322 PROFESSOR E. HULL, LL.D., F.R.S., F.G.8., ON THE 
Egypt had already been hollowed out of the Eocene lime- 
stone strata, and the whole region was re-submerged to a 
depth of over 200 or 250 feet below its present level, rela- 
tively to the surface of the Mediterranean and Red Seas. It 
is since that period of submergence that the alluvial deposits 
of the Delta have been accumulated. 
Part V.—PuHysicaAL History oF EGYPT AND THE NILE 
VALLEY. 
(1.) During the Cretaceous and Eocene periods, the whole 
region embraced by Egypt and the Libyan Desert was sub- 
merged beneath the waters of the sea, which extended south- 
wards from the Mediterranean area, probably as far as 
lat. 12° in the meridian of the Nile Valley (see map). The 
limits of the Eocene sea were probably defined by the 
Sinaitic and Arabian mountain chain extending southwards 
into the Abyssinian Highlands. The southern limits are at 
present uncertain. Without doubt the unsubmerged land of 
the period imecluded the high region surrounding the great 
Central African lakes, and extending.in a north-westerly direc- 
tion into the Air and Tibesti district, constitutmg the Asgar 
(or Ahaggar) Mountains; composed, according to Zittel, of 
Paleeozoic (Devonian ?) sandstone, slate, gneiss, and granite 
with volcanic rocks, forming the southern border of the desert. 
Towards the north the borders of this Tertiary sea were 
formed by the Morocco Atlas and Algerian Highlands, 
amongst which various Paleozoic rocks appear, sometines 
penetrated by granite and porphyry. Such were in brief 
the general hmits of the Tertiary inland sea, and into its 
waters some of the existing affluents of the Nile, from the 
great equatorial lakes in the south, and the Abyssinian 
Highlands in the east, emptied themselves. 
With the succeeding Miocene epoch, the quiescent con- 
dition of the earth’s crust over this region came to a close. 
A general elevation of the sea-bed into land surfaces took 
place over Northern Africa and the adjoining tracts of 
Sinai and Palestine. Faulting and flexuring of the strata 
also supervened. It was durmg this period that the great 
Jordan-Arabah fault, which has been traced from the 
Lebanon to the Gulf of Akabah, was produced ;* as also, 
in the Egyptian area, the fault running parallel with the 
* “Geol, Arabia Petrza and Palestine,” Wem. P. E. F., p. 108. 
