﻿Beelevation 
  of 
  the 
  St. 
  Lawrence 
  river 
  hasm. 
  9 
  

  

  present 
  St. 
  Clair 
  and 
  Detroit 
  rivers, 
  by 
  which 
  the 
  earliest 
  out- 
  

   flow 
  of 
  the 
  old 
  glacial 
  lake 
  probably 
  passed 
  southward 
  and 
  

   thence 
  ran 
  east 
  as 
  a 
  glacial 
  River 
  Erie, 
  at 
  first 
  tributary 
  to 
  

   Lake 
  Lundy. 
  As 
  soon 
  as 
  that 
  very 
  briefly 
  existing 
  glacial 
  

   lake 
  was 
  drained 
  away, 
  the 
  river 
  followed 
  the 
  lowest 
  part 
  of 
  

   the 
  shallow 
  bed 
  of 
  the 
  present 
  Lake 
  Erie 
  along 
  all 
  its 
  extent, 
  

   which 
  then 
  had 
  an 
  eastward 
  descent 
  of 
  probably 
  200 
  feet, 
  

   allowing 
  no 
  lake 
  or 
  only 
  a 
  very 
  small 
  one 
  to 
  exist 
  in 
  the 
  

   deepest 
  depression 
  of 
  the 
  basin 
  ; 
  and 
  north 
  of 
  Buffalo 
  it 
  coin- 
  

   cided 
  with 
  the 
  course 
  of 
  the 
  Niagara 
  river. 
  

  

  Gilbert, 
  Wright, 
  and 
  Spencer, 
  have 
  thought 
  that 
  for 
  a 
  long 
  

   time 
  the 
  outflow 
  of 
  the 
  three 
  great 
  lakes 
  above 
  Lake 
  Erie 
  

   passed 
  by 
  the 
  way 
  of 
  Lake 
  Nipissing 
  to 
  the 
  Mattawa 
  and 
  Ot- 
  

   tawa 
  rivers. 
  It 
  seems 
  to 
  me 
  far 
  more 
  probable, 
  however, 
  that 
  

   the 
  epeirogenic 
  uplift 
  of 
  the 
  Nipissing 
  region, 
  which 
  had 
  ele- 
  

   vated 
  it 
  already 
  about 
  400 
  feet 
  during 
  the 
  existence 
  of 
  Lake 
  

   Warren, 
  continued 
  so 
  fast 
  that 
  both 
  the 
  Trent 
  and 
  JNipissing- 
  

   Mattawa 
  passes 
  were 
  raised 
  the 
  additional 
  50 
  feet 
  needed 
  to 
  

   place 
  them 
  above 
  the 
  level 
  of 
  Lake 
  Algonquin 
  before 
  the 
  

   glacial 
  retreat 
  uncovered 
  the 
  country 
  east 
  of 
  them 
  so 
  that 
  out- 
  

   lets 
  could 
  be 
  obtained 
  there. 
  

  

  With 
  the 
  continuance 
  of 
  the 
  uplift 
  of 
  the 
  Lake 
  Superior 
  

   basin 
  after 
  the 
  formation 
  of 
  the 
  Algonquin 
  beach, 
  the 
  mouth 
  

   of 
  Lake 
  Superior 
  and 
  the 
  Sault 
  Ste. 
  Marie 
  came 
  into 
  existence 
  ; 
  

   and 
  this 
  movement 
  allowed 
  the 
  lake 
  level 
  at 
  Duluth 
  to 
  fall 
  

   probably 
  40 
  or 
  50 
  feet 
  beneath 
  the 
  Algonquin 
  and 
  present 
  

   shore 
  line. 
  Subsequent 
  differential 
  elevation 
  of 
  the 
  eastern 
  

   and 
  northern 
  parts 
  of 
  the 
  basin, 
  as 
  compared 
  with 
  Duluth, 
  has 
  

   again 
  brought 
  the 
  west 
  end 
  of 
  the 
  lake 
  up 
  to 
  the 
  Algonquin 
  

   shore, 
  but 
  not 
  until 
  the 
  St. 
  Louis 
  river, 
  while 
  the 
  water 
  sur- 
  

   face 
  stood 
  considerably 
  lower 
  than 
  now, 
  had 
  deeply 
  eroded 
  its 
  

   broad 
  channel 
  through 
  the 
  very 
  gently 
  sloping 
  expanse 
  of 
  till 
  

   from 
  Fond 
  du 
  Lac 
  to 
  the 
  harbor 
  of 
  Duluth 
  and 
  Superior. 
  

  

  The 
  differential 
  uplift 
  of 
  the 
  Algonquin 
  beach, 
  as 
  compared 
  

   with 
  Chicago 
  and 
  the 
  previous 
  mouth 
  of 
  Lake 
  Warren, 
  has 
  

   been 
  about 
  60 
  feet 
  near 
  the 
  mouth 
  of 
  Lake 
  Huron 
  and 
  at 
  

   Duluth 
  ; 
  110 
  feet 
  at 
  the 
  mouth 
  of 
  Lake 
  Superior 
  ; 
  200 
  feet 
  at 
  

   Lake 
  Xipissing 
  ; 
  and 
  240 
  to 
  290 
  feet 
  at 
  Barrie, 
  Lorneville, 
  and 
  

   Orillia, 
  on 
  Lake 
  Simcoe. 
  A 
  broad 
  lobe 
  of 
  the 
  waning 
  ice 
  

   sheet, 
  terminating 
  on 
  the 
  highland 
  area 
  between 
  the 
  south 
  end 
  

   of 
  Georgian 
  bay 
  and 
  the 
  west 
  end 
  of 
  Lake 
  Ontario, 
  appears 
  to 
  

   have 
  delayed 
  the 
  elevation 
  of 
  that 
  district, 
  so 
  that 
  subsequent 
  

   to 
  the 
  formation 
  of 
  the 
  Algonquin 
  beach 
  more 
  uplifting 
  took 
  

   place 
  there 
  than 
  at 
  the 
  north 
  side 
  of 
  Georgian 
  bay 
  and 
  about 
  

   Lake 
  Xipissing. 
  The 
  ascent 
  of 
  the 
  Algonquin 
  beach 
  in 
  nearly 
  

   200 
  miles 
  from 
  the 
  mouth' 
  of 
  Lake 
  Huron 
  northeasterly 
  to 
  

   Lake 
  Simcoe 
  averages 
  about 
  a 
  foot 
  per 
  mile 
  ; 
  and 
  thence 
  in 
  

  

  