LETTER VI.[45]

The account of the formation of the Monte Nuovo, by Pietro Giacomo di Toledo, is given in a dialogue between the feigned personages of Peregrino and Svessano; the former of which says, "It is now two years that this province of Campagna has been afflicted with earthquakes, the country about Pozzuolo much more so than any other parts; but the 27th and the 28th of the month of September last, the earthquakes did not cease day or night, in the abovementioned city of Pozzuolo; that plain, which lies between the lake of Averno, the Monte Barbaro, and the sea, was raised a little, and many cracks were made in it, from some of which issued water; and at thesame time the sea, which was very near the plain, dried up about two hundred paces, so that the fish were left on the sand, a prey to the inhabitants of Pozzuolo. At last, on the 29th of the said month, about two hours in the night, the earth opened near the lake, and discovered a horrid mouth, from which were vomited furiously, smoak, fire, stones, and mud composed of ashes; making, at the time of its opening, a noise like very loud thunder: the fire, that issued from this mouth, went towards the walls of the unfortunate city; the smoak was partly black and partly white; the black was darker than darkness itself, and the white was like the whitest cotton: these smoaks, rising in the air, seemed as if they would touch the vault of heaven; the stones that followed were, by the devouring flames, converted to pumice, the size of which (of some I say) were much larger than an ox. The stones went about as high as a cross-bow cancarry, and then fell down, sometimes on the edge, and sometimes into the mouth itself. It is very true that many of them in going up could not be seen, on account of the dark smoak; but, when they returned from the smoaky heat, they shewed plainly where they had been, by their strong smell of fetid sulphur, just like stones that have been thrown out of a mortar, and have passed through the smoak of inflamed gunpowder. The mud was of the colour of ashes, and at first very liquid, then by degrees less so; and in such quantities, that in less than twelve hours, with the help of the abovementioned stones, a mountain was raised of a thousand paces in height. Not only Pozzuolo and the neighbouring country was full of this mud, but the city of Naples also, the beauty of whose palaces were, in a great measure, spoiled by it. The ashes were carried as far as Calabria by the force of the winds,burning up in their passage the grass and high trees, many of which were borne down by the weight of them. An infinity of birds also, and numberless animals of various kinds, covered with this sulphureous mud, gave themselves up a prey to man. Now this eruption lasted two nights and two days without intermission, though, it is true, not always with the same force, but more or less: when it was at its greatest height, even at Naples you heard a noise or thundering like heavy artillery when two armies are engaged. The third day the eruption ceased, so that the mountain made its appearance uncovered, to the no small astonishment of every one who saw it. On this day, when I went up with many people to the top of this mountain; I saw down into its mouth, which was a round concavity of about a quarter of a mile in circumference, in the middle of which the stones that had fallen were boilingup, just as in a great cauldron of water that boils on the fire. The fourth day it began to throw up again, and the seventh much more, but still with less violence than the first night; it was at this time that many people, who were unfortunately on the mountain, were either suddenly covered with ashes, smothered with smoak, or, knocked down by stones, burnt by the flame, and left dead on the spot. The smoak continues to this day[39], and you often see in the night-time fire in the midst of it. Finally, to complete the history of this new and unforeseen event, in many parts of the new-made mountain, sulphur begins to be generated." Giacomo di Toledo, towards the end of his dissertation uponthe phÃ¦nomena attending this eruption, says, that the lake of Avernus had a communication with the sea, before the time of the eruption; and that he apprehended that the air of Puzzole might come to be affected in summer time, by the vapours from the stagnated waters of the lake; which is actually the case.

You have, Sir, from these accounts, an instance of a mountain, of a considerable height and dimensions, formed in a plain, by mere explosion, in the space of forty-eight hours. The earthquakes having been sensibly felt at a great distance from the spot where the opening was made, proves clearly, that the subterraneous fire was at a great depth below the surface of the plain; it is as clear that those earthquakes, and the explosion, proceeded from the same cause, the former having ceased upon the appearance of the latter. Does not this circumstance evidently contradict the system of M. Buffon, and of all the natural historians, who have placed the seat of the fireof Volcanos towards the center, or near the summit of the mountains, which they suppose to furnish the matter emitted? Did the matter which proceeds from a Volcano in an eruption come from so inconsiderable a depth as they imagine, that part of the mountain situated above their supposed seat of the fire must necessarily be destroyed, or dissipated in a very short time: on the contrary, an eruption usually adds to the height and bulk of a Volcano; and who, that has had an opportunity of making observations on Volcanos, does not know, that the matter they have emitted for many ages, in lavas, ashes, smoak, &c. could it be collected together, would more than suffice to form three such mountains as the simple cone or mountain of the existing Volcano? With respect to Vesuvius, this could be plainly proved; and I refer to myletterupon the subject of Etna, to shew the quantity of matter thrown up in one single eruption, by that terrible Volcano. Another proof, that the real seat of the fire of Volcanoslies even greatly below the general level of the country whence the mountain springs, is, that was it only at an inconsiderable depth below the basis of the mountain, the quantity of matter thrown up would soon leave so great a void immediately under it, that the mountain itself must undoubtedly sink and disappear after a few eruptions.

In the above accounts of the formation of the new mountain, we are told that the matter first thrown up, was mud composed of water and ashes, mixed with pumice stones and other burnt matter: on the road leading from Puzzole to Cuma, part of the cone of this mountain has been cut away, to widen the road. I have there seen that its composition is atufaintermixed with pumice, some of which are really of the size of an ox, as mentioned in Toledo's account, and exactly of the same nature as thetufaof which every other high ground in its neighbourhood is composed; similar also to that which coversHerculaneum. According to the above accounts, after the muddy shower ceased, it rained dry ashes: this circumstance will account for the strata of loose pumice and ashes, that are generally upon the surface of all thetufasin this country, and which were most probably thrown up in the same manner. At the first opening of the earth, in the plain near Puzzole, both accounts say, that springs of water burst forth; this water, mixing with the ashes, certainly occasioned the muddy shower; when the springs were exhausted, there must naturally have ensued a shower of dry ashes and pumice, of which we have been likewise assured. I own, I was greatly pleased at being in this manner enabled to account so well for the formation of thesetufastones and the veins of dry and loose burnt matter above them, of which the soil of almost the whole country I am describing is composed; and I do not know that any one has ever attended to this circumstance, though I find that many authors, who havedescribed this country, have suspected that parts of it were formed by explosion. Wherever then this sort oftufais found, there is certainly good authority to suspect its having been formed in the same manner as thetufaof this new mountain, for, as I said before, Nature is generally uniform in all her operations.

It is commonly imagined that the new mountain rose out of the Lucrine lake, which was destroyed by it; but in the above account, no mention is made of the Lucrine lake; it may be supposed then, that the famous dam, which Strabo and many other ancient authors mention to have separated that lake from the sea, had been ruined by time or accident, and that the lake became a part of the sea before the explosion of 1538.

If the above-described eruption was terrible, that which formed the Monte Barbaro (or Gauro, as it was formerly called), must have been dreadful indeed. It joins immediately to the new mountain, whichin shape and composition it exactly resembles; but it is at least three times as considerable. Its crater cannot be less than six miles in circumference; the plain within the crater, one of the most fertile spots I ever saw, is about four miles in circumference: there is no entrance to this plain, but one on the East side of the mountain, made evidently by art; in this section you have an opportunity of seeing that the matter of which the mountain is composed is exactly similar to that of the Monte Nuovo. It was this mountain that produced (as some authors have supposed) the celebrated Falernian wine of the ancients.

Cuma, allowed to have been the most ancient city of Italy, was built on an eminence, which is likewise composed oftufa, and may be naturally supposed a section of the cone formed by a very ancient explosion.

The lake of Avernus fills the bottom of the crater of a mountain, undoubtedly producedby 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 appearanceat 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 BaÃ¯a stands upon a considerable eminence, composed of the usualtufaand 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, ormofete, 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 ahollow 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 BaÃ¯a 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 eighteenmiles 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. Inmany 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 placesventaroli. May not the quantity of nitre, with which all these places abound, account in some measure for such extremecold? My thermometer was unluckily broken, or I would have informed you of the exact degree of the cold in thisventaroliof 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 alltufaor 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 TimÃ¦us, 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 calledLe 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 earthquakesare 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 thelike manner. According to Pliny, in the 4th year of thecxxxvth Olympiad, 237 years before the Christian Ã¦ra, 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 ripÃ¦ et maris spatio, terrÃ¦ 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 atufa, 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 thrownup 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 ancientsCampania 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 MountVesuvius, and the wonderful phÃ¦nomena 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, particularlythose 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, haveassured 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 ofFerilli. 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 heremofete, 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 themofeteof the Grotto del Cane, it appears that all itsknown 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 amofete, 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 thesemofetesoften, 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 thespirit 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, themofetesare very frequent and powerful, so that the excavations that are carrying on there are often interrupted by them; at all timesmofetesare 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 uponmofetes, he has recorded several curious experiments relative to this phÃ¦nomenon. The Canonico Recupero, who, as I mentioned to you in a formerletter, is watching the operations of Mount Etna, has just informed me, that a very powerfulmofetehas 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 circumstanceof thismofete, 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 obedienthumble servant,W. Hamilton.

