228  PRE-CAMBRIAN   ROCKS    OF    NORTH    AMERICA.  (bull.  86. 
southeastern  boundary  of  the  great  granite  area,  (2)  the  ceutral 
granite  area,  (3)  a  band  of  noncalcareous  nietamorphic  slate  and 
quartzite  lying  immediately  northwest  of  the  granite  area.  The  south- 
ern slate  band  extends  from  Magaguadavic  lake  to  the  southwest  Mira- 
michi,  its  breadth  varying  from  9  J  miles  on  the  St.  John  river  to  17 
miles  on  the  Miramichi.  The  rocks  consist  of  argillaceous  and  mica- 
ceous clay-slates,  with  interposed  bands  of  crystalline,  quartzose,  mica- 
ceous and  feldspathic  rocks  resembling  sandstone.  They  are  doubtless 
altered  sediments.  In  one  place  apparently  in  this  series  are  fossils, 
probably  of  Upper  Silurian  or  Devonian  age.  The  central  granite  occu- 
pies a  considerable  area  to  the  northwest  of  the  slates.  The  line 
between  the  slates  and  granite  is  somewhat  arbitrary,  for  the  slate  and 
quartzite  band  includes  three  very  considerable,  with  some  smaller, 
bands  of  granite.  The  various  feldspathic  rocks  of  the  region  seem  to 
merge  into  each  other.  This  is  true,  not  only  of  the  granite  and  gneiss, 
but  even  of  the  foliated  semicrystalline  slates  and  quartzites.  Occa- 
sionally fragments  of  gneiss  of  all  shapes  and  sizes  are  found  imbedded 
or  incorporated  in  the  granite,  and  vice  versa ;  but  no  appearance  of 
granite  veins  cutting  the  laminated  rocks  are  noted.  The  slates,  mica- 
schists,  and  quartzites  of  the  northern  slate  belt  locally  assume  a  crys- 
talline aspect.  Bands  of  crystalline  rocks  resembling  granite,  syenite, 
and  diorite  are  intercalated  in  the  manner  of  conformable  or  interbed- 
ded  masses.  At  one  place  is  found  a  slate- con  glomerate  which  is  believed 
to  occupy  a  depression  in  the  older  rocks. 
RoBB,14in  1872,  gives  some  additional  facts  in  continuation  of  his 
studies.  The  central  granite  area  is  divided  into  two  granitic  bands. 
Much  of  the  granite  area  is  of  a  gneissoid  character.  Where  the  change 
from  granite  to  slate  occurs,  the  granite  near  the  line  of  contact  is 
often  of  a  red  variety  and  rather  line  grained,  gradually  passing  into 
the  ordinary  color  and  texture  in  receding  from  the  line.  All  attempts 
to  elucidate  the  structural  relations  of  the  granite  have  proved  futile. 
In  the  slate  band  northwest  of  the  granite  are  conformable  dikes  of 
diorite,  syenite,  and  other  feldspathic  rocks.  Immediately  at  the  junc- 
tion of  the  granite  with  this  series  is  a  band  of  pure  crystalline  lime- 
stone. 
Ells,15  in  1881,  reports  on  the  geology  of  northern  New  Brunswick. 
The  pre-Cambrian  rocks  are  believed  to  underlie  unconformably  the 
Cambro- Silurian.  The  typical  rock  is  a  grayish  feldspathic  gneiss, 
frequently  containing  hornblende.  The  rocks  referred  to  the  pre-Oam- 
brian  include  granites,  felsites,  gneisses,  and  schists.  Granites,  diorites, 
dolerites,  and  felsites  are  found.  A  portion  of  these  are  mingled  with 
the  pre-Cambrian,  but  others,  and  especially  the  basic  eruptives,  are 
found  in  the  slates  and  other  rocks  belonging  to  the  fossiliferous  series. 
At  the  contact  of  the  granites  with  the  slates  in  places  the  latter 
become  crystalline  and  contain  crystals  of  staurolite. 
Ells,16  in  1883,  finds  crystalline  mica-schists,  quartzites,  etc.,  which 
