i6 Sig. Dal Negro's Magneto-electric Experiments, 



sophers Nobili and Antinori, it occurred to me to examine 

 the effect of an ordinary magnet on similar spirals at the mo- 

 ment when one of the poles traversed the axis of the spiral 

 {Erp. Res. 39. 41. Hi.)? and I obtained such results as indi- 

 cated the path which it would be proper for me to follow, in 

 order to profit by this new property of magnetism. Ultimately 

 I succeeded in constructing a new electrometer, by means of 

 which the efficacy of the instantaneous currents discovered by 

 the celebrated Faraday may be augmented without limit, and 

 obtained in succession with such celerity as to render (as it 

 •were) continual the action of these currents*. He [Dr. Fusi- 

 nieri] has already witnessed the principal part of these my ex- 

 periments, and more than once has been so good as to assist 

 me faithfully in registering the results, and has solicited a 

 description that might be made public. I did not hesitate 

 to make a brief exposition that might be transmitted and in- 

 serted in the forthcoming number of his Journal. He returned 

 from us as quickly as possible, and did not forget to take with 

 him the magnet I had promised. 



His most affectionate friend, 

 Padua, April 20, 1832. Salvatoke Dal Negro. 



New Experimetits, Sj-c. Sfc. 



1. Place a cylindrical tube of paper surrounded by a spiral 

 of silk-covered copper wire upright upon a little table, and 

 connect the extremities of the spiral with a very sensible gal- 

 vanometer, constructed according to the method of Signor 

 Nobili : introduce the north pole of an ordinary horse-shoe 

 magnet into the axis of the cylinder, and an electric current 

 will be obtained, which will act strongly on the galvanometer. 

 {Exp. Res. 39. 147.) On withdrawing the pole of the magnet, 

 a current, in the contrary direction, will be obtained (Exp. 

 Res. 39.). On repeating the experiment with the south pole, 

 currents will be manifested in the contrary direction {Exp. 

 Res. 114. &c.) to those caused by the north pole, and less 

 powerful, as has been observed. 



2. Introduce into the same spiral the north pole of a more 

 powerful magnet than the first, and the conflict will pro- 

 duce a much greater effect; I say, "conflict," because the 



December 21, 1831. As my brief letter to M. Haclietteis continually taken 

 instead of my memoirs as representing my views of magneto-electricity, 

 I venture to add a few notes and references to this paper, in the same man- 

 ner as I have done to the paper by Signori Nobili and Antinori, at page 

 401. of the last volume of the Phil. Mag. and Annals.— M. F.] 



[* I have described at length a different but perfect way of obtaining a 

 continuous current by magneto-electric induction. {Exp. Res. 1)0. 154. 

 loo. 156. &c.)- M.F.J 



