﻿produced 
  in 
  Air 
  by 
  the 
  Motion 
  of 
  Negative 
  Ions. 
  223 
  

  

  Therefore 
  

  

  3Lv/, 
  b 
  

  

  Vlo 
  g 
  (l 
  + 
  f)lo 
  g 
  * 
  

  

  lies 
  between 
  11 
  and 
  22. 
  

  

  The 
  limiting 
  voltage 
  of 
  the 
  aluminium 
  cylinder 
  at 
  which 
  

   the 
  increase 
  of 
  the 
  negative 
  current 
  should 
  be 
  just 
  measurable 
  

   therefore 
  falls 
  between 
  

  

  22 
  log 
  - 
  

  

  e 
  a 
  

  

  and 
  

  

  11 
  log- 
  

  

  b 
  

  

  a 
  

  

  "*< 
  1+ 
  t) 
  

  

  log 
  (l 
  + 
  

  

  317 
  ' 
  

  

  a 
  j 
  

  

  These 
  limits 
  calculated 
  for 
  the 
  

  

  pressures 
  in 
  the 
  table 
  are 
  

  

  sspectively 
  : 
  

  

  

  

  

  for 
  A 
  

  

  102 
  

  

  and 
  

  

  51 
  

  

  B 
  

  

  70 
  

  

  

  35 
  

  

  C 
  

  

  57 
  

  

  

  28 
  

  

  D 
  

  

  52 
  

  

  

  26 
  

  

  E 
  

  

  45 
  

  

  

  22 
  

  

  F 
  

  

  42 
  

  

  

  21 
  

  

  G 
  

  

  40 
  

  

  

  20 
  

  

  H 
  

  

  37 
  

  

  

  18 
  

  

  I 
  

  

  31 
  

  

  

  15 
  

  

  J 
  

  

  28 
  

  

  

  14 
  

  

  K 
  

  

  25 
  

  

  

  12 
  

  

  It 
  will 
  be 
  seen 
  that 
  where 
  the 
  limiting 
  voltages 
  can 
  be 
  

   detected 
  in 
  the 
  tables 
  they 
  fall 
  between 
  these 
  limits. 
  

  

  1 
  5. 
  This 
  is 
  another 
  test 
  which 
  is 
  too 
  rough 
  to 
  be 
  conclusive. 
  

   Yet 
  if 
  the 
  mean 
  ionizing 
  full 
  of 
  an 
  ion 
  were 
  taken 
  to 
  be 
  one 
  

   which 
  fell 
  outside 
  the 
  limits 
  (11, 
  22) 
  determined 
  above, 
  con- 
  

   spicuous 
  discrepancies 
  would 
  arise 
  between 
  the 
  numbers 
  of 
  

   the 
  tables 
  and 
  those 
  furnished 
  by 
  theory. 
  And, 
  as 
  a 
  matter 
  

   of 
  fact, 
  it 
  is 
  often 
  difficult 
  to 
  fix 
  the 
  limiting 
  voltage 
  of 
  the 
  

   cylinder 
  by 
  observation 
  more 
  accurately 
  than 
  the 
  calculated 
  

   numbers 
  determine 
  it. 
  

  

  16. 
  It 
  has 
  been 
  shown 
  that 
  the 
  observations 
  presented 
  in 
  

   this 
  paper 
  are, 
  so 
  far 
  as 
  it 
  has 
  been 
  found 
  practicable 
  to 
  

   submit 
  them 
  to 
  analysis, 
  in 
  accord 
  with 
  Professor 
  Townsend's 
  

   Theory 
  of 
  Collisions. 
  And 
  to 
  this 
  extent 
  they 
  afford 
  addi- 
  

   tional 
  evidence 
  of 
  its 
  truth. 
  Thus 
  it 
  appears 
  necessary 
  to 
  

   suppose 
  that 
  negative 
  ions, 
  when 
  moving 
  with 
  adequate 
  

   velocity, 
  disintegrate 
  otner 
  molecules 
  upon 
  colliding 
  with 
  

   them. 
  This 
  at 
  least 
  must 
  be 
  the 
  case 
  when 
  the 
  pressure 
  is 
  

  

  