GEO. E. SELLERS LOCOMOTIVE FOR "MIDDLE RAIL" 1847

     This engine had the usual pair of cylinders, working coupled driving wheels on the level and moderately inclined portions of the line while by means of an extra pair of cylinders and a corresponding pair of wheels working on vertical axles and gripping a middle rail on steep inclines, the effective adhesion might be increased to almost any extent. The method of working the gripping wheels from the upper pair of cylinders and through bevel gearing will be seen on drawing.

     Each pair of cylinders had its own throttle valve.

     Mr. Sellers constructed 4 or 5 of these engines at Philadelphia for the Panama Railroad, but were never used.