Plate VI.

Referencesto theMap,[Plate VI.]

ToMathew Maty, M. D. Secretary to the RoyalSociety.

Naples, March 5, 1771.

Since I had the pleasure of sending you myletter, 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 ancientVolcano 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 eruptedmatter, 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 believehas 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 theother 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 thetufaof 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 thetufa, 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 littlestone 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 phÃ¦nomenon, 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.[6]From what I have seen and read of eruptions of Vesuvius and Etna, I am convinced that Volcano's lie dormant for several years, nay even for centuries, as probably was the case of Vesuvius before its eruption in the reign of Titus, and certainly was so before that of the year 1631. When I arrived at Naples in 1764, Vesuvius was quiet, very seldom smoak was visible on its top; in the year 1766, it seemed to take fire, and has never since been three months without either throwing up red hot stones, or disgorging streams of lava, nor has its crater been ever free from smoak. At Naples, when a lava appears, and not till then, it is styled an eruption; whereas I look upon the five nominal eruptions I have been witness to, from March 1766 to May 1771, as, in effect, but one continued eruption.[7]It is certain, that, by constant attention to the smoak that issues from the crater, a very good guess may be given as to the degree of fermentation within the Volcano. By this alone I foretold[47]the two last eruptions, and, by another very simple observation, I pointed out, some time before, the very spot from whence the lava has issued. When the cone of Vesuvius was covered with snow, I had remarked a spot on which it would not lie: concluding very naturally that this was the weakest part of the cone, and that the heat from within prevented the snow from lying; it was as natural to imagine that the lava, seeking a vent, would force this passage sooner than another; and so indeed it came to pass.[8]These are his words: "Nubes (incertum procul intuentibus ex quo monte Vesuvium fuisse postea cognitum est) oriebatur, cujus similitudinem & formam, non alia magis arbor, quam pinus expresserit. Nam longissimo veluti trunco elata in altum, quibusdam ramis diffundebatur, credo quia recenti spiritu evecta, dein senescente eo destituta, aut etiam pondere suo victa, in latitudinem evanescebat: candida interdum, interdum sordida & maculosa, prout terram cineremve sustulerat." Plin. lib. vi. ep. 16.[9]The windows at Naples open like folding-doors.[10]In several accounts of former eruptions of Vesuvius, I have found mention of the ashes falling at a much greater distance; that, in the year 472 and 473, they had reached Constantinople: Dio says, that during the eruption of Vesuvius in the time of Titusâ€”"tantus fuit pulvis ut ab eo loco in Africam et Syriam et Ã†gyptum penetraverit." A book printed at Lecce, in the kingdom of Naples, inmdcxxxii, and intituled,Discorso sopra l'origine de fuochi gettati dal Monte Vesuvio di Gio Francesco Sorrata Spinola Galateo, says, that the 16th of December, 1631, the very day of the great eruption of Vesuvius (though perfectly calm), it rained ashes at Lecce, which is nine days journey from the mountain: that the day was darkened by them, and that they covered the ground three inches deep; that ashes of a different quality fell at Bari the same day; and that at both these places the inhabitants were very greatly alarmed, not being able to conceive the occasion of such a phÃ¦nomenon. Antonio Bulifon, in his account of the same eruption, says, that the ashes fell, and lay several inches deep at Ariano in Puglia; and I have been assured, by many persons of credit at Naples, that they have been sensible of the fall of ashes, during an eruption, at above two hundred miles distance from Vesuvius. The Abbate Giulio Cesare Bracini, in his account of the eruption of Vesuvius, in 1631, says, that the height of the column of smoak and ashes, taken from Naples by a quadrant, was upwards of thirty miles. Though such uncertain calculations demand but little attention; yet, by what I have seen, I am convinced, that in great eruptions the ashes are sent up to so great a height as to meet with extraordinary currents of air, which is the most probable way of accounting for their having been carried to so great a distance in a few hours. In a book, intituled,Salvatoris Varonis Vesuviani incendii Libri tres: Neapoli,mdcxxxiv, I found a very poetical description of the ashes that lay in the neighbourhood of Vesuvius, after the eruption of 1631, in depth, from twenty to a hundred palms: "Quare," says this author, "multi patrio in solo requirunt patriam, et vix ibi se credunt vivere ubi certo sciant sese natos, adeo totam loci speciem tempestas vertit."[11]This conjecture has proved true; for, even in the month of April 1771, I again thrust sticks into some crevices of this lava, and they immediately took fire. On Mount Etna, in 1769, I observed the lava, that had been disgorged in 1766, smoak in many parts.[12]In all accounts of great eruptions of Mount Etna and Mount Vesuvius, I have found mention of this sort of lightning. Pliny the younger, in his second letter to Tacitus upon the eruption of Vesuvius in the time of Titus, says, that a black and horrible cloud covered them at Misenum (which is above fifteen miles from the Volcano), and that flashes of zig-zag fire, like lightning, but stronger, burst from it; these are his words: "ab altero latere nubes atra et horrenda ignei spiritus tortis vibratisque discursibus rupta, in longas flammarum figuras dehiscebat; fulgoribus illÃ¦ et similes et majores erant." This was evidently the same electrical fire, and with which I am convinced that the smoak of all Volcanos is pregnant. In several accounts of the great eruption of Vesuvius in 1631, mention is made of damage done by the lightning that issued from the column of smoak. Bulifon, in particular, says, that, in the neighbourhood of the Volcano, people were struck dead in the same manner as if by lightning, without having their cloaths singed. Pliny mentions a like instance, which shews that the ancients had observed this phÃ¦nomenon; for he says, that at Pompeii, the day being fair, Marcus Herennius was struck dead by lightning. These are his words; "In Catilianis prodigiis, Pompeiano ex municipio M. Herennius Decurioserena die, fulmine ictus est." Plin. Hist. Nat. lib. II. cap.li.The learned and ingenious Father Beccaria, at Turin, assured me, that he had been greatly pleased with my observations on this species of lightning, as coinciding perfectly with several of his electrical experiments.[13]"I am well convinced, by this collection, that many variegated marbles, and many precious stones, are the produce of Volcanos; and that there have been Volcanos in many parts of the world, where at present there are no traces of them visible." This is taken from a prior letter to Lord Morton, dated April 7, 1767.[14]In some accounts of an eruption of Vesuvius in 1660, I find mention made of ashes which fell in the shape of crosses, and were looked upon as highly miraculous; but in one book upon this subject, intituled,Athanasii Kircheri Soc. Jes. De prodigiosis crucibus, &c. RomÃ¦,mdclxi, a very philosophical account is given of this phÃ¦nomenon; he says, that, in 1660, from the 16th of August to the 15th of October, Vesuvius cast up ashes, impregnated with nitrous, saline, and bituminous sulphur, which upon linen garments took the form of crosses, probably directed by the cross-threads in the linen, and therefore that the salts did not shoot into such a shape when they fell upon garments of woollen; a very particular description of these crosses may be found in page 38, of the abovementioned book.[15]I have since found in this stratum of erupted matter at Pompeii, stones weighing eight pounds: but many accounts of the great eruption of Vesuvius, particularly that of Antonio Bulifon, mention that a stone like a bomb was thrown from the crater of Vesuvius in 1631; and fell upon the Marquis of Lauro's house at Nola, which it set on fire. As Nola is twelve miles from Vesuvius, this circumstance seems rather extraordinary: however, I have seen stones of an enormous size shot up to a very great height by Mount Vesuvius. In May 1771, having a stop watch in my hand, I observed that one of these stones was eleven seconds falling from its greatest height, into the crater from whence it had been ejected. In 1767, a solid stone, measuring twelve feet in height, and forty-five in circumference, was thrown a quarter of a mile from the crater; the eruption of 1767, though by much the most violent of this century, was, comparatively to those of the year 79 and 1631, very mild.[16]SeeLetter V.in this collection.[17]It is the common received opinion, that this mountain rose from the bottom of the Lucrine lake. I had not seen the very curious and particular account of its formation (which account is in my nextletter) when I wrote this, and was therefore in the same error.