NEW   ENGLAND.  579 
limestones,  as  chondrodite,  wernerite,  dark  pyroxene,  and  hornblende; 
and  coarsely  crystallized  graphite;  also  considerable  beds  of  pyrrho- 
tite,  magnetite,  and  graphite. 
Because  of  the  presence  of  the  heavy  \n^\>  of  limestones,  which  were 
probably  derived  from  shells  and  corals,  we  may  assume  that  the 
whole  series,  except  the  hornblende  gneiss  of  East  Lee,  was  of  sedi- 
mentary origin,  but  we  know  nothing  of  the  limits  of  the  sea  in  which 
they  were  spread.  These  rocks  are  overlain  by  the  Cambrian  Beckei 
gneiss  and  Cheshire  quartzite.  As  shown  by  the  basal  conglomerate 
at  the  Dalton  Club  House,  these  rocks  rest  unconformably  upon  the 
Algonkian. 
Emerson,68  in  1895,  describes  the  geology  of  Old  Hampshire  County 
in  Massachusetts,  which  includes  the  present  counties  of  Franklin, 
Hampshire,  and  Hampden.  On  the  western  Border  of  the  Green 
Mountain  area,  as  it  crosses  Massachusetts  and  overlooking  the  Hous- 
atonic  Valley,  is  a  series  of  pre-Cambrian  outcrops,  which  are  the 
oldest  rocks  of  the  State  and  the  substratum  on  which  the  others  rest. 
They  consist  of  coarse  gneisses,  especially  characterized  by  blue  quartz 
and  allanite,  coarse  porphyritic  structure,  and  stretching;  and  great 
beds  of  highly  crystalline  limestone,  containing  chondrodite.  coccolite, 
titanite,  phlogopite,  and .  wernerite.  The  most  important  of  these 
limestone  beds  are  those  of  the  Hoosac,  the  Hinsdale,  and  the  Tyring- 
ham  areas.  The  limestone  beds  connected  with  the  two  latter  have 
caused  the  two  most  important  passes  through  the  range — the  West- 
field  Valley  and  the  East  Lee-Farmington  V alley. 
On  the  pre-Cambrian  rocks  rest  the  Becket  conglomerate  gneisses, 
of  Cambrian  age,  and  above  them  a  great  series  of  sericite  schists  (the 
Hoosac  schists,  Rowe  schists,  Chester  amphibolite,  and  Hawley 
schists),  which  are  about  contemporaneous  with  the  Stockbridge  lime- 
stone of  the  Housatonic  Valley. 
Emerson,09  in  1898,  describes  the  Algonkian  rocks  occurring  in  the 
southwest  corner  of  the  Holyoke  quadrangle,  Massachusetts,  and  in 
the  area  to  the  west.  These  are  gneisses  and  limestones  making  up  a 
scries  called  the  Washington  gneiss.  They  are  of  sedimentary  origin, 
with  the  possible  exception  of  the  hornblende  gneiss  of  East  Lee. 
In  general  in  western  Massachusetts  the  Washington  gneiss  appears 
in  oval  areas  surrounded  by  younger  strata,  the  line  of  these  oVals 
extending  south  from  Hoosac  Tunnel  along  the  crest  of  the  Green 
Mountain  plateau.  The  gneiss  enters  the  Holyoke  quadrangle  at  the 
southwest  corner  and  runs  up  across  the  town  of  Tolland,  narrowing 
to  a  point  near  Black  Pond. 
Hobbs,70  in  1906,  summarizes  the  geology  of  southwestern  Massa- 
chusetts and  western  Connecticut.  There  arc  peculiar  difficulties  in 
discriminating  the  pre-Cambrian  from  the  Paleozoic  which  do  not 
exist  farther  we>t.  In  the  western  area,  the  knowledge  of  which 
is  summarized  by  Smith,  near  the  base  of  the  Paleozoic  there  is  a 
