Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/367



earthquake of December 16, 1857, consisted, irrespective of tremulous movements, such as those last discussed, of two shocks: the first and more powerful of the two, was felt over the whole area disturbed; the second, which occurred about an hour after the first, was less powerful, however, and limited in its seismal area to a much smaller region than the former.

These two, however, appear to have been, distinct earthquakes, due to separate originating impulses, though from a common originating point, only following each other, with but a brief interval of time; but in some places, as recorded a second shock of considerable intensity, was felt following the first, in rapid succession. In every instance, this second appears to have been a reflected shock, the first, the direct one, and the two difiered often very considerably, in wave-path.

The conditions conducing these, will be best explained further on, in treating of the disturbing efiects, of local position, &c., upon the shock. In the case of Naples itself, where a distinct moment of pause, was observed, after the