Arbela, after which it runs S.W. and S.W. by S. to the Tigris. Its
course among the mountains is from 80 to 90 miles, exclusive of small
windings; and it runs more than 100 miles through the plain. Its
ordinary width, just above its confluence with the Tigris, is 25 feet.

The Diyaleh, which lies mostly within the limits that have been here
assigned to Assyria, is formed by the confluence of two principal
streams, known respectively as the Holwan, and the Shirwan, river. Of
these, the Shirwan seems to be the main branch. This stream rises from
the most eastern and highest of the Zagros ranges, in lat. 34° 45',
long. 47° 40' nearly. It flows at first west, and then north-west,
parallel to the chain, but on entering the plain of Shahrizur, where
tributaries join it from the north-east and the north-west, the
Shirwan changes its course and begins to run south of west, a direction,
which, it pursues till it enters the low country, about lat. 35° 5',
near Semiram. Thence to the Tigris it has a course which in direct
distance is 150 miles, and 200 if we include only main windings. The
whole course cannot be less than 380 miles, which is about the length of
the Great Zab river. The width attained before the confluence with the
Tigris is 60 yards, or three times the width of the Greater, and seven
times that of the Lesser Zab.

On the opposite side of the Tigris, the traveller comes upon a region
far less favored by nature than that of which we have been lately
speaking. Western Assyria has but a scanty supply of water; and unless
the labor of man is skilfully applied to compensate this natural
deficiency, the greater part of the region tends to be, for ten months
out of the twelve, a desert. The general character of the country is
level, but not alluvial. A line of mountains, rocky and precipitous, but
of no great elevation, stretches across the northern part of the region,