The two Ala-tau chains, which have a total length of about 150 miles, are limited eastwards by the San-tash Pass and the Aktogoï defile, westwards by the Büam defile, which is traversed by the river Chu, and which separates them abruptly from the Alexander Mountains. This gloomy gorge is strevn with enormous blocks, between which rise fantastic porphyry pillars. But it lacks the savage grandeur of the Aktogoï gorge. Below the junction of the Great Kebin the Chu crosses the western continuation of the Northern Ala-tau, after which it receives the Little Kebin at the head of a broad plain skirted by two detached branches of the Tian-shan, which merge gradually with the desert. The southermnost of these chains, another Ala-tau, now more usually known as the Alexander Mountains, is a snowy range running east and west over 180 miles, and culminating with the Hamîsh, or Mount Semyonov of the Russians.
Lake Issik-kul and Western Tian-shan Highlands.
The geographical centre of the whole Tian-shan system is the Great Issik-kul, or "Hot Lake," as it is called by the natives. It is encircled on all sides by mountains, on the north by the Ala-tau Kungei, on the south by the Ala-tau Terskei, the vast amphitheatre forming an oval tract of over 400 miles in circumference. The Issik-kul is not only the largest lake in the Tian-shan highlands, but the only great survivor of the numerous reservoirs that formerly filled the basins between the parallel ridges. But it was at one time far larger than at present, as shown by the water marks on the hillsides 30 miles west of its present limits. Even in the ten years from 1867 to 1877 it has fallen nearly 7 feet, implying at least a temporary, if not a permanent, drying up of the land. The river Chu, which formerly flowed to its western corner, now reaches it only during the freshets and melting of the snows. According to a Kirghiz tradition the Kutemaldi was dug by the inhabitants of the country, anxious to get rid of the Issik-kul, but, owing to a miscalculation, they gave a new affluent instead of an outlet to the lake. Yet, although it has no present outflow, it is about ten times larger than Lake Geneva, its area being estimated at 2,300 square miles.
It stands some 5,000 feet above sea-level, but never freezes, whence, according to Sieverzov, its name the "Hot Lake," though this title is more probably due to the numerous hot springs round its shores. The lake is slightly brackish and teems with fish, of which, however, not more than four species have been discovered in its clear blue waters. In 1872 the first boat worthy of the name was launched on its surface; yet its desert shores seem to have been formerly thickly peopled. Crania, bones, and various objects of human industry are occasionally thrown up by the waves, and bits of iron and potsherds have been found by Kolpakovsky at a depth of 3 or 4 feet.
East of Lake Issik-kul are grouped the Khan-tenghri Mountains, which may be regarded as the dominant mass of the whole Tian-shan system. Although exceeded in height by the principal Trans-Alaï peaks, the Khan-tenghri contains the greatest
