CAPILLARY MOVEMENT OF SOIL MOISTURE. 

 Table 44. — Movement of moisture downioard from wet soil. 



65 



Days. 



Riverside soil, 

 initial percentage. 



Idaho lava soil, 

 initial percentage. 



Whittier soil, 

 initial percentage. 



20 per 

 cent. 



15 per 

 cent. 



14 per 

 cent. 



20 per 

 cent. 



25 per 

 cent. 



41 per 

 cent. 



30 per 

 cent. 



1 



2 

 3 

 4 

 5 

 7 

 8 

 9 

 13 

 16 

 22 

 27 

 31 

 36 

 41 

 43 

 49 

 71 

 76 



Inches. 

 4.50 



Inches. 

 4.00 

 5.75 

 6.37 



7.00 



Inches. 

 0.75 



Inches. 

 2.00 



Inches. 

 3.00 

 5.25 



Inches. 



Inches. 







7.50 











4.75 

 5. no 











1.75 















9.00 







11.75 



8.50 









4.00 



8.00 









14.00 

 15. 75 

 17.25 



9.50 

 10. 75 

 11.25 

 12.00 



12.00 







4.50 



8.50 







15.25 















21.50 







16.25 

 17.25 



2.25 



2.00 



14.25 

 15.00 





11.50 











25.50 









16.25 





12.75 











21.50 

 22.25 

































COMPARISON OF CAPILLARY MOVEMENT OF MOISTURE UPWARD AND DOWNWARD FROM 



A BODY OF WET SOIL. 



A series of experiments were outlined to determine the relative 

 extent and rate of movement of moisture upward and downward 

 from a body of soil containing a known percentage of moisture. In 

 this experiment a section in the middle of the box was filled with 

 wet soil and air-dried soil was packed at both ends. The box was 

 then placed vertically. In this experiment the capillary movement 

 occurred with gravity downward and in opposition to gravity. There 

 was a secondary factor which must be considered, and that is the 

 gradual concentration of moisture in a wet soil at the lower end of a 

 vertical column due to gravity. That is, while the middle part of the 

 flume was filled with a soil containing a uniform percentage of 

 moisture it would be found after a few days, depending upon the de- 

 gree of wetness of the soil, that there was a greater percentage of 

 moisture near the bottom than near the top of the wet soil column. 

 The more nearly the soil was wetted to the point of capillary satura- 

 tion the greater would be the difference in percentage of moisture 

 near the bottom and near the top. 



Table 45 shows the upward and downward movement of moisture 

 in two of the boxes. 



The box containing the Idaho soil was 8 feet long and the middle 

 32 inches was packed with wet soil. There was an equal length of air- 

 dry soil at each end. 



The box containing the Eiverside soil was 8 feet long and the mid- 

 dle 4 feet was packed with wet soil. 

 147697°— 20— Bull. 835 5 



