An Hiatus in History: The British Claim for Neptune's Co-Prediction,1845–1846: Part 1

Letter, Challis to Airy, 19 Dec. 1846, RGON: McA, 33.12.f.12–14.

Keats John , On first looking into Chapman's Homer, 1820.

Dio, ix/1 (1999), 5: “Celestial mechanics' most miraculous day.”.

See www.ucl.ac.uk/sts/nk/neptuneletters.htm for summaries of 435 Neptune-discovery related letters.

Letter, Herschel to Sheepshanks, 17 December 1846, RS:HS 16:50.

Schaffer Simon , “Scientific discoveries and the end of natural philosophy”, Social studies of science, xvi (1986), 387–420, p. 401.

For the concept of ‘discovery’ as socially-constructed in retrospect, see Kragh Helge Smith Robert , “Who discovered the expanding universe?”, History of science, xli (2003), 141–62, p. 142.

Smith Robert , “The Cambridge network in action: The discovery of Neptune”, Isis, lxxx (1989), 395–422.

Standage Tom , The Neptune file (London, 2000).

Moore Patrick , The planet Neptune: An historical survey before Voyager (Cambridge, 1986, 1998).

Ridpath Ian , “Who stole the Neptune papers?”, Popular astronomy, January 1988, 5; Rawlins Dennis , “The Neptune conspiracy: British astronomy's post-discovery discovery”, Dio, ii/3 (1992), 115–42; Rawlins Dennis , “The ‘theft’ of the Neptune papers”, ibid., iv/2 (1994), 92–102. I have greatly benefitted from Rawlins's thesis on the role of Adams in the discovery.

Moore Patrick , “The hunt for Neptune”, Sky & telescope, xcii/3 (March 1996), 42–43; Sheehan William Baum Richard , “Neptune's discovery 150 years later”, Astronomy, xxiv/9 (September 1996), 42–49; and Chapman Allan , “The story of a failed discovery”, Astronomy now, x/9 (September 1996), 42–45.

Eggen Olin J. , entries on Airy Challis in Dictionary of scientific biography Secretary E. MaCauliffe at La Serena Observatory, Cerro Tololo, Chile, phoned the RGO.

Moore , Neptune (ref. 10), 116–19 (list compiled by David Dewhirst).

Chapman Allan , “Private research and public duty: George Biddell Airy and the search for Neptune”, Journal for the history of astronomy, xix (1988), 121–39.

Smart W. M. , “John Couch Adams and the discovery of Neptune”, ONRAS, ii (1947), 33–88.

Chapman , “Private research” (ref. 15), 139, n. 54.

Ibid., 139, n. 57. It was however also present in the McAlister collection: McA 34.17.1.

Ibid., 136, n. 6.

Grosser Morton The discovery of Neptune (Cambridge, MA, 1962; based on his Ph.D. dissertation of 1961).

Chapman , “Private research” (ref. 15), 126.

Smart , “Adams” (ref. 16), 74.

Letter, Sedgwick to Airy, 9 December 1846, 2, RGON, McA 33:10.

Airy G. B. , “Account of some circumstances historically connected with the discovery of the planet exterior to Uranus”, MNRAS, vii (1846), 121–44, p. 135; Airy G. B. , “Account…”, MRAS, xvi (1847), 385–414, p. 402 (reproduced in Moore , Neptune (ref. 10), 87–106).

Letter, Airy to Challis , 9 July 1846: COA no. 2; RGON.

Turner H. , Astronomical discovery (London, 1904), 65.

Harrison H. M. (a descendent of John Couch Adams), Voyager in time and space: The life of John Couch Adams (Lewes, Sussex, 1994).

Moore , Neptune (ref. 10), 104.

SP, pp. lvi–lviii; Jones H. Spencer , John Couch Adams and the discovery of Neptune (Cambridge 1947), 15–18; or see the author's website www.ucl.ac.uk/sts/nk/neptune/crown.htm.

Airy , “Account” (ref. 25, 1846), 130; Moore , Neptune (ref. 10), 100.

Challis J. , “An account of observations undertaken in search of the planet discovered at Berlin on Sept 23, 1846”, MRAS, xvi (1847), 415–26, p. 423; Airy , “Account” (ref. 25, 1846), 145–9, p. 147.

Challis's sweep book, COA, xxxix, 53.

Letters, Airy to Hussey , 23 November 1834, and Airy to Bouvard , 12 October 1837, RGON.

