SECONDARY UNDULATIONS OF OCEANIC TIDES. 39 



being very narrow as compared with others may be put out 

 of consideration. Tlie Avestern neck Bisanseto is much wider 

 than the eastern neck Akashiseto, the cross section of the 

 former being more than twice that of tlio latter. Moreover the 

 tidal range at Bisanseto is much greater than tliat at Akashi- 

 seto so that the flux of the sea water through the former neck 

 will proba]3ly amount to more than three times that through 

 the latter. Thus sea-level in Harimanada is principally deter- 

 mined by the tide from the western neck. The tidal wave of 

 the Pacific enters tlie inland sea of Seto through the channel 

 of Bungo, propagates eastward through the seas of lyonada 

 and Bingonada and arrives at Bisanseto, so that it requires 

 about 5 liours to travel through the distance. This wave takes 

 still 40 or 50 minutes to get at the strait of Naruto, so that 

 inside and outside the strait, the phase differs by about 6 hours, 

 as actually observed. 



It is a matter of considerable interest to compare tlie 

 phases of the components constituting the tidal wave on both 

 sides of the strait. By means of a rectifier constructed by one 

 of us,* we may eliminate the semi-diurnal or diurnal component, 

 if it be known to exist. In this way, wo may resolve a tidal 

 wave into a certain number of components. Thus, the tides at 

 Hinoura (PL XXX, Fig. 1) and Shioyasumi (PI. XXVIII, Fig. 3) 

 were respectively resolved into three components as shown in 

 PL XXXI, Fig. 1, 2. They clearly show that the principal 

 semi-diurnal components have opposite phases for Hinoura and 

 Shioyasumi. In a similar way, the tides at Kameura (PL 

 XXIX, Fig. 3) and Ogeura (PL XXX, Fig. 3) were respectively 



*) T. Terada, A Tide rectifier, Publications of the Earthquake Investigation Comiuittee 

 in Foreign Languages. No. 18, 190 1. 



