﻿LAURENTIAN 
  LIMESTONES 
  OF 
  NORTH 
  AMERICA. 
  53 
  

  

  colite, 
  or 
  green 
  pyroxene, 
  occuring 
  in 
  rounded 
  and 
  wrinkled 
  

   grains 
  in 
  a 
  Laurentian 
  limestone 
  from 
  New 
  York. 
  These, 
  accord- 
  

   ing 
  to 
  Gumbel, 
  present 
  the 
  same 
  connecting 
  cylinders 
  and 
  branch- 
  

   ing 
  stems 
  as 
  the 
  pargasite, 
  and 
  are 
  by 
  him 
  supposed 
  to 
  have 
  been 
  

   moulded 
  in 
  the 
  same 
  manner. 
  The 
  continuity 
  of 
  the 
  casts 
  of 
  the 
  

   tuhuli 
  appears 
  to 
  have 
  been, 
  for 
  {he 
  most 
  part, 
  destroyed 
  by 
  the 
  

   subsequent 
  crystallization 
  of 
  the 
  carbonate 
  of 
  lime, 
  in 
  more 
  com- 
  

   pact 
  portions 
  of 
  which 
  they 
  are, 
  however, 
  occasionally 
  preserved. 
  

   The 
  fine 
  residue 
  from 
  the 
  solution 
  of 
  the 
  lime 
  in 
  acids 
  gave 
  other 
  

   minute 
  organic 
  forms, 
  similar 
  to 
  those 
  noticed 
  by 
  him 
  in 
  the 
  

   Eozoon 
  limestone 
  of 
  Bavaria. 
  Very 
  beautiful 
  evidences 
  of 
  the 
  

   same 
  organic 
  structure, 
  consisting 
  of 
  the 
  casts 
  of 
  tubuli 
  and 
  their 
  

   ramifications, 
  were 
  also 
  observed 
  by 
  Gumbel 
  in 
  a 
  finely 
  crystalline 
  

   limestone, 
  enclosing 
  granules 
  of 
  chondrodite, 
  hornblende, 
  and 
  

   garnet, 
  from 
  Boden, 
  in 
  Saxony. 
  Other 
  specimens 
  of 
  limestone, 
  

   both 
  with 
  and 
  without 
  serpentine 
  and 
  chondrodite, 
  were 
  examined 
  

   without 
  exhibiting 
  any 
  traces 
  of 
  these 
  peculiar 
  forms, 
  and 
  these 
  

   negative 
  results 
  are 
  justly 
  deemed 
  by 
  Gumbel 
  as 
  going 
  to 
  prove 
  

   that 
  their 
  structure 
  is 
  really, 
  like 
  that 
  of 
  Eozoon, 
  the 
  result 
  of 
  the 
  

   intervention 
  of 
  organic 
  forms. 
  In 
  this 
  connection, 
  an 
  observation 
  

   made 
  by 
  Sir 
  William 
  Logan 
  with 
  regard 
  to 
  the 
  Eozoon 
  rock 
  of 
  

   Canada 
  is 
  very 
  important, 
  namely 
  : 
  that 
  the 
  granular 
  mixture 
  of 
  

   carbonate 
  of 
  lime 
  and 
  serpentine 
  which 
  accompanies 
  the 
  perfect 
  

   forms 
  of 
  Eozoon, 
  consists 
  of 
  broken 
  and 
  comminuted 
  portions 
  of 
  

   the 
  fossil, 
  still 
  exhibiting 
  minute 
  structure, 
  and 
  having 
  a 
  stratified 
  

   arrangement. 
  Besides 
  the 
  minerals 
  mentioned 
  above 
  as 
  having 
  

   been 
  observed 
  as 
  the 
  replacing 
  substance 
  of 
  the 
  Eozoon 
  in 
  Canada, 
  

   namely, 
  serpentine, 
  pyroxene, 
  and 
  loganite, 
  Gumbel 
  adds 
  chon- 
  

   drodite, 
  hornblende, 
  scapolite 
  (?), 
  and 
  probably, 
  also 
  pyrallolite, 
  

   quartz, 
  and 
  iolite 
  or 
  dichroite. 
  

  

  Accompanying 
  the 
  crystalline 
  limestones 
  of 
  the 
  Laurentian 
  sys- 
  

   tem 
  in 
  Canada, 
  are 
  often 
  found 
  strata 
  made 
  up 
  of 
  foreign 
  minerals 
  

   to 
  the 
  entire 
  exclusion 
  of 
  carbonate 
  of 
  lime, 
  by 
  an 
  admixture 
  of 
  

   which, 
  however, 
  they 
  gradually 
  pass 
  into 
  the 
  adjacent 
  limestones. 
  

   These 
  strata 
  generally 
  consist 
  of 
  pyroxene, 
  sometimes 
  nearly 
  

   pure, 
  and 
  at 
  other 
  times 
  mingled 
  with 
  mica, 
  or 
  with 
  quartz 
  and 
  

   orthoclase, 
  often 
  associated 
  with 
  hornblende, 
  epidote, 
  magnetite, 
  

   sphene 
  and 
  graphite. 
  These 
  beds, 
  which 
  may 
  for 
  the 
  most 
  part 
  

   be 
  described 
  as 
  pyroxenites, 
  from 
  the 
  prevailing 
  mineral, 
  and 
  

   which 
  have 
  been 
  briefly 
  noticed 
  in 
  the 
  Geology 
  of 
  Canada, 
  page 
  

  

  [Senate, 
  No. 
  92.] 
  6 
  

  

  