Seiches in Some Lakes of Japan. 



33 



Of these, the first motion was seen well developed after a thunder- 

 storm. The motion with a period 6.0 was also pretty clear. 



Ötsu. 



This place is situated at the south end of the lake, which is 

 very shallow in that part lying south of the neck near Katada. 

 The periods observed during the interval Aug. 13-15 are given 

 in the next table. 



TABLE 17. 



Otsu. I. 



m. 



m. 



va. 



234.5 X 1 



202.0 X 2 



25.8x11 



282.5 X 2 



72.9 X 1 



25.1x14 



230.0 X 1 



71.8x10 



12.4 X 8 



224.5 X 1 



65.5 X 3 



8.6 X 9 



224.2 X 2 



32.1 X 7 





209.2 X 2 



29.1x11 





A motion with a wonderfully long period of about 230 minutes 

 was excited after a very heavy thunder storm. The initial double 

 amplitude was 15 cms., and subsided gradually after making a few 

 oscillations (PI. II}. Other series of observations were made in 

 order to confirm the presence of this slowly oscillating seiche. 

 The clockwork was made to rotate once rapidly to record motions 

 with short periods, and then slowly for motions with long periods. 

 The presence of the motion with the 230-minute period was thus 

 established in ordinary conditions of weather. It is remarkable 

 that this extraordinary motion was nowhere else observed during 



