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  PROF. 
  T. 
  G. 
  BONNET 
  ON 
  TWO 
  TEAVEESES 
  OF 
  THE 
  

  

  less, 
  making 
  every 
  allowance 
  for 
  this, 
  I 
  believe, 
  even 
  after 
  the 
  fog 
  

   which 
  arose 
  from 
  Burlington 
  House 
  last 
  September, 
  that 
  the 
  more 
  

   important 
  of 
  the 
  results 
  mentioned 
  above 
  are 
  not 
  very 
  far 
  from 
  the 
  

   truth. 
  

  

  IV. 
  APPENDIX. 
  

  

  Descriptions 
  of 
  Miceoscopic 
  Structures. 
  

  

  A. 
  "Western 
  Alps. 
  

  

  (a) 
  Schists 
  of 
  the 
  Combe 
  cle 
  Gavet. 
  

  

  (a) 
  Strong 
  Mica-schist 
  near 
  the 
  Octroi 
  de 
  Vizille 
  (fig. 
  8). 
  — 
  This 
  

   rock 
  (p. 
  71) 
  chiefly 
  consists 
  of 
  mica, 
  kyanite, 
  and 
  quartz. 
  The 
  first 
  

   mineral 
  varies 
  from 
  a 
  brown, 
  strongly 
  dichroic 
  mica, 
  to 
  a 
  very 
  pale 
  

  

  Pig. 
  8. 
  — 
  Pen-and-ink 
  Diagram 
  of 
  Schist 
  from 
  near 
  Octroi, 
  Vizille. 
  

   ( 
  X 
  29 
  diameters.) 
  

  

  A 
  

  

  (A) 
  kyanite 
  showing 
  linear 
  enclosures. 
  The 
  divergence 
  of 
  these 
  bands 
  in 
  the 
  

   grains 
  is 
  more 
  marked 
  in 
  some 
  other 
  parts 
  of 
  the 
  slide, 
  which, 
  however, 
  

   were 
  not 
  otherwise 
  so 
  well 
  fitted 
  for 
  representation. 
  

  

  straw-coloured 
  mineral 
  (the 
  more 
  abundant). 
  The 
  latter 
  exhibits 
  

   no 
  marked 
  dichroism, 
  but 
  gives 
  rich 
  colours 
  with 
  crossed 
  nicols. 
  

   This 
  mineral 
  may 
  result 
  from 
  a 
  " 
  bleaching" 
  of 
  the 
  brown 
  mica, 
  by 
  

   separation 
  of 
  the 
  iron 
  constituent 
  ; 
  but 
  I 
  am 
  doubtful 
  whether 
  all 
  of 
  

   it 
  can 
  thus 
  be 
  explained. 
  The 
  kyanite 
  occurs 
  in 
  grains, 
  from 
  sub- 
  

  

  