Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/342

Rh It was pointed out in our sketch of the physical configuration of South Italy (Part I.), and is indicated by the Maps A and B, and by the general direction of the watercourses delivering into the Gulf of Tarentum, that the main prevailing directions, of all the lower ranges of hills to the east, of the great north and south Apennine range, ran in a direction nearly N.W. to S.E.; that is to say, in one, nearly parallel to the major axes, of the meizoseismal and of all the isoseismal curves, and all these hill ranges abut with small but various obliquity, upon the great north and south Apennine chain. Hence the transverse vibration of the latter, was transmitted under, the most favourable condition to its propagation, to the S.E. "end on" through these lower ranges. But further, it was also pointed out, that to the east of the great north and south Apennine, the mountains become lower; the country is no longer truly mountainous, but rolling, with vast plains, whose formations are bedded, on the whole, nearly horizontally. These are conditions again favourable, in the highest degree, to the distant propagation of the wave to the south-east. As soon as it passed the great north and south range, it was delivered as it were into a wrinkled and corrugated, but still comparatively level, continuous and unbroken plate, of hard and pretty uniform formations, whose main corrugations all ran in the N. W. and S.E. direction, that is, in the same direction with its transit.

At the S.E. end, the full swell, of the curve of the first isoseismal, will be observed, however, to be sensibly flattened, between Latronico and Tursi. Examining the Map B, it will be seen that here it runs close along by the course of the river Sinno, falling into the Gulf of Tarentum, and that