Indeed, the evidences, so far as they have been examined, appear to warrant the conclusion that the region of the western Tian-shan, from Lake Issyk-kul southwards, was in great part the scene of probably five successive glacial periods, each being less severe than the period which immediately preceded it.
The result of these geological changes is that, although the internal structure of the Tian-shan region is highly mountainous, its external appearance, or in other words its geographical aspect, is that of a plateau."
Instead of 24,000 ft., stands, not on the main watershed of the central Tian-shan, but on a spur which projects from the watershed towards the south-west.
It used to be supposed that the Tian-shan confronted the basin of the Tarim with a steep, wall-like versant.
In altitude, sloping from the Tian-shan, and intersected by numerous rivers, flowing towards the Oxus.