20 K. HONDA, T. lERADA, Y. YOSlJlDA, AND D. ISITANI. 



Kamiiso were carried out, the fundamental oscillation only ap- 

 peared on our record«. The comparison of our records shows 

 that the phase of the oscillation is the same for these two stations. 



The simultaneous observations between Hakodate and Ta- 

 chimachizaki showed that notwithstanding the conspicuous un- 

 dulation appearing in the bay, the undulation just outside the 

 bay was almost insignificant. This is a good example for 

 illustrating our view regarding the secondary undulation, which 

 we have propounded in the foregoing section. Beside the 

 periods above described, a longer period of about 120" is some- 

 times traceable. 



The amplitude of secondary undulation is usually increased 

 by a low barometric pressure approaching the bay. As a good 

 example, we may cite a cyclone on Sept. 21-22, 1904, wliich 

 was approaching from the Pacific side of Honshiu toward Hako- 

 date. The undulation in the bay (PI. HI, Fig. 1) continued 

 over a whole day with a considerable amplitude, its maximum 

 exceeding 40 cm. ; the periods of conspicuous undulation were 

 47.1™-56.9" and its octave. 



The bay is especially sensitive to incident sea waves ; 

 waves originating on the American coasts were often beautifully 

 recorded by the tide-gauge in tlie bay. The periods of the 

 Eeuador wave in the bay were 21.9'" and 40.9™- 49.2'" ; while 

 those of the Valparaiso wave were 22.1'" and 48.0"- 53.0'". 



The periods of the great sea waves of Sanriku (PI. HI, 

 Fig. 2) in 1896 were 18.8", 39.5"", and 57.5'"; those of the 

 small sea waves (PI. Ill, Fig. 3) in 1897 were 22.1'" and 45.5'". 



II. JAPAN SEA COASTS OF HONSHIU. 



(1) Aomori (July 18-21, 1905). Top. 9. PL IV, Fig. 1-2. 



