CH. XXX THE DRIED-UP ' NEW LAKE' 361
from such intermittent inundations. The total absence of vegetation in certain intervening depressions was attributed by my hunters to the depth of the water once held in them.
On December 14th I succeeded in getting the camels to move off by 8 A.M., and to do a march of close on sixteen miles before nightfall in spite of the increasing trouble which the ground gave to the animals. The succession of salt pools and dry salt-covered lake-beds, large and small, which we passed all day, showed that we were still within the ` Yangi-köl ' depression, which the latest inundation period had affected. But we had scarcely covered more than four miles, and just left behind what might be described as the area of scanty but continuous desert vegetation, when we had the first indication that we were now nearing that zone of strongly marked wind erosion which from Hedin's description I knew to constitute so striking a feature of the northern portion of the Lop desert.
It was a belt of narrow ridges or terraces in hard clay, separated by small Nullahs, not deep as yet but showing sharply cut banks, such as only the erosive action of wind and driven sand could produce in this region. The top of the terraces or ' Yardangs,' as we may call them after the Turki term adopted by Hedin, invariably showed shallow parallel furrows, all running like the Nullahs or trenches in the direction of the prevailing winds which had carved them, north-east to south-west. The soil exposed on the sides of the Yardangs was a hard stratified clay, unmistakably the sediment of an ancient lake-bed. Erosion could not have been long at work here, or else returning moisture must have temporarily stopped denudation ; for in places I found dead reeds which had grown between the Yardangs.
Beyond this first outpost line of the true desert northward there came again dry lagoons large and small. The water of the rare pools left behind in these salt-encrusted depressions was so salt that in spite of the cold it had nowhere yet frozen. The fact of only a single patch of living tamarisk and reeds being met with on the day's march after crossing those Yardangs suggested that the
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