wyo.      197 
are  in  marked  contrast  with  the  more  equidimensional  lumps  of  the 
Eagle  coal  from  the  Silvertip  and  Bridger  mines. 
Most  of  the  Fort  Union-Laramie  coals  on  the  east  side  of  the  Big- 
horn Basin  are  finely  banded.  At  the  Rogers  &  Gapin  mine  the 
coal  is  composed  of  thin  layers  of  bright,  shiny  coal  of  vitreous  luster, 
alternating  with  less  conspicuous,  thinner  layers  of  dull,  lusterless 
coal.     The  bright  layers  predominate. 
The  Eagle  coal  is  banded  in  a  similar  way,  but  the  structure  is  not 
nearly  so  conspicuous.  The  bright  bands  are  not  so  bright  as  those 
of  the  higher  coals,  and  they  have  a  pitchy  or  varnish-like  luster. 
The  intervening  bands  are  not  so  dull  as  the  similar  bands  in  the 
Fort  Union  coal,  but  they  have  a  faint,  satiny  luster.  As  a  result  of 
those  differences  the  banding  of  the  Eagle  coal  is  less  conspicuous. 
The  effect  is  intensified  by  the  spreading  of  a  sheen  over  some  faces 
of  Eagle  coal,  possibly  the  result  either  of  slight  shearing  or  of  the 
deposition  of  a  lustrous  coaly  substance  on  those  faces.  Faces  hav- 
ing this  sheen  do  not  exhibit  the  banding  as  clearly  as  other  faces  in 
the  same  specimen  that  lack  it.  This  feature  has  not  been  observed 
in  any  of  the  Laramie  or  Fort  Union  coals. 
The  color  of  the  Eagle  coal  is  always  jet-black.  That  of  the  Lara- 
mie-Fort  Union  coals  ranges  from  jet-black  to  brownish  black.  The 
streak  of  the  Eagle  coal  is  dark  brown  on  a  white  plate;  that  of 
the  Laramie-Fort  Union  coals  is  also  dark  brown,  but  of  a  lighter 
tint.  When  scratched  with  a  knife,  none  of  the  coals  shows  a  pul- 
verulent streak,  but  one  that  is  shiny,  greasy,  dark  brown,  almost 
black. 
The  coals  are  said  to  be  more  easily  ignited  than  eastern  soft  coals 
and  to  burn  with  longer,  smokier  flames.  The  Eagle  coal  has  a  shorter, 
bluer  flame  than  the  Laramie-Fort  Union  coal  and  is  more  satisfac- 
tory for  use  under  locomotive  and  other  strong-draft  furnaces, 
because  less  of  the  coal  is  blown  out  by  the  draft.  A  locomotive 
burning  either  coal  emits  a  shower  of  glowing  cinders  greatly  in  excess 
of  that  seen  behind  the  funnel  of  a  locomotive  that  is  burning 
eastern  coal. 
In  their  weathering  and  keeping  properties  lies  the  most  important 
commercial  difference  between  the  two  groups  of  coals.  The  Eagle 
coal  may  bo  kept  in  stock  for  a  year  or  more  without  much  deterio- 
ration; the  Laramie-Fort  Union  coals  begin  to  slack  in  one  month. and 
in  a  year  are  likely  to  be  reduced  to  a  mass  of  small  pieces.  Moreover, 
the  latter  are  more  subject  to  spontaneous  combustion. 
