estimated length of the former, including main windings, is 1146 miles;
that of the latter is 1780 miles. Like most rivers that have their
sources in high mountain regions, they are strong from the first, and,
receiving in their early course a vast number of important tributaries,
become broad and deep streams before they issue upon the plains. The
Euphrates is navigable from Sumeisat (the ancient Samosata), 1200 miles
above its embouchure; and even 180 miles higher up, is a river "of
imposing appearance," 120 yards wide and very deep. The Tigris is often
250 yards wide at Diarbekr, which is not a hundred miles from its
source, and is navigable in the flood time from the bridge of Diarbekr
to Mosul, from which place it is descended at all seasons to Baghdad,
and thence to the sea. Its average width below Mosul is 200 yards, with
a depth which allows the ascent of light steamers, unless when there is
an artificial obstruction. Above Mosul the width rarely exceeds 150
yards, and the depth is not more in places than three or four feet. The
Euphrates is 250 yards wide at Balbi, and averages 350 yards from its
junction with the Khabour to Hit: its depth is commonly from fifteen to
twenty feet. Small steamers have descended its entire course from Bir to
the sea. The volume of the Euphrates in places is, however, somewhat
less than that of the Tigris, which is a swifter and in its latter
course a deeper stream. It has been calculated that the quantity of
water discharged every second by the Tigris at Baghdad is 164,103 cubic
feet, while that discharged by the Euphrates at Hit is 72,804 feet.

The Tigris and Euphrates are very differently circumstanced with respect
to tributaries. So long as it runs among the Armenian mountains, the
Euphrates has indeed no lack of affluents; but these, except the Kara
Su, or northern Euphrates, are streams of no great volume, being chiefly
mountain-torrents which collect the drainage of very limited basins.
After it leaves the mountains and enters upon a low country at Sumefsat,