Mr Wilson, On a Sensitive Gold- Leaf Electrometer. 137 



which one point was connected to the case, allowed the potential 

 of the gold-leaf to be varied as desired. The current through the 

 potentiometer was supplied by a storage cell. 



When the plate was maintained at a potential of 207 volts and 

 the apparatus was tilted to give the maximum sensitiveness (the 

 plate being then inclined at an angle of about 30° to the vertical) 

 a change of potential of one volt caused the gold-leaf to move 

 almost completely across the 120 divisions of the micrometer scale, 

 and the sensitiveness over the central portion of this range 

 exceeded 200 divisions per volt. The curve (fig. 2) shows the 

 relation between the deflections, read on the horizontal scale of the 

 eye-piece micrometer, and the potential of the gold-leaf, the case 

 being earthed and the plate kept at 207 volts. The crosses and 

 circles indicate observations taken in ascending and descending 

 order respectively. 



Fig. 3 shows the results obtained when the gold-leaf was kept 

 in metallic connexion with the plate and the potential of the plate 

 was varied over a wide range ; a low-power microscope was used 



80 



120 



160 



200 



240 



Volts 

 Fig. 3. 



for these observations. It will be observed that the change in 

 deflection in passing from 207 to 209 volts is as great as the whole 

 deflection for 207 volts. 



For any particular angle of tilt of the apparatus there is a 



