TROPICAL CLIMATES. 773 



vast difference between their climates. For al- 

 though the mean annual temperature is nearly 

 the same, it rises 20 higher during the heat of 

 the day in central Africa, while it often descends 

 to 60 at night, and sometimes to 50, or even to 

 42 in the morning before sun rise, making a 

 diurnal range of from 50 to 70o ; whereas in the 

 West India islands it is only from 10 to 20. 

 Besides, owing to the vast bodies of alluvial lands, 

 which are converted into swamps or morasses, by 

 periodical inundations of the rivers in tropical 

 Africa, a much larger amount of malaria is gene- 

 rated, than in islands of moderate size and a 

 milder temperature. 



Corresponding with this state of things, we 

 learn from the travels of Adanson, Mungo Park, 

 Winterbottom, Denham, Clapperton, and others, 

 that the negroes on the Senegal, Gambia, and 

 Niger, like those of Fezzan, Soudan, and other 

 portions of central Africa, are generally a feeble, 

 indolent, and phlegmatic race, who seldom live 

 beyond sixty years, who are grey, wrinkled, and 

 decrepid with age at forty-five ; while in health, 

 strength, beauty, and intelligence, they are 

 greatly inferior to the natives of the elevated plains 

 of ancient Ethiopia and Abyssinia, or those of 

 north and south Africa. But when removed to the 

 milder climate of St. Domingo, and other West 

 India islands, it is said by Collins and others, 

 that in two or three generations, they improve 

 greatly in all the endowments of body and mind. 



