308  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
Pumpelly,  Walcott,  and  Yan  Hise,129  in  1890,  under  the  guid- 
ance 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  tor  the  most  part  of  white  and  red,  regularly  laminated 
gneisses,  very  frequently  garnetiferous,  and  in  lesser  quantity  of  gar- 
netiferous  quartz-schist,  crystalline  limestone,  graphitic  gneiss,  and 
beds  of  magnetic  iron  ore,  dipping  as  a  whole  at  rather  a  flat  angle 
toward  the  east  and  southeast.  The  garnetiferous  quartz-schists  were 
found  in  rather  persistent  beds.  A  graphite  mine  in  the  neighborhood  of 
Hague  is  a  layer  of  very  graphitic  gneiss,  comparable,  as  said  by  Wal- 
cott,  to  a  coal  seam  in  an  ordinary  bedded  succession.  Scales  of 
graphite  are  uniformly  disseminated  through  the  coarsely  crystalline 
limestone,  the  amount  often  being  very  considerable.  Below  the 
crystalline  limestone  is  a  coarse  black  hornblendic  gneiss,  the  contacts 
between  it  and  the  limestone  being  of  a  most  extraordinary  character. 
The  plane  between  them  is  one  of  great  irregularity.  In  the  limestone 
are  contained  numerous  fragments,  and  even  great  bowlders  of  the 
gneiss,  and  also  for  a  distance  of  some  feet  away  from  the  contact  are 
numerous  crystals  of  feldspar.  The  appearance  is  such  as  to  suggest 
very  strongly  that  here  is  an  unconformable  contact,  the  limestone 
being  deposited  along  an  encroaching  shore  line.  The  phenomena  are, 
however,  probably  due  to  the  breaking  up  of  layers  of  gneiss  and  veins  of 
pigmatite  by  powerful  dynamic  movements.  In  passing  from  West- 
port  within  a  short  distance  appeared  coarse  gabbro,  which  continued 
as  far  as  the  region  was  penetrated,  near  to  mount  Marcy.  This  rock 
in  the  interior  is  generally  massive,  but  on  its  outer  border  grades  into 
a  regularly  laminated  rock,  resembling  in  exposure  very  closely  the 
laminated  gneisses.  The  whole  is,  however,  clearly  an  eruptive  rock. 
Granite  was  seen  locally  associated  with  the  gneisses. 
Williams  and  Yan  Hise,130  in  1890,  examined  the  western  side  of 
the  Adirondacks.  Just  as  on  its  eastern  side,  there  was  found  a  pe- 
ripheral succession  of  regularly  laminated  gneisses  and  crystalline  lime- 
stones of  great  "thickness.  The  latter  is  particularly  well  seen  in  the 
neighborhood  of  Gouverneur.  The  contacts  between  the  limestones 
and  lower  gneiss  were  found  to  be  almost  identical  with  those  on  the 
eastern  side  of  the  mountains,  but  the  appearance  here  strongly  sug- 
gests that  the  relations  have  been  produced  by  interior  movements  of 
the  rocks,  the  irregular  contact  surface  being  a  contorted  one  as  a  re- 
suit  of  folding,  and  the  contained  fragments  broken  off  and  included  in 
the  limestone  by  means  of  dynamic  action.  The  interior  of  the  Adiron- 
dacks was  here  found  to  consist  of  gabbro,  in  every  respect  like  that 
on  the  east  side  of  the  mountains. 
In  passing  inward  from  the  gneissic  series  this  is  first  found  in  small 
quantity,  then  appears  more  and  more  abundant,  until  finally  it  be. 
