184 THE PULSE OF ASIA
sand dunes, from ten to a hundred or more feet high. There had been a high wind two days before, and the air was still so full of dust that we could scarcely see half a mile. In the dense haze the larger dunes loomed like distant mountains, and again and again we were amazed to find ourselves suddenly at the foot of a small hill, which we had felt must be a mountain miles away. As we zigzagged hither and thither in climbing the steep western fronts of the larger dunes, or as we walked along the narrow crests and looked down the apparently precipitous slopes into the remote, hazy hollows, we experienced the sensations of genuine mountain-climbing. There was a sense of height and space; we involuntarily drew back at the sound of an avalanche, though it was only sand slipping from under our feet; we gained each crest with the joy of achievement; and we walked warily, to avoid a fall that would plunge us down a thousand feet, as it seemed.
In the midst of this weird illusion, we unexpectedly arrived at the top of a bluff. Below us lay the fair savannah of the band of vegetation along the Keriya River, a narrow plain dotted with clumps of tamarisk bushes, or groves of poplars rising from a gold-flecked, silver-plumed undergrowth of green reeds. We traveled down the left bank of the meandering river, sometimes in the open plain of reeds, sometimes among the poplars, and occasionally out into the tedious sand of the desert, when the stream swung far to our side. Now and then we passed a shepherd's hut of tamarisk branches, or, more rarely, a flat-roofed cabin of poplar poles, reeds, and mud.
Sixty miles below Keriya, we left the river, which contin-
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