William Oughtred, English mathematician, 17th century.
© Science Museum / Science & Society Picture Library
Engraving of William Oughtred (1575-1660) who wrote extensively on mathematics. In 'Clavis Mathematica' (1631), a textbook on arithmetic and algebra, Oughtred introduced many new symbols including multiplication and proportion signs. He also invented trigonometrical abbreviations and the slide rule, and is said to have died of joy at hearing of the restoration of King Charles II (1630-1685).