GLENKOCK    COAL  FIELD,    WYOMING.  163 
At  many  places  in  the  field  coal  is  mined  for  local  consumption  by 
stripping.  The  comparatively  thin  beds  which  are  common  in  this 
field  are  much  more  easily  worked  by  stripping  and  in  small  mines 
than  they  are  some  distance  below  the  surface. 
A  very  common  class  of  coal  workings  comprises  those  in  which 
coal  is  taken  out  through  slopes  10  to  200  feet  long.  These  workings 
have  been  made  principally  for  prospecting.  In  most  of  them  it  was 
hoped  that  better  coal  or  more  of  it  would  be  reached  by  drifting  in 
on  the  bed,  but  generally  it  was  found  that  the  coal  beds  were  not 
thick  enough  to  be  worked  with  profit. 
There  are  two  mines  which  use  steam  power,,  the  Glenrock  and  the 
Big  Muddy.  The  Inez  mine  also  used  steam  when  it  was  being 
worked.  In  most  of  the  mines  the  main  gangway  is  driven  down  the 
dip,  and  entries  are  driven  from  this  gangway  on  each  side,  rooms 
being  turned  off  up  the  rise  of  the  bed.  Thus,  the  Big  Muddy  mine 
has  been  worked  down  the  dip  for  about  1,000  feet,  and  has  three 
entries  on  each  side  which  are  800  to  1,000  feet  long.  The  Glenrock 
mine  has  two  openings,  one  down  the  dip  for  3,000  feet  and  the  other 
nearly  on  the  strike  for  about  1,200  feet. 
The  deepest  part  of  the  Glenrock  mine  is  more  than  200  feet  below 
the  surface,  and  it  is  nearly  under  the  river.  This  necessitates  con- 
stant pumping.  A  bore  hole  has  just  been  put  down  to  the  deepest 
part  of  the  mine,  to  be  used  in  pumping  water.  The  Glenrock  Com- 
pany has  an  air-compressing  plant  and  fan.  Mining  is  done  by 
undercutting  with  a  machine,  and  then  breaking  the  coal  down  with 
picks.  From  the  rooms  the  cars  are  hauled  to  the  main  gangway  by 
mules,  and  thence  to  the  surface  by  cable. 
The  Big  Muddy  Company  uses  a  similar  room  and  pillar  system; 
but  at  Big  Muddy  the  dip  is  much  steeper  than  at  Glenrock,  so  that 
cross  entries  are  driven  out  from  the  car  track  and  other  entries  par- 
allel to  the  main  gangway,  from  which  the  rooms  are  driven  in  the 
direction  of  the  strike.  The  coal  is  taken  out  of  the  rooms  to  the 
dip  entry,  then  let  down  the  dip  to  the  cross  entry,  where  it  is  hauled 
across  to  the  main  gangway  by  mules,  and  thence  to  the  surface  by 
cable. 
PRODUCTION  AND   MARKET, 
The  coal  production  of  Converse  County  in  1907  was  48,700  short 
tons.  Big  Muddy  is  very  close  to  the  western  boundary  of  Con- 
verse County,  but  the  mine  is  in  this  county  and  its  production  is 
included  in  the  above  figures. 
Natrona  County  has  no  producing  mines,  except  for  local  use,  and 
its  production  is  slight  and  comes  from  ninny  mines  and  prospects. 
It  is  probable  that  in  1907  the  total  production  of  Converse  and 
Natrona  counties  was  not  1,000  tons  in  excess  of  the  output  of  the 
