584 Mr. S. H. Burbury on the 



crest and hollow of successive waves of 1*5 inch. At 1 A.M. 

 on June 17, when the copy of the record ends, there were 

 still very distinct signs of movement due to the Japanese 

 earthquake. 



The distance from the epicentre to Sausalito is 4787 miles, 

 the time-interval is lOh. 34m., and the mean velocity between 

 the two places 6t)4 feet per second. On the same assumption 

 as before, the mean depth of the ocean would be 13,778 feet. 



Mean Depth of Pacific Ocean as ascertained from Soundings. 

 — I have estimated roughly the depth of the ocean along the 

 two lines from the epicentre to Honolulu and Sausalito, 

 making us? for the purpose of the .Physical Chart of the 

 World which accompanies the "Narrative"''' of the Voyage 

 of H. M.S. ' Challenger '*. 



The epicentre-Honolulu line traverses a part of the ocean 

 whose depth is very variable : indeed, the long chain of 

 islands of which the Hawaiian Islands form the eastern end 

 almost lies alony; the great circle joining the two places. 

 Along the most direct course which the wave might take, the 

 mean depth is about 13.500 feet. But along a very slight 

 deviation from this line the depth is much greater ; and it is 

 probable that the earliest waves which reached Honolulu 

 would take some such course. It is therefore useless to com- 

 pare this result with that obtained above from the velocity of 

 the seismic sea-wave. 



Along the epicentre-Sausalito line the conditions are very 

 different. The great circle joining the two places is entirely 

 free from islands, and crosses the sub-oceanic contour-lines 

 approximately at right angles. The mean depth along this 

 line is more than 17,000 feet, while that obtained from 

 the formula is 13,778 feet, or about f- of the measured value. 



LVII. On the Law of Partition of Energy. 

 By S. H. Burbury, AJ.A.,'P.E.S\\ 



1. ~FF a material system be defined by the generalized 

 X coordinates q 1 . . . q n with the corresponding momenta 

 p x . . . p>ni so that the kinetic energy is ^(p\qi+ . • . +jV/»)> 

 the law of partition of energy is the relation between the 

 several products p'q on average of time when the system is in 

 stationary motion. The law of equal partition asserts that, 

 under certain conditions to be investigated, p x q x = p 2 q 2 = &c. 



* Report on the Scientific Results of the Voyage of II. M.S. ' Chal- 

 lenger,' Narrative, vol. i. pt. 1 (1885). 

 f Communicated by the Author. u 



