BONES

An instrument contrived by the celebrated Lord Napier, the inventor of the logarithms,for the purpose of performing mechanically the arith metical operations of multiplication and division. Napier's rods consist of small squared pieces of bone or ivory, box or silver, about 3 inches long, and 3-IOths of an inch in breadth, the faces of which are divided into nine little squares or cells, each of which is parted by a diagonal into two triangles. Thus: [s. 823]