﻿22 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  pany 
  with 
  Prof. 
  C. 
  R. 
  Van 
  Hise 
  and 
  secure 
  his 
  criticism 
  and 
  ap- 
  

   proval 
  of 
  the 
  principal 
  points 
  discussed. 
  

  

  With 
  the 
  permission 
  of 
  the 
  Director 
  of 
  the 
  United 
  States 
  Geo- 
  

   logical 
  Survey, 
  the 
  data 
  obtained 
  under 
  his 
  auspices 
  in 
  the 
  field 
  work 
  

   of 
  completing 
  the 
  Harlem 
  sheet 
  are 
  herewith 
  incorporated. 
  

  

  THE 
  CRYSTALLINE 
  ROCKS 
  OF 
  SOUTHEASTERN 
  

   i 
  NEW 
  YORK. 
  

  

  The 
  crystalline 
  rocks 
  of 
  southeastern 
  New 
  York 
  lie 
  on 
  the 
  east 
  

   of 
  the 
  Hudson 
  River, 
  in 
  New 
  York, 
  Westchester, 
  Putnam 
  and 
  

   Dutchess 
  counties, 
  from 
  whence 
  they 
  extend 
  into 
  Connecticut; 
  and 
  

   on 
  the 
  west 
  of 
  the 
  river, 
  in 
  Orange 
  and 
  Rockland 
  counties, 
  whence 
  

   they 
  extend 
  southwesterly 
  into 
  New 
  Jersey. 
  The 
  lowest 
  member 
  is 
  

   a 
  coarse 
  hornblende 
  granite 
  which 
  forms 
  the 
  central 
  mass 
  of 
  the 
  

   range 
  of 
  mountains 
  known 
  as 
  the 
  Highlands 
  of 
  the 
  Hudson, 
  and, 
  in 
  

   their 
  highest 
  peak, 
  Breakneck 
  Mountain, 
  is 
  exposed 
  through 
  a 
  ver- 
  

   tical 
  height 
  of 
  nearly 
  1,200 
  feet. 
  (PI. 
  L) 
  With 
  these 
  greater 
  

   masses 
  of 
  hornblende 
  granite, 
  are 
  associated 
  other 
  local 
  masses 
  of 
  

   granite 
  comparatively 
  free 
  from 
  hornblende, 
  which 
  are 
  extensively 
  

   used 
  for 
  building 
  stone. 
  (PL 
  H.) 
  These 
  granites 
  are 
  probably 
  

   igneous 
  and 
  of 
  great 
  age, 
  and 
  on 
  their 
  flanks 
  are 
  branded 
  gneisses 
  

   consisting 
  chiefly 
  of 
  quartz 
  and 
  orthoclase 
  with 
  biotite 
  and 
  horn- 
  

   blende, 
  containing 
  numerous 
  beds 
  of 
  magnetic 
  iron-ore. 
  The 
  

   gneisses 
  on 
  the 
  south 
  side 
  of 
  the 
  Highlands 
  (PI. 
  HI) 
  extend 
  

   through 
  Westchester 
  county 
  in 
  a 
  series 
  of 
  folds 
  with 
  south- 
  

   westerly 
  trend, 
  and 
  on 
  the 
  northern 
  slope 
  of 
  the 
  Highlands 
  at 
  several 
  

   places 
  in 
  Dutchess 
  county, 
  are 
  overlain 
  unconformably 
  by 
  Palaeozoic 
  

   basal 
  quartzites, 
  which 
  are 
  believed 
  to 
  be 
  of 
  Cambrian 
  age 
  and 
  are 
  

   bordered 
  by 
  Ordovician 
  limestone 
  and 
  slate 
  or 
  schist. 
  Some 
  of 
  the 
  

   principal 
  valleys 
  of 
  Putnam 
  county 
  contain 
  belts 
  of 
  limestone 
  asso- 
  

   ciated 
  with 
  quartzite 
  and 
  mica 
  schist, 
  which 
  are 
  probably 
  to 
  be 
  cor- 
  

   related 
  with 
  similar 
  rocks 
  hereafter 
  described 
  as 
  altered 
  palaeozoic 
  

   strata. 
  

  

  From 
  the 
  relation 
  of 
  the 
  quartzite, 
  limestone 
  and 
  schist 
  of 
  West- 
  

   chester 
  county 
  to 
  the 
  underlying 
  gneiss, 
  which 
  is 
  precisely 
  similar 
  

   to 
  that 
  of 
  the 
  Palaeozoic 
  strata 
  in 
  southern 
  Dutchess 
  county 
  and 
  

  

  