Observations on Mount Vesuvius, Mount Etna, and Other Volcanos Part 2

LETTER III.

To MATHEW MATY, M. D. Secretary to the Royal SOCIETY.

Villa Angelica, near Mount Vesuvius, October 4, 1768.

SIR,

I have but very lately received your last obliging letter, of the 5th of July, with the volume of Philosophical Transactions.

I must beg of you to express my satisfaction at the notice which the Royal Society hath been pleased to take of my accounts of the two last eruptions of Mount Vesuvius. Since I have been at my villa here, I have enquired of the inhabitants of the mountain, after what they had seen during the last eruption. In my letter to Lord Morton, I mentioned nothing but what came immediately under my own observation: but as all the peasants here agree in their account of the terrible thunder and lightning, which lasted almost the whole time of the eruption, upon the mountain only; I think it a circ.u.mstance worth attending to. Besides the lightning, which perfectly resembled the common forked lightning, there were many meteors, like what are vulgarly called _falling stars_. A peasant, in my neighbourhood, lost eight hogs, by the ashes falling into the trough with their food: they grew giddy, and died in a few hours.

The last day of the eruption, the ashes, which fell abundantly upon the mountain, were as white almost as snow[14]; and the old people here a.s.sure me, that is a sure symptom of the eruption being at an end.

These circ.u.mstances, being well attested, I thought worth relating.

It would require many years close application, to give a proper and truly philosophical account of the Volcanos in the neighbourhood of Naples; but I am sure such a history might be given, supported by demonstration, as would destroy every system hitherto given upon this subject. We have here an opportunity of seeing Volcanos in all their states. I have been this summer in the island of Ischia; it is about eighteen miles round, and its whole basis is lava. The great mountain in it, near as high as Vesuvius, formerly called Epomeus, and now San Nicolo, I am convinced, was thrown up by degrees; and I have no doubt in my own mind, but that the island itself rose out of the sea in the same manner as some of the Azores. I am of the same opinion with respect to Mount Vesuvius, and all the high grounds near Naples; as having not yet seen, in any one place, what can be called virgin earth. I had the pleasure of seeing a well sunk, a few days ago, near my villa, which is, as you know, at the foot of Vesuvius, and close by the sea-side. At twenty-five feet below the level of the sea, they came to a stratum of lava, and G.o.d knows how much deeper they might have still found other lavas. The soil all round the mountain, which is so fertile, consists of stratas of lavas, ashes, pumice, and now-and-then a thin stratum of good earth, which good earth is produced by the surface mouldering, and the rotting of the roots of plants, vines, &c. This is plainly to be seen at Pompeii, where they are now digging into the ruins of that ancient city; the houses are covered about ten or fifteen feet, with pumice and fragments of lava, some of which weigh three pounds (which last circ.u.mstance I mention, to shew, that, in a great eruption, Vesuvius has thrown stones of this weight six miles[15], which is its distance from Pompeii, in a direct line); upon this stratum of pumice, or _rapilli_, as they call them here, is a stratum of excellent mould, about two feet thick, on which grow large trees, and excellent grapes. We have then the Solfaterra, which was certainly a Volcano, and has ceased erupting, for want of metallic particles, and over-abounding with sulphur. You may trace its lavas into the sea. We have the Lago d'Averno and the Lago d'Agnano, both of which were formerly Volcanos; and Astroni, which still retains its form more than any of these. Its crater is walled round, and his Sicilian Majesty takes the diversion of boar-hunting in this Volcano; and neither his Majesty nor any one of his Court ever dreamt of its former state. We have then that curious mountain, called Montagno Nuovo, near Puzzole, which rose, in one night, out of the Lucrine Lake; it is about a hundred and fifty feet high, and three miles round. I do not think it more extraordinary, that Mount Vesuvius, in many ages, should rise above two thousand feet; when this mountain, as is well attested, rose in one night, no longer ago than the year 1538. I have a project, next spring, of pa.s.sing some days at Puzzole, and of dissecting this mountain, taking its measures, and making drawings of its stratas; for, I perceive, it is composed of stratas, like Mount Vesuvius, but without lavas. As this mountain is so undoubtedly formed intirely from a plain, I should think my project may give light into the formation of many other mountains, that are at present thought to have been original, and are certainly not so, if their strata correspond with those of the Montagno Nuovo. I should be glad to know whether you think this project of mine will be useful; and, if you do, the result of my observations may be the subject of another letter[16].

