﻿

  752 
  Pi 
  of. 
  0. 
  W. 
  Richardson 
  on 
  the 
  Specific 
  

  

  accuracy 
  we 
  may 
  use 
  

  

  i 
  = 
  (£ 
  

  

  ZeJ 
  x 
  ' 
  r 
  Ae 
  ' 
  

   4-71 
  Xl0~ 
  7 
  -12X10" 
  7 
  

  

  The 
  values 
  of 
  the 
  two 
  terms, 
  to 
  the 
  same 
  degree 
  of 
  approxi- 
  

   mation, 
  are 
  written 
  below 
  them. 
  The 
  ratio 
  is 
  about 
  40 
  to 
  1. 
  

   Neglecting 
  terms 
  involving 
  squares 
  of 
  this 
  ratio 
  we 
  get 
  

  

  2msj 
  

   Ze 
  

  

  and 
  fZ 
  

  

  /2m\i 
  , 
  

   KTe) 
  "**'• 
  

  

  (2mz 
  l 
  \i 
  C)m 
  2 
  iv 
  z 
  l 
  

  

  On 
  substituting 
  these 
  values 
  the 
  equation 
  for 
  x—x 
  

   becomes 
  

  

  *-*»=( 
  s 
  ) 
  "•— 
  b 
  "« 
  + 
  s^ 
  rzrj 
  — 
  irKzr) 
  

  

  The 
  values 
  of 
  these 
  terms 
  taken 
  in 
  order 
  from 
  the 
  left 
  are 
  

   28-26 
  x 
  10" 
  3 
  , 
  -72 
  x 
  10- 
  3 
  , 
  129 
  x 
  10~ 
  3 
  , 
  -29 
  x 
  10~ 
  3 
  , 
  '194 
  x 
  10~ 
  3 
  , 
  

   and 
  2-48 
  x 
  10" 
  3 
  . 
  

  

  It 
  will 
  be 
  noticed 
  that 
  four 
  of 
  these 
  terms 
  contain 
  u 
  as 
  a 
  

   factor. 
  The 
  method 
  adopted 
  in 
  carrying 
  out 
  the 
  experiments 
  

   was 
  to 
  measure 
  the 
  ratio 
  of 
  the 
  current 
  through 
  the 
  slit 
  to 
  

   that 
  received 
  by 
  the 
  plates 
  for 
  different 
  values 
  of 
  x 
  r 
  the 
  

   position 
  of 
  the 
  slit. 
  This 
  was 
  first 
  done 
  in 
  the 
  absence 
  of 
  a 
  

   magnetic 
  field 
  (H 
  = 
  0), 
  and 
  the 
  fraction 
  of 
  the 
  total 
  number 
  

   of 
  ions 
  traversing 
  the 
  slit 
  was 
  plotted 
  as 
  a 
  function 
  of 
  its 
  

   displacement 
  #]=# 
  — 
  # 
  . 
  This 
  curve 
  had 
  a 
  sharp 
  maximum 
  

   opposite 
  the 
  centre 
  of 
  the 
  strip. 
  The 
  maximum 
  in 
  this 
  case 
  

   was 
  just 
  opposite 
  the 
  centre 
  of 
  the 
  strip, 
  the 
  shape 
  of 
  the 
  

   curve 
  being 
  approximately 
  that 
  which 
  would 
  result 
  if 
  the 
  

   distribution 
  of 
  velocity 
  among 
  the 
  particles 
  emitted 
  by 
  the 
  

   strip 
  was 
  that 
  given 
  by 
  Maxwell's 
  law 
  for 
  a 
  gas 
  at 
  the 
  temper- 
  

   ature 
  of 
  the 
  metal. 
  The 
  position 
  of 
  this 
  maximum 
  therefore 
  

   gave 
  the 
  position 
  of 
  those 
  ions 
  for 
  which 
  u 
  , 
  the 
  original 
  

   sideways 
  velocity, 
  was 
  equal 
  to 
  zero. 
  The 
  experiment 
  was 
  

   then 
  repeated 
  with 
  a 
  magnetic 
  field 
  great 
  enough 
  to 
  displace 
  

   the 
  particles, 
  which 
  reached 
  the 
  plates, 
  a 
  measurable 
  distance. 
  

   The 
  effect 
  of 
  this 
  was 
  simply 
  to 
  displace 
  the 
  curve 
  previously 
  

   obtained 
  a 
  little 
  to 
  the 
  right 
  or 
  left 
  of 
  its 
  former 
  position, 
  

  

  