s already mentioned. It contains four
monasteries, the remains of the famous anchorite settlement of
Nitriae. South of the Wadi Natron, and parallel to it, is a sterile
valley called the Bahr-bela-Ma, or "River without Water."

_The Sinai Peninsula._--The triangular-shaped Sinai peninsula has its
base on the Mediterranean, the northern part being an arid plateau,
the desert of Tih. The apex is occupied by a massif of crystalline
rocks. The principal peaks rise over 8500 ft. Owing to the slight
rainfall, and the rapid weathering of the rocks by the great range of
temperature, these hills rise steeply from the valleys at their feet
as almost bare rock, supporting hardly any vegetation. In some of the
valleys wells or rock-pools filled by rain occur, and furnish
drinking-water to the few Arabs who wander in these hills (see also
SINAI).

[_Geology._--Just as the Nile valley forms the chief geographical
feature of Egypt, so the geology of the country is intimately related
to it. The north and south direction of the river has been largely
determined by faults, though the geologists of the Egyptian Survey are
finding that the influence of faulting in determining physical outline
has, in some cases, been overestimated. The oldest rocks, consisting
of crystalline schists with numerous intrusions of granite, porphyry
and diorite, occupy the eastern portion of the country between the
Nile south of Assuan and the Red Sea. The intrusive rocks predominate
over the schists in extent of area covered. They furnished the chief
material for the ancient monuments. At Assuan (Syene) the well-known
syenite of Werner occurs. It is, however, a hornblende granite and
does not possess the mineralogical composition of the syenites of
modern petrology. Between Thebes and Khartum the western banks of the
Nile are composed of Nubian Sandstone, which extends westward from the
river to the edge of the great Libyan Desert, where it forms the bed
rock. The age of this sandstone has given rise to much dispute. The
upper part certainly belongs to the Cretaceous formation; the lower
part has been considered to be of Karroo age by some geologists, while
others regard the whole formation to be of Cretaceous age. In the
Kharga Oasis the upper portion consists of variously coloured
unfossiliferous clays with intercalated bands of sandstone containing
fossil silicified woods (_Nicolia Aeg