blue smoke ascends from rents and cracks, the breadth of the widest
measuring about a yard. Red heat appears at the depth of about four
fathoms. No marks of any extensive change appear on the surface, near
these burning fissures, although the growth of large trees in old cracks
on the opposite slope, where ignition has ceased, shows that this fire
has continued for a very considerable time, or that the same thing had
occurred at a much earlier period. In the form of the adjacent hills I
observed nothing peculiar, unless it be a contraction not very common of
the lower parts of ravines. The geological structure is, as might be
expected, more remarkable. Other summits of the range are porphyritic,**
but the hills of Wingen present a variety of rocks, within a small space.
In the adjacent gullies to the south of the hill, we find clay of a grey
mottled appearance, and shale containing apparently a small quantity of
decomposed vegetable matter; and near the fissure then on fire, occurred
a coarse sandstone with an argillaceous basis. To the north-west, in a
hollow containing water which drains from beneath the part ignited, is a
coarse sandstone, in some places highly charged with decomposed felspar,
and containing impressions of spirifers. The hill nearest to the part on
fire, on the south-west (b) consists of basalt with grains apparently of
olivine; and on a still higher hill, on the east (a) I found ironstone. A
small hill (c) connecting these two, and nearest to the part actually
burning, appears to consist of trap-rock, and is thickly strewed with
agates. The hills on the opposite or south side of the valley are
composed of compact felspar, with acicular crystals of glassy or common
felspar and grains of hornblende, crevices of the stone being coated with
films of serpentine or green earth.

(*Footnote. Volume 4 part 1 Second Series Geological Transactions,
Professor Buckland and Mr. De la Beche on the Geology of the
neighbourhood of Weymouth.)