4 8 
THE TANGANYIKA PROBLEM. 
eastern faces of these islands are steep, precipitous cliffs, com- 
posed of somewhat metamorphosed sandstones, which have 
been worn out at their bases into caves by the great ocean- 
like surf of the lake. On the western side these islands 
slope less steeply into the lake, and from their crests can 
be seen, over an expanse of deep blue water, 25 miles 
away, the gigantic scarps of the main western coast- 
line of Tanganyika. Soundings in the open water, between 
the islands of Kinyamkolo and the great western scarps, 
showed great depths, 200 fathoms and upwards being 
encountered ; but not far from the abrupt west coast, 
some distance north of Mbeti, there is a submerged plat- 
form, which rises slightly, like the islands, from west to 
east, and terminates in that direction in a submerged cliff, 
its relation to the main western scarps being shown in 
Diagram facing p. 44. 
Passing still westward over the western scarps, we find 
them to be composed of massive quartzites, sandstones, 
conglomerate and shales, 2,000 feet and more being 
exposed along the main western coast-line of the lake, 
and, finally, having ascended the magnificent red and 
yellow precipices which these exposures form, we reach a 
table-land, but one which has everywhere a slight dip to 
the west, and we are now, as a matter of fact, on the long 
main western slope of the whole continental mass. Through 
the contemplation of the above facts relating to the structure 
of the Great Central Range in the region of the south end 
of Lake Tanganyika, it will have become apparent that 
the phenomena presented by the crest of the ridge are here 
more complex than in the region of Nyassa, although it 
will, at the same time, have also become obvious that these 
phenomena are precisely similar in kind. The complexity 
in this region is due, in fact, simply to the existence of a 
