PHYSIOGRAPHY OF NORTHWESTERN CHINA. 215 
rise from the loess basins consist chiefly of slates and have monotonous, 
mature profiles. By reason of their maturity they take their place in 
relative age with the high spurs, which represent the old valleys of the 
Ts’ing-shui-ho and T’ai-shan-ho, designated by b, Plate XXX; they have 
not, however, been cut by younger canyons as that surface has been. They 
are well shown in Fig. A, Plate XXV, and Fig. A, Plate XXXIV. 
On entering the limestone district, southeast of the loess basins, one 
is impressed with the wild, youthful aspect of the canyons (Plate XX and 
Fig. B, Plate XXXIV), and one might conclude that here, also, there was 
but one phase of topography represented. Thence it would be but a short 
step to the conclusion that the mature topography of the soft slate hills and 
the young topography of the limestone mountains were of one and the same 
stage of development, and differed only on account of the unequal wear 
of the rocks. But such is not the case. In the Yau-t’6u district and 
generally over the Ki-chéu-shan, one may recognize a surface of mod- 
erate, mature relief, which corresponds with that of the slate hills, and 
within it are cut the deep, young canyons (Plate XXXV). The parallel 
with the stages of the Wu-t’ai-shan (b and c of Plate XXX) is complete, 
except that the canyons in the limestone are narrower, as they should be 
in the harder rocks. 
This parallel is sustained if we trace the topographic forms in the 
ridge south of Wu-t’ai-hién, west of the Sing-ho. Over its western slope 
is the heavy mantle of Huang-t’u, which extends to the crest; there, 1,100 
feet, 335 meters, above the river and cut off by its canyon wall, are partly 
bare hills of slate, exhibiting the mature surface of the hills of similar rock 
down in the basin (Fig. A, Plate XXVI). Tracing the ridge southward, 
we follow the mature surface on to the Sinian limestone, where, though 
the relief is somewhat greater, the forms are unmistakably the same. 
Thus we here find the Huang-t’u overlying an old topography, which is 
common to the soft slate and hard limestone, and is trenched by the 
younger canyon of the Sing-ho. 
Among the mountains we crossed in Chi-li and Shan-si, there is no 
height so striking as the Ki-chéu-shan, seen from the Hin-chéu basin. 
The great Wu-t’ai-shan, though 4,000 feet, 1,200 meters, higher, is like the 
top of a dome—too huge to be overlooked; there is no point from which 
its magnitude can be appreciated. But the Ki-chéu-shan is a wall, which, 
rising full 3,500 feet, 1,000 meters, from the basin plain, adds all the 
advantage of contrast to its imposing height. 
The face of the Ki-chéu-shan is unlike any topographic form we had 
seen in China—straight, steep, and but slightly eroded. It is representa- 
tive of those great scarps of the Ho-shan, Hua-shan, and Ts’in-ling-shan, 
which we recognized as evidences of comparatively recent normal faulting. 
