﻿280 
  Ray 
  Leigh 
  and 
  Ramsay 
  — 
  Argo7i, 
  a 
  New 
  

  

  tion, 
  even 
  provisionally, 
  we 
  had 
  to 
  face 
  the 
  improbability 
  that 
  

   a 
  gas 
  surrounding 
  us 
  on 
  all 
  sides, 
  and 
  present 
  in 
  enormous 
  

   quantities, 
  could 
  have 
  remained 
  so 
  long 
  unsuspected. 
  

  

  The 
  method 
  of 
  most 
  universal 
  application 
  by 
  which 
  to 
  test 
  

   whether 
  a 
  gas 
  is 
  pure 
  or 
  a 
  mixture 
  of 
  components 
  of 
  different 
  

   densities 
  is 
  that 
  of 
  diffusion. 
  By 
  this 
  means 
  Graham 
  suc- 
  

   ceeded 
  in 
  effecting 
  a 
  partial 
  separation 
  of 
  the 
  nitrogen 
  and 
  

   oxygen 
  of 
  the 
  air, 
  in 
  spite 
  of 
  the 
  comparatively 
  small 
  dif- 
  

   ference 
  of 
  densities. 
  If 
  the 
  atmosphere 
  contain 
  an 
  unknown 
  

   gas 
  of 
  anything 
  like 
  the 
  density 
  supposed, 
  it 
  should 
  be 
  possi- 
  

   ble 
  to 
  prove 
  the 
  fact 
  by 
  operations 
  conducted 
  upon 
  air 
  which 
  

   had 
  undergone 
  atmolysis. 
  This 
  experiment, 
  although 
  in 
  view 
  

   from 
  the 
  first, 
  was 
  not 
  executed 
  until 
  a 
  later 
  stage 
  of 
  the 
  

   inquiry 
  (§ 
  6), 
  when 
  results 
  were 
  obtained 
  sufficient 
  of 
  them- 
  

   selves 
  to 
  prove 
  that 
  the 
  atmosphere 
  contains 
  a 
  previously 
  

   unknown 
  gas. 
  

  

  But 
  although 
  the 
  method 
  of 
  diffusion 
  was 
  capable 
  of 
  decid- 
  

   ing 
  the 
  main, 
  or 
  at 
  any 
  rate 
  the 
  first 
  question, 
  it 
  held 
  out 
  no 
  

   prospect 
  of 
  isolating 
  the 
  new 
  constituent 
  of 
  the 
  atmosphere, 
  

   and 
  we, 
  therefore, 
  turned 
  our 
  attention 
  in 
  the 
  first 
  instance 
  to 
  

   the 
  consideration 
  of 
  methods 
  more 
  strictly 
  chemical. 
  And 
  

   here 
  the 
  question 
  forced 
  itself 
  upon 
  us 
  as 
  to 
  what 
  really 
  was 
  

   the 
  evidence 
  in 
  favor 
  of 
  the 
  prevalent 
  doctrine 
  that 
  the 
  inert 
  

   residue 
  from 
  air 
  after 
  withdrawal 
  of 
  oxygen, 
  water, 
  and 
  car- 
  

   bonic 
  anhydride, 
  is 
  all 
  of 
  one 
  kind. 
  

  

  The 
  identification 
  of 
  " 
  phlogisticated 
  air 
  " 
  with 
  the 
  con- 
  

   stituent 
  of 
  nitric 
  acid 
  is 
  due 
  to 
  Cavendish, 
  whose 
  method 
  

   consisted 
  in 
  operating 
  with 
  electric 
  sparks 
  upon 
  a 
  short 
  column 
  

   of 
  gas 
  confined 
  with 
  potash 
  over 
  mercury 
  at 
  the 
  upper 
  end 
  of 
  

   an 
  inverted 
  U'tube-* 
  

  

  Attempts 
  to 
  repeat 
  Cavendish's 
  experiment 
  in 
  Cavendish's 
  

   manner 
  have 
  only 
  increased 
  the 
  admiration 
  with 
  which 
  we 
  

   regard 
  this 
  wonderful 
  investigation. 
  Working 
  on 
  almost 
  micro- 
  

   scopical 
  quantities 
  of 
  material, 
  and 
  by 
  operations 
  extending 
  

   over 
  days 
  and 
  weeks, 
  he 
  thus 
  established 
  one 
  of 
  the 
  most 
  

   important 
  facts 
  in 
  chemistry. 
  And 
  what 
  is 
  still 
  more 
  to 
  the 
  

   purpose, 
  he 
  raises 
  as 
  distinctly 
  as 
  we 
  could 
  do, 
  and 
  to 
  a 
  certain 
  

   extent 
  resolves, 
  the 
  question 
  above 
  suggested. 
  The 
  passage 
  is 
  

   so 
  important 
  that 
  it 
  will 
  be 
  desirable 
  to 
  quote 
  it 
  at 
  full 
  length. 
  

  

  " 
  As 
  far 
  as 
  the 
  experiments 
  hitherto 
  published 
  extend, 
  we 
  

   scarcely 
  know 
  more 
  of 
  the 
  phlogisticated 
  part 
  of 
  our 
  atmo- 
  

   sphere, 
  than 
  that 
  it 
  is 
  not 
  diminished 
  by 
  lime-water, 
  caustic 
  

   alkalies, 
  or 
  nitrous 
  air 
  ; 
  that 
  it 
  is 
  unfit 
  to 
  support 
  fire, 
  or 
  main- 
  

   tain 
  life 
  in 
  animals 
  ; 
  and 
  that 
  its 
  specific 
  gravity 
  is 
  not 
  much 
  

   less 
  than 
  that 
  of 
  common 
  air 
  : 
  so 
  that 
  though 
  the 
  nitrous 
  acid, 
  

  

  * 
  Experiments 
  on 
  Air, 
  Phil. 
  Trans., 
  vol. 
  lxxv, 
  p. 
  372, 
  1785. 
  

  

  