ABSORPTIVE POWEK OF THE SOIL. 333 



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 siihstances that exist in all soils 

 are capable of forming and tend to form a multitude of 

 combinations. In our enumeration of tlie 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 verj^ 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 tlie 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 the fact that various substances, when 

 put in contact with the soil, in a stale 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 are withdrawn from the liquid and held by the soil.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. Po;ir gradually into the bottle thick and 

 putrefied dung-liquor until its contents are saturated. The 



