THE MEDITERRANEAN NATURALIST 
126 
This cretaceous depression continued on through 
the Eocene period in which great thicknesses of 
limestone beds (5) were deposited. These eocene 
strata are divisible into three series, the lower 
reaching from the south to about the 26th parallel 
of latitude. The middle eocene extends thence to 
Cairo, The upper eocene is scarcely represented 
there, but occurs more largely a long way off— in 
the western side of the Libyan desert — where it 
appears at heights from 70 metres below , to 130 
meters above the level of the sea. 
The most characteristic fossils are the numerous 
species of NummuUies , so called from tiie resem- 
blance of the larger kinds to pieces of money 
i (nummus). A large number of the mollusca are 
the same as in our own eocene beds, c. g., Nautilus 
ziczac , common to the London clay and the Paris 
basin. 
The Middle Eocene is well represented at the 
Mokattam hills, which rise to 61ft. behind the 
citadel of Cairo: The same beds support the 
Great Pyramid, but they constitute a “down- 
throw/' being only 160ft. above the Nile, which 
flows along the line of fault. Nummidites , Gize- 
hensis , curvispira, discorbina , &c., are characteristic 
ot the basement beds of this Middle Eocene series, 
associated with Cerithium giganteum , and other 
species familiar to English geologists. 
Above the preceding bed follows others, with 
shells shewing a correspondence with the lower 
Parisian beds, containing Pecten porisiensis , &c. 
Much gypsum occurs in these beds here. 
This Mokattam limestone contains flints resem- 
bling those of the U pper Chalk. By the weathering 
of the limestone, they form complete surface 
layers. On the west of the Nile most denudation 
has taken place, so that- there pebbles occur strewn 
over the desert. They split through the action of 
heat and cold, for the temperature often varies to 
the extent of 35 degrees in seven hours. They are 
often coloured in bands by oxide of iron. 
A brown uppermost layer contains many oysters, 
Coma , Valuta, Turritella , and the characteristic 
bivalves, Placuna and Carolia . 
the Upper Eocene strata are developed, as sta- 
ted, mainly at the extreme western part of the 
Libyan desert. They consist of limestone beds of 
10 metres in thickness, and are the equivalent of 
the Barton Clay. 
The first important elevation took place at the 
close of the Eocene times, so that the beds of that 
I age formed .soils for trees of the genus Nicolio, as 
I well of palms and pines, now constituting the 
| well-known fossil forests near Cairo. They belong 
’ to eight genera, including one palm, a conifer, seven 
j exogens, some of which were from 70ft. to 80ft. in 
j height. They are allied to the existing Sudan flora. 
A bill called Gebel-ahmar, or the red mountain, 
! is supposed to be also of Miocene age. It is com- 
posed of sandstones and conglomerates, and 
coutains what have been supposed to be 
old Geyser-pipes. The induration of the rocks, 
! and silicification of the trunks of the trees, 
| are thought to be due to these old hot 
1 silicious springs. The hard sandstone is used for 
! millstone and statues, a very ancient one being at 
| Ismailia. 
No recognised deposits occur of the Pliocene age, 
as during this time the land was continental, the 
the Nile emptying itself into a great enclosed 
saline basin on the east. 
As the elevation of Lower Egypt took place, 
the Nile valley became still more contracted, 
patches of sea-beaches being now discoverable at 
intervals as at Mokattam, near the Great Pyra- 
mid and up to Silsilis, proving that an arm of the 
sea extended far up the Nile. These beaches also 
occur at Alexandria, the Red Sea, Syria, Jaffa, and 
at Beyroot to the height of 200ft., indicating an 
extensive pleistocene submergence. 
As an illustration, in the cliffs behind the tombs 
of the Khalifs at Cairo, and at an elevation of 
about 30ft., the rocks, are perforated by the Litho- 
domus of the Mediterranean Sea, and abound with 
Ostrea cueullata of the Red Sea, as well as with 
Balani , ail being of existing species. 
Near the Pyramids there is another example at 
the summit of a knoll known as Het-el-orab, or” 
Crow’s Wall;” where a depression occurs between 
it and the Pyramids, which is partly natural and 
partly artificial, as the Sphinx is cut out of the 
solid rock. The beach consists of rounded frag- 
ments of limestone, with a few basaltic-like pebbles, 
the interstices being packed with oyster shells. It 
is about 40ft. above the bottom of the valley. 
As the land rose and the sea retreated, Egypt 
became higher than at present, as sand is found at 
a depth of 30ft. to 40ft, below the Nile mud, show- 
