curious observations, than the island of Ischia, called Enaria, Inarime,
and Pithecusa, by the ancients. I have visited it three times; and this
summer passed three weeks there, during which time I examined, with
attention, every part of it. Ischia is eighteen miles in circumference:
the whole of its soil is the same as that near Vesuvius, Naples, and
Puzzole. There are numberless springs, hot, warm, and cold[41],
dispersed over the whole island, the waters of which are impregnated
with minerals of various sorts; so that, if you give credit to the
inhabitants of the country, there is no disorder but what finds its
remedy here. In the hot months (the season for making use of these
baths), those who have occasion for them flock hither from Naples. A
charitable institution sends and maintains three hundred poor patients
at the baths of Gurgitelli every season. By what I could learn of these
poor patients, those baths have really done wonders, in cases attended
with obstinate tumours, and in contractions of the tendons and muscles.
The patient begins by bathing, and then is buried in the hot sand near
the sea. In many parts of the island, the sand is burning hot, even
under water. The sand on some parts of the shore is almost entirely
composed of particles of iron ore; at least they are attracted by the
load-stone, as I have experienced. Near that part of the island called
Lacco, there is a rock of an ancient lava, forming a small cavern, which
is shut up with a door; this cavern is made use of to cool liquors and
fruit, which it does in a short time as effectually as ice. Before the
door was opened, I felt the cold to my legs very sensibly; but when it
was opened, the cold rushed out so as to give me pain; and within the
grotto it was intolerable. I was not sensible of wind attending this
cold; though upon Mount Etna and Mount Vesuvius, where there are caverns
of this kind, the cold is evidently occasioned by a subterraneous wind:
the natives call such places _ventaroli_. May not the quantity of nitre,
with which all these places abound, account in some measure for such
extreme cold? My thermometer was unluckily broken, or I would have
informed you of the exact degree of the cold in this _ventaroli_ of
Ischia, which is by much the strongest in its effects I ever felt. The
ancient lavas of Ischia shew, that the eruptions there have been very
formidable; and history informs us, that its first inhabitants were
driven out of the island by the frequency and the violence of them.
There are some of these ancient lavas not less than two hundred feet in
depth. The mountain of St. Nicola, on which there is at present a
convent of hermits, was called by the ancients Epomeus; it is as high,
if not higher, than Vesuvius, and appears to me to be a section of the
cone of the ancient and principal Volcano of the island, its composition
being all _tufa_ or lava. The cells of the convent abovementioned are
cut out of the mountain itself; and there you see plainly that its
composition no way differs from the matter that covers Herculaneum, and
forms the Monte Nuovo. There is no sign of a crater on the top of this
mountain, which rises almost to a sharp point: time, and other
accidents, may be reasonably supposed to have worn away this distinctive
mark of its having been formed by explosion, as I have seen to be the
case in other mountains, formed evidently by explosion, on the flanks of
Etna and Vesuvius. Strabo, in his 5th book, upon the subject of this
island, quotes Timaeus, as having said, that, a little before his time, a
mountain in the middle of Pithecusa, called Epomeus, was shook by an
earthquake, and vomited flames.
There are many other rising grounds in this island, that, from the
nature of their composition, must lead one to think the same as to their
origin. Near the village of Castiglione, there is a mountain formed
surely by an explosion of a much later date, having preserved its
conical form and crater entire, and producing as yet but a slender
vegetation: there is no account, however, of the date of this eruption.
Nearer the town of Ischia, which is on the sea shore, at a place called
_Le Cremate_, there is a crater, from which, in the year 1301 or 1302, a
lava ran quite into the sea; there is not the least vegetation on this
lava, but it is nearly in the same state as the modern lavas of
Vesuvius. Pontano, Maranti, and D. Francesco Lombardi, have recorded
this eruption; the latter of whom says, that it lasted two months; that
many men and beasts were killed by the explosion; and that a number of
the inhabitants were obliged to seek for refuge at Naples and in the
neighbouring islands. In short, according to my idea, the island of
Ischia must have taken its rise from the bottom of the sea, and been
increased to its present size by divers later explosions. This is not
extraordinary, when history tells us (and from my own observation I have
reason to believe) that the Lipari islands were formed in the like
manner. There has been no eruption in Ischia since that just mentioned,
but earthquakes are very frequent there; two years ago, as I was told,
they had a very considerable shock of an earthquake in this island.
