The author observed a tidal current ' ,using his current meter [11 and two others of different kinds simultaneously . He explained that the observed velocity fluctuation with the period of 1 .5 hours was caused by the instantaneous penetration of the waters broken from the disturbance, and the time variation of velocity was due to the effect of vertical eddy viscosity and the change of the surface slope with time . Further. he analysed the shorter period disturbance and found that its eddy diffusion coefficient K-269 c.g.s, its mean length of edddy /-12.1 cm .

s : Fluctuations of water temperature observed at a station off Turumi, Yokohama, were analyzed.As shown in Fig. 1, the long-period oscillations seem to have been caused by the tidal current, T=12h 25m, and a local internal wave, T=4h 20m. Furthermore there was another kind of fluctuation caused by a turbulon whose passage time is 110 min as shown in Fig. 2. It will support the theoretical result such as R (t) =1-(t/T0)4/3 obtained by Dr. E. Inoue. The internal waves with shorter period, T=2 min, theoretically expected were not observed as the measurement was made at an interval of 10 minutes.

The component of turbulent velocity in the direction of the mean flow has been studied for the tidal current off Cape Kan'non. The periods of the turbulent fluctuations recorded varied from several seconds up to a few minutes and these fluctuations seem to be caused by turbulence.The ratio of mean amplitude of fluctuations to the mean current was greatest at the bottom and smallest at mid-depths. The calculated values of R(t), the auto-correlation coefficients, were seldom in accord with the theoretical result as 1-R(t)oct213.

Deep current observations by neutrally-buoyant floats have been carried out ten times during the period from 1960 to 1965 and the results are compared with the previous views. The direct current observations indicate the presence of the deep water flowing southward along the Japan Trench at speed of few cm per sec. It seems that the deep water flow in the area surrounding the Japan Trench and its neighborhood occupies the depth of 2,000 to 3,000m. It starts at the north end of the Japan Trench and flows till about 30•KN latitude crossing under the Kuroshio Current. This result seems to support the concept advanced by KISHINDO.

Though the author had once made a new current meter using a phototube[1] and observed many interesting facts with it already [2] [3] , it is very expensive to use it. Now the author has made another and simpler current meter which will record current speed fluctuations more minutely but directions more roughly than the former.With it he observed ocean currents very well and discussed about them.