Napier's bones
Napier's bones is a manually-operated calculating device created by John Napier of Merchiston for calculation of products and quotients of numbers. The method was based on Arab mathematics and the lattice multiplication used by Matrakci Nasuh in the Umdet-ul Hisab and Fibonacci's work in his Liber Abaci. The technique was also called
Rabdology (from Greek ῥάβδoς, "rod" and -λογία, "study"). Napier published his version in 1617 in
Rabdologiæ, printed in Edinburgh, Scotland, dedicated to his patron Alexander Seton. Using the multiplication tables embedded in the rods, multiplication can be reduced to addition operations and division to subtractions. More advanced use of the rods can even extract square roots. Note that
Napier's bones are not the same as logarithms, with which Napier's name is also associated. The complete device usually includes a base board with a rim; the user places Napier's rods inside the rim to conduct multiplication or division. The board's left edge is divided into 9 squares, holding the numbers 1 to 9. The
Napier's rods consist of strips of wood, metal or heavy cardboard.