THE WAXING AND WANING OF LOP-NOR 283
were abandoned, including Rawak, the major part, if not all, of Dandan-Uilik, Karadong, the Niya River town, Tuholo, Lulan, and possibly others whose dates are as yet unknown. At the same time, the great trade route through Lulan was given up in favor of a longer one. At a later date, roughly between the ninth and the sixteenth centuries, there appears to have been an epoch of somewhat more favorable climatic conditions. Choka was built on the Karatash River; Kenan and Lachinata, as well as Chira and Gulakhma, flourished lower down on the main stream; a road existed across the desert north of the present end of the Keriya River; Bilel Konghan grew up to succeed Tuholo; and Ying-pen, which appears to have been abandoned by its Buddhist builders, was reoccupied by Mohammedans. During the last few centuries, as the vegetation shows, there has been again a tendency toward aridity.
If the climatic pulsations outlined above have actually taken place, the level of Lop-Nor ought to have fluctuated in harmony with them. Apparently it has done so. The problem of its fluctuations is complicated, however, by the fact that the location of the lake has varied in response to changes in the course of the Tarim River. Hedin, by means of a careful survey with a transit, has proved that the western part of the old bed of Lop-Nor contains two slight depressions. One of these, the more southerly, is occupied by the present lake, which the natives call Kara Koshun. The other lies just south of Lulan. During the early centuries of the Christian era, the Tarim River, which then watered Lulan, discharged into this northern depression. It doubtless filled it and formed a large lake, which included the other depres-
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