PHYSIOGRAPHY OF NORTHWESTERN CHINA. 220 
hills above. Between Ling-shi and Ho-chéu the channel of the river is 
probably very narrow, at least in some stretches, for the highway, which 
would otherwise naturally follow it, is carried over the two high passes, 
the Si-sin-ling and the Si-yau-ling. The difficulties which these present 
to the heavy traffic on this principal route through the province are so 
great that nothing short of an impassable gorge would seem to justify the 
course the road takes. 
As we cross the pass there are many views over the wide hill country 
above the Fén-ho, westward to the distant O-shan and eastward to the 
nearer and imposing Ho-shan. The Huang-t’u formation extends over the 
hill summits, and rises in long terraced slopes to the base of the Ho-shan 
(panorama, atlas sheet A III). One is reminded of the surfaces of the 
warped lake deposits to be seen in the southern Sierra Nevada, where the 
once horizontal surfaces exhibit differences of elevation of as much as 1,200 
feet, 365 meters. It seems apparent that, with the relative upthrow of the 
great fault-scarp of the Ho-shan, the adjacent valley segment on the down- 
thrown side has been inclined to a slight degree in the upward movement. 
Beneath the Huang-t’u is a mature topography cut in the Shan-si 
coal series. The rocks are frequently exposed at the bottom and in 
the sides of the loess canyons. Von Richthofen’s impression that the 
Huang-t’u formation might have a thickness of 1,500 feet or more was 
erroneous. It is an uneven mantle which once covered the entire surface, 
but which is probably not more than a few hundred feet thick. We 
recognize in these relations of the Huang-t’u and the underlying topography 
the same conditions that we saw in the hills about Wu-t’ai-hién and the 
Hin-chéu basin, but with a difference: In those localities the Huang-t’u 
occupies a depression, and has been preserved from erosion or added to; 
in this district the Huang-t’u is elevated and is being rapidly eroded. 
A physiographic study of the fault-scarp of the Ho-shan was one of 
the attractions of the region which we were obliged to pass by. We saw 
the scarp from a distance of 10 miles, 16 kilometers, or more, and could 
recognize that it was very steep and deeply gashed by ravines which had 
grown at right angles to the face. 
In the vicinity of Chau-chéng the Fén-ho flows in a valley, which 
has a canyon only about 80 feet, 24 meters, deep, in rocks of the Shan-si 
series, bounded above by bluffs of loess. Whereas further north, near 
Ling-shi-hién, the valley suggests that of the Monongahela above Pittsburg, 
the shallow canyon and rolling upland in this section remind one of the 
Ohio near Cincinnati. 
Approaching P’ing-yang-fu, the highway lies chiefly in the alluvial 
plain of the Fén-ho, a highly cultivated, irrigated district, which widens 
