324 Mr. W. P. Boynton on the 



Then, in the primary circuit, 



By making the proper substitutions, and disregarding 

 small quantities, this may be reduced to the form 



. f I i*< ft = 2(Ll .H 1 + M«B 1 ) - " " " (30) 

 In the secondary circuit 



i 



f 1 



0* + /S a )(A, 8 + B 2 2 ) , 7 C, 2 



1,-«M = 



Jo 



which similarly can be reduced to the form 



I 



* _ V *M*K 



( ±2 2(L 2 2 R 1 + M 2 H 2 )* ' * ' ^ 



Description of Apparatus. 



In the experiments to be described, the immediate source of 

 current was a large induction-coil, capable of giving at the 

 secondary terminals on open circuit an effective difference of 

 potential of twenty-one thousand (21,000) volts when operated 

 from the commercial alternating circuit of fifty volts. This 

 w r as excited in various ways-^by current from a storage 

 battery, by the commercial circuit spoken of above, and by 

 current from a small alternator kindly loaned by Prof. Pupin, 

 of Columbia University. 



The condensers in the primary circuit of the oscillating 

 system were sheets of micanite, 10 x 12 x ?0 inches, coated on 

 both sides with tinfoil to within about an inch and a half of 

 the edge. They were arranged symmetrically in two groups 

 of two, and their capacity measured in electromagnetic units 

 by the method suggested by Maxwell * and employed by 

 J. J. Thomson | and Glazebrook %. 



The condenser employed in the secondary circuit consisted 

 of two circular brass disks, slightly convex, of about ten 

 centimetres diameter, immersed in kerosene oil (petroleum). 

 Its capacity was computed approximately, but no attempt was 

 made to measure it. 



The primary coil contained 34*5 turns of heavy wire, was 

 22 cms. long, and 8'3 cms. in mean diameter. The secondary 



* Treatise, vol. ii. § 776. 



t Phil. Trans, clxxiv. part 3, p. 707 (1883). 



% Phil. Mag. (5) xviii. p. 98 (1884). 



