Viscount William Brouncker

1620-1684

English Mathematician

In 1662, Viscount William Brouncker proposed to the newly restored English monarch Charles II that an institution be established to advance scientific discussion and learning. The result was the Royal Society of London, of which Brouncker served as first president. In a career that put him into contact with such preeminent figures as Pierre de Fermat (1601-1665) and John Wallis (1616-1703), Brouncker examined a number of problems, particularly the use of continued fractions to express π.

Other than the fact that he was born in Castle Lyons, Ireland, to Sir William and Lady Winefrid Brouncker in 1620, the details of Brouncker's childhood are sketchy. He and his younger brother Henry probably studied with tutors; then at age 16, Brouncker entered Oxford, where he excelled at a range of subjects that included mathematics, music, languages, and medicine. While he was still in school, in 1645, his father was named a viscount by King Charles I. The elder William died a year later, and thus at age 26, the son became a peer of the realm.

Brouncker received the degree of Doctor of Physick in 1647, a year that would prove monumental in more than one respect. It was then that the forces led by Oliver Cromwell deposed Charles I, establishing a theocratic and egalitarian dictatorship under which all persons with ties to the royalty or nobility were in danger of imprisonment or even death. Therefore with apparent deliberation, Brouncker began a period of virtual invisibility that would last until the restoration of the monarchy 13 years later. During this time of self-imposed internal exile, his only notable work was a translation of Musicae compendium by René Descartes (1596-1650). Indeed, this was the only book of Brouncker's entire career, his other writings being confined to correspondence, manuscripts, and contributions published in other mathematicians' works.

In 1660, with the restoration of the monarchy under Charles II, son of Charles I, Brouncker suddenly reappeared at center-stage of English public life. He won election to parliament in that year, and in 1662, when Charles established the Royal Society as a result of a proposal put forth by Brouncker, the latter was elected its first president with no opposition. Brouncker would be reelected annually until 1677, when he decided to step down from leadership of the Royal Society.

Brouncker enjoyed a lively interaction with other mathematicians of the day. When Wallis requested help in developing an expression of π other than as an endless decimal, Brouncker applied the use of continued fractions to the problem. He also used continuous fractions for the quadrature, or squaring, of a rectangular hyperbola. He and Fermat both worked on the Pell Equation, and he interacted with James Gregory (1638-1675) on the subject of binomial series.

The fact that he never married made it easier for Brouncker to devote his time to a number of institutions and offices. In 1664, he became president of Gresham College, and entered government service as commissioner of the navy. He held the latter position until 1668, at which time he became comptroller of the treasurer's accounts. He also served as master of St. Catherine's Hospital in London from 1681 to 1684, the year he died. Since he had no heirs, his title passed to his brother Henry, who was also unmarried; therefore upon Henry's death in 1687, the family line and its title came to an end.

JUDSON KNIGHT