## Math in Computing## Mechanical and Electronic Calculating Devices |

## How did the slide rule evolve? |

In 1620 English astronomer Edmund Gunter (1581–1626) was responsible for constructing a scale rule that could be used to multiply. He divided his scale according to Napier’s principle of logarithms, meaning that multiplication could be done by measuring and adding lengths on the scale. (It is also often considered the first analog computer.)

But there is disagreement as to the true inventor of the slide rule. Many historians give the credit to English reverend William Oughtred (c. 1574-1660), who improved upon Gunter’s idea. About 1630 (although that date is highly debated), Oughtred placed two of Gunter’s scales directly opposite each other and demonstrated that one could do calculations by simply sliding them back and forth.

The slide rule was not immediately embraced by scientists, mathematicians, or the public. It took until about 1850, when French artillery officer Victor Mayer Amédée Mannheim (1831–1906) standardized the modern version of the slide rule, adding the movable double-sided cursor that gives the slide rule its familiar appearance. Slide rules were used for many decades as the major calculator for the sciences and mathematics, and ranged in shapes from straight rules to rounded.