Chapter VI: Letter V (2)

The lake of Avernus fills the bottom of the crater of a mountain, undoubtedly produced by explosion, and whose interior and exterior form, as well as the matter of which it is composed, exactly resemble the Monte Barbaro and Monte Nuovo. At that part of the basis of this mountain which is washed by the sea of the bay of Puzzole, the sand is still very hot, though constantly washed by the waves; and into the cone of the mountain, near this hot sand, a narrow passage of about 100 paces in length is cut, and leads to a fountain of boiling water, which, though brackish, boils fish and flesh without giving them any bad taste or quality, as I have experienced more than once. This place is called Nero's bath, and is still made use of for a sudatory, as it was by the ancients; the steam that rises from the hot fountain abovementioned, confined in the narrow subterraneous passage, soon produces a violent perspiration upon the patient who sits therein. This bath is reckoned a great specifick in that distemper which is supposed to have made its appearance at Naples before it spread its contagion over the other parts of Europe.

Virgil and other ancient authors say, that birds could not fly with safety over the lake of Avernus, but that they fell therein; a circumstance favouring my opinion, that this was once the mouth of a Volcano. The vapour of the sulphur and other minerals must undoubtedly have been more powerful, the nearer we go back to the time of the explosion of the Volcano; and I am convinced that there are still some remains of those vapours upon this lake, as I have observed there are very seldom any water-fowl upon it; and that when they do go there, it is but for a short time; whilst all the other lakes in the neighbourhood are constantly covered with them, in the winter season. Upon Mount Vesuvius, in the year 1766, during an eruption, when the air was impregnated with noxious vapours, I have myself picked up dead birds frequently.

The castle of Baia stands upon a considerable eminence, composed of the usual _tufa_ and strata of pumice and ashes; from which I concluded I should find some remains of the craters from whence the matter issued: accordingly, having ascended the hill, I soon discovered two very visible craters, just behind the castle.

The lake called the Mare-morto was also, most probably, the crater, from whence issued the materials which formed the Promontory of Misenum, and the high grounds around this lake. Under the ruins of an ancient building, near the point of Misenum, in a vault, there is a vapour, or _mofete_, exactly similar in its effects to that of the Grotto del Cane, as I have often experienced.

The form of the little island of Nisida shews plainly its origin[40]. It is half a hollow cone of a Volcano cut perpendicularly; the half crater forms a little harbour called the Porto Pavone; I suppose the other half of the cone to have been detached into the sea by earthquakes, or perhaps by the violence of the waves, as the part that is wanting is the side next to the open sea.

The fertile and pleasant island of Procita shews also most evident signs of its production by explosion, the nature of its soil being directly similar to that of Baia and Puzzole; this island seems really, as was imagined by the ancients, to have been detached from the neighbouring island of Ischia.

There is no spot, I believe, that could afford a more ample field for 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.

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.