M7' Lahy, A string electrometer. 



109 



the sensitiveness (deflection per volt) was observed for a range of 

 plate potential differences. With a new tension the same observa- 

 tions were repeated. In this way the equal tension potential 

 difference-sensitiveness curves (figs. 2 and 3) were obtained. The 



S- '0 



Potential difference between plates in volts 

 Fig. 3. 



sensitiveness is expressed in eye-piece divisions per volt on the 

 fibre: one eye-piece division =-0012 cm. movement of the fibre 

 itself. These curves express many of the properties of the instru- 

 ment. We see from them that a high sensitiveness was obtained 

 with the fibre not very tight (curves 1, 2, figs. 2 and 3), which in- 

 creased with the P.D. between the plates to its greatest value in fig. 3 

 for 18 volts, when the sensitiveness was 60. There is a practical 



