Dr. W. F. Hume—Origin of the Nile Valley. 387 
Egyptian Nile from Aswan to beyond Qena owes its origin to denu- 
dation of the softer Cretaceous beds, as already suggested in the Cairo 
Scientific Journal. This view is, I believe, shared by Mr. Beaduell. 
Owing to the temporary dominance of a transverse roll near Qena 
the river has turned, following the direction of outcrop of these softer 
strata until its further course north-westward was determined by 
a well-marked syncline. North of Assiut a second fold may have 
determined the northward deflection of the Nile, the river breaking 
through where the Nubian Sandstone may have had an outcrop 
north of the Pyramids near Abu Roash. This conception is not so 
imaginative as might at first sight appear, there being an exposure 
of Nubian Sandstone in the Abu Roash Hills close to the river-valley.' 
The slipping of heavy masses of Eocene limestone on Cretaceous 
shales has exaggerated the fold effects in the region between Luxor, 
the slip-faults being often on a gigantic scale, but these presumably 
cannot be regarded as evidence in favour of true trough-faulting. 
So far as the Nile is concerned, therefore, I hold that folding plus 
erosion plus slip-faulting is sufficient to account for all the 
phenomena observed, a view still further emphasized by a recent visit 
to the desert plateau immediately north of the Qena depression. 
Here it is possible to study valleys in every stage of formation. The 
country is remarkably folded, though the individual dips seldom 
exceed 10°, and it is possible within a very short area to find evidence 
of the most varying causes of erosion. At the head of Wadi Gurdi 
the valley has obviously been formed along a cracked anticline; 
elsewhere synclinal folds have been responsible for the principal 
drainage-lines, whilst multiple small folds, like the waves of the sea, 
have determined many of the twists‘and turns. In addition to this 
complex folding, which was entirely unexpected, the rocks themselves 
are of a nature which specially lends itself to erosion by water. The 
lower part of the Eocene Series in this region is a white chalk, 
showing evidence of intense current-action. In these strata, caves, 
honeycombing of the limestone, natural bridges, and cylindrical 
channels, cut through the solid rock, testify to the intense activity 
of the erosive forces; while the deep ravines, which seam every part 
of this desert area, vie with the Nile Valley itself in the height of 
their bounding cliff-walls and the steepness of their sides. If it be 
remembered that the Nile Valley ravine is in its southern portion 
cut through these easily denuded materials, the conception of the 
erosion of the Nile Valley is not one which involves too great a tax 
on our imagination. 
When, however, we consider the origin of the Gulf of Suez, 
I must confess that I am not prepared to go so far as my friend and 
colleague Dr. Ball is prepared to do. Let us grant fully the broken 
anticline character of the Wadi Araba area; but what does that 
very admission involve? Why do the Miocene beds which are found 
north of the northern limb of this broken anticline (the North 
Galala Hills) pass across into Sinai, and only reappear again in the 
Eastern Desert of Egypt to the south of the southern limb of 
1 See Mr. Beadnell’s map of Abu Roash. 
