THE TANGANYIKA PROBLEM. 53 



generally been produced by the formation of heights and 

 valleys due to lateral pressure, and consequently the 

 crushing down of their floors (which as we saw in the 

 region of Nyassa is actually taking place at the present 

 time) must have produced tremendous heat, while the 

 tendency for water to accumulate in these depressions will 

 have led naturally to the production of volcanic phenomena 

 along the hollow courses of the folds. 



