Aikitu Tanakadate and the Controversy over Vertical Electrical Currents in Geomagnetic Research

Aikitu Tanakadate (1856-1952) was a pioneer in geomagnetic research in Japan. This paper focuses on Tanakadale's investigation of vertical, electrical currents between the Earth and his atmosphere and his role in a controversy over these currents. This controversy arose after Adolf Schmidt (1860-1944) hypothesized these vertical currents in 1895. Debate was aroused over this question for two reasons: firstly it might upset the premise of the Gaussian theory of geomagnetic potential; and secondly it seemed to provide a key to revealing the mechanism of geomagnetism. Tanakadale did not doubt the existence of such currents, but he was skeptical about the method with which the hypothesis was tested. After 1939 the controversy died down, but never ended. The recent solution of this problem in 1992 shows that Tanakadate was far-sighted in criticizing the validity of the method which others used to test the hypothesis.