﻿526 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  bro 
  at 
  no. 
  90 
  (see 
  large 
  map 
  of 
  Whitehall)' 
  is 
  a 
  dike 
  of 
  which 
  at 
  

   least 
  50 
  feet 
  are 
  exposed 
  across 
  the 
  foliation 
  and 
  the 
  contact 
  with 
  

   the 
  inclosing 
  gneiss 
  is 
  visible 
  and 
  is 
  irregular, 
  though 
  its 
  general 
  

   strike 
  is 
  east 
  and 
  west. 
  The 
  gabbro 
  near 
  the 
  crest 
  of 
  the 
  hill 
  is 
  

   similar 
  in 
  appearance 
  to 
  the 
  others 
  but 
  its 
  shape 
  or 
  other 
  rela- 
  

   tions 
  could 
  not 
  be 
  determined. 
  The 
  large 
  outcrop 
  along 
  the 
  high- 
  

   way 
  to 
  the 
  south 
  is 
  the 
  most 
  extensive 
  of 
  those 
  found. 
  The 
  con- 
  

   tact 
  with 
  the 
  granitic 
  gneisses 
  which 
  form 
  the 
  country 
  rock 
  on 
  

   the 
  south 
  is 
  well 
  shown 
  and 
  is 
  irregular, 
  apparently 
  as 
  if 
  offset- 
  

   ting 
  tongues 
  of 
  gabbro 
  had 
  been 
  pinched 
  into 
  the 
  gneiss. 
  The 
  

   gabbro 
  itself 
  becomes 
  very 
  gneissoid. 
  

  

  Precambrian 
  quartzite. 
  In 
  the 
  closing 
  paragraphs 
  under 
  the 
  head 
  

   of 
  the 
  gneisses 
  the 
  peculiar 
  schistose 
  rocks 
  were 
  described 
  which 
  

   simulate, 
  if 
  they 
  actually 
  do 
  not 
  represent 
  quartzites. 
  Should 
  our 
  

   impression 
  that 
  they 
  are 
  quartzites 
  be 
  corroborated 
  by 
  more 
  de- 
  

   tailed 
  work, 
  they 
  would 
  add 
  an 
  interesting 
  and 
  important 
  mem- 
  

   ber 
  to 
  the 
  Precambrian 
  strata. 
  

  

  Series 
  4. 
  The 
  paleozoics 
  cover 
  two 
  thirds 
  of 
  the 
  township. 
  The 
  

   lowest 
  member 
  is 
  the 
  Georgian 
  slate 
  of 
  the 
  lower 
  Cambrian. 
  

   The 
  next 
  formation 
  present 
  is 
  the 
  Potsdam 
  sandstone 
  of 
  the 
  

   upper 
  Cambrian, 
  which 
  appears 
  in 
  the 
  base 
  of 
  Skeen 
  mountain. 
  

   The 
  Calciferous 
  rests 
  on 
  it 
  forming 
  the 
  top 
  of 
  the 
  eminence 
  and 
  

   is 
  also 
  met 
  elsewhere. 
  Slates 
  determined 
  as 
  Hudson 
  by 
  Mr 
  Wal- 
  

   cott 
  form 
  a 
  broad 
  belt 
  east 
  of 
  the 
  Calciferous, 
  and 
  are 
  the 
  latest 
  

   paleozoic 
  beds 
  present. 
  As 
  already 
  stated 
  we 
  have 
  given 
  almost 
  

   no 
  attention 
  to 
  the 
  paleozoic 
  exposures, 
  inasmuch 
  as 
  they 
  had 
  

   been 
  already 
  mapped 
  by 
  Mr 
  Walcott, 
  whose 
  results 
  have 
  been 
  

   incorporated 
  in 
  the 
  state 
  geological 
  map. 
  

  

  Series 
  5. 
  Only 
  one 
  trap 
  dike 
  has 
  been 
  discovered. 
  This 
  occurs 
  

   south 
  of 
  Whitehall 
  at 
  specimen 
  68. 
  It 
  is 
  6 
  feet 
  wide, 
  and 
  strikes 
  — 
  

   N 
  65 
  E 
  — 
  being 
  a 
  fine 
  example 
  of 
  its 
  kind. 
  It 
  outcrops 
  in 
  a 
  barn- 
  

   yard. 
  

  

  Series 
  6. 
  Glacial 
  drift 
  is 
  not 
  infrequent 
  on 
  the 
  ridge. 
  In 
  only 
  

   one 
  place 
  in 
  the 
  extreme 
  southwest 
  corner 
  were 
  striae 
  discov- 
  

   ered 
  of 
  a 
  measurable 
  distinctness. 
  These 
  bore 
  N 
  40 
  E, 
  and 
  are 
  

   shown 
  on 
  the 
  map 
  by 
  the 
  double-pointed 
  arrow. 
  

  

  