﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  I25 
  

  

  ^nisms, 
  such 
  as 
  mollusks 
  and 
  brachiopods, 
  will 
  also 
  find 
  this 
  a 
  

   convenient 
  resting 
  place. 
  Thus 
  the 
  organically 
  formed 
  limestone 
  

   masses 
  and 
  the 
  fragmental 
  limestones 
  will 
  interlock 
  and 
  overlap 
  

   each 
  other 
  around 
  the 
  borders 
  of 
  a 
  growing 
  reef. 
  It 
  follows 
  then 
  

   that 
  in 
  the 
  neighborhood 
  of 
  the 
  growing 
  coral 
  masses 
  the 
  sands 
  

   derived 
  from 
  their 
  destruction 
  will 
  be 
  coarser, 
  the 
  finer 
  material 
  

   "being 
  carried 
  farther 
  out 
  to 
  sea, 
  and 
  deposited 
  at 
  a 
  distance 
  from 
  

   the 
  source. 
  Thus 
  an 
  approximate 
  criterion 
  for 
  the 
  determination 
  

   of 
  the 
  distance 
  of 
  any 
  given 
  bed 
  of 
  calcareous 
  sand 
  from 
  its 
  place 
  

   •of 
  origin 
  is 
  furnished. 
  If 
  deposits 
  of 
  such 
  calcareous 
  sand 
  are 
  made 
  

   in 
  shallow 
  water, 
  cross-bedding 
  and 
  ripple 
  marks 
  will 
  be 
  found 
  just 
  

   as 
  in 
  the 
  quartz 
  sands, 
  and, 
  as 
  we 
  have 
  seen, 
  the 
  former 
  structure 
  

   is 
  characteristic 
  of 
  most 
  of 
  the 
  strata 
  of 
  Lockport 
  Hmestone 
  exposed 
  

   in 
  the 
  gorge 
  section 
  at 
  Niagara. 
  It 
  may 
  be 
  added 
  that, 
  as 
  the 
  

   organic 
  limestone 
  will 
  continue 
  to 
  form 
  as 
  long 
  as 
  the 
  conditions 
  

   are 
  favorable, 
  the 
  supply 
  of 
  calcareous 
  sand 
  is 
  practically 
  inex- 
  

   haustible. 
  Hence 
  thick 
  beds 
  of 
  such 
  lime-sandstones 
  may 
  form. 
  

  

  In 
  the 
  Niagaran 
  seas 
  the 
  chief 
  reef-building 
  corals 
  were 
  F 
  a 
  v 
  o 
  - 
  

   sites, 
  Hal 
  y 
  sites 
  and 
  H 
  e 
  1 
  i 
  o 
  1 
  i 
  t 
  e 
  s 
  , 
  together 
  with 
  the 
  hy- 
  

   dro-coralline 
  Strom 
  atopora. 
  Bryozoans 
  also 
  added 
  largely 
  

   to 
  the 
  supply 
  of 
  organically 
  formed 
  limestone 
  of 
  the 
  various 
  reefs. 
  

   But 
  perhaps 
  the 
  most 
  important 
  contributors 
  in 
  this 
  connection 
  

   were 
  the 
  crinoids 
  and 
  related 
  organisms, 
  which 
  may 
  at 
  times 
  have 
  

   constituted 
  reefs 
  of 
  their 
  own. 
  Their 
  abundance 
  is 
  testified 
  to 
  by 
  the 
  

   frequent 
  thick 
  beds 
  of 
  limestone, 
  which 
  are 
  almost 
  wholly 
  made 
  up 
  of 
  

   broken 
  and 
  worn 
  crinoid 
  fragments. 
  The 
  crinoids 
  fell 
  an 
  easy 
  prey 
  

   to 
  the 
  waves, 
  for, 
  on 
  the 
  death 
  of 
  the 
  animal, 
  the 
  calyx, 
  arms 
  and 
  

   stem 
  would 
  quickly 
  fall 
  apart 
  into 
  their 
  component 
  sections, 
  and 
  

   hence 
  yield 
  fragments 
  readily 
  transported 
  by 
  the 
  waves. 
  In 
  the 
  

   case 
  of 
  the 
  corals 
  and 
  the 
  shells, 
  which 
  latter 
  probably 
  formed 
  no 
  

   unimportant 
  part 
  of 
  the 
  organic 
  contributions 
  to 
  the 
  reefs, 
  the 
  work 
  

   of 
  grinding 
  the 
  solid 
  limestone 
  masses 
  into 
  a 
  sand 
  probably 
  required 
  

   the 
  aid 
  of 
  tools, 
  such 
  as 
  large 
  blocks 
  that 
  could 
  be 
  rolled 
  about 
  by 
  

   the 
  waves, 
  or 
  it 
  may 
  have 
  been 
  aided 
  by 
  the 
  omnipresent 
  reef-de- 
  

   stroying 
  organisms. 
  

  

  The 
  infrequency 
  of 
  exposure 
  of 
  the 
  fossil 
  reefs, 
  which 
  furnished 
  

   the 
  calcareous 
  sand, 
  need 
  not 
  disturb 
  us. 
  We 
  must 
  remember 
  that 
  

  

  