Theories of an electric current generated by the earth's magnetic field are presented. Preliminary measurements d of the current were undertaken, using telephone cables in the Pacific Ocean near Australia. Voltage at the ends of the cables, one end being earthed'' under the ocean, was measured. The voltage differences were taken to eliminat the dominant tidal currents. An approximately sinusoidal earth current with a period of 12 hours and a potential gradient of less than 0.1 mv/km was obtained. (M.J.T.)