THE TANGANYIKA PROBLEM. 123 



also not wanting indications that Nyassa was at one time 

 directly connected with Lake Shirwa, and it is probable 

 that at some more remote period both these lakes as one 

 threw their surplus water down the valley of Lujenda River. 

 Besides general falls in the level of Nyassa, there are, 

 however, indications of local disturbances of level, such as 

 those to which I have referred in Chapter III., and these 

 changes are undoubtedly due to the geological distortion 

 which is still going on along the course of the Great Central 

 African Range, within the folds of which Nyassa lies. The 

 floor of the lake valley is very deep indeed, reaching we 

 found in one place 430 fathoms, and these results have 

 been subsequently closely confirmed by my friend Lieu- 

 tenant Rhoades. Over large areas, generally, in fact, 

 the floor of the lake is as low and lower than the sea 

 level ; and consequently we may say broadly that the lake 

 valley is a chasm, or fold, in the earth's surface over 300 

 miles long and about 50 miles broad, and 10,000 to 11,000 

 feet deep. Owing to its latitude the climate of Nyassa 

 is warm and tropical, but since the lake's surface is 1,500 

 feet above the sea level, the monotonous heat experienced 

 on the equatorial African sea coasts is perceptibly tem- 

 pered, especially at night. 



Observations have been made on the fauna of Nyassa by 

 a number of explorers, by Sir John Kirk, Livingstone, 

 Joseph Thomson, Mr. Crawshay and others, and in 1895 

 and 1899 extensive examinations of the lake were made by 

 myself and my colleagues during the Tanganyika expedi- 

 tions. The investigations undertaken during both these 

 journeys extended over three months, and the results 

 obtained throughout all the different regions of the lake 

 which we examined were of such a definite and similar 

 character that there can be no doubt we have pretty well 



