556  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
porphyritic  gneiss  and  the  Bethlehem  group;  (2)  the  Atlantic,  con- 
sisting of  the  Lake  or  Berlin  and  Montalban  gneisses  and  the  Fran- 
conia  breccia;  (3)  the  labradorite;  (4)  the  Huronian ;  (5)  the  Mer- 
rimac  schists;  (6)  the  andalusite  schist  group;  (7)  eruptions  of  por- 
phyry; (8)  eruptions  of  the  Conway,  Albany,  and  Chocorua  granites 
and  syenites;  (9)  the  formation  of  the  Mount  Pequawket  or  Mount 
Mote  porphyritic  breccia.  This  order  is  somewhat  different  from 
that  stated  at  the  beginning  of  the  chapter.  The  Huronian  barely 
touches  the  White  Mountain  area.  With  it  are  placed  certain  quartz- 
ites  which  are  lithologically  like  those  of  Canada.  The  Green  Moun- 
tain 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  of  Cambrian  age  which 
dip  away  from  them  both  to  the  east  and  to  the  west,  because  the 
Labrador  series  is  present,  and  because  fossiliferous  Helderberg  strata 
are  found  on  both  the  east  and  the  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  fol- 
lowing succession  is  found :  (1)  Laurentian,  consisting  of  the  porphy- 
ritic and  Bethlehem  gneisses;  (2)  Atlantic  gneiss,  represented  by 
the  Lake  division;  (3)  Huronian,  embracing  the  Lisbon  and  Lyman 
groups  and  the  auriferous  conglomerate;  (-1)  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  jaspers. 
In  the  area  between  Haverhill  and  Claremont  the  subdivisions  are 
as  follows:  (1)  Bethlehem  gneiss;  (2)  Huronian,  with  three  or  four 
subdivisions;  (3)  Cambrian  clay  slate;  (4)  Coos  quartzites;  (5) 
Coos  slates  and  schists;  (G)  calciferous  mica  schist;  (7)  eruptive 
granites,  including  the  Mount  Ascutney  area,  which  is  partly  com- 
posed of  rocks  older  than  Huronian. 
In  the  Connecticut  Valley  district,  between  Claremont  and  Hinsdale, 
the  succession  is  as  follows,  beginning  with  the  lowest :  ( 1)  Bethlehem 
gneiss;  (2)  gneisses  of  the  Montalban  series;  (3)  Huronian;  (4) 
Coos  quartzites;  (5)  Coos  slates  and  schists;  (6)  calciferous  mica 
schist;  (7)  eruptive  granite.  The  Coos  quartzites  and  calciferous 
mica  schists  are  only  semicrystalline  rocks,  all  the  thoroughly  crystal- 
line schists  being  placed  with  the  pre-Cambrian.  The  thickness  of 
the  Huronian  rocks  in  New  Hampshire  is  placed  in  the  neighborhood 
of  10,000  feet. 
Huntington  gives  the  order  of  superposition  of  the  rocks  in  the 
western  part  of  the  Merrimac  district  as  follows:  (1)  Porphyritic 
gneiss;    (2)    Bethlehem  or  protogene  gneiss;    (3)    common  or  Lake 
