enough by a row of five small ` P`ao-t`ais', such as usually adorn main stages on the modern Chinese high roads of these parts and of Hsin-chiang. It was a curious sign of administrative attention extended to the river's right bank where no definite track could be seen, though camel caravans probably descend along it on occasion to An-hsi. Three miles farther on we reached a small ruin, T. xL. a, lying close to the river and almost exactly opposite to the above-mentioned two towers on the left bank. It consisted, as the plan Pl. 14 shows, of a small walled enclosure, about i9 feet square inside, with a tower 8-s- feet square at its north-eastern corner. This tower, built of bricks of the size usual in structures of the Han Limes, 13 inches by 7 and 4 inches in thickness, bore a distinctly ancient look. In order to strengthen it, walls of later construction had been added to it on the north and south. The walls of the enclosure seemed of later date and moreover showed clear signs of repairs. The addition, usually at a later period, of walled enclosures to watch-towers is of frequent occurrence along the Limes on both sides of Tun-huang, and there are examples of it also at other watch-stations farther east.6 The examination of what refuse was traceable near the north wall and in the little conning room on the top of the tower yielded no dateable remains ; nor were ancient potsherds found in the sandy soil outside.
Another tower, T. xL. b, was within sight about two miles' distant to the east, at the entrance of the gorge-like portion of the defile. Above it there rose a third tower, T. xL. c, conspicuously placed on the top of a bold hill, which forms the last projection of the spur overlooking the river from the north and facing Wan-shan-tzû. On moving towards T. xL. b we passed over gently rising ground, where the bare clay was completely furrowed into Ydrdangs running from ENE. to WSW. and from 5 to 7 feet in height.
We had covered about half the distance to T. xL. b when a dark line of gravel crossing the eroded ground on our right towards the river attracted our attention. On reaching its western end it proved to be an unmistakable agger, running with a bearing of S. ioo° E. towards the eastern end of the defile. The bank, thickly covered with gravel, was about 34 feet wide at the foot and about 9 feet at the top and rose to about 8 or 9 feet. To the north of the agger a shallow ditch about to feet wide at its bottom marked the ground from which earth had been dug to form the mound. No trace of fascines or other reinforcing material could be found in the construction of the latter. On the opposite side of the ditch ran what appeared to be a smaller mound, nowhere more than about 5 feet in height, forming a kind of counterscarp. The direction of the agger pointed straight towards T. xL. a, though farther west wind-erosion had completely effaced its remains. There could be no doubt any longer that it was there that the Limes had been carried across the river.
Having followed the line of the agger for over half a mile we turned to the watch-tower T. XL. b (Fig. 205) rising a short distance to the north of it on higher ground. It proved to be exactly of the type of the towers guarding the Tun-huang Limes and had remained in remarkable preservation. It measured 20 feet square at its base, was built of solid layers of stamped clay, 6 inches thick, and still rose to 26 feet in height. Plenty of mat-marked dark potsherds lay around it, also many large stones which might once have been stored on the top for defence.' A well-preserved Wu-chu coin of the large type was picked up close to the tower.
I next ascended the steep detritus-covered spur which rises to the north of the defile. Small water-cut Nullahs fissure its slopes on all sides ; but the surface of the narrow ridges between can have suffered little change, as proved by the clear traces at many points of an old track ascending to the top. This was found by clinometric readings to rise more than 30o feet above the riverine flat. The view from the summit was very extensive. It comprised the whole of the defile and the broad valley eastwards as far as the great circumvallation of Bulungir (Map No. 40. B. 4). The
6 See Serindia, iii. PI. 34 ; also below, pp. 377, 389, 394. 7 Cf. ibid., ii. p. 738.