  Pierre Duhem (2002), in his classic analysis of the logic of nineteenth-century chemistry at the end of that century, construed it as being independent of, and offering no support for, atomism. Paul Needham (2004a, 2004b) has recently supported his case. Klein (2003, 18–20) notes that many of the pioneers of the developments in organic chemistry referred to combining volumes or portions or proportions rather than atoms. She attributes the productivity of the use of formulae to the fact that they ‘conveyed a building-block image of chemical proportions without simultaneously requiring an investment in atomic theories, together with the simplicity of their maneuverability on paper’ (2003, 35).