Joseph Priestley

Joseph Priestley was born on March 13, 1733, in Birstall, a village in the West Riding of Yorkshire, the eldest son of Jonas Priestley, a cloth finisher, and Mary Swift ^[1]. His mother died when he was six, and he was sent to live with his aunt Sarah Keighley, a devout Calvinist whose household welcomed dissenting ministers of many stripes. That early exposure to religious debate shaped him for life.

A sickly but precocious child, he learned Latin, Greek, and Hebrew at local schools, and later taught himself French, Italian, German, and elements of Chaldean, Syriac, and Arabic ^[2]. Poor health interrupted plans for a career in trade, and he turned instead toward the ministry. Because he rejected key Calvinist doctrines, including original sin as commonly taught, he could not subscribe to the orthodoxy required by many institutions.

In 1752 he entered Daventry Academy, one of the dissenting academies that educated Nonconformists barred from Oxford and Cambridge ^[1]. Daventry encouraged students to argue both sides of disputed questions, and Priestley left the academy holding heterodox views that would keep drifting further from mainstream Christianity for the rest of his life.

Priestley's first ministries, at Needham Market in Suffolk and then Nantwich in Cheshire, were modest. A stammer hampered his preaching, and his unorthodox theology unsettled some congregations. At Nantwich he opened a school and began teaching natural philosophy with air pumps and electrical machines, an early sign of the experimental bent that would define him ^[2].

In 1761 he became a tutor in languages at Warrington Academy, the leading dissenting academy of the day. There he wrote textbooks on grammar, history, and education, and argued that students should study modern subjects useful for practical life rather than a purely classical curriculum ^[3]. His years at Warrington established his reputation as one of England's most innovative educators.

A visit to London brought him into contact with Benjamin Franklin, who encouraged his growing interest in electricity. The result was The History and Present State of Electricity (1767), a work that combined a survey of the field with Priestley's own experiments, including his suggestion that electrical attraction follows an inverse square law ^[4]. The book earned him election as a Fellow of the Royal Society in 1766. Anyone asking who was Joseph Priestley in the late 1760s would have heard of a rising historian of science, a schoolmaster, and an increasingly controversial dissenting minister.

Priestley's chemical career began in earnest at Leeds, where he ministered at Mill Hill Chapel from 1767. Living next to a brewery, he experimented with the heavy gas that collected above fermenting vats, and in 1772 he published a method for dissolving that gas, now called carbon dioxide, in water ^[5]. His invention of carbonated water brought him the Royal Society's Copley Medal in 1773 and eventually gave rise to an entire soft drink industry, though Priestley never profited from it.

His most famous experiment came on August 1, 1774, while he served as librarian and companion to Lord Shelburne at Calne in Wiltshire. Using a large burning lens to heat mercuric oxide, he collected a colorless gas in which a candle burned with remarkable vigor and a mouse survived far longer than in ordinary air ^[1]. Priestley called it dephlogisticated air, interpreting it through the phlogiston theory he defended all his life. Later that year he described the experiment to Antoine Lavoisier in Paris, who repeated and reinterpreted it, named the gas oxygen, and used it to overturn phlogiston chemistry entirely ^[6]. The Swedish apothecary Carl Wilhelm Scheele had prepared the same gas independently, probably earlier, but published later, so any account of Joseph Priestley achievements must note that priority for oxygen remains shared and disputed ^[6].

Oxygen was only one of a remarkable string of discoveries. Priestley isolated and described roughly ten gases, including nitrous oxide, ammonia, sulfur dioxide, nitrogen dioxide, and carbon monoxide, at a time when most chemists recognized only a handful of distinct airs ^[5]. He also observed that green plants restore the ability of air to support flame and animal life, an experiment with a sprig of mint that pointed toward what later scientists explained as photosynthesis ^[3]. His six volumes of Experiments and Observations on Different Kinds of Air (1774 to 1786) made pneumatic chemistry a central field of eighteenth century science.

Science never displaced religion at the center of Priestley's life. He regarded his theological writing as his most important work. Over decades he moved from Calvinism through Arianism to a fully Unitarian position, denying the Trinity and arguing in An History of the Corruptions of Christianity (1782) that doctrines such as the divinity of Christ were later distortions of a simple original faith ^[2]. He helped Theophilus Lindsey establish the first avowedly Unitarian congregation in England at Essex Street Chapel, London, in 1774, and he remains a founding figure of British Unitarianism ^[7].

