1. Sir John Herschel and the Development of Spectroscopy in Britain
2. J. C. Maxwell,Theory of Heat, London, 1870, pp. 306–8. The vibrational model was not without its difficulties, however. Spectroscopic theorists failed repeatedly in efforts to show that the combinations of frequencies in spectra of various substances conformed mathematically to har-monic series. Even more ominous, the alliance between kinetic theory and the acoustic explanation deteriorated by the mid-187os into an adversary relationship. By 1875 Maxwell recognized that the calculated ratio of specific heats at constant pressure and constant volume according to the kinetic theory of gases disagreed with experimentally determined values. He bode ill for the vibrational explanation of spectra when he observed that the maximum calculated ratio for diatomic molecules was already smaller than the empirical value of the ratio and that the necessity of increasing the number of internal degrees of freedom to allow spectra-producing vibrations would decrease the calculated ratio still further. In that same year, at Strassburg, August Kundt and Emil Warburg found that mercury vapour gave a value of 1.66 for the ratio of its specific heats. This, according to kinetic theory, meant that the mercury molecule was mon-atomic—a development pleasing to chemists who had reached the same conclusion based upon vapour density methods of determining atomic weights. Yet it perplexed spectroscopic theorists, because it disallowed any intra-molecular degrees of freedom thought necessary to permit the vibrations assumed responsible for emission lines in mercury's spectrum. On this, see William McGucken,Nineteenth-Century Spectroscopy, Development of the Understanding of Spectra, Baltimore and London, 1969, pp. 10–26, 157–63.
3. Ueber Inductionserscheinungen, hervorgerufen durch die electrischen Vorgänge in Isolatoren