Sec. v] LOU-LAN RE-ESTABLISHED AS SHAN-SHAN 341
to forward provisions to meet the Chinese envoys ; but being frequently exposed to the oppressive raids of the soldiery, they at last resolved that it was inconvenient to hold intercourse with China. Afterwards, again on the revolt of the Hsiung-nu, they several times intercepted and killed the Chinese envoys.'
This passage is of special interest for the ancient geography of the Lop region ; for it clearly indicates the extent eastwards of the territory then known to the Chinese as Lou-lan, and also throws light on the serious physical difficulties with which the use of the route leading through it from Tun-huang had already to contend, whether for military or commercial purposes.
[The topographical details of the line which the direct route through the desert from Tun-huang to the Lou-lan territory had followed, during Han times and for some time later, were first cleared up by the explorations I effected in the winter of 1914. The main results have been briefly given in the preliminary report on my third Central-Asian expedition, published in the Royal Geographical Society's , ournal)2 A full account of these explorations and of the archaeological evidence which enabled me definitely to trace the ancient Chinese route to Lou-lan can, however, be made available only when the time comes for preparing the detailed Report on my journey of 1913-16. In the meantime I must content myself here with a reference to the above preliminary account and a statement concerning the special topographical point to which the Han Annals, as above quoted, refer.
I believe that the designation of Po-lung-tui, ` the White Dragon Mounds ', was applied by the Chinese, from the time of the first opening of the route, to that particular portion where it skirts and then crosses the extreme north-eastern extension of the dried-up salt bed of the ancient Lop-nor. There strings of salt-coated clay terraces, all undoubtedly carved out by wind-erosion from what was the lake bottom of an earlier geological period, run parallel to each other in the direction from east-north-east to west-south-west, and extend for a considerable distance along both the western and eastern shores of the ancient salt-encrusted lake bed.13 Their fantastic and yet curiously uniform shapes would readily suggest to Chinese eyes the form of ` a dragon in earth which was without a head but had a tail. The highest rise to two or three chaug (twenty or thirty feet) ; the lowest to over one chang (over ten feet). All of them are turned towards the north-east and resemble each other.' Thus a Chinese commentator of the Former Han Annals, writing in the third century A. D., accurately and graphically describes them.14
These belts of salt-impregnated ` Mesas ' form the most striking feature of the dismal ground crossed by the last two marches but one of the ancient route before it reached the extreme eastern limit of the Lou-lan area which once possessed water and vegetation. This explains why the Wei Ho, where it describes ` the route of the Centre ' which led direct from Tun-huang towards Kuchâ, places the Lung-iui or ` Mounds in the shape of Dragons ' immediately before the station of
the ancient Lou-lan'.1u My explorations of 1914 have proved that on the line followed by the old Han route, the Wei lids route of the Centre ',16 there was, for a distance of over 120 miles, a stretch of ground to be crossed which in Han times was already a waterless desert of salt, bare clay, or gravel. This forbidding waste lay between the line of wells still available in the long-extended depression which connects the terminal Su-lo Ho drainage with the easternmost end of the ancient salt lake-bed of Lop-nor 17 and the furthest point reached by the Kuruk-daryâ, the river branch
12 See Geogr. Journal, 1916, xlviii. pp. 226 sqq.
" Cf. ibid., p. 228.
" Cf. Chavannes, T'oung-pao, 1905, pp. 529 sq., note 7.
'6 Cf. ibid., p. 529.
16 For the reason of this designation, cf. below, chap. xt .
sec. ii ; also Desert Cathay, i. p. 525.
37 As regards this well-marked depression or valley connecting the terminal bed of the Su-lo Ho and the northeastern extremity of the salt-encrusted Lop-nôr basin, cf. Desert Cathay, i. p. 535 ; also below, chap. xlv. sec. i.