PHILOSOPHICAL SOCIETY OF WASHINGTON. 25T 



In the Philosophical Magazine for November, 1834, appeared 

 «, paper b\' Faraday, "On a peculiar condition of electric and 

 magneto-electric Induction:" in which he notices as a remark- 

 able fact, that while a short circuit wire from a single galvanic 

 element, gives little or no visible spark, a long conductor gives a 

 very sensible spark. "It is however very interesting thus to 

 observe an original current of electricity having a very low in- 

 tensity producing ultimately a counter current having an intensity 

 probably a hundred fold greater than its own, and the experi- 

 ment constitutes one of the very few modes we have at command 

 of converting quantity into intensity as respects electricity in cur- 

 rents." And he remarks: "If the connecting wire be much 

 lengthened, then the spark is much increased."* 



In this interesting research, Faraday appears to have entirely 

 overlooked Henry's earlier labors in tlie same field ; — as contrary 

 to his usual custom, he makes no allusion to the same results 

 having been obtained, and published in Silliman's Journal two 

 years and a half before, f These observations were made by 

 Faraday the subject of his "ninth series of Researches," in a 

 communication "On the influence by induction of an electric cur- 

 rent on itself:" read before the Royal Society January 29th 

 1835. In this paper he repeats, that with a single galvanic pair, 

 a short wire will not give a shock; while the wire surrounding 

 an electro-magnet will give a shock at each breaking of the cir- 

 cuit. He found a similar result with the wire helix alone, — with- 

 out its magnetic core "The power of producing these phe- 

 nomena exists therefore in the simple helix, as well as in the elec- 

 tro-magnet, although by no means in the same high degree." With 

 continuous straight wire of the same length, he obtained a similar 

 effect, — "yet not so bright as that from the helix " When a short 

 wire is used, "all these effects disappear;" although there is un- 

 doubtedly a greater "quantity" of electric current in the shorter 

 wire; thus giving "the strange result of a diminished spark and 

 shock from the strong current, and increased effects from the 

 weak one. "I 



While Henry derived only satisfaction from these extended 

 verifications of his own observations, by one whom he had ac- 

 customed himself to look up to with admiration and regard, Dr. 

 A. Dallas Bache, his attached friend, then Professor of Natural 

 Philosophy in the University of Pennsylvania,— more jealous 

 than himself of his scientific fame, strongly urged and insisted 

 that he should immediately publish an account of his later re- 

 searches. Henry accordingly sent to the American Philosophical 



* Philosoph Mag. Nov. 1834. vol. v. pp. 351, 352. 



t Sill. Aw. Jour Sci. .luly. 1832. vol. xxii. p. 408. above qtiotfd. 



t Phil. Trnna. Rm/ri/ Snr. .T^in. 20, 1835, vol. oxxv. art. 1061-10^7. and 

 1073, pp. 43-45. Er/ierhnental Refpnrr/ifis in Elpdrlcitii, vol. i. pp. 325-328. 

 This memoir did not reach this coautry of course till a year later. 



