122 RESEARCH IN CHINA. 
A similar granite is exposed along the T’ai-shan-ho, 2 miles, 3 kilo- 
meters, south of Shi-tsui, but in this case the relation of the granite to 
the adjacent rocks was not observed. It is possible that the gneiss in 
Pei-t’ai represents a third batholitic intrusion in the Wu-t’ai rocks, but of 
this the evidence is even less conclusive. 
Black biotite-schist and hornblende-schist occur sparingly in dike-like 
bodies, which cut across the quartzites and schists of the Shi-tsui group. 
They are evidently ancient intrusives, which have been severely metamor- 
phosed. A single thin sheet of serpentine was found interbedded with the 
gray augen-gneiss northwest of Shi-tsui, and on account of the known 
igneous origin of most other serpentines, this is presumed to be the meta- 
morphic product of some basic igneous rock. 
The most numerous dikes in the Wu-t’ai-shan region consist of greenish 
black schistose amphibolites, or greenstones, of fine texture. The dikes 
are 20 to 100 feet, 6 to 30 meters, thick, and they penetrate both the T’ai- 
shan gneisses and the Wu-t’ai schists. Similar greenstones have been 
found as dikes in the younger Hu-t’o strata. They are especially plentiful 
along the T’ai-shan-ho, between Shi-tsui and Wu-t’ai-shan. 
Unaltered intrusives.—The remaining igneous rocks are as fresh as 
most Tertiary lavas; and so far as our observations go they consist only of 
siliceous porphyries. About 4 miles, 6.5 kilometers, northwest of Shi-tsui, 
there are numerous small dikes of quartz-porphyries. The rocks vary 
from blue-gray to pale brown and are distinguished by phenocrysts of 
quartz and feldspar. Four miles, 6.5 kilometers, farther up the river a 
thin dike of reddish-brown porphyry occurs, in which all of the phenocrysts 
are feldspars. Greenish hornblende-porphyries also were observed in a few 
places. They are usually much decayed, and aside from the black horn- 
blende crystals, little can be distinguished in the hand specimen. 
PRE-HU-T’O UNCONFORMITY. 
In the typical district of the Wu-t’ai system, the Hu-t’o slates are 
the next overlying younger rocks. From the fact that the schists are pro- 
foundly metamorphosed and present an isoclinal structure, whereas the 
strata of the Hu-t’o series are but slightly metamorphosed and lie in more 
open folds, we infer with confidence that there is an unconformity between 
the two. Should the Hu-t’o series anywhere rest upon the T’ai-shan 
complex, as may very likely be the case, the unconformity would be still 
more pronounced. 
Our route was not favorably conditioned for observation of the contact 
which is probably well exposed in the mountains west of Nan-t’ai and 
Shi-tsui (atlas sheet D I). From the summit of the peak 4 miles, 6.5 kilo- 
