﻿184: 



Mr. J. Trowbridge on Electrical 



This formula, moreover, does not hold for the first instants, 

 lne electricity seems to be separated only along the wires at 

 tot, and the circuit vibrates more like a closed organ-pipe 

 than an open one. 



If a unidirectional primary spark excites oscillations in 

 neighbouring circuits which are slightly out of tune, the 

 phenomenon of electrical beats or interferences can be pro- 

 duced in these circuits, and can be shown by photography. 

 11 j A P nm ? 1 7 s P ark cease s to be unidirectional and is 

 allowed to oscillate, the oscillations of the primary spark tend 

 to compel those of the secondary or neighbouring circuits to 

 follow them ; if they are not sufficiently powerful to do this, 

 they beat with the oscillation of the secondary circuit. More- 

 over, if all capacity is removed from the neighbouring circuits, 

 they oscillate m tune with the primary circuit, following the 

 latter exactly. The secondary circuits without capacity act 

 like sensitive plates and exactly reproduce every disturbance 

 in the primary oscillating circuit. Leaving for the end of 

 this paper a more detailed account of my results, I will now 

 describe my apparatus. 



Fig. 1. 



In fig. 1, S, S', S" are three spark-gaps in the same vertical 

 plane, but not immediately over each other, in order that the 

 photographs may not overlap. B, A, C are three coils placed 

 vertically on the same axis. These circular coils consisted of 

 trom one to four turns of well insulated wire. The mean 

 radius of the coils was 915 centim. D, E, and F are the con- 

 densers respectively of the three independent circuits : the^e 

 condensers were made of hard sheet-rubber 03 centim. thick • 

 the coated surfaces could be varied by rolling up the layers' 

 of tinfoil which formed the coating. In certain cases air- 

 condensers were substituted for the india-rubber condensers 

 both tor the condenser E of the primary circuit and for the con- 

 denser D of one of the secondary circuits. The air-condenser 



