Observations on Mount Vesuvius, Mount Etna, and Other Volcanos

by Sir William Hamilton

We come next to the new mountain near Puzzole, which, being of so very late a formation, preserves its conical shape entire, and produces as yet but a very slender vegetation. It has a crater almost as deep as the cone is high, which may be near a quarter of a mile perpendicular, and is in shape a regular inverted cone. At the basis of this new mountain (which is more than three miles in circumference), the sand upon the sea shore, and even that which is washed by the sea itself, is burning hot for above the space of an hundred yards; if you take up a handful of the sand below water, you are obliged to get rid of it directly, on account of its intense heat.

I had been long very desirous of meeting with a good account of the formation of this new mountain, because, proving this mountain to have been raised by mere explosion in a plain, would prove at the same time, that all the neighbouring mountains, which are composed of the same materials, and have exactly or in part the same form, were raised in the like manner; and that the seat of fire, the cause of these explosions, lies deep; which I have every reason to think.

Fortunately, I lately found two very good accounts of the phænomena that attended the explosion, which formed the new mountain, published a few months after the event. As I think them very curious, and greatly to my purpose, and as they are rare, I will give you a literal translation of such extracts as relate to the formation of the Monte Nuovo. They are bound in one volume[37].

The title of the first is, Dell Incendio di Pozzuolo, Marco Antonio delli Falconi all Illustrissima Signiora Marchesa della Padula nel MDXXXVIII.

At the head of the second is, Ragionamento del Terremoto, del Nuovo Monte, del Aprimento di Terra in Pozzuolo nell' Anno 1538, é della significatione d'essi. Per Piero Giacomo da Toledo; and at the end of the book, Stampata in Nap. per Giovanni Sulztbach Alemano, a 22di Genaro 1539, con gratia, é privilegio.

"First then (says Marco Antonio delli Falconi), will I relate simply and exactly the operations of nature, of which I was either myself an eye-witness, or as they were related to me by those who had been witnesses of them. It is now two years that there have been frequent earthquakes at Pozzuolo, at Naples, and the neighbouring parts; on the day and in the night before the appearance of this eruption, above twenty shocks great and small were felt at the abovementioned places. The eruption made its appearance the 29th of September 1538, the feast of St. Michael the angel; it was on a Sunday, about an hour in the night; and, as I have been informed, they began to see on that spot, between the hot baths or sweating rooms, and Trepergule, flames of fire, which first made their appearance at the baths, then extended towards Trepergule, and fixing in the little valley that lies between the Monte Barbaro and the hillock called del Pericolo (which was the road to the lake of Avernus and the baths), in a short time the fire increased to such a degree, that it burst open the earth in this place, and threw up so great a quantity of ashes and pumice stones mixed with water, as covered the whole country; and in Naples a shower of these ashes and water fell a great part of the night. The next morning, which was Monday, and the last of the month, the poor inhabitants of Pozzuolo, struck with so horrible a sight, quitted their habitations, covered with that muddy and black shower, which continued in that country the whole day, flying death, but with faces painted with its colours; some with their children in their arms, some with sacks full of their goods; others leading an ass, loaded with their frightened family, towards Naples; others carrying quantities of birds of various sorts, that had fallen dead at the time the eruption began; others again with fish which they had found, and were to be met with in plenty upon the shore, the sea having been at that time considerably dried up. Don Pedro di Toledo, Viceroy of the kingdom, with many gentlemen, went to see so wonderful an appearance; I also, having met with the most honourable and incomparable gentleman, Signior Fabritio Moramaldo, on the road, went and saw the eruption and the many wonderful effects of it. The sea towards Baïa had retired a considerable way; though, from the quantity of ashes and broken pumice stones thrown up by the eruption, it appeared almost totally dry. I saw likewise two springs in those lately-discovered ruins, one before the house that was the Queen's, of hot and salt water; the other of fresh and cold water, on the shore, about 250 paces nearer to the eruption: some say, that, still nearer to the spot where the eruption happened, a stream of fresh water issued forth like a little river. Turning towards the place of the eruption, you saw mountains of smoak, part of which was very black and part very white, rise up to a great height; and in the midst of the smoak, at times, deep-coloured flames burst forth with huge stones and ashes, and you heard a noise like the discharge of a number of great artillery. It appeared to me as if Typheus and Enceladus from Ischia and Etna with innumerable giants, or those from the Campi Phlegrei (which, according to the opinions of some, were situated in this neighbourhood), were come to wage war again with Jupiter. The natural historians may perhaps reasonably say, that the wise poets meant no more by giants, than exhalations, shut up in the bowels of the earth, which, not finding a free passage, open one by their own force and impulse, and form mountains, as those which occasioned this eruption have been seen to do; and methought I saw those torrents of burning smoak that Pindar describes in an eruption of Etna, now called Mon Gibello, in Sicily; in imitation of which, as some say, Virgil wrote these lines:

"Ipse sed horrificis juxta tonat Ætna ruinis, &c.

