QUEBEC    NORTH   AND    WEST    OF    ST.    LAWRENCE    RIVER.       ,  453 
proof  of  life.  The  Laurentian  system  as  a  whole  consists  of,  (1) 
orthoclase  gneiss,  sometimes  granitoid,  with  quartzite,  hornblendic 
and  micaceous  schists,  pyroxene,  and  garnet  rock;  (2)  white  crystal- 
line limestone  and  dolomites  in  numerous  thick  beds,  containing 
serpentine,  pyroxene,  hornblende,  mica,  graphite,  iron  ores,  apatite, 
fiuor,  etc.,  and  interstratified  with  bands  of  gneiss;  (3)  lime-feldspar 
rock,  or  anorthosite,  containing  hypersthene,  ilmenite,  pyroxene, 
hornblende,  graphite,  etc.  These  three  groups  are  traversed  by  gran- 
itic and  metalliferous  veins. 
Macfarlane,14  in  1866,  describes  the  Laurentian  rocks  of  several 
towns  in  the  county  of  Hastings.  The 'rocks  here  found  include 
granite,  granite  gneiss,  gneiss,  petrosilex,  conglomerates,  and  lime- 
stones. At  Madoc  are  conglomerates  consisting  of  pebbles,  generally 
of  quartzite,  in  a  schistose  matrix,  lithologically  not  unlike  some  of 
the  Huronian  rocks. 
Logan,15  in  1867,  states  that  the  Hastings  series  is  arranged  in  the 
form  of  a  trough,  and  that  to  the  east,  and  probably  beneath  them, 
are  rocks  which  resemble  those  of  the  Grenville,  and  it  is  supposed 
that  the  Hastings  series  is  somewhat  higher  than  the  Grenville.  The 
Madoc  limestone  is  overlain  unconforniably  at  several  places  by  the 
horizontal  Lower  Silurian  limestone.  In  Tudor  the  limestone  is  sud- 
denly interrupted  for  a  considerable  part  of  its  breadth  by  a  mass  of 
anorthosite  rock,  rising  150  feet  above  the  general  plain,  which  is  sup- 
posed to  belong  to  the  unconformable  Upper  Laurentian. 
Vennor,16  in  1867,  gives  the  ascending  section  of  Laurentian  rocks 
in  Hastings  County  as  follows:  Red  feldspathic  gneiss,  5,000  feet; 
dark-green  chloritic  slates,  200  feet;  crystalline  limestone,  2,200  feet; 
siliceous  and  micaceous  slates,  400  feet;  bluish  and  grayish  mica 
slates,  500  feet;  pinkish  dolomite,  100  feet;  micaceous  limestone  or 
calc  schist  containing  Eozoon,  2,000  feet;  green  diorite  slates,  7,500 
feet ;  reddish  granitic  gneiss,  2,100  feet ;  total,  20,000  feet. 
Dawson,17  (Sir  William),  in  1869,  states  that  the  graphite  of  the 
Laurentian  is  scattered  through  a  great  thickness  of  limestones,  and 
is  found  also  in  veins.  In  one  bed  of  limestone  600  feet  thick  the 
amount  of  disseminated  graphite  must  amount  to  as  much  as  a  solid 
bed  20  or  30  feet  thick.  The  graphite  is  believed  to  be  of  organic 
origin  because,  first,  it  contains  obscure  traces  of  organic  structure; 
second,  its  arrangement  and  microscopical  structure  correspond  with 
those  of  micaceous  and  bituminous  matter  in  marine  formations  of 
modern  date;  third,  if  of  metamorphic  origin,  it  has  only  undergone 
the  metamorphism  which  is  known  to  affect  organic  material  of  la  tri- 
age; fourth,  it  is  associated  with  beds  of  limestone,  iron  ore.  and 
metallic  sulphides,  presumably  of  organic  origin. 
Yknnor,18  in  1870,  in  a  report  on  Hastings  County,  describes  the 
pre-Silurian  rocks.     The  rocks  are  divided  into  three  divisions,  A, 
