THE DESICCATION OF AFRICA. 155 



and there is nothing, therefore, to stop one assuming that a 

 river of the vokime of the Congo in flood may have cut down 

 some 900 feet in comparatively recent times. 



The whole plan of the river system on the inside of the 

 coastal rampart shows that the barrier existed quite recently, 

 and that the rivers have not yet had time to adjust their beds 

 to the changed direction of flow. The Kwango River and 

 all the northwards-flowing rivers, as far as the Sankuru 

 River, now deliver their waters to the Congo by the Kwa 

 River, but the first ten or a dozen apparently gathered 

 together and ran north through the Leopold II. Lake and Lake 

 Tumba, from here, northwards, along the valley of the 

 Ubangui River and thence down the Gribingi River to the 

 Shari River and so to Lake Chad. The next eight or so of 

 the northwards-flowing rivers originally took a similar 

 course, but all trace of them has been lost in the great plain 

 in the embrace of the horseshoe of the Congo; this area is 

 now drained by rivers flowing west and which rise quite 

 abnormally close to the left bank of the Lomami River. 

 The next two rivers, the Lomami and the Lualaba, maintain 

 a northernly course for a greater distance before being 

 deflected westwards ; their original courses were, probably, 

 across the flat divide, between the Congo and the Ubangui 

 River, which is some 120 feet above the level of the main 

 stream, and found an outlet into the Ubangui River some- 

 where near where the Welle River now enters that river. The 

 progressive stages of the deflection of the northwards-flowing 

 rivers, as one passes eastwards, is very instructive ; near the 

 breach in the coastal rampart, the rivers have been drawn 

 closely in, and as one goes further away, the westerly drag 

 becomes less and less felt. The whole horseshoe of the Congo, 

 from Stanley Falls (1,391 feet) to Stanley Pool (923 feet) 

 has a fall of 478 feet; as the distance is quite 1,000 miles, 

 this gives an average fall of less than half a foot in the mile. 

 Lake Chad is 81 feet lower than Stanley Pool, but from 

 Stanley Falls it is 200 miles further, so there is a nice balance 

 between the two outlets. To appreciate this, one must 

 obliterate all valleys as they now exist and think of the 

 country as an inclined, featureless plain ; we then see that the 

 rivers, were they free to flow without their present confining 

 banks, would have very little choice between Stanley Pool 

 and Lake Chad ; in practice, however, the more vigorous 

 coastal streams always prevail over the more encumbered ones 

 of the interior. 



Stanley Pool has absorbed the Congo drainage for a 

 very long time, but the sluggishness of the river above the 

 Pool shows that the capture has not been so very remote. 

 The horseshoe of the Congo represents the bend of the Niger 



