rise from the plain. At several points on the coast of the Red Sea,
particularly near Koser, at a height of 600-950 ft. above the sea-level, we
find rock of the late tertiary or diluvial era containing coral, which
shows how much the land must have risen since that period. With these
coral-reefs the petroleum wells of Gebel ez-Zet and the sulphur which
occurs on the Ras el-Gimsah appear to be closely connected.
To the miocene , or middle tertiary period, belong several isolated
deposits of sandstone near Cairo, in which are found the beautiful fos¬
sil sea-urchins (Clypeaster Aegyptiacus) frequently offered for sale near
the Pyramids. The place where they occur, on the margin of the
desert, about 2 M. to the S. of the Sphinx, has been visited and de¬
scribed by Prof. Fraas.
One of the principal geological curiosities near Cairo is the Petri¬
fied Forest (comp. p. 339). About 5 M. to the E. of the town begins the
Khashab ('wood') desert, the surface of which for many miles is sprinkled
with whole trunks and fragments of silicified wood. Few travellers go
beyond the 'small' petrified wood; the 'great' lies about 20 M. to the
E. of Cairo. 'The desert here is so completely covered with trunks,
that, except the fine sand itself, no other kind of stone is visible than
the flint into which the Nicoliae have been converted'. (Fraas.) Trunks
of 60-90 ft. in length and 3 ft. in thickness have sometimes been found.
These have been described by Unger as Nicolia Aegypliaca (of the family
of the Sterculiaceae), hut, according to more recent investigations, it
would seem that the forest contained various other trees also (palms and
dicotyledonous plants). Whether the trunks have grown and been silici¬
fied on the spot, or were brought here by inundations from the south, is
still an open question. At all events these remarkable deposits date
from the late tertiary period.
Above Cairo, to the S. , the Nile is flanked by ranges of hills, the
valley between which is generally 4-9 M. in width. On the east side of
the Nile begins the Arabian, and on the west side the Libyan desert,
both of which are very inhospitable, being ill provided with water, and
covered at places only with scanty vegetation. From the northernmost
spur of the Arabian desert (the Mokattam near Cairo) to a point above
Edfu, both banks of the Nile consist of early tertiary nummulite lime¬
stone. The strata dip gradually from south to north, so that the farther
we ascend the Nile the older are the strata that we meet with. The
limestone of the Mokattam, with its millions of nummulites, is the ma¬
terial of which the new buildings of the European suburbs of Cairo are
constructed, and it was from the venerable quarries of Tura and Ma'-
sara that the ancient Egyptians obtained the stone for their pyramids.
The blocks for these stupendous structures were conveyed to them by
means of a huge stone dyke, of which all trace has now disappeared. On
the Mokattam, near Minyeh, Beni Hasan, Siut, Thebes, Esneh, and at
other places the limestone is rich in fossils, and in the vicinity of Cairo
geologists can easily form a considerable collection of them. The quar-
rymen on the Mokattam offer visitors fossil crabs (Xanthopsis Paulino-
Wiirtembergicus) and sharks' teeth for a moderate bakhshish.
To the south of Edfu the nummulite limestone disappears, being re¬
placed by marl and rocks of calcareous and sandy character, which,
according to Figari-Bey, contain chalk fossils. After these we come to
quartzose sandstone, belonging to the middle chalk formation, and form¬
ing considerable cliffs at the Gebel Selseleh, which confine the river
within a narrow bed.
This last formation, known as 'Nubian sandstone', which covers
many thousands of square miles of Nubia and the Sudan, was the ma¬
terial almost exclusively used for the construction of the ancient temples
of Upper Egypt; and near Selseleh, and in the Arabian desert between
Keneh and Koser, are still to be seen the extensive quarries which yielded
ihe material for the colossal structures of Thebes.
From Assuan to Selseleh the Nile flows through Nubian sandstone,
but near the ancient Syene a transverse barrier of granite and 'syenite'
advances from the east, forming the boundary between Egypt and Nubia.