Abstract
The atmospheric potential gradient was observed at the summit of Mt. Fuji (3778m), 5.5 go (2800m), Tarobo (1290m) and Gotemba (460m), each during two or three days in August, 1947, and January, 1948. The polonium-collector was attached to the opposite side of the Shimizu's unifilar electrometer made by the Institute of Physical and Chemical Research and it was mounted on the top of the tripod. The visual observation was made hourly or half-hourly to investigate the diurnal variation of the atmospheric potential gradient.
According to the observational results, the ordinary semidiurnal variation (i. e. two maxima and two minima) prevails at Gotemba, and at Tarobo the diurnal variation is not so conspicuous, whereas at 5.5 go and at the summit the potential is greater through the daytime and smaller in the night. Thus it was made clear that the large semi-diurnal variation of the atmospheric potential gradient has the local character not only in the geographical locality but also in the vertical extent in the free atmosphere.
