The conservation of energy, theories of absorption and resonating molecules, 1851--1854: G. G. Stokes, A. J. Ångström and W. Thomson (Q2740940)

The bulk of this paper is concerned with Stokes; much of his interpretation of the phenomenon of ``fluorescence''---absorption of ultraviolet light and emission of blue light---is based on an elastic aether affected by the vibrations of the illuminated molecules somewhat like ships huddled together on an ocean. The paper is readable and has made good use of the manuscript sources (which are equally as important as the printed material in this case, especially Notebook 28). Several points are not mentioned by the author. Stokes's Notebook 28 is in the style of Faraday, with dated entries and a fairly systematic treatment of the solutions exhibiting and not exhibiting the change in refrangibility; Stokes respected, even ``reverenced'', Faraday as is shown by their correspondence (cf. William's two volumes of Faraday's correspondence). Stokes's hesitancy to proceed without evidence (p. 97), ``I perceived that the connection was explicable but not that it was necessary'', was characteristic of the man, and sometimes he carried it to extremes (cf. Whittaker's history of the aether); it was part of his genius that he was able to reduce physical situations to the bare minimum of assumptions, as he did for Thomson and the electric telegraph in 1854 and for (visco-) elasticity in his major paper of 1845. Finally, while the author gives an introduction to the theories of light via Fresnel and Wrede, he does not mention Cauchy, MacCullagh and George Green; certainly Stokes read the literature on elasticity, especially Green, as his notebooks show, and Stokes himself made substantial contributions to the theory of elasticity in the decade prior to his election to the Royal Society in 1851; Cauchy and MacCullagh had written on light in the 1830's and Green in the period 1833-1841; Stokes used their work in his paper on diffraction in 1850-1851, and this work on physical optics, hydrodynamics and mechanics was to earn him entry to the Royal Society, as this paper on change in refrangibility was to earn him the Society's Rumford Medal in 1853.