﻿2,6 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  above 
  the 
  sea, 
  an 
  elevation 
  sufficient 
  to 
  overtop 
  the 
  highest 
  peak 
  of 
  

   the 
  present 
  Laurentides 
  ; 
  for, 
  according 
  to 
  Logan, 
  " 
  in 
  the 
  country 
  

   between 
  the 
  Ottawa 
  and 
  Lake 
  Huron 
  the 
  highest 
  summits 
  do 
  not 
  

   appear 
  to 
  exceed 
  1500 
  or 
  1700 
  feet, 
  though 
  one 
  . 
  . 
  . 
  profcably 
  

   attains 
  2300 
  feet 
  ".^ 
  We 
  assume 
  of 
  course 
  with 
  good 
  reason 
  that 
  

   the 
  Laurentides 
  at 
  that 
  period 
  were 
  much 
  higher 
  than 
  now, 
  for 
  they 
  

   must 
  have 
  suffered 
  enormous 
  erosion 
  during 
  the 
  long 
  interval 
  since 
  

   the 
  close 
  of 
  Siluric 
  time.^ 
  

  

  Since 
  the 
  deposition 
  of 
  these 
  Siluric 
  strata 
  the 
  region 
  under 
  con- 
  

   sideration 
  has 
  suffered 
  an 
  enormous 
  amount 
  of 
  denudation, 
  having 
  

   been 
  brought 
  to 
  the 
  condition 
  of 
  a 
  low 
  nearly 
  level 
  tract 
  or 
  pene- 
  

   plain, 
  but 
  little 
  above 
  sea 
  level, 
  not 
  once, 
  but 
  probably 
  a 
  number 
  

   of 
  times, 
  separated 
  by 
  periods 
  of 
  elevation 
  and 
  at 
  least 
  one 
  of 
  sub- 
  

  

  ^Logan. 
  Geol. 
  Canada. 
  1863. 
  p. 
  5. 
  

  

  ^The 
  Niagara 
  beds 
  of 
  Lake 
  Temiscaming, 
  in 
  the 
  great 
  pre-Cambric 
  area 
  

   of 
  Canada 
  and 
  150 
  miles 
  distant 
  from 
  the 
  nearest 
  beds 
  of 
  the 
  same 
  age, 
  

   are 
  of 
  interest 
  in 
  this 
  connection. 
  They 
  occupy 
  an 
  area 
  about 
  300 
  miles 
  

   due 
  north 
  of 
  Lewiston 
  and 
  on 
  the 
  north 
  side 
  of 
  the 
  present 
  Laurentide 
  

   chain. 
  According 
  to 
  Logan 
  they 
  do 
  not 
  properly 
  belong 
  to 
  the 
  former 
  

   extension 
  of 
  the 
  Niagara 
  beds 
  of 
  the 
  region 
  under 
  consideration, 
  but 
  rather 
  

   to 
  the 
  Hudson 
  bay 
  area 
  on 
  the 
  north. 
  They 
  are 
  of 
  interest 
  however 
  as 
  

   showing 
  the 
  great 
  former 
  extent 
  of 
  these 
  formations. 
  They 
  lie 
  uncon- 
  

   formably 
  on 
  the 
  pre-Cambric 
  rocks, 
  and 
  the 
  basal 
  members 
  are 
  generally 
  

   sandstones 
  and 
  often 
  conglomerates 
  " 
  containing 
  large 
  pebbles, 
  fragments, 
  

   and 
  frequently 
  huge 
  boulders 
  of 
  the 
  subjacent 
  rock" 
  (Logan, 
  p. 
  335)- 
  The 
  

   thickness 
  of 
  the 
  formation 
  here 
  is 
  estimated 
  at 
  between 
  300 
  and 
  500 
  feet. 
  

   The 
  Ordovicic 
  and 
  Cambric 
  strata 
  are 
  absent, 
  showing 
  a 
  progressive 
  

   encroachment 
  of 
  the 
  sea 
  on 
  the 
  old-land, 
  and 
  a 
  consequent 
  overlapping 
  

   of 
  the 
  strata. 
  OutHers 
  of 
  earlier 
  strata 
  are 
  found 
  in 
  more 
  southern 
  por- 
  

   tions 
  of 
  Canada, 
  resting 
  on 
  the 
  pre-Cambric 
  surface, 
  and 
  many 
  of 
  these 
  

   indicate 
  a 
  progressive 
  overlapping 
  of 
  later 
  over 
  earlier 
  beds. 
  Lawson 
  

   holds 
  that 
  this 
  indicates, 
  that 
  most 
  of 
  the 
  Canadian 
  old-land 
  was 
  covered 
  

   by 
  the 
  early 
  Paleozoic 
  strata, 
  and 
  that 
  erosion 
  since 
  Paleozoic 
  time 
  has 
  

   resulted 
  in 
  simply 
  removing 
  these 
  overlying 
  rocks. 
  (Bui. 
  geol. 
  soc. 
  Am. 
  

   I 
  : 
  169 
  et 
  seq.) 
  He 
  holds 
  that 
  comparatively 
  little 
  erosion 
  of 
  the 
  old-land 
  

   has 
  occurred 
  since 
  Paleozoic 
  time, 
  the 
  present 
  surface 
  being 
  essentially 
  

   pre-Cambric 
  and 
  only 
  revealed 
  by 
  stripping 
  of 
  the 
  overlying 
  rocks. 
  It 
  is 
  

   not 
  improbable 
  however 
  that 
  some 
  of 
  these 
  distant 
  outliers 
  may 
  have 
  been 
  

   preserved 
  during 
  the 
  extensive 
  denudation 
  of 
  the 
  old-land, 
  by 
  having 
  been 
  

   faulted 
  down 
  previously 
  in 
  a 
  manner 
  well 
  known 
  to 
  have 
  occurred 
  in 
  the 
  

   Scandinavian 
  old-lands, 
  a 
  solution 
  suggested 
  to 
  me 
  by 
  my 
  friend, 
  A. 
  W. 
  G. 
  

   Wilson, 
  of 
  Harvard 
  university. 
  

  

  