[18]This must depend greatly upon the quality of the lava's; some have been in a more perfect state of vitrification than others, and are consequently less liable to the impressions of time. I have often observed on Mount Vesuvius, when I have been close to the mouth from whence a lava was disgorging itself, that the quality of it varied greatly from time to time: I have seen it as fluid and coherent as glass when in fusion: and I have seen it farinacious, the particles separating as they forced their way out, just like meal coming from under the grindstones. A stream of lava of this sort, being less compact, and continuing more earthy particles, would certainly be much sooner fit for vegetation, than one composed of the more perfect vitrified matter.[19]This earthquake happened in the year 1693, and destroyed forty-nine towns and villages, nine hundred and twenty-two churches, colleges, and convents; and near one hundred thousand persons were buried in their ruin.[20]It is intituled, "A true and exact relation of the late prodigious earthquake and eruption of Mount Ã†tna, or Monte Gibello; as it came in a letter written to his Majesty from Naples, by the Right Honourable the Earl of Winchelsea, his Majesty's late Embassador at Constantinople, who, in his return from thence, visiting Catania in the island of Sicily, was an eye-witness of that dreadful spectacle; together with a more particular narrative of the same, as it is collected out of the several relations sent from Catania; published by authority. Printed by T. Newcomb, in the Savoy, 1669.""I accepted, says the author, p. 38, the invitation of the Bishop of Catania, to stay a day with him, that so I might be the better able to inform your Majesty of that extraordinary fire, which comes from Mount Gibel, fifteen miles distant from that city, which, for its horridness in the aspect, for the vast quantity thereof (for it is fifteen miles in length, and seven in breadth), for its monstrous devastation and quick progress, may be termed an inundation of fire, a flood of fire, cinders, and burning stones, burning with that rage as to advance into the sea six hundred yards, and that to a mile in breadth, which I saw; and that which did augment my admiration was, to see in the sea this matter like ragged rocks, burning in four fathom water, two fathom higher than the sea itself, some parts liquid, and throwing off, not with great violence, the stones about it, which, like a crust of a vast bigness, and red hot, fell into the sea every moment, in some place or other, causing a great and horrible noise, smoak, and hissing in the sea; and that more and more coming after it, making a firm foundation in the sea itself. I stayed there from nine a clock on Saturday morning, to seven next morning;" (this must have been towards the middle or latter end of April;) "and this mountain of fire and stones with cinders had advanced into the sea twenty yards at least, in several places; in the middle of this fire, which burnt in the sea, it hath formed like to a river, with its banks on each side very steep and craggy; and in this channel moves the greatest quantity of this fire, which is the most liquid, with stones of the same composition, and cinders all red hot, swimming upon the fire of a great magnitude; from this a river of fire doth proceed under the great mass of the stones, which are generally three fathoms high all over the country, where it burns, and in other places much more. There are secret conduits or rivulets of the liquid matter, which communicates fire and heat into all parts more or less, and melts the stones and cinders by fits in those places where it toucheth them, over and over again; where it meets with rocks or houses of the same matter (as many are), they melt and go away with the fire; where they find other compositions, they turn them to lime or ashes (as I am informed). The composition of this fire, stones, and cinders, are sulphur, nitre, quicksilver, sal ammoniac, lead, iron, brass, and all other metals. It moves not regularly, nor constantly down hill[48]; in some places it hath made the vallies hills, and the hills that are not high are now vallies. When it was night, I went upon two towers, in divers places; and could plainly see at ten miles distance, as we judged, the fire to begin to run from the mountain in a direct line, the flame to ascend as high and as big as one of the greatest steeples in your Majesty's kingdoms, and to throw up great stones into the air; I could discern the river of fire to descend the mountain of a terrible fiery or red colour, and stones of a paler red to swim thereon, and to be some as big as an ordinary table. We could see this fire to move in several other places, and all the country covered with fire, ascending with great flames[49], in many places, smoaking like to a violent furnace of iron melted, making a noise with the great pieces that fell, especially those which fell into the sea. A Cavalier of Malta, who lives there, and attended me, told me, that the river was as liquid where it issues out of the mountain, as water, and came out like a torrent with great violence, and is five or six fathom deep, and as broad, and that no stones sink therein. I assure your Majesty, no pen can express how terrible it is, nor can all the art and industry of the world quench or divert that which is burning in the country. In forty days time, it hath destroyed the habitations of 27,000 persons; made two hills of one, 1000 paces high apiece, and one is four miles in compass; of 20,000 persons, which inhabit Catania, 3000 did only remain; all their goods are carried away, the cannons of brass are removed out of the castle, some great bells taken down, the city-gates walled up next the fire, and preparations made to abandon the city."That night which I lay there, it rained ashes all over the city, and ten miles at sea it troubled my eyes. This fire in its progress met with a lake of four miles in compass; and it was not only satisfied to fill it up, though it was four fathom deep, but hath made of it a mountain."[21]I have heard since, from some of our countrymen who have measured this tree, that its dimensions are actually as abovementioned, but that they could perceive some signs of four stems having grown together, and formed one tree.[22]No great stress should be laid upon these observations, as the many inconveniences we laboured under, and the little practice we had in such nice operations, must necessarily have rendered them very inaccurate. The Canon Recupero, who was our guide, attended Mess. Glover, Fullerton, and Brydone, up Mount Etna in June 1770. The latter is a very ingenious and accurate observer, and has taken the height of many of the highest mountains in the Alps. His observations, as the Canon informed me, were as follows: At the top of the mountain the quicksilver in the thermometer was 9 degrees below freezing point, when at the foot of the mountain it rose to 76. At the foot of the little mountain that crowns the Volcano the barometer stood at 20Â° 42/3', half way up this little mountain it was at 19Â° 6'; but the wind was too violent for them to attempt any more observations. The barometer and thermometer were of Fahrenheit's. Mr. Brydone remarked, as he went up in the night, that he could distinguish the stars in the milky way with wonderful clearness, and that the cold was much more intense than he had ever felt upon the highest mountains of the Alps.[23]This passage, in Cornelius Severus's poem upon Etna, seems to confirm my opinion:"Placantesque etiam cÃ¦lestia numina thure"Summo cerne jugo, vel quÃ¢ liberrimus Ã†tna"Improspectus hiat; tantarum semina rerum"Si nihil irritet flammas, stupeatque profundum."[24]A better account of the formation oftufawill be seen in my nextletter.[25]The dates of the eruptions of Mount Etna, recorded by history, are as follows: Before the Christian Ã¦ra four, in the years 3525. 3538. 3554. 3843. After Christ, twenty-seven have been recorded, 1175. 1285. 1321. 1323. 1329. 1408. 1530. 1536. 1537. 1540. 1545. 1554. 1556. 1566. 1579. 1614. 1634. 1636. 1643. 1669. 1682. 1689. 1692. 1702. 1747. 1755. 1766.The dates of the eruptions of Vesuvius are as follows: After Christâ€”79. 203. 472. 512. 685. 993. 1036. 1043. 1048. 1136. 1506. [1538, the eruption at Puzzole.] 1631. 1660. 1682. 1694. 1701. 1704. 1712. 1717. 1730. 1737. 1751. 1754. 1760. 1766. 1767. 1770. 1771.[26]Pliny, in his account of these islands, in theixchapter of the third book of his Natural History, seems to confirm this opinion."Lipara cum civium Romanorum oppido, dicta Ã Liparo rege, qui successit Ã†olo, antea Melogonis vel Meliganis vocitata, abestxiimillia pass. ab Italia, ipsa circuitu paulo minori. Inter hanc et Siciliam altera, antea Therasia appellata, nunc Hiera; qui sacra Vulcano est, colle in ea nocturnas evomente flammas. Tertia Strongyle, a Lipara millia passuum ad exortum solis vergens, in qua regnavit Ã†olus, quÃ¦ Ã Lipara liquidiore flamma tantum differt: e cujus fumo equinam flaturi sint venti, in triduum prÃ¦dicere incolÃ¦ traduntur; unde ventos Ã†olo paruisse existimatum. Quarta Didyme, minor quam Lipara. Quinta Ericusa; sexta PhÅ“nicusa; pabulo proximarum relicta.Novissima, eademque Minima, Evonymos."[27]SeePlate V.[28]The Abate Giulio Cesare Bruccini describes very elegantly, in his account of the eruption of Vesuvius in 1631, his having made an observation of the like natureâ€”his words are (after having particularized the different strata of erupted matter lying one over another)â€”"parendo appunto che la natura ci abbia voluto lasciare scritto in questa terra tutti gli incendii memorabili raccontati delli autori."