Napier's Bones, 1671-1700.
© Science Museum / Science & Society Picture Library
John Napier (1550-1617), discoverer of logarithms, also created this popular calculating tool known as Napier's cylindrical 'rods' or 'bones'. Napier's rods reduced multiplication to a sequence of simple additions and could also be used for division and to calculate square roots. This example dates from the 17th century and consists of ten bras square section rods in a gold stamped leather case with short manuscript details, in Italian, for using the rods.