558  PRE-CAMBRIAN    GEOLOGY   OF    NORTH   AMERICA. 
the  Lanrentian,  but  all  of  the  preceding  are  regarded  as  underlying 
the  Huronian.  It  is  thus  concluded  to  place  the  porphyritic,  Beth- 
lehem, 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  the  lower  quartzose  feldspathic.  The  greenstones  seem  to  be 
closely  allied  to  the  Upper  Huronian  and  the  porphyries  to  the  lower 
division,  and  to  this  may  belong  the  supposed  eruptive  porphyries  of 
the  White  Mountains.  The  Merrimac,  Rockingham,  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  thickness  of  the  doubtful  Paleozoic  is  placed  at  11,600  feet;  the 
Upper  Huronian,  12,129  feet ;  Lower  Huronian,  not  estimated ; 
Montalban,  13,700;  Laurentian,  34,900.  The  Labrador  system  if 
present  in  New  Hampshire  is  in  very  limited  amount.  Certain  of 
the  labradorites  are  surely  injected  dikes,  and  hence  it  is  doubtful 
whether  the  Waterville  area  really  represents  the  Labrador  system  of 
Canada. 
Hawes,13  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,  how- 
ever 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,  granites  filling  well-defined  dikes, 
granites  which  so  far  as  can  be  seen  are  entirely  devoid  of  structural 
relations,  and  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  crystalline  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  correspond  with  original 
bedding  in  case  they  are  completely  metamorphosed  material.  The 
gneisses  in  their  minerals,  inclusions,  and  microscopic  characters  are 
like  granites,  and  pressure  may  have  been  as  effective  in  producing 
lateral  movements  and  forming  foliation  in  a  plastic  mass  as  sedimen- 
tation. If,  then,  the  stratification  of  the  gneiss  is  regarded  as  an 
induced  structure,  it  would  not  follow  that  the  stratification  should 
correspond  with  the  original  bedding;  and  even  if  the  lamination 
does  correspond  with  the  plane  of  the  strata,  the  lamination  can  not 
be  referred  to  stratification  of  sediments,  for  the  cleavage  of  the 
adjacent  rocks  may  also  be  due  to  pressure  and  be  different  from  the 
plane  of  bedding.  The  greenstones,  including  metamorphic  diorite, 
quartz  diorite,  and  amphibolite,  are  regarded  as  metamorphosed  sedi- 
mentary rocks.    These  have  marked  lithological  distinctions  from  the 
