Page:Great Neapolitan Earthquake of 1857.djvu/516

416 timbers, with its mouth facing S. E. The centre of gravity of the bell, was 7 feet horizontally, distant from the centre of the tower, and the direction of its throw from the centre of the tower was 149° E. of north (Fig. No. 250).

This direction, I found coincided closely with that given by fissures, Photog. No. 249 (Coll. Roy. Soc.), two pairs of which gave a wave-path of 145° E. of north, and an angle of emergence from the N. W. = 16° 25′. This angle, as given by the isolated buildings before adverted to, appeared to be but 11° to 11° 30′; I rely, however, upon those of the church.

The bell had fallen vertically 30 palmi = 30 × 0.862 ft. = nearly 26 feet English. We have, therefore,

and the value of

$$\mathrm{V} = 9.78 \mbox{ feet per second;}$$

a result necessarily below the truth, as the effort of the wave, was communicated to the bell, not through the centre of gravity, but by the pintles; so that the first effect, was merely to make it swing, contrary to the direction of throw. We may estimate the velocity as at least 2 feet per second more, or about 12 feet per second for the wave here, which, although not exact, sufficiently corroborates previous determinations.

Several very thick and very ancient walls here, built of small bad rubble, and showing themselves to have been very dead and inelastic, presented quoin fissures, open $4 1⁄2$, 5, and even $6 1⁄2$ inches, at 20 to 30 feet from base; the average might be taken at $4 3⁄4$ to $5 3⁄4$ inches, and seem to indicate a wave of long amplitude here.