22 NOMOS. 



back again along the earth to the point from which 

 we started the rubber. On further inquiry we 

 find, also, that the action which is exercised by the 

 lining of the jar upon the coating is exercised by 

 the " conductor " upon bodies at a distance, as upon 

 the walls of the room in which the machine is 

 worked, and that in this case the intervening air 

 performs the same insulating office as the glass. In 

 short, induction is the term which is used to express 

 the passage of electricity across non-conductors, and 

 conduction is the term for expressing the same 

 passage through conductors. In other words, con- 

 duction is an action between contiguous particles ; 

 induction^ an action at a distance. 



If now we continue to work the machine, we find 

 that there is a limit beyond which the Leyden jar 

 cannot be charged. Beyond this limit we get dis- 

 charge ; that is to say, the electricity in the lining 

 of the jar combines with the electricity in the coating 

 of the jar, and both disappear with the production of 

 light, heat, magnetism, and certain chemical pheno- 

 mena. Or the same discharge may be produced by 

 connecting the lining and coating of the jar by some 

 conductor, when the discharge takes place princi- 

 pally by conduction. In either case, the electricity 

 is said to travel round the circle, and this travelling 

 is spoken of as a current. Before discharge there 

 is no current, and what the actual state is it is not 

 easy to understand. It is generally spoken of, how- 

 ever, as a state of tension. It is apparently the 

 electro-tonic state of Dr. Faraday. 



In galvanism the electricity is generated, not by 



