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  XL 
  I 
  II. 
  Note 
  on 
  Fox 
  Talbot's. 
  Method 
  of 
  obtaining 
  Coloured 
  

   Flames 
  of 
  Great 
  Intensity. 
  By 
  G. 
  A. 
  Hemsalech, 
  Ho- 
  

   norary 
  Research 
  Fellow 
  in 
  the 
  University 
  of 
  Manchester*. 
  

  

  LORD 
  RAYLEIGH 
  has 
  very 
  kindly 
  called 
  my 
  attention 
  

   to 
  a 
  short 
  hut 
  interesting 
  paper 
  by 
  Talbot, 
  in 
  which 
  

   the 
  latter 
  describes 
  an 
  exceedingly 
  simple 
  device 
  of 
  pro- 
  

   ducing 
  intensely 
  luminous 
  metal 
  vapours 
  in 
  the 
  flame 
  of 
  a 
  

   spirit-lampf 
  . 
  In 
  view 
  of 
  the 
  historic 
  interest 
  attached 
  to 
  

   this 
  paper 
  as 
  recording 
  an 
  example 
  of 
  the 
  endeavours 
  made 
  

   by 
  the 
  early 
  spectroscopists 
  to 
  improve 
  upon 
  the 
  efficiency 
  

   of 
  the 
  light 
  sources 
  at 
  their 
  disposal, 
  and 
  also 
  in 
  consideration 
  

   of 
  the 
  fact 
  that 
  the 
  method 
  is 
  not 
  mentioned 
  in 
  modern 
  works 
  

   on 
  spectroscopy, 
  it 
  may 
  perhaps 
  be 
  of 
  some 
  use 
  to 
  recall 
  

   Talbot's 
  experiment, 
  and 
  to 
  give 
  the 
  results 
  of 
  a 
  few 
  

   personal 
  observations 
  on 
  the 
  same 
  subject. 
  

  

  In 
  Talbot's 
  own 
  words 
  the 
  method 
  is 
  as 
  follows 
  : 
  — 
  " 
  It 
  is 
  

   only 
  requisite 
  to 
  place 
  a 
  lump 
  of 
  common 
  salt 
  upon 
  the 
  wick 
  

   of 
  a 
  spirit-lamp, 
  and 
  to 
  direct 
  a 
  stream 
  of 
  oxygen 
  gas 
  from 
  

   a 
  blowpipe 
  upon 
  the 
  salt. 
  The 
  light 
  emitted 
  is 
  quite 
  homo- 
  

   geneous 
  and 
  of 
  dazzling 
  brightness. 
  If 
  instead 
  of 
  common 
  

   salt 
  we 
  use 
  the 
  various 
  salts 
  of 
  strontium, 
  barytes, 
  etc., 
  we 
  

   obtain 
  the 
  well-known 
  coloured 
  flames, 
  which 
  are 
  charac- 
  

   teristic 
  of 
  those 
  substances, 
  with 
  far 
  more 
  brilliancy 
  than 
  by 
  

   any 
  other 
  method 
  with 
  which 
  I 
  am 
  acquainted." 
  It 
  is 
  to 
  be 
  

   noted 
  that 
  Talbot 
  precisely 
  states 
  that 
  the 
  stream 
  of 
  oxygen 
  

   is 
  directed 
  upon 
  the 
  salt. 
  No 
  explanation 
  is, 
  however, 
  given 
  

   to 
  account 
  for 
  the 
  result 
  achieved, 
  and 
  it 
  is 
  not 
  certain 
  

   whether 
  the 
  greater 
  luminosity 
  obtained 
  in 
  the 
  manner 
  set 
  

   forth 
  is 
  due 
  to 
  an 
  actual 
  combustion 
  of 
  the 
  salt 
  or 
  to 
  a 
  more 
  

   effective 
  dissociation 
  of 
  the 
  latter, 
  caused 
  by 
  a 
  rise 
  in 
  tem- 
  

   perature 
  of 
  the 
  flame. 
  The 
  following 
  series 
  of 
  experiments 
  

   was 
  made 
  with 
  the 
  object 
  of 
  elucidating 
  the 
  mode 
  of 
  action 
  

   of 
  the 
  oxygen 
  in 
  Talbot's 
  experiment 
  and 
  of 
  applying 
  his 
  

   method 
  to 
  the 
  air-coal 
  gas 
  flame. 
  

  

  1. 
  Obsenmtions 
  with 
  a 
  spirit 
  flame. 
  

  

  With 
  a 
  small 
  piece 
  of 
  salt 
  on 
  the 
  wick 
  the 
  flame 
  appeared 
  

   feebly 
  coloured 
  yellow 
  and 
  showed 
  the 
  D-lines 
  only. 
  A 
  

   current 
  of 
  oxygen 
  gas 
  escaping 
  from 
  a 
  glass 
  nozzle 
  was 
  then 
  

   directed 
  towards 
  the 
  salt, 
  and 
  the 
  latter 
  immediately 
  burst 
  

   out 
  in 
  a 
  brilliant 
  light, 
  emitting 
  the 
  D-lines 
  most 
  strongly, 
  

  

  * 
  Communicated 
  by 
  Sir 
  E. 
  Rutherford, 
  F.R.S. 
  

  

  t 
  H. 
  F. 
  Talbot, 
  Philosophical 
  Magazine, 
  vol. 
  iii. 
  p. 
  35 
  (1833). 
  

  

  