Cylindrical form of Napier's bones, c 1700.
© Science Museum / Science & Society Picture Library
John Napier (1550-1617), discoverer of logarithms, also created this popular calculating tool known as Napier's bones or rods. Napier's bones reduced muliplication to a sequence of simple additions; division and square roots could also be achieved. This example consists of a wooden box containing ten rotating cylinders each of which bears the numbers '0 times' to '9 times'. The inside of the lid is inscribed; 'This box was the identical property of the author of ye Logs, Napier 1824'. This type of Napier's bones was first published by Gaspard Schott in 1668, so it is unlikely that they were actually the property of the inventor.