432 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
Sundance  region. — At  several  localities  south  and  west  of  Sundance 
there  are  found  local  deposits  of  coal  in  a  northward  extension  of  the 
Cambria  coal  field.  The  deposits  are  not  continuous,  and  they 
thicken  and  thin  irregularly.  Owing  to  the  talus  of  sandstone  blocks, 
which  accumulates  on  the  slopes  of  the  coal  measures,  there  is  great 
difficulty  in  exploring  the  coal  horizon,  and  only  at  a  very  few  points 
was  it  found  bare  of  talus,  while  even  at  these  localities  the  coal  may 
have  weathered  or  burned  out  and  the  sandstone  roof  closed  down. 
Coal  has  been  mined  to  some  extent  for  local  use  2  miles  south- 
east of  Holwell  ranch  and  at  several  localities  west  of  Sundance. 
Kecently  some  openings  have  been  made  3  miles  west  of  Inyankara 
Mountain,  exposing  a  thick  deposit.  The  main  opening  southeast  of 
Holwell's  is  on  the  southeast  quarter  of  sec.  31,  T.  48,  E.  62.  An  adit 
about  115  feet  in  depth  has  been  run,  exposing  a  face  of  coal  8J  feet 
thick,  comprising  5  feet  of  hard,  pure  coal,  1^  feet  of  bone  merging 
into  cannel  coal,  and  at  the  base  about  2  feet  of  pure,  very  hard  coal, 
which  is  particularly  valuable  for  blacksmiths'  use.  The  upper  coal 
contains  considerable  sulphur,  which  is  of  infrequent  occurrence  in 
the  lower  bed.  Over  the  coal  are  about  2  feet  of  sandy  shale  over- 
lain by  hard  sandstone,  which  makes  an  admirable  roof.  The  floor 
is  sandstone  of  the  basal  bed  of  the  Lakota  formation.  The  bone 
burns  well,  but  leaves  a  large  amount  of  white  ash,  and  it  slacks  read- 
ily. The  dip  is  very  gentle  to  the  southwest.  About  00  feet  above 
the  main  bed  is  a  smaller  one,  varying  from  H  feet  to  3  feet  in  thick- 
ness. It  consists  of  a  mixture  of  clay,  sand,  and  coal,  too  impure  for  j 
fuel.  The  following  analyses  of  the  coals  of  the  main  bed  have  been 
furnished  through  the  kindness  of  Mr.  Bidwell,  of  the  Chicago  and 
Northwestern  Railroad  Company : 
Analyses  of  coal  from 
Sundance  reg  ton. 
Sample  No.  1, 
from  large 
tunnel. 
Sample  No.  2, 
from  small 
tunnel. 
Sample  No.  3, 
bituminous 
shale  parting. 
Moisture 1 
Volatile  combustible  matter  ...   
Fixed  carbon ... 
Per  cent. 
10.45 
39.51 
41.87 
8.17 
Per  cent. 
11.00 
41.16 
40.37 
7.47 
Per  cent. 
4.77 
30.85 
25.69 
Ash 
38.69 
Total  
Sulphur 
100.00 
3.63 
100.00 
4.03 
100. 00 
2.40 
In  the  same  quarter  section,  about  500  feet  farther  west,  is  another 
adit,  100  feet  long,  on  the  main  coal  bed,  which  is  here  6-|  feet  thick, 
and  does  not  contain  the  bony  deposit  near  its  bottom.  The  coal  is 
very  firm  and  of  excellent  quality.     It  is  overlain  by  3  feet  of  light- 
