John Napier

Portrait of John Napier

Who Spared The World Its Multiplying · Laird & Mathematician · 1550–1617

The Scottish laird who spent twenty years by hand building the tables that turn a multiplication into an addition — and who fixed the decimal point in place while describing a set of calculating rods.

Who was Napier?

John Napier was born at Merchiston Castle outside Edinburgh in 1550, the son of Sir Archibald Napier, and succeeded to the estate. He regarded himself first as a theologian. His Plaine Discovery of the Whole Revelation of Saint John, published in 1593, is a work of Protestant polemic identifying the Pope as Antichrist; it went through many editions and translations, and he thought it the important thing he had done. The world has preferred the other book. Astronomers and navigators of his day spent enormous stretches of their lives multiplying and dividing six- and seven-figure numbers, and Napier set out to abolish that labour. The Mirifici Logarithmorum Canonis Descriptio of 1614 gives a canon of numbers so arranged that a multiplication may be performed by an addition and a division by a subtraction. Building it took him about twenty years of computation done by hand. Henry Briggs, professor at Gresham College, travelled from London to Edinburgh to meet him, and the two agreed a change to the arrangement that made the tables far more convenient. Briggs computed the revised tables after Napier's death. In 1617, the year he died, Napier published the Rabdologiae, describing a set of numbered rods — Napier's bones — for carrying out multiplication by laying rods side by side. In that book he writes fractions of a unit by setting a point after the units figure and continuing in tenths, hundredths and thousandths, and he recommends the practice as the plainest available. Simon Stevin had argued for decimal fractions thirty years earlier in De Thiende, but with a cumbersome notation of circled numbers; it is Napier's point that survived and spread. He was also an active improver of his estate, experimenting with fertiliser and drainage, and drew up designs for engines of war against a threatened Spanish invasion. Locally he had a reputation as a sorcerer, which appears to have amused him and which he occasionally exploited.

Major achievements

Life in brief

Explore the life of Napier — five chapters

  1. The Laird of Merchiston — An estate, a reputation for sorcery, and a black cockerel
  2. The Book He Cared About — A Plaine Discovery, 1593
  3. Twenty Years of Arithmetic — Abolishing a labour by enduring it
  4. Briggs Comes North — A quarter of an hour of silence
  5. The Point After the Units — The smallest thing he did, and the one everybody uses

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