STONE. 
THE  ELDERS  RIDGE  COAL  EIELD,   PENNSYLVANIA. 
318 
On  the  accompanying-  sketch  map  of  the  Elders  Ridge  coal  field  most 
of  the  points  where  a  clean  face  of  the  Pittsburg  coal  may  be  seen  are 
Areas  underlain  V/7, 
by  Pittsburg  coal  vY/. 
Scale 
o ^ imlle 
Fig.  8.— Map  of  the  Elders  Ridge  coal  field,  Pennsylvania. 
indicated  by  crossed  hammers,  the  usual  symbol  for  a  mine  or  quarry. 
