204 Mr J. D. FORBES on eliciting an Electric Spark 



The notice of Signer NOBILI'S experiment, to which I have 

 alluded in my paper as having reached me whilst my investi- 

 gations were in progress, was that contained in the Literary 

 Gazette for March 24, stating simply the report of the fact, 

 though without naming any authority. I learn from Mr PARA- 

 DAY, that it appeared there by a circuitous channel of informa- 

 tion, actually derived from Signer NOBILI'S communication to 

 himself. The first information I had of NOBILI'S method of 

 making the experiment, which was in its simplest form almost 

 the same with my own, and explained in terms nearly identical, 

 was not till the Annaks de Chimie for December reached my 

 hands, which was on the 30th of April, when the foregoing paper 

 was in the press. 



I take this opportunity of adding, that the experiment upon 

 the frog, simply mentioned above, was made at the suggestion 

 and with the assistance of Dr HOPE, on the 3d of April. It 

 appears from Mr FARADAY'S paper*, that he was not successful 

 in exciting muscular action by Dr KNIGHT'S great compound 

 magnet belonging to the Royal Society, but he afterwards ob- 

 tained the effect by making a very sudden rupture of contact of 

 the armature of a smaller magnet. The same result was obtained 

 by NOBILI and ANTINORI-J-, who justly remark the striking proof 

 which it affords of the extreme delicacy of the Frog Galvanome- 

 ter, since the magneto-electric currents (to use the language of 

 FARADAY) resemble the thermo-electric ones in the very great 

 difficulty with which they pass through moist conductors. 



Finally, as far as yet known, no one except Signori NOBILI 

 and ANTINORI and myself have yet obtained the spark from the 

 natural or permanent magnet. This, indeed, must be in a 

 great measure owing to the power of the magnets we have been 



* Article 56. 



f Annales de Chimie, Dec. 1831, p. 425. 



