230 SOILS: PROPERTIES AND MANAGEMENT 



supporting power of the films. As a silt soil contains a 

 larger number of such angles, its capillary pull is greater 

 than that of a sand, and consequently the ultimate move- 

 ment would be of greater scope. The finer the texture, 

 then, the slower is the rate of capillary movement but the 

 greater is the distance. 1 



The relation of texture to rate and height of capillary 

 movement in dry soil is shown by the following un- 

 published data, obtained in the laboratory of the Depart- 

 ment of Soil Technology, Cornell University : — 



Effect of Texture on Rate and Height of Capillary 

 Rise from a Water Table through Dry Soil 



It is seen that the movement in sand is rapid, one-half 

 of the total rise being attained in one hour. The maxi- 

 mum height is reached in about three days. The silt in 

 this case seems to be of just about the right textural con- 

 dition for a fairly rapid rise, yet it exerts enough capil- 

 lary pull to attain a good distance above the water table. 

 The friction in the clay is greater, however, and this 

 results in a slower rate. Whether the clay would ever be 

 able to exhibit a rise comparable with its tremendous pull- 



1 Wollny, E. Untersuchungen iiber die Kapillare Leitung 

 des Wassers im Boden. Forsch. a. d. Gebiete d. Agri.-Physik, 

 Band 7, Seite 269-308. 1884. Also, Forsch. a. d. Gebiete d. 

 Agri.-Physik, Band 8, Seite 206-220. 1885. 



