Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/398

Rh The whole of the results obtained, accord singularly well, with my own experimental determinations of wave-transit in granite and in sand, ('Report Brit. Assoc, 1851,') which gave the transit rate in dense wet sand, = 825 feet per second, within a mile of the origin; and also correspond remarkably with the mean result, obtained with so much care and accuracy by Schmidt, for the Hungarian shock of 1858, viz., from 700 to 735 feet per second, (French feet); and also with the shock of 26th July, 1855, which gave a transit rate, of from five to seven geographical miles per minute. My highest transit velocity, however, is more than 300 feet per second, below that assigned by Nöggerath, to the Rhenish earthquake of 29th July, 1846, viz., 1376 French feet per second, which is equal to my experimental determination for granite; a difference, however, that we might quite expect, as a high velocity is highly probable, in the hard, elastic, and comparatively unbroken rocks, of the Devonian and Trappean formations, about Coblentz. (Compare also with Table 8, of transit rates, 'Report Brit. Assoc, 1851.')

The velocities that have been here obtained, are those of the transit of the wave upon the surface. They are not the same, with the transit velocities in the direct wave-path through the solid materials beneath, from the mean focal point, to each respective station. These distances being greater, than those from the seismic vertical to each station upon the surface, in the proportion of $$1 : \cos e$$, and the time