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

94 GEOLOGICAL RESEARCHES IN
Crossing the valley of the Shiribetz we came to the foot of the Raiden promontory, a bold headland presenting vertical cliffs toward the sea, and apparently made
up of lava flows and tufa-conglomerate. In crossing this mountain we frequently
found fragments of a black scoria with long-drawn cells.
After a laborious journey of several hours we descended into a deep and gloomy
gorge containing a warm spring. Here again we found the same variety of white
quartziferous porphyry that we had seen at Kakumi and elsewhere. It is impregnated with iron pyrites which in places is represented only by cubical cavities
containing sulphur. The rock traversed by this porphyry is of a brecciated argillaceous character, resembling that at Kakumi. It is from this rock that the springs
flow, with a temperature varying, in different ones, from 46~ to 50~ C. These rocks
are exposed only in the bottom of the ravine, on either side of which they are
covered by the volcanic formation.
August 17th. Rising from the ravine we continued our journey over the northern
part of the Raiden, the outcrops here, as yesterday, being of a gray trachytic lava
with a tendency to tabular structure. This continued till we descended at the creek
Nibitzunai to a terrace that reaches many miles northward and eastward, low near
the sea, but rising rapidly toward the mountains. Skirting this for a few miles
we reached. Iwanai.
August 18th. At Iwanai we left the sea and made an excursion to the volcano
Iwaounobori' about thirteen miles inland.
The first five miles of the road lay over the terrace which, as we approached the
mountains, rose very rapidly. During the first mile or two, after leaving the sea,
the surface was covered with a dense growth of long-jointed grass, six or seven feet
high, to which succeeded the usual forest of large maples, oaks, mountain and whiteash, beech, birch, fir, and scattered magnolias, filled in with an impenetrable undergrowth of cane eight to twelve, and even fifteen feet high. The road through this
region, being deep with mud which was full of sharp pointed stumps of the cane,
was one of the worst I have ever seen.
Entering the mountains we passed through a crateriform valley, once the bed of
a lake, and, ascending to a pass in the hills beyond, we saw, beneath us, a beautiful
little lake. On the other side of this rose the volcano, or rather solfatara, with its
yellow, sulphur-coated cliffs. Here again the regular slopes and symmetrical outlines of an undisturbed cone are entirely wanting; the outer as well as the inner
walls were rocky precipices, and the ruin seemed greater than at Esan. We reached
the summit without much difficulty.
The present mountain is evidently only part of the skeleton of a former cone of
large size. The predominating formation, from the spurs at the base to the summit,
is a dark gray volcanic rock, showing in places a tendency to stratiform structure,
and apparently of the trachytic family, the chief ingredient being crystals of a
white felspar.2 The former mantle seems to be still represented by fragmentary
Japanese. Iwaou, sulphur; and nobori, a term for mountain, from noboru, to climb.
a With the exception of one specimen of rock, and a few minerals, the entire collection of rocks,
shells, etc. from north of Odaszu, was lost by the wreck of a junk on the way to Hakodade.