THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



OCTOBER 1891. 



XL I. On the Discharge of Electricity through Exhausted 

 Tubes without Electrodes. By J. J. Thomson, M.A., 

 F.P.S., Cavendish Professor of Experimental Physics, 

 Cambridge* 



THE following experiments, of which a short account was 

 read before the Cambridge Philosophical Society last 

 February, were originally undertaken to investigate the phe- 

 nomena attending the discharge of Electricity through Gases 

 when the conditions are simplified by confining the discharge 

 throughout the whole of its course to the gas, instead of, as 

 in ordinary discharge-tubes, making it pass from metallic or 

 glass electrodes into the gas, and then out again from the gas 

 into the electrodes. 



In order to get a closed discharge of this kind we must 

 produce a finite electromotive force round a closed circuit, 

 and since we cannot do this by the forces arising from a 

 distribution of electricity at rest, we must make use of the 

 electromotive forces produced by induction. To break down 

 the electric strength of the gas such forces must be very 

 intense while they last, though they need not last for more 

 than a short time. Forces satisfying these conditions occur 

 in the neighbourhood of a wire through which a Ley den jar 

 is discharged. During the short time during which the oscil- 

 lations of the jar are maintained enormous currents pass 

 through the wire, and as with a moderate-sized jar these 

 currents change their direction millions of times in a second, 



* Communicated by the Author. 

 Phil Mag. S. 5. Vol, 32. No. 197. Oct. 1891, Z 



