1CS 



Physics of the Soil. 



193. Rate of Capillary Rise of Water in Wet Soil, There 

 is yet no very satisfactory data as to just how rapidly wa- 

 ter may be moved by capillarity through wet soils. It is 

 probable that the case cited in (195) represents about the 

 maximum rate in that coarse quartz sand, through that 

 height, namely, 44.09 inchos in depth per 24 hours. This 

 is an enormous quantity of water to be raised by capil- 

 larity and was rendered possible only by expanding the 

 column of sand at the top, as shown in the figure, so as to 

 increase the rate of evaporation until it exceeded the abil- 

 ity of capillarity to bring the water to the surface. 



Experiments have shown that with a strong current of 

 air passing across the wet surface of the soil, water was 

 lifted by capillarity in a square foot of soil, through the 

 different distances and at the rates given in the table be- 

 low: 



It is quite certain that these figures do not represent the 

 maximum rate of capillary rise through these soils; be- 

 cause, as the surface of the soil had no greater area than 

 the section of the soil column, the rate of rise could not 

 exceed the rate of evaporation. 



197. Rate of Capillary Movement of Water in Dry Soil. 



The movement of water through a thoroughly dry soil, by 

 capillarity, is not as rapid as it is through the same soil 

 when wet; the case being analogous to the much slower 

 absorption of water by a dry cloth or sponge than by a 

 similar one when damp. 



In the table which follows is given the rate at which 

 water entered 5 cylinders of water-free soil, 6 inches in 



