Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/78

Rh if united. The weight of the capping did not affect them, nor adhesion between it and base; because, as will be evident on considering Fig. 1 (Diagram No. 295), the instant the whole structure rocked, through a very small angle towards the S.W., the capping then rested momentarily only, upon the front block, and on those opposite it, (marked "flat" in Diagram), and the head of the block at $$s$$ was left free.

Applying, again, the preceding equation, we have here

therefore,

for the horizontal velocity, required to have overset either of these side blocks.

But they were not overthrown ; therefore,

or,$$\sec e$$ greater than 5·50;

and hence,$$e$$ greater than 79° 30'.

This is therefore the angle of greatest possible maximum, for the emergence here, derived from this structure, assuming that there was not any adhesion or hold, of these side blocks by or upon the others, to prevent their fall. There was some, however, and therefore the true angle of emergence will be less than 79° 30', and will be further slightly reduced by the fact (now to be shown), that the wave-path here, was a little oblique to the faces of the monument.

The Chiesa Madre (Fig. 296, Sketch, Coll. Roy. Soc.) has its axial line 30° W. of north, and shows new fissures, $$f\ f\ f$$, &c., obliquely across the vaulted ceiling of the nave, and oblique, but very nearly longitudinal to those of the