180 



EAETHQUAKES. 



third wave, tlien diminishing, then once more renewed, 

 after which it died away. 



The result of calculations based on these data were : — 





Distance 

 geographi- 

 cal miles 



Time 

 of trans- 

 mission 



Velocity 

 in feet 

 per sec. 



Depth of 

 ocean in 

 fathoms 



Simoda to San Diego 

 Simoda to San Francisco 



4917 

 4527 



h. m. 

 12 13 

 12 39 



545 



528 



2100 

 2500 or 2230 



The difference for the depths in the San Francisco 

 path depends whether the length of the waves is reckoned 

 at 210 or 217 miles. The length of the waves on the 

 San Diego path were 186 or 192 miles.^ 



The wave of 1868. — On August 11, 1868, a sea wave 

 ruined many cities on the South American coast, and 

 25,000 lives were lost. This wave, like all the others, 

 travelled the length and breadth of the Pacific. 



In Japan, at Hakodate, it was observed by Captain T. 

 Blakiston, E.A., who very kindly gave me the following 

 account : 



On August 15, at 10.30 a.m., a series of bores or tidal 

 waves commenced, and lasted until 3 p.m. In ten minutes 

 there was a difference in the sea level of ten feet, the water 

 rising above high water and falling below low water mark 

 with great rapidity. The ordinary tide is only two and a 

 half to three feet. The disturbance producing these waves 

 originated between Iquique and Arica, in about lat. 18.28 

 S. at about 5 P.M. on August 1 3. In Greenwich time this 

 wouJd be about 13h. 9m. 40s. August 13. The arrival of 

 the wave at Hakodate in Greenwich time would be about 

 14h. 7m. 6s. August 14: that is to say, the wave took 

 about 24h. 57m. to travel about 8,700 miles, which 



' Prof. A. D. Bache, United States Coast Survey Rej^ort, 1855, p. 342, 



