Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/390

Rh to Caggiano (see Map A) are almost exactly in one right line. The moment of the occurrence of the first shock at Melfi was 10h 3m 0s·0 Naples mean time, and at Vietri, 9h 59m 16s·2 Naples mean time. Melfi is 24·25 geographical miles from the seismic vertical, and Vietri is two geographical miles from the same. The difierence in time between Melfi and Vietri is therefore = 3m 43s·8, or we may say 3m 44s, and the distance between them is 24·25 geographical miles, which gives 9·23 seconds for the time of transit per geographical mile between them, and a transit velocity of 658·2 feet per second.

Vietri di Potenza, being two geographical miles from the seismic vertical, the instant of the occurrence of the shock at that central point, must have been equal to the time at Vietri, less the transit time for the two miles, or,

We may therefore take this as the starting-point for all the other determinations, and call it 9h 58m 58s Naples mean time. The time of the shock at Naples, is given diflerently by two authorities, both worthy of attention. Signor Fiodo's clock gave it 10h 13m 26s·0 (tempo meridiano), that is the time as per observation of the sun's crossing the meridian. The time, as published in the 'Giornale Reale,' from the Osservatorio, and certified to by Professor Capocci, is 10h 10m 0s·0 Naples mean solar time.