Observations on Mount Vesuvius, Mount Etna, and Other Volcanos. Sir William Hamilton
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 principal 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 assured 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 passed 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 pass; 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 passed 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