﻿•418 
  Lord 
  Rayleigh 
  on 
  the 
  Question 
  of 
  

  

  The 
  spectroscopic 
  evidence 
  here 
  set 
  forth 
  is 
  certainly 
  far 
  

   from 
  suggesting 
  that 
  air, 
  previously 
  to 
  any 
  addition, 
  already 
  

   contains 
  2 
  parts 
  in 
  10,000 
  o£ 
  free 
  hydrogen. 
  The 
  passage 
  

   from 
  2 
  to 
  3 
  parts 
  in 
  10,000 
  might 
  possibly 
  produce 
  the 
  

   observed 
  change 
  of 
  visibility 
  which 
  followed 
  the 
  introduction 
  

   of 
  one 
  ten-thousandth 
  of 
  hydrogen 
  ; 
  and 
  the 
  behaviour 
  with 
  

   chlorine 
  and 
  hot 
  copper 
  oxide 
  is 
  not 
  absolutely 
  inconsistent 
  

   with 
  the 
  initial 
  hydrogen. 
  But 
  the 
  reconciliation 
  seems 
  to 
  

   involve 
  coincidences 
  of 
  little 
  a 
  priori 
  probability. 
  

  

  Determinations 
  by 
  Combustion. 
  

  

  In 
  M. 
  Gautier's 
  experiments 
  large 
  volumes 
  of 
  dried 
  air 
  

   were 
  passed 
  through 
  tubes 
  containing 
  copper 
  oxide 
  heated 
  in 
  

   a 
  specially 
  constructed 
  furnace, 
  the 
  water 
  formed 
  being 
  col- 
  

   lected 
  in 
  suitable 
  phosphoric 
  tubes 
  and 
  accurately 
  weighed. 
  

   In 
  unsystematic 
  experiments 
  the 
  source 
  of 
  the 
  water 
  so 
  

   collected 
  might 
  be 
  doubtful, 
  but 
  it 
  is 
  explained 
  that 
  the 
  

   apparatus 
  was 
  tested 
  with 
  pure 
  dry 
  oxygen, 
  and 
  that 
  under 
  

   these 
  conditions 
  the 
  phosphoric 
  tube 
  showed 
  no 
  increase 
  of 
  

   weight 
  exceeding 
  *1 
  rag. 
  The 
  work 
  w 
  T 
  as 
  evidently 
  very 
  

   careful 
  and 
  thorough 
  ; 
  and 
  the 
  impression 
  left 
  upon 
  the 
  mind 
  

   of 
  the 
  reader 
  is 
  that 
  the 
  case 
  is 
  completely 
  made 
  out. 
  Indeed, 
  

   had 
  I 
  been 
  acquainted 
  with 
  the 
  details, 
  as 
  set 
  forth 
  in 
  Ann. 
  

   d. 
  Chimie, 
  t. 
  xxii. 
  Jan. 
  1901, 
  at 
  an 
  earlier 
  stage, 
  I 
  should 
  

   probably 
  have 
  attempted 
  no 
  experiments 
  of 
  my 
  own. 
  It 
  so 
  

   happens, 
  however, 
  that 
  I 
  had 
  already 
  begun 
  some 
  work, 
  

   which 
  has 
  since 
  been 
  further 
  extended, 
  and 
  which 
  has 
  yielded 
  

   results 
  that 
  I 
  find 
  rather 
  embarassing, 
  and 
  am 
  even 
  tempted 
  

   to 
  suppress. 
  For 
  the 
  conclusion 
  to 
  which 
  these 
  determina- 
  

   tions 
  w 
  T 
  ould 
  lead 
  me 
  is 
  that 
  the 
  hydrogen 
  in 
  country 
  air 
  is 
  

   but 
  a 
  small 
  fraction, 
  perhaps 
  not 
  more 
  than 
  one 
  eighth 
  part, 
  

   of 
  that 
  given 
  by 
  M. 
  Gautier. 
  Although 
  I 
  am 
  well 
  aware 
  that 
  

   my 
  experience 
  in 
  these 
  matters 
  is 
  much 
  inferior 
  to 
  his, 
  and 
  

   that 
  I 
  may 
  be 
  in 
  error, 
  I 
  think 
  it 
  proper 
  that 
  some 
  record 
  

   should 
  be 
  made 
  of 
  the 
  experiments, 
  which 
  were 
  carefully 
  

   conducted 
  with 
  the 
  assistance 
  of 
  Mr. 
  Gordon 
  and 
  many 
  

   times 
  repeated. 
  

  

  The 
  quantity 
  of 
  air 
  upon 
  which 
  I 
  operated 
  was 
  almost 
  

   uniformly 
  10 
  litres, 
  much 
  less 
  than 
  was 
  used 
  by 
  M. 
  Gautier. 
  

   A 
  glass 
  aspirating 
  bottle, 
  originally 
  filled 
  with 
  water, 
  was 
  

   discharged 
  upon 
  the 
  lawn, 
  so 
  that 
  the 
  water 
  was 
  replaced 
  by 
  

   fresh 
  country 
  air. 
  During 
  an 
  experiment 
  the 
  air 
  was 
  driven 
  

   forward, 
  at 
  the 
  rate 
  of 
  about 
  1£ 
  litres 
  per 
  hour, 
  by 
  water 
  

   entering 
  below. 
  After 
  traversing 
  a 
  bubbler 
  charged 
  with 
  

   alkali, 
  it 
  was 
  desiccated 
  first 
  by 
  passing 
  over 
  a 
  surface 
  of 
  

  

  