58 Additional Notes. 



VII. The spark from the conductor, and of electric light. 



When either the vitreous or resinous electric ether is accumulated 

 on an insulated conductor, and an uninsulated conductor, as the finger 

 of an attendant, is applied nearly in contact with it, what happens? 

 The attractive and repulsive powers of the accumulated electric ether 

 pass through the nonconducting plate of air, and if it be of the vitreous 

 kind, it attracts the resinous electric ether of the finger towards it, 

 and repels the vitreous electric ether of the finger from it. 



Hence there exists for an instant a charged plate of air between 

 the finger and the prime conductor, with an accumulation of vitreous 

 ether on one side of it, and of resinous ether on the other side of it; 

 and lastly these two kinds of electric ethers suddenly unite by their 

 powerful attraction of each other, explode, and give out heat and 

 light, and rupture the plate of nonconducting air, which separated 

 them. 



The rupture or disjunction of the plate of air is known by the 

 sound of the spark, as of thunder; which shows that a vacuum of air 

 was previously produced by the explosion of the electric fluids, and 

 a vibratio^i of the air in consequence of the sudden joining again of 

 the sides of the vacuum. 



The light which attends electric sparks and shocks, is not accounted 

 for by the Theory of Dr. Franklin. I suspect that it is owing to the 

 combination of the two electric ethers, from which as from all chemi- 

 cal explosions both light and heat are set at liberty, and because a 

 smell is said to be perceptible from electric sparks, and even a taste 

 which must be deduced from new combinations, or decompositions, 

 as in other explosions : add to this that the same thing occurs, when 

 electric shocks are passed through eggs in the dark, or through water, 

 a luminous line is seen like the explosion of a train of gunpowder; 

 lastly, whether light is really produced in the passage of the Galvanic 

 electricity through the eyes, or that the sensation alone of light is 

 perceived by its stimulating the optic nerve, has not yet been inves- 

 tigated; but I suspect the former, as it emits light from its explo- 



