van  hiss.]  EASTERN    UNITED    STATES.  353 
as  follows:  (1)  Bethlehem  gneiss;  (2)  Huronian,  with  three  or  four 
subdivisions;  (3)  Cambrian  clay  slate;  (4)  Coos  quartzites;  (5)  Coos 
slates  and  schists;  ((>)  calciferous  mica-schist;  (7)  eruptive  granites, 
including  the  mount  Asentney  area,  which  is  partly  composed  of  rocks 
older  than  Huronian. 
In  the  Connecticut  valley  district,  between  Clareinont and  Hinsdale, 
the  succession  is  as  follows,  beginning  with  the  lowest:  (1)  Bethlehem 
gneiss;  (2)  gneisses  of  the  Montalban  series;  (3)  Huroniau;  (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  crystalline  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  west 
part  of  the  Merrimac  district,  as  follows:  (1)  Porphyritic  gneiss;  (2) 
Bethlehem  or  Protogene  gneiss;  (3)  common  or  Lake  gneiss;  (4)  ferru- 
ginous concretionary  schist;  (5)  fibrolite  schist,  sometimes  gneissic  and 
passing  into  common  mica-schist;  (0)  quartzites  and  quartz  conglom- 
erates; (7)  intrusive  rocks  and  veinstones.  Hitchcock  gives  the  order 
in  the  east  part  of  the  district  thus :  (1)  Porphyritic  gneiss;  (2)  Lake 
gneiss;  (3)  Montalban  series,  including  the  Concord  granite;  (4)  ferru- 
ginous schist;  (5)  Andalusite  mica-schists,  with  coarse  granite  veins; 
(6)  Rockingham  mica-schist;  (7)  Kearsarge  andalusite  group;  (8)  Mer- 
rimac group,  including  a  little  clay  slate.  There  are  no  eruptive  rocks 
in  this  area  of  sufficient  importance  to  find  a  place  upon  the  map. 
Hitchcock  gives  the  succession  in  the  Lake  district,  embracing  the 
Winnipiseogee  lake  and  the  flat  country  to  the  north,  as  follows:  (1) 
Porphyritic  gneiss;  (2)  Lake  gneiss;  (3)  Montalban.  The  eruptive 
rocks  are  more  plentiful  and  varied,  consisting  of  (1)  Conway;  (2) 
Albany:  (3)  Chocorua  granites;  (4)  porphyry;  (5)  Pequawket  brec- 
cia; (6)  Labradorite  diorite;  (7)  syenite;  (8)  granite,  not  allied  to  any 
of  the  foregoing. 
The  succession  in  the  Coast  district,  including  the  southeast  corner 
of  the  State,  is  as  follows:  (1)  Porphyritic  gneiss;  (2)  Lake  gneiss 
(including  the  Laurentian  of  Massachusetts) ;  (3)  Montalban ;  (4)  Rock- 
ingham group;  (5)  Merrimac  group ;  (0)  Kearsarge  group ;  (7)  Huronian 
and  Cambrian  of  Massachusetts.  The  unstratified  rocks  are  the  sye- 
nites of  Exeter  and  Pawruckaway,  inferior  granites,  and  the  well  de- 
veloped granites  and  porphyries  of  York  county,  besides  a  great  many 
trap  dikes  along  the  coast. 
In  considering  the  principles  of  classification,  as  guiding  principles 
it  is  premised  that  in  this  field  are  inverted  flexures  and  dislocations  of 
the  strata.  Also  that  formations  of  the  same  mineral  composition  in 
one  part  of  the  field  may  be  identified  with  those  of  like  composition  in 
another  part  of  the  field,  as,  for  instance,  the  porphyritic  gneiss  in 
thirty  areas  has  feldspar  crystals  very  cons})icuous  for  their  size.  All 
Bull,  SO 23 
