332 



Prof. A. Anderson on 



Kick of needle due to self-inO _ 



duction of coil . . . . J " 

 Kick due to charge or dis- ") 



charge of condenser, capa- > =46*125 „ 



city *5 microfarad ... J 

 Kick for capacity of *45 micro- ) _ . -, .o 7 r 



farad | ~" f " 



43*208 scale-divisions. 



The capacity which would give a kick of 43*208 is found 

 from these numbers to be *4657 microfarad. The coefficient 

 of self-induction, when reduced to absolute measure, is 

 therefore 



10 3 x '9314 x 150*51 x 489*7 = *06865 x 10 9 , 



or, in practical measure, '06865 henry. 



2. The method can easily be adapted to determine the 

 coefficient of mutual induction of the coil E and another coil 

 H, a slightly more complicated key being used. There are 

 two additional mercury-cups m, n (fig. 2) which are the 



terminals of the coil H, and the cups G x G 2 , the galva- 

 nometer terminals, are lengthened into equal portions of a 

 circular groove, so that the rocker, when turned round as far 

 as possible to the left, will connect G-j with p and Gr 2 with 

 q ; and, when turned to the right, G } with m and G 2 with n. 

 In its middle position it can connect G 2 with r and G 2 with 

 s. With such a key, a ballistic galvanometer of known 

 resistance, and a condenser, we can without difficulty deter- 

 mine both the coefficient of self-induction of E, and the 

 coefficient of mutual induction of E and H, Let the rocker 



