Observations on Mount Vesuvius, Mount Etna, and Other Volcanos Part 6

[10] In several accounts of former eruptions of Vesuvius, I have found mention of the ashes falling at a much greater distance; that, in the year 472 and 473, they had reached Constantinople: Dio says, that during the eruption of Vesuvius in the time of t.i.tus--"tantus fuit pulvis ut ab eo loco in Africam et Syriam et gyptum penetraverit." A book printed at Lecce, in the kingdom of Naples, in MDCx.x.xII, and int.i.tuled, _Discorso sopra l'origine de fuochi gettati dal Monte Vesuvio di Gio Francesco Sorrata Spinola Galateo_, says, that the 16th of December, 1631, the very day of the great eruption of Vesuvius (though perfectly calm), it rained ashes at Lecce, which is nine days journey from the mountain: that the day was darkened by them, and that they covered the ground three inches deep; that ashes of a different quality fell at Bari the same day; and that at both these places the inhabitants were very greatly alarmed, not being able to conceive the occasion of such a phnomenon. Antonio Bulifon, in his account of the same eruption, says, that the ashes fell, and lay several inches deep at Ariano in Puglia; and I have been a.s.sured, by many persons of credit at Naples, that they have been sensible of the fall of ashes, during an eruption, at above two hundred miles distance from Vesuvius. The Abbate Giulio Cesare Bracini, in his account of the eruption of Vesuvius, in 1631, says, that the height of the column of smoak and ashes, taken from Naples by a quadrant, was upwards of thirty miles. Though such uncertain calculations demand but little attention; yet, by what I have seen, I am convinced, that in great eruptions the ashes are sent up to so great a height as to meet with extraordinary currents of air, which is the most probable way of accounting for their having been carried to so great a distance in a few hours. In a book, int.i.tuled, _Salvatoris Varonis Vesuviani incendii Libri tres: Neapoli_, MDCx.x.xIV, I found a very poetical description of the ashes that lay in the neighbourhood of Vesuvius, after the eruption of 1631, in depth, from twenty to a hundred palms: "Quare," says this author, "multi patrio in solo requirunt patriam, et vix ibi se credunt vivere ubi certo sciant sese natos, adeo totam loci speciem tempestas vert.i.t."

[11] This conjecture has proved true; for, even in the month of April 1771, I again thrust sticks into some crevices of this lava, and they immediately took fire. On Mount Etna, in 1769, I observed the lava, that had been disgorged in 1766, smoak in many parts.

[12] In all accounts of great eruptions of Mount Etna and Mount Vesuvius, I have found mention of this sort of lightning. Pliny the younger, in his second letter to Tacitus upon the eruption of Vesuvius in the time of t.i.tus, says, that a black and horrible cloud covered them at Misenum (which is above fifteen miles from the Volcano), and that flashes of zig-zag fire, like lightning, but stronger, burst from it; these are his words: "ab altero latere nubes atra et horrenda ignei spiritus tortis vibratisque discursibus rupta, in longas flammarum figuras dehiscebat; fulgoribus ill et similes et majores erant." This was evidently the same electrical fire, and with which I am convinced that the smoak of all Volcanos is pregnant. In several accounts of the great eruption of Vesuvius in 1631, mention is made of damage done by the lightning that issued from the column of smoak. Bulifon, in particular, says, that, in the neighbourhood of the Volcano, people were struck dead in the same manner as if by lightning, without having their cloaths singed. Pliny mentions a like instance, which shews that the ancients had observed this phnomenon; for he says, that at Pompeii, the day being fair, Marcus Herennius was struck dead by lightning. These are his words; "In Catilianis prodigiis, Pompeiano ex municipio M. Herennius Decurio _serena die_, fulmine ictus est." Plin. Hist. Nat. lib. II. cap.

LI. The learned and ingenious Father Beccaria, at Turin, a.s.sured me, that he had been greatly pleased with my observations on this species of lightning, as coinciding perfectly with several of his electrical experiments.

[13] "I am well convinced, by this collection, that many variegated marbles, and many precious stones, are the produce of Volcanos; and that there have been Volcanos in many parts of the world, where at present there are no traces of them visible." This is taken from a prior letter to Lord Morton, dated April 7, 1767.

