In the present paper the tendency of the persistence of weather was ascertained using the days of fair weather (cloud amount less than 8) and cloudy weather (cloud amount 8 or more than 8) in the interval from 1905 to 1929 at Tokyo. The ratio of the observed mean duration of any weather to the mean duration of the same weather calculated from the probability of that weather was studied. And it was found that the persistence factor ff, fc could be derived from the ratio and that there was a relation between the persistence factor ff, fc and probability. The monthly values of the persistence factor and the ratio of the meau duration were calculated. The value of the ratio is large for July and August, and small for Jan., Apr. and Nov., but it is confined within the limits of 1.2 and 1.6. The annual change of ff is almost parallel to pc, while the change of fc is antiparallel. For this point an explanation was given by the relation between the persistence factors ff, fc and the ratio of the mean duration.
It has been generally known that earthquakes take place at any depth in the crust as far as about 500km. below the surface. For the investigation of near earthquakes, a standard table of travel time of seismic waves transmitted from the origin of variable depths is required to be made by the recent materials obtained in the seismometrical observation. For this purpose, the time-distance curve of the great earthquake occurred in North Idu district on Nov. 26, 1930 is adopted and the values of seismic wave velocity calculated by Mr. Honda are used in this paper. Thus, several tables of the travel time concerning the depth of focus and the epicentral distance are obtained. They are considered to be applicable for various branches of our practical seismology. Further, we have also calculated a table of the correction due to the depth of focus which must be applied on the travel time at a large epicentral distance in the case of distant earthquakes. As for further investigations of seismic wave propagation based upon the present tables, we shall write in the next report.
Diatomaceae: As were the cases observed by other authors, diatoms among phytoplankton were most predominated in the spring-time. However, in the present case their maximum abundance appeared comparatively early, namely on March 11, 1932 and their number was 16, 020 per 10c.c. holding 95, 6% of the total individuals of phytoplankton and the surface temperature being 10, 3°c at 13h. of that day. The second annual maximum occurred on Dec. 5, 1931. counting 1, 320 per 10c.c. and 89, 2%. The number of important species observed during the time of May 1931-April 1932, were in all 16 belonging to the genera, Synedra, Melosira, Fragilaria, Asterionella etc. The first two of them were the main genera in the spring outburst, and the maximum growth of Melosira, counting 5, 650 on March 26, occurred a little later (about 15 days) than that of Synedra. Asterionella was found in a moderate number in the high winter. On the whole, the quantity of diatoms was found more at the bottom layer than at the surface. Chlorophyceae: This group was fairly less in quantity compared with diatoms. Its maximum growth appeared on May 26 counting 830 and the water temperature showing about 20°c. Scenedesmus was the representative among 15 species observed. Cyanophyceae: 4 species were found out. Clathrocystis occurred in summer, especially on June 9, counting 1, 850 per 10c.c. at the surface layer and 600 at the bottom. Aphanocapsa was found more or less in the spring-time.
The hourly observations were made from May 4 to 6 in the moat where Potamogeton cripsis was abundantly growing. We could make clear the state of O2-consumption due to the respiration of the aquatic plant during the night. The amplitude of the change of O2 on May 4 was 7, 09c.c./L. The minimum value of O2 appeared at 6h. on 4, showing 4, 51c.c./L (63, 8%) and on 6 it came about two hours late in the bottom layer as it was cloudy in the morning. It was recognizable that a lineal relation between the increased volume (d) of O2 from the minimum and the amount of the solar radiation (S) which was summed up from sun-rise till each time of the observation on May 4 as that described in the previous paper, while the relation on 5 was relatively irregular in the surface layer. This irregularity is due to the disturbance of the surface water caused by the south wind (about 9m./sec.) during 12 and 14h. The phenolphthalein-alkalinity of the water was determined with the titration of N/10. HCl, using phenolphthalein as an indicator. The feature of its variation was resemble to that of pH.
Correlations between the yield of rice-crop in Hokkaidô and the winter temperatures at Nemuro and Dutch Harbour (year 1892-1919) have already been published in the Memoirs of the Imperial Marine Observatory (Vol. 1. 1922-24) by Prof. T. Okada. The present note is merely the continuation of his study; we have plotted the mean of the mean air temperatures in January, February and March at Nemuro and that at Dutch Harbour and the yield of ricecrop in Hokkaidô for the 11 years from 1920 to 1930. Then we calculated the correlation coefficients and probable errors of both quantities between the year 1892 to 1930 and arrived at just the same conclusion formerly attained by Prof. T. Okada. Now it is affirmed that rice-crop in Hokkaidô may be foreshadowed by using the winter temperatures at Nemuro and Dutch Harbour.