In architecture

Architecture

Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...

, an abacus (from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 abax, slab; or French abaque, tailloir; plural abacuses or abaci) is a flat slab forming the uppermost member or division of the capital

Capital (architecture)

In architecture the capital forms the topmost member of a column . It mediates between the column and the load thrusting down upon it, broadening the area of the column's supporting surface...

 of a column

Column

A column or pillar in architecture and structural engineering is a vertical structural element that transmits, through compression, the weight of the structure above to other structural elements below. For the purpose of wind or earthquake engineering, columns may be designed to resist lateral forces...

, above the bell

Capital (architecture)

In architecture the capital forms the topmost member of a column . It mediates between the column and the load thrusting down upon it, broadening the area of the column's supporting surface...

. Its chief function is to provide a large supporting surface (wider than the capital) to receive the weight of the arch

Arch

An arch is a structure that spans a space and supports a load. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.-Technical aspects:The...

 or the architrave

Architrave

An architrave is the lintel or beam that rests on the capitals of the columns. It is an architectural element in Classical architecture.-Classical architecture:...

 above. The diminutive of abacus, abaculus, is used to describe small mosaic

Mosaic

Mosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials. It may be a technique of decorative art, an aspect of interior decoration, or of cultural and spiritual significance as in a cathedral...

 tiles, also called abaciscus or tessera

Tessera

A tessera is an individual tile in a mosaic, usually formed in the shape of a cube. It is also known as an abaciscus, abaculus, or, in Persian کاشي معرق. In antiquity, mosaics were formed from naturally colored pebbles, but by 200 BC purpose-made tesserae were being used...

, used to create ornamental floors with detailed patterns of chequers or squares in a tessellated pavement.

In classical architecture

Classical architecture

Classical architecture is a mode of architecture employing vocabulary derived in part from the Greek and Roman architecture of classical antiquity, enriched by classicizing architectural practice in Europe since the Renaissance...

, the shape of the abacus and its edge profile varies in the different classical order

Classical order

A classical order is one of the ancient styles of classical architecture, each distinguished by its proportions and characteristic profiles and details, and most readily recognizable by the type of column employed. Three ancient orders of architecture—the Doric, Ionic, and Corinthian—originated in...

s. In the Greek Doric order

Doric order

The Doric order was one of the three orders or organizational systems of ancient Greek or classical architecture; the other two canonical orders were the Ionic and the Corinthian.-History:...

, the abacus is a plain square slab without moulding

Molding (decorative)

Molding or moulding is a strip of material with various profiles used to cover transitions between surfaces or for decoration. It is traditionally made from solid milled wood or plaster but may be made from plastic or reformed wood...

s, supported on an echinus

Echinus

Echinus may refer to:* Mallotus , synonym for a genus of the plant* Echinus , a genus of animals* Echinus , a window manager* Molding , similar to the ovolo molding...

. In the Roman and Renaissance Doric orders, it is crowned by a moulding (known as "crown moulding

Crown molding

Crown molding encapsulates a large family of moldings which are designed to gracefully flare out to a finished top edge. Crown molding is generally used for capping walls, pilasters, and cabinets, and is used extensively in the creation of interior and exterior cornice assemblies and door and...

"). In the Tuscan

Tuscan order

Among canon of classical orders of classical architecture, the Tuscan order's place is due to the influence of the Italian Sebastiano Serlio, who meticulously described the five orders including a "Tuscan order", "the solidest and least ornate", in his fourth book of Regole generalii di...

 and Roman Doric capital, it may rest on a boltel

Bowtell

Bowtell is derived from the medieval term bottle; in architecture it refers to a round or corniced molding below the abacus in a Tuscan or Roman Doric capital; the word is a variant of boltel, which is probably the diminutive of bolt, the shaft of an arrow or javelin...

.

In the archaic Greek Ionic order

Ionic order

The Ionic order forms one of the three orders or organizational systems of classical architecture, the other two canonic orders being the Doric and the Corinthian...

, the abacus is rectangular in plan, owing to the greater width of the capital, and consists of a carved ovolo

Ovolo

Ovolo in architecture, is a convex molding known also as the echinus, which in Classical architecture was invariably carved with the egg-and-dart ornament. The molding is called a quarter-round by woodworkers...

 moulding. In later examples, the slab is thinner and the abacus remains square, except where there are angled volute

Volute

A volute is a spiral scroll-like ornament that forms the basis of the Ionic order, found in the capital of the Ionic column. It was later incorporated into Corinthian order and Composite column capitals...

s, 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

Ogee

An ogee is a curve , shaped somewhat like an S, consisting of two arcs that curve in opposite senses, so that the ends are parallel....

 moulding with curved edges over angled volutes.

