Set of Napier's rods in boxwood case
John Napier, the inventor of logarithms, also invented this aid to calculation known as 'Napier's Bones' in 1617. 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 as shown, 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.
Set of Napier's bones in boxwood, in a boxwood case. John Napier (1550-1617), discoverer of logarithms, also created this popular calculating tool known as Napier's cylindrical 'rods' or 'bones'. Napier's bones reduced muliplication to a sequence of simple additions and could also be used for division and to calculate square roots.
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- Major-General H.P. Babbage
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