Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/103

66 The total horizontal velocity of both fracture and overthrow, is therefore

and not greater, as the two surfaces of the fracture lay close together, at the angle of rotation. The angle of emergence here, however, as will immediately be shown, is $$e = 23^\circ 7'$$, and hence the total velocity of the wave

a sensible though apparently not very large reduction in velocity from that ascertained for points much nearer the focus.

In passing along the streets I noticed that several of the lamp irons had been shaken down from the walls. They consisted of wrought-iron arms, extending horizontally about 8 feet from the faces of the walls, with three spur braces or stays, also of iron, two above and one beneath: all being spiked into the mortar joints, and carrying a lantern for an oil light. The chuck that would be required to dislodge these, must have been pretty sharp: they would scarcely warrant calculation, however.

The house of Don Dominico Antonio Burso, stands upon the old town walls to the north side, (under $$b$$, Photog. No. 302, Coll. Roy. Soc.,) between the two old semi-cylindric towers. It is on a free-lying brow, of the slope to the north, and is considerably fissured, and the north walls have gone out. It gives a wave-path 119° 15' E. of north. The towers rather indicate a wave-path, from the south due north.