﻿448 
  Sir 
  J. 
  J. 
  Thomson 
  on 
  

  

  showing 
  that 
  at 
  this 
  stage 
  the 
  electric 
  force 
  is 
  positive 
  

   throughout 
  the 
  tube. 
  This 
  repulsion 
  o£ 
  the 
  cathode 
  rays 
  is 
  

   however 
  only 
  momentary 
  : 
  the 
  spot 
  jumps 
  back, 
  and 
  after 
  a 
  

   very 
  short 
  interval 
  the 
  spot 
  is 
  attracted 
  towards 
  the 
  cathode, 
  

   showing 
  that 
  the 
  force 
  in 
  this 
  region 
  is 
  now 
  negative. 
  Thus 
  

   during 
  this 
  interval 
  the 
  ions 
  in 
  the 
  gas 
  and 
  those 
  clinging 
  to 
  

   the 
  walls 
  of 
  the 
  tube 
  have 
  rearranged 
  themselves 
  in 
  such 
  a 
  

   way 
  as 
  to 
  reverse 
  the 
  force 
  in 
  the 
  field. 
  This 
  momentary 
  

   deflexion 
  is 
  much 
  more 
  perceptible 
  near 
  the 
  anode 
  than 
  some 
  

   distance 
  away 
  from 
  it 
  ; 
  the 
  rearrangement 
  seems 
  to 
  spread 
  

   from 
  the 
  cathode^ 
  and 
  to 
  be 
  established 
  so 
  rapidh^ 
  close 
  to 
  

   that 
  electrode 
  that 
  there 
  is 
  no 
  time 
  to 
  observe 
  it_, 
  while 
  as 
  we 
  

   travel 
  away 
  from 
  the 
  cathode 
  the 
  steady 
  state 
  is 
  reached 
  after 
  

   longer 
  and 
  longer 
  intervals, 
  and 
  there 
  is 
  time 
  to 
  observe 
  the 
  

   initial 
  distribution 
  of 
  the 
  electric 
  field. 
  

  

  We 
  see 
  that 
  the 
  result 
  of 
  the 
  experiments 
  with 
  tlie 
  cathode 
  

   rays 
  is 
  to 
  confirm 
  the 
  indications 
  of 
  the 
  w^ire 
  detector, 
  even 
  

   when 
  the 
  main 
  current 
  is 
  travelling 
  against 
  the 
  electric 
  force. 
  

   That 
  the 
  wdres 
  in 
  this 
  case 
  should 
  indicate 
  the 
  potential 
  is 
  

   very 
  remarkable, 
  and 
  must 
  be 
  due 
  I 
  think 
  to 
  the 
  pre- 
  

   sence 
  in 
  the 
  discharge 
  of 
  slowly 
  moving 
  ions 
  in 
  addition 
  to 
  

   the 
  swiftly 
  moving 
  ones 
  which 
  carry 
  the 
  main 
  portion 
  of 
  

   the 
  current, 
  having 
  acquired 
  in 
  other 
  parts 
  of 
  the 
  field 
  

   sufficient 
  impetus 
  to 
  carry 
  them 
  for 
  some 
  distance 
  against 
  

   an 
  opposing 
  electric 
  force. 
  The 
  slowly 
  moving 
  ions 
  would 
  

   be 
  produced 
  by 
  the 
  collisions 
  of 
  the 
  quick 
  ones, 
  and 
  those 
  

   produced 
  near 
  the 
  tips 
  of 
  the 
  wire 
  electrodes 
  would 
  follow 
  

   the 
  lines 
  of 
  electric 
  force 
  near 
  the 
  w^ire 
  and 
  equalize 
  the 
  

   potentials 
  between 
  the 
  w^ire 
  and 
  the 
  gas. 
  

  

  The 
  great 
  change 
  in 
  the 
  electric 
  force 
  which 
  occurs 
  at 
  the 
  

  

  bright 
  fronts 
  of 
  the 
  striations 
  shows 
  that 
  in 
  these 
  regions 
  we 
  

  

  have 
  a 
  great 
  accumulation 
  of 
  negative 
  electricity, 
  w^hile 
  the 
  

  

  distribution 
  of 
  the 
  electric 
  force 
  in 
  other 
  parts 
  of 
  the 
  striations 
  

  

  and 
  in 
  the 
  dark 
  parts 
  between 
  two 
  striations 
  shows 
  that 
  in 
  

  

  those 
  regions 
  there 
  is 
  a 
  slight 
  excess 
  of 
  positive 
  electricity. 
  

  

  The 
  magnitude 
  of 
  the 
  charo-es 
  in 
  the 
  electric 
  force 
  is 
  shown 
  

  

  • 
  ... 
  

  

  by 
  the 
  following 
  numbers 
  which 
  indicate 
  the 
  electric 
  force 
  

  

  in 
  volts 
  per 
  centimetre 
  at 
  different 
  parts 
  of 
  the 
  striation. 
  

  

  e^' 
  in 
  the 
  following 
  table 
  is 
  the 
  distance 
  in 
  millimetres 
  from 
  

  

  the 
  bright 
  head 
  of 
  the 
  striation: 
  x 
  is 
  taken 
  positive 
  when 
  

  

  measured 
  tow^ards 
  the 
  anode, 
  negative 
  towards 
  the 
  cathode, 
  

  

  thus 
  .1'= 
  —1 
  denotes 
  a 
  place 
  1 
  millimetre 
  from 
  the 
  bright 
  head 
  

  

  of 
  the 
  striation 
  on 
  the 
  cathode 
  side. 
  X 
  is 
  the 
  electric 
  force 
  

  

  in 
  volts 
  per 
  centimetre 
  at 
  x. 
  The 
  gas 
  was 
  hydrogen 
  at 
  a 
  

  

  low 
  pressure. 
  

  

  