Observations on Mount Vesuvius, Mount Etna, and Other Volcanos Part 1

Observations on Mount Vesuvius, Mount Etna, and Other Volcanos.

by William Hamilton.

LETTER I.

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

Naples, June 10, 1766.

My LORD,

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

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

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

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

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

The smoke, that appeared black in the day-time, for near two months before the eruption, had the appearance of flame in the night.

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

The 29th, the mountain was very quiet, and the lava did not continue.

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

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

Annunciata_.

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

The lava, after having run pure for about a hundred yards, began to collect cinders, stones, &c.; and a sc.u.m was formed on its surface, which in the day-time had the appearance of the river Thames, as I have seen it after a hard frost and great fall of snow, when beginning to thaw, carrying down vast ma.s.ses of snow and ice. In two places the liquid lava totally disappeared, and ran in a subterraneous pa.s.sage for some paces; then came out again pure, having left the sc.u.m behind. In this manner it advanced to the cultivated parts of the mountain; and I saw it, the same night of the 12th, unmercifully destroy a poor man's vineyard, and surround his cottage, notwithstanding the opposition of many images of St. Januarius, that were placed upon the cottage, and tied to almost every vine. The lava, at the farthest extremity from its source, did not appear liquid, but like a heap of red hot coals, forming a wall in some places ten or twelve feet high, which rolling from the top soon formed another wall, and so on, advancing slowly, not more than about thirty feet in an hour[4].

The mouth of the Volcano has not thrown up any large stones since the second eruption of lava on the 10th of April; but has thrown up quant.i.ties of small ashes and pumice stones, that have greatly damaged the neighbouring vineyards. I have been several times at the mountain since the 12th; but, as the eruption was in its greatest vigour at that time, I have ventured to dwell on, and I fear tire your Lordship with, the observations of that day.

In my last visit to Mount Vesuvius, the 3d of June, I still found that the lava continued; but the rivers were become rivulets, and had lost much of their rapidity. The quant.i.ty of matter thrown out by this eruption is greater than that of the last in the year 1760; but the damage to the cultivated lands is not so considerable, owing to its having spread itself much more, and its source being at least three miles higher up. This eruption seems now to have exhausted itself; and I expect in a few days to see Vesuvius restored to its former tranquillity.

Mount Etna in Sicily broke out on the 27th of April; and made a lava, in two branches, at least six miles in length, and a mile in breadth; and, according to the description given me by Mr. Wilbraham, (who was there, after having seen with me part of the eruption of Mount Vesuvius) resembles it in every respect, except that Mount Etna, at the place from whence the lava flowed (which was twelve miles from the mouth of the Volcano), threw up a fountain of liquid inflamed matter to a considerable height; which, I am told, Mount Vesuvius has done in former eruptions.

I beg pardon for having taken up so much of your time; and yet I flatter myself, that my description, which I a.s.sure your Lordship is not exaggerated, will have afforded you some amus.e.m.e.nt. I have the honour to be,

My LORD, Your Lordship's Most obedient and most humble servant,

WILLIAM HAMILTON.

Naples, February 3, 1767.

Since the account of the eruption of Mount Vesuvius, which I had the honour of giving to your Lordship, in my letter of the 10th of June last; I have only to add, that the lava continued till about the end of November, without doing any great damage, having taken its course over antient lavas. Since the cessation of this eruption, I have examined the crater, and the crack on the side of the mountain towards _Torre dell' Annunciata_, about a hundred yards from the crater from whence this lava issued: and I found therein some very curious salts and sulphurs; a specimen of each sort I have put into bottles myself, even upon the mountain, that they might not lose any of their force, and have sent them in a box directed to your Lordship, as you will see, by the bill of lading: I am sure, you will have a pleasure in seeing them a.n.a.lyzed[5]. I have also packed in the same box some lava, and cinders, of the last eruption; there is one piece in particular very curious, having the exact appearance of a cable petrified. I shall be very happy if these trifles should afford your Lordship a moment's amus.e.m.e.nt.

It is very extraordinary, that I cannot find, that any chemist here has ever been at the trouble of a.n.a.lyzing the productions of Vesuvius.

The deep yellow, or orange-color salts, of which there are two bottles, I fetched out of the very crater of the mountain, in a crevice that was indeed very hot. It seems to me to be powerful, as it turns silver black in an instant, but has no effect upon gold. If your Lordship pleases, I will send you by another opportunity specimens of the sulphurs and salts of the Solfa terra, which seem to be very different from these.

Within these three days, the fire has appeared again on the top of Vesuvius, and earthquakes have been felt in the neighbourhood of the mountain. I was there on Sat.u.r.day with my nephew Lord Greville; we heard most dreadful inward grumblings, rattling of stones, and hissing; and were obliged to leave the crater very soon, on account of the emission of stones. The black smoak arose, as before the last eruption; and I saw every symptom of a new eruption, of which I shall not fail to give your Lordship an exact account.

LETTER II.

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

Naples, December 29, 1767.

