Dalton, John (1766–1844), British chemist and physicist. One of the fathers of modern physical science, Dalton formulated the atomic theory of matter, a theory that established chemistry as a true science. He determined the relative weights of atoms and developed the laws of definite and multiple proportions. He formulated several laws relating to gases, including Dalton's law or the law of partial pressures. His wide interests included meteorology, in which he made valuable observations on the aurora borealis, trade winds, and rain. In 1794 he systematically described and explained the form of color blindness known as Daltonism. He himself was color-blind.