Abacus, is, says Harris, [1] and following Harris the authors of Trévoux, [2] the upper part of the crown of the capital of a column. The abacus is square in the Tuscan, Doric, and ancient Ionic orders, and notched on the capitals’ faces in Corinthian and Composite capitals. [3] In these two orders, its angles are called horns, the middle is called the broom [4], and the curve is called an arc and generally has a rose [5] in the middle. Mauclerc and Harris add that workmen also call abacus a Gothic ornament with a fillet or chaplet half as wide as the ornament, and this fillet is called the fillet or the chaplet of the abacus. In the Corinthian order, the abacus is the seventh part of the capital. Andrea Palladio [6] calls abacus the plinth that surrounds the quarter-round called the ovolo  [7]; the abacus is also called the plinth.  [8] Scamozzi [9] also gives the name abacus to a hollow molding that forms the capital of the pedestal in the Tuscan order. See Harris, first and second part.

1. John Harris, 1666-1719, a London clergyman, wrote the Lexicon Technicum: or, An Universal English Dictionary of Arts and Sciences: Explaining not only the Terms of Art, but the Arts Themselves, the first volume of which was published in in 1704. The entire work was completed in 1736; a one-volume supplement would be added in 1744. The Lexicon Technicum was the main rival to the Cyclopaedia of Ephraim Chambers.

2. This refers to the reference work entitled Dictionnaire universel François et latin, but commonly referred to as the Dictionnaire de Trévoux, prepared by Jesuits working initially from Furetière’s notorious Dictionnaire universel of 1690; their identities are not known with precision. Various editions of the Dictionnaire de Trévoux were published between 1704 and 1771, originally in Trévoux, near Lyons, under the auspices of the Jesuit order.

3. The three classical orders described by Vitruvius (c. 80-15 BCE) were the Doric, the Ionic, and the Corinthian; they originated in ancient Greece. The composite order (not generally capitalized today, but capitalized in the article) was an imperial Roman form of the Corinthian order. The Tuscan order, a simplification of the Doric, was unknown to Antiquity: it was an invention of the Italian Renaissance.

4. French: balai.

5. Usually called a fleuron.

6. This Venetian architect, who lived from 1508 to 1580, is widely regarded as the most influential individual in the entire history of architecture.

7. Misprint in the 1751 edition: échime (for échine).

8. French: tailloir.

9. Vincenzo Scamozzi, 1548-1616, a Venetian architect who inherited Palladio’s projects when the latter died in 1580.