216 SOILS: PROPERTIES AND MANAGEMENT 



curvature. A thinning of these films results, but not to 

 such an extent as in the particles above. The action 

 continues in this manner through each capillary surface 

 until equilibrium is established, the change in thickness 

 of film being less and less in each case due to the cumu- 

 lative support of the films above. If the amount of 

 capillary water present is too great to be supported by 

 the films, enough is lost by gravity at the bottom to 

 bring about an equilibrium. The film is at its maximum 

 at the bottom of the column, but decreases in thickness 

 as the column is ascended, not only on the particles 

 themselves, but in the angle interstices as well. This is 

 necessary, as each successive film must support an in- 

 creased weight of water. It is, therefore, evident that 

 it is impossible to assign any definite figure as to the 

 capillary water capacity of a soil. Only relative or 

 comparative data may be quoted. The following diagram 



Fig. 34. — Diagram showing the distribution of moisture in capillary 

 columns of soil of different textures. The end of each soil column 

 rests in free water. 



