330 ' Leyden Pbial. [Book IV. 



about two inches from the top) with tinfoil, or any 

 other conducting fubftance. 



If one fide of this jar is electrified, while the other 

 fide communicates with the earth, it is faid to be 

 charged. 



When a communication is formed from one fide of 

 the jar to the other by a conducting fubftance, .after it 

 has been charged, an explofion will take place, and 

 this is called difcharging the jar. .This phial is inca- 

 pable of being charged when it is infulated j that is, 

 when neither fide communicates with the earth. When 

 it is charged, the two fides are in contrary Rates, the 

 one being pofitively, the other negatively electrified. 



A jar is faid to be pofitively electrified when the in- 

 fide receives the fluid from the conductor, and the 

 outfide is connected with the earth. It is negatively 

 electrified when the outfide receives the fluid from the 

 conductor, and the infide communicates with the 

 earth ; but it is neceflary that the jar charging nega- 

 tively fhould be infulated, becaufe the fluid is, in the 

 firft inftance, conveyed to the coating, and would be 

 immediately carried to the earth if it was not infu- 

 lated. 



The moft ufual forms of the Leyden phial are re- 

 prefented in Fig. 3. and 5.^ Plate XXVI i. and its 

 nature may be exemplified by the following experi- 

 ment: 



Place the phial (Fig. 5.) on an infulated ftand; bring 

 the coating in contact with the conductor ; turn the 

 machine (lowly, and after a few turns remove the phial 

 from the conductor ; then form a communication be- 

 tween the outfide and the infide of the phial, by plac- 

 ing one end of the difcharging rod firft upon the coat- 

 'ing, and then bringing the other end of the rod to the 

 brafs ball of the bottle ; in this cafe there will be no 



explofion, 



