Gothic architecture might be defined as a localization and balancing of structural strains, emphasizing vertical lines, ribbed vaults, and pointed forms. It evolved through the solution of mechanical problems set by ecclesiastical needs and artistic aspiration. Fear of fire led to vaults of stone or brick; heavier ceilings necessitated thick walls and clumsy piers; the ubiquity of downward pressure limited window space, the thick walls shadowed the narrow windows, and the interior was left too dark for northern climes. The invention of the ribbed vault lessened the ceiling weight, allowing slenderer columns and localized strains; the concentration and balancing of pressures gave the building stability without heaviness; the localization of support through buttresses allowed longer windows in thinner walls; the windows offered inviting scope for the already existing art of stained glass; and the stone frames surmounting compound windows aroused the new art of pierced design or tracery. The arches of the vault became pointed to allow arches of uneven length to reach their crowns at an even height; and other arches, and window forms, became pointed to harmonize with the arches of the vault. Better ways of bearing pressure permitted higher naves; the towers and spires and pointed arches emphasized verticality of line, and produced the soaring flight and buoyant grace of the Gothic style. All these together made the Gothic cathedral the supreme achievement and expression of the soul of man.
But it is presumptuous to concentrate a century of architectural evolution into a paragraph. Some steps in the development invite calmer scrutiny. The problem of reconciling light grace with stable strength was better solved by Gothic than by any architecture before our time; and we do not know how long our own bold challenges to gravity will escape the leveling jealousy of the earth. Neither did the Gothic architect always succeed; Chartres is still without a crack, but the choir of Beauvais Cathedral crumbled twelve years after it was built. The essential feature of the Gothic style was the functional rib: the transverse and diagonal arch ribs rising from each bay of the nave united to form a light and graceful web upon which a thin vault of masonry could rest. Each bay of the nave became a structural unit, bearing the weight and thrusts brought down by the arches rising from its piers, and supported by counter pressures from the corresponding bays of the aisles, and by outer buttresses applied to the walls at the inward springing of each transverse arch.
The buttress was an old device. Many pre-Gothic churches had pillars of masonry externally added at points of special strain. A flying buttress, however, carries a thrust or strain over open space to a base support and to the ground. Some Norman cathedrals used half arches in the triforium to prop up the arches of the nave; but such internal buttresses reached the nave wall at too low a point, and gave no strength to the clerestory where the explosive pressure of the vault was most intense. To apply support at this high point it was necessary to take the buttress out of its hiding place, let it rise from the solid ground and throw it through open space over the aisle roof to directly sustain the clerestory wall. The earliest known use of such an external flying buttress was in the cathedral of Noyon about 1150.7 By the end of that century it had become a favorite device. It had serious faults: sometimes it gave the impression of a structural skeleton, a scaffolding negligently unremoved, or the makeshift afterthought of a designer whose building sagged; “the cathedral had crutches,” said Michelet. The Renaissance would reject the flying buttress as an unsightly obstruction, and would support by other means such burdens as St. Peter’s dome. The Gothic architect thought differently; he liked to expose the lines and mechanisms of his art; he developed a fondness for buttresses, and perhaps multiplied them beyond need; he compounded them, so that they would give support at two or more points, or to one another; he beautified their stabilizing piers with pinnacles; and sometimes, as at Reims, he proved that at least one angel could stand on the point of a pinnacle.
