462 ACROSS AFRICA. [Chap. 



cut away the sandstone, and left the harder rocks standing out 

 in their present forms. Of this sea, most probably a fresh- 

 water one, Tanganyika, the Nyanzas, and the Livingstone lakes 

 are probably the remains. 



It may have been salt — witness salt soil of Uvinza and Ugo- 

 go — and freshened by the continued rain-fall of thousands of 

 years. The country, except for a gradual elevation of the 

 whole mass, was most probably left unvisited by any great 

 geological convulsion after the days when subterranean fires 

 formed the granite which constitutes the great mass of the 

 whole. 



The hills now again overhang the lake, and navigation is 

 rendered dangerous by the number of sunken pinnacle and 

 other rocks, some being only a foot or two below the surface 

 of the water. 



The Makakomo islands, which were next passed, had, accord- 

 ing to the guides, once been part of the main-land — some with- 

 in their own remembrance — and the outer island, which a few 

 years back was populated and fertile, is now a mere barren 

 iieap of rocks, half submerged by the waters of the lake, prov- 

 ing that the wasting action is rapidly progressing. 



A short way beyond the Makakomo islands some remarka- 

 ble masses of granite were seen, two in particular towering up 

 above the rest to a height of seventy or eighty feet, like a pair 

 of giant brothers. Wooded hills now again formed the bound- 

 aries of the Tanganyika, but every here and there land-slips ex- 

 posed the stony nature of their formation. The line of hills 

 continued for some time nearly parallel to the shore. 



At Has Masungi, near the island of Polungo, the hills consist 

 of loose masses of granite, looking as if they would slide down 

 into the lake beneath at the slightest jar of an earthquake ; in- 

 deed, they appeared so insecure that it seemed scarcely safe to 

 camp at their base. Soon afterward, white limestone cliffs, ris- 

 ing up like columns and pillars, were seen from the lake. 



At Kas Yamini the cliffs were very high, and composed of 

 innumerable thin strata of a red stone about the thickness of a 

 Roman brick. These cliffs were worn and broken by the ac- 

 tion of weather and waves into fantastic forms bearing much 

 resemblance to ruins of castles and fortresses, arches being lion- 



