On Electric Phenomena. 7 



face of electricity in it. If we, however, fasten the rod to 

 handle of glass or sealing-wax, or if we WTap the part of 

 which we take hold in silk, and then rub it, it will become 

 strongly electrical, and we can observe all the same pheno- 

 mena which we learned from the piece of glass or the sealiag- 

 T^ax. 



As soon as we touch any part of it with the hand, then 

 all electricity immediately vanishes from it. If we continue 

 to rub a piece of sealing-wax or a glass rod at one end, and 

 then test another part, wliich has not been rubbed, with the 

 ball of pith, we shall find them quite non-electric. On the 

 <jontrary, if we rub a metallic rod which is fixed to a handle 

 of glass, in a certain place, and then test it in any other 

 part we may choose, it wiU show itself as electrical. The 

 tw^o bodies, glass and metal, manifest themselves quite dif- 

 ferently with regard to their relation towards electrical fluids. 

 p In metals, the electricity excited in one part, conveys it- 

 -self easily to another, and spreads itseK over the whole body; 

 in glass, the transition of the electricity finds a resistance; 

 therefore, the spreading of it takes place very slowly, or not 

 at all. Metal is therefore called a conductor of electricity; 

 on the contrary, glass, seahng-wax etc. are non-conductors or 

 itisidators. The human body is also a conductor. A rod of 

 metal rubbed with the hand, immediately sends the whole of 

 its electricity into the ground ; if, on the contrary, the rod is 

 fastened to a non-conductor, the electricity finds a boundary, 

 over which it cannot pass, and it remains in the metal ; there- 

 fore the metal, with which the experiment is made, must be 

 fastened to a piece of glass or sealing-wax, or hung up by a 

 silken cord, that is, to use the technical term, insulated. Air 

 is naturally a non-conductor, or else, through it all electricity 



(129) 



