CLAY   RESOURCES    OF    ST.  LOUIS    DISTRICT,  MISSOURI.  321 
the  fire  clay  consists  of  workable  shale,  generally  of  a  red  or  brown 
color,  but  with  some  blue  shale  at  its  base. 
Similar  clays  from  a  place  4  miles  northwest  of  Glencoe,  a  station 
on  the  Missouri  Pacific  Railroad,  about  20  miles  west  of  St.  Louis, 
are  largely  used  in  St.  Louis  in  the  manufacture  of  terra  cotta  and 
sewer  pipe,  though  shales  from  this  vicinity  have  also  been  used 
extensively  for  brick.  Yellow  and  blue  shales  that  occupy  the  same 
stratigraphic  position  are  extensively  mined  at  Prospect  Hill,  a  few 
miles  north  of  St.  Louis,  and  used  in  the  manufacture  of  Portland 
cement,  being  mixed  for  that  purpose  with  the  St.  Louis  limestone. 
RED   BRICK. 
Many  yards  in  and  around  St.  Louis  are  making  red  brick  from  the 
loess,  which  is  commonly  called  " yellow  clay."  This  is  rarely  less 
than  10  to  15  feet  thick,  and  near  the  bluffs  may  be  three  or  four 
times  that  thick.  It  differs  in  texture  at  different  depths,  the  upper 
portion  being  " stronger,"  more  clay-like,  and  less  mealy  than  the 
main  body.  Partly  to  obtain  a  thorough  mixture  of  these  different 
grades  and  partly  to  allow  some  weeks  or  months  of  "  sweating," 
thus  reducing  all  lumps,  large  quantities  of  the  loess  are  commonly 
brought  in  from  the  pits  and  kept  under  shed  for  some  time  before 
using.  A  good  grade  of  red  brick  is  made,  and  the  supply  of  good 
loess  here  and  elsewhere  is  limitless. 
