¹ The standard account of this area of research is Whittaker, Edmund T., A History of the Theories of Aether and Electricity. Vol. 1: The Classical Theories (2nd edn., London, 1951) 1 128–69.Google Scholar

² Young, Thomas, ‘Theoretical investigations intended to illustrate the phenomena of polarisation: being an addition made by Dr Young to M. Arago's “Treatise on the polarisation of light”’, in Miscellaneous Works of the late Thomas Young, ed. Peacock, George and Leitch, John (London, 1855), i. 415–17.Google Scholar Young wrote this piece in 1823.

³ Herschel, John, ‘Light’, in Encyclopaedia Metropolitan (London, 1845), iv. 535.Google Scholar Herschel's statement derived its importance both from his own exalted position (see Cannon, Walter F., ‘John Herschel and the idea of science’, Journal of the History of Ideas, xxii [1961], 238)Google Scholar and from the fact that his article provided Fresnel's theory with its first substantial support in England. The article first appeared in 1827.

⁴ Preston, Thomas, The Theory of Light (London, 1890), p. 29.Google Scholar This was a widely used textbook which went through five editions, the fifth appearing in 1928.

⁵ For Kelvin and Maxwell, see Thomson, William [later Lord Kelvin], ‘The wave theory of light’, in Popular Lectures and Addresses. Vol. 1: Constitution of Matter (London, 1889), 348Google Scholar; and Maxwell, James Clerk, ‘Ether’, in The Scientific Papers of James Clerk Maxwell, ed. Niven, W. D. (Cambridge, 1890), ii. 769.Google Scholar For an indication of the role of Stokes's theory with respect to relativity, see Swenson, Loyd S. Jr., ‘The Michelson-Morley-Miller experiments before and after 1905’, Journal for the History of Astronomy, i (1970), 56–78.CrossRefGoogle Scholar

⁶ I am aware of only one other treatment of Stokes's thought in this area: three scattered paragraphs in Whittaker, , op. cit. (1), 110, 128, and 386–7.Google Scholar For biographical information on Stokes, see Rayleigh, Lord, ‘Sir George Gabriel Stokes, Bart., 1819–1903’, Proceedings of the Royal Society of London, Ixxv (1905), 199–216Google Scholar; Larmor, Joseph, ‘Stokes, Sir George Gabriel, first baronet (1819–1903)’, Dictionary of National Biography; and Memoir and Scientific Correspondence of the late Sir George Gabriel Stokes, ed. Larmor, Joseph (Cambridge, 1907).Google Scholar

⁷ Fresnel, , ‘Sur l'influence du mouvement terrestre dans quelques phénomènes d'optique’, in Oeuvres Complètes d'Augustin Fresnel, ed. Senarmont, Henride et al. (Paris, 1868), ii. 627–36.Google Scholar

⁸ Bradley, , ‘A letter from the Reverend Mr James Bradley … to Dr Edmond Halley … giving an account of a new discovered motion of the fix'd stars’, Philosophical Transactions of the Royal Society of London, xxxv (1728), 646–8.Google Scholar

⁹ Young, , ‘Experiments and calculations relative to physical optics’, Phil. Trans., xciv (1804), 12–13.Google Scholar

¹⁰ Arago, François, ‘Vitesse de la lumière’, in Oeuvres Complètes de François Arago, ed. Barral, J. A. (Paris, 1858), vii. 562–8.Google Scholar

¹¹ Fresnel, , op. cit. (7), ii. 628.Google Scholar

¹² ibid., 632.

¹³ ibid.

¹⁴ See, for example, Jenkins, Francis A. and White, Harvey E., Fundamentals of Optics (3rd edn., New York, 1957), pp. 396–7.Google Scholar

¹⁵ For another discussion of Fresnel's theory, see Whittaker, , op. cit. (1), 108–10.Google Scholar

¹⁶ See Clerke, Agnes M., ‘Challis, James (1803–1882)’Google Scholar, Dictionary of National Biography, and J. W. L. G., ‘James Challis’, Monthly Notices of the Royal Astronomical Society, xliii (1883), 160–79.Google Scholar Considering the ether strictly as a fluid, Challis presented his own ‘undulatory’ theory of light in four papers published in volume viii of the Transactions of the Cambridge Philosophical Society. His magnum opus was his Notes on the Principles of Pure and Applied Calculation; and Applications of Mathematical Principles to Theories of the Physical Forces (Cambridge, 1869).Google Scholar

¹⁷ Memoir and Scientific Correspondence of Stokes, i. 8.Google Scholar

¹⁸ Challis, to Stokes, , 7 05 1842Google Scholar, in Stokes's correspondence, University Library, Cambridge.

