﻿LAURENTIAN 
  LIMESTONES 
  OF 
  NORTH 
  AMERICA. 
  97 
  

  

  of 
  carbon 
  that 
  has 
  assumed 
  the 
  form 
  of 
  graphite 
  {Cosmos, 
  June 
  23, 
  

   18t>4). 
  This 
  hypothesis, 
  evidently 
  inadmissible 
  for 
  the 
  graphite 
  

   found 
  as 
  a 
  disseminated 
  mineral 
  in 
  stratified 
  rocks, 
  is 
  not 
  less 
  so 
  

   for 
  that 
  found 
  in 
  veins, 
  where 
  its 
  associates 
  are 
  minerals 
  whose 
  

   presence 
  is 
  incompatible 
  with 
  the 
  high 
  temperature 
  supposed. 
  

   Graphite, 
  when 
  ignited 
  with 
  carbonate 
  of 
  lime, 
  gives 
  rise 
  to 
  car- 
  

   bonic 
  oxyd, 
  and 
  under 
  similar 
  conditions 
  reduces 
  iron 
  from 
  its 
  

   oxyd 
  to 
  the 
  metallic 
  state. 
  It 
  even 
  decomposes 
  the 
  vapor 
  of 
  

   water 
  at 
  a 
  red 
  heat. 
  We 
  are 
  hence 
  led 
  to 
  regard 
  the 
  graphite 
  

   of 
  bedded 
  rocks 
  as 
  having 
  been 
  formed 
  by 
  the 
  alteration 
  of 
  coal 
  

   and 
  similar 
  carbonaceous 
  matters 
  at 
  a 
  temperature 
  below 
  redness, 
  

   while 
  its 
  subsequent 
  translation 
  into 
  the 
  veins, 
  and 
  its 
  deposition 
  

   in 
  a 
  crystalline 
  form, 
  together 
  with 
  various 
  other 
  minerals, 
  as 
  it 
  

   occurs 
  in 
  the 
  Lauren 
  tian 
  veins, 
  have 
  been 
  effected 
  under 
  conditions 
  

   which, 
  although 
  imperfectly 
  understood, 
  probably 
  included 
  aque- 
  

   ous 
  solution, 
  and 
  a 
  temperature 
  not 
  far 
  below 
  a 
  red 
  heat. 
  

  

  [Anthracite. 
  — 
  Under 
  this 
  name, 
  for 
  want 
  of 
  a 
  better 
  term, 
  may 
  

   be 
  described 
  the 
  black 
  carbonaceous 
  matter 
  which 
  has 
  already 
  

   been 
  noticed 
  as 
  associated 
  with 
  native 
  gold, 
  bitter-spar 
  and 
  a 
  red- 
  

   dish 
  ochre, 
  derived 
  from 
  the 
  decomposition 
  of 
  the 
  latter, 
  at 
  the 
  

   Richardson 
  mine 
  in 
  Madoc, 
  Ontario. 
  The 
  anthracite 
  seems 
  like 
  

   the 
  similar 
  material 
  associated 
  with 
  quartz 
  crystals 
  in 
  Herkimer 
  

   county, 
  New 
  York, 
  to 
  have 
  been 
  deposited 
  contemporaneously 
  

   with 
  the 
  quartz 
  and 
  bitter-spar, 
  in 
  some 
  cases 
  lining 
  the 
  walls 
  of 
  

   the 
  vein, 
  and 
  in 
  others 
  appearing 
  in 
  masses 
  an 
  inch 
  or 
  more 
  in 
  

   diameter 
  in 
  the 
  middle 
  of 
  the 
  veinstone. 
  It 
  is 
  jet 
  black 
  in 
  color, 
  

   with 
  a 
  conchoidal 
  fracture 
  and 
  a 
  somewhat 
  resinous 
  lustre, 
  and 
  is 
  

   soft 
  and 
  easily 
  crushed 
  between 
  the 
  fingers. 
  

  

  When 
  exposed 
  to 
  heat 
  in 
  a 
  tube 
  it 
  give 
  out 
  some 
  water, 
  but 
  no 
  

   bituminous 
  matter; 
  in 
  the 
  open 
  air 
  at 
  a 
  red 
  heat, 
  it 
  takes 
  fire 
  and 
  

   burns 
  readily 
  without 
  flame, 
  leaving 
  a 
  somewhat 
  abundant 
  ash, 
  

   whitish 
  and 
  sometimes 
  reddish, 
  consisting 
  of 
  carbonate 
  of 
  lime 
  

   with 
  some 
  silicious 
  and 
  ferruginous 
  matter, 
  including 
  a 
  quantity 
  

   of 
  gold. 
  This 
  metal 
  is 
  visible 
  in 
  the 
  form 
  of 
  grains 
  and 
  scales 
  in 
  

   the 
  recent 
  fractures 
  of 
  the 
  black 
  substance, 
  which, 
  although 
  coal- 
  

   like 
  in 
  its 
  aspect, 
  resembles 
  more 
  the 
  carbonaceous 
  matter 
  which 
  

   has 
  been 
  described 
  in 
  the 
  Geology 
  of 
  Canada 
  as 
  filling 
  veins 
  or 
  

   fissures 
  in 
  the 
  rocks 
  of 
  the 
  Quebec 
  group, 
  and 
  is 
  doubtless 
  derived 
  

   from 
  the 
  transformation 
  of 
  bitumen. 
  This 
  substance, 
  as 
  I 
  have 
  

   shewn, 
  is 
  in 
  some 
  cases 
  so 
  far 
  altered 
  by 
  oxydation 
  as 
  to 
  have 
  a 
  

  

  