SWIFT ROTATIONS OF METALLIC PLATES. 



37 



paring the quantities of electricity produced, the 

 rotating metallic plate does not at all fall short of 

 the glass one ; for it produces a constant electric 

 current capable of turning a galvanometer needle, 

 which the latter cannot." 



The excitation induced by the swift rotation of 

 a metallic plate directly over, or beneath, a com- 

 pass needle, even with a non-conducting sheet of 

 glass intervening, turns the needle as regularly 

 as if it were fixed on the same axis. 



This experiment demonstrates that the circula- 

 tion of ekctric currents, artificially produced by 

 the rotation of one body near a-nother, is capable 

 of transmitting mechanical action even through 

 non-conducting glass. 



Soon after the publication of Faraday's experi- 

 ment made with the slow motion imparted by 

 hand, the writer employed water-power to rotate a 

 metallic plate several thousand times per minute. 

 An unexpected result occurred on using a circular 

 disc of soft Russia sheet-iron, when it touched a 

 steel magnet, as represented in Fig. 10. 



At the point of contact, the swift rotation of 

 the plate excited a steel-bar 

 magnet to a glowing red heat, 

 and large steel files yielded be- 

 fore the rotating disc of thin 

 sheet-iron, like wax before a 

 flame. The fused particles fell 

 on the floor beneath, while the Fig. 10. 



