yanjiisk]  LAKE    SUPERIOR    REGION.  157 
tli e literature,  from  which,  by  means  of  the  footnotes,  the  material  may 
be  traced  to  the  originals. 
The  four  series  to  be  arranged  are  those  known  as  the  lake  Superior 
sandstone,  the  Keweenawan,  the  Huronian,  and  the  Laurentian.  The 
last  two  have  by  certain  later  writers  been  again  subdivided. 
LAKE    SUPERJLOK    SANDSTONE. 
The  horizontal  red  sandstone  of  lake  Superior  was  recognized  as  the 
most  extensive  formation  of  the  lake  by  the  earliest  geological  voy- 
ageurs,  and  in  what  follows  this  formation  will  be  called  the  lake 
Superior  sandstone.  The  early  travelers,  Schoolcraft,  Bigsby,  and 
Bayfield,  regarded  it  as  the  Old  Red  sandstone,  although  Bayfield  later 
considered  it  to  probably  underlie  the  fossiliferous  red  sandstone  of  St. 
Marys  river.  It  was  placed  by  Jackson,  Marcou,  and  for  a  long  time 
by  Bell,  as  the  New  Red  sandstone.  Yery  early  others,  including  Daw- 
son (Sir  William),  Foster,  Houghton,  Logan,  Owen,  Whitney,  and 
Rogers,  regarded  the  sandstone  as  Lower  Silurian  or  Potsdam.  In 
1873  Rominger  finally  demonstrated  what  Houghton  had  long  before 
stated,  that  the  horizontal  sandstone  is  directly  overlapped  by  the  Cal- 
ciferous  formation.  The  sandstone  was  therefore  placed  as  Potsdam, 
which  position  it  has  held  since  that  time  without  dispute  by  anyone 
acquainted  with  the  region. 
It  was  very  early  seen  that  the  horizontal  sandstone  is  newer  than 
the  granites  and  slates  of  lake  Superior,  which  occupy  a  lower  position 
than  the  Keweenawan.  Schoolcraft  saw,  as  early  as  1821,  the  uncon- 
formity between  the  granite  and  sandstone  at  Granite  point,  and  that 
between  the  latter  and  the  slates  on  the  St.  Louis  river  at  the  head  of 
lake  Superior.  Bayfield  recognized  this  unconformity  in  1829,  saying 
that  the  many  instances  of  the  conjunction  of  the  sandstone  and  granite 
proved  that  the  sandstone  was  deposited  after  the  granite  occupied  its 
present  position.  Rogers  saw  the  same  relations  between  the  sandstone 
and  the  slates  of  Chocolate  and  Carp  rivers,  although  at  first  he  regarded 
the  latter  as  Primal.  Owen,  in  1847,  described  in  northern  Wisconsin 
ike  unconformable  relations  between  the  horizontal  sandstone  referred 
to  the  Potsdam  and  the  crystalline  rocks.  Norwood,  in  1847,  again  saw 
the  unconformity  between  the  lake  Superior  sandstone  and  St.  Louis 
date,-,  at  Fond  du  Lac,  described  by  Schoolcraft  many  years  before. 
Foster,  in  1848,  saw  the  same  unconformable  relations  between  the 
andstones  and  slates  at  L'Anse.  Since  these  early  discoveries  of  the 
relations  between  the  sandstone  and  the  crystalline  rocks  were  an 
lounced  they  have  been  conn rined  at  these  original  localities  and  at 
nunerous  other  localities  by  many  observers. 
As  to  the  relations  of  the  lake  Superior  sandstone  with  the,  sand- 
stones interstratified  with  the  trappean  rocks,  i.e.,  the  Keweenawan, 
here  has  been  the  greatest  diversity  of  opinion,  and  the  question  is  one 
I  which  there  is  not  yet  entire  unanimity,  although  the  weight  of  the 
