392  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull. 86. 
toga  county,  as  in  the  other  district,  most  attention  is  given  to  the 
limestones.  At  Warwick  the  white  limestone  is  rarely  stratified  or 
shows  any  distinct  traces  of  stratification,  but  in  some  places  it  exhib- 
its a  regular  gradation  into  the  gray  and  blue  limestone,  which  is  fos- 
siliferous  in  some  places  and  oolitic  in  others,  and  stratified  in  nearly 
horizontal  strata.  The  limestones  of  the  Highlands  of  Orange,  Kock- 
land,and  Putnam  counties  are  in  long  narrow  belts  associated  with  the 
granite,  syenite,  hornblende  and  augite  rocks  and  some  anomalous  ag- 
gregates. The  limestones  of  Washington  county  are  coarse,  white  and 
crystalline.  They  contain  various  imbedded  crystalline  and  amorphous 
minerals,  the  most  common  of  which  are  plumbago,  augite,  and  horn- 
blende. Hornblende,  coccolite,  and  plumbago  are  the  most  constant 
associates.  Scapolite  is  not  uncommon.  In  some  places  the  limestone 
is  so  much  intermixed  with  other  materials  found  in  the  gneissoid  and 
granitic  rocks,  that  without  close  examination  it  would  not  be  sus- 
pected as  a  limestone.  Quartz  is  frequently  found  in  it,  transparent  or 
translucent,  with  irregular,  rounded  forms,  as  if  it  had  been  partially 
melted.  Many  localities  that  I  have  visited  show  that  it  has  been  soft- 
ened, if  not  melted.  The  similarity  of  the  crystalline  limestones  of  the 
northern  counties  to  the  crystalline  phases  of  those  at  Warwick  which 
grade  unmistakably  into  fossiliferous  forms  leads  to  the  conclusion  that 
they  are  all  really  the  same  rock.  The  limonitic  and  hematitic  ores  are 
confined  to  the  valleys  of  the  Taconic  and  metamorphic  rocks  and  are 
usually  associated  with  talcy  slate  on  one  side  and  limestone  on  the 
other. 
Under  Primary  rocks  are  included  those  usually  called  by  that  name 
and  those  not  yet  described  as  Taconic  or  metamorphic,  though  some 
of  them  are  probably  of  the  same  age  as  the  metamorphic  rocks.  This 
is  particularly  the  case  with  the  plutonic  rocks,  as  granites,  syenites, 
hornblende  rocks,  some  of  the  trappean  rocks,  and  the  metalliferous 
beds  and  veins  which  have  intruded  themselves  among  and  altered 
the  adjacent  rocks.  The  hornblendic  gneiss,  micaceous  gneiss,  and 
mica-slate  may  perhaps  be  referred  to  the  same  period.  The  primary 
rocks  in  the  different  districts  are  very  similar.  They  include  granite, 
syenite,  gneiss,  mica-slate,  augite-rock,  greenstone,  hornblende  rocks, 
quartz  rock,  talcose  slate,  limestone,  serpentine,  and  steatite,  although 
the  last  five  have  been  already  included  among  the  metamorphic  rocks. 
In  Eockland  and  Orange  counties  the  strata  dip  to  the  southeast  at 
angles  from  50°  to  90°,  but  there  are  localities  where  the  strike  and  dip 
are  transverse  to  the  general  directions.  Granite  veins  are  very  nu- 
merous in  the  granitic  gneiss ;  the  greenstones  include  basaltic  green- 
stone or  trap,  granular  greenstone,  and  primitive  greenstone.  Asso- 
ciated with  the  primary  rocks  is  magnetic  oxide  of  iron,  confined  to  the 
southern  counties  of  the  Highlands  and  forming  masses  in  gneiss  and 
hornblendic  gneiss  rocks  which  might  be  called  beds,  but  which  are 
thought  to  be  veins.     Their  course  is  parallel  to  the  layers  of  rock,  but 
