92 Messrs. K. Honda, T. Terada, and D. Isitani on the 
of constant depth. Suppose a regular series of long waves 
are continuously propagated in the direction of the length of 
the bay and are reflected at its end. Through the interference 
of the incident and reflected waves, a standing wave is formed 
having its loop of the vertical motion at the end of the bay. 
If the wave-length be such as to form the node of the vertical 
motion at the mouth of the bay, the period is the same as 
that of the fundamental oscillation of a tank having double 
the length of the bay; and therefore the amplitude of oscil- 
lation must necessarily be magnified by the successive 
occurrences of the long waves. The period of the oscillation 
is then, neglecting the mouth correction, expressed by the 
relation 
y/gh' 
where y/gJi is the velocity of the long wave. This action of 
the bay may then be suggestively compared to the experiment 
in which a column of air in a resonance tube is made to 
vibrate in unison with a tuning-fork placed over its mouth. 
If the waves of different periods proceed from the ocean 
toward the shore, the one whose period coincides with that 
of the oscillation having its node at the mouth of the bay 
will excite the most energetic oscillation of the bay water. 
Thus, bays on the coast-line may be compared with a series 
of resonators, each of which takes up selectively from the 
chaos of very complicated sounds or noises and resonates to 
the note of its proper period. The plausibility of such a 
conception seems to be heightened to a rather unexpected 
degree by the present investigation. Moreover, the fact that 
the rising and falling motion of the level of the bay in respect 
to the principal undulation is in the same phase for several 
stations, stands in favour of the above view. Darwin and 
Otto Krummel* seem to have entertained an analogous idea. 
In a bay, besides the uninodal oscillation above referred 
to, oscillations with two nodes, three nodes, &c, are also 
possible ; the periods of these oscillations are respectively 
A, 1, &c. of the period of the fundamental oscillation. In 
some cases, a lateral oscillation of the bay excited by incident 
waves is also possible, the period of which is principally 
determined by the oscillating water in the bay. These addi- 
tional modes of oscillation were actually found to exist in 
some bays such as Hososhima, Ofunato, Hakodate, &c. 
* Darwin : < The Tide,' ch. x. p. 169. Otto Krummel : * Ueber 
Gezeitenwellen," Itede bei Antrittd. Rectorates d. Kcinigl. Christ- Albr.- 
Univ. zu Kiel, Marz b, 1897. 
