GEOLOGY 8l 



interesting to note also that an hydrographic survey of French 

 Equatorial Africa has been organized. 



Of importance in all the regions bordering the Sahara is a 

 method of determining the depth of water in arid country developed 

 by Dr. J. Ball (1927 and 1933), Director of the Egyptian Desert 

 Survey, working in the Libyan Desert. Dr. Ball was able to 

 determine a regular slope of the static water level from the hills 

 near the Mediterranean coast-line southwards into the desert. He 

 mapped the slope of the water level by the use of depth 'contour 

 lines', and wells sunk at selected points found water at the pre- 

 dicted depths. In 1932 K. S. Sandford (1935a) applied similar 

 methods to the south and south-west, in French, Italian, and 

 Sudan territory. He was able to continue Ball's contour mapping 

 of the water level with a few minor alterations. It would appear 

 that this method of establishing the depth of underground water 

 has possibilities in many of the arid parts of Africa, though ob- 

 viously it would not apply to granite rocks and some other 

 geological formations where the water usually occurs in pockets. 



For many years G. W. Grabham, Director of the Geological 

 Survey of the Anglo-Egyptian Sudan, has interested himself deeply 

 in the water-supplies of that country. He has published several 

 papers on the subject, as well as a recent general work (1935), 

 which should be of value in many African territories. 



Concerning developments for hydro-electric power, although 

 there are many waterfalls scattered through Africa they have 

 been used remarkably little, chiefly because the falls are distant 

 from industrial regions or towns. It was stated in Nature, 1930? 

 that the total hydro-electric power generated in Africa is scarcely 

 equal to the production of a first-class steam power station in 

 England. Since then, however, the Tanganyika Government has 

 completed negotiations for harnessing the Pangani Falls, the 

 power from which, it is estimated, could be made sufficient to 

 supply the whole of the territory. Suggestions were put forward 

 a long time ago for using the Victoria Falls for this purpose, but 

 so far only a small hydro-electric plant is in operation there, which 

 supplies the neighbouring town of Livingstone. There are water- 

 power stations in Northern Rhodesia in connection with the 

 copper-mining industry, and in Katanga the Cornet Falls on the 



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