CHAPTER LIV
BY THE ANCIENT WALL NORTH OF TUN-HUANG
FROM the height of the town wall a watch-tower had been sighted to the north-north-east, and for that we set out on the morning of March 25th, with an icy wind sweeping down from the east. At first our progress was greatly impeded by the swampy condition of the ground, which was being purposely flooded for sowing. Large patches of the scrub-covered waste, once no doubt fields, had been cleared by burning, and water was now being brought to them in a rather erratic fashion by damming up channels which originally might in parts at least have been cut for irrigation. The camels and the men, now on foot, were forced to great détours and remained far behind.
But with a few of my people on horseback I struggled across to the ' Pao-t'ai,' which proved to be about four miles off. It was, as I had surmised from the first, a watch-tower of ancient construction. The material here consisted of hard lumps of salt-impregnated clay quarried from the low ridge on which the tower was raised ; but any doubt as to its age was removed by observing in this strange masonry the same layers of reeds and tamarisk twigs at regular intervals which were characteristic of the towers guarding the old wall farther west. The whole formed a remarkably compact mass about twenty feet square at its base, and still over eighteen feet high, the permeating salts acting apparently like a sort of cement. Its solidity could be gauged from the fact that, though wind erosion had attacked and worn away the natural clay beneath the corners, the structure overhung there without any injury.
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