ACROSS THE JARDANG DESERT TO ALTMISCH-BULAK. 71
channel between two lake-basins, many instances of which I have noted amongst the lakes of the existing Tarim.
Want of water compelled us on March 22nd to make direct for Altmischbulak. Accordingly we continued towards the north-east between the jardang ridges, the going being now in every way excellent; for we had not so much as a single threshold to cross over. After we left the short patch of forest behind us at the truncated piece of river just mentioned, köiäk became exceedingly scarce, in fact it was conspicuous by its absence. Only in one spot did we come across a few living jantak, a scrub plant which camels, both tame and wild, are very fond of. In the more sheltered places slight traces of glittering white salt now began to make their appearance pretty frequently, and in such places the clay surface was generally somewhat granular. The reason that saline crystallisations of this kind had hitherto been so rare was, no doubt, that they had been planed away by the wind, as also that the lake, at any rate in this part, had contained fresh water, as may readily be inferred from the vast quantities of mollusc-shells which everywhere occur. But when the inflow was cut off from it, and it was condemned to dry up, its water would of course assume a certain degree of salinity. In fact, the circumstances which then supervened were the same as those which exist now in the case of the Kara-koschun, in which those parts of the lake that lie at a distance from the mouth of the inflowing river, as well as those parts which are relatively cut off from the main body of the lake, are frequently so salt that the water is undrinkable. When crossing the basin of Lop-nor later we encountered areas in which the water had manifestly been strongly impregnated with salt; for one result of the wind-erosion is to bring to the surface fresh underlying saliferous layers of the clay. The causes of these saline crystallisations showing themselves thus preferably in the northern parts of the desert may have been the relatively greater humidity and the relatively heavier precipitation in the neighbourhood of the mountains.
Fig. 64. FORMATION OF A JARDANG BY A POPLAR.
Here again we came across pieces of a very large vessel of burnt clay, as hard as stone, with thick sides and small handles, and of a greyish blue colour. We picked them up close to some big toghrak-trunks, the only ones we saw in this direction; no doubt a hut or homestead once stood under their shade. Still there were no signs of dunes; nothing more than an occasional very thin layer of sand behind some sheltering jardang. On the northern outskirts of the clay desert the jardangs now began to appear in two distinct superimposed stages or storeys, though of the upper stage, which rises 2 to 3 m. above the level of the lower one, not
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