Napier's Bones

Grand Illusions Verified independent store

→

John Napier (1550-1617), discoverer of logarithms, designed this popular calculating tool known as Napier's cylindrical 'rods' or 'bones'. This calculating device allowed the user to carry out multiplication and division. The 'bones' consist of a set of rectangular rods, each marked with a counting number at the top, and the multiples of that number down their lengths. When aligned against the row of multiples, any multiple of the top number can be read off from right to left by adding the digits in each parallelogram in the appropriate row. Multiplication is thus reduced to addition and the bones can also be used for division and to calculate square roots. A detailed instruction booklet is included. Show more