rvrchard]     LIGNITES  OF  MIDDLE  AND  UPPER  MISSOURI  VALLEY.     281 
Gas-producing  capacities  of  other  lignites  and  standard  gas  coals. 
Sample  and  locality. 
1.  Lignite,  Rock  Springs,  Wjo.a. 
2.  Cannel  coal,  Kentucky  « 
3.  Lignite,  Ouachita  County,  Ark.  h 
4.  Cannel  coal,  Beaver  County,  Pa. h 
5.  Cannel  coal,  Kentucky'' 
6.  Cannel  coal,  Scotland  b 
7.  Bituminous  coal,  Newcastle,  England'' 
8.  Bituminous  coal,  .Upper  Monongahela  River'' 
Gas  yielded 
per  ton. 
Cubicfeet. 
11,069 
10,  661 
11, 886 
10,  L60 
12,  540 
12,  350 
10,  760 
10, 000 
Coke. 
Per  cent. 
55.  8 
42.0 
<t  Experiments  by  the  writer. 
7>Taff,  J.  A.,  Preliminary  report  on  the  Camden  coal  field  of  southwestern  Arkansas:  Twenty-first 
Ann.  Rept.  U.  S.  Geol.  Survey,  pt.  2,  1900,  p.  329. 
In  chemical  composition  the  Dakota  County  lignites  are  fair  repre- 
sentatives of  their  class  of  fuels.  Unfavorable  points  are  the  high 
content  of  moisture  in  fresh  samples  and  the  high  percentage  of  ash. 
In  total  combustibles  they  take  a  medium  rank  and  the  low  percentage 
of  sulphur  is  worthy  of  note. 
Gas-producing  capacity. — The  high  percentage  of  volatile,  com- 
bustible matter  first  suggested  that  the  lignite  should  be  of  value  as  a 
gas  coal.  The  experiments  verify  this  idea.  The  foregoing  tables 
present  a  comparison  between  the  gas  yield  of  this  lignite  and  various 
standard  gas  coals.  The  illuminating  power  is  weak,  however,  and 
the  gas  would  have  to  be  enriched  to  be  made  a  good  illuminant,  but 
for  fuel  purposes  it  might  prove  satisfactory. 
Possibility  of  better  coal  at  greater  depth. — There  is  no  evidence  to 
show  that  the  lignites  improve  in  quality  with  depth,  nor  to  support 
the  popular  misconception  that  lignite  seams  outcropping  from  a  bluff 
are  likely  to  be  of  better  quality  farther  back  under  the  hill.  The 
deeper  lignites  and  those  within  the  bod}^  of  the  bluff  are  at  present 
subject  to  slightly  greater  pressure  than  those  nearer  the  surface,  but 
the  additional  pressure  is  too  slight  to  be  of  significance.  By  analysis 
lignite  from  the  third  bed  was  proved  to  be  of  poorer  quality  than  that 
from  the  second  bed,  while  material  from  outcrop  and  shaft  in  the 
same  vein  showed  but  little  variation  in  composition. 
It  likewise  seems  highly  improbable  that  bituminous  coal  will  ever 
be  found  in  this  locality.  Deep  wells  have  been  drilled  at  Sioux  City, 
Iowa,  and  at  Ponca,  Nebr.,  neither  of  which  encountered  any  indica- 
tions of  coal.  The  well  at  Sioux  City  is  2,011  feet  deep.  It  reached 
limestones  at  540  feet  which  have  been  doubtfully  referred  to  the 
Carboniferous/'     The  well  at  Ponca  is  698  feet   deep   and   entered 
a  Bain,  II.  F.,  Iowa  Geol.  Survey,  vol.  5,  1895,  p.  258. 
