THE PHENOMENA OF ELECTROSTATICS. 



201 



110, The frictional electric machine. This machine consists of 

 a rotating glass disk DD, Fig. 126, the various parts of which 

 come in succession into intimate contact with two leather 

 cushions AA which are impregnated with an amalgam of tin, 

 zinc and mercury. The surface of the glass plate as it leaves 

 these cushions is left highly charged with positive electricity, and 



side view 



top view 



Fig. 126. 



the cushions are left negatively charged. The negative charge 

 flows into the insulated conductor N which is connected to the 

 cushions by means of the metal springs SS, and the positive 

 charge is carried on the surface of the glass disk to the collecting 

 combs CC whence it flows into the insulated conductor P. 

 Two silk aprons pp, one on each side of the rotating disk, tend 



