44  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1907,   PART   II. 
the  rocks  in  that  direction  is  scarcely  greater  than  the  gradient  of  the 
river.  About  70  miles  northeast  of  Miles  City,  near  Glendive,  there 
is  a  pronounced  anticline,  which  brings  the  Pierre  shale  to  the  sur- 
face. This  flexure  has  a  northwest-southeast  axis  and  is  believed  to 
mark  the  northeast  limit  of  the  basin  in  which  Miles  City  is  situated. 
A  few  miles  south  of  this  district  the  lower  member  of  the  Fort  Union 
formation  rises  to  the  summit  of  the  divide  between  Tongue  and 
Powder  rivers,  and  it  is  thought  that  here  also  there  may  be  a  broad 
anticline  separating  the  Miles  City  field  from  the  Sheridan  field  of 
Wyoming. 
THE   COAL. 
GENERAL  CONDITIONS. 
Coal  beds  are  distributed  at  short  intervals  through  the  entire  sec- 
tion of  rocks  exposed,  but  many  of  them  are  too  thin  to  work,  or,  if 
thick  enough  to  work,  are  too  impure  for  commercial  use.  The  drill 
holes  sunk  about  Miles  City  in  search  of  artesian  water  have  revealed 
no  coal  beds  of  consequence  to  a  depth  of  500  feet  below  the  river 
level,  indicating  that  the  Kircher  coal,  which  lies  about  50  feet  above 
river  level,  is  the  lowest  workable  bed  and  practically  the  base  of  the 
coal-bearing  rocks. 
A  distinct  change  in  the  character  of  the  coals,  as  in  that  of  the  other 
strata,  can  be  noted  in  passing  from  the  lower  to  the  upper  beds. 
The  former  vary  greatly  in  thickness  and  purity  from  place  to  place. 
In  many  localities  they  contain  numerous  thin  partings  and  seem  to 
have  been  deposited  under  changeable  conditions.  On  close  exami- 
nation a  majority  of  the  lower  coals  are  found  to  be  black  in  color  and 
to  exhibit  comparatively  little  of  the  woody  texture  characteristic  of 
the  higher  coals.  The  absence  of  woody  texture  is  attributed  to  more 
complete  maceration  of  the  carbonaceous  material  during  the  time  of 
its  deposition. 
The  character  of  the  lignite  in  the  upper  beds  indicates  that  the  con- 
ditions during  its  deposition  were  comparatively  stable;  the  beds  are 
more  uniform  in  thickness  and  contain  fewer  sand  and  clay  partings 
than  the  lower  beds.  The  coal-forming  material  suffered  little  change 
while  accumulating,  for  its  woody  texture  is  clearly  visible.  In  luster 
and  color  the  coal  is  more  lignitic  than  that  of  the  lower  beds,  and 
it  is  more  liable  to  spontaneous  combustion,  as  is  shown  by  the 
prevalence  of  clinkers  along  the  outcrop  of  the  beds. 
The  number  of  coal  or  lignite  beds  visible  in  the  badlands  has  nat- 
urally led  to  the  conclusion  that  great  quantities  of  coal  are  available 
in  the  immediate  vicinity  of  Miles  City,  but  although  it  is  true  that 
the  quantity  is  great  the  percentage  that  can  be  mined  economically 
is  relatively  small,  and  before  any  large  area  is  purchased  for  mining 
purposes  it  should  be  thoroughly  tested  by  drilling.     In  the  upland 
