BULL   MOUNTAIN    COAL   FIELD,    MONTANA.  63 
the  eastern  part,  lying  roughly  east  of  Golden  Creek  and  including 
the  Bull  Mountains,  contains  a  large  quantity  of  coal  of  commercial 
value.  This  area  is  known  as  the  Bull  Mountain  coal  field,  and  the 
purpose  of  the  present  paper  is  to  set  forth  briefly  the  information 
gathered  in  this  field. 
The  first  examination  of  any  detail  in  the  Bull  Mountain  coal  field 
was  made  by  the  geologists  of  the  Transcontinental  Survey  about 
1881.  At  that  time  Waldemar  Lindgren  and  the  late  George  H. 
Eldridge  examined  the  stratigraphy  and  coal  beds  of  this  general 
region,  and  the  results  of  their  studies  are  briefly  given  in  the  Report 
of  the  Tenth  Census  of  the  United  States.0  Two  pages  illustrated 
by  columnar  and  cross  sections  are  devoted  to  a  description  of  the 
rocks  and  a  discussion  of  the  stratigraphy  of  the  Bull  Mountains  and 
surrounding  country.  Though  the  authors  group  all  the  rocks  in  the 
"Laramie  series,"  they  describe  them  in  units  that  correspond  fairly 
well  with  the  Fort  Union  "somber  beds''  and  Laramie,  which  were 
traced  and  mapped  during  the  last  season  as  separate  formations. 
The  coals,  which  they  call  black  lignites  and  which  are  "in  every 
way  much  superior  to  the  lignites  farther  east,"  are  described  in  two 
pages  dealing  almost  entirely  with  the  Mammoth  coal  bed.  Two 
plates  of  sections  and  57  proximate  analyses  of  this  coal  are  given. 
The  description  of  the  coal  is  good,  considering  its  brevity;  it  brings 
out  carefully  the  essential  facts  concerning  the  extent,  character,  and 
thickness  of  the  coal,  as  well  as  its  general  physical  appearance. 
The  sections  of  the  Mammoth  coal  bed  are  given  in  detail,  but,  unfor- 
tunately, the  locations  of  many  of  the  sections  are  too  brief  for 
identification.  Wherever  identification  was  possible,  however,  the 
measurements  checked  well  with  those  made  by  the  Geological  Sur- 
vey party.  The  analyses  give  no  calorific  determinations,  but  in 
other  respects  they  compare  very  favorably  with  the  analyses  given 
in  the  present  paper.  On  the  whole,  therefore,  in  view  of  the  diffi- 
culties under  which  this  early  work  was  carried  on,  owing  to  the 
rough,  unsettled  condition  of  the  western  country  at  that  time,  the 
work  seems  to  have  been  carefully  done,  and  the  report,  so  far  as  it 
goes,  may  be  regarded  as  generally  reliable,  except  in  the  identifica- 
tion of  the  formations.  This  judgment,  however,  is  based  on  a 
study  of  only  about  one-fourth  of  the  Bull  Mountain  field  examined 
by  the  geologists  of  the  Transcontinental  Survey. 
LOCATION  AND   EXTENT. 
Practically  all  of  the  Bull  Mountain  coal  field  lies  south  of  Mussel- 
shell River,  which  is  roughly  its  northern  boundary,  and  it  extends 
southward,   including  Bull  Mountains.     Its  length  from   north   to 
a  Eldridge,  G.  H.,  Montana  coal  Gelds:  Tenth  Census,  vol.  15,  1886,  pp.  753-755. 
