﻿On 
  the 
  Pressure 
  Effect 
  in 
  Corona 
  Discharge. 
  261 
  

  

  It 
  does 
  not 
  appear 
  to 
  be 
  worth 
  while 
  at 
  this 
  stage 
  of 
  the 
  

   investigation 
  to 
  give 
  the 
  wave-lengths 
  of 
  the 
  lines 
  in 
  the 
  

   more 
  complicated 
  groups 
  excited 
  by 
  the 
  quartz 
  arc 
  operating 
  

   at 
  various 
  voltages, 
  as 
  the 
  simpler 
  series 
  excited 
  by 
  the 
  

   Cooper-Hewitt 
  lamp 
  does 
  not 
  appear 
  at 
  the 
  present 
  time 
  to 
  

   conform 
  to 
  any 
  law. 
  The 
  cause 
  of 
  this 
  may 
  appear 
  when 
  

   the 
  relation 
  of 
  this 
  spectrum 
  to 
  the 
  band 
  spectrum 
  developed 
  

   when 
  the 
  iodine 
  is 
  in 
  helium 
  has 
  been 
  studied. 
  This 
  will 
  

   require 
  exposures 
  of 
  many 
  days, 
  however. 
  

  

  XXIX. 
  On 
  the 
  Pressure 
  Effect 
  in 
  Corona 
  Discharge. 
  

   By 
  A. 
  M. 
  Ttndall, 
  D.Sc, 
  and 
  Miss 
  N. 
  S. 
  Searle, 
  B.Sc* 
  

  

  SEVERAL 
  papers 
  have 
  been 
  published 
  within 
  the 
  past 
  few 
  

   years 
  on 
  what 
  has 
  been 
  termed 
  " 
  the 
  ionization 
  pres- 
  

   sure 
  in 
  corona 
  discharge/'' 
  When 
  a 
  glow 
  or 
  " 
  corona 
  " 
  

   discharge 
  starts 
  between 
  a 
  cylinder 
  and 
  an 
  axial 
  wire 
  in 
  a 
  

   closed 
  tube 
  at 
  atmospheric 
  pressure, 
  a 
  sudden 
  rise 
  in 
  pressure 
  

   is 
  observed. 
  Farwellf 
  and 
  KunzJ 
  have 
  contended 
  that 
  this 
  

   pressure 
  effect 
  is 
  quite 
  distinct 
  from 
  that 
  produced 
  by 
  the 
  

   heating 
  effect 
  of 
  the 
  discharge, 
  and 
  have 
  suggested 
  that 
  it 
  is 
  

   due 
  to 
  the 
  increase 
  in 
  the 
  number 
  of 
  gas 
  particles 
  resulting 
  

   from 
  ionization 
  in 
  the 
  tube. 
  

  

  Kunz 
  also 
  has 
  deduced 
  the 
  following 
  formula 
  connecting 
  

   the 
  rise 
  in 
  pressure 
  u 
  p\— 
  p 
  " 
  with 
  the 
  current 
  " 
  i" 
  potential 
  

   difference 
  " 
  e,* 
  9 
  and 
  the 
  volume 
  of 
  the 
  tube 
  " 
  v 
  

  

  a 
  

  

  i=t 
  -r(Pi-Po)> 
  

  

  In 
  support 
  of 
  this 
  formula 
  Warner 
  § 
  has 
  shown 
  experi- 
  

   mentally 
  in 
  a 
  number 
  of 
  gases 
  that, 
  if 
  the 
  potential 
  differ- 
  

   ence 
  is 
  constant, 
  " 
  i 
  " 
  is 
  proportional 
  to 
  "pi—p 
  " 
  Arnold 
  |], 
  

   however, 
  has 
  suggested 
  that 
  the 
  pressure 
  effect 
  can 
  be 
  

   accounted 
  for 
  by 
  thermal 
  considerations 
  alone,, 
  and 
  has 
  

   pointed 
  out 
  that 
  the 
  small 
  magnitude 
  of 
  the 
  current 
  excluded 
  

   the 
  possibility 
  of 
  any 
  appreciable 
  contribution 
  to 
  pressure 
  by 
  

   ionization. 
  Recently 
  Warner^ 
  has 
  replied 
  to 
  this 
  criticism. 
  

   He 
  has 
  described 
  a 
  number 
  of 
  experiments 
  on 
  the 
  pressure 
  

  

  # 
  Communicated 
  by 
  the 
  Authors. 
  

  

  t 
  Farwell, 
  Proc. 
  A.M.I.E.E. 
  vol. 
  xxxiii. 
  p. 
  1717 
  (1914). 
  

  

  X 
  Kunz, 
  Phys. 
  Rev. 
  vol. 
  viii. 
  p. 
  28 
  (1916). 
  

  

  § 
  Warner, 
  Phvs. 
  Rev. 
  vol. 
  viii. 
  p. 
  285 
  (1916). 
  

  

  || 
  Arnold, 
  Phys. 
  Rev. 
  vol. 
  ix. 
  p. 
  93 
  (1917). 
  

  

  H 
  Warner, 
  Phys. 
  Rev. 
  vol. 
  x. 
  p. 
  483 
  (1917). 
  

  

  