Page:Great Neapolitan Earthquake of 1857.djvu/480

384 But where the are of horizontal rotation is great, as it is in this instance, where the chimney was twisted round 30° to the westward, the latter must have been extremely small or nil.

Calling these two small corrections $$d$$ and $$f$$, the whole interval in time $$\text{I}$$, between the shocks is We therefore obtain  or without the two latter,  and estimating $$d$$, assuming $$f$$ as small $$= 0$$, we may consider  This is the difference in time, between the arrival of the two shocks; both of which started at the same moment and from the same origin. The evidence for the position of the latter has yet to be adduced; anticipating the fact, however, the Certosa, is distant from it, $16 1⁄2$ geographical miles, or 33,415 English yards in the right line, which was the path of the second shock, arriving directly 15° W. of north to south, through the deep clays and gravels, &c., of the Vallone; while that of the first shock, was through the east lateral range of solid limestone mountains, but whose length (as respects the wave-path) we may consider as one-fifth of a mile greater.

From facts (also yet to be adduced), I found that the general velocity of translation of the wave of shock, through the limestone country, was at the rate of 240 yards per