322 RESEARCH IN CHINA. 
Si-an-fu, but it is very doubtful if such be the case, though the range 
appeared higher and bolder in the distant view we had from the city wall 
than in those sections which we saw more nearly. The views (Plate XXII) 
present it as we observed it east and west of our route, south of Chéu-chi- 
hién, and it is also represented on atlas sheet a1. Fig. A shows the straight 
front, which bounds the plain almost by a ruled line, and which is here 
and there characterized by the flat facets that cut diagonally across the 
structure of the schists and are regarded as elements of the fault-plane. 
Toward the west the slope shown in Fig. B does not retain these features 
of a scarp; it is less even, becomes gentler, and appears to pass into a 
warped surface. It is inferred that the fault dies out westward. 
Though the fault-scarp of the range is a structural feature, its history 
is to be read only in the canyons which have developed in the uplifted 
block, for the downthrow is buried and the schists of the mountain front 
are severed from any connections they formerly had. 
Heart of the Ts’in-ling-shan.—The canyon of the Hei-shui-ho may be 
taken as a type of the channels cut in the northern Ts’in-ling-shan, as it 
compares closely with the description, given by von Richthofen and Pére 
David, of those by which they crossed far to the east and west of it. Yet 
it is less precipitous than their accounts might lead one to expect. The 
view from above Liu-ytié-ho (atlas sheet a1) gives its principal features 
at a glance: an inner canyon 1,300 feet, 395 meters, deep, which is bolder 
in the massive granite, wider in the weaker schists; an outer canyon which 
opens upwards; and shoulders on the mountain spurs, which, being covered 
with deep alluvial soil, are cultivated and are therefore conspicuous on the 
wooded mountain sides. If the river level at Liu-ytié-ho is 2,000 feet, 
600 meters, above sea, these benches occur near 3,400, 4,500, and 5,500 
feet, 1,035, 1,375, and 1,675 meters, on the spur followed by the trail 
to Ir-ling-p’u, and for that immediate locality they are well shown on the 
topographic and geologic maps. They also occur elsewhere in the canyons 
of the Hei-shui-ho and its tributaries, rising with the rising profiles of the 
streams, but we were not able to map them in detail. 
The stream which flows past Mu-tzi-p’ing, 10 miles, 16 kilometers, 
east of the Hei-shui-ho, is sunk in a similar but wilder canyon, cut across 
ledges of massive limestone and quartzite that leave all too scant room 
for the mountaineer’s path in the bottom gorge, but support benches at 
intervals in the higher slopes. 
It is noted by von Richthofen and by Pére David that the deep and 
narrow canyons are confined to the lower courses of the streams, and 
that the upper valleys are more open and hospitable. We observed the 
same contrast in those valleys whose headwaters do not flow across harder 
