﻿218 
  Taylor 
  — 
  Scoured 
  Bowlders 
  of 
  the 
  Mattawa 
  Valley. 
  

  

  on 
  the 
  shores 
  of 
  lakes 
  or 
  expanded 
  portions 
  of 
  the 
  valley. 
  

   Some 
  of 
  these 
  too 
  were 
  explored, 
  but 
  were 
  found 
  devoid 
  of 
  

   scoured 
  bowlders. 
  It 
  was 
  only 
  in 
  the 
  rapids 
  of 
  the 
  ancient 
  

   outlet, 
  where 
  a 
  swift 
  and 
  powerful 
  current 
  flowed 
  over 
  them, 
  

   and 
  where 
  there 
  was 
  a 
  supply 
  of 
  gravel 
  for 
  the 
  current 
  to 
  roll 
  

   along 
  that 
  the 
  higher 
  types 
  of 
  scoured 
  bowlders 
  were 
  made. 
  

  

  The 
  principal 
  conclusions 
  suggested 
  by 
  the 
  scoured 
  bowlders 
  

   may 
  be 
  summed 
  up 
  briefly 
  as 
  follows, 
  and 
  in 
  these 
  Dr. 
  Bell 
  is 
  

   in 
  substantial 
  agreement 
  with 
  the 
  author. 
  

  

  1. 
  The 
  modified 
  bowlders 
  which 
  show 
  the 
  more 
  pronounced 
  

   forms 
  of 
  scour 
  must 
  have 
  remained 
  a 
  relatively 
  long 
  time 
  in 
  

   one 
  position 
  and 
  in 
  a 
  current 
  which 
  was 
  substantially 
  constant 
  

   in 
  strength 
  and 
  direction 
  of 
  flow 
  in 
  order 
  to 
  have 
  received 
  

   their 
  deep 
  worn 
  and 
  peculiar 
  markings. 
  This 
  conclusion 
  is 
  

   further 
  supported 
  by 
  the 
  fact 
  that 
  all 
  the 
  bowlders 
  are 
  of 
  hard 
  

   crystalline 
  rock 
  — 
  mostly 
  of 
  the 
  hardest 
  gneiss 
  and 
  granite. 
  

  

  2. 
  There 
  must 
  have 
  been 
  a 
  constant 
  but 
  not 
  too 
  voluminous 
  

   supply 
  of 
  gravel 
  or 
  pebbles 
  for 
  the 
  current 
  to 
  roll 
  along 
  over 
  

   the 
  bowldery 
  bottom 
  in 
  order 
  that 
  the 
  work 
  of 
  scour 
  might 
  be 
  

   accomplished. 
  

  

  3. 
  Many 
  of 
  the 
  bowlders, 
  especially 
  the 
  larger 
  ones, 
  were 
  

   scoured 
  in 
  situ 
  and 
  in 
  some 
  cases 
  the 
  forms 
  of 
  their 
  scour 
  

   marks 
  show 
  clearly 
  the 
  direction 
  in 
  which 
  the 
  current 
  flowed. 
  

  

  4. 
  All 
  the 
  indications 
  gathered 
  from 
  the 
  bowlders 
  of 
  the 
  

   morainic 
  terrace 
  upon 
  which 
  Mattawa 
  is 
  built 
  show 
  that 
  the 
  

   scouring 
  current 
  came 
  from 
  the 
  Mattawa 
  valley 
  and 
  not 
  from 
  

   the 
  Ottawa. 
  And 
  this 
  is 
  true, 
  although 
  the 
  best 
  examples 
  

   relied 
  upon 
  for 
  this 
  conclusion 
  are 
  situated 
  so 
  as 
  to 
  be 
  equally 
  

   exposed 
  to 
  any 
  current 
  that 
  might 
  have 
  come 
  down 
  the 
  latter 
  

   valley. 
  

  

  5. 
  The 
  scoured 
  bowlders 
  typified 
  by 
  those 
  at 
  Mattawa 
  and 
  

   Des 
  Epines 
  rapids 
  constitute 
  a 
  distinct 
  class, 
  which 
  has 
  received 
  

   secondary 
  modifications 
  of 
  form 
  in 
  consequence 
  of 
  relatively 
  

   long 
  continued 
  and 
  powerful 
  current 
  action. 
  

  

  6. 
  Beds 
  of 
  scoured 
  bowlders 
  like 
  those 
  here 
  described, 
  mark- 
  

   ing 
  the 
  place 
  of 
  rapids 
  in 
  great 
  rivers 
  no 
  longer 
  in 
  existence, 
  

   may 
  serve 
  (with 
  due 
  consideration 
  of 
  other 
  attendant 
  condi- 
  

   tions) 
  as 
  valuable 
  aids 
  in 
  the 
  study 
  of 
  later 
  Pleistocene 
  history, 
  

   especially 
  in 
  the 
  bowldery 
  Archaean 
  areas 
  of 
  the 
  north. 
  

  

  In 
  the 
  opinion 
  of 
  the 
  writer 
  the 
  scoured 
  bowlders 
  are 
  one 
  of 
  

   the 
  best 
  of 
  several 
  lines 
  of 
  evidence 
  that 
  clearly 
  establish 
  the 
  

   existence 
  of 
  the 
  great 
  Nipissing-Mattawa 
  river 
  as 
  the 
  outlet 
  of 
  

   the 
  three 
  npper 
  Great 
  Lakes 
  in 
  very 
  recent 
  times. 
  The 
  con- 
  

   clusion 
  maintained 
  heretofore 
  by 
  Gilbert, 
  Wright 
  and 
  the 
  

   author, 
  but 
  on 
  evidence 
  less 
  complete, 
  seems 
  now 
  fairly 
  proven, 
  

   viz 
  : 
  that 
  for 
  a 
  considerable 
  period 
  of 
  time, 
  while 
  this 
  northern 
  

   outlet 
  was 
  active, 
  .Niagara 
  Falls 
  was 
  robbed 
  of 
  much 
  the 
  larger 
  

   part 
  of 
  its 
  water. 
  

  

  Fort 
  Wayne, 
  Ind.. 
  Nov. 
  28, 
  1896. 
  

  

  