Dr. John Ball—The Nile Valley and Gulf of Suez. 790 
The nature of the cliffs is no more evidence of faulting here than 
in the case of the Grand Caton of Colorado. Moreover, cliffs of the 
same character occur in many lateral valleys, and any argument as to 
the one applies equally to the other; this difficulty was clearly 
perceived by Dr. Blanckenhorn,! who in accepting the trough-fault 
theory for the valley ascribed the origin of many of the lateral wadies 
to faulting. The absence of high river-terraces is easily explained by 
the frequent landslips at the face of the scarp and the action of the 
sand-blast through long ages. Outliers of the plateau within the valley 
would necessarily be infrequent on a theory of river-erosion without 
faulting. As to the bounding faults, there is no doubt whatever 
of the accuracy of Messrs. Barron and Beadnell’s observations of 
the facts. I have seen many of the places myself and confirmed their 
sections. But one may dissent from their interpretation. The faulting 
observed is by no means continuous; it is most pronounced where soft, 
shaly beds have formed the base of the main scarp; no observation 
has ever been made of faulted-down rocks far from the scarps; and 
the faulted-down portions are exactly similar to those which occur 
in the oases, in the Wadi Araba, and along the coast of the Gulf 
of Suez, wherever there is an exposed face of a great plateau without 
any suggestion of trough-faulting. The true interpretation of the 
bounding faults of the valley is that they are landslips, and have 
nothing to do with the primitive formation of the valley. The valley 
was croded first, and the landslips occurred afterwards. Faults or 
lines of weakness may have influenced the path of the river in its 
early stages, but the material which formerly extended from cliff 
to cliff has been removed seawards by erosion, not let down under 
the present Nile-bed. The great eastern wadies were formed con- 
temporaneously with the Nile Valley by the same process of erosion, 
being the paths of tributary streams. They are on a scale quite 
comparable with the main valley, and there is no evidence whatever 
to support the view expressed by Captain Lyons that they originated 
after the main valley was formed. That the Nile Valley is geologically 
young is undoubted, but I know of no facts which would support the 
belief that it is of insufficient age for it to have been entirely excavated 
by erosion. 
After coming to the above conclusion, I have had the pleasure of 
discussing the matter with Mr. Beadnell, who informed me that he 
has for some time abandoned the trough-fault interpretation of his 
observations, and he authorizes me to state that he has lately convinced 
himself that all the faults along the scarps of the Nile Valley can be 
explained as landslips, the harder limestones having slipped down 
over the softer underlying shales which have been eroded by the river. 
ConcLusions. 
(1) The hypothesis that the Nile Valley and the Gulf of Suez owe 
their origin to trough-faulting is unwarranted by geological evidence. 
(2) The Gulf of Suez is an eroded anticline. 
(3) The Nile Valley is essentially a valley of erosion, and the 
1 «¢ Geschichte des Nilstroms’’: Zeits. fiir Erdkunde, Berlin, 1902. 
