﻿386 
  Mr. 
  G. 
  A. 
  Hemsalech 
  on 
  Fox 
  Talbot's 
  Method 
  oj 
  

  

  effect 
  is 
  obtained 
  when 
  the 
  ox}^gen 
  enters 
  the 
  flame 
  near 
  its 
  

   base, 
  and 
  the 
  effect 
  vanishes 
  near 
  the 
  top. 
  The 
  reason 
  for 
  

   this 
  is 
  of 
  course 
  the 
  same 
  as 
  before, 
  namely, 
  the 
  accelerated 
  

   combustion 
  of 
  the 
  unburnt 
  gases 
  which 
  predominate 
  near 
  

   the 
  base. 
  It 
  is, 
  however, 
  well 
  to 
  remark 
  that 
  the 
  intensity 
  

   of 
  the 
  coloured 
  flame 
  produced 
  in 
  this 
  way 
  falls 
  appreciably 
  

   short 
  of 
  that 
  obtained 
  when 
  the 
  oxygen 
  is 
  thoroughly 
  mixed 
  

   with 
  the 
  air 
  and 
  coal 
  gas 
  before 
  these 
  gases 
  reach 
  the 
  burner 
  

   plate*. 
  

  

  In 
  order 
  to 
  observe 
  the 
  effect 
  of 
  varying 
  the 
  relative 
  pro- 
  

   portions 
  of 
  the 
  gases 
  in 
  the 
  air-coal 
  gas 
  mixture, 
  an 
  electric 
  

   sprayer 
  was 
  used 
  in 
  connexion 
  with 
  burner 
  No. 
  1 
  described 
  

   in 
  a 
  previous 
  paper 
  f. 
  With 
  this 
  arrangement 
  the 
  funda- 
  

   mental 
  condition 
  for 
  the 
  successful 
  working 
  of 
  Talbot's 
  

   method, 
  namely, 
  the 
  presence 
  of 
  unburnt 
  gases, 
  is 
  most 
  

   strikingly 
  demonstrated 
  by 
  the 
  following 
  experiment: 
  — 
  The 
  

   glass 
  nozzle 
  through 
  which 
  passes 
  the 
  oxygen 
  is 
  held 
  close 
  

   to 
  the 
  edge 
  of 
  the 
  flame 
  about 
  \ 
  inch 
  above 
  the 
  burner- 
  

   plate. 
  The 
  velocity 
  of 
  the 
  oxygen 
  is 
  such 
  that 
  its 
  curved 
  

   path 
  can 
  be 
  distinctly 
  followed 
  to 
  the 
  opposite 
  edge. 
  When 
  

   the 
  air-coal 
  gas 
  mixture 
  is 
  so 
  adjusted 
  that 
  the 
  explosion 
  

   region 
  just 
  begins 
  to 
  rise 
  from 
  the 
  burner-plate, 
  otherwise 
  

   stated 
  when 
  there 
  is 
  an 
  excess 
  of 
  coal 
  gas 
  in 
  the 
  mixture 
  

   with 
  consequent 
  deficiency 
  of 
  combustion, 
  then 
  the 
  portion 
  

  

  Fig. 
  3. 
  

  

  Path 
  of 
  Oxygen 
  

  

  Oxygt 
  

  

  Excess 
  ot 
  Coal 
  Gas. 
  

  

  of 
  the 
  coloured 
  flame 
  situated 
  above 
  the 
  sharply 
  defined 
  

   oxyoen 
  path 
  is 
  most 
  notably 
  increased 
  in 
  luminosity, 
  as 
  

   indicated 
  by 
  the 
  shaded 
  portion 
  of 
  fig. 
  3. 
  If 
  now 
  more 
  air 
  

  

  * 
  Heniralech, 
  Philosophical 
  Magazine, 
  vol. 
  xxxiv. 
  p. 
  243 
  (1917). 
  

   | 
  Hemsalech, 
  ibid. 
  vol. 
  xxxiii. 
  p. 
  6 
  (1917). 
  

  

  