Seiches iu Some Lakes of Japan. 55 



B=Bo + ^B 



respectively. The period is to be calculated by the formula 

 hitherto used, which is in the new notation 



T=2lJ ^" 



gSo 



He has also shown a method of determining the positions of nodes. 

 The results arrived at by him in the case of Hakoné lake using our 

 data given in the Table 27, are 



(a) The calculated periods are 15.50 minutes for the uninodal 

 seiche and 6.87 minutes for the binodal seiche. 



(b) The node for the uninodal seiche is situated at 0.572 of 

 the total length of the lake measured along the median 

 line from the Southern, Hakoné end ; while those for the 

 binodal lie at 0.347 and 0.759 of the total length from the 



same end. 

 These are in close agreement with our results above given. 



Mr. D. Ishitani* has studied the effect of slight variations in 

 the breadths and the areas of transverse sections of a lake upon 

 the periods of its seiches, and has deduced a formula analogous to 

 that of Mr. Terada. With his formula, he calculated, at our 

 request, the period of the uninodal seiche and the position of the 

 node taking as the path of integration I the middle stream line 

 determined by the experiment on the model above described, and 

 the transverse sections drawn perpendicular to it. The results of 

 his calculations are : 



(a) The period of the uninodal seiche is 14. 1 minutes. 



* Ishitani. Proc. Tokyo Math. Phys. Soc, Vol. III. p. 170. 



