﻿Notes 
  upon 
  the 
  Lithology 
  of 
  the 
  Adirokdacks. 
  83 
  

  

  gneisses 
  and 
  quartzites. 
  The 
  limestones 
  are 
  both 
  calcites 
  and 
  

   dolomites, 
  the 
  latter 
  interstratified 
  with 
  the 
  former, 
  or 
  more 
  or 
  

   less 
  mechanically 
  mingled 
  with 
  them. 
  They 
  also 
  occur 
  sepa- 
  

   rately, 
  as 
  rock-masses 
  of 
  great 
  extent. 
  Serpentine, 
  hornblende, 
  

   tremolite, 
  mica 
  and 
  graphite, 
  are 
  imbedded 
  in 
  these 
  rocks, 
  

   frequently 
  in 
  bands 
  plainly 
  or 
  obscurely 
  parallel 
  with 
  the 
  

   beds 
  ; 
  also 
  pyroxene, 
  wollastonite, 
  apatite, 
  chondrodite, 
  quartz, 
  

   scapolite, 
  pyrite, 
  and 
  more 
  rarely, 
  zircon, 
  spinel, 
  fluor 
  spar, 
  

   idocrase, 
  tourmaline, 
  corundum 
  and 
  chalcopyrite.* 
  

  

  At 
  the 
  time 
  of 
  the 
  publication 
  of 
  the 
  Canadian 
  Gfeol. 
  Report 
  

   of 
  1863, 
  the 
  identity 
  of 
  the 
  Laurentian 
  gneisses 
  with 
  the 
  " 
  Fun- 
  

   damental 
  Gneiss" 
  of 
  the 
  Western 
  Isles 
  of 
  Scotland, 
  had 
  been 
  

   recognized 
  by 
  Sir 
  Roderick 
  Murchison, 
  and 
  the 
  term 
  Laurentian 
  

   correspondingly 
  extended, 
  f 
  Emmons 
  had 
  previously 
  given 
  

   the 
  name 
  of 
  Hypersthene 
  Rock, 
  rather 
  than 
  that 
  of 
  Labradorite 
  

   Rock, 
  which 
  latter 
  he 
  appears 
  to 
  have 
  preferred, 
  to 
  the 
  mixtures 
  

   of 
  labradorite 
  and 
  hypersthene, 
  occurring 
  in 
  the 
  Adirondacks, 
  

   for 
  two 
  reasons 
  ; 
  1st, 
  on 
  the 
  ground 
  of 
  identity 
  of 
  these 
  rocks 
  

   with 
  those 
  occurring 
  in 
  Scotland, 
  and 
  2ndly, 
  the 
  priority 
  of 
  

   MacCulloch's 
  name 
  of 
  hypersthene 
  rock 
  as 
  applied 
  to 
  them 
  in 
  

   the 
  isle 
  of 
  Skye 
  and 
  elsewhere.^ 
  In 
  the 
  Canada 
  Report 
  above 
  

   quoted, 
  these 
  hypersthene 
  rocks, 
  were 
  referred 
  under 
  the 
  

   appellation 
  of 
  anorthosites, 
  to 
  the 
  Laurentian 
  system. 
  The 
  

   rocks 
  of 
  the 
  Adirondack 
  Mts., 
  were 
  stratigraphically 
  connected 
  

   with 
  the 
  main 
  body 
  of 
  the 
  Laurentian 
  range, 
  through 
  the 
  

   exposure 
  of 
  azoic 
  rocks, 
  which 
  crosses 
  the 
  St. 
  Lawrence 
  at 
  the 
  

   outlet 
  of 
  Lake 
  Ontario. 
  Subsequently, 
  these 
  anorthosites 
  were 
  

   shown 
  by 
  Sir 
  Wm. 
  Logan 
  to 
  be 
  unconformable 
  with 
  the 
  ortho- 
  

   clase-gneisses, 
  limestones 
  and 
  quartzites, 
  with 
  which 
  in 
  certain 
  

   portions 
  of 
  Canada 
  they 
  were 
  interstratified, 
  and 
  were 
  separated 
  

   from 
  them 
  under 
  the 
  name 
  of 
  Upper 
  Laurentian. 
  This 
  term 
  

   was 
  preferable 
  to 
  the 
  "Labradorian 
  System," 
  a 
  name 
  which 
  

   Sir 
  Wm. 
  Logan 
  also 
  used, 
  on 
  account 
  of 
  the 
  extensive 
  develop- 
  

   ment 
  of 
  these 
  anorthosites 
  in 
  Labrador, 
  and 
  the 
  predominance 
  

   of 
  labradorite 
  among 
  their 
  feldspathic 
  constituents. 
  

  

  In 
  one 
  of 
  the 
  most 
  recent 
  of 
  his 
  very 
  valuable 
  contributions 
  

   to 
  American 
  lithology, 
  Dr. 
  T. 
  Sterry 
  Hunt 
  has 
  urged 
  the 
  adop- 
  

   tion 
  of 
  the 
  title 
  of 
  Norian, 
  instead 
  of 
  Labradorian 
  or 
  Upper 
  

  

  * 
  Geolog. 
  Report 
  of 
  Canada, 
  1863, 
  p. 
  24-31. 
  f 
  Geol. 
  of 
  Canada, 
  1863, 
  pp. 
  22. 
  

   % 
  Geol. 
  2nd. 
  District 
  New 
  York, 
  pp. 
  27, 
  28. 
  

  

  