Abstract
It is well known that the variations of earth current correspond to those of terrestrial magnetism, but there are few quantitative studies of them except the diurnal variations.
The author investigated the ratio of the amplitudes of their variations, using the data at Toyohara for the period from August 1932 to July 1933 and found that the shorter the period, the larger the ratio, and that this ratio is roughly proportional to T-0.4 where T denotes the period.
Next, considering the east-west component of earth potential gradient induced by the horizontal component of terrestrial magnetism, so far as the variations are concerned, we theoretically calculated the ratio of the amplitudes and the result is in a good accordance with the observed fact.
