a decomposed by the hot issuing gases.
Hydrochloric acid is said to frequently issue from the crater; the gases
that were most abundant appeared to be sulphurous acid and steam. The
interior of the crater appeared to be very similar to that of the
Solfatara near Puzzuoli. During the descent from the cone we collected
various specimens of ash and cinder, some red, others black and very
vesicular, others crystalline, some pale pink. The steep slope of the
cone was well shown by the fact that, although the surface is either
extremely rugged owing to the accumulation of masses of lava, or soft
and yielding on account of the depth of cinders, a large mass of lava
set rolling at the top rushes down with increasing velocity until it
bounds off to the level plain below.

[Illustration: View of the Val de Bove]

The great cone is formed by the accumulation of sand, scoriae, and masses
of rock ejected from the crater; it is oval in form, and has varied both
in shape and size in the course of centuries. When we saw it, it was not
full of smoke or steam; but it was possible to see to the bottom of it,
in spite of small jets of steam which issued from the sides. It
presented the appearance of a profound funnel-shaped abyss; the sides of
which were covered with an efflorescence of a red or yellow, and
sometimes nearly white, colour. The crater presented the same appearance
when it was seen by Captain Smyth in 1814, but he was so fortunate as to
witness it in a less quiescent state. "While making these observations,"
he writes, "on a sudden the ground trembled under our feet, a harsh
rumbling with sonorous thunder was heard, and volumes of heavy smoke
rolled over the side of the crater, while a lighter one ascended
vertically, with the electric fluid escaping from it in frequent flashes
in every direction.... During some time the ground shook so violently
that we apprehended the whole cone would tumble into the burning gulf
(as it actually had done several times before) and destroy us in the
horrible consequences; however, in less than a couple of hours all was
again clear above and quiet within." When Mr. Gladstone ascended in
1838, the volcano was in a slight state of eruption: "The great
features of this action," he writes, "are the sharp and loud claps,
which perceptibly shook from time to time the ground of the mountain
under our feet; the sheet of flame which leapt up with a sudden
momentary blast, and soon disappeared in smoke