bands or bars of stone, wood, or other material, either subdividing an opening or standing in relief against a wall and forming an ornamental pattern of solid members and open spaces. The term refers especially to the subdivisions in the arched openings of Gothic architecture. In Romanesque design the enclosing of twin openings within a single arch created a wall space above them, where a circular or quatrefoil opening was pierced as an ornament. This plate tracery became more complex in 12th-century rose windows of the Cathedral of Chartres and in early Gothic English churches. Later, windows became larger, areas of solid stone smaller, and masonry members more slender; the patterns in the spaces above the arches were created by bars of stone rather than by a pierced design. Such bar tracery (e.g., in the cathedral at Reims) prevailed in both France and England by the first half of the 13th cent., creating circles, trefoils, quatrefoils, and other varied geometrical designs. The…