The Western Middle anthracite field is one of four structural basins containing anthracite in eastern Pennsylvania.  This report describes the geology of the part of the Western Middle field that lies in the western half of the Ashland quadrangle.  (See index map, sheet 2.)  The mapped area covers about 19 square miles in Columbia and Schuylkill Counties.  The town of Centralia is in the northern part of the area, and the town of Ashland is in the southern part.