366 The Philosophy of Earthquakes. 



true wave velocity ; and thirdly, when, from some cause the 

 determination was below the truth. 



The mean velocity of ten determinations was found to be 

 12'039 feet per second, of which the highest was experienced 

 by a vase projected from a gate of the prince's garden at 

 Certosa. This exceeded twenty-one feet, ' ' but at least eight 

 feet per second was due to the elastic oscillation at the top of 

 the pier itself/'' A little hill, colline, at Saponara, appears to 

 have had a velocity of oscillation = 1*724 per second. These 

 low velocities did not coincide with preconceived ideas; 

 but Mr. Mallet observes, that we are by no means to con- 

 sider twelve or thirteen feet per second as the greatest possible 

 velocity of an earthquake shock, as when the town of Eio- 

 bamba was totally destroyed, Humboldt informs us that the 

 bodies of many of the inhabitants were thrown upon the hill of 

 La Calla, which rises to the height of several hundred feet at 

 the other side of the Lican torrent. "The actual range of 

 vertical projection of these bodies has been estimated at 100 

 feet. The velocity due to this height of projection is V = 

 V~2~% H = 80 feet per second; and this is probably the greatest 

 velocity of shock recorded, or perhaps at present possible upon 

 our earth ; it is nearly as great as that with which the body of 

 one who should leap from the top of the Duke of York's 

 column at London would strike the pavement; and taking the 

 greatest velocity that we have ascertained for this (the Neapoli- 

 tan earthquake) at fifteen feet per second, this maximum 

 velocity is ff, = 5 - 33 times greater than the velocity of our 

 Neapolitan shock/' 



Bearing in mind the probable identity of the causes of 

 earthquakes and volcanoes, it is evident that the height of 

 volcanic cones should be proportioned to the earthquake 

 intensity, and Mr. Mallet finds that the velocity of the Bio- 

 bamba shock exceeds that of the Naples shock as much as the 

 Andes are higher than Vesuvius. 



If the focus of an earthquake was always at the same depth 

 from the surface, the area of noticeable disturbance would be 

 a measure of the force of the shock, but very violent con- 

 cussions have been known to affect very limited spaces, and in 

 such instances the foci must have been proportionably near the 

 surface that was disturbed. "We may generally infer from 

 this that earthquakes, like that of Lisbon, which have a very 

 great area <•'.' ensible disturbance, have also a very deep 

 seismal focus, and also that the greatest y ilr alii of seismal focus 

 within 'in,- planet is pro bably not greater than that ascertained 

 for this Neapolitan earthquaJce, rmdtvplied by the ratio that the 

 Riobamba wave bears to that of its wave; or, what is the same 

 thing, by the ratio of the altitudes of the volcanoes of the 



