﻿124 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  of 
  overlying 
  rock 
  which 
  has 
  been 
  worn 
  away, 
  from 
  the 
  close 
  of 
  

   the 
  Siluric 
  to 
  the 
  present. 
  Where 
  the 
  various 
  members 
  of 
  the 
  

   Paleozoic 
  form 
  the 
  surface 
  rocks, 
  erosion 
  is 
  correspondingly 
  less, 
  

   and 
  since 
  the 
  Precambric 
  is 
  at 
  the 
  surface 
  over 
  but 
  a 
  small 
  fraction 
  

   of 
  the 
  region, 
  the 
  general 
  erosion 
  has 
  been 
  less 
  than 
  that 
  figure. 
  

   Considering 
  the 
  great 
  length 
  of 
  time 
  involved, 
  this 
  represents 
  no 
  

   great 
  erosion, 
  and 
  seems 
  to 
  point 
  to 
  land 
  of 
  no 
  great 
  altitude 
  for 
  

   much 
  of 
  the 
  time. 
  It 
  seems 
  to 
  be 
  further 
  demonstrable 
  that 
  at 
  least 
  

   one 
  half 
  of 
  this 
  erosion 
  took 
  place 
  in 
  Tertiary 
  time, 
  which 
  argues 
  

   all 
  the 
  more 
  strongly 
  for 
  general 
  low 
  altitude 
  during 
  the 
  preceding 
  

   ages 
  of 
  the 
  Mesozoic 
  and 
  later 
  Paleozoic. 
  

  

  Original 
  drainage 
  

  

  As 
  uplifted 
  at 
  the 
  close 
  of 
  the 
  Siluric, 
  and 
  following 
  the 
  deposi- 
  

   tion 
  of 
  the 
  Oswego 
  sandstone, 
  our 
  area 
  became 
  the 
  marginal 
  portion 
  

   of 
  land 
  masses 
  to 
  the 
  north 
  and 
  the 
  east, 
  and 
  in 
  all 
  probability 
  

   possessed 
  a 
  gentle 
  slope 
  to 
  the 
  southwest. 
  The 
  original 
  streams 
  

   must 
  have 
  followed 
  down 
  this 
  slope 
  to 
  the 
  margins 
  of 
  the 
  later 
  

   Paleozoic 
  water 
  bodies 
  of 
  central 
  New 
  York, 
  thus 
  flowing 
  in 
  the 
  

   direction 
  of 
  the 
  rock 
  dip, 
  and 
  at 
  right 
  angles 
  to 
  the 
  strike. 
  Having 
  

   taken 
  position 
  they 
  would 
  commence 
  to 
  carve 
  valleys, 
  whose 
  possi- 
  

   ble 
  depth 
  would 
  depend 
  upon 
  the 
  altitude 
  of 
  the 
  land. 
  Streams 
  of 
  

   this 
  type 
  are 
  called 
  consequent 
  streams. 
  With 
  valley 
  cutting 
  in 
  

   progress, 
  tributaries 
  to 
  these 
  original 
  streams 
  commence 
  to 
  develop, 
  

   beginning 
  as 
  gullies 
  in 
  the 
  valley 
  sides, 
  and 
  steadily 
  cutting 
  head- 
  

   wards. 
  Obviously 
  they 
  form 
  most 
  readily 
  where 
  the 
  valley 
  walls 
  are 
  

   weakest, 
  and 
  tend 
  to 
  remain 
  in 
  the 
  weak 
  rock 
  belts, 
  following 
  their 
  

   strike, 
  hence 
  with 
  courses 
  which 
  make 
  substantially 
  a 
  right 
  angle 
  

   with 
  those 
  of 
  the 
  original 
  streams. 
  Such 
  streams 
  are 
  called 
  subse- 
  

   quent, 
  since 
  their 
  development 
  must 
  wait 
  on 
  that 
  of 
  the 
  consequent 
  

   streams. 
  With 
  a 
  belt 
  of 
  weak 
  rocks 
  to 
  follow, 
  these 
  subsequent 
  

   streams 
  may 
  eventually 
  become 
  the 
  chief 
  streams 
  of 
  a 
  region, 
  divert- 
  

   ing 
  or 
  " 
  capturing 
  " 
  the 
  headwaters 
  of 
  the 
  old 
  consequent 
  streams. 
  

   Tlie 
  Utica 
  and 
  Lorraine 
  shales 
  constitute 
  such 
  a 
  weak 
  rock 
  belt 
  in 
  

   this 
  region, 
  with 
  the 
  great 
  Ontario 
  valley 
  eaten 
  out 
  along 
  it, 
  the 
  

   Adirondack 
  highland 
  blocking 
  its 
  extension 
  further 
  east. 
  

  

  With 
  chiefly 
  low 
  lands, 
  drainage 
  adjustments 
  would 
  go 
  on 
  

   but 
  slowly, 
  and 
  the 
  drainage 
  may 
  have 
  been 
  considerably 
  modified 
  

   from 
  time 
  to 
  time 
  by 
  tilting 
  of 
  the 
  land, 
  under 
  these 
  low 
  altitude 
  

   conditions. 
  With 
  the 
  passage 
  of 
  time, 
  however, 
  it 
  has 
  come 
  about 
  

   that 
  the 
  chief 
  streams 
  of 
  the 
  region 
  are 
  now 
  in 
  subsequent 
  position, 
  

  

  