540 PROF. HENRY ON THE INFLUENCE OF A SPIRAL CONDUCTOR 



would be much stronger, and assist in destroying the remaining weaker 

 magnetism in the other magnet. There would therefore be a moment 

 when the magnetism became = 0, and at that moment I expected that 

 the armature would be disengaged, and then be attracted to the active 

 electro-magnet. However, this interval was of such momentary du- 

 ration that the armature remained attached to the passive magnet. I 

 then took, instead of the armature of soft iron, a steel magnet of exactly 

 the same form and shape, and placed it so that its poles were always 

 opposite to the similar poles of the electro-magnets ; but even with 

 this alteration the same result took place ; it also happened when the 

 electric current was sent at the same time, but in an opposite direction, 

 to the other electro-magnet. As the power of the electro-magnet was 

 considerably greater than that of the steel magnet, I could not expect 

 to obtain more powerful effects than I had obtained with the soft iron. 

 At last I determined to prevent any possible contact between the arma- 

 ture and the electro-magnets : this I effected by wrapping the armature 

 up in papei", so as always to keep it at a small distance from the poles 

 of the magnet. The result was now quite satisfactoiy. I also enveloped 

 the steel magnet in the same way, and it appeared to me that with the 

 first-mentioned armature the motion was quicker and more energetic 

 than with the latter. If we consider that electro-magnets have already 

 been made which were capable of carrying 20 cwt., and that there is 

 no reason to doubt that they may be made infinitely more powerful, I 

 think I may assert boldly that electro-magnetism may certairdy be em- 

 ployed for the purpose of moving machines. 



On the Influence of a Spiral Conductor in increasing the In- 

 tensity of Electricity from a Galvanic Arrangement of a 

 Single Pair, Sfc. By Professor Henry, of Neiv Jersey, 



U. ^S* 



XN the American Journal of Science for July 1832, I announced a 

 fact in Galvanism which I believe had never before been published. 

 The same fact, however, appears to have been since observed by Mr. 

 Faraday, and has lately been noticed by him in the November number 

 of the London and Edinburgh Journal of Science for 1 834. 



The phaenomenon as described by me is as follows : " When a small 



* Read before the American Philosophical Society, Feb. Gth, 1835. — This 

 has been annoxed to the preceding papers as being referred to in them, and as 

 a sHglit notice of ^t only has appeared in this country : sec Phil. Mag. and 

 Annals, vol. x. p. 314. 



