of Magnet iam : -jcith Notes hy Mr. Faraday. 411 



sidered as other than the consequence of a movement of the 

 same nature which takes place around each particle of the 

 magnetic metal. This induction seems sufficiently natural ; 

 and for its greater confirmation we have instituted the follow- 

 ing experiment: — a ring of copper was taken, and the two con- 

 joining wires intended to complete the communication with the 

 galvanometer soldered to it at the extremities of one of its 

 diameters. On placing this ring between the two poles of a 

 horse-shoe magnet, in the place where we introduced our 

 electro-dynamic spiral, motions were instantly manifested at 

 the galvanometer, due to the presence of currents excited by 

 the magnetism in the copper ring *. 



Our ideas being thus fixed relative to the circular currents, 

 which we believed ought to be produced in the mass of cop- 

 per submitted to the influence of the magnetic pole, let us pass 

 to the question of magnetism by rotation, the wonderful dis- 

 covery of M. Arago. Here we have magnetic poles in pre- 

 sence of a disc, which instead of being quiescent as in the pre- 

 ceding case, is continually moving on its own axis. The lat- 

 ter condition is the only one added, and by it we see that the 

 final result of the phaenomena will be excessively complicated, 

 but that in reality nothing new will happen. In all cases it 

 is the currents developed by the magnetism at the place of 

 the disc which is directly acted upon by this magnetism which 

 are concerned. This part is rapidly removed by the rotation, 

 and another comes forward, which is subjected to the same in- 

 fluence, which always tends to form currents in the contrary 

 direction to those which may be supposed to exist in the mag- 

 netic pole {Exp. Res. 53.255.). These currents, by their nature, 

 tend to be inverted so soon as they are withdrawn from the 

 presence of the cause which produced them, and are in fact 

 inverted every time that the velocity of rotation will permit 

 it. The theory of this species of magnetism appears mature f ; 

 we shall endeavour to develope its physical principles in a 

 more detailed manner in a separate paper, being content here 

 to state the particular character which distinguishes it from 



[• This experiment will bear another interpretation. 1 do not (as I un- 

 derstand the descri|)tion) believe the ring to have anything particular to 

 do with the result ; the whole appears to me a repetition of the experiment 

 1 have described (E.rp. lies. 10!)).— M. F.] 



[t Sig. Nobili and Antinori have mistaken the character of the acting 

 causes in Arago's experiment altogether; the view which they have briefly 

 expressed and mean to pursue, is precisely that which 1 at first entertained 

 and pursued, but which I soon found exiierimental reason to reject. How- 

 ever, I need merely refer here to the fourth divisi(<n of my first |)aper, ex- 

 pressly on that pbacnomenon, and to parts of the sixth division in the con- 

 tinuation of the Researches, for what 1 believe to be a true view of the 

 phaenomenon (sec especially E.vp. Res. 121. VZ'^. \^i'6.). — M. F.j 



.3 G 2 all 



