Page:Great Neapolitan Earthquake of 1857.djvu/147

Rh the place, and find a large district whose length is almost parallel with the well-preserved main street and yet is a mass of rubbish. No house stands to tell us of what they were; but, on examining the character of the stones, and of the timbers, the shattered doors and window-shutters, and so forth, we find this was one of the poorest quarters of the town, and, as always happens (except in rapidly growing cities), one of the oldest. The buildings here are in heaps, because before the shock they were tottering and ready to fall. The whole matter has become clear, and the fact has been learned, that entire towns give little information to the seismic observer, and that but of a general and often uncertain character—that single buildings are his proper objects.

Had the direction of shock been $$a'$$ to $$b'$$, in place of what was assumed, a little examination of the figure will make it evident that the whole train of phenomena would have been changed. Hence the prodigious complexity of phenomena presented by towns that have been subjected to two or more shocks in different or in orthogonal directions in quick succession. It is needful to state these circumstances, trivially simple as they appear, because hitherto they have been unnoticed and unregarded by previous earthquake describers. Even the scientific reporters of Calabrian and other earthquakes, who multiply such facts, seem to have had no clear conception of their cause and connection.

The Photogs. Nos. 66, (67 and 68, Coll. Roy. Soc.,) illustrate also some examples. In No. 66, a street in Polla, the direction of shock, was nearly perpendicular to the plane of the picture, and from the observer. The face of the houses, built well and with a batter, here receiving the