RECONNAISSANCE IN CENTRAL TURKESTAN. 
191 
and slate, and accordingly is well weathered. The brook cnts through it in a 
narrow valley with steep sides. In front of IV is a nearly flat plain of silt and 
fine gravel, due to the obstruction of drainage by the next older moraine, III. This 
lies I >/< or 2 miles in front of IV and less than 200 feet lower. It is well dissected 
and graded, with kettle-holes only on the edges near the mountains, where it 
approaches its successor. The stream flows through it in a broad valley. The 
next moraine, II, is far larger, as it belongs to the whole \alley and not merely to the 
tributaiy-. It is 4 or 5 miles wide, 10 or 12 long, and several hundred feet thick. 
Because of its great size and because of its composition of granite, often in large 
blocks, it is less dissected than its small neighbor, III, but its location shows that 
it must be older. The stream valley which is cut through it is not of great width, 
although its sides are well graded. In the downstream half of the moraines the 
valley is wider and has three terraces. At the very front a moraine of later age, 
probably corresponding to the third in the above series, comes down from the 
north and covers the older moraine and its terraces. Below this there is an 
interval of nearlv 9 miles with no moraines except a few small ones which come 
Fig. 136. — Sketch map showing the location of the Mudirunv Moraines. 
from side valleys and do not extend into the central portion of the main valley basin. 
Large bowlders of granite, sometimes reaching a diameter of 20 or 30 feet, are 
scattered here and there. The open valley floor is of gentle descent and falls but 
100 feet in the 9 miles. Then begins the lowest and oldest moraine, I. At first 
it is complicated by a side moraine of later date, coming in from the south, but in 
its course of 7 or 8 miles farther west it becomes more and more smooth and free 
from surface bowlders and irregularities. Near its end two subangular masses of 
granite, from 10 to 15 feet in diameter, were noticed lying in the middle of the flat 
\-alley where they could not have been brought by water. Beyond this it is impos- 
sible to tell where the moraine ends and the gravel plain at its front begins. 
Three examjjles have been described in the preceding paragraphs where 
the ancient glaciers have formed moraines at five different points successively 
farther and farther up-valley. These moraines may represent successive pauses of 
one retreat, in which the glacier retired quickly for a certain distance and then 
stood still for a considerable time, or they may represent distinct glacial advances 
