two detached segments of a circle. These
escarpements are turned towards the mountain
; the highest, on the southern side, is
called the Puy de Goutte ; that on the
northern side is much lower, but is very
distinct. They are formed of scoriaceous
and compact lava in fragments, intermixed
with red ochrous earth. The annexed
cut represents the position o f the Puy de
Chopine, in the crater, but as this station
was too near to take in the whole mountain,
I have given the outline of it, which I took
north of Riom.
But the most remarkable circumstance
attending the Puy de Chopine, is its singular
composition ; one part of the mountain
being composed of trachyte, and the other
o f granite and syenite. Here we have a
mixture in the same mountain of volcanic
rocks, with rocks regarded as primitive. The
granite and syenite occur on the east, and
part of the south-east side of the mountain,
and the south-west and north-west
are formed of trachyte. On the north
side there are blocks of a rock that much
resemble basalt*, which I thought I could
* I have mentioned a rock of a similar kind, imbedded
in granite, and alternating with it near the road