Wednesday, July 29, 2009

William Oughtred and the Oughtred Society

William Oughtred (1574-1660) was an English Ordained Episcopal Minister who is best known for his mathematical work. He was a Fellow of Kings College, Cambridge.

Oughtred is credited with the invention of the slide rule in  1622.  While it was John Napier who invented logarithms and Edmund Gunther who invented the logarithmic scale, it was Oughtred who recognized that by using two Gunther scales sliding by each other he could perform multiplication and division more rapidly than on a Gunther scale alone.  He conceived of this as two circular Gunther logarithmic scales.

In addition to the slide rule he is also known for the introduction of the symbols "x" for multiplication, and "sin" and "cos" for the sine and cosine functions, and "::" for proportion. The book he wrote which he is most noted for is Clavis Mathematicae (1631). 

A very good biography of William Oughtred was written by Florian Cajori entitled William Oughtred, a Great Seventeenth-Century Teacher of Mathematics, Open Court Publishing Co., Chicago, 1916. Cajori also wrote History of the Logarithmic Slide Rule, Engineering News Publishing Co., 1909 which contains many references to Oughtred. There are in print reprints of this volume.

The Oughtred Society is a non-profit educational organization dedicated to the preservation and history of the slide rule and other calculating instruments. Their goals include the dissemination and sharing of information and encouragement for collectors. They are affiliated with organizations in the United Kingdom, Germany, and The Netherlands with similar goals. The Journal of the Oughtred Society, a scholarly publication is put out semiannually by the Society. They have a number of meetings each year, usually on the East Coast and West Coast.  They have a website: and encourage membership.
When I attended the last meeting in Mountain View, CA on June 27 it was held at the Computer History Museum.  It was great to see so many familiar faces again.

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