Page:Great Neapolitan Earthquake of 1857.djvu/525

Rh The Castello, and the portion of the town below it to the east, gave abundant measures, of direction and emergence. The wave-path was sub-abnormal to almost every building in the place, and vast wedge-shaped masses were thrown out everywhere, some of which may be seen in the Photographs.

The examination of the buildings of the Castello resulted in a wave-path 150° E. of north to south, and an emergence of 14° to 16° from the north.

The buildings on the east slope gave a rather different wave-path; the average of a great many giving 120° 30′ E. of north, and a less emergence 12° to 15° from the north.

I take the former, however, as the true wave-path here, and deem the difference lower down to arise from the gyratory oscillation of the hill itself. A further proof of this was, that on traversing round its base, I found that while all the buildings there situated, gave a prevalent direction of wave-path about the same as above, they also showed complicated secondary fissures in directions that indicated their production by oscillations, emanating everywhere radially from the centre of the hill. I conclude, therefore, that the first great blow which prostrated in a moment the town, came as above. The hill itself, set to oscillate in the same plane as that of the path of the wave, rapidly began to oscillate in other planes, in fact, became a conical pendulum, and hence whatever buildings remained standing but fissured, by the primary blow, were again fissured in new directions or prostrated by this proper motion of the mass of the hill.

There were even evidences in the Castello at top (where these secondary motions were, of course, a maximum) of