Seiclies in Some Lakes of Japan. 



The periods obtained at the several stations were as fellows: 



TABLE 39. 



Senju 



7.77x80, 

 7.81x24, 

 7.72x40, 

 7.94 X 9, 



Chüzenji 



Ulagahama 



Shübugahama 



As the amplitudes in other stations were too small, they are here 

 omitted in determining the period. The weighted mean of the- 

 above value is ■ 



T — 7.71 minutes. 



From the above observations, it can be seen that the seiche of 

 this lake is pure and simple, being a uninodal longitudinal oscil- 

 lation with a period of 7.77 minutes. Owing to its great depth, a 

 motion once excited continues for a long time without a sensible 

 damping. During the course of the observations, it was also- 

 clearly seen that the chief agency agitating the mass of water and 

 exciting the seiche in the lake is the wind. 



From the bathymétrie data, we have 

 L = 5.87x10' cm., 

 /i = 8.54xiœcm., 

 where h is obtained by dividing the total volume by the total 

 surface area of the lake, and the formula of Mérian gives us 6.72 

 minutes as the period of the uninodal seiche. The discrepancy 

 between the calculated and the observed periods may perhaps arise- 

 from the fact that though the west half of the lake is approxi- 

 mately rectangular in shape, the other half extends considerably 

 towards the south, so that as a "whole, the form of the lake can by 



