Set of Napier's rods, 1770-1790.
© Science Museum / Science & Society Picture Library
Napier's rods, set in wooden box with trade label 'J Imison Clock and Watch Maker, Optician &tc, No 58 Hay-market, London'. John Napier (1550-1617), discoverer of logarithms, created the popular calculating tool known as Napier's rods or bones. Napier's rods reduced muliplication to a sequence of simple additions; division and square roots could also be achieved.