QUEBEC    NORTH    AND    WEST    OF    ST.    LAWRENCE    RIVER.  467 
the  limestone  is  overlain  by  a  considerable  breadth  of  Huronian-look- 
ing  schists,  etc.,  which  have  been  described  under  the  name  of  Hast- 
ings series.  The  limestone  has  its  most  westerly  outcrop  on  the 
Ottawa  in  the  vicinity  of  Coulonge  Lake,  a  short  distance  west  of 
Black  Eiver.  From  here  west  to  the  mouth  of  the  Mattawa  the 
limestone  occurs  as  separate  belts  occupying  synclines  in  the  upper 
stratified  gneisses. 
The  rocks  along  the  route  of  Mattawa  and  French  rivers  to  Lake 
Huron  are  chiefly  those  which  have  been  regarded  as  Laurentian 
gneisses.  There  is  very  little  of  the  crystalline  limestone  which  forms 
such  an  abundant  constituent  of  the  Laurentian  farther  east,  and  this, 
as  well  as  the  apparent  inferior  position  of  the  gneisses,  according  to 
their  banding,  caused  them  early  to  be  placed  at  the  very  base  of  the 
geological  series  and  called  the  Lower  Laurentian  series.  Crystalline 
limestone  occurs  at  Talon  Lake,  on  the  east  shore  of  the  Great  Mani- 
tou  or  Newman  Island,  in  the  eastern  part  of  Lake  Nipissing,  as  well 
as  on  two  of  the  small  islands  composing  this  group  and  on  Iron 
Island.  All  the  evidence  seems  to  point  to  the  fact  that  the  limestone 
has  been  caught  up  in  the  gneisses  during  its  eruption. 
The  foliation  of  the  gneisses  is  produced  either  (1)  by  alternation 
of  light  and  dark  bands  or  (2)  by  the  more  or  less  parallel  distribu- 
tion of  the  component  minerals.  In  many  of  the  plutonic  rocks,  and 
particularly  in  the  granites  and  similar  rocks,  there  is  a  marked  ten- 
dency for  the  bisilicates  to  aggregate  themselves  in  certain  belts  or 
patches  (called  Auscheidungen  in  the  granites).  The  result  of  pres- 
sure on  a  rock  characterized  by  the  presence  of  these  masses  would 
be  the  flattening  of  the  dark  areas  into  more  or  less  lenticular  areas. 
Again,  many  of  the  dark  bands  are  seen  to  have  had  their  origin  as 
dikes,  which  have  been  intruded  along  the  planes  of  foliation. 
Bonnev,39  in  1805,  states  that  the  Eozoon  of  Cote  St.  Pierre  is  either 
a  record  of  an  organism  or  a  very  peculiar  and  exceptional  condition 
of  a  pyroxene  marble  of  Laurentian  age,  which  is  not  a  result  of  con- 
tact metamorphism  in  the  ordinary  sense  of  the  term. 
Adams,40  in  1896,  describes  and  maps  the  Laurentian  area  north 
of  St.  Lawrence  River,  in  the  northwest  corner  of  the  southwest 
sheet  of  the  Eastern  Townships  map  (Montreal  sheet ).  This  Lauren- 
tian area  is  a  portion  of  the  southern  margin  of  the  great  north- 
ern Canadian  area  of  Laurentian  rocks.  The  area  is  about  equally 
divided  between  the  rocks  of  the  Laurentian  system  and  intrusions 
of  anorthosite  which  break  through  them.  The  Laurentian"  con- 
sists of  red  and  gray  orthoclase  gneisses,  presenting  gn.it  variations 
in  both  structure  and  composition,  with  which  are  associated  crys- 
talline limestones,  quartzites,  and  amphibolites.  In  certain  parts  of 
the  area  two  divisions  can  be  recognized  in  the  Laurentian — an  upper 
"The   term    Lauivnl  ian    is   thus   used   as   it    was   by    I 
