78 



NORTH AMERICA 



Whereas in Europe the absence of high altitudes 

 allows the moisture of the westerly winds to spread far 

 into the continent, in western North America the inter- 

 position of a multiple barrier of lofty mountains keeps 

 that moisture for a narrow fringe and leaves the interior 

 quite arid. On the east, the Appalachians correspond 

 in some measure with the Chinese Alps, but being 



FIG. 20. Seasonal Distribution of Rainfall in North America. 



much lower they are not so effective a barrier in 

 keeping the rains out of the middle of the continent. 

 The free communication that exists between the polar 

 seas and the Atlantic, in contrast with the narrow gates 

 of the Bering Sea, is also probably an important factor 

 in reducing the temperature over the north-eastern 

 portions of the New World, and carrying far south the 



