Il6 SCIENCE IN AFRICA 



Shari by the Benue River, unless the process can be thwarted by 

 engineering works. 



Schwarz's well-known scheme (1923) for making a lake in the 

 Kalahari Desert by restoring water to the Okavango drainage 

 system which is now tapped by the Kunene, has been found im- 

 practicable by engineers, but the possibility of forming great arti- 

 ficial lakes in Africa in order to create cultivable land and sources 

 of hydro-electric power has been discussed more recently by 

 H. Soergel of Munich (1936). He suggests that a great dam two 

 and a half miles long about 500 miles from the mouth of the Congo 

 would turn the basin into an inland sea with an area of about 

 350,000 square miles. An outlet by the lower Congo would provide 

 abundant water power, or, alternatively, an outlet could be 

 arranged to the north to create a second inland sea centring on 

 Lake Chad. A further suggestion is for a dam on the Zambesi 

 River above the Victoria Falls in order to create an inland sea 

 over much of the Kalahari Desert. These suggestions are men- 

 tioned here merely in order to indicate how the physiography of 

 Africa might favour change at some future date. 



Apart from such comparatively rapid change as that produced 

 by river capture, the Sahara appears to be noticeably extending 

 southwards, especially in the Chad region and along the border 

 of northern Nigeria. Wells are said to be drying up, villages have 

 been deserted and a general southerly movement of population has 

 been noticed. All this evidence has been put on record and dis- 

 cussed, by several authors, notably Hubert (1920), Bovill (1921), 

 and Mangeot (1932). 



More recently Professor Stebbing (1935), after travelling through 

 the area, concluded that the only way to arrest the advance of the 

 desert is to establish a great belt of protected forest along its south- 

 ern boundary. Other experts, however, deny that the Saharan 

 advance is really a menace to civilization in that area. The mem- 

 bers of the geological department of Nigeria, for instance, who 

 carried out the surveys of water resources mentioned in Chapter 

 HI, do not accept Professor Stebbing's evidence as conclusive. 

 Dr. Raeburn (1928) concluded that this region, like the rest of 

 Africa, has undoubtedly undergone a process of desiccation in the 

 remote past since the pluvial periods, but 'whether this regional 



