CH. XLVIII TERMINAL BASIN OF SU-LO HO 535
by inset A of Map 1., we discovered that a considerable river flows out of the Khara-nor during the spring and summer floods ; after draining a series of smaller lakes and marshes lower down, it carries its water right through to the southern portion of the great lake bed which we had passed so much farther west, and had then thought finally dried up. But like most new facts, this discovery, too, raised its crop of fresh problems. I cannot set them forth here in detail, nor have they all yet found their solution.
How was the maze of high clay terraces scattered over the lake bed to be accounted for ? That their clay was built up by lacustrine sediments, deposited perhaps in some earlier geological periods, was clear, and equally also that their separation was the result of erosion which gradually broke up the ancient lake bottom. But was this erosion solely the work of the winds during periods of excessive desiccation, or had the cutting action of running water prepared and helped it on ? Only close examination on the spot by a competent geologist could furnish a definite answer. But in the meantime it may be well to record here that I observed exactly corresponding clay formations in abundance around the Khara-nor and other lake basins. In their direction and grouping I often found proof of the fact that ridges originally cut out by the erosive action of drainage had subsequently been subjected to the grinding force of the prevailing east winds and the sand driven before them, and in due course been broken up into those curious isolated terraces.
Another problem with which my thoughts were closely concerned at the time was suggested by the obvious relation between the true terminal bed of the Su-lo Ho just discovered and the unmistakable valley we had traced ascending to within a few miles of it near Besh-toghrak, from the north-eastern extremity of the salt-encrusted Lop-nor basin. It was impossible not to draw the conclusion that once, and that probably within the present geological period, the waters of the Su-lo Ho flowed out of the newly discovered terminal basin westwards, just as they still pass out of the Khara-nor, and that entering the Besh-toghrakAchchik-kuduk valley they reached down to the Lop-nor
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