VAN  RISE.] 
EASTERN  UNITED  STATES.  357 
tains,  is  unknown.  No  examples  have  been  found  of  decided  pebbles 
in  a  gneiss. 
At  Whately,  Massachusetts,  on  Aseutney,  and  at  Barnet  and  (Iran by, 
Vermont,  are  conglomerates  which  have  as  a  matrix  granite  and  por- 
phyry. The  granite  sometimes  passes  into  syenite.  At  Aseutney  the 
syenite  abounds  in  black  rounded  masses  which  are  for  the  most  part 
crystalline  hornblende  and  feldspar,  and  are  probably  transmuted  peb- 
bles. At  Granbythe  pebbles,  manifestly  rounded,  are  either  mica  schist 
or  white  almost  hyaline  quartz,  just  such  as  form  the  pebbles  in  the 
conglomerates  at  Wall  in  "ford  and  Plymouth,  and  the  base  is  a  fine- 
grained syenite,  passing  sometimes  almost  into  mica-schist.  A  peb- 
ble of  hornblende-schist  is  also  sometimes  seen.  In  bowlders  of  this  con- 
glomerate found  at  Northampton,  Massachusetts,  and  probably  derived 
from  Whately,  the  most  abundant  pebbles  are  those  of  the  brown  sand- 
stone, considerably  metamorphosed  and  flattened.  Those  of  horn- 
blende schist  art  common.  Sometimes  they  are  merely  crystalline  horn- 
blende, not  foliated  generally,  however,  but  mixed  with  some  feldspar, 
and  they  may  become  syenite,  and  are  frequently  pOrphyritic  by  dis- 
tinct crystals  of  feldspar.  The  cement  is  syenite,  often  more  horn- 
blendic  than  usual.  When  the  pebbles  are  highly  crystallized  they 
become  so  incorporated  with  the  matrix  that  it  is  difficult  to  separate 
them  with  a  smooth  surface,  and  if  we  are  not  mistaken  they  pass  in- 
sensibly into  those  rounded  nodules,  chiefly  hornblendic,  so  common  in 
syenite,  especially  that  of  Aseutney.  These  occurrences  are  regarded 
as  proof  that  the  completely  crystalline  granular  matrix  is  a  metamor- 
phfc  rock. 
The  pre-Potsdam  rocks  of  Vermont  are  called  Laurentianor  Hypozoic, 
although  it  does  not  follow  that  they  are  not  equivalent  with  the  fossil- 
iferous  series  elsewhere.  It  is  only  believed  that  if  fossils  once  existed 
in  them  they  have  been  obliterated.  Of  the  Hypozoic  rocks,  Vermont 
contains,  so  far  as  known,  only  a  small  belt,  which  is  the  eastern  edge 
of  an  immense  development  of  the  same  in  New  York.  These  are  re- 
ferred here  because  there  seems  to  be  a  discordance  in  the  stratification 
between  these  rocks  and  the  Lower  Silurian,  to  which  they  are  adjacent. 
The  oldest  of  the  Paleozoic  series  lies  directly  upon  the  Hypozoic  at  least 
at  one  point.  As  we  approach  the  Green  mountains,  metamorphism 
has  so  nearly  destroyed  the  fossils  that  the  identification  of  the  strata 
becomes  extremely  problematical,  until  at  length  the  clue  is  lost  entirely 
and  the  age  of  the  formations  can  only  be  conjectured;  hence  they  are 
distinguished  mainly  by  lithological  grounds  and  are  grouped  into  a 
third  class,  Azoic  rocks.  Probably  most  of  the  Azoic  rocks  of  Vermont 
will  be  found  to  be  inore  recent  than  the  Lauren tian  of  Logan.  The 
fossiliferous  rocks  are  sometimes  found  under  those  that  are  more  crys- 
talline and  uon  fossil  if  erons,  and  these  cases  are  thought  to  be  the  result 
of  inversions.  Certain  great  thicknesses  of  schists  of  uniform  character 
are  regarded  as  folded  several  times  so  as  to  be  vertical,  because  other- 
