Aug. 20, 191 7 



Relation of Soil Water Movement 



417 



RELATION OK RATE OP PENETRATION TO INITIAL MOISTNESS 



The influence of the initial moisture content upon the rate of penetra- 

 tion of the water may be seen from Table VIII. In the case of all the 

 soils at the end of the first 

 hour the water had pene- 

 trated farthest in the moist- 

 est form of the soil, and, ex- 

 cept with soils K and M, the 

 shortest distance in the driest 

 form ; in soil K the penetra- 

 tion was practically the same 

 in the driest as in the inter- 

 mediate condition, while with 

 M it was least when in the 

 latter moisture condition. 



At the end of the third 

 hour and each subsequent in- 

 terval in the case of every 

 • soil, including K and M,the 

 penetration was greatest 

 with the soil in the most moist 

 form and least with that in 

 the driest. 



However, in most of the 

 cylinders equilibrium had 

 not yet set in at the end of 

 the fifth day after the addi- 

 tion of the water. Where 

 the driest forms (Experi- 

 ment I) were used, apprecia- 

 ble movement appeared to 

 have ceased with the finest 

 textured soils at the end of 

 the third or fourth day, but 

 this was not the case with 

 the moister forms. This 

 lack of dependence of the dis- 

 tance of movement upon the 

 hygroscopicity holds even 

 after long periods, as may be 

 seen from the data on soils 

 A, B, L, and M in the earUer experiments (2, p. 49). 



The rate of downward movement in soils A, D, H, and M is shown 

 graphically in figure i. These well illustrate the movement in all those 

 soils with hygroscopic coefficients above 3.0. With each there was at 

 100304°— 17 4 



£)^^yj 



LEGEND 

 fia/f ffie hydroscopic coeff/dent 



One arii/ one/ja/ffimes ■ 



Fig. I. — Graphs showing the penetration of i inch of water in 

 soils A, D, H, and M, each in three moisture conditions — 

 viz, with a moisture content of 0.5, 1.0, and 1.5 times the hy- 

 groscopic coefficient. 



