NAPIER'S BONES, an invention of the celebrated Napier (q.v.) of Merchiston fur the purpose of performing mechanically the operations of multiplication and division. The "bones" were narrow slips of bone, wood, ivory. or metal, about 3 in. long by ?Ohs of an inch in breadth, and divided by transverse lines into nine compartments; each of these compartments being divided into two portions by a diagonal line running from the upper right hand to the lower left hand corners. The " bones were divided into sets, all those of one set haying the same digit occupying the top compartment, and the several multiples of that digit occupying in order the eight lower compartments; when the mul tiple consisted of two figures, these were placed one on each side of the diagonal line. There. was necessarily a set of bones for each digit. There was also another rod simi larly divided into compartments, in which were placed the nine digits; this was called the Multiplication was performed as follows; e.g., if 6795 is to be multiplied
by four rods whose top digits were 6, 7, 9, 5 are selected and arranged in the order of the figures in the multiplicand, and the index-rod placed alongside them; the several figures of the multiplier are then sought for on the index-rod. the two lines of figures opposite each figure on the index are then added together diagonally, and the five sums Hies eiltained are arranged as follows: 9 61155 7 47565 8 54360 3 20385 4, 27180 664782080 = the product required.
Division is performed in an analogous manner. The contemporaneous invention of logarithms for the same purpose of converting multiplication and division into addition aLd subtraction caused Napier's bones to be overlooked, and they are now scarcely ever used.