RECONNAISSANCE IN CENTRAL TURKESTAN. 
189 
The two upper gorges of the Khoja Ishken \'alley and part of the lower are 
cut in a inetamorpluc limestone which sometimes becomes marble, and in each the 
grade is so steep that the stream is still active!)- cutting downward. Hence the 
width of the gorges relative to the size of the stream gives a good measure of the 
time that has elapsed since each gorge was formed. The upper gorge, the one 
associated with the fifth moraine, is exceedingly young ; so young that though it is 
cut to a depth of over 50 feet in solid rock it has scarcely widened at all, and the 
top is but slightly wider than the bottom (fig. 132). It is so narrow in one place 
that it has twnce been naturally bridged by bowlders. One of these bridges is 
utilized by the road; the other is a great granite bowlder, 25 or 30 feet in diameter. 
Fig. 133. — Marble Bowlders, and beginning ot (he Gorge associated with the {ourth Khoja Ishken Cladei. 
which lies directly across the narrow slit cut by the stream. The next gorge (fig. 
133), belonging to the fourth moraine, though not much deeper than the upper one, 
is decidedly wider both relatively and absolutely, as shown by the accompanying 
cross-sections (figs. 134, 135). In spite of the fact that it is cut in marble somewhat 
harder than the limestone of the upper gorge, its sides have a slope of about 45° 
instead of nearly 90°. In one place it shows a little terrace near the bottom. It 
seems to be two or three times as old as its successor. The gorge of the third 
moraine, which is the oldest and the farthest downstream, is so broad that the road 
runs at or close to the bottom, and the sides have a slope of only 25° or 30° even 
where it is cut in granite or slaty quartzite. The terrace, which lies 200 or 300 
feet above the stream, has been consumed to a mere fringe on the valle>'-side, and 
