262 Prof. Kijke on some Properties of the Induced Current. 



T representing the duration of the extra current. Now, opera- 

 ting as I have described, the rupture of the primary current in 

 air, in a jlame, and between the poles of an electro-magnet, always 

 gave rise to the same deflection of the moveable helix. 



14. I described some years ago (Pogg. Ann. vol. lxxxi. p. 168, 

 Phil. Mag. S. 3. vol. xix. p. 240), the increase in length which in- 

 duction sparks undergo when the primary current is broken be- 

 tween the poles of an electro-magnet. I believe that, by analogous 

 considerations, an explanation might be given why the striking- 

 distance of an induced current increases when the molecules of 

 the gas or of the liquid in which contact is broken are endowed 

 with a certain velocity. In fact, when the circuit is opened, the 

 current is not interrupted so suddenly as is usually supposed. 

 At the part at which the circuit is broken, a more or less intense 

 voltaic arc is produced, which continues until the electrodes have 

 reached a certain distance. It is clear that this arc, though 

 offering a more and more considerable resistance, allows the cur- 

 rent to pass from one electrode to the other. It is also clear 

 that, if the gaseous or liquid molecules in which the voltaic arc 

 is formed are endowed with a certain velocity, they will commu- 

 nicate part of their motion to the particles which constitute the 

 voltaic arc. It will follow that this arc will not remain so long, 

 and that therefore the velocity of the variation in the intensity 

 of the induced current will increase. But the electromotive 

 force of the induced current, as well as its striking distance, are 

 quite proportional to this velocity of variation. Then a certain 

 degree of velocity imparted to the molecules of the gas or of the 

 liquid in which the rupture of the inducing circuit is effected 

 ought to increase the striking distance of the induced current. 

 But, it will doubtless be objected, the physiological effect, the 

 thermal effect, as well as the action on the dynamometer, why 

 will they not increase at the same time ? I admit that to these 

 questions, the number of which might be increased, I cannot 

 give a satisfactory answer. I merely beg to observe that Ohm's 

 laws are tacitly allowed to be applicable to induced cur- 

 rents obtained by opening or closing an inducing circuit. But 

 that is an entirely gratuitous supposition. Ohm's laws are only 

 applicable to circuits in which a state of electrodynamic equili- 

 brium has been established. But no one will aver that this is 

 the case with the circuits in question. 



With regard to the specific action exercised by different gases, 

 I do not think we can dream of accounting for it in the present 

 state of the science. 



Leyden, September 1862. 



