5 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



Moving Water and Ice. Water, moving from higher to lower 

 levels, uses the rock particles it carries as tools to scour channels 

 even in the hardest rocks. The sides of the channel, being under- 

 mined by the stream and loosened by frost, fall into the stream. 

 The rocks grind each other to smaller fragments. All of this 

 material is on its way to the sea or to a lower level and is ground 

 finer as it is carried on. 



The rate of movement depends upon the size of the rock, and 

 the size and velocity of the stream. A portion of the material 

 is deposited by the stream, perhaps building up alluvial soils, but 

 sooner or later the stream will begin moving it towards the sea 



Fig. n. A glacier in the Alps. 



again. Water-borne materials are sorted, that is, material of 

 nearly the same size is deposited together. Layers of different 

 material may alternate, varying with the velocity of the water 

 current. 



Rivers of ice, or glaciers, are formed in very cold climates, or 

 flow from the sheets of perpetual snow covering high moun- 

 tains. They move slowly, grinding rocks together with enormous 

 force, and form deposits different in character from those of 

 rivers. The fragments are more angular and the deposit consists 