[14] In some accounts of an eruption of Vesuvius in 1660, I find mention made of ashes which fell in the shape of crosses, and were looked upon as highly miraculous; but in one book upon this subject, int.i.tuled, _Athanasii Kircheri Soc. Jes. De prodigiosis crucibus, &c. Rom_, MDCLXI, a very philosophical account is given of this phnomenon; he says, that, in 1660, from the 16th of August to the 15th of October, Vesuvius cast up ashes, impregnated with nitrous, saline, and bituminous sulphur, which upon linen garments took the form of crosses, probably directed by the cross-threads in the linen, and therefore that the salts did not shoot into such a shape when they fell upon garments of woollen; a very particular description of these crosses may be found in page 38, of the abovementioned book.

[15] I have since found in this stratum of erupted matter at Pompeii, stones weighing eight pounds: but many accounts of the great eruption of Vesuvius, particularly that of Antonio Bulifon, mention that a stone like a bomb was thrown from the crater of Vesuvius in 1631; and fell upon the Marquis of Lauro's house at Nola, which it set on fire. As Nola is twelve miles from Vesuvius, this circ.u.mstance seems rather extraordinary: however, I have seen stones of an enormous size shot up to a very great height by Mount Vesuvius. In May 1771, having a stop watch in my hand, I observed that one of these stones was eleven seconds falling from its greatest height, into the crater from whence it had been ejected. In 1767, a solid stone, measuring twelve feet in height, and forty-five in circ.u.mference, was thrown a quarter of a mile from the crater; the eruption of 1767, though by much the most violent of this century, was, comparatively to those of the year 79 and 1631, very mild.

[16] See Letter V. in this collection.

[17] It is the common received opinion, that this mountain rose from the bottom of the Lucrine lake. I had not seen the very curious and particular account of its formation (which account is in my next letter) when I wrote this, and was therefore in the same error.

[18] This must depend greatly upon the quality of the lava's; some have been in a more perfect state of vitrification than others, and are consequently less liable to the impressions of time. I have often observed on Mount Vesuvius, when I have been close to the mouth from whence a lava was disgorging itself, that the quality of it varied greatly from time to time: I have seen it as fluid and coherent as gla.s.s when in fusion: and I have seen it farinacious, the particles separating as they forced their way out, just like meal coming from under the grindstones. A stream of lava of this sort, being less compact, and continuing more earthy particles, would certainly be much sooner fit for vegetation, than one composed of the more perfect vitrified matter.

[19] This earthquake happened in the year 1693, and destroyed forty-nine towns and villages, nine hundred and twenty-two churches, colleges, and convents; and near one hundred thousand persons were buried in their ruin.

[20] It is int.i.tuled, "A true and exact relation of the late prodigious earthquake and eruption of Mount tna, or Monte Gibello; as it came in a letter written to his Majesty from Naples, by the Right Honourable the Earl of Winchelsea, his Majesty's late Emba.s.sador at Constantinople, who, in his return from thence, visiting Catania in the island of Sicily, was an eye-witness of that dreadful spectacle; together with a more particular narrative of the same, as it is collected out of the several relations sent from Catania; published by authority. Printed by T. Newcomb, in the Savoy, 1669."

"I accepted, says the author, p. 38, the invitation of the Bishop of Catania, to stay a day with him, that so I might be the better able to inform your Majesty of that extraordinary fire, which comes from Mount Gibel, fifteen miles distant from that city, which, for its horridness in the aspect, for the vast quant.i.ty thereof (for it is fifteen miles in length, and seven in breadth), for its monstrous devastation and quick progress, may be termed an inundation of fire, a flood of fire, cinders, and burning stones, burning with that rage as to advance into the sea six hundred yards, and that to a mile in breadth, which I saw; and that which did augment my admiration was, to see in the sea this matter like ragged rocks, burning in four fathom water, two fathom higher than the sea itself, some parts liquid, and throwing off, not with great violence, the stones about it, which, like a crust of a vast bigness, and red hot, fell into the sea every moment, in some place or other, causing a great and horrible noise, smoak, and hissing in the sea; and that more and more coming after it, making a firm foundation in the sea itself. I stayed there from nine a clock on Sat.u.r.day morning, to seven next morning;" (this must have been towards the middle or latter end of April;) "and this mountain of fire and stones with cinders had advanced into the sea twenty yards at least, in several places; in the middle of this fire, which burnt in the sea, it hath formed like to a river, with its banks on each side very steep and craggy; and in this channel moves the greatest quant.i.ty of this fire, which is the most liquid, with stones of the same composition, and cinders all red hot, swimming upon the fire of a great magnitude; from this a river of fire doth proceed under the great ma.s.s of the stones, which are generally three fathoms high all over the country, where it burns, and in other places much more. There are secret conduits or rivulets of the liquid matter, which communicates fire and heat into all parts more or less, and melts the stones and cinders by fits in those places where it toucheth them, over and over again; where it meets with rocks or houses of the same matter (as many are), they melt and go away with the fire; where they find other compositions, they turn them to lime or ashes (as I am informed).

