SECONDARY UNDIlLATIONS OF OCEANIC TIDES. 33 



Before the present investigation was commenced, the oscil- 

 lation of the Ba}^ was observed loy the seiches -party of the 

 Committee, S. Nakamiira, K. Honda, Y. Yoshida, S. Iwamoto 

 witli Dr. Nakamnra's limni meters. 



For tlie convenience of reference, tlie resnlt is included in 

 the present pnpor. The Bay has the form of an ellipse and 

 communicates by two necks xVkashiseto and Yuraseto to Harima- 

 nada and tlie Pacific respectively. 



Stations were chosen at Imazu, Kishiwada, Yura, and Iwaya, 

 and observations were made simultaneous! v. As shown in the 

 topograph, these stations are evenly distributed aloug tlie shore 

 line of the elliptical bay. 



The original records, in whicli waves of short periods are 

 l)eautifully traced (PI. XXIII, XXIV, XXV), are not convenient 

 for detecting the secondary undulations with long periods of 

 several tens of minutes, or for studying the tide itself. For this 

 purpose, the original records were reduced to a proper scale, 

 some examples of which are given in PI. XXI and XXTI. Since 

 the tide in Harimanada is nearly in opposite phase to that of 

 the Pacific, the tidal wave at the stations is not naturally 

 simple. Comparing tlie tidal phases at these four stations, it 

 may be concluded that as we go from Yura inwards along the 

 eastern coast of the bay, the tidal phase is gradually retarded, 

 and at Kishiwada, the difference amounts to about 20'" to 75'". 

 The phase of the tide at Imazu is not however much retarded 

 on the average as compared with that of Kishiwada. At 

 Iwaya, facing Akashiseto, on the two sides of which the tidal 

 phase is considerably different, the tide is naturally very 

 complex. 



Thus, as compared with the tide at Yura, the phase of the 



