A NEW JAPANESE G.E.K. 



By K. SuDA, Kl'Roda-Masao, D. Shoji and Sawayanagi-Fumiwo 

 Hydrographic Office^ Tokyo, Japan 



(1) Introduction 



An insulated conductor is drifted along the ocean current flows, 

 cutting the geomagnetism; then there must occur an electric motive- 

 force by Faraday's electro-magnetic induction law. If this e.m.L can be 

 picked up, the velocity of the conductor, which is the same as that of 

 the current, may be known, as the distribution of the geomagnetism 

 is already known all over the world. Electromotive force will be in- 

 duced in the current too, but it is dropped as negligible, because the 

 sea water is conductive and its volume is immensely large, even in the 

 superficial part, as Stommel proved. If both ends are shortened to 

 the sea water, an electric current flows through the wire and sea water. 



We utilise this e^m-f. for measuring the velocity of the current as 

 above mentioned. 



In practice, there remain the following difficulties; 



1. Sea water is an electrolytic solution, so a contact of metal intro- 

 duces an ionization potential and the measuring is disturbed very much. 

 We conquered this trouble by using a special electrode of silver^silver 

 chloride. 



2. The resistance of these electrodes is very high and the electric 

 current decays them even as small as less than 0.1 micro-ampere. These 

 problems have been easily solved since the electronic potentiometer was 

 produced in Japan. 



We composed a system of measuring apparatus from a couple of 

 specially designed electrodes, an electronic potentiometer, a set of lead- 

 ing cable made by special order, and a switch pannel having switches, 

 electric condensers, etc. 



Some confirming experiments were done very cautiously on the 

 characteristics of the electrodes on the temperature effect, density effect 

 of salt water and some points of handling for practical uses. 



(2) Practical Method of Measurement 

 The electrodes are connected directly to the pannel board of the 

 potentiometer by two lines of the specially made cord of a single core. 

 The length of the cord is 200 m. and 100 m. respectively for the elec- 



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