68 THE TANGANYIKA PROBLEM. 



very large part of the interior, most of the region between 

 Tanganyika and Nyassa, many districts east of this line to 

 the north and to the south, together with huge areas to the 

 west, were all portions of a great depression which in many 

 places extended across the axis of the Great Central Range. 

 At some time or other there were wide, deep waters in 

 these regions, so wide and so deep that more than 

 three thousand feet of sandstones were quietly laid 

 down in them, and, consequently, there was a time 

 when the present Central African region was vastly 

 different from what it is now.* It may very probably have 

 been that portions of this area, the Shiri highlands, some of 

 the high granitoid ridges of the Great Central Range, and 

 portions of British and German East Africa, were even then 

 dry land, but there must unquestionably have been wide 

 stretches of open, deep water between whatever land-masses 

 existed, and these land-masses in all probability formed a 

 group of islands occupying the position of the equatorial 

 portion of the continent of to-day. The changes which 

 followed were produced by the initial stages in the forma- 

 tion of the great central chain. The areas of ancient 

 depression in which the Old African sandstones had been 

 deposited became disturbed and gradually more and more 

 involved with the extension of the folding and the crinkling 

 of the earth's crust along axes running north and south, until 

 in time their floors were raised up, as we have seen, into part 

 of the hog's back of the modern African peninsula ; the sand- 

 stones and conglomerates being, finally, in places folded up 

 and broken into the high crests and scarps of the Great 

 Central Range as we find it now. 



* It would seem indeed to be indicated that there was at some time an east and west 

 depression of considerable breadth which very possibly separated the northern and 

 southern portions of the continent, and connected up the oceans on its east and west 

 coasts (see map facing p. 75). 



