Joseph Priestley was an English Unitarian clergyman and chemist. He was born in 1733 and died in 1804. He worked on gases and discovered oxygen as did Scheele. His theological views wereunpopular with the masses, and in 1791 his church and property were destroyed by a mob. In 1794 he emigrated to the United States from London and continued his investigations in science and philosophy at Northumberland, Pennsylvania. Research Joseph Priestley