CHAPTER III 



THE SOIL, HOW MADE, AND FROM WHAT 



SOILS are the earthy materials in which plants root, 

 serving them as a foothold and source of moisture and 

 food. 



How are soils formed ?/ Soils are made by the pow- 

 dering and decay oFrocks of all kinds. Each kind of 

 rock makes a different kind of soil. These different soils 

 are usually mixed together in various ways. 'Thus there 

 are many more kinds of soils than there are of rocks. 



ROCKS ARE BEING POWDERED IN DIFFERENT WAYS 



First, by grinding. This may be done by the slow 

 flow of the rivers of ice called glaciers^^We see this 

 going on in the high mountains (Oregon, Washing- 

 ton, British Columbia, and Alaska). In their slow 

 movement these ice rivers produce all grades of rock 

 powder, from finest flour to large cobbles and bowlders. 

 Glaciers in times^past also flowed down from the Sierra 

 Nevada of California, and other glaciers covered the 

 part of North America which lies north of the Ohio 

 River; for there we find ground rock and cobbles and 

 polished bowlders, scratched by movements of the ice. 



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