Collier's New Encyclopedia (1921)/Abacus
ABACUS, in architecture, a constituent part of the capital of a column, which supports the horizontal entablement. In arithmetic, the name of an instrument employed to teach the elementary principles of the science of numbers. The Chinese abacus is also an instrument for facilitating arithmetical calculations. It consists of several series of beads or counters strung upon brass wires stretched from the top to the bottom of an instrument, and divided in the middle by a cross-piece from side to side. In the upper compartment every wire has two beads, each of which counts five; in the lower space every wire has five beads of different values; the first being counted as one, the second as 10, the third as 100, and so on.