Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/152

local emergence of 40°, we have the horizontal velocity—

$V^{2}={\frac {g}{2}}\times {\frac {a^{2}}{b-a\tan e}}$

$a=14$, ⁠$b=43$. ⁠$e=40^{\circ }$,

and $V=11.36$ feet per second ;

but $V$, the velocity in the actual wave-path (i.e. the primary path) $=V\sec e$, and $e$ here = 15°; therefore

$V=11.36\times 1.035=11.757$

feet per second,

which is probably very near the truth, though derived from data somewhat unprecise.

The monastery has its long axis north and south, 10° W. of north: its broadside faces the lake or crater, and its rear is, in great part, built up against the lava cliff behind, in a cavern of which, the church which contains the miraculous image of St. Michael, said to have been found embedded in the solid lava, has been excavated. The church has its axial line west and east 118° W. of north. In the masonry portion of it outside the cavern, one large fissure is visible across the side wall and arch of the nave, on the north side of the church next the altar. There is also another smaller one at the east quoin at the north side. At the south side of the church, at its actual abutment with the lava rock, there is another fissure. The direction of wave-path given by these, is about 33° E. of north, and they are much sloped towards the S.W. at top, nearly 40° with the vertical. I hesitate to conclude anything positive, from these fissures, as the contact direct with the mountain side must have powerfully afifected their directions.