100 K. HONDA, T. ÏERADA, Y. YOSHIDA, AND D. ISITANI. 



to be associated with unstable distribution of pressure, in which 

 case a sudden local change of pressure may be possible. 



It is to be remarked tliat at a station, the period of the 

 most prominent undulations accompanying a cyclonic storm are 

 sometimes different for different cases. Thus, in Kushimoto, the 

 most prominent undulations of the sea wave of February 8, 

 1904, were of 21" -24'", while the period recorded at the time of 

 cyclone on September 28, 1900, was about 10"\ Again, during 

 the cyclone on November 17, 1900, the Ayukawa tide-gauge 

 (PI. LXII, Fig. 2) showed a remarkable undulation with the 

 period of 22"\ superposed by waves of shorter period pecuhar 

 to the bay, while in the cyclone of September 28, 1902, the 

 proper period of the bay are most pronounced. 



Thus far, we have confined our description on the records 

 obtained on the Pacific coast. Now, the records of tide-gauges 

 situated on the coast of Japan Sea show somewhat different 

 aspects, when compared with those of the Pacihc coast. The 

 former is generally characterized by extremely small tides 

 usually superposed by conspicuous secondary undulations (PL 

 LXII, Fig. 3 ; PI. LXIIl, Fig. 1-4), whether the station be on 

 the open coast or in a bay. During a cyclonic storm, the 

 amplitude of secondary waves is generally increased and the 

 undulation lasts for a considerable time. Comparing the records 

 for different stations widely apart from each other, the remark- 

 able fact is generally found that periods of conspicuous waves 

 for different stations and for different occasions are nearly 

 similar. It is not seldom that a series of waves recorded at 

 one station on one occasion is quite a facsimile of that obtained 

 in another station on another occasion. Taking the wave with 

 the period of 20"\ whicli is very prevalent, its wave length 