Airy G. B. , Gravitation: An elementary explanation of the principal perturbations in the solar system (London, 1834), 38.

Letter, Airy to Schumacher , 24 February 1838, published as “Schreiben des Herrn Airy, Astronomer Royal, an den Herausgeber”, Astronomische Nachrichten, xv (1838), cols 217–20. See esp. col. 219 (on the radius-vector of Uranus).

Bouvard A. , Tables astronomiques publiées par le Bureau des Longitudes de France contenant les tables de Jupiter, de Saturne et d'Uranus construites d'après la théorie de la mécanique celeste (Paris, 1821). Bouvard's nephew Eugene Bouvard had continued the endeavour and briefly described new tables that he had constructed in “Nouvelles tables d'Uranus”, CR, xxi/9 (1 September 1845), 524–5. For a discussion of the younger Bouvard's never-published and now lost study of Uranus's motions, see Lias E. , L'histoire de la découverte de la planète Neptune (Leipzig, 1892); also Baum R. Sheehan W. , In search of planet Vulcan: The ghost in Newton's clockwork universe (London, 1997), 85–86.

The nautical almanac and astronomical ephemeris for the year 1834 (1833) was the first to have this new format.

Astronomical observations made at the Royal Greenwich Observatory (published yearly by the Board of Admiralty).

They also used the same 17 pre-discovery observations of Uranus given by Bouvard's Tables (ref. 37), p. xiii, from that of Flamsteed in 1690 to Lemonnier in 1771. See ref. 75 re accuracy.

“Lettre de M. Wartmann, de Genève, à M. Arago, sur un astre ayant l'aspect d'une étoile et qui cependant était doué d'un mouvement propre”, CR, ii, séance of 28 March 1836, 307–11.

Baum Sheehan , Search (ref. 37), 120.

Bode's law uses the formulation 0.4 + 0.3 × 2n, giving 19.6 AU for Uranus (n = 8) and 38.8 AU for Neptune (n = 9).

Hubbell J. Smith R. , “Neptune in America: Negotiating a discovery”, Journal for the history of astronomy, xxiii (1992), 261–91, p. 266.

Peirce B. , [untitled note], Proceedings of the American Academy of Arts and Sciences, i (1846), 41–42.

Hind J. , “On Wartmann's supposed planet”, MNRAS, vii (1847), 274.

Oppolzer T. , “Ueber den von Wartmann im Jahre 1831 Gesehen Planeten”, Astronomische Nachrichten, xcvii (1880), cols 253–4; Baum Sheehan , Search (ref. 37), 276–7, n.15.

The computations were done yearly for the instant of solar opposition, the point at which heliocentric and geocentric positions coincided. Adams averred in his 13 November 1846 RAS presentation that Uranus's “error at the present time exceeds two minutes of space, and is still rapidly increasing”: “An explanation of the observed irregularities in the motion of Uranus, on the hypothesis of disturbances caused by a more distant planet”, MRAS, xvi (1847), 427–59, p. 427. Lai H. M. , “Perturbation of Uranus by Neptune: A modern perspective”, American journal of physics, lviii (1990), 946–53. See our Appendix III.

Le Verrier U. J. , “Note sur les inégalités introduites dans la longitude des planètes par les variations à longue période de leurs éléments”, CR, xiv/13 (28 March 1842), 487–508; “Seconde note sur les perturbations de la planète Uranus”, CR, xiv/18 (5 May 1842), 660–3.

Le Verrier U. J. , “Sur les variations séculaire des éléments des orbites, pour les sept planètes principales, Mercure, Venus, le Terre, Mars, Jupiter, Saturne et Uranus”, Connaissance des temps pour 1844 (Paris, 1841), 28–110.

Le Verrier U. J. , “Premier mémoire sur la théorie d'Uranus”, CR, xxi/19 (10 November 1845), 1050–5; “Recherches sur les mouvements d'Uranus”, CR, xx/22 (1 June 1846), 907–18; and “Recherches sur les mouvements d'Uranus”, Astronomische Nachrichten, no. 580 (12 October 1846), cols 53–64; no. 581 (22 October 1846), cols 65–80.

