QUEBEC    NORTH    AND    WEST    OF    ST.    LAWRENCE    RIVER.  471 
an  intrusive  rock,  and  its  remaining  members  belonging  to  the  Gren- 
ville  series. 
8.  In  all  cases  of  supposed  unconformable  superposition  of  the 
anorthosite  upon  the  Laurentian  gneisses,  which  have  been  carefully 
investigated,  the  unconformity  is  found  to  be  due  to  intrusion. 
9.  The  anorthosites  are  probably  of  pre-Cambrian  age,  and  seem 
to  have  been  intruded  about  the  close  of  the  Laurentian. 
10.  The  Canadian  anorthosites  are  identical  in  character  with  the 
anorthosites  associated  with  the  Archean  rocks  of  the  United  States, 
Norway,  Russia,  and  Egypt.  The  Norwegian  occurrences,  however, 
are  probably  more  recent  in  age  than  those  of  Canada. 
Ells,45  in  1898,  sketches  the  development  of  geological  work  in  the 
Province  of  Quebec. 
Miller,46  in  1898,  describes  the  occurrence  of  corundum  in  gneiss, 
syenite,  and  quartz  pegmatite  of  the  Laurentian  in  the  counties  of 
Hastings,  Renfrew,  and  Peterborough  in  eastern  Ontario. 
Ells,47  in  1901,  describes  and  maps  the  geology  of  the  area  of  the 
Three  Rivers  sheet  of  the  Eastern  Townships  map,  Province  of 
Quebec.  Archean  rocks  occupy  most  of  the  northwestern  portion  of 
the  area  north  of  St.  Lawrence  River.  A  portion  of  this  area,  includ- 
ing anorthosite  masses,  had  previously  been  described  by  Adams.44 
The  great  mass  of  the  rocks  seen  pertain  to  the  Grenville  series, 
rather  than  to  the  so-called  Fundamental  gneiss.  The  composition 
of  the  Grenville  series,  with  its  crystalline  limestones  and  rusty  gneiss 
bands,  very  closely  resembles  that  met  with  in  the  lower  Ottawa  dis- 
trict, but  the  calcareous  members  are  much  less  widely  developed. 
There  are  also  large  areas  of  anorthosite,  red  granite,  augen  gneiss, 
and  masses  of  green  pyroxenic  diabase.  Quartzite  is  an  important 
component  of  this  series,  and  large  areas  of  this  rock,  similar  to  that 
found  along  the  Ottawa,  are  found  associated  with  the  gneiss  as  far 
north  as  the  northern  limit  of  the  map  sheet. 
The  definition  of  the  so-called  Fundamental  gneiss  is,  as  a  matter 
of  fact,  not  always  possible  in  this  district.  If  the  latter  appears  at 
all  it  must  be  along  the  crests  of  some  of  the  numerous  north-south 
anticlines,  which  are  generally  low,  the  rocks  over  a  large  area  being 
inclined  at  low  angles.  The  prevailing  gneiss  is  a  grayish  and  horn- 
blendic  variety,  generally  quartzose,  with  frequent  bands  in  which 
garnets  are  abundant. 
The  anorthosites  are  intrusive  in  the  Grenville  series.  The  Gren- 
ville series  is  correlated  with  the  Hastings  series  and  both  are  equiva- 
lent to  the  Huronian.     The  Fundamental  gneiss  is  Laurentian. 
Ells,48  in  1902,  maps  and  describes  the  geology  of  Argenteuil,  Ot- 
tawa, and  part  of  Pontiac  counties,  Province  of  Quebec,  and  portions 
of  Carleton,  Russell,  and  Prescott  counties,  Province  of  Ontario,  cov- 
