148 



THE PRINCIPLES OF SOIL MANAGEMENT 



diaphragms stretched across at frequent intervals from 

 the top to the bottom. If now a heavy ball is dropped 

 upon the upper membrane, it will be weighed down 

 upon the next membrane below, and this in turn will 

 be depressed, until the ball has brought enough of the 

 membranes in contact to support its weight. Under these 

 conditions, the upper membrane will be stretched most 

 severely, and will therefore be thin, while the lower 



ui 



40 



"J 30 



20 



< 

 a 



UJ 



x 



10 



30 



35 



in 



15 20 25 



PERCENT. OF WATER 



Fig. 46. Curves showing the distribution of water in columns of soil 

 ^apillarily saturated, as given in Table XX. 



membrane will be very slightly stretched. If, now, 

 we calculate the actual amount of rubber in each section 

 of the cylinder it will be found smallest at the top 

 and largest at the bottom. 



In the same way, gravity affects the distribution 

 of water in the soil. It forms thick, bulging films in 

 the lower part of the column, and thin, closely drawn 

 films at the top of the column. Consequently, the sur- 

 face of a soil of uniform texture is normally less moist 

 than the subsoil. 



