202 Mr J. D. FORBES on eliciting an Electric Spark, 



I afterwards procured. The intensity of light varies consider- 

 ably, as it depends on the degree of accuracy with which the 

 circuit is broken at the moment of contact. Sometimes it is 

 highly vivid, and has been seen some yards off in a dark place. 



As soon as I had the circumstances under my command, I 

 hastened to show the experiment to my brother, who was pre- 

 sent, and to Dr GREGORY, acting secretary of this Society. I 

 afterwards had the satisfaction of showing it to Dr HOPE, to Sir 

 JOHN LESLIE, and several other gentlemen. 



I have now stated, I hope not with fatiguing minuteness, the 

 mode by which I have arrived at a result of some interest for 

 science of that striking character, too, which at once seizes the 

 imagination and the attention, and which may even give it a de- 

 gree of importance superior to what, weighed in the balance of 

 calm philosophy, it may perhaps deserve. The multiplier and 

 the frog are to the eye of science as sure tests of an electric cur- 

 rent, as is the spark to the eye of sense. 



I beg to repeat, that the success of Signer NOBILI'S experi- 

 ment is only known to me through the medium of the public 

 prints ; I am quite ignorant of the channel by which the report 

 reached this country ; and, at all events, not the slightest clew 

 has been given as to his mode of arriving at the result. 



Let the minor circumstances turn out as they may, all who 

 have had any share in this interesting research, must agree in 

 giving to Mr FARADAY the great, almost the sole, merit of a dis- 

 covery, of which his researches formed the basis, and whose libe- 

 rality in throwing open to the scientific world an interesting 

 truth, which he might fairly have retained until he had worked 

 it out in its various details, merits as much praise as the origina- 

 lity and fertility of his genius. 



