Priestley, Joseph, 1733–1804, English theologian and scientist.
He prepared for the Presbyterian ministry and served several
churches in England as pastor but gradually rejected orthodox
Calvinism and adopted Unitarian views. He settled in London in
1765 and moved to Birmingham some years later. In both cities he
became associated with some of the outstanding figures of his
day, such as Benjamin Franklin, James Boswell, James Watt,
Josiah Wedgwood, and Erasmus Darwin. Priestley's Essay on
Government (1768) suggested the idea of "the greatest happiness
of the greatest number" to Jeremy Bentham. In 1769 he founded
the Theological Repository for critical discussion. In his
History of Electricity (1767), he explained the rings (known as
Priestley's rings) formed by a discharge upon a metallic
surface. His improvements in the manipulation of gases enabled
him to investigate the properties of gases and to discover new
ones, including sulfur dioxide, ammonia, and what Priestley
called "dephlogisticated air," the gas