Brouncker, William (1620-1684)

Irish mathematician who was a founder-member and first president of the Royal Society 1662-77. One of the most brilliant mathematicians of his time, Brouncker was the first to express pi as a continuing fraction, and calculated logarithms by infinite series. Together with the English mathematician John Wallis, he solved Pierre de Fermat's questions about Pell's equation, giving a general method for their solution.

Brouncker was born at Castle Lyons, County Cork, and educated at Oxford, graduating in 1647. He was president of Gresham College, London, 1664-67. He was a friend of the English diarist Samuel Pepys, appearing frequently in his Diary (1616-69), and had a keen amateur interest in music.