THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



OCTOBER 1862. 



XXXIV. On some Propei^ties of the Induced Current. By Dr. 

 P. L. Rijke, Professor of Natural Philosophy in the University 

 of Ley den*. 



1. nHHE mode in which an inducing current is broken, 

 J- exercises, as is known, a considerable influence on 

 the striking distance of the induced current. Although in most 

 cases we could not account for every increase or decrease in length 

 which the induction spark undergoes when we use a given mode 

 of breaking contact, yet some results have appeared capable of 

 being reduced to a general principle ; and thus the experiments 

 of MM. Fizeau and Poggendorff have shown that everything 

 which tends to diminish the electric density at the place where 

 the circuit is broken, exerts a favourable influence on the length 

 of the spark of the induced current. 



In referring to the principle to which we have just alluded a 

 fact known for some time (the instantaneous loss of electricity 

 which every conductor undergoes when placed in contact with a 

 flame), I have been led to think that it would be possible to 

 increase the striking distance of an induced current, by effecting 

 the interruption of the inducing current in the middle of aflame. 



2. The experiments which I am about to describe have con- 

 firmed these anticipations. 



The rupture always took place between platinum wires termi- 

 nated in the form of a ring, which were made to slide rapidly 

 one along the other. Of course these wires, which were held in 

 the hand, were insulated sufficiently to prevent the extra current 

 from passing through the arms of the operator. The ends of the 

 induced wire were connected with a spark-micrometer. The 

 spark passed between two copper knobs, each 16'G millims. in 



* Communicated by the Author. 



Phil Mag. S. 4. Vol. 24. No. 161. Oct. 18G2. S 



