﻿186 Mr. J. Trowbridge on Electrical 



set the circuit C into oscillatory movement, and that this 

 oscillatory movement continues long after the exciting blow 

 has ceased. A careful study of many photographs of this 

 nature shows that a circuit containing capacity and self- 

 induction acts at the first instant as if no capacity were in the 

 circuit. It then begins to oscillate with a higher period than 

 it afterwards reaches, acting at first like a closed organ-pipe 

 and subsequently like a pipe open at both ends. 



In fig. 3, S' represents an oscillating primary discharge. 

 S represents the photograph of the spark produced in the circuit 

 B from which the capacity had been removed. The move- 

 ments in this circuit B exactly follow those of the excitino- 

 circuit A. S" is the photograph of the oscillating movement 

 produced in the circuit C. It is of a different period from 

 that of the exciting circuit S' and continues much longer. A 

 secondary circuit without capacity acts like a sensitive plate, 

 and accurately follows every movement of the exciting 

 circuit. 



In fig. 4 S' represents again the oscillating primary circuit, 

 S the oscillating secondary circuit C. The circuits are nearly 

 in geometrical resonance. Slight beats, however, can be 

 observed. The duration of the secondary is nearly the same 

 as that of the primary. 



Fig. 5 shows clearly the phenomena of beats. In this 

 case the secondary circuit was 20 centim. from the primary 

 circuit. 



Fig. 6 also shows the phenomenon of beats, and also the 

 rise to a maximum in the oscillations of the secondary circuit, 

 S. In this case an iron wire constituted a portion of circuit C. 

 It seemed as if the effort to magnetize the iron diminished 

 the power to produce the initial movement in the secondary 

 circuit with as much energy as was the case when a copper 

 wire of inductance equal to the iron wire was introduced in 

 its place. 



1 have stated that Stefan * has given a theory of electrical 

 oscillations, and in his interpretation of his equation points 

 out the necessity of supposing under certain conditions an 

 aperiodic movement superimposed upon an oscillatory move- 

 ment, in conductors containing self-induction and capacity. 

 In regard to this latter point, my experiments seem to sup- 

 port his theoretical conclusions. I am inclined to believe, 

 however, that the behaviour of condensers in secondary cir- 

 cuits, which are suddenly submitted to electrical disturbances, 

 cannot properly be explained by the theory in Stefan's paper. 

 Moreover, it results from his theory that electrical oscillations 

 * Ann. der PJiysik und Chemie, xli. 1890, p. 422. 



