GENERAL 



197 



The western extension of the continent for thirty 

 degrees of longitude under the northern tropic, the 

 excessive heating of the atmosphere over the broiling 



INCHES 

 Under 10 

 10 - 20 



ao - «o £= 



40 - 80 

 Over 80 



Fjo. 72. Mean Annual Rainfall of Africa. 



Fig. 73. Seasonal Distribution of Rainfall. 

 TO 



Fig. 74. Mean Temperature of Africa, reduced to sea-level. 



surface of that desert, and the existence of a sufficient 

 relief along the Guinea coast at sub-equatorial latitudes, 

 combine to produce a partly monsoon and partly 



