92 WRITINGS OF JOSEPH HENRY. [1835 



CONTEIBUTIONS TO ELECTEICITY AND MAGNETISM. No. II. 



ON THE INFLUENCE OF A SPIRAL CONDUCTOR IN INCREASING 

 THE INTENSITY OF ELECTRICITY FROM A GALVANIC ARRANGE- 

 MENT OF A SINGLE PAIR, ETC. 



(Transactions American Philosophical Society, n. s., vol. v, pp. 223-231.) 

 Read February 6th, 1835. 



In the American Journal of Science for July, 1832, 1 an- 

 nounced 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 1834. 



The phenomenon as described by me is as follows : " When 

 a small battery is moderately excited by diluted acid, and its 

 poles, terminated by cups of mercury, are connected by a 

 copper wire not more than a foot in length, no spark is per- 

 ceived when the connection is either formed or broken ; but 

 if a wire thirty or forty feet long be used instead of the short 

 wire, though no spark *will be perceptible when the connec- 

 tion is made, yet when it is broken by drawing one end of 

 the wire from its cup of mercury, a vivid spark is produced. 

 If the action of the battery be very intense, a spark will be 

 given by a short wire ; in this case it is only necessary to 

 wait a few minutes until the action partially subsides, and 

 until no more sparks are given from the wire; if the long 

 wire be now substituted a spark will be again obtained. 

 The effect appears somewhat increased by coiling the wire 

 into a helix; it seems also to depend in some measure on 

 the length and thickness of the wire. I can account for 

 these phenomena only by supposing the long wire to be- 

 come charged with electricity, which by its re-action on 

 itself projects a spark when the connection is broken."* 



The above was published immediately before my removal 

 from Albany to Princeton, and new duties interrupted for 



*Silliman's Journal of Science, vol. 22, page 408. [See ante, p. 79.] 



