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 1 8 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 



