1835] WRITINGS OF JOSEPH HENRY. 87 



FACTS IN REFERENCE TO THE SPARK, ETC., FROM A LONG CON- 

 DUCTOR UNITING THE POLES OF A GALVANIC BATTERY.* 



(Journal of the Franklin Institute, March, 1835, vol. xv, pp. 169, 170.) 



Extraatfi'om the proceedings of the stated meefuig of the American Philo- 

 sophical Society, January IG, 1835.t 



The following facts in reference to the spark, shock, &c., 

 from a galvanic battery of a single pair when the poles are 

 united by a long conductor, were communicated by Prof 

 Joseph Henry, and those relating to the spark were illus- 

 trated experimentally: 



1. A long wire gives a more intense spark than a short 

 one. There is however with a given surface of zinc a length 

 beyond which the effect is not increased ; a wire of one hun- 

 dred and twenty feet gave about the same intensity of spark 

 as one of two hundred and forty feet. 



2. A thick wire gives a larger spark than a smaller one of 

 the same length. 



3. A wire coiled into a helix gives a more vivid spark 

 than the same wire when uncoiled. 



4. A ribbon of copper, coiled into a flat spiral, gives a 

 more intense spark than any other arrangement yet tried. 



*To THE Committee on Publications. 



Gentlemen : The American Philosophical Society, at their last stated 

 meeting, authorized the publication of the following abstract of a verbal 

 communication made to the Society by Professor Henry on the sixteenth of 

 January last. A memoir on this subject has been since submitted to the So- 

 ciety containing an extension of the subject, the primary fact in relation to 

 which was observed by Professor Henry as early as 1832, and announced by 

 him in the American Journal of Science (vol. xxii, p. 408). Mr. Faraday 

 having recently entered upon a similar train of observations, the immediate 

 publication of the accompanying is important, that the prior claims of our 

 fellow-countryman may not be overlooked. 



Very respectfully, yours, 



A. D. Bache, 

 One of the Secretaries Am,. Philos. Soc. 



Philadelphia, Feb. 7th, 1835. 



t[The Minutes of the Am. Phil. Soc. from 1743-1837 have only recently 

 been published, (1885,) the first volume of the published "Proceedings" 

 commencing with 1838.] 



