﻿362 
  PROCEEDINGS 
  OP 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Apr. 
  27, 
  

  

  from 
  its 
  habitable 
  zone 
  by 
  oscillations 
  of 
  level, 
  and 
  not 
  ejected 
  by 
  

   the 
  sea, 
  it 
  either 
  remains 
  entangled 
  in 
  a 
  position 
  where 
  death 
  

   ensues 
  sooner 
  or 
  later, 
  or 
  it 
  falls 
  to 
  the 
  sea-bottom 
  and 
  plunges 
  

   into 
  the 
  soft 
  chalky 
  coral 
  r 
  mud. 
  In 
  the 
  first 
  instance 
  the 
  soft 
  tissues 
  

   are 
  soon 
  washed 
  away 
  by 
  the 
  force 
  of 
  the 
  sea, 
  and 
  the 
  bare 
  scleren- 
  

   chyma 
  becomes 
  covered 
  with 
  living 
  Corals, 
  Bryozoa, 
  &c. 
  The 
  

   structural 
  details 
  are 
  well 
  preserved, 
  and 
  it 
  is 
  difficult 
  to 
  imagine 
  

   the 
  possibility 
  of 
  the 
  occurrence 
  of 
  decomposition. 
  

  

  4. 
  By 
  prefossil 
  accidents 
  attending 
  the 
  imbedding 
  of 
  Corals. 
  — 
  

   When 
  the 
  mass 
  of 
  coral 
  falls 
  to 
  the 
  sea-bottom 
  and 
  reaches 
  the 
  

   coral-mud, 
  it 
  must 
  come 
  under 
  the 
  destructive 
  influences 
  of 
  all 
  the 
  

   various 
  decompositions 
  which 
  are 
  constantly 
  in 
  progress 
  there. 
  

   This 
  mud 
  performs 
  a 
  most 
  important 
  function 
  in 
  the 
  economy 
  of 
  a 
  

   coral-reef, 
  and 
  is 
  equally 
  worthy 
  of 
  study 
  when 
  raised 
  up 
  and 
  

   forming 
  part 
  of 
  a 
  coral-formation. 
  It 
  is 
  formed 
  by 
  the 
  natural 
  

   wear 
  and 
  tear 
  of 
  the 
  reef 
  above 
  : 
  on 
  to 
  its 
  surface 
  fall 
  the 
  dead 
  and 
  

   dying 
  organisms 
  which 
  lived 
  in 
  and 
  about 
  the 
  corals 
  and 
  their 
  excreta, 
  

   and 
  it 
  teems 
  with 
  Foraminifera. 
  The 
  mud 
  is 
  ever 
  on 
  the 
  increase 
  ; 
  

   and 
  although 
  nothing 
  is 
  known 
  about 
  the 
  manner 
  in 
  which 
  it 
  

   is 
  brought 
  about, 
  still 
  its 
  depths 
  undergo 
  a 
  geologic 
  chemistry, 
  

   which 
  produces 
  even 
  in 
  recent 
  coral- 
  areas 
  the 
  appearances 
  of 
  clay, 
  

   chalk, 
  and 
  even 
  oolitic 
  grains 
  *. 
  The 
  decomposing 
  corals 
  are 
  

   sqon 
  crammed 
  with 
  the 
  calcareous 
  mud, 
  and 
  this 
  is 
  ever 
  under 
  

   the 
  influence 
  of 
  a 
  warm 
  and 
  highly 
  aerated 
  sea 
  f 
  . 
  The 
  Marl 
  of 
  

   Antigua 
  is 
  a 
  Miocene 
  coral-mud, 
  so 
  is 
  the 
  base 
  of 
  the 
  Nivaje 
  de- 
  

   posit 
  in 
  San 
  Domingo, 
  and 
  every 
  coral 
  in 
  them 
  is, 
  or 
  has 
  been, 
  

   stuffed 
  with 
  carbonate 
  of 
  lime 
  and 
  Foraminifera. 
  It 
  does 
  not 
  re- 
  

   quire 
  much 
  imagination 
  to 
  admit 
  that 
  a 
  coral, 
  with 
  decomposing 
  

   soft 
  parts, 
  falling 
  into 
  the 
  mud, 
  is 
  likely 
  to 
  be 
  differently 
  affected 
  

   from 
  one 
  whose 
  sclerenchyma 
  happened 
  to 
  be 
  free 
  from 
  its 
  mem- 
  

   branes. 
  In 
  the 
  first 
  the 
  particles 
  of 
  mud 
  would, 
  after 
  filling 
  the 
  

   corallites, 
  come 
  in 
  contact 
  with 
  the 
  decomposing 
  tissues 
  and 
  the 
  

   softening 
  sclerenchyma 
  ; 
  they 
  would 
  participate 
  in 
  the 
  effects 
  of 
  the 
  

   decomposition, 
  and, 
  of 
  course, 
  the 
  greater 
  the 
  amount 
  of 
  chemical 
  

   action, 
  the 
  greater 
  would 
  be 
  the 
  alteration 
  of 
  the 
  enclosed 
  mud. 
  

   When 
  there 
  was 
  no 
  membrane, 
  the 
  coral 
  would 
  simply 
  be 
  filled 
  

   with 
  mud, 
  which 
  would 
  retain 
  its 
  own 
  peculiar 
  mineralogical 
  cha- 
  

   racters. 
  Now, 
  it 
  would 
  appear 
  that 
  the 
  greater 
  number 
  of 
  the 
  

   peculiar 
  appearances 
  of 
  the 
  Antiguan 
  corals 
  are 
  to 
  be 
  traced 
  to 
  these 
  

   last 
  prefossil 
  accidents, 
  and 
  that 
  the 
  perfect 
  silicification 
  of 
  the 
  

   corals 
  supervenes 
  on 
  a 
  filling 
  up 
  of 
  the 
  interstices 
  of 
  the 
  scleren- 
  

   chyma 
  by 
  coral-mud, 
  and 
  the 
  greater 
  or 
  less 
  alteration 
  of 
  this 
  and 
  

   the 
  sclerenchyma 
  in 
  contact 
  with 
  it, 
  the 
  silica 
  replacing 
  a 
  salt 
  of 
  

   lime 
  by 
  ordinary 
  chemical 
  transposition. 
  

  

  These 
  prefossil 
  accidents 
  are 
  evidently 
  the 
  same 
  which 
  occurred 
  

   formerly, 
  for 
  their 
  results 
  can 
  be 
  traced 
  in 
  the 
  fossil 
  condition 
  of 
  

   corals 
  of 
  all 
  ages. 
  The 
  formation 
  of 
  one 
  kind 
  of 
  cast, 
  which 
  is 
  

  

  * 
  See 
  specimens 
  of 
  recent 
  coral-mud 
  in 
  Geol. 
  Soc. 
  Coll., 
  Captain 
  Nelson's 
  

   Collection, 
  

   t 
  The 
  fcetidity 
  of 
  exposed 
  coral-mud 
  is 
  well 
  known. 
  

  

  