THE DESICCATION OF AFRICA. 



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Fig 6. — Lake Chad. 



watershed on the south. The expedition of Captain Arnaud 

 visited the southern end of the Ennedi Hills and no outlet was 

 observed through the escarpment. Such an outlet may exist, 

 although it may not be visible from a distance. Many of the 

 deepest poorts cutting the coastal mountains of Cape Colony, 

 like Meiring's Poort, cannot be identified from a distance, nor 



