Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
|
See also:ABACUS (Gr. 15t(34, a slab; Fr. abaque, tailloir) , in See also:architecture, the upper member of the See also:capital of a See also:column . Its See also:chief See also:function is to provide a larger supporting See also:surface for the See also:architrave or See also:arch it has to carry . In the See also:Greek Doric See also:order the See also:abacus is a See also:plain square slab . In the See also:Roman and See also:Renaissance Doric orders it is crowned by a moulding . In the Archaic-Greek Ionic order, owing to the greater width of the capital, the abacus is rectangular in See also:plan, and consists of a carved See also:ovolo moulding . In later examples the abacus is square, except where there are See also:angle volutes, when it is slightly curved over the same, In the Roman and Renaissance Ionic capital, the abacus is square with a See also:fillet, on the See also:top of an See also:ogee moulding, but curved over angle volutes . In the Greek Corinthian order the abacus is moulded, its sides are See also:concave and its angles canted (except in one or two exceptional Greek capitals, where it is brought to a See also:sharp angle); and the same shape is adopted in the Roman and Renaissance Coring thian and Composite capitals, in some cases with the ovolo moulding carved . In Romanesque architecture the abacus is square with the See also:lower edge splayed off and moulded or carved, and the same was retained in See also:France during the See also:medieval See also:period; but in See also:England, in See also:Early See also:English See also:work, a circular deeply moulded abacus was introduced, which in the 14th and 15th centuries was transformed into an octagonal one . The diminutive of Abacus, ABACISCUS, is applied in architecture to the chequers or squares of a See also:tessellated See also:pavement . " Abacus " is also the name of an See also:instrument employed by the ancients for arithmetical calculations; pebbles, bits of See also:bone or coins being used as counters . Fig . 1 shows a Roman abacus taken from an See also:ancient See also:monument .
It contains seven See also:long and seven shorter rods or bars, the former having four perforated beads See also:running on them and the latter one
.
The See also:bar marked I indicates See also:units, X tens, and so on up to millions
.
The beads on the shorter bars denote See also:fives,—five units, five tens, &c
.
The See also:rod 0 and corresponding See also:short rod are for marking ounces ; and the short See also:quarter rods for fractions of an See also:ounce
.
The See also:Swan-See also:Pan of the See also:Chinese (fig
.
2) closely resembles the Roman abacus in its construction and use
.
Computations are made with it by means of balls of bone or See also:ivory running on slender See also:bamboo rods, similar to the simpler See also:board, fitted up with beads strung on wires; which is employed in teaching the rudiments of See also:arithmetic in English See also:schools
.
The name of " abacus " is also given, in See also:logic, to an
instrument, often called the " logical See also:machine," analogous to the mathematical abacus
.
It is constructed to show all the possible combinations of a set of logical terms with their negatives, and, further, the way in which these combinations are affected by the addition of attributes or other limiting words, i.e. to simplify mechanically the See also:solution of logical problems
.
These See also:instruments are all more or less elaborate developments of the " logical See also:slate," on which were written in See also:vertical columns all the combinations of symbols or letters which could be made logically out of a definite number of terms
.
These were compared with any given premises, and those which were incompatible were crossed off
.
In the abacus the combinations are inscribed each on a single slip of See also:wood or similar substance, which is moved by a See also:
The See also:principal examples of such See also:machines are those of W
.
S
.
See also:Jevons (See also:Element
.
Lessons in Logic, c. See also:xxiii.), See also: |
|
|
[back] ABACA, or ABAIIA |
[next] ABADDON |
There are no comments yet for this article.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.
Links to articles and home page are encouraged.