﻿406 
  PROF. 
  J. 
  D. 
  DANA 
  ON 
  THE 
  GEOLOGICAL 
  

  

  exist 
  where 
  the 
  high 
  and 
  broad 
  mountain 
  masses 
  occur, 
  and 
  are 
  

   apparently 
  the 
  occasion 
  of 
  both 
  the 
  breadth 
  and 
  the 
  height. 
  

  

  These 
  are, 
  in 
  brief, 
  the 
  facts 
  relating 
  to 
  the 
  stratification 
  of 
  the 
  

   Taconic 
  schists 
  and 
  limestones, 
  and 
  to 
  the 
  paheontological 
  evidence 
  

   of 
  their 
  age. 
  For 
  the 
  details 
  I 
  refer 
  those 
  interested 
  to 
  the 
  works 
  

   and 
  memoirs 
  that 
  have 
  been 
  already 
  mentioned. 
  

  

  I 
  have 
  not 
  said, 
  nor 
  do 
  I 
  believe, 
  that 
  all 
  the 
  hydromica-schists 
  

   west 
  of 
  the 
  Taconic 
  range 
  that 
  have 
  been 
  referred 
  to 
  the 
  Taconic 
  

   system, 
  and 
  first 
  by 
  Emmons, 
  are 
  equivalents 
  of 
  the 
  Hudson-river 
  

   group. 
  Part 
  are 
  unquestionably 
  Primordial, 
  as 
  their 
  association 
  with 
  

   the 
  underlying 
  quartzite 
  proves. 
  But 
  that 
  this 
  is 
  the 
  age 
  of 
  the 
  

   chief 
  part 
  of 
  the 
  schists 
  of 
  the 
  Taconic 
  range 
  appears 
  to 
  be 
  established 
  

   both 
  stratigraphically 
  and 
  palaaontologically. 
  

  

  The 
  occurrence 
  of 
  hydromica-schists 
  with 
  the 
  quartzite, 
  and 
  their 
  

   interstratification, 
  I 
  have 
  observed 
  to 
  be 
  a 
  common 
  fact 
  in 
  Vermont, 
  

   where 
  the 
  quartzite 
  is 
  largely 
  developed, 
  as 
  well 
  as 
  in 
  Dutchess 
  

   County, 
  where 
  it 
  is 
  sparingly 
  found. 
  The 
  area 
  marked 
  as 
  quartzite 
  on 
  

   the 
  coloured 
  geological 
  map 
  of 
  the 
  Vermont 
  Geological 
  Report 
  really 
  

   consists 
  of 
  both 
  rocks, 
  but 
  with 
  the 
  quartzite 
  greatly 
  predominating 
  

   in 
  some 
  parts. 
  

  

  In 
  connexion 
  with 
  this 
  paper 
  on 
  the 
  Taconic 
  system, 
  I 
  send 
  also 
  

   to 
  the 
  Geological 
  Society 
  a 
  map 
  of 
  New 
  England 
  (a 
  portion 
  of 
  the 
  

   State 
  of 
  Maine 
  excluded) 
  on 
  which 
  is 
  shown 
  the 
  position 
  and 
  

   general 
  arrangement 
  of 
  the 
  Taconic 
  schists 
  and 
  the 
  associated 
  lime- 
  

   stones 
  of 
  Western 
  New 
  England 
  and 
  Eastern 
  New 
  York 
  (PI. 
  XVII.) 
  

   It 
  will 
  be 
  found 
  to 
  be 
  a 
  weighty 
  argument 
  of 
  itself 
  for 
  the 
  

   essential 
  unity 
  in 
  system 
  of 
  the 
  rocks 
  referred 
  to. 
  The 
  Archaean 
  

   enters 
  into 
  the 
  area 
  from 
  the 
  State 
  of 
  New 
  Jersey 
  on 
  the 
  west 
  (where 
  

   it 
  constitutes 
  the 
  "Highlands"), 
  covers 
  nearly 
  all 
  of 
  Putnam 
  

   County, 
  and 
  occurs 
  in 
  isolated 
  areas 
  in 
  Connecticut, 
  Massachusetts, 
  

   and 
  probably, 
  as 
  held 
  by 
  Prof. 
  C. 
  H. 
  Hitchcock, 
  in 
  Vermont, 
  east 
  of 
  

   that 
  of 
  the 
  quartzite. 
  The 
  quartzite 
  I 
  believe 
  now 
  to 
  be 
  mainly, 
  

   if 
  not 
  wholly, 
  Primordial, 
  and 
  to 
  rest 
  unconformably 
  on 
  the 
  Archaean 
  

   rocks, 
  whenever 
  the 
  two 
  come 
  in 
  contact. 
  

  

  The 
  map 
  also 
  shows 
  the 
  position 
  of 
  unaltered 
  Lower 
  Silurian 
  

   rocks 
  west 
  of 
  the 
  north 
  end 
  of 
  the 
  Taconic 
  range, 
  in 
  Central 
  Ver- 
  

   mont. 
  The 
  Red 
  Sand 
  Rock 
  has 
  been 
  proved 
  by 
  fossils 
  to 
  be 
  Pri- 
  

   mordial 
  ; 
  and 
  if 
  the 
  quartzite 
  on 
  the 
  east 
  (with 
  the 
  interstratified 
  

   hydromica-schist) 
  is 
  also 
  Primordial, 
  then 
  the 
  two 
  are 
  the 
  same 
  

   formation. 
  The 
  next 
  formation 
  to 
  this 
  Red 
  Sand 
  Rock 
  on 
  the 
  west 
  

   is 
  the 
  Hudson-river 
  Group, 
  the 
  beds 
  lying 
  against 
  those 
  of 
  the 
  Red 
  

   Sand 
  Rock 
  in 
  consequence 
  of 
  a 
  prolonged 
  fault, 
  the 
  existence 
  of 
  which 
  

   was 
  first 
  indicated 
  by 
  Sir 
  William 
  Logan. 
  

  

  The 
  sources 
  referred 
  to 
  for 
  the 
  outlines 
  of 
  the 
  areas 
  of 
  Taconic 
  

   schists 
  and 
  the 
  associated 
  limestones 
  laid 
  down 
  on 
  the 
  map 
  are, 
  for 
  

   the 
  States 
  of 
  Vermont 
  and 
  Massachusetts, 
  the 
  coloured 
  maps 
  accom- 
  

   panying 
  the 
  Geological 
  Reports 
  of 
  those 
  States 
  ; 
  and 
  for 
  Dutchess, 
  

   Putnam, 
  and 
  Wesjtchester 
  Counties, 
  New 
  York, 
  my 
  own 
  maps, 
  as 
  

   published 
  in 
  my 
  papers. 
  Some 
  corrections 
  for 
  the 
  Vermont 
  part 
  

   have 
  been 
  made 
  from 
  a 
  small 
  map 
  by 
  Mr. 
  Wing, 
  and 
  slight 
  changes 
  

  

  