﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  139 
  

  

  that 
  district 
  since 
  the 
  ice 
  left 
  that 
  locality. 
  The 
  Gilbert 
  plane 
  

   declines 
  to 
  the 
  south 
  and 
  southwest 
  and 
  on 
  the 
  south 
  border 
  of 
  

   our 
  area 
  the 
  beaches 
  are 
  390 
  feet 
  [pi. 
  45]. 
  North 
  of 
  Lafargeville 
  

   [pi. 
  46] 
  strong 
  beaches 
  He 
  at 
  440 
  feet, 
  and 
  2 
  miles 
  southeast 
  of 
  

   Redwood 
  a 
  bar 
  is 
  found 
  at 
  450 
  feet 
  altitude 
  [pi. 
  47]. 
  

  

  It 
  has 
  not 
  seemed 
  practicable 
  to 
  make 
  maps 
  for 
  this 
  writing 
  

   to 
  show 
  all 
  the 
  Gilbert 
  shore 
  lines 
  of 
  the 
  area, 
  but 
  the 
  strongest 
  

   shore 
  features 
  are 
  indicated 
  on 
  the 
  maps, 
  plates 
  45-47. 
  These 
  

   are 
  wave-built 
  bars 
  and 
  spits 
  and 
  w^ave-washed 
  limestones. 
  Some 
  

   of 
  tliese 
  features 
  are 
  shown 
  in 
  the 
  halftones, 
  plates 
  48-53. 
  The 
  

   southeast 
  portion 
  of 
  our 
  area, 
  being 
  the 
  southeast 
  diagonal 
  half 
  

   of 
  the 
  Theresa 
  sheet, 
  was 
  mostly 
  above 
  the 
  Gilbert 
  waters. 
  The 
  

   submerged 
  parts 
  are 
  such 
  as 
  lie 
  below 
  400 
  feet 
  at 
  the 
  south 
  edge 
  

   of 
  the 
  sheet 
  and 
  below 
  440 
  feet 
  at 
  the 
  north 
  edge. 
  It 
  will 
  be 
  

   seen 
  that 
  this 
  is 
  the 
  low^ 
  ground 
  north 
  and 
  northeast 
  of 
  Brown- 
  

   ville, 
  the 
  valley 
  of 
  Perch 
  river, 
  the 
  low 
  ground 
  about 
  Theresa 
  

   and 
  the 
  valley 
  of 
  Indian 
  river. 
  All 
  the 
  rest 
  of 
  the 
  region 
  was 
  

   under 
  the 
  full 
  Gilbert 
  level 
  except 
  the 
  three 
  limestone 
  hills 
  north- 
  

   west 
  of 
  Dexter; 
  the 
  limestone 
  plateau 
  between 
  Stone 
  Mills, 
  De- 
  

   pauville 
  and 
  Lafargeville 
  ; 
  the 
  limestone 
  plateaus 
  north 
  of 
  Depau- 
  

   ville; 
  the 
  boulder-kame 
  hill 
  2 
  miles 
  north 
  of 
  St 
  Lawrence 
  cor- 
  

   ners, 
  known 
  as 
  the 
  " 
  Hogback 
  '' 
  ; 
  and 
  the 
  group 
  of 
  boulder- 
  

   moraine 
  hills 
  north 
  of 
  Lafargeville; 
  one 
  being 
  cut 
  by 
  the 
  edge 
  

   of 
  the 
  Theresa 
  sheet. 
  These 
  areas 
  which 
  received 
  wave 
  action 
  

   so 
  as 
  to 
  leave 
  beach 
  records 
  are 
  mostly 
  shown 
  in 
  the 
  plates 
  

   45, 
  46 
  and 
  48. 
  

  

  While 
  all 
  surfaces 
  between 
  the 
  highest 
  Iroquois 
  and 
  the 
  Gil- 
  

   bert 
  planes 
  have 
  been 
  wave-swept 
  by 
  the 
  subsiding 
  waters, 
  and 
  

   many 
  patches 
  of 
  bared 
  rocks 
  are 
  found 
  at 
  various 
  levels, 
  no 
  

   beach 
  phenomena 
  have 
  been 
  noted 
  between 
  the 
  two 
  planes. 
  All 
  

   the 
  high 
  level 
  shoreline 
  features 
  in 
  our 
  district 
  are 
  confidently 
  

   referred 
  to 
  the 
  sea-level 
  waters.^ 
  

  

  1 
  Since 
  this 
  paper 
  has 
  been 
  in 
  type 
  Prof. 
  George 
  H. 
  Chadwick 
  discovered 
  

   heavy 
  beaches 
  and 
  dehas 
  of 
  Lake 
  Iroquois 
  in 
  St 
  Lawrence 
  county, 
  and 
  also 
  

   extensive 
  deltas 
  inferior 
  to 
  the 
  Iroquois 
  plane 
  and 
  of 
  uncertai-n 
  relationship. 
  

   In 
  August 
  1910 
  we 
  examined 
  these 
  features 
  and 
  carried 
  the 
  study 
  north- 
  

   eastward 
  into 
  Canada. 
  

  

  The 
  Iroquois 
  plane 
  is 
  now 
  definitely 
  known 
  at 
  several 
  points, 
  the 
  farthest 
  

   east 
  being 
  at 
  Chateaugay 
  with 
  altitude 
  975 
  feet. 
  On 
  the 
  international 
  

   boundary 
  at 
  Covey 
  hill 
  the 
  full-hight 
  plane 
  is 
  not 
  much 
  above 
  looo 
  feet. 
  

   The 
  head 
  of 
  Covey 
  gulf, 
  the 
  outlet 
  of 
  the 
  lower 
  or 
  Second 
  Iroquois, 
  is 
  

   about 
  980 
  feet. 
  

  

  A 
  recent 
  survey 
  on 
  the 
  Canadian 
  side 
  of 
  the 
  boundary 
  gives 
  us 
  precise 
  

   altitudes 
  for 
  the 
  sea-level 
  beaches 
  (Gilbert 
  gulf), 
  which 
  have 
  at 
  Covey 
  Hill 
  

   post 
  ofifice 
  a 
  hight 
  of 
  a 
  least 
  523 
  feet. 
  

  

  These 
  altitudes 
  are 
  entirely 
  consistent 
  with 
  the 
  figures 
  and 
  facts 
  relating 
  

   to 
  the 
  Iroquois 
  and 
  Gilbert 
  gulf 
  water 
  planes 
  given 
  in 
  this 
  report. 
  

  

  