DISCOURSE OF W. B. TAYLOR. 237 



experiment of drawing sparks from the magnet by Mr. James D. 

 Forbes of Edinburgh, who obtained a sparicon the 30tli of March:* 

 my experiments being made during the last two weeks of June. 

 A simple notification of his result is given, without any account of 

 the experiment, Avhich is reserved for a communication to the Royal 

 Society of Edinburgh. My result is therefore entirely independent 

 of his, and was undoubtedly obtained by a different process." f 



Henry's gratification at the acquisition of the new insight into 

 natural law, quite absorbed all sentiment of personal pride in its 

 independent attainment; and his appreciation ' and congratulation 

 of Faraday as the first discoverer of magneto-electricity, were 

 hearty and unreserved. He was also particular always to assign to 

 Faraday the first observation of the curious phenomena of mo- 

 mentary galvanic induction; although himself an independent 

 discoverer of the fact. 



Discovery of the "Extra Current." — In the course of these experi- 

 ments he made a very important original observation on a peculiar 

 case of self-induction, whereby he was enabled to convert a galvanic 

 current of "quantity" into one of "intensity." This entirely new 

 result seemed to contradict all previous experience. He thus con- 

 cludes his paper: 



" I may however mention one fact which I have not seen noticed 

 in any work, and which appears to me to belong to the same class of 

 phenomena as those above described. It is this: — when a small 

 battery is moderately excited by diluted acid and its poles (which 

 should be terminated by cups of mercury) are connected by a cop- 

 per wire not more than a foot in length, no spark is perceived 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 connection is made, yet when it is 

 broken by drawing one end of the wire from its cup of mercury, a 

 vivid spark is produced. - - - The effect appears somewhat 

 incrctiscd by coiling the wire into a helix: it sterns also to depend 

 in some measure on the length and thickness of the wire. I can 



* Philosoph. Mag. and Annals, May, 1832, vol. xl. pp. 359, 360. 

 tSllliman's Am. Jour. Set. July, 1832, vol. xxii. pp. 403-108. 



