(.30  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1903.  [btjll.225. 
suitable  for  the  manufacture  of  the  finer  grades  of  porcelain  ware. 
Analyses  3-6  in  the  table  on  page  433  show  the  composition  of  several' 
varieties  of  clay  from  this  section. 
Lower  Silurian  and  Cambrian. — Associated  with  the  cherty  lime- 
stones and  brown  iron-ore  beds  of  the  formations  above  named — beds 
of  line  white  clay,  much  of  it  china  clay — are  not  uncommon.  Analysis 
7  of  the  tabic  shows  the  composition  of  a  white  clay  from  the  brown 
ore  hank  at  Rock  Run,  in  Cherokee  County,  where  the  clay  is  about  30 
feet  in  thickness.  Analyses  8  and  9  are  also  from  Rock  Run.  No.  10, 
from  near  Gadsden,  No.  11,  from  Blount  County,  and  No.  12,  from 
Oxanna,  in  Calhoun  County,  are  of  clays  which  seem  to  be  adapted  to 
cement  making.  While  no  great  number  of  the  clays  of  these  forma- 
tions have  been  analyzed,  they  are  known  to  be  widely  distributed  in 
Calhoun,  Talladega,  Jefferson,  Tuscaloosa,  and  other  counties  in  con- 
nection with  the  brown  ore  deposits. 
Cretaceous. — In  many  respects  the  most  important  formation  of 
Alabama,  in  respect  of  its  clays,  is  the  lowermost  division  of  the  Cre- 
taceous, which  has  been  called  the  Tuscaloosa,  and  which  is,  in  part  at 
least,  of  the  same  geologic  horizon  as  the  Raritan  cla}'  s  of  New  Jersey. 
The  prevailing  strata  of  this  formation  are  yellowish  and  grayish 
sands,  but  subordinated  to  them  are  great  lenses  of  massive  clay  vary- 
ing in  quality  from  almost  pure-white  burning  clay  to  dark-purple  and 
mottled  varieties  high  in  iron. 
The  formation  occupies  a  belt  of  country  extending  from  the  north- 
western corner  of  the  State  around  the  edges  of  the  Paleozoic  forma- 
tions to  the  Georgia  line  at  Columbus.  Its  greatest  width  is  at  the 
northwest  boundary  of  the  State,  where  it  covers  an  area  30  or  40 
miles  wide  in  Alabama  and  of  about  the  same  width  in  Mississippi. 
The  breadth  at  Wetumpka  and  thence  eastward  to  the  Georgia  line  is 
only  a  few  miles.  The  most  important  part  of  this  belt  is  where  it  is 
widest,  in  Elmore,  Bibb,  Tuscaloosa,  Pickens,  Fayette,  Marion,  Lamar, 
Franklin,  and  Colbert  counties,  and  the  deposits  are  traversed  by  the 
lines  of  the  Mobile  and  Ohio;  the  Alabama  Great  Southern;  the  Louis- 
ville and  Nashville;  the  Southern;  and  the  Kansas  City,  Memphis  and 
Birmingham  railroads;  as  well  as  by  the  Warrior  and  Tombigbee 
rivers. 
These  clays  have  been  described  in  some  detail.  Many  analyses  and 
physical  tests  have  been  presented  in  Bulletin  No.  6  of  the  Alabama 
Geological  Survey.  From  this  bulletin  have  been  selected  certain 
analyses  which  appear  to  indicate  the  fitness  of  the  clays  for  cement 
making. 
In  Elmore  County  in  the  vicinity  of  Coosada,  along  the  banks  of  the 
river,  about  Robinson  Springs,  Edge  wood,  and  Chalk  Bluff,  there  are 
many  occurrences  of  these  clays,  some  of   which  have  been  used  in 
