Engraving by Ambroise Tardieu. Joseph Priestley (1733-1804) discovered various gaseous elements and compounds, and in an experiment in 1774 obtained a gas which he named 'dephlogisticated air'. This was in fact oxygen, although it was not named thus until the French chemist Lavoisier (1743-1794) repeated Priestley's experiment. Priestley had originally trained as a Church minister, but his radical theological and political views made him a controversial preacher. He strongly supported the French Revolution, and after his house in Birmingham was attacked and burnt by a mob in 1791, he left Britain for America.
© Science Museum / Science & Society Picture Library