WORLD AREAS 



33 



of America, only one third of the whole surface 

 receives above 20 inches of rainfall annually; one 

 third receives from 10 to 20 inches, and one third 

 receives less than 10 inches. That is, about 

 1,267,000,000 acres in Australia are subject to 

 reclamation by dry-farming methods. This condi- 

 tion is not far from that which prevails in the United 

 States, and is re]3resentative of every continent of the 

 world. The map on jmges 30-31 shows graphically 

 the approximate rainfall over the various parts of the 

 earth's land surface. The following table gives the 

 proportions of the earth's land surface under various 

 degrees of annual precipitations : — 



Fifty-five per cent, or more than one half of the 

 total land surface of the earth, receives an annual 

 precipitation of less than 20 inches, and must be 

 reclaimed, if at all, by dry-farming. At least 10 



