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  NEW 
  *ORK 
  STATE 
  MUSEUM 
  

  

  Niagara 
  

   Onondaga 
  

   Lower 
  Helderberg 
  

   Upper 
  Helderberg 
  

   Goniatite 
  

   Tully 
  

  

  The 
  most 
  important 
  of 
  these 
  are 
  the 
  Calciferous, 
  Trenton, 
  

   Niagara, 
  Lower 
  Helderberg 
  and 
  Upper 
  Helderberg. 
  The 
  Calcif- 
  

   erous 
  and 
  Niagara 
  sometimes 
  contain 
  sufficient 
  magnesia 
  to 
  be 
  

   called 
  true 
  dolomites 
  and 
  this 
  fact 
  together 
  with 
  the 
  freedom 
  

   from 
  impurities 
  which 
  they 
  exhibit 
  at 
  some 
  localities 
  gives 
  them 
  

   a 
  special 
  usefulness. 
  

  

  Calciferous. 
  The 
  rock 
  of 
  this 
  formation 
  is 
  frequently 
  highly 
  

   magnesian, 
  and 
  a 
  high 
  percentage 
  of 
  silica 
  is 
  likewise 
  not 
  un- 
  

   common 
  in 
  it. 
  On 
  this 
  account 
  it 
  is 
  sometimes 
  called 
  Calciferous 
  

   sandrock. 
  

  

  The 
  Calciferous 
  limestones 
  occur 
  as 
  isolated 
  patches 
  or 
  belts 
  

   in 
  several 
  portions 
  of 
  the 
  state, 
  and 
  show 
  considerable 
  variation 
  

   in 
  character. 
  With 
  few 
  exceptions 
  they 
  are 
  magnesian 
  and 
  in- 
  

   deed 
  may 
  pass 
  into 
  true 
  dolomites. 
  On 
  the 
  other 
  hand 
  they 
  are 
  

   often 
  highly 
  siliceous, 
  so 
  much 
  so 
  as 
  to 
  render 
  them 
  practically 
  

   worthless 
  for 
  any 
  of 
  the 
  uses 
  considered 
  in 
  this 
  report. 
  Again 
  

   they 
  may 
  run 
  very 
  low 
  in 
  silica, 
  as 
  near 
  Glens 
  Falls. 
  

  

  The 
  formation 
  first 
  appears 
  in 
  the 
  southeastern 
  portion 
  of 
  the 
  

   state 
  in 
  Orange 
  co. 
  extending 
  northeastward 
  across 
  the 
  county 
  

   to 
  the 
  Hudson 
  river, 
  and 
  across 
  it 
  through 
  Dutchess 
  into 
  Colum- 
  

   bia 
  CO. 
  

  

  Another 
  series 
  of 
  belts 
  begins 
  in 
  Westchester 
  co. 
  and 
  

   extends 
  from 
  New 
  York 
  city 
  northward 
  to 
  the 
  county 
  line 
  and 
  

   through 
  Putnam 
  and 
  Dutchess 
  co. 
  to 
  Pawling 
  and 
  beyond. 
  a 
  

   The 
  character 
  of 
  these 
  is 
  mentioned 
  in 
  the 
  county 
  descriptions. 
  

  

  Another 
  belt 
  of 
  Calciferous 
  limestone 
  extends 
  from 
  Saratoga 
  

   westward 
  through 
  Montgomery, 
  Fulton 
  and 
  Herkimer 
  counties. 
  

   With 
  the 
  exception 
  of 
  the 
  outcrops 
  in 
  the 
  vicinity 
  of 
  Glens 
  

  

  o 
  These 
  Westchester 
  limestones 
  are 
  probably 
  Trenton 
  in 
  part. 
  

  

  