148 THE PULSE OF ASIA
brown or gray in color, and causing the sun, though bright and hot at noon, to fade into a molten ball and finally disappear an hour or more before sunset. Everywhere we found drifts of sand and deposits of loess half dissected by the wind. Evidently, at no remote date this region near the base of the mountains, at an elevation of seven or eight thousand feet, was more thickly covered with vegetation, so that loess could accumulate as it still does three or four thousand feet higher up among the moraines and grassy slopes of what may be called the loess-pasture zone. Within a few hundred or at most a few thousand years, there appears to have been such a change of climate that the vegetation has largely died, and the former region of aeolian deposition has been changed to one of erosion.
Puski proved to be like Sanju, a fair green ribbon lying on two low terraces of loess beside a swift stream flowing in a broad flood-plain of cobblestones. On either side rise the low desert foothills; to the south, the mountains rise higher, and the stream is confined to a narrow gorge; while to the north, the vast naked beach of the zone of piedmont gravel slopes gently to the zone of vegetation. It took us a day to cross the gravel between Puski and Zanguya, the first town in the zone of vegetation. We grew sleepy in riding over the hot, monotonous plain. There was nothing to look at except pebbles, wonderfully smoothed and faceted by wind-blown sand, or dense columns of whirling dust, thirty or forty feet in diameter at the base and rising to a height of hundreds or thousands of feet, where they spread out after the manner of thunder-clouds. Twice I counted between twenty and thirty dust-whirls visible at one time, and
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