The Astronomer Royal's journal 1836–1847, RGO 6.24; Airy , “Account…” (ref. 25, 1847), 395; letter, Airy to Arago, 29 September 1845, alluding to “M. Le Verrier's undertaking”; and also Rawlins D. , “My calculations of some of Bouvard's terms”, Dio, ix/1 (1999), 18, fn. 69. Not in RGON. See Bouvard , Tables (ref. 37) re Bouvard E. ,.

Airy G. B. , “Report on the progress of astronomy during the present century”, in Report of the first and second meetings of the British Association for the Advancement of Science; at York in 1831, and at Oxford in 1832, 2nd edn (London, 1835), 125–89, p. 154.

Letter, Airy to Schumacher, 24 February 1838 (ref. 36).

Peirce B. , untitled paper, Proceedings of the American Academy of Arts and Sciences, i (1846–48), 286–95.

Smart , “Adams” (ref. 16), 82.

Brown E. W. , “On a criterion for the prediction of an unknown planet”, MNRAS, xcii (1932), 80–101; Rawlins D. , “Some simple results regarding gravitational disturbance by exterior planets — With historical applications”, MNRAS, cxlvii (1970), 177–86.

Baghdady M. , “The discovery of Neptune: A critical examination of the theory of Leverrier”, Ph.D. dissertation, University of Aston, Birmingham, 1980.

For how Le Verrier arrived at his predictions, see Grant Robert , History of physical astronomy, from the earliest ages to the middle of the nineteenth century (London, 1852), 175–90.

“This distance of 35.3 [AU] then, is a complete barrier to any logical deduction …”, Peirce B. , in “The new planet Neptune”, American journal of arts & science, ix (1847), 441–3, p. 443, owing to a 2:5 resonance periodicity with Uranus. For the hypothetical planet, “There are two different mean distances of least possible error — One of which is 36, and the other 30 [AU]”: Gould Benjamin , Report on the history of the discovery of Neptune (Washington, DC, 1850; written in Cambridge), 5. Gould reviewed Peirce's views. Hubbell Smith , op. cit. (ref. 44), 271.

Le Verrier U. J. , “Sur la planète qui produit les anomalies observées dans le mouvements d'Uranus — Détermination de sa masse, de son orbite et de sa position actuelle”, CR, xxiii/9 (31 August 1846), 428–38; a supplement to this paper was published as “Sur la planète qui produit les anomalies observées dans le mouvements d'Uranus. Cinquième et dernière partie, relative à la détermination de la position du plan de l'orbite”, CR, xxiii/14 (5 October 1846), 657–9.

Letter, Verrier Le to Airy , 28 June 1846, RGON.

Le Verrier U. J. , “Recherches sur les mouvements d'Uranus”, Astronomische Nachrichten, no. 580 (12 October 1846), cols 53–64; no. 581 (22 October 1846), cols 65–80; no. 582 (5 November 1846), cols 85–92. This paper contained four sections: Part 1 (“Calcul des perturbations produites par Jupiter et Saturne”) in cols 55–60; Part 2 (“Comparaison de la théorie avec les observations”) in cols 61–68; Part 3 (untitled) in cols 69–78; and Part 4 (“Détermination plus précise de l'orbite de la planète troublante, et de sa position actuelle”) in cols 77–80, 85–92. The cover letter from Le Verrier to Schumacher, dated 8 September 1846, was published as “Schreiben des Herrn Le Verrier an den Herausgeber”, Astronomische Nachrichten , no. 580 (12 October 1846), cols 53–54. An English translation of the letter and of extracts of the first three parts of the text appeared, respectively, as “The new planet Le Verrier” and “Researches on the motions of Uranus”, The sidereal messenger, i/8 (Cincinatti, December 1846), 57 and 57–59. The translated text was later reprinted in Shapley Harlow Howarth Helen E. (ed.), A source book in astronomy (New York and London, 1929), 249–50.

Editorial of The sidereal messenger , i/8 (December 1846), 57.

Letter, Le Verrier to Galle, 18 September 1846; reprinted in Turner H. , “Obituary notice of Johann Gottfried Galle”, MNRAS, lxxi (1911), 275–81, pp. 278–9; Grosser , op. cit. (ref. 20), 115–16.

There was only a degree or so difference between Neptune's heliocentric longitude, used for the computations, and the geocentric longitude required for finding it with a telescope (these converged annually at its solar opposition, in August): Date1 Oct. 1845 29 Aug. 1846 23 Sept. 1846 1 Jan. 1847 Neptune long. heliocentric 324°.7 326°.8 326°.9 327°.5 geocentric 323°.6 326°.5 325°.9 326°.2.

