GKEAT   DIVIDE   BASIN    COAL   FIELD,    WYOMING.  221 
balancing  the  recorded  distances  about  two  perpendicular  right  lines 
intersecting  near  the  center  of  the  map  that  the  distortions  due  to 
convergence  of  meridians  and  errors  of  surveying  are  distributed 
equally  over  the  sheet.  As  a  result  of  this  balanced  plotting  of  dis- 
tances rather  than  directions  the  length  of  the  sides  of  any  given 
township  or  section  on  PI.  XII  agrees  with  that  given  on  the  Land 
Office  plat,  but  the  shape  of  the  township  or  section  may  be  different 
from  the  shape  shown  on  that  plat  or  from  the  true  shape.  Because 
of  this  method  of  construction  PL  XII  does  not  exactly  agree  in  the 
shape  of  the  land  subdivisions  in  the  parts  where  it  coincides  with 
the  maps  of  the  Little  Snake  River  coal-field  (PL  XIII),  of  the  north- 
ern part  of  the  Rock  Springs  coal  field  (PL  XIV),  and  of  the  east-cen- 
tral Carbon  County  fields. a 
TOPOGRAPHY  AND   DRAINAGE. 
Most  of  the  topography  of  this  area  is  simple  and  very  favorable 
to  economic  development  of  the  coal  beds.  At  no  place  does  the  coal 
reach  an  altitude  greater  than  7,400  feet.  About  five-sixths  of  the 
total  area,  comprising  the  entire  central,  western,  and  southern  parts, 
and  a  small  fraction  of  the  east-central  part,  is  a  region  of  very  low 
relief.  It  is  characterized  by  broad  flats  containing  small  alkaline 
lakes  and  scattered  silt  and  sand  dunes;  low,  flat-topped  hills,  many 
of  which  are  capped  by  gravel;  low,  abrupt  escarpments  at  the  edges 
of  the  flat-topped  hills;  broad,  gently  sloping  outwash  plains;  and 
relatively  low,  parallel  ridges  formed  by  the  outcrops  of  highly 
inclined,  rather  soft  beds  of  sandstone.  The  last-mentioned  feature 
is  peculiar  to  a  narrow  belt  running  a  little  west  of  north  from  Solon, 
on  the  Union  Pacific  Railroad,  to  Lost  Soldier,  in  T.  26  N.,  R.  90  W.; 
and  coinciding  with  the  outcrops  of  the  upper  members  of  the  Cre- 
taceous system. 
In  the  remaining  sixth  of  the  area  the  relief  is  much  greater,  the 
altitude  ranging  from  6,450  feet  above  sea  level  near  Boundary  Lake, 
in  T.  23  N.,  R.  88  W.,  to  9,200  feet  at  the  top  of  Whisky  Peak,  in 
T.  27  N.,  R.  90  W.  This  part  of  the  basin  may  be  divided  into  four 
districts,  each  having  its  own  topographic  characteristics.  The 
Rawlins  Hills,  in  Tps.  21  to  24  N.,  R.  88  W.,  form  one  district  char- 
acterized by  abrupt  scarp  faces  and  long  dip  slopes.  The  Ferris 
Mountains,  in  T.  26  N.,  R.  88  W.,  T.  27  N.,  Rs.  88  and  89  W.,  and 
T.  28  N.,  R.  89  W.,  form  another  district  resembling  that  of  the 
Rawlins  Hills,  but  with  a  much  greater  range  of  elevation.  The 
Green  Mountains,  of  which  Whisky  Peak  forms  the  east  end,  compose 
the  third  district,  They  are  situated  in  Tps.  27  and  28  X..  Rs.  90  to 
92  W.  This  district  is  characterized  by  a  broad,  plateau-like  summit 
with  high,  irregular,  systemless  spurs  and  deep  valleys  running  out 
oVcatch,  A.  c,  Bull.  U.  S.  Geol.  Survey  No.3i6,  L906   PI   XIV. 
