41 8 Journal of Agricultural Research voi. x, no. s 



first a very rapid rise, after which the movement rapidly slackened 

 until it became almost or quite imperceptible; the higher the initial 

 moisture content the more gradual was the transition from the rapid to 

 the slow movement. The early rapid movement might be regarded as 

 being due chiefly to gravity and the later slow movement entirely to 

 capillarity. 



REI/ATION OF WATER CONTENT OF MOISTENED LAYER TO INITIAL MOISTNESS 



Table VIII shows that the initial moisture content has no distinct 

 effect upon the moisture content at the end of the first hour, the maximum 

 being shown by three of the soils when driest and by four of them when 

 in the moistest condition. Even at the end of the third hour, there is 

 no regularity to be observed except with the coarser members of the 

 series, J to M, in which the moisture content varies inversely as the 

 initial moisture content, the higher rate of penetration in the moister 

 forms being more than sufficient to compensate for the differences in 

 the initial moisture content. After 24 hours the same is to be observed. 

 At the end of the five days the differences with these coarser members 

 are of the same character but much smaller, while the finer-textured soils 

 show the highest moisture content in those cylinders filled with the 

 moistest form of the soils. 



RELATION OF LOSS OF MOISTURE DURING DRY WEATHER FOLLOWING A 

 RAIN TO THE HYGROSCOPICITY OF THE SOIL AND ITS MOISTNESS BEFORE 

 THE RAIN 



From the above it would appear that the character of the weather 

 immediately following a rain would determine the loss of moisture 

 from the surface soil much more in the case of a sandy soil than in one 

 of finer texture. In the coarser soils, on account of the tardiness with 

 which equilibrium is reached in the immediate surface layer and the 

 greater possible distance of penetration, a period of low evaporation 

 (of low temperature, cloudy skies, high atmospheric humidity, slight 

 wind movement) following a rain of an inch or less will be more mark- 

 edly beneficial, provided that a period of high evaporation is to occur 

 before the next rain, and that in the interval there are no plants present 

 to make use of the moisture of the surface soil. 



Under similar assumed subsequent weather conditions the ultimate 

 effect of a lower initial moistness of the surface layers will be a greater 

 loss of water through direct evaporation on account of the lesser depth 

 of penetration and the equal or even higher water content in the imme- 

 diate surface layers. 



