﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  

  

  83 
  

  

  It 
  is 
  practically 
  certain 
  that 
  preglacial 
  streams 
  were 
  here 
  north- 
  

   flowing 
  rather 
  than 
  south-flowing, 
  because 
  during 
  long 
  Tertiary 
  

   time 
  such 
  tributaries 
  to 
  the 
  large 
  stream 
  in 
  the 
  Ontario 
  basin 
  must 
  

   have 
  developed 
  across 
  the 
  steep 
  north 
  slopes 
  of 
  the 
  Niagara 
  and 
  

   Helderberg 
  escarpments, 
  and 
  also 
  because 
  the 
  slope 
  of 
  the 
  Genesee 
  

  

  uAORE/V/ 
  r/ 
  

  

  Fig. 
  27 
  Grabau's 
  interpretation 
  of 
  late 
  Tertiary 
  drainage 
  in 
  the 
  eastern 
  

   Great 
  Lakes 
  region, 
  the 
  intention 
  being 
  to 
  show 
  the 
  general 
  kind 
  of 
  drainage 
  

   rather 
  than 
  the 
  exact 
  location 
  of 
  the 
  streams. 
  The 
  " 
  Rome 
  " 
  river 
  with 
  

   source 
  at 
  Little 
  Falls 
  is 
  well 
  shown. 
  The 
  three 
  south-flowing 
  streams 
  should, 
  

   in 
  the 
  writer's 
  opinion, 
  be 
  represented 
  as 
  north-flowing, 
  at 
  least 
  immediately 
  

   prior 
  to 
  the 
  great 
  Ice 
  Age. 
  

  

  After 
  Grabau, 
  N. 
  Y. 
  State 
  M 
  s. 
  B.l. 
  45, 
  fig. 
  6 
  

  

  river 
  is 
  now, 
  at 
  least, 
  so 
  decidedly 
  downward 
  toward 
  the 
  north. 
  

   If 
  the 
  late 
  Tertiary 
  Genesee 
  flowed 
  southward, 
  the 
  reversal 
  of 
  its 
  

   course 
  must 
  have 
  been 
  caused 
  by 
  a 
  very 
  marked 
  tilting 
  of 
  the 
  land, 
  

   but 
  we 
  have 
  no 
  evidence 
  for 
  such 
  a 
  decided 
  land 
  movement. 
  

  

  In 
  our 
  discussion 
  of 
  Mesozoic 
  drainage 
  (see 
  chapter 
  5) 
  we 
  found 
  

   that, 
  during 
  the 
  early 
  part 
  of 
  that 
  era, 
  nearly 
  all 
  the 
  drainage 
  of 
  

  

  