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  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  the 
  Niagara 
  period, 
  when 
  the 
  CoralHne 
  Hmestone 
  of 
  Schoharie 
  was 
  

   laid 
  down. 
  Westward, 
  however, 
  the 
  adjustment 
  of 
  conditions 
  went 
  

   on 
  more 
  rapidly, 
  and 
  the 
  Clinton 
  limestones, 
  with 
  the 
  calcareous 
  

   shales 
  and 
  limestones 
  of 
  the 
  upper 
  Niagaran, 
  became 
  the 
  charac- 
  

   teristic 
  deposits. 
  During 
  nearly 
  the 
  entire 
  Niagara 
  period 
  Hfe 
  was 
  

   abundant 
  in 
  the 
  Siluric 
  sea, 
  and 
  the 
  Bay 
  of 
  New 
  York 
  had 
  its 
  mar- 
  

   velous 
  succession 
  of 
  faunas, 
  which 
  have 
  made 
  these 
  strata 
  the 
  stand- 
  

   ard 
  for 
  the 
  Siluric 
  beds 
  of 
  this 
  continent. 
  

  

  All 
  the 
  Siluric 
  limestones 
  of 
  the 
  Niagara 
  section 
  show 
  characters 
  

   pointing 
  to 
  a 
  fragmental 
  origin, 
  and 
  in 
  this 
  respect 
  they 
  contrast 
  

   strongly 
  with 
  the 
  Devonic 
  limestones 
  in 
  the 
  southern 
  part 
  of 
  the 
  

   district. 
  The 
  latter, 
  as 
  before 
  mentioned, 
  show 
  the 
  characteristics 
  

   of 
  an 
  ancient 
  coral 
  reef, 
  and 
  we 
  may 
  therefore 
  assume 
  that 
  they 
  

   were 
  built 
  up 
  in 
  situ 
  by 
  the 
  polyps 
  and 
  other 
  lime-secreting 
  or- 
  

   ganisms. 
  Not 
  so 
  ^ 
  with 
  the 
  Siluric 
  Hmestones. 
  These, 
  to 
  be 
  sure, 
  

   were 
  derived 
  from 
  similar 
  deposits 
  by 
  lime-secreting 
  organisms, 
  but 
  

   these 
  deposits 
  were 
  originally 
  made 
  in 
  a 
  different 
  place 
  from 
  that 
  

   in 
  which 
  we 
  find 
  the 
  limestones 
  today. 
  A 
  sedimentary 
  limestone 
  or 
  

   lime-sandstone 
  is 
  similar 
  to 
  a 
  quartz 
  sandstone 
  or 
  a 
  shale, 
  in 
  that 
  

   the 
  material 
  of 
  which 
  it 
  is 
  formed 
  is 
  the 
  product 
  of 
  erosion 
  of 
  pre- 
  

   existing 
  rocks. 
  In 
  the 
  case 
  of 
  the 
  quartz 
  sandstone, 
  this 
  is 
  gen- 
  

   erally 
  an 
  inorganically 
  formed 
  rock, 
  while 
  the 
  sedimentary 
  lime- 
  

   stones 
  are 
  most 
  usually 
  derived 
  from 
  organically 
  formed 
  rocks. 
  In 
  

   the 
  former 
  case, 
  the 
  source 
  of 
  the 
  material 
  is 
  often 
  a 
  distant 
  one, 
  

   while 
  in 
  the 
  latter 
  it 
  is 
  generally, 
  though 
  not 
  necessarily 
  always, 
  

   close 
  at 
  hand. 
  A 
  coral 
  reef 
  growing 
  in 
  moderately 
  shallow 
  water 
  

   is 
  attacked 
  by 
  the 
  waves, 
  as 
  are 
  all 
  rocks 
  which 
  come 
  within 
  their 
  

   reach. 
  Erosion 
  results, 
  and 
  the 
  product 
  of 
  this 
  activity 
  is 
  carried 
  

   away 
  and 
  deposited 
  on 
  the 
  ocean 
  floor 
  as 
  a 
  calcareous 
  sand. 
  Thus 
  

   stratified 
  deposits 
  of 
  limestones 
  are 
  formed, 
  whereas 
  in 
  the 
  original 
  

   organic 
  reef, 
  no 
  stratification 
  is 
  to 
  be 
  expected. 
  In 
  the 
  immediate 
  

   neighborhood 
  of 
  the 
  growing 
  reef, 
  the 
  beds 
  of 
  calcareous 
  sand 
  will 
  

   slowly 
  envelop 
  the 
  original 
  deposit 
  from 
  which 
  they 
  were 
  derived, 
  

   and 
  thus 
  the 
  source 
  of 
  supply 
  is 
  chiefly 
  the 
  upper 
  growing 
  portion 
  

   of 
  the 
  reef. 
  On 
  the 
  lime-sandstone 
  strata 
  which 
  flank 
  the 
  reef, 
  in- 
  

   dependent 
  masses 
  of 
  coral 
  may 
  at 
  times 
  grow, 
  while 
  other 
  or- 
  

  

  