The composition of this fire, stones, and cinders, are sulphur, nitre, quicksilver, sal ammoniac, lead, iron, bra.s.s, and all other metals. It moves not regularly, nor constantly down hill[48]; in some places it hath made the vallies hills, and the hills that are not high are now vallies. When it was night, I went upon two towers, in divers places; and could plainly see at ten miles distance, as we judged, the fire to begin to run from the mountain in a direct line, the flame to ascend as high and as big as one of the greatest steeples in your Majesty's kingdoms, and to throw up great stones into the air; I could discern the river of fire to descend the mountain of a terrible fiery or red colour, and stones of a paler red to swim thereon, and to be some as big as an ordinary table. We could see this fire to move in several other places, and all the country covered with fire, ascending with great flames[49], in many places, smoaking like to a violent furnace of iron melted, making a noise with the great pieces that fell, especially those which fell into the sea. A Cavalier of Malta, who lives there, and attended me, told me, that the river was as liquid where it issues out of the mountain, as water, and came out like a torrent with great violence, and is five or six fathom deep, and as broad, and that no stones sink therein. I a.s.sure your Majesty, no pen can express how terrible it is, nor can all the art and industry of the world quench or divert that which is burning in the country. In forty days time, it hath destroyed the habitations of 27,000 persons; made two hills of one, 1000 paces high apiece, and one is four miles in compa.s.s; of 20,000 persons, which inhabit Catania, 3000 did only remain; all their goods are carried away, the cannons of bra.s.s are removed out of the castle, some great bells taken down, the city-gates walled up next the fire, and preparations made to abandon the city.

"That night which I lay there, it rained ashes all over the city, and ten miles at sea it troubled my eyes. This fire in its progress met with a lake of four miles in compa.s.s; and it was not only satisfied to fill it up, though it was four fathom deep, but hath made of it a mountain."

[21] I have heard since, from some of our countrymen who have measured this tree, that its dimensions are actually as abovementioned, but that they could perceive some signs of four stems having grown together, and formed one tree.

[22] No great stress should be laid upon these observations, as the many inconveniences we laboured under, and the little practice we had in such nice operations, must necessarily have rendered them very inaccurate.

The Canon Recupero, who was our guide, attended Mess. Glover, Fullerton, and Brydone, up Mount Etna in June 1770. The latter is a very ingenious and accurate observer, and has taken the height of many of the highest mountains in the Alps. His observations, as the Canon informed me, were as follows: At the top of the mountain the quicksilver in the thermometer was 9 degrees below freezing point, when at the foot of the mountain it rose to 76. At the foot of the little mountain that crowns the Volcano the barometer stood at 20 4-2/3', half way up this little mountain it was at 19 6'; but the wind was too violent for them to attempt any more observations. The barometer and thermometer were of Fahrenheit's. Mr. Brydone remarked, as he went up in the night, that he could distinguish the stars in the milky way with wonderful clearness, and that the cold was much more intense than he had ever felt upon the highest mountains of the Alps.

[23] This pa.s.sage, in Cornelius Severus's poem upon Etna, seems to confirm my opinion:

"Placantesque etiam clestia numina thure "Summo cerne jugo, vel qu liberrimus tna "Improspectus hiat; tantarum semina rerum "Si nihil irritet flammas, stupeatque profundum."

[24] A better account of the formation of _tufa_ will be seen in my next letter.

