xix THE RIFT VALLEY AND ITS LAKES 251 



increases the specific gravity of the water. Thus, the 

 water of the Dead Sea which lies 1300 feet below the 

 level of the Mediterranean Sea, contains 25 per cent, of 

 solids. The water of Salt Lake, Utah, has about the 

 same proportion of solids. Lake Nakuru is in a similar 

 condition. Lake Rudolf is probably undergoing a like 

 change, due to the prolonged drought which has affected 

 the northern section of the Rift Valley. 



Soda Lakes. There is a deposit of natural soda 

 covering an area of thirty square miles, known as Lake 

 Magadi, at the southern end of the eastern arm of the 

 Rift Valley. The deposit is estimated to contain 

 200,000,000 tons of soda ; whenever a portion of the 

 surface soda is removed, it is quickly replaced, as though 

 it were pushed up from below. Further south in 

 German territory there exists another soda lake, known 

 as Lake Natron, discovered by Fischer (1883). 



References. 



Moore, J. E. S. ... The Tanganyika Problem. London, 1903. 



Gregory,,). \\ . ... The Great Rift Valley. London, 1896. 



Huxley, T. H. ... Hatiaadrcft Adotntwre. Essays on Contro- 



verted Questions. London, 1892. 



Holmel, L. von ... Discovery of Lakes Rudolf and Stefanie. 



Translated by Nancy Bell. 1894. 



Powell-Cotton, P. H. G. In Unknown Africa. London, 1904. 



Smith, A. Donaldson... Through Unknown African Countries. 



London, 1897. 



Neumann, A. H. ... Elephant Hunting in East Equatorial 



Africa. 



