WINTER'S ELECTRICAL MACHINE. 



595 



charged with positive electricity by induction from the 

 glass plate, the induced negative electricity being dis- 

 charged through the points across the intervening air 

 to the plate and neutralising its positive electricity. 



The rubber as it appears when seen from the left side of fig. 315, 

 is represented in fig. 316 A.- The wooden block has a rectangular 

 piece cut out of the middle and is open at the top, so that the plate 

 may pass through it without touching the wood. 



Within this frame, on each side of the plate, is a cushion, consist- 

 ing of an oblong wooden board, to which a piece of thick soft felt is 

 glued. On the outside of each board, between it and the frame, 



FIG. 316 (B an. proj. ; A and B | real size). 



there is a metal spring which presses the board with moderate force 

 against the glass plate. As the plate turns, the rubbers are pre- 

 vented from being forced out of the frame through the friction by 

 projecting ledges which press against the frame when the plate is 

 turned in the direction of the arrow. At B one of the rubbers is 

 shown separately, I being the ledge, / the metal spring ; the wing of 

 silk attached to the rubber is left out in this figure. If the rubbers 

 are to be taken out, it is only necessary to turn the plate in the 

 opposite direction and they will come out of themselves. When 



Q Q 2 



