4 6 THE TANGANYIKA PROBLEM. 
phenomena are apparent : — The country rises towards 
the eastern scarps which flank the trough-like de- 
pression of Lake Rukwa, where a line of faulting 
occurs. At the base of these eastern cliffs, which were 
found by Mr. Wallace to be about 400 feet in height, 
there is a flat, dusty plain of modern lake deposit, and 
then another series of scarps facing those on the east 
and marking another parallel line of faults. Above these 
western scarps of the Rukwa depression the land rises 
gradually ; it is composed in places of sandstones and 
conglomerates, which, further to the west, are pierced by 
the intrusive granitoid material of the mountains flanking 
the east coast of Tanganyika, and these in turn overlook to 
the west the great depression of this lake. On the western 
slopes of these heights sandstones and quartzites are again 
found piled up at varying angles upon the intrusive core, 
and sloping towards Lake Tanganyika in a succession of 
flat-topped, forest -clad terraces, between which there are 
faults represented in Diagram iv. at F.F.F. These 
sandstone slopes finally dip under the water of the south- 
eastern corner of Tanganyika at a fairly high angle. Having 
reached this point on the shore of Lake Tanganyika, we 
find before us to the west a deep depression, soundings 
showing a depth, in places, of 180 fathoms, and away 
over the lake, at a distance of 18 miles, there is the rocky 
promontory of Kituta and some islands. This pro- 
montory and these islands have the following structure: — 
The eastern face of the cape is a precipitous cliff of 
red sandstone and quartzite, rising to a height of 600 to 
800 feet ; on its western side the ridge slopes much more 
gradually for two or three miles, until it dips under the 
channel which separates the island of Kinyamkolo from 
the mainland. Like that of the Kituta promontory, the 
