﻿670 
  Prof. 
  J. 
  J. 
  Thomson 
  on 
  

  

  was 
  about 
  2*5 
  mm. 
  A 
  flat 
  piece 
  of 
  wire 
  gauze 
  was 
  fixed 
  

   parallel 
  to 
  the 
  upper 
  face 
  of 
  the 
  cathode 
  (the 
  face 
  most 
  

   remote 
  from 
  the 
  anode), 
  and 
  insulated 
  from 
  it 
  : 
  the 
  distance 
  

   of 
  the 
  gauze 
  from 
  the 
  cathode 
  was 
  about 
  3 
  mm. 
  The 
  Canal- 
  

   strahlen 
  travel 
  at 
  right 
  angles 
  to 
  the 
  lower 
  face 
  AB 
  of 
  the 
  

   cathode. 
  If 
  the 
  wire 
  gauze 
  is 
  connected 
  with 
  the 
  anode, 
  and 
  if 
  

   the 
  particles 
  in 
  the 
  Canalstrahlen 
  are 
  charged, 
  they 
  will 
  after 
  

   passing 
  through 
  the 
  cathode 
  be 
  acted 
  on 
  by 
  a 
  force 
  which 
  

   has 
  a 
  component 
  at 
  right 
  angles 
  to 
  their 
  direction 
  of 
  projection: 
  

   thus 
  if 
  they 
  are 
  positively 
  charged 
  they 
  will 
  be 
  bent 
  to 
  the 
  

   right, 
  if 
  they 
  are 
  negatively 
  charged 
  to 
  the 
  left, 
  while 
  if 
  they 
  

   are 
  uncharged 
  they 
  will 
  be 
  undeflected. 
  The 
  path 
  of 
  the 
  

   rays 
  when 
  the 
  pressure 
  of 
  the 
  gas 
  is 
  not 
  too 
  low, 
  can 
  readily 
  

   be 
  traced 
  by 
  the 
  luminosity 
  they 
  produce 
  in 
  the 
  gas 
  as 
  they 
  

   pass 
  through 
  it. 
  On 
  trying 
  the 
  experiment, 
  it 
  was 
  found 
  

   that 
  when 
  the 
  gauze 
  was 
  connected 
  with 
  the 
  anode 
  the 
  path 
  of 
  

   the 
  few 
  rays 
  which 
  got 
  through 
  the 
  gauze 
  was 
  a 
  straight 
  line, 
  

   coinciding 
  in 
  direction 
  with 
  their 
  path 
  before 
  passing 
  through 
  

   the 
  cathode. 
  An 
  easy 
  way 
  of 
  seeing 
  this 
  is 
  to 
  connect 
  by 
  means 
  

   of 
  a 
  key 
  the 
  gauze 
  in 
  quick 
  succession 
  with 
  the 
  anode 
  and 
  

   the 
  cathode, 
  when 
  it 
  is 
  easily 
  seen 
  that 
  though 
  the 
  Canal- 
  

   strahlen 
  are 
  much 
  more 
  numerous 
  in 
  the 
  latter 
  case 
  than 
  in 
  

   the 
  former, 
  the 
  paths 
  of 
  those 
  which 
  do 
  get 
  through 
  are 
  

   identical, 
  so 
  that 
  even 
  when 
  the 
  gauze 
  is 
  connected 
  with 
  the 
  

   anode 
  some 
  of 
  the 
  rays 
  get 
  through 
  the 
  space 
  between 
  cd 
  

   and 
  cf 
  without 
  suffering 
  any 
  deflexion, 
  showing 
  that 
  they 
  

   must 
  be 
  uncharged 
  as 
  they 
  pass 
  through 
  this 
  region. 
  It 
  is 
  

   thus 
  evident 
  that 
  a 
  considerable 
  number 
  of 
  the 
  positively 
  

   •charged 
  Canalstrahlen 
  lose 
  their 
  positive 
  charge 
  by 
  attract- 
  

   ing 
  when 
  in 
  the 
  neighbourhood 
  of 
  the 
  cathode 
  a 
  negatively 
  

   electrified 
  corpuscle 
  ; 
  the 
  mass 
  of 
  the 
  corpuscle 
  is 
  so 
  small 
  

   in 
  comparison 
  with 
  that, 
  of 
  the 
  particles 
  forming 
  the 
  Canal- 
  

   strahlen, 
  that 
  the 
  addition 
  of 
  the 
  corpuscle 
  will 
  not 
  materially 
  

   reduce 
  the 
  velocity 
  of 
  the 
  Canalstrahlen. 
  These 
  rapidly 
  

   moving 
  uncharged 
  particles 
  will 
  soon 
  get 
  ionized 
  by 
  collision, 
  

   and 
  by 
  losing 
  a 
  negatively 
  electrified 
  corpuscle 
  again 
  become 
  

   positively 
  charged. 
  

  

  In 
  my 
  first 
  paper 
  on 
  the 
  positive 
  rays 
  (Phil. 
  Mag. 
  xiii. 
  

   p. 
  561) 
  I 
  showed 
  that 
  at 
  not 
  too 
  low 
  pressures 
  the 
  appearance 
  

   presented 
  by 
  the 
  phosphorescence 
  on 
  the 
  screen 
  indicated 
  

   that 
  many 
  of 
  the 
  particles 
  in 
  the 
  Canalstrahlen 
  were 
  posi- 
  

   tively 
  charged 
  for 
  only 
  a 
  portion 
  of 
  their 
  path; 
  the 
  experiments 
  

   just 
  described 
  are 
  very 
  direct 
  evidence 
  of 
  this 
  effect. 
  

  

  Again, 
  at 
  not 
  too 
  low 
  pressures 
  the 
  Canalstrahlen 
  are 
  

   accompanied 
  by 
  negatively 
  electrified 
  particles 
  having 
  

   masses 
  and 
  velocities 
  equal 
  to 
  those 
  of 
  the 
  positive 
  particles 
  ; 
  

  

  

  