148 THE DESICCATION OF AFRICA. 



1,100 feet above sea-level; thus the Niger has a fall of 1,664 

 feet in 260 miles and the rest of the course of this great 

 river, which amounts to 2,340 miles, has to be accomplished 

 with a fall of a little over two feet to the mile. Further down, 

 the Sankarain River joins the Niger from the south, rising in 

 Mt. Kon, 4,550 feet, part of the Mt. Drouple group. Finally, 

 the two rivers, the Baoule and the Bagoe, a little further east, 

 rise in the same way, but unite as the Bani River ; the latter, 

 after following a course parallel to the main river for some 

 distance, falls into the Debo Swamp. This is the first stage 

 in the capture of the tributaries ; the Baoule and the Bagoe 

 are hesitating in their courses, and loose themselves in a 

 level swamp, ready to be deflected. The next river to the 

 east, which rises in the same way from the coastal rampart, 

 is the Black Volta; this flows northwards as the others do, 

 but a coastal stream still further east has eaten back through 

 the rampart, stolen the waters of the northwards-flowing 

 stream, and this in turn has captured the waters of the Black 

 Volta, uniting, thus, three original rivers in one great stream. 

 A small tributary from the north, flowing into the Volta at 

 the bend, marks the former course of the stream into the 

 Niger.* This precisely is the history of the Niger itself, 

 carried out on a smaller scale. The other branch of the Volta, 

 the White Volta, does not show this diversion so clearly; its 

 headstreams penetrate nearly to the Hombori Mountains in 

 the bend of the Niger, and a string of lakes on the north of 

 the mountains lie in depressions which probably mark the 

 course of the river before its waters were captured and 

 brought south. 



All the tributaries east of the Bagoe have been reft from 

 the Niger, and a very little further erosion by the Bandama 

 River will bring the waters of the Bagoe southwards ; then 

 the Baoule will form a bend similar to that of the Black Volta. 

 Its waters will flow southwards along the drained channel of 

 the Bagoe, and will reach the sea at Grand Lahou by the 

 Bandama River- The Bani, now forming the common conduit 

 for the Baoule and the Bagoe, will then gradually silt up and 

 all connection with the Niger will be lost. We shall see later, 

 in connection with the Benue and Cunene Rivers, that some 

 African rivers are just in this stage when the waters are 

 hesitating as to which way they shall run, and the river with 

 the shorter course always wins in the end, draining the area 

 and leaving the bigger river without its natural tributaries. 



Not only has the Niger lost the waters of the White and 

 Black Voltas, but, nearer its source, the Senegal River has 



* Attention was first drawn to this capture by R. de Lamothe, in> 

 "Contribution a I'etude geologique des territoires du Haut Senegal - 

 Niger." Bull. Soc. geol. Fr. (4), IX., 1Q09, p. 528. 