[29]These are his words, book II. chap. vi."De Pulvere Puteolano."Est etiam genus pulveris, quod efficit naturaliter res admirandas. Nascitur in regionibus BaÃ¯anis, et in agris municipiorum, quÃ¦ sunt circa Vesuvium montem, quod commixtum cum calce et cÃ¦mento non modo cÃ¦teris Ã¦dificiis prÃ¦stat firmitates, sed etiam moles, quÃ¦ construuntur in mari, sub aqua solidescunt. Hoc autem fieri hac ratione videtur, quod sub his montibus et terra ferventes sunt fontes crebri, qui non essent, si non in imo haberent, aut de sulfure, aut alumine, aut bitumine ardentes maximos ignes: igitur penitus ignis, et flammÃ¦ vapor per intervenia permanans et ardens, efficet levem eam terram, et ibi, qui nascitur tophus, exugens est, et sine liquore. Ergo cum tres res consimili ratione, ignis vehementia formatÃ¦ in unam pervenerint mixtionem, repente recepto liquore una cohÃ¦rescunt, et celeriter humore duratÃ¦ solidantur, neque eas fluctus, neque vis aquÃ¦ potest dissolvere."About BaÃ¯a, Puzzole, and Naples, we have an opportunity of remarking the truth of these last words. Several of the piers of the ancient harbour of Puzzole, vulgarly called Caligula's bridge, and which are composed of bricks joined with this sort of cement, are still standing in the sea, though much exposed to the waves; and upon every part of the shore you find large masses of brick-walls rounded and polished by friction in the sea, the brick and mortar making one body, and appearing like a variegated stone. Large pieces of old walls are likewise often cut out into square pieces, and made use of in modern buildings instead of stone.Soon after the first quotation, Pliny says, "Si ergo in his locis aquarum ferventes inveniuntur fontes, et in montibus excavatis calidi vapores, ipsaque loca ab antiquis memorantur pervagantes in agris habuisse ardores, videtur esse certum ab ignis vehementia ex topho terraque, quemadmodum in fornacibus et a calce, ita ex his ereptum esse liquorem. Igitur dissimilibus, et disparibus rebus correptis, et in unam potestatem collatis, callida humoris jejunitas aqua repente satiata, communibus corporibus latenti calore confervescit et vehementer effecit ea coire, celeriterque una soliditatis percipere virtutem."[30]Scipione Falcone, a very good observer, in hisDiscorso naturale delli cause et effetti del Vesuvio, says, that he saw, after the eruption of Vesuvius in 1631 (which was attended with hot water), the mud harden almost to a stone in a few days; his words are theseâ€”"fatta dura a modo di calcina e di pietra non altrimenti di cenere, perchÃ© dopÃ² alcuni giorni vi ci e caminato per sopra e si e conosciuta durissima che ci vogliono li picconi per romperla." This account, with other circumstances mentioned in this letter, make it highly probable, that all thetufasin the neighbourhood of Vesuvius have been formed by a like operation.[31]This piece is now in the Museum of the Royal Society, together with other specimens, mentioned in this and in thefollowing letter. M. M.[32]Letter IV.[33]Strabo, in his fifth book of Geography, says, "Supra hÃ¦c loca situs est Vesuvius mons agris cinctus optimis: dempto vertice, qui magna sui parte planus, totus sterilis est, adspectu cinÃ¦reus, cavernasque ostendens fistularum plenas et lapidum colore fuliginoso, utpote ab igni exesorum, ut conjecturam facere possit ista loca quondam arsisse, et crateras ignis habuisse, deinde materia deficiente restincta fuisse."Diodorus Siculus, in his fourth book, describing the voyage of Hercules into Italy, says, "PhlegrÃ¦us quoque campus is locus appellatur a colle nimirum, qui Ã†tnÃ¦ instar SiculÃ¦ magnam vim ignis eructabat; nunc Vesuvius nominatur, multa inflammationis pristinÃ¦ vestigia reservans." And Vitruvius, in the sixth chapter of the second book, says, "Non minus etiam memoratur antiquitus crevisse ardores et abundasse sub Vesuvio monte et inde evomuisse circa agros flammas." Tacitus, mentioning the eruption of Vesuvius in the reign of Titus, seems to hint likewise at former eruptions, in these words: "Jam verÃ² novis cladibus, vel post longam sÃ¦culorum repetitis afflictÃ¦, haustÃ¦ aut abrutÃ¦ fecundissima CampaniÃ¦ ora et urbs incendiis vastata."[34]Bracini, in his account of the eruption of 1613, says, that he found many sorts of sea shells on Vesuvius after that eruption; and P. Ignatio, in his account of the same eruption, says, that he and his companions picked up many shells likewise at that time upon the mountain: this circumstance would induce one to believe, that the water thrown out of Vesuvius, during that formidable eruption, came from the sea.[35]In book xi. c. 93. he observes, that about Sinuessa and Puteoli, "Spiracula vocantâ€”alii Caroneas scrobes, mortiferum spiritum exhalantes." And Seneca, Nat. QuÃ¦st. lib. vi. cap. 28. "Pluribus ItaliÃ¦ locis per quÃ¦dam foramina pestilens exhalatur vapor, quem non homini ducere, non ferÃ¦ tutum est. Aves quoque si in illum inciderint, antequam cÅ“lo meliore leniatur, in ipso volatu cadunt, liventque corpora, et non aliter quam per vim elisÃ¦ fauces tument."[36]I have remarked, that, after a great fall of rain, the degree of heat in this water is much less, which will account for what the Padre Torre says (in his book, entituled,Histoire et Phenomenes du Vesuve), that, when he tried it in company with Monsieur de la Condamine, the degree of heat, upon Reaumur's thermometer, was 68Â°.[37]This very scarce volume has been presented by Sir William Hamilton to the British Museum. M. M.[38]Here again we have an example of the electrical fire attending a great eruption.[39]The cup, or crater, on the top of the new mountain is now covered with shrubs; but I discovered at the bottom of it, in the year 1770, amidst the bushes, a small hole, which exhales a constant hot and damp vapour, just such as proceeds from boiling water, and with as little smell; the drops of this steam hang upon the neighbouring bushes.[40]The noxious vapours which Lucan mentions to have prevailed at Nisida, favour my opinion as to its origin:"â€”Tali spiramine Nesis"Emittit stygium nebulosis aÃ«ra saxis."Lucan. lib. vi.[41]Giulio Cesare Capaccio, in his account of this island, says, that there are eleven springs of cold water, and thirty-five of hot and mineral waters.[42]By having remarked, that all the implements of stone brought by Mess. Banks and Solander from the new-discovered islands in the South-Seas, are evidently of such a nature as are only produced by Volcanos; and as these gentlemen have assured me, that no other kind of stone is to be met with in the islands; I am induced to think, that these islands (at so great a distance from any continent) may have likewise been pushed up from the bottom of the sea by like explosions.[43]Any one, the least conversant in Volcanos, must be struck with the numberless evident marks of them the whole road from the lake of Albano to Radicofani, between Naples and Florence; and yet, though this soil bears such fresh and undoubted marks of its origin, no history reaches the date of any one eruption in these parts.[44]May not the air in countries replete with sulphur be more impregnated with electrical matter than the air of other soils? and may not the sort of lightning, which is mentioned by several ancient authors to have fallen in a serene day, and was considered as an omen, have proceeded from such a cause?Horace says, Ode xxxiv."â€”Namque Diespeter"Igni corusco nubila dividens"Plerumque per purum tonantes"Egit equos volucremque currum.""Non alias cÅ“lo ceciderunt plura sereno"Fulguraâ€”â€”"Virgil. Georgic. i."Aut cum terribili perculsus fulmine civis"Luce serenanti vitalia lumina liquit."Cic. i. de Divin. n. 18."â€”Sabinos petit aliquanto tristior, quod sacrificanti hostia aufugerat: quodque tempestate serena tonuerat."Sueton.Tit.cap. 10.[45]This letter was not received by Dr. Maty in its present form: and is rather the substance of an explanatory catalogue, which was sent to that gentleman with sundry specimens of the different materials that compose the soil described in the precedingletter; which catalogue remains, with the specimens, in the Museum of the Royal Society, for the inspection, and, I flatter myself, the satisfaction, of the curious in natural history.[46]Seep. 103of this collection.[47]SeeLetter I.p. 18.[48]Having heard the same remark with respect to the lava's of Vesuvius, I determined, during an eruption of that Volcano, to watch the progress of a current of lava, and I was soon enabled to comprehend this seeming phÃ¦nomenon; though it is, I fear, very difficult to explain. Certain it is, that the lava's, whilst in their most fluid state, follow always the law of other fluids; but when at a great distance from their source, and consequently incumbered with scoriÃ¦ and cinders, the air likewise having rendered their outward coat tough, they will sometimes (as I have seen) be forced up a short ascent, the fresh matter pushing forward that which went before it, and the exterior parts of the lava acting always as conductors (or pipes, if I may be allowed the expression), for the interior parts, that have retained their fluidity by not having been exposed to the air.[49]The flames Lord Winchelsea mentions, were certainly produced by the lava having met with trees in the way; or perhaps his Lordship may have mistaken the white smoak which constantly rises from a lava (and in the night is tinged by the reflection of the red hot matter), for flame, of which indeed it has greatly the appearance at a distance. I have observed upon Mount Vesuvius, that, soon after a lava has borne down and burned a tree, a bright flame issues from its surface; otherwise I have never seen any flame attending an eruption.

