CLAY    KESOURCES    OF    ST.  LOUIS    DISTRICT/ MISSOURI.  317 
The  same  gentle  downward  folding  that  has  resulted  in  the  preser- 
vation of  the  fire  clays  from  erosion  has  preserved  a  few  thin  beds  of 
coal.  One  of  these,  which  is  of  small  areal  extent  and  has  a  maximum 
thickness  (in  this  part  of  the  field)  of  perhaps  1^  feet,  lies  immediately 
above  the  fire  clay.  Another,  equally  small,  with  a  maximum  thick- 
ness of  4  to  6  feet,  lies  40  to  50  feet  higher.  The  early  history  of  the 
city  shows  that  both  of  these  were  once  mined,  and  although  their 
content  was  such  as  would  now  be  considered  insignificant,  their  influ- 
ence on  the  early  development  of  St.  Louis  industries  was  great.  They 
are  not  now  mined,  except  incidentally,  in  mining  the  clay. 
SECTIONS. 
The  details  of  sections  showing  the  beds  passed  through  in  sinking 
shafts  would  be  of  little  value  because  of  the  local  character  of  some 
of  them  and  the  variation  in  the  thickness  of  all.  A  comparison  of 
many  sections,  however,  shows  certain  more  or  less  constant  features 
as  follows: 
Generalized  section  of  coal  measures. 
Ft.         in. 
1.  Soil,  loess,  and  clays  of  variable  thickness. 
2.  Weathered  limestone  ("tumble  rock ") 0-4  0 
3.  Pipeclay,  etc. — maximum 0  -15  0 
4.  Coal  (local) 0-6  0 
5.  Limestone  or  "very  hard  blue  rock,"  often  blasted  with 
dynamite 3  -15  0 
6.  Red  and  blue  clays,  "keel,"  pipeclay,  etc 13-36  0 
7.  Coal  (very  local) 0-1  6 
8.  "Roof,"  consisting  of  dark  shaly  sandstone  or  arenaceous 
shale,  often  preserving  "weeds " 1-7     0 
9.  "Clod,"  an  impure  clay,  liable  to  fall  down  (local) 0  -        8 
10.  Coal  streak  (very  local) 0-        3 
11.  Fire  clay — Cheltenham  seam 2^-12     0 
12.  Light-colored  sandstone  with  pyrite  crystals  and  ferrugi- 
nous nodules,  commonly  forming  the  "floor " 1-9     0 
13.  Limestone  containing  red  cherts. 
As  illustrations,  the  actual  sections  of  two  shafts  are  given  below: 
Section  at  Jamieson- French  mine,  1\  miles  south  of  Clayton. 
Ft.    in. 
Loess  and  soil 15  0 
Red  clay 10  0 
"Gravel " 1  0 
Limestone  fragments  in  clay 3  0 
Gray  pipeclay 15  0 
Very  hard  limestone 6  0 
Red  shale. . . : 10  0 
Soft  black  shale 3  0 
Coal 0  8 
Black  sandy  shale 1  6 
Fire  clay — Cheltenham  seam ;  good  clay  taken  out 8  6 
Depth  to  floor 73     8 
Bull.  315—07 21 
