SECONDARY UNDULATIONS OF OCEANIC TIDES. 



95 



velocity in the case of Aburatsnbo, when sea wave had a con- 

 siderable long period, is probably due to the effect of the wave 

 length, on the velocity. The increase of velocity with distance 

 is also noticed in the case of the sea waves accompanied by the 

 Krakatoa eruption. This seems to indicate that the earthquake 

 may excite short waves almost simultaneously with shocks, but 

 it takes some time to excite long waves of a permanent type 

 of a considerable period. 



In the sea waves above referred to, the observed velocities 

 nearly coincide witli the values of i^'gh , except for Hakodate 

 and Ayukawa, in which the difference is considerable. 



The sea waves also slightly affected the tide-gauge* at San 

 Francisco, San Diego and Honolulu (PI. LVHI, Fig. 3-4 ; PI. 

 LIX, Fig. 1-3). The times of arrival of the waves in the 

 standard times of these stations and the periods of the waves 

 are given in the foUowino" table : — ■ 



Thus, if we compare the periods of several sea waves observed 

 at these American bays, it may also be concluded that the 

 periods of the different sea waves observed at each bay are 

 proper to the bay. Honolulu affords the best example ; a simple 

 wave of the period varying from 23'" to 28'" has always been 

 found for s( a waves originated near the Pacific coast of America 



*) The Ikle-gange recorrls utilized are those furnished by Dr. Tittmann. 



