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  XXXII. 
  — 
  On 
  two 
  New 
  Processes 
  for 
  the 
  detection 
  of 
  Fluorine 
  when 
  accompanied 
  by 
  

   Silica 
  ; 
  and 
  on 
  the 
  presence 
  of 
  Fluorine 
  in 
  Granite, 
  Trap, 
  and 
  other 
  Igneous 
  

   Rocks, 
  and 
  in 
  the 
  Ashes 
  of 
  Recent 
  and 
  Fossil 
  Plants. 
  By 
  George 
  Wilson, 
  M.D. 
  

  

  (Read 
  April 
  19, 
  1852.) 
  

  

  In 
  several 
  communications 
  made 
  to 
  this 
  Society 
  and 
  to 
  the 
  British 
  Associa- 
  

   tion, 
  I 
  have 
  announced 
  the 
  results 
  of 
  a 
  series 
  of 
  observations 
  on 
  the 
  distribution 
  

   of 
  Fluorine 
  throughout 
  the 
  mineral, 
  vegetable, 
  and 
  animal 
  kingdoms. 
  To 
  myself, 
  

   the 
  least 
  satisfactory 
  part 
  of 
  these 
  investigations 
  has 
  been 
  the 
  inquiry 
  into 
  the 
  

   presence 
  of 
  fluorine 
  in 
  plants, 
  for 
  I 
  have 
  been 
  more 
  frequently 
  foiled 
  than 
  suc- 
  

   cessful 
  in 
  my 
  attempts 
  to 
  detect 
  it 
  in 
  them. 
  Others 
  have 
  not, 
  apparently, 
  been 
  

   more 
  successful. 
  Daubeny 
  was 
  as 
  unable 
  as 
  Sprengel 
  at 
  an 
  earlier 
  period 
  had 
  

   been, 
  to 
  obtain 
  evidence 
  that 
  the 
  element 
  under 
  notice 
  is 
  present 
  in 
  vegetable 
  

   structures 
  ; 
  and 
  Will 
  of 
  Giessen, 
  the 
  discoverer 
  of 
  fluorine 
  in 
  plants, 
  speaks 
  only 
  

   of 
  " 
  traces" 
  of 
  it 
  having 
  been 
  detected 
  in 
  barley. 
  Later 
  observers 
  have 
  not 
  spoken 
  

   more 
  confidently 
  concerning 
  its 
  abundance 
  in 
  vegetables 
  ; 
  and 
  in 
  the 
  many 
  ana- 
  

   lyses 
  of 
  the 
  ashes 
  of 
  plants 
  which 
  have 
  recently 
  been 
  published, 
  it 
  seldom, 
  if 
  ever, 
  

   finds 
  a 
  place. 
  

  

  That 
  one 
  cause 
  of 
  this 
  apparent 
  rarity 
  of 
  fluorine 
  in 
  vegetables, 
  is 
  the 
  small 
  

   extent 
  to 
  which 
  it 
  occurs 
  in 
  them 
  is 
  certain 
  ; 
  but 
  I 
  have 
  never 
  doubted 
  that 
  the 
  

   chief 
  reason 
  why 
  it 
  appeared 
  to 
  be 
  so 
  scanty 
  a 
  constituent 
  of 
  plants, 
  was 
  its 
  

   occurrence 
  along 
  with 
  silica, 
  which 
  makes 
  its 
  recognition 
  very 
  difficult. 
  I 
  had 
  

   given 
  up, 
  accordingly, 
  all 
  hopes 
  of 
  satisfactorily 
  demonstrating 
  its 
  wide 
  distribu- 
  

   tion, 
  till 
  better 
  processes 
  than 
  are 
  at 
  present 
  in 
  use, 
  were 
  devised 
  for 
  its 
  de- 
  

   tection 
  when 
  accompanied 
  by 
  silica. 
  

  

  For 
  the 
  same 
  reason 
  I 
  have 
  thought 
  it 
  hitherto 
  useless 
  to 
  endeavour 
  to 
  trace 
  

   back 
  fluorine 
  from 
  the 
  plants, 
  animals, 
  natural 
  waters, 
  and 
  more 
  accessible 
  strata 
  

   which 
  are 
  the 
  main 
  seats 
  of 
  life 
  at 
  the 
  present 
  day, 
  to 
  those 
  earlier 
  rocks 
  and 
  

   geological 
  formations 
  which 
  have 
  furnished 
  our 
  soils, 
  and 
  have 
  contributed 
  the 
  

   chief 
  soluble 
  matters 
  which 
  are 
  found 
  in 
  the 
  lakes, 
  rivers, 
  and 
  seas 
  of 
  the 
  globe. 
  

   The 
  more 
  ancient 
  rocks 
  abound 
  in 
  silica, 
  and, 
  with 
  our 
  present 
  processes, 
  the 
  

   prospect 
  of 
  discovering 
  fluorine 
  in 
  trap 
  and 
  similar 
  siliceous 
  masses, 
  was 
  not 
  

   encouraging. 
  A 
  representation, 
  however, 
  from 
  Professor 
  Jameson, 
  as 
  to 
  the 
  im- 
  

   portance 
  attaching 
  to 
  the 
  detection 
  of 
  fluorine 
  in 
  the 
  most 
  ancient 
  rocks, 
  led 
  me 
  to 
  

   reconsider 
  the 
  geological 
  and 
  mineralogical 
  interest 
  which 
  the 
  inquiry 
  possessed 
  ; 
  

   and 
  within 
  the 
  last 
  six 
  weeks 
  I 
  have 
  put 
  in 
  practice 
  two 
  methods 
  of 
  investigation, 
  

   which 
  I 
  shall 
  now 
  explain. 
  

  

  vol. 
  xx. 
  part 
  in. 
  6 
  o 
  

  

  