I cannot have a greater pleasure than to employ my leisure hours in what may be of some little use to mankind; and my lot has carried me into a country, which affords an ample field for observation. Upon the whole, if I was to establish a system, it would be, that _Mountains are produced by Volcanos, and not Volcanos by Mountains_.

I fear I have tired you; but the subject of Volcanos is so favourite a one with me, that it has led me on I know not how: I shall only add, that Vesuvius is quiet at present, though very hot at top, where there is a deposition of boiling sulphur. The lava that ran in the Fossa Grande during the last eruption, and is at least two hundred feet thick, is not yet cool; a stick, put into its crevices, takes fire immediately.

On the sides of the crevices are fine crystalline salts: as they are the pure salts, which exhale from the lava that has no communication with the interiour of the mountain, they may perhaps indicate the composition of the lava.

I have done. Let me only thank you for the kind offers and expressions in your letter, and for the care you have had in setting off my present to the Museum to the best advantage; of which I have been told from many quarters.

I am, SIR, Your most obedient humble servant,

W. HAMILTON.

LETTER IV.

To MATHEW MATY, M. D. Secretary to the Royal SOCIETY.

An Account of a Journey to MOUNT ETNA.

"Artificis natur ingens opus aspice, nulla "Tu tanta humanis rebus spectacula cernes."

P. CORNELII SEVERI _tna_.

Naples, Oct. 17, 1769.

SIR,

Encouraged by the a.s.surances you give me, in your last obliging letter of the 15th of June, that any new communication upon the subject of Volcano's would be received with satisfaction by the Royal Society; I venture to send you the following account of my late observations upon Mount Etna, which you are at liberty to lay before our respectable Society, should you think it worth its notice. [See Plate IV.]

[Ill.u.s.tration: _Plate IV._ A View of MOUNT TNA from Taormina.]

After having examined with much attention the operations of Mount Vesuvius, during the five years that I have had the honour of residing as his Majesty's Minister at this Court, and after having carefully remarked the nature of the soil for fifteen miles round this capital; I am, in my own mind, well convinced that the whole of it has been formed by explosion. Many of the craters, from whence this matter has issued, are still visible; such as the Solfaterra near Puzzole, the lake of Agnano, and near this lake a mountain composed of burnt matter, that has a very large crater surrounded with a wall, to inclose the wild boars and deer, that are kept there for the diversion of his Sicilian Majesty; it is called Astruni: the Monte Nuovo, thrown up from the bottom of the Lucrine lake[17] in the year 1538, which has likewise its crater; and the lake of Averno. The islands of Nisida and Procida are entirely composed of burnt matter; the island of Ischia is likewise composed of lava, pumice, and burnt matter; and there are in that island several visible craters, from one of which, no longer ago than the year 1303, there issued a lava, which ran into the sea, and is still in the same barren state as the modern lavas of Vesuvius. After having, I say, been accustomed to these observations, I was well prepared to visit the most ancient, and perhaps the most considerable, Volcano that exists; and I had the satisfaction of being thoroughly convinced there, of the formation of very considerable mountains by meer explosion, having seen many such on the sides of Etna, as will be related hereafter.

On the 24th of June last, in the afternoon, I left Catania, a town situated at the foot of Mount Etna, or, as it is now called, Mon-Gibello, in company with Lord Fortrose and the Canonico Recupero, an ingenious priest of Catania, who is the only person there that is acquainted with the mountain: he is actually employed in writing its natural history; but, I fear, will not be able to compa.s.s so great and useful an undertaking, for want of proper encouragement.

