OBSERVATIONS IN CENTRAL SHAN-SI. 177 
In journeying from Chau-chéng-hién to P’ing-yang-fu, one at first 
has the magnificent scarp of the Ho-shan in view on the east, but south- 
eastward the face sinks to a gentler slope and the mountains recede eastward 
from the valley. The profile of the crest declines at an angle of perhaps 
10° and finally merges into a flat upland surface. Nearly east of P’ing- 
yang-fu another range, much less conspicuous than the Ho-shan, rises 
perhaps 2,000 feet, 600 meters. It is inferred from the aspect of the 
topography that the fault which is marked by the scarp of the Ho-shan 
dies out and passes into a warped surface, where the mountains become 
less prominent and the slopes less steep. 
Southward from P’ing-yang-fu the route continues to the valley of 
the Fén-ho for 35 miles, 56 kilometers, and then leaving it, crosses an 
abandoned river valley to the basin of the salt lake, Yen-t’si, at the base of 
the Féng-huang-shan. ‘The mountains to the east are remote and it is not 
possible to observe their structural relations. The plain of the salt lake 
basin is an ancient alluvial plain, probably modified by lake and wind 
deposits. It extends with a gentle slope directly to the base of the moun- 
tains, which rise abruptly from it. The face of the range is remarkably 
steep and straight. Its slopes rise at angles of 25° to 40° to a height of 
2,000 feet, 600 meters, or more without marked change. The alluvial cones 
are very small and the front is sharply but not deeply gashed with canyons. 
The larger spurs are truncated by triangular facets, which are considered 
to represent a fault-scarp and which extend westward to a bend in the 
range southeast of P’u-chéu-fu. Beyond this the features of a fault-scarp 
die out and pass into a steeply warped surface representing a once level 
plain now arched up and only in part eroded. The trend of the range 
changes from nearly east-west to south by west, and the heights decline 
in a remarkably straight line toward the Tung-kuan, the fortress at the 
narrowest point in the valley of the Yellow river. The Féng-huang-shan 
is like the Ki-chéu-shan in geological and geographical relations. In each 
case a bold mountain range rises abruptly from the broad basin which 
stretches along its northwestern base, and in each case the evidence of 
faulting is found in the character of the straight mountain front, which 
presents a surface not due to erosion nor greatly modified by it. The 
stratigraphic evidence is wanting, since the rocks on the downthrown side 
are in each case deeply covered by recent deposits. 
Pursuing the chain of normal faults toward the southwest, we cross 
the Huang-ho from the province of Shan-si into that of Shen-si. The 
river makes a sharp elbow, turning from a southward course to one east by 
north, and passes between the Féng-huang-shan and the eastward contin- 
uation of the Ta-hua-shan. The crests of the two mountain ranges are 
nearly, parallel, and the course of the river between them is taken on the 
