74  PRE-CAMBRJAN    ROCKS    OF    NORTH    AMERICA.  [bull. 8(5. 
stones,  hornblende-rock,  gneiss,  and  mica-slate.  Magnesian  and  mag. 
netic  slates  are  capped  unconformable  by  pebbly  sandstones  for  nearly 
a  mile  along  Black  river.  The  red  sandstone  of  lake  Superior  on  Ray- 
monds  creek  is  estimated  by  Randall  to  Ipe  10,000  feet  in  thickness. 
Norwood,56  in  1847,  describes  various  rocks  on  the  St.  Louis  river 
in  the  district  between  Fond  du  Lac  and  the  falls  of  St.  Anthony,  and 
from  the  mouth  of  the  Montreal  river  to  the  headwaters  of  the  Wis- 
consin river  by  way  of  lake  Flambeau.  On  the  St.  Louis  river  a  con- 
glomerate is  found  to  rest  unconformably  upon  the  lower  slates,  the 
junction  of  the  slates  and  conglomerates  being  exposed. 
Rogers,'''7  in  1848,  remarks  that  the  south  shore  of  lake  Superior  is 
outlined  by  a  series  of  east  and  west  dikes. 
Whitney,58  in  1848,  finds  in  the  townships  near  the  Anse  fossiliferous 
limestone,  which  seems  to  be  surrounded  by  and  has  been  deposited  on 
the  lake  Superior  sandstone. 
Foster,5!/  in  1848,  in  passing  from  Copper  harbor  to  L'Anse,  finds 
that  the  trap,  instead  of  being  forced  through  the  layer  of  sandstone, 
as  on  the  northern  slope  of  Keweenaw  point,  protrudes  through  a  fissure 
in  it,  causing  an  anticlinal  axis.  A  few  miles  farther  *south  the  sand- 
stone is  nearly  horizontal,  being  in  a  series  of  gentle  undulations.  At 
L'Anse  the  sandstones  overlie  the  talcose,  argillaceous,  and  hornblendic 
slates  unconformably,  while  15  miles  southeast  of  L'Anse  the  granites 
protrude  through  these  schists. 
Upon  the  Michigamme  river  were  found  in  order  beds  of  quartz  and 
feldspar,  hornblende,  and  specular  oxide  of  iron,  associated  with  talcose 
and  argillaceous  schists.  On  the  left  bank  of  the  Michigamme.  (Sec.  1, 
T.  46  N".,  R.  30  W.)  is  a  hill  170  feet  high,  which  exposes  a  very  large 
mass  of  nearly  pure  specular  oxide  of  iron.  About  40  feet  from  the 
escarpment  is  a  metamorphic  rock  composed  of  rounded  particles  of 
quartz  and  feldspar  with  masses  of  ore  intermingled  like  the  pebbles  of 
a  conglomerate. 
Iron  ore  and  marble  were  observed  along  the  Menominee,  as  well  as 
various  other  kinds  of  rocks,  including  granite,  hornblende-slate,  tal- 
cose slate,  etc.  At  Sandy  portage,  on  the  Menominee,  is  a  class  of  pho- 
tonic rocks  older  than  the  traps  of  Keweenaw  point,  which  were  pro- 
truded among  the  slates  and  then  denuded  before  the  deposition  of  the 
sandstone;  for  the  slates  are  intercalated  among  the  igneous  rocks 
with  a  vertical  inclination,  while  the  sandstone  rests  horizontally  or 
nearly  so  upon  them.  This  sandstone  is  regarded  as  the  oldest  of  the 
Paleozoic  rocks  and  is  the  equivalent  of  the  sandstone  on  the  northern 
slope  of  the  upper  peninsula.  Resting  upon  this  sandstone  is  a  lime- 
stone which  is  sparingly  fossiliferous. 
Jackson,00  in  1849,  describes  the  sandstone  of  Keweenaw  point  re- 
mote from  the  trap  as  horizontal  or  but  slightly  waving,  while  near  the 
trap  rock  it  is  as  high  as  30°.  The  conglomerate  is  limited  to  the  bor- 
ders of  the  trap  and  is  of  the  same  age  as  the  finer  grained  sandstone 
