LAVTS OF ELECTRO-MAGNETIC ACTION". M5 



CHAPTER V. 

 DISCOVERY OF THE LAWS OF ELECTRO-MAGNETIC ACTK N. 



ON attempting to analyse the electro-magnetic phenomena observcu 

 by Oersted and others into their simplest forms, they appeared, at 

 least at first sight, to be different from any mechanical actions which 

 had yet been observed. It seemed as if the conducting wire exerted on 

 the pole of the magnet a force which was not attractive or repulsive, 

 but transverse ; not tending to draw the point acted on nearer, or to 

 push it farther off, in the line which reached from the acting point, but 

 urging it to move at right angles to this line. The forces appeared to 

 be such as Kepler had dreamt of in the infancy of mechanical con- 

 ceptions ; rather than such as those of which Newton had established 

 the existence in the solar system, and such as he, and all his successors, 

 had supposed to be the only kinds of force which exist in nature. 

 The north pole of the needle moved as if it were impelled by a vortex 

 revolving round the wire in one direction, while the south pole seemed 

 to be driven by an opposite vortex. The case seemed novel, and 

 almost paradoxical. 



It was soon established by experiments, made in a great variety of 

 forms, that the mechanical action was really of this transverse kind. 

 And a curious result was obtained, which a little while before would 

 have been considered as altogether incredible ; that this force would 

 cause a constant and rapid revolution of either of the bodies about the 

 other ; of the conducting wire about the magnet, or of the magnet 

 about the conducting wire. This was effected by Mr. Faraday in 

 1821. 



The laws which regulated the intensity of this force, with reference 

 to the distance and postiion of the bodies, now naturally came to be 

 examined. MM. Biot and Savart in France, and Mr. Barlow in Eng- 

 land, instituted such measures ; and satisfied themselves that the ele- 

 mentary force followed the law of magnitude of all known elementary 

 forces, in being inversely as the square of the distance ; although, in 

 its direction, it was so entirely different from other forces. But tli.' 

 investigation of the laws of phenomena of the subject was too closeh 

 connected with the choice of a mechanical theory, to be established 



