Voltaic Induction. 43 



these circumstances, I should be led to conclude, that the mass of 

 positive and negative currents, generated under the magnet, proceed- 

 ed directly towards the opposite points C B, and completed the cir- 

 culation, along the same line, upon the opposite side of the plate. 



The supposition, that they form two distinct circles upon the upper 

 surface of the plate, one on either side of the magnet, seems, howev- 

 er, to be admitted both by Faraday and Nobili. I shall, accordingly 

 adopt it, and proceed to illustrate the movements of the magnet. 



1st. Rotation with the plate. — It will be seen, by reference to the 

 2nd fig. at the commencement of this enquiry, that the magnetic force 

 which issues from the interior of a voltaic circuit, gives to that side 

 of the circle, its active polarity. This is a general rule; and if we 

 examine the voltaic currents upon the revolving plate, (fig. 7.) we 

 shall perceive that the one, generated by the particle a, has a north 

 pole issuing from the interior, upwards. Hence this voltaic circle, de- 

 noted by R, must tend to repel the magnet, whose north pole is 

 down ; whereas the voltaic circle A, generated in the particle 6, hav- 

 ing a south pole issuing from its interior, must attract it. As both 

 these circles act obliquely upon N, above them, their tendency will 

 be to move the magnet horizontally, and in the direction of the re- 

 volving plate. 



2nd. Repulsion of the magnet perpendicularly from the plate. 

 In order to explain this fact, I do not consider it necessary to suppose, 

 with Faraday, that the currents require a certain portion of time for 

 generation j but simply, that they exist for a short period after their 

 creation, which, indeed, seems to follow as a matter of course. Pre- 

 suming that such is the fact, it is obvious that, in consequence of the 

 motion of the plate being necessarily much greater than that of the 

 magnet, the circle of repuhion R, gets under the magnet and forces 



it directly upwards. 



3rd. and 4th. Motion of the magnet towards the circumference and 

 centre of the plate. — If, during the revolution of the plate, the mag- 

 net be moved along the line C B towards B, the circle of repulsion 

 R, by the motion of the plate, gets more or less between the magnet 

 and the centre C, and hence repels it towards the circumference of 

 the plate : — but, when the magnet is made to approach C, the same 

 circle advances so as to pass between it and the circumference, and 

 thus compels the magnet to incline towards the centre. 



All these movements will, it is hoped, be sufficiently intelligible, by 



a reference to the figure, and the hypothesis is equally applicable, 