¹⁹ Challis, , ‘On the analytical condition of the rectilinear motion of fluids’, Philosophical Magazine, 3rd ser., xxi (1842), 101–7Google Scholar; Stokes, , ‘Remarks on a paper by Professor Challis, “On the analytical condition of the rectilinear motion of fluids”’, Philosophical Magazine, 3rd ser., xxi (1842), 297–300Google Scholar; Challis, , ‘On the analytical condition of rectilinear fluid motion, in reply to Mr Stokes's remarks’, Philosophical Magazine, 3rd ser., xxi (1842), 423–6Google Scholar; Stokes, ‘On the analytical condition of rectilinear fluid motion’, in reply to Professor Challis, , Philosophical Magazine, 3rd ser., xxii (1843), 55–6Google Scholar; and Challis, , ‘A further investigation of the analytical conditions of rectilinear fluid motion’, Philosophical Magazine, 3rd ser., xxii (1843), 97–107.Google Scholar

²⁰ The letters are in Stokes's correspondence, University Library, Cambridge.

²¹ Stokes reported this information at the beginning of his report; see Stokes, , ‘Report on recent researches in hydrodynamics’, Report of the British Association for the Advancement of Science, 1846 (London, 1847), p. 1.Google Scholar

²² Memoir and Scientific Correspondence of Stokes, i. 9.Google Scholar The notes were published in the Cambridge and Dublin Mathematical Journal, ii–iv (1847–1849).Google Scholar Thomson edited the journal, which was a continuation of the Cambridge Mathematical Journal.

²³ Larmor, loc. cit. (6).

²⁴ Stokes, , ‘On the effect of the internal friction of fluids on the motion of pendulums’, Transactions of the Cambridge Philosophical Society, ix (1856)Google Scholar, [12]. Brackets are around the page number in the journal.

²⁵ Stokes, , ‘On the theories of the internal friction of fluids in motion, and of the equilibrium and motion of elastic solids’, Transactions of the Cambridge Philosophical Society, viii (1849), 287.Google Scholar Read 14 April 1845.

²⁶ Stokes, , op. cit. (21), p. 19.Google Scholar

²⁷ Stokes, , op. cit. (25), 317.Google Scholar

²⁸ ibid., 318.

²⁹ Stokes, , ‘On the aberration of light’, Philosophical Magazine, 3rd ser., xxvii (1845), 9.Google Scholar This paper was first read to the Cambridge Philosophical Society on 12 May 1845 (abstract in Proceedings of the Cambridge Philosophical Society, i [1843–1863], 19)Google Scholar and secondly to the British Association meeting of 1845 (abstract in Report of the British Association for the Advancement of Science, 1845 [London, 1846], part 2, p. 8).Google Scholar It was printed in the issue of Philosophical Magazine for July 1845, pp. 9–15 (see first item in this footnote), and finally was picked up by the Philosophical Magazine from the Proceedings of the Cambridge Philosophical Society and printed in abstract form in Philosophical Magazine, 3rd ser., xxviii (1846), 62–3.Google Scholar

³⁰ Stokes, , ‘On the constitution of the luminiferous aether’, Philosophical Magazine, 3rd ser., xxxii (1848), 343.Google Scholar

³¹ For references to the paper see note 29.

³² See note 29, and Challis, , ‘On the aberration of light’, Report of the British Association for the Advancement of Science, 1845, part 2, p. 8.Google Scholar

³³ Powell, Baden, ‘Remarks on some points of the reasoning in the recent discussions on the theory of the aberration of light’, Philosophical Magazine, 3rd ser., xxix (1846), 425.Google Scholar After corresponding with Challis and Stokes, Powell added a supplement to his first paper: ‘Note to a former paper on the theory of the aberration of light’, Philosophical Magazine, 3rd ser., xxx (1847), 93–5.Google Scholar

³⁴ See note 29.

³⁵ Stokes, , ‘On the constitution of the luminiferous aether, viewed with reference to the phenomenon of the aberration of light’, Philosophical Magazine, 3rd ser., xxix (1846), 6–10.Google Scholar

³⁶ Stokes, , op. cit. (30), 343–9.Google Scholar

³⁷ Stokes, , Philosophical Magazine, 3rd ser., xxvii (1845), 9–10.Google Scholar

³⁸ ibid., 10.

