■of Varying Currents in Inductive Circuits. 



267 



terminals of a magnetizing coil containing a core of fine iron 

 wire. The full discussion of these curves must be reserved 

 until the publication of the investigation to which they pro- 

 perly belong. It is only necessary to point out in this place 

 that the irregularities which appear in them, and on the 

 larger drawing from which they are reduced, are not due 

 to accidental error, since identical experimental curves are 



Fig. 8. 



obtained on repetition ; their origin must be sought for in 

 the physical nature of the circuit through which the current 

 flows. 



The reversal of the current was effected by connecting the 

 magnetizing coil, as shown in fig. 8, in a network similar to 

 Wbeatstone's bridge. The resistances P, Q, S were so chosen 

 that on breaking one arm of the circuit by means of the key 

 K 1? the current in the coil changed to a final value equal and 

 opposite to its value before the break was made. This 

 method effects reversal in a perfectly definite manner. It 

 should be further noticed that if there is no inductance except 

 that of the coil, no spark can pass when the arm is broken. 

 The break-circuit keys referred to form part of a Helmholtz 

 pendulum interrupter, by means of which the time interval 

 between the instants of rupture is accurately obtained. 



In the foregoing paper we have given an account of the 

 application of the method to the measurement of a fall of 

 potential down a non-inductive resistance : the method is, 



T2 