We pa.s.sed through the inferior district of the mountain, called by its inhabitants La Regione Piemontese. It is well watered, exceedingly fertile, and abounding with vines and other fruit trees, where the lava, or, as it is called there, the _sciara_, has had time to soften, and gather soil sufficient for vegetation, which, I am convinced from many observations, unless a.s.sisted by art, does not come to pa.s.s for many ages[18], perhaps a thousand years or more; the circuit of this lower region, forming the basis of the great Volcano, is upwards of one hundred Italian miles. The vines of Etna are kept low, quite the reverse of those on the borders of Vesuvius; and they produce a stronger wine, but not in so great abundance. The Piemontese district is covered with towns, villages, monasteries, &c. and is well peopled, notwithstanding the danger of such a situation. Catania, so often destroyed by eruptions of Etna, and totally overthrown by an earthquake towards the end of the last century[19], has been re-built within these fifty years, and is now a considerable town, with at least thirty-five thousand inhabitants. I do not wonder at the seeming security with which these parts are inhabited, having been so long witness to the same near Mount Vesuvius.

The operations of Nature are slow: great eruptions do not frequently happen; each flatters himself it will not happen in his time, or, if it should, that his tutelar saint will turn away the destructive lava from his grounds; and indeed the great fertility in the neighbourhoods of Volcanos tempts people to inhabit them.

In about four hours of gradual ascent, we arrived at a little convent of Benedictine monks, called St. Nicolo dell' Arena, about thirteen miles from Catania, and within a mile of the Volcano from whence issued the last very great eruption in the year 1669; a circ.u.mstantial account of which was sent to our court by a Lord Winchelsea, who happened to be then at Catania in his way home, from his emba.s.sy at Constantinople. His Lordship's account is curious, and was printed in London soon after; I saw a copy of it at Palermo, in the library of the Prince Torremuzzo[20]. We slept in the Benedictines convent the night of the 24th, and pa.s.sed the next morning in observing the ravage made by the abovementioned terrible eruption, over the rich country of the Piemontese. The lava burst out of a vineyard within a mile of St.

Nicolo, and, by frequent explosions of stones and ashes, raised there a mountain, which, as near as I can judge, having ascended it, is not less than half a mile perpendicular in height, and is certainly at least three miles in circ.u.mference at its basis. The lava that ran from it, and on which there are as yet no signs of vegetation, is fourteen miles in length, and in many parts six in breadth; it reached Catania, and destroyed part of its walls, buried an amphitheatre, an aqueduct, and many other monuments of its ancient grandeur, which till then had resisted the hand of Time, and ran a considerable length into the sea, so as to have once formed a beautiful and safe harbour; but it was soon after filled up by a fresh torrent of the same inflamed matter: a circ.u.mstance the Catanians lament to this day, as they are without a port. There has been no such eruption since, though there are signs of many, more terrible, that have preceded it.

For two or three miles round the mountain raised by this eruption, all is barren, and covered with ashes; this ground, as well as the mountain itself, will in time certainly be as fertile as many other mountains in its neighbourhood, that have been likewise formed by explosion. If the dates of these explosions could be ascertained, it would be very curious, and mark the progress of time with respect to the return of vegetation, as the mountains raised by them are in different states; those which I imagine to be the most modern are covered with ashes only; others of an older date, with small plants and herbs; and the most ancient, with the largest timber-trees I ever saw: but I believe the latter are so very ancient, as to be far out of the reach of history. At the foot of the mountain, raised by the eruption of the year 1669, there is a hole, through which, by means of a rope, we descended into several subterraneous caverns, branching out and extending much farther and deeper than we chose to venture; the cold there being excessive, and a violent wind frequently extinguishing some of our torches. These caverns undoubtedly contained the lava that issued forth, and extended, as I said before, quite to Catania. There are many of these subterraneous cavities known, on other parts of Etna; such as that called by the peasants La Baracca Vecchia, another La Spelonca della Palomba (from the wild pigeons building their nests therein), and the cavern Thalia, mentioned by Boccaccio. Some of them are made use of as magazines for snow; the whole island of Sicily and Malta being supplied with this essential article (in a hot climate) from Mount Etna. Many more would be found, I dare say, if searched for, particularly near and under the craters from whence great lavas have issued, as the immense quant.i.ties of such matter we see above ground, must necessarily suppose very great hollows underneath.

