154 ROUTE ACROSS DRIED-UP LOP SEA CH. 1X
Kuruk-darya and still marked by trunks of wild poplars and tamarisks dead for centuries. Then we came upon the ruins of a small walled castrum which, as close examination showed, had served as an advanced point d'appui for Chinese missions and troops where they first reached habitable Loulan territory from the side of Tun-huang. Its walls, built with alternate layers of carefully secured reed fascines and stamped clay, and remarkably well preserved after two thousand years' exposure, showed such close agreement in all constructive details with the westernmost extension of the ancient Han border wall in the desert of Tun-huang that there could be no doubt about its dating, just as this does, from the first military advance of the Chinese into the Tarim basin. It represented the western bridge-head, as it were, of the route by which that advance was made possible.
The walls of the castrum, constructed with the same technical skill as on the ancient Tun-huang Limes, had withstood well the attacks of that most formidable enemy in this region, wind erosion. Its destructive force, at work for two thousand years, had not succeeded in seriously breaching these massive walls. But inside the circumvallation the force of the wind had wrought terrible havoc, scooping out hollows down to twenty feet and more below the ground level. However, in a refuse-heap sheltered by the north wall, dated Chinese records survived, belonging like most of those found at the Lou-lan station to the period preceding the final abandonment of the route, soon after the end of the third century A.D.
Beyond this large fortified station other remains were traced. Of special interest was a small ruined fort discovered some three miles to the north-east on the top of a precipit-
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