190         CONTRIBUTIONS    TO    ECONOMIC   GEOLOGY,   1907,   PAKT   II. 
high  and  is  utilized  to  some  extent  in  the  mining.  When  the  working 
face  of  the  coal  is  undercut  and  left  for  a  few  hours,  the  face  breaks 
off  extensively  as  a  result  of  the  roof  pressure.  Heavy  timbering  is 
required  on  the  slopes.  Mining  is  done  largely  by  blasting  down  the 
coal  with  black  powder;  the  coal  is  very  hard  and  can  usually  be  mined 
only  by  shooting.  The  mine  employs  about  100  men,  working  two 
shifts  a  day  of  eight  hours  each.  The  miners  are  paid  $1  per  ton  for 
mining  coal.  This  is  25  cents  per  ton  in  excess  of  the  wages  paid  to 
the  miners  at  Bear  Creek  or  Red  Lodge,  the  higher  price  being  due  to 
the  thinness  of  the  bed  at  Bridger  and  to  the  fact  that  the  coal  is 
harder,  which  renders  mining  more  difficult.  The  miners  produce 
from  3  to  6  tons  per  day  per  man.  The  main  slope  has  a  length  at  the 
present  time  (1907)  of  5,000  feet.  This  slope  runs  west-southwest- 
ward  down  the  dip  of  the  bed,  which  here  amounts  to  6°  SW.  The 
maximum  output  of  the  mine  is  about  250  tons  per  day.  The  coal 
is  hoisted  up  the  incline  by  a  250-horsepower  electric  hoist.  The 
trains  of  coal  cars,  or  trips,  are  coupled  to  an  electric  motor  at  the 
top  of  the  slope,  and  drawn  over  a  trolley  line  three-fourths  of  a  mile 
to  the  tipple. 
The  coal  is  sold  both  as  lump  and  nut  coal.  The  egg  and  pea  sizes 
go  into  the  cars  without  being  separated  from  the  rest.  The  waste 
coal  and  slack  is  used  in  generating  electricity.  The  quality  of  the 
coal  at  Bridger  is  practically  the  same  as  that  of  the  coal  in  the  other 
mines  on  the  same  bed,  namely,  the  McCarthy  and  Gebo  mines,  near 
Fromberg;  the  Burgin  mine,  near  Joliet,  Mont.;  and  the  Silvertip 
mine,  in  northern  Wyoming.  It  is  superior  in  many  respects  to  the 
coal  of  the  Fort  Union  and  Laramie  formations  which  is  mined  at 
Red  Lodge  and  Bear  Creek,  Mont.,  and  near  Basin,  Wyo.  The  supe- 
riority consists  chiefly  in  its  better  keeping  qualities,  due*  largely  to 
its  hardness  and  compactness,  and  it  is  said  that  for  this  reason  it  sells 
in  the  Montana  market  for  about  $1  per  ton  more  than  the  Red  Lodge 
and  Bear  Creek  coals.  The  moisture  content  and  fuel  ratio  are  prac- 
tically the  same  as  in  those  coals,  but  the  ash  content  is  somewhat 
higher.  The  Bridger  coal  shows  the  first  indication  of  slacking  in 
about  two  months  after  it  is  mined,  but  the  deterioration  is  not 
sufficient  to  affect  the  value  of  the  coal  for  about  one  year.  When 
kept  in  stock  it  is  much  less  subject  to  spontaneous  combustion  than 
the  Sheridan,  Bear  Creek,  and  other  coals  of  the  Fort  Union  forma- 
tion. The  partings  of  the  coal  bed  thicken  and  thin,  the  middle 
parting  decreasing  from  a  maximum  thickness  of  about  4  feet  in  the 
upper  part  of  the  mine  to  a  minimum  thickness  of  only  6  inches  at  the 
present  working  face.  The  miners  believe  that  this  indicates  that  the 
parting  will  disappear  at  a  greater  depth. 
From  Bridger  the  outcrop  of  the  coal  bed  trends  north-northwest- 
ward across  T.  6  N.     No  prospects  were  noted  in  this  township. 
