Calculating Machines, 17th Century Napier's Bones, 1671-1700

Calculating Machines, 17th Century Napier's Bones, 1671-1700. John Napier (1550-1617), discoverer of logarithms, created the popular though comparatively trivial invention of the calculation device known as Napier's Rods or Bones. Napier's Rods reduced multiplication to a sequence of simple additions; division and square roots could also be achieved. Logarithms made the manipulation of large calculations simpler by adding or subtracting the index of two numbers and looking up the result in tables. This instrument consists of a wooden box containing twelve rotatable cylinders each marked with the multiplication tables from 0 to 9. This is the type of Napier's bones illustrated by Gaspard Schott in 1668. ©SSPL/Science Museum