Chap. 3. 



CHAP. III. 



OF THE VITREOUS AND RESINOUS, OR 

 POSITIVE AND NEGATIVE ELECTRI- 

 CITY. 



DiJiinSlion in the attrafti-Tje Powers of certain EleRrics. Tbefe 

 Ejfefts found to depend not on the Nature of the Subftance, but the 

 Roughnefs or Smoothness of the Surface. Theory of Two diJtinB 

 Fluids, Franklin's Theory, Difficulties attending it. 



IN a very early ftage of the fcicnce, we have feen, 

 that a diftinction was obfervcd with refpect to the 

 attractive and repulfive powers of certain electric bo- 

 dies. Thus if we electrify with the fame fubftance, 

 for inftance, either with excited glafs or with fealing 

 wax, two cork balls in an infulated flate, that is, fuf- 

 pended by filk lines about fix inches long, the balls 

 will feparate and repel each other j but if we electrify 

 one of the balls with glafs, and the other with fealing 

 wax, they will be mutually attracted. This circum- 

 ftance gave rife to the opinion, that two different fpe- 

 ci'es'of electricity exifted, and the one was termed the 

 vitrt'jus electricity, or that produced from glafs ; and 

 the other, which was produced from fealing wax, re- 

 fmous fubftances, and fulphur, was termed ihe refinous 

 electricity. 



Subsequent experiments ferved to mew, that in the 

 common ekctrical machine, the rubber exhibited the 

 appearances of the refmous electricity, and the cylin- 

 der that of the vitreous, while the former was con- 

 nected with. the earth. A divergent cone or brufh of 

 electrical light was obferved to be the obvious mark 

 Y 2 of 



