 Contemporary textbooks typically locate discussions of chemical atomism in the 19th century work of John Dalton (1766–1844). Boyle’s ambitions of reducing elemental minima to structured constellations of mechanical atoms had been abandoned by this time, and Dalton’s theory simply assumes that each element has smallest parts of characteristic size and mass which have the property of being of that elemental kind. Lavoisier’s elements are considered to be collections of such characteristic atoms. Dalton argued that this atomic hypothesis explained the law of constant proportions (see section 1.5).