They Told The Story
A Neptune Chronology
Adams Dated Computations
The Forgotten Diary
Within One Degree
The Crown Jewels Document
Announcing The Discovery
Challis' Unseen Testimony
A Retrospective History
A Cantab. Clique
Adam's July Ephemeris
Mapless In Cambridge
Airy Tells the Truth
The Radius Vector: A Trivial Question?
Airy Blows His Top
Eggen Takes the Papers
Selected Correspondence
Primary Sources
Related Links.


British Accounts of Neptune’s Discovery, 1852 - 2000

Over the century after the discovery, all five of the main authors who told the story between 1852 and 1947 were at some stage RAS presidents: Glaisher, Turner, Sampson, Smart and Spencer-Jones . Adams had twice been president. Naturally, they were all cantabs, all but one being from Trinity or John's College (see:" A Cantab. clique?").

  • 1852 History of Physical Astronomy, Ch.12 by Robert Grant p124-164, Appendix 603-617. (35 pages).
  • 1896 Biographical Notice, foreword to The Scientific Papers of J.C.Adams Vol.1, ppi – xxxi (30 pages) by James Lee Glaisher, FRS, son of James Glaisher.

  • Glaisher studied at Trinity college, Cambridge, was on the Greenwich staff from the 1830s to the 1870s, attained eminence in astronomy and mathematics, knew both Airy and Adams, and was offered but declined the post of Astronomer Royal after Airy. He had originally been an assistant to Airy in Cambridge. RAS President 1886-8 and 1901-3.

  • 1904 Astronomical Discovery Herbert Turner.
  • Turner was at Trinity College, Cambridge. He became Chief Assistant at the RGO 1884-1894, after which he became Savilian Professor of Astronomy at Oxford. RAS President 1903-4

  • 1904 A Description of Adams’s Manuscripts on the Perturbations of Uranus,

    R.A.Sampson FRS Memoirs of RAS, LIV, pp.143-161. Sampson was at John’s College Cambridge, and was RAS President in 1915, then became Astronomer Royal for Scotland.

  • 1947 John Couch Adams and the Discovery of Neptune , in ‘Occasional Notes of the RAS’, vol.2 33-88, by William Smart.

  • Smart was at Trinity college, Cambridge, then became the first ‘John Couch Adams Astronomer’ of the University of Cambridge, and wrote a textbook on positional astronomy. He was RAS President 1949-51.

  • 1947 John Couch Adams and the Discovery of Neptune Harold Spencer Jones, CUP.

  • Spencer Jones was at Jesus’ college, Cambridge, then Chief Assistant at the RGO 1913-23, then the Astronomer Royal , RAS President 1937-9, then became President of the IAU 1945-48.

  • 1953 The Discovery of Neptune, A.Pannekoek, Centaurus 3 126-37 (11 pp). 1962 The Discovery of Neptune, Morton Grosser, from PhD at Harvard, in 1961, 167 pp. HUP.
  • 1988 Private Research and Public Duty: George Biddell Airy and the Search for Neptune, Allan Chapman, Journal for the History of Astronomy 1988 19 121-39. (18 pp)'
  • 1989 The Cambridge Network in Action: The discovery of Neptune Robert Smith, Isis
  • 1989, 80, p.395-422. 1997 In Search of Planet Vulcan Chs 7,8 Richard Baum & William Sheehan
  • 2000 The Neptune File, Tom Standage, Penguin