248 Mr. T. Mizuno on the Function of 



In this case, the following phenomena were observed :— 



(i.) When the secondary S of the induction-coil was open,. 

 i. e. its terminals were so far apart that no sparks 

 could take place across them, the interruptor was 

 active. 



(ii.) The terminals were placed at such a distance that 

 the play of sparks could occur. In this case, the 

 action of the interruptor immediately stopped, and 

 the active electrode became red-hot, the main current 

 indicated by the amperemeter being very much 

 reduced. 



(iii.) The iron bundles were put in the coil N", and the 

 terminals of S were maintained in the same condition 

 as in the case (ii.). In this state of affairs, the action 

 of the interruptor went on without any hindrance, 

 and the incessant play of the sparks of the secondary 

 was observed. 



(iv.) During the above experiment (iii.), taking away the 

 iron bundles from the coil N, the action of the 

 interruptor ceased at once, the main current being 

 simultaneously reduced to a large extent. It is to be 

 remembered that when the interruptor is thus once 

 made inactive, the re-introduction of the iron bundles 

 into the coil N has, of course, no effect at all. 



(c) The coil N, the induction-coil M, and the interruptor 

 B were joined in series, and they were shunted by the 

 condenser. In this case, the interruptor was found to act 

 well, as might be a priori expected, whether the coil N 

 contained the iron bundles or not, and also whether the 

 spark-gap of the secondary S was opened or closed. 



So far, I have given a mere description of the phenomena 

 observed with the interruptor. 



Now the experiment (a) tells us that with a given current,, 

 or, more strictly speaking, a given electromotive force, a 

 certain particular value of the self-induction is necessary for 

 the action of the interruptor ; and that when the self-induction 

 becomes less than this particular value, the interruption can- 

 not then go on, the process being simply an ordinary 

 electrolysis. As to the experiment (b), we also see that a 

 certain value of self-induction is indispensable in order to 

 maintain the action of the interruptor. 



The cases (iii.) and (iv.) prove this. Again, the cases (i.) 

 and (ii.) can be explained by the following theoretical con- 

 sideration : that when the secondary of a given induction-coil 

 is closed, the effective self-induction of the primary coil "is 



