﻿(E.) 
  

  

  ON 
  THE 
  MINERALOGY 
  OF 
  THE 
  LAURENTIAN 
  

   LIMESTONES 
  OF 
  NORTH 
  AMERICA. 
  

  

  By 
  T\ 
  Sterhy 
  HutfT, 
  LL. 
  D., 
  F. 
  R. 
  S., 
  of 
  the 
  Geological 
  Survey 
  of 
  Canada. 
  

  

  Introduction. 
  

  

  In 
  a 
  general 
  report 
  of 
  the 
  Geological 
  Survey 
  published 
  in 
  1863, 
  

   under 
  the 
  title 
  of 
  the 
  Geology 
  of 
  Canada, 
  the 
  ancient 
  gneissic 
  sys- 
  

   tem 
  of 
  the 
  Laurenticles 
  of 
  Canada 
  and 
  the 
  Adirondacks 
  of 
  New 
  

   York, 
  is 
  described 
  under 
  the 
  name 
  of 
  the 
  Laurentian 
  system. 
  Far- 
  

   ther 
  researches 
  have 
  shown 
  that 
  under 
  this 
  title 
  were 
  included 
  two 
  

   distinct 
  and 
  unconformable 
  groups 
  of 
  rocks, 
  which 
  have 
  since 
  been 
  

   distinguished 
  as 
  the 
  Lower 
  Laurentian 
  and 
  the 
  Upper 
  Laurentian, 
  

   or 
  Labrador 
  series, 
  The 
  first 
  and 
  most 
  ancient 
  of 
  these, 
  to 
  which 
  

   it 
  will 
  be 
  well 
  for 
  the 
  future 
  to 
  restrict 
  the 
  name 
  of 
  Laurentian, 
  

   corresponds 
  to 
  the 
  primitive 
  gneiss 
  of 
  Scandinavia 
  and 
  of 
  the 
  

   west 
  of 
  Scotland. 
  This 
  opinion 
  was 
  put 
  forward 
  by 
  the 
  author 
  

   in 
  1855, 
  and 
  has 
  since 
  been 
  confirmed 
  by 
  Sir 
  R. 
  I. 
  Murchison, 
  for 
  

   Scotland. 
  More 
  recently, 
  Messrs 
  Gumbel 
  and 
  Hochstetter, 
  after 
  

   a 
  lengthened 
  study 
  of 
  the 
  older 
  gneiss 
  of 
  Bavaria 
  and 
  Bohemia, 
  

   have 
  declared 
  it 
  to 
  be 
  identical 
  with 
  the 
  Laurentian 
  of 
  North 
  

   America, 
  a 
  conclusion 
  sustained 
  by 
  the 
  discovery 
  by 
  Gumbel 
  of 
  

   the 
  fossil 
  remains 
  of 
  the 
  rhizopod 
  Eozoon 
  Canadense, 
  in 
  the 
  lime- 
  

   stone 
  of 
  the 
  Bavarian 
  gneiss. 
  

  

  The 
  lower 
  or 
  true 
  Laurentian 
  consists 
  in 
  great 
  part 
  of 
  orthoclase 
  

   gneiss, 
  sometimes 
  granitoid, 
  with 
  quartzites, 
  occasionally 
  becom- 
  

   ing 
  conglomerates 
  ; 
  hornblendic 
  and 
  micaceous 
  schists, 
  pyroxen- 
  

   ites, 
  serpentines 
  and 
  limestones, 
  sometimes 
  magnesian. 
  These 
  

   limestones, 
  generally 
  very 
  crystalline, 
  are 
  seen 
  on 
  the 
  Ottawa, 
  in 
  

  

  