﻿THE 
  

   LONDON, 
  EDINBUROH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  i 
  

  

  I 
  

  

  Q 
  [SIXTH 
  SERIES.] 
  

   "^ 
  JSOV 
  EMBER 
  1909. 
  

  

  LXX. 
  The 
  Kinetic 
  Energy 
  of 
  the 
  Ions 
  emitted 
  hy 
  Hot 
  Bodies. 
  

   — 
  11. 
  By 
  0. 
  W. 
  Richardson, 
  i/.A., 
  B.Sc, 
  Professor 
  of 
  

   Physics^ 
  Princeton 
  University^ 
  . 
  

  

  IX 
  the 
  first 
  part 
  of 
  this 
  paper 
  t 
  the 
  writer 
  showed 
  how- 
  

   valuable 
  information 
  concerning 
  the 
  initial 
  kinetic 
  energy 
  

   of 
  the 
  thermions 
  could 
  be 
  obtained 
  from 
  observations 
  of 
  the 
  

   way 
  in 
  which 
  they 
  spread 
  out 
  in 
  a 
  uniform 
  electric 
  field. 
  

   The 
  method 
  employed 
  was 
  to 
  apply 
  the 
  electric 
  field 
  between 
  

   two 
  parallel 
  conducting 
  planes. 
  In 
  one 
  of 
  these 
  lay 
  a 
  narrow 
  

   straight 
  platinum 
  strip 
  which 
  could 
  be 
  heated 
  by 
  means 
  of 
  

   an 
  electric 
  current. 
  The 
  opposite 
  plane 
  was 
  movable 
  by 
  

   small 
  measurable 
  amounts 
  in 
  a 
  direction 
  perpendicular 
  to 
  the 
  

   length 
  of 
  the 
  strip. 
  It 
  contained 
  a 
  narrow 
  slit 
  whose 
  edges 
  

   were 
  parallel 
  to 
  those 
  of 
  the 
  strip, 
  and 
  thus 
  perpendicular 
  to 
  

   the 
  direction 
  of 
  motion. 
  The 
  proportion, 
  which 
  passed 
  

   through 
  the 
  slit, 
  of 
  the 
  total 
  number 
  of 
  ions 
  received 
  by 
  the 
  

   plane 
  was 
  measured 
  for 
  a 
  series 
  of 
  positions 
  of 
  the 
  former. 
  

  

  It 
  was 
  pointed 
  out 
  that 
  the 
  apparatus 
  used 
  in 
  the 
  above 
  

   investigation 
  had 
  been 
  designed 
  for 
  another 
  purpose, 
  and 
  

   was 
  far 
  from 
  fulfilling 
  several 
  of 
  the 
  geometrical 
  conditions 
  

   laid 
  down 
  by 
  the 
  theory. 
  The 
  results 
  obtained 
  could, 
  there- 
  

   fore, 
  only 
  be 
  regarded 
  as 
  approximate. 
  The 
  present 
  experi- 
  

   ments 
  have 
  been 
  carried 
  out 
  with 
  a 
  new 
  apparatus 
  involving 
  

   the 
  same 
  principles, 
  but 
  made 
  larger 
  and 
  constructed 
  so 
  as 
  

   to 
  satisfy 
  accurately 
  the 
  geometrical 
  conditions. 
  It 
  is 
  believed 
  

  

  •* 
  Communicated 
  bv 
  the 
  Author, 
  

   t 
  Phil. 
  Mag. 
  '6] 
  xvi. 
  p. 
  890 
  (1908). 
  

  

  Phil. 
  May. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  107. 
  Nov. 
  1909. 
  2 
  Z 
  

  

  