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Show 366 SUBTERRANEAN OAVERNS OF ETNA, open one of the sol.id walls w~1ich flan~<ed the current near B el pas so, a nd immediately forth Issued a rivul.e t ofb m' elted mf atter which took the direction of Paterno; but the mba 1tants o that town, being alarmed for their safety, took up arms .and put a ·stop to farther operations*. As another 1llustrat10n of the l'd't of the walls of an advancing lava-stream, we may men~ f0~1 1 a~ adventure related by Recupero, who, i.n 1766, had ascended a small hill formed of ancient volcamc matter, to behold the slow and gradual approach of a fiery current, two miles and a half broad ; when suddenly two small threads of liquid matter issuing from a crevice detached th~mselves from the main stream, and ran rapidly towards the hill. ~e and his guide had just time to e~cape, when they. saw the h1ll, which was fifty feet in height, surrou~ded, and m a quarter ·of an hour melted down into the burnmg mass, s~ as to flow 'thl't But it must not be supposed that this complete on w1 · · 1 · f · fusion of rocky matter coming in contact w1th ava IS o um-versal, or even common occurrence. It probably ha~pens when fresh portions of incandescent matter come s~ccessiv~ly in contact with fusible materials. In many of ~he dikes wh1ch intersect the tuffs and lavas of Etna, there IS scarcely any perceptible alteration effected by heat. on the edges of the horizontal beds, in contact with the vertical and more crystal.- 1m. e mass. On the site of Mompiliere, o. ne of the town.s over-flowed in the great eruption above descnbed, an excavatiOn was d . 1704. and by immense labour the workmen reached, at rna e m ' h · · 1 h · b the depth of thirty-five feet, the gate. of .t e prmcip~ c me ' where there were three statues, held m high veneratwn. . One of these, together with a bell, some money~ and other artic:s, were extracted in a good state of preservatiOn from ben~~t a great arch formed by the lava. It seems very c~trao~ m~~ that any works of art, not encased wit? tu.ff, hkllc t ose ld h d fuswn m ho ow spaces Herculaneum shou ave escape C · ' h' h as so hot at atama left open in this lava-current, w JC w . im ossible eight years after it entered the to":n, that It was P to hold the hand in some of the crevices. . a sub· We mentioned the entrance of the ~ava-s~ea~~n~ere par· terranean grotto, whereby the foundatwns o a • Ferrara1 Descriz, dell' Etna, P• 108• ERUPTIONS OF ETNA ·IN 1811 AND· l819. · '367 tially un?ermined. Such underground passages are among the most curiOus feature~ on Etna, and appear to have been produced by the ha~dem~g of the lava, during the escape of great volum.es of elast?c ·flmds, which are often discharged for many days m. succ~ss10n, after the crisis of the eruption is over. Near NIColosi, not far from Monti Rossi one of these great openings may be seen, called the Fossa della Palomba 69l5 ~eet in circumferenc~ at its mouth, and 78 deep. After 1:eachmg the. bottom ~f thts, we .enter another dark cavity, and then others m successwn, sometimes descending precipices by means of ladders. At length the vaults terminate in a great gallery ninety feet long, and from fifteen to fifty broad beyond which there is still a passage, never yet explored; so 'that the extent of these caverns remains unknown*. The walls and roofs of these great vaults are composed of rough and bristling scorioo of the most fantastic forms. ' We shall now proceed to offer some observations on the two last eruptions in 1811 and 1819. It appears, from the relation of Signor Gemmellaro, who witnessed the phenomena that the great crater in 1811 testified, by its violent detonations, that ~he lava had ascended to near the summit of the mountain, by Its central duct. A violent shock was then felt, and a stream broke out from the side of the cone, at no great distance from its apex. Shortly after this had ceased to flow, a second stream burst for.th at. another opening, considerably below the first ; then a thn·d still lower, and so on till seven different issues had ~een thus successively formed, all lying upon the same straight lme .. It ha~ been supposed that this line was a perpendicular rent In the mternal framework of the mountain, which rent was.probably not produced at one shock, but prolonged successive!~ downwards, by the luteral pressure and intense heat o~ the mternal column of lava, as it subsided by gradual d1scharge through each venti·. In 181.9 three large mouths or caverns opened vet·y near tho.se which were formed in the eruptions of 1811, from w~uch flames, 1·ed hot cinders, and sand, were thrown up With loud explosions. .A few minutes afterwards another .mouth opened below, from which flames and smoke issued ; *Ferrara, Descriz, dell' .Etna. Palermo, 1618. t Scrope on Volcanos, p.153. |
