Page:Great Neapolitan Earthquake of 1857.djvu/491

Rh I have stated that there was evidence of a third shock, different in direction from either of those already considered. This was visible in many small objects, which gave indications of disturbance, by the main shock or by the transverse one, and also of immediately subsequent disturbance, by another, or by several other minute vibrations or little shocks, in directions from south to north, varying 10° to 15° to the east or west of that. This last shock, or jarring succession of shocks, appears to have been a true earthquake echo, or reflection of the main shocks back, from the limestone mountains to the S., S. W., and S. E. of the Certosa.

In the line of buildings to the east side of the great front entrance square, between B and B (Figs. 1 and 2, Diagram No. 240) a great number of pyramidal brick chimney caps were thrown off from the tops of the stalks, in a general direction to the S. E. The mean direction of their throw I found to be 136° E. of north, which is one not so widely different from that of the resultant path of projection due to the two main shocks, but that all of these might have been projected off at the same moment and by these shocks; the differences in direction being due to the irregular figure of the pyramids, and to their ordinal position with reference to the resultant path, as well as to their having in some cases probably slided after their fall upon the sloping tiling of the roofs. The position of several of these caps, however, and the wide diversity from the resultant path of others, caused me to conclude that several of them had been loosened by the main shocks, and afterwards overthrown by this third movement in reverse.

To the same repetition of movements I attributed the