The Tigris.—The principal source of this river ie on the southern declivity of the mountain range which forms the southern wall of the valley of the Murad-Chai, near Anshan, and not much more than 10 miles distant from the most easterly point of the bend of the Euphrates, between 3Ialatiyah and Someisat. The Tigris runs from its source 25 miles to the north-east, and about 4568 feet above tho sea. It then flows southward for nearly the same distance, and, receiving near the mines of Arghsam-3Iaden a small stream from tho west, adopts the course of this tributary, and then flows again towards Diar-Bekr (about 37° 55' N. lat., 39° 55' E. long.), distant 40 miles In a straight line. Opposite Diar-Bekr the Tigris Is about 250 yards wide in the season of floods, but it is only used to float timber-rata from the mountains. At Diar-Bekr the Tigris turns suddenly round to the east, and continues to flow in that direction for 105 miles, till it receives the Bitlis River on its left bank. In this part of its course the Tigris flows parallel to the high mountains which separate its valley from that of the 3lurad-Chai, an extensive plain intervening between its banks and their bases. On the south the river has the bill range, on the opposite side of which are the sources of the Khabur. This upper plain of the Tigris is described in the article Alumna (vol. L cols. 514-516).
From its junction with the Bitlis River, tho Tigris bends round to the south, and it continues nearly in the direction of south-east to the mouth of the Great Zab (36' N. lat., 43° 20' E. long.). For tho greater part of this distance the range of hills which separates tho valley of Diar-Bekr from the basin of the upper Khabur accompanies the Tigris on the south-east ; they terminate on its banks a little to the north of Mosul (36° 20' N. let., 43° 15' E. long.). In this interval the Tigris receives a number of afflueuts on both banks, the most important of which is the Eastern Khabur. The Khabur, at its junction with the Tigris, comes from the north of east, but 30 miles farther up it comes from the north. It rises high up among the Arjerosh-Dagh, which bound the southern shores of Lake Van.
The main branch of , the Zab Ala, Upper or Great Zab, has its mane on the slope of the Sar-el-Bagh range, at an elevation of about 300 feet above the ma, and nearly midway between the lakes of Van sad Uramlyab. [Aamextr, vol. L col. 518.) At first the 7Ab flows to the south, but about 37' 19' N. lat it tarns to the wait-south-west. Near the village of Klyau it receives the Berdizawi (called also by the Inhabit-lieu the Lamer Zab), which it said to rise in the Erdosh, or Arjerosh•Tei, a few miles south of the eastern termination of Lake Van, and which descends to the principal stream in a encomeion of estareete. After the junction the 7Ab flows south-east till about 12 miles east of Amadiyalt from which point it. course is rather to the north of east, to I0 miles west of Rowe:Air, where it receives a large affluent Between Amadiyah and Rowandis, the Zab has on the north the colossal mountains in which it has its rise; on the south a range of bills which stretch from near the mouth of the Eastern to the base of Mount Itomuidiz (1I,000 feet above the an).
round between the base of Rowandis and the eastern extremity of this ridge, the Zabcrosses a hill-range parallel to it on the south, and tows south-west to the Tigris, which it enters with • deep stream 60 feet wide, but the width is much greater • little higher up.
About 84 miles below the mouth of the Great Lab the Tigris forces its way through the Ilamrin Bills. About 12 miles below the Great Zeb there is • ford in the Tigris; 20 miles farther down it receiTes an ailment from the west near Kalah Shirkat; and 28 miles below this it is joined by the 7Ab-Aefal, Lower or Lesser Zab from the north-east. The main branch of this tributary rises 20 miles south-west of the south extremity of Lake Urumiyah; flows 30 miles to the south-east, and then turns abruptly to the south-west; about 20 miles onwards it receives four affluents from the mountains to the south-east, and carries to the Tigris, after flowing parallel to the Great Zab for the last 50 or 60 miles of its course, a deep stream 25 feet broad. At the point of junction the Tigris has a breadth of 500 yards. Below the passage of the river through the Hamrin Hills, high grounds, which separate its valley from the Valley of the Tarthar, extend close to the termination of the Median Wall. Here the Tigris issues from the bills Into the great central plain. Between Diar-Bekr and Mosul (296 miles) the river is navigable for rafts at certain seasons; below Mosul it is navigable throughout the year; in 1838 the 'Euphrates' steamer ascended It to within 20 miles of MosuL A few mile. below Baghdad the Tigris is joined by the Diyalah, which is known in its upper course as the river of Shirwan. This river rises among the mountains above Hamadan near 34° 40' N. lat., 17' 30'F long., and !fowl for about 30 miles from east to west ; then, turning at first to the north of west, for nearly 100 miles in a semi circular sweep round the baso of Mount Dalahu, it receives a number of streams on its south bank. Some of the summits of this moun tain group rise, by the estimate of Major Rawlineon, 5000 feet above their base. At the moat northern part of its course the Shirwan receive. the waters of the Taj, one of whose branches comes from Sulelmaniyah. It then flows south-east for about 80 miles, till it hones into the plain through a gap in the Hamrin Hills. Above these hills the river flows in a strong rapid current 400 yards broad. Its breadth at its month at Ctesiphon, above the Zak Kesm, is about CO yards. From the Kermanshah district the Diyalah receives the Ilotwan and the Arwand. The other feeders of the Tigris above Kurnah, and the tributaries of the Shalul Arab below that town, are noticed in the article BAGHDAD, Pashatio of (voL 1. cola. 820, 824 Five mile. below Baghdad the Saklawlyah Canal, from the Euphrates, joins the ligris; the distance along this canal from river to river was found by Lieutenant Lynch (who sailed along it in 1838, in the Euphrates eteairser) to be 45 toilet The current (in the season of floods) was about 4 miles an hour, from the Euphrates to the Tigris.