mountain rampart being pierced at intervals by passes practicable during a considerable portion of the year for mounted men and transport.
Thus to the south-west of the Turfan depression there descends from the grazing plateaux of Yulduz the wide valley of Kara-shahr, which has at all times served as an open gate for nomadic inroads into the north-eastern corner of the Tarim basin. Farther to the west, we note that under corresponding conditions the great oases of Kucha and Kashgar are equally liable to attack across the Tien-shan.
From the mountain barriers which enclose the Tarim basin we may now turn to a summary survey of the basin itself. Of its vast dimensions an adequate idea may be gained from the fact that from west to east it stretches over a direct distance of some goo miles. Its greatest width is fully 33o miles. Vast as these dimensions are, the uniformity of the prevailing conditions makes it easy to take a bird's-eye view of the several zones represented in this basin and to describe them briefly. By far the greatest among them comprises the huge central desert of bare sand-dunes which is popularly known as the Taklamakan.
Not one of the numerous rivers descending from the snowy Kun-lun succeeds in making its way through the Taklamakan, except the Khotan river, and that too only during a few summer months. All the rest are lost in this `sea of sand' at a greater or lesser distance from the line occupied by the oases or the areas of desert vegetation which they adjoin. But within historical times a number of these terminal river-courses carried their water considerably farther north. This is conclusively proved by the ancient sites which I explored in the Taklamakan.
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