towards the middle of the lake. The layer of salt is barely half an inch thick.
It was positively affirmed that this lake was permanent, and never disappeared during the heat of summer, a circumstance which shows that its surface is on a level with the ground-water. It is clear that it occupies the deepest depression of the Kevir basin, but it can also be taken for granted that its surface fluctuates. It must rise after heavy rain, as is also manifest from the recently flooded shore belt with its wave-marks. It must shrink in summer, when evaporation and the insolation of the desert are excessive. But it must also be gradually filling up with mud brought by the temporary streams which enter it from all sides after rain. The large river we saw below Fahanunch was thick with mud, but the lake water was quite clear, so that the mud must have settled on the bottom of the shallow lake. When this process has been repeated every year, century after century, the depression must be levelled, filled up, and obliterated. Different kevir depressions are in different stages. Thus the parts of the great Kevir we crossed were quite filled up, and only allowed small sheets of water to collect on their salt layers. But here we had found a kevir with its deepest part not yet filled up, and where, therefore, the water still lay exposed. This phenomenon has its counterpart in certain of Tsaidam's salt lakes.
It was not easy to obtain any accurate notion of the dimensions of this lake. Its shores are, especially on the south-east and north-west, exceedingly flat, and a very trifling rise would cause large areas of land to be flooded. Therefore the lake may be often larger than in this year. It is, however, long, and parallel to the longer axis of the basin. On the north-eastern shore the hard detritus-covered ground abuts in terraces on the present flat shore belt. It is, indeed, intersected by a number of ravines and trenches, but its front is, nevertheless, sharply defined, and there need not be a moment's doubt as to its origin ; it is an old shore terrace left behind from a time when the sea was much larger than now.
The lake has no particular name ; it is called ab-i-kevir,
IIIFカラー高解像度
