Magnetic Deflection by common Electricity. 171 



alternations of this kind, the vibration increased to 40° or 

 more. 



303. On changing the direction of the current through the 

 galvanometer, the direction of the deflection of the needle was 

 also changed. In all cases the motion of the needle was the 

 same in direction as that caused by the use of an electric bat- 

 tery or a voltaic trough (300.). 



304. I now rejected the wet string, and substituted a cop- 

 per wire, so that the electricity of the machine passed at once 

 into wires communicating directly with the discharging train, 

 the galvanometer coil being one of the wires used for the 

 discharge. The effects were exactly those obtained above 

 (302.). 



305. Instead of passing the electricity through the system, 

 by bringing the discharging rod at the end of it into contact 

 with the conductor, four points were fixed on to the rod; 

 when the current was to pass, they were held about twelve 

 inches from the conductor, and when it was not to pass, they 

 were turned away. Then, except with this variation operat- 

 ing as before (302.), the needle was soon powerfully deflected, 

 and in perfect consistency with the former results. Points 

 afforded the means by which Colladon, in all cases, made his 

 discharges. 



306. Finally, I passed the electricity first through an ex- 

 hausted receiver, so as to make it there resemble the aurora 

 borealis, and then through the galvanometer to the earth; 

 and it was found still effective in deflecting the needle, and 

 apparently with the same force as before. 



307. From all these experiments, it appears that a current 

 of common electricity, whether transmitted through water or 

 wire, or rarefied air, or by means of points in common air, is 

 still able to deflect the needle ; the only requisite being, ap- 

 parently, to allow time for its action : that it is, in fact, just as 

 magnetic in every respect as a voltaic current, and that in this 

 character therefore no distinction exists. 



308. Imperfect conductors, as water, brine, acids, &c. &c. 

 will be found far more convenient for exhibiting these effects 

 than other modes of discharge, as by points or balls ; for the 

 former convert at once the charge of a powerfal battery into 

 a feeble spark, or rather continuous current, and involve little 

 or no risk of deranging the magnetism of the needles (294.) . 



[To be continued.] 



Z2 



