386 Dr. W. F. Hume—Origin of the Nile Valley. 
Thus far the evidence showed that disturbances of a tectonic nature 
were widespread in Egypt, that they had given rise to important 
surface features, but at the same time the rift or trough-fault view 
for the Nile Valley was not gaining the required basis of fact to make 
its position impregnable. The highly tilted gravel ridges south of 
Helwan, the long ridge of Gebelain in Southern Egypt, bringing up 
steeply dipping Cretaceous beds, the great slip-faults of the Qena— 
Luxor district could be invoked, but all these manifestations of earth- 
movement do not fit into a regular plan of trough-faulting, and for 
some years my colleagues and myself had, if I mistake not, abandoned 
(if we ever had them) any pronounced view as to the form of the Nile 
Valley near Cairo being directly influenced by faults. At the same 
time the great differences of structure between the two sides of the 
Nile both near Cairo and in the Qena—Luxor reach seemed to demand 
some explanation, which might be of wider character than mere 
erosion. 
Till 1900 I may frankly say that all my studies in the outer deserts 
of Egypt had biassed me in favour of a fault origin for the major 
portion of the Nile Valley; from that period onward the tide of 
thought took pause. Many visits to Nubia showed that faults were 
of minor importance there, while a study between Esna and Aswan, 
which was carried out on foot, every point of any interest within 
reasonable distance of the river being examined, further strengthened 
the view that in this reach of the river longitudinal faults were of 
no significance. On the contrary, transverse faults, such as the one 
at Kom Ombo, produce the most striking effects. The difference 
between the high Nubian Sandstone cliffs and hills on the right bank 
near Edfu, etc., and the comparatively low gravel ridges on the left 
or west bank, led to the view that the river was eroded along the 
original outcrop of the softer Cretaceous strata, to whose line of 
strike the present stream is roughly parallel. In 1906 satisfactory 
evidence was obtained of a transverse anticlinal roll in the hills 
south-east of Qena, a roll which in large measure explains the 
abrupt bend of the river at this point, along the outcrop of these 
Cretaceous beds. 
This does not, however, satisfy the problem to the full; we have 
still to explain the remarkable ravine of the Nile between Sohag 
and Assiut, and the north-westward bend near Cairo. For the latter 
feature it seems reasonable to suggest that the river has in the main 
taken advantage of the more easily denuded Upper Moqattam Beds, 
the geology of the two banks between Cairo and the Fayum differing 
geologically in marked respects. As regards the straight-lined ravine 
of the Nile, it is of interest to note that its long axis corresponds 
with a synclinal arrangement of the strata, which is also the cause 
of the marked differences between the two sides of the Nile south 
of Qena. AsI hope a general geological map of Egypt on a scale of © 
1: 1,000,000 will appear in the course of the late summer, there will 
be an opportunity for all interested in the subject to weigh the 
evidence and form their own opinions. 
The direction, therefore, in which my own views tend at the 
present time are put dogmatically. The southern portion of the 
