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OBSERVATIONS
ON
MOUNT VESUVIUS,
MOUNT ETNA,
AND OTHER VOLCANOS:

IN
A SERIES OF LETTERS,

Addressed to THE ROYAL SOCIETY,

From the Honourable Sir W. HAMILTON,
K.B. F.R.S.

His Majesty's Envoy Extraordinary and Plenipotentiary
at the Court of NAPLES.

To which are added,

Explanatory NOTES by the AUTHOR,
hitherto unpublished.

A NEW EDITION.

LONDON,
Printed for T. CADELL, in the Strand.
M DCC LXXIV.




THE EDITOR
TO
THE PUBLIC.


Having mentioned to Sir WILLIAM HAMILTON the general Desire of all
Lovers of Natural History, that his Letters upon the Subject of VOLCANOS
should be collected together in one Volume, particularly for the
Convenience of such as may have an Opportunity of visiting the curious
Spots described in them: He was not only pleased to approve of my
having undertaken this Publication, but has likewise favoured with the
additional explanatory Notes and Drawings,

                              The PUBLIC's most obliged,
                              and devoted
                              humble Servant,

                              T. CADELL.

May 30, 1772.




OBSERVATIONS
ON
MOUNT VESUVIUS, &c.




LETTER I.

To the Right Honourable the Earl of MORTON, President of the Royal
Society.


                              Naples, June 10, 1766.

My LORD,

As I have attended particularly to the various changes of Mount
Vesuvius, from the 17th of November 1764, the day of my arrival at this
capital; I flatter myself, that my observations will not be unacceptable
to your Lordship, especially as this Volcano has lately made a very
considerable eruption. I shall confine myself merely to the many
extraordinary appearances that have come under my own inspection, and
leave their explanation to the more learned in Natural Philosophy.

During the first twelvemonth of my being here, I did not perceive any
remarkable alteration in the mountain; but I observed, the smoke from
the Volcano was much more considerable in bad weather than when it was
fair[1]; and I often heard (even at Naples, six miles from Vesuvius) in
bad weather, the inward explosions of the mountain. When I have been at
the top of Mount Vesuvius in fair weather, I have sometimes found so
little smoke, that I have been able to see far down the mouth of the
Volcano; the sides of which were incrusted with salts and mineral of
various colors, white, green, deep and pale yellow. The smoke that
issued from the mouth of the Volcano in bad weather was white, very
moist, and not near so offensive as the sulphureous steams from various
cracks on the sides of the mountain.

Towards the month of September last, I perceived the smoke to be more
considerable, and to continue even in fair weather; and in October I
perceived sometimes a puff of black smoke shoot up a considerable height
in the midst of the white, which symptom of an approaching eruption grew
more frequent daily; and soon after, these puffs of smoke appeared in
the night tinged like clouds with the setting sun.

About the beginning of November, I went up the mountain: it was then
covered with snow; and I perceived a little hillock of sulphur had been
thrown up, since my last visit there, within about forty yards of the
mouth of the Volcano; it was near six feet high, and a light blue flame
issued constantly from its top. As I was examining this phaenomenon, I
heard a violent report; and saw a column of black smoke, followed by a
reddish flame, shoot up with violence from the mouth of the Volcano; and
presently fell a shower of stones, one of which, falling near me, made
me retire with some precipitation, and also rendered me more cautious of
approaching too near, in my subsequent journies to Vesuvius.

From November to the 28th of March, the date of the beginning of this
eruption, the smoke increased, and was mixed with ashes, which fell, and
did great damage to the vineyards in the neighbourhood of the
mountain[2]. A few days before the eruption I saw (what Pliny the
younger mentions having seen, before that eruption of Vesuvius which
proved fatal to his uncle) the black smoke take the form of a pine-tree.
The smoke, that appeared black in the day-time, for near two months
before the eruption, had the appearance of flame in the night.

