PREFACE vii 



model were ever observed. We are now in a position to infer 

 from the study of models how the bay oscillates without 

 entering into tlie actual registration of the secondary oscillations. 



The contour lines of equal depths in different bays were 

 drawn by Dr. Isitani, who also undertook the laborious task of 

 integrating and determining the volume of the liay ; after suit- 

 ably choosing the median line, he also calculated tlie periods. 

 They generally agree quite closely with the observed values. 



Tlie problem which still remains unsolved is how the waves 

 of different periods are generated in the surrounding ocean and 

 especiall}^ on the Pacific side. They may be due to local varia- 

 tions of atmospheric pressure, earthquakes, and such allied 

 causes. The following hint may also not be out of place as to 

 the cause of these waves on the Pacific coast. By far the 

 greater part of the destructive sea waves, which from time to 

 time have devastated our coast, seem to have had their origin 

 on the waves originating off the eastern coasts of Japan. The 

 existence of a sort of standing waves with the land on one 

 side and on the other the ocean current running nearly parallel 

 to the shore is quite imaginable. Along the east coast of 

 Rikuchii and the southern part of Hokkaido, the gulf of Tosa 

 and the adjacent districts, the course of the current is nearly 

 parallel to the line of equal depth. In such cases, the presence 

 of standing waves with the land and the current as the 

 boundaries is a matter beyond dispute. The current will not 

 behave exacth^ like a solid shore, but on account of its high 

 speed, it will partake the nature of a quasi-elastic solid, making 

 the waves rebound , It resembles a liquid jet in the ocean ; it 

 will oscillate with periods peculiar to itself ; it will thereby be 

 capable of transmitting vibration to the bounding waters ; it 