Father Goree's account of the formation of the new island in the
Archipelago (situated between the two islands called Kammeni, and near
that of Santorini) of which he was an eye-witness, strongly confirms the
probability of the conjectures I venture to send you, relative to the
formation of those islands and that part of the continent above
described: it seems likewise to confirm the accounts given by Strabo,
Pliny, Justin, and other ancient authors, of many islands in the
Archipelago, formerly called the Ciclades, having sprung up from the
bottom of the sea[42] in the like manner. According to Pliny, in the
4th year of the CXXXVth Olympiad, 237 years before the Christian aera,
the island of Thera (now Santorini) and Theresia were formed by
explosion; and, 130 years later, the island Hiera (now called the great
Kammeni) rose up. Strabo describes the birth of this island in these
words: "In the middle space between Thera and Theresia flames burst out
of the sea for four days, which, by degrees, throwing up great masses,
as if they had been raised by machines, they formed an island of twelve
stadia in circuit." And Justin says of the same island, "Eodem anno
inter insulas Theramenem et Theresiam, medio utriusque ripae et maris
spatio, terrae motus fuit: in quo, cum admiratione navigantium, repente
ex profundo cum calidis aquis Insula emersit."
Pliny mentions also the formation of Aspronisi, or the White Island, by
explosion, in the time of Vespasian. It is known, likewise, that in the
year 1628, one of the islands of the Azores, near the island of St.
Michael, rose up from the bottom of the sea, which was in that place 160
fathoms deep; and that this island, which was raised in fifteen days, is
three leagues long, a league and a half broad, and rises three hundred
and sixty feet above water.
Father Goree, in his account of the formation of the new island in the
Archipelago, mentions two distinct matters that entered into the
composition of this island, the one black, the other white. Aspronisi,
probably from its very name, is composed of the white matter, which if,
upon examination, it proves to be a _tufa_, as I strongly suspect, I
should think myself still more grounded in my conjectures; though I must
confess, as it is, I have scarcely a doubt left with respect to the
country I have been describing having been thrown up in a long series
of ages by various explosions from subterraneous fire. Surely there are
at present many existing Volcanos in the known world; and the memory of
many others have been handed down to us by history. May there not
therefore have been many others, of such ancient dates as to be out of
the reach of history[43]?
Such wonderful operations of Nature are certainly intended by all-wise
Providence for some great purpose. They are not confined to any one part
of the globe, for there are Volcanos existing in the four quarters of
it. We see the great fertility of the soil thrown up by explosion, in
part of the country I have described, which on that account was called
by the ancients _Campania Felix_. The same circumstance is evident in
Sicily, justly esteemed one of the most fertile spots in the world, and
the granary of Italy. May not subterraneous fire be considered as the
great plough (if I may be allowed the expression), which Nature makes
use of to turn up the bowels of the earth, and afford us fresh fields to
work upon, whilst we are exhausting those we are actually in possession
of, by the frequent crops we draw from them? Would it not be found, upon
enquiry, that many precious minerals must have remained far out of our
reach, had it not been for such operations of Nature? It is evidently so
in this country. But such great enquiries would lead me far indeed. I
will only add a reflection, which my little experience in this branch of
natural history furnishes me with. It is, that we are apt to judge of
the great operations of Nature on too confined a plan. When first I came
to Naples, my whole attention, with respect to natural history, was
confined to Mount Vesuvius, and the wonderful phaenomena attending a
burning mountain: but, in proportion as I began to perceive the evident
marks of the same operation having been carried on in the different
parts above described, and likewise in Sicily in a greater degree, I
looked upon Mount Vesuvius only as a spot on which Nature was at present
active; and thought myself fortunate in having an opportunity of seeing
the manner in which one of her great operations (an operation, I
believe, much less out of her common course than is generally imagined)
was effected.
Such remarks as I have made on the eruptions of Mount Vesuvius, during
my residence at Naples, have been transmitted to the Royal Society, who
have done them more honour than they deserved. Many more might be made
upon this active Volcano, by a person who had leisure, a previous
knowledge of the natural history of the earth, a knowledge of chemistry,
and was practised in physical experiments, particularly those of
electricity[44]. I am convinced, that the smoak of Volcanos contains
always a portion of electrical matter; which is manifest at the time of
great eruptions, as is mentioned in my account of the great eruption of
Vesuvius in 1767. The peasants in the neighbourhood of my villa,
situated at the foot of Vesuvius, have assured me, that, during the
eruption last mentioned, they were more alarmed by the lightning and
balls of fire that fell about them with a crackling noise, than by the
lava and the usual attendants of an eruption. I find in all the accounts
of great eruptions mention made of this sort of lightning, which is
distinguished here by the name of _Ferilli_. Bracini, in his account of
the great one of Vesuvius in 1631, says, that the column of smoak, which
issued from its crater, went over near an hundred miles of country, and
that several men and beasts were struck dead by lightning, issuing from
this smoak in its course.
