T H E 



LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 

 JULY 1859. 



I. Observations on the Electric Discharge. By M. Pi.iiciCER. 



[Continued from vol. xvi. p. 418.] 



On the Action of the Magnet upon tlie Electric Current, from a 



new point of view. 

 76. ^r^HE rotary motion of a magnetic pole around the con- 

 A ducting wire, and of the conducting wire around a 

 magnetic pole, are phsenomena which, on their discovery by 

 Faraday, arrested the attention the more, because they were not 

 connected by analogy with any previously observed phsenomena. 

 Laplace and Biot, by considering the action between the pole 

 and a single element of the linear conductor of the current, 

 obtained an elementary force whose magnitude is inversely pro- 

 portional to the distance between the pole and the current- 

 element, and whose direction is perpendicular both to the direc- 

 tion of the stream-element and to that of the straight line con- 

 necting this element with the pole. This force, which is reversed 

 in direction both by an inversion of the magnetic polarity and 

 by an inversion of the direction of the current, would move the 

 stream-element, if it were free to move, parallel to itself, in a 

 circle around the line which passes through the pole and is 

 parallel to the stream-element. 



If, instead of the imaginary polar ])oint, which must always 

 be a mathematical fiction, we place a magnet of arbitrary form, 

 then in determining the direction of the force, the straight line 

 passing through the pole becomes replaced by that magnetic 

 curve which is perfectly defined in position by passing through 

 the current-element. There is no force present either to ciiange 

 the direction of the ciu-rent-element, or to force it along the 



magnetic curve to a point of greater magnetic activity. 



* Translated by Dr. F. Giitlirie, from Fofi;{<enilortt"s Annulen, vol. civ. 

 p. 622. 



Phil. Mag. S. 4. Vol. 18. No. 117. July 1S59. B 



