ADIRONDACK    MOUNTAINS.  611 
others,  with  equal  certainty,  arc  altered  sediments.  But  by  far  the 
larger  part  of  the  gneisses  have  not  yet  received  careful  study.  The 
limestones  are  certainly  sedimentary.  Their  relations  to  the  gneisses 
are  in  doubt,  but  some  parts  of  the  gneisses  are  certainly  younger 
than  the  limestones,  and  this  may  be  true  of  all.  The  gabbro  breaks 
through  both  gneisses  and  limestones.  It  presents  two  phases — an 
anorthosite  and  a  gabbro  containing  abundant  pyroxene  and  other 
ferromagnesian  minerals.  In  places  also  in  the  western  Adirondacks 
the  granites  and  syenites  break  through  the  limestone. 
Gushing,45  in  1899,  describes  an  augite  syenite  gneiss  near  Loon 
Lake  in  the  Adirondacks.  It  is  nearly  related  to  the  anorthosites  in 
age,  inasmuch  as  it  is  intrusive  in  the  Grenville  series,  but  it  is  much 
older  than  the  pre-Potsdam  diabases  of  the  region.  A  study  of  the 
relations  of  the  syenites  and  anorthosites  indicates  that  the  syenites 
are  in  part  a  result  of  differentiation  in  the  anorthosite  magma  after 
reaching  its  place  of  final  cooling,  and  in  part  somewhat  later  in 
date.a 
Kemp  and  Newland,40  in  1899,  make  a  preliminary  report  on  the 
geology  of  Washington,  Warren,  and  parts  of  Essex  and  Hamilton 
counties,  N.  Y.     Some  of  the  points  particularly  noted  are: 
The  excessive  mashing  and  granulation  of  the  gneisses,  giving 
them  in  places  semblance  to  quartzite.  The  greenish  gneisses,  con- 
si  sling  in  largest  part  of  microperthite,  were  originally  eruptive 
rocks.  The  discovery  is  reported  of  quartzose  gneisses  or  foliated 
quartzites  which  are  certainly  metamorphosed  sediments.  They  form 
notable  areas  along  the  head  of  South  Bay,  Whitehall  Township. 
Their  presence  indicates  the  probable  presence  of  a  considerable 
series  of  clastic  sediments.  The  crystalline  limestones  themselves 
have  been  found  in  small  exposures  over  almost  all  of  Warren 
County,  and  generally  in  the  crystalline  belt  of  Washington.  They 
are  most  extensive  in  Newcomb  and  Minerva  townships  of  Essex,  and 
to  the  south  become  thinner  and  more  scattered.  So  far  as  Ave  have 
observed  they  are  less  common  in  eastern  Hamilton  County.  There 
is  evidence  to  show  that  stratigraphic  relations  can  be  proved  and 
that  anticlines  and  synclines  can  be  demonstrated. 
Dikes  of  basic  gabbro,  usually  of  moderate  width,  but  lithologic- 
ally  like  the  larger  masses  in  Essex  County,  have  been  met  over  a 
wide  area — in  fact,  in  almost  every  township  in  Warren,  but  the 
basaltic  traps  almost  disappear. 
Smyth,47  in  1899,  discusses  certain  features  of  recent  work  in  the 
western  Adirondack  region.  lie  concludes  that  the  rock  previously 
called  gabbro  by  Xason.  Van  Hise,  Williams,  and  himself,  south  of 
the  belt  of  limestone  in  the   Diana-Pitcairn  area   in   Lewis  and  Si. 
°The  anorthosites  are  ;i  pari  of  tin-  greal  urni>i>ro  mass  which  forms  the  core  of  die 
Adirondacks  intruding  pre-Cambrian  sedimentary  and  Igneous  gneissi 
