Indirectly this assumption is supported by the scantiness of the salt efflorescence which I observed in this lake bed. Were all the waters brought down by the Su-lo Ho floods finally to disappear there by evaporation, we should reasonably expect the surface of the lake bed to be thickly encrusted with salt cakes just like that of the ancient Lop-nor bed. It is impossible to give here further details. But enough has been said to justify my belief that the well-marked valley we had surveyed on our way to Besh-toghrak was the passage through which the waters of the Su-lo Ho and its chief tributary, the river of Tunhuang, had once made their way down to Lop-nor, and that this period was, geologically speaking, quite recent.
The geographical importance of this observation scarcely needs to be set forth at length ; for if it be accepted, the true easternmost limit of the great Turkestan basin is shifted from about 91° 3o' to circ. 99° of E. longitude, where it touches the extreme western limit of the Pacific drainage. I may add here, in passing, that my subsequent explorations fully confirmed this observation by showing the close affinity which exists between practically all physical features in the Tun-huang—Su-lo Ho drainage area and those of the Tarim Basin.
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