The chief natural division of the country is that made by the Tigris, which, having a course nearly from north to south, between Til and Samarah, separates Assyria into a western and an eastern district. Of these two, the eastern or that upon the left bank of the Tigris, although considerably the smaller, has always been the more important region. Comparatively narrow at first, it broadens as the course of the river is descended, till it attains about the thirty-fifth parallel a width of 130 or 140 miles. It consists chiefly of a series of rich and productive plains, lying along the courses of the various tributaries which flow from Mount Zagros into the Tigris, and often of a semi-alluvial character. These plains are not, however, continuous. Detached ranges of hills, with a general direction parallel to the Zagros chain, intersect the flat rich country, separating the plains from one another, and supplying small streams and brooks in addition to the various rivers, which, rising within or beyond the great mountain barriers, traverse the plains on their way to the Tigris. The hills themselves—known now as the Jebel Maklub, the Ain-es-sufra, the Karachok, etc.—are for the most part bare and sterile. In form they are hogbacked, and viewed from a distance have a smooth and even outline but on a nearer approach they are found to be rocky and rugged. Their limestone sides are furrowed by innumerable ravines, and have a dry and parched appearance, being even in spring generally naked and without vegetation. The sterility is most marked on the western flank, which faces the hot rays of the afternoon sun; the eastern slope is occasionally robed with a scanty covering of dwarf oak or stunted brushwood. In the fat soil of the plains the rivers commonly run deep and concealed from view, unless in the spring and the early summer, when through the rains and the melting of the snows in the mountains they are greatly swollen, and run bank full, or even overflow the level country.
The most important of these rivers are the following:—the Kurnib or Eastern Khabour, which joins the Tigris in lat. 37° 12’; the Greater Zab (Zab Ala), which washes the ruins of Nimrud, and enters the main stream almost exactly in lat. 30°; the Lesser Zab (Zab Asfal), which effects its junction about lat. 35° 15’; the Adhem, which is received a little below Samarah, about lat. 34°; and the Diyaleh, which now joins below Baghdad, but from which branches have sometimes entered the Tigris a very little below the mouth of the Adhem. Of these streams the most northern, the Khabour, runs chiefly in an untraversed country—the district between Julamerik and the Tigris. It rises a little west of Julamerik in one of the highest mountain districts of Kurdistan, and runs with a general south-westerly course to its junction with another large branch, which reaches it from the district immediately west of Amadiyeh; it then flows due west, or a little north of west, to Zakko, and, bending to the north after passing that place, flows once more in a south-westerly direction until it reaches the Tigris. The direct distance from its source to its embouchure is about 80 miles; but that distance is more than doubled by its windings. It is a stream of considerable size, broad and rapid; at many seasons not fordable at all, and always forded with difficulty.
The Greater Zab is the most important of all the tributaries of the Tigris. It rises near Konia, in the district of Karasu, about lat. 32° 20’, long. 44° 30’, a little west of the watershed which divides the basins of Lakes Van and Urymiyeh. Its general course for the first 150 miles is S.S.W., after which for 25 or 30 miles it runs almost due south through the country of the Tiyari. Near Amadiyeh it makes a sudden turn, and flows S.E. or S.S.E. to its junction with the Rowandiz branch whence, finally, it resumes its old direction, and runs south-west past the Nimrud ruins into the Tigris. Its entire course, 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° 40’, long. 46° 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° 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° 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, running nearly due east and west, and extending from the Euphrates at Rum-kaleh to Til and Chelek upon the Tigris. Below this, a vast slightly undulating plain extends from the northern mountains to the Babylonian alluvium, only interrupted about midway by a range of low limestone hills called the Sinjar, which leaving the Tigris near Mosul runs nearly from east to west across central Mesopotamia, and strikes the Euphrates half-way between Rakkeh and Kerkesiyeh, nearly in long. 40°.
The northern mountain region, called by Strabo “Mons Masius,” and by the Arabs the Karajah Dagh towards the west, and towards the east the Jebel Tur, is on the whole a tolerably fertile country. It contains a good deal of rocky land; but has abundant springs, and in many parts is well wooded. Towards the west it is rather hilly than mountainous; but towards the east it rises considerably, and the cone above Mardin is both lofty and striking. The waters flowing from the range consist, on the north, of a small number of brooks, which after a short course fall into the Tigris; on the south, of more numerous and more copious streams, which gradually unite, and eventually form two rather important rivers. These rivers are the Belik, known anciently as the Bileeha, and the Western Khabour, called Habor in Scripture, and by the classical writers Aborrhas or Chaboras. [PLATE XXII., Fig. 1.]
The Belik rises among the hills east of Orfa, about long. 39°, lat. 37° 10’. Its course is at first somewhat east of south; but it soon sweeps round, and, passing by the city of Harran—the Haran of Scripture and the classical Carrh—proceeds nearly due south to its junction, a few miles below Rakkah, with the Euphrates. It is a small stream throughout its whole course, which may be reckoned at 100 or 120 miles.