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Napier's Rabdologiæ

Calculating with rods and strips

John Napier's Rabdologiæ, published in 1617, described three devices to aid arithmetic calculations, most famously the inscribed rods known as Napier's bones.

Napier's Rabdologiæ

In 1617, after John Napier's death and three years after the publication of his book describing the discovery of the logarithm, his book Rabdologiæ, seu numerationis per virgulas libri duo was published in Edinburgh. The term "rabdology" was coined by Napier by combining the Greek words for rod and calculation. Rabdologiæ described three devices to aid arithmetic calculations: Napier's bones, a promptuary (set of strips for multiplying numbers) and a grid with counters to perform binary arithmetic. The most interesting of these are Napier’s bones, which consist of a set of rods inscribed with the multiplication table.

Artifact origin

Edinburgh, United Kingdom

Current artifact location

British Library


Arithmetic timeline Rhind Papyrus Egyptian Mathematical Problem Papyrus Salamis Tablet Bakhshali Manuscript Pacioli's Summa Incan Yupana Napier's Rabdologiæ

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Additional Reading

  • Menninger, K. W. Number Words and Number Symbols : A Cultural History of Numbers. New York: Dover, pp. 443–444 , 2013.
  • Napier, J. Rabdologiæ, seu numerationis per virgulas libri duo. Edinburgh, Scotland: A. Hart, 1617.
  • Pappas, T. The Joy of Mathematics: Discovering Mathematics All Around You. San Carlos, CA: Wide World Publishing/Tetra, pp. 64–65, 1989.
  • Richardson, W. F. (trans.). Rabdology. Cambridge, MA: MIT Press, 1990.