SYMPOSIUM ON PHYSICAL AND CHEMICAL 

 PROPERTIES OF PACIFIC OCEAN WATERS 



ELECTRICAL AND MAGNETIC EFFECTS OF OCEAN CURRENTS 



By G. E. R. Deacon, Admiralty Research Laboratory, England 



Summary of Discussion 



Dr. TuLLY inquired as to the manner of hooking up the electrodes used, 

 and also the material of which they were constructed. They were stated 

 to be of silver and silver chloride, protected in glass wool and soldered to 

 the cable. Measurements were made by a flux meter so as not to take 

 too much current from the electrodes. How quantitative could the 

 investigation be made ? The potential gradient would have to be 

 correlated directly with some actual measurements. There would be 

 perhaps an inaccuracy of only 10 per cent., which was good in any kind of 

 physical oceanography. An investigation of the earth current had been 

 made in the United States to establish correlation between magnetic 

 disturbance of aurora and earth currents. A very definite correlation does 

 exist, although there was not yet established any field measuring station. 

 * If observations were made in an estuary there might be other tribu- 

 tary channels converging on the main current which greatly complicate 

 the results. Dr. Deacon proceeded to ask himself the question as to 

 whether measurements could be made across a permanent current of 

 great dimensions such as the Gulf Stream. In a section from Florida to 

 Key West there might be a gradient of 3 or 4 volts. Might it not be 

 reasonable to suppose this Mould ha\-e an effect on the deposition of 

 sediments. 



Mr. Allen inquired about observations on inland water effects. It 

 was replied that the significance of this problem was appreciated. 



Dr. Emery questioned what would be the results in the Strait of Gib- 

 raltar where an outward current existed below and an inward at the top. 

 It was replied that a resultant of the two effects would tend to be estab- 

 lished. Dr. Emery mentioned the cable from Hawaii to the mainland 

 and raised the point of its bearing upon sedimentation measurements. 

 It was held that tidal streams in the American coastal region would give 

 the predominant effect. 



A New Zealand member asked about possible Cook Strait applications 

 of Deacon's work. Tidal currents up to 7 knots were here established, 

 and in the 40 m. from Wellington to Plimmerton there was a 5| hour 

 tide difference producing consequently a very strong current. There was 

 also the effect of oceanic currents in Cook Strait. Dr. Deacon assured 

 the inquirer that the physics department of any University College could 

 set up the apparatus, though it was agreed that interpretation of data 

 might raise local difficulties. 



TIDAL INVESTIGATIONS IN THE PACIFIC 



By E. C. McKay, U.S. Coast and Geodetic Survey 



Prior to World War II, tidal information for the Pacific Ocean area had 

 been accumulating slowly from various sources for many years, but it 

 required the impetus of war operations to accelerate its correlation and 

 analysis and to emphasize the need for additional and more comprehen- 

 sive tidal data. 



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