232 SOILS: PBOPEBTIES AND MANAGEMENT 



ments already made regarding the relation of texture 

 to capillary power : — 



Thb Capillary Lift of Soil Separates as Determined by 



Lynde and Dupre 



Soil 



DlAMETEE OF GkAIN, 



I^r MlLIilMETBES 



LiFT or Water 

 Column, in Feet 



Medium sand .... 



Fine sand 



Very fine sand .... 



Silt 



Clay 



.5 -.25 

 .25 -.10 

 .10 -.05 

 .05 -.005 

 .005- 



.98 



1.78 



4.05 



9.99 



26.80 



The capillary pull may also be established, at least 

 comparatively, by the height of the wetted soil and the 

 amounts of water at various points in a soil column that 

 has reached a capillary equilibrium when its base is in 

 contact with a constant supply of water. The curves 

 from Buckingham ^ (Fig. 34, p. 216) determined after the 

 soil had stood for sixty^eight days, illustrate this. 



156. Effect of stmcture on capillary movement. — 

 Structure has already been shown to affect capillary 

 capacity by its influence on the angle interstices. Evi- 

 dently, therefore, it may alter both the rate and the height 

 of capillary rise. The loosening of a clay soil or the 

 compacting of a sandy soil will lessen the effective film 

 friction, while at the same time it will strengthen the 

 capillary pull resulting in a faster and a higher capillary 

 flow of water. The exact structural condition of any soil 

 in which this result is realized to its highest efficiency it 

 is impossible to judge exactly. In general, however, this 



1 Buckingham, E. Studies on the Movement of Soil Mois- 

 ture. U. S, D. A., Bur. Soils, Bui. 38, p. 32. 1907. 



