QUEBEC    NORTH    AND    WEST    OF    ST.    LAWRENCE    RIVER.  449 
glomerates  are  found  on  the  mainland,  and  the  latter  is  cited  as 
decisive  evidence  of  the  metamorphic  character  of  the  series  as  a 
whole. 
Murray,4  in  1854,  remarks  that  south  of  the  Laurentian  series  are 
the  more  recent  fossiliferous  rocks.  The  Laurentian  series  consists  of 
masses  of  micaceous  and  hornblendic  gneiss  and  masses  of  interstrati- 
fiecl  crystalline  limestone.  Intrusive  granite  is  found  in  the  gneiss. 
The  magnesian  crystalline  limestone  layers,  one  TOO  feet  thick,  are 
persistent.  A  section  of  gneiss,  mica  schist,  and  quartzite,  all  some- 
times garnetiferous,  and  two  belts  of  limestone,  together  140  feet 
thick,  make  up  a  succession  1,369  feet  thick  at  Birch  Lake.  In  the 
series  is  a  conglomerate,  the  matrix  of  which  in  one  case  is  a  lime- 
stone and  the  pebbles  are  quartz  and  feldspar.  In  another  conglom- 
erate are  distinct  pebbles  in  a  talcose  slaty  matrix.  These  pebbles  are 
sometimes  distinctly  rounded  and  flattened,  the  flat  sides  always  lying 
parallel  with  the  bedding.  The  pebbles  vary  from  5  or  6  inches  in 
diameter  to  those  so  small  as  not  to  exceed  the  size  of  snipe  shot. 
Logan,5  in  1854,  applies  to  the  series  before  called  "  metamorphic," 
underlying  the  fossiliferous  formations  of  Canada,  the  name  Lau- 
rentian series,  because  metamorphic  is  applicable  to  any  series  of 
altered  rocks.  The  proposed  name  is  founded  on  that  given  by 
Garneau  to  the  chain  of  hills  which  they  compose.  Above  the  Lau- 
rentian series  is  the  Potsdam  sandstone. 
Logan,6  in  1857,  describes  the  Laurentian  formation  for  some  dis- 
tance north  of  Ottawa  River,  between  rivers  Rouge  and  du  Nord. 
The  rocks  are  found  to  be  limestone,  gneiss,  and  quartzite.  The  lime- 
stone formations  are  used  chiefly  in  working  out  the  structure,  but 
even  with  this  guide  the  work  is  very  difficult  on  acount  of  the  repe- 
tition of  layers  by  folding  and  of  lack  of  fossils.  All  of  the  above 
rocks  are  taken  to  be  metamorphosed  sediments.  They  are  cut  by 
eruptives,  such  as  syenite,  porphyry,  and  greenstone,  which  are  older 
than  the  fossiliferous  formations. 
Hunt,7  in  1857,  states  that  stratified  feldspathic  rocks  are  closely 
associated  with  the  crystalline  limestones,  which  alternate  with 
gneissoid  and  quartzose  rocks  of  the  Laurentide  Mountains.  These 
rocks,  besides  containing  pyroxene,  which  passes  over  into  hypers- 
thene  and  a  triclinic  feldspar,  contain,  as  accidental  minerals,  mica, 
garnet,  and  ilmenite. 
Murray,8  in  1857,  finds  Laurentian  rocks  largely  exposed  between 
Georgian  Bay  and  Ottawa  River.  The  rocks  are  red  and  gray 
gneisses,  micaceous  and  hornblendic  schists,  quartzite,  and  crystalline 
limestone.  On  Lake  Nipissing  and  its  islands  is  found  the  Lauren- 
tian formation,  consisting  of  gneiss,  mica  schist,  hornblende  schist, 
crystalline  limestone,  and,  associated  with  this,  beds  of  specular  ore. 
55721— Bull.  360—09 29 
