﻿from 
  Uncharged 
  Molecules. 
  909 
  

  

  the 
  velocity 
  of 
  the 
  ions 
  when 
  passing 
  from 
  the 
  arc 
  to 
  the 
  

   condensing 
  chamber 
  was 
  approximately 
  28,000 
  cm. 
  per 
  sec. 
  

   Since 
  the 
  velocity 
  of 
  the 
  ions 
  must 
  decrease 
  as 
  they 
  move- 
  

   up 
  into 
  the 
  condensing 
  chamber, 
  it 
  must 
  take 
  at 
  least 
  

   O'OOl 
  sec. 
  for 
  the 
  ions 
  to 
  move 
  from 
  the 
  arc 
  to 
  the 
  Jimit 
  of 
  

   the 
  luminous 
  region. 
  During 
  this 
  time 
  there 
  would 
  be 
  5 
  X 
  10 
  11 
  

   vibrations 
  of 
  the 
  ion. 
  It 
  is 
  highly 
  improbable 
  that 
  an 
  ion 
  

   will 
  continue 
  to 
  give 
  out 
  energy 
  through 
  so 
  many 
  vibrations 
  

   and 
  at 
  the 
  end 
  of 
  that 
  time 
  have 
  enough 
  energy 
  left 
  to 
  

   produce 
  vibrations 
  which 
  affect 
  the 
  eye. 
  

  

  Again, 
  if 
  the 
  light 
  came 
  from 
  ions 
  which 
  are 
  formed 
  in 
  the 
  

   arc, 
  it 
  would 
  seem 
  reasonable 
  to 
  expect 
  that 
  the 
  light 
  might 
  

   be 
  concentrated 
  by 
  an 
  electric 
  field. 
  Such 
  a 
  field 
  could 
  move 
  

   the 
  vibrating 
  ions, 
  but 
  could 
  not 
  destroy 
  the 
  vibrations. 
  If 
  

   it 
  moved 
  the 
  ions 
  towards 
  the 
  arc, 
  for 
  example, 
  we 
  would 
  

   have 
  the 
  light 
  which 
  was 
  previously 
  spread 
  through 
  the 
  

   condensing 
  chamber 
  concentrated 
  in 
  the 
  region 
  near 
  the 
  arc. 
  

   Nothing 
  of 
  this 
  sort 
  was 
  found 
  to 
  occur. 
  

  

  Neither 
  is 
  it 
  possible 
  that 
  the 
  light 
  is 
  due 
  to 
  ionization 
  

   occurring 
  in 
  the 
  region 
  above 
  the 
  arc. 
  The 
  first 
  reason 
  for 
  

   this 
  statement 
  is 
  that 
  there 
  is 
  no 
  known 
  cause 
  for 
  the 
  pro- 
  

   duction 
  of 
  ions 
  in 
  this 
  region. 
  The 
  light 
  cannot 
  be 
  due 
  to 
  

   ions 
  which 
  are 
  produced 
  by 
  an 
  electric 
  field, 
  for 
  the 
  region 
  is 
  

   distinctly 
  visible 
  when 
  F 
  is 
  at 
  the 
  same 
  potential 
  as 
  the 
  

   middle 
  of 
  the 
  arc. 
  The 
  luminosity 
  is 
  not 
  caused 
  by 
  any 
  

   form 
  of 
  radiation 
  from 
  the 
  arc, 
  as 
  was 
  shown 
  in 
  the 
  previous 
  

   experiment 
  to 
  which 
  reference 
  has 
  been 
  made. 
  

  

  However, 
  there 
  may 
  be 
  some 
  unknown 
  cause 
  for 
  ionization 
  ; 
  

   so 
  that 
  a 
  more 
  important 
  reason 
  for 
  saying 
  that 
  the 
  light 
  is 
  

   not 
  due 
  to 
  ionization 
  occurring 
  above 
  the 
  arc 
  is 
  that 
  the 
  

   matter 
  which 
  gives 
  out 
  the 
  light 
  must 
  have 
  been 
  ionized 
  

   before 
  it 
  reached 
  that 
  region. 
  This 
  is 
  true, 
  since 
  the 
  

   luminosity 
  can 
  be 
  entirely 
  removed 
  by 
  an 
  electric 
  field 
  

   under 
  the 
  proper 
  conditions, 
  and 
  an 
  electric 
  field 
  cannot 
  

   move 
  matter 
  which 
  is 
  not 
  ionized. 
  It 
  must 
  be 
  that 
  the 
  light 
  

   comes 
  from 
  matter 
  which 
  is 
  ionized 
  in 
  the 
  arc 
  but 
  is 
  set 
  in 
  

   vibration 
  in 
  the 
  region 
  above 
  it. 
  

  

  Light 
  caused 
  by 
  Recombination. 
  — 
  As 
  far 
  as 
  we 
  know, 
  the 
  

   only 
  cause 
  which 
  can 
  produce 
  vibrations 
  in 
  matter 
  which 
  

   has 
  been 
  previously 
  ionized 
  is 
  the 
  recombination 
  of 
  the 
  

   positive 
  and 
  negative 
  ions. 
  The 
  assumption 
  that 
  this 
  is 
  

   the 
  cause 
  of 
  the 
  light 
  in 
  the 
  mercury 
  vapour 
  would 
  explain 
  

   all 
  of 
  the 
  observations 
  satisfactorily. 
  When 
  either 
  kind 
  of 
  

   the 
  ions 
  is 
  removed 
  by 
  an 
  electric 
  field 
  there 
  can 
  be 
  no 
  

   recombination, 
  and 
  the 
  luminosity 
  is 
  destroyed. 
  Again, 
  the 
  

   field 
  cannot 
  concentrate 
  both 
  kinds 
  of 
  ions 
  in 
  the 
  same 
  

  

  