³⁹ This type of fluid motion free of whirlpools has come to be called ‘irrotational’. Although not using the term irrotational, Stokes gave a physical definition of this kind of flow in 1845. When udx + vdy + wdz is exact, he explained, it means that if a small portion of fluid were ‘suddenly solidified and detached from the rest of the fluid’, it would not rotate at all but would ‘move with a motion simply of translation’, see Stokes, op. cit. (25), 310. Irrotational had come into use by the late 1870s when Maxwell utilized the same technique of a suddenly solidified portion of fluid to illustrate the type of motion ‘said to be irrotational’; see Maxwell, ‘Atom’, in Scientific Papers of Maxwell, ii. 467. For such a portion of fluid, dw/dy – dv/dz, dw/dx – du]dz, and dv/dx – du/dy represent the rotation around the x, y, and z axes, respectively. The rotation will be zero, therefore, when dw/dy = dv/dz, dw/dx = du/dz, and dv/dx = du/dy. These are precisely the set of equalities that result from udx + vdy + wdz being an exact differential.

⁴⁰ Figures 1 and 2 and the discussion in these three paragraphs are based on Stokes's argument and figures in Stokes, , Philosophical Magazine, 3rd ser., xxvii (1845), 12–15.Google Scholar I have borrowed Figure 3 from H. A. Lorentz's discussion of Stokes's theory in ‘De l'influence du mouvement de la terre sur les phénomenes lumineux’, in H. A. Lorentz: Collected Papers (The Hague, 1937), iv. 157–60.Google Scholar Stokes also showed in his paper that neither a motion of the heavenly body being observed nor a motion of the whole solar system through the ether would have a measurable effect on the angle of aberration.

⁴¹ Challis, to Stokes, , 14 02 1846Google Scholar, in Stokes's correspondence, University Library, Cambridge.

⁴² Challis, , ‘On the aberration of light’, Philosophical Magazine, 3rd ser., xxvii (1845), 323.Google Scholar

⁴³ Challis, , Notes on the Principles of Pure and Applied Calculation, p. xvii.Google Scholar His 1852 paper is ‘On the cause of the aberration of light’, Philosophical Magazine, 4th ser., iii (1852), 53–4.Google Scholar

⁴⁴ Challis, , op. cit. (42), 323.Google Scholar

⁴⁵ ibid.

⁴⁶ ibid., and Challis, , ‘On the aberration of light, in reply to Mr Stokes’, Philosophica Magazine, 3rd ser., xxviii (1846), 90–3.Google Scholar

⁴⁷ Challis, , op. cit. (46), 93.Google Scholar

⁴⁸ Stokes, , op. cit. (35), 9.Google Scholar

⁴⁹ ibid.

⁵⁰ Stokes to Powell, Baden, 10 12 1846Google Scholar, in Stokes's correspondence, University Library, Cambridge.

⁵¹ There seems to be a contradiction here in Stokes's work. First, Stokes said that the direction from which a light ray appeared to come depended on the orientation of the wave front. Later he implied that it was independent of the front's orientation. Stokes did not address himself to this issue, and I do not know how he would have resolved the matter. However, the existence of this contradiction does not bear on the main points of this study.

⁵² Stokes to Powell, in the letter cited in note 50.

⁵³ Stokes, , op. cit. (35), 9.Google Scholar

⁵⁴ Stokes, , ‘On Fresnel's theory of the aberration of light’, Philosophical Magazine, 3rd ser., xxviii (1846), 81.Google Scholar The paper referred to is cited in note 29.

⁵⁵ On at least one occasion Stokes specifically noted that Challis regarded the ether as a fluid; see Stokes, , op. cit. (30), 344.Google Scholar

⁵⁶ Stokes, , op. cit. (35), 7.Google Scholar

⁵⁷ Stokes, op. cit. (25).

⁵⁸ Stokes, op. cit. (35), 7.Google Scholar

⁵⁹ ibid., 8. The irregularities are small and therefore susceptible to propagation by the ether. Because they are propagated as soon as they occur, there is no time for them to accumulate into large irregularities.

⁶⁰ Stokes, , op. cit. (30), 347.Google Scholar

⁶¹ ibid., 346–7.

⁶² Babinet, Jacques, ‘Sur l'aberration de la lumière’, Comptes Rendus hebdomadaires des Séances de l'Académie des Sciences, ix (1839), 774.Google Scholar

⁶³ Stokes, , op. cit. (54), 76–81.Google Scholar

⁶⁴ ibid., 81.

⁶⁵ Stokes, , Burnett Lectures. On Light (2nd edn., London, 1892), p. 24.Google Scholar The lecture was given in 1883.