On the south of the Ferghana valley is the lofty range of the Alai, backed by the parallel range of the Trans-Alai. Both ranges abut at their eastern extremity upon the Pamir plateau, and both extend a long way out into the desert. The Alai is a well-defined ridge with steep slopes, and both it and Terek-tau, which prolongs it towards the Kokshal-tau, are flanked next the Ferghana valley Palaeozoic metamorphic limestones and newer Tertiary series of softer conglomerates and sandstones. The general altitude of both ranges is 16,00o-19,000 ft., but the Trans-Alai cul minates in peak Kaufmann (23,386 ft.). The Trans-Alai is a true border range, the ascent to it from the Pamir plateau (13,000 ft.) on the south-east being gentle and relatively short, while both it and the Alai tower above the valley of the Alai to an altitude of 11,000 to 14,000 ft. This valley is 75 miles in length and is continued towards the south-west by the valley of Karateghin. Its breadth varies from three to 12 miles, and it falls from 10,5oo ft. (north-east) to 8,200 ft. (south-west). It is drained by the Kyzyl-su, which, under the name of Vakhish, finally enters the Amu Darya. Despite frequent avalanches of snow it is an import ant highway of communication between Bukhara and the Pamirs on the one hand and Kashgar and Ferghana on the other. The principal passes over it into the valley of Ferghana are Taldyk, ii,C005 ft. with a military road; Jiptyk, 13,605 ft.; Saryk-mogal, 14,110 ft.; Tenghiz-bai, 12,630 ft.; and Kara-kazyk, 14,305 ft. The Pamir plateau is reached by the Kyzyl-art pass at 14,015 ft.
The Alai Mountains are continued westwards in the radiating ranges of the Karateghin, Zarafshan and Hissar Mountains and the Turkistan range, which reach altitudes of 18,500 ft. The Trans-Alai are continued in the Peter the Great range, which culminates in the Sandal group ft.). The passes across these ranges are difficult and at 10,00o-13,00o ft. The last outly
ing range of the Tien-shan system in this direction is the Nura-tau. It rises abruptly from the desert and lifts its snowy peaks to alti tudes of 15,000-16,000 ft., separating the river Syr Darya from the river Zarafshan. The passes over it lie at io,000-13,000 ft.
Routes.-The traditional routes between China, and West Turkistan and Persia have crossed the Tien-shan system at some half a dozen points. After traversing the desert of Gobi from Sa-chou to Hami, the northern route crossed over into the Dzun garian valley either by the Otun-koza depression or by the gap at Urumchi, or else it proceeded over the Muz-art pass on the east side of Khan-tengri or over the Bedel pass in the Kokshal-tau and so down into the valley of Kulja. The shortest route, though not the easiest, between Kashgar and East Turkistan, and Ferghana and West Turkistan is over the Terek pass or the pass at the head of the Alai valley, a dangerous route in winter by reason of snow.