Ice crystals were captured on Mt. Zao and their nuclei were studied by using the electron-microscope and hydrogen fluoride. The record of radio sounding indicates these ice crystals were formed at a temperature of about -9°C. The observation shows that most of the nuclei are soil particles, such as hematite, limonite, etc. On the other hand, very few combustion nuclei are found.
Applying his theory of isotropic turbulent diffusion to the practical problem of atmospheric pollution, the author studies theoretically on the distribution of airborne pollution from an elevated continuous point source, considering to some extent the non-isotropy of atmospheric turbulence. The expression obtained here is in its form similar to those of Sutton's and Lowry's but in detail different from them. The most striking difference is that the numerical parameters involved in the previous authors' results are not constant in the case of the present author and are represented as the functions of the length of the sampling period. In the latter part of this paper, some discussions are made on the atmospheric diffusion from an instantaneous point source and, furthermore some numerical examples are shown.