Donkin slide rule; wood, length 9 1/8", stamped "Donkin" in corner at back of rule

William Oughtred, now considered the inventor of the slide rule, said: ‘The use of instruments is indeed excellent if a man be an Artist, but contemptible being set and opposed to Art.’ But Richard Delamain, his protagonist, answered: ‘For none to know the use of mathematical instruments except he [who] knows the cause of its operation is somewhat too strict.’ In fact slide rules were only widespread for carpenters and excise men until the early 19th century, when the introduction of more general and simple instruments, such as this one for engineers, made the slide rule a ubiquitous tool.