Memoirs of the Kakioka Magnetic Observatory Vol.06 No.01， p.68, April, 1951
Earth Current due to Stress
In summer 1944, the author recorded the earth potential gradient and the induced current in a horizontal loop in order to investigate the pulsations in the earth magnetic field at Yabuki-machi, in Fukushima Prefecture. On that occasion, noticeable change was always recorded in the earth potential gradient when the train was running at a distance of about 300m from the nearest electrode. The amount was 1 - 2 mV/km. After several examinations and discussions, the mechanism may be considered to be due to the potential of flow produced by the stress of the soil which the train weighed down.