﻿208 
  Taylor 
  — 
  Scoured 
  Bowlders 
  of 
  the 
  Mattawa 
  Valley. 
  

  

  Art. 
  XIX. 
  — 
  The 
  Scoured 
  Bowlders 
  of 
  the 
  Mattawa 
  Valley 
  • 
  

   by 
  F. 
  B. 
  Taylor. 
  

  

  Introduction. 
  

  

  The 
  author 
  spent 
  the 
  last 
  week 
  in 
  September 
  and 
  the 
  first 
  

   half 
  of 
  October 
  just 
  passed 
  in 
  exploring 
  the 
  valley 
  of 
  the 
  

   Mattawa 
  river 
  in 
  the 
  Province 
  of 
  Ontario. 
  The 
  chief 
  object 
  

   of 
  search 
  was 
  to 
  discover 
  whether 
  there 
  is 
  any 
  clear 
  evidence 
  

   of 
  the 
  recent 
  flow 
  of 
  a 
  great 
  river 
  eastward 
  along 
  this 
  course 
  

   to 
  the 
  Ottawa 
  valley. 
  For 
  this 
  is 
  the 
  site 
  of 
  a 
  supposed 
  former 
  

   outlet 
  of 
  the 
  upper 
  Great 
  Lakes. 
  It 
  has 
  been 
  supposed, 
  first 
  

   by 
  Mr. 
  G. 
  K. 
  Gilbert, 
  and 
  later 
  by 
  Prof. 
  G. 
  F. 
  Wright 
  and 
  the 
  

   author, 
  that 
  there 
  was 
  a 
  period 
  since 
  the 
  disappearance 
  of 
  the 
  

   ice-sheet 
  during 
  which 
  Lakes 
  Superior, 
  Michigan, 
  and 
  Huron 
  

   discharged 
  their 
  waters 
  eastward 
  to 
  the 
  Ottawa 
  valley 
  along 
  

   the 
  present 
  course 
  of 
  the 
  Mattawa 
  river. 
  During 
  this 
  period 
  

   Lake 
  Erie 
  alone 
  retained 
  its 
  outlet 
  through 
  Niagara 
  river 
  to 
  

   the 
  basin 
  of 
  Lake 
  Ontario. 
  It 
  does 
  not 
  fall 
  within 
  the 
  

   intended 
  scope 
  of 
  this 
  paper 
  to 
  discuss 
  all 
  the 
  facts 
  relating 
  to 
  

   the 
  existence 
  of 
  the 
  ISTipissing-Mattawa 
  river, 
  as 
  the 
  ancient 
  

   outlet 
  river 
  may 
  be 
  called, 
  nor 
  to 
  discuss 
  exhaustively 
  the 
  facts 
  

   relating 
  to 
  its 
  duration 
  and 
  date. 
  It 
  will 
  suffice 
  here 
  to 
  state 
  

   that 
  from 
  several 
  kinds 
  of 
  evidence 
  the 
  existence 
  of 
  the 
  great 
  

   outlet 
  river 
  is 
  believed 
  to 
  be 
  established 
  beyond 
  a 
  doubt; 
  and 
  

   further, 
  that 
  it 
  endured 
  for 
  a 
  comparatively 
  long 
  period 
  of 
  

   time 
  and 
  ceased 
  to 
  exist 
  probably 
  considerably 
  less 
  than 
  ten 
  

   thousand 
  years 
  ago. 
  Hence, 
  while 
  it 
  is 
  geologically 
  a 
  very 
  

   recent 
  thing, 
  it 
  may 
  very 
  properly 
  be 
  spoken 
  of 
  in 
  a 
  historical 
  

   sense 
  as 
  ancient. 
  

  

  No 
  more 
  conclusive 
  evidence 
  of 
  the 
  existence 
  of 
  the 
  ancient 
  

   river 
  could 
  be 
  expected 
  than 
  that 
  which 
  has 
  been 
  gathered 
  this 
  

   season 
  from 
  a 
  study 
  of 
  the 
  numerous 
  bowlders 
  that 
  lay 
  in 
  its 
  

   rapids. 
  The 
  volume 
  of 
  the 
  river, 
  it 
  is 
  fair 
  to 
  assume, 
  was 
  

   practically 
  the 
  same 
  as 
  that 
  of 
  the 
  St. 
  Clair 
  river 
  to-day, 
  and 
  

   was 
  equally 
  steady 
  in 
  its 
  flow. 
  In 
  rapids 
  of 
  moderate 
  velocity, 
  

   where 
  the 
  river 
  flowed 
  over 
  a 
  sill 
  closely 
  paved 
  with 
  large 
  

   bowlders, 
  the 
  action 
  of 
  the 
  current 
  rolling 
  small 
  quantities 
  of 
  

   gravel 
  over, 
  around 
  and 
  between 
  the 
  bowlders 
  produced 
  cer- 
  

   tain 
  wearing 
  or 
  scouring 
  effects 
  which 
  are 
  very 
  characteristic. 
  

   The 
  forms 
  so 
  produced 
  are 
  not 
  known 
  to 
  be 
  made 
  in 
  any 
  other 
  

   way. 
  It 
  is 
  the 
  object 
  of 
  this 
  paper 
  to 
  present 
  a 
  brief 
  account 
  

   of 
  these 
  peculiar 
  bowlders 
  as 
  they 
  appear 
  today 
  in 
  the 
  valley 
  

   of 
  the 
  Mattawa, 
  many 
  of 
  them 
  as 
  much 
  as 
  forty 
  feet 
  above 
  

   the 
  present 
  river. 
  A 
  few 
  remarks 
  will 
  also 
  be 
  added 
  about 
  the 
  

   conditions 
  and 
  the 
  processes 
  of 
  their 
  production. 
  

  

  