﻿Emission 
  of 
  Electrons 
  from 
  Tungsten. 
  345 
  

  

  I 
  am 
  indebted 
  to 
  Mr. 
  Gr. 
  G. 
  E. 
  Collis 
  for 
  taking 
  the 
  

   photographs 
  reproduced 
  in 
  PL 
  X., 
  and 
  for 
  help 
  in 
  the 
  

   observations, 
  and 
  to 
  Dr. 
  Sadler 
  for 
  assistance 
  in 
  many 
  of 
  

   the 
  experiments. 
  

  

  Physical 
  Laboratory, 
  

  

  University 
  College, 
  Reading. 
  

  

  Feb. 
  25, 
  1913. 
  

  

  XXII. 
  The 
  Emission 
  of 
  Electrons 
  from 
  Tungsten 
  at 
  High 
  

   Temperatures: 
  an 
  Experimental 
  Proof 
  that 
  the 
  Electric 
  

   Current 
  in 
  Metals 
  is 
  carried 
  by 
  Electrons. 
  By 
  0. 
  W. 
  

   Richardson, 
  ill. 
  A., 
  D.Sc, 
  F.R.S.* 
  

  

  THAT 
  the 
  carriers 
  of 
  the 
  negative 
  thermionic 
  current 
  from 
  

   incandescent 
  solids 
  are 
  negative 
  electrons 
  was 
  first 
  estab- 
  

   lished 
  by 
  J. 
  J. 
  Thomson 
  t- 
  In 
  1901 
  J 
  the 
  writer 
  developed 
  the 
  

   view 
  that 
  this 
  emission 
  of 
  negative 
  electrons 
  occurred 
  by 
  

   virtue 
  of 
  the 
  kinetic 
  energy 
  of 
  thermal 
  agitation 
  of 
  some 
  of 
  

   the 
  electrons 
  in 
  the 
  solid 
  exceeding 
  the 
  work 
  which 
  was 
  

   necessary 
  to 
  overcome 
  the 
  forces 
  which 
  tend 
  to 
  retain 
  them 
  

   in 
  the 
  body 
  and 
  which 
  prevent 
  them 
  from 
  escaping 
  at 
  lower 
  

   temperatures. 
  This 
  conception 
  has 
  proved 
  a 
  very 
  fruitful 
  

   one, 
  and 
  its 
  consequences 
  have 
  been 
  verified 
  in 
  a 
  number 
  of 
  

   ways. 
  It 
  has 
  provided 
  a 
  quantitative 
  explanation 
  of 
  the 
  

   variation, 
  with 
  the 
  temperature 
  of 
  the 
  body, 
  of 
  the 
  number 
  

   of 
  electrons 
  emitted. 
  It 
  led 
  to 
  the 
  prediction 
  of 
  a 
  cooling 
  

   effect 
  when 
  electrons 
  are 
  emitted 
  by 
  a 
  conductor, 
  and 
  a 
  

   corresponding 
  heating 
  effect 
  when 
  they 
  are 
  absorbed. 
  Both 
  

   these 
  effects 
  § 
  have 
  since 
  been 
  detected 
  experimentally, 
  and 
  

   found 
  to 
  be 
  of 
  the 
  expected 
  magnitude, 
  within 
  the 
  limits 
  of 
  

   •experimental 
  error. 
  The 
  magnitude 
  and 
  distribution 
  of 
  energy 
  

   of 
  the 
  emitted 
  electrons 
  has 
  been 
  found 
  by 
  experiment 
  to 
  be 
  

   that 
  given 
  by 
  Maxwell's 
  law||,in 
  accordance 
  with 
  the 
  re- 
  

   quirements 
  of 
  the 
  theory. 
  Finally, 
  the 
  same 
  general 
  train 
  

   of 
  ideas 
  has 
  led 
  to 
  useful 
  applications 
  in 
  the 
  direction 
  of 
  the 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  t 
  Phil. 
  Mag. 
  vol. 
  xlviii. 
  p. 
  547 
  (1899). 
  

  

  I 
  Camb. 
  Phil. 
  Proc. 
  vol. 
  xi. 
  p. 
  286 
  (1901) 
  ; 
  Phil. 
  Trans. 
  A. 
  vol. 
  cci. 
  

   p. 
  497 
  (1903). 
  

  

  § 
  Richardson 
  and 
  Cooke, 
  Phil. 
  Mag. 
  vol. 
  xx. 
  p. 
  173 
  (1910), 
  vol. 
  xxi. 
  

   p. 
  404 
  (1911). 
  Cooke 
  and 
  Richardson, 
  Phil. 
  Mag. 
  vol. 
  xxv. 
  p. 
  624 
  

   (1913). 
  

  

  || 
  Richardson 
  and 
  Brown, 
  Phil. 
  Mag. 
  vol. 
  xvi. 
  p. 
  353(1908); 
  Richardson, 
  

   Phil. 
  Mag. 
  vol. 
  xvi. 
  p. 
  890 
  (1908), 
  vol. 
  xviii. 
  p. 
  681 
  (1909). 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  152. 
  Aug. 
  1913. 
  2 
  A 
  

  

  