312  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull.  225. 
Structure. — This  coal  field  lies  in  a  structural  basin  known  as  the 
Elders  Ridge  syncline.  The  position  of  the  axis  is  shown  on  the  accom- 
panying sketch  map  (fig.  8).  It  crosses  the  river  above  Edri,  passes 
close  to  the  Foster  mine  (No.  12),  a  few  rods  east  of  the  Robert  Fritz 
hank  (No.  8),  and  through  Elders  Ridge  near  the  academy.  It  enters 
the  northern  block  between  the  W.  B.  Davis  and  John  D.  Hart  heirs 
banks  (No.  6),  passes  west  of  West  Lebanon,  and  leaves  the  field  near 
Holsten  Brothers  bank  (No.  1).  The  beginning  of  the  sharp  deflection 
to  the  east,  which  takes  the  axis  to  Crooked  Creek,  nearly  2  miles  east 
of  Shelocta,  is  shown  north  of  the  coal  banks  on  the  Hugh  Blakley 
(No.  2)  and  Madison  Craig  (No.  3)  farms.  All  of  the  coal  on  the  east 
side  of  this  syncline  rises  toward  Blacklegs  Creek,  and  all  on  the  west 
toward  Long  Run.  The  basin  is  deeper  in  the  vicinity  of  Elders 
Ridge  than  at  Edri  or  West  Lebanon,  so  that  the  structural  shape  of 
the  field  is  a  broad  canoe-like  fold,  with  the  rocks  dipping  from  all 
sides  toward  the  center.  The  dip  is  gentle,  being  just  enough  to  aid 
the  operations  of  the  miner. 
The  profile  of  the  axis  of  the  basin  is  shown  by  the  elevations  of  the 
Pittsburg  coal  above  mean  sea  level.  From  the  northeast  to  the 
southwest  along  the  bottom  of  the  syncline  the  elevations  at  six  points 
are  as  follows: 
Elevations  of  Pittsburg  coal  above  sea  level. 
Feet. 
Holsten  Brothers,  No.  1 1, 180 
John  D.  Hart,  No.  6 1, 112 
Elders  Ridge,  deep  well  near  creamery 1,  070 
Eobert  Fritz,  No.  8 1,  022 
Foster,  No.  12 1, 100 
West  side  of  Kiskiminitas  River 1, 150 
This  shows  that  the  deepest  part  of  the  syncline  lies  between  Elders 
Ridge  and  the  point  where  the  axis  crosses  Big  Run.  The  axis  rises 
slowly  from  Big  Run  to  the  northeast,  but  more  rapidly  from  the 
Fritz  farm  to  Foster,  the  coal  rising  in  this  direction  about  60  feet  in 
little  more  than  a  mile. 
DEVELOPMENT. 
It  may  be  well  here  to  define  certain  terms  in  common  use.  An 
opening  is  a  small  excavation  which  reveals  the  coal  in  place  and  the 
thickness  of  the  bed.  A  coal  bank  is  a  small  mine  in  which  a  few  men, 
from  1  to  10,  are  employed,  and  in  which  the  coal  is  mined  and 
brought  out  to  the  scaffold  without  the  use  of  machinery.  A  coal 
mine  employs  enough  men  to  require  a  mine  boss,  probably  uses 
nmchines  for  undercutting  the  coal,  and  hauls  by  means  other  than 
hand.  Coalpit  is  a  term  applied  without  discrimination  to  openings, 
banks,  and  mines. 