After having pa.s.sed the morning of the 25th in these observations, we proceeded through the second or middle region of Etna, called La Selvosa, _the woody_, than which nothing can be more beautiful. On every side are mountains, or fragments of mountains, that have been thrown up by various ancient explosions; there are some near as high as Mount Vesuvius; one in particular (as the Canon our guide a.s.sured me, having measured it) is little less than one mile in perpendicular height, and five in circ.u.mference at its basis. They are all more or less covered, even within their craters, as well as the rich vallies between them, with the largest oak, chesnut, and firr trees, I ever saw any where; and indeed it is from hence chiefly, that his Sicilian Majesty's dockyards are supplied with timber. As this part of Etna was famous for its timber in the time of the Tyrants of Syracusa, and as it requires the great length of time I have already mentioned before the matter is fit for vegetation, we may conceive the great age of this respectable Volcano.

The chesnut-trees predominated in the parts through which we pa.s.sed, and, though of a very great size, are not to be compared to some on another part of the Regione Selvosa, called Carpinetto. I have been told by many, and particularly by our guide, who had measured the largest there, called La Castagna Cento Cavalli, that it is upwards of twenty-eight Neapolitan canes in circ.u.mference. Now as a Neapolitan cane is two yards and half a quarter, English measure, you may judge, Sir, of the immense size of this famous tree[21]. It is hollow from age, but there is another near it almost as large and sound. As it would have required a journey of two days to have visited this extraordinary tree, and the weather being already very hot, I did not see it. It is amazing to me, that trees should flourish in so shallow a soil; for they cannot penetrate deep without meeting with a rock of lava; and indeed great part of the roots of the large trees we pa.s.sed by are above ground, and have acquired, by the impression of the air, a bark like that of their branches. In this part of the mountain, are the finest horned cattle in Sicily; we remarked in general, that the horns of the Sicilian cattle are near twice the size of any we had ever seen; the cattle themselves are of the common size. We pa.s.sed by the lava of the last eruption in the year 1766, which has destroyed above four miles square of the beautiful wood abovementioned. The mountain raised by this eruption abounds with sulphur and salts, exactly resembling those of Vesuvius; specimens of which I sent some time ago to the late Lord Morton.

In about five hours from the time we had left the convent of St. Nicolo dell' Arena, we arrived at the borders of the third region, called La Netta, or Scoperta, _clean_ or _uncovered_, where we found a very sharp air indeed; so that, in the same day, the four seasons of the year were sensibly felt by us, on this mountain; excessive summer heats in the Piemontese, spring and autumn temperature in the middle, and extreme cold of winter in the upper region. I could perceive, as we approached the latter, a gradual decrease of vegetation; and from large timber trees we came to the small shrubs and plants of the northern climates: I observed quant.i.ties of juniper and tanzey; our guide told us that later in the season there are numberless curious plants here, and that in some parts there are rhubarb and saffron in plenty. In Carrera's History of Catania, there is a list of all the plants and herbs of Etna in alphabetical order.

