stretches the deepest portion, descending to close on a thousand feet below sea-level, of a great fault trough which forms the most striking feature of the basin. With its salt lake and marshes dried up for the most part it recalls the Lop sea-bed on a small scale. From the barren slopes of the high mountain range to the north there stretches downwards a wide, waterless glacis of gravel corresponding to that of the K`un-lun east of Khotan. Above its foot rises an utterly barren chain of hills thrown up by the same mighty geological dislocation which created the fault trough below it. The forbidding look of this hill chain, glowing red with its bare deposits of sandstones and conglomerates, explains its Chinese name of `Hills of Fire'.
It is solely from the foot of this fault ridge that the oases of the depression secure their supply of water. It is utilized to the utmost for irrigation and accounts for their rich produce. Curiously enough, most of the irrigation thus secured depends not upon the surface flow from springs in which the drainage from the Tien-shan heights comes to light again but upon an elaborate system of Karezes or underground wells and canals which tap the subterraneous drainage from the mountains. The climate of the basin is extremely arid and, owing to the low level of the trough, very hot during the greater part of the year. This warmth of climate, together with the assured supply of water provided by springs and Karezes, makes it possible in the oases of the basin to reap two annual harvests. The fertility of the soil when irrigated under such favourable conditions is great, and accounts for the abundance of produce in cereals as well as in fruits and cotton.
But these favourable agricultural conditions would, in
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