly revealed in other spheres of ob- 
servation, or from the changes we are able to bring about 
and measure by the art of chemical analysis. 
Absorptive Power of the Soil.—We have already 
drawn attention to tlie fact that various substances, when 
put in contact with the.soil, in a state of solution in water, 
are withdrawn from the liquid and held by the soil. As 
has been mentioned on p. 175, the first appreciative rec- 
ord of this fact appears to have been published by 
Bronner, in 1836. In his work on Grape Culture occur 
the following passages: “Fill a bottle which has a small 
hole in its bottom with fine river sand or half-dry sifted 
garden earth. Pour gradually into the bottle thick and 
-putrefied dung-liquor until its contents are saturated, The - 
