George Berkeley – Il Vesuvio e l’eruzione del 1717

Inserito da: · febbraio 1, 2012

April 17,1717. With much difficulty I reached the top of Mount Vesuvius, in which I saw a vast aperture full of smoke, which hindered the seeing its depth and figure. 1 heard within that horrid gulf certain odd sounds, which seemed to proceed from the belly of the mountain; a sort of murmuring, sighing, throbbing, churning, dashing (as it were) of waves, and between whiles a noise like that of thunder or cannon, which was constantly attended with a clattering like that of tiles falling from the tops of houses on the streets…

George Berkeley – Il Vesuvio e l’eruzione del 1717 – vesuvioweb

… Sometimes, as the wind changed, the smoke grew thinner, discovering a very ruddy flame, and the jaws of the pan or crater streaked with red and several shades of yellow. After an hour’s stay the smoke, being moved by the wind, gave us short and partial prospects of the great hollow, in the flat bottom of which I could discern two furnaces almost contiguous: that on the left, seeming about three yards in diameter, glowed with red flame, and threw up red-hot stones with a hideous noise, which, as they fell back, caused the fore-mentioned clattering. May 8, in the morning, I ascended to the top of Vesuvius a second time, and found a different face of things. The smoke ascending upright gave a full prospect of the crater, which, as I could judge, is about a mile in circumference, and a hundred yards deep. A conical mount had been formed since my last visit, in the middle of the bottom: this mount, I could see, was made of the stones thrown up and fallen back again into the crater. In this new hill remained the two mounts or furnaces already mentioned: that on our left was in the vertex of the hill which it had formed round it, and raged more violently than before, throwing up every three or four minutes with a dreadful bellowing a vast number of red-hot stones, sometimes in appearance above a thousand, and at least three thousand feet higher than my head as 1 stood upon the brink: but there being little or no wind, they fell back perpendicularly into the crater, increasing the conical hill. The other mouth to the right was lower in the side of the same new-formed hill: I could discern it to be filled with red-hot liquid matter, like that in the furnace of a glass-house, which raged and wrought as the waves of the sea, causing a short abrupt noise like what may be imagined to proceed from a sea of quicksilver dashing among uneven rocks. This stuff would sometimes spew over and run down the convex side of the conical hill; and appearing at first red-hot it changed colour, and hardened as it cooled, shewing the first rudiments of an eruption, or if I may say so, an eruption in miniature. Had the wind driven in our faces, we had been in no small danger of stifling by the sulphureous smoke, or being knocked on the head by lumps of molten minerals, which we saw had sometimes fallen on the brink of the crater, upon those shots from the gulf at bottom. But as the wind was favourable, I had an opportunity to survey this odd scene for above an hour and a half together; during which it was very observable, that all the volleys of smoke, flame, and burning stones, came only out of the hole to our left, while the liquid stuff in the other mouth wrought and overflowed as hath been already described. June 5, after a horrid noise, the mountain was seen at Naples to spew a little out of the crater. The same continued the 6th. The 7th, nothing was observed till within two hours of night, when it began a hideous bellowing, which continued all that night and the next day till noon, causing the windows, and as some affirm, the very houses, in Naples to shake. From that time it spewed vast quantities of molten stuff to the south, which streamed down the side of the mountain like a great pot boiling over. This evening I returned from a voyage through Apulia, and was surprised, passing by the north side of the mountain, to see a great quantity of ruddy smoke lie along a huge tract of sky over the river of molten stuff, which was itself out of sight. The 9th, Vesuvius raged less violently: that night we saw from Naples a column of fire shoot between whiles out of its summit. The 10th, when we thought all would have been over, the mountain grew very outrageous again, roaring and groaning most dreadfully. You cannot form a juster idea of this noise in the most violent fits of it, than by imagining a mixed sound made up of the raging of a tempest, the murmur of a troubled sea, and the roaring of thunder and artillery, confused all together. It was very terrible, as

we heard it in the further end of Naples, at the distance of above twelve miles: this moved my curiosity to approach the mountain. Three or four of us got into a boat, and were set ashore at Torre del Greco, a town situate al the foot of Vesuvius to the south-west, whence we rode four or live miles before we came to the burning river, which was about midnight. The roaring of the volcano grew exceeding loud and horrible as we approached. I observed a mixture of colours in the cloud over the crater, green, yellow, red, and blue; there was likewise a ruddy dismal light in the air over that tract of land where the burning river flowed; ashes continually showered on us all the way from the sea-coast: all which circumstances, set off and augmented by the horror and silence of the night, made a scene the most uncommon and astonishing 1 ever saw, which grew still more extraordinary as we came nearer the stream. Imagine a vast torrent of liquid fire rolling from the top down the side of the mountain, and with irresistible fury bearing down, and consuming vines, olives, fig-trees, houses; in a word, every thing that stood in its way. This mighty flood divided into different channels, according to the inequalities of the mountain: the largest stream seemed half a mile broad at least, and five miles long. The nature and consistence of these burning torrents hath been described with so much exactness and truth by Iiorellus in his Latin treatise of Mouut iEtna, that I need say nodiing of it, I walked so far before my companions up the mountain, along the side of the river of fire, that I was obliged to retire in great haste, the sulphureous stream having surprised me, and almost takeu away my breath. During our return, which was about three o’clock in the morning, we constantly heard the murmur and groaning of the mountain, which between whiles would burst out into louder peals, throwing up huge spouts of fire and burning stones, which falling down again, resembled the stars in our rockets. Sometimes I observed two, at others three distinct columns of flames; and sometimes one vast one that seemed to fill the whole crater. These burning columns and the fiery stones seemed to be shot one thousand feet perpendicular above the summit of the volcano. The 11th at night, 1 observed it, from a terrace in Naples, to throw up incessantly a vast body of fire, and great stones, to a surprising height. The liith in the morning it darkened the sun with ashes and smoke, causing a sort of eclipse. Horrid bellowings, this and the foregoing day, were heard at Naples, whither part of the ashes also reached: at night I observed it throwing up flame, us on the 11 th. On ihe 13th, the wind changing, we saw a pillar of black smoke shot upright to a prodigious height: at night I observed the mount cast up fire as before, though not so distinctly because of the smoke. The 14th, a thick black cloud hid the mountain from Naples. The 15th in the morning, the court and walls of our house in Naples were covered with ashes. The 16th, the smoke was driven by a westerly wind from the town to the opposite side of the mountain. The 17th, the smoke appeared much diminished, fat and greasy. The 18th, the whole appearance ended; the mountain remaining perfectly quiet, without any visible smoke or Uame. A gentleman of my acquaintance, whose window looked towards Vesuvius, assured me that he observed several flashes, as it were of lightning, issue out of the mouth of the volcano. It is not worth while to trouble you with the conjectures * I have formed concerning the cause of these phenomena, from what I observed in the Lacus Amsancti, the Solfatara, &c. as well as in Mount Vesuvius. One thing I may venture to say, that I saw the fluid matter rise out of the centre of the bottom of the crater, out of the very middle of the mountain, contrary to what Borellus imagines, whose method of explaining the eruption of a volcano by an inflexed syphon and the rules of hydrostatics, is likewise inconsistent with the torrent’s flowing down from the very vertex of the mountain. I have not seen the-crater since the eruption, but design to visit it again before I leave Naples. I doubt there is nothing in this worth shewing the Society: as to that, you will use your discretion.

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