978 IN THE DESERT DELTA OF SISTAN [Chap. XXX
open and the atmosphere after rain was of rare clearness, we failed to discover any ancient remains, whether ruined structures or marks of prehistoric occupation, for fully five miles. A small ruin passed in the second bed from the north was clearly shown by its bricks, 12"X 12"x 2", and the glazed potsherds near it to belong to late Muhammadan times, like the domes of Yak-gumbaz and the Muhammadan graveyards to the south-west and north of it.
But when the fourth and last of the river-beds, known as the Hadâli outlet, had been passed, we very soon sighted again a line of ruined posts extending from boundary pillar i6, as marked on the map, to the ESE. The first, R.R. xxii, lay just across the boundary in Afghan territory, and into this I did not hesitate to commit here a short trespass. The ruin was badly decayed, but the rough measurement still possible showed that like the next two it was that of a massively built small post or tower, of the same size and type as R.R. xxv to be described presently. Like the other posts farther on it was built on a wind-eroded terrace on which relics of the chalcolithic period could be seen. Only a quarter of a mile off rose a somewhat better preserved post, R.R. xxiit ; here courses of bricks set on edge and measuring 24"X z 2"x 4", like those in the stations on the north-western portion of the line, were clearly recognizable. R. R. xxiv, about mile beyond, was again badly decayed ; but the ruin xxv (Fig. 502), which we reached after proceeding another half-mile, fortunately revealed its plan and construction quite clearly (Pl. 59).
It still rose to over io feet and retained its vaulted entrance on the south. Within walls 6 feet thick on three sides and 9 feet on the fourth, there was a single chamber, i6 feet by 8+. The bricks, well made and full of wheat straw, which formed the vaulting both over it and the entrance, measured 42" x 6" and were set on their longer edge. The additional thickness of the west wall was needed to leave room for stairs 3 feet wide leading to an upper story. The features of this remarkably massive little structure left no possible doubt that it was meant for a watch-tower capable of defence, and its erection on the top of an erosion terrace fully agreed with this.
The line of towers could be seen to have its continuation to the SE. along similar detached terraces. But the evidence already obtained here as to its character was so clear that I did not consider myself justified in farther extending my trespass on Afghan territory, against which I had been warned. The direction of the defensive line thus traced definitely pointed to its having lain towards the western extremity of the Gaud-i-Zirrah. There its flank could rest quite safely, like the north-western section, where, as we have seen, it touched the edge of the Haman. For the break which appears to occur in it just along the stretch where the Rûd-i-biyaban debouches in several outlets, it is difficult to offer any conclusive explanation. It is possible, even likely, that the beds here have greatly shifted during historical times and considerably changed the aspect of the ground. But the possibility should also be kept in view that cultivation, of which there is here definite evidence in comparatively modern times, may well have helped to efface earlier remains.
Taking general stock of the observations made along the whole chain of watch-posts that I had been able rapidly to survey, it may be confidently asserted that it dates back well before Muhammadan times. This is proved by all constructive features, the great size of the bricks, and the absence of glazed pottery remains. These posts, built, as it were, ` to specification ', clearly point by their uniform plan to a contemporary origin. How far back this lies only systematic excavation of a number of them might be expected to show. Impressions derived from comparison with other ruined structures examined by me in Sistan, together with quasi-historical considerations, incline me to look to the early centuries of our era as a possible approximate dating. A protective chain of watch-stations is not likely to have been needed during periods when efficient rule prevailed over the whole of Iran, including Khorasan, as it certainly did during the greater portion of the Sasanian period.