MOISTURE OP SAND. 89 



Again we find the effect intensified most of all by the admixture 

 of humus, the operation of which is some three-fold that of clay and 

 lime. Sand again is desiccated more rapidly than the other sub- 

 stances mentioned. 



According to Schuebler, of 100 parts of absorbed water, reduced 

 to the extent of 90 parts by exposure to a temperature of 15°, these 

 substances yielded it up in the following times stated : 



In one hour. In four hoars. 



Further, it has been found by experiments by Kerner, that the 

 finer the sand the longer does it retain moisture. And the observa- 

 tions cited show, that while this property is increased by an admixture 

 of clay or lime, it is increased most of all by an admixture of humus. 



The rainfall sinks quickly into porous sand. When rain falls 

 slowly we find no puddles ; the rain is drawn off to feed subterranean 

 waters, while, when it falls in deluges, it falls faster than it can sink, 

 and, instead of flowing away over the surface, it flows away, carrying 

 the sand with it, and often depositing this on ground at a lower level, 

 to its utter devastation. 



The coarser the sand the more quickly is it permeated by water. 

 Kerner, in experiments, found the time to vary with this from two to 

 twenty minutes. 



With sand soil manured for agriculture it is otherwise. Grouven 

 found, on experiments with turnip ground of diluvial sand, that in 

 two hours 72 grammes of water dropped through an 8-inch layer, but 

 he found the quantity in five other specimens to range from 15 to 62 

 grammes only; while in five others it was doubled, ranging from 117 

 to 119 grammes; while in four other specimens it was fourfold as 

 much, ranging from 261 to 286. 



The capillary attraction manifested by sand is remarkable. It not 

 only operates quickly, but more quickly from below upward than 

 water sinks from above downward when it falls in quantity. 



According to Meister, quoted by Mayer in his AgricuUur-Chemie, 

 1871, the ascent of water by capillary attraction in different sub- 

 stances was as follows : 



M 



