442  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
Gulf  formation,  which  very  generally  in  this  section  overlies  the  lime- 
stone. Sonic  analyses  of  the  last-named  clays  have  been  made  from 
material  occurring  near  St.  Stephens,  and  near  Manistee  Junction  on 
the  Repton  Branch  of  the  Louisville  and  Nashville  Railroad.  At  this 
last-named  locality  the  clay  is  present  in  sufficient  quantity  to  be  of 
value  if  the  composition  is  suitable. 
DETAILS    OF    LOCALITIES. 
St.  Stephens. — The  first  locality  to  be  considered  is  the  bluff  at 
Si.  Stephens,  a  section  of  which  has  been  given,  and  it  may  be  taken  as 
a  typical  section  of  the  formation  everywhere.  At  St.  Stephens  the 
whole  of  the  soft  orbitoidal  limestone  or  u  chimney  rock"  might  be. 
used,  as  the  composition  is  uniform  throughout.  The  overlying 
harder  limestone  has  almost  the  same  composition,  but  it  is  less  easily 
crushed  and  handled.  It  may  be  quarried  here  from  the  surface  down, 
as  it  is  covered  only  by  a  thin  layer  of  residual  clay.  The  characters 
of  the  limestone  and  of  the  clay  from  here  are  sufficiently  well  shown 
by  the  subjoined  anatyses  (36,  56).  The  character  of  the  clay  near  St. 
Stephens  at  the  water  level  (No.  6  of  the  St.  Stephens  section)  is 
shown  in  analysis  60. 
Below  St.  Stephens  there  is  deep  water  to  Mobile,  with  the  exception 
of  one  bar,  which  may  be  removed  without  much  trouble  or  expense. 
Oven  Bluff. — From  Hobson\s  quarry,  just  above  the  Lower  Salt 
Works  Landing,  down  to  Oven  Bluff,  a  distance  of  2  miles,  the  orbitoidal 
limestone  or  chimney  rock  occurs  at  the  base  of  bluffs  of  Tertiary  age. 
At  the  quarry  the  hard  limestone,  which  is  being  taken  up  for  riprap 
work,  lies,  as  at  St.  Stephens,  just  above  the  soft  chimney  rock. 
Along  the  stretch  of  river  above  described  this  chimney  rock  is  seen 
in  a  bed  15  or  20  feet  in  thickness,  just  above  the  river  bottom,  and  is 
easily  accessible.  As  regards  clay  three  varieties  have  been  examined, 
a  residual  clay  from  over  the  limestone,  a  swamp-bottom  clay  from  the 
low  grounds  of  Leatherwood  Creek,  and  clay  from  strata  of  the  Grand 
Gulf  formation,  which  here  overlies  the  St.  Stephens  limestone.  The 
analyses  of  these  clays  have  not  yet  been  made. 
The  first  shoal  in  the  river  above  Mobile  is  a  few  miles  above  Oven 
Bluff,  so  that  from  this  place  down  there  is  a  9-foot  channel  at  all 
seasons,  which  will  give  to  Oven  Bluff  a  certain  advantage  over  other 
localities  in  regard  to  transportation.  The  shoal  mentioned  is  one 
which  can  be  removed,  so  that  St.  Stephens  may  be  classed  with  Oven 
Bluff  as  regards  transportation  by  water,  except  that  the  former  is 
some  miles  farther  from  the  Gulf  than  the  latter. 
