2 SOILS AND PLANT LIFE 



ices in rocks become filled with water and freeze, the rocks 

 are broken apart, just as a jug is broken if the water in it 

 is allowed to freeze. The particles of rock are not only 

 broken and washed into finer and finer pieces but are 



Fig. 1. 



- Rook split by freezing. 



mixed thoroughly with other kinds of rocks and with de- 

 caying plants and animals to make the rich, fertile soil 

 as we know it. 



Let us study first, then, how the water mixes and lays 

 down the soil. 



