NORTH AMERICA 



77 



hence the contrasts in the distribution and forms of life 

 are less emphatic and sharp. 



The main features of the relief of North America are 



Under 10 Inches 

 10 to 20 

 20-40 - 



40 " 80 

 Over 80 



FIG. 19. Mean Annual Rainfall of North America. 



directed from north to south; while in Asia they run 

 broadly from east to west, and grass and desert belts 

 also stretch in a meridianal direction in the western 

 continent. 



