﻿Charge 
  of 
  the 
  Ions 
  emitted 
  hy 
  Hot 
  Bodies. 
  755 
  

  

  The 
  distance 
  z 
  between 
  the 
  plates 
  in 
  these 
  experiments 
  

   was 
  *688 
  cm. 
  and 
  the 
  potential-difference 
  55 
  volts. 
  

  

  If 
  the 
  deflexions 
  produced 
  by 
  the 
  magnetic 
  field 
  were 
  

   sufficiently 
  small 
  and 
  the 
  geometrical 
  conditions 
  sufficiently 
  

   near 
  to 
  those 
  which 
  obtain 
  with 
  infinite 
  planes, 
  the 
  theory 
  of 
  

   this 
  method 
  would 
  be 
  the 
  same 
  as 
  that 
  already 
  discussed. 
  

   For 
  the 
  pattern 
  formed 
  by 
  the 
  ions 
  on 
  the 
  slit 
  plates, 
  in 
  the 
  

   absence 
  of 
  a 
  magnetic 
  field, 
  is 
  symmetrical 
  about 
  the 
  plane 
  

   of 
  symmetry 
  of 
  the 
  strip, 
  so 
  that 
  when 
  the 
  plates 
  receive 
  

   equal 
  charges 
  the 
  centre 
  of 
  the 
  slit 
  will 
  coincide 
  with 
  the 
  

   position 
  of 
  the 
  maximum 
  in 
  the 
  other 
  method. 
  The 
  same 
  

   will 
  be 
  true 
  after 
  the 
  magnetic 
  field 
  has 
  been 
  applied 
  if 
  the 
  

   magnetic 
  field 
  simply 
  shifts 
  the 
  pattern 
  without 
  altering 
  its 
  

   form. 
  If 
  these 
  conditions 
  are 
  satisfied 
  the 
  displacement 
  x 
  

   will 
  be 
  given 
  by 
  the 
  formula 
  

  

  1 
  

  

  *~3 
  V 
  mV~ 
  * 
  

  

  For 
  V 
  and 
  z 
  constant 
  x 
  should 
  therefore 
  be 
  proportional 
  

   to 
  H. 
  The 
  numbers 
  in 
  the 
  preceding 
  table 
  do 
  not 
  satisfy 
  

   this 
  relation. 
  If 
  the 
  values 
  of 
  x 
  are 
  plotted 
  against 
  H 
  the 
  

   points 
  lie 
  very 
  nearly 
  on 
  a 
  smooth 
  curve 
  which 
  curves 
  away 
  

   from 
  the 
  axis 
  of 
  H. 
  On 
  taking 
  logarithms 
  it 
  is 
  found 
  that 
  

   these 
  points 
  and 
  the 
  point 
  a? 
  = 
  *0254, 
  H 
  = 
  500, 
  obtained 
  by 
  

   extrapolation, 
  lie 
  very 
  nearly 
  on 
  the 
  line 
  corresponding 
  to 
  

   x 
  = 
  HI 
  1 
  " 
  15 
  , 
  where 
  k 
  is 
  a 
  constant. 
  The 
  deviation 
  from 
  a 
  

   straight 
  line 
  is 
  therefore 
  not 
  very 
  great 
  but 
  is 
  nevertheless 
  

   definite. 
  This 
  deviation 
  might 
  arise 
  either 
  from 
  the 
  positive 
  

   ions 
  not 
  being 
  homogeneous 
  or 
  from 
  the 
  theoretical 
  conditions 
  

   not 
  being 
  satisfied. 
  It 
  was 
  felt 
  that 
  it 
  was 
  very 
  important 
  

   to 
  settle 
  the 
  question 
  as 
  to 
  whether 
  there 
  were 
  more 
  kinds 
  

   than 
  one 
  of 
  positive 
  ions, 
  and 
  furthermore 
  to 
  be 
  able 
  to 
  do 
  

   this 
  during 
  any 
  experiment 
  at 
  any 
  time. 
  For 
  these 
  reasons 
  

   this 
  zero 
  deflexion 
  method 
  was 
  discarded 
  in 
  favour 
  of 
  the 
  

   method 
  of 
  exploring 
  the 
  actual 
  distribution 
  of 
  the 
  ions 
  on 
  

   the 
  plates 
  which 
  has 
  already 
  been 
  described. 
  

  

  If 
  w 
  r 
  e 
  assume 
  that 
  for 
  small 
  values 
  of 
  H 
  the 
  formula 
  

  

  _1 
  / 
  2e 
  

  

  "3 
  V 
  mV 
  

  

  z 
  2 
  R 
  

  

  may 
  be 
  applied 
  to 
  the 
  results 
  given 
  by 
  the 
  zero 
  method, 
  we 
  

   find 
  e/m 
  = 
  310 
  E 
  M. 
  units. 
  If 
  each 
  ion 
  carries 
  the 
  same 
  

   charge 
  as 
  an 
  atom 
  of 
  hydrogen 
  during 
  electrolysis, 
  the 
  value 
  

   of 
  ejm 
  for 
  which 
  is 
  9*66 
  X 
  10 
  3 
  E.M. 
  units, 
  the 
  average 
  mass 
  

   of 
  the 
  ions 
  is 
  31"2 
  times 
  that 
  of 
  an 
  atom 
  of 
  hydrogen. 
  

  

  3D2 
  

  

  