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

CHINA, MONGOLIA, AND JAPAN. 99
fracture. Fragments break off with a very hackly surface. The structure varies
from slightly cellular to scoriaceous, the cells being lined with a light greenish or
bluish film. It contains thin crystals of white, glassy felspar, the number of which
seems to be in an inverse ratio to that of the cells. The felspar is, at least in
part, a triclinic variety.
The Tomari creek, which enters the sea near Shimakomaki, brings down among
its rubble, diorite, granular limestone containing nephrite, clay schist, and varieties
of quartz and jasper. This stream rises in the hills that have furnished, in part at
least, the auriferous gravels of Kunnui, and it is probable that similar deposits
occur also in the valley of the Tomari;
August 29th. Embarking in a large boat we sailed close under the lofty cliffs
of a grandly picturesque, but dangerous coast, as far as Setanai.
The volcanic conglomerate exists as the principal formation of the coast, between
Shimakomaki and Setanai. At Cape Shiraita the thickness of the conglomerate,
above the sea, is between 100 and 200 feet; above this is a bed, perhaps 150 feet
thick, apparently of a looser material, with many white fragments scattered through
it; and, finally, covering this, for a distance of one or two miles, is a bed of lava,
150 to 200 feet thick.
From this point to Cape Moteta the cliffs are entirely of the volcanic conglomerate, of which a lower bed is sometimes visible, with white fragments, those of the
upper beds being dark brown or black.
At Cape Moteta the volcanic conglomerate, occupying the lower part of the cliffs
to the height of between 100 and 200 feet above the sea, is covered by a thick bed
of columnar lava. Near this point a broad dyke rises through the conglomerate
to the overlying lava bed, but it was impossible to determine, at a distance, the
relative ages of the latter and the dyke.
Numerous dykes traverse the conglomerate between Cape Moteta and Setanal.
At Abura the latter approaches sandstone in texture; at one place it was seen to
pass abruptly into a white deposit, probaby a pumiceous tufa.
South of Abura the conglomerate is covered by a lava bed, and this by white,
apparently tufaceous, strata.
Several miles north of Setanai a thick bed of columnar lava is visible, high up
the face of the cliff, lying between two members of the neptuno-volcanic formation,
and dipping gently toward the south. Before reaching Setanai a thick flow of lava,
beautifully columnar and probably the continuation of the bed just mentioned,
occupies the lower half or more of the cliff, while needles of the same rock rising
high out of the sea form picturesque islands.
This rock is a dark brown, much weathered, cellular lava. The cells are coated
with a soft, brittle mineral, dark green in the fracture, and light bluish-green on
the surface; and being flattened and parallel, with their planes at right angles to
the axes of the columns, they give to the rock a slaty structure. Overlying this
lava bed there are strata of tufa-conglomerate, made up mostly of fragments of
cellular and scoriaceous volcanic products.
Just south of Setanai the Toshibetz-here several hundred feet broad-the river,
on which lie the gold washings of Kunnui, empties into the sea-its valley, here