NEW   ENGLAND.  559 
fresh  basic  rocks  recognized  as  eruptives.  The  clay  slates  and  quartz 
schists  are  semicrystalline  rocks.  The  slaty  cleavage  and  bedding- 
are  sometimes  discordant. 
Ha wes,14  in  1881,  describes  the  Albany  granite  as  penetrating  and 
metamorphosing  the  schists,  and  as  having  a  porphyritic  structure 
near  its  contact  with  them,  and  it  is  therefore  concluded  to  be  in- 
trusive. 
Hitchcock  (C.  H.),15  in  1890,  regards  the  oval  granitoid  areas  oc- 
curring in  the  White  Mountains,  about  which  occur  foliated  rocks 
with  an  anticlinal  quaquaversal  arrangement,  as  the  oldest  known  or 
fundamental  rocks  of  the  region,  which  are  remains  of  an  ancient 
archipelago. 
Williams,15  in  1890,  with  the  same  facts  before  him,  gives  an 
interpretation  exactly  opposite  to  that  of  Hitchcock — that  is,  that  the 
central  granites  are  younger  intrusive  masses. 
Hitchcock  (C.  H.),16  in  1896,  gives  a  general  account  of  the  geol- 
ogy of  New  Hampshire,  including  a  sketch  of  the  work  and  con- 
clusions of  the  first  and  second  New  Hampshire  State  surveys  and  of 
subsequent  workers  in  the  field.  Some  of  the  modifications  indicated 
by  work  done  since  the  close  of  the  second  State  survey  are:  (1) 
Archean  rocks  exist  as  oval  areas  in  the  Stamford  gneiss  and  south 
of  Mount  Killington,  Vt.,  in  the  Hinsdale,  Mass.,  area,  the  Hoosac 
Mountain,  and  elsewhere.  (2)  The  masses  of  Bethlehem  gneiss  are 
batholiths,  with  inclusions  of  adjacent  mica  schists.  (3)  A  study  of 
several  areas  of  hornblende  schist  proves  that  they  are  igneous. 
Daly,17  in  1897,  discusses  the  porphyritic  gneiss  of  New  Hamp- 
shire, and  concludes  that  it  is  an  eruptive  porphyritic  granite,  at  least 
in  its  three  most  important  areas,  of  post-Devonian  age. 
Hitchcock,18  in  1904,  concludes  that  a  long  list  of  what  were  for- 
merly 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  re- 
sults of  his  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. 
SECTION  3.     VERMONT. 
SUMMARY   OF  LITERATURE. 
Adams,  19  in  1845,  divides  the  older  rocks  of  Vermont  into  Primary 
strata  and  Paleozoic  rocks.  The  Primary  system  is  highly  crystal- 
line and  destitute  of  fossils.  It  is  divided  into  argillaceous  slate, 
calcareo-mica  slate,  mica  slate,  talcose  slate,  Green  Mountain  gneiss, 
and  gneiss  proper,  which  however  does  not   represent   the  order  of 
