vanhise.i  LAKE    SUPERIOR    REGION.  85 
stone  of  the  southern  coast  exhibits  undulations  of  8°  or  10°  at  several 
places.  Two  instances  of  this  are  the  point  des  Grands  Sables,  begin- 
ning with  the  horizontal  strata  of  the  Pictured  rocks,  and  the  second  is 
at  Grand  island. 
Whitney,85  in  1850,  describes  the  northeastern  side  of  lake  Superior, 
from  Gros  cap  to  Nipigon  bay,  as  consisting  of  rocks  of  the  Azoic  system. 
On  the  south  shore  of  the  lake,  and  along  the  northwest  shore  as  far  as 
the  northeastern  extremity  of  Nipigon  bay,  are  found  the  shales,  sand- 
stones, conglomerates,  and  trappean  rocks  of  the  Potsdam  system,  ex- 
cept at  Thunder  bay  and  Carp  river,  where  the  Azoic  appears.  The  south 
side  of  the  Azoic  on  the  north  side  of  the  lake  runs  from  Kakabikka 
falls  on  the  Kaministiquia  in  an  almost  straight  line  southwest,  keeping  a 
few  miles  from  the  lake.  Thunder  cape  consists  of  thinly  bedded  slates 
for  800  feet  of  its  thickness,  above  which  is  a  sheet  of  trappean  rock 
200  or  300  feet  thick. 
Whitney,80  in  1850,  maintains  that  the  iron  ores  of  lake  Superior, 
Scandinavia,  Missouri,  and  northern  New  York,  form  a  class  by  them- 
selves belonging  to  the  Azoic  age,  and  they  have  been  poured  out  like 
other  igneous  rocks  from  the  interior  in  a  molten  or  plastic  state. 
Besides  the  purest  ores  are  others  interlaminated  with  bands  of  quartz 
which  are  distinctly  bedded  and  probably  are  of  sedimentary  origin. 
Tbe  iron  ore  injbhese  may  have  been  introduced  either  by  sublimation 
during  the  deposition  of  the  siliceous  particles,  or  by  precipitation  from 
a  ferriferous  solution  at  the  time  of  formation  of  the  stratified  rocks. 
Whitney,87  in  1857,  again  maintains  the  Potsdam  age  of  the  sand- 
stones of  the  Cupriferous  series.  Underlying  this  series  un  conform- 
ably on  the  south  shore  is  the  Azoic  series,  which  is  identical  in  char- 
acter with  the  rocks  of  Thunder  and  Black  bays.  The  rocks  on  the 
north  shore  of  lake  Huron  and  in  the  north  and  east  of  Canada  are 
dentical  in  position  and  lithological  character  with  the  Azoic  system. 
Jackson,88  in  1800,  again  asserts  that  the  red  sandstones  of  Kewee- 
law  point  are  certainly  coeval  with  the  sandstone  of  Nova  Scotia, 
Jonnecticut  river,  and  New  Jersey,  as  proved  by  identity  of  composi- 
tion, mode  of  disruption,  character  of  associated  minerals,  and  above 
ill,  by  the  fact  that  they  rest  upon  Devonian  limestones.  Orthocerati It- 
it  Copper  Falls  mine  and  Pentamerus  in  the  underlying  limestone  of 
tfurgeon  river  show  that  the  sandstones  are  not  Potsdam.   This  is  also 
thown  by  the  occurrence  of  pitchstone  porphyry  upon  isle  Royale  such 
s  are  found  in  the  isle  of  Arran  of  Triassic  or  Devonian  age.  The 
author  is  not  disposed  to  place  the  sandstones  of  the  Pictured  rocks  in 
he  same  formation  with  Keweenaw  point  and  isle  Royale. 
Eogers,89  in  1860,  maintains  that  the  argillaceous  shales  and  con- 
lomerates  of  a  part  of  the  southern  shore  of  lake  Superior  are  the 
quivalent  of  the  Primal  series.     The  Cupriferous  series  is  in  direct 
I~  ssociation  with  the  Potsdam,  and  therefore  the  argument  for  Triassic 
