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THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



Fio-. 1. 



[SIXTH SERIES.] 



MAY 1907. 



XL VII. On Rays of Positive Electriei 

 By J. J. Thomson, M.A., F.R.S.* 



IN 1886 Goldstein discovered that when the cathode in a 

 discharge -tube is perforated, rays pass through the 

 openings and produce luminosity in the gas behind the 

 cathode ; the colour o£ the light depends on the 

 gas with which the tube is filled and coincides 

 with the colour of the velvety glow which 

 occurs immediately in front of the cathode. 

 The appearance of these rays is indicated in 

 fig. 1, the anode being to the left of the 

 cathode KK. Since the rays appeared through 

 narrow channels in the cathode, Goldstein called 

 them " Kanalstrahlen " : now that we know 

 more about their nature, "positive rays" would, 

 I think, be a more appropriate name. Gold- 

 stein showed that a magnetic force which would 

 deflect cathode rays to a very considerable 

 extent was quite without effect on the " Kanal- 

 strahlen/' By using intense magnetic fields, 

 "W. Wien showed that these rays could be 

 deflected, and that the deflexion was in the 

 opposite direction to that of the cathode rays, indicating 

 that these rays carry a positive charge of electricity. 

 This was confirmed by measuring the electrical charge 

 received by a vessel into which the rays passed through 

 a small hole, and also by observing the direction in which 

 * Communicated by the Author. 

 PKil. Mag. S. 6. Vol. 13. No. 77. May 1907. 2 Q 



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