196 ANCIENT SITES OF THE KHOTAN OASIS [Chap. VIII
hiding the relics 10. But it only needed a careful examination of this very feature to dispel the notion of the conjectural catastrophe.
The strata containing the old remains are everywhere covered by a considerable layer of pure soil, which from the first interested me greatly on both antiquarian and geological grounds.
It shows a fairly uniform thickness from 9 to II feet in the banks near Allama, while in those exposed south of Khalche it varies from a minimum of I I feet to a maximum of about
20 feet at different points. This layer is easily distinguished by its light colour from the
` culture-strata' below, and is absolutely free from remains which might indicate subsequent occupation of the site. The latter fact is realized by the villagers, who everywhere would
readily show the limit up to which the old stratum extends, and above which there begins
what they call bekâr yer (` unprofitable ground '), i.e. the natural soil, yielding neither gold nor antiques. Wherever I examined the earth overlying the ` culture-strata ' it proved exactly the
same in substance and colour as that which is to-day turned up by the plough of the Yôtkan cultivator. Another important fact, which the careful examination of this layer established with equal clearness, is the total absence in it of any traces of stratification.
These observations conclusively prove that the present position of the culture-strata of Yôtkan cannot possibly be the result of a great flood or series of floods which have over-
whelmed the site ; for such a catastrophe, if it had ever occurred, would have been bound to leave its mark in stratified deposits of varied character. But the facts thus observed on the spot did more than dispose of a vaguely suggested hypothesis ; they also led on to what I still hold to be in the main the true explanation of the deep cover under which the remains of the old town have rested.
In my ` Preliminary Report ' I did not hesitate to express my belief that this great layer of pure soil, above what we can show to be the débris accumulations of the ancient capital,
was due mainly to silt-deposit, the necessary result of intensive and long continued irrigation ' 11.
The reasons for this conclusion were derived solely from what local observation had shown me within the Khotan oasis. Having since my return fully realized the geological interest involved
in the question and its close relation to the much-discussed problems of loess, I feel specially gratified that the opinion then formed on the spot has stood the test of the analysis to which an exceptionally qualified geologist, Prof. L. Lbczy, has been kind enough to subject the specimens of soil brought back by me from Yôtkan.
Without anticipating the information which Professor Lbczy's instructive communications in 1903 enabled me to gather with regard to a very important subsidiary factor, I may be allowed
to state in the first place the case as it presented itself to me solely on the basis of my local
impressions, and as I have already recorded it in my Personal Narrative 12. Cultivation in the Khotan oasis, as everywhere else in Eastern Turkestan, demands constant and ample irrigation.
The Kara-kash river, from which the water for the Yôtkan fields is drawn in the spring and
summer, carries down during this season enormous quantities of disintegrated soil from the eroded ranges it drains. Its water, full of suspended sediment, and hence of a dark yellow or
chocolate colour, is allowed to stand on the carefully terraced fields until it is completely absorbed or evaporated. As all the fine detritus or mud borne down by the river-water thus finds its way to the fields and is ultimately deposited there, the accumulation of silt over the latter must be constant and relatively rapid. Since the conditions are exactly the same in the
10 See Hoernle, Report on C.-A. antiquities, i. p. xiii ; " See Preliminary Report, p. 29.
Mission D. de Rhins, iii. p. 126. 12 Ruins of Khotan, p. 263.