438 RESEARCH IN CHINA. 
Some of the sand-grains show undulatory extinction, while a few of 
the quartzes have been fractured and the breaks have been subsequently 
filled with hematite. Considering the fact that the strata lie in a sharply 
overturned and overthrust fold, these marks of distortion are extremely 
inconspicuous. 
TS’IN-LING DISTRICT. 
This district is limited to a narrow strip extending southward across 
the Ts’in-ling mountains from Chou-chi-hién to the southern boundary of 
the large granitic intrusion which forms the axial portion of the range. The 
rest of the southern slope of the Ts’in-ling range will be discussed in con- 
nection with the Han river district. The rocks in this area are for the 
most part sedimentary in origin and either highly metamorphosed or only 
slightly altered. Large intrusions of granite and occasional dikes of other 
igneous rocks are associated with them. 
Doubtless more than one series of rocks is represented in this district. 
One large group carries impure coaly layers and bears such a close resem- 
blance to the known Paleozoic strata in the valley of the Han, that we regard 
the two series as approximately equivalent. The other has every appear- 
ance of being much older; it consists largely of green and gray chloritic 
schists which resemble certain phases of the Wu-t’ai system in Shan-si. 
HEI-SHUI SYSTEM (PALEOZOIC?). 
These rocks are mostly metamorphosed limestone and slates, with 
quartzites and occasional layers of conglomerate. The strata are highly 
folded and are in some places schistose. Granites of later age cut through 
them in various places. 
Rocks OF SEDIMENTARY ORIGIN. 
Olive-green slate, No. 111.—The green slate is one phase of the series 
of quartzites, slates, and siliceous limestones which is characteristic of the 
higher mountains just north of the Ts’in-ling divide. 
Specimen collected in the canyon 2.25 miles, 3.6 kilometers, below 
Chang-k’ou-shi. 
A dense, light olive-colored slate in which no mineral grains are visible 
to the unaided eye. Slaty cleavage is rather imperfectly developed at an 
angle of about 30 degrees to the alternate darker and lighter bands which 
indicate the original bedding. Most of the slaty planes are striated as if 
they had been the loci of slipping movements. The rock also shows a 
subordinate tendency to cleave along the bedding-planes. 
The microscope shows that the rock is composed of an aggregation of 
exceedingly minute grains of quartz, with clay-like materials, among which 
it is possible to identify with reasonable certainty chlorite, sericite, kaolin, 
