Mr. "W. R. Pidgeon on an Influence-Machine. 269 



being displaced from the positions they would occupy were 

 the sectors radial so as to touch the latter at the right moment. 

 In order to increase the capacity of each sector while re- 

 ceiving its charge, two stationary inductors are placed opposite 

 each disk, one at each of the points where the sectors on that 

 disk are earthed. Each inductor consists of a sheet of tin- 

 foil imbedded in wax and supported on a disk of ebonite, and 

 is charged from a pin-point connected to it through an 

 ebonite tube ; this pin-point stands opposite to the outer 

 knobs on another part of the large disk, where their sign and 

 potential are such as are required to charge the inductor. 

 Each sector at the moment of being earthed is thus placed 

 between two similarly charged inductors, — the sectors on 

 the opposite disk on the one side and the fixed inductor on 

 the other, each of which is large in comparison with itself ; 

 its capacity is thereby greatly increased and it is enabled to 

 carry forward a much larger charge of electricity than it can 

 when the stationary inductors are removed. 



The effect produced on the output of the machine by using 

 these stationary inductors is remarkable, for though they 

 practically make no difference to the length of the sparks, 

 they greatly increase their apparent thickness ; and with 

 other things precisely similar they increase their frequency 

 three-fold. To compare the output of the machine with and 

 without the stationary inductors, I counted the number of 

 sparks which overflowed a Leyclen jar, and the revolutions of 

 the disks, for 30 seconds, both when using the inductors and 

 when they were taken off, and I was careful, in every case, 

 to keep the speed of the disks as nearly as possible constant. 

 I thus found that a 25 -ounce Leyden jar overflowed 19 times 

 in 80 seconds without inductors and 54 times with them ; or, 

 making a slight correction for the revolutions of the disks 

 being less in the second case, the output was increased as 

 3 to 1 by the use of the inductors. The explanation of this 

 greatly increased output is, I think, to be sought in the fact 

 that connecting the positive and negative terminals of this 

 machine does not stop its action, as it does in the case of the 

 Wimshurst machine, and that it is therefore ready to start 

 sparking, with almost full vigour, the moment they are sepa- 

 rated. For when the inductors are removed, and two or three 

 Leyden jars connected to the terminals, it is perfectly easy to 

 note the discharge of the disks with each spark, and the time 

 they take to recover, slowly at first and very rapidly at last, 

 depending on the size of the condensers they are charging ; 

 but when the fixed inductors are replaced the recovery is very 

 much more rapid, especially in its early stages, owing 1 



