DISTUKBANCES IN THE OCEAN. 183 



The mean depths represent a mean of two sets of 

 calculations, one made with the aid of Airy's formula, and 

 the other by Scott-Eussell's formula. The result of my 

 own investigation about this disturbance, the origin of 

 which, by several methods of calculation, is shown to have 

 been beneath the ocean, near 71° 5' west long., and 21° 22' 

 south lat., are given on next page. 



Dr. Greinitz considers that his calculated depths of 

 the ocean and those obtained by actual soundings are in 

 accordance, a result which is diametrically opposed to 

 that which I have obtained. 



This difference between my calculations and those of 

 Dr. Greinitz, Hochstetter, and others, chiefly rests on the 

 origin we have assigned for the sea waves. Dr. Greinitz, 

 for instance, although he says that the origin of the 1877 

 earthquake was not on the continent but to the west in 

 the ocean, bases all his calculations on the assumption 

 that the centrum was at or near to Iquique, and the 

 time at which that city was disturbed was the time at 

 which the waves commenced to spread across the ocean. 

 This time is 8.25 p.m. At this time, however, it appears 

 that the waves must have been more than double the 

 distance between the true origin and Iquique, from 

 Iquique on their way towards the opposite side of the 

 Pacific. Introducing this element into the various cal- 

 culations which have been made respecting the depth of 

 the Pacific Ocean as derived from observations on earth- 

 quake waves — which element, insomuch as the waves 

 appear to have come in to inundate the land some time 

 after the shock, needs to be introduced— we reduce the 

 velocity of transit of the earthquake wave and, conse- 

 quently, the resultant depths of the ocean. 



In Dr. Geinitz's paper there are also some slight 

 differences in the times at which the earthquake phe- 



