Joseph Priestley, an English philosopher, born at Fieldhead, Yorkshire, March 13, 1733, died in Northumberland, Pa., Feb. 6, 1804. He was the son of a cloth dresser, and was instructed in the classics in a free grammar school. He learned Hebrew in his holidays under a dissenting minister, and with little instruction ntfade progress in the Chaldaic, Syriac, Arabic, French, Italian, and German. At the age of 19 he entered the dissenting academy at Daventry (now incorporated with New college, London) as a theological student. He had become an Arminian before leaving home, and on account of his doubts concerning orthodoxy had not been admitted a communicant of the Calvinistic church. While at the academy he composed the first part of his "Institutes of Natural and Revealed Religion " (3 vols., 1772-'4). In 1755 he became assistant minister to the Independent congregation in Needham Market, Suffolk, where he remained three years, suspected of heresy and not popular either as a preacher or teacher. He there renounced the doctrine of the atonement, and wrote his " Scripture Doctrine of Remission," published in 1761. In 1758 he opened a day school at Nantwich, Cheshire, and with a limited apparatus, including an air pump and electrical machine, began his researches in natural philosophy.

In 1761 he became professor of belles-lettres in Warrington academy. While there he wrote " Theory of Language and Universal Grammar " (1762), " Chart of Biography " (1765), " Essay on a Course of Liberal Education for Civil and Active Life " (1765), and " History and Present State of Electricity, with Original Experiments" (1767), for which Dr. Franklin, to whom Priestley had been introduced in London, furnished the requisite books. About this time he was elected to the royal society, and received the degree of LL. D. from the university of Edinburgh. In 1768 he was chosen pastor of a large congregation in Leeds, where he devoted much of his attention to theological subjects. In 1769 he published his "Chart of History." In 1772 appeared his " History and Present State of Discoveries relating to Vision, Light, and Colors," "Laws and Constitution of England," and a pamphlet on " Impregnated Water with Fixed Air." In 1773 he received from the royal society the Copley medal for " Observations on the Different Kinds of Air." He discovered oxygen gas, which he named dephlogisticated air; showed that the red color of the arterial blood is due to its combination with oxygen from the atmosphere; proved the abstraction of oxygen from the atmosphere in the processes of combustion and putrefaction; and recognized the property of vegetables to restore this constituent.

He adhered to the phlogistic theory after Lavoisier had overthrown it. He discovered also nitrous oxide gas, carbonic oxide gas, sulphurous oxide gas, ammoniacal gas, which he called alkaline air, and hydrochloric acid gas; and he was the principal inventor of the pneumatic trough. From 1773 to 1780 he was librarian and literary companion to the earl of Shelburne, accompanying him in 1774 on a journey to the continent. He continued his chemical experiments, making discoveries concerning aeriform bodies, which he reported in his "Experiments and Observations on Air" (5 vols., 1774-'80). He published in 1775 his " Examination " of Drs. Reid, Beattie, and Oswald, designed to refute the Scotch philosophy of common sense; in 1777, his " Disquisitions relating to Matter and Spirit," a defence of avowed materialism, "Doctrine of Necessity," of which also he became the champion, and "Oratory and Criticism." In 1780 his connection with Lord Shelburne was dissolved; he retired with a pension for life of £150, and became pastor of a dissenting congregation at Birmingham. At the same time a subscription was raised by his friends to defray the expenses of his experiments.

In 1780 he published " Letters to a Philosophical Unbeliever," and in 1781 "State of the Evidence of Revealed Religion." In 1782 appeared his "History of the Corruptions of Christianity," which was burned by the common hangman in the city of Dort, and a refutation of which was one of the subjects of the Hague prize essays; and in 1786 his "History of Early Opinions concerning Jesus Christ." In each of these works the divinity and preexistence of Christ are controverted on historical grounds. During the French revolution he was regarded as the mover and champion of antagonism to all establishments, political and religious. His attachment to freedom he had evinced by several pamphlets and by his interest in the cause of America during the war of the revolution. He exasperated the populace by his " Familiar Letters to the Inhabitants of Birmingham" (1790), by advocating the claims of dissenters, and by answering Burke's "Reflections" (1791), on account of which he was nominated a citizen of the French republic. In 1791 some of his friends celebrated the anniversary of the capture of the Bastile; and though he was not present, the event was the occasion of a riot in which his house was broken open, his library, apparatus, and manuscripts destroyed, and himself obliged to flee with his family.

His books were strewn over the high road for half a mile; the scraps of the manuscripts covered the floors; and an attempt was made to set the house on fire. He received ample remuneration from the county and from private benevolence, and removed to Hackney to succeed Dr. Price; but noticing that his society was avoided even by his philosophical associates, he emigrated to America, arriving in New York June 4, 1794, and went to reside on his son's farm in Northumberland, Pa. He delivered two courses of public lectures in Philadelphia in 1796 and 1797 on the " Evidences of Revelation." He wrote and published in America his "Continuation of the History of the Christian Church from the Fall of the Western Empire to the Present Times" (4 vols., Northampton, 1803), and also several minor theological works, among which were answers to Volney's and Paine's attacks on revelation. His " Doctrines of Heathen Philosophy compared with those of Revelation" appeared posthumously. His autobiography to March, 1795, continued by his son, was also published in America posthumously, and in London (2 vols. 8vo, 1806-7), and is contained with his correspondence in the edition of his "Theological and Miscellaneous Works" published by John To well Rutt (25 vols., Hackney, 1817 et seq.). The centennial of the discovery of oxygen was celebrated by American chemists at Northumberland, Pa., Aug. 1, 1874, and on the same day a statue of Priestley was unveiled in Birmingham, England. A statue of him had been placed in the museum of Oxford university in 1860. A bibliography of his productions, prepared in the library of congress for the centennial celebration of 1876, comprises more than 300 published books and pamphlets on chemistry, history, theology, metaphysics, physics, politics, and miscellaneous subjects.