258  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
not  far  from  10,000  feet,  and  at  three  other  places  on  the  coast  between 
the  last  point  and  Sault  Ste.  Marie. 
As  to  the  age  of  this  series,  the  fact  that  the  generally  moderate 
dips  of  the  red  sandstone  at  Sault  Ste.  Marie  contrast  with  the  higher 
inclinations  of  the  copper-bearing  rocks,  while  none  of  the  many  dikes 
are  known  to  intersect  the  Sault  Ste.  Marie  sandstone,  leads  to  the 
suspicion  that  the  latter  may  overlie  unconformably  the  rocks  which, 
associated  with  the  trap,  constitute  the  copper-bearing  series.  The 
affinities  of  the  Sault  Ste.  Marie  red  sandstone  appear  to  bring  it  into 
the  position  of  the  Chazy  rather  than  the  Potsdam  formation,  and  if 
this  were  established  the  copper-bearing  portion  of  the  Lake  Superior 
rocks  might  reasonably  be  considered  to  belong  to  the  Calciferous  and 
the  Potsdam  formations. 
Macfarlane,227  in  1866,  gives  observations  on  the  Laurentian,  Hu- 
ronian,  and  Upper  Copper-bearing  rocks  of  Lake  Superior.  Here  the 
Laurentian  series  seems  to  differ  somewhat  from  the  same  series  in 
other  parts  of  Canada.  The  rocks  are  all  highly  crystalline,  seldom 
thoroughly  gneissoid,  and  all  are  unaccompanied  by  crystalline  lime- 
stone, which  is  such  a  marked  feature  in  some  Laurentian  districts. 
The  gneiss  strata  are  much  contorted  and  are  intersected  with  granite 
in  almost  equal  quantity  with  the  gneiss  itself;  and  although  the 
granite  occurs  in  irregular  veins,  at  the  point  of  junction  it  is  as  firmly 
cemented  with  the  gneiss  as  any  two  pieces  of  one  and  the  same  rock 
could  well  be.  On  the  Goulais  Bay  fragments  of  hornblende  rock  or 
schist  up  to  3  feet  in  diameter  are  inclosed  in  a  coarse-grained  sye- 
nitic  granite.  In  this  series  the  oldest  rock  is  the  most  basic  in  consti- 
tution, and  this  is  the  case  without  regard  to  mineralogical  composi- 
tion or  structure  of  the  rocks  associated  together.  The  indistinctness 
of  parallelism  in  the  rocks  renders  it  a  matter  of  extreme  difficulty 
to  form  any  clear  ideas  as  to  their  succession,  even  if  such  should 
exist.  Besides  the  above  rocks  there  are  considerable  areas  of  granite, 
syenite,  dolerite,  diorite,  and  melaphyre  found  in  the  Laurentian. 
The  rocks  of  the  Huronian  system  consist  in  large  part  of  diabase, 
amygdaloid,  diabase  schist,  greenstone,  breccias,  and  slaty  green- 
stones. Interstratified  with  these  are  slate,  slate  conglomerate,  and 
quartzite.  The  bowlders  and  pebbles  of  the  conglomerate  of  Dore 
River  are  for  the  most  part  granite;  they  are  elongated  and  flattened, 
the  pebbles  sometimes  being  scarcely  distinguishable  from  the  slate. 
Granitic  veins  or  masses,  like  the  Laurentian,  are  found  in  the  schis- 
tose greenstones,  which  are  regarded  as  belonging  to  the  Huronian. 
As  to  the  succession  of  the  strata,  the  author  is  as  much  at  a  loss 
among  the  irregular  schistose  Huronian  greenstones  as  among  the 
gneissoid  granites  of  the  Laurentian. 
The  Mamainse  section  of  Upper  Copper-bearing  rocks  consists  of 
interbedded  basic  lava  flows,  often   amygdaloidal,  sandstones,  and 
