BULL   MOUNTAIN    COAL   FIELD,    MONTANA.  77 
The  flow  of  the  ground  waters  is  controlled  chiefly  by  the  geologic 
structure;  consequently  the  northward  dip  of  the  coals  on  the  south 
slope  Of  the  mountains  accounts,  as  already  suggested,  for  the  scarcity 
of  springs  in  that  portion  of  the  field.  Nevertheless,  drifts  down  the 
dip  of  the  coal  beds,  even  in  this  locality,  would  probably  fill  with 
water,  which  would  have  to  be  removed  by  some  artificial  means. 
For  this  purpose  the  siphon  maybe  used  to  advantage.  On  the  north 
slope  of  the  mountains,  however,  the  northerly  dip  of  the  rocks  would 
form  natural  drainage  for  mines  on  the  upper  coals.  Indeed,  it  is 
believed  that  coal  beds  occurring  high  up  in  the  mesas  should  be 
mined  chiefly  from  the  north  side.  The  lower  coals  of  the  north 
slope,  including  the  one  now  mined  at  Roundup,  lie  on  the  northeast 
limb  of  the  syncline  and  have  a  general  southerly  dip.  Hence  for 
mines  on  these  beds  a  pumping  plant  is  a  necessity.  Furthermore,  the 
siphon  method,  owing  to  the  flatness  of  the  country,  could  not  be 
used  so  advantageously  as  on  the  south  slope. 
The  place  at  which  it  would  be  most  economical  to  locate  a  mine 
with  a  view  to  natural  drainage  is  the  lowest  point  on  the  axis  of  the 
syncline,  which  crosses  the  field  between  the  Bull  Mountains  and 
Roundup.  A  mine  so  located  might  work  the  lower  coals  up  the  rise 
toward  the  north,  east,  and  south,  and  thus  obtain  a  natural  westerly 
or  northwesterly  drainage.  The  ideal  position  for  such  a  mine  can 
not  be  given  from  the  present  partial  knowledge  of  the  field.  Any 
plan  for  the  development  of  the  whole  field  along  the  most  economical 
lines  presupposes  cooperation  among  the  various  operators.  For 
example,  a  drainage  tunnel  or  a  shaft  and  pumping  plant  located  at  the 
lowest  point  of  the  syncline,  the  expense  being  borne  in  common  by 
all  operators,  might  save  outlays  for  the  construction  and  mainte- 
nance of  pumping  plants  at  each  mine. 
The  geographic  position  of  the  coals  of  the  Bull  Mountain  field, 
together  with  their  character  and  relation  to  those  of  other  fields, 
shows  that  there  is  every  likelihood  of  their  increasing  development 
in  the  near  future.  The  territory  to  be  supplied  about  the  Bull 
Mountains  is  not  thickly  populated,  and  Billings  is  the  largest  town 
of  importance.  The  towns  on  Musselshell  River,  though  at  present 
small,  will  increase  in  population  with  the  advent  of  the  new  trans- 
continental railroad,  but  owing  to  the  fact  that  the  agricultural 
region  is  naturally  restricted  by  lack  of  water,  it  is  doubtful  if  these 
towns  will  grow  to  the  size  of  those  on  Yellowstone  River.  Agricul- 
ture in  this  region  is  largely  limited  at  present  to  grazing,  but  the 
rural  population  also  will  no  doubt  be  augmented  along  the  line  of 
railroad.  Moreover,  irrigation  of  narrow  strips  of  land  along  some 
of  the  main  tributaries  of  Musselshell  River  is  feasible  and  will 
probably  be  extended  in  the  near  future.  The  resulting  increase  in 
population  will  therefore  help  enlarge  the  demand  for  coal. 
