﻿212 
  Taylor 
  — 
  Scoured 
  Bowlders 
  of 
  the 
  Mattawa 
  Valley. 
  

  

  appeared 
  to 
  be 
  absent 
  also 
  in 
  the 
  ancient 
  bowldery 
  rapids 
  next 
  

   below 
  Pimisi 
  bay 
  and 
  at 
  the 
  Rapide 
  des 
  Rochers 
  below 
  Lac 
  

   des 
  Aiguilles. 
  At 
  all 
  these 
  places 
  the 
  current 
  issued 
  directly 
  

   from 
  a 
  lake 
  and 
  was 
  probably 
  clear 
  and 
  free 
  of 
  gravelly 
  sedi- 
  

   ments. 
  

  

  So 
  far 
  as 
  seen 
  the 
  best 
  place 
  to 
  observe 
  bowlders 
  being 
  scoured 
  

   by 
  the 
  work 
  of 
  the 
  modern 
  Mattawa 
  river 
  is 
  at 
  the 
  Chute 
  des 
  

   Parasseux, 
  fourteen 
  miles 
  above 
  Mattawa. 
  

  

  Descriptive 
  Details 
  of 
  Varieties. 
  

  

  Pierced 
  and 
  basined 
  bowlders 
  are 
  in 
  reality 
  merely 
  two 
  

   stages 
  of 
  the 
  same 
  process. 
  When 
  the 
  current 
  begins 
  to 
  cause 
  

   pebbles 
  and 
  sand 
  to 
  spin 
  round 
  and 
  round 
  on 
  one 
  particular 
  spot 
  

   on 
  the 
  surface 
  of 
  a 
  bowlder, 
  the 
  process 
  of 
  wearing 
  out 
  a 
  basin 
  

   is 
  begun. 
  Given 
  only 
  time 
  enough, 
  with 
  constancy 
  of 
  the 
  con- 
  

   ditions 
  on 
  which 
  the 
  whirl 
  depends, 
  and 
  the 
  basin 
  will 
  sink 
  

   deeper 
  and 
  deeper 
  into 
  the 
  solid 
  bowlder 
  until 
  the 
  bottom 
  is 
  

   cut 
  through 
  and 
  the 
  basin 
  becomes 
  a 
  hole. 
  The 
  bowlder 
  is 
  

   then 
  pierced 
  through 
  and 
  becomes 
  a 
  ring-bowlder. 
  The 
  hole 
  

   is 
  usually 
  nearly 
  circular 
  on 
  cross 
  section, 
  but 
  sometimes 
  tapers 
  

   towards 
  the 
  bottom. 
  The 
  periphery 
  or 
  outer 
  surface 
  of 
  the 
  

   stone 
  generally 
  shows 
  considerable 
  irregularity, 
  for 
  the 
  hole 
  is 
  

   seldom 
  symmetrically 
  placed. 
  Otherwise 
  these 
  bowlders 
  have' 
  

   the 
  common 
  sub-angular 
  form. 
  Pierced 
  or 
  ring-bowlders 
  are 
  

   the 
  highest 
  type 
  or 
  variety 
  of 
  the 
  several 
  forms 
  produced 
  by 
  

   scour. 
  They 
  are 
  scarce, 
  even 
  where 
  other 
  lower 
  varieties 
  are 
  

   abundant. 
  Only 
  one 
  was 
  found 
  on 
  the 
  course 
  of 
  the 
  ancient 
  

   outlet 
  river 
  within 
  the 
  Mattawa 
  valley, 
  and 
  this 
  lies 
  in 
  such 
  a 
  

   position 
  and 
  at 
  so 
  low 
  a 
  level 
  with 
  reference 
  to 
  the 
  modern 
  

   river 
  that 
  it 
  probably 
  was 
  made 
  by 
  it. 
  This 
  ring-bowlder 
  lies 
  

   in 
  a 
  side 
  channel 
  at 
  Parasseux 
  Chute. 
  A 
  dam 
  was 
  constructed 
  

   across 
  the 
  head 
  of 
  the 
  rapids 
  several 
  years 
  ago 
  and 
  this 
  left 
  a 
  

   side 
  channel 
  east 
  of 
  the 
  present 
  rapids 
  dry. 
  In 
  the 
  bottom 
  of 
  

   this 
  channel 
  about 
  opposite 
  the 
  middle 
  of 
  the 
  present 
  rapids 
  

   below 
  the 
  dam 
  lies 
  the 
  ring-bowlder. 
  It 
  is 
  broken 
  in 
  two 
  

   pieces, 
  but 
  they 
  are 
  separated 
  only 
  a 
  few 
  inches 
  and 
  their 
  

   former 
  solidity 
  as 
  an 
  unbroken 
  ring 
  is 
  at 
  once 
  obvious. 
  The 
  

   hole 
  is 
  not 
  perfectly 
  circular, 
  but 
  has 
  a 
  large 
  diameter 
  com- 
  

   pared 
  with 
  the 
  diameter 
  of 
  the 
  bowlder 
  itself. 
  The 
  hole 
  is 
  

   about 
  eighteen 
  inches 
  across, 
  while 
  for 
  about 
  one-third 
  of 
  the 
  

   circumference 
  the 
  ring 
  of 
  rock 
  is 
  only 
  six 
  or 
  seven 
  inches 
  

   thick. 
  

  

  But 
  the 
  most 
  magnificent 
  specimen 
  of 
  this 
  variety 
  that 
  the 
  

   writer 
  has 
  seen 
  is 
  on 
  the 
  bank 
  of 
  the 
  Ottawa 
  river 
  near 
  

   Klock's, 
  ten 
  miles 
  below 
  Mattawa. 
  This 
  bowlder 
  is 
  large 
  — 
  

   about 
  seven 
  feet 
  long, 
  five 
  wide 
  and 
  four 
  thick. 
  The 
  hole 
  is 
  

  

  