CH. iv.] BY CATHODE RAYS 37 



matter, the surface or boundary of the matter acting 

 as the locality for an electric charge ; and no other 

 locality for a charge was known. The facts of 

 electrolysis had suggested or proved that the atoms 

 themselves could carry charges, and hence that if a 

 liquid were electrified, it must be due to some of the 

 atomic charges of one sign, appearing in overbalancing 

 proportion at the surface ; though perhaps still in 

 association with their respective atoms. 



Yet at the same time the occurrences at an 

 electrode, where an ion plainly gave up its charge 

 and escaped without it, indicated the possibility that 

 perhaps the electric charge could exist alone ; at any 

 rate that it could be handed from one atom to 

 another, and thus might conceivably exist alone for 

 an instant. During this momentary isolation some 

 charges might, in the freedom of a rarefied gas 

 discharge, possibly escape, and wander about free. 



To such hypothetical isolated charges, the unit 

 charge or charge of a monad atom, the name 

 "electron" had been given ; and when I speak of an 

 "electron" I mean to signify the, at first purely 

 hypothetical, isolated electric charge. Whereas by 

 the term "ion" I always signify the atom and its j 

 charge together. The ions consist of Faraday's anions 

 and cations. Lord Kelvin prefers the term electrion 

 to electron. 



Now if the flying particles which constitute the 

 cathode rays were electrons rather than ions, if they 

 were detached charges, leaving their atoms behind 

 them (necessarily leaving those atoms positively 

 charged), their extreme mobility and diffusiveness 

 and high speed would be perfectly natural ; and 

 although they would not be ' matter ' in the ordinary 

 sense, yet no difficulty need be felt at their possessing 



