Abacus of the romans
The abacus is a replica of an original that is kept in the collection of the Bibilothéque Nationale in Paris. The abacus is also called a counting frame and is a calculating tool that was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants, traders and clerks.
The normal method of calculating in ancient Rome, as in Greece, was by moving counters on a smooth table. Originally pebbles (calculi) were used. Later, and in medieval Europe, jetons were manufactured. Marked lines indicated units, fives, tens etc. as in the Roman numeral system. This system of ‘counter casting’ continued into the late Roman empire and in medieval Europe, and persisted in limited use into the nineteenth century. Due to Pope Sylvester II’s reintroduction of the abacus with very useful modifications, it became widely used in Europe once again during the 11th century. This abacus used beads on wires unlike the traditional Roman counting boards which meant the abacus could be used much faster.
Writing in the 1st century BC, Horace refers to the wax abacus, a board covered with a thin layer of black wax on which columns and figures were inscribed using a stylus.
Our example of the Roman abacus dates to the 1st century AD. It has eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each. The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives –five units, five tens etc., essentially in a bi-quinary coded decimal system, obviously related to the Roman numerals. The short grooves on the right may have been used for marking Roman “ounces” (i.e. fractions).
- Size 123 x 83 mm Roman abacus
- handmade from real bronze
- fully functional
R. Fellmann, Römische Rechentafeln aus Bronze. Antike Welt 14, 1, 1983, 36-40
Kretzschmar, Fritz ; Heinsius, Elli: Über einige Darstellungen altrömischer Rechenbretter. - S. 96-108, Taf. 3-4