OUGHTRED, WILLIAM

born March 5, 1574, Eton, Buckinghamshire, Eng. died June 30, 1660, Albury, Surrey English mathematician and Episcopal minister who invented the earliest form of the slide rule, two identical linear or circular logarithmic scales held together and adjusted by hand. Improvements involving the familiar inner rule with tongue-in-groove linear construction came later. In 1604 Oughtred became vicar of Shalford, Surrey, and subsequently rector of Albury. Although his years in the ministry included the period of the Commonwealth, when more than 8,000 clerics were deprived of their charges, he was permitted to continue in his parish. Oughtred's most important published work was the Clavis Mathematicae (1631; The Keys to Mathematics), which included a description of HinduArabic notation and decimal fractions and a considerable section on algebra. He experimented with many different algebraic symbols and was responsible for the use of the symbol :: in writing a proportion and the symbol for multiplication. His work on slide rules was an adaptation to a physical scale of the tabular logarithms of John Napier of Scotland. His early form of circular slide rule was invented before 1632 and the pair of rectilinear, relatively slidable members by 1633. His claim of priority of the circular rule was contested by one of his former students, Richard Delamaine the Elder. Oughtred's Trigonometria (1657) treated plane and spherical trigonometry.