Page:Great Neapolitan Earthquake of 1857.djvu/490

from the Campanile, but in the opposite direction. Its path was 58° W. of north to south.

It was, no doubt, thrown off by the recoil of the pier upon which it stood, when making its second oscillation, produced by the first shock (41° 30′ E. of north to south), when the main shock reached it, which increasing the movement already impressed, and at the same time changing the plane of projection, threw it to an horizontal range of 18 feet, from an elevation on the pier of the same (18 feet).

Assuming $e=20^{\circ }$ as before, we have from the equation

$\mathrm {V} ^{2}={\frac {a^{2}g}{2\cos ^{2}e\left(b+a\tan e\right)}}$,

the velocity of projection of this vase,

$\mathrm {V} =21.23{\mbox{ feet per second,}}$

which is about 8 1/4 feet per second in excess of that of the wave of shock, the difference being due to the angular velocity of elasticity acquired by the pier itself, added to that of the wave. In fact, in such examples, the body thrown is projected like a stone from a sling.

There was every reason for my believing that the vase remained where I found it, half embedded in a flower-border, in the locked-up garden of the prior, and untouched since the earthquake; and the splintered and disjointed state of the limestone blocks of the pier, itself indicated the extent to which it had vibrated. The corresponding vase was not thrown though loosened, nor was the pier as much shattered, though I could not discover any very certain cause for the difference in effect upon both. Each vase had been steadied when in place by a slender iron dowal.