THE 

 LONDON EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[STXTH SERIBS4- 

 APRIL 1901. 



. — ; " ' 0I ' 



XXXIII. On a hind of easily Absorbed Radiation produced by • 

 the Impact of slowly moving Cathode Rays; tog ether \%vitl^ 

 a Theory of the Negative Glow, the Dark Spare, and the 

 Positive Column. By J. J. Thomson, M.A., F.R.S., 

 Professor of Experimental Physics, Cambridge*. 



THE following investigation originated in an attempt to 

 find whether any radiation analogous to Rontgen 

 radiation was produced at the surfaces of the anode or 

 cathode — the places where the current through a rarefied gas 

 passes from the gas to the metal. 



For this purpose a tube like that shown in fig. 1 was 



Fisr.l. 



to£?ec£vme&r. 



3 



L 



used. One end of the tube was made of a brass plate A, 

 perforated with five holes placed near together ; the holes were 

 covered on the outside by very thin aluminium foil, '00013 cm. 

 thick. The face of the plate inside the tube was covered with 

 a disk of mica, with a hole cut in the middle sufficiently large 

 to allow the electric discharge to have access to the part of 

 the plate containing the holes. A long metal tube was 



* Communicated by the Author. 

 Phil Mag. S. 6. Vol. 1. No. 4. April 1901. 2 B 



