Volta 



27 



their origin at least, lie accurately within the line of magnetic in- 

 duction. These circumstances, (independently of the consideration 

 that a voltaic current, which theory supposes to have an atomic cir- 

 culation, exclusively, cannot be supposed to operate beyond such 

 limits,) are sufficient, in my opinion, to prove that we should regard 

 magnetic induction as the remote, and magnetic rotation as the im- 

 mediate cause of the existence and direction of all such voltaic cur- 

 rents* In order that these views may be perceived more clearly, I 

 shall explain them by references to fig. 2. 



Fig. 2. 



S 



Let a denote a particle taken from a magnet, around which 

 circulates a voltaic current generated at a, and represented by the 

 elliptical arrows; at right angles to this current revolve the magnetic 

 forces in circles, R, R. From the inside of this current a north po- 

 lar force revolves towards N, and hence that side of the particle, a, 

 will act like the north pole of a magnet ; whereas the other, since a 

 south polar force revolves from the inside of the current towards S, 

 will have the properties of a south pole, and the line S, N, will cor- 

 respond with the magnetic axis of the particle. The action of one 

 such particle must represent that of a magnet, which Ampere's hy- 

 pothesis supposes to consist of an assemblage of them, arranged sym- 

 metrically ; therefore let us suppose voltaic induction to take place. 

 The elliptical arrows c and d represent the only directions in which it 

 can occur ; one of them corresponds with the current of a, but the 

 other is in opposition, and neither is in the plane of its action, since 

 both are parallel to it. Therefore, admitting the possibility that the 

 current of a can act beyond its own limits, the positions of c and d 

 necessarily place them out of the directions towards which the posi- 

 tive or negative fluids can possibly tend. But the planes of magnetic 



