62  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull. 86 
the  Laurentian  or  Huroniaii  bills  narrow  strips  or  patches  of  rocks  o 
the  Upper  Copper-bearing  group.  Such  localities  are  Gros  cap,  soutl 
shore  of  Batchawana  bay,  and  cape  Gargantua.  The  conglomerate! 
are  full  of  Huronian  debris,  and  in  Batchawana  bay  bowlders  may  b< 
observed  of  red  jasper  conglomerate,  the  characteristic  rock  of  tin 
typical  Huronian.  On  Michipicoten  island  the  igueous  and  sedimentary 
strata  of  the  Upper  Copper-bearing  rocks  have  a  dip  of  25°  to  tin 
southeast,  while  the  nearest  Huronian  rocks  dip  34°  to  55°  northward 
Bell,28  in  1883,  gives  a  further  account  of  the  distribution  of  tin 
rocks  of  the  lake  of  the  Woods  and  adjacent  country.  They  are  nott 
different  from  those  mentioned  in  his  previous  report  for  1872-73.  The 
line  between  the  Laurentian  and  Huronian  system  crosses  the  Winni- 
peg river  at  Eat  portage,  keeps  near  the  railway  to  a  point  between 
lake  Lulu  and  Keewatin  mills,  where  it  crosses  it  diagonally  and  con- 
tinues in  a  westerly  direction  on  the  south  side  of  the  track. 
Selwyn,29  in  1883,  as  a  result  of  an  examination  of  the  north  shore 
of  lake  Superior  from  Thunder  bay  to  Sault  Ste.  Marie,  and  thence 
eastward  to  Echo  lake,  fails  to  find  evidence  of  the  supposed  uncon- 
formability  of  the  Huronian  and  Laurentian.  The  author  can  give  no 
better  reason  for  supposing  that  certain  sets  of  beds  belong  to  the  so* 
called  Laurentian  and  others  to  the  Huronian  systems  than  a  consider- 
able difference  in  the  lithological  characters.  The  Laurentian  are  em 
sentially  granitoid,  gneissic  and  feldspathic,  while  the  Huronian  are 
quartzose,  hornblendic,  schistose  and  slaty.  As  a  whole  the  latter 
have  a  somewhat  altered  aspect  and  contain  pebbles  of  rocks — granite, 
gneiss,  quartzite,  etc. — similar  to  those  which  form  the  Laurentian 
strata  beneath  them,  while  others,  however,  are  not  recognizable  ai 
from  any  known  Laurentian  sources.  Bands  of  limestone  and  dolomite, 
more  or  less  crystalline,  are  found  in  both  Laurentian  and  Huronian 
areas,  and,  if  we  except  the  disputed  form  Eozoon,  no  fossil  what- 
ever. The  Huronian  follows  and  does  not  rest  un  conformably  upon 
the  Laurentian.  The  Mpigon  or  Keweenian  is  later  in  age  than  the] 
Animikie.  No  definite  opinion  can  be  expressed  as  to  the  position  of 
the  crowning  overflow  of  Thunder  cape. 
Selwyn,30  in  1883,  describes  the  trap  and  sandstone  of  lake  Supe- 
rior as  unconformably  upon  and  entirely  distinct  from  the  Huronian. 
The  series  is  divisible  on  the  Canadian  shore  into  two,  and  perhaps 
three  divisions,  between  which  there  may  be  slight  unconformities, 
which  are,  however,  no  greater  than  might  be  occasioned  by  the  inter- 
mingling of  sedimentary  strata  with  volcanic  material.  The  groups  in 
ascending  order  are  (1)  the  shales,  cherts,  dolomites  and  sandstones 
interbedded  with  massive  diabase  or  dolerite  of  Pie  island,  McKay! 
mountain  and  Thunder  cape.  (2)  Conglomerates,  shales,  sandstones: 
and  dolomites,  interstratified  with  massive  beds  of  volcanic  material, 
amygdaloids,  melaphyres,  tuffs,  etc.,  many  thousands  of  feet  thick, 
occupying  the  east  shore  of  Black  bay,  Mpigon   strait,  St.  Ignace, 
