PIIYSIOGRAPHIC OBSERVATIONS. 131
distance. In the distance, a silvery sheet of water reflects and dances on the plain. For a moment there seem to be men and animals moving on the shore, but then the lake slides away into space, the men and animals disappear, and there, instead, is the mocking plain.
A far-off dust column appears on the horizon. At first it seems motionless, but soon there is a visible movement as it approaches, growing denser and taller, and turning, it rapidly crosses the steppe with an irregular motion. It may fade away in the distance ; it may disappear suddenly .in some unexpected place. These dust storms tell a story. During the wann hours of the day there is nearly always one, often there are two or more in sight. The desert surface here shows a
Fig. 90.—Deflated bowlder of granite.
Fig. 9I.—Deflated bowlder of granite, hollowed side facing east. Taken at 10.30 a. m.
Fig. 93.—A glacial bowlder of crystalline limestone cracking from the changes of temperature.
Fig. 92.—A talus-shrouded mass of crystalline limestone.
remarkable lack of loose, fine material. But the inclosing mountains are largely made up of rotten gypsum and limestone with earthy surface, from which great quantities of fine stuff are brought down during cloudbursts and left on the fans, always to be carried away bÿ the winds and deposited elsewhere ; probably, according to Richthofen's theory, as loess in some neighboring zone of vegetation.
Kara Kul is a lake of bitter salt water. Its sloping shores are white with salt accumulated into low ridges where the brine from each wave-wetting has dried out after the recession. Behind some of these natural dams there are lagoons of brine collected from the overflow of larger waves, and thus, in places, extending the salt belt ioo feet or more from the shore. I could find no shells and saw no fishes.