two discordant elements must have sustained, when the liquid
lava encountered the waves of the ocean. The effects of
such a struggle are still more distinctly seen on an extraordinary
insulated rock of a pyramidal form, which rises out of
the sea a little to the right of the entrance into the crater.
The height of this rock is from two to three hundred feet, and
it is composed of forty or fifty horizontal layers piled very
regularly on each other; and these are again cracked and
divided by a number of perpendicular fissures, the whole exhibiting
a huge mass of basaltic columns. The marks of fusion
are evident on every part of its surface, which has the appearance
of scoria from an iron furnace. Many of the perpendicular
fissures were filled with veins of obsidian or volcanic glass,
which we could perceive to be extended several feet below
the surface of the sea. In other clefts we found some curious
specimens of zeolite, but looked for this substance in vain in
the fragments of solid lava. We were the more desirous of
establishing this fact, as it is one of the contested points between
the Plutonists and the Neptunists. Zeolite being frequently
found in the midst of basalt, and being well known
to contain a considerable quantity of water, has furnished
one of the strongest arguments in favour of the Neptunists;
in so far a t least as it militates against the doctrine of basaltic
columns being produced by the agency of subterranean heat.
Zeolite and volcanic glasses, such as obsidian and pumice
stone, we found abundantly on every part off the coast of
the island.
On the two causeways in the breach made by the sea into
the crater, and in many places on its-slanting sides, we found
several thermal springs, some running freely, and others oozing
out in a mere paste or mud. In some of these springs Fahrenheit’s
thermometer ascended from 62°, in the open air, to 196 ;
in some to 204°; and in others to 212% or the boiling point.
The spots where they are to be found are easily discoverable,
before sunrise or after sunset, by a thin vapour which may be
seen distinctly on applying the eye to the ground. In several
places we observed patches' of soft verdure, composed of a
fine delicate moss, blended with a species of Lycopodium
and another of Marchantia. These green patches were
found to be floating on a hot paste, whose temperature, at
eight or ten inches below the surface, upon which the roots
of the plants spread, was 186°. This was the more remarkable,
as the same species of Lycopodium or club-moss, for
such it was thought to be, grows with ^great luxuriance, even
in the winter season, on the bleak heaths of North Britain.
On every part of the sloping surface of the island we met with
swamps and stagnant pools of hot water, varying in temperature
from 80° to 130°. The soil is of a spongy porous texture,
and the ground feels tremulous under the feet. Where-
ever the ear is applied to the surface, a bubbling noise may.
be heard like the boiling of water. Most of the springs are
rather brackish, but one in particular on the side of the great
crater is strongly chalybeate, and the temperature only 112 .
From the perusal of a paper in the 20th volume of the Philosophical
Transactions, we were prepared to meet with springs
of boiling water; and on the strength of tlie information contained
in the said paper, “ that the fish caught in the cold
“ water might instantly be boiled in the hot,” we took care
to provide ourselves with plenty of fishing-tackle. We caught