16  CONTRIBUTIONS   TO    ECONOMIC    GEOLOGY,   1907,   PART   II. 
The  geologic  investigations  were  undertaken  primarily  for  the  pur- 
pose of  classifying  the  public  lands  with  special  regard  to  lignite.  In 
order  to  do  this,  the  character,  depth,  and  horizontal  distribution  of 
the  beds  of  lignite  were  studied  in  detail,  and  outcrops  and  exposures 
were  located  with  reference  to  established  land  corners. 
This  region  has  been  investigated  in  a  general  way  by  a  number  of 
geologists,  notably  by  Wood,  Wilder,  and  Leonard,  of  the  North 
Dakota  Geological  Survey,  and  byStorrs,of  the  Federal  Survey.  In 
the  field  work  the  writers  were  ably  assisted  by  Fred  H.  Kay  and 
W.  H.  Clark,  and  in  the  office  Mr.  Kay  compiled  the  accompanying 
map  from  the  original  township  plats  used  in  the  field. 
ACCESSIBILITY. 
Much  of  the  lignite  of  this  field  is  accessible  without  great  difficulty. 
The  area  is  traversed  from  east  to  west  by  the  Northern  Pacific  Rail- 
way, which  is  not  more  than  15  or  18  miles  from  any  part  of  it.  Many 
of  the  lignite  beds  that  outcrop  along  Little  Missouri  River  could  be 
readily  reached  by  a  branch  line  along  the  valley  of  that  stream,  and 
the  same  is  true  of  the  lignite  on  Beaver  Creek.  Other  parts  of  the 
field  would  be  accessible  to  railways  built  across  the  upland  plains. 
DRAINAGE  AND    WATER   RESOURCES. 
With  the  exception  of  an  area  drained  by  a  few  streams  heading  in 
the  westernmost  tier  of  townships  and  flowing  northwestward  into 
Yellowstone  River,  the  field  lies  in  the  drainage  basin  of  Little  Mis- 
souri River,  which  flows  northward  across  the  eastern  part  and  con- 
tains running  water  throughout  the  year.  Beaver  Creek,  also  a  per- 
ennial stream,  runs  northeastward  across  the  western  part  of  the  field 
and  joins  Little  Missouri  River  some  distance  north  of  the  area 
mapped.  All  the  other  streams  are  intermittent,  but  some  of  them 
contain  water  in  pools  during  dry  seasons. 
TOPOGRAPHY. 
Broadly  characterized,  the  region  is  a  rolling  plain  which  is  minutely 
dissected  near  the  larger  streams,  the  result  being  so-called  bad- 
lands. Three  important  eastward-flowing  streams — Andrews,  Knut- 
son,  and  Wannigan  creeks — empty  into  Little  Missouri  River.  All 
these  streams  have  cut  deep  valleys  in  the  plain  and  exposed  to  view 
the  strata  which  underlie  its  surface.  The  badlands  are  confined 
chiefly  to  a  strip  of  country  bordering  Little  Missouri  River  and  ex- 
tending about  an  equal  distance  on  either  side.  This  very  rough  area , 
with  its  bare  clay  slopes,  sharp  divides,  and  rain-carved  buttes,  occu- 
pies a  belt  15  to  20  miles  wide.  The  entire  width  of  the  badlands, 
however,  is  not  included  in  the  district  studied,  as  they  extend  from 
