I 673 ] 



.XLVIII. 



AN APPARATUS POP THE PRODUCTION OP HIGH STATIC 



VOLTAGES. 



By J. J. DOWLING, MA. 



(University College, Dublin). 



Bead November 25, 1919. Published January 2, 1920. 



In the course of recent work I required a steady potential difference of 

 several thousand volts, maintained between a pair of insulated plates. It 

 was inconvenient to employ a battery of accumulators, in view of the 

 excessive number necessary. The following apparatus was devised for the 

 purpose, and has answered so well that it seems worth while giving a 

 description of it: — 



In principle it is the " condensing electroscope " of Volta, operated in a 

 continuous manner by mechanical means. The same principle was employed 

 by Einstein 1 in an apparatus designed for a slightly different purpose, namely, 

 to multiply up minute potential differences so as to render them measurable 

 with comparatively insensitive electrostatic voltmeters. I had at one time 

 constructed an apparatus on the same lines as Einstein ; but when I became 

 aware of his paper, I did not further pursue the matter. However, when my 

 present necessities arose, I tried my original machine to see whether it was 

 capable of producing a sufficiently high potential for my purpose. 



In this machine a brass inductor-plate, mounted on the face of an ebonite 

 disc, was revolved in its own plane past a fixed plate, kept at a steady 

 potential by a battery. Contacts were made by suitably situated springs, so 

 as (1) to earth the inductor-plate when it passed opposite the charged plate, 

 and (2) to connect the inductor, when it had moved away from the fixed 

 plate, with the apparatus to be charged. 



I found, however, that, in consequence of the potential of the inductor- 

 plate rising rapidly, while the plates were still close together, there was a 

 limit to the maximum potential obtainable. With the machine in question 

 1500 volts was about the highest steady potential obtainable, above which 

 sparking sec in between the plates. 



1 Eiustein, Phys. Zeitschr. 9 (21G-217), April 1, 1908. 



SCIEN'f. PROC. R.D.S., VOL. XV., NO. XLVIII. 5 M 



