A Short Slide Rule History

Within a few decades following the invention of the logarithm in the early 1600s, logarithmic scales were developed where adding lengths measured along the scale – at first by using “dividers” or “calipers” – could result in the product of two numbers, allowing for quick multiplication and division operations. Instruments improved in both accuracy and function over many years and by 1900 had gained widespread use in mathematics, science, engineering and finance. The story of the slide rule developed over the course of 350 years until the mid-1970’s at which time – essentially overnight – the introduction of the electronic calculator and the personal digital computer replaced the slide rule for everyday computational use.

The following page presents a condensed time line of the history of the slide rule. It was produced primarily from an appendix in the book Deci-Lon: An Instruction Manual, published by Keuffel & Esser Co. (K&E Slide Rules: Deci-Lon, an Instruction Manual 1962), and from the book Slide Rules: Their History, Models and Makers, by Peter M. Hopp (Hopp 1999). And following that is a short description of some of the mathematical motivation behind the early calculations of logarithms by their inventor, John Napier.