Letter, Challis to Airy , 22 September 1845, RGON.

Letter, Airy to Challis, 29 September 1845, RGON; COA, V.

Airy Wilfrid (ed.), Autobiography of Sir George Biddell Airy (Cambridge, 1896), 172.

Letter, Richarda Airy to Sedgwick, 5 December 1846, Richarda Townsend collection (see also her letter of 9 December to Sedgwick).

Letter, Adams to parents, 23 October 1845, McA 25:2.3; JCL 16.2.3.

Letter, Airy to Adams, 5 November 1845, JCL, 2.1.1; RGON.

Adams to Airy, unsent draft, 13 November 1845, Cornwall Record Office, Adams family papers, AM 330 (found by Craig Waff in 2004, as mis-dated in the archive to 1846).

Smart , “Adams” (ref. 16), 57: To Glaisher in 1883.

The column of thirty ‘error-values’ in this note were mostly given to l/100th of an arcsecond. Le Verrier's computations as given in Comptes rendues were presented to one-twentieth of an arcsecond. Littlewood J. E. , re-checking Adams computation, found “It is worth while to work to work to 0.1” (A mathematician's miscellany (London, 1957), 121).

Much later, in December 1846, Challis correctly described these arcsecond values, as “a list of the residual errors” of the mean longitude of Uranus: Challis J. , “A report to the Cambridge Observatory Syndicate”, 12 December 1846, published as “Report of proceedings in the Cambridge Observatory relative to the new planet”, The London, Edinburgh, and Dublin philosophical magazine and journal of science, ser. 3, no. 198 (January 1847), 33–41, p. 36; “First report to the Cambridge Observatory Syndicate upon the new planet”, SP, pp. xlix–liv.

Adams obtained his solution of −50° 34’ on 18 September, as the angular distance in longitude between the Uranus and “hypothetical planet” mean motions, for the solar-opposition epoch of 3 May 1810: Sampson R. A. , “A description of Adams's manuscripts on the perturbations of Uranus” (1901), in the St John's College Library Adams MS EIII, 6–13; Sampson , “A description …”, MRAS, liv (1904), 143–70, p. 166. Rawlins has argued (Dio, ii/3 (1992)) that Adams's mss showed that he was setting up the formulae for perturbations on 28 November and 6 and 24 December 1845 ( Sampson , op. cit., 1904, 158, 168), and that the 16 December 1845 work rightly should have occurred at the beginning of the calculation of what he later called his ‘Hyp 1’ (which indeed is where Adams places it in his published 13 November 1846 presentation to the RAS), and not after its alleged submission to Airy in October 1845.

“Sampson's conjecture” is pertinent to what, if anything, Challis received in September 1845: In 1901 Professor Sampson found an undated and unaddressed piece of paper amongst Adams's notes and surmised: “It is very likely the above sheet is a copy of the communication Adams sent to Challis” (op. cit. (ref. 77, 1904), 166). The document exists both as EIII p. 14 in Adams's notes (see ref. 77, 1901) and as COA 32. Challis never made public any values from it.

www.ucl.ac.uk/sts/nk/neptune/unseen.htm.

Sampson , “A description” (ref. 77, 1904), 167, Adams MS EVII, p. 15: Eccentricity, apse position and mean longitude were here cited for the hypothetical planet for the first time, enabling the solution to be sent to Airy on 2 September.

Turner , Astronomical discovery (ref. 27), 70–71.

Sampson R. A. , “The decade 1830–1840”, in Dreyer J. L. E. Turner H. H. (ed.), History of the Royal Astronomical Society, 1820–1920 (London 1923), 82–109, p. 93.

Verrier Le , “Premier mémoire” (ref. 51).

Airy , “Account” (ref. 25, 1846), 131.

Smart , “Adams” (ref. 16), 66 fn. has Adams, Challis and Airy then meeting; Airy's journal (ref. 52) records a visit to Cambridge, 4–6 December.

Warwick A. , Masters of theory: Cambridge and the rise of mathematical physics (Chicago, 2004).

Sampson , “A description” (ref. 77, 1904), 168.

Letter, Sedgwick to Mrs Airy, 6 December 1846, RGON; McA 33.10.

Rawlins D. , “The Neptune conspiracy”, Dio, ii/3 (1992), 115–42, p. 137; Sampson , “A description” (ref. 77, 1904), 167, 168.

