96 Messrs. K. Honda, T. Terada, and D. Isitani on the 
are respectively 108 m and 303 m . The undulation o£ the 
shortest period may be the higher mode of the lateral 
oscillation. 
A 
(iii.) Ufunato, 
The bay of Ofunato has an elongated form, and is some- 
what crooked near its mouth, so that at Ofunato, which is 
situated at the end of the bay, the sea is extremely calm. 
Fijy. 3. 
Ofunato, 
Sunagozak/, 
//osouff/i x 
This affords a good example for illustrating the effect of 
shadow, i. e. a wave whose wave-length is large compared 
with the size of the obstacle goes round it, but a w r ave whose 
wave-length is comparatively small has its influence nullified 
by the obstacle, and the sea behind it remains quite calm. 
The form of the bay is specially adapted to permit of 
comparison of the phases of the secondary undulations at 
different stations along its length; those chosen were Ofunato, 
Sunagosaki, Takonoura, and Hosoura. The periods observed 
are 5 m '5, 12 m -8-16 m 8, 36 m 0-39 m *l, and 41 m *5-43 m, 5. The 
phase of the significant undulation 36 m '0-39 m, l is found to 
be the same for these four stations ; which undulation is 
probably the fundamental oscillation of the bay. The calcu- 
lated period is 36 m, 4 — in close agreement with the observed. 
At Ofunato and Hosoura, where an undulation of the period 
12 m, 8-16 m *8 was sometimes observed, its phases were opposite 
to each other. The undulation was quite imperceptible at 
Sunagosaki, which is situated about midway between Ofunato 
and Hosoura, so that this may probably be a binodal oscilla- 
tion of the bay. Waves of the short period 5 m, 5 appeared at 
Hosoura and Sunagosaki, but not at Takonoura and Ofunato; 
the absence of the wave at the latter stations is possibly due 
to the effect of shadow. 
