farther in the direction in which the wind blows; but they are for all time inflexibly fixed both as to position and as to dimensions, that is until such time as disintegration shall have altered the surface relations of the neighbourhood. Another proof of the immobility_ of these dunes is furnished by the fact that the first one, farthest south-west, is slightly grassed on the outside, and consequently its movement is in this way partly arrested. The other two dunes are however still bare of grass; from which it is to be inferred, that the interchange of sand is so active that grass gets no opportunity to grow on their changeable and unstable surface. They are thus more exposed to the wind, whereas the first dune gets a slight degree of shelter from the mountains on the right of the glen, although they are very low. The sand of which the dunes are built up is certainly derived from the weathered products of the spurs of these mountains and their south-western slopes, which go down gently towards the Batsa-singi. It is not conceivable, that the sand should come from any more distant locality, not only because the whole of the bottom of the valley for a long way towards the west is occupied by the last-mentioned lake and its gypsum expanse, but also because we always found the atmosphere clear, even when it was blowing a perfect gale. However, sand-dunes are, as I have already said, such a great rarity in this region, that they involuntarily arrest attention when one does come across them ; in fact, to me they seemed almost to convey a sympathetic greeting from the boundless sandy oceans of East Turkestan and the Gobi.
The pass is rounded and comfortable, though the last bit of the acclivity is distinctly felt, without however being strictly speaking steep. The summit is crowned by a cairn of stones. The altitude is 4858 m., showing an ascent of 450 m. from the bottom of the valley.' The glen that descends towards the north-west is steeper and narrower than that on the south, and is joined by several side-glens, one of which, coming from the east, is of considerable dimensions. From the pass we perceived to the N. 9° W. a minor snowy peak. In about the same direction there appeared also the western end of a salt lake, situated in a fresh latitudinal valley more to the north, and parallel to that in which we had hitherto travelled, and which leads, I was told, straight to Rudok. As far as we could see from the distance, the new lake appeared to possess about the same characteristic traits as that which we had just left behind us, being extremely flat, for the most part dried up, and with a gypsum deposit, gleaming as white as snow, where the lake formerly was. This lake is said to bear the name of Detsche-tso, after the pass of Detsche-la, which we had just crossed over. Farther towards the north-east there is said to be yet another lake, called Nas-tso, though we were unable to see it from the pass.
Camp CXXI was pitched in a little expansion of the glen known as Dungga, though according to others as Jagäng. Its absolute altitude was 4721 m. In it is a spring, which had given origin to extensive sheets of ice. From yet other springs there issued a little rivulet, which made its way through a transverse glen towards the north, though the glen cuts off only an insignificant portion of an offshoot from the main chain that we had just crossed over. Kulans, partridges, and wolves occurred in this region.
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