568  PRE-CAMBRIAIN    GEOLOGY   OF   NORTH   AMERICA. 
occurs  on  both  sides  of  the  Hoosac.  Argillaceous  slate  occurs  in  the 
valleys  connected  with  the  limestone. 
Dewey,38  in  1820,  finds  the  section  from  the  Taconic  Range  at 
Williamstown  to  the  city  of  Troy  to  consist  of  chlorite  slate,  gray- 
wacke,  and  argillaceous  slate,  this  being  the  order  of  succession.  The 
strata  all  incline  to  the  east  from  10°  to  40°,  the  general  inclination 
being  20°  or  25°. 
Hitchcock  (Edward),39  in  1823,  describes  granite  as  occurring  at 
many  localities  in  the  region  contiguous  to  Connecticut  River.  It 
sometimes  shows  a  tendency  to  stratification — at  Southampton  it 
occurs  in  beds  in  the  mica  slates  and  at  Bellows  Falls  it  grades  into 
mica  slate — and  frequently  veins  of  it  cut  the  strata.  These  veins 
divide  and  subdivide,  like  the  top  of  a  tree.  In  this  region  are  also 
found  gneisses,  hornblende  slate,  mica  slate,  talcose  slate,  chlorite  slate, 
syenite,  greenstone,  argillite,  and  limestone,  all  of  which  are  referred 
to  the  Primitive.  The  gneiss  is  the  most  abundant  rock,  and  often 
alternates  with  mica  slate  and  passes  into  it.  The  dips  of  the  layers 
are  from  20°  E.  to  90°.  At  Hatfield,  by  following  up  the  syenitic 
ridge,  a  rock  is  found  which  contains  numerous  embedded  masses  of 
other  Primitive  rocks;  these  embedded  fragments  are  almost  uni- 
formly rounded,  and  in  many  places  are  so  numerous  as  to  make  the 
rock  appear  like  a  real  Secondary  conglomerate.  Thus  Ave  have  a 
really  conglomeratic  syenite.  The  Primitive  greenstones  are  distin- 
guished from  the  Secondary  because  the  latter  are  more  coarse  and 
crystalline. 
Dewey,40  in  1824,  in  a  sketch  of  the  geology  of  western  Massachu- 
setts, divides  the  principal  rocks  into  granite,  gneiss,  mica  slate, 
granular  limestone,  argillaceous  slate,  quartz  rock,  Transition  lime- 
stone, and  graywacke,  mica  slate  being  the  most  abundant  rock.  The 
granite  is  not  stratified,  and  must  be  considered  as  beds  or  veins  rather 
than  a  continuous  rock  like  the  mica  slate.  In  the  town  of  Windsor 
is  a  conglomeratic  mica  slate. 
Nash,41  in  1827,  finds  the  rocks  of  Hampshire  County  to  include 
granite,  mica  slate,  micaceous  limestone,  hornblende  rock,  talcose 
slate,  Old  Red  sandstone,  etc.  The  limestone  often  alternates  with 
mica  slate,  and  frequently  passes  into  it  by  insensible  gradations.  It 
is  in  many  places  garnetiferous.  The  granite  veins  are  of  all  sizes 
up  to  3  or  4  feet,  cut  the  rocks  in  every  possible  direction,  and  intrude 
granite  as  well  as  the  mica  slate. 
Hitchcock  (Edward)  ,42  in  1833,  divides  the  rocks  of  Massachusetts 
into  stratified  and  unstratified.  Below  the  New  Red  sandstone  in  the 
former  are  graywacke,  argillaceous  slate,  limestone,  scapolite  rock, 
quartz  rock,  mica  slate,  talcose  slate,  serpentine,  hornblende  slate,  and 
gneiss.  The  unstratified  rocks  are  greenstone,  porphyry,  syenite,  and 
trap,  each  of  which  is  discussed.     Among  the  agents  which  have  con- 
