250  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
head  of  Rock  Creek,  which  has  completely  obliterated  the  coal-bearing 
rocks. 
The  Upper  field  has  received  very  much  more  attention  than  the 
Middle  or  Lower  fields  and  a  number  of  slopes  have  been  sunk  on  the 
coal  beds.  Great  activity  was  manifest  in  this  region  a  few  years  ago 
and  extensive  developments  were  projected  but,  owing  to  the  inacces- 
sibility of  the  field,  they  were  never  completed.  In  the  meantime 
claims  have  been  staked  in  both  the  Middle  and  Lower  fields  and  a 
number  of  prospect  holes  have  been  dug  which  show  that  the  coal 
beds  are  practically  continuous  throughout  the  region. 
The  writer  made  a  hurried  examination  of  the  Upper  field  and  found 
the  coals  in  much  the  same  condition  as  described  in  the  report  just 
cited.  The  development  was  done  so  long  ago  that  most  of  the 
openings  are  not  now  accessible,  consequently  no  new  information 
could  be  obtained  regarding  the  coal.  The  beds  strike  parallel  with 
the  main  axis  of  the  synclinal  trough  and  dip  strongly  to  the  south. 
Although  it  is  extremely  difficult  to  find  continuous  exposures,  the 
structure  seems  to  be  that  of  a  number  of  minor  folds  whose  axes  are 
parallel  with  the  main  axis  of  the  synclinal  trough.  The  result  of 
such  a  structure  is  to  expose  the  same  set  of  coal  beds  a  number  of 
times  across  the  basin;  consequently  the  number  of  beds  actually 
present  has  probably  been  greatly  overestimated.  As  stated  in  the 
report  previously  mentioned,  40  distinct  seams  of  bituminous  shale 
and  coaly  matter  have  been  reported  in  a  distance  of  2,700  feet  on  the 
surface,  included  in  a  mass  of  strata  2,100  feet  thick.  The  maximum 
measure  of  the  coal-bearing  shale  and  sandstone  in  other  parts  of  the 
basin  is  not  over  500  feet.  Hence  it  seems  highly  probable  that  these 
500  feet  of  sediments  have  been  folded  in  such  a  way  as  to  measure 
2,100  feet  across  their  outcropping  edges. 
At  one  place  only  in  the  Upper  field  was  the  coal  exposed,  and  at 
this  point  the  following  section  was  measured: 
/Section  of  coal  in  Upper  field. 
Ft.  In. 
Coal  (good) 0      8} 
Coal  and  shale 2      4 
Sandstone 0      3 
Carbonaceous  shale 0  11 
Coal  (crushed) 0      9 
Total 4     11 J 
As  noted  by  the  commission  in  1885,  these  coals  show  great  crushing, 
and  are  in  poor  condition  for  commercial  mining. 
The  writer  saw  no  coal  outcrops  in  the  Middle  field,  but  a  number 
of  openings  are  reported.  It  seems  altogether  probable  that  the  same 
beds  are  present  in  this  field  as  shown  in  the  Upper  field,  and  also  as 
wore  seen  at  the  Reed  shaft  in  the  Lower  field. 
The  Lower  field  has  not  received  much  attention,  but  lately  several 
