When chloride
of iron has been produced by sublimation, we may collect it inside a
glass bell placed over the fumarole, or upon a piece of brick; but when
it is produced by the action of hydrochloric acid on the scoriae, it will
only be found on the scoriae themselves.

If, therefore, the origin of micaceous peroxide of iron were due to the
decomposition of the sesqui-chloride of iron requiring a more elevated
temperature for its decomposition, it would follow that its genesis
would be easier near the discharging mouths, and more difficult on the
lavas, but there the fact was verified: for example, in the great bomb
on the fumarole, where we observed micaceous iron transformed into
chloride of iron. We may therefore consider it _proved_ that some
chlorides--for instance, chloride of sodium--issue from the lava itself,
either being there pre-existent, or being formed there; and that others
are derived from the oxides which precede them, as undoubtedly is the
case with chloride of copper; hence, the theory that derives the oxides
always from the chlorides cannot be considered true. Granting that this
theory might be applicable to the origin of micaceous iron, we should
still want to know how it is found with the paste of the new lava
itself, which forms the exterior coating of the bombs above described.

Many of these rounded masses, which have been rolled along by the lava,
contain scoriae partly decomposed by the long action of the acids found
on the fumaroles of the craters. They disintegrate easily, and have a
more or less yellowish tint. In the greater number of cases the interior
of these masses is formed of leucitic lava, with cavities lined with
micaceous iron. In short, their contents appeared to me quite similar to
the material of the cone of 1871 and 1872, which in all probability was
engulfed in the large crevasse or fissure that opened below it; and the
fragments having thus fallen down into the lava, were enveloped by it
and carried out by it after having been more or less rounded. The
external envelope of these spheres is not at all scoriaceous, but
compact and lithoidal, and sometimes composed of concentric folds or
plaits.

As to the gaseous emanations of fumaroles, watery vapour with few
exceptions comes first; this conveys the material which first appears in
the sublimations, viz., sea-salt, and for the most part oxide of copper.
If the fumarole continue active, it passes from the neutral period to