﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  41 
  

  

  from 
  1500 
  feet 
  to 
  2000 
  feet, 
  the 
  northern 
  extremity 
  of 
  which 
  lies 
  

   in 
  the 
  central 
  part 
  of 
  Wyoming 
  county. 
  To 
  the 
  north 
  of 
  this 
  

   there 
  are 
  three 
  well-defined 
  terraces 
  gradually 
  stepping 
  down 
  to 
  

   the 
  level 
  of 
  Lake 
  Ontario, 
  the 
  first 
  of 
  which 
  varies 
  from 
  1000 
  to 
  

   1500 
  feet 
  above 
  tide; 
  the 
  second, 
  from 
  500 
  to 
  1000 
  feet, 
  and 
  the 
  

   third, 
  between 
  about 
  250 
  and 
  500 
  feet. 
  Lake 
  Ontario 
  lies 
  at 
  a 
  

   mean 
  elevation 
  of 
  217 
  feet 
  above 
  tidewater. 
  It 
  is 
  by 
  these 
  several 
  

   successive 
  steps 
  that 
  the 
  northern 
  spurs 
  of 
  the 
  New 
  York 
  plateau 
  

   gradually 
  run 
  out 
  and 
  merge 
  themselves 
  almost 
  imperceptibly 
  

   into 
  the 
  flatlands 
  about 
  and 
  in 
  the 
  vicinity 
  of 
  Lake 
  Ontario 
  and 
  

   the 
  St 
  Lawrence 
  river. 
  The 
  course 
  of 
  the 
  streams 
  of 
  this 
  region 
  

   has 
  thus 
  been 
  defined 
  by 
  the 
  topography. 
  With 
  the 
  exception 
  of 
  

   those 
  trubutary 
  to 
  the 
  Allegheny 
  river, 
  their 
  course 
  is 
  generally 
  

   to 
  the 
  north, 
  to 
  either 
  Lake 
  Erie, 
  Niagara 
  river 
  or 
  Lake 
  Ontario. 
  

  

  Farther 
  east 
  we 
  find 
  a 
  number 
  of 
  mountain 
  or 
  semimountain 
  

   ranges 
  which 
  are 
  a 
  part 
  of 
  the 
  great 
  Appalachian 
  system, 
  and 
  

   which 
  extend 
  across 
  the 
  State 
  in 
  a 
  general 
  course 
  from 
  southwest 
  

   to 
  northeast. 
  The 
  first 
  of 
  this 
  series 
  extends 
  into 
  New 
  York 
  from 
  

   Pennsylvania 
  and 
  extends 
  northeast 
  through 
  Broome, 
  Delaware, 
  

   Otsego, 
  Schoharie, 
  Montgomery 
  and 
  Herkimer 
  counties 
  to 
  the 
  

   Mohawk 
  valley. 
  This 
  mountain 
  system 
  consists 
  of 
  broad, 
  irregu- 
  

   lar 
  hills, 
  broken 
  by 
  deep 
  ravines, 
  with 
  many 
  of 
  the 
  slopes 
  steep 
  

   and 
  precipitous. 
  To 
  the 
  north 
  of 
  that 
  river 
  an 
  elevated 
  area 
  of 
  

   crystalline 
  rocks 
  forms 
  the 
  Adirondack 
  mountain 
  range, 
  which 
  

   extends 
  to 
  Lake 
  Champlain. 
  To 
  the 
  westward 
  of 
  this 
  area 
  the 
  

   land 
  is 
  more 
  level, 
  gradually 
  declining 
  to 
  the 
  northwest 
  until 
  it 
  

   finally 
  terminates 
  at 
  the 
  level 
  of 
  Lake 
  Ontario 
  and 
  the 
  St 
  Law- 
  

   rence 
  river. 
  The 
  streams 
  of 
  these 
  sections 
  mostly 
  flow 
  west 
  and 
  

   northwest 
  to 
  the 
  east 
  end 
  of 
  Lake 
  Ontario 
  and 
  to 
  the 
  St 
  Lawrence 
  

   river, 
  while 
  a 
  short 
  distance 
  from 
  the 
  Mohawk 
  they 
  flow 
  south 
  to 
  

   the 
  Susquehanna 
  river. 
  The 
  Chenango 
  river 
  is 
  the 
  typical 
  stream 
  

   of 
  the 
  section, 
  tributary 
  to 
  the 
  Susquehanna. 
  

  

  Still 
  farther 
  east 
  and 
  south 
  of 
  the 
  Susquehanna 
  valley 
  a 
  second 
  

   series 
  of 
  mountains 
  enters 
  New 
  York 
  from 
  Pennsylvania 
  and 
  

   extends 
  northeast 
  through 
  Sullivan, 
  Ulster 
  and 
  Greene 
  counties, 
  

   terminating 
  in 
  the 
  Oatskill 
  mountains 
  upon 
  the 
  Hudson. 
  The 
  

  

  