588 ACTION OF POINTS. 



and the greatest tension is obtained when the extremity 

 of the conductor is an actual point. 



Move the two corks upon the wire nearer to the ring 

 and push the wire into the tube so that the ring may be 

 in contact with the ball. Arrange the electroscope upon . 

 some support so that its knob may be 30 cm from the 

 point of the wire, and charge the conductor strongly by 

 drawing the rubbed glass rod repeatedly along its 

 surface. The gold leaves will diverge. Discharge the 

 conductor by touching it with the hand. The diverg- 

 ence becomes smaller but does not disappear altogether, 

 although no electricity exists in the conductor. It 

 follows that the electroscope has been charged and that 

 the electricity must have passed into it from the point. 

 Discharge the electroscope and place it by the side of 

 the conductor, instead of opposite the pointed wire, 

 with its knob 4 cm from the sphere and charge the con- 

 ductor as strongly as in the previous experiment. The 

 gold leaves will again diverge, but they will imme- 

 diately drop when the conductor is again discharged. 

 It follows that in the latter experiment no electricity 

 has been actually transferred to the electroscope from 

 the conductor; the divergence was solely a consequence 

 of inductive action. 



The density of the electricity at a point, and hence the 

 tension, is so great that the electricity passes to the 

 particles of the surrounding air; these become electri- 

 fied and convey the charge of the point like so many 

 intermediate conductors to surrounding conductors. 

 This action proceeds gradually. If the finger or any 

 other conducting body be slowly brought near the point 

 until it touches it, the electricity of the conductor dis- 



