GLACIAL EROSION IN THE HIGHER RANGES. 89 
have again a case, like the one already considered in connection with the terraced 
valleys of the Kopet-Dagh, of a series of decreasing maximum records, before and 
between which a number of minimum records ma}- have been made, only to be 
destroyed by the next stronger record. The preservation of four or five records 
makes it probable that the total number of glacial epochs in the Tian Shan was as 
many as six, eight, or ten. 
We fully concur with earlier observers to the effect that there are no indica- 
tions of general glaciation in the region that we crossed. 
GLACIAL EROSION IN THE HIGHER RANGES. 
This excursion across the Tian Shan gave me the first opportunity of seeing 
high mountains since reading Richter's Geomorphologische Untersuchnngen in der 
Hochalpen (1900). I therefore gave especial attention to the form of the mountains 
to determine how far Richter's thesis holds good as to the action of glaciers in 
sharpening the peaks and crests by causing the retreat of cirque walls. There was 
repeated occasion to test the thesis, and it seemed to hold good in every case. 
The Kugart pass, over 10,000 feet in altitude, and with the higher summits of 
the Fergana range on either side, presented no sign of glaciation. It is possible 
that some cirques occur not far to the southeast, but clouds covered the mountains 
too heavily in that direction at the time of our crossing to make sure. All the 
mountain forms by the pass were the result of the normal processes of erosion. 
The ridges were all dominated by the down-slope lines of creeping and washing ; 
and all the down-slope lines, decreasing in declivity as they were followed, combined 
in an elaborate branch-work system, adjacent lines alwa}-s meeting in accordant 
grade at their innumerable points of junction. In other words, the ridges were 
maturely dissected. As seen in profile, the down-slope lines had relatively little 
variety. Except for a small convexity near and at the crests, they were concave to 
the sky, and were systematically of decreasing slope downward through all their 
length, from mountain top far down the valley. This was particularly true for the 
stream lines of the many ravines which gather water and waste from the sides of 
their inclosing spurs, and which were prevailingly graded along their courses. It 
was true, also, to a remarkable degree for the waste-stream lines on the spur slopes, 
which were broken only by scattered outcrops of the stronger rock masses, and then 
only to a moderate amount. Here and there patches of hackly, ungraded ledges 
stood forth, not >et reduced to order; but on the whole the graded down-slope lines 
were remarkably well developed. The variety of these lines was shown in their 
plan rather than in their profile, and even in plan their variety is sj-stematic. 
The stream lines branch over and over again, as they are followed uphill, and 
the spurs are split repeatedly by the large and small ravines that fork beneath 
them ; but that is all. When the mountains are looked at hastily their variety of 
form seems confused, but when the fonns are more patiently analyzed their \-ariety 
is seen to result almost entirely from small changes on a simple scheme, and even,' 
element of form finds its explanation in the processes of nonnal erosion carried to 
a mature stage. 
