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 
