ORDER, (I.) in classic architecture, a column or pilaster, with its base, shaft and capital, and the entablature (q.v.) above it (sometimes called epistyle), consisting of architrave, frieze and cornice, considered as a single architectural feature; the "orders" are systematized classifications of five different types, Tuscan, Doric, Ionic, Corinthian and Composite. (2.) In mediaeval archi tecture, in an arched door or other opening, where the opening is larger on the outer face of a thick wall than on the inner face, one of the breaks in the steps in the thickness of the wall, consisting of an arch above and a pier on each side, by which the transition from larger exterior to smaller interior opening is effected.
Greek architecture had developed three easily recognizable classes of order which had been adopted by the Romans, with modifications, by the middle of the 1st century, B.C. It was natural, therefore, that Vitruvius, in his remarkable treatise on architecture (last quarter of 1st century, B.C.) should have attempted to give rules for the construction of these three orders. Moreover, as the Etruscan architects had developed a simple order of their own, using a wooden entablature, he added a section dealing with that. With the republication of Vitruvius in the second half of the 15th century, he was at once hailed as the authority on all things architectural, and architectural writers of the later Italian Renaissance attempted to imitate him by giving ideal rules for the orders, which should be efforts to recon cile the standards of Vitruvius with the many varying examples of Roman work that they knew. They added as a fifth order the Composite type of capital. The two most famous of these Renais sance compilations, those of Vignola (Giacomo Barocchio, or Barozzi), published in 1563, and Palladio (157o), exerted a tre mendous influence over 17th and 18th century architecture throughout Europe, and gave rise to the idea that these compila tions were not merely statements of average usage, but rules to be absolutely followed, an idea contradicted by the architectural work of the two authors themselves. Lacking knowledge of Greek remains, and of the structural systems and details of Etruscan temples, the Tuscan order, which they described, is merely a simplified Roman Doric. Their passion for regularization showed also in the fact that they specify a definite pedestal and even a definite baluster as a part of each order. Various 18th century and modern architectural writers have attempted to simplify the order descriptions of Vignola and Palladio, and have thus per petuated the Renaissance myth of the immutability of the orders.
In general, Vignola's work was followed in France and Palladio's in England. The orders, as thus systematized, are as follows : Tuscan.—This is the simplest of the orders. It is characterized by a column seven diameters high, the capital and base each occupying one-half the diameter in height. The base consists of a plain, square plinth (q.v.) with a large torus (q.v.) and a fillet above. The capital has an astragal (q.v.) at the top of the shaft, a necking (q.v.), which is merely a short continuation of the line of the column, and above that an echinus (q.v.) consisting of a simple ovolo (q.v.) or quarter round with a fillet below it, and carrying a simple, square abacus (q.v.). The entablature, as in all the orders, is supposed to be one-quarter of the height of the column, and consists of a plain architrave (q.v.), or lower mem ber, with a simple square projection or taenia (q.v.) at the top, a plain frieze, or central member, and a cornice with a single moulding as a bed-mould (q.v.), an undecorated corona (q.v.) or projecting rectangular portion, and a cymatium (q.v.) or crowning moulding that is an ovolo.
The column is eight diameters high, and carries 20 flutes, separated by arrises (q.v.) or sharp edges. The base has two toruses, the lower one larger than the upper, and the capital is given a projecting moulding at the top of the echinus and addi tional fillets or an astragal below the ovolo. The necking is orna mented with eight rosettes. The architrave in the entablature is sometimes given two faces, the upper one projecting slightly, being wider than the lower. The taenia is decorated with a moulding and beneath each triglyph (q.v.) of the frieze, a small block called a regula (q.v.), with six guttae, or small conical forms on its under side. The frieze is ornamented by triglyphs, or vertical projections decorated with a series of vertical grooves. Between each two triglyphs is a square metope (q.v.), a plain surface carrying sculpture ; a triglyph is arranged over the centre of each column. Two forms of cornice are described; the denticular, in which the chief feature of the bed-mould is a row of dentils or little projecting blocks, and the mutular, in which the under side of the corona is decorated with projecting blocks, one over each triglyph. In both cases guttae are used on the soffit or under side of the cornice. In the denticular cornice they ornament square panels over each triglyph ; in the mutular, the under side of the projecting blocks or mutules. The cymatium consists either of a cavetto or a cyma recta, a moulding of double curvature, the convex portion below and concave portion above.