﻿64 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  prominent 
  in 
  this 
  part 
  of 
  the 
  Adirondack^. 
  Among 
  these 
  factors 
  

   are: 
  (1) 
  character 
  and 
  distribution 
  of 
  the 
  rocks 
  whereby 
  small 
  to 
  

   large 
  masses 
  of 
  hard, 
  homogeneous, 
  igneous 
  rocks 
  have 
  broken 
  

   through 
  the 
  comparatively 
  weak 
  Grenville 
  strata 
  to 
  produce 
  a 
  sort 
  

   of 
  " 
  patchwork 
  " 
  effect 
  so 
  that, 
  as 
  a 
  result 
  of 
  long 
  erosion, 
  the 
  hard, 
  

   igneous 
  masses 
  have 
  stood 
  out 
  prominently 
  above 
  the 
  Grenville; 
  

   (2) 
  faulting, 
  whereby 
  the 
  " 
  patchwork 
  " 
  effect 
  and 
  steep 
  scarps 
  

   have 
  been 
  either 
  produced 
  or 
  sharply 
  accentuated; 
  (3) 
  glaciation, 
  

   whereby 
  the 
  isolated 
  mountains 
  of 
  igneous 
  rock 
  were 
  swept 
  clean 
  

   of 
  decomposed 
  surface 
  rock 
  and 
  more 
  or 
  less 
  smoothed 
  or 
  rounded 
  

   off, 
  thus 
  favoring 
  postglacial 
  exfoliation; 
  and 
  (4) 
  temperature 
  

   changes, 
  humidity 
  etc., 
  whereby 
  the 
  bare 
  slopes 
  of 
  the 
  isolated 
  

   elevations 
  of 
  crystalline 
  rock, 
  under 
  the 
  conditions 
  of 
  comparatively 
  

   rapid 
  temperature 
  changes 
  in 
  this 
  the 
  driest 
  part 
  of 
  the 
  State, 
  are 
  

   favorable 
  for 
  exfoliation. 
  

  

  PENEPLAINS 
  

  

  It 
  is 
  well 
  known, 
  especially 
  as 
  a 
  result 
  of 
  the 
  work 
  of 
  Professor 
  

   Kemp 
  and, 
  more 
  recently, 
  that 
  of 
  Professor 
  Cushing 
  on 
  the 
  Sara- 
  

   toga 
  sheet 
  and 
  of 
  the 
  writer 
  on 
  the 
  Broadalbin 
  sheet, 
  that 
  the 
  south- 
  

   eastern 
  Adirondack 
  region 
  had 
  been 
  worn 
  down 
  to 
  the 
  condition 
  

   of 
  a 
  fairly 
  good 
  peneplain 
  immediately 
  prior 
  to 
  the 
  advance 
  of 
  the 
  

   upper 
  Cambric 
  (Potsdam) 
  sea. 
  Altitudes 
  above 
  the 
  general 
  pene- 
  

   plain 
  level 
  were 
  not 
  over 
  a 
  few 
  hundred 
  feet 
  at 
  the 
  most. 
  This 
  

   conclusion 
  has 
  been 
  reached 
  through 
  a 
  study 
  of 
  those 
  places 
  along 
  

   the 
  borders 
  of 
  the 
  Adirondacks 
  where 
  the 
  Paleozoic 
  rocks 
  directly 
  

   overlie 
  the 
  Precambrics. 
  The 
  position 
  of 
  the 
  North 
  Creek 
  quad- 
  

   rangle 
  renders 
  it 
  practically 
  certain 
  that 
  this 
  very 
  ancient 
  (Cam- 
  

   bric) 
  peneplain 
  extended 
  over 
  its 
  area, 
  but 
  because 
  of 
  the 
  exten- 
  

   sive 
  faulting 
  and 
  erosion 
  of 
  the 
  region, 
  that 
  old 
  peneplain 
  surface 
  

   is 
  nowhere 
  certainly 
  recognizable. 
  

  

  Again, 
  it 
  is 
  well 
  known 
  that, 
  by 
  the 
  close 
  of 
  the 
  Mesozoic 
  era, 
  

   a 
  fairly 
  well-developed 
  peneplain 
  condition 
  had 
  once 
  more 
  been 
  

   produced 
  over 
  this 
  region 
  in 
  common 
  with 
  southern 
  New 
  England, 
  

   New 
  York, 
  and 
  the 
  northern 
  Appalachians. 
  Professor 
  Davis 
  has 
  

   shown 
  1! 
  that 
  the 
  Berkshire 
  hills 
  area, 
  during 
  the 
  late 
  Mesozoic, 
  had 
  

   been 
  worn 
  down 
  to 
  a 
  fairly 
  good 
  peneplain 
  with 
  occasional 
  low 
  

   mountains 
  (monadnocks) 
  rising 
  above 
  the 
  general 
  level. 
  There 
  is 
  

   strong 
  reason 
  to 
  believe 
  that 
  a 
  similar 
  condition 
  prevailed 
  over 
  

   the 
  southeastern 
  Adirondack 
  region, 
  but 
  with 
  the 
  monadnock 
  

  

  1 
  Physical 
  Geography 
  of 
  Southern 
  New 
  England 
  in 
  Physiography 
  of 
  the 
  

   United 
  States. 
  

  

  