﻿THE 
  

   LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  [SIXTH 
  SERIES.] 
  

  

  SEPTEMBER 
  1908. 
  

  

  XXX. 
  The 
  Kinetic 
  Energy 
  of 
  the 
  Negative 
  Electrons 
  emitted 
  

   by 
  Hot 
  Bodies. 
  By 
  0. 
  W. 
  Richardson 
  - 
  , 
  Professor 
  of 
  

   Physics, 
  and 
  F. 
  C. 
  Brown, 
  Experimental 
  Science 
  Fellow, 
  

   Princeton 
  University*. 
  

  

  THAT 
  the 
  carriers 
  of 
  negative 
  electricity 
  emitted 
  by 
  hot 
  

   metals 
  are 
  electrons 
  was 
  first 
  proved 
  by 
  the 
  experiments 
  

   of 
  J. 
  J. 
  Thomson 
  f 
  on 
  their 
  deflexion 
  in 
  a 
  magnetic 
  field. 
  

   This 
  result 
  alone 
  did 
  not 
  compel 
  any 
  definite 
  view 
  oE 
  the 
  

   origin 
  of 
  this 
  ionization. 
  Somewhat 
  later 
  one 
  of 
  the 
  authors 
  { 
  

   showed 
  that 
  the 
  phenomena 
  then 
  known 
  were 
  such 
  as 
  would 
  

   arise 
  if 
  the 
  electrons 
  originate 
  in 
  the 
  metals, 
  from 
  which 
  

   they 
  were 
  able 
  to 
  escape 
  when 
  their 
  velocity 
  normal 
  to 
  the 
  

   surface 
  exceeded 
  a 
  certain 
  value. 
  This 
  method 
  of 
  looking 
  

   at 
  the 
  question 
  was 
  found 
  to 
  give 
  a 
  particularly 
  satisfactory 
  

   account 
  of 
  the 
  thermal 
  relations 
  of 
  the 
  phenomena 
  which 
  

   were 
  then 
  accurately 
  investigated 
  for 
  the 
  first 
  time. 
  In 
  

   Richardson's 
  method 
  of 
  developing 
  the 
  subject 
  (Joe. 
  cit.) 
  the 
  

   assumption 
  is 
  justified 
  by 
  theoretical 
  considerations, 
  that 
  the 
  

   translational 
  kinetic 
  energy 
  of 
  the 
  electrons 
  inside 
  the 
  metal 
  

   has 
  the 
  same 
  value 
  as 
  that 
  of 
  the 
  molecules 
  of 
  a 
  gas 
  at 
  the 
  

   same 
  temperature 
  as 
  that 
  of 
  the 
  metal. 
  From 
  the 
  principles 
  

   there 
  laid 
  down 
  it 
  also 
  follows 
  that 
  the 
  translational 
  kinetic 
  

   energy 
  of 
  the 
  electrons 
  outside 
  the 
  metal 
  possesses 
  the 
  same 
  

   value. 
  This 
  equality 
  applies 
  not 
  only 
  to 
  the 
  average 
  value, 
  

  

  * 
  Communicated 
  bv 
  the 
  Authors. 
  

   f 
  Phil. 
  Mag. 
  [5] 
  vol. 
  xlviii. 
  p. 
  547 
  (1899). 
  

  

  X 
  0. 
  AY. 
  Richardson, 
  Camb. 
  Phil. 
  Proc. 
  vol. 
  xi. 
  p. 
  286 
  (1901) 
  ; 
  Phil. 
  

   Trans. 
  A, 
  vol. 
  cci. 
  p. 
  497 
  (1903). 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  16. 
  No. 
  93. 
  Sept. 
  1908. 
  2 
  B 
  

  

  