44 THE TARIM RIVER.
hanced power of erosion, a consequence of its being confined to such a narrow passage, its depth exceeded the depth in the adjacent parts of the two lakes which it connects. It is through this channel that the more southerly lake of Tschöl-köl becomes filled every summer; and at that season there is always a steady, though at the same time gentle, current flowing into it, caused by the rapid evaporation which takes place over its open surface. When, however, the Jarkent-darja drops in the autumn, the current turns and flows back towards the north. Yet, by reason of the shallowness of the watercourses which unite the Sorun-köl with the river, neither that lake, nor, consequently, the Tschöl-köl, can be entirely emptied. In the beginning of October, at the time of our visit, their surface was however very
Fig. 5t. THE CHANNEL BETWEEN SORUN-KÖL AND TSCHÖL-KÖL.
appreciably lower than it was in the height of the summer. Similar lateral lakes or lagoons are very common, especially along the lower course of the Jarkent-darja, for the most part on the right side of the stream; they prove, wherever they occur, that the country there lies at a lower level than the surface of the river.
Wild-duck swarmed in extraordinary numbers on both these lakes, and on the Sorun-köl there were also some swans.
I have described the Tschöl-köl in Peter,nann's Mitteilungen (Ergänzungsheft, I 3 I) in the account of my 1895 journey, and consequently there is no need for me to dwell upon it again here. Except for its northernmost extension, where there
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