TRACERY, the term given in architecture to the upright curving or intersecting bars or ribs, used in a window or other opening to give beauty and variety to its silhouette. The term is also applied to similar forms used in relief, as wall decoration (sometimes called wall-tracery), and hence, figuratively, of any intricate line pattern. The word is often restricted to the elabor ate system of window decoration, with its derivative forms, developed in Europe during the Gothic period, but it may, with equal validity, be applied to the pierced marble screens common in the Mogul work of India, or to the pierced plaster windows of Persia, Turkey, Syria and Egypt.
The origin of European tracery is confused. Pierced marble screens, with the openings glazed, were used occasionally in Byzantine work. The Byzantines also used, commonly, groups of two, three
even more narrow, arched windows, placed close together, under a single, large, relieving arch above. In this they were followed by most of the Romanesque styles. In such groups, the supports between the adjacent openings of each group usually consisted of single colonnettes, hence the arches over them were thin and shallow; and the tympanum, or section of wall supported by them and filling the space between them and the great enclosing or relieving arch over the whole group, was necessarily thin also. Such windows are found in the greater num ber of Italian campaniles and Romanesque towers, as well as in many Romanesque triforium arcades. To decorate the tympanum, piercing was an obvious and simple method. The result was the germ of tracery.
is found in early Gothic work both in France and England. In its simplest forms the tympanum is pierced with a single opening, usually circular, but occasionally taking a four-lobed or quatrefoil form. The points between the lobes, known as cusps (q.v.), later became an important element in much Gothic ornament. In time, greater elaboration was sought by increasing the number and complexity of the piercings, and thus both the size and beauty of the entire unit. The climax of plate tracery appears in France in the group of magnificent win dows of Chartres cathedral ( I'94-1212); and in England in the rose window at Lincoln cathedral (122o), known as the Dean's eye.
As skill in stone cutting and desire for com plexity increased, the area of the tympanum wall left solid grew continually smaller, finally leaving only thin bars of stone sep arating the adjacent openings. Moreover, in Notre Dame cathe dral, Park, certain small, interior, round windows constituting a sort of upper triforium in the original design, carried decorations of little inverted arches built of stone—a sort of rudimentary tracery. About 1220 the next inevitable step in the development was taken, and a window was considered not as a group of lights carrying a little piece of pierced tympanum wall, but as a group of lights where arches are formed of a bar of stone similar in section to that of the mullion or support between them, with the space between these arches and the enclosing arch—the old tympanum—occupied by a pattern of similar stone bars. In
early work this pattern usually consists of a circle, sometimes cusped, tangent both to the enclosing arch and to the small arches of the lights below it. The cusps are usually of the type known as "soffit cusping," cut on separate pieces of stone set into grooves in the inner faces of the circle.
In France, bar tracery occurs in the rebuilt clerestorey of Notre Dame (between 1220 and 1230) in the simplest possible form, and in a more developed type, with cusps, in the apse chapels of Reims cathedral (prior to 1230). From about 1240 on it becomes common, rapidly increasing in lightness and complexity. In general, the pattern types are re stricted. There are two, three or four lights. In two-light win dows, a single cusped circle is the crowning feature. In three light windows three smaller cusped circles fill the space above. Four-light windows are formed of two two-light windows, with an additional cusped circle above. In France the spring of the arches of the lower lights is kept far below that of the enclosing arch, so that the crowning circle is large. During the late 13th century, curved-sided triangles, and trefoil and quatrefoil forms, without enclosing circles, are occasionally used. In four-light windows, the central mullion is often made heavier than the side mullions, both in depth and width, and this additional size carried around the enclosing arches of the side pairs. This heavier bar will have a section or profile, part of which is a duplicate of the smaller bars or mullions. Thus tracery of two planes and two moulding types is developed—one, that of the smaller bars, and the other, that of the larger. Each moulding type plane is known as an "order," and such a window is said to have tracery of two orders. The climax of French Rayonnant tracery can be seen in S. Urbain at Troyes (127o), S. Chapelle in Paris (1246-48) and S. Nazaire at Carcassonne (early i4th century). The rose win dows (q.v.) of the style, such as those of Notre Dame at Paris (c. 1270), designed with radiating patterns using similar combi nations of forms—arches, circles, cuspings, etc.—are perhaps the most remarkable traceried windows of the style. During the later Rayonnant period, tracery forms came to be used decoratively, for wall surfaces, pinnacles, gables, etc. Especially noteworthy is the filling of the gables of porches, above the door arches, with tracery forms. At first this was done simply, with little piercing; later, as in the Portail des Libraires, at Rouen cathedral (c. 128o), the gable became a mere decorative screen of lace-like open tracery. French Rayonnant tracery was the controlling influence in all continental tracery outside Italy.