DEFINITIONS 



25 



classification there is an unavoidable overlapping. 

 However, no one factor so fully represents varying 

 degrees of aridity as the annual precipitation, and 

 there is a great need for concise definitions of the 

 terms used in describing the parts of the country 



FiQ. 10. Sagebrush growing in infertile sandy soil under an annual rain- 

 fall of less than 10 inches. Utah. 



that come under dry-farming discussions. In this vol- 

 ume, the terms "arid," "semiarid," "sub-humid" 

 and "humid" are used as above defined. 



Precipitation over the dry-farm territory 



The map on page 23, based upon the work of 

 Professor A. J. Henry of the United States Weather 

 Bureau, shows graphically the normal annual pre- 

 cipitation in the United States of America. Exami- 



