ADIRONDACK    MOUNTAINS.  615 
now  possible.  The  gneisses  are  the  most  widespread  of  the  pre- 
Cambrian  rocks.  The  schists  and  quartzites,  as  seen  in  place,  arc 
found  to  be  cut  and  veined  in  every  direction  by  a  granite  gneiss,  and 
fragments  of  schist  and  quartzite  in  every  way  identical  with  the 
main  mass  are  scattered  through  the  granite  gneiss  and  are  them- 
selves penetrated  by  networks  of  dikes  running  in  from  the  latter. 
The  granite  is  also  intrusive  into  the  sedimentary  series,  but  its  rela- 
tions to  the  gneisses  are  doubtful,  although  it  has  a  close  genetic  rela- 
tionship with  them  as  a  whole. 
Kemp  and  Hill,54  in  1901,  report  progress  of  work  on  the  pre- 
Cambrian  formations  in  parts  of  Warren,  Saratoga,  Fulton,  and 
Montgomery  counties. 
Cr suing/'5  in  1901,  maps  and  describes  the  geology  of  Rand  Hill 
and  vicinity,  Clinton  County.  The  basal  rocks  are  gneisses  of  the 
Dannemora  formation  occurring  in  the  southwestern  portion  of  the 
area.  These  are  of  doubtful  origin,  but  probably  mostly  igneous. 
Intrusive  in  them  are  undoubted  igneous  rocks — gabbro,  anorthosite 
gabbro,  augite  syenite,  syenite,  and  dikes  of  syenite  and  diabase. 
Cushing,50  in  1902,  describes  a  pre-Cambrian  outlier  at  Little  Falls, 
in  Herkimer  County,  N.  Y.,  and  points  of  difference  from  the  syenite 
of  the  Adirondacks. 
Cushing,57  in  1902,  discusses  recent  geological  work  in  Franklin 
and  St.  Lawrence  counties,  N.  Y.,  and  concludes  that: 
1.  The  Adirondack  anorthosite  is  cut  intrusively  by  an  augite  sye- 
nite, which  is  therefore  younger. 
2.  While  the  larger  part  of  the  augite  syenite  of  the  Adirondacks 
is  in  such  situation  with  respect  to  the  anorthosite  as  to  render  im- 
possible any  determinations  of  relative  age.  its  general  character  is 
so  uniform  throughout  that  it  is  exceedingly  probable  that  it  is  all 
of  the  same  approximate  age  and  consists  of  intrusions  from  the 
same   source. 
3.  At  their  borders  these  syenites  pass  over  into  granites,  part  of 
which  at  least  cut  the  syenite  eruptively  and  are  therefore  younger. 
4.  The  syenite  grades  into  granite  on  the  one  hand  and  into  gabbro 
cliorite  on  the  other,  and  apparently  into  anorthosite  as  well. 
5.  The  three  together— anorthosite,  syenite,  and  granite — form  a 
great  eruptive  complex  in  the  heart  of  the  Adirondack'  region,  and 
::!1  are  younger  than  the  (in  part  at  least)  sedimentary  Grenville 
rocks. 
Cushing,58  in  1905,  maps  and  describes  the  Little  Falls  quadrangle, 
bordering  the  Adirondacks  and  the  Mohawk  Valley.  Pre-Cambrian 
rocks  occupy  the  northeastern  portion  of  the  quadrangle,  forming  ;i 
part  of  the  main  Adirondack  area,  and  are  found  also  at  three  dis- 
connected localities  to  the  southwest  Little  Falls,  Middleville,  and 
a  spot  :M  mill's  northeast  of  Little  Falls. 
