SECONDARY UNDULATIONS OF OCEANIC ÏIDKS. 



85 



Thus, the velocities in the first and third rows in the 

 above table are decidedly less than the velocity in the second 

 row ; this discrepancy is probably due to the fact that, the 

 first wave was not observed at Hakodate and Kazusa probably 

 on account of its small amplitude. Here also the value 

 of i/ cjk is a little greater than the actual velocity. 



(c) Sea waves of the Krakatoa eruption, 1883. 



Great sea waves caused by the eruption of Krakatoa, 

 August 27, 1883, swx^pt over the entire area of the Indian 

 ocean and forced their way as far as to the northern parts 

 of the Atlantic and the Pacific, leaving their traces on the 

 tide-gauges situated along their way, the records of which are 

 reproduced in the Report of the Royal Society of 1888, and 

 described by Captain W. J. H. Wharton. Tiiese records as 

 well as numerous matters of information from difTerent quarters 

 of the world, in wdiich the Report abounds, if reviewed under 

 the light of the results of our present investigations, may be of 

 some interest, inasmuch as the former reporter seems to have 

 put a little wx^ight on the secondary undulation peculiar to bays 

 and estuaries. 



As to the cause of the periods of the great Krakatoa waves, 

 few theories have been proposed. Captain Wharton" attempted 



*) Wharton, The leport of the Krakatoa eruption, p. 97. 



