国立情報学研究所 - ディジタル・シルクロード・プロジェクト
『東洋文庫所蔵』貴重書デジタルアーカイブ

664   THE WESTERNMOST LIMES WALL   [Chap. XVIII

mountains on the south. The larger sheets of open water to be found within the marshes extended, at the time of my visit, up to r 2 miles in length, and all were fringed by dense reed-beds. Salt-covered bogs stretched further away in the line of the drainage north-westwards and showed signs of being liable to periodical inundations. To what extent, if any, these might be caused by overflow from the Su-lo Ho bed, or by percolation from the marshes and lakes which further to the east, from the vicinity of T. xvii onwards, are certainly fed by the river, I could not investigate with sufficient closeness. In some other parts of these depressions, mainly near the Lop route and to the south of it, all trace of water had disappeared from the surface, but the growth of tamarisk bushes, with other hardy scrub and thin reed-beds, showed that here also subsoil water was near it.

The marshes and salt-encrusted bogs were found quite impassable for horses or camels, and in most places for men, too. Generally detours, of miles were needed to take me from one tower to another round the edges of the marshes or over strips of less treacherous ground. The remains of the towers, owing to the commanding position they invariably occupied, proved most helpful in guiding me from a distance. But, after the swamps had been passed, I still had to search for the remains of the ancient wall. Along the section extending from T. x to T. xvii, a total distance of nearly i8 miles on the line of watch-stations, the wall had been carried unfailingly over every bit of firm ground capable of offering a passage for the enemy's inroads, and right down to the edge of the marshy inlets. Across their bottoms the lakes and bogs necessarily took the place of the wall, providing a natural defence and thus saving the labour of construction over a considerable number of miles. How important this gain was can easily be appreciated if we take into account the huge difficulties of supplies and transport which must have attended the maintenance of adequate labour for building the wall in absolute desert and often at great distances from drinkable water.

The gain resulting from this use of the great natural obstacle offered by impassable marsh must have been even greater along the eastern section of the line here under consideration, which extends from T. xvit to the west shore of the Khara-nôr near T. xxxi. c, and is of about the same length as the other. Along the greater part of this section the belt of marginal lagoons and marshes formed by the Su-lo Ho is so wide that the construction of a wall along its southern edge appears to have been thought unnecessary. In any case, it is only on two short stretches of this portion of the line, marked by the towers T. xix—xx and T. xxii. b, c, that I was able to trace remains of the ancient agger, and as both these stretches are found just where the Su-lo Ho happens to flow in a well-defined narrow channel between firm banks, the exception here may well be held, as it were, to confirm the rule.

I must add, however, that where the soil was soft and scrub-covered, as it was near the marshes, the eye sometimes failed at first to discover the traces of the agger; for the remains of the rampart constructed, here as elsewhere, with alternate layers of earth and fascines had on such ground suffered particularly marked decay through the moisture rising from below. The coarse but abundant vegetation, which finds nourishment in this salt-permeated soil, necessarily also helps to obscure any remains that may survive. It was, of course, different on the gravel plateaus of the section further west, from T. x to T. xvii, and there ordinarily it did not take long, after once their edges were gained, to discover the familiar track of the wall running straight in the direction of the nearest watch-station.

A general observation of distinct geographical interest, which was obtained from what I may call the two marsh sections of the Limes, may also conveniently find brief mention here. It had occurred to me from the beginning of my explorations on the Limes that the line of its wall, drawn

Marshes and reed-beds in depressions.

Wall guards ground between marshes.

' Wet border' towards Khara-nör.

Difficulty of tracing wall over soft soil.

Wall as gauge for ancient water-level.