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Show 414 EARTHQUAKF.: IN CA LABRtA, A,D, 1783. in a rational manner many events which, as related in the language of some eye-witnesses, .appeared m.arvcllous and incredible. Dolomieu also exammed Calabna, soon after the catastrophe, and wrote an account of the earthquake, correcting a mistake into which Hamilton had fall~n, who supposed that a part of the tr~ct shaken had . cons1sted of volcanic tuff. It is, indeed, a circumstance whtch enhances the geological interest of the commotions which so often modify the surface of Calabria, that they are confined to a country where there are neither ancient nor modern rocks of igneous origin· so that at some future time, when the era of disturbance shall };ave passed by, the cause ?f !ormer rcvol.utions wi~l be as latent as in parts of Great Br1tam now occupted exclusively by ancient marine formations. . The convulsion of the earth, sea, and a1r, extended over the whole of Calabria Ultra, the south-east part of Calabria Citra and across the sea to Messina and its environs-a distri~t lying between the 88th and 89th degrees of lati~u~e. 1.'he concussion was perceptible over a great part of Stelly, and as far north as Naples; but the surface over which the shocks acted so forcibly as to excite intense alarm, did not generally exceed five hundred sq~ar.e miles in circ~mferen.ce. The soil of that part of Calabria Is composed chiefly, hke the southern part of Sicily, of calcareo-argill~ceous ~trata of great thickness, containing marine shells. .This clay 1s~ sometimes associated with beds of sand and limestone. E or the most part these formations resem ~le in. appearance ~nd consistency the Subapennine marls, w1th their acco~panywg sands and sandstones; and the whole group bears considerable resem· blance, in the yielding nature of its materials, to most o~ our tertiary deposits in France and England.. Chronolog1cally considered, however, the Calabrian formatwns are compar~tively of very modern date, and abo~nd in fossil shells refemble to species now living in the Mediterranean. We learn from Vivenzio, that on the ~Oth and 9l6th of March, 1783, earthquakes occurred in the islands ?f Za~te, Cephalonia, and St. Maura ; and in the last-mentwned Isle several public edifices and private houses were overthrown, and many people destroyed. We have already shown that t~e Ionian Isles fall within the line of the same great volcamc region as Calabria ; so that both earthquakes were probably EXTENT OF TERRITORY CONVULSED. 415 derived from a. common so urce, an d 1· t 1. s not I. mprobable that the bed of the whole intermediate sea was 1 d If the cit f 0 'd · convtt se · Y 0 PPI. o, m Calabria, be taken as a centre, and round .t hat ce. ntre a circle be described wi'th a rad 'J us of twenty-tw~ miles, this space will comprehend the surface of the country which. suffered the greatest alteration, and where all the towns a~d Vlllag~s were destroyed. But if we describe the circle with a radius of seventy-two miles, this will then comprehend the whole country that had any permanent marks of having been affected by the earthquake. The first shock, of February 5th, 17~8, threw d~~n, in two minutes, the greater part of the houses m all the c1tl:s, towns, and villages, from the western fla. n.k s of the Apennmes in Calabria Ultt·a , to Me ss·m a m· SICily, and convulsed the whole surface of the country. ~nother occ,urred on the ~8th of March, with almost equal viOlence. 'l he granitic chain which passes through Calabria from north to south, a~d ~ttains the height of many thousand feet, was shaken .but shghtly; but it is said that a great part of the shocks whiCh were propagated with a wave-like motion through the recent strata ~rom w.est t~ east, became very violent when they reached the pomt of JUnction with the granite as if a reaction was produced where the undulatory movem~nt of tl~e soft strata was suddenly arrested by the more solid rocks. 'I he surface of the country often heaved like the billows of a s~elling sea, ':hich ~roduced a swimming in the head like seasiCkn. ess. It Is particularly stated, in almost all the accounts, that Just before each shock the clouds appeared motionless . and alth?ugh no explanation is offered of this phenomenon: it is o?viOusl~ the same as that observed in a ship at sea when it pitches vwlently. The clouds seem arrested in their career as often as the vessel r~ses in a direction contrary to their course; so that t?e Calabr1ans must have experienced precisely the same motiOn on the land. We shall first consider that class of physical changes pro~ uced by t.he earthquake, which are connected with changes m the relative level of the different parts of the land; and afterw~ rds describe those which are more immediately connected With the derangement of the regular drainage of the eountry and where the force of running .water co-operated with that of the earthquake. In regard to alterations of relative level, none of the accounts |