CH. LX RECORDS FOUND NEAR FORT 117
tunnel belonged to the first two decades after Christ, the reign of Wang Mang the Usurper. In both sets the documents seemed to have been addressed to some superior officer. The presumption was that here we had struck the site of some sectional headquarters for this part of the Limes. It received support when I learned that at least one of the records certainly emanated from the general officer commanding at Tun-huang, while several others contained reports or orders to superior officers holding charge of ' the barrier of Yü-mên.'
All along I had surmised that this ancient frontier station of the ' Jade Gate ' must have been located during Han times at some point along the line we were exploring. But where was its exact position, and had this always been the same ? It was impossible as yet to arrive at any definite answer. But with the documents before me I now began to realize what advantages this site offered for a chief watch-station commanding the ancient route westwards, and how little reason there was for doubts about the antiquity and the purpose of the ruined fort at this point.
Well withdrawn behind the protective line of wall and towers, and defended to the north-west and south-east by impassable marshes, its position was admirably adapted to serve both as a point d'aftj5ui for the posts along this portion of the Limes and as a station controlling traffic along the main road. Only the day before I had discovered that the fort lay exactly in the line of a secondary wall running due south from the main wall in the direction of Nan-hu, and, though badly decayed, still traceable on the Sai. This secondary wall showed exactly the same manner of construction with alternate layers of gravel and fascines, but only a thickness of a little under five feet. It seemed clear from the first that this transverse wall was a subsequent work ; for without the main wall beyond, it would have been quite easy to turn it from the north flank.
But what had been the true object of this cross wall ? I had first thought of an inner line built, not for defence, but for purposes of police control in order to prevent the unauthorized entrance of individual travellers into Chinese territory. But evidence subsequently accumulating
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