July 16, 1917 Movement and Distribution of Moisture in Soil i^'j 



taining 30 per cent of water, the former gained moisture for the first 21 

 inches only. The results indicate the value of fairly moist sandy strata 

 as sources to supply moisture for heavier soils above, and the inadequacy 

 of heavy soils below as moisture supplies. 



Rate op Rise of Moisture 



Figure 27 shows graphically the rate of rise of moisture obtained from 

 the last two experiments on the effect of soil types. The most striking 

 features of the curves are the extremely small rise of moisture from clay 

 into loam and the exceedingly large and rapid rise from sand into loam. 

 Other interesting points in the curves are (i) the small difference in the 



W /S Ze ZS 30 ^ W tS 5e £S 6fi ii X? 7S so gS 9C SS 1/2 IJJ 139 



Time in days 

 Fig. 27. — Diagram showing the effect of type of air-dried soil on the rate of capillary movement from various 



soils used as a source of supply. 



rapidity and the total rise from sands having high and low moisture 

 contents into loam; (2) that this rise shows no sign of ceasing even after 

 94 days; (3) that movement from loam into loam, where the source of 

 supply contains a large percentage of moisture, is quite rapid, but very 

 slow where the source of moisture contains but 15 per cent of water; 

 (4) that movement is at first quite rapid from loam into sand, but exceed- 

 ingly slow after two weeks; (5) that movement from moist loam into 

 clay is fairly slow, but continues for a considerable length of time. 



These facts show the importance of having coarser subsoils rather than 

 the reverse, because moisture moves slowly into them and rapidly up 

 out of them into heavier soils above. 



