﻿S38 
  Sir 
  J. 
  J. 
  Thomson 
  on 
  

  

  mixture, 
  would 
  be 
  less 
  than 
  the 
  observed 
  velocity 
  of 
  the 
  

   positive 
  ion, 
  which 
  was 
  about 
  that 
  of 
  a 
  charged 
  hydrogen 
  

   atom. 
  It 
  is 
  clear, 
  then, 
  that 
  the 
  positive 
  ion 
  is 
  not 
  the 
  

   molecule 
  of 
  methyl 
  iodide. 
  Thus 
  the 
  ionization 
  of 
  the 
  methyl 
  

   iodide 
  has 
  produced 
  positive 
  ions 
  which 
  are 
  not 
  molecules 
  of 
  

   methyl 
  iodide. 
  It 
  might 
  perhaps 
  be 
  urged 
  that 
  the 
  molecules 
  

   of 
  methyl 
  iodide 
  which 
  were 
  positively 
  charged 
  to 
  begin 
  

   with, 
  have, 
  by 
  the 
  electric 
  force 
  they 
  exert, 
  pulled 
  a 
  corpuscle 
  

   out 
  of 
  the 
  neighbouring 
  hydrogen 
  molecule, 
  and 
  that 
  this 
  

   corpuscle 
  neutralizes 
  the 
  methyl 
  iodide 
  molecule 
  and 
  leaves 
  

   the 
  hydrogen 
  molecule, 
  from 
  which 
  it 
  has 
  escaped, 
  with 
  the 
  

   positive 
  charge. 
  There 
  are 
  several 
  objections 
  to 
  this 
  view 
  

   of 
  which 
  I 
  will 
  only 
  mention 
  one. 
  The 
  result 
  of 
  this 
  process 
  

   is, 
  by 
  the 
  electrical 
  forces 
  between 
  the 
  molecules 
  of 
  methyl 
  

   iodide 
  and 
  hydrogen, 
  to 
  transfer 
  the 
  charge 
  from 
  the 
  larger 
  

   system 
  (the 
  methyl 
  iodide 
  molecule) 
  to 
  the 
  smaller 
  (the 
  

   hydrogen 
  molecule). 
  

  

  Since 
  the 
  potential 
  energy 
  of 
  a 
  given 
  charge 
  is 
  greater 
  

   when 
  the 
  charge 
  is 
  on 
  a 
  small 
  system 
  than 
  when 
  it 
  is 
  on 
  

   a 
  large 
  one, 
  the 
  change 
  under 
  consideration 
  would 
  involve 
  

   an 
  increase 
  in 
  the 
  potential 
  energy, 
  and 
  would 
  therefore 
  not 
  

   be 
  brought 
  about 
  by 
  the 
  action 
  of 
  the 
  electrical 
  forces. 
  

  

  The 
  results 
  obtained 
  by 
  Wellisch 
  are 
  exactly 
  what 
  we 
  

   should 
  expect 
  if 
  there 
  were 
  a 
  definite 
  positive 
  unit 
  of 
  

   electricity 
  which 
  could, 
  like 
  the 
  corpuscle, 
  be 
  detached 
  from 
  

   the 
  molecule 
  of 
  the 
  gas. 
  I 
  have 
  elsewhere 
  suggested 
  that 
  

   the 
  process 
  of 
  ionization 
  consists 
  in 
  the 
  detachment 
  of 
  a 
  

   neutral 
  doublet 
  from 
  the 
  molecule, 
  the 
  doublet 
  consisting 
  of 
  

   a 
  positive 
  unit 
  and 
  a 
  corpuscle, 
  and 
  that 
  this 
  breaks 
  up 
  into 
  

   its 
  components, 
  which 
  subsequently 
  attach 
  themselves 
  to 
  the 
  

   molecules 
  by 
  which 
  they 
  are 
  surrounded. 
  

  

  Slowly 
  moving 
  Positive 
  Rays 
  and 
  the 
  Size 
  of 
  the 
  Carriers. 
  

  

  The 
  slowly 
  moving 
  rays 
  were 
  studied 
  in 
  the 
  following 
  

   way 
  : 
  — 
  The 
  gas 
  at 
  a 
  very 
  low 
  pressure 
  was 
  ionized 
  by 
  the 
  

   cathode 
  rays 
  emitted 
  from 
  a 
  Wehnelt 
  cathode 
  W 
  (fig. 
  7, 
  p. 
  829) 
  . 
  

   By 
  means 
  of 
  a 
  feeble 
  electric 
  field 
  between 
  the 
  plate 
  D, 
  called 
  

   the 
  collector, 
  and 
  a 
  piece 
  of 
  wire 
  gauze 
  /, 
  the 
  positive 
  ions 
  

   were 
  then 
  driven 
  through 
  this 
  gauze, 
  which 
  was 
  distant 
  about 
  

   •5 
  mm. 
  from 
  the 
  top 
  of 
  the 
  plate 
  d. 
  

  

  Between 
  this 
  gauze 
  and 
  the 
  top 
  of 
  the 
  plate 
  was 
  the 
  

   potential 
  relied 
  upon 
  to 
  give 
  the 
  positive 
  ions 
  their 
  velocity. 
  

  

  The 
  difference 
  of 
  potential 
  between 
  the 
  collector 
  plate 
  and 
  

   the 
  gauze 
  was 
  10 
  volts, 
  that 
  between 
  the 
  gauze 
  and 
  d 
  varied 
  

   from 
  40 
  to 
  200 
  volts. 
  There 
  was 
  a 
  very 
  small 
  hole 
  in 
  the 
  

  

  