396  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
outcrop  is  a  prominent  feature  of  the  landscape  and  will  serve  as  a 
guide  in  locating  the  position  of  the  coal.  The  crop  of  the  Henryetta 
coal  has  been  traversed  from  the  vicinity  of  Henryetta  northward 
beyond  Okmulgee.  No  trace  of  the  coal,  however,  was  obtained  from 
a  point  northeast  of  Okmulgee  to  Arkansas  River.  At  the  river 
south  of  Broken  Arrow  it  was  taken  up  again  and  traced  to  the  Creek- 
Cherokee  Nation  line.  Workable  coal  4  feet  thick  is  reported  to  out- 
crop 4  to  5  miles  west  of  Bluejacket  in  northern  Cherokee  Nation, 
and  it  is  not  improbable  that  it  will  prove  to  be  the  northward  con- 
tinuation of  the  Henryetta  bed. 
This  coal  bed  has  received  the  greatest  attention  near  Henryetta, 
where  three  mines  have  been  in  operation  during  the  last  year,  pro- 
ducing 35,600  tons.  The  bed  is  3  feet  thick  and  mines  in  block,  sep- 
arating into  two  or  three  benches  along  stratification  lines  of  distinct 
cleavage.  In  the  southernmost  strip  pits  east  of  the  town  a  shale 
parting  was  discernible  near  the  middle  of  the  coal.  Three  and  one- 
half  miles  southeast  of  Henryetta  an  outcrop  of  the  coal  shows  that 
the  shale  parting  has  increased  to  10  inches,  separating  the  bed  into 
two  branches,  the  upper  12  to  15  inches  and  the  lower  15  to  20  inches 
in  thickness.  At  the  mines  2  miles  north  of  Henryetta,  2  miles  south- 
east of  Schulter,  and  east  of  Okmulgee,  the  Henryetta  coal  maintains 
its  thickness  of  3  feet  to  3  feet  4  inches,  and  shows  no  appreciable 
change  in  character  except  the  presence  of  a  thin  shale  in  the  open- 
ings near  Okmulgee.  The  outcrop  has  been  traced  between  these 
localities  and  to  a  point  6  miles  east  of  Okmulgee.  No  openings  are 
known  to  have  been  made  on  the  coal  between  Okmulgee  and  Arkan- 
sas River.  Southeast  of  Broken  Arrow,  however,  the  coal  is  shown 
in  workings  to  be  3  feet  thick.  Northeast  of  this  town,  in  sec.  5, 
T.  18  N.,  R.  15  E.,  it  is  seen  in  the  mines  to  be  30  inches  to  3  feet 
thick.  The  coal  in  the  vicinity  of  Broken  Arrow  is  essentially  the 
same  as  that  found  between  Okmulgee  and  Henryetta. 
Dawson  coal. — The  highest  coal  bed  of  known  workable  thickness 
is  found  in  northwest  Creek  Nation,  where  its  outcrop  has  been 
mapped  from  Dawson,  on  the  St.  Louis  and  San  Francisco  Railway, 
near  the  edge  of  the  Creek  Nation,  southward  to  the  vicinity  of 
Mounds.  Outcropping  in  association  with  the  coal  on  the  west  and 
occurring  nearly  DO  feet  above  it  is  a  thin  bed  of  light-blue  limestone 
which  Aveathers  to  a  bright  yellow  color.  The  outcrop  of  this 
limestone  has  been  mapped  from  Tulsa  southwestward  nearly  50 
miles  and  beyond  the  known  occurrence  of  the  coal.  This  peculiar 
limestone  is  easily  recognized  and  its  outcrop  is  a  ready  reference  in 
locating  the  coal.  The  Dawson  coal  is  here  unusually  clean  for  a 
bituminous  coal.  It  mines  in  block  separating  near  the  middle  along 
a  distinct  bedding  plane,  and  resembles  very  closely  the  Henryetta 