[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 phÃ¦nomenon, 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.

[6]From what I have seen and read of eruptions of Vesuvius and Etna, I am convinced that Volcano's lie dormant for several years, nay even for centuries, as probably was the case of Vesuvius before its eruption in the reign of Titus, and certainly was so before that of the year 1631. When I arrived at Naples in 1764, Vesuvius was quiet, very seldom smoak was visible on its top; in the year 1766, it seemed to take fire, and has never since been three months without either throwing up red hot stones, or disgorging streams of lava, nor has its crater been ever free from smoak. At Naples, when a lava appears, and not till then, it is styled an eruption; whereas I look upon the five nominal eruptions I have been witness to, from March 1766 to May 1771, as, in effect, but one continued eruption.

[7]It is certain, that, by constant attention to the smoak that issues from the crater, a very good guess may be given as to the degree of fermentation within the Volcano. By this alone I foretold[47]the two last eruptions, and, by another very simple observation, I pointed out, some time before, the very spot from whence the lava has issued. When the cone of Vesuvius was covered with snow, I had remarked a spot on which it would not lie: concluding very naturally that this was the weakest part of the cone, and that the heat from within prevented the snow from lying; it was as natural to imagine that the lava, seeking a vent, would force this passage sooner than another; and so indeed it came to pass.

[8]These are his words: "Nubes (incertum procul intuentibus ex quo monte Vesuvium fuisse postea cognitum est) oriebatur, cujus similitudinem & formam, non alia magis arbor, quam pinus expresserit. Nam longissimo veluti trunco elata in altum, quibusdam ramis diffundebatur, credo quia recenti spiritu evecta, dein senescente eo destituta, aut etiam pondere suo victa, in latitudinem evanescebat: candida interdum, interdum sordida & maculosa, prout terram cineremve sustulerat." Plin. lib. vi. ep. 16.

[9]The windows at Naples open like folding-doors.

[10]In several accounts of former eruptions of Vesuvius, I have found mention of the ashes falling at a much greater distance; that, in the year 472 and 473, they had reached Constantinople: Dio says, that during the eruption of Vesuvius in the time of Titusâ€”"tantus fuit pulvis ut ab eo loco in Africam et Syriam et Ã†gyptum penetraverit." A book printed at Lecce, in the kingdom of Naples, inmdcxxxii, and intituled,Discorso sopra l'origine de fuochi gettati dal Monte Vesuvio di Gio Francesco Sorrata Spinola Galateo, says, that the 16th of December, 1631, the very day of the great eruption of Vesuvius (though perfectly calm), it rained ashes at Lecce, which is nine days journey from the mountain: that the day was darkened by them, and that they covered the ground three inches deep; that ashes of a different quality fell at Bari the same day; and that at both these places the inhabitants were very greatly alarmed, not being able to conceive the occasion of such a phÃ¦nomenon. Antonio Bulifon, in his account of the same eruption, says, that the ashes fell, and lay several inches deep at Ariano in Puglia; and I have been assured, by many persons of credit at Naples, that they have been sensible of the fall of ashes, during an eruption, at above two hundred miles distance from Vesuvius. The Abbate Giulio Cesare Bracini, in his account of the eruption of Vesuvius, in 1631, says, that the height of the column of smoak and ashes, taken from Naples by a quadrant, was upwards of thirty miles. Though such uncertain calculations demand but little attention; yet, by what I have seen, I am convinced, that in great eruptions the ashes are sent up to so great a height as to meet with extraordinary currents of air, which is the most probable way of accounting for their having been carried to so great a distance in a few hours. In a book, intituled,Salvatoris Varonis Vesuviani incendii Libri tres: Neapoli,mdcxxxiv, I found a very poetical description of the ashes that lay in the neighbourhood of Vesuvius, after the eruption of 1631, in depth, from twenty to a hundred palms: "Quare," says this author, "multi patrio in solo requirunt patriam, et vix ibi se credunt vivere ubi certo sciant sese natos, adeo totam loci speciem tempestas vertit."

[11]This conjecture has proved true; for, even in the month of April 1771, I again thrust sticks into some crevices of this lava, and they immediately took fire. On Mount Etna, in 1769, I observed the lava, that had been disgorged in 1766, smoak in many parts.

[12]In all accounts of great eruptions of Mount Etna and Mount Vesuvius, I have found mention of this sort of lightning. Pliny the younger, in his second letter to Tacitus upon the eruption of Vesuvius in the time of Titus, says, that a black and horrible cloud covered them at Misenum (which is above fifteen miles from the Volcano), and that flashes of zig-zag fire, like lightning, but stronger, burst from it; these are his words: "ab altero latere nubes atra et horrenda ignei spiritus tortis vibratisque discursibus rupta, in longas flammarum figuras dehiscebat; fulgoribus illÃ¦ et similes et majores erant." This was evidently the same electrical fire, and with which I am convinced that the smoak of all Volcanos is pregnant. In several accounts of the great eruption of Vesuvius in 1631, mention is made of damage done by the lightning that issued from the column of smoak. Bulifon, in particular, says, that, in the neighbourhood of the Volcano, people were struck dead in the same manner as if by lightning, without having their cloaths singed. Pliny mentions a like instance, which shews that the ancients had observed this phÃ¦nomenon; for he says, that at Pompeii, the day being fair, Marcus Herennius was struck dead by lightning. These are his words; "In Catilianis prodigiis, Pompeiano ex municipio M. Herennius Decurioserena die, fulmine ictus est." Plin. Hist. Nat. lib. II. cap.li.The learned and ingenious Father Beccaria, at Turin, assured me, that he had been greatly pleased with my observations on this species of lightning, as coinciding perfectly with several of his electrical experiments.

[13]"I am well convinced, by this collection, that many variegated marbles, and many precious stones, are the produce of Volcanos; and that there have been Volcanos in many parts of the world, where at present there are no traces of them visible." This is taken from a prior letter to Lord Morton, dated April 7, 1767.

[14]In some accounts of an eruption of Vesuvius in 1660, I find mention made of ashes which fell in the shape of crosses, and were looked upon as highly miraculous; but in one book upon this subject, intituled,Athanasii Kircheri Soc. Jes. De prodigiosis crucibus, &c. RomÃ¦,mdclxi, a very philosophical account is given of this phÃ¦nomenon; he says, that, in 1660, from the 16th of August to the 15th of October, Vesuvius cast up ashes, impregnated with nitrous, saline, and bituminous sulphur, which upon linen garments took the form of crosses, probably directed by the cross-threads in the linen, and therefore that the salts did not shoot into such a shape when they fell upon garments of woollen; a very particular description of these crosses may be found in page 38, of the abovementioned book.

[15]I have since found in this stratum of erupted matter at Pompeii, stones weighing eight pounds: but many accounts of the great eruption of Vesuvius, particularly that of Antonio Bulifon, mention that a stone like a bomb was thrown from the crater of Vesuvius in 1631; and fell upon the Marquis of Lauro's house at Nola, which it set on fire. As Nola is twelve miles from Vesuvius, this circumstance seems rather extraordinary: however, I have seen stones of an enormous size shot up to a very great height by Mount Vesuvius. In May 1771, having a stop watch in my hand, I observed that one of these stones was eleven seconds falling from its greatest height, into the crater from whence it had been ejected. In 1767, a solid stone, measuring twelve feet in height, and forty-five in circumference, was thrown a quarter of a mile from the crater; the eruption of 1767, though by much the most violent of this century, was, comparatively to those of the year 79 and 1631, very mild.

[16]SeeLetter V.in this collection.

[17]It is the common received opinion, that this mountain rose from the bottom of the Lucrine lake. I had not seen the very curious and particular account of its formation (which account is in my nextletter) when I wrote this, and was therefore in the same error.

[18]This must depend greatly upon the quality of the lava's; some have been in a more perfect state of vitrification than others, and are consequently less liable to the impressions of time. I have often observed on Mount Vesuvius, when I have been close to the mouth from whence a lava was disgorging itself, that the quality of it varied greatly from time to time: I have seen it as fluid and coherent as glass when in fusion: and I have seen it farinacious, the particles separating as they forced their way out, just like meal coming from under the grindstones. A stream of lava of this sort, being less compact, and continuing more earthy particles, would certainly be much sooner fit for vegetation, than one composed of the more perfect vitrified matter.

[19]This earthquake happened in the year 1693, and destroyed forty-nine towns and villages, nine hundred and twenty-two churches, colleges, and convents; and near one hundred thousand persons were buried in their ruin.

