Thornton PIC Electrical and Mechanical Engineer’s Rule dated from around 1939. 10 inch celluloid faced mahogany slide rule with a metal and glass PC7A cursor. It has a green, cloth covered card case. With slide references of S, L, T, HP, KW, AMP, Prod, Quot, Volt & Dynamo.

A slide rule is a mechanical analogue computer which was one of the primary methods of calculation up until the mid-20th Century with the introduction of the desktop calculator and electronic computers. They were used for calculations including multiplication and division, as well as functions such as exponents, roots, logarithms, and trigonometry.

A.G. Thornton Ltd was a British manufacturer of slide rules, drawing, surveying and scientific Instruments. The company was founded in 1880 by Alexander George Thornton. Thornton’s took over The Precision Instrument Company (PIC) in 1901 and continued to use the PIC brand name until the 1970s. In the 1960s they introduced slide rules made of plastic, and the firm was renamed British Thornton. They stopped manufacturing slide rules in 1980. British Thornton merged with Education and Science Furniture (ESF) in January 1992 and moved to Burley, Wharfedale in Yorkshire.

This slide rule was very kindly donated by Jim Odell.

Manufacturer: Thornton
Date: 1939

This exhibit has a reference ID of CH31222. Please quote this reference ID in any communication with the Centre for Computing History.

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