﻿214 
  Taylor 
  — 
  Scoured 
  Bowlders 
  of 
  the 
  Mattawa 
  Valley. 
  

  

  Shallow, 
  smooth-worn 
  hollows 
  are 
  often 
  found 
  on 
  the 
  slant- 
  

   ing 
  sides 
  of 
  bowlders, 
  and 
  sometimes 
  on 
  stones 
  no 
  larger 
  than 
  

   a 
  foot 
  in 
  diameter. 
  The 
  origin 
  of 
  such 
  forms 
  can 
  seldom 
  be 
  

   made 
  out 
  with 
  certainty 
  unless 
  it 
  is 
  clear 
  that 
  the 
  stone 
  has 
  

   remained 
  unmoved. 
  In 
  a 
  few 
  cases 
  two 
  bowlders 
  lying 
  close 
  

   together 
  had 
  complementary 
  grooves 
  or 
  hollows 
  in 
  them. 
  

   Probably 
  nearly 
  all 
  true 
  niches 
  were 
  caused 
  by 
  the 
  diversion 
  of 
  

   the 
  current 
  by 
  one 
  bowlder 
  so 
  as 
  to 
  strike 
  the 
  side 
  of 
  another. 
  

  

  Guttered 
  bowlders 
  in 
  typical 
  form 
  are 
  almost 
  as 
  rare 
  as 
  ring- 
  

   bowlders. 
  It 
  requires 
  a 
  bowlder 
  having 
  considerable 
  flat 
  or 
  

   nearly 
  flat 
  surface 
  area 
  on 
  its 
  top 
  to 
  lead 
  to 
  the 
  formation 
  of 
  a 
  

   gutter. 
  Hence 
  this 
  variety 
  is 
  confined 
  mainly 
  to 
  bowlders 
  of 
  

   large 
  size. 
  The 
  flat 
  surface 
  must 
  have 
  some 
  slight 
  inequalities 
  

   that 
  will 
  tend 
  to 
  guide 
  the 
  sand 
  and 
  pebbles 
  which 
  the 
  current 
  

   rolls 
  along. 
  If 
  these 
  irregular 
  features 
  are 
  so 
  arranged 
  that 
  

   the 
  wearing 
  materials 
  are 
  always 
  guided 
  along 
  the 
  same 
  path 
  

   they 
  will 
  Anally 
  wear 
  it 
  smooth 
  and 
  deepen 
  it 
  more 
  or 
  less, 
  

   making 
  a 
  sort 
  of 
  gutter 
  across 
  the 
  surface 
  of 
  the 
  bowlder. 
  

   Such 
  smooth-worn 
  grooves 
  are 
  often 
  found 
  where 
  streams 
  flow 
  

   over 
  solid 
  rock 
  ledges. 
  But 
  they 
  are 
  not 
  so 
  common 
  on 
  bowl- 
  

   ders. 
  Where 
  they 
  exist 
  under 
  such 
  circumstances 
  that 
  the 
  

   bowlder 
  has 
  clearly 
  not 
  been 
  moved, 
  they 
  show 
  the 
  direction 
  of 
  

   the 
  current 
  very 
  accurately. 
  There 
  is 
  one 
  fairly 
  good 
  example 
  

   of 
  this 
  variety 
  in 
  Mattawa, 
  and 
  also 
  several 
  others 
  less 
  note- 
  

   worthy. 
  But 
  even 
  this 
  best 
  one 
  is 
  not 
  so 
  strongly 
  marked 
  nor 
  

   so 
  perfect 
  as 
  could 
  be 
  wished. 
  Still, 
  it 
  has 
  the 
  distinct 
  charac- 
  

   ters 
  of 
  a 
  gutter, 
  and 
  was 
  produced 
  by 
  the 
  process 
  just 
  

   described. 
  Twenty-five 
  or 
  thirty 
  rods 
  north 
  of 
  the 
  bridge 
  on 
  

   the 
  east 
  side 
  of 
  the 
  Mattawa 
  river 
  at 
  its 
  mouth 
  are 
  several 
  very 
  

   large 
  bowlders. 
  One 
  is 
  of 
  gigantic 
  size, 
  having 
  dimensions 
  of 
  

   about 
  27 
  feet 
  in 
  length, 
  24 
  feet 
  in 
  width 
  and 
  fully 
  15 
  feet 
  in 
  

   height, 
  with 
  probably 
  a 
  third 
  of 
  its 
  bulk 
  buried 
  under 
  ground. 
  

   It 
  is 
  about 
  150 
  feet 
  back 
  from 
  the 
  river 
  and 
  the 
  ground 
  at 
  its 
  

   base 
  is 
  about 
  ten 
  feet 
  above 
  the 
  water. 
  It 
  is 
  a 
  block 
  of 
  foliated 
  

   gneiss 
  and 
  shows 
  considerable 
  differential 
  weathering 
  or 
  wear- 
  

   ing 
  on 
  its 
  sides 
  where 
  the 
  black 
  hornblendic 
  bands 
  project 
  as 
  

   ribs 
  nearly 
  horizontal, 
  while 
  the 
  gray 
  quartz-feldspar 
  bands 
  

   between 
  are 
  relatively 
  depressed 
  by 
  being 
  worn 
  or 
  dissolved 
  out. 
  

   The 
  top 
  of 
  this 
  great 
  bowlder 
  is 
  somewhat 
  uneven, 
  but 
  it 
  

   slopes 
  in 
  a 
  general 
  way 
  toward 
  the 
  south-southwest 
  or 
  up-stream 
  

   with 
  reference 
  to 
  the 
  Mattawa. 
  The 
  uneven 
  features 
  of 
  the 
  

   top 
  surface 
  present 
  their 
  sharper 
  edges 
  and 
  bolder 
  faces 
  toward 
  

   the 
  northeast. 
  A 
  fairly 
  well 
  developed 
  gutter 
  runs 
  across 
  

   diagonally 
  from 
  corner 
  to 
  corner 
  in 
  a 
  straight 
  line. 
  Starting 
  

   at 
  the 
  southwestern 
  corner, 
  it 
  runs 
  up 
  a 
  slope 
  of 
  about 
  20° 
  to 
  

   the 
  northeast. 
  Near 
  the 
  lower 
  edge 
  the 
  surface 
  is 
  compara- 
  

   tively 
  plane, 
  having 
  few 
  irregularities 
  and 
  the 
  gutter 
  is 
  scarcely 
  

   noticeable. 
  But 
  within 
  a 
  foot 
  or 
  two 
  a 
  slight 
  depression 
  

   appears 
  between 
  very 
  gently 
  sloping 
  sides, 
  and 
  the 
  sand 
  and 
  

  

  