﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  49 
  

  

  the 
  preglacial 
  divide 
  has 
  an 
  elevation 
  of 
  440 
  feet 
  above 
  sealevel.^ 
  

   The 
  following 
  diagram 
  (fig. 
  8) 
  shows 
  the 
  present 
  relation 
  of 
  the 
  

   deepest 
  part 
  of 
  the 
  channel 
  of 
  Lake 
  Ontario 
  to 
  sealevel, 
  and 
  the 
  

   relation 
  which 
  would 
  result 
  by 
  a 
  tilting 
  of 
  the 
  land 
  back 
  to 
  its 
  

   probable 
  position 
  in 
  preglacial 
  times. 
  The 
  last 
  profile 
  shows 
  a 
  con- 
  

   tinuous 
  westward 
  slope 
  of 
  the 
  floor 
  of 
  the 
  valley, 
  steeper 
  in 
  the 
  

   eastern 
  portion, 
  where 
  the 
  rocks 
  are 
  harder 
  and 
  the 
  valley 
  narrower, 
  

   and 
  more 
  gentle 
  in 
  the 
  western 
  portion, 
  where 
  the 
  softer 
  rocks 
  have 
  

   allowed 
  the 
  opening 
  of 
  a 
  broad 
  lowland. 
  

  

  Fig. 
  8 
  Diagram 
  showing 
  the 
  present 
  deepest 
  e-w 
  channel 
  of 
  Lake 
  Ontario 
  along 
  line 
  l-i, 
  and 
  Its 
  re- 
  

   lation 
  to 
  sealevel 
  s. 
  1. 
  and 
  the 
  level 
  of 
  Lake 
  Ontario 
  1 
  o. 
  At 
  1, 
  leftside 
  of 
  diagram 
  is 
  represented 
  the 
  

   bottom 
  of 
  the 
  channel 
  at 
  Vienna, 
  200 
  ft 
  below 
  level 
  of 
  Lake 
  Erie 
  or 
  370 
  ft 
  above 
  sealevel. 
  At 
  1, 
  

   right 
  side, 
  is 
  the 
  divide 
  at 
  Littlefalls 
  440 
  ft 
  A. 
  T. 
  The 
  line 
  1-2, 
  is 
  the 
  line 
  1-1, 
  but 
  elevated 
  on 
  the 
  

   east 
  (right) 
  so 
  as 
  to 
  give 
  a 
  continuous 
  westward 
  drainage. 
  Horizontal 
  scale 
  1 
  Inch 
  = 
  100 
  miles. 
  Ver- 
  

   tical 
  scale 
  1 
  inch 
  = 
  4000 
  feet. 
  

  

  Numerous 
  theories 
  have 
  been 
  advanced 
  to 
  account 
  for 
  the 
  deep 
  

   basin 
  of 
  Lake 
  Ontario. 
  Spencer 
  believed 
  it 
  to 
  have 
  been 
  formed 
  by 
  

   an 
  eastward 
  flowing 
  stream, 
  the 
  ancient 
  Laurentian 
  river, 
  which 
  re- 
  

   ceived 
  the 
  Erian 
  river 
  as 
  a 
  tributary 
  through 
  the 
  Dundas 
  valley. 
  

   The 
  eastward 
  continuation 
  of 
  this 
  river 
  Spencer 
  believed 
  to 
  have 
  

   been 
  essentially 
  along 
  the 
  course 
  of 
  the 
  modern 
  St 
  Lawrence, 
  the 
  

   present 
  great 
  elevation 
  of 
  the 
  rocky 
  bed 
  of 
  this 
  stream, 
  above 
  that 
  

   of 
  Lake 
  Ontario, 
  being 
  explained 
  by 
  a 
  warping 
  of 
  the 
  land. 
  Up- 
  

   ham 
  also 
  believes 
  that 
  the 
  basin 
  is 
  in 
  part 
  due 
  to 
  warping, 
  but 
  he 
  

   considers 
  it 
  the 
  valley 
  of 
  a 
  westward 
  flowing 
  stream. 
  Russell 
  also 
  

   holds 
  this 
  latter 
  view; 
  for 
  he 
  says^ 
  that, 
  "previous 
  to 
  the 
  glacial 
  

   epoch, 
  the 
  greater 
  part 
  of 
  the 
  Laurentian 
  basin 
  discharged 
  its 
  

   waters 
  southward 
  to 
  the 
  Mississippi 
  and 
  . 
  . 
  . 
  during 
  the 
  first 
  

   advance 
  of 
  the 
  ice 
  from 
  the 
  north 
  the 
  drainage 
  was 
  not 
  obstructed 
  

   so 
  as 
  to 
  form 
  important 
  lakes 
  ". 
  Westgate^, 
  in 
  tracing 
  out 
  the 
  de- 
  

  

  •Bigelow. 
  Bui. 
  geol. 
  soc. 
  Am. 
  9*183. 
  

   ^ 
  Lakes 
  of 
  North 
  America, 
  p. 
  97. 
  

   ^Loc, 
  cit. 
  p. 
  92. 
  

  

  