s. Nakamura and K, Honda, 



Jour. Soi, 'Coll. ^ Vol. XXVIII., Art. 67PI. VII. 



Fit?. 1. 



Lake Biwa, ti= 1.58 sec. 



Fis. 2. 



Lake Biwa, t2=0.67 sec. 



Fig. 3. 



Chûzenji lake , t=1.12 sec. 



f-'-n- 



