SOILS AND FLANT LIFE 



CHAPTER I 

 HOW SOILS ARE MADE AND MIXED 



1. What the Soil Is. — The soil, as we now see it, is 

 composed of broken-down rock, mixed with decaying 

 plant and animal matter. For millions upon millions of 

 years, no doubt, the work of soil making has been going on. 



2. Grinding up the Rocks. — The earth was once made 

 up of rock. Men who have studied the subject long and 

 carefully tell us that the heat and the cold, the wind and 

 the water, the gases of the air, the plants, and the animals 

 have all had a part in breaking down the rocks into rock 

 powder and mixing it through and through that more 

 plants and animals might exist. We are told that vast 

 fields of ice, called glaciers, moved slowly over many parts 

 of the country ages ago, carrying with them rock masses 

 and grinding to powder whatever came beneath their 

 mountain-like weight. We read about these great gla- 

 ciers and see pictures of them as well in our geographies. 



We are told also that rocks expand with heat and con- 

 tract with cold, becoming broken up in this way. We 

 know that hot water will break a cold tumbler. We have 

 seen stones cracked or broken about the fire where we 

 cooked our picnic or camp supper. We have seen where 

 the water has washed out great hollow places in the rock. 

 Moreover, we must know that when the cracks and crev- 

 B 1 



