COMPOSITION OF SOIL-FORMING MATERIALS 17 



Composition of Soil-forming Materials. - There seems 

 to be no doubt that the soluble salts of the soils have come 

 from the same materials as the soils. The exact chemical 

 reactions that have brought about these changes and the 

 methods of concentrating the soluble constituents are, 

 however, not so well known. The materials composing 

 the soil have been derived largely from the rocks and 

 minerals which constitute the crust of the earth, together 

 with a greater or lesser quantity of organic matter coming 

 from the dead bod ies of plants. 



Table V. Average Composition of the Lithosphere 



