32 THE TANGANYIKA PROBLEM. 



logical structure of the African interior, resulting from 

 recent exploration, is particularly germane to the enquiry 

 with which this work is concerned. 



Most, if not all, the existing views of the nature and past 

 history of the African land-mass have been built upon the 

 old conception that the physical characters of the con- 

 tinent, the distribution of land and water upon its surface, 

 the shape and the configuration of the equatorial region 

 as a whole, have been almost unique in their stability 

 and long permanence. That, in fact, the great mass 

 of Africa, lay in waving hill, and plain, and ravine, 

 much as it does now, even under the paleozoic sun ; 

 or, at any rate, since the suns which rose over this 

 portion of the earth, when the new red sandstone was 

 being deposited, finally set. This conception of the past 

 history of Africa was first definitely brought forward, 

 now many years ago, by Sir Roderick Murchison* in a 

 Presidential address to the Royal Geographical Society, 

 and it has ever since formed the chord upon which those 

 who have concerned themselves with the geology of the 

 continent have harped. It was, for example, resuscitated 

 by Dr. Gregoryf while discussing Suess' conception of 

 the nature of the great Central African "graben" (rift 

 valleys), and from this single instance, taken at random, 

 it will be sufficiently obvious that, although we have until 

 lately known almost nothing of the nature of the African 

 interior, this ignorance, as usual, has in no way deterred 

 investigators from speculating a good deal. What we 

 require at the present time, and for the particular investi- 

 gations upon which we are entering, is a review of the 

 most recently ascertained facts touching the geology 



* Journal Royal Geographical Society, Vol. xxii. (1852) ; Ibid. Vol. xxviii. (1858). 

 t The Great Rift Valley (1896). 