Night coming on, we here pitched a tent, and made a good fire, which was very necessary; for without it, and very warm cloathing, we should surely have perished with cold; and at one of the clock in the morning of the 26th, we pursued our journey towards the great crater. We pa.s.sed over vallies of snow, that never melts, except there is an eruption of lava from the upper crater, which scarcely ever happens; the great eruptions are usually from the middle region, the inflamed matter finding (as I suppose) its pa.s.sage through some weak part, long before it can rise to the excessive height of the upper region, the great mouth on the summit only serving as a common chimney to the Volcano. In many places the snow is covered with a bed of ashes, thrown out of the crater, and the sun melting it in some parts makes this ground treacherous; but as we had with us, besides our guide, a peasant well accustomed to these vallies, we arrived safe at the foot of the little mountain of ashes that crowns Etna, about an hour before the rising of the sun. This mountain is situated in a gently inclining plain of about nine miles in circ.u.mference; it is about a quarter of a mile perpendicular in height, very steep, but not quite so steep as Vesuvius; it has been thrown up within these twenty-five or thirty years, as many people at Catania have told me they remembered when there was only a large chasm or crater, in the midst of the abovementioned plain. Till now, the ascent had been so gradual (for the top of Etna is not less than thirty miles from Catania, from whence the ascent begins) as not to have been the least fatiguing; and if it had not been for the snow, we might have rode upon our mules to the very foot of the little mountain, higher than which the Canon our guide had never been: but as I saw that this little mountain was composed in the same manner as the top of Vesuvius, which, notwithstanding the smoak issuing from every pore, is solid and firm, I made no scruple of going up to the edge of the crater; and my companions followed. The steep ascent, the keenness of the air, the vapours of the sulphur, and the violence of the wind, which obliged us several times to throw ourselves flat upon our faces to avoid being overturned by it, made this latter part of our expedition rather inconvenient and disagreeable. Our guide, by way of comfort, a.s.sured us, that there was generally much more wind in the upper region at this time.

Soon after we had seated ourselves on the highest point of Etna, the sun arose, and displayed a scene that indeed pa.s.ses all description. The horizon lighting up by degrees, we discovered the greatest part of Calabria, and the sea on the other side of it; the Phare of Messina, the Lipari Islands; Stromboli, with its smoaking top, though at above seventy miles distance, seemed to be just under our feet; we saw the whole island of Sicily, its rivers, towns, harbours, &c. as if we had been looking on a map. The island of Malta is low ground, and there was a haziness in that part of the horizon, so that we could not discern it; our guide a.s.sured us, he had seen it distinctly at other times, which I can believe, as in other parts of the horizon, that were not hazy, we saw to a much greater distance; besides, we had a clear view of Etna's top from our ship, as we were going into the mouth of the harbour of Malta some weeks before; in short, as I have since measured on a good chart, we took in at one view a circle of above nine hundred English miles. The pyramidal shadow of the mountain reached across the whole island, and far into the sea on the other side. I counted from hence forty-four little mountains (little I call them in comparison of their mother Etna, though they would appear great any where else) in the middle region on the Catania side, and many others on the other side of the mountain, all of a conical form, and each having its crater; many with timber trees flourishing both within and without their craters.

The points of those mountains that I imagine to be the most ancient are blunted, and the craters of course more extensive and less deep than those of the mountains formed by explosions of a later date, and which preserve their pyramidal form entire. Some have been so far mouldered down by time, as to have no other appearance of a crater than a sort of dimple or hollow on their rounded tops, others with only half or a third part of their cone standing; the parts that are wanting having mouldered down, or perhaps been detached from them by earthquakes, which are here very frequent. All however have been evidently raised by explosion; and I believe, upon examination, many of the whimsical shapes of mountains in other parts of the world would prove to have been occasioned by the same natural operations. I observed that these mountains were generally in lines or ridges; they have mostly a fracture on one side, the same as in the little mountains raised by explosion on the sides of Vesuvius, of which there are eight or nine. This fracture is occasioned by the lava's forcing its way out, which operation I have described in my account of the last eruption of Vesuvius. Whenever I shall meet with a mountain, in any part of the world, whose form is regularly conical, with a hollow crater on its top, and one side broken, I shall be apt to decide such a mountain's having been formed by an eruption; as both on Etna and Vesuvius the mountains formed by explosion are without exception according to this description. But to return to my narrative.

