﻿Pressure 
  Effect 
  in 
  Corona 
  Discharge, 
  263 
  

  

  down 
  i£ 
  one 
  takes 
  into 
  account 
  the 
  potent 
  influence 
  of 
  the 
  

   electric 
  wind 
  in 
  distributing 
  the 
  heat 
  generated 
  in 
  the 
  gas 
  

   and 
  conveying 
  it 
  to 
  the 
  walls 
  of 
  the 
  surrounding 
  tube. 
  It 
  

   may 
  be 
  presumed 
  that 
  the 
  following 
  process 
  is 
  in 
  operation. 
  

   As 
  in 
  all 
  cases 
  of 
  discharge 
  from 
  wires 
  or 
  points, 
  the 
  outgoing 
  

   ions 
  set 
  up 
  movements 
  of 
  the 
  gas 
  to 
  which 
  the 
  name 
  electric 
  

   wind 
  has 
  been 
  given. 
  Heat 
  generated 
  in 
  the 
  gas 
  by 
  the 
  

   corona 
  discharge 
  causes 
  a 
  rise 
  in 
  pressure 
  ; 
  but 
  since 
  the 
  

   wind 
  distributes 
  this 
  heat 
  throughout 
  the 
  gas, 
  the 
  rise 
  in 
  

   pressure 
  is 
  quickly 
  checked 
  by 
  the 
  large 
  cooling 
  effect 
  of 
  the 
  

   metal 
  wall 
  of 
  the 
  tube 
  to 
  which 
  the 
  heat 
  is 
  being 
  rapidly 
  

   conveyed. 
  With 
  a 
  large 
  cooling 
  surface 
  and 
  a 
  small 
  rate 
  of 
  

   dissipation 
  of 
  electrical 
  energy, 
  the 
  heat 
  may 
  be 
  removed 
  by 
  

   the 
  walls 
  as 
  fast 
  as 
  it 
  is 
  generated, 
  in 
  which 
  case 
  the 
  pressure, 
  

   after 
  a 
  small 
  initial 
  sudden 
  rise, 
  remains 
  constant. 
  If 
  the 
  

   rate 
  of 
  generation 
  is, 
  however, 
  too 
  great 
  for 
  this 
  to 
  be 
  the 
  

   case, 
  a 
  subsequent 
  gradual 
  rise 
  in 
  pressure 
  will 
  occur 
  as 
  

   the 
  temperature 
  of 
  the 
  gas 
  and 
  of 
  the 
  wall 
  of 
  the 
  tube 
  rises. 
  

   This 
  is 
  well 
  seen 
  in 
  figures 
  3 
  and 
  4 
  in 
  Warner's 
  second 
  paper. 
  

  

  In 
  the 
  case 
  of 
  a 
  supply 
  of 
  heat 
  by 
  a 
  current 
  in 
  the 
  wire, 
  

   no 
  electric 
  wind 
  is 
  present 
  and 
  the 
  cooling 
  effect 
  of 
  the 
  walls 
  

   can 
  only 
  operate 
  through 
  the 
  ordinary 
  convection 
  currents, 
  

   which 
  are 
  far 
  less 
  effective. 
  Hence, 
  for 
  the 
  same 
  energy 
  

   supply 
  the 
  rise 
  in 
  temperature 
  of 
  the 
  gas, 
  and 
  consequently 
  

   its 
  pressure, 
  is 
  considerably 
  greater 
  and 
  reaches 
  its 
  full 
  value 
  

   later 
  in 
  time 
  than 
  when 
  the 
  electric 
  wind 
  is 
  present. 
  This 
  is 
  

   in 
  agreement 
  with 
  experimental 
  results. 
  

  

  Again, 
  Warner 
  states 
  that 
  the 
  return 
  to 
  normal 
  pressure 
  

   after 
  a 
  heating 
  current 
  in 
  the 
  wire 
  is 
  cut 
  off 
  is 
  less 
  rapid 
  than 
  

   it 
  is 
  after 
  the 
  cessation 
  of 
  corona 
  discharge; 
  the 
  numbers 
  

   quoted 
  for 
  the 
  two 
  cases 
  under 
  similar 
  conditions 
  being 
  25 
  

   and 
  18 
  seconds 
  respectively. 
  But 
  this 
  also 
  receives 
  a 
  simple 
  

   explanation 
  in 
  terms 
  of 
  the 
  electric 
  wind, 
  since 
  the 
  movement 
  

   of 
  air 
  does 
  not 
  instantaneously 
  cease 
  when 
  the 
  discharge 
  

   current 
  is 
  cut 
  off. 
  

  

  It 
  follows 
  that 
  computations 
  in 
  which 
  conduction 
  and 
  

   convection 
  losses 
  are 
  neglected 
  break 
  down 
  entirely 
  when 
  

   the 
  electric 
  wind 
  is 
  present, 
  however 
  admissible 
  they 
  may 
  be 
  

   in 
  its 
  absence. 
  

  

  Exception 
  must 
  also 
  be 
  taken 
  to 
  some 
  other 
  opiDions 
  

   expressed 
  in 
  support 
  of 
  the 
  ionization 
  theory. 
  

  

  First, 
  the 
  statement 
  that 
  near 
  the 
  wire 
  every 
  molecule 
  

   may 
  be 
  ionized 
  and 
  still 
  the 
  resultant 
  current 
  may 
  be 
  very 
  

   small 
  is 
  incompatible 
  with 
  the 
  statement 
  that 
  the 
  potential 
  

   gradient 
  near 
  the 
  wire 
  is 
  very 
  high. 
  The 
  latter 
  is, 
  no 
  doubt, 
  

   correct, 
  and 
  the 
  result 
  is 
  that 
  the 
  ions 
  near 
  the 
  wire 
  have 
  a 
  

  

  