590  PEE- CAMBRIAN   GEOLOGY   OF   NORTH   AMERICA. 
metamorphic  origin  for  granite  long  delayed  the  proper  comprehen- 
sion of  the  true  significance  of  the  large  bodies  of  granite  and  granite 
gneiss  and  their  importance  as  structural  elements  in  this  province. 
Even  the  latest  revision  of  the  systematic  work  in  western  Massachu- 
setts affords  evidence  of  this  tardy  recognition  of  the  igneous  rather 
than  metamorphic  character  of  a  granite  gneiss  the  pre-Cambrian 
age  of  which  is  now  established. 
In  Maine  and  New  Hampshire  the  amount  of  systematic  work 
done  during  the  last  decade  has  been  insufficient  to  allow  much  re- 
vision of  the  results  of  the  earlier  surveys.  Recent  mapping  on  the 
Maine  coast  has  shown  the  presence  of  several  metamorphic  forma- 
tions, which  represent  old  sediments  and  ancient  volcanics,  mostly 
of  Paleozoic  age.  The  oldest  of  the  crystalline  schists  in  the  vicinity 
of  Penobscot  Bay  is  a  green  quartz-mica  schist,  which  may  be  of 
pre-Cambrian  age.  It  is  noteworthy  that  in  this  area  and  elsewhere 
on  the  Maine  coast,  as  far  as  known,  the  granite  is  of  late  Paleozoic 
age  and  is  usually  the  youngest  of  the  rocks  present.  It  is  possible, 
however,  that  the  granite  of  the  mountainous  portion  of  western 
Maine  is  older.  In  the  upper  valley  of  Androscoggin  River  the 
granite  is  characterized  by  a  well-developed  gneissoid  texture,  with 
crushing  and  banding  of  the  constituent  minerals,  and  thus  appears 
quite  distinct  from  the  granite  known  to  be  of  Paleozoic  age. 
In  New  Hampshire  the  progress  in  the  study  of  the  crystalline 
rocks  may  best  be  summarized  by  quoting  two  recent  statements  by 
C.  H.  Hitchcock.0 
A  long  list  of  what  were  formerly  called  metamorphic  schists  may  now  be 
classed  as  eruptive  igneous  rocks,  such  as  the  porphyritic  granite,  Bethlehem 
granite,  Lake  gneiss,  diorites,  and  protogenes,  to  say  nothing  of  what  has 
always  been  recognized  as  granite  and  diabase.  The  periods  of  their  extrusion 
were  evidently  middle  or  late  Paleozoic. 
The  general  results  of  our  studies  tend  to  restrict  the  areas  of  the  more 
ancient  rocks  and  to  increase  those  representing  the  Paleozoic  groups  in  the 
adjoining  regions  of  northern  New  England. 
In  southern  Vermont  and  western  Massachusetts  the  systematic 
areal  work  of  Wolff  and  Emerson  has  resulted  in  valuable  contribu- 
tions to  the  knowledge  of  the  pre-Cambrian  of  the  Green  Mountain 
range.  In  southern  Vermont  Wolff  describes  the  axis  of  this  range  as 
composed  of  a  gneissic  complex.  The  many  lithologic  types  include 
coarse  reddish  and  white  gneisses,  fine-grained,  bluish-gray  garnet- 
iferous  gneiss,  biotitic  schist,  pegmatite,  amphibolite,  and  graphite 
gneiss.  The  constituent  minerals  and  the  structures  are  largely  sec- 
ondary and  are  referred  to  pressure  metamorphism.  Another  pre- 
Cambrian  gneiss  occurring  in  this  area  is  the  Stamford  gneiss,  which 
is  best  known  as  forming  the  core  of  Hoosac  Mountain.     This  rock 
"Bull.  Geol.  Soc.  America,  vol.  15,  1904,  pp.  479-480. 
