﻿CRYSTALLINE 
  ROCKS 
  OF 
  THE 
  WESTERN 
  ADIRONDACK 
  REGION 
  497 
  

  

  gneisses 
  are 
  igneous 
  and 
  others 
  sedimentary 
  is 
  assumed 
  to 
  be 
  

   proved 
  and 
  examples 
  of 
  both 
  kinds 
  have 
  been 
  cited. 
  But 
  in 
  the 
  

   gray 
  hornblende 
  gneiss 
  of 
  the 
  lake 
  region 
  we 
  have 
  a 
  great 
  forma- 
  

   tion 
  of 
  whose 
  origin 
  nothing 
  is 
  known 
  from 
  direct 
  and 
  positive 
  

   evidence. 
  

  

  That 
  it 
  is 
  part 
  of 
  the 
  limestone 
  formation 
  the 
  writer 
  finds 
  it 
  

   difficult 
  to 
  believe 
  in 
  view 
  of 
  its 
  extreme 
  uniformity 
  and 
  lack 
  of 
  

   banding, 
  in 
  both 
  of 
  which 
  respects 
  it 
  is 
  totally 
  different 
  from 
  the 
  

   gneisses 
  which 
  evidently 
  belong 
  with 
  the 
  limestone. 
  

  

  This 
  uniformity 
  together 
  with 
  the 
  composition 
  and 
  structure 
  of 
  

   the 
  gneiss 
  seems 
  to 
  the 
  writer 
  to 
  indicate 
  with 
  great 
  probability 
  

   an 
  igneous 
  origin. 
  This 
  idea 
  is 
  strengthened 
  on 
  comparing 
  the 
  rock 
  

   with 
  the 
  syenite 
  gneiss 
  of 
  Diana 
  above 
  described, 
  the 
  two 
  rocks 
  

   being 
  somewhat 
  similar 
  in 
  composition 
  and 
  structure. 
  Pointing 
  

   in 
  the 
  same 
  direction 
  are 
  the 
  facts 
  presented 
  on 
  the 
  north 
  shore 
  

   of 
  Sixth 
  lake, 
  where 
  in 
  a 
  steep 
  cliff 
  the 
  limestone 
  is 
  cut 
  through 
  

   and 
  through 
  with 
  typical 
  intrusive 
  contact 
  zones 
  by 
  a 
  granite 
  

   which 
  runs 
  over 
  into 
  gneissic 
  facies 
  closely 
  resembling 
  the 
  horn- 
  

   blende 
  gneiss. 
  Nevertheless 
  this 
  rock 
  is 
  not 
  continuous 
  at 
  the 
  

   surface 
  with 
  the 
  main 
  mass 
  of 
  the 
  hornblende 
  gneiss, 
  and 
  so, 
  

   while 
  the 
  occurrence 
  is 
  suggestive, 
  it 
  is 
  far 
  from 
  conclusive. 
  At 
  

   no 
  other 
  point 
  is 
  there 
  any 
  direct 
  evidence 
  as 
  to 
  the 
  relations 
  be- 
  

   tween 
  the 
  limestone 
  and 
  the 
  gneiss. 
  

  

  Thus, 
  while 
  in 
  the 
  writer's 
  opinion, 
  this 
  great 
  formation 
  will 
  in 
  

   all 
  probability 
  prove 
  ultimately 
  to 
  be 
  of 
  igneous 
  origin, 
  the 
  evi- 
  

   dence 
  thus 
  far 
  obtained 
  is 
  clearly 
  insufficient 
  to 
  establish 
  beyond 
  

   question 
  that 
  such 
  is 
  the 
  case. 
  

  

  Hamilton 
  College, 
  Clinton, 
  N. 
  Y. 
  

  

  February 
  1898 
  

  

  