Definition
In classical architecture, the shape of the abacus and its edge profile varies in the different classical orders. In the Greek Doric order, the abacus is a plain square slab without mouldings, supported on an echinus. In the Roman and Renaissance Doric orders, it is crowned by a moulding (known as "crown moulding"). In the Tuscan and Roman Doric capital, it may rest on a boltel.
In the archaic Greek Ionic order, the abacus is rectangular in plan, owing to the greater width of the capital, and consists of a carved ovolo moulding. In later examples, the slab is thinner and the abacus remains square, except where there are angled volutes, where the slab is slightly curved. In the Roman and Renaissance Ionic capital, the abacus is square with a fillet on the top of an ogee moulding with curved edges over angled volutes.
In an angular capital of the Greek Corinthian order, the abacus is moulded, its sides are concave, and its angles canted (except in one or two exceptional Greek capitals, where it is brought to a sharp angle); the volutes of adjacent faces meet and project diagonally under each corner of the abacus. The same shape is adopted in the Roman and Renaissance Corinthian and Composite capitals, in some cases with the carved ovolo moulding.
In Romanesque architecture, the abacus survives as a heavier slab, generally moulded and decorated. It is often square with the lower edge splayed off and moulded or carved, and the same was retained in France during the medieval period. In Early English work, a circular deeply moulded abacus was introduced, which in the 14th and 15th centuries was transformed into an octagonal one.
In Gothic architecture, the moulded forms of the abacus vary; it may even be a flat disk or drum. The form of the Gothic abacus is often affected by the shape of a vault that springs from the column, in which case it is called an impost block.
Read more about this topic: Abacus (architecture)
Famous quotes containing the word definition:
“I’m beginning to think that the proper definition of “Man” is “an animal that writes letters.””
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
“The man who knows governments most completely is he who troubles himself least about a definition which shall give their essence. Enjoying an intimate acquaintance with all their particularities in turn, he would naturally regard an abstract conception in which these were unified as a thing more misleading than enlightening.”
—William James (1842–1910)
“It is very hard to give a just definition of love. The most we can say of it is this: that in the soul, it is a desire to rule; in the spirit, it is a sympathy; and in the body, it is but a hidden and subtle desire to possess—after many mysteries—what one loves.”
—François, Duc De La Rochefoucauld (1613–1680)