72  PKE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
direction ,  caused  the  present  fluted  outcrop  of  the  formations  of  the 
Steep  Rock  series.  That  the  basement  complex  itself  yielded  to  this 
latter  force  is  shown  by  the  irregular  outcrops  of  the  dikes  cutting  it. 
Asa  result  of  the  study  the  folio  wiug  general  conclusions  are  reached  : 
The  contact  of  the  lowest  horizon  of  the  Steep  Rock  series  with  the 
basement  complex  is  one  of  erosion.  The  complex  at  the  time  of  the 
deposition  of  the  Steep  Rock  series  was  made  up  of  consolidated  crys- 
talline rocks,  and  there  is  no  evidence  whatever  that  it  has  since  under- 
gone fusion  or  recurred  to  the  condition  of  a  magma.  The  rocks  of  the 
Steep  Rock  series  have  been  subjected  at  two  periods,  more  or  less  dis- 
tant from  one  another,  to  great  orotechnic  forces,  which  acted — the  first 
in  a  northeast  and  southwest  direction,  and  the  second  in  a  northwest 
and  southeast  direction.  The  latter  force  has  imposed  upon  all  the 
rocks  of  the  region  a  northeast  structure  which  has  largely,  but  not 
entirely,  obliterated  preexisting  lamination  in  the  sediments  and 
schists  of  the  Steep  Rock  series.  The  two  orotechnic  actions  have 
produced  great  developments  of  autoclastic  schists,  both  in  the  gran- 
ites and  in  the  rocks  of  the  Steep  Rock  series,  the  present  structure 
of  which  was  induced  and  determined  in  direction  by  the  later  force. 
SECTION  II.   WORK   OF   THE  EARLY  UNITED   STATES   GEOLOGISTS  AND 
ASSOCIATES. 
Schoolcraft,42  in  1821,  in  his  Narrative  Journal  of  Travels  in  the 
Northwest,  makes  various  observations  on  the  crystalline  rocks.  At 
Granite  point  is  found  a  bluff  of  granite  which  is  traversed  by  irregu- 
lar veins  of  greenstone  trap.  The  sandstone  laps  upon  the  granite  and 
fits  into  its  irregular  indentations  in  a  manner  that  shows  it  to  have 
assumed  that  position  subsequently  to  the  upheaving  of  the  granite. 
Its  horizontality  is  i:>reserved  even  to  the  immediate  point  of  contact. 
All  the  rock  along  the  south  shore  of  Lake  Superior  is  either  red  or 
gray  variegated  sandstone,  which  appears  to  be  referable  to  one  forma- 
tion. On  passing  by  the  Porcupine  mountains,  the  red  sandstone  is 
visible  along  the  shore  in  a  position  nearly  vertical,  dipping  under  the 
lake  toward  the  north.  Red  sandstone  in  a  vertical  position  is  found 
at  the  mouth  of  the  Montreal  river  and  for  a  few  miles  beyond  it 
toward  Chequainegon  bay.  On  the  St.  Louis  river,  after  passing  red 
sandrock  in  a  horizontal  position,  is  found  on  the  banks  of  the  river  a 
slate  (argillite)  in  a  vertical  position  traversed  by  greenstone  and  milky 
quartz.  At  the  grand  portage  of  the  St.  Louis  the  country  is  rough, 
consisting  of  slate  in  a  vertical  position.  This  continues  foiva  long- 
way  and  is  succeeded  by  Jiornblende,  which  continues  to  the  head  of 
Grand  rapids. 
Catlin,43  in  1840,  finds  the  red  pipestone'  quarries  of  the  coteau  des 
Prairies  to  consist  of  a  perfectly  stratified  rock  in  layers  of  light  gray 
and  rose  or  flesh  colored  quartz,  the  deposit  being  evidently  sedimen- 
tary and  of  secondary  age. 
