some places, covered the micaceous iron with a yellow
coating of chloride of iron. From small apertures, on the lower side of
the mass, white and green stalactites of chloride of calcium were
visible. In one spot only of lava I found a fumarole, with a small
quantity of micaceous peroxide of iron, evidently in a state of
formation; but this was the very spot where the lava became eruptive,
and whence issued the column of smoke which was so well
photographed--the place under the hill of Apicella. (See Plate 4a.)

I have enumerated the products which are constantly collected in
fumaroles, although they are not all found at the same time or place, in
order to show that the sublimations follow a certain law in their
appearance. _Tenorite_, for instance, was formerly considered an
accidental product of certain eruptions, and I have always found it; but
if you visit the fumarole when the acids have had time to transform it,
you will no longer see it. I found the crystallized chloride of lead, or
"cotunuite," as it is called, for the first time in the lavas of 1855,
and thought it a singular circumstance; but from that time I recognised
it in all the lavas, though not always so beautiful and abundant; and
even when not found as a distinct substance, I observed it in
combination with chloride of copper. In the lavas of the 26th April
_cotunuite_ and _tenorite_[E] were not very abundant, because the
chloride of iron disturbed the greater number of the sublimations. I
found sal ammoniac very abundantly on the fumaroles of the lavas that
invaded the cultivated ground. Although chloride of ammonia, contrary to
opinion, was not wanting in the sublimations of the fumaroles of the
lavas deposited on other lavas, yet it was neither abundant nor
crystallized, but combined in small quantities with other substances. It
appeared in great abundance in all the fumaroles of lavas which covered
cultivated or woody ground. At first it was scarce enough, and mixed
with chloride of sodium; but when the rains came the sea-salt was washed
away, and sal ammoniac formed beautiful crystals, nearly free from
adventitious matters, as was the case with the fumaroles of the last
lava. Afterwards, when chloride of iron was produced, ferro-chloride of
ammonia was found. Crystals of sal ammoniac were sometimes found of a
beautiful amber yellow. This colour was, in the opinion of my colleague,
Professor Scacchi, produced by such small traces of chloride of iro