The balancing of strains was far more vital to Gothic than the ogive or pointed arch, but this became the outward and visible sign of an inward grace. The pointed arch was a very old form. At Diarbekr in Turkey it appears on a Roman colonnade of uncertain date. The earliest dated example is at Qasr-ibn-Wardan in Syria in 561.8 The form is found in the Dome of the Rock and the Mosque of el-Aqsa at Jerusalem in the seventh century; on a Nilometer in Egypt in 861; in the Mosque of Ibn Tulun at Cairo in 879; it was in frequent use among Persians, Arabs, Copts, and Moors before its first appearance in Western Europe in the second half of the eleventh century.9 It may have come to Southern France from Moslem Spain or through pilgrims returning from the East; or it may have arisen spontaneously in the West to meet mechanical problems in architectural design. It should be noted, however, that the problem of bringing arches of uneven length to an even crown could be solved without the ogive by “stilting” the shorter arches, i.e., raising their point of inward springing from pier or wall. This, too, had an esthetic effect, as emphasizing vertical lines; and the device was widely adopted, seldom as a substitute for the pointed arch, often as a helpful accompaniment. The ogive solved a further problem: since the aisles were narrower than the nave, an aisle bay had more length than width, and the crowns of its transverse arches would fall far short of those of its diagonals, unless the transverse arches were either pointed, or stilted so high as to prevent their harmonious inward movement with the diagonals. The ogive offered a similar solution for the difficult task of vaulting with arches of even crown the ambulatory of the apse, where the outer wall was longer than the inner, and each bay formed a trapezoid whose vault could not be forgivably designed without the pointed arch. That this was not at first chosen for its grace appears from the large number of buildings in which it was used to meet these problems, while the round arch continued to be used in windows and portals. Gradually the vertical lift of the ogive, and perhaps a desire for harmonized form, gave the pointed arch the victory. The ninety years of struggle between the round and the pointed arch—from the appearance of the ogive in the Romanesque cathedral of Durham (1104) to the final building of Chartres (1194)—constitute, in French Gothic, the period of the transition style.
The application of the pointed arch to windows created new problems, new solutions, and new charms. The channeling of strains through ribs from vault to piers, and from piers to specific points supported by buttresses, ended the need for thick walls. The space between each point of support and the next bore relatively little pressure; the wall there could be thinned, could even be removed. So large an opening could not be safely fitted with a single pane of glass. The space was therefore divided into two or more pointed windows (lancets), surmounted by an arch of stone; in effect the outer wall, like that of the nave, became a series of arches, an arcade. The four-pointed “shield” of masonry left between the upper ends of the paired and pointed windows and the top of the enclosing stone arch made an ugly blank, and cried out for decoration. About 1170 the architects of France responded with plate tracery; i.e., they pierced this shield in such a way as to leave stone bars or mullions in ornamental designs—circular, cusped, or lobed; and they filled the interstices, as well as the windows, with stained glass. In the thirteenth century the sculptors cut away more and more of the stone, and inserted into the opening little bars of stone carved into cusps or other forms. This bar tracery took on ever more complex paterns, whose predominating lines gave names to styles and periods of Gothic architecture: lancet, geometrical, curvilinear, perpendicular, and flamboyant. Similar processes applied to wall surfaces over the portals produced the great “rose windows,” whose radiating tracery generated the term rayonnant for the style that began at Notre Dame in 1230 and reached perfection in Reims and Sainte Chapelle. In the Gothic cathedral only the soaring articulation of the vault transcends the beauty of the “rose.”
Stone tracery, in the large sense of any piercing of stone in a decorative design, passed from the walls to other parts of the Gothic cathedral—the buttress pinnacles, the gables above the portals, the soffits and spandrels of arches, the triforium arcade, the sanctuary screen, the pulpit and reredos; for the Gothic sculptor, in the joy of his art, could scarcely touch a surface without adorning it. He crowded façades and cornices and towers with apostles, devils, and saints, with the saved and the damned; he cut his fancy into capitals, corbels, moldings, lintels, frets, and jambs; he laughed in stone with the whimsical or terrifying animals that he invented as gargoyles (“little throats”) to carry staining rain away from the walls or channel it into the ground through buttresses. Never elsewhere have wealth and skill, piety and lusty humor combined to provide such a feast of ornament as revels in the Gothic cathedral. Undeniably the decoration was sometimes too profuse, the tracery was carried to a fragile excess, the statues and capitals must have been too gaudy with the paint that time has cleansed away. But these are the signs of a vital exuberance, to which almost any fault can be forgiven. Wandering in these jungles and gardens of stone, it dawns upon us that Gothic art, despite its heaven-pointing lines and spires, was an art that loved the earth. Amid these saints proclaiming the vanity of vanities and the terror of the Judgment soon to come, we perceive the unseen but omnipresent medieval artisan, proud of his skill, joyful in his strength, laughing at theologies and philosophies, and drinking with relish, and to the last drop, the bubbling, brimming, lethal cup of life.