After having feasted our eyes with the glorious prospect above-mentioned (for which, as Spartian tells us, the Emperor Adrian was at the trouble of ascending Etna), we looked into the great crater, which, as near as we could judge, is about two miles and a half in circ.u.mference; we did not think it safe to go round and measure it, as some parts seemed to be very tender ground. The inside of the crater, which is incrusted with salts and sulphurs like that of Vesuvius, is in the form of an inverted hollow cone, and its depth nearly answers to the height of the little mountain that crowns the great Volcano. The smoak, issuing abundantly from the sides and bottom, prevented our seeing quite down; but the wind clearing away the smoak from time to time, I saw this inverted cone contracted almost to a point; and, from repeated observations, I dare say, that in all Volcanos, the depth of the craters will be found to correspond nearly to the height of the conical mountains of cinders which usually crown them; in short, I look upon the craters as a sort of suspended funnels, under which are vast caverns and abysses. The formation of such conical mountains with their craters are easily accounted for, by the fall of the stones, cinders, and ashes, emitted at the time of an eruption.

The smoak of Etna, though very sulphureous, did not appear to me so fetid and disagreeable as that of Vesuvius; but our guide told me, that its quality varies, as I know that of Vesuvius does, according to the quality of the matter then in motion within. The air was so very pure and keen in the whole upper region of Etna, and particularly in the most elevated parts of it, that we had a difficulty in respiration, and that, independent of the sulphureous vapour. I brought two barometers and a thermometer with me from Naples, intending to have left one with a person at the foot of the mountain, whilst we made our observation with the other, at sun-rising, on the summit; but one barometer was unluckily spoilt at sea, and I could find no one expert enough at Catania to repair it: what is extraordinary, I do not recollect having seen a barometer in any part of Sicily. At the foot of Etna, the 24th, when we made our first observation, the quicksilver stood at 27 degrees 4 lines; and the 26th, at the most elevated point of the Volcano, it was at 18 degrees 10 lines. The thermometer, on the first observation at the foot of the mountain was at 84 degrees, and on the second at the crater at 56[22]. The weather had not changed in any respect, and was equally fine and clear, the 24th and 26th. We found it difficult to manage our barometer in the extreme cold and high wind on the top of Etna; but, from the most exact observations we could make in our circ.u.mstances, the result was as abovementioned. The Canon a.s.sured me, that the perpendicular height of Mount Etna is something more than three Italian miles, and I verily believe it is so.

