mass of masonry built against a wall to strengthen it. It is especially necessary when a vault or an arch places a heavy load or thrust on one part of a wall. In the case of a wall carrying the uniform load of a floor or roof, it is more economical to buttress it at certain intervals than to make the entire wall thicker. Even when a wall carries no load, it is usually buttressed rather than uniformly thickened. For a load-bearing brick wall more than 8 ft (2 m) high a buttress is used every 20 ft (6 m). The decorative possibilities of the buttress were discovered in the ancient temples at Abu Shahrein in Mesopotamia (3500–3000 B.C. ), where they were used both as utilitarian and decorative forms. The Romans employed buttresses, which sometimes projected from the exteriors of the walls and were then left as mere piles of masonry, without architectural treatment. But in the large structures, such as basilicas and baths, the buttresses that received the thrusts from the main vaulting were…