1916] 



Sharp: Soluble Salts and Soil Colloids 



297 



ing the soil practically free of salt, meanwhile washing with 

 pure water a similar portion of soil from v/hich the salt has 

 been omitted to serve as a control. The difference in the rate of 

 percolation of the two soils has proved to be sufficiently great to 

 be easily discernible even in the case of sandy soils. Frequently 



qO 5 6 7£ 106 144 ISO 216 252 288 324 360 396 452 468 504 540 576 



End of Soil Column 



Fig. 2. Curves Representing the Downward Movement of Water Through 

 the Davis Soil to which Salts Have Been Added. 

 The penetration of the water downward in the soil column is expressed 

 in inches by the ordinates, while the abscissas represent the time of 

 observations in hours. 



the fine material mentioned by Van Bemmelen and Warington 

 appears in the percolate. 



It has also been found possible to simulate fairly the condi- 

 tions existing in the field cylinders by means of glass tubes care- 



