RECONNAISSANCE IN CENTRAL TURKESTAN. 183 
and in the Tian Shan Mountains, where the greater number were seen, the ice rarely 
descends much below a height of 12,000 feet. Among the Alai Mountains the 
Khoja Ishkeu glacier comes down to an altitude of about 11,500 feet, while others 
stand higher ; and even the largest of those on the north side of the Pamir, descend- 
ing toward the great Alai basin, comes down only to an altitude of 10,500 feet. 
In former times, however, these small glaciers were much expanded, so that 
the Altyn glacier, one of those on the north slope of the Pamir, stretched out 20 
miles ; those of Yak Tash on the Tian Shan plateau and of Khoja Ishken in the 
Alai Mountains both reached a length of 30 miles; and the Mudirum glacier on the 
Tian Shan plateau must have been nearly 50 miles long at the time of its greatest 
extent. All these Quaternary glaciers were small compared with those of similar 
mountains in Europe and America. The lowest of them in the steepest valleys was 
not able to descend to an elevation below 7,500 feet. The large ones on the Tian 
Shan plateau did not descend below 11,000 feet — that is, only 2,000 feet below the 
ice of to-day ; and of those in ordinary valleys, where the ice was free to advance 
indefinitely down a steep, narrow trough, not one descends over 3,500 feet below the 
present glacier. No trace of a general ice-sheet was seen. The significance of this 
will be discussed later. At present it serves to show that the area of glaciation was 
very restricted and that its effect on the topograph}- of the region is purely local. 
The effects of glacial erosion will not be described here, since they differ in no 
essential respect from what has been described under similar conditions in other 
countries. Bold Alpine scenery- is found among the aretes and three-edged peaks 
of the southeastern Tian Shan, the cirques of the northern Pamir, and the main 
valleys with over-steepened walls and hanging side valleys in the Alai range. The 
green moraines not only provide the traveler with an easy road, but furnish fine 
pasture for the flocks of the nomadic Kirghiz, whose roimd felt tents one is almost 
sure to find in summer not far from every old moraine. The most peculiar feature 
of glacial erosion is the broad troughs cut in the smoothly sloping surface of the 
warped Tertiary peneplain where it has been uplifted in the Alai Mountains and 
still more in the Tian Shan plateau. The troughs resemble a series of grooves. 
They head in cirques in the crest of the ridge and widen and deepen as the branch 
grooves join the trunk trough during descent, until at the lower end they are 
typical glacial valleys with over-steepened sides. They may be considered as the 
elongated form which a cirque takes in an inclined plateau. 
THE SUBDIVISION OF THE GLACIAL, PERIOD IN ASIA. 
In America and Europe geologists as a whole have come to the conclusion 
that the glacial period included several cold epochs separated by inter\-als as warm 
or warmer than the present. Hence, after finding that old moraines abounded in 
Central Turkestan, it was of the first importance to learn whether they indicated a 
similar subdivision of glacial time in Asia ; for if there were several glacial epochs, 
not only might it become possible to correlate Quaternar}- events in Asia with those 
in the other northern continents, but a definite time-scale might be establi-^lied 
which could probably be extended to the lowlands of Western Turkestan. An 
