that, if it did not
always appear as a distinct mineral, it was easily discovered in
combination with other chlorides. The specimens which I have collected
are not the most beautiful, but the presence of lead in the sublimations
is not less common.

Micaceous peroxide of iron, when found on the lava, has been mostly
conveyed from the eruptive mouths, as I have already stated, and perhaps
never so abundantly and evidently as on this occasion. The lava of the
26th of April carried along a large quantity of round masses or bombs,
varying in size, among which were found antecedent lava more or less
covered with micaceous iron, either collected in the cavities of the
lava, or incorporated with its mass. Sometimes the micaceous iron
appears like little veins in the paste of new lava enveloping the
exterior of these rounded masses, an exterior compact and lithoidal, and
not resembling scoriae. Among these spherical masses I found one of
enormous size, four to five metres in diameter, which, having broken up
where the exterior envelope was thinnest, I found filled with a great
mass of lapilli and fragments of other lavas covered with micaceous
iron. This bomb still preserves (June 5th) an elevated temperature
within, and emits smoke and hydrochloric acid, which, meeting the
micaceous iron discovered by breaking the envelope with blows of a
hammer, transforms it superficially into chloride of iron, showing most
clearly how, on some occasions at least, chloride of iron is formed from
the oxide which precedes it. That those lapilli and the pieces of lava
were solid when enveloped in the paste of the new lava, we infer from
seeing the impressions on the inside of the said envelope. The chloride
of calcium, which I found in this spherical mass almost pure, caused me
to suspect that the sulphate of lime which is so often found on Vesuvius
is a transformation of the chloride produced by the contact of
sulphurous acid, which easily becomes transformed into sulphuric acid.
The hydrochloric acid which escapes from a fumarole coming into contact
with the scoriae near its mouth, produces chloride of iron, which is,
therefore, not always obtained by sublimation, although, when the
temperature is very high, chloride of iron is conveyed from the interior
of the lava, and sublimes on the exterior and colder parts; for
instance, the chloride of iron which issues from the eruptive cones is
sometimes found sublimed on the rocks of Monte di Somma.