2 RUINS EN ROUTE TO TUN-HUANG CH. L
This conclusion was soon confirmed after we had started on the day's march. Having skirted the winding south shore of the lake for about a mile and a half, the track took us to the foot of a steep ridge which edged the lake on its east side. On the highest knoll overlooking the route there rose a massive square watch-tower, T. xi., surrounded by a crumbling wall of clay. The latter looked rough and of late origin. But a short scramble along the back of the ridge sufficed to reveal again the line of the old Limes wall with its characteristic reed fascines. It started from the lake shore opposite to the one where I had last traced it, and crossed the ridge
` down to another marsh basin.
As I noticed two more towers beyond the latter eastwards, I felt assured now that the line of the wall ran more or less parallel to the end of the Su-lo Ho drainage, and that the route we were following would keep within it and probably near it. The next tower was passed, indeed, after about five miles from camp near the southern end of that second basin ; but the wall was not traceable there, evidently running farther north. For the rest of the day's march the succession of towers kept by our left above the grey horizon like a line of yellowish beacons. The stretch of scrubby desert or gravel Sai separating us from them was, however, too great to permit me to visit them without risk of losing touch with my caravan. Luckily the plane-table enabled us to fix their positions with precision from the route, showing that the distance from tower to tower averaged two to three miles.
At the end of close on ten miles by the side of a long-stretched depression full of luxuriant reed-beds and evidently containing springs, we came upon a small ruined fort of massive appearance, as seen in Fig. 154. Its walls, built of remarkably hard and well-laid strata of stamped clay, each about three inches thick, rose in very fair preservation to a height of nearly thirty feet. Fully fifteen feet thick at the base, they formed a solid square about ninety feet on each side. What splendid shelter they might give, not against human attack alone, but also against those cutting east winds, the very home of which
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