﻿374 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [May 
  11, 
  

  

  destroyed 
  by 
  the 
  deposition 
  of 
  homogeneous 
  black 
  flint, 
  that 
  this 
  

   destruction 
  must 
  have 
  commenced 
  after 
  the 
  coral 
  was 
  imbedded. 
  

  

  In 
  the 
  course 
  of 
  this 
  communication 
  facts 
  and 
  hypotheses 
  have 
  

   been 
  determined 
  and 
  propounded, 
  which 
  have 
  led 
  to 
  the 
  following 
  

   conclusions 
  : 
  — 
  

  

  1. 
  Silica, 
  whether 
  homogeneous, 
  granular, 
  or 
  crystalline, 
  does 
  not 
  

   appear 
  to 
  be 
  deposited 
  at 
  first 
  in 
  the 
  interspaces 
  of 
  corals, 
  but 
  re- 
  

   places 
  a 
  salt 
  of 
  lime 
  which 
  was 
  infiltrated 
  partly 
  in 
  solution 
  or 
  

   partly 
  in 
  a 
  state 
  of 
  mechanical 
  suspension 
  in 
  a 
  compound 
  fluid. 
  The 
  

   replacement 
  does 
  not 
  commence 
  until 
  the 
  salt 
  of 
  lime 
  has 
  acquired 
  

   a 
  certain 
  density, 
  and 
  it 
  occurs 
  first 
  of 
  all 
  in 
  the 
  central 
  parts 
  of 
  the 
  

   loculi 
  in 
  the 
  form 
  of 
  granular 
  points*. 
  

  

  The 
  combinations 
  of 
  the 
  silica 
  with 
  water, 
  the 
  production 
  of 
  its 
  

   hydrates, 
  and 
  the 
  evolution 
  of 
  coloured 
  varieties 
  would 
  appear 
  to 
  be 
  

   determined 
  by 
  the 
  presence 
  of 
  decomposing 
  animal 
  and 
  vegetable 
  

   matters, 
  and 
  of 
  salts 
  of 
  iron, 
  at 
  the 
  time 
  of 
  the 
  entombment 
  of 
  the 
  

   corallum 
  in 
  the 
  bed 
  of 
  the 
  detritus 
  of 
  the 
  reef. 
  

  

  2. 
  The 
  opal 
  lines, 
  the 
  opaque 
  lines 
  in 
  agates, 
  the 
  broad 
  wavy 
  

   milky 
  clouds 
  in 
  otherwise 
  transparent 
  flint, 
  and 
  the 
  porcellanous 
  

   opaque 
  silica 
  are 
  found 
  to 
  have 
  a 
  very 
  close 
  relation 
  with 
  the 
  form 
  

   of 
  silicification, 
  in 
  which 
  much 
  destruction 
  of 
  the 
  hard 
  parts 
  of 
  the 
  

   corallum 
  is 
  noticed. 
  

  

  3. 
  Every 
  grade 
  of 
  a 
  silicification 
  which 
  destroj~s 
  the 
  textures 
  of 
  

   corals 
  and 
  reduces 
  them, 
  at 
  last, 
  to 
  pure 
  homogeneous 
  black 
  flint, 
  

   like 
  that 
  of 
  the 
  upper 
  Chalk, 
  is 
  to 
  be 
  distinguished. 
  Moreover, 
  

   crystalline 
  quartz, 
  chalcedony, 
  and 
  every 
  variety 
  of 
  transparent 
  or 
  

   opaque 
  silica 
  constantly 
  replace 
  the 
  carbonate 
  of 
  lime 
  or 
  the 
  usual 
  

   coral-salts 
  of 
  part 
  or 
  of 
  the 
  whole 
  of 
  a 
  corallum, 
  without 
  preserving 
  

   the 
  structural 
  details. 
  

  

  These 
  destructive 
  sihceous 
  fossilizations, 
  not 
  peculiar 
  to 
  the 
  West 
  

   Indian 
  beds 
  alone, 
  form 
  one 
  of 
  the 
  causes 
  of 
  the 
  deficiency 
  of 
  the 
  

   geological 
  record. 
  

  

  Mat 
  11, 
  1864. 
  

  

  Thomas 
  Carrington, 
  jun., 
  Esq., 
  Chesterfield, 
  Derby 
  ; 
  J. 
  B. 
  Even, 
  

   Esq., 
  C.E., 
  Mem. 
  Soc. 
  Geol. 
  Er., 
  36 
  Rue 
  Montagu, 
  Brussels 
  ; 
  The 
  

   Rev. 
  John 
  Henry 
  Timins, 
  M.A., 
  of 
  Trinity 
  College, 
  Cambridge, 
  

   Vicar 
  of 
  West 
  Mailing, 
  Kent; 
  and 
  Henry 
  Woodward, 
  Esq., 
  E.Z.S., 
  

   of 
  the 
  British 
  Museum, 
  and 
  144 
  Leighton 
  Road, 
  N.W., 
  were 
  elected 
  

   Fellows. 
  

  

  The 
  following 
  communications 
  were 
  read 
  : 
  — 
  

  

  1. 
  On 
  a 
  Section 
  with 
  Mammalian 
  Remains 
  near 
  Thame. 
  

   By 
  T. 
  Codrington, 
  Esq., 
  E.G.S. 
  

  

  In 
  excavating 
  a 
  cutting 
  near 
  Thame, 
  on 
  the 
  Railway 
  between 
  Thame 
  

   and 
  Oxford, 
  a 
  section 
  remarkable 
  in 
  itself 
  and 
  yielding 
  a 
  large 
  

  

  * 
  The 
  phenomena 
  of 
  orbicular 
  silex 
  in 
  the 
  silicified 
  corals 
  will 
  form 
  the 
  

   subject 
  of 
  a 
  future 
  communication. 
  

  

  