THE MEDITERRANEAN NATURALIST 
180 
into the side valleys, depositing the Nile mud as a j 
level bottom across the valleys. Gradually the 
deposits rose, the wind ploughed down the hills, 
and laid the material in the water around, until 
at present we only see the tops of the denuded 
hills just appearing as patches and ridges of sand 
amid an expanse of mud. Meanwhile the coast 
sank, and the large region of Menzaleh was in 
Arab times inundated by the sea, and lost to cul- 
tivation. The Isthmus at the same time was 
rising; until, by the general elevation, and the 
masses of sand blown into the water, the head of 
the Red Sea was broken up and formed only a 
chain of half-choked saline lakes, through which 
the Suez Canal now runs. But whether we turn 
to the north coast or to the isthmus, we see that 
the wind-action is probably a cause of change of 
equal power with the deposits of the Nile or the 
variations of level of the land. 
So far we have only reviewed the changes of 
the historical period; but up the Nile valley are 
some of the most brilliant evidences of the enor- 
mous climatic differences which rendered the 
country in the prehistoric human period wholly 
different from what it now is. That the land was 
low T er, and that the Nile ran into a long estuary, 
in prehistoric times is usually granted. But there 
is also no question that a great rainfall over all 
the country swelled the volume of the river, so that 
it far exceeded the present stream of even the 
inundation. The problems yet to be solved are, 
what was the limit of salt water, and the limits 
of river and estuary? What was the volume of 
the Nile? and what was the dare in chronology 
and in civilisation when the present state of the 
country was established? As illustrations in point 
I would instance the following examples. The 
enormous rainfall of the Nile valley is shown 
by the cliffs at Thebes. There a narrow ridge of 
limestone, a sort of wall, separates the vertical 
cliffs at Deir el Bahri from the equal precipices at 
the head of the Valley of the Tombs of the Kings. 
This ridge cannot possibly have received surface 
flow from either end — nor, being limited by cliffs 
on either side — can more than the catchment of a 
few hundred feet in width have ever poured over 
the edges of this dividing wall. Yet the hard 
limestone is grooved out into a row of wide 
pipe-shaped grooves down either face, the breath 
j and close order of which show the volume of 
rain which must have poured down them. The 
same story is shown equally plainly in the water- 
courses which cut up the Nile cliffs into a fringe 
of ridges divided by deep ravines. These ravines 
are often a couple of miles in length, and a quarter 
of a mile in width, cut down through two or three 
hundred feet depth of rock by a waterfall, of 
which the evidence remains in the precipitous 
head of the ravine, the polished rock surfaces over 
which the cascade has poured, and the deep 
cauldron scooped out by the descending stream. 
Yet the catchment basins of such eroding forces 
are sometimes not over a few square miles in 
area. 
That such erosion took place during the period 
of the high level of water in the valley, be 
it fluvial or estuarine, is shown by the height 
reached by the great banks of debris washed 
out of the ravines, and piled up as a foreshore to 
the cliffs next below those torrential valleys. This 
is very finely seen at Beni Hasan. And it seems 
most probable that the celebrated wash-beds at 
Thebes, in which General Pitt Rivers — and later 
myself — have found wrought flints, were also 
deposited beneath the water, by the torrent from 
the Valley of the Kings’ Tombs. It seems im- 
probable to suppose a subaerial stream spreading 
out its material in such a wide fan; rather we see, 
both here and at Beni Hasan, how a subaerial 
stream will, on the contrary, cut through such 
broad beds of subaqueous deposit by deep subse- 
quent ploughings. That the age of the high water 
was within the human period, and that therefore 
the Theban beds might be subaqueous, is proved 
by the river-worn palaeolith of characteristic ap- 
pearance, which I picked up hundreds of feet 
above the present Nile on the desert cliffs of 
Esneh. 
I have now briefly shown what an interesting 
ground for research still awaits the geographer 
and geologist in Egypt; and how the conditions 
of the country render certain problems far more 
simple than they are in lands with continuous 
rainfall. Let us hope that our present facilities 
in Egypt may bring about some complete study of 
the subjects on wdiich we have now 7 touched. 
