238 AN-HSI, THE ' WEST-PROTECTING' CH. LXXI
a small modern reception-hall built near it. I t seemed very probable that the core of the tower was ancient, and that continuity of local tradition had something to do with selecting the spot where the road passed through the Limes for what Chinese custom treats as the conventional mark of a district headquarters boundary.
The ruined town, situated about two miles south-east of the present An-hsi on a barren waste of fine gravel, was also an interesting place to examine. According to local information it had been deserted towards the close of the eighteenth century, after repeated destruction by fire, and its interior was absolutely clear of buildings. The enclosing walls, solidly built in stamped clay of about fifteen feet thickness, formed a square of about 600 yards ; but that they could not be of any great age was certain from many indications. All the more striking was the extraordinary effect which wind erosion had produced upon them. The east face, and to a somewhat lesser extent also the west face, had been breached at short intervals by deep fissures resulting from the scouring with driven sand. Many breaches thus effected reached down to within five or six feet of the ground, and at the north-east corner, as seen in Fig. 208, they had been carried down so low that the wall there has been razed off altogether.
The cuttings which had not yet advanced so far were always broader on the east than on the west face of the wall, and the scouring which produced these trumpet-shaped troughs could be studied with clearness at their bottom. One measured cutting of average size was thirteen feet deep and eight broad on the east side. The sand carried by the prevalent east and north-east wind through these troughs had accumulated under the shelter of the west or inner side of the eastern wall face in dunes up to eighteen or twenty feet. Outside this face but little drift sand remained. Whatever sand is carried through the breached east wall is subsequently driven across the open interior to repeat its work of destruction on the west wall.
While the east and west faces are thus gradually undergoing erosion which will ultimately efface them altogether, the town walls facing north and south parallel
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