Joseph Priestley discovers oxygen - Aug 01, 1774 - HISTORY.com

On this day in 1774, dissenting British minister Joseph Priestly, author of Observations on Civil Liberty and the Nature and Justice of the War with America, discovers oxygen while serving as a tutor to the sons of American sympathizer William Petty, 2nd Earl of Shelburne, at Bowood House in Wiltshire, England.

Joseph Priestley shared the liberal religious and political philosophy of many of America’s revolutionary leaders, including Benjamin Franklin, John Adams and Thomas Jefferson, all of whom became his friends and correspondents. Priestley first met Franklin while both were living in London during the 1760s. Both were Renaissance men with established reputations as scientists and political philosophers and they embarked on an enduring friendship. In 1774, Franklin and Priestley attended the first Unitarian sermon given at the first Unitarian church founded in London. Unitarianism evolved out of a dissenting Christian tradition that denied the concept of the Trinity and the divinity of Christ. Unitarians instead believed that God was one being and that Christ was a human spokesman of God’s truth. Priestley had been born into a dissenting (non-Anglican Protestant) family and gradually found his way to Unitarianism by the early 1760s. Franklin’s views were very similar and sympathetic to Unitarians, but he never joined a Unitarian congregation.

Although still living in England, Priestley endorsed both the American and French revolutions, authoring pamphlets in support of each. On the second anniversary of Bastille Day, a mob in Birmingham, England, burned Priestley’s home, including his first-class scientific laboratory and the Unitarian church where he preached. As a result of the attack, he decided that he could no longer live in England and immigrated to the United States in 1794.

Priestley settled in Northumberland, Pennsylvania, where he lived until his death in 1804. While there, Priestley established the first Unitarian church in Philadelphia, where then-Vice President John Adams attended his sermons.