GEK
The Geomagnetic ElectroKinetograph (GEK) measures currents by measuring the electrical potential induced in sea water when a conductor (sea water) moving in a magnetic field (Earth's field). It consisted of a pair of electrodes towed behind a ship. The electrodes were at the beginning and end of line several hundred meters long. Or, the electrodes were at ends of submarine telephone cables. The accuracy of the technique was difficult to quantify and the technique fell from favor. The primary error was due to unknown shorting of current by conduction through the sea floor and in still water below moving surface currents. Additional information available at "http://www-ocean.tamu.edu/education/common/notes/chap10.html" [Summary provided by Texas A&M University]
Current/Wind Meters