John Dalton (1766-1844) British chemist, born near Cockermouth, Cumbria. In 1794 he described colour blindness (Daltonism) from which both he and his brother suffered. He also proposed an atomic theory and studied gases. As a Quaker he was unable to attend an English university. He supported himself as a schoolmaster and tutor. Engraving after a Daguerreotype.