GREAT    NORTHERN    INTERIOR    OF    CANADA.  545 
Winisk  beds  may  belong  to  the  same  series.  They  have  been  classed 
as  Animikie. 
Wilson,68  in  1905,  reports  on  Little  Current  and  Drowning  rivers, 
branches  of  the  Albany,  east  of  Lake  Nipigon,  and  notes  the  existence 
of  granitic  and  gneissic  and  green  schistose  rocks  at  many  points. 
A  considerable  mass  of  Silurian  limestone  is  found  along  Pagwachuan 
River. 
McInnis,69  in  1905,  reports  on  the  upper  parts  of  Winisk  and 
Attawapiskat  rivers.  Archean  biotite  gneisses,  varying  but  slightly 
in  composition  and  always  well  foliated,  are  the  prevailing  rocks. 
They  are  much  disturbed  by  the  intrusion  of  coarse  white  granite  or 
pegmatite.  Two  belts  of  Keewatin,  made  up  for  the  most  part  of 
massive  diorite  and  diabase  and  chloritic  and  feldspathic  schists,  were 
noted,  one  occupying  the  valley  of  Kawinogans  River  for  a  distance 
of  about  25  miles,  and  the  other  being  an  irregularly  shaped  area 
immediately  south  of  Nibinamik  Lake  on  Winisk  River. 
Camsell,70  in  1905,  reports  on  the  country  around  the  headwaters 
of  Severn  River.  The  whole  area  is  occupied  by  Archean  granites 
and  gneisses  with  a  few  bands  of  dark  basic  rocks  called  Huronian. 
SUMMARY  OF  PRESENT  KNOWLEDGE. 
A  great  area  of  pre-Cambrian  rocks,  frequently  called  the  pre- 
Cambrian  shield  of  North  America,  extends  from  the  Great  Lakes 
and  St.  Lawrence  River  northwest,  north,  and  northeast  to  the  Arctic 
Ocean,  Hudson  Bay,  and  Atlantic  Ocean — a  larger  area  than  all  the 
remaining  pre-Cambrian  areas  of  North  America  combined.  Por- 
tions of  the  pre-Cambrian  shield  adjacent  to  the  Great  Lakes  and  to 
St.  Lawrence  River  have  been  separately  considered  under  the  head- 
ings Lake  Superior  region,  original  Huronian  region,  original 
Laurentian  region,  etc.,  because  they  have  been  studied  in  some  detail. 
Under  the  heading  Great  Northern  region  are  treated  all  of  the  pre- 
Cambrian  shield  not  already  covered. 
The  Great  Northern  region  is  not  yet  penetrated  by  railways  and 
is  almost  uninhabited.  Exploration  has  consisted  for  the  most  part 
in  following  canoe  routes,  and  because  of  the  difficulties  of  travel, 
great  distances,  and  short  summers,  even  such  exploration  has  had  to 
be  hurriedly  done.  Hence  it  is  that  the  geological  study  of  this  region 
has  been  merely  reconnaissance  along  canoe  routes.  The  account  of 
this  reconnaissance  appears  for  the  most  part  in  the  reports  of  the 
Canadian  Geological  Survey  and  the  Ontario  Bureau  of  Mines. 
A  granite  gneiss  complex,  mapped  by  the  Canadian  geologists  as 
"Laurentian,"  occupies  much  the  largest  part  of  this  vast  region.  So 
far  as  can  be  ascertained  from  the  reconnaissance  reports,  this  com- 
55721— Bull.  300—01) 35 
