F VESUVIUS
OF
_1871-1872_

I.

ACCOUNT OF THE ERUPTION.

The great and disastrous conflagration of Vesuvius, which took place on
the 26th of April, 1872, was, in my opinion, the last phase of an
eruption which commenced at the end of January, 1871, an account of
which I was unwilling to write, because I was convinced that it would
not really terminate without a more or less violent explosion, such as I
had often predicted. I shall now state the reasons upon which my
prediction was founded.

When the central crater begins to heave, with slight eruptions, one may
always predict a series of slight convulsions of greater or less
duration, which are preparatory to the grand explosion, after which the
Volcano remains for the most part in repose. Thus, when I observed the
cone fissuring in November, 1868, and copious lava streams issuing from
it, and flowing over the beautiful and fertile plains of the Novelle,
through the Fossa della Vetrana, instead of announcing the beginning of
an eruption, I announced the termination of one which had been manifest
for upwards of a year by the constant flow of lava from the summit of
the cone.

From the month of November, 1868, until the end of December, 1870, the
mountain remained quiet, except that the fumaroles at the head of the
fissure showed a degree of activity by which chlorides and sulphides of
copper, sulphide of potash and other products, were engendered.

But in the beginning of 1871 the seismograph was disturbed,[1] and the
crater discharged, with a slight detonation, a few incandescent
projectiles. Then I announced that _a new eruption had commenced, which
might be of long duration, but with phases that could not possibly be
foreseen_; and on the 13th January, on the northern edge of the upper
plain of the Vesuvian cone, an aperture appeared, from which at first a
little lava issued, and then a small cone arose and threw out
incandescent projectiles, with much smoke of a reddish colour, whilst
the central crater continued to detonate more loudly and frequently. The
lava-flow continued to increase until the beginning of March, without
extending much beyond the base of the cone, although it had great
mobility. In March, this little cone appeared not only to subside, but
even partly to give way, as almost happens with eccentric cones when
their activity is at an end. Upon visiting it, I observed that four
prismatic or pillar-like masses remained standing, three