[25] The dates of the eruptions of Mount Etna, recorded by history, are as follows: Before the Christian ra four, in the years 3525. 3538.

3554. 3843. After Christ, twenty-seven have been recorded, 1175. 1285.

1321. 1323. 1329. 1408. 1530. 1536. 1537. 1540. 1545. 1554. 1556. 1566.

1579. 1614. 1634. 1636. 1643. 1669. 1682. 1689. 1692. 1702. 1747. 1755.

1766.

The dates of the eruptions of Vesuvius are as follows: After Christ--79.

203. 472. 512. 685. 993. 1036. 1043. 1048. 1136. 1506. [1538, the eruption at Puzzole.] 1631. 1660. 1682. 1694. 1701. 1704. 1712. 1717.

1730. 1737. 1751. 1754. 1760. 1766. 1767. 1770. 1771.

[26] Pliny, in his account of these islands, in the IX chapter of the third book of his Natural History, seems to confirm this opinion.

"Lipara c.u.m civium Romanorum oppido, dicta Liparo rege, qui successit olo, antea Melogonis vel Meliganis vocitata, abest XII millia pa.s.s. ab Italia, ipsa circuitu paulo minori. Inter hanc et Siciliam altera, antea Therasia appellata, nunc Hiera; qui sacra Vulcano est, colle in ea nocturnas evomente flammas. Tertia Strongyle, a Lipara millia pa.s.suum ad exortum solis vergens, in qua regnavit olus, qu Lipara liquidiore flamma tantum differt: e cujus fumo equinam flaturi sint venti, in triduum prdicere incol traduntur; unde ventos olo paruisse existimatum. Quarta Didyme, minor quam Lipara. Quinta Ericusa; s.e.xta Phoenicusa; pabulo proximarum relicta. NOVISSIMA, eademque Minima, Evonymos."

[27] See Plate V.

[28] The Abate Giulio Cesare Bruccini describes very elegantly, in his account of the eruption of Vesuvius in 1631, his having made an observation of the like nature--his words are (after having particularized the different strata of erupted matter lying one over another)--"parendo appunto che la natura ci abbia voluto lasciare scritto in questa terra tutti gli incendii memorabili raccontati delli autori."

[29] These are his words, book II. chap. vi.

"De Pulvere Puteolano.

"Est etiam genus pulveris, quod efficit naturaliter res admirandas.

Nascitur in regionibus Baanis, et in agris municipiorum, qu sunt circa Vesuvium montem, quod commixtum c.u.m calce et cmento non modo cteris dificiis prstat firmitates, sed etiam moles, qu construuntur in mari, sub aqua solidesc.u.n.t. Hoc autem fieri hac ratione videtur, quod sub his montibus et terra ferventes sunt fontes crebri, qui non essent, si non in imo haberent, aut de sulfure, aut alumine, aut bitumine ardentes maximos ignes: igitur penitus ignis, et flamm vapor per intervenia permanans et ardens, efficet levem eam terram, et ibi, qui nascitur tophus, exugens est, et sine liquore. Ergo c.u.m tres res consimili ratione, ignis vehementia format in unam pervenerint mixtionem, repente recepto liquore una cohresc.u.n.t, et celeriter humore durat solidantur, neque eas fluctus, neque vis aqu potest dissolvere."

About Baa, Puzzole, and Naples, we have an opportunity of remarking the truth of these last words. Several of the piers of the ancient harbour of Puzzole, vulgarly called Caligula's bridge, and which are composed of bricks joined with this sort of cement, are still standing in the sea, though much exposed to the waves; and upon every part of the sh.o.r.e you find large ma.s.ses of brick-walls rounded and polished by friction in the sea, the brick and mortar making one body, and appearing like a variegated stone. Large pieces of old walls are likewise often cut out into square pieces, and made use of in modern buildings instead of stone.

Soon after the first quotation, Pliny says, "Si ergo in his locis aquarum ferventes inveniuntur fontes, et in montibus excavatis calidi vapores, ipsaque loca ab antiquis memorantur pervagantes in agris habuisse ardores, videtur esse certum ab ignis vehementia ex topho terraque, quemadmodum in fornacibus et a calce, ita ex his ereptum esse liquorem. Igitur dissimilibus, et disparibus rebus correptis, et in unam potestatem collatis, callida humoris jejunitas aqua repente satiata, communibus corporibus latenti calore confervescit et vehementer effecit ea coire, celeriterque una soliditatis percipere virtutem."

