THE TANGANYIKA PROBLEM. 61 
characters which its surrounding mountain masses now pre- 
sent were first acquired. Half way up Nyassa at Mount 
Waller, however, we encounter the complete change in the 
geological character of the country to which I alluded in 
the preceding chapter, thick sandstone deposits appearing 
sandwiched in between granitoid hills to the north and 
south. We in fact here encounter a stratified neck composed 
of sandstone, quartzites, conglomerates, and yellow and grey 
shales which are between two and three thousand feet thick, 
and stretch completely across the lake from east to west. 
They have been cut by two chief lines of faulting, which are 
coincident with the opposing shores of the lake, so that faces 
of the sandstone and conglomerates, etc., have been raised 
up into imposing lines of cliffs more than two thousand feet 
above the lake shore on either side. They extend to the 
east of Nyassa, but how far in this direction has not, I 
believe, been hitherto ascertained.* To the west they cer- 
tainly pass into the Loangwa valley, where similar faulting 
has been observed, they reappear among the mountains 
flanking the north of the lake, and they extend along the 
track of the old Stevenson Road as far as the hills which 
flank to the north the depression which exists about 
Fort Hill. These sandstones are often much distorted, 
often metamorphosed; and at the north end of Nyassa, 
between Karonga and Fort Hill, they are greatly tilted 
and broken, sloping at a high angle out of the bed of 
the lake. 
The massive sandstones and conglomerates just 
* It appears, however, from Bornhardt’s map of the German territory about the 
north of Lake Nyassa that these deposits actually extend into the great depression 
of the Rovuma valley ; which in turn stretches directly to the Indian Ocean. Still 
later, observations have come to hand, which show that similar deposits cover a con- 
siderable area to the east of Nyassa and extend probably as far south as Pemba on the 
coast of the Mozambique. 