[20]It is intituled, "A true and exact relation of the late prodigious earthquake and eruption of Mount Ã†tna, or Monte Gibello; as it came in a letter written to his Majesty from Naples, by the Right Honourable the Earl of Winchelsea, his Majesty's late Embassador at Constantinople, who, in his return from thence, visiting Catania in the island of Sicily, was an eye-witness of that dreadful spectacle; together with a more particular narrative of the same, as it is collected out of the several relations sent from Catania; published by authority. Printed by T. Newcomb, in the Savoy, 1669.""I accepted, says the author, p. 38, the invitation of the Bishop of Catania, to stay a day with him, that so I might be the better able to inform your Majesty of that extraordinary fire, which comes from Mount Gibel, fifteen miles distant from that city, which, for its horridness in the aspect, for the vast quantity thereof (for it is fifteen miles in length, and seven in breadth), for its monstrous devastation and quick progress, may be termed an inundation of fire, a flood of fire, cinders, and burning stones, burning with that rage as to advance into the sea six hundred yards, and that to a mile in breadth, which I saw; and that which did augment my admiration was, to see in the sea this matter like ragged rocks, burning in four fathom water, two fathom higher than the sea itself, some parts liquid, and throwing off, not with great violence, the stones about it, which, like a crust of a vast bigness, and red hot, fell into the sea every moment, in some place or other, causing a great and horrible noise, smoak, and hissing in the sea; and that more and more coming after it, making a firm foundation in the sea itself. I stayed there from nine a clock on Saturday morning, to seven next morning;" (this must have been towards the middle or latter end of April;) "and this mountain of fire and stones with cinders had advanced into the sea twenty yards at least, in several places; in the middle of this fire, which burnt in the sea, it hath formed like to a river, with its banks on each side very steep and craggy; and in this channel moves the greatest quantity of this fire, which is the most liquid, with stones of the same composition, and cinders all red hot, swimming upon the fire of a great magnitude; from this a river of fire doth proceed under the great mass of the stones, which are generally three fathoms high all over the country, where it burns, and in other places much more. There are secret conduits or rivulets of the liquid matter, which communicates fire and heat into all parts more or less, and melts the stones and cinders by fits in those places where it toucheth them, over and over again; where it meets with rocks or houses of the same matter (as many are), they melt and go away with the fire; where they find other compositions, they turn them to lime or ashes (as I am informed). The composition of this fire, stones, and cinders, are sulphur, nitre, quicksilver, sal ammoniac, lead, iron, brass, and all other metals. It moves not regularly, nor constantly down hill[48]; in some places it hath made the vallies hills, and the hills that are not high are now vallies. When it was night, I went upon two towers, in divers places; and could plainly see at ten miles distance, as we judged, the fire to begin to run from the mountain in a direct line, the flame to ascend as high and as big as one of the greatest steeples in your Majesty's kingdoms, and to throw up great stones into the air; I could discern the river of fire to descend the mountain of a terrible fiery or red colour, and stones of a paler red to swim thereon, and to be some as big as an ordinary table. We could see this fire to move in several other places, and all the country covered with fire, ascending with great flames[49], in many places, smoaking like to a violent furnace of iron melted, making a noise with the great pieces that fell, especially those which fell into the sea. A Cavalier of Malta, who lives there, and attended me, told me, that the river was as liquid where it issues out of the mountain, as water, and came out like a torrent with great violence, and is five or six fathom deep, and as broad, and that no stones sink therein. I assure your Majesty, no pen can express how terrible it is, nor can all the art and industry of the world quench or divert that which is burning in the country. In forty days time, it hath destroyed the habitations of 27,000 persons; made two hills of one, 1000 paces high apiece, and one is four miles in compass; of 20,000 persons, which inhabit Catania, 3000 did only remain; all their goods are carried away, the cannons of brass are removed out of the castle, some great bells taken down, the city-gates walled up next the fire, and preparations made to abandon the city."That night which I lay there, it rained ashes all over the city, and ten miles at sea it troubled my eyes. This fire in its progress met with a lake of four miles in compass; and it was not only satisfied to fill it up, though it was four fathom deep, but hath made of it a mountain."

"I accepted, says the author, p. 38, the invitation of the Bishop of Catania, to stay a day with him, that so I might be the better able to inform your Majesty of that extraordinary fire, which comes from Mount Gibel, fifteen miles distant from that city, which, for its horridness in the aspect, for the vast quantity thereof (for it is fifteen miles in length, and seven in breadth), for its monstrous devastation and quick progress, may be termed an inundation of fire, a flood of fire, cinders, and burning stones, burning with that rage as to advance into the sea six hundred yards, and that to a mile in breadth, which I saw; and that which did augment my admiration was, to see in the sea this matter like ragged rocks, burning in four fathom water, two fathom higher than the sea itself, some parts liquid, and throwing off, not with great violence, the stones about it, which, like a crust of a vast bigness, and red hot, fell into the sea every moment, in some place or other, causing a great and horrible noise, smoak, and hissing in the sea; and that more and more coming after it, making a firm foundation in the sea itself. I stayed there from nine a clock on Saturday morning, to seven next morning;" (this must have been towards the middle or latter end of April;) "and this mountain of fire and stones with cinders had advanced into the sea twenty yards at least, in several places; in the middle of this fire, which burnt in the sea, it hath formed like to a river, with its banks on each side very steep and craggy; and in this channel moves the greatest quantity of this fire, which is the most liquid, with stones of the same composition, and cinders all red hot, swimming upon the fire of a great magnitude; from this a river of fire doth proceed under the great mass of the stones, which are generally three fathoms high all over the country, where it burns, and in other places much more. There are secret conduits or rivulets of the liquid matter, which communicates fire and heat into all parts more or less, and melts the stones and cinders by fits in those places where it toucheth them, over and over again; where it meets with rocks or houses of the same matter (as many are), they melt and go away with the fire; where they find other compositions, they turn them to lime or ashes (as I am informed). The composition of this fire, stones, and cinders, are sulphur, nitre, quicksilver, sal ammoniac, lead, iron, brass, and all other metals. It moves not regularly, nor constantly down hill[48]; in some places it hath made the vallies hills, and the hills that are not high are now vallies. When it was night, I went upon two towers, in divers places; and could plainly see at ten miles distance, as we judged, the fire to begin to run from the mountain in a direct line, the flame to ascend as high and as big as one of the greatest steeples in your Majesty's kingdoms, and to throw up great stones into the air; I could discern the river of fire to descend the mountain of a terrible fiery or red colour, and stones of a paler red to swim thereon, and to be some as big as an ordinary table. We could see this fire to move in several other places, and all the country covered with fire, ascending with great flames[49], in many places, smoaking like to a violent furnace of iron melted, making a noise with the great pieces that fell, especially those which fell into the sea. A Cavalier of Malta, who lives there, and attended me, told me, that the river was as liquid where it issues out of the mountain, as water, and came out like a torrent with great violence, and is five or six fathom deep, and as broad, and that no stones sink therein. I assure your Majesty, no pen can express how terrible it is, nor can all the art and industry of the world quench or divert that which is burning in the country. In forty days time, it hath destroyed the habitations of 27,000 persons; made two hills of one, 1000 paces high apiece, and one is four miles in compass; of 20,000 persons, which inhabit Catania, 3000 did only remain; all their goods are carried away, the cannons of brass are removed out of the castle, some great bells taken down, the city-gates walled up next the fire, and preparations made to abandon the city.

"That night which I lay there, it rained ashes all over the city, and ten miles at sea it troubled my eyes. This fire in its progress met with a lake of four miles in compass; and it was not only satisfied to fill it up, though it was four fathom deep, but hath made of it a mountain."

[21]I have heard since, from some of our countrymen who have measured this tree, that its dimensions are actually as abovementioned, but that they could perceive some signs of four stems having grown together, and formed one tree.

[22]No great stress should be laid upon these observations, as the many inconveniences we laboured under, and the little practice we had in such nice operations, must necessarily have rendered them very inaccurate. The Canon Recupero, who was our guide, attended Mess. Glover, Fullerton, and Brydone, up Mount Etna in June 1770. The latter is a very ingenious and accurate observer, and has taken the height of many of the highest mountains in the Alps. His observations, as the Canon informed me, were as follows: At the top of the mountain the quicksilver in the thermometer was 9 degrees below freezing point, when at the foot of the mountain it rose to 76. At the foot of the little mountain that crowns the Volcano the barometer stood at 20Â° 42/3', half way up this little mountain it was at 19Â° 6'; but the wind was too violent for them to attempt any more observations. The barometer and thermometer were of Fahrenheit's. Mr. Brydone remarked, as he went up in the night, that he could distinguish the stars in the milky way with wonderful clearness, and that the cold was much more intense than he had ever felt upon the highest mountains of the Alps.

[23]This passage, in Cornelius Severus's poem upon Etna, seems to confirm my opinion:"Placantesque etiam cÃ¦lestia numina thure"Summo cerne jugo, vel quÃ¢ liberrimus Ã†tna"Improspectus hiat; tantarum semina rerum"Si nihil irritet flammas, stupeatque profundum."

