CHAPTER VIII 

 SOIL FORMATION 



Soils are the earthy material in which plants have their an- 

 chorage and from which they obtain their water and part of their 

 food. They are in reality disintegrated rock intimately mixed 

 with varying quantities of decaying plant and animal residues. 

 They are derived from the native rocks by the complex process 

 known as weathering. The agents at work in this process are 

 physical, chemical, and biological. The work of the physical 

 agencies is disintegration and consists in the changing of the ulti- 

 mate size of the particles which constitute the surface of the 

 earth. The chemical and biological agencies produce new com- 

 pounds. Sometimes they are more simple, sometimes more com- 

 plex. It is "as where an entire building is r^zed to the ground 

 and another of quite diif erent architectural features is constructed 

 from the old materials; or again, where, without change of gen- 

 eral plan, old timbers are here and there replaced by new; so 

 here we have at work a series of processes in part seemingly de- 

 structive and part constructive, but all tending toward one 

 end. 



"The firm and everlasting hills we must learn to regard as 

 neither firm nor everlasting. Whole mountain chains of the 

 geological yesterdays have disappeared from view, and as with 

 the ancient cities of the East, we read their histories only in the 

 ruins. Y|t, in all this seemingly destructive process of breaking 

 down, decomposition, and erosion, there is traceable the one un- 

 derlying principle of transformation from the unstable toward 

 that which is today more stable. Nothing is lost or wasted. It 

 is a change which began with the beginning of matter; which 

 will end only with the blotting out of matter itself. There are 

 no traces of a beginning, there is no prospect of an end." 



