Dalton, John (1766-1844), an English chemist, formulated the law of partial pressures in gases in 1802. The law states that for an ideal gas the total pressure of a confined gas mixture equals the sum of the pressures each gas would exert alone in the same volume. In 1803, Dalton proposed an atomic theory of matter that became one of the foundations of chemistry. From this theory, Dalton determined chemical formulas that showed the atomic composition of molecules. Dalton made the first, although inaccurate, table of atomic weights. He also investigated colour blindness (called Daltonism), which he had.