166 DISCOVERY OF ANCIENT BORDER LINE CH. X
remarkably high and steep. These lake-beds proved to represent an ancient terminal basin of Su-lo-ho which now finds its end in large salt-marshes more than fifteen miles farther south. The Khara-nor lake of the maps where the Su-lo-ho was previously believed to lose itself was proved to lie still more than a degree of longitude farther to the east.
The discovery of that more ancient terminal basin, now dried up, is of considerable geographical interest. It presents a very instructive analogy to the riverine changes which have taken place in historical times in the terminal branches of the Tarim and Kuruk-darya. It suggests that at an earlier period the Su-to-ho, which drains a great portion of the high snowy Nan-shan ranges, emptied itself into the great Lop sea. Thus the drainage area of the latter then extended from the Pamirs right across innermost Asia to the watershed of the Pacific Ocean.
There was constantly with me the thought of the ancient traffic which the earliest Chinese route to the `Western Countries' through Lou-lan had seen since the days of that brave pioneer of China's Central-Asian expansion, Chang Chien, and no less the thought of all the human toil and suffering it had witnessed. From brief notices in the Imperial Annals of the Han dynasty I knew that the Lou-lan route, as we may briefly call it, started in the east from a fortified border station, famous in early Chinese historical records by the name of `Yü-mên-kuan', the `Barrier of the Jade Gate'. It took its significant name from that precious jade (yü) of Khotan which from early down to modern times formed an important article of trade export from the Tarim basin to China. But neither Chinese nor Western scholar-
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