82 THE TANGANYIKA PROBLEM. 



the lake, the more desiccated, inland steppes became covered 

 with euphorbia trees, clumps of bush and groups of park- 

 trees, the valley assuming more and more the characters of 

 a park, until typical African-park scenery was reached some 

 miles before the village of Buta-gata. All this country pre- 

 sented, in fact, in a striking manner, the peculiar zoned- 

 character in its vegetation, which, as* I have shown else- 

 where, marks the recession of water from land under a 

 tropical sun. We were, indeed, passing over older and 

 older ground as we moved away from the lake, and as 

 we gradually rose from ioo to 200 feet above its 

 surface, the plains composed of modern alluvium were 

 found in places to be intersected by the deep cuttings 

 formed by the storm torrents, which periodically flow from 

 the eastern scarps, and in some of these cuttings, which 

 were at times from 80 to 90 feet deep, older stratified 

 materials were exposed. These strata were composed of 

 brown and yellow sandstones, with a slight dip to the south, 

 and embedded in them there were apparent numerous 

 fossilised remains. Examination of these showed that they 

 consisted chiefly of the fragments of shells, but I obtained 

 a number ol fairly preserved specimens, and these un- 

 questionably belonged to several of the molluscs which now 

 inhabit Tanganyika (Neothauma, Nassoftsis and Para- 

 mellania). 



From these observations, it becomes clear that, at some 

 time, Tanganyika extended many miles north of its present 

 limit as a deep lake, and that besides its general water-level 

 having fallen, the floor of the valley, north of Tanganyika, 

 has also actually been raised, in the same manner that 

 portions of the east coast have been raised, between Ujiji 

 and Usambora. Beyond this point, i.e., north of Buta-gata, 



* See Chapter VI. 



