Page:Great Neapolitan Earthquake of 1857.djvu/320

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262 PET]NA. in Fig. 137, which dip pretty sharply to the south. I find upon inquiry here that Petina, which is just five Italian miles $.W. of uletta, and about six from Pertosa, has nevertheless sugered absolutely nothing, although these latter towns are in great part prostrated. The immunity of Castelluccio from injury arose, as I before remarked, from the l d m of its well-but- tressed knoll being o �d to t/ l of / �/, as well as to the barrier interposed between it and any shock com n from the eastward, b the mass of vertical breccia beds to the east of the town. Petina has owed its immunity, first to the peculiarly stren form of the terrace uP'on which it is perched to resist any vibration in the mass itself, secondly, to the fact . .t from where I stand at Auletta Bridge, there is about 1,000 feet of piled-up limestone beds between me and Petina, so that any shock emergent at a steep angle, here or further eastward, must have passed up transversely through all these succes- sive plates of v riable hardness, and none n a solute con- tact with each other, and so the of the shock be enormously reduced before reaching the elevation of the