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6,200 miles. Two years ago Professor 

 Perry and he had suggested a name for 

 the practical unit of self-induction, it not 

 having previously received any name. If 

 the practical unit were exactly a thousand 

 million centimeters, the name quadrant 

 would be an appropriate one, but it was 

 about ^ per cent, less than the earth's 

 quadrant, and they had therefore sug- 

 gested the name "secohm" (a contrac- 

 tion of second and ohm). Professor 

 Ayrton next referred to a standard of 

 self-induction which he exhibited on 

 behalf of Professor Perry and himself, 

 and which he thought was the first com- 

 mercial standard of self induction ever 

 issued. It consisted of two coils of 

 platinoid wire, one fixed in position, and 

 the other pivoted so that it could be 

 turned about a diameter, and placed in 

 different positions relatively to the fixed 

 coil. By putting the coils in different 

 positions the arrangement had different 

 and definite coefficients of self-induction, 

 the values of which were indicated on the 

 scale in secohms from 0.013 to 0.036 



