Rural School Leaflet. qqc 



irig] for after seeing that there are differences in the soil, the question 

 arises as to how these differences came about. 



To begin with, we must remember that the soil is chiefly ground-up 

 rock. Few plants, and those very small, simple ones, grow on bare rocks 

 because there is no place for their roots to spread and not enough food 

 or moisture for their need. Perhaps some of the stunted plants you 

 have observed for your lesson last month are the result of a shallow soil. 

 If the soil is rich and deep it must have been formed by the breaking 

 up of the rock. 



There are many forces at work forming soil. All rocks have cracks 

 and crevices into which water may come. If this freezes, h expands 

 and pries the rock further apart, and may form new cracks just as a jug 

 may be broken by freezing when filled with water. 



It is not necessary to be in a rocky, mountainous region to see this 

 process. Saturate a piece of soft brick in the winter and let it freeze 

 and thaw a few times while wet and it will sliver up into small pieces. 

 This is why the tile placed in the ground for drainage purposes some- 

 times break up. 



Into the cracks formed by the water, the roots of plants find their way 

 and by their growth pry the rocks still further apart and break them up. 

 You may be able to find boulders which are soft at the surface for these 

 reasons. 



Not only the freezing water and the roots are at work but the water 

 that runs over the surface dissolves some of the rock substance permitting 

 the remainder to fall apart. And even more active than all of these is 

 the grinding together of the boulders in the bottom of a stream. They 

 are thrown against each other as they roll along and are' broken up 

 and the comers worn off so that they become smooth and round. Go 

 to some stream and examine the stones on the bottom. What becomes 

 of the small pieces that have been ground off? ' 



If you look in the quiet pools you will see the fine sand and silt that 

 has been worn off from the rocks arranged in even layers, or you may 

 find sand in one place, silt in another and clay in another. Now examine 

 the soil along the bank and see whether it is composed of layers of soil 

 in the same way. Then go higher up where the stream does not reach 

 and see whether the soil is the same or different. 



Not all soils are formed by streams. The rock may have decayed or 

 fallen apart and formed soil in this way. Such soil is called residual 

 because it is the residue of the rock. 



The wind is also contributing dust to the formation of soil. And 

 remember that all the time the ice and water and wind are at work that 



