68 



ALTERNATING CURRENTS 



of 120. Between B and L is interposed a damping vane of mica. 

 The cylinder B carries a glass tube GT, through which passes a 

 suspending band. This is taken round a pulley, and supports a 

 counterweight. The glass vessel containing the fixed and movable 

 systems is completely filled with resin oil, which provides the 



DAMPING VANE 



OYABLE PAN 



MICA INSULATION 



FIXED PLATE- 

 FIG. 47. Volt Balance. 



dielectric strength necessary to prevent a disruptive discharge at 

 these high voltages. 



In Fig. 49 is shown a further recent example of an instrument 

 intended to measure very high voltages. As in the case of the 

 instrument just described, the working parts are completely immersed 

 in oil. The instrument is constructed by the Westinghouse Co., and 

 has recently been described by Kintner.* The movable system con- 

 sists of two hollow cylinders with hemispherical caps attached to 

 the ends of a light cross-arm; spring control is used. The fixed 



* Electrical WoM and Enyinetr, vol. xlv. p. 117G (1905). 