Letter, Sedgwick to Airy , 3 December 1846, RGON; McA 33:9.

JCL Box 10: Recollections to Clerke Agnes , “forty years later”; Smith , “The Cambridge network” (ref. 8), 401.

McA Box 39: MacAlister Donald states, “I cannot find any diaries between 1843 & 1847”.

Diary fragment from 9 to 28 March 1846; JCL 20.22.3.

Herschel John , Outlines of astronomy (London, 1849), 359.

Moore Patrick , History of astronomy (London, 1961, 1983), 117: This was a short-period comet that had been seen only once before. It returned as a double-comet in 1852, and thereafter gave rise to a meteor-shower, the Andromedids. For a description of the various apparitions of Biela's comet, see Kronk Gary W. , Comets: A descriptive catalog (Hillside, N.J., and Aldershot, Hants, 1984).

Hall A. Rupert , The Cambridge Philosophical Society: A history 1819–1969 (Cambridge, 1969), 14.

Letter, Airy Richarda to Sedgwick , 9 December 1846, private collection of Richarda Townsend (great-granddaughter of Airy), present location unknown.

Harrison , Voyager (ref. 28), 78.

Glaisher J. W. L. , “Preface” to SP.

Letter from Hind to Adams, 28 February 1846, JCL 9:23 (alluded to a letter from Adams as “received yesterday”).

Letter from Challis on Biela's Comet, MNRAS, vii/5 (1846), 73–74; Adams J. C. , “Duplicity of Biela's comet”, MNRAS, vii/6 (1846), 83; Hind J. , “Biela's comet”, MNRAS, vii/1 (1846), 2–3.

Glaisher , “Preface” (ref. 99), p. xxxi; Standage , The Neptune file (ref. 9), 79.

Letter, Herschel to Adams, 23 January 1846, CU AM 9:15. This letter has not hitherto been noticed (compare, Adams to his brother George, 10 July 1845, McA 35:12). My colleague Dr Craig Waff doubted this date, on the grounds that Adams's expertise in lunar theory only developed years later, and, in response, archivists at St John's College have confirmed that the date here given is correct.

Challis proposed Adams as Fellow in letter to RAS, 6 May, and he became one on 14 November 1845: MNRAS, vii/1 (1845), 1.

Letter, Sedgwick to Airy, 3 December 1846, RGON; McA 33:9.

Smith , “The Cambridge network” (ref. 8), 408.

Ibid., 418, on the extent to which such a term could be warranted.

Letter, Airy to Le Verrier, 26 June 1846, Obs. de Paris Ms 1072.4; RGON.

Letter, Airy to Whewell, 25 June 1846, Trinity College 0.15.48,5; found by Smith , “The Cambridge network” (ref. 8), 402. Whewell averred that he had put in press by August 1846 the note in the second edition of History of the inductive sciences (1847), 306, concerning Adams's work, based on this latter from Airy.

Letter, Le Verrier to Airy, 28 June 1846, RGON; an extract of this letter was published as document no. 14 in Airy's “Account”: Moore , Neptune (ref. 10), 97–99; Bouvard , “Tables” (ref. 37).

Airy , “Account” (ref. 25, 1846), 135.

The annual Visitation of the Observatory fell on 6 June, a fact not discernable (I believe) in any telling of the Neptune story, and Airy then delivered his 11-page report. The same group reassembled on 10 June for a Board of Admiralty meeting and heard the previous minutes. Owing to a letter which Airy had sent to the first Lord of the Treasury, an “adjoined meeting” was then held on 29 June at the Admiralty, with copies of the letter circulated. Babbage put a motion concerning Airy's status, in the light of the proposed improvement in international collaboration between observatories. Airy's diary used the phrase “Board of Directors” for that meeting: Astronomer Royal's journal (ref. 52).

Visitors of the Royal Observatory at Greenwich minute book, Public Records Office, Kew, London ADM. 190/4, 213–19, 220–4; “Report of the Astronomer Royal to the Board of Visitors”, 6 June 1848, 1–11, in: Royal Observatory Greenwich Report of the Astronomers Royal 1836–68, RGO publication; see also CUL RGO archives, Board of Visitors, add. ms. for 29 June 1846; Smith , “The Cambridge network” (ref. 8), 412.

No letters from Hansen about Neptune are known, except for one published by Benjamin Gould, who was in Europe in 1847: Report (ref. 60), 11–12.

