THE WILD CAMEL - OVER THE ASTIN-TAGH. 31I
as the gathering-ground of the brooks that run down off the adjacent mountains. Outside the lower end of each larger transverse glen there is a scree of sedimentary matter. These are however very flat, and their lower edges generally reach all the way down to the central part of the basin, which is occupied by an expanse of yellow clay, perfectly flat and fairly hard, as well as dry and barren, often cracked into polygonal masses and drawn out in the direction of the long axis of the valley. During the course of this day's march we crossed over seven of these minor basins, three of them being large, the others very small, and decreasing in area from west to east. They made an excellent road for marching on, being as level and as easy as the asphalt-paved streets of the capitals of Europe. Across these level expanses it is plain that the old road also led, although in this particular region all traces of it are of course obliterated; but a cairn of stones crowns every heap of gravel and also each small dividing-ridge between the several basins.
But though the great morphological features of this latitudinal valley forcibly recall the latitudinal valleys of Tibet, the climatic differences give rise to differences between the basins corresponding to differences between the mountain-ranges themselves. For while the self-contained basins of Tibet generally possess a salt lake in the middle, into which brooks and streams of greater or less magnitude gather, often from very considerable distances, these self-contained basins of the Astin-tagh are very small in area, and it is extremely seldom that their central parts receive any water at all, only in fact after copious rain. These »terminal lakes», or more accurately sedimentary plains, are therefore almost always dry, or are covered by only a very thin sheet of water, perhaps for only one or it may be two days in the year; and yet it is conceivable that there are years in which they do not even receive any water at all.
Fig. 248. SOME VIEWS FROM THE OPEN ASTIN-TAGH VALLEY.
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