The nature of the noxious vapours, called here _mofete_, that are
usually set in motion by an eruption of the Volcano, and are then
manifest in the wells and subterraneous parts of its neighbourhood, seem
likewise to be little understood. From some experiments very lately
made, by the ingenious Dr. Nooth, on the _mofete_ of the Grotto del
Cane, it appears that all its known qualities and effects correspond
with those attributed to fixed air. Just before the eruption of 1767, a
vapour of this kind broke into the King's chapel at Portici, by which a
servant, opening the door of it, was struck down. About the same time,
as his Sicilian Majesty was shooting in a paddock near the palace, a dog
dropped down, as was supposed, in a fit; a boy going to take him up
dropped likewise; a person present, suspecting the accident to have
proceeded from a _mofete_, immediately dragged them both from the spot
where they lay, in doing which, he was himself sensible of the vapour;
the boy and the dog soon recovered. His Sicilian Majesty did me the
honour of informing me himself of this accident soon after it had
happened. I have met with these _mofetes_ often, when I have been making
my observations on the borders of Mount Vesuvius, particularly in
caverns, and once on the Solfaterra. The vapour affects the nostrils,
throat, and stomach, just as the spirit of hartshorn, or any strong
volatile salts; and would soon prove fatal, if you did not immediately
remove from it. Under the ancient city of Pompeii, the _mofetes_ are
very frequent and powerful, so that the excavations that are carrying on
there are often interrupted by them; at all times _mofetes_ are to be
met with under ancient lavas of Vesuvius, particularly those of the
great eruption of 1631. In Serao's account of the eruption of 1737, and
in the chapter upon _mofetes_, he has recorded several curious
experiments relative to this phaenomenon. The Canonico Recupero, who, as
I mentioned to you in a former letter, is watching the operations of
Mount Etna, has just informed me, that a very powerful _mofete_ has
lately manifested itself in the neighbourhood of Etna; and that he
found, near the spot from whence it rises, animals, birds, and insects,
dead, and the stronger sort of shrubs blasted, whilst the grass and the
tenderer plants did not seem to be affected. The circumstance of this
_mofete_, added to that of the frequent earthquakes felt lately at
Rhegio and Messina, makes it probable that an eruption of Mount Etna is
at hand.
I am alarmed at the length of this letter. By endeavouring to make
myself clearly understood, I have been led to make, what I thought,
necessary digressions. I must therefore beg of your goodness, that,
should you find this memoir, in its present state, too tedious (which I
greatly apprehend) to be presented to our respectable Society, you will
make only such extracts from it as you shall think will be most
agreeable and interesting. I am,
SIR,
With great truth and regard,
Your most obedient
humble servant,
W. HAMILTON.
[Illustration: _Plate VI._]
REFERENCES to the MAP,
[Plate VI.]
1. Naples.
2. Portici.
3. Resina, under which Herculaneum is buried.
4. Torre del Greco.
5. Hermitage, at which travellers usually rest, in their way up
Mount Vesuvius.
6. St. Angelo, a convent of Calmaldolese, situated upon a cone of
a mountain formed by an ancient explosion.
7. Cones formed by the eruption of 1760, and lava that ran from
them almost into the sea.
8. Mount Vesuvius and Somma.
9. Village of Somma.
10. The convent of the Madona del Arco, under which lavas have
been found at 300 feet depth, and which must have proceeded
from the mountain of Somma, when an active Volcano.
11. Ottaiano.
12. Torre del Annunziata.
13. Castel a Mare, near which the ancient town of Stabia is
buried, and where Pliny the elder lost his life.
14. Vico.
15. Sorrento, and the plain formed evidently by subterraneous
fire.
16. Massa.
17. Island of Caprea.
18. The Grotto of Pausilipo, cut through the mountain anciently,
to make a road from Naples to Puzzole.
19. Point of Pausilipo.
20. The Gaiola, where there are ruins of ancient buildings,
supposed to have belonged to Lucullus.
21. The island of Nisida, evidently formed by explosion.
22. The Lazaret.
23. The Bagnoli.
24. Puzzole, or Pozzuolo.
25. The Solfaterra, anciently called Forum Vulcani: between the
Solfaterra and the lake of Agnano, are the boiling waters of
the Pisciarelli.
