conductor, and a brimstone one at tlie otli^r, rrof a. 

 spark of fire can be obtained ; one receiving it in as- 

 fast as it is given out by the other. Hence also if a, 

 phial be suspended on the prime conductor, with a 

 chain from its coating to the table, and only one globe 

 turned, it will be electrified or charged as they term it) 

 by twenty turns of the wheel : after which it may be 

 discharged, thai is, unelect rifted, by twenty turns of the 

 other wheel. 



The difference between non electrics (vulgarly speak- 

 ing) and electrics per se, is chiefly this. 1 . A non electric 

 easily suffers a change in the quantity of fire it con- 

 tains. Its whole quantity may be lessened, by drawing 

 out a part, which it will afterwards resume. But you 

 ean only lessen the quantity contained in one of the 

 surfaces of an electric : and not that, bat by adding at 

 the same time an equal quantity to the other surface ; 

 so that the whole glass will always have the same 

 quantity ia its two surfaces. And even this can be only 

 done in glass that is thin : beyond a certain thickness 

 "we know no power that can make this change. 2. The 

 ethnical fire freely moves from place to place, in and 

 through the substance of a non-electric, but through the 

 guhstaice of an electric it will by no means pass. Jt 

 freely enters an iron rod, and moves from one end to 

 another, where the overplus is discharged. Bat it will 

 3iot enter, or move through a glass rod. Neither will 

 the thinnest glass whiclrean be made suffer any particle 

 of it eateii ig one of its surfaces to pass through to the 

 other. 



Indeed it is only metals and liquids that perfectly 

 conduct (or transmit) this lire. Otuer bodies seem to 

 conduct it only so far as they contain a mixture of 

 these ; accordingly, moist air will conduct it in pro- 

 portion to its moistnesvs. But dry air will not conduct 

 it at all: on the contrary, it is the main instrument in 

 confining any electric atmosphere to the body which it 

 Surrounds. Dry air prevents it dissipating (which it doe* 



