ILLUSTRATIONS. 
Page. 
Plate  I.  Map  showing  coal  fields  of  the  United  States 6 
II.  Map  of  the  Sentinel  Butte  lignite  field,  North  Dakota  and  Montana. .  24 
III.  Map  of  the  Miles  City  coal  field,  Montana 46 
IV.  Map  of  southwestern  part  of  Bull  Mountain  coal  field,  Montana 64 
V.  Map  showing  outcrop  of  Eagle  sandstone  near  the  Crazy  Mountains, 
Montana 82 
VI.  Map  and  sections  of  the  Red  Lodge  coal  field,  Montana 94 
VII.  Map  of  the  Lewistown  coal  field,  Montana 110 
VIII.  Map  of  Sheridan  coal  field,  Wyoming 1 24 
IX.  Map  of  Glenrock  coal  field,  Wyoming 154 
X.  Map  of  the  coal  fields  of  the  northeast  side  of  the  Bighorn  Basin, 
Wyoming 170 
XI.  Map  of  the  coal  fields  of  the  southwest  side  of  the  Bighorn  Basin, 
Wyoming,  with  sections  of  coal  beds 200 
XII.  Map  of  the  eastern  part  of  the  Great  Divide  Basin  coal  field,  Wyoming.  220 
XIII.  Map  of  the  western  part  of  the  Little  Snake  River  coal  field,  Wyoming.  244 
XIV.  Map  of  the  northern  part  of  the  Rock  Springs  coal  field,  Wyoming.  258 
XV.  Detailed  map  of  northern  part  of  Rock  Springs  coal  zone,  Wyoming.  262 
XVI.  Map  of  western  part  of  Yam  pa  coal  field,  Routt  County,  Colo 294 
XVII.  Map  of  the  lower  White  River  coal  field,  north  of  the  base  line, 
Colorado 298 
XVIII.  Reconnaissance  map  of  the  Douglas  Creek  district,  lower  White  River 
coal  field,  south  of  the  base  line,  Colorado 302 
XIX.  Map  of  the  Vernal  coal  field,  Utah 306 
XX.  Map  of  part  of  the  Henrys  Fork  coal  field,  Utah  and  Wyoming 310 
X  XL  Map  of  the  Grand  Mesa  coal  field,  Colorado 316 
XXII.  Map  of  the  coal  field  between  Gallina  and  Raton  Spring,  N.  Mex.,  in 
the  San  Juan  coal  region 336 
XXIII.  Map  of  the  coal  field  between  Durango,  Colo.,  and  Monero,  N.  Mex. .  352 
XXIV.  Map  of  coal  field  between  Gallup  and  San  Mateo,  N.  Mex 364 
XXV.  Map  of  western  part  of  southern  Utah  coal  region 380 
Figure  1.  Index  map  showing  location  of  Sentinel  Butte  lignite  field,  North 
Dakota  and  Montana 13 
2.  Section  from  Bridger,  Mont.,  through  the  International  Coal  Com- 
pany's mine  to  the  base  of  the  mountain,  showing  relation  of  coal 
beds  mined  at  Red  Lodge  to  that  mined  at  Bridger 96 
3.  Index  map  showing  location  of  Sheridan  coal  field,  Wyoming 124 
4.  Index  map  showing  location  of  Glenrock  coal  field,  Wyoming 151 
5.  Map  of  Colorado  and  northeastern  Utah  coal  fields,  showing  areas 
represented  by  Tls.  XVI-XX 293 
6.  Map  of  Rogue  River  valley  and  other  coal  fields  of  southwestern 
Oregon 401 
7.  Sketch  map  of  the  Pocket  coal  district,  Virginia,  in  the  Little  Black 
Mountain  coal  field. _ _  _  410 
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