smith.]  CEMENT    RESOUKCES    OF    ALABAMA.  429 
THE    CLAYS. 
The  most  important  clays  in  the  Paleozoic  region  occur  in  the  Coal 
Measures,  in  the  lower  Carboniferous,  and  in  the  lower  Silurian  and 
Cambrian  formations.  But,  inasmuch  as  a  later  formation — the  Tus- 
caloosa of  the  Cretaceous — borders  the  Paleozoic  on  the  west  and 
south,  and  as  it  contains  a  great  variety  as  well  as  abundance  of  clays, 
we  shall  include  it  here,  although  it  is  not  Paleozoic. 
Coal  Measures. — In  this  group  are  numerous  beds  of  shale  which 
have  been  utilized  in  the  manufacture  of  vitrified  brick  and  fire  brick, 
but  many  of  them  will  probably  be  adapted  to  cement  making.  A 
great  body  of  these  shales  occurs  in  connection  with  the  coal  seams 
of  the  Horse  Creek  or  Mary  Lee  group,  in  Jefferson  and  Walker 
counties,  and  in  position  where  they  are  conveniently  situated  with 
reference  to  limestone  and  coal  and  also  to  transportation  lines.  They 
are  therefore  well  worth  the  attention  of  those  contemplating  the  loca- 
tion of  cement  plants. 
On  the  property  of  Mr.  W.  H.  Graves,  near  North  Birmingham, 
overlying  the  coal  seam  mined  by  him,  there  are  two  beds  of  shale- 
one  yellowish,  the  other  gra}^.  These  two  shales  have  been  tested  and 
analyzed,  and  their  composition  is  shown  in  Nos.  107  and  108  of  the 
table. 
Similar  shales  are  used  also  at  Coaldale,  in  Jefferson  County,  and  at 
Pearce's  mill,  in  Marion.  Of  these  we  have  reports  of  physical  tests, 
but  no  analyses. 
So  also  most  of  the  coal  seams  mined  in  Alabama  rest  upon  clay 
beds  which  have  not  as  yet  been  specially  examined  as  to  their  fitness 
for  cement  making;  but,  in  vdew  of  the  proximity  of  the  coal  mines  to 
the  limestones,  it  might  be  worth  while  to  investigate  these  underckiys 
of  the  coal  seams. 
Lower  Carboniferous. — Associated  with  the  cherty  limestones  of  the 
lowermost  division  of  the  lower  Carboniferous  of  some  of  the  anticlinal 
valleys  are  beds  of  clay  of  excellent  quality,  much  of  it  being  of  the 
nature  of  china  clay. 
Probably  the  best  of  the  exposures  of  these  clays  are  to  be  seen  in 
Little  Wills  Valley,  between  Fort  Payne  and  the  Georgia  border,  and 
on  the  line  of  the  Alabama  Great  Southern  Railroad,  where  for  many 
years  quarries  have  been  in  operation  in  supplying  material  for  tile 
works  and  potteries.  The  clays  lie  near  the  base  of  the  formation, 
close  above  the  black  shale  of  the  Devonian,  and  average  about  40  feet 
in  thickness,  though  in  places  they  reach  200  feet.  The  clay  beds 
alternate  with  seams  of  chert  which  are  from  2  to  8  inches  in  thickness, 
while  the  clay  beds  vary  from  12  to  18  inches.  The  upper  half  of  the 
clav  is  more  gritty  than  the  lower  half,  which  often  contains  material 
