396  PRE-CAMBRIAN   ROCKS    OF   NORTH   AMERICA.  m        [bull. 86. 
Hall  (Ghas.  E.),120  in  1885,  states  that  between  the  limestones  and 
the  magnetic  ore  series  or  lower  members  of  the  Lanrentian  there 
is  an  undoubted  unconformity;  but  the  relations  of  the  Labrador  series 
to  the  limestone  are  not  clear.  In  ascending  order  are  the  Lower  Lan- 
rentian or  Magnetic  Iron  Ore  series;  the  Lanrentian  Sulphur  Ore  se- 
ries; the  limestones  and  the  Labrador  series,  or  Upper  Lanrentian  with 
its  Titanic  Iron  Ores.  The  relations  of  the  sulphur  ores  and  limestone 
series  are  still  undetermined.  Between  fort  Ann  and  South  bay,  along 
the  east  side  of  the  valley,  the  Silurian  limestones  lie  against  and  ap- 
parently dip  under  the  crystalline  rocks  of  the  Lanrentian.  The  Pots- 
dam sandstone,  resting  on  the  crystalline  rocks  of  the  valley,  dips  to 
the  eastward  under  the  Silurian  limestones. 
Britton,121  in  1886,  states  that  a  schistose  series  of  crystalline  rocks 
occurs  in  the  Adirondacks.  It  consists  of  schistose  gneiss,  mica-schist, 
and  hornblende-schist,  and  occurs  north  of  Harrietstown  and  near  the 
northern  end  of  the  Lower  Saranac  lake.  Norite  occurs  at  Miller's 
hotel,  about  a  mile  distant. 
Julien,122  in  1886,  states  that  the  borders  of  the  Adirondack  region 
consist  very  largely  of  thinly  bedded  gneisses,  especially  to  the  east- 
ward. 
Smock,123  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  resemble  closely  those 
of  the  Highlands  of  the  Hudson.  The  rocks  of  the  East  mountain  com- 
prise  gneiss,  granite,  granulite,  quartz-syenite,  syenite- gneiss,  and  mica- 
schist  chiefly.  Between  the  quartzite  and  the  gneiss,  when  they  are 
seen  close  to  one  another,  is  a  want  of  conformability .  The  more  common 
of  the  rocks  of  the  Highlands  of  the  Hudson  are  gneiss,  syenite-gneiss, 
granite,  quartz-syenite,  granulite,  and  hornblende-schist.  The  Pough- 
quag-Fishkill  quartzite  is  found  to  rest  unconformably  upon  the  High- 
land gneisses,  the  discordance  being  best  seen  on  the  New  York  and 
New  England  Bailroad,  1  mile  west  of  West  Pawling  railroad  station. 
Here  the  quartzite  has  a  dip  of  15°  or  20°,  while  the  gneiss,  but  300  feet 
distant,  has  an  almost  vertical  inclination.  Belonging  with  the  Ar- 
chean  gneisses  are  limestones,  among  which  is  that  at  Sprout  brook. 
On  the  eastern  side  of  the  Highlands  the  Archean  border  has  the  mi- 
caceous, schistose  rocks  and  the  quartzites  resting  upon  it.  These 
relations  are  particularly  well  shown  at  Towner's  station.  Near  here 
the  limestones  and  schists  in  a  syncline  rest  unconformably  upon  the 
granulitic  gneiss.  Provisionally  the  rocks  of  the  Highlands  are  re- 
ferred to  the  Archean.  They  may  be  all  Lauren tian  also,  but  the  Huron- 
ian  has  not  been  identified.  In  Westchester  county  is  a  great  variety 
of  crystalline  rocks.  To  these  is  applied  the  name  Manhattan  gneiss, 
proposed  by  Hall.    These  rocks  are  less  massive  than  those  of  the 
