﻿Geology 
  and 
  Mineralogy, 
  69 
  

  

  2. 
  Changes 
  of 
  level 
  in 
  the 
  region 
  of 
  the 
  Great 
  Lakes 
  in 
  recent 
  

   geological 
  time; 
  by 
  Frank 
  B. 
  Taylor. 
  (Letter 
  to 
  J. 
  D. 
  Dana.) 
  — 
  

   " 
  First, 
  as 
  to 
  the 
  probable 
  place 
  of 
  the 
  highest 
  shore 
  line 
  on 
  the 
  

   north 
  coast 
  of 
  Lake 
  Superior. 
  It 
  seems 
  to 
  me 
  that 
  when 
  we 
  take 
  

   full 
  account 
  of 
  all 
  that 
  is 
  now 
  known 
  about 
  the 
  highest 
  shore 
  

   line 
  in 
  the 
  regions 
  adjacent 
  to 
  Lake 
  Superior 
  we 
  are 
  bound 
  to 
  

   conclude, 
  pending 
  further 
  exploration, 
  that 
  this 
  line 
  probably 
  

   attains 
  an 
  altitude 
  of 
  at 
  least 
  1200 
  to 
  1300 
  feet 
  above 
  sea 
  level 
  in 
  

   the 
  Nipigon 
  region 
  at 
  the 
  north-northwestern 
  extremity 
  of 
  the 
  

   lake, 
  and 
  at 
  least 
  1100 
  to 
  1200 
  feet 
  on 
  the 
  northeastern 
  side 
  at 
  

   Lake 
  Missinaibi. 
  The 
  facts 
  upon 
  which 
  this 
  opinion 
  rests 
  are 
  as 
  

   follows: 
  The 
  altitude 
  of 
  the 
  Herman 
  beach 
  of 
  "Lake 
  Agassiz 
  " 
  

   (ancient 
  Gulf 
  of 
  Winnipeg) 
  is 
  1055 
  feet 
  at 
  Lake 
  Traverse, 
  and 
  

   1220 
  feet 
  at 
  the 
  international 
  boundary. 
  On 
  the 
  east 
  side 
  of 
  

   Red 
  river 
  in 
  Minnesota 
  this 
  beach 
  rises 
  a 
  little 
  more 
  rapidly. 
  On 
  

   the 
  southeast 
  side 
  of 
  Beltrami 
  island 
  in 
  northeastern 
  Minnesota 
  

   it 
  occurs 
  at 
  1087 
  feet 
  and 
  on 
  the 
  northwest 
  side 
  at 
  1195 
  feet. 
  At 
  

   Duluth, 
  1134 
  feet, 
  and 
  at 
  Mt. 
  Josephine 
  on 
  the 
  northwest 
  coast 
  

   of 
  Lake 
  Superior, 
  1207 
  feet. 
  Near 
  L'Anse 
  and 
  again 
  near 
  Mar- 
  

   quette 
  on 
  the 
  south 
  coast, 
  1190 
  feet. 
  Near 
  Sault 
  Ste. 
  Marie 
  1014 
  

   feet. 
  Near 
  Cartier, 
  Ontario, 
  about 
  1200 
  feet, 
  and 
  at 
  the 
  ancient 
  

   Nipissing 
  strait 
  at 
  North 
  Bay, 
  Ontario, 
  1140 
  feet 
  on 
  the 
  north 
  

   and 
  more 
  than 
  1220 
  feet 
  on 
  the 
  south 
  side. 
  

  

  It 
  is 
  noticeable 
  that 
  the 
  lowest 
  level 
  of 
  the 
  line 
  in 
  this 
  list 
  is 
  at 
  

   Sault 
  Ste. 
  Marie. 
  If 
  the 
  highest 
  shore 
  line 
  passes 
  downward 
  to 
  

   the 
  north 
  from 
  this 
  place, 
  or 
  even 
  on 
  a 
  level, 
  it 
  must 
  cut 
  off 
  the 
  

   supposed 
  straits 
  to 
  the 
  north 
  of 
  Lake 
  Superior. 
  But 
  considering 
  

   the 
  high 
  altitude 
  of 
  the 
  shore 
  line 
  in 
  all 
  the 
  regions 
  bordering 
  the 
  

   lake, 
  Green 
  Bay 
  only 
  excepted, 
  the 
  chance 
  of 
  this 
  seems 
  extremely 
  

   small. 
  The 
  highest 
  beach, 
  rising 
  northward 
  from 
  1134 
  feet 
  at 
  

   Duluth 
  to 
  1207 
  feet 
  on 
  Mt. 
  Josephine, 
  (supposing 
  Lawson's 
  

   observations 
  at 
  the 
  latter 
  place 
  to 
  be 
  correct) 
  must 
  meet 
  the 
  

   beach 
  which 
  passes 
  northward 
  from 
  Sault 
  Ste. 
  Marie 
  somewhere 
  

   in 
  the 
  north, 
  because 
  they 
  are 
  the 
  margin 
  of 
  one 
  water 
  plane. 
  It 
  

   seems 
  almost 
  certain, 
  therefore, 
  that 
  the 
  highest. 
  beach 
  must 
  rise 
  

   more 
  rapidly 
  northward 
  from 
  Sault 
  Ste. 
  Marie 
  than 
  it 
  does 
  from 
  

   Duluth. 
  For 
  it 
  starts 
  from 
  a 
  level 
  about 
  120 
  feet 
  lower. 
  I 
  am 
  

   bound 
  to 
  conclude, 
  therefore, 
  for 
  the 
  present 
  that 
  the 
  highest 
  

   shore 
  line 
  rises 
  at 
  least 
  \\ 
  to 
  2 
  feet 
  per 
  mile 
  northward 
  from 
  Sault 
  

   Ste. 
  Marie 
  and 
  keeps 
  well 
  up 
  along 
  the 
  north 
  shore, 
  leaving 
  the 
  

   open 
  straits 
  to 
  the 
  north, 
  as 
  stated 
  in 
  my 
  paper. 
  (As 
  I 
  remember 
  

   Prof. 
  Lawson's 
  figures, 
  the 
  Missinaibi 
  pass 
  is 
  about 
  1044 
  feet 
  

   above 
  sea 
  level 
  and 
  the 
  Kenogami 
  pass 
  1109 
  feet.) 
  I 
  see 
  no 
  

   escape 
  from 
  this 
  conclusion, 
  then, 
  unless 
  it 
  be 
  by 
  some 
  abrupt 
  

   and 
  very 
  exceptional 
  dip 
  of 
  the 
  ancient 
  water 
  plane 
  downward 
  to 
  

   the 
  north. 
  It 
  would 
  appear, 
  therefore, 
  that 
  the 
  mean 
  height 
  of 
  

   the 
  highest 
  shore 
  line 
  in 
  the 
  Superior 
  basin 
  can 
  hardly 
  be 
  less 
  

   than 
  1100 
  feet 
  or 
  more 
  than 
  1200. 
  On 
  present 
  data 
  the 
  most 
  

   probable 
  mean 
  that 
  I 
  can 
  name 
  for 
  the 
  whole 
  basin 
  is 
  about 
  1150 
  

   feet. 
  I 
  think 
  this 
  estimate 
  is 
  conservative 
  and 
  likely 
  to 
  prove 
  

   too 
  low 
  rather 
  than 
  too 
  high. 
  

  

  