PHYSIOGRAPHY OF SOUTHERN SHEN-SI. a7 
region is characterized by mountainous ridges of limestone, which are more 
or less deeply eroded anticlines. Their arched surfaces formerly rose to 
greater altitudes than now, and in some places much higher than in others, 
but at present the outcropping strata maintain a somewhat uniform height 
although cut into precipitous peaks of extremely rugged form. Having 
traced the Ts’in-ling surface southward to the altitude of the Ki-sin-ling 
pass and finding it there essentially coincident with the summits of these 
dissected ridges, we recognized that they represent it. As they consist of 
the harder rocks, which are associated with very much softer strata, we 
may infer that they are the hills from about which the valley levels have 
been extensively eroded in the process of deeper denudation. 
Apart from its own characteristic topographic type the Ts’in-ling 
stage may be recognized by its relation to the very characteristic and wide- 
spread form of the Yang-tzi stage, the canyons in which all streams of the 
province are more or less deeply sunk. 
THE YVANG-TZI STAGE. 
The canyon, which is the characteristic feature of the Yang-tzi stage, 
is widely developed throughout the entire mountain province south of 
latitude 34°. Every stream is sunk in a narrow steep-banked or steep- 
walled channel, which may be 100 or 4,000 feet, 30 or 1,200 meters, deep. 
This character has been so often referred to in the preceding pages as to 
require no further description. As an almost universal characteristic, it 
stamps the entire province as one which has been elevated in later geologic 
time, and it is this fact of mountain growth which marks the Yang-tzi 
epoch. In general terms it may be said to have resulted in two great up- 
warps, of which the northern has developed the Ts’in-ling-shan, between 
latitudes 33° and 34° and east of longitude 105°; and the southern has 
resulted in the Kiu-lung-shan, which appears to trend from northeast to 
southwest, extending from the lower Han valley to the upper Yang-tzi, 
from about latitude 32°, longitude 112°, toward latitude 28°, longitude 107°, 
and beyond. Between the two is a downwarp which is occupied by the 
watershed of the Han, but there are very decided differences of elevation, 
due apparently to local upwarps and downwarps of strongly accented 
character. These are prominent and modify the relief of the broader 
general downwarp in a manner to obscure its character, by introducing 
high ranges. 
The study of the rivers shows that, with reference to the warps of 
the Yang-tzi stage, they are in part antecedent and in part consequent. 
Among the former we may probably place the Hei-shui-ho and possibly 
the upper P’u-ho, on account of their diagonal courses and adjustment 
to the divide on the granite mass of the central Ts’in-ling-shan; and we 
