In recent years it has become evident that the atmosphere and oceans have been produced by the outgassing of volatile materials from the earth's interior, principally from volcanoes. In 1950 W. W. Rubey presented geological evidence indicating that sea water has progressively accumulated in this way. At about the same time, Harrison Brown pointed out that the very low abundances of the noble gases in the earth's atmosphere constituted compelling evidence that at least the atmospheric oxygen and nitrogen were almost entirely of secondary origin, having been outgassed, possibly in different chemical form.