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Show 328 VOLCANIC ERUPTION S IN ISCIIIA. . f th it has given vent to a lava- Auvergne, and, hke s?me od fe~t' ummit. A small ravine . b e mstea o I s s . h stream at Its as ' the structure of the cone, whtc swept out by a torrent expbolse~ lt'ned and slightly undulating d f 'nnumera e me 1 is compose 0 I . 1 't lapi'lli and enormous angu ar f · sconce w 11 e ' layers o pumice, h~se last have evidently been thrown blocks of trachyte. ! l'k those which in 189l9l, launched out by viol~nt explostoont, ~o:enic lava, of many tons weight, from V ~suvius a mass ~y which fell in the garden of Prince to the distance of three ~I ~s, t . is covered with the arbutus, Ottajano. The cone o o ato Such is the strength of the and other beautiful ever~re~s. e become almost arborescent; virgin soil, that the shru ; th:v smaller wild plants has been so an. d the grotlw tth booft asmo.mstes oh ave scarcely been able to recognise vigorous, 1a . h . b the Syracusan colony was the species. The erudptwhn w eii.eve~ rise to that miahty current . 1 d d . suppose to ave g o, ~ dis o ge ' Is f Zaro and Caruso. 'I he sur lace which forms th~ pr?montor~r~d and bristling, and is covered of these lavas IS still vhery . . t wi'thout great labour that . k · . so t at It IS no d with bla.c d scot riceh a' s redeeme d some small spots ' and converte human. m u.s ry ds From t 11 e d a t eof the great eruption la.st them mto vmeyar . t' Ischia has en1oyed tranqm1- d d to our own Ime, " b allude to, own f . 1 • 0. h t' n of lava hereafter to e 11 0 one emtss lity, With t e excep to 1 't ccasioned much local damage, described, which, althougdl 1 ~ t d the whole country, in the does not appear to have evas. a e manner of more ancient exp~olsions. unts at present to about 'l'he popu1 a tw· n of the. 1s e 1a m. o They are supporte d . 1 d nd IS on t 1e mcrease. h twenty-five t Jousan 'a d . f their vineyards. T e . 1 the pro uct10n o . almost entire y on S N' h l on this island, IS com-lofty central hill, Epomeo ord . ;c of a, rodigious thickness, f . . 1 indurate tuu' o a p d h . posed o giee~Is 1 'th ar illaceous marl, an ' ere interstratified m some parts wfi . d grated lava. Visconti ascer- and there, w.i t h grea t s.t reams o m. u t that this mountam· was tained by trigonometncal measmemen 'I mineral composition G'l605 feet above the level of the s~a. fn . I't resembles the i(.ln d in form as seen f rom many pOlnts o vte'wt ,o f which stan ds a ' N 1 on the summi h hill to the north of ape~{. h is 1643 feet in height. Bot. the convent of Camaldoh, w JlC t f those in the Terra dt these mountains, like the grea~ei~l~~:lt~lough it has frequently Lavoro, are of subaqueous or g ' EPOMEO OF SUBMARINE ORIGIN. 329 happened to them, as to Epomeo, that, after being elevated above the level of the sea, fresh eruptions have broken through at different points. I found more than one argillaceous stratum containing marine shells, within eight hundred feet of the summit of Epomeo; and from this circumstance, and from the general structure of the mountain, I am compelled to dissent from the opinion expressed by Mr. Scrope, who sup~osed it to have been once a great habitual volcano, like Vesuvius*. At least it is certain, that if any one of the cones on the present mountain gave vent to several streams of lava in succession, this happened when the whole mass was still beneath the level of the sea. Brocchi long ago announced, that the igneous rocks of this island rest on a plastic clay containing shells. Of these a considerable number have now been obtained, and identified with species still living in the Mediterranean. 'l'here are, upon the whole, on different parts of Epomeo, or scattered througl1 the lower tracts of the island, twelve considerable volcanic cones, which have been thrown up since the island was raised above the surface of the deep ; and many streams of lava may have flowed, like that of" Arso'' in 1302, without cones having been produced; so that this isle may, for ages before the period of the remotest tt·aditions, have served as a safety-valve to the whole r.rerra di Lavoro, while the fires of Vesuvius wel'e dormant. It seems also clear, that Avernus, a circular lake near Puzzuoli, about half a mile in diameter, which is now a salubrious and cheerful spot, once exhaled mephitic vapours, such as are often emitted by craters after eruptions. There is no reason for discrediting the account of Lucretiust, that birds could not fly over it without being stifled, although they may now frequent it uninjured. 'I' here must have h.een a time wlten this crater was in action; and for many centunes afterwards it may have deserved the appellation of "atri janua Ditis,'' emitting, perhaps, gases as destructive of animal life as those suffocating vapours which were given out by Lake Quilotoa, in Quito, in 1797, by which whole herds of cattle on its shores were killed t, or as those deleterious "' Geol. Trans., vol. ii., part 3, p. 388; second series. t, ~c Rerum Nat., VI., 740.-Mr. Forbes on tho Bay of Na}Jlcs, Edin, Journ. of Sc1ence, No. 31 new se1·ies, p. 87, J au. 1830. : Humboldt, Voy., p. 317, |