of Magnetism : with Notes by Mr. Faraday. 413 



thus quiescent, if a horse-shoe magnet be advanced towards 

 the plate so as to embrace it without interrupting its motion, 

 it will be seen that the deviation of the needle will augment or 

 diminish according as the poles act in the one direction or the 

 other. This effect is a sure proof ol the current manifested 

 in the disc by the action of the magnet : but because the wires 

 connected w th the galvanometer are arranged with their ends 

 in the direction of the radius of the disc, are we to conclude 

 that they are exactly in the direction in which the current 

 excited by the magnetism exists * ? We do not believe it, for 

 the reasons given above; and though we should, with Mr. 

 Faraday, admit this species of irradiating currents, there 

 would still exist for us a great difference between this mode 

 of exciting electricity, and the ordinary one of our common 

 electrical machines. There is here a great void to fill, in 

 passing from a superlative conductor, like the metallic disc of 

 M. Arago, to the worst, such as the glass plate of an ordi- 

 nary machine f. 



But these our particular opinions do not in any way dimi- 

 nish the intrinsic merit of Mr. Faraday's discovery. It is one 

 of the most beautiful of our time, whether it be considered in 

 itself for the largeness of the vacancy which it serves to fill, 

 or for the light which it throws over the various theories, and 

 especially that of magnetism of rotation. 



We hope that these our first researches will justify the 

 lively interest which we have taken in this new branch of 

 electro-dynamics. We have but one regret, namely, that of 

 having entered into a path before we knew all the steps taken 

 in it by the illustrious philosopher who threw it open. 

 Florence, Jan. 31, 1832. 



[• I have nowhere drawn such conclusions. — M. F.] 



[t The case of the currents tending to be formed, or really existing in 

 the direction of tiie radii throughout the whole plate, occurs only when the 

 axis of the magnet approached coincides with the axis of the revolving 

 plate {Exp. lies. 156. 158.), or when the magnetic curves intersected by tiie 

 revolving plate are of equal strength, and pass through all parts of the plate 

 in the same direction, as happens when the earth's magnetism is used as the 

 exciting cause (ii'.r/^. Res. 14!). 155 ). My reasons for calling the revolving 

 plate an electrical machine {Exp. Res. 154. 168.) are entirely untouched by 

 what is said in the text. 



It must not be supposed that in these notes I am criticizing Sig. Nobili 

 and Antinori for not understanding niy views. It was impossible that I could 

 |)ut forth in a brief letter, matter which, though I have condensed it as nuich 

 as possible, still occupies seventy quarto pages of the Philoso[)hical Transac- 

 tions ; and I may perhaps be allowed to say, (more in reference however to 

 what I think ought to be a general regulation than to the present case,) that 

 had I thought that that letter to M. Hachette would l)e considered as giving 

 the subject to the philosophical world for general pursuit, I should not have 

 written it; or at least not until after the publication oi my first pajirr.— M. !<'.] 



LVI. On 



