SURVEYING THE DESERT. 243
itself in shallow places. The idea that these ripplings were caused by waterwaves was suggested by their occurring only under the lee of the jardangs. Did they owe their origin to the wind, they would have been found in open and exposed situations; but they extended from north-west to south-east, that is at right angles to the direction of the prevailing wind. Wave-ripplings of this character are absent from the usual hard schor; either they have been planed away by the wind or else they disappear - spontaneously when the saliferous mud dries.
Here too, as on our more westerly route, the dead vegetation diminished as we advanced from north to south. There was however this difference, that whereas in I goo vegetation of some sort accompanied us all the way, here in the east since the close of the third day's march the surface had not produced a single blade or a single shoot. Nor did the schor contain the least intimation of organic life. Near our camp on that day we lighted upon a single poplar-trunk, greatly decayed by time; but it had no doubt floated there on the surface of an ancient lake. The schor surface was however peculiarly favourable for our surveying operations. Amongst the jardangs it was hard work, for we had to cross over them all at right angles; here however we were able to continue in a straight line, and the distance between the telescope and staff was increased to 112.5 m. Consequently I had no difficulty whatever in taking my readings; the schor expanse was as level as the surface of the sea, except for slight swellings of no consequence. If, after adjusting the level, I moved the telescope all round the horizon, the distance between the horizon and the middle horizontal hair-line across the lens was always exactly the same. Thanks to the hardness of the ground, there was now less danger than formerly of the staff sinking in, though this risk was, as I have said, entirely counteracted by the brass-plated foot upon which the staff rested.
After we had finished our day's work a storm sprang up in the north-east, and it lasted all night, though fortunately it died away about noon on the 14th March, so that we only lost a few hours. It was very interesting to observe the effects which it produced. We were here, it will be remembered, in the middle of the flat schor desert, where there was no trace of even a rudimentary dune; search failed to detect anywhere even the smallest attempt of the sand to drift together. In fact the only sand we saw was the three dunes I have mentioned, and they evidently belonged to the extreme eastern outposts of the sandy desert which lies in that quarter. Nor were there many other dunes to the south of them; and in the vicinity of Camp No. CLXII there were none even of these outposts within sight. But on the morning of the 14th, after a violent storm of only 27 hours' duration, a little circular dune had formed all round my light Mongolian jurt, which in shape exactly resembled an ordinary tamarisk-mound, that is, it was dome-shaped or beehive-shaped. The little dune around it exhibited therefore the same shape as the circular dunes which grow up round the tamarisk-mounds, and which I have already compared to the Monte Somma that encircles the culminating-point of Mt Vesuvius. This one-night-old dune was of course quite an insignificant thing, not more than 1 dm. high. The greater part of the sand was heaped up, not on the lee side, but to the windward of the tent; inside the tent there was also a considerable quantity of sand, so that all my belongings had to be fished out from underneath
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