628  PRE-CAMBR1AN    GEOLOGY    OF    NORTH    AMERICA. 
Dana,75  in  1880  and  1881,  considers  the  geological  relations  of  the 
limestone  belts  of  Westchester  County.  The  rocks  here  found  are 
divided  into  metamorphic  rocks,  not  calcareous;  calcareous  rocks  or 
limestones;  serpentines  and  other  hydrous  minerals;  augitic  and 
hornblendic  rocks  not  above  included.  Of  metamorphic  rocks  the 
prevalent  kinds  are  micaceous  gneiss,  mica  schist,  ordinary  gneiss, 
and  granitoid  gneiss.  The  calcareous  rocks  are  white  and  coarsely 
crystalline,  although  locally  they  are  feebly  crystalline.  The  horn- 
blendic and  augitic  rocks  constituting  the  Cortlandt  series  include 
soda  granite,  norite,  augite  norite,  diorite,  hornblendite,  pyroxenite, 
and  chrysolitic  kinds.  These  rocks  are  held  to  be  conformable  with  a 
part  of  the  adjoining  schists  and  limestone,  which  are  of  metamorphic 
origin,  although  they  may  have  been  in  a  former  state  of  fusion  or 
plasticity.  The  limestones  and  adjoining  schists  are  found  to  be  one 
in  series  and  system  of  disturbance,  are  considered  a  part  of  the 
Green  Mountain  system,  younger  than  the  Highland  Archean,  and 
probably  Lower  Silurian.  At  Annsville  there  is  evidence  of  uncon- 
formity between  the  Archean  and  this  series.  The  limestone  here 
lies  unconformably  against  the  hornblendic  contorted  Archean  gneiss. 
A  similar  unconformity  exists  half  a  mile  northeast,  although  the 
upturning  of  the  limestone  and  its  associated  schist  has  usually  placed 
them  in  near  conformity  to  the  strike  of  the  Archean  rocks. 
Dana,70  in  1882,  ascertained  that  a  large  part  of  the  rocks  referred 
to  the  Taconic  Range  are  shown  by  their  fossiliferous  contents  to  be 
Silurian  and  the  equivalent  of  the  Hudson  River  group,  although  it 
is  not  asserted  that  all  of  the  hydromica  schists  belong  here.  A 
part  are  Primordial. 
Newtberry,77  in  1882,  states  that  the  mottled  serpentine  of  New 
York  Island  is  like  the  Moriah  marble  of  the  Adirondack  region, 
which  affords  strong  indication  of  a  Laurentian  age  of  the  New  York 
Island  and  Staten  Island  rocks. 
Dana,78  in  1884,  finds  that  the  hornblendic  and  augitic  rocks  of  the 
Cortlandt  series  have  such  relations  to  the  schists  as  to  show  that  they 
are  of  igneous  origin,  the  eruptions  taking  place  subsequent  to  the  era 
of  the  limestone,  mica  schist,  and  soda  granite. 
Smock,79  in  1886,  describes  the  crystalline  rocks  of  Dutchess,  Put- 
nam, and  Westchester  counties.  This  district  is  divided  into  four 
belts:  Stissing  Mountain,  East  or  Dover  Mountain,  Highlands  of  the 
Hudson,  and  Westchester  County.  The.  prevailing  rocks  of  Stissing 
Mountain  are  gneisses,  granites,  granulite,  and  syenite,  which  resem- 
ble closely  those  of  the  Highlands  of  the  Hudson.  The  rocks  of  the 
East  Mountain  comprise  chiefly  gneiss,  granite,  granulite,  quartz 
syenite,  syenite  gneiss,  and  mica  schist.  Between  the  quartzite  and 
the  gneiss,  when  they  are  seen  close  to  each  other,  is  a  lack  of  con- 
formity.    The  more  common  of  the  rocks  of  the  Highlands  of  the 
