﻿406 
  Prof. 
  R. 
  W. 
  Wood 
  on 
  the 
  Electrical 
  Resonance 
  of 
  

  

  bulbs 
  with 
  carefully 
  dried 
  hydrogen 
  gas. 
  after 
  the 
  film 
  had 
  

   be>ui 
  formed, 
  but 
  the 
  traces 
  of 
  oxygen 
  present 
  in 
  the 
  gas 
  were 
  

   sufficient 
  to 
  bleach 
  the 
  films. 
  By 
  employing 
  two 
  adjoining- 
  

   bulbs, 
  each 
  lined 
  with 
  a 
  coloured 
  film, 
  and 
  cooling 
  one 
  

   of 
  these 
  in 
  carbonic 
  acid 
  and 
  ether, 
  I 
  was 
  enabled 
  to 
  fill 
  

   the 
  bulbs 
  with 
  hydrogen 
  at 
  atmospheric 
  pressure 
  without 
  

   destroying 
  the 
  coloured 
  film 
  in 
  the 
  cooled 
  bulb. 
  The 
  low 
  

   temperature 
  prevented 
  chemical 
  action, 
  and 
  the 
  oxygen 
  was 
  

   wholly 
  removed 
  by 
  the 
  film 
  in 
  the 
  warmer 
  bulb. 
  On 
  warming 
  

   the 
  bulb 
  again, 
  the 
  colours 
  persisted, 
  showing 
  that 
  no 
  change 
  

   was 
  produced 
  by 
  the 
  presence 
  of 
  pure 
  hydrogen. 
  

  

  I 
  find 
  that 
  it 
  is 
  even 
  possible 
  to 
  fill 
  a 
  bulb 
  with 
  air 
  at 
  

   atmospheric 
  pressure 
  without 
  destroying 
  the 
  colour, 
  if 
  the 
  

   bulb 
  is 
  thoroughly 
  cooled 
  with 
  the 
  carbon 
  dioxide 
  and 
  ether, 
  

   the 
  chemical 
  action 
  not 
  taking 
  place 
  at 
  this 
  low 
  temperature. 
  

   These 
  experiments 
  were 
  tried 
  to 
  test 
  a 
  certain 
  theory 
  of 
  the 
  

   cause 
  of 
  the 
  colours 
  which 
  occurred 
  to 
  me 
  one 
  day, 
  which 
  it 
  is 
  

   not 
  necessary 
  to 
  go 
  into 
  as 
  it 
  was 
  found 
  to 
  be 
  worthless. 
  

   The 
  extreme 
  sensitiveness 
  of 
  these 
  coloured 
  films 
  to 
  minute 
  

   traces 
  of 
  oxygen 
  makes 
  it 
  seem 
  probable 
  that 
  they 
  will 
  prove 
  

   useful 
  in 
  the 
  study 
  of 
  the 
  flow 
  of 
  gases 
  through 
  small 
  apertures 
  

   and 
  capillaries. 
  I 
  have 
  noticed 
  that 
  if 
  the 
  capillary 
  is 
  

   exceedingly 
  fine, 
  the 
  film, 
  instead 
  of 
  disappearing 
  all 
  at 
  once, 
  

   gradually 
  melts 
  away, 
  beginning 
  at 
  the 
  end 
  of 
  the 
  bulb 
  near 
  

   the 
  capillary. 
  Sometimes 
  it 
  is 
  half-a-minute 
  before 
  the 
  colour 
  

   at 
  the 
  other 
  end 
  of 
  the 
  bulb 
  bleaches 
  out. 
  It 
  is 
  as 
  if 
  a 
  fluid 
  

   were 
  slowly 
  rising 
  in 
  the 
  bulb 
  and 
  dissolving 
  the 
  film. 
  This 
  

   seems 
  rather 
  surprising, 
  in 
  view 
  of 
  the 
  ideas 
  which 
  we 
  hold 
  

   about 
  the 
  diffusion 
  of 
  gases 
  in 
  highly 
  exhausted 
  receivers. 
  

  

  Relation 
  between 
  the 
  Colour 
  of 
  the 
  Film 
  and 
  the 
  Size 
  and 
  

   Distribution 
  of 
  the 
  Particles. 
  

  

  One 
  peculiarity 
  of 
  the 
  coloured 
  films 
  is 
  that 
  the 
  colour 
  

   produced 
  under 
  a 
  given 
  condition 
  seems 
  to 
  depend 
  in 
  some 
  

   way 
  on 
  the 
  condition 
  of 
  the 
  glass 
  surface 
  on 
  which 
  the 
  film 
  

   is 
  deposited. 
  Circular 
  pink 
  spots 
  are 
  frequently 
  found 
  on 
  a 
  

   blue 
  field, 
  while 
  sometimes 
  circular 
  spots 
  quite 
  devoid 
  of 
  

   colour 
  are 
  observed. 
  The 
  centre 
  of 
  the 
  circle 
  is 
  usually 
  

   occupied 
  by 
  a 
  dark 
  speck, 
  which 
  I 
  believe 
  to 
  be 
  a 
  small 
  

   particle 
  of 
  the 
  metal 
  thrown 
  up 
  when 
  the 
  globule 
  is 
  heated. 
  

   This 
  speck, 
  strangely 
  enough, 
  seems 
  to 
  modify 
  the 
  nature 
  of 
  

   the 
  surface 
  of 
  the 
  glass 
  over 
  a 
  circular 
  area 
  surrounding 
  it, 
  

   so 
  that 
  a 
  film 
  of 
  a 
  different 
  colour 
  forms 
  on 
  it, 
  or 
  in 
  certain 
  

   cases 
  no 
  film 
  at 
  all 
  forms. 
  One 
  of 
  these 
  spots 
  which 
  I 
  studied 
  

   under 
  the 
  microscope 
  proved 
  interesting. 
  The 
  black 
  speck 
  

   in 
  the 
  centre 
  was 
  found 
  to 
  be 
  made 
  up 
  of 
  a 
  number 
  of 
  coarse 
  

  

  