High-Frequency Induction- Coil. 325 



had 84 turns in three layers, was about 30 cms. long, and 

 10*6 ems. in external diameter. The coefficients of induction 

 were measured by the simple bridge method suggested by 

 Maxwell *, using alternating current and telephone ; and as 

 a standard a coil of rectangular cross section, whose self- 

 induction was computed by the method of Stefan f. 



Fiar. 1. 



Hiyh Frequency Coil 



K 



The primary spark passed between two balls of zinc, 

 2 centim. in diameter, and was blown out by an air-blast 

 from a Sturtevant blower driven by a small electric motor. 

 The phenomena so obtained were more regular than when 

 the spark passed in oil. 



The electrical dimensions of different parts of the system, 

 in c.g.s. absolute electromagnetic units, are as follows : — 



1,105,000 = Self-induction of standard coil. 

 L x = 54,000 = Self-induction of primary coil. 

 L 2 = 454,000 = Self-induction of secondary coil. 

 M = 77,000 = Mutual-induction of the two coils. 

 K x = 1*6 x 10~ 18 = Capacity of primary condenser. 

 K 2 = 2 x 10 _20 = Capacity of secondary condenser, 

 present. 



* Treatise, vol. xi. §§756, 757. 

 t Wied. Ann. xxii. pp. 107-117 (1884). 

 Phil. Mag. S. 5. Vol. 46. No. 280. Sept. 1898. 



when 



2 A 



