﻿TO 
  Scientific 
  Intelligence. 
  

  

  Second. 
  As 
  to 
  the 
  origin 
  of 
  the 
  highest 
  beach, 
  I 
  believe 
  that 
  it 
  

   was 
  all 
  made 
  at 
  sea 
  level 
  and 
  that 
  the 
  Iroquois 
  beach 
  in 
  the 
  

   Ontario 
  basin, 
  the 
  highest 
  beach 
  in 
  the 
  northern 
  parts 
  of 
  the 
  

   Huron 
  and 
  Michigan 
  basins 
  with 
  that 
  of 
  the 
  Superior 
  basin, 
  and 
  

   also 
  the 
  upper 
  beach 
  of 
  the 
  Red 
  river 
  and 
  Winnipeg 
  basin, 
  are 
  

   all 
  one 
  continuous 
  beach 
  and 
  of 
  the 
  same 
  age 
  in 
  all 
  parts. 
  In 
  the 
  

   Michigan 
  and 
  Huron 
  basins 
  this 
  beach 
  slopes 
  downward 
  toward 
  

   the 
  south 
  and 
  passes 
  under 
  the 
  present 
  lake 
  level, 
  thus 
  leaving 
  

   Lake 
  Erie 
  with 
  all 
  its 
  beaches 
  and 
  also 
  the 
  Chicago 
  outlet 
  entirely- 
  

   above 
  that 
  plane. 
  The 
  Erie 
  beaches 
  are 
  undoubtedly 
  the 
  shores 
  

   of 
  an 
  ice-dammed 
  lake 
  of 
  the 
  glacial 
  recession. 
  It 
  was 
  much 
  the 
  

   largest 
  lake 
  produced 
  in 
  this 
  way. 
  But 
  there 
  were 
  other 
  smaller, 
  

   shorter 
  lived 
  ones 
  at 
  the 
  south 
  ends 
  or 
  sides 
  of 
  all 
  the 
  basins. 
  

   The 
  Ontario 
  basin 
  was 
  probably 
  also 
  partly 
  filled 
  by 
  a 
  large 
  

   temporary 
  lake 
  of 
  this 
  kind, 
  emptying 
  through 
  the 
  Mohawk 
  valley. 
  

   But 
  the 
  record 
  it 
  may 
  have 
  left 
  has 
  been 
  wiped 
  out 
  by 
  the 
  later 
  

   marine 
  invasion 
  which 
  made 
  the 
  Iroquois 
  beach. 
  

  

  Third. 
  As 
  to 
  the 
  relations 
  of 
  Niagara, 
  Lake 
  Erie, 
  etc., 
  I 
  have 
  

   the 
  data 
  to 
  show 
  conclusively 
  that 
  the 
  present 
  period 
  of 
  the 
  great 
  

   cataract's 
  activity 
  began 
  at 
  a 
  point 
  a 
  few 
  rods 
  above 
  the 
  canti- 
  

   lever 
  railroad 
  bridge. 
  Before 
  that 
  time 
  the 
  outlet 
  of 
  the 
  upper 
  

   lakes 
  was 
  eastward 
  over 
  Nipissing 
  pass 
  and 
  down 
  the 
  Ottawa 
  

   river, 
  and 
  greater 
  Niagara 
  was 
  replaced 
  for 
  a 
  long 
  period 
  of 
  time 
  

   by 
  a 
  very 
  much 
  smaller 
  stream 
  (the 
  " 
  Erigan 
  " 
  river), 
  which 
  

   drained 
  only 
  the 
  Erie 
  basin 
  and 
  possibly 
  not 
  all 
  of 
  that. 
  This 
  

   smaller 
  stream 
  made 
  the 
  narrower, 
  more 
  shallow 
  gorge 
  of 
  the 
  

   whirlpool 
  rapids, 
  extending 
  from 
  Foster's 
  flat 
  below 
  the 
  whirl- 
  

   pool 
  up 
  to 
  the 
  cantilever 
  bridge. 
  The 
  time 
  which 
  was 
  required 
  

   to 
  do 
  this 
  must 
  have 
  been 
  many 
  times 
  longer 
  than 
  Mr. 
  Gilbert's 
  

   estimate 
  of 
  the 
  age 
  of 
  the 
  whole 
  gorge 
  from 
  Lewiston 
  up. 
  I 
  

   should 
  say 
  that 
  the 
  multiplier 
  would 
  have 
  to 
  be 
  tens 
  rather 
  than 
  

   units. 
  As 
  a 
  measure 
  of 
  the 
  duration 
  of 
  postglacial 
  time, 
  there- 
  

   fore, 
  I 
  do 
  not 
  see 
  how 
  the 
  gorge 
  can 
  have 
  any 
  value 
  worth 
  men- 
  

   tioning. 
  But 
  without 
  meeting 
  this 
  demand, 
  it 
  goes 
  far 
  enough 
  

   to 
  show 
  that 
  postglacial 
  time 
  must 
  have 
  been 
  much 
  longer 
  than 
  

   the 
  current 
  estimate. 
  

  

  But 
  to 
  go 
  a 
  step 
  farther, 
  there 
  is 
  considerable 
  evidence 
  to 
  show 
  

   that 
  the 
  greater 
  Niagara 
  had 
  another 
  earlier 
  period 
  of 
  postglacial 
  

   activity, 
  during 
  w 
  r 
  hich 
  it 
  cut 
  out 
  the 
  gorge 
  from 
  Lewiston 
  to 
  

   Foster's 
  flat. 
  Overhanging 
  Foster's 
  flat 
  is 
  the 
  old 
  fall 
  ledge 
  of 
  

   the 
  greater 
  cataract 
  with 
  the 
  narrower 
  gorge 
  of 
  the 
  smaller 
  

   stream 
  cut 
  back 
  on 
  the 
  south 
  side. 
  At 
  this 
  old 
  ledge 
  the 
  great 
  

   cataract 
  ceased 
  for 
  a 
  long 
  period 
  of 
  time, 
  and 
  when 
  it 
  returned 
  the 
  

   smaller 
  stream 
  had 
  cut 
  back 
  in 
  the 
  interval 
  to 
  the 
  cantilever 
  

   bridge. 
  Thus 
  the 
  great 
  cataract 
  has 
  been 
  intermittent 
  in 
  its 
  

   activity. 
  It 
  has 
  had 
  two 
  active 
  periods 
  separated 
  by 
  the 
  long, 
  

   almost 
  indefinitely 
  long, 
  period 
  during 
  which 
  the 
  falls 
  of 
  the 
  

   smaller 
  stream 
  carried 
  on 
  the 
  work. 
  And 
  all 
  this 
  plus 
  a 
  short 
  

   period 
  for 
  the 
  Chicago 
  outlet 
  has 
  been 
  since 
  the 
  ice 
  age. 
  There 
  

  

  