326 MAN'S USE AND CONSERVATION OF SOILS 



It was found in Experiment 91 that each little particle 

 of soil was surrounded by a film of water, even though there 

 was apparently no water in the soil. This film will be re- 

 placed, if removed, just as the water in the top of the wick 

 (Experiment 97) was replaced by water flowing up the wick. 



Roots get a large 

 part of their water 

 by absorbing the 

 water films of the 

 soil particles. 



Gravity is con- 

 tinually pulling the 

 soil water deeper 

 and deeper into the 

 ground. This deep 

 soil water is fre- 

 quently diverted to 

 lower ground by 

 impervious layers of 

 soil or rock and 



A NATURAL SPRING COmeS . to the SUrf ace 



Coining to the surface between rock layers. as Springs, Or it may 



come gradually to 



the surface over a broad area a long distance away from 

 where it fell and make a region, otherwise barren, fertile by 

 subirrigating it. 



Although land must be properly drained, the loss of water 

 by drainage may in some cases be too rapid. It is often 

 very essential to stop as far as possible downward passage 

 of water, or seepage, as it is called. The water in seeping 

 through the soil dissolves plant food and if allowed to drain 

 off would decrease the fertility of the soil. Whatever de- 



