Chemist and physicist, born near Cockermouth, of a Quaker family; took early an interest in meteorology, and kept through life a record of meteorological observations; taught mathematics and physics in Manchester; made his first appearance as an author in 1793 in a volume of his observations and essays, and in 1808 published "A New System of Chemical Philosophy," which he finished in 1810; famous for his experiments on the elastic force of steam, for his researches on the proportional weights of simple bodies, for his discovery of the atomic theory, as also for his investigations on color-blindness by experimenting on himself and his brother, who along with himself was color-blind (1766-1844).