POCKET    (OAT,   DISTRICT,    VIRGINIA.  411 
Gap.  Its  principal  tributaries  are  Gin  Creek,  Baley  Trace,  Puckell 
Creek,  and  Stone  Creek,  all  entering  from  the  west.  Fawn  Branch 
and  Ely  Creek,  tributaries  of  Baley  Trace  and  Stone  ( !reek .  respectively , 
also  drain  small  areas  in  the  western  part  of  the  district.  These  are 
all  vigorous  mountain  streams,  carrying  considerable  ,,  ater  except  in 
very  dry  seasons. 
STRUCTURE. 
The  structure  of  the  rocks  in  the  Pocket  coal  district  is  compara- 
tively simple.  Throughout  the  greater  part  of  the  area  the  beds  lie 
nearly  horizontal,  dipping  gently  northwestward.  Along  the  base  of 
Stone  Mountain,  however,  they  are  sharply  upturned,  and  this  moun- 
tain is  composed  of  vertical  strata  which  produce  sharp,  knife- blade 
ridges.  It  is  possible  that  the  beds  are  more  or  less  faulted  along  the 
northern  side  of  Stone  Mountain,  where  their  dips  change  from  a  low 
angle  to  vertical  within  less  than  one-fourth  of  a  mile.  No  definite 
evidence  of  a  fault  along  this  line,  however,  was  observed  in  the  field. 
Throughout  the  central  part  of  the  district,  where  the  rocks  are  nearly 
horizontal,  no  faults  were  observed  or  reported. 
GEOLOGIC  OCCURRENCE  OF  COAL. 
The  rocks  of  the  Pocket  coal  district  all  belong  to  the  Pottsville 
group,  of  Pennsylvanian  age.  They  have  an  estimated  thickness  of 
about  4,000  feet.  The  beds  constituting  the  lower  half  of  the  section 
have  not  been  subdivided  into  formations  in  this  district.  They  con- 
sist mainly  of  sandstone  and  shale  with  many  beds  of  coal  distributed 
throughout.  The  beds  of  workable  thickness,  however,  are  confined 
largely  to  the  upper  half  of  the  section. 
During  the  present  investigation  information  was  obtained  from 
representatives  of  the  Black  Mountain  Coal  Land  Company,  the  prin- 
cipal owner  of  this  part  of  the  Little  Black  Mountain  coal  field,  con- 
cerning the  relative  position  of  all  the  important  workable  coal  beds 
with  respect  to  a  gray,  coarse-grained  sandstone  occurring  near  the 
summit  of  Little  Black  Mountain,  which  is  said  to  be  the  Harlan  sand- 
stone. This  information,  together  with  observations  on  the  quality 
of  the  coal  of  the  different  beds,  is  here  set  forth. 
There  are  twelve  known  workable  coal  beds  in  this  district  and  two 
which  may  possibly  be  workable.  They  have  a  combined  thickness 
of  about  54  feet,  and  occur  within  a  stratigraphic  interval  of  about 
2,090  feet.  These  beds  are  designated  by  numbers  ranging  from  1  to 
12.  Bed  1,  the  lowest  in  the  series,  occurs  about  2,090  feel  below 
the  so-called  Harlan  sandstone,  and  bed  12,  the  highest,  immediately 
beneath  it.     A  generalized  section,  omitting  all  details  and  showing 
