the defile by which the Narin escapes westwards. Here the Tian-shan system is completely limited by the Ferghana plains, but at the south-west corner of the Tian-shan proper various offshoots run south-westwards, connecting the main range with the Alaï and the Pamir. But till the beginning of the tertiary period a large marine strait still connected Ferghana and Kashgaria through the Kog-art, thus completely separating the Pamir from the Tian-shan plateau. The whole Tian-shan system was at that time crossed from north-east to south-west by a chain of inland seas, of which all that now remains is the Issik-kul. Those of Kulja and Ferghana have long been drained off.
| Fig. 98.—Western Chains of the Tian-shan. |
| Scale 1 : 9,000,000 |
|
 240 Miles.
|
North of the Upper Narin valley the main range is known as the Terskei Ala-tau, or Ala-tau "of the Shade," in contradistinction to the Kungei Ala-tau, or Ala-tau "of the Sun," skirting the other side of the Issik-kul. Owing to the greater moisture of its slopes the former is far better wooded, the pine forests and pastures at many points reaching the snow-line. It culminates with the Ugus-bas, which attains an elevation of over 16,500 feet. Near the Barskaûn Pass, on its southern slopes, rises the Narin, chief head-stream of the Sir, while other affluents flow from the southern region of the Ak-shiirak glaciers, south of which rise the farthest sources of the Kashgarian Ak-su. A large portion of the country comprised between the Terskei Ala-tau and the Kok-shaal north and south forms an extensive plain, or
