﻿Resonance and Electrical Interference. 187 



on an iron circuit of the same geometrical form and dimension 

 as a copper circuit have the same period as oscillations on 

 the copper circuit, supposing the capacity in the two circuits 

 to be equal. I am led to suspect that there is a change of 

 the period of electrical oscillations when an iron wire is sub- 

 stituted for a copper wire of the same geometrical form. I 

 shall return to this subject of the change of period on iron 

 wires in a following paper. 



Oettingen* has given some beautiful examples of the 

 interference of electrical oscillations of different periods when 

 they are led, so to speak, to the same spark-gap. I believe 

 that my photographs are the first ones, however, which show 

 the existence of such electrical beats or interference between 

 independent circuits. 



In order to present electrical beats between two secondary 

 circuits both of which were excited by a unidirectional move- 

 ment in a primary, I employed in certain cases two primary 

 coils of one turn each, connected in series, and placed these 

 primaries at right angles to each other ; the secondaries 

 corresponding to these two primaries were thus also at right 

 angles to each other. This disposition of my apparatus 

 enabled me to study the effect of two secondaries on each 

 other ; for on varying the angle between the planes of the 

 primary coils and their accompanying secondaries, the beats 

 can be made to appear or disappear. 



It seems to me that we have in these photographs evidence 

 of what may be termed the electrokinetic momentum of elec- 

 tricity. Something very like inertia is certainly shown by the 

 gradual rise to a maximum and the behaviour of secondary 

 circuits to unidirectional impulses from a primary circuit. A 

 mental picture of the disturbance produced in secondary 

 circuits can be produced in my mind by analogies drawn from 

 the subject of the motion of fluids. In such analogies, to my 

 mind, the idea of inertia is always present. I remarked in 

 the opening of this paper that the formula t — ^ir \Z~LC does 

 not apply at the instant of starting an oscillating current in 

 a secondary conductor by means of a unidirectional flow in a 

 primary circuit. This formula is true only after the full 

 effect of the capacity of the oscillating circuit comes into play. 

 My photographs show that at first neighbouring secondary 

 circuits act like circuits without capacity, the oscillations in 

 such circuits rise to a maximum in intensity and then fall, 

 after the rate is established. This is true also when air- 

 condensers are employed, and cannot therefore be attributed 

 to the action of a solid or liquid dielectric. 



* Ann. der Physik imd Che?nie, xxxiv. 1888. 



