to account for the Phanomenn of Electricity . 405 



rendered inadmissihle by other mfepences that may be drawn. 

 Thus, in charging a pliial, the quantity of natural electricity to be 

 changed, is, as Mr. Eeles su])poses, equal on both sides. The re- 

 sistance to the change on each side is the attraction of dissimilar 

 powers : the dissimilar powers combined in the natural state 

 being on each side equal in quantity and in force of combination, 

 the resistance on both sides must be the same. The quantities 

 on one side attracted, and on the other repelled, are equal. 

 Now the resistances aud quantities attracted and repelled being 

 equal, it follows that the separate forces of attraction and re- 

 pulsion are equal. This will beconie more evident when the 

 theory of charging the Leyden phial comes to be examined. 



The remaining part of this principle maintains, that when the 

 contrary ]3owers meet in ecjual proportions, they condense each 

 other in the form of flame, and no longer display sensiljle pro- 

 perties. Previously to the application of this to the Leyden 

 phial, it will be necessary to consider the quantity of each fluid 

 on the surfaces of the glass. The phial in its natural state con- 

 tains an equal quantity of each power on its surfaces, and each 

 surface contains equal quantities of both powers. During the 

 process of charging, the action of the electric machine is to 

 withdraw from the inside one of the natural quantities of either 

 fluid, and to communicate an equal quantity of a power con- 

 trary to what was abstracted, but similar to what remained of 

 the natural- portion after the aljstraction. Hence, when a phial 

 is charged in the usual manner l)efore the negative power, half of 

 the whole sensible charge must be thrown in from the conductor, 

 before the negative power can be all drawn out. 



From the principle under consideration, it appears that con- 

 trary powers in equal proportions destroy each others properties. 

 Kvery positive spark thrown from the conductor into the phial 

 must combine with an equal quantity of negative electricity de- 

 rived from the natural combination, and thus the properties of 

 the spark thrown in should be destroyed or suspended. Yet 

 experience proves, that if any quantity of positive electricity, how 

 .small soever, be thrown into a phial, the surface receiving it 

 will evince unquestionable indications of being positively elec- 

 trified. 



3. Goncerning the third principle Mr. Eeles observes, that 

 Franklin supposes glass to be impervious to the electric jjovver : 

 he adds, " this may be confuted by so easy experiments that I am 

 surprised that Mr. Franklin could have missed them. Take a 

 piece of bog down, suspend it by silk, then take a pane of clean 

 sash-ghiss, and warm it, and let the down hang by the side of 

 it ; then bring an excited electric to the other side of the ghiss, 

 and the down shall fly off perfectly electrified.— This shows that 



C c 3 the 



