﻿Report 
  of 
  the 
  State 
  Geologist. 
  689 
  

  

  or 
  less 
  segregated. 
  Serpentinous 
  varieties 
  are 
  not 
  uncommon, 
  

   the 
  serpentine 
  being 
  secondary 
  after 
  amphibole, 
  pyroxene, 
  etc. 
  

   The 
  limestone 
  often 
  contains 
  black 
  horn 
  blend 
  ic 
  and 
  pyroxenic 
  

   bands, 
  which 
  are 
  twisted 
  into 
  a 
  great 
  variety 
  of 
  fantastic 
  forms. 
  

   Knots 
  and 
  bumps 
  of 
  various 
  silicates 
  are 
  also 
  common, 
  partic- 
  

   ularly 
  in 
  the 
  vicinity 
  of 
  granite. 
  Sometimes, 
  the 
  limestone 
  

   becomes 
  tremolitic 
  and 
  passes 
  into 
  a 
  tremolite 
  schist, 
  an 
  import- 
  

   ant 
  fact 
  from 
  an 
  economic 
  standpoint, 
  as 
  the 
  tremolite 
  schist 
  

   seems 
  to 
  be 
  the 
  source 
  of 
  the 
  talc 
  now 
  mined 
  on 
  a 
  large 
  scale. 
  

  

  The 
  sandstone 
  is 
  usually 
  rather 
  fine-grained 
  and 
  indurated 
  by 
  

   secondary 
  silica, 
  forming 
  a 
  compact 
  quartzite. 
  Occasionally 
  

   coarse 
  conglomerate 
  varieties 
  are 
  seen. 
  The 
  color 
  varies 
  from 
  

   white 
  to 
  red, 
  often 
  with 
  complex 
  mottling 
  and 
  striping. 
  

  

  A 
  brief 
  examination 
  suffices 
  to 
  show 
  that 
  the 
  sandstone 
  is 
  

   much 
  younger 
  than 
  the 
  other 
  rocks 
  of 
  the 
  region 
  and 
  lies 
  uncon- 
  

   formable 
  upon 
  them. 
  It 
  is 
  of 
  Potsdam 
  age 
  and 
  its 
  relation 
  to 
  

   the 
  older 
  rocks 
  has 
  been 
  recognized 
  by 
  all 
  geologists 
  who 
  have 
  

   studied 
  the 
  region, 
  excepting 
  Brooks,* 
  who 
  regarded 
  it 
  as 
  con- 
  

   formable 
  with 
  the 
  limestone. 
  

  

  With 
  this 
  unconformity 
  established, 
  the 
  chief 
  structural 
  prob- 
  

   lem 
  of 
  the 
  region 
  lies 
  in 
  the 
  relation 
  of 
  the 
  limestone 
  to 
  the 
  

   gneiss. 
  In 
  the 
  hope 
  of 
  shedding 
  some 
  light 
  upon 
  this 
  problem 
  

   a 
  limited 
  area 
  was 
  examined 
  with 
  much 
  care, 
  an 
  effort 
  being 
  

   made 
  to 
  collect 
  as 
  many 
  facts 
  as 
  possible 
  in 
  regard 
  to 
  dips 
  and 
  

   strikes, 
  contacts, 
  etc. 
  The 
  highly 
  unsatisfactory 
  results 
  thus 
  

   obtained 
  have 
  been 
  stated 
  in 
  the 
  papers 
  above 
  cited. 
  The 
  mas- 
  

   sive 
  character 
  of 
  the 
  limestone, 
  the 
  difficulty 
  of 
  establishing 
  

   definite 
  horizons 
  to 
  be 
  traced 
  from 
  point 
  to 
  point, 
  and 
  the 
  rarity 
  

   of 
  contacts 
  combined 
  to 
  render 
  ail 
  efforts 
  in 
  this 
  direction 
  nearly 
  

   futile. 
  It 
  was, 
  therefore, 
  determined 
  to 
  prepare 
  a 
  map 
  showing 
  

   the 
  areal 
  relations 
  of 
  the 
  rocks 
  over 
  a 
  more 
  extended 
  surface, 
  

   in 
  the 
  hope 
  that 
  the 
  distribution, 
  combined 
  with 
  such 
  other 
  data 
  

   as 
  might 
  be 
  collected, 
  would 
  give 
  the 
  key 
  to 
  the 
  structure 
  of 
  

   the 
  region. 
  The 
  accompanying 
  map 
  represents 
  what 
  has 
  thus 
  

   far 
  been 
  done 
  in 
  this 
  direction. 
  For 
  the 
  field 
  work 
  only 
  very 
  

   inaccurate 
  township 
  maps, 
  which 
  required 
  much 
  readjustment 
  in 
  

   order 
  to 
  be 
  fitted 
  together, 
  were 
  available. 
  With 
  such 
  a 
  

   basis 
  in 
  consideration 
  of 
  the 
  particular 
  object 
  in 
  view, 
  it 
  

  

  * 
  T. 
  B. 
  Brooks, 
  Amer. 
  Jour. 
  Set 
  (3), 
  IV, 
  p. 
  22. 
  

  

  87 
  

  

  