We were now surrounded on every side except the north by fairly high mountains, giving rise to picturesque scenery, which unfortunately I was unable to photograph because of the violence of the wind. Along the slopes we perceived in many places the characteristic dark lines and cornices, the origin of which cannot admit of a moment's doubt when their perfectly horizontal courses are borne in
mind.
At the spot where we first struck the lake, the rock consisted of very hard conglomerate, dipping 3o° towards the N. 52° E., and at the point where we again left it behind us the same specimen of rock was clipping 83° towards the N. 3o° E., though of this I am not perfectly sure. The strata appeared however to dip predominantly towards the north and north-east, for the southern slopes of the mountains are always steep, as they were during the preceding day's journey. The soil of all the low, level expanses, or valley embouchures, that open upon the lake is heavily impregnated with gypsum. It gleamed white through the sand and gravel, and clouds of white dust were whirled up in the track of our caravan. This expanse of gypsum, with its white mounds, pyramids, and knobs rising only a few meters from our camp, formed a very strange and unusual spectacle. Its outer margins were just as sharply drawn as those of the other similar areas which we had passed. This glittering white expanse, embedded amongst the dark mountain walls and lying beside the green waters of the lake, gave to the scene a remarkable air of chilliness and desolation; in fact, it looked more like a snow-drift, in which the snow had assumed unusual shapes, or like the rough and porous surface of a glacier exposed to the melting influence of the summer sun. Apart from these little elevations, the surface of the gypsum expanse was perfectly level, that is to say its base forms practically a plain. That the gypsum was derived from the lake, and was deposited on its former bottom, is perfectly evident, for the white level expanse continues a little way in under the water. Originally these gypsum deposits were horizontal, the horizontal rings can be distinctly seen in the sides of the mounds; but erosion, rain, and wind have all conspired to eat them away and make their surfaces irregular. The effects which the wind produces here during the dry seasons of winter and spring are the same in kind as those which we have studied in the Desert of Lop, though the irregularities of surface there are of a different character, namely the parallel jardangs. When you walk between the mounds towards the interior of the expanse, and find that the white surface is soft and brashy, often thin and powdery like potato flour, you are astonished that the entire deposit was not long ago blown right away by those violent westerly winds. Seeing however that this particular expanse rises only a very slight degree above the existing level of the lake, at our camp only about 2 m., it would seem that the area has been exposed at relatively so recent a date that the wind has not yet been able to complete the work of destruction. A specimen of the gypsum which I brought home with me has been subjected to a preliminary analysis by Mr. G. Aminoff, and he tells me that »it consists for by far the greater part of round particles of gypsum, amongst, which occur a smaller number of angular grains of quartzite.» The latter are being carried thither now every day by the wind, and formerly, when the area was under water, by both wind and brooks. The river appears practically to disappear in the
IIIF Color HighRes
