224 WESTWARDS TO LADAK.
a height of several meters, occur only in those parts of the bed which are at a great distance from the existing lake. The gypsum between the surviving sheets of water is level, owing to its having been exposed at relatively so recent a date that wind and weather have not yet been able to sculpture its surface ; but in the case of the deposits that lie farther away, and consequently at a higher level, they have been able to produce some result. These gypsum formations possess however but little power of resistance, and after a sufficient interval of time has elapsed they will be entirely planed away. Hence we did not observe them at any great distance from the Lakor-tso and the other lakes. They are evanescent phenomena. After that we came to the open lake, which, although in itself small, is nevertheless bigger than the open surfaces of the Luma-ring-tso and the Tsolla-ring-tso. Close along the entire southern shore of the lake runs a narrow fringe of pure white gypsum, interrupted at one point only by an isolated pool of water. There is a similar belt of gypsum along the northern shore, but it appeared to be broader. Shortly afterwards we passed the broadest part of the lake, after which it narrows again towards the north-west. This lake, like all the others on the high plateau of Tibet, is long and narrow, and for the whole of the next day we continued to follow its shore. On the whole half the lake-basin was covered with water, the other half being white gypsum. The expanse of gypsum is broadest in the east. According to my hypsometrical instruments, this lake lies somewhat lower than its predecessor, or at an altitude of 4346 m.; but its relatively greater volume would appear to indicate, that it has not yet advanced so far towards extinction as its more southern neighbours, though in this matter the altitude above sea-level is of less moment than the inflow of water. Although the lowest slopes of the mountains on the south reach all the way down to the lake shore, there are no old strand-terraces or beach-lines visible on them, this being, I dare say, due to the fact that that shore is relatively sheltered. Farther on however they show quite distinctly in a more exposed position on the northern shore.
Passing over a threshold between the foot of the mountains on the south and a small free-standing butte, we reached a spring, the rivulet from which had given rise to a ribbon of ice. The altitude was 4470 m., and the name of the place Tsebu, while a black bluff to the S. 52° W. was said to be Schuschü. The grazing in this locality was comparatively good.
Porphyritic tuff cropped out in a watercourse near the shore, and a little bit farther on a red variety of rocklike conglomerate. The strata were indistinct; but the horizontal stratification was easy to make out in the beds of gypsum beside the lake.
November 8th. Continuing on towards the north-north-west over ridges and offshoots from the mountains, we soon came in sight of the lake again. In one place this appeared to be cut in two, in that it consists of two basins separated from one another by a marshy tongue of land, both short and narrow, just as is the case with the Luma-ring-tso and the Tsolla-ring-tso. All day we travelled quite close to the southern shore of the western basin of the lake. Here also, except for one or two short interruptions, the lake is encircled by a girdle of gypsum, with small elevations like platforms and pyramids. Between these and beyond them we saw everywhere open water; while on the northern shore there is an even
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