﻿348 
  Prof. 
  0. 
  W. 
  Richardson 
  on 
  the 
  Emission 
  of 
  

  

  <2x 
  10~ 
  6 
  mm. 
  in 
  5 
  minutes 
  with 
  an 
  emission 
  of 
  '050 
  amp. 
  

   It 
  the 
  gas 
  is 
  assumed 
  to 
  be 
  hydrogen, 
  which 
  makes 
  most 
  

   impacts, 
  using 
  a 
  liberally 
  high 
  estimate 
  of 
  the 
  temperature 
  

   of 
  the 
  copper 
  electrode 
  which 
  determines 
  the 
  temperature 
  

   of 
  the 
  gas, 
  I 
  find 
  that 
  the 
  maximum 
  number 
  N 
  7 
  of 
  mole- 
  

   cules 
  impinging 
  per 
  second 
  during 
  the 
  interval 
  would 
  be 
  

   < 
  7'0 
  X 
  10 
  13 
  . 
  The 
  number 
  of 
  electrons 
  emitted 
  per 
  second 
  

   would 
  be 
  N 
  2 
  = 
  3-13 
  x 
  10 
  17 
  . 
  The 
  ratio 
  N 
  2 
  /N' 
  is 
  thus 
  

   > 
  4'47 
  x 
  10 
  3 
  . 
  If 
  the 
  putative 
  hydrogen 
  atoms 
  simply 
  

   turned 
  into 
  a 
  cloud 
  of 
  electrons 
  whose 
  total 
  mass 
  was 
  equal 
  

   to 
  that 
  of 
  the 
  hydrogen, 
  the 
  value 
  of 
  N 
  2 
  /JST' 
  would 
  be 
  only 
  

   3*68 
  x 
  10 
  3 
  . 
  The 
  data 
  already 
  referred 
  to 
  for 
  the 
  tube 
  with 
  

   the 
  filament 
  8 
  cm. 
  long 
  give 
  an 
  even 
  larger 
  ratio 
  for 
  N 
  2 
  /N', 
  

   namely 
  1*5 
  x 
  10 
  4 
  . 
  Moreover, 
  in 
  some 
  of 
  the 
  experiments 
  

   the 
  changes 
  in 
  gas 
  pressure 
  were 
  much 
  larger 
  than 
  those 
  

   recorded 
  above, 
  but 
  they 
  were 
  never 
  accompanied 
  by 
  any 
  

   change 
  in 
  the 
  electronic 
  emission 
  : 
  also 
  the 
  admission 
  of 
  

   mercury 
  vapour 
  at 
  its 
  pressure 
  (about 
  0*001 
  mm.) 
  at 
  room 
  

   temperature 
  produces 
  no 
  appreciable 
  change 
  in 
  the 
  emission. 
  

   Thus 
  there 
  is 
  no 
  room 
  for 
  the 
  idea 
  that 
  the 
  emission 
  of 
  

   electrons 
  has 
  anything 
  to 
  do 
  with 
  the 
  impact 
  of 
  gas 
  molecules 
  

   under 
  the 
  conditions 
  of 
  these 
  experiments. 
  

  

  (3) 
  The 
  emission 
  is 
  a 
  result 
  of 
  some 
  process 
  involving 
  

   consumption 
  of 
  the 
  tungsten. 
  

  

  To 
  test 
  this 
  question 
  some 
  of 
  the 
  lamps 
  were 
  sealed 
  off 
  

   after 
  being 
  exhausted 
  in 
  the 
  manner 
  described. 
  The 
  filaments 
  

   were 
  then 
  heated 
  so 
  as 
  to 
  give 
  a 
  constant 
  thermionic 
  current 
  

   which 
  was 
  allowed 
  to 
  flow 
  for 
  long 
  intervals 
  of 
  time. 
  In 
  

   this 
  way 
  the 
  total 
  quantity 
  of 
  negative 
  electricity 
  emitted 
  

   by 
  the 
  filament 
  was 
  determined. 
  The 
  wire 
  was 
  placed 
  in 
  

   one 
  arm 
  of 
  a 
  Wheatstone's 
  bridge 
  so 
  that 
  the 
  resistance 
  

   could 
  be 
  recorded 
  simultaneously. 
  The 
  cold 
  resistance 
  was 
  

   also 
  checked 
  up 
  from 
  time 
  to 
  time. 
  

  

  At 
  these 
  high 
  temperatures 
  the 
  resistance 
  of 
  the 
  filaments 
  

   increases 
  slowly 
  but 
  continuously. 
  This 
  increase 
  is 
  believed 
  

   to 
  be 
  due 
  to 
  evaporation 
  of 
  the 
  tungsten. 
  It 
  was 
  found 
  to 
  

   be 
  proportional 
  to 
  the 
  time 
  of 
  heating 
  when 
  the 
  thermionic 
  

   current 
  was 
  kept 
  constant, 
  in 
  the 
  case 
  of 
  any 
  particular 
  

   filament. 
  In 
  the 
  case 
  of 
  one 
  filament 
  which 
  gave 
  0*05 
  amp. 
  

   for 
  12 
  hours, 
  the 
  increase 
  in 
  the 
  resistance 
  of 
  the 
  hot 
  filament 
  

   was 
  9 
  per 
  cent. 
  The 
  accompanying 
  proportionate 
  increase 
  

   in 
  the 
  cold 
  resistance 
  was 
  slightly 
  lower, 
  namely 
  7 
  per 
  cent. 
  

   The 
  latter 
  may 
  probably 
  be 
  taken 
  as 
  a 
  fair 
  measure 
  of 
  the 
  

   amount 
  of 
  tungsten 
  lost 
  by 
  the 
  filament. 
  The 
  increase 
  in 
  

   resistance 
  of 
  the 
  hot 
  filament, 
  which 
  is 
  less 
  favourable 
  for 
  our 
  

  

  