Sussik-kul in the south, though the Rang-kul still retains its sweetness, thanks to the stream through which it drains to a tributary of the Oxus. In many places the old lakes are now indicated by incrustations of salt and magnesia.
The Kara-kul, or "Black Lake," so called from its deep blue colour, is the largest on the Pamir, but seems at present to be passing through a transition period. Situated immediately south of the Kizil-art, it is everywhere enclosed by snowy mountains, but its vast basin is no longer entirely flooded. Its present area is about 120 square miles, but former extent is clearly marked by numerous islands, peninsulas, swampy flats, and the dazzling white incrustations of magnesia met with along its shores. It is divided into two halves by a ridge running north and south, and connected with the mainland by a strip of sand. Its feeders no longer compensate for the loss by evaporation, the rainfall is very slight, and nearly all the moisture is discharged either as hail in summer or snow in winter. Before Kostenko's visit the lake was represented as draining either to the Kashgar or to the Oxus, or even to both basins. But if it ever existed the outlet through the Markan-su north-east to the Kashgar has long been dried up, while that flowing south to the Oxus seems to be intermittent, during high floods still sending a little water through the Chon-su or Ak-baïtal to that river. Being thus without a regular outflow, its waters have become so bitter that animals will only drink them when suffering from extreme thirst. But they are always clear, and apparently stocked with fish. According to the nomads the level of the lake rises regularly every Friday, a belief Kostenko seems half inclined to credit. Korostovzev also speaks of regular risings, without, however, indicating their duration.
The Alaï Highland.
North of the Pamir the two parallel ramparts of the Trans-Alaï and Alaï belong to the Tian-shan system, and their geological structure, according Mushketov, is the same. But these diorite and granite masses being separated by the Kog-art and Terek-davan* Passes from that range, they may be regarded as forming an independent system. This western section of the Tian-shan, merging in the Turkestan plains between the Sir and Oxus basins, has a length of 420 miles, and, like the Tian-shan proper, consists of various ridges running either east-north-east or north-west, and crossing each other at intervals.
At the north-east corner of the Pamir the two ranges present a remarkably regular appearance. The Alaï, or Kichi-Alaï, forming the water-parting between the Sir, Oxus, and Tarim basins, sharply limits the Ferghana depression by a barrier of crests with a mean elevation of from 13,000 to 18,000 feet, which are separated from each other by elevated passes. Of these one of the lowest is the Isfaïram Pass, 12,000 feet high, at one of the "breaks" in the Alaï, where the chain suddenly takes a westerly direction. From a neighbouring bluff a view is afforded of the snowy monarch of the Trans-Alaï, which Fedchenko has named
* The Tian-shan passes bear the Tatar names of davan or daban, art or yart, bel and kutal. The davan is a difficult rocky defile, the art a dangerous gap at a high elevation, the bel a low and easy pass, and the kutal a broad opening between low hills (Fedchenko).
