SINO-MONGOLIAN FRONTIER 
was very noticeable. Working south-east from 
Pao-t€ Chou, we shortly encountered limestone, 
belonging to the Ki-ch’ou formation, the strata of 
which dipped gently to the west. Rising steadily 
up through this, we reached a high ridge of lime- 
stone, descending from which we again reached 
the sandstone of the Shansi formation, in which 
the town of K’o-lan Chou is situated, and which 
extends eastward from here to the Fén Ho. Though 
we had crossed the great ridge dividing the basin 
of the Fén Ho from the Yellow River, we did not 
encounter any of the usual archaic formations. 
This then forms one of the few breaks in the con- 
tinuity of the archaic ridge, which runs from Ning- 
wu Fu to Yung-ning Chow in Western Shansi. 
From K’o-lan Chou we journeyed northward 
to Wu-tsai Hsien, crossing a low ridge in the 
Shansi formation, and from Wu-tsai eastward to 
Ning-wu Fu, crossing a somewhat higher ridge 
in the same formation. Here we noticed bitumi- 
nous coal being mined close to the city. North- 
ward from Ning-wu Fu I noticed the Shansi 
formation extending for some distance, but I 
did not pursue my investigation very far in this 
direction. 
Leaving Ning-wu Fu we journeyed eastward, 
soon encountering the Sinian limestone, followed by 
limestone of the Hu-t’o series, originally described 
from close to this very region by Bailey Willis. 
A little to the west of T’ai-niu-tien, the limestone 
201 
