exclusive of small windings, is above 350 miles, and of these nearly 100 are across the plain country, which it enters soon after receiving the Rowandiz stream.  Like the Khabour, it is fordable at certain places and during the summer season; but even then the water reaches above the bellies of horses.  It is 20 yards wide a little above its junction with the main steam.  On account of its strength and rapidity the Arabs sometimes call it the “Mad River.”

The Lesser Zab has its principal source near Legwin, about twenty miles south of Lake Urumiyeh, in lat. 36 deg. 40’, long. 46 deg. 25’.  The source is to the east of the great Zagros chain; and it might have been supposed that the waters would necessarily flow northward or eastward, towards Lake Urumiyeh, or towards the Caspian.  But the Legwin river, called even at its source the Zei or Zab, flows from the first westward, as if determined to pierce the mountain barrier.  Failing, however, to find an opening where it meets the range, the Little Zab turns south and even south-east along its base, till about 25 or 30 miles from its source it suddenly resumes its original direction, enters the mountains in lat. 36 deg. 20’, and forces its way through the numerous parallel ranges, flowing generally to the S.S.W., till it debouches upon the plain near 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 deg. 45’, long. 47 deg. 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 deg. 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.