496 Lord Rayleigh on the Self-induction and 



induction, very curious results may follow the application of 

 a periodic electromotive force. I have lately submitted the 

 matter to experimental test, by which theoretical anticipations 

 have been fully confirmed. 



The two conductors in parallel were constructed out of the 

 three wires of a heavy and compact triple coil of copper wire* 

 mounted in a mahogany ring, which has been in my possession 

 for many years. Of these wires two are combined in series 

 (with maximum self-induction) to constitute one of the 

 branches in parallel. The other branch is the third wire of 

 the triple coil, so connected that steady currents would circu- 

 late the same way round them all. The variable currents 

 were obtained from a battery and scraping-contact apparatus 

 (p. 472), connected directly. Under these conditions, if the 

 intermittence be rapid enough, the currents distribute them- 

 selves in the two branches so as nearly to neutralize one 

 another's magnetizing-power ; and this requires that the cur- 

 rent in the single wire should be of about twice the magnitude 

 of the current in the double wire, and in the opposite direction. 

 If we call these currents 2 and —1, the current in the mains 

 must be +1. 



As may be seen from formula (13)t, such a state of things 

 leads to a high equivalent resistance for the system ; and the 

 question might be investigated on this basis with the apparatus 

 already described. I preferred, however, to examine directly 

 whether it were true that the current in one of the branches 

 exceeded that in the main ; and this could be readily done by 

 "tapping" with the telephone. For this purpose the two 



Fig. 2. 



one wire, 

 two wires, 

 main. 



branches and the main were led through short lengths of 

 similar German-silver wire to the junction, composed of a 

 copper plate to which the wires were soldered (fig. 2). One 

 telephone terminal was soldered to the plate ; the other was 

 brought into contact with some point of the German-silver 



* The three wires were wound on together. t Loc. cit. p. 377 