[23]This passage, in Cornelius Severus's poem upon Etna, seems to confirm my opinion:

"Placantesque etiam cÃ¦lestia numina thure"Summo cerne jugo, vel quÃ¢ liberrimus Ã†tna"Improspectus hiat; tantarum semina rerum"Si nihil irritet flammas, stupeatque profundum."

[24]A better account of the formation oftufawill be seen in my nextletter.

[25]The dates of the eruptions of Mount Etna, recorded by history, are as follows: Before the Christian Ã¦ra four, in the years 3525. 3538. 3554. 3843. After Christ, twenty-seven have been recorded, 1175. 1285. 1321. 1323. 1329. 1408. 1530. 1536. 1537. 1540. 1545. 1554. 1556. 1566. 1579. 1614. 1634. 1636. 1643. 1669. 1682. 1689. 1692. 1702. 1747. 1755. 1766.The dates of the eruptions of Vesuvius are as follows: After Christâ€”79. 203. 472. 512. 685. 993. 1036. 1043. 1048. 1136. 1506. [1538, the eruption at Puzzole.] 1631. 1660. 1682. 1694. 1701. 1704. 1712. 1717. 1730. 1737. 1751. 1754. 1760. 1766. 1767. 1770. 1771.

The dates of the eruptions of Vesuvius are as follows: After Christâ€”79. 203. 472. 512. 685. 993. 1036. 1043. 1048. 1136. 1506. [1538, the eruption at Puzzole.] 1631. 1660. 1682. 1694. 1701. 1704. 1712. 1717. 1730. 1737. 1751. 1754. 1760. 1766. 1767. 1770. 1771.

[26]Pliny, in his account of these islands, in theixchapter of the third book of his Natural History, seems to confirm this opinion."Lipara cum civium Romanorum oppido, dicta Ã Liparo rege, qui successit Ã†olo, antea Melogonis vel Meliganis vocitata, abestxiimillia pass. ab Italia, ipsa circuitu paulo minori. Inter hanc et Siciliam altera, antea Therasia appellata, nunc Hiera; qui sacra Vulcano est, colle in ea nocturnas evomente flammas. Tertia Strongyle, a Lipara millia passuum ad exortum solis vergens, in qua regnavit Ã†olus, quÃ¦ Ã Lipara liquidiore flamma tantum differt: e cujus fumo equinam flaturi sint venti, in triduum prÃ¦dicere incolÃ¦ traduntur; unde ventos Ã†olo paruisse existimatum. Quarta Didyme, minor quam Lipara. Quinta Ericusa; sexta PhÅ“nicusa; pabulo proximarum relicta.Novissima, eademque Minima, Evonymos."

[26]Pliny, in his account of these islands, in theixchapter of the third book of his Natural History, seems to confirm this opinion.

"Lipara cum civium Romanorum oppido, dicta Ã Liparo rege, qui successit Ã†olo, antea Melogonis vel Meliganis vocitata, abestxiimillia pass. ab Italia, ipsa circuitu paulo minori. Inter hanc et Siciliam altera, antea Therasia appellata, nunc Hiera; qui sacra Vulcano est, colle in ea nocturnas evomente flammas. Tertia Strongyle, a Lipara millia passuum ad exortum solis vergens, in qua regnavit Ã†olus, quÃ¦ Ã Lipara liquidiore flamma tantum differt: e cujus fumo equinam flaturi sint venti, in triduum prÃ¦dicere incolÃ¦ traduntur; unde ventos Ã†olo paruisse existimatum. Quarta Didyme, minor quam Lipara. Quinta Ericusa; sexta PhÅ“nicusa; pabulo proximarum relicta.Novissima, eademque Minima, Evonymos."

[27]SeePlate V.

[28]The Abate Giulio Cesare Bruccini describes very elegantly, in his account of the eruption of Vesuvius in 1631, his having made an observation of the like natureâ€”his words are (after having particularized the different strata of erupted matter lying one over another)â€”"parendo appunto che la natura ci abbia voluto lasciare scritto in questa terra tutti gli incendii memorabili raccontati delli autori."

[29]These are his words, book II. chap. vi."De Pulvere Puteolano."Est etiam genus pulveris, quod efficit naturaliter res admirandas. Nascitur in regionibus BaÃ¯anis, et in agris municipiorum, quÃ¦ sunt circa Vesuvium montem, quod commixtum cum calce et cÃ¦mento non modo cÃ¦teris Ã¦dificiis prÃ¦stat firmitates, sed etiam moles, quÃ¦ construuntur in mari, sub aqua solidescunt. Hoc autem fieri hac ratione videtur, quod sub his montibus et terra ferventes sunt fontes crebri, qui non essent, si non in imo haberent, aut de sulfure, aut alumine, aut bitumine ardentes maximos ignes: igitur penitus ignis, et flammÃ¦ vapor per intervenia permanans et ardens, efficet levem eam terram, et ibi, qui nascitur tophus, exugens est, et sine liquore. Ergo cum tres res consimili ratione, ignis vehementia formatÃ¦ in unam pervenerint mixtionem, repente recepto liquore una cohÃ¦rescunt, et celeriter humore duratÃ¦ solidantur, neque eas fluctus, neque vis aquÃ¦ potest dissolvere."About BaÃ¯a, Puzzole, and Naples, we have an opportunity of remarking the truth of these last words. Several of the piers of the ancient harbour of Puzzole, vulgarly called Caligula's bridge, and which are composed of bricks joined with this sort of cement, are still standing in the sea, though much exposed to the waves; and upon every part of the shore you find large masses of brick-walls rounded and polished by friction in the sea, the brick and mortar making one body, and appearing like a variegated stone. Large pieces of old walls are likewise often cut out into square pieces, and made use of in modern buildings instead of stone.Soon after the first quotation, Pliny says, "Si ergo in his locis aquarum ferventes inveniuntur fontes, et in montibus excavatis calidi vapores, ipsaque loca ab antiquis memorantur pervagantes in agris habuisse ardores, videtur esse certum ab ignis vehementia ex topho terraque, quemadmodum in fornacibus et a calce, ita ex his ereptum esse liquorem. Igitur dissimilibus, et disparibus rebus correptis, et in unam potestatem collatis, callida humoris jejunitas aqua repente satiata, communibus corporibus latenti calore confervescit et vehementer effecit ea coire, celeriterque una soliditatis percipere virtutem."

[29]These are his words, book II. chap. vi.

"De Pulvere Puteolano.

"Est etiam genus pulveris, quod efficit naturaliter res admirandas. Nascitur in regionibus BaÃ¯anis, et in agris municipiorum, quÃ¦ sunt circa Vesuvium montem, quod commixtum cum calce et cÃ¦mento non modo cÃ¦teris Ã¦dificiis prÃ¦stat firmitates, sed etiam moles, quÃ¦ construuntur in mari, sub aqua solidescunt. Hoc autem fieri hac ratione videtur, quod sub his montibus et terra ferventes sunt fontes crebri, qui non essent, si non in imo haberent, aut de sulfure, aut alumine, aut bitumine ardentes maximos ignes: igitur penitus ignis, et flammÃ¦ vapor per intervenia permanans et ardens, efficet levem eam terram, et ibi, qui nascitur tophus, exugens est, et sine liquore. Ergo cum tres res consimili ratione, ignis vehementia formatÃ¦ in unam pervenerint mixtionem, repente recepto liquore una cohÃ¦rescunt, et celeriter humore duratÃ¦ solidantur, neque eas fluctus, neque vis aquÃ¦ potest dissolvere."

About BaÃ¯a, Puzzole, and Naples, we have an opportunity of remarking the truth of these last words. Several of the piers of the ancient harbour of Puzzole, vulgarly called Caligula's bridge, and which are composed of bricks joined with this sort of cement, are still standing in the sea, though much exposed to the waves; and upon every part of the shore you find large masses of brick-walls rounded and polished by friction in the sea, the brick and mortar making one body, and appearing like a variegated stone. Large pieces of old walls are likewise often cut out into square pieces, and made use of in modern buildings instead of stone.

Soon after the first quotation, Pliny says, "Si ergo in his locis aquarum ferventes inveniuntur fontes, et in montibus excavatis calidi vapores, ipsaque loca ab antiquis memorantur pervagantes in agris habuisse ardores, videtur esse certum ab ignis vehementia ex topho terraque, quemadmodum in fornacibus et a calce, ita ex his ereptum esse liquorem. Igitur dissimilibus, et disparibus rebus correptis, et in unam potestatem collatis, callida humoris jejunitas aqua repente satiata, communibus corporibus latenti calore confervescit et vehementer effecit ea coire, celeriterque una soliditatis percipere virtutem."

[30]Scipione Falcone, a very good observer, in hisDiscorso naturale delli cause et effetti del Vesuvio, says, that he saw, after the eruption of Vesuvius in 1631 (which was attended with hot water), the mud harden almost to a stone in a few days; his words are theseâ€”"fatta dura a modo di calcina e di pietra non altrimenti di cenere, perchÃ© dopÃ² alcuni giorni vi ci e caminato per sopra e si e conosciuta durissima che ci vogliono li picconi per romperla." This account, with other circumstances mentioned in this letter, make it highly probable, that all thetufasin the neighbourhood of Vesuvius have been formed by a like operation.

