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Show 368 MODE OF ADVANCE OF A LAVA-CURRENT. 1 t •11 hence a torrent of lava flowed and finally a fifth, ow_erh s 1 , wt velocity over the valley ' del 1 · h ad itself Wit grea ~ w uc spre . fl d t 0 miles in the first twenty-1our B , Tlus stream owe w · 1 Th ove. :f . tl succeeding day and mg lt. e hours, and nearly ahs arlin lteh united into one large crater, and 1 : O'inal mout sat eng h t Jl'ee ollb did the four inferior apertures, so t at an errorsent forth lava, as d d th great valley ' del Bove.' When t ·rent poure own e . . h m. ou.s . . OeI d at a vast an d a1 m o st perpendicular. prec1p1eed, at t de It arnv of Calanna, it poured over m a casca e, an.' head of the vall~y . d t made an inconceivable crash as It b . h rdened m Its escen , . h 1 f emdg ha ed aO'a.m st t h e b o tto m. So immense was t e coh u' m1n ho was as b b . f the tufaceous hill over w Ic 1 t e dust raised by the a radsiodn tol at the Catanians were in great h d d mass descen e , J h d ar ene . tion to have burst out in t e woo y alarm, supposi.ng ~ ne':le rup that near the summit of Etna. · exceedmO' m v10 ence h regwn, l P during this eruption, not more t an Of the cones t.Jrown uO'nitude to be numbered among those t~o are of. sufficiente;::eo reckoned as adorning the flanks of eighty which we~ b f tlJe lava which deluged the valley' del Et The surJ.ace o d h · na~ . k and an ular blocks, tosse toget er m Dove consists of roc y h' g be more rugged, or more t d. rder Not mg can the utmos ISO • d perficies which those who are unlike the smooth an 1 ev.en su ntries may have pictured to unacquainted with vo c~mc t~~~ which had consolidated from themselves, in a mass o rna b d this current in the year . . d t Mr Scrope o serve a hqm sta e. . . d nsiderable slope, at the rate 1819, slowly progressmg o~n a c:ths after its first emission. b d an hour mne mo f h of a out a yar . ' t d b the resistance o t e The lower stratum bemg alrres et .Ia.ually protruded itself, d h r or centra par gt groun ' t e uppe d i' 11 d •n 'l'his in its turn was b · pporte J.e O\\ • • and emg unsu l' 'd lava which swelled over It d b ass of more Iqm ' h covere y a m l d ll the appearance of a huge eap from above. '"£he cu~·r~t 1a 11~ over and over upon itself by of rough and large em ers ~o mg ulsion from behind. The the effect of an extremely. s owl'd~firopd nd the friction ofthesco- contract.w n of th e cr· ust as 1t so 1 I e 'ad d a crackli.n g soun d· k . t one another, pro uce . ht riform ca es agams d h t ight be seen by mg ' Within the .cre;ice~ a du~1 re ble ;la:::ity was visible by day*. and vapour Issumg m consl era tit Scrope, on Volcanos, P· lOZ. FLOODS ON ETNA. 369 The erosive and transporting power of running water is rarely exerted on Etna with gl'eat force, the rain which falls being immediately imbibed by the porous lavas ; so that, vast as is the extent of the mountain, it feeds only a few small rivulets, and these, even, are dry throuO'hout the O't·eater portion ,., 0 0 of the year. 'I he enormous rounded boulders, therefot·e, of tJ•achyte and basalt, a line of which can be traced from the sea, from neat· Giardini, by Mascali, and Zafarana, to the valley ' del Bove,' would offer a perplexing problem to the geologist, if history had not preserved the memorials of a tremendous flood which happened in this district in the year 1755. It appears that two streams of lava flowed in that yeat·, on the flnd of March, from the highest crater: they were immediately precipitated upon an enormous mass of snow, which then covered the whole mountain, and was extremely deep near the summit. The sudden melting of this frozen mass, by a fiery torrent three miles in length, produced a frightful inundation, which de\·astated the sides of the mountain for eight miles in length, and afterwards covered the lower flanks of Etna, where they were less steep, together with the plains near the sea, with great deposits of sand, scorire, and blocks of lava. Many absurd stories circulated in Sicily respecting this event, such as that the water was boiling, and that it was vomited fl'Om the highest crater; that it was as salt as the sea, and full of marine shells; but these were mere inventions, to which Recupero, although he relates them as tales of the mountaineers, seems to have attached rather too much importance. Floods of considerable violence have been sometimes produced on Etna, by the fall of heavy rains, aided, probably, by the melting of snow. By this cause alone, in 1761, sixty of the inhabitants of Acicatena were killed, and many of their houses swept away*. A remat·kable discovery has lately been made on Etna of a great mass of ice, preserved for many years, perhaps for centuries from melting, by the singular event of a current of red hot lava having flowed ovet· it. The following are the facts in attestation of a phenomenon which must at fit·st sight appear of so pamdoxical a charactet·. The extraordinary heat expet·ienced in the South of Europe, during the summer • Ferrara, Descriz. dell' Etna, p. 116. VoL, I, 2B |