"After the stones and ashes with clouds of thick smoak had been sent up, by the impulse of the fire and windy exhalation (as you see in a great cauldron that boils), into the middle region of the air, overcome by their own natural weight, when from distance the strength they had received from impulse was spent, rejected likewise by the cold and unfriendly region, you saw them fall thick, and, by degrees, the condensed smoak clear away, raining ashes with water and stones of different sizes, according to the distance from the place: then, by degrees, with the same noise and smoak, it threw out stones and ashes again, and so on by fits. This continued two days and nights, when the smoak and force of the fire began to abate. The fourth day, which was Thursday, at 22 o'clock, there was so great an eruption, that, as I was in the gulph of Puzzole, coming from Ischia, and not far from Misenum, I saw, in a short time, many columns of smoak shoot up, with the most terrible noise I ever heard, and, bending over the sea, came near our boat, which was four miles or more from the place of their birth; and the quantity of ashes, stones, and smoak, seemed as if they would cover the whole earth and sea. Stones, great and small, and ashes more or less, according to the impulse of the fire and exhalations, began to fall, so that a great part of this country was covered with ashes; and many, that have seen it, say, they reached the vale of Diana, and some parts of Calabria, which are more than 150 miles from Pozzuolo. The Friday and Saturday nothing but a little smoak appeared; so that many, taking courage, went upon the spot, and say, that with the stones and ashes thrown up, a mountain has been formed in that valley, not less than three miles in circumference, and almost as high as the Monte Barbaro, which is near it, covering the Canettaria, the castle of Trepergule, all those buildings and the greatest part of the baths that were about them; extending South towards the sea, North as far as the lake of Avernus, West to the Sudatory, and joining East to the foot of the Monte Barbaro; so that this place has changed its form and face in such a manner as not to be known again: a thing almost incredible, to those who have not seen it, that in so short a time so considerable a mountain could have been formed. On its summit there is a mouth in the form of a cup, which may be a quarter of a mile in circumference, though some say it is as large as our market-place at Naples, from which there issues a constant smoak; and though I have seen it only at a distance, it appears very great. The Sunday following, which was the 6th of October, many people going to see this phænomenon, and some having ascended half the mountain, others more, about 22 o'clock there happened so sudden and horrid an eruption, with so great a smoak, that many of these people were stifled, some of which could never be found. I have been told, that the number of the dead or lost amounted to twenty-four. From that time to this, nothing remarkable happened; it seems as if the eruption returned periodically, like the ague or gout. I believe henceforward it will not have such force, though the eruption of the Sunday was accompanied with showers of ashes and water, which fell at Naples, and were seen to extend as far as the mountain of Somma, called Vesuvius by the ancients; and, as I have often remarked, the clouds of smoak proceeding from the eruption moved in a direct line towards that mountain, as if these places had a correspondence and connection one with the other. In the night, many beams and columns of fire were seen to proceed from this eruption, and some like flashes of lightning[38]. We have then, many circumstances for our observation, the earthquakes, the eruption, the drying up of the sea, the quantity of dead fish and birds, the birth of springs, the shower of ashes with water and without water, the innumerable trees in that whole country, as far as the Grotto of Lucullus, torn from their roots, thrown down, and covered with ashes, that it gave one pain to see them: and as all these effects were produced by the same cause that produces earthquakes; let us first enquire how earthquakes are produced, and from thence we may easily comprehend the cause of the abovementioned events." Then follows a dissertation on earthquakes, and some curious conjectures relative to the phænomena which attended this eruption, clearly and well expressed, considering, as the author himself apologizes, that at that time the Italian language had been little employed on such subjects.

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 the same 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 can carry, 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 boiling up, 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 upon the phænomena 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 fire of 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 my [letter] upon 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 Volcanos lies 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.