Robertson-type slide rule

This large slide rule, listed in the Conservatoire’s collections in 1853, is of the kind invented by the Englishman John Robertson, director of the Royal Naval Academy in Portsmouth. An improvement of the logarithmic slide rule devised by the London-based mathematician Edmund Gunter and furthering Napier’s work on logarithms, this wood and brass slide rule has several fixed scales and a sliding scale, a screw adjustment mechanism and a cursor. It was widely used for marine navigation calculations. Incorporating numerous innovations, the slide rule was increasingly used from the mid-19th century onwards, and remained the principal computational tool of engineers and scientists until it was superseded by electronic calculators in the 1970s.