My LORD,

The favourable reception, which my account of last year's eruption of Mount Vesuvius met with from your Lordship; the approbation which the Royal Society was pleased to shew, by having ordered the same to be printed in their Philosophical Transactions; and your Lordship's commands, in your letter of the 3d instant; encourage me to trouble you with a plain narrative of what came immediately under my observation, during the late violent eruption, which began October 19, 1767, and is reckoned to be the twenty-seventh since that, which, in the time of t.i.tus, destroyed Herculaneum and Pompeii.

The eruption of 1766 continued in some degree till the 10th of December, about nine months in all[6]; yet in that s.p.a.ce of time the mountain did not cast up a third of the quant.i.ty of lava, which it disgorged in only seven days, the term of this last eruption. On the 15th of December, last year, within the ancient crater of Mount Vesuvius, and about twenty feet deep, there was a crust, which formed a plain, not unlike the Solfa terra in miniature; in the midst of this plain was a little mountain, whose top did not rise so high as the rim of the ancient crater. I went into this plain, and up the little mountain, which was perforated, and served as the princ.i.p.al chimney to the Volcano: when I threw down large stones, I could hear that they met with many obstructions in their way, and could count a hundred moderately before they reached the bottom.

Vesuvius was quiet till March 1767, when it began to throw up stones from time to time; in April, the throws were more frequent, and at night fire was visible on top of the mountain, or, more properly speaking, the smoak, which hung over the crater, was tinged by the reflection of the fire within the Volcano. These repeated throws of cinders, ashes, and pumice stones, increased the little mountain so much, that in May the top was visible above the rim of the ancient crater. The 7th of August, there issued a small stream of lava, from a breach in the side of this little mountain, which gradually filled the valley between it and the ancient crater; so that, the 12th of September, the lava overflowed the ancient crater, and took its course down the sides of the great mountain; by this time, the throws were much more frequent, and the red hot stones went so high as to take up ten seconds in their fall. Padre Torre, a great observer of Mount Vesuvius, says they went up above a thousand feet.

The 15th of October, the height of the little mountain (formed in about eight months) was measured by Don Andrea Pigonati, a very ingenious young man, in his Sicilian Majesty's service, who a.s.sured me that its height was 185 French feet.

From my villa, situated between Herculaneum and Pompeii, near the convent of the Calmaldolese (marked 7 in Plate I.) I had watched the growing of this little mountain; and, by taking drawings of it from time to time, I could perceive its increase most minutely. I make no doubt but that the whole of Mount Vesuvius has been formed in the same manner; and as these observations seem to me to account for the various irregular strata, which are met with in the neighbourhood of Volcanos, I have ventured to inclose, for your Lordship's inspection, a copy of the abovementioned drawings. (Plate III.)

The lava continued to run over the ancient crater in small streams, sometimes on one side, and sometimes on another, till the 18th of October, when I took particular notice that there was not the least lava to be seen; owing, I imagine, to its being employed in forcing its way towards the place where it burst out the following day. As I had, contrary to the opinion of most people here, foretold the approaching eruption[7], and had observed a great fermentation in the mountain after the heavy rains which fell the 13th and 14th of October; I was not surprized, on the 19th following, at seven of the clock in the morning, to perceive from my villa every symptom of the eruption being just at hand. From the top of the little mountain issued a thick black smoak, so thick that it seemed to have difficulty in forcing its way out; cloud after cloud mounted with a hasty spiral motion, and every minute a volley of great stones were shot up to an immense height in the midst of these clouds; by degrees, the smoak took the exact shape of a huge pine-tree, such as Pliny the younger described in his letter to Tacitus, where he gives an account of the fatal eruption in which his uncle perished[8]. This column of black smoak, after having mounted an extraordinary height, bent with the wind towards Caprea, and actually reached over that island, which is not less than twenty-eight miles from Vesuvius.

I warned my family, not to be alarmed, as I expected there would be an earthquake at the moment of the lava's bursting out; but before eight of the clock in the morning I perceived that the mountain had opened a mouth, without noise, about a hundred yards lower than the ancient crater, on the side towards the Monte di Somma; and I plainly perceived, by a white smoak, which always accompanies the lava, that it had forced its way out: as soon as it had vent, the smoak no longer came out with that violence from the top. As I imagined that there would be no danger in approaching the mountain when the lava had vent, I went up immediately, accompanied by one peasant only. I pa.s.sed the hermitage (3.

in Plate I.), and proceeded as far as the spot marked (X), in the valley between the mountain of Somma and that of Vesuvius, which is called Atrio di Cavallo. I was making my observations upon the lava, which had already, from the spot (E) where it first broke out, reached the valley; when, on a sudden, about noon, I heard a violent noise within the mountain, and at the spot (C), about a quarter of a mile off the place where I stood, the mountain split; and, with much noise, from this new mouth, a fountain of liquid fire shot up many feet high, and then, like a torrent, rolled on directly towards us. The earth shook, at the same time that a volley of pumice stones fell thick upon us; in an instant, clouds of black smoak and ashes caused almost a total darkness; the explosions from the top of the mountain were much louder than any thunder I ever heard, and the smell of the sulphur was very offensive.