After having pa.s.sed at least three hours on the crater, we descended, and went to a rising ground, about a mile distant from the upper mountain we had just left, and saw there some remains of the foundation of an ancient building; it is of brick, and seems to have been ornamented with white marble, many fragments of which are scattered about. It is called the Philosopher's Tower, and is said to have been inhabited by Empedocles. As the ancients used to sacrifice to the celestial G.o.ds on the top of Etna[23], it may very well be the ruin of a temple that served for that purpose. From hence we went a little further over the inclined plain abovementioned, and saw the evident marks of a dreadful torrent of hot water, that came out of the great crater at the time of an eruption of lava in the year 1755, and upon which phnomenon the Canonico Recupero, our guide, has published a dissertation. Luckily this torrent did not take its course over the inhabited parts of the mountain; as a like accident on Mount Vesuvius in 1631 swept away some towns and villages in its neighbourhood, with thousands of their inhabitants. The common received opinion is, that these eruptions of water proceed from the Volcanos having a communication with the sea; but I rather believe them to proceed merely from depositions of rain water in some of the inward cavities of them. We likewise saw from hence the whole course of ancient lava, the most considerable as to its extent of any known here; it ran into the sea near Taormina, which is not less than thirty miles from the crater whence it issued, and is in many parts fifteen miles in breadth. As the lavas of Etna are very commonly fifteen and twenty miles in length, six or seven in breadth, and fifty feet or more in depth; you may judge, Sir, of the prodigious quant.i.ties of matter emitted in a great eruption of this mountain, and of the vast cavities there must necessarily be within its bowels. The most extensive lavas of Vesuvius do not exceed seven miles in length. The operations of nature on the one mountain and the other are certainly the same; but on Mount Etna, all are upon a great scale. As to the nature and quality of their lavas, they are much the same; but I think those of Etna rather blacker, and in general more porous, than those of Vesuvius. In the parts of Etna that we went over, I saw no stratas of pumice stones, which are frequent near Vesuvius, and cover the ancient city of Pompeii; but our guide told us, that there are such in other parts of the mountain. I saw some stratas of what is called here _tufa_; it is the same that covers Herculaneum, and that composes most of the high grounds about Naples; it is, upon examination, a mixture of small pumice stones, ashes, and fragments of lava, which is by time hardened into a sort of stone[24]. In short, I found, with respect to the matter erupted, nothing on Mount Etna that Vesuvius does not produce; and there certainly is a much greater variety in the erupted matter and lavas of the latter, than of the former; both abound with pyrites and crystallizations, or rather vitrifications. The sea sh.o.r.e at the foot of Etna, indeed, abounds with amber, of which there is none found at the foot of Vesuvius. At present there is a much greater quant.i.ty of sulphur and salts on the top of Vesuvius than on that of Etna; but this circ.u.mstance varies according to the degree of fermentation within; and our guide a.s.sured me, he had seen greater quant.i.ties on Etna at other times. In our way back to Catania, the Canon shewed me a little hill, covered with vines, which belonged to the Jesuits, and, as is well attested, was undermined by the lava in the year 1669, and transported half a mile from the place where it stood, without having damaged the vines.

In great eruptions of Etna, the same sort of lightning, as described in my account of the last eruption of Vesuvius, has been frequently seen to issue from the smoak of its great crater. The antients took notice of the same phnomenon; for Seneca (lib. ii. Nat. Qust.) says,--"tna aliquando multo igne abundavit, ingentem vim aren urentis effudit, involutus est dies pulvere, populosque subita nox terruit, _illo tempore aiunt plurima fuisse tonitrua et fulmina_."

Till the year 252 of Christ, the chronological accounts of the eruptions of Etna are very imperfect: but as the veil of St. Agatha was in that year first opposed to check the violence of the torrents of lava, and has ever since been produced at the time of great eruptions; the miracles attributed to its influence, having been carefully recorded by the priests, have at least preserved the dates of such eruptions. The relicks of St. Januarius have rendered the same service to the lovers of natural history, by recording the great eruptions of Vesuvius. I find, by the dates of the eruptions of Etna, that it is as irregular and uncertain in its operations as Vesuvius[25]. The last eruption was in 1766.

On our return from Messina to Naples, we were becalmed three days in the midst of the Lipari islands, by which we had an opportunity of seeing that they have all been evidently formed by explosion[26]; one of them, called Vulcano, is in the same state as the Solfaterra. Stromboli is a Volcano, existing in all its force, and, in its form of course, is the most pyramidal of all the Lipari Islands; we saw it throw up red hot stones from its crater frequently, and some small streams of lava issued from its side, and ran into the sea[27]. This Volcano differs from Etna and Vesuvius, by its continually emitting fire, and seldom any lava; notwithstanding its continual explosions, this island is inhabited, on one side, by about an hundred families.

[Ill.u.s.tration: _Plate V._ STROMBOLI, one of the LIPARI ISLANDS.]

These, as well as I can recollect, are all the observations that I made with respect to Volcanos, in may late curious tour of Sicily; and I shall be very happy should the communication of them afford you, or any of our countrymen (lovers of natural history) satisfaction or entertainment.

I am, SIR, With great regard and esteem, Your most obedient humble servant,

W. HAMILTON.

LETTER V.

To MATHEW MATY, M. D. Secretary to the Royal SOCIETY.