Recent theoretical theories of ocean circulation by STOMMEL and MUNK indicate the broad features of the climatological mean circulation pattern, In contrast, the problem of the maintenance of the ocean circulation does not appear to have attracted the same attention. Some insight is given through the analogy of the maintenance of the westerlies in the atmosphere. The mechanism of conversion of the eddy kinetic energy into the mean kinetic energy of the ocean circulation is discussed.

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The Stokes wave of finite amplitude has been said to have a very nearly trochoidal form. But this is a lucky guess. There is a mistake in the comparison between the equation of the wave form and that of the trochoidal curve. In this note A. B. Basset's text-book (1888) is renewed concerning the above-mentioned wave, and the coincidence of the two curves is confirmed.

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One type of lasting wave meter was newly manufactured. It is of pressure-recorder-type and is capable of obtaining continuous wave records covering two weeks; the recording paper is moved at the speed of about 30 cm per hour. Thus this instrument is very suitable for measuring wave-heights and wave-periods of ordinary wind waves and swells. Descriptions are also made on the wave records obtained by this instrument at Port Omaezaki on the western coast of Suruga Bay.

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Turbidity in the sea was discussed from the physical point of view, especially with its relation to radiation energy. This study was advanced along the following course.
(1) Absorption of solar heat radiation in the sea, and its relation to the turbidity of the sea water.
By using a thermopile, radiation energies which reach different depths in the sea were directly measured in Maizuru Bay and Turuga Bay. An equation was derived which relates these energies to the wave-length of light and the turbidity of the sea water. Computed values of the energies from this equation were compared with observational data. For facility in use, the amounts of total energies as different depths and for different extinction coefficients were represented in a graph and a table.
(2) Distribution of extinction coefficients of light in the sea.
Among data on underwater illumination, which have been obtained by many investigators, there are only few which have illustrated together with the state of sea concerned. The present author have attempted to obtain the reduction of intensity of light on a vertical distance using a simple submarine photometer, together with the water temperature, the chlorinity, etc. Various types of the distribution of extinction coefficients were found in different areas and in vertically stratified layers, and the change with time of extinc tion was also shown.
(3) Measurement of turbidity of sea water, and the character of turbidity.
Measurements of underwater illumination are restricted by natural conditions, so that a series of laboratory experiments was made of turbidity of sea water samples by measuring photoelectric current of transmitted ray of light through the samples. The method of measurement was explained in detail. The influence of plankton and of salinity upon turbidity Was discussed. experimentally for the former, and theoretically for the latter. Physical character of seston, which may play an important role in the turbidity of seawater, was examined, with regard to factors such as the size distribution of seston, and the time-change of seston itself.
(4) Distribution of turbidity in the sea.
The above laboratory method was applied to actual cases in the sea. Various types of distribution of turbidity were found to exist, which have not been detectable by means of a transparency disc. A close correlation was noted between the distribution of turbidity, so found and the sea conditions, which are estimated by such quantities as temperature, salinity, etc. This indicates that turbidity may become one of the elements characterizing the sea conditions.

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The samples taken in the vicinity of Funka-Bay (Volcanic Bay) in September, 1951 were investigated.
The characteristic species were Chaetoceros curvisetus, C. distans, C. constrictus, Thalassiothrix Frauenfeldii, and Climacodium biconcavum, the distributions of which divided the area into the following three parts ; Tsugaru-Strait area, area of Funka-Bay, and that off Hidaka. These results showed good correspondence to those from the oceanographical observations.

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