42 



Proceedings of the Royal Irish Academy. 



Variation oj 'uctionofi ving surface, 



and with pressurt between surfo ■ 



The Hist point investigated with the apparatus just described was the etl'eet 

 of the speed of the moving surface on the rate o\ production of electricity. 

 Low speeds were first investigated, the metal cap being fixed so that it was 

 rubbed by a length of 6 inches of .-ilk in each revolution. The results with 

 platinum, iron, and silver, rubbing on silk and getting in each case a negative 

 charge, are shown on fig. 1. 



* 



£ 



- 

 - 



FIG I . 

 MetalsHonSilk 



N° of Revolutions of Disc per sec (l Re* "'6 inches) 



19 20 



It i- ind from others not reproduced in the paper, 



that for small speeds the rate of production is proportional t" the excess of 



n small value which differs f'>r different metals. The 



relative notion for different metals undei the same pressure would 



therefore diffi ling to the speed of the rubbing . The maximum 



- in h_r 1 is only 12 inches per Becond. 



II - i ire then dealt with. The circumference of the circle which 



the metal cap travelled "\er in one revolution was now 2 feet, ami 28 revolu- 



tioi ■ <>m1<1 1* obtained from the motor, giving a maximum speed 



of the nibbing snrfai second. In stating the result- we must 



°ingui8h between cases where the metal got a positive charge and cases 



