Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/394

Rh {| class="wikitable"
 * || h. || m. || s.
 * Moment of the shock at Naples as stated from the Osservatorio Reale || 10 || 10 || 0
 * Moment of shock at the seismic vertical || 9 || 58 || 58
 * Difference || 0 || 11 || 2
 * }
 * Difference || 0 || 11 || 2
 * }
 * }
 * }

which, on the 68 miles' total distance between them, gives 9s·735 transit rate per geographical mile = 624·03 feet per second; and applying the same correction as before, for refractive retardation, the transit rate becomes 9s·457 per geographical mile, and the velocity $$=642.36$$ feet per second; and assuming the difference of transit rate, between the limestone and tufa, to be as last obtained; then the transit rate from this observation, in the limestone, would be $$642.36 + 167.70 = 810.06$$ feet per second, or 64 feet per second below that of the preceding determination. I am therefore disposed to believe, that the Observatory clocks were stopped, by a movement shortly subsequent to that, which arrested Signor Fiodo's; and as we cannot know what the interval was, I reject the Observatory observation, as probably the least correct, and adhere to Fiodo's, as the best time measure we have, at Naples, and, per se, essentially a good one.

Monte Peloso is 36 geographical miles from the seismic vertical. At D'Errico's station,