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, the affluents almost entirely cease; one, the river of Sajur, is received from the right, in about lat. 36 deg. 40’; and two of more importance flow in from the left-the Belik (ancient Bilichus), which joins it in long. 39 deg. 9’; and the Khabour (ancient Habor or Chaboras), which effects a junction in long. 40 deg. 30’, lat. 35 deg. 7’. The Belik and Khabour collect the waters which flow from the southern flank of the mountain range above Orfa, Mardin, and Nisibin, best known as the “Mons Masius” of Strabo. They are not, however, streams of equal importance. The Belik has a course which is nearly straight, and does not much exceed 120 miles. The Khabour, on the contrary, is sufficiently sinuous, and its course may be reckoned at fully 200 miles. It is navigable by rafts from the junction of its two main branches near the volcanic cone of Koukab, and adds a considerable body of water to the Euphrates. Below its confluence with this stream, or during the last 800 miles of its course, the Euphrates does not receive a single tributary. On the contrary, it soon begins to give off its waters right and left, throwing out branches, which either terminate in marshes, or else empty themselves into the Tigris. After awhile, indeed, it receives compensation, by means of the Shat-el-Hie and other branch streams, which bring back to it from the Tigris, between Mugheir and Kurnah, the greater portion of the borrowed fluid. The Tigris, on the contrary, is largely enriched throughout the whole of its course by the waters of tributary streams. It is formed originally of three main branches: the Diarbekr stream, or true Tigris, the Myafarekin River, and the Bitlis Chai, or Centrites of Xenophon, which carries a greater body than either of the other two. From its entry on the low country near Jezireh to the termination of its course at Kurnah, it is continually receiving from the left a series of most important additions. The chain of Zagros, which, running parallel to the two main springs, shuts in the Mesopotamian plain upon the east, abounds with springs, which are well supplied during the whole summer from its snows, and these when collected form rivers of large size and most refreshing coolness. The principal are, the eastern Khabour, which joins the Tigris in lat. 37 deg. 12’: the Upper Zabo which falls in by the ruins of Nimrud: the Lower Zab, which joins some way below Kileh Sherghat: the Adhem, which unites its waters half way between Samarah and Baghdad: and the Diyaleh