smith.]  CEMENT   RESOURCES    OF    ALABAMA.  437 
viz,  about  10  or  15  feet  below  the  hard  ledges  of  pure  limestone  form- 
ing the  base  of  the  middle  (Demopolis)  division  the  dark-colored  argil- 
laceous rock  shows  a  tendency  to  flake  off  and  weather  into  caves, 
sometimes  several  feet  deep  and  20  feet  or  more  in  length.  These  holes 
extend  in  some  places  for  great  distances  along  the  bluffs,  as  on  Ala- 
bama River  just  above  Kings  Landing,  on  the  Tombigbee  below  Roes 
Bluff,  and  at  Jordans  Ferry.  The  outcrop  of  the  argillaceous  rocks  of 
this  division  gives  rise  to  black  prairie  soils,  in  which  beds  of  fossil 
shells,  mainly  0}^sters,  are  common. 
It  has  been  suggested  that  the  argillaceous  rocks  of  this  and  the 
uppermost  division  could  be  mixed  with  the  purer  limestone  of  the 
middle  division  in  such  proportions  as  to  constitute  a  good  cement 
mixture.  In  this  case  it  would  be  easy  to  select  localities  near  the 
junction  of  the  two  divisions  where  both  varieties  of  the  rock  could  be 
quarried,  if  not  in  the  same  pits,  at  least  in  pits  closely  adjacent.  This 
would  do  away  with  the  need  of  adding  other  clay  to  the  limestone. 
Localities  of  this  sort  would  be  found  along  the  borders  north  and 
south  of  the  belt  of  outcrop  of  the  white  Demopolis  rock. 
Details  of  localities. — The  general  characters  of  the  rocks  of  this 
formation  have  been  mentioned  above,  and  it  remains  to  give  details 
of  the  special  localities  examined,  together  with  analyses  of  the  lime- 
stones collected.  In  making  the  collections  material  from  the  middle 
or  Demopolis  division  of  the  formation  has  been  generally  chosen, 
since  most  of  the  limestone  of  the  formation  which  contains  75  per 
cent  or  more  of  carbonate  of  lime  is  to  be  found  in  this  division. 
At  the  same  time  specimens  of  the  more  argillaceous  material,  espe- 
cially of  the  lower  (Selma)  division  of  the  formation,  have  been  taken 
for  comparison  and  analysis,  Avith  a  view  to  ascertaining  whether  or 
not  it  will  be  practicable  to  provide  a  cement  mixture  by  using  the 
proper  proportions  of  the  purer  and  more  argillaceous  materials. 
Inasmuch  as  suitable  material  for  cement  manufacture  can  be  had  in 
practically  unlimited  quantity  all  along  the  outcrop  of  the  purer  lime- 
stone of  the  Demopolis  division,  the  location  of  the  plants  for  the 
manufacture  of  this  product  will  be  determined  by  other  considerations 
than  the  quality  of  the  rock.  Chief  among  these  will  be  facilities  for 
transportation,  cheapness  of  fuel,  and  cost  of  labor  and  abundance  of 
it  at  command. 
Examinations  have  consequently  been  confined  to  those  localities 
which  appear  to  be  most  favorably  situated  in  these  respects,  and 
especially  to  those  localities  which  are  on  navigable  streams  or  on 
north-south  railroad  lines,  or  on  both. 
The  first  place  considered  on  Tombigbee  River  is  Gainesville,  where 
the  limestone  appears  on  the  river  bluff  in  a  thickness  of  30  to  40  feet, 
beneath  a  heavy  covering  of  Lafayette  sands  and  pebbles.  A  short 
distance  inland  from  the  river,  however,  the  rock  appears  at  the  surface 
