﻿Positive 
  Rays. 
  083 
  

  

  quantity 
  of 
  gas 
  shows 
  that 
  it 
  is 
  due 
  to 
  the 
  alteration 
  in 
  

   pressure 
  and 
  not 
  to 
  a 
  change 
  produced 
  by 
  the 
  discharge 
  in 
  

   the 
  surface 
  of 
  the 
  electrode. 
  This 
  can 
  also 
  be 
  proved 
  in 
  the 
  

   following 
  way 
  : 
  two 
  discharge-tubes 
  A 
  and 
  B 
  are 
  connected 
  

   together 
  and 
  with 
  the 
  pump, 
  and 
  the 
  pressure 
  is 
  adjusted 
  so 
  

   that 
  both 
  A 
  and 
  B 
  show 
  the 
  lag 
  ; 
  then 
  if 
  the 
  discharge 
  is 
  sent 
  

   through 
  A 
  until 
  the 
  lag 
  disappears 
  from 
  that 
  tube, 
  it 
  will 
  be 
  

   found 
  to 
  have 
  simultaneously 
  disappeared 
  from 
  B, 
  though 
  no 
  

   discharge 
  has 
  been 
  running 
  through 
  this 
  tube. 
  

  

  It 
  is 
  somewhat 
  remarkable 
  that 
  we 
  do 
  not, 
  when 
  the 
  tube 
  

   is 
  filled 
  with 
  oxygen, 
  get 
  any 
  trace 
  in 
  the 
  Canalstrahlen 
  of 
  

   particles 
  having 
  masses 
  comparable 
  with 
  those 
  of 
  the 
  ions 
  in 
  

   oxygen. 
  For 
  though 
  such 
  ions 
  would 
  not 
  be 
  formed 
  in 
  very 
  

   intense 
  electric 
  fields, 
  there 
  are 
  places 
  in 
  the 
  discharge-tube 
  

   where 
  the 
  electric 
  field 
  is 
  weak, 
  as, 
  for 
  example, 
  outside 
  the 
  

   cathode 
  dark 
  space 
  ; 
  we 
  might 
  expect 
  positive 
  ions 
  to 
  be 
  

   formed 
  in 
  these 
  regions, 
  and 
  then 
  dragged 
  by 
  the 
  electric 
  

   field 
  up 
  to 
  and 
  through 
  a 
  perforated 
  cathode 
  mingling 
  with 
  

   the 
  Canalstrahlen. 
  The 
  reason 
  that 
  we 
  get 
  no 
  evidence 
  of 
  

   these 
  oxygen 
  ions 
  in 
  the 
  Canalstrahlen 
  is, 
  I 
  think, 
  as 
  follows 
  : 
  

   Let 
  A 
  be 
  a 
  positive 
  ion, 
  B 
  a 
  corpuscle, 
  and 
  let 
  the 
  relative 
  

   velocity 
  of 
  A 
  and 
  B 
  at 
  the 
  instant 
  under 
  consideration 
  be 
  at 
  

   right 
  angles 
  to 
  AB 
  and 
  equal 
  to 
  V. 
  Then 
  it 
  is 
  easy 
  to 
  show 
  

  

  mV 
  2 
  . 
  e 
  2 
  

  

  that 
  A 
  and 
  B 
  will 
  not 
  part 
  company 
  if 
  —^- 
  is 
  less 
  than 
  -p~ 
  , 
  

  

  where 
  m 
  is 
  the 
  mass 
  and 
  e 
  the 
  charge 
  of 
  the 
  corpuscle, 
  M 
  the 
  

  

  mass 
  of 
  the 
  ion 
  being 
  supposed 
  very 
  large 
  compared 
  with 
  m. 
  

  

  Thus 
  if 
  the 
  relative 
  velocity 
  falls 
  below 
  a 
  certain 
  value 
  the 
  

  

  ion 
  and 
  the 
  corpuscle 
  will 
  form 
  a 
  neutral 
  doublet 
  and 
  will 
  

  

  cease 
  to 
  be 
  a 
  possible 
  constituent 
  of 
  the 
  Canalstrahlen. 
  If 
  

  

  the 
  ion 
  is 
  moving 
  much 
  more 
  rapidly 
  than 
  the 
  corpuscle, 
  

  

  then 
  V 
  will 
  be 
  the 
  velocity 
  of 
  the 
  ion, 
  and 
  we 
  see 
  that 
  the 
  

  

  smaller 
  this 
  velocity 
  the 
  more 
  likely 
  is 
  it 
  to 
  have 
  its 
  charge 
  

  

  neutralized. 
  M 
  being 
  the 
  mass 
  of 
  the 
  ion 
  ^MV 
  2 
  = 
  P^, 
  where 
  

  

  P 
  is 
  the 
  potential-difference 
  moved 
  through 
  by 
  the 
  ion, 
  thus 
  

  

  M 
  e 
  

   the 
  ion 
  will 
  be 
  neutralized 
  unless 
  P 
  > 
  — 
  . 
  -^ 
  . 
  Thus 
  to 
  

  

  m 
  An 
  

  

  protect 
  a 
  heavy 
  ion, 
  for 
  which 
  Mj 
  is 
  large, 
  from 
  being 
  

  

  neutralized 
  it 
  must 
  be 
  subject 
  to 
  a 
  much 
  stronger 
  electric 
  

  

  field 
  than 
  would 
  be 
  necessary 
  for 
  a 
  light 
  ion 
  ; 
  thus, 
  if 
  there 
  

  

  were 
  a 
  mixture 
  of 
  different 
  gases 
  in 
  the 
  discharge-tube, 
  the 
  

  

  ions 
  formed 
  from 
  the 
  lighter 
  gases 
  would 
  persist 
  longer 
  than 
  

  

  those 
  formed 
  from 
  the 
  heavier 
  ones. 
  

  

  An 
  illustration 
  of 
  this 
  result 
  is 
  furnished 
  by 
  the 
  fact 
  that, 
  

  

  as 
  I 
  showed 
  in 
  the 
  paper 
  (Phil. 
  Mag. 
  ser. 
  5, 
  vol. 
  xiii. 
  p. 
  561), 
  

  

  