﻿of 
  Pressure 
  ivhich 
  accompany 
  Point 
  Discharge. 
  29 
  

  

  which 
  repeated 
  discharges 
  will 
  not 
  permanently 
  take 
  us. 
  

   Now 
  in 
  all 
  cases 
  where 
  contraction 
  has 
  been 
  known 
  to 
  be 
  due 
  

   to 
  combination 
  of 
  oxygen 
  with 
  the 
  hydrogen, 
  it 
  has 
  been 
  

   recognizable 
  by 
  two 
  marked 
  characteristics. 
  Negative 
  

   electricity 
  has 
  produced 
  a 
  larger 
  effect 
  than 
  positive 
  (for 
  

   small 
  amounts 
  of 
  oxygen 
  many 
  times 
  larger) 
  ; 
  and 
  if 
  the 
  

   discharges 
  have 
  been 
  repeated 
  often 
  enough 
  the 
  effect 
  has 
  

   ceased, 
  presumably 
  because 
  the 
  oxygen 
  has 
  come 
  to 
  an 
  end 
  *. 
  

   Neither 
  of 
  these 
  statements 
  is 
  true 
  of 
  the 
  residual 
  contraction, 
  

   and 
  it 
  therefore 
  seems 
  unlikely 
  that 
  this 
  can 
  be 
  due 
  to 
  a 
  trace 
  

   of 
  impurity. 
  

  

  On 
  the 
  other 
  hand, 
  its 
  amount 
  is 
  roughly 
  proportional 
  to 
  

   the 
  quantity 
  of 
  electricity 
  passed 
  from 
  the 
  point 
  ; 
  that 
  is 
  to 
  

   the 
  number 
  of 
  ions. 
  

  

  For 
  these 
  and 
  other 
  reasons 
  we 
  are 
  at 
  present 
  inclined 
  to 
  

   connect 
  it 
  with 
  a 
  temporary 
  absorption 
  of 
  the 
  ions 
  themselves 
  

   at 
  the 
  electrodes. 
  

  

  The 
  limiting 
  value 
  of 
  N 
  = 
  l'l 
  means 
  that 
  about 
  two 
  atoms 
  

   of 
  hydrogen 
  (if 
  that 
  is 
  the 
  only 
  gas 
  present) 
  disappear 
  per 
  

   ion. 
  This 
  is 
  consistent 
  with 
  the 
  view 
  that 
  when 
  the 
  ions 
  

   arrive 
  at 
  the 
  electrodes 
  it 
  is 
  only 
  the 
  single 
  electrified 
  atom, 
  

   which 
  may 
  be 
  thought 
  of 
  as 
  holding 
  the 
  complex 
  carrier 
  

   together, 
  that 
  peuetrates 
  the 
  electrode 
  and 
  gets 
  absorbed; 
  

   the 
  unelectrified 
  remainder 
  being 
  as 
  it 
  were 
  brushed 
  off 
  at 
  

   the 
  surface 
  of 
  the 
  metal 
  and 
  so 
  rendered 
  free 
  to 
  evaporate. 
  

  

  An 
  examination 
  of 
  the 
  pressure 
  changes 
  occurring 
  after 
  

   discharge 
  is 
  over 
  does 
  in 
  fact 
  suggest 
  that 
  these 
  remainders 
  

   do 
  not 
  at 
  once 
  evaporate 
  on 
  giving 
  up 
  the 
  charged 
  atoms 
  ; 
  and 
  

   we 
  believe 
  that 
  with 
  improved 
  apparatus 
  now 
  in 
  course 
  of 
  con- 
  

   struction, 
  we 
  may 
  be 
  able 
  indirectly 
  to 
  obtain 
  the 
  value 
  of 
  p 
  

   corresponding 
  to 
  complete 
  absorption 
  of 
  the 
  ions, 
  by 
  obser- 
  

   vations 
  on 
  these 
  after 
  effects. 
  

  

  Be 
  this 
  as 
  it 
  may, 
  it 
  is 
  only 
  necessary 
  here 
  to 
  show 
  that 
  

   hydrogen 
  was 
  obtained 
  so 
  pure 
  that 
  the 
  changes 
  of 
  pressure 
  

   produced 
  in 
  it 
  were 
  small 
  compared 
  with 
  those 
  due 
  to 
  the 
  

   quantities 
  of 
  oxygen 
  with 
  which 
  we 
  experimented, 
  and 
  this 
  

   will 
  be 
  found 
  to 
  have 
  been 
  the 
  case. 
  Repeated 
  pumpings 
  

   out 
  and 
  refillings 
  brought 
  down 
  p 
  to 
  about 
  the 
  same 
  average 
  

   limiting 
  values 
  as 
  did 
  prolonged 
  discharge; 
  and 
  as 
  an 
  addition 
  

   of 
  one 
  volume 
  of 
  oxygen 
  in 
  about 
  ten 
  million 
  of 
  hydrogen 
  

   would 
  have 
  perceptibly 
  raised 
  p 
  it 
  follows 
  that, 
  unless 
  there 
  

   is 
  a 
  lower 
  limit 
  to 
  the 
  quantity 
  of 
  oxygen 
  with 
  which 
  hydrogen 
  

   will 
  combine 
  under 
  point 
  discharge, 
  our 
  hydrogen 
  must 
  have 
  

   contained 
  less 
  than 
  O00001 
  per 
  cent, 
  of 
  oxygen. 
  The 
  

  

  * 
  See 
  page 
  35. 
  

  

  