ser 6 RESEARCH IN CHINA. 
the Huang-t’u in the eastern of the two show interstratified peaty layers, 
and the valley is drained by a loess canyon to the western one. The west- 
ern has no outflow. Streams entering it are carried in artificial raised 
canals to a reservoir, and the waters are used for irrigation. At the natural 
outlet on the southeastern side the Huang-t’u fills an old channel, as may 
be seen in the deeply sunken road leading to the T’ién-hua coal-mines; 
but the dam which closes the valley against the present drainage is the 
alluvial cone of a mountain brook descending from the southwest. At 
present the brook discharges into the basin, but at any time it may take 
the more natural course down the valley. 
The loess basin of Wu-t’ai-hién, the third in the series, is the valley 
of the Sing-ho and its tributaries. It conforms closely to the valleys of 
erosion, corresponding with their broader sections; yet it is not simply 
a valley widened in the softer slates and aggraded above the canyon in 
harder limestones, as one might at first sight suppose. Its peculiarities 
are apparently effects of warping. 
The floor of Huang-t’u, in the body of the basin, has an elevation of 
about 3,500 feet above sea; the surface sweeps up on the mountain slopes 
irregularly, but several hundred feet higher; upstream it follows the 
valley; downstream the Huang-t’u covers the northeastern slope of the 
canyon and_also fills a broad valley, which is southwest of the canyon 
and separated from it by a ridge 1,100 feet, 335 meters, high. The 
Huang-t’u covers the summit of the ridge and extends to the windgap 
at the southeastern head of the valley. The difference of level of the 
Huang-t’u surface in the entire basin is 1,200 feet, 375 meters, and it is 
highest on the southeastern side. This is in large measure an effect of 
eolian deposition. The depth of the Huang-t’u varies from a feather 
edge, where it is wasting away from a mature surface on which it was 
deposited, to something more than 200 feet, 60 meters, as appears in the 
deepest loess canyons. 
The drainage of the Wu-t’ai-hién basin is peculiarly arranged (see 
Fig. 57). The course of the Sing-ho, AB, is directly southeast, but like 
that of other rivers of the district, it is from the wide basin into a narrow 
canyon. Of the four streams which join it on the west bank, the northern 
one, CD, follows the course of a normal tributary, but the others, EF, 
GH, and IJ, flow in the opposite direction. IJ once continued around the 
end of the ridge that divides it from the Sing-ho, while now it is diverted 
through the remarkable gorge at J shown in the section, Fig. 38, which 
expresses the intricate structure. The diversion was accomplished on 
a vertical zone of soft red shale. Recognizing in this northward-flowing 
stream one which has been inverted, we find its former channel in the 
