BUTTRESS (OF. boutcrets, from banter, boter, to thrust). A structure, usually in the form of a pier, erected for the purpose of giving additional stability to a wall. It is not par ticularly necessary, except in vaulted construc tion, so little trace of it is found in Egyptian or Greek art. As its purpose is to 'balance the outward pressure or thrust, it was not re quired in the concrete Roman structures, where the pressure, as in a casting, was only down ward. The use of buttresses begins in Byzan tine architecture (see BYZANTICE ART), is con tinued in Romanesque (see ROMANESQUE ART ) and receives its complete and logical develop ment in Gothic (see GOTHIC ARCHITECTURE), for these styles used a system of balanced thrusts. This balance was at first largely secured without buttresses, which are useful only where the pressure is concentrated at certain given points, which the buttresses are used to strengthen. For instance, in a Romanesque tunnel-vaulted church, the thrust of the high vault of the nave is continuous, and is met, say, by semi-tunnel vaults over the aisles, whose out line is like that of the later Gothic flying but tresses—like a continuous flying buttress. But tresses are of four main varieties: (1) Inter nal; (2) external: (3) pier buttresses; (4) flying buttresses. In Saint Sophia, at Constan tinople, two enormous pier buttresses brace the central donie on either long side, doing what the semi-domes perform on the other sides; but the main strain is passed down toward the ground by a skillfully arranged series of vaults over galleries, aisles, etc. In other and less bold Byzantine constructions, all the buttressing is internal. As early as the Romanesque period there is a stronger tendency to reveal structural methods on the outside. The use of external buttressing in the form of piers became then very common, but they remained secondary in usefulness to the aisle vaulting. in resisting the pressure of the nave vaulting, and their capa bility by increased projection to strengthen the outer walls was not thoroughly utilized. But when, as in Norman Romanesque. ribbed cross vaulting was adopted, which concentrated the thrusts on the piers and on the points in the walls opposite them at the base of the vaulting compartments (see VAULT ) . then the buttress was enabled to fulfil its real function. The Gothic framework which then developed was composed of three interacting parts, which se cured a perfect equilibrium : ( I) The cross ribbing of the vaults; (3) the supporting piers; (3) the retaining buttresses. These Gothic but tresses consisted of two parts—pier and flying arch. The flying buttress was a purely Gothic invention. Suppose a five-aisled Gothic cathe dral, with buttresses outside opposite the fall of each vaulting compartment, and occupying substantially all the space between the large stained-glass windows. A heavy buttress pier
rises from the ground, projecting from the outer aisle wall to a point about opposite the base of the vaulting of the nave. it is divided into three stories—the first is part of the outer aisle wall, and receives its vault thrust directly; the second is joined to the upper part of the wall of the gallery, over the inner side aisle, by a flying half arch abutting against its pier but tress; the third is joined in the same way by a longer arch to the base of the vault of the main nave. These flying arches receive the thrust and transmit it along the line of greatest re sistance to the main pier buttress. The de velopment of this system by Gothic architects is one of the most interesting details of the style. The earliest examples—in about 1140, at Saint Germer—are low and ineffective; they inerease in height and heaviness as the Twelfth Century advances (Esserent, Novon) ; and toward 1200 architects know just what form, position. and size are the most effective. They are then able to reduce them in hulk, the more skillfully they use them, and they begin to use for decorative purpose what would seem likely to be an awk ward blemish on the exterior of their buildings. A comparison of the buttresses of the cathedrals of Soissons, Notre Dame, Amiens. and Rheims will show how this was managed during the course of the Thirteenth Century in France_ Colonnettes against the piers, pinnacles and finials as a crown, tabernacles, engaged shafts and blind arcades, gargoyles and grouped mold ings, contributed, together with increased ele gance of form and harmony of proportions, to make the developed Gothic buttress a beautiful detail, as well as the most vital part of Gothic structure. by which heavy walls were rendered unnecessary. On French facades, the four great piers that divide them into three sections are buttresses, though other Gothic schools besides the French used the buttress: but as they did not develop it nor thoroughly grasp its function in all its delicacy, they used it less successfully and generally. The Spanish school follows the French most closely, but often omits the ondary pier buttress (cathedral at Burgos). Next in purity collies the English. where some times, as at Westminster, an approach is made to French perfection. Then comes Germany, at a great distance; while in Italy, with its de fective grasp of constructive principles. the gothic buttress is used in two or three eases .only (e.g. F'rari, Venice). Since the Gothic period the buttress has been practically elimi nated. The Renaissanee returned to the Roman method of concealed balance of thrusts, and the sonic method was followed by subsequent styles.