In the present paper, it is explained theoretically that the maximum amplitudes, of a dispersive wave is propagated with maximum, minimum or mini-max group velocities and their magnitudes are O(-5/6) or O(-3/4) according as their group velocities are maximum and minimum or mini-max respectively, where ris the distance from the center of region in which the initial displacement or velocity are concentrated. It is also shown that the wave groups, the indivisual waves of which have the wave length of ∞ or infinitesimal, can not be so predominant as the wave groups above stated even if their group velocities are extremum. Finally, it is proved that if the initial distribution of displacement or velocity fulfils a certain condition occasionally, the amplitude of wave group with an extremum group velocity may be inferior to those of other wave groups.
In order to study the polarization of the light from the sky, cloud-layers, sea surface and skirts of mountains, and to improve the visibility (contrast of objects) by using Polaroid, we did some fundamental observations on Mt. Fuji in July, 1944. The Principal part of our instrument is composed of twp cylindrical tubes; the former half, having Polaroid plate at its end, can be rotated around its center oxis, contacting with the rear half. Matsuda's photocell set at the end of the rear half will change the intensity of the polarized light into photo-current which can be measured by Siemens photometer. By the aid of a tripodal, the tube can be pointed towards any direction arbitrarily. The result can be summarized as follows: (1) The polarization of light from the sea surface, skirts of mountains and cloudlayers depends mainly upon light-scattering caused by the air between objects and observer not receiving the reflected light from the objects themselves. This polarization is in accordance with the well-known facts of polarization of the sky light; except the fact that the degree of polarization is smaller than the case of sky light. (2) Moreover, we observed the polarization of the light from white rainbow, sky in moonlight night, corona etc. White rainbow caused by cloud-layers showed strong polarization and was measured quantitatively. (3) As we can expect from the idea of Koschmieder's contrast, in cases of (i) comparing two objects, polarization of the darker one is stronger, and (ii) if the brightness is the same, either one can be stronger, and we can improve the vis_??_bility by using polaroid plate. This effect is striking, especially in cloud observation at twilight or moonlight night.
The turbulence of wind was investigated in the yard of Electric Communication Laboratory at Wakkanai, at the beginning of May, 1948 (solar eclipse occurred at that time). Three hot-wire anemometers were set on a wooden pillar. Their heights were 0.65m. 1.4m. and 2.4m respectively from the ground. Two more hot-wire anemometers were set on a wireless tower. The relation between the wind structure and the change in lapse rate of air temperature accompanied with the solar eclipse could not be observed. But it was certain that the pattern of turbulence differs from those which were observable on flat plains. It is because of the narrowness of the place of observation.
Sea Fogs on the shore of Hokkaido and Kurile Islands are supposed to be associated with warm air which steams northward over the cold ocean current. Authors intended to ascertain this assumption by constructing the trajectory diagram of the air on the weather chart. The result shows that the assumption is correct and when the air travels over the ocean, east to Honshu, Northern Fogs are formed, and when it travels over Honshu or Japan Sea, fogs are seldom observed. However there were exceptions according as the position and the time of observation, so we also inquired into the circumstances of these cases.