great bluff cutting across the valley—rises to a height of about 200 feet above 
the stream-bed (Plate 46). 
At Ho-shui Hsien the bed-rock is chiefly in the form of dark-maroon or 
grey shale, finely laminated. This gives place at Ch’ing-yang Fu to grey 
sandstone with marked bedding. Immediately west of this city the loess 
plateaux commence again. The country is noticeably drier than that to the 
east, and the plateaux continue for about sixty miles, ending abruptly at 
Chén-yiian Hsien. 
From here westward, the loess formations become much deeper and less 
regular. The bed-rock rises gradually and is no longer perfectly horizontal. 
Immediately west of Chén-yiian Hsien, the sections exposed on the side of the 
valley show a red sandstone with marked bedding. It dips towards the west 
at an angle of 20°. This is very clearly shown in the accompanying 
photograph (Plate 57) of a view looking westward about five miles west of 
Chén-yiian Hsien. 
The sedimentary formations from Chén-yiian westward rise steadily in 
altitude till the Liu-p’an Shan are reached. This great range of mountains 
(8000 to 10,000 feet high), composed of crystalline rocks, and extending from 
north-west to south-east, lies to the west of Ku-yiian Chou and Wa-t’ing and 
may be considered as the western rim of the great North Shensi basin. The 
highest peaks are very precipitous, and resemble the Chiao-ch’éng Shan of 
Western Shansi in their formation. The lower peaks are composed of lime- 
stone, through which run many deep ravines. 
Ku-yiian Chou is situated in an immense loess basin, bounded north, east 
and south by hills of sedimentary origin, and on the west and south-west by 
the Liu-p’an Shan. On the western side of this range the formation is chiefly 
of limestone, at a higher level than the sedimentary rocks to the east of the 
range. 
From Ku-yiian the path lies in a general south-westerly direction till 
Ching-ning Chou is reached. Immediately north of this city the limestone 
formations are deeply cut through by a stream coming down from Liu-p’an 
Shan. Westward from Ching-ning Chou the loess deposits increase 
enormously in depth. High loess-covered mountains occur, divided by deep 
ravines, and the substratum appears in only a few places. A photograph of 
one of the deep cafions is given (Plate 39). This was taken at Ying-t’ao-ho 
immediately east of a high loess pass, and about sixty miles west of Ching- 
ning. Itis typical of the formations that occur throughout this area as far as 
Hsiao-shui-tzti, near Lan-chou Fu. In places the loess is replaced by a dark, 
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