In an angular capital of the Greek Corinthian order

Corinthian order

The Corinthian order is one of the three principal classical orders of ancient Greek and Roman architecture. The other two are the Doric and Ionic. When classical architecture was revived during the Renaissance, two more orders were added to the canon, the Tuscan order and the Composite 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

Composite order

The composite order is a mixed order, combining the volutes of the Ionic order capital with the acanthus leaves of the Corinthian order. The composite order volutes are larger, however, and the composite order also has echinus molding with egg-and-dart ornamentation between the volutes...

 capitals, in some cases with the carved ovolo moulding.

In Romanesque architecture

Romanesque architecture

Romanesque architecture is an architectural style of Medieval Europe characterised by semi-circular arches. There is no consensus for the beginning date of the Romanesque architecture, with proposals ranging from the 6th to the 10th century. It developed in the 12th century into the Gothic style,...

, 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

Gothic architecture

Gothic architecture is a style of architecture that flourished during the high and late medieval period. It evolved from Romanesque architecture and was succeeded by Renaissance 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.

Examples in England

Early Saxon

Anglo-Saxon architecture

Anglo-Saxon architecture was a period in the history of architecture in England, and parts of Wales, from the mid-5th century until the Norman Conquest of 1066. Anglo-Saxon secular buildings in Britain were generally simple, constructed mainly using timber with thatch for roofing...

 abaci are frequently simply chamfered, but sometimes grooved as in the crypt at Repton

Repton

Repton is a village and civil parish on the edge of the River Trent floodplain in South Derbyshire, about north of Swadlincote. Repton is close to the county boundary with neighbouring Staffordshire and about northeast of Burton upon Trent.-History:...

 (fig. 1) and in the arcade of the refectory at Westminster Abbey

Westminster Abbey

The Collegiate Church of St Peter at Westminster, popularly known as Westminster Abbey, is a large, mainly Gothic church, in the City of Westminster, London, United Kingdom, located just to the west of the Palace of Westminster. It is the traditional place of coronation and burial site for English,...

. The abacus in Norman work is square where the columns are small; but on larger piers it is sometimes octagonal, as at Waltham Abbey

Waltham Abbey (abbey)

The Abbey Church of Waltham Abbey has been a place of worship since at least 1030, and is in the town of Waltham Abbey, Essex, England. The Prime Meridian passes through its grounds. Harold Godwinson is said to be buried just outside the present abbey...

. The square of the abacus is often sculptured with ornament

Ornament (architecture)

In architecture and decorative art, ornament is a decoration used to embellish parts of a building or object. Large figurative elements such as monumental sculpture and their equivalents in decorative art are excluded from the term; most ornament does not include human figures, and if present they...

s, as at the White Tower

Tower of London

Her Majesty's Royal Palace and Fortress, more commonly known as the Tower of London, is a historic castle on the north bank of the River Thames in central London, England. It lies within the London Borough of Tower Hamlets, separated from the eastern edge of the City of London by the open space...

 and at Alton, Hampshire

Alton, Hampshire

Alton is a historic market town and civil parish in the East Hampshire district of the English county of Hampshire. It had a population of 16,584 at the 1991 census and is administered by East Hampshire district council. It is located on the source of the River Wey and is the highest town in...

 (fig. 2). In Early English work, the abacus is generally circular, and in larger work, a group of circles (fig. 4), with some examples of octagonal and square shapes. The mouldings are generally half-rounds, which overhang deep hollows in the capital. In France, the abacus in early work is generally square, as at Chateau Blois (fig. 3).

Examples in France

The first abacus pictured below (fig. 5) is decorated with simple mouldings and ornaments, common during the 12th century, in Île-de-France, Normandy, Champagne, and Burgundy regions, and from the choir of Vézelay Abbey

Vézelay Abbey

Vézelay Abbey was a Benedictine and Cluniac monastery in Vézelay in the Yonne département in Burgundy, France. The Benedictine abbey church of Ste-Marie-Madeleine Vézelay Abbey (now known as Basilique Sainte-Marie-Madeleine) was a Benedictine and Cluniac monastery in Vézelay in the Yonne...

 (fig. 6). Figure 7 shows a circular abacus used at windows in the side chapels of Notre Dame de Paris

Notre Dame de Paris

Notre Dame de Paris , also known as Notre Dame Cathedral, is a Gothic, Roman Catholic cathedral on the eastern half of the Île de la Cité in the fourth arrondissement of Paris, France. It is the cathedral of the Catholic Archdiocese of Paris: that is, it is the church that contains the cathedra of...

. Towards the end of the 13 century, this element decreases in importance—they became short with a narrow profile during the 14th century, and disappeared almost entirely during the 15th century (fig. 8).

External links

• Abacus, Smith's Dictionary of Greek and Roman Antiquities