A mechanical device consisting of a sliding portion and a fixed case, each marked with logarithmic axes. By lining up the ticks, it is possible to do multiplication by taking advantage of the additive property of logarithms. More complicated slide rules also allow the extraction of roots and computation of trigonometric functions.
According to Steinhaus (1999, p. 301), the principle of the slide rule was first enumerated by E. Gunter in 1623, and in 1671, S. Partridge constructed an instrument similar to the modern slide rule. The Oughtred Society, a group of slide rule collectors, claims that W. Oughtred invented the first slide rule in 1622.
The slide rule was an indispensable tool for scientists and engineers through the 1960s, but the development of the desk calculator (and subsequently pocket calculator) rendered slide rules largely obsolete beginning in the early 1970s.