My guide, alarmed, took to his heels; and I must confess, that I was not at my ease. I followed close, and we ran near three miles without stopping; as the earth continued to shake under our feet, I was apprehensive of the opening of a fresh mouth, which might have cut off our retreat. I also feared that the violent explosions would detach some of the rocks off the mountain Somma, under which we were obliged to pa.s.s; besides, the pumice-stones, falling upon us like hail, were of such a size as to cause a disagreeable sensation upon the part where they fell. After having taken breath, as the earth still trembled greatly, I thought it most prudent to leave the mountain, and return to my villa; where I found my family in a great alarm, at the continual and violent explosions of the Volcano, which shook our house to its very foundation, the doors and windows swinging upon their hinges. About two of the clock in the afternoon another lava forced its way out of the same place from whence came the lava last year, at the spot marked B (in Plate II.); so that the conflagration was soon as great on this side of the mountain, as on the other which I had just left.

The noise and smell of sulphur increasing, we removed from our villa to Naples; and I thought proper, as I pa.s.sed by Portici, to inform the Court of what I had seen; and humbly offered it as my opinion, that his Sicilian Majesty should leave the neighbourhood of the threatening mountain. However, the Court did not leave Portici till about twelve of the clock, when the lava had reached as far as (4. in Plate I.)--I observed, in my way to Naples, which was in less than two hours after I had left the mountain, that the lava had actually covered three miles of the very road through which we had retreated. It is astonishing that it should have run so fast; as I have since seen, that the river of lava, in the Atrio di Cavallo, was sixty and seventy feet deep, and in some places near two miles broad. When his Sicilian Majesty quitted Portici, the noise was greatly increased; and the concussion of the air from the explosions was so violent, that, in the King's palace, doors and windows were forced open; and even one door there, which was locked, was nevertheless burst open. At Naples, the same night, many windows and doors flew open; in my house, which is not on the side of the town next Vesuvius, I tried the experiment of unbolting my windows[9], when they flew wide open upon every explosion of the mountain. Besides these explosions, which were very frequent, there was a continued subterraneous and violent rumbling noise, which lasted this night about five hours. I have imagined, that this extraordinary noise might be owing to the lava in the bowels of the mountain having met with a deposition of rain water; and that the conflict between the fire and the water may, in some measure, account for so extraordinary a crackling and hissing noise. Padre Torre, who has wrote so much and so well upon the subject of Mount Vesuvius, is also of my opinion. And indeed it is natural to imagine, that there may be rain-water lodged in many of the caverns of the mountain; as, in the great eruption of Mount Vesuvius in 1631, it is well attested, that several towns, among which Portici and Torre del Greco, were destroyed, by a torrent of boiling water having burst out of the mountain with the lava, by which thousands of lives were lost. About four years ago, Mount Etna in Sicily threw up hot water also, during an eruption.

The confusion at Naples this night cannot be described; his Sicilian Majesty's hasty retreat from Portici added to the alarm; all the churches were opened and filled; the streets were thronged with processions of saints: but I shall avoid entering upon a description of the various ceremonies that were performed in this capital, to quell the fury of the turbulent mountain.

Tuesday the 20th, it was impossible to judge of the situation of Vesuvius, on account of the smoak and ashes, which covered it entirely, and spread over Naples also, the sun appearing as through a thick London fog, or a smoaked gla.s.s; small ashes fell all this day at Naples. The lavas on both sides of the mountain ran violently; but there was little or no noise till about nine o'clock at night, when the same uncommon rumbling began again, accompanied with explosions as before, which lasted about four hours: it seemed as if the mountain would split in pieces; and, indeed, it opened this night almost from the spot E to C (in Plate I.). The annexed plans were taken upon the spot at this time, when the lavas were at their height; and I do not think them exaggerated. The Parisian barometer was, as yesterday, at 279, and Fahrenheit's thermometer at 70 degrees; whereas, for some days preceding the eruption, it had been at 65 and 66. During the confusion of this night, the prisoners in the public jail attempted to escape, having wounded the jailer; but were prevented by the troops. The mob also set fire to the Cardinal Archbishop's gate, because he refused to bring out the relicks of Saint Januarius.

Wednesday 21st, was more quiet than the preceding days, though the lavas ran briskly. Portici was once in some danger, had not the lava taken a different course when it was only a mile and a half from it; towards night, the lava slackened.

Thursday 22d, about ten of the clock in the morning, the same thundering noise began again, but with more violence than the preceding days; the oldest men declared, they had never heard the like; and, indeed, it was very alarming: we were in expectation every moment of some dire calamity. The ashes, or rather small cinders, showered down so fast, that the people in the streets were obliged to use umbrellas, or flap their hats; these ashes being very offensive to the eyes. The tops of the houses, and the balconies, were covered above an inch thick with these cinders[10]. Ships at sea, twenty leagues from Naples, were also covered with them, to the great astonishment of the sailors. In the midst of these horrors, the mob, growing tumultuous and impatient, obliged the Cardinal to bring out the head of Saint Januarius, and go with it in procession to the Ponte Maddalena, at the extremity of Naples, towards Vesuvius; and it is well attested here, that the eruption ceased the moment the Saint came in sight of the mountain; it is true, the noise ceased about that time, after having lasted five hours, as it had done the preceding days.