﻿REPORT 
  OF 
  THE 
  DIRECTOR 
  TTJ 
  

  

  fifty 
  feet 
  is 
  shown 
  in 
  section. 
  In 
  the 
  Harlem 
  River 
  a 
  thickness 
  of 
  

   about 
  seven 
  hundred 
  feet 
  is 
  indicated. 
  

  

  The 
  age 
  of 
  this 
  Hmestone 
  is 
  probably 
  Calciferous-Trenton. 
  In 
  the 
  

   absence 
  of 
  fossils, 
  which 
  could 
  not 
  have 
  withstood 
  the 
  extreme 
  meta- 
  

   morphism, 
  the 
  exact 
  age 
  is 
  indeterminate. 
  

  

  The 
  crystalline 
  limestone, 
  though 
  frequently 
  well 
  exposed, 
  must 
  

   often 
  be 
  traced 
  by 
  its 
  absence 
  as 
  well 
  as 
  its 
  presence. 
  Its 
  solubility 
  

   in 
  water 
  containing 
  carbonic 
  acid 
  renders 
  it 
  an 
  easy 
  prey 
  to 
  the 
  ele- 
  

   ments, 
  and 
  its 
  position 
  is 
  almost 
  everywhere 
  emphasized 
  by 
  low 
  

   ground 
  ana 
  usually 
  by 
  deep 
  valleys. 
  Throughout 
  all 
  the 
  

   principal 
  valleys 
  small 
  outcrops 
  may 
  be 
  found, 
  though 
  usu- 
  

   ally 
  for 
  considerable 
  distances 
  it 
  is 
  buried 
  in 
  river 
  gravel 
  

   and 
  alluvium. 
  Where 
  it 
  has 
  undergone 
  the 
  maximum 
  of 
  

   leaching 
  the 
  granular 
  particles 
  of 
  limestone 
  have 
  disappeared 
  entirely 
  

   and 
  in 
  its 
  stead 
  we 
  find 
  a 
  mass 
  of 
  aluminous 
  and 
  magnesian 
  material, 
  

   whitish, 
  green 
  with 
  scales 
  of 
  prochlorite, 
  red 
  with 
  peroxide 
  of 
  iron, 
  

   and 
  sometimes 
  black 
  with 
  separated 
  carbon. 
  In 
  these 
  conditions 
  it 
  

   is 
  often 
  mistaken 
  for 
  clay 
  or 
  kaolin, 
  and 
  was 
  thus 
  reported 
  from 
  the 
  

   railroad 
  cutting 
  at 
  Morrisania, 
  from 
  the 
  Blackwell's 
  Island 
  tunnel 
  

   and 
  from 
  dredgings 
  in 
  the 
  East 
  River 
  on 
  the 
  Middle 
  Ground, 
  Shell 
  

   Reef 
  and 
  at 
  the 
  mouth 
  of 
  Newtown 
  Creek. 
  The 
  same 
  material 
  was 
  

   also 
  found 
  overlying 
  the 
  Fordham 
  Gneiss 
  in 
  a 
  deep 
  boring 
  on 
  Tall- 
  

   man's 
  Island 
  near 
  College 
  Point. 
  On 
  the 
  uplands 
  the 
  presence 
  of 
  

   limestone 
  is 
  evidenced 
  by 
  coarse 
  yellowish 
  white 
  sand, 
  consisting 
  of 
  

   partially 
  dissolved 
  cleavage 
  fragments 
  of 
  the 
  dolomite. 
  This 
  may 
  

   be 
  seen 
  on 
  the 
  plain 
  east 
  of 
  Inwood. 
  

  

  To 
  the 
  presence 
  of 
  the 
  limestone 
  is 
  due 
  the 
  commercial 
  promi- 
  

   nence 
  of 
  iNJew 
  York, 
  as 
  all 
  the 
  navigable 
  channels 
  about 
  the 
  city 
  

   are 
  submerged 
  valleys 
  which 
  owe 
  their 
  origin 
  to 
  the 
  solution 
  of 
  

   the 
  limestone 
  along 
  the 
  lines 
  of 
  its 
  outcrop 
  and 
  exposure. 
  With- 
  

   out 
  the 
  submergence 
  the 
  limestone 
  valleys 
  would 
  not 
  be 
  navigable 
  

   channels 
  and 
  without 
  the 
  presence 
  of 
  limestone 
  there 
  would 
  have 
  

   been 
  no 
  valleys 
  for 
  the 
  submergence 
  to 
  render 
  navigable. 
  

  

  Long 
  Island 
  Sound 
  owes 
  its 
  existence 
  to 
  the 
  same 
  cause. 
  

  

  