CHAPTER IV. 



REGION OF THE UPPER NILE TRIBUTARIES. 



HE section of the Nilotic basin comprised between Lake Albert and 

 the Babr-el-Ghazal confluence presents a marked contrast to the 

 suiTounding land in its abundant waters, its converging streams, 

 extensive marshy tracts, and the general tmiformity of its slope. 

 The natural limits of this distinct geographical domain are formed 

 by the course of the Nile and Asua on the east and south-east, and of the Bahr- 

 el-Ghazal on the north. In the historic life of the continent the inhabitants of 

 this watery region have also played a separate part. Here lies the chief connecting 

 route between the Nile and Congo basins. The water-parting being marked by no 

 perceptible " divide," no barrier is presented to the migration of peoples between 

 the two great arteries. Thus the hydrographie parting-line forms no natural limit 

 between ethnical groups, some of which, such as the Niam-Niam, occupy both 

 sides of the slope, while continually encroaching northwards. Through this region 

 of transition must pass the future continental highway from east to west between 

 the Red Sea and the Bight of Benin. It has already been partly opened by 

 Peney, Lejean, Petherick, Piaggia, Schweinfurth, Junker, Bohndorff, and other 

 explorers are eagerly following in their footsteps. 



Northwards this region has a natural limit ; indicated, however, not by any 

 water-parting, but by the climate, which produces a marked contrast in the aspect of 

 the land, its vegetation, fauna and inhabitants. The latitudinal depression flooded 

 by the waters of the Bahr-el-Arab coincides in a general way with this climatic 

 frontier. South of it the rainfall is sufficiently copious to feed perennial streams, 

 or at all events rivers flowing for six months in the year. But on the north side 

 we have nothing but wadies flushed only during the heavy rains. Hence the great 

 difference presented bj' the forest vegetation along the right and left banks of the 

 Bahr-el-Arab. On one side we find the baobab, with its huge inflated tr\mk, on 

 the other the lulu, or butter-tree, in some places covering hundreds of square miles. 

 The large apes rfever cross the frontier into Kordofan ; nor does the elephant 

 venture north of the Bahr-el-Ghazal, where the flocks and herds are also free from 

 the ravages of the tsetse-fly. The southern region belongs to the Negro and his 

 horned cattle, the northern to the horse and camel- breeding Arab. 



