CHAP. XIII 



ORIGINAL SOURCES OF THE NILE 



259 



the Nile. Later on this river system was broken up by 

 earth-movements and change of climate. Owing to the latter 

 cause the glaciers and snowfields of Lebanon and Central 

 Africa shrank in area, the rainfall became less, the lake 

 levels were lowered, and the rivers diminished in volume. 

 At the same time the elevation of the ridge of El Sate across 

 the Arabah portion of the Rift Valley cut off the southward 

 discharge of the Jordan, a change more readily produced 

 owing to its lessened size. The continued depression of the 

 region to the south brought it below the level of the Indian 

 Ocean, and thus the Red Sea took the place of the Erythrean 

 River. An elevation of the land across the valley of the Omo 

 separated the basins of Basso 

 Narok and Afar, and along 

 the chain of volcanoes of 

 Elgon and Chibchagnani 

 severed the connection of 

 the Victoria Nyanza with 

 the eastern Rift Valley. A 

 parallel depression to the 

 west continued the western 

 Rift Valley farther to the 

 north, and formed the gorge 

 between Wadelai and Lado 



by which the great lakes are Fig. 16. — Diagram of possible former Source 

 . , .., ^, TV7., of the Nile and Outlet from the ereat 



connected with the Nile. Equatorial Lakes. 



This view is put forward 

 only as the theory which seems to me to best harmonise the 

 known facts. For proof or disproof we must wait, until the 

 river-courses and the gravels of the valleys between the Nyanza, 

 Southern Abyssinia, and Somaliland have been investigated. 

 The theory seems, however, to explain the three main 

 difficulties : — 



1. The occurrence of the equatorial fish in the Jordan ; 

 for it shows the possibility of direct river connection between 

 Equatorial Africa and the north of Palestine. 



2. The absence of some species of fish which occur in 

 the Jordan from the Lower Nile, by assuming the comparatively 

 late date of the connection between the Nile and these rivers. 



3. The complete difference of the faunas of the Medi- 



