106        CONTRIBUTIONS  TO  .ECONOMIC   GEOLOGY,  1907/  PART  It. 
should  be  noted,  however,  in  making  these  comparisons,  that  the  sam- 
ples are  from  different  parts  of  one  field,  and  not  from  beds  which 
occupy  different  stratigraphic  positions.  In  volatile  matter  there  is 
only  a  slight  difference  between  the  Red  Lodge  and  the  Bear  Creek 
coals.  The  fixed  carbon  of  the  Red  Lodge  samples  is  slightly  below 
that  of  the  others  in  the  table.  The  ash  content  is  about  the  same 
in  all  the  samples.  In  general,  the  analyses  show  that  the  Bear  Creek 
coals  are  better  than  the  Red  Lodge  coals,  though  there  is  only  a  slight 
difference.. 
The  coals  of  the  Red  Lodge  field  contain  an  average  on  air-dried  sam- 
ples of  36.8  per  cent  of  volatile  matter  and  46  per  cent  of  fixed  carbon. 
Sulphur  ranges  from  0.86  to  3.18  per  cent.  The  amount  of  ash  is 
rather  high.  The  coal  ignites  readily  and  burns  freely  without  fusion. 
Analyses  of  coals  from  adjacent  and  competing  fields  are  given  by 
other  writers  in  this  volume,  and  by  means  of  these  the  coals  from 
the  Red  Lodge  field  may  be  compared  with  other  coals  entering  the 
same  market. 
AMOUNT  OF  COAL  AVAILABLE. 
Only  a  general  estimate  of  the  amount  of  coal  available  in  the  Red 
Lodge  field  can  be  made,  because  of  the  meager  knowledge  of  the  beds 
at  places  where  they  are  covered.  Their  condition  along  the  fault 
at  the  foot  of  the  mountains  is  also  uncertain.  If  we  consider  that 
none  of  the  coal  in  the  field  lies  below  workable  depths,  and  that  the 
exposures  represent  the  general  condition  over  the  field,  an  approxi- 
mation may  be  obtained  by  assuming  that  a  layer  of  coal  45.3  feet 
thick"  is  spread  evenly  over  24  square  miles,  the  area  of  the  produc- 
tive part  of  the  field,  and  that  the  specific  gravity  of  the  coal  is  1.3. 
Such  an  assumption  gives  1,238,896,581  short  tons.  As  this  enor- 
mous tonnage  conveys  only  a  vague  notion  of  the  amount  of  coal 
within  the  field,  perhaps  a  clearer  idea  may  be  obtained  by  supposing 
that  the  coal  if  placed  in  a  single  block  would  form  a  body  1  mile 
square  and  one-fifth  mile  high. 
MARKETS. 
The  mines  of  the  Red  Lodge  field  supply  coal  extensively  to  the 
Northern  Pacific  Railway,  to  smelters  near  Butte  and  Anaconda, 
and  to  an  extensive  domestic  trade.  The  output  of  the  Northwest- 
ern Improvement  Company's  mine  at  Red  Lodge  is  shipped  to  points 
as  far  east  as  Bismarck,  N.  Dak.,  and  west  to  the  Idaho-Washington 
line.  The  coals  shipped  from  this  field  come  into  competition  with 
the  product  of  several  fields  in  Montana  and  northern  Wyoming,  but 
they  are  of  sufficiently  high  grade  to  be  successful  in  the  competition. 
a  An  average  of  the  coal  sections  measured  throughout  the  field  gives  45.3  feet. 
