600  PRE-CAMBRTAN    GEOLOGY   OF   NORTH   AMERICA. 
blendic  gneiss,  mica  schist,  gneiss  granite,  granite,  tourmaline  rock, 
coarsely  granular  saccharoidal  crystalline  limestone,  and  diorite. 
The  strata  are  in  an  almost  vertical  position. 
Leeds,15  in  1878,  describes  the  rocks  of  the  Adirondacks.  They  are 
found  to  be  stratified  rocks  which  belong  in  the  Xorian  system,  and 
are  composed  of  hypersthene,  diallage,  and  labradorite  with  menac- 
canite. 
Hunt,16  in  1883,  describes  coarsely  crystalline  limestones  in  the 
highly  inclined  Laurentian  gneisses  near  Port  Henry,  in  which  are 
inclosed  irregular  masses  and  layers  of  the  adjacent  gneiss.  Although 
regarded  by  Emmons  and  Mather  as  eruptive  and  by  another  eminent 
geologist  as  evidence  that  the  crystalline  limestone  unconformably 
overlies  the  gneiss,  it  is  believed  to  be  a  great  calcareous  vein  stone. 
The  Norian,  massive,  bedded,  labradoritic  rocks  are  well  displayed 
between  Westport  and  Port  Kent. 
Hall  (C.  E.),17  in  1885,  states  that  between  the  limestones  and  the 
magnetic  ore  series  or  lower  members  of  the  Laurentian  there  is  an 
undoubted  unconformity;  but  the  relations  of  the  Labrador  series 
to  the  limestone  are  not  clear.  In  ascending  order  are  the  Lower 
Laurentian,  or  magnetic  iron-ore  series;  the  Laurentian  sulphur  ore 
series;  the  limestones;  and  the  Labrador  series,  or  Upper  Laurentian, 
with  its  titanic  iron  ores.  The  relations  of  the  sulphur  ores  and  lime- 
stone series  are  still  undetermined.  Between  Fort  Ann  and  South 
Bay,  along  the  east  side  of  the  valley,  the  Silurian  limestones  lie 
against  and  apparently  dip  under  the  crystalline  rocks  of  the  Lauren- 
tian. The  Potsdam  sandstone,  resting  on  the  crystalline  rocks  of 
the  valley,  dips  to  the  east  under  the  Silurian  limestones. 
Britton,18  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  north  end  of  the  Lower  Saranac  Lake.  Norite  occurs  at 
Miller's  hotel,  about  a  mile  distant. 
Julien,19  in  1886,  states  that  the  borders  of  the  Adirondack  region 
consist  very  largely  of  thinly  bedded  gneisses,  especially  toward  the 
east. 
Pumpelly,  Walcott,  and  Van  Hise,20  in  1890,  under  the  guidance 
of  Walcott,  who  had  seen  most  of  the  localities  before,  examined 
various  districts  on  the  eastern  side  of  the  Adirondacks  from  Fort 
Ann,  south  of  Whitehall,  to  Westport.  The  peripheral  area  of  this 
part  of  the  Adirondacks  was  found  to  be  a  great  series  of  laminated 
rocks,  consisting  for  the  most  part  of  white  and  red,  regularly  lami- 
nated gneisses,  very  frequently  garnetiferous,  and  in  lesser  quantity 
of  garnetiferous  quartz  schist,  crystalline  limestone,  graphitic  gneiss, 
and  beds  of  magnetic  iron  ore,  dipping  as  a  whole  at  a  rather  flat 
angle  toward  the  east  and  southeast.    The  garnetiferous  quartz  schists 
