THE TANGANYIKA PROBLEM. 97 



angle into the Semliki valley. If we consider a section 

 through the Albert Edward Nyanza south of the Moun- 

 tains of the Moon, we have the following structural features. 

 Passing over the Victoria Nyanza plateau, from east to 

 west, we find that this plateau in general slightly rises 

 until the eastern edge of the central depression is 

 reached, when it suddenly breaks away in a fault face, 

 or a succession of fault faces, above the extensive plain 

 which, here, forms the flat bottom of the lake. On 

 the other side of the Albert Edward Nyanza, in the 

 west, there is an opposite and corresponding series of 

 fault faces, and instantly beyond their crests we find 

 ourselves on the Congo watershed. If now, in compari- 

 son with this, we consider a section through the great 

 central depression somewhat farther to the north and 

 through the Mountains of the Moon, we have the 

 following features. Beginning again in the east, we 

 find that the Victoria plateau ends upon the flanks of 

 the great range, but that where it does so the layers of 

 schist of which it is composed are abruptly tilted and 

 piled upon the flanks of the range. Passing still farther 

 to the west, we find a succession of huge ridges of 

 intruded lower rock, which project through and above 

 the uptilted schists ; and on the other side of these 

 intruded ridges we encounter the schists again, lying on 

 their western flanks, and sloping at a very high angle 

 into the floor of the Semliki valley. The surface of this 

 valley, where I could examine it [at the source of the 

 Semliki from the Albert Edward Nyanza, and near its 

 mouth in the Albert Nyanza], was composed of little dis- 

 turbed layers of modern alluvium and old lake deposits, 

 containing in both situations the fossil shells of the molluscs 

 which now live in the Albert and Albert Edward lakes. 



