﻿JO 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  exposed 
  in 
  many 
  localities, 
  as 
  on 
  Bald 
  mountain 
  near 
  Greenwich, 
  

   about 
  Granville, 
  etc. 
  The 
  name 
  is 
  taken 
  from 
  the 
  fine 
  exposures 
  

   two 
  miles 
  south 
  of 
  Schodack 
  Landing, 
  N. 
  Y., 
  on 
  the 
  bank 
  of 
  

   the 
  Hudson 
  river 
  and 
  the 
  belt 
  of 
  these 
  rocks 
  in 
  the 
  town 
  of 
  

   Schodack, 
  N. 
  Y. 
  

  

  5 
  Nassau 
  beds 
  (divisions 
  A-E 
  of 
  Dale's 
  series 
  in 
  Rensselaer 
  

   county). 
  In 
  Rensselaer 
  county 
  the 
  Olive 
  grit 
  or 
  Bomoseen 
  grit 
  

   is 
  underlain 
  by 
  a 
  series 
  of 
  alternating 
  reddish 
  and 
  greenish 
  shales 
  

   and 
  quartzites 
  containing 
  Oldhamia, 
  about 
  150 
  to 
  800 
  feet 
  thick. 
  

   This 
  is 
  especially 
  well 
  exposed 
  in 
  the 
  town 
  of 
  Nassau, 
  N. 
  Y. 
  

  

  6 
  Diamond 
  Rock 
  quartzite 
  (division 
  G 
  of 
  Dale's 
  Rensselaer 
  

   series). 
  This 
  division 
  10 
  to 
  40 
  feet 
  thick 
  and 
  composed 
  of 
  gran- 
  

   ular 
  quartzite 
  and 
  associated 
  calcareous 
  sandstone, 
  is 
  well 
  exposed 
  

   in 
  Oakwood 
  cemetery 
  and 
  the 
  " 
  Diamond 
  Rock 
  " 
  in 
  Lansingburgh 
  

   (North 
  Troy), 
  from 
  which 
  it 
  takes 
  its 
  name. 
  

  

  7 
  Troy 
  shales 
  (division 
  H 
  of 
  Dale's 
  Rensselaer 
  series). 
  This 
  

   formation, 
  which 
  follows 
  upon 
  the 
  Diamond 
  Rock 
  quartzite, 
  con- 
  

   sists 
  of 
  25 
  to 
  100 
  feet 
  of 
  colored 
  shales 
  with 
  small 
  beds 
  of 
  cal- 
  

   careous 
  quartzite. 
  The 
  shale 
  has 
  furnished 
  Oldhamia, 
  a 
  calcareous 
  

   sandstone 
  bed 
  in 
  the 
  upper 
  part 
  Hyolithes 
  and 
  Hyolithellus. 
  These 
  

   beds 
  are 
  well 
  exposed 
  at 
  Troy, 
  at 
  the 
  dam 
  in 
  the 
  Poesten 
  kill 
  and 
  

   other 
  localities. 
  

  

  8 
  Zion 
  Hill 
  quartzite 
  (Ferruginous 
  quartzite 
  Dale). 
  This 
  

   name, 
  taken 
  from 
  Zion 
  hill, 
  Hubbardtown, 
  Vt, 
  where 
  according 
  to 
  

   Dale 
  the 
  ferruginous 
  quartzite 
  is 
  exposed 
  in 
  a 
  thickness 
  of 
  70 
  feet, 
  

   is 
  proposed 
  here 
  for 
  the 
  sake 
  of 
  completeness. 
  

  

  On 
  the 
  Schuylerville 
  sheet 
  we 
  find 
  well 
  represented 
  only 
  division 
  

   A 
  and 
  the 
  limestone 
  and 
  shales 
  of 
  D. 
  We 
  have 
  separated 
  the 
  areas 
  

   occupied 
  by 
  these 
  two 
  divisions 
  on 
  the 
  map, 
  the 
  boundaries 
  being 
  

   only 
  approximate 
  on 
  account 
  of 
  the 
  interfolding 
  of 
  the 
  beds. 
  

  

  The 
  olive 
  grit 
  occupies 
  the 
  southern 
  half 
  of 
  the 
  area. 
  It 
  is 
  easily 
  

   recognized 
  by 
  the 
  pale 
  brick-red 
  color 
  of 
  the 
  w 
  r 
  eathered 
  crust 
  that 
  

   forms 
  on 
  it 
  ; 
  typically 
  it 
  is 
  seen 
  on 
  the 
  many 
  ledges 
  north 
  of 
  Green- 
  

   wich, 
  but 
  it 
  also 
  appears 
  on 
  all 
  sides 
  of 
  Louse 
  hill 
  and 
  extends 
  to 
  

   the 
  southern 
  boundary 
  of 
  the 
  Georgian 
  areas. 
  From 
  Greenwich 
  the 
  

   grit 
  skirts 
  the 
  eastern 
  side 
  of 
  Bald 
  mountain. 
  It 
  is 
  described 
  by 
  

   Dale 
  as 
  follows 
  : 
  

  

  A 
  greenish, 
  usually 
  olive-colored, 
  very 
  rarely 
  purplish, 
  more 
  or 
  less 
  massive 
  

   grit, 
  generally 
  somewhat 
  calcareous, 
  and 
  almost 
  always 
  spangled 
  with 
  very 
  

   minute 
  scales 
  of 
  hematite 
  or 
  graphite. 
  Under 
  the 
  microscope 
  it 
  is 
  seen 
  to 
  

   consist 
  mainly 
  of 
  more 
  or 
  less 
  angular 
  grains 
  of 
  quartz, 
  with 
  a 
  considerable 
  

  

  