now disappeared. Both to the north and south of the Lop basin, regions which once were the home of nomadic shepherds are now uninhabited because there is not enough water and grass.
When we turn to the rivers, it appears that in the seven hundred miles from Khotan eastward, seventeen are worthy of notice by reason of their size or because they support oases. Of the seventeen all but four come to an end in the zone of vegetation, and hence it is impossible to determine whether they have diminished in length. The remaining four all once flowed from eight to twenty-five miles farther into the sand than they now do, as appears from dead vegetation. Thirteen of the seventeen rivers have on their lower courses the ruins of towns dating from the Buddhist era, a thousand or more years ago. In almost every case, the ancient towns were larger than their successors, this being notably true of Niya, Yartungaz, Endereh, Cherchen, Vash Sheri, and Miran. And finally, with the possible exception of old Cherchen, Charklik, and Karadong on the Keriya River, the older ruins are situated so far out in the desert, or upon rivers so small or so saline, that it would be impossible again to locate towns of equal size in the same places, unless a far better system of irrigation were introduced. There is not the slightest trace of such a system, although if it had existed, its canals would surely have been more durable than those built under the present crude system. Moreover, in three places, Vash Sheri, Miran, and Ying-pen, almost the entire irrigation system of old times is preserved, including both dams and canals; and it is evident that the ancient methods of utilizing water were precisely like those
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