the waves to be emitted when a pressure oscillation suddenly begins at a 
limited area of the sea, and intends to explain the generation of swell. 
Masamori Miyazaki(3l) published a statistical study of the breakers, use 
being made of the observations along the coasts near Tokyo during the period 
194-1915. The relation between the typhoons and swell and microseisms was 
investigated by Kabazawa(35) and Kimura.(36) Recently Sato(36) published 
the investigation of the wind waves caused by the typhoon "Kitty" of 19h9. 
He(37) also examined the surfs by the stereophotogrammetry. In 1950 
Yoshida(3& investigated how Comoe currents are deformed as they 
approach the coast. Miyazaki 39) showed that the amplitude of the surface 
waves in a fluid moving in a fixed direction depends upon its direction of 
propagation. Yamada\40) considers a method of obtaining electricity from 
ocean Waves. 
Tsunami. Many investigations have been carried out recently in this 
branch, presumably because this country abounds so much in this phenomenon. 
Yoshida's theory (30) on waves in general is, of course, applicable to 
tsunami. But there are many researches related to pure tsunami, especially 
after the Aleutian Tsumami attacked the Hawaiian Islands in 1946. Hidaka 
and Hikozaka\41) made a mathematical research on Hawaiian tsunami, obtained 
the waveheight on the coasts of Kauai Island, assuming this island to be 
circular in form, snd compared the result with the observations. (It should 
be remembered that nearly the same computation was made by Homma, 1) and 
by Omer in America, though the laws of depth around the island are 
different. Recently Okano(42) published a possible explanation of the un- 
equal heights of Aleutian Tsunami around the Hawaiian Islands. Hikozaka 3) 
recently treated the refraction o tidal waves by a shoal with parallel 
straight bottom contours. Yoshida 4) discussed the partial reflection of 
long waves travelling in a canal of varying section and its application to 
the occuirence of seiches in the sea. There are so many theoretical in- 
vestigations on tsunami. Matsuzawa) gave a Sate for the generation 
of tsunami due to the bottom disturbances. Ichie 4 treats the dissipation 
of the energy of tsunami by reflection and frictional effect during its 
course over the shelves, and the esppas (h7 caused by a distrubance travel- 
ling along the ocean floor. Takagi (45 discusses the theory of tsunami 
invading the continental shelf and intends to investigate whether the periods 
recorded in tsunami attack are those peculiar to the original pee ie 
or those caused on invading the bays as the stationary undulations. He 9) 
also obtained the records of sea shock on 10 August 1949 by installing a 
seismograph on board an anchored ship. Recently Homma O) treated the 
distribution of heights in tsunami obliquely attacking a straight coast. 
Several] authors made model experiments on the propagation of tsunami. 
In this respect we can mention the work of Ogiwara( 1) on the effect a 
viscosity on model experiments of tsunami and that of Ogiwara and Okita 52) 
for the case of aa? invading Shizukawa Harbor. Another model experi- 
ment was made by Ichie for the invasion of tsunami into Osaka Bay. 
Recently Ichie (54) discussed the sudden changes of the density and 
temperature of the coastal waters induced by the influence of typhoon and 
depressions offshore. 
