THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZ INE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JULY 1864 



I. On the Extra Current of the Induction Current, 



By J. C. POGGENDORFF*. 



IN my latest investigation laid before the Royal Academy in 

 August last, on the thermal action of electrical sparks, in 

 order to test the view propounded by Reitlinger, that this action 

 is proportional to the intensity of the current, I had interposed 

 very long wires, in the form of coils, in the path of an induction 

 current. I thereby observed that the sparks, notwithstanding 

 the considerable enfeeblement in intensity produced by this in- 

 terposition, lost scarcely any of their heat, just as they have long 

 been known to become thereby more fully luminous, but to lose 

 little or none of their striking-distance. 



I observed on this occasion that when the circuit of the in- 

 ductorium is completely metallic through such accessory coils, 

 the current, in spite of this metallic circuit, and in spite of the 

 great enfeeblement which it experiences through the resistance 

 of a very long and thin wire, possesses such tension that ex- 

 tremely piercing sparks are obtained if the wires are merely 

 touched in one point with the hand. • 



I further found that the free electricity at the end of the ac- 

 cessory coil turned towards the positive pole of the inductorium 

 is positive, and negative at the other end ; and that if two such 

 accessory coils are placed end to end, the wire joining them ex- 

 hibits far less tension than the two wires leading from the coils 

 to the inductorium, from which I concluded that in the long 

 metallic circuit there must be a zero point of tension. Finally, 

 I convinced myself, by individual interruptions of the voltaic ex- 



* Translated from the Monatsbericht der Berliner Akademie, November 

 1863, by Dr. E. Atkinson. 



Phil. Mag. S. 4. Vol. 28. No. 186. July 1864. B 



