Sec. i] BY THE DESERT EDGE TO KHOTAN 95
Now my explorations at ancient sites east of Khotan demonstrated that such ' terminal oases ', as we may appropriately call them, possess an archaeological interest considerably in excess of their geographical importance. Through a variety of powerful causes, partly physical and partly historical, which we shall have to examine in detail hereafter, these ' terminal oases ' are liable to undergo considerable changes in position and extent at different periods 1. Owing to the relative frequency of these shiftings within historical times, and the close vicinity of the desert sand which preserves whatever it buries, ancient sites, with structures intact or other recognizable remains, can be traced far more readily in the vicinity of such oases than in the case of oases of the other type. There the variations of the boundary line between oasis and desert have ordinarily been small in proportion to the whole occupied area, and ancient sites within the latter have always been subject to the danger either of being constantly built over and thus effaced, or else of being effectively hidden under the silt deposit resulting from prolonged cultivation 2.
It is only if we bear in mind the general observations here indicated that we can fully recognize the interesting evidence which is afforded for the ancient topography of the KarghalikKhotan route by the antiquarian remains I was able to trace near almost every one of the small oases along it. These remains are not in themselves of striking archaeological value ; but they prove conclusively, in my opinion, that, though the area irrigated from each of the above-named streams has undergone considerable change in lateral directions, i.e. to the west or east, the line formed by the terminal oases and followed by the trade route has not shifted for the last thousand years, and probably for a yet longer period. I shall give an account of those ancient remains in the order in which I met with them on my journey towards Khotan. Before, however, proceeding it will be useful to note the historical references we possess for this route, and also to indicate briefly the conditions which seem to explain the stability of the line of oases which it follows.
The need of such an explanation presents itself forcibly before us when we compare this stability with the great changes which, as the account of my subsequent explorations will show, have taken place within historical times in the position of the oases fringing the edge of the Taklamakân east of Khotan, and thus also in the direction of the once important route eastwards dependent on these oases. My explorations at Dandân-Uiliq, the Niya Site, Endere, and UzunTati, establish the fact that there, during the first eight centuries of our era, a series of oases, manifestly of the ' terminal ' type, extended much further north into the great desert than the present line of small cultivated areas belonging to the Keriya district. There is also good reason to believe that the once much frequented route which connects Khotan with Cherchen, Lop-Nor, and westernmost China, though perhaps not following throughout the line of terminal oases, led considerably further north than it does at the present day.
This striking difference between the persistence of the route west of Khotan and the great variation of the line followed by the route eastwards can, I think, be adequately explained if we take into account the diversity of physical conditions. Without going into details, which would require a long digression, I may call attention to some important geographical facts. A look at the map will show that the belt of sterile ' Sai', which separal<es the line of small
I Compare below the remarks on the terminal oases of 2 Compare below the explanations given for the silt
Yartunguz and Endere, chap. xii., Domoko and Gulakhma, deposits covering the remains of the ancient capital of
chap. xiii. ; also on the ancient sites representing terminal Khotan, chap. vin. sec. ii.
oases, of Dandàn-Uiliq, chap. ix., Niya, chap. xi., Uzun-Tati, chap. xiii.