Richard Delamain

Richard Delamain, also written Delamaine and known as the elder (born about 1600, died about 1645), was an English engineer and teacher of mathematics known as the inventor of the slide rule. His book Grammelogia, or the Mathematicall Ring, of 1630 presented a circular slide rule of two concentric rings, each carrying a logarithmic scale and needing no cursor, and he gave the first such instrument to King Charles I, to whom he was tutor in mathematics, and obtained a ten year patent. His design differed from the one William Oughtred devised afterwards, and a priority quarrel followed in which William Forster's Circles of Proportion of 1631 accused him of plagiarism, a charge his source calls untrue. Both designs rested on the logarithmic ruler Edmund Gunter invented in 1624. In 1631 he also published a description of a horizontal quadrant for astronomical calculation.