[30] Scipione Falcone, a very good observer, in his _Discorso naturale delli cause et effetti del Vesuvio_, says, that he saw, after the eruption of Vesuvius in 1631 (which was attended with hot water), the mud harden almost to a stone in a few days; his words are these--"fatta dura a modo di calcina e di pietra non altrimenti di cenere, perch dop alcuni giorni vi ci e caminato per sopra e si e conosciuta durissima che ci vogliono li picconi per romperla." This account, with other circ.u.mstances mentioned in this letter, make it highly probable, that all the _tufas_ in the neighbourhood of Vesuvius have been formed by a like operation.

[31] This piece is now in the Museum of the Royal Society, together with other specimens, mentioned in this and in the following letter. M. M.

[32] Letter IV.

[33] Strabo, in his fifth book of Geography, says, "Supra hc loca situs est Vesuvius mons agris cinctus optimis: dempto vertice, qui magna sui parte pla.n.u.s, totus sterilis est, adspectu cinreus, cavernasque ostendens fistularum plenas et lapidum colore fuliginoso, utpote ab igni exesorum, ut conjecturam facere possit ista loca quondam arsisse, et crateras ignis habuisse, deinde materia deficiente restincta fuisse."

Diodorus Siculus, in his fourth book, describing the voyage of Hercules into Italy, says, "Phlegrus quoque campus is locus appellatur a colle nimirum, qui tn instar Sicul magnam vim ignis eructabat; nunc Vesuvius nominatur, multa inflammationis pristin vestigia reservans."

And Vitruvius, in the sixth chapter of the second book, says, "Non minus etiam memoratur antiquitus crevisse ardores et abunda.s.se sub Vesuvio monte et inde evomuisse circa agros flammas." Tacitus, mentioning the eruption of Vesuvius in the reign of t.i.tus, seems to hint likewise at former eruptions, in these words: "Jam ver novis cladibus, vel post longam sculorum repet.i.tis afflict, haust aut abrut fecundissima Campani ora et urbs incendiis vastata."

[34] Bracini, in his account of the eruption of 1613, says, that he found many sorts of sea sh.e.l.ls on Vesuvius after that eruption; and P.

Ignatio, in his account of the same eruption, says, that he and his companions picked up many sh.e.l.ls likewise at that time upon the mountain: this circ.u.mstance would induce one to believe, that the water thrown out of Vesuvius, during that formidable eruption, came from the sea.

[35] In book xi. c. 93. he observes, that about Sinuessa and Puteoli, "Spiracula vocant--alii Caroneas scrobes, mortiferum spiritum exhalantes." And Seneca, Nat. Qust. lib. vi. cap. 28. "Pluribus Itali locis per qudam foramina pestilens exhalatur vapor, quem non homini ducere, non fer tutum est. Aves quoque si in illum inciderint, antequam coelo meliore leniatur, in ipso volatu cadunt, liventque corpora, et non aliter quam per vim elis fauces tument."

[36] I have remarked, that, after a great fall of rain, the degree of heat in this water is much less, which will account for what the Padre Torre says (in his book, ent.i.tuled, _Histoire et Phenomenes du Vesuve_), that, when he tried it in company with Monsieur de la Condamine, the degree of heat, upon Reaumur's thermometer, was 68.

[37] This very scarce volume has been presented by Sir William Hamilton to the British Museum. M. M.

[38] Here again we have an example of the electrical fire attending a great eruption.

[39] The cup, or crater, on the top of the new mountain is now covered with shrubs; but I discovered at the bottom of it, in the year 1770, amidst the bushes, a small hole, which exhales a constant hot and damp vapour, just such as proceeds from boiling water, and with as little smell; the drops of this steam hang upon the neighbouring bushes.

[40] The noxious vapours which Lucan mentions to have prevailed at Nisida, favour my opinion as to its origin:

"--Tali spiramine Nesis "Emitt.i.t stygium nebulosis ara saxis."

Lucan. lib. vi.

[41] Giulio Cesare Capaccio, in his account of this island, says, that there are eleven springs of cold water, and thirty-five of hot and mineral waters.