﻿Taylor 
  — 
  Scoured 
  Bowlders 
  of 
  'the 
  Mattawa 
  Valley. 
  211 
  

  

  deepening 
  beds, 
  that 
  they 
  produce 
  generally 
  only 
  the 
  smoothed 
  

   variety, 
  which 
  does 
  not 
  require 
  constancy 
  of 
  position. 
  Nearly 
  

   all 
  streams 
  produce 
  this 
  simplest 
  form. 
  Scour 
  effects 
  on 
  bowl- 
  

   ders 
  are 
  sometimes 
  found 
  even 
  in 
  small 
  streams, 
  where 
  their 
  

   courses 
  are 
  permanently 
  choked 
  with 
  great 
  bowlders 
  through 
  

   which 
  the 
  stream 
  trickles 
  constantly. 
  But 
  so 
  far 
  as 
  known 
  to 
  

   the 
  writer, 
  the 
  Mattawa 
  valley 
  is 
  the 
  first 
  case 
  where 
  the 
  exist- 
  

   ence 
  of 
  a 
  great 
  ancient 
  river 
  now 
  extinct 
  has 
  been 
  inferred 
  from 
  

   such 
  evidence. 
  

  

  Besides 
  the 
  scoured 
  bowlders 
  on 
  the 
  terrace 
  at 
  Mattawa 
  

   there 
  is 
  but 
  one 
  other 
  place 
  higher 
  up 
  the 
  Mattawa 
  valley 
  

   where 
  these 
  peculiar 
  stones 
  were 
  made 
  in 
  large 
  numbers 
  in 
  

   rapids 
  of 
  the 
  ancient 
  river. 
  At 
  Des 
  Epines 
  rapids, 
  eight 
  and 
  

   one-quarter 
  miles 
  above 
  Mattawa, 
  scoured 
  bowlders 
  are 
  devel- 
  

   oped 
  in 
  great 
  profusion 
  and 
  perfection 
  of 
  form 
  at 
  heights 
  

   entirely 
  above 
  the 
  reach 
  of 
  the 
  modern 
  river. 
  At 
  this 
  place 
  

   bowlders 
  with 
  deep 
  basins 
  or 
  potholes 
  in 
  them 
  were 
  found 
  on 
  

   the 
  north 
  side 
  over 
  forty 
  feet 
  above 
  the 
  water. 
  

  

  On 
  a 
  comparison 
  of 
  the 
  results 
  of 
  observations 
  on 
  the 
  several 
  

   bowldery 
  rapids 
  of 
  the 
  ancient 
  river, 
  a 
  very 
  clear 
  explanation 
  

   of 
  the 
  plentiful 
  occurrence 
  of 
  scoured 
  bowlders 
  in 
  some 
  rapids 
  

   and 
  their 
  scarcity 
  or 
  absence 
  in 
  others 
  was 
  found. 
  Wherever 
  

   a 
  stream 
  of 
  sufficient 
  volume 
  to 
  transport 
  gravel 
  in 
  considera- 
  

   ble 
  quantities 
  descended 
  from 
  the 
  adjacent 
  high 
  drift-covered 
  

   country 
  and 
  poured 
  its 
  contribution 
  into 
  the 
  ancient 
  outlet 
  at 
  

   or 
  just 
  above 
  a 
  rapid, 
  scoured 
  bowlders 
  are 
  numerous. 
  But 
  

   where 
  the 
  water 
  that 
  passed 
  over 
  the 
  bowlders 
  issued 
  directly 
  

   from 
  a 
  lake, 
  and 
  hence 
  without 
  any 
  such 
  supply 
  of 
  gravel, 
  

   scoured 
  bowlders 
  are 
  few 
  or 
  absent 
  altogether. 
  Boom 
  creek 
  

   entered 
  the 
  ancient 
  outlet 
  on 
  the 
  south 
  side 
  about 
  a 
  mile, 
  above 
  

   Mattawa 
  and 
  furnished 
  an 
  abundant 
  supply 
  of 
  gravel 
  for 
  the 
  

   current 
  to 
  roll 
  along 
  over 
  the 
  bowlders 
  of 
  the 
  Mattawa 
  terrace. 
  

   That 
  Boom 
  creek 
  did 
  in 
  fact 
  supply 
  a 
  large 
  amount 
  of 
  gravel 
  

   is 
  attested 
  by 
  the 
  present 
  existence 
  of 
  a 
  very 
  considerable 
  delta 
  

   of 
  sand 
  and 
  gravel 
  50 
  to 
  60 
  feet 
  above 
  the 
  modern 
  Mattawa 
  

   river 
  where 
  the 
  creek 
  enters 
  the 
  old 
  channel. 
  The 
  influence 
  

   of 
  the 
  ancient 
  outlet 
  current 
  is 
  shown 
  by 
  the 
  fact 
  that 
  these 
  

   sediments 
  have 
  been 
  carried 
  down 
  that 
  side 
  of 
  the 
  channel 
  

   quite 
  extensively 
  and 
  spread 
  over 
  part 
  of 
  the 
  bowldery 
  terrace. 
  

   At 
  Des 
  Epines 
  rapids 
  the 
  gravel 
  supply 
  came 
  from 
  the 
  Amable 
  

   du 
  Fond 
  river, 
  which 
  enters 
  on 
  the 
  south 
  side 
  less 
  than 
  half 
  a 
  

   mile 
  above. 
  This 
  stream 
  is 
  nearly 
  as 
  large 
  as 
  the 
  Mattawa 
  

   itself 
  and 
  it 
  cuts 
  extensive 
  gravel 
  beds 
  a 
  short 
  distance 
  above 
  

   its 
  mouth. 
  

  

  On 
  the 
  other 
  hand, 
  in 
  the 
  bowldery 
  rapids 
  at 
  the 
  head 
  of 
  

   Lost 
  river 
  (foot 
  of 
  Turtle 
  lake) 
  no 
  basined 
  bowlders 
  and 
  few 
  

   even 
  of 
  the 
  less 
  pronounced 
  forms 
  of 
  scour 
  were 
  found. 
  They 
  

  

  