across instead of down the main slope. If such were the case, whenever the stream accidentally broke through the retaining wall of sand, it would swing to the right. It would thus gradually assume a normal course in the lowest part of the basin.
Coming now to evidence as to variations in the size of the lake, we have first the ancient name, the Great Salt Lake. The old Chinese, however, also called Lop-Nor a " marsh," and the "Lake of Reeds," which seems very contradictory, unless these names were applied during the arid period after the fall of Lulan. The history of the first Han Dynasty, written, it will be remembered, about the beginning of the Christian era, gives the size of the lake as seventy-five miles each way. At this time, Lulan must have consumed much of the river for irrigation, which would naturally lessen the area of open water. A later record of unknown date, but perhaps belonging to the centuries of great aridity, gives the size of the lake as only fifty miles by twenty-five, and another as one hundred miles in circumference, which comes to nearly the same thing. Whether these figures refer to the entire marsh, or only to the area of open water, is uncertain. Hedin gives the size of the modern Kara Koshun as seventy-five miles by eighteen, including all the marshy tract, which, he says, comprises nine tenths of the entire area. Przhevalski gives sixty or seventy miles by thirteen, but his map diminishes this. So far as any conclusion is justifiable from such meagre data, it appears that, in the very earliest times, Lop-Nor was larger than now, in spite of the greater population known to have existed then on the Tarim and its upper tributaries. Somewhat later, at an
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