On Good Friday, the 28th of March, at 7 o'clock at night, the lava began
to boil over the mouth of the Volcano, at first in one stream; and soon
after, dividing itself into two, it took its course towards Portici. It
was preceded by a violent explosion, which caused a partial earthquake
in the neighbourhood of the mountain; and a shower of red hot stones and
cinders were thrown up to a considerable height. Immediately upon sight
of the lava, I left Naples, with a party of my countrymen, whom I found
as impatient as myself to satisfy their curiosity in examining so
curious an operation of nature. I passed the whole night upon the
mountain; and observed that, though the red hot stones were thrown up in
much greater number and to a more considerable height than before the
appearance of the lava, yet the report was much less considerable than
some days before the eruption. The lava ran near a mile in an hour's
time, when the two branches joined in a hollow on the side of the
mountain, without proceeding farther. I approached the mouth of the
Volcano, as near as I could with prudence; the lava had the appearance
of a river of red hot and liquid metal, such as we see in the
glass-houses, on which were large floating cinders, half lighted, and
rolling one over another with great precipitation down the side of the
mountain, forming a most beautiful and uncommon cascade; the color of
the fire was much paler and more bright the first night than the
subsequent nights, when it became of a deep red, probably owing to its
having been more impregnated with sulphur at first than afterwards. In
the day-time, unless you are quite close, the lava has no appearance of
fire; but a thick white smoke marks its course.

The 29th, the mountain was very quiet, and the lava did not continue.
The 30th, it began to flow again in the same direction, whilst the mouth
of the Volcano threw up every minute a girandole of red hot stones, to
an immense height. The 31st, I passed the night upon the mountain: the
lava was not so considerable as the first night; but the red hot stones
were perfectly transparent, some of which, I dare say of a ton weight,
mounted at least two hundred feet perpendicular, and fell in, or near,
the mouth of a little mountain, that was now formed by the quantity of
ashes and stones, within the great mouth of the Volcano, and which made
the approach much safer than it had been some days before, when the
mouth was near half a mile in circumference, and the stones took every
direction. Mr. Hervey, brother to the Earl of Bristol, was very much
wounded in the arm some days before the eruption, having approached too
near; and two English gentlemen with him were also hurt. It is
impossible to describe the beautiful appearance of these girandoles of
red hot stones, far surpassing the most astonishing artificial
fire-work.

From the 31st of March to the 9th of April, the lava continued on the
same side of the mountain, in two, three, and sometimes four branches,
without descending much lower than the first night. I remarked a kind of
intermission in the fever of the mountain[3], which seemed to return
with violence every other night. On the 10th of April, at night, the
lava disappeared on the side of the mountain towards Naples, and broke
out with much more violence on the side next the _Torre dell'
Annunciata_.

I passed the whole day and the night of the twelfth upon the mountain,
and followed the course of the lava to its very source: it burst out of
the side of the mountain, within about half a mile of the mouth of the
Volcano, like a torrent, attended with violent explosions, which threw
up inflamed matter to a considerable height, the adjacent ground
quivering like the timbers of a water-mill; the heat of the lava was so
great, as not to suffer me to approach nearer than within ten feet of
the stream, and of such a consistency (though it appeared liquid as
water) as almost to resist the impression of a long stick, with which I
made the experiment; large stones thrown on it with all my force did not
sink, but, making a slight impression, floated on the surface, and were
carried out of sight in a short time; for, notwithstanding the
consistency of the lava, it ran with amazing velocity; I am sure, the
first mile with a rapidity equal to that of the river Severn, at the
passage near Bristol. The stream at its source was about ten feet wide,
but soon extended itself, and divided into three branches; so that these
rivers of fire, communicating their heat to the cinders of former lavas,
between one branch and the other, had the appearance at night of a
continued sheet of fire, four miles in length, and in some parts near
two in breadth. Your Lordship may imagine the glorious appearance of
this uncommon scene, such