i8o 
EXPLORATIONS IN TURKESTAN. 
westward near the uorthern side of a valley 8 or lo miles wide and 60 miles long. 
Like most of the streams in the valley basins, whether large or small, it wanders 
freely over its broad gravel flood-plain in a score of intricately braided channels. 
At the edge of the flood-plain, on either side, is a terrace 20 or 25 feet high, above 
which are many miles of gravel sloping smoothly from tlie base of the mountains 
to the edge of the terrace. The broader slope is on the south, where lie the higher 
Trans-Alai Mountains. They form the northern front of the great Pamir plateau, 
Fig. 130. — Limestone Gorge of the Western Kichik Alai, where it enters the Ispairan 
River on the north side of the Alai Mountains. Probably the upper portion of the 
gorge was widened by a glacier, and the narrow slit at the bottom represents post- 
glacial cutting. The main valley, from the side of which the photograph was 
taken, is clearly of glacial origin, and the side valley must have borne a hanging 
relation lo that of the master stream. 
rising from 15,000 to 23,000 feet above the sea and from 9,000 to 14,000 feet above the 
valley. On the north also the mountains are by no means low, for the snowy crest 
lies at a height of about 14,000 feet, and glaciers are numerous. Near the western 
end of the valley basin, where it narrows before the stream enters the fine gorge 
which forms the boundary^ of the khanate of Bokhara, the water wells up from 
a subterranean course under the heavy gravel deposits and bursts forth in numerous 
great springs, crystal clear, but very dark. One of these at Mama gives rise to a 
