nd through Babylon; the Tigris passes near Opis, and at Baghdad
runs at the foot of an embankment made to confine it by Nebuchadnezzar.
The changes traceable are less in the main courses than in the branch
streams, which perpetually vary, being sometimes left dry within a few
years of the time that they have been navigable channels.

The most important variations of this kind are on the side of Arabia.
Here the desert is always ready to encroach; and the limits of Chaldaea
itself depend upon the distance from the main river, to which some branch
stream conveys the Euphrates water. In the most flourishing times of the
country, a wide and deep channel, branching off near Hit, at the very
commencement of the alluvium, has skirted the Arabian rock and gravel for
a distance of several hundred miles, and has entered the Persian Gulf by
a mouth of its own. In this way the extent of Chaldaea has been at times
largely increased, a vast tract being rendered cultivable, which is
otherwise either swamp or desert.

Such are the chief points of interest connected with the two great
Mesopotamian rivers. These form, as has been already observed, the only
marked and striking characteristics of the country, which, except for
them, and for one further feature, which now requires notice, would be
absolutely unvaried and uniform. On the Arabian side of the Euphrates,
50 miles south of the ruins of Babylon, and 25 or 30 miles from the
river, is a fresh-water lake of very considerable dimensions--the
Bahr-i-Nedjif, the "Assyrium stagnum" of Justin. This is a natural
basin, 40 miles long, and from 10 to 20 miles broad, enclosed on three
sides by sandstone cliffs, varying from 20 to 200 feet in height, and
shut in on the fourth side--the north-east--by a rocky ridge, which
intervenes between the valley of the Euphrates and this inland sea. The
cliffs are water-worn, presenting distinct indications of more than one
level at which the water has rested in former times. At the season of
the inundation this lake is liable to be confounded with the extensive
floods and marshes which extend continuously from the country west of
the Birs Nimrud to Samava. But at other tines the distinction between
the Bahr and the marshes is very evident, the former remaining when the
latter disappear altogether, and not diminishing very greatly in size
even in the driest season. The water of the lake is fresh and sweet, so
long as it communicates with the Eup