9 S 
THE TANGANYIKA PROBLEM. 
Passing still farther to the west, these lacustrine plains 
came to an end abruptly beneath the western flanks of 
the Semliki valley, and over these we are instantly once 
more on the Congo watershed. It will thus be seen, 
that in the regions of the Mountains of the Moon, we are 
still dealing with precisely the same phenomena encountered 
when we considered the construction of the great eurycolpic 
depression in the region of Nyassa and Tanganyika. That 
is to say, the gross, geological characteristics of the region 
have been brought into existence by a folding of the earth’s 
surface along two parallel lines of up-push, each of which 
is apparently coincident with the faulted walls of the 
depression itself. The only modification of this process 
which has occurred in the region of the Mountains of the 
Moon being, that, for about a hundred miles on the eastern 
side of the Semliki river, the crinkling and uprising has 
been so violent that the lower rock masses underlying the 
Victoria Nyanza plateau have been forced through it, just 
as if the igneous base, upon which the sandstones of Mount 
Waller rest, was to be forced up and up, until it tilted 
the sandstones on both sides of it, and, finally, towered 
above these old aqueous deposits in ridges of intrusive 
igneous matter, 15,000 ft. to 16,000 ft. in height. I do not 
think there is the least doubt that this has been the real 
method and nature of the formation of the Ruwenzori 
range, and, consequently, we must view the massif as simply 
a more vigorous and local expression of the flanking 
mountain chains which appear along the sides of the 
eurycolpic folds in other places, as in the region of the 
Livingstone range on Nyassa, or the great outstanding 
masses which, at several points, tower over the general 
level of the sides of the Tanganyika basin. 
From these considerations it would appear that Stuhl- 
