352  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
is  considered  as  the  probable  equivalent  of  the  Labrador  system  of 
Logan  and  Hunt.  It.  includes  the  Conway  granite,  Albany  granite, 
Otoconia  granite,  Ossipyte  or  Labradorite  rocks,  and  various  compact 
and  crystalline  feldspars  or  porphyries.  The  relations  of  the  Albany 
granite  and  the  Andalusite  slate  do  not  show  that  the  underlying  gran- 
ites are  certainly  not  sediments,  although  they  have  been  so  thoroughly 
metamorphosed  as  to  have  lost  their  lines  of  original  bedding;  but  the 
evidence  in  favor  of  their  eruption  since  the  deposition  of  the  andalusite 
slates  is  increasing.  The  slates  are  twisted  and  broken  in  many  places, 
the  fragments  being  cemented  together  by  a  granitic  paste;  also,  frag- 
ments of  slate  occur  imbedded  in  the  underlying  granite.  The  Labra- 
dor group  is  found  in  seven  areas.  The  Labrador  rocks  lie  uncon- 
formably  upon  the  upturned  edges  of  the  Montalban  gneisses,  the 
discordance  varying  from  45°  to  70°.  Porphyry  occurs  in  this  system, 
which  is  regarded  as  intrusive.  Syenite  has  quite  a  widespread  occur- 
rence. The  andalusite  slates  are  regarded  as  the  equivalent  of  the  Coos 
series,  but  they  are  similar  to  the  Huronian  system.  The  Pequawket 
series  is  regarded  as  late  eruptives.  The  stratigraphic  order  in  the 
White  mountains  is  finally  concluded  upon  as  follows :  (1)  the  Lau- 
rentian,  represented  by  the  Porphyritic  gneiss  and  the  Bethlehem 
group ;  (2)  the  Atlantic,  consisting  of  the  Lake  or  Berlin  and  Mont- 
alban gneisses,  and  the  Franconia  breccia;  (3)  the  Labradorite;  (4)  the 
Huronian;  (5),  the  Merrimac  schists;  (6)  the  Andalusite  schist  group; 
(7)  eruptions  of  porphyry;  (8)  eruptions  of  the  Conway,  Albany  and 
Chocorua  granites  and  syenites;  (9)  the  formation  of  the  mount  Pequaw- 
ket or  mount  Mote  porphyritic  breccia.  This  order  is  somewhat  dif- 
ferent from  that  stated  at  the  beginning  of  the  chapter.  The  Huronian 
barely  touches  the  White  mountain  area.  With  it  are  placed  certain 
quartzites  which  are  lithologically  like  those  of  Canada.  The  Green  and 
White  mountain  gneisses  are  regarded  as  Eozoic  because  they  are  a 
continuation  of  the  Eozoic  rocks  of  New  Jersey  and  New  York,  because 
they  are  bordered  by  quartzites  which  are  of  Cambrian  age,  which  dip 
away  from  them  both  to  the  east  and  west,  because  the  Labrador  series 
is  present,  and  because  fossiliferous  Helderberg  strata  are  found  on 
both  the  east  and  west  sides  of  the  White  mountains  side  by  side  with 
the  metamorphic  schists,  the  former  containing  fossils. 
In  the  Ammonoosuc  gold  field  of  the  Connecticut  valley  the  follow- 
ing succession  is  found:  (1)  Laurentian,  consisting  of  the  Porphyritic 
and  Bethlehem  gneisses;  (2)  Atlantic  gneiss,  represented  by  the 
Lake  division;  (3)  Huronian,  embracing  the  Lisbon  and  Lyman  groups 
and  the  auriferous  conglomerate;  (4)  Cambrian  clay-slate;  (5)  Coos 
group;  (6)  Swift  water  series;  (7)  Helderberg  quartzites,  slates  and 
limestones.  The  Huronian  formations  embrace  schists,  conglomerates, 
the  pebbles  being  sometimes  flattened,  quartzites,  dolomites  and  jas- 
pers. 
In  the  area  between  Haverhill   and  Olaremont  the  subdivisions  are 
