il PREFACE. 



One recognises at once a close resemblance of these oscil- 

 lations to the seiches observed in lakes. An interview with 

 Mr. E. Sarasin dnring the Physical Congress at Paris in 1900, 

 and subsequent visit to Genève where the limnimeter is con- 

 stantly recording the motion of tlie lake, led me to suggest to 

 the Earthquake Investigation Committee the desirability of in- 

 vestigating the same subject in Japanese lakes, and search 

 after any effect which may be associated with earthquakes. 

 The proposal was at once taken up and limnological work was 

 begun in 1901, in Lakes Biwa and Hakone with Sarasin's 

 limnimeter. Although slight earthquakes liave been encountered 

 during the excursions, no special signs in the oscillation either 

 before or after the shock were experienced. 



The Bay of Osaka being of elliptic form, and connected with 

 the sea at both extremities by narrow necks, partakes the charac- 

 ter of a large lake ; the question whether motion of the nature 

 of the seiches is to be traced as secondary oscillations of tides 

 was studied in 1902, by Drs. Nakamura, Honda, and Yoshida 

 with the assistance of two other students. In the records of 

 tide gauges at several stations were found superposed on the 

 principal tidal curve small undulations of constant periods, which 

 were approximately given by the wellknown Merian's formula. 

 In 1903, observations were made on the coasts of Tosa, Kii 

 Tôtômi, Shimôsa and PJkuchu which are open to the Pacific 

 Ocean. From these diagrams, it was found that on open coasts 

 the secondary oscillations are inconspicuous, but in bays and 

 inlets wliich open into the Pacific, they are significantly indicated 

 by the remarkable see- saw motions. 



In the mean time, it appeared to me that Green's investiga- 

 tion concerning the motion of waves in a variable canal of 



