LAKE   SUPERIOR   REGION.  253 
SECTION  4.  PART  OF  ONTARIO  NORTHWEST,  NORTH,  AND 
NORTHEAST  OF  LAKE  SUPERIOR. 
SUMMARY   OF  LITERATURE. 
Bigsby,216  in  1825,  describes  in  detail  the  rocks  at  many  points  along 
the  north  shore  of  Lake  Superior,  between  the  Falls  of  St.  Mary  and 
Grand  Portage,  an  interval  of  445  miles.  The  varieties  of  rocks  are 
few  in  number  when  compared  with  a  similar  extent  of  country  in 
Europe.  Of  mica  slate,  clay  slate,  etc.,  not  a  vestige  was  found,  not 
even  in  debris,  nor  of  any  secondary  deposits  above  the  Mountain 
limestone.  Sandstone,  under  various  modifications,  occupies  the 
greatest  space,  in  intimate  connection  with  the  next  prevailing  rocks, 
the  amygdaloids,  porphyries,  and  greenstone  trap.  The  alternating 
granites  and  greenstones  of  the  northeastern  and  eastern  coasts  are 
nearly  equal  in  quantity  to  these.  The  granites  and  syenites  are  not 
stratified.  The  porphyry,  amygdaloid,  and  sandstone  are  considered 
contemporaneous  and  newer  than  the  granites,  although  not  much,  as 
indicated  by  the  transitions  and  alternations  occurring  about  Gargan- 
tua.  The  age  and  connections  of  the  greenstone  trap  the  author  is 
not  prepared  to  state.  The  sandstone  is  most  probably  Old  Red,  a 
conclusion  reached  from  the  materials  composing  it,  and  its  direct 
superposition  on  inclined  rocks  in  this  and  other  great  lakes  of  the  St. 
Lawrence,  and  because  it  supports  a  fossiliferous  limestone  full  of 
Products,  Turbinoliae,  Caryophyllise,  trilobites,  Conulariee,  encrinites, 
and  orthoceratites,  etc.  The  granite  and  syenite  seem  to  be  of  the 
same  age  and  belong  to  the  Transition  or  to  the  youngest  of  the 
Primitive. 
On  the  old  route  from  Lake  Superior  to  the  Lake  of  the  Woods  ( for 
430  miles)  is  an  alternation  of  chloritic  greenstone  and  amphibolitic 
granite,  but  at  and  toward  the  Lake  of  the  Woods  the  greenstone 
passes  into  gneiss  and  mica  slate,  traversed  in  many  ways  and  in  great 
quantities  by  graphic  granite. 
Bayfield,217  in  1829,  gives  an  outline  of  the  geology  of  Lake 
Superior.  The  rocks  of  the  lake  are  divided  into  four  divisions: 
First,  the  inferior  order,  comprising  granites,  which  almost  always 
contain  more  or  less  hornblende.  In  this  division  neither  gneiss  nor 
mica  slate  was  met  with,  although  the  granite  by  the  abundance 
of  its  mica  or  lamellar  structure  may  for  a  short  distance  assume 
the  appearance  of  either.  Second,  the  submedial  order,  which  in- 
cludes greenstones,  common  jaspery  variety  of  greenstone  slates, 
flinty  chlorite,  talcose  slate,  and  in  one  place  alone  Transition  lime- 
stone, with  perhaps  traces  of  graywacke.  Third,  trap  or  overlying 
rock,  the  most  of  which  is  amygdaloid  :  various  kinds  of  porphyry  are 
next  in  quantity;   then   trap,  greenstone,   syenites,  and   pitchstone. 
