OCR Text |
Show 416 EARTIIQUAI\.E OF CALABRIA, A.D. 1783. establish that they were on a considerable scale; but it must always be remembered, that in proportion to the area moved is the difficulty of proving that the general level has undergone any change, unless the sea-coast happens to have participated in the principal movement. Even then it is often impossible to determine whether an elevation or depression even of several feet has occurred, because there is nothing novel in a band of sand and shingle of unequal breadth above the level of the sea, marking the point reached by the waves during springtides or the most violent tempests. The scientific investigator has not sufficient topographical knowledge to discover whether the extent of beach has diminished 01~ increased ; and he who has the necessary local information feels no interest in ascertaining the amount of the rise or fall of the ground. Add to this the great difficulty of making correct observations, in consequence of the enormous waves which roll in upon a coast during an earthquake, and efface every landmark near the shore. It is evidently _in sea-ports alone that we can look fot· very accurate indications of slight changes of level; and when we find them, we may presume that they would not be rare at other points, if equal facilities of comparing relative altitudes were afforded. Grimaldi states (and his account is confirmed by Hamilton and others) that at Messina in Sicily the shore was rent; and the soil along the port, which before the · shock was perfectly level, was found afterwards to be inclined towards the sea, the sea itself near the '' Banchina" becoming deeper, and its bottom in several places disordered. The quay also sank down about fourteen inches below the level of the sea, and the houses in its vicinity were much fissured*. Among various proofs of partial elevation and depression in the interior, the Academicians mention, in their Survey, that the ground was sometimes on the same level on both sides of new ravines and fissures, but sometimes there had been a considerable shifting, either by the upheaving of one side or t~c subsidence of the other. Thus, on the sides of long rents m the territory of Soriano, the stratified masses had altered their relative position to the e1,ttent of from eight to fourteen palms (six to ten and a half feet). Similar shifts in the strata are alluded to in the territory of Polistena, where there appeared * Phil. Trans., 1783. CUANGES OF RELATIVE LEVEL. 417 innumerable fissures in the earth 0 length and depth . d . • ne of these was of great ' an 111 pat·ts, the level of the corresponding Deep.JIIIure !lear Pollllena, callud by the earthquake oJ' 1703, sides was greatly changed. In the to f T 1 . wn o erranuova, some 1ouses were seen uphfted above the com 1 1 d . . . k d . mon eve and others a ~ommg sun own mto the earth In l , d h · severa streets, the soil appeare t rust up, and abutted aO'ainst tl ll f h 1 . 1 o 1e wa s o ouses . a arge c1rcu ar tower of solid masonry h. 1 h d . h ' general destruction, was divided b' w lc ~ . al Wit stood the 'd . Y a vei tlca rent and one s1 e was upraised, and the foundation s h eave d ou' t of the Shift or" /au't" lnlher d 1 · V . OUif ower oJ' l'erranJjova ill C414brla, owuior~ed biJIM earthquake oJ' 1703 Ot.l. • 2 E |