370 WELLS'S NATURAL PHILOSOPHY. 



tract light bodies ; and the name electricity, used to designate such pheno- 

 mena has been derived from the Greek word tjXektpov, electron, signiiying 

 amber. 



What other ef- ^^ *^^ frictioii of the glass, wax, amber, etc., 

 tractiontreno- ^^ vigorous, Small strcams of light will be seen, 

 eiectricitr''b"/ ^ crackling noise heard, and sometimes a re- 

 friction? markable odor will be perceived. 

 whenisabody 733. When, by friction or other means, elec- 

 trified?''^ ^''"'' tricity is developed in a body, it is said to be 



electrified, or electrically excited. 

 What is electric The tendency which an electrified body has 



to move toward other bodies, or of other bodies 

 toward it, is ascribed to a force called electric attraction. 

 whatis electric Evcry electrified body, in addition to its at- 

 repuision? tractivc'forcc, manifests also a repulsive force. 

 This is proved by the fact that light substances, after 

 touching an electrified body, recede from it just as actively 

 as they approached it before contact. Such action is as- 

 cribed to a force called electric repulsion. 



* Thus, if we take a dry glass rod, rub it well 



Fig 308 j n ^ 



' with silk, and present it to a light pith ball, or 



feather, P, suspended from a support by a silk 

 thread, the ball or feather will be attracted to- 

 ward the glass, as seen at G, Fig. 308. After it 

 has adhered to it a moment, it will fly off, or be 

 repelled, as P' from G'. 



The same thing will happen if sealing-wax bo 

 rubbed with dry flannel, and a like experiment 

 made ; but with this remarkable difference, that 

 when the glass repels the ball, the sealing-wax attracts it, j-j^ ^q^ 

 and when the wax repels, the glass will attract. Thus if we 

 suspend a light pith baU, or feather, by a silk thread, as in 

 Fig. 309, and present a stick of excited sealing-wax, S, on 

 one side, and a tube of excited glass, G, on the other, the ball 

 will commence vibrating like a pendulum from one to the 

 other, being alternately attracted and repelled by each, the 

 one attracting when the other repels; hence we conclude 

 that the electricities excited in the glass and wax are different. 



784. As the electricity developed by the 



Is there more „ . . -. , , i -i-i i 



than one kind frictiou 01 glass and other like substances is 

 essentially difierent from that developed by 



