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this property water tends to distribute itself in all directions through- 
out the soil. 
There may be properly considered to be three kinds of water present 
in soils — capillary, gravitation, and hygroscopic moisture. The 
capillary water is that which wiU not drain away but is held around 
the soil particles in the form of a moisture film; that is to say, 
there is an equilibrium between the forces of gravity and surface 
tension. However, capillary action is itself dependent upon and abso- 
lutely governed by such subfactors as density or gravity, viscosity, 
surface tension of the soil solution, and the size and composition (both 
organic and inorganic) of the soil particles. 
Fig. 1.— Relative capillarity following addition of salts in equal quantity and in molecular proportions. 
When an object is removed from an immersion in water it retains 
a thin film upon its surface through the property of surface tension. 
In the same manner the soil particles are surrounded by a film or 
elastic membrane of water under a high pressure, the thickness vary- 
ing within certain limits with the moisture content of the soil. As 
water is lost at the surface by evaporation or around the roots by 
absorption, there is a movement of water in the direction of in- 
creased tension, thereby tending to maintain an equal distribution of 
water. On the other hand, viscosity, acting in an opposite manner 
from surface tension, tends to retard the movement of water. 
Water in soils is never pure, and all dissolved substances affect the 
degree of surface tension and viscosity of the solvent. Practically 
