10 STEPPES AND DESERTS. 



If, therefore, one side of our planet has a moister atmo- 

 sphere than the other, the consideration of the present 

 condition of things is amply sufficient to explain the problem 

 presented by this inequality. The physical inquirer needs 

 not to clothe the explanation of these phenomena in a 

 mantle of geological myths. He needs not to assume that 

 on our planet the harmonious reconciliation of the destructive 

 conflict of the elements took place at different epochs in the 

 eastern and the western hemispheres ; or that America emerged 

 later than the other parts of the globe from the chaotic 

 watery covering, ( 19 ) as an island of swamps and marshes 

 tenanted by alligators and serpents. 



There is, indeed, a striking similarity between South 

 America and the southern peninsula of the old continent in 

 the form of the outline and in the direction of the coasts; 

 but the nature of the soil, and the relative position of the 

 neighbouring masses of land, produce in Africa that extra- 

 ordinary aridity which over an immense area checks the 

 development of organic life. Four-fifths of South America 

 are situated on the southern side of the equator; or 

 in a hemisphere which from the greater proportion of sea 

 and from other causes is cooler and moister than our 

 northern half of the globe> ( 20 ) to which the larger part of 

 Africa belongs. The breadth of the South American Steppe, 

 measured from east to west, is only a third of that of the 

 African Desert. The Llanos receive the influence of the 

 tropical sea wind, while the African Deserts, being situated 

 in the same zone of latitude as Arabia and the south of 

 Persia, are in contact with strata of air which have blown 



