DISTUKBANCES IN THE OCEAN. 179 



ing to determine when the lead actually reaches the 

 bottom. Until oceans have been more thoroughly sur- 

 veyed with the improved forms of sounding apparatus, 

 we shall not be able to verify the truth of the results 

 which have been given to us by earthquake waves. 



Examples of Calculations on Sea Waves. 



1. The wave of 1854. — This wave originated near 

 Japan, and it was recorded on tide gauges at San Francisco, 

 San Diego, and Astoria. 



On December 23, ^t 9.15. a.m., a strong shock was felt 

 at Simoda in Japan, which, at 10 o'clock, was followed by a 

 large wave thirty feet in height. The rising and falling 

 of the water continued until noon. Half an hour after, 

 the movement became more violent than before. At 

 2.15 P.M. this agitation decreased, and at 3 p.m. it was 

 comparatively slow. Altogether there were five large 

 waves. 



On December 23 and 25, unusual waves were recorded 

 upon the self-registering tide gauges at San Francisco, 

 San Diego, and Astoria. 



At San Francisco three sets of waves were observed. 

 The average time of oscillation of one of the first set was 

 thirty-five minutes, whilst one of the second and third sets 

 was almost thirty-one minutes. 



At San Diego three series of waves were also shown, but 

 with average times of oscillation of from four to two minutes 

 shorter than the waves at San Francisco. 



The San Francisco waves appear to indicate a re- 

 currence of the same phenomena. 



The record at San Diego shows what was probably the 

 effect of a series of impulses, the heights increasing to the 



