Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

CHINA, MONGOLIA, AND JAPAN. 21
where a low ridge of granite runs N. S. and is succeeded on its western side by
the vertical coal rocks, also trending N. S., while almost everywhere else in the
district the strike of these last is E. W.
The preceding section is simply intended to show the relation of the strata to the
granite.1 The limestone d, is about 600 feet thick, and seems to be a member of
the Coal measures proper. The black shale e, with its seams of anthracite f, is
about 500 feet thick.
From the Plain of Peking to Kalgan.
As we approach the Nankau pass, through which lies the great high-road from
Peking to Central and Western Asia, we find the edge of the plain deposit rising
with a more rapid slope toward the bordering mountains, while at the same time,
the firm, fine loam gives place to rolled fragments and gravel of limestone and
granite, from the neighboring hills. The pass is reached by the transverse valley of
the Nankau creek.
Leaving the plain, we pass between lofty cliffs of limestone for about six miles,
before reaching the axial granite of the ridge. The trend of the strata, which is
N. 60~ E., with a dip of 40~ to S. E. by S. ^ S. at the edge of the plain, becomes
irregular as we approach the granite, the beds being in places almost horizontal,
and in others vertical and striking E. W. The latter case occurs at about two and
a half miles from the plain, where a side ravine discloses a dyke of a black eruptive rock, inclosed between the strata to which its plane is parallel. This rock has,
in a black compact base, thin transparent crystals of amber colored triclinic feldspar.
The dyke is only a few feet thick, and is made up of transverse columns. Near
the grand marble arch of the Kiiyungkwan, the limestone is cut through by red
porphyry, which is itself traversed by a greenstone dyke. The porphyry contains
a little quartz, green mica, and crystals of orthoclase in a compact pink base. The
greenstone is apparently a fine-grained diorite.
The granite of the Nankau pass consists chiefly of large crystals of flesh-colored
orthoclase, black mica, and comparatively little quartz, with crystals of white triclinic
feldspar. Near the middle of the pass there is a different and somewhat remarkable variety, almost free from mica, and consisting of pearly white orthoclase and
gray quartz in nearly equal proportions. It is slightly cellular, containing prismatic
crystals of white and smoky quartz in the small cavities.
The first of these varieties is traversed near Chatau by dykes of a pink rock,
consisting of a fine-grained mixture of orthoclase and quartz with very little greenish mica-one of those rocks that form the link between quartziferous porphyry
and true granite. These dykes are in places crossed by others, probably of diorite,
consisting of a fine-grained mass of hornblende and feldspar.
The ridge we have just crossed extends to the S. W., forming, in Shansi near
the Chihli boundary, a series of high peaks which, on the 26th of April, 1864, were
1 Unfortunately most of the specimens and notes from this interesting locality were lost.