The right and left arms appear to have been of about equal in length, and may be estimated at 150 or 160 miles; the central arm had a shorter course, not exceeding 110 miles.

The volume of water which the Nile pours into the Mediterranean during a day and night is estimated at from 150,000 millions to 700,000 millions of cubic metres.

It was by far the largest of all the rivers of the Empire.
The Indus, which was the next largest of the Persian rivers to the Nile, rose (like the Nile) outside the Persian territory.

Its source is in the region north of the Himalaya range, about lat.

31 deg., long.