﻿658 
  

  

  Prof. 
  J. 
  J. 
  Thomson 
  on 
  

  

  described 
  in 
  a 
  paper 
  read 
  before 
  the 
  Physical 
  Society 
  of 
  Berlin 
  

   (republished 
  Phil. 
  Mag. 
  Mar. 
  1908), 
  has 
  led 
  him 
  to 
  distinguish 
  

   five 
  kinds 
  of 
  rays 
  besides 
  the 
  cathode 
  rays. 
  Recent 
  experi- 
  

   ments 
  made 
  by 
  Villard 
  (Comptes 
  Mendus, 
  cxliii. 
  p. 
  673, 
  1906) 
  

   and 
  the 
  author 
  (Phil. 
  Mag. 
  xiv. 
  p. 
  359, 
  1907) 
  have 
  shown 
  

   that 
  some 
  of 
  these 
  rays 
  are 
  deflected 
  in 
  electric 
  and 
  strong 
  

   magnetic 
  fields, 
  and 
  the 
  direction 
  of 
  the 
  deflexion 
  indicates 
  

   that 
  they 
  carry 
  a 
  positive 
  charge 
  of 
  electricity. 
  The 
  

   fact 
  that 
  these 
  positively 
  charged 
  rays 
  travel 
  with 
  high 
  

   velocities 
  away 
  from 
  the 
  cathode, 
  and 
  thus 
  against 
  the 
  

   direction 
  of 
  the 
  electric 
  force, 
  makes 
  the 
  investigation 
  of 
  

   their 
  properties 
  a 
  very 
  interesting 
  problem, 
  and 
  I 
  have 
  

   lately 
  made 
  a 
  series 
  of 
  experiments 
  with 
  the 
  object 
  of 
  obtain- 
  

   ing 
  some 
  information 
  as 
  to 
  their 
  nature 
  and 
  origin. 
  

  

  The 
  tube 
  used 
  in 
  the 
  first 
  series 
  of 
  experiments 
  is 
  repre- 
  

   sented 
  in 
  fig. 
  1. 
  A 
  is 
  a 
  perforated 
  electrode 
  through 
  which 
  

  

  rays 
  can 
  pass 
  on 
  their 
  way 
  to 
  the 
  phosphorescent 
  screen 
  S 
  

   covered 
  with 
  Willemite 
  ; 
  the 
  rays 
  on 
  their 
  journey 
  to 
  the 
  

   screen 
  traverse 
  strong 
  electric 
  and 
  magnetic 
  fields, 
  the 
  

   former 
  produced 
  by 
  charging 
  the 
  plates 
  LM 
  to 
  different 
  

   potentials 
  and 
  the 
  latter 
  by 
  placing 
  the 
  tube 
  between 
  the 
  

   poles 
  of 
  a 
  powerful 
  electromagnet. 
  From 
  the 
  deflexions 
  

   which 
  these 
  produce 
  on 
  the 
  rays, 
  the 
  velocities 
  and 
  values 
  of 
  

   e/m 
  for 
  the 
  rays 
  can 
  be 
  determined 
  in 
  the 
  usual 
  way. 
  B 
  is 
  

   a 
  flat 
  electrode 
  at 
  the 
  other 
  end 
  of 
  the 
  tube 
  ; 
  this 
  electrode 
  

   is 
  carried 
  by 
  a 
  stopper 
  working 
  in 
  a 
  ground-glass 
  joint, 
  and 
  

   can 
  be 
  rotated 
  about 
  a 
  vertical 
  axis. 
  C 
  is 
  an 
  auxiliary 
  elec- 
  

   trode 
  at 
  the 
  side 
  of 
  the 
  tube. 
  D 
  is 
  a 
  side 
  tube 
  in 
  which 
  a 
  

   metallic 
  obstacle 
  is 
  placed 
  at 
  the 
  end 
  of 
  a 
  rod, 
  this 
  end 
  is 
  

   fastened 
  to 
  a 
  closed 
  glass 
  vessel 
  containing 
  a 
  piece 
  of 
  iron. 
  

   By 
  moving 
  this 
  vessel 
  along 
  D 
  by 
  means 
  of 
  a 
  magnet, 
  the 
  

   obstacle 
  can 
  either 
  be 
  inserted 
  in 
  the 
  line 
  of 
  fire 
  of 
  the 
  rays 
  

  

  