56 THE KURUK-TAGH AND THE KURUK-DARJA.
rounded hills, very often pierced by erosion gullies, in the ends of which the light yellow clay was always exposed. Below the terrace extends a gently sloping belt of saj, which merges imperceptibly in the level clay desert. At a very short distance away the Kuruk-darja betrays its course by its jar terraces, its tamarisk-mounds, and the kötäk on its banks. After the termination of the greater part of the gullies which issue from the confines of the mountains there is a gravel-and-silt slope, down which the rain-water rivulets, radiating outwards like deltas, are clearly indicated. For a short distance we kept to the edge of the upper saj. The clay was distinctly stratified, the beds being sometimes horizontal, sometimes with a gentle
Fig. 51. CAMPING BETWEEN THE JARDANGS.
inclination, the dip being in one place 20° E. Descending by a narrow, barren transverse gully, we once more came out upon the clay desert, which I proposed to cross south-eastwards until we struck the belt of sand. In this locality there exist immense quantities of Lirnœa shells, some amongst the low sand, others amongst the loose clay. In places they lie so thickly that they could be gathered up by thousands; and they accompanied us throughout the rest of the day's march. Seeing that they are in this way distributed pretty evenly over a tolerably wide area, it is fair to suppose that we were travelling across the bed of a former lake, or a chain of lakes and marshes, linked together by a river, or else one or several marginal lakes which extended by the side of the old river. Otherwise the mollusc-shells would have been arranged in rows. It is likely too that the wind may to some extent have assisted to scatter them over the surface, for they are light and
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