42 THE TANGANYIKA PROBLEM. 



flats surrounding the Arab settlement, to the moun- 

 tains beyond the west coast of the lake. Having scaled 

 these, we find that we have also arrived on the western slope 

 of the continent. The gradual rise in this region is thus 

 seen to culminate in a high ridge with two cusps and an 

 extremely deep narrow valley in between them. The trend 

 of the granitoid rock on both sides of these cusps is directed 

 towards them, and they are themselves evidently the loci 

 of vertical upthrust. Accompanying these phenomena in 

 Nyassa there are to be found all the subsidiary phenomena 

 which usually accompany such movements of the earth ; 

 that is, we have everywhere abundant evidence of local 

 elevation and depression of adjacent areas relatively to one 

 another. Thus, if we take a section rather further to the 

 north through a conspicuous promontory known as Mount 

 Waller (see diagram No. 2), we find that the crests on 

 opposite sides of the lake are not here composed of 

 granitoid material, but of stratified sandstones and 

 conglomerates in layers. These strata on the east 

 of Nyassa are tilted up slightly towards the lake, 

 until they break away immediately above its shore in 

 an imposing series of scarps. Crossing the lake from 

 east to west, its floor is here found to be shallower and 

 formed of sheets of nearly horizontal sandstones, similar 

 in all respects to those composing the eastern scarps. 

 Along the east coast at this point there is a great line of 

 faulting, and a vast cliff face has been upraised in the east 

 above the beds which form the floor of the lake. On the 

 west coast of the lake, we find the same series of 

 phenomena repeated like a reflection on the other side. 

 South of Deep Bay and near Mount Waller on the 

 west there are sandstone ridges protruding above 

 the water with a slight dip to the west (see diagram 



