"كتيّب بلاد الرافدين. المجلد I. ١٩١٨" [‎٢‎١] (٥٦٨/٣٠)

BOUNDAEIES AND PHYSICAL FEATUEES 21
Lake Van. They rise to about 7,000-9,000 ft., and are formed
mainly of Archaean crystalline schists, with Eocene rocks (limestone
and sandstone) on their lower slopes, and large outcrops of volcanic
rock appearing here and there. West of Bitlis the mountain-belt
broadens out in the Sassun country, which before the war contained
a considerable number of Armenian villages. The main crossings of
the eastern Taurus leading from Mesopotamia to western Armenia
are the Arghana defile NW. of Diarbekr, the Kulp valley 50 miles
W. of Bitlis, and the Bitlis Pass and valley.
(e) The Syrian Desert. —The country bordering the middle
Euphrates valley on the west is arid desert in its southern part, and
becomes gradually less arid towards the north, until, above the line
Raqqah—Hama, more or less cultivable soil is reached. The country
N. of this line up to the foot of the Taurus is described in the
Handbook of Syria and Palestine.
The Syrian I)esert(Hamad)is a plain sloping towards the Euphrates,
and at its eastern edge falling away in a drop of some 100-200 ft. to
the bottom of the Euphrates trough. The plain is broken here and
there by ranges of low hills. The surface is generally sand or shingle,
varied here and there by outcrops of volcanic rock. In the spring
wide areas are covered with grass, which withers a few weeks later
in the heat ot early summer. Wells and water-holes are very scarce
in the southern Hamad (as, for instance, between Hit and Damascus),
and are somewhat more frequent in the northern desert, as on the
line Deir ez-Zor-—Damascus. The wadis (watercourses) which inter
sect the plain are generally dry except for a few hours after rain.
The water-supply is at its best in spring.
Eiver System
The Euphrates and the Tigris are the channels through which
drainage from the Armenian tableland, from the western side of the
Persian plateau, from the hill-country of northern Mesopotamia, and
from the upper Mesopotamian plains is carried into the Persian Gulf.
The Karun and the smaller streams to the east of it bring down to
the gulf the drainage from the south-western side of the Persian
plateau. The common outlet of the Euphrates, the Tigris, and the
Karun on to the gulf is the Shatt el-Arab. On the navigation of
these rivers see pp. 280-7.
The Euphrates
The main sources of the Euphrates are two considerable streams
(the Qara or Erat Su and the Mui-ad Su), which, after traversing the