where we crossed it was about two miles wide.4 Beyond it the ground was covered with fine sand supporting an abundance of reeds, tamarisks and scrub.
As we were moving across it towards the low banks of clay marking the foot of the glacis, I noticed moist soil at about six miles' distance from camp. It was clear proof of the presence of subsoil water here close to the surface, and on digging a well we found a plentiful supply at a depth of only three feet. It tasted perfectly fresh, far better than the water of the wells at Kum-kuduk and Yantak-kuduk. Considering the utterly barren nature of the hill range overlooking the whole valley, the comparative nearness of its crest, and the extremely scanty drainage which can ever descend from it in the short channels cut into its glacis, it appeared to me very unlikely that the water found here and at other points along the northern edge of the valley could have any other source than a flow of subsoil moisture fed from the head of the valley near Bésh-toghrak. The origin of this subterranean water-supply is an interesting question which will best be discussed later on in connexion with that of the hydrography of the ancient terminal basin of the Su-lo-ho farther east.5
The sand across which we moved became steadily coarser until we reached the gravel Sai below a line of low clay banks manifestly eroded by water, like the banks of a river. Here I noticed quite clearly an old track, distinct though only faintly impressed, coming from west-south-west. No footprints of wild camels were observed anywhere near it. It was the same track that Lai Singh and Afrâz-gul coming from their Camp 96 had traced for a much longer distance and found in places actually marked by small cairns. Their report, as recorded below, fully bore out the impression I gained here that it was a path which had first been trodden by men. Following the line of clay banks eastwards we soon lost the old track in a reed-covered depression. Beyond this we arrived, at a distance of about fourteen miles from Yantak-kuduk, at a bold Mesa, about eighty feet high, which had clearly been detached by erosion from a foot spur of the hill range projecting into the trough of the valley. I clambered with difficulty to the top, in order to fix the plane-table, and found, to my surprise, remains of dead tamarisk woods Considering the position, there could be no possible doubt about the antiquity of these remains. They suggest distinctly moister climatic conditions than those now prevailing ; for at that height neither subsoil water nor a surface flow could possibly account for the former growth of vegetation.
From the top of the Mesa I noticed ground which looked as if it might hold patches of open water. So I turned now to the east-south-east, and after about two and a half miles' march across reed-beds reached a salt bog extending for a considerable distance in the same direction. It was fully seventy yards wide where we skirted it near its western extremity. The salt-encrusted soil immediately to the north of it proved water-logged below the surface, and it was with some difficulty that we extricated the camels which were foundering on the treacherous ground. The presence of this well-defined marsh-bed close to the foot of the low and utterly barren outer hill range of the Pei-shan distinctly pointed to a considerable flow of subterranean drainage from the head of the valley eastwards. After another mile's march over light sand we pitched camp and found water at a depth of only four feet, which, though tasting slightly brackish, was yet drinkable. The well passed through a thin layer of shôr embedded in fine sand.
Next morning we moved east-north-east in the face of a bitterly cold wind from the same direction, and passed over ground mostly covered with hard salt-impregnated clay. After a march
4 Owing to a mistake in the compilation of our several routes the symbols indicating the shôr-covered ground passed on my route north of Kum-kuduk, as well as that of the well dug beyond it, have been shown in Map No. 35. A. 4 about
two miles too far northward.
5 See below, pp. 334 sqq•
6 The piece Kum. 03 (see List at end of section) is a specimen of this wood ; see also above, p. 320, C. cvi. 03.