Seiclies in Some Lakes of Japan. 69 



US, as the periods of seiches in the lake of Yamanaka, 



Ti=15.Ql minutes, 



^2=10.57 ,, 



Ts= 5.46 ,, 

 which are in the ratios of 



1.00:0.68:0.35. 

 Ti was observed at the two end stations, and as an examination of 

 the records shows, the two stations were in opposite phases, which 

 indicates that the motion T^ must be the uninodal longitudinal 

 seiche. T2 was observed at Ipponyanagi, Nagaiké, and Yamanaka, 

 though only a few times in all. The amplitudes were too small to 

 enable us to compare the phases at these stations and to draw an 

 exact conclusion from them. It is however, without doubt, the 

 binodal longitudinal seiche, as will be seen further on. 



The total surface area A and the total volume V of the lake 

 are calculated from the data furnished by our soundings, and found 

 to be 



^ = 6.74X10'° sq. cm., 



F=5.53xlO'^ c. cm., 

 which give us as the mean depth 



/i=820 cm. 

 The length and the width measured along the deepest points are 

 5.42 xlO^ and 2.04x10* cm. respectively, from which we deduce 

 that the period of the uninodal longitudinal seiche is 20.1 minutes 

 and that the ratio of the periods of the uninodal longitudinal and 

 the transversal seiches is 1.00:0.38. Though the value, 20.1 

 minutes, very much exceeds the observed value, Ti= 15.61 minutes, 

 yet as the ratio ]. 00: 0.38 comes so near the ratio T^-.T^ above 

 obtained, it is very probable that the motion T^ is the uninodal 

 transversal seiche. 



