﻿480 
  Mr. 
  L. 
  Yegard 
  on 
  the 
  Electric 
  Discharge 
  

  

  discharge 
  is 
  broken. 
  This 
  fact 
  makes 
  it 
  very 
  improbable 
  

   that 
  the 
  absorption 
  can 
  be 
  due 
  to 
  any 
  secondary 
  effects, 
  but 
  

   leads 
  us 
  to 
  find 
  the 
  cause 
  in 
  some 
  property 
  o£ 
  the 
  discharge 
  

   itself. 
  The 
  peculiar 
  abruptness 
  in 
  the 
  occurrence 
  of 
  the 
  

   absorption, 
  as 
  well 
  with 
  regard 
  to 
  current 
  as 
  pressure^ 
  must 
  

   show 
  that 
  the 
  absorption 
  is 
  not 
  a 
  necessary 
  accompaniment 
  

   to 
  the 
  discharge, 
  but 
  sets 
  in 
  when 
  peculiar 
  conditions 
  occur. 
  

  

  We 
  have 
  seen 
  that 
  the 
  great 
  absorption 
  is 
  always 
  accom- 
  

   panied 
  with 
  a 
  large 
  cathode 
  fall, 
  and 
  if 
  we 
  suppose 
  that 
  the 
  

   absorption 
  per 
  coulomb 
  {q) 
  is 
  mainly 
  a 
  function 
  of 
  the 
  

   cathode 
  fall, 
  and 
  suppose 
  further 
  that 
  this 
  function 
  has 
  the 
  

   character 
  that 
  it 
  increases 
  very 
  abruptly 
  when 
  the 
  cathode 
  

   fall 
  is 
  raised 
  above 
  a 
  certain 
  value, 
  then 
  the 
  character 
  

   of 
  the 
  absorption 
  phenomenon 
  will 
  be 
  immediately 
  under- 
  

   stood. 
  This 
  will 
  be 
  apparent 
  by 
  looking 
  at 
  the 
  curves 
  

   (fig. 
  9), 
  giving 
  the 
  variation 
  of 
  the 
  cathode 
  fall. 
  For 
  some- 
  

   what 
  high 
  pressures 
  the 
  cathode 
  fall 
  after 
  " 
  saturation 
  " 
  

   increases 
  very 
  slowly 
  with 
  increase 
  of 
  current, 
  reaches 
  a 
  

   maximum 
  value 
  and 
  f 
  falls 
  again. 
  If, 
  now, 
  the 
  cathode 
  fall 
  

   for 
  which 
  the 
  great 
  absorption 
  sets 
  in 
  is 
  greater 
  than 
  this 
  

   maximum 
  value, 
  the 
  large 
  absorption 
  cannot 
  be 
  got 
  at 
  all 
  

   for 
  that 
  pressure 
  even 
  for 
  very 
  large 
  currents. 
  First, 
  when 
  

   the 
  pressure 
  becomes 
  somewhat 
  low 
  there 
  will 
  be 
  a 
  current 
  

   for 
  which 
  the 
  cathode 
  fall 
  is 
  big 
  enough 
  to 
  produce 
  the 
  

   great 
  absorption. 
  

  

  Our 
  assumption 
  also 
  explains 
  the 
  fact 
  that 
  even 
  for 
  the 
  

   same 
  pressure 
  the 
  absorption 
  first 
  sets 
  in 
  for 
  a 
  certain 
  

   strength 
  of 
  current. 
  

  

  The 
  cathode 
  fall, 
  for 
  which 
  the 
  great 
  absorption 
  sets 
  in, 
  

   we 
  might 
  call 
  the 
  critical 
  cathode 
  fall. 
  The 
  value 
  of 
  this 
  

   may 
  depend 
  on 
  the 
  quality 
  and 
  form 
  of 
  the 
  electrodes 
  and 
  the 
  

   quality 
  of 
  the 
  gas, 
  and 
  it 
  may 
  also 
  be 
  somewhat 
  different 
  at 
  

   different 
  pressures. 
  For 
  O2 
  and 
  HBr 
  with 
  the 
  tube 
  used 
  it 
  

   is 
  about 
  650 
  volts. 
  

  

  The 
  rapid 
  absorption 
  with 
  diminution 
  of 
  pressure 
  is 
  also 
  

   observed 
  by 
  Willows 
  for 
  air, 
  nitrogen, 
  and 
  hydrogen 
  ; 
  but 
  

   he 
  comes 
  to 
  the 
  conclusion 
  that 
  the 
  absorption 
  is 
  due 
  to 
  a 
  

   chemical 
  combination 
  between 
  the 
  gas 
  and 
  the 
  walls 
  of 
  the 
  

   tube. 
  Such 
  a 
  chemical 
  combination 
  seems 
  a 
  'priori 
  very 
  un- 
  

   likely 
  ; 
  for 
  it 
  would 
  mean 
  that 
  the 
  discharge 
  in 
  a 
  mysterious 
  

   way 
  imparted 
  to 
  the 
  walls 
  a 
  chemical 
  activity 
  ichich 
  should 
  

   only 
  he 
  j^ossessed 
  hy 
  the 
  icalls 
  as 
  long 
  as 
  the 
  discharge 
  loas 
  

   running. 
  Another 
  objection 
  to 
  Willows's 
  explanation, 
  which 
  

   he 
  also 
  mentions 
  himself, 
  is 
  that 
  the 
  absorption 
  seems 
  not 
  to 
  

   depend 
  essentially 
  on 
  the 
  chemical 
  character 
  of 
  the 
  gas, 
  but 
  

   is 
  found 
  even 
  for 
  inert 
  gases. 
  

  

  