114 THE ROYAL SOCIETY OF CANADA 



It is easy for negative electricity as electrons, to leave a white 

 hot filament, difficult for negative electricity to return to it within 

 the exhausted bulb. 



When a positive body moves towards the lamp, a number of 

 electrons readily leave the filament by induction. As the positive 

 body is moved from the glass, it is necessary for equilibrium either 

 that electrons should return to the filaments, or that positive ions 

 should move to them. This is only possible at a very slow rate. 

 The filaments therefore are repelled, and open outwards like the two 

 leaves of a common gold-leaf electroscope, and for the same reason. 

 They gradually close owing to a small ionization current in the highly 

 exhausted bulb. This ionization current can be greatly increased 

 by bringing some radium near the lamp, hence the more rapid return 

 to the rest position. The result of this investigation may be sum- 

 narized thus: If the electric equilibrium demands that negative 

 electricity should leave the loops the equilibrium is achieved by an 

 escape of electrons. If equilibrium requires that positive electricity 

 should leave the loops, then this cannot take place otherwise than 

 slowly; the loops themselves are displaced until equilibrium is attained. 



