1832] WRITINGS OF JOSEPH HENRY. 75 



Before having any knowledge of the method given in the 

 above account, I had succeeded in producing electrical effects 

 in the following manner, which differs from that employed 

 by Mr, Faraday, and which appears to me to develop some 

 new and interesting facts. A piece of copper wire, about 

 thirty feet long and covered with elastic varnish, was closely 

 coiled around the middle of the soft iron armature of the 

 galvanic magnet, described in vol. xix of the American 

 Journal of Science, and which, when excited, will readily 

 sustain between six hundred and seven hundred pounds. 

 The wire was wound upon itself so as to occupy only about 

 one inch of the length of the armature which is seven 

 inches in all. The armature, thus furnished with the wire, 

 was placed in its proper position across the ends of the gal- 

 vanic magnet, and there fastened so that no motion could 

 take place. The two projecting ends of the helix were 

 dipped into two cups of mercury, and there connected with 

 a distant galvanometer by means of two copper wires, each 

 about forty feet long. This arrangement being completed, 

 I stationed myself near the galvanometer and directed an 

 assistant at a given word to immerse suddenly, in a vessel 

 of dilute acid, the galvanic battery attached to the magnet. 

 At the instant of immersion, the north end of the needle 

 was deflected 30° to the west, indicating a current of elec- 

 tricity from the helix surrounding the armature. The ef- 

 fect however appeared only as a single impulse, for the 

 needle, after a few oscillations, resumed its former undis- 

 turbed position in the magnetic meridian, although the gal- 

 vanic action of the battery, and consequently the magnetic 

 power was still continued. I was however much surprised 

 to see the needle suddenly deflected from a state of rest to 

 about 20° to the east, or in a contrary direction when the 

 battery was withdrawn from the acid, and again deflected 

 to the west when it was re-immersed. This operation wn=! 

 repeated many times in succession, and uniformly with the 

 same result, the armature the whole time remaining im- 

 movably attached to the poles of the magnet, no motion 

 being required to produce the effect, as it appeared to take 

 place only in consequence of the instantaneous development 