His politics were equally radical. Priestley campaigned against the Test and Corporation Acts, which restricted the civil rights of Dissenters, and his Essay on the First Principles of Government (1768) argued that governments should be judged by the happiness of the governed, a formulation that influenced the young Jeremy Bentham ^[3]. He supported the American colonists in the 1770s and welcomed the French Revolution in 1789, replying publicly to Edmund Burke's attacks on it.

That combination of heresy and radicalism made him notorious. Critics nicknamed him Gunpowder Joe after a sermon metaphor about laying grains of gunpowder beneath the old structures of error. In Birmingham, where he had settled in 1780 as minister of the New Meeting, hostility finally turned violent.

In 1762 Priestley married Mary Wilkinson, daughter of the Welsh ironmaster Isaac Wilkinson and sister of the industrialist John Wilkinson ^[1]. Contemporaries described her as capable and intelligent, managing the household so that her husband could write and experiment without interruption. The couple had a daughter, Sarah, and three sons, Joseph, William, and Henry.

Birmingham gave Priestley the happiest decade of his life. He joined the Lunar Society, the informal club of industrialists and natural philosophers that included Matthew Boulton, James Watt, Josiah Wedgwood, and Erasmus Darwin, and its members supplied him with funds and apparatus for his laboratory ^[8]. Friends across his life, from Franklin to Shelburne to the Lunar men, repeatedly organized subscriptions so that a minister of modest income could afford serious research.

Everything changed in July 1791. When a dinner was held in Birmingham to mark the second anniversary of the fall of the Bastille, a Church and King mob rioted for three days, burning Dissenting chapels and homes. Priestley's house, laboratory, and papers at Fairhill were destroyed, and he and his family escaped only because they fled before the crowd arrived ^[7]. He never returned to Birmingham.

After the riots Priestley moved to Hackney, near London, where he taught at New College and continued to preach. Public hostility did not fade. Effigies of him were burned, tradesmen refused his custom, and former colleagues in the Royal Society grew distant. When France made him an honorary citizen in 1792 and war between Britain and France followed in 1793, his position became still more precarious ^[2].

In April 1794 he sailed for America with his wife, following their sons who had already emigrated. He declined invitations to settle in Philadelphia, turning down a chemistry professorship at the University of Pennsylvania, and instead built a house at Northumberland, Pennsylvania, at the confluence of the branches of the Susquehanna River ^[9]. There he assembled a new laboratory, identified carbon monoxide as a distinct gas, and preached to a small congregation, helping to plant Unitarianism in the United States.

His final years mixed quiet work with grief. His son Henry died in 1795 and Mary Priestley in 1796. He remained a friendly correspondent of Thomas Jefferson, who consulted him on plans for the University of Virginia and later wrote of the comfort he took from Priestley's religious writings ^[9]. Priestley died at Northumberland on February 6, 1804, still dictating corrections to his manuscripts on his last morning, and was buried in the town's Riverview Cemetery ^[1].

Priestley's scientific reputation rests on an unmatched record of gas discoveries and on experimental methods that others built upon, even as his loyalty to phlogiston left him on the losing side of the chemical revolution he helped to start. Lavoisier's new chemistry absorbed Priestley's findings while discarding his theory, a fate that has made him a favorite case study for historians weighing discovery against interpretation ^[6]. The American Chemical Society traces its origins to an 1874 gathering of chemists at his Northumberland home marking the centennial of the oxygen experiment, and it now designates his house a National Historic Chemical Landmark ^[5].

His influence reached well beyond the laboratory. Unitarian congregations in Britain and America counted him among their founders, utilitarian philosophers acknowledged his early formulations, and his educational writings anticipated the modern teaching of science and history ^[7]. The Joseph Priestley House in Pennsylvania operates as a museum, and Birstall and Birmingham both maintain statues of him.

Joseph Priestley facts still surprise readers: the discoverer of oxygen was a stammering preacher who never took a university degree, the inventor of soda water made no money from it, and one of the Royal Society's most honored experimenters ended his life as a political refugee. Any Joseph Priestley biography must hold those threads together, because he saw his chemistry, his theology, and his politics as one continuous search for truth ^[3].