...which he hopes to escape, if defeated. A guard stationed at Bridge Eighty-four on the Northern Central Railroad, heard firing in that direction, like that of flying artillery; whence it is believed Pleasanton is again at work with his dashing cavalry, fighting for the possession of the gap. Columbia, Pa., July 3.--Capt. Roberts, of Philadelphia, who was captured near Gettysburg and paroled, has arri...