Sampson , “Description” (ref. 77), 156.

Letter, Airy to Sedgwick , 4 December 1846, RGON; McA, 34.17.1.

Brewster David , “Mr Adams' and M Le Verrrier's researches respecting the new planet Neptune”, North British review, May 1847, 207–46, p. 221.

Challis , “Account” (ref. 32), 415, 416.

The document can be viewed at www.ucl.ac.uk/sts/nk/neptune/july.htm. It is mis-filed in the Cambridge Observatory manuscripts now in the CUL, with pages belonging to January 1847 (COA, 41).

See Rawlins , Dio, ix/1 (1999), 13–14 re circularity of orbit in Adams's July ephemeris.

Baily Francis , “The British catalogue of stars”, in An account of the Revd. John Flamsteed (London, 1835), 439. Baily noted re this phantom star, seen by Flamsteed as 7th magnitude in March 1695: “I cannot find any star that will correspond with the position here given”, 550.

Sampson , “Description” (ref. 77), 154.

Challis , “Report” (ref. 76), esp. p. liii.

Letter, Challis to Main , 7 August 1846, RGON.

Letter, Adams to Airy , 2 September 1846, RGON; Airy's “Account” (ref. 25, 1847); Moore , xiiiNeptune (ref. 10), 100–2.

Brookes C. J. , “On the prediction of Neptune”, Celestial mechanics, iii/1 (December 1970), 67–80, esp. p. 71: “the first hypothesis was the more accurate of the two.” Brookes reconstructed Adams's equations for his “The discovery of Neptune: A critical examination of the theory of Adams”, Ph.D. dissertation, University of Aston, Birmingham, 1969. Smart (ref. 16, p. 55) argued au contraire that Adams's second hypothesis had “a small advantage over the first”.

Grant , History (ref. 59), 185.

With hindsight one can appreciate the quicksand into which the argument was sinking, with the radius near to the 5:2 resonance position between the planetary periods causing the perturbation-equations to go awry. This large error results from a discontinuity at 35.3 AU, as was argued by Benjamin Peirce (op. cit., ref. 60). Brookes (“Prediction” (ref. 126), 78) showed how solutions derived from Adams's equations varied with orbit-radius, and his simulation obtained a value of 317° at 34 AU; see also Rawlins D. , “Some simple results regarding gravitational disturbances by exterior planets — With historical applications”, MNRAS, cxlvii (1970), 177–86.

Letter, Adams to Airy , 15 October 1846, RGON; McA, 33.3. ff.16–17.

Rawlins D. , “British Neptune-disaster file recovered”, Dio, ix/1 (June 1999), 17.

Adams's error was 2–3 times that of Le Verrier: “Le Verrier was less than 1° out (Adams between 2° and 3°)”, Littlewood, Mathematician's miscellany (ref. 75), 128.

Letter, Adams to Main , 7 September 1846, RGON; McA 33:1.

Sampson , “Description” (ref. 77), 146, described Adams's endeavour during this period with the node equations as “unsuccessful”.

Letter, Adams to Main (ref. 132).

Letter, Hind to Challis , 16 September 1846, COA no. 10.

A report on the conference was published as “Sixteenth meeting of the British Association for the Advancement of Science”, The Athenaeum, no. 986 (19 September 1846), 961–73; no. 987 (26 September 1846), 992–1006; no. 988 (3 October 1846), 1024–8; no. 989 (10 October 1846), 1048–54. Report of the 16th meeting of the British Association for the Advancement of Science (London, 1847).

Letter, Adams to Airy , 18 November 1846, RGON; McA, 33.8. ff. 48–50.

Grosser , Neptune (ref. 20), 114; The Cambridge Advertiser, 30 September 1846, “Report on BAAS meeting”.

Herschel averred that he had spoken these words, in a letter to The Athenaeum of 3 October 1846, “Le Verrier's Planet”, 1019. A letter from John Stavelly of Belfast to Herschel corroborates this: “I remember the words most distinctly”, letter to Herschel, 8 October 1846, RS:HS 17.233.

Crowe M. J. , A calendar of the correspondence of Sir John Herschel (Cambridge 1998), 329: Letter of Charles Piazzi Smyth to Herschel, 5 September 1846, RS:HS 16:227.

Letter, Herschel to Sheepshanks , 17 December 1846, RS:HS 25.B2.26c, 16.49.