46 THE KURUK-TAGH AND THE KURUK-DARJA.
torrents are able to reach down to the lowlands, and enter the former river-bed. The gullies of which I have just spoken lie undoubtedly along the line of continuation of some more noteworthy transverse valley or glen in the Kuruk-tagh. They have in course of time brought down with them vast quantities of solid matter, so that, as I have already suggested, the augmentation and spread of the detritus slope have at all events encroached upon the left bank and affected the position of the river as a whole. Immediately beyond these gullies, the Kuruk-darja bends so far to the south that it, together with its poplars, disappears completely out of sight. From the perfectly level expanses of barren soil, as hard as asphalt, and the patches of yellow argillaceous silt it is perfectly evident that the water spreads out and forms shallow lakes, which must evaporate and dry up very swiftly, leaving behind them the silt as a sediment. One of these expanses was pretty large, and afforded excellent ground to ride over.
Fig. 42. TERRACE FORMATIONS AT THE SOUTH FOOT OF THE KURUK-TAGH.
Then we once more approached the middle terrace, which possibly coalesces with the upper terrace to form a yet larger one. This last is frequently pierced by sluice-like openings, through which the rain-torrents pour down into the Kuruk-darja. At one or two kilometers' distance we again perceived, towards the north, the extreme outliers of the Kuruk-tagh, in the form of low, rounded heights. For a short space we kept quite close to the edge of the terrace. In two or three of the openings already alluded to its sides were perfectly perpendicular, and consisted throughout of fine yellow clay, capped only by a superficial layer of fine gravel. To the south the clay surface was furrowed by innumerable gullies eroded by the wind, and separated from each other by jardangs, or »ridges», about 2 M. in height. Amongst these the
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