26. The New Mountain, formed by explosion in the year 1538; the
sand of the sea shore at its basis burning hot.
27. The lake of Agnano, supposed the crater of an ancient Volcano:
here are the baths called St. Germano, and the famous Grotto
del Cane.
28. Astruni, which has been evidently a Volcano, and is now a
Royal Chace, the crater being surrounded with a wall.
29. The Monte Gauro or Barbaro, anciently a Volcano.
30. The lake of Avernus, evidently the crater of an ancient
Volcano.
31. Lake of Fusaro.
32. Point of Misenum, from whence Pliny the elder discovered the
eruption of Vesuvius that proved fatal to him; near this
place, in a vault of an ancient building, is a constant
vapour, or _mofete_, of the same quality with that of the
Grotto del Cane.
33. The Mare Morto, the ancient Roman Harbour.
34. Baia; behind the castle are two evident craters of ancient
Volcanos.
35. Island of Procita.
36. A perfect cone and crater of a Volcano near Castiglione in the
island of Ischia.
37. Lava that ran into the sea in the last eruption on this
island, in the year 1301, or 1302: the place now called Le
Cremate.
38. Town of Ischia and castle.
39. Lake of Licola.
40. Lake of Patria.
41. The river Volturnus.
42. Capua.
43. Caserta.
44. Aversa.
45. Mataloni.
46. Acerra.
47. Island of Ischia, anciently called AEnaria, Inarime, and
Pithecusa.
48. The mountain of St. Nicola, anciently called Mons Epomeus,
supposed the remains of the principal Volcano of the island.
49. Castiglione, near which are the baths of Gurgitelli.
50. Lacco, near which is that very cold vapour called by the
natives _ventarole_.
51. Ancient city of Pompeii, where his Sicilian Majesty's
excavations are carrying on at present.
52. Rovigliano.
53. River of Sarno.
54. Cuma.
55. Hot sands and sudatory, called Nero's baths.
56. The Lucrine lake, supposed to have been here, and of which
there is still some little remain.
57. Villa Angelica, Sir William Hamilton's villa, from whence he
has made many of his observations upon Mount Vesuvius.
58. Cones formed by an ancient eruption called _viuli_; here are
likewise cold vapours called _ventaroli_.
59. High grounds, probably sections of cones of ancient Volcanos,
being all composed of _tufa_ and strata of loose pumice and
burnt matter.
60. Plain of the Campagna Felice, four or five feet of excellent
soil, under which are strata of burnt and erupted matter.
...... Marks the boundary of Sir William Hamilton's observations.
LETTER VI.[45]
To MATHEW MATY, M. D. Secretary to the Royal SOCIETY.
Naples, March 5, 1771.
Since I had the pleasure of sending you my letter, in which the nature
of the soil of more than twenty miles round this capital is described;
examining a deep hollow way cut by the rain waters into the outside cone
of the Solfaterra, I discovered, that a great part of the cone of that
ancient Volcano has been calcined by the hot vapours above described.
Pumice calcined seems to be the chief ingredient, of which several
specimens of (as I suppose) variegated unformed marble are composed, and
the beautiful variegations in them may have probably been occasioned by
the mineral vapours. As these specimens are now sent to the Royal
Society, you will see that these variegations are exactly of the same
pattern and colours as are met in many marbles and flowered alabasters;
and I cannot help thinking that they are marble or alabaster in its
infant state. What a proof we have here of the great changes the earth
we inhabit is subject to! What is now the Solfaterra, we have every
reason to suppose to have been originally thrown up by a subterraneous
explosion from the bottom of the sea. That it was long an existing
Volcano, is plain, from the ancient currents of lava, that are still to
be traced from its crater to the sea, from the strata of pumice and
erupted matter, of which its cone, in common with those of other
Volcanos, is composed, and from the testimony of many ancient authors.
Its cone in many parts has been calcined, and is still calcining, by the
hot vapours that are continually issuing forth through its pores; and
its nature is totally changed by this chemical process of Nature. In the
hollow way, where I made these remarks, you see the different strata of
erupted matter, that compose the cone, in some places perfectly
calcined, in others not, according as the vapours have found means to
insinuate themselves more or less.
A hollow way, cut by the rains on the back of the mountain on which part
of Naples is situated, towards Capo di China, shews that the mountain is
composed of strata of erupted matter, among which are large masses of
bitumen, in which its former state of fluidity is very visible. Here it
was I discovered that pumice stone is produced from bitumen, which I
believe has not yet been remarked. Some specimens shew evidently the
gradual process from bitumen to pumice: and you will observe that the
crystalline vitrifications, which are visible in the bitumen, suffer no
alteration, but remain in the same state in the perfect pumice as in the
bitumen.
