The tower is known to the people of the oasis by the name of T`ou-tun , ` the chief
(or first) tower'. This application of a special name, like the continued occupation of the post down to later times, suggests that this section of the Limes, otherwise wholly deserted, is crossed somewhere in the vicinity by a track still occasionally frequented. And in fact, one of our men from Ying-p`an averred knowledge of a route leading northward to a place vaguely described as ` a hundred li off in the Pei-shan '. But for what purpose the local people visited it we did not succeed in eliciting.
The examination of the wall to the north-west of T. XLIII. I. and of the ground immediately beyond it revealed two curious features. At a distance of about 4o yards from the tower survived what looked like the reed fascine foundations of four small structures built within, and immediately against, the Limes wall. They measured about 13 feet from north to south and were separated from each other by intervals of about 18 feet. Could these mark the position of shelters erected at a point of the wall which seems to have required special watch and guard ? This need may have been occasioned by the proximity of a succession of swelling gravel ridges, which here stretch from the north to within fifty yards or so of the wall and threatened its security. It is evident that they greatly facilitated unobserved attack. On the most westerly of these ridges were found two massive stacks of tamarisk brushwood, at points about 5o and 6o yards to the north-west of the previously mentioned position on the wall, as shown by the plan (Pl. 15). They measured 13 feet square at the basè and still rose to over 7 feet in height. On a second ridge to the east and at about the same distance, we found a somewhat smaller stack of reeds, containing also horse-dung. It occurred to me, as I looked at these stacks, that by setting them on fire, the foreground would be well lit up at night and risks from sudden attack at this point much reduced. But, of course, the possibility of other explanations must be kept in view, e. g. the intention to use them for signal fires.
Beyond T. x1.III. 1 the wall could be followed eastwards for half a mile. Then it became completely lost in a wide depression of soft eroded clay covered with closely packed tamarisk-cones. We continued our search over a distance of about three miles beyond the tower without coming upon traces of the wall. Nor had Lai Singh been able to find any when he pushed an independent reconnaissance north-eastwards, to within sight of the Sai marking the foot of the Pei-shan. This and my previous experience of the very deceptive nature of such ground decided me to seek a fresh base to the east from which we might endeavour to locate the continuation of the line of the Limes. Practical considerations as regards water, doubly important now with the advance of the season, and the necessity of husbanding time in our move towards Su-chou and the Etsin-gol, indicated as a suitable place for this purpose the next halting-place with a well on the route to Su-chou. Before, however, recording the work carried out from that point, some remarks may be offered here concerning the geographical position of the Hua-hai-tzû basin and its bearing upon the line followed by the Han Limes.
The geographical interest of the Hua-hai-tzil basin, as it may conveniently be called from the designation of its single oasis, is due to the fact that it forms the terminal depression of a small but independent and typical drainageless area, intermediate between the far larger depressions in which the waters gathered by the Su-lo-ho and the Etsin-gol finally disappear. The northern
limit of this area is marked by the southernmost hill range of the Pei-shan, the southern by that portion of the outermost Nan-shan which lying approximately between the 97th and 98th degrees of longitude separates the catchment area of the Su-lo-ho from that of the Pei-ta-ho or Su-chou river (Map No. 41. c, D. I, 2).
On the west and east the limits are not so sharply defined. Towards the Su-lo-ho the watershed is formed by an outlier of the Nan-shan which descends west of Ch`ih-chin-sê and flattens out in