DRY-FARMING 



nights. Thus it is that in some parts of 

 the United States, notably California, 

 summer fogs have a markedly good effect 

 upon vegetation. And although this 

 moistm-e is of but little value save in 

 times of severe drought, it is not to be 

 despised by any means. During the hot 

 days of smnmer a soil of a high ab- 

 sorptive power such as a well-tilled clay 

 loam, will retain its moisture for a much 

 longer time than a soil of low absorptive 

 power, such as a shallow sandy soil, 

 whose store of moisture will be exhausted 

 in a few hours, while the surface of the 

 land itself is heated up to the scalding 

 point, thereby searing the stems and 

 root-crowns of the growing crop. It is 

 also worthy of note that, generally speak- 

 ing, soils of high absorptive power are 

 also those of high capillary power. 



Hilgard svmmiarizes the effect of hy- 

 groscopic moisture as foUows: 

 80 



