2 PROCEEDINGS OF THE AMERICAN ACADEMY 



Matteucci,* Guillemin,t Wertheim,| "\Vartraann,§ Janniar,]| Joiile,11 

 Laborde,** Legat,tt Reis,tl PoggeiidorfF,§§ Du Moucel,|||| Dele- 

 zenne,1[ir and others.*** 



2. In the autumn of 1874, I discovered that the sounds emitted by 

 an electro-magnet under the influence of a discontinuous current of 

 electricity are not due wholly to sudden changes in the magnetic con- 

 dition of the iron core (as heretofore supposed), but that a portion of 

 the effect results from vibrations in the insulated copper-wires composing 

 the coils. An electro-magnet was arranged upon circuit with an in- 

 strument for interrupting the current, — the rheotome being placed 

 in a distant room, so as to avoid interference with the experiment. 

 Upon applying the ear to the magnet, a musical note was clearly per- 

 ceived, and the sound persisted after the iron core had been removed. 

 It was then much, feebler in intensity, but was otherwise unchanged, 

 — the curious crackling noise accompanying the sound being well 

 marked. 



The effect may probably be explained by the attraction of the coils 

 of the wire for one another during the passage of the galvanic current, 



* Matteucci. Inst., 1845, p. 315 ; Arch, cle I'Electr., V., 389. 

 t Gui/leniin. Corap. Rend., XXII., p. 264; Inst., 1846, p. 30; Arch. d. So. 

 Phys. (2d series), I., p. 191. 



I G. Wertheim. Comp. Rend., XXII., pp. 336, 544; Inst., 1846, pp. 65, 100; 

 Pogg. Ann., LXVIII.,p. 140; Comp. Rend., XXVI., p. 505; Inst., 1848, p. 142; 

 Ann. de Chim. et de Phys., XXIII., p. 302; Arch. d. Sc. Phys. et Nat., VIII., 

 p. 206 ; Pogg. Ann., LXXVII., p. 43 ; Borl. Ber., IV., p. 121. 



§ Elie ]Vartmann. Comp. Rend., XXII., p. 544; Phil. Mag. (3d series), 

 XXVIII., p. 544; Arch. d. Sc. Phys. et Nat. (2d series), I., p. 419; lust., 1846, 

 p. 290; Monatscher. d. Berl. Akad., 1846, p. 111. 



II Janmar. Comp. Rend., XXIII., p. 319; Inst., 1846, p. 269; Arch. d. Sc. 

 Phys. et Nat. (2d series), II., p. 394. 



IF J. P. Joule. Piiil. Mag., XXV., pp. 76, 225 ; Berl. Ber., III., p. 489. 



** Lahorde. Comp. Rend., L., p. 692; Cosmos, XVII., p. 514. 



tt Legal. Brix. Z. S., IX., p. 125. 



\X Reis. " Te'le'phonie." Polytechnic Journ., CLXVIII., p. 185; Bottger's 

 Notizbl., 1863, No. 6. 



§§ J. C. Poggendorff. Pogg. Ann., XCVIII., p. 192; Berliner Monatsber., 

 1856, p. 133 ; Cosmos, IX., p. 49 ; Berl. Ber., XII., p. 241 ; Pogg. Ann., 

 LXXXVII., p. 139. 



nil Du Moncel. Expose, II., p. 125; also. III., p. 83. 



Tn[ Delezenne. " Sound produced by Magnetization," Bibl. Univ. (new series), 

 1841, XVI., p. 406. 



*** See London Journ., XXXII., p. 402; Polytechnic Journ., CX., p. 16; 



Cosmos, IV., p. 43 ; Glosener Traite' gene'ral, &c., p. 350 ; Dove.-Repert.,VI., 



p. 58 ; Pogg. Ann., XLIII., p. 411 ; Berl. Ber., I., p. 144; Arch. d. Sc. Phys. et 

 Nat., XVI., p. 406 ; Kuhn's Encyclopedia der Physik, pp. 1014-1021. 



