66 AGRICULTURE 



dipped into a bowl of water, the water which adheres to 

 their surfaces is capillary moisture. It forms a very thin 

 layer. There may be millions upon millions of soil grains 

 in every cubic inch of soil, and to cover every one of these 



Coortnjr of Doublrdcjr. P(r ft Co. 



FIG. 43. SHOWING THE AMOUNTS OF LIQUID REQUIRED TO MOISTEN THE SUR- 

 FACE OF EVERY PEBBLE IN THE TUMBLER ON THE LEFT AND or EVERY 

 GRAIN OF SAND IN THAT ON THE RIGHT 



over its entire surface with the thinnest possible coat of 

 moisture requires a large amount of water (Fig. 43). 



Movements of free and of capillary moisture. The 

 farmer endeavors to remove a part of the free water from 

 the soil by drainage and to retain in the soil as much cap- 

 illary moisture as possible. He desires the free water to 

 drain away, because it occupies the spaces between the 

 loil grains and thus keeps out the air, which is needed by 

 the roots. Free water moves only toward a lower level ; 