[31]This piece is now in the Museum of the Royal Society, together with other specimens, mentioned in this and in thefollowing letter. M. M.

[32]Letter IV.

[33]Strabo, in his fifth book of Geography, says, "Supra hÃ¦c loca situs est Vesuvius mons agris cinctus optimis: dempto vertice, qui magna sui parte planus, totus sterilis est, adspectu cinÃ¦reus, cavernasque ostendens fistularum plenas et lapidum colore fuliginoso, utpote ab igni exesorum, ut conjecturam facere possit ista loca quondam arsisse, et crateras ignis habuisse, deinde materia deficiente restincta fuisse."Diodorus Siculus, in his fourth book, describing the voyage of Hercules into Italy, says, "PhlegrÃ¦us quoque campus is locus appellatur a colle nimirum, qui Ã†tnÃ¦ instar SiculÃ¦ magnam vim ignis eructabat; nunc Vesuvius nominatur, multa inflammationis pristinÃ¦ vestigia reservans." And Vitruvius, in the sixth chapter of the second book, says, "Non minus etiam memoratur antiquitus crevisse ardores et abundasse sub Vesuvio monte et inde evomuisse circa agros flammas." Tacitus, mentioning the eruption of Vesuvius in the reign of Titus, seems to hint likewise at former eruptions, in these words: "Jam verÃ² novis cladibus, vel post longam sÃ¦culorum repetitis afflictÃ¦, haustÃ¦ aut abrutÃ¦ fecundissima CampaniÃ¦ ora et urbs incendiis vastata."

Diodorus Siculus, in his fourth book, describing the voyage of Hercules into Italy, says, "PhlegrÃ¦us quoque campus is locus appellatur a colle nimirum, qui Ã†tnÃ¦ instar SiculÃ¦ magnam vim ignis eructabat; nunc Vesuvius nominatur, multa inflammationis pristinÃ¦ vestigia reservans." And Vitruvius, in the sixth chapter of the second book, says, "Non minus etiam memoratur antiquitus crevisse ardores et abundasse sub Vesuvio monte et inde evomuisse circa agros flammas." Tacitus, mentioning the eruption of Vesuvius in the reign of Titus, seems to hint likewise at former eruptions, in these words: "Jam verÃ² novis cladibus, vel post longam sÃ¦culorum repetitis afflictÃ¦, haustÃ¦ aut abrutÃ¦ fecundissima CampaniÃ¦ ora et urbs incendiis vastata."

[34]Bracini, in his account of the eruption of 1613, says, that he found many sorts of sea shells on Vesuvius after that eruption; and P. Ignatio, in his account of the same eruption, says, that he and his companions picked up many shells likewise at that time upon the mountain: this circumstance would induce one to believe, that the water thrown out of Vesuvius, during that formidable eruption, came from the sea.

[35]In book xi. c. 93. he observes, that about Sinuessa and Puteoli, "Spiracula vocantâ€”alii Caroneas scrobes, mortiferum spiritum exhalantes." And Seneca, Nat. QuÃ¦st. lib. vi. cap. 28. "Pluribus ItaliÃ¦ locis per quÃ¦dam foramina pestilens exhalatur vapor, quem non homini ducere, non ferÃ¦ tutum est. Aves quoque si in illum inciderint, antequam cÅ“lo meliore leniatur, in ipso volatu cadunt, liventque corpora, et non aliter quam per vim elisÃ¦ fauces tument."

[36]I have remarked, that, after a great fall of rain, the degree of heat in this water is much less, which will account for what the Padre Torre says (in his book, entituled,Histoire et Phenomenes du Vesuve), that, when he tried it in company with Monsieur de la Condamine, the degree of heat, upon Reaumur's thermometer, was 68Â°.

[37]This very scarce volume has been presented by Sir William Hamilton to the British Museum. M. M.

[38]Here again we have an example of the electrical fire attending a great eruption.

[39]The cup, or crater, on the top of the new mountain is now covered with shrubs; but I discovered at the bottom of it, in the year 1770, amidst the bushes, a small hole, which exhales a constant hot and damp vapour, just such as proceeds from boiling water, and with as little smell; the drops of this steam hang upon the neighbouring bushes.

[40]The noxious vapours which Lucan mentions to have prevailed at Nisida, favour my opinion as to its origin:"â€”Tali spiramine Nesis"Emittit stygium nebulosis aÃ«ra saxis."Lucan. lib. vi.

[40]The noxious vapours which Lucan mentions to have prevailed at Nisida, favour my opinion as to its origin:

"â€”Tali spiramine Nesis"Emittit stygium nebulosis aÃ«ra saxis."

[41]Giulio Cesare Capaccio, in his account of this island, says, that there are eleven springs of cold water, and thirty-five of hot and mineral waters.

[42]By having remarked, that all the implements of stone brought by Mess. Banks and Solander from the new-discovered islands in the South-Seas, are evidently of such a nature as are only produced by Volcanos; and as these gentlemen have assured me, that no other kind of stone is to be met with in the islands; I am induced to think, that these islands (at so great a distance from any continent) may have likewise been pushed up from the bottom of the sea by like explosions.

[43]Any one, the least conversant in Volcanos, must be struck with the numberless evident marks of them the whole road from the lake of Albano to Radicofani, between Naples and Florence; and yet, though this soil bears such fresh and undoubted marks of its origin, no history reaches the date of any one eruption in these parts.

[44]May not the air in countries replete with sulphur be more impregnated with electrical matter than the air of other soils? and may not the sort of lightning, which is mentioned by several ancient authors to have fallen in a serene day, and was considered as an omen, have proceeded from such a cause?Horace says, Ode xxxiv."â€”Namque Diespeter"Igni corusco nubila dividens"Plerumque per purum tonantes"Egit equos volucremque currum.""Non alias cÅ“lo ceciderunt plura sereno"Fulguraâ€”â€”"Virgil. Georgic. i."Aut cum terribili perculsus fulmine civis"Luce serenanti vitalia lumina liquit."Cic. i. de Divin. n. 18."â€”Sabinos petit aliquanto tristior, quod sacrificanti hostia aufugerat: quodque tempestate serena tonuerat."Sueton.Tit.cap. 10.

Horace says, Ode xxxiv.

"â€”Namque Diespeter"Igni corusco nubila dividens"Plerumque per purum tonantes"Egit equos volucremque currum.""Non alias cÅ“lo ceciderunt plura sereno"Fulguraâ€”â€”"

"â€”Namque Diespeter"Igni corusco nubila dividens"Plerumque per purum tonantes"Egit equos volucremque currum."

"Non alias cÅ“lo ceciderunt plura sereno"Fulguraâ€”â€”"

Virgil. Georgic. i.

"Aut cum terribili perculsus fulmine civis"Luce serenanti vitalia lumina liquit."

Cic. i. de Divin. n. 18.

"â€”Sabinos petit aliquanto tristior, quod sacrificanti hostia aufugerat: quodque tempestate serena tonuerat."

Sueton.Tit.cap. 10.

[45]This letter was not received by Dr. Maty in its present form: and is rather the substance of an explanatory catalogue, which was sent to that gentleman with sundry specimens of the different materials that compose the soil described in the precedingletter; which catalogue remains, with the specimens, in the Museum of the Royal Society, for the inspection, and, I flatter myself, the satisfaction, of the curious in natural history.

[46]Seep. 103of this collection.

[47]SeeLetter I.p. 18.

[48]Having heard the same remark with respect to the lava's of Vesuvius, I determined, during an eruption of that Volcano, to watch the progress of a current of lava, and I was soon enabled to comprehend this seeming phÃ¦nomenon; though it is, I fear, very difficult to explain. Certain it is, that the lava's, whilst in their most fluid state, follow always the law of other fluids; but when at a great distance from their source, and consequently incumbered with scoriÃ¦ and cinders, the air likewise having rendered their outward coat tough, they will sometimes (as I have seen) be forced up a short ascent, the fresh matter pushing forward that which went before it, and the exterior parts of the lava acting always as conductors (or pipes, if I may be allowed the expression), for the interior parts, that have retained their fluidity by not having been exposed to the air.

[49]The flames Lord Winchelsea mentions, were certainly produced by the lava having met with trees in the way; or perhaps his Lordship may have mistaken the white smoak which constantly rises from a lava (and in the night is tinged by the reflection of the red hot matter), for flame, of which indeed it has greatly the appearance at a distance. I have observed upon Mount Vesuvius, that, soon after a lava has borne down and burned a tree, a bright flame issues from its surface; otherwise I have never seen any flame attending an eruption.

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