APSE.--A semicircular or polygonal termination to, or projection from, a church or other public building. ARCADE.--A range of arches, supported on piers or columns. ARCH.--A construction of wedge-shaped blocks of stone, or of bricks, of a curved outline, and spanning an open space. The principal forms of arch in use are Semicircular; Acutely-pointed, or Lancet; Equilateral, or Less Acutely-pointed; Four-centred, or Depressed Tudor; Three-centred, or Elliptic; Ogival; Segmental; and Stilted. (Figs. _A_ to _F_.) ARCHITRAVE.--(1) The stone which in Classic and Renaissance architecture is thrown from one column or pilaster to the next. (2) The moulding which in the same styles is used to ornament the margin of a door or window opening or arch. ASHLAR.--Finely-wrought masonry, employed for the facing of a wall of coarser masonry or brick. ATTIC (In Renaissance Architecture).--A low upper story, distinctly marked in the architecture of the building, usually surmounting an order; (2) in ordinary building, any story in a roof. BAILEY (from _vallum_).--The enclosure of the courtyard of a castle. BALL-FLOWER.--An ornament representing a globular bud, placed usually in a hollow moulding. BALUSTER.--A species of small column, generally of curved outline. BALUSTRADE.--A parapet or rail formed of balusters. [Illustration: FIG. _A_.--SEMICIRCULAR ARCH.] [Illustration: FIG. _B_.--STILTED ARCH.] The Semicircular and the Stilted Semicircular Arch were the only arches in use till the introduction of the Pointed Arch. Throughout the Early English, Decorated, and Perpendicular periods they occur as exceptional features, but they were practically superseded after the close of the 12th cent. [Illustration: FIG. _C_.--EQUILATERAL ARCH.] [Illustration: FIG. _D_.--LANCET ARCH.] The Lancet Arch was characteristic of the Early English period, is never found earlier, and but rarely occurs later. The Equilateral Arch was the favourite arch of the architects of the geometrical Decorated, but is not unfrequently met with in the early part of the Perpendicular period. [Illustration: FIG. _E_.--OGIVAL ARCH.] [Illustration: FIG. _F_.--DEPRESSED TUDOR ARCH.] The Depressed (or Four-centred) Tudor Arch is characteristic of the Perpendicular period, and was then constantly employed. The Ogival Arch is occasionally employed late in that period, but was more used by French and Italian architects than by those of Great Britain. BAND.--A flat moulding or projecting strip of stone. BARREL-VAULTING.--See Waggon-head vaulting. BARGE-BOARD (OR VERGE-BOARD).--An inclined and pierced or ornamented board placed along the edge of a roof when it overhangs a gable wall.