Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/91

54 vertically over the origin. I cannot see anything upon the surface sufficient to render account of the difference.

The hill upon which Tito stands, is well connected with the range to the N.E., the Serra del Cerro. One circumstance, however, may probably be sufficient fully to account for the severity with which it was shaken. Directly to the east and S.E. of the town, with a slight depression between, rises the immense mass of limestone, of the lofty Monte Petrucco, a continuous ridge, running for four or five miles about S.W. and N.E., and distant about two miles from crest to town. This ridge runs almost transverse to the wave-path. The shock reaching Tito, therefore, had an earthquake echo from this mountain, and must have received a shock in reverse, nearly as severe as the original one. This shock was necessarily a divergent one, with reference to an horizontal plane; reflection and refraction, both sending the return waves back at different angles, from the great axial line of the chain; and this, no doubt, is sufficient also to account for the great discrepancy in the wave-paths, given by the different buildings, the extremes being 59° 30' and 87° 30' E. of north.

The more I become acquainted with earthquake effects, in this mountainous country, the more important I perceive the effects to be, of position with reference to adjacent great masses, in modifying the effects of the primary shock.

From the summits above Tito, looking off to the westward, II Torre di Satriano may be seen, at about two miles, with the telescope, perched on the top of a low colline, midway between Monte Carona on the north and