378  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [huli  .  so. 
down  by  Werner — clay- slate,  including  beds  of  trap;  mica-slate; 
gneiss.  Granite  crowns  the  whole,  although  it  occupies  but  a  small 
extent  compared  with  the  gneiss  and  slaty  rocks.  As  a  whole  the 
slates  occupy  the  lowest  and  the  granites  and  gneiss  the  highest  situa- 
tions. 
Mather,75  in  1832,  describes  the  succession  from  Killingly  to  Haddam 
as  consisting  of  gneiss,  granite,  syenite,  mica-slate,  hornblende-slate, 
granular  quartz  rock,  the  latter  underlying  thick  strata  of  gneiss. 
Powerful  veins  of  granite  traverse  the  gneiss,  while  in  other  places  the 
granite  is  found  both  in  veins  and  beds. 
Mather,76  in  1834,  divides  the  rocks  of  Connecticut  into  gneiss, 
hornblende- slate,  mica-slate,  granular  feldspar,  granular  quartz,  syen- 
ite, granite,  limestone.  The  strata  generally  show  themselves  in  long 
belts  extending  unbroken  to  a  considerable  distance.  The  thickness 
of  the  gneiss  at  one  locality  is  not  less  than  1.0,000  feet.  At  Lebanon 
the  gneiss  surrounding  a  great  part  of  the  syenite  dips  so  as  apparently 
to  pass  under  the  latter  rock.  The  syenite  is  not  stratified,  but  the 
granite  is  partly  so.  The  limestone  occurs  in  beds  from  1  to  20  feet 
thick,  embraced  in  the  contorted  gneiss  in  the  northwest  part  of  Ston- 
ington. 
Percival,77  in  1842,  divides  the  consolidated  rocks  of  Connecticut 
into  Primary,  Secondary,  and  Trap  rocks.  The  Primary  rocks  occupy 
the  greater  portion  of  the  surface  of  the  state  and  are  divided  into  the 
western  and  eastern  sections.  These  primary  rocks  are  formed  en- 
tirely of  original  materials,  exhibiting  no  appearance  of  any  fragment 
or  remains  of  any  anterior  formation.  The  trap  rocks  are  chiefly  con- 
nected with  the  secondary  rocks,  although  they  also  cut  the  Primary. 
These  are  regarded  as  intrusive  and  igneous.  In  describing  the  Pri- 
mary locks  the  term  parallel  is  preferred  to  stratified,  as  simply 
expressing  the  fact  as  to  the  arrangement  of  the  minerals  without  im- 
plying any  opinion  as  to  the  mode  of  formation.  The  western  primary 
system,  which  extends  on  the  west  and  southwest  into  the  state  of  New 
York  and  on  the  north  into  Massachusetts,  is  divided  into  a  large 
number  of  local  formations,  including  the  classes,  mica-slate,  argillite, 
granite,  calciferous  schist,  limestone.  The  formations  as  a  whole  pre- 
sent a  series  of  parallel  ridges  which  have  a  general  curvature  with  a 
convexity  toward  the  east.  The  central  portion  exhibits  a  series  of 
granitic  and  micaceous  alternations,  which  appear  partly  as  elongated 
bands  and  partly  as  isolated  nuclei,  generally  granitic,  around  which 
the  more  micaceous  formations  are  concentrically  arranged.  The  east- 
ern primary  system  is  divided  into  several  main  groups,  the  rocks  here 
including  gneiss,  micaceous  and  chloritic  rocks.  In  one  of  the  granitic 
formations  the  arrangement  consists  of  a  central  nucleus  of  granite- 
gneiss  surrounded  by  narrow  concentric  ranges  of  various  characters. 
The  zone  immediately  adjoining  the  granitic  nucleus  is  characterized 
by  the  almost  constant  presence  of  anthophyllite.     From  the  coarsest 
