42(>  PRE-OAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.M. 
gradations  into  the  gneiss,  beds  of  the  two  sometimes  alternating,  and 
thelatter  also  passing  into  the  stratified  mica-slates.  Gneiss  also  passes 
into  the  stratified  mica-slate,  and  the  mica-slate  into  talcose  slate.  The 
graywacke  is  the  beginning  of  the  transition. 
Little,208  in  1875,  mentions  crystalline  rock,  presumably  primary, 
at  various  points. 
Campbell  (J.  L.)  and  Ruffner,  209  in  1883,  divide  the  Archean  upon 
chemical,  lithological,  and  structural  grounds  into  Laurentian  and 
Huronian.  In  the  metamorphosed  rocks  the  prevailing  dips  are  toward 
the  southeast.  It  is  believed  that  while  they  were  somewhat  plastic 
they  were  folded  and  overturned,  although  sometimes  left  in  a  vertical 
position,  and  not  infrequently  found  in  a  nearly  horizontal  position,  or 
s< unetimes  resting  in  arches  and  depressions.  In  the  Choccolocco  valley 
the  railroad  passes  abruptly  to  the  Lower  Silurian  rocks.  This  rela- 
tion between  the  Silurian  and  Archean  is  attributed  to  a  fault,  with  a 
downthrow  of  the  former. 
LITERATURE  OF  ALABAMA. 
Tijomey,210  in  1850,  places  the  granites,  gneisses,  and  associated 
crystalline  rocks  as  primary  and  metamorphic.  The  slates  sometimes 
carry  plumbago,  and  true  granite  is  found  only  at  Talladega. 
Tuomet,211  in  1858,  finds  in  various  sections  granite,  syenitic  gneiss, 
ordinary  gneiss,  hornblende- slate,  mica-slate,  talcose  slate,  and  soap- 
stone.  In  certain  localities  are  found  limestones,  and  also  occasionally 
3 nter stratified  quartz-rocks  occur.  Granite  is  found  about  Rockford 
in  large  masses. 
Smith,212  in  1875,  states  that  the  counties  of  Chilton,  Talladega,  Cal- 
houn, Cleburne,  Lee,  Tallapoosa,  and  Elmore  lie  partly,  and  Coosa, 
Clay,  Randolph,  and  Chambers  wholly,  within  the  Archean  region  of 
the  state.  On  account  of  the  absence  of  fossils,  it  is  difficult  to  deter- 
mine the  relative  ages  of  the  subdivisions  of  the  crystalline  rocks. 
Lithologically  they  are  classified  into  Laurentian,  Huronian,  and  White 
mountain  series,  following  Hunt's  characterization  of  these  terms.  The 
rocks  here  included  are  granite,  gneiss,  mica-schist,  mica-slate,  hydro- 
mica-slate,  clay-slate  or  argillite,  syenite,  syenitic  gneiss,  hornblen de- 
schist,  diorite,norite,  talcose  slate,  soapstone  or  steatite,  eblorite-schist, 
quartzite,  siliceous  slate,  itacolumite,  itabarite,  jasper,  crystalline  lime- 
stone, dolomite,  and  igneous  rocks.  Crystalline  limestone  occurs  in 
Chilton  county.  It  is  succeeded  in  apparent  conformity  by  semicrys- 
tallines  15,000  to  20,000  feet  in  thickness. 
Schmitz,213  in  1884,  describes  a  metamorphic  region  in  Alabama  as 
covering  the  whole  or  parts  of  counties  Chilton,  Coosa,  Talladega,  Cal- 
houn, Cleburne,  Lee,  Tallapoosa,  Elmore,  Clay,  Randolph,  and  Cham- 
bers, with  about  5,000  square  miles  of  area.  The  rocks  of  this  region 
are  partly  metamorphosed  Lower  Silurian  rocks  (Calciferous,  Potsdam, 
