OBSERVATIONS IN CENTRAL SHAN-SI. 179 
130 meters. The relations which are expressed in Fig. 55 are those which 
are inferred. The diminishing fault is supposed to split; one branch con- 
tinues westward, wholly in Huang-t’u, and gradually dies out into the 
plain; the other extends southwestward and probably passes into a 
warped surface. The phenomena are closely similar to those observed 
where the Féng-huang-shan turns south, near P’u-ché6u-fu. 
From Hua-chéu westward the profile of the range, in a section at 
right angles to its trend, is convex upward, somewhat as is that represented 
in Fig. 56 by the line abc. The steep lower facet bc is one of many which 
are nearly continuous along the range and fall into one surface, which is 
taken to be that part of the fault-scarp most recently exposed. The upper 

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Fic. 55 (Willis)—Near Hua-chéu, Shen-si. Diagrammatic plan of the normal fault at the 
western end of the Ta-hua-shan, showing the branch fault which is believed to extend west- 
ward into the deposit of the Huang-t’u of the Wei valley, and to give rise to the terrace of 
that formation, which stretches westward from the main range. 
portion ab is supposed to represent the older section of the fault-scarp, 
which has been more deeply eroded. The arc abcd, partly observed in the 
slope, but inferred between c and d, is believed to result from revolution 
of the mountain block about a fulcrum within it and between the northern 
raised margin and the depressed southern part.* 
The occurrence of the Huang-t’u formation to a height of several 
hundred feet on the lower slopes of the Ta-hua-shan may result from 
either one or both of two conditions: faulting and eolian deposition. The 
Huang-t’u being deposited over the sloping surface of the fault-scarp, it 
is clear by inspection of Fig. 56 that part of the deposit would probably 
be raised with the mountain block, should movement now take place. 
*In conversation with the writer Gilbert once gave this explanation of the profile of the Wasatch 
range, Utah, which the Ta-hua-shan closely resembles, 
