﻿6SQ 
  Prof. 
  0. 
  W. 
  Richardson 
  o?i 
  tJie 
  Kinetic 
  

  

  nnd 
  the 
  slit 
  and 
  phites. 
  Iq 
  is 
  thus 
  the 
  value 
  of 
  I 
  when 
  .i' 
  = 
  0. 
  

   This 
  formula 
  presumes 
  that 
  the 
  widths 
  of 
  the 
  strip 
  and 
  slit 
  

   respectively 
  are 
  negligibly 
  small, 
  a 
  condition 
  which 
  was 
  

   satisfied 
  in 
  the 
  experiments. 
  

  

  For 
  the 
  deduction 
  of 
  formula 
  (1) 
  it 
  will 
  be 
  sufficient 
  to 
  

   refer 
  to 
  the 
  former 
  paper. 
  It 
  follows 
  directly 
  from 
  the 
  

   assumption 
  that 
  the 
  electrons 
  leaving 
  the 
  metal, 
  do 
  so 
  with 
  a 
  

   distribution 
  of 
  velocity, 
  which 
  is 
  identical 
  with 
  that 
  given 
  by 
  

   Maxwell's 
  law 
  for 
  the 
  particles 
  of 
  a 
  gas 
  of 
  equal 
  molecular 
  

   weight 
  leaving 
  the 
  same 
  surface 
  at 
  the 
  same 
  temperature. 
  

   The 
  fact 
  that 
  the 
  normal 
  component 
  of 
  the 
  velocity 
  of 
  the 
  

   escaping 
  electrons 
  is 
  that 
  required 
  by 
  Maxwell's 
  law 
  has 
  

   already 
  been 
  proved 
  by 
  Richardson 
  and 
  Brown*. 
  If 
  the 
  

   present 
  experiments 
  confirm 
  formula 
  (1) 
  it 
  will 
  be 
  legitimate 
  to 
  

   conclude 
  that 
  the 
  velocity 
  components 
  parallel 
  to 
  the 
  emitting 
  

   surface 
  also 
  obey 
  MaxwelFs 
  law, 
  and 
  the 
  observed 
  disagree- 
  

   ment 
  will 
  set 
  a 
  superior 
  limit 
  to 
  the 
  amount 
  of 
  deviation 
  

   from 
  the 
  requirements 
  of 
  the 
  theoretical 
  law. 
  

  

  The 
  apparatus 
  used 
  in 
  this 
  part 
  of 
  the 
  investigation 
  was 
  

   not 
  quite 
  the 
  same 
  as 
  that 
  shown 
  in 
  figs. 
  1 
  and 
  2. 
  The 
  

   slit 
  D 
  was 
  not 
  cut 
  in 
  the 
  plate 
  A. 
  Instead 
  of 
  lying 
  in 
  the 
  

   slit 
  the 
  strip 
  C 
  was 
  1 
  mm. 
  in 
  front 
  of 
  the 
  conducting 
  plane 
  

   A, 
  and 
  it 
  was, 
  therefore, 
  only 
  4 
  mm. 
  distant 
  from 
  the 
  

   plane 
  B. 
  Otherwise 
  the 
  arrangements 
  were 
  the 
  same 
  as 
  

   those 
  described 
  above. 
  It 
  was 
  intended 
  at 
  first 
  to 
  have 
  the 
  

   strip 
  mounted 
  in 
  front 
  of 
  the 
  plane 
  in 
  this 
  way 
  throughout 
  

   the 
  investigation, 
  but 
  it 
  was 
  found 
  that 
  when 
  a 
  difference 
  of 
  

   potential 
  was 
  applied 
  between 
  A 
  and 
  B 
  the 
  experimental 
  

   curves 
  instead 
  of 
  having 
  only 
  one 
  maximum 
  had 
  wings 
  on 
  

   each 
  side 
  of 
  it. 
  These 
  were 
  clearly 
  due 
  to 
  ions 
  from 
  the 
  

   back 
  of 
  the 
  strip 
  being 
  drawn 
  out 
  by 
  the 
  electric 
  field. 
  The 
  

   arrangement 
  with 
  the 
  slit 
  D 
  was 
  adopted 
  to 
  avoid 
  this 
  eff'ect 
  

   and 
  was 
  found 
  to 
  be 
  successful. 
  In 
  the 
  case 
  where 
  no 
  

   electric 
  field 
  was 
  applied 
  there 
  could 
  be 
  no 
  objection 
  to 
  the 
  

   strip 
  being 
  in 
  front 
  of 
  the 
  plane. 
  The 
  results 
  of 
  the 
  experi- 
  

   ments 
  with 
  the 
  apparatus 
  arranged 
  in 
  this 
  way, 
  which 
  were 
  

   made 
  with 
  great 
  care, 
  have 
  been 
  retained, 
  and 
  are 
  those 
  

   which 
  are 
  described 
  in 
  detail 
  below. 
  In 
  order 
  to 
  be 
  quite 
  

   sure, 
  however, 
  fresh 
  experiments 
  were 
  made 
  after 
  the 
  slit 
  

   had 
  been 
  constructed, 
  and 
  the 
  position 
  of 
  the 
  strip 
  changed. 
  

   These 
  were 
  found 
  to 
  agree 
  satisfactorily 
  with 
  the 
  results 
  

   obtained 
  with 
  the 
  first 
  arrangement. 
  

  

  The 
  temperature 
  of 
  the 
  strip 
  was 
  regulated 
  by 
  keeping 
  its 
  

   resistance 
  constant. 
  The 
  observed 
  resistances 
  also 
  served 
  to 
  

   measure 
  the 
  temperature, 
  the 
  resistance 
  corresponding 
  to 
  

   * 
  Phil. 
  Mag. 
  [6] 
  xvi. 
  p. 
  353 
  (1908). 
  

  

  