354  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA,  [mjLL.86. 
these  areas  are  assumed  to  be  identical  in  age,  and  in  placing  the  rela- 
tive positions  of  the  intervening  groups  this  is  relied  upon  for  a  start- 
ing point.  The  general  order  of  succession  for  New  Hampshire,  from 
the  base  upward,  is,  Porphyrinic  gneiss;  Bethlehem  gneiss;  Lake  and 
Montalban  series;  argillaceous,  talcose,  hydroinicaceous  and  calcareous 
series;  Labrador  series  (present  in  New  Hampshire,  limited  in  amount) ; 
various  types  of  mica-schists.  Andalusite  slate  in  this  mica-schist  for- 
mation lies  un conformably  upon  the  Montalban  at  mounts  Monad- 
nock  and  Kearsarge.  The  principal  eruptive  masses  are  the  Conway, 
Albany,  Ohocorua  granites,  syenites,  other  granites,  and  labradorite, 
diorites  and  dolerites.  The  granites  cut  rocks  as  high  as  the  Coos 
group.  The  Porphyrinic  gneiss  and  the  Bethlehem  group  are  referred 
to  the  Laurentian.  The  Lake  gneiss  can  not  easily  be  assigned.  The 
Montalban  certainly  is  not  characteristic  of  the  Laurentian,  but  all  of 
the  preceding  are  regarded  as  underlying  the  Huronian.  It  is  thus 
concluded  to  place  the  Porphyritic,  Bethlehem,  and  Lake  gneisses  with 
the  Laurentian,  leaving  the  position  of  the  Huronian  and  Montalban  to 
be  settled  by  other  considerations. 
The  Huronian  is  divided  into  two  divisions,  the  upper  chloritic,  and 
tin4  lower  quartzose  and  feldspathic.  The  greenstones  seem  to  be 
closely  allied  to  the  upper  Huronian  and  the  porphyries  to  the  lower 
division,  ami  to  this  may  belong  the  supposed  eruptive  porphyries  of 
the  White  mountains.  The  Merrimack,  Bockingham,  and  Kearsarge 
mica-schists  are  somewhat  related  to  the  Huronian,  as  well  as  to  the 
Cambrian.  They  are  all  referred  doubtfully  to  the  Paleozoic  system. 
The  doubtful  Paleozoic  is  placed  at  11,600  feet  thick;  the  Upper  Huro- 
nian, 12,129  feet;  Lower  Huronian,  not  estimated;  Montalban,  13,700; 
Laurentian,  34.900.  The  Labrador  system  if  present  in  New  Hamp- 
shire is  in  very  limited  amount.  Certain  of  the  labradorites  are  surely 
injected  dikes,  and  hence  it  is  doubtful  whether  the  Water ville  area 
really  represents  the  Labrador  system  of  Canada. 
Hawes,14  in  1878,  regards  the  diabases,  diorites,  gabbros,  felsites, 
granites,  and  syenites  of  New  Hampshire  as  eruptive  rocks.  Some  of 
them  may  have  been  produced  by  the  fusion  of  sediments,  but  however 
this  may  be,  they  have  all  been  in  a  molten  condition  and  been  free  to 
crystallize.  There  are  beds  of  granite  which  are  unconformable  with 
the  associated  stratified  rocks;  there  are  granites  filling  well  defined 
dikes;  there  are  granites  which  so  tar  as  can  be  seen  are  entirely  de- 
void of  structural  relations;  there  are  granites  which  are  mixed  with 
other  rocks,  or  which  hold  huge  fragments  of  other  rocks  inclosed  in 
their  masses.  All  these  features  are  often  repeated.  Among  the  crys- 
talline schists  are  placed  gneiss,  mica-schist,  argillitic  mica-schist,  and 
quartz- schist.  The  gneisses,  like  the  granites,  are  believed  to  be  of 
eruptive  origin,  or  at  least  to  have  acted  like  an  eruptive  rock,  the 
lamination  being  an  induced  structure  which  may  or  may  not  cor- 
respond with  original  bedding  in  case  they  are  completely  metamor- 