In a piece of stratum, calcined from the outside of the Solfaterra, the
form and texture of the pumice stones is very discernible. In several
parts of the outside cone, this calcining operation is still carried on,
by the exhalation of constant very hot and damp vapours, impregnated
with salts, sulphur, alum, &c. Where the abovementioned vapours have not
operated, the strata of pumice and erupted matter, that compose the cone
of the Solfaterra, are like those of all the high grounds in its
neighbourhood, which I suppose to have been thrown up likewise by
explosion. I have seen here, half of a large piece of lava perfectly
calcined, whilst the other half out of the reach of the vapours has
been untouched; and in some pieces the centre seems to be already
converted into true marble.
The variegated specimens then, above described, are nothing more than
pumice and erupted matter, after having been acted upon in this manner
by the hot vapours; and if you consider the process, as I have traced
it, from bitumen to pumice, and from pumice to marble, you will think
with me, that it is difficult to determine the primitive state of the
many wonderful productions we see in Nature.
I found, in the _tufa_ of the mountain of Pausilipo, a fragment of lava:
one side I polished, to shew it to be true lava; the other shews the
signs of the _tufa_, with which it is incorporated. It has evidently
been rounded by friction, and most probably by rolling in the sea. Is it
not natural then to imagine that there must have been Volcanos near this
spot, long before the formation of the mountain of Pausilipo? This
little stone may perhaps raise in your mind such reflections as it did
in mine, relative to the great changes our globe suffers, and the
probability of its great antiquity.
FOOTNOTES:
[1] Having reflected since upon this circumstance, I rather believe that
the weight of the atmosphere in bad weather, preventing the free
dissipation of the smoke, and collecting it over the crater, gives it
the appearance of being more considerable; whereas in fine weather the
smoke is dispersed soon after its emission. It is, however, the
common-received opinion at Naples (and from my own observation is, I
believe, well founded), that when Vesuvius grumbles, bad weather is at
hand. The sea of the Bay of Naples, being particularly agitated, and
swelling some hours before the arrival of a storm, may very probably
force itself into crevices, leading to the bowels of the Volcano, and,
by causing a new fermentation, produce those explosions and grumblings.
[2] These ashes destroy the leaves and fruit, and are greatly
detrimental to vegetation for a year or two; but are certainly of great
service to the land in general, and are among the principal causes of
that very great fertility which is remarkable in the neighbourhood of
Volcano's.
[3] In the subsequent eruptions of Vesuvius, I have constantly remarked
something of the same nature, as appears in my account of the great
eruption of 1767. I have found the same remark in many accounts of
former eruptions of Vesuvius: in the very curious one of the formation
of a new mountain near Puzzole, in 1538, (as may be seen in my letter to
Dr. Maty, Oct. 16, 1770[46],) the same observation is made. This
phaenomenon, is well worthy of a curious inquiry, which might give some
light into the theory of the earth, of which, I believe, we are very
ignorant.
[4] I am convinced, that it might be very practicable to divert the
course of a lava when in this state, by preparing a new bed for it, as
is practised with rivers. I was mentioning this idea at Catania in
Sicily, when I was assured, that it had been done with success during
the great eruption of Etna, in 1669; that the lava was directing its
course towards the walls of Catania, and advancing slowly like the
abovementioned, when they prepared a channel for it round the walls of
the town, and turned it into the sea; that a succession of men, covered
with sheep-skins wetted, were employed to cut through the tough flanks
of the lava, till they made a passage for that in the centre (which was
in perfect fusion) to disgorge itself into the channel prepared for it.
A book I have since met with gives the same account of this curious
operation; it is intituled, _Relatione del nuovo incendio fatto da
Mongibello 1669. Messina, Giuseppe Bisagni, 1670_. His Sicilian
Majesty's palace at Portici, and the valuable collection of antiquities
that have been recovered from beneath the destructive lava's of
Vesuvius, are in imminent danger of being overwhelmed again by the next
that shall take its course that way; whereas, by taking a level, cutting
away and raising ground, as occasion might require, the palace and
museum would, in all probability, be insured, at least against one
eruption; and, indeed, I once took the liberty of communicating this
idea to the King of Naples, who seemed to approve of it.
[5] The late Lord Morton was pleased to give these specimens to Dr.
Morris, who has made several chemical experiments on them, the result of
which will be communicated to the Royal Society.