of Magnetic and Non-magnetic Bodies. 4<27 



current ; experiment confirms this. With regard to the in- 

 terruptions in the intensity of the sound in this last case, after 

 the continuous current has ceased to pass, they are probably 

 attributable to the fact that the particles, disturbed from their 

 natural position for a longer or shorter time, only return after 

 a more or less prolonged series of oscillations, which the un- 

 interrupted action of the discontinuous current favours. 



In aid of the explanation which I have just given, I will 

 add that, having covered a copper wire with an iron en- 

 velope which was contiguous to it, and, so to say, plated, I 

 obtained, by passing the discontinuous current through the 

 copper wire, the same effects, excepting intensity, as if the 

 wire had been entirely of iron ; only the sound was not mu- 

 sical, but resembled that which would have been emitted by 

 filings strongly agitated. As this result might be attri- 

 buted to the fact that a part of the current traversed the 

 iron covering itself, instead of circulating exclusively through 

 the copper wire, I isolated this last by means of a layer of silk 

 or wax, so that the thin cylinder of sheet-iron which sur- 

 rounded it was not in metallic communication with the copper. 

 The effect was exactly the same as in the preceding case ; 

 that is to say, the copper wire being traversed by a disconti- 

 nuous current, caused a series of vibrations, or dry and me- 

 tallic sounds, in the iron covering. This covering underwent, 

 therefore, a transversal magnetization analogous to that which 

 the surface of a wire entirely of iron experiences ; this, indeed, 

 was easily proved from the fact, that the iron-filings were at- 

 tracted on the two sides of a small longitudinal slit which this 

 covering presented in some parts of its surface, and that the 

 two margins possessed an opposite magnetic polarity. All these 

 effects were more marked when a continuous current, going 

 in the same direction as the discontinuous one, was transmitted 

 through the copper wire ; they ceased entirely as soon as the 

 two currents no longer passed. This increase in intensity of 

 the sound produced by the passage of the continuous current 

 was due to the fact that the discontinuous current had not 

 alone, from acting at a distance, power enough to surmount 

 the coercitive force of the iron covering, which itself was very 

 much hardened, and that it needed the aid of the continuous 

 current to impress a transversal position on the particles of the 

 iron. 



Before concluding this first part of my researches, I must 

 again observe, that the passage of a continuous current, passing 

 in a contrary direction to the discontinuous one, diminishes 

 the sound instead of destroying it completely, when the wire 

 submitted to the experiment is of soft iron ; it modifies without 



