﻿496 
  NEW 
  YORK 
  'STATE 
  MUSEUM 
  

  

  Lewis 
  co>, 
  though 
  there 
  the 
  limestone 
  is 
  more 
  abundant 
  and 
  there 
  

   is 
  a 
  greater 
  variety 
  of 
  rocks. 
  

  

  A 
  considerable 
  area 
  in 
  southwestern 
  Hamilton 
  co. 
  exam- 
  

   ined 
  by 
  the 
  writer 
  some 
  years 
  since 
  is 
  made 
  up 
  almost 
  entirely 
  

   of 
  a 
  gray 
  gneiss 
  practically 
  identical 
  with 
  that 
  of 
  the 
  lake 
  region 
  

   here 
  described 
  and 
  having 
  the 
  same 
  prevailing 
  strike 
  and 
  dip. 
  

   We 
  have 
  thus 
  three 
  areas 
  stretching 
  entirely 
  across 
  the 
  western 
  

   half 
  of 
  the 
  Adirondack 
  region, 
  one 
  at 
  the 
  north, 
  one 
  at 
  the 
  south 
  

   and 
  the 
  third 
  midway 
  between, 
  and 
  in 
  all 
  of 
  these 
  areas 
  the 
  rocks 
  

   are 
  essentially 
  gneisses 
  with 
  more 
  or 
  less 
  limestone, 
  and 
  always 
  

   with 
  a 
  prevailing 
  northeast 
  strike. 
  So 
  far 
  as 
  the 
  writer 
  is 
  in- 
  

   formed 
  these 
  facts 
  fall 
  closely 
  in 
  line 
  with 
  the 
  results 
  obtained 
  by 
  

   Professors 
  Kemp 
  and 
  Cushing 
  on 
  the 
  east 
  and 
  lead 
  indubitably 
  

   to 
  the 
  conclusion 
  that 
  the 
  Adirondack 
  region, 
  instead 
  of 
  consist- 
  

   ing 
  of 
  a 
  great 
  central 
  mass 
  of 
  gabbro 
  surrounded 
  by 
  a 
  narrow 
  

   fringe 
  of 
  gneisses 
  and 
  limestones 
  with 
  quaquaversal 
  dip, 
  is 
  essen- 
  

   tially 
  composed 
  of 
  gneisses 
  with 
  numerous 
  limestone 
  belts, 
  hav- 
  

   ing 
  northeast 
  strike 
  and 
  north 
  dip, 
  and 
  cut 
  through 
  on 
  the 
  east 
  

   by 
  immense 
  intrusions 
  of 
  gabbro. 
  It 
  is 
  still 
  possible 
  of 
  course 
  

   that 
  some 
  areas 
  of 
  gabbro 
  may 
  be 
  found 
  in 
  the 
  unexplored 
  por- 
  

   tions 
  of 
  the 
  western 
  half, 
  but 
  even 
  should 
  this 
  be 
  so 
  it 
  would 
  not 
  

   materially 
  modify 
  the 
  above 
  conclusion, 
  as 
  they 
  must 
  necessarily 
  

   be 
  isolated 
  intrusions 
  of 
  no 
  great 
  extent, 
  rather 
  than 
  parts 
  of 
  a 
  

   large 
  area. 
  Very 
  small 
  intrusions 
  of 
  gabbro 
  have 
  been 
  as 
  a 
  

   matter 
  of 
  fact 
  found 
  in 
  abundance, 
  and 
  the 
  writer 
  has 
  thought 
  

   that 
  they 
  were 
  derived 
  from 
  a 
  central 
  core, 
  but 
  this 
  supposition 
  

   must 
  now 
  be 
  abandoned 
  and 
  these 
  gabbro 
  intrusions 
  recognized 
  

   as 
  quite 
  independent 
  phenomena. 
  

  

  The 
  foregoing 
  accentuates 
  the 
  fact 
  emphasized 
  by 
  the 
  writer 
  

   in 
  his 
  last 
  report 
  that 
  the 
  great 
  problem 
  of 
  the 
  Adirondack 
  region 
  

   lies 
  in 
  the 
  origin 
  of 
  the 
  gneisses 
  and 
  their 
  relations 
  to 
  the 
  lime- 
  

   stone 
  formation. 
  As 
  to 
  the 
  importance 
  of 
  this 
  problem 
  it 
  is 
  

   only 
  necessary 
  here 
  to 
  add 
  that 
  it 
  is 
  if 
  possible 
  increased 
  by 
  the 
  

   establishment 
  of 
  the 
  great 
  area 
  which 
  these 
  rocks 
  occupy. 
  

  

  On 
  this 
  problem 
  the 
  facts 
  above 
  enumerated 
  have 
  a 
  bearing 
  

   though 
  they 
  are 
  far 
  from 
  affording 
  a 
  solution. 
  That 
  some 
  of 
  the 
  

  

  