﻿the 
  Pre- 
  Cambrian 
  Era. 
  43 
  

  

  Allen 
  and 
  Barrett 
  agree 
  as 
  well 
  as 
  Leith 
  and 
  I, 
  and 
  of 
  granite 
  

   dikes 
  in 
  the 
  Thunder 
  Bay 
  iron 
  formation, 
  make 
  Lawson's 
  

   hypothesis 
  of 
  less 
  working* 
  value. 
  

  

  In 
  the 
  second 
  place, 
  in 
  order 
  to 
  construct 
  his 
  correlation 
  

   table 
  with 
  only 
  two 
  periods 
  of 
  granitic 
  intrusion 
  he 
  has 
  to 
  cor- 
  

   relate 
  Alien's 
  Presque 
  Isle 
  granite 
  with 
  his 
  Algoman 
  granite, 
  

   and 
  quite 
  disregard 
  Allen's 
  own 
  correlations.* 
  

  

  In 
  doing 
  this 
  he 
  seems 
  to 
  have 
  accepted 
  without 
  question 
  

   Allen's 
  work 
  on 
  the 
  eastern 
  Gogebic 
  Range, 
  but 
  assumes 
  that 
  

   because 
  in 
  his 
  recent 
  able 
  reports 
  Allen 
  has 
  confined 
  himself, 
  

   except 
  in 
  his 
  correlation 
  tables, 
  pretty 
  much 
  to 
  Michigan, 
  (his 
  

   own 
  "bailiwick" 
  p. 
  4) 
  he 
  was 
  not 
  therefore 
  an 
  authority 
  worth 
  

   considering 
  outside. 
  As 
  a 
  matter 
  of 
  fact 
  I 
  first 
  met 
  Allen 
  in 
  

   the 
  original 
  Animikie 
  Region 
  near 
  Loon 
  Lake, 
  — 
  he 
  has 
  visited 
  

   Canada 
  more 
  than 
  once, 
  has 
  written 
  a 
  report 
  for 
  the 
  Ontario 
  

   Bureau, 
  and 
  his 
  correlation 
  of 
  the 
  Animikie 
  slate 
  of 
  Thunder 
  

   Bay 
  and 
  the 
  Mesabi 
  with 
  the 
  Gogebic 
  Tyler 
  slate 
  is 
  not 
  a 
  mere 
  

   echo 
  of 
  the 
  universal 
  opinion 
  of 
  previous 
  writers, 
  but 
  is 
  the 
  

   deliberate 
  opinion 
  of 
  one 
  familiar 
  with 
  both. 
  If 
  that 
  correla- 
  

   tion 
  holds 
  Lawson's 
  scheme 
  falls. 
  Apparently 
  for 
  that 
  reason 
  

   he 
  rejects 
  it 
  (loc. 
  cit. 
  p. 
  15), 
  for 
  he 
  accepts 
  Allen's 
  conclusion 
  

   that 
  the 
  Tyler 
  slate 
  and 
  Ironwood 
  formation 
  of 
  the 
  Gogebic 
  

   Range 
  is 
  earlier 
  than 
  the 
  Presque 
  Isle 
  granite, 
  and 
  believes 
  in 
  

   spite 
  of 
  all 
  the 
  facts 
  stated 
  by 
  Leith 
  (and 
  Allen 
  and 
  myself) 
  

   that 
  the 
  Animikie 
  slates 
  are 
  not 
  cut 
  by 
  granite. 
  Otherwise 
  

   he 
  thinks 
  his 
  hypothesis 
  would 
  not 
  work. 
  I 
  had 
  rather 
  assume, 
  

   if 
  I 
  were 
  he, 
  that 
  the 
  granites 
  by 
  which 
  they 
  are 
  cut 
  are 
  

   Keweenawan. 
  

  

  Why 
  should 
  one 
  imagine, 
  however, 
  that 
  in 
  a 
  region 
  over 
  1500 
  

   miles 
  long, 
  during 
  a 
  time 
  when 
  there 
  were, 
  even 
  according 
  to 
  

   Lawson, 
  at 
  least 
  three 
  unconformities 
  and 
  seven 
  series 
  of 
  rocks 
  

   of 
  different 
  character 
  and 
  considerable 
  thickness, 
  only 
  two 
  

   periods 
  of 
  granite 
  intrusion, 
  especially 
  when 
  Leith 
  and 
  Allen 
  

   and 
  so 
  many 
  of 
  us 
  who 
  know 
  the 
  ground 
  say 
  there 
  are 
  more 
  ? 
  

   Is 
  it 
  not 
  generally 
  true 
  that 
  in 
  eveiw 
  period 
  of 
  mountain 
  build- 
  

   ing 
  and 
  igneous 
  intrusion 
  one 
  will 
  find 
  somewhere 
  at 
  the 
  core 
  

   of 
  the 
  mountain 
  uplift 
  granitic 
  batholitic 
  rocks 
  1 
  I 
  will 
  not 
  

   go 
  into 
  the 
  question 
  recently 
  raised 
  as 
  to 
  the 
  age 
  of 
  the 
  granite 
  

   at 
  the 
  Creighton 
  Mine 
  near 
  Sudbuiy, 
  since 
  I 
  really 
  believe 
  

   that 
  Lawson 
  favors 
  this 
  hypothesis 
  because 
  with 
  his 
  scientific 
  

   and 
  unifying 
  mind 
  he 
  wants 
  some 
  wide 
  basis 
  for 
  correlation 
  

   when 
  fossils 
  fail, 
  not 
  because 
  it 
  is 
  inherently 
  very 
  probable, 
  

   certainly 
  not 
  because 
  it 
  fits 
  the 
  facts 
  very 
  well, 
  but 
  "faute 
  de 
  

   mieux." 
  

  

  *See 
  R. 
  C. 
  Allen 
  and 
  L. 
  P. 
  Barrett, 
  "A 
  revision 
  of 
  the 
  Sequence 
  and 
  

   Structure 
  of 
  the 
  Pre-Keweenawan 
  Formatione 
  of 
  the 
  Eastern 
  Gogebic 
  Iron 
  

   Range 
  of 
  Michigan," 
  Journal 
  of 
  Geology, 
  xxiii, 
  Nov. 
  -Dec, 
  1915; 
  also 
  Pub. 
  18 
  

   of 
  the 
  Michigan 
  Geological 
  and 
  Biological 
  Survey. 
  I 
  have 
  nut 
  tried 
  to 
  give 
  

   full 
  references 
  as 
  Allen 
  and 
  Lawson 
  give 
  them. 
  

  

  