38  CONTRIBUTIONS   TO   ECONOMIC    GEOLOGY,  1907,   PART   II. 
At  present  no  coal  is  shipped  away  from  this  part  of  Montana. 
Miles  City,  with  a  population  of  about  5,000,  furnishes  the  best 
market,  but  the  coal  is  used  for  domestic  purposes  by  nearly  all  the 
ranchmen  and  farmers  throughout  the  surrounding  country.  The 
largest  individual  consumers  at  the  present  time  are  the  electric 
light  and  water  companies  of  Miles  City. 
A  broader  field  of  usefulness  for  these  fuels  will  probably  be  found 
in  the  production  of  power  for  irrigating  many  small  detached  tracts 
of  land  for  which  elaborate  systems  of  canals  are  impracticable. 
Such  tracts  are  especially  numerous  along  Tongue  and  Powder  rivers, 
and  several  pumping  plants,  some  of  which  use  steam  and  others 
gasoline  engines,  are  already  in  operation. 
The  valley  of  the  Yellowstone  is  in  most  places  broad,  but  the 
meandering  of  the  stream  from  bluff  to  bluff  has  left  the  flats  dis- 
connected. Two  such  flats,  known  as  Sadie  Bottom  and  Keogh 
Flat,  lie  a  short  distance  above  Miles  City,  and  a  project  to  irrigate 
them  by  pumping  water  from  the  Yellowstone,  using  the  lignite 
near  by  as  fuel,  is  under  consideration  by  the  Reclamation  Service. 
About  9,000  acres  along  Tongue  and  Yellowstone  rivers  are  under 
irrigation  by  a  ditch  which  takes  water  out  of  Tongue  River  10  miles 
above  its  mouth. 
DRAINAGE. 
Yellowstone  River,  rising  in  the  Rocky  Mountains  several  hundred 
miles  to  the  southwest,  flows  diagonally  across  the  northwest  corner 
of  the  field  and  carries  a  large  volume  of  water  during  all  seasons  of 
the  year.  Tongue  and  Powder  rivers,  rising  in  the  Bighorn  Moun- 
tains of  Wyoming,  flow  northward  across  the  area  and  join  the 
Yellowstone.  Both  of  these  streams  are  perennial,  but  during  the 
latter  part  of  the  summer  water  in  them  is  extremely  low.  Back 
from  the  valleys  of  these  master  streams  the  region  is  drained  by  an 
intricate  network  of  intermittent  watercourses,  usually  in  narrow 
canyons  or  gulches.  Moon,  Pumpkin,  Mizpah,  Cottonwood,  and 
Locate  creeks,  the  principal  tributaries  of  the  main  rivers,  usually 
contain  water  in  pools,  but  do  not  flow  continuously  except  in  wet 
seasons. 
TOPOGRAPHY. 
The  total  relief  between  the  highest  and  lowest  points  in  the  field 
does  not  exceed  900  feet,  but  much  of  the  topography  is  exceedingly 
complicated  in  detail.  Four  rather  distinct  topographic  types — 
lowlands,  plateaus  or  uplands,  badlands,  and  river  terraces — can  be 
recognized  and  are  indicated  on  the  profile  accompanying  PL  III. 
The  lowlands  are  situated  in  the  valleys  of  the  larger  streams  and 
include  most  of  the  irrigable  land. 
