CHAPTER V 



AFRICA 



General. Well astride of the equator, the dark conti- 

 nent is the most symmetrical of the large land masses. 

 With its centre in the belt of equatorial calms and rains, 

 it passes through the regions of trade winds into those 

 of tropical high pressures, clear skies, and droughts, 

 exposing only a narrow fringe on either side to the 

 mediterranean climates. In its broad features, African 

 vegetation may be summarized as follows : 



Mediterranean 

 Tropical Deserts 

 Tropical Savanas 

 Equatorial Selva 



Tropical Savanas 



Tropical Deserts 



Mediterranean. 



The symmetry of this diagram is broken by the 

 unequal distribution of African lands in the two hemi- 

 spheres. The much greater area under the northern 

 tropic not only exposes a larger surface to drought 

 but tends to emphasize the aridity of the climate, by 

 a sort of cumulative effect : hence the striking disparity 

 between the Sahara and the austral deserts. Yet that 

 the ratios between arid and total areas on the two 

 sides of the equator are so disproportionate is not 

 adequately explained by a mere consideration of total 

 surfaces. South Africa is open to the moisture- bearing 

 winds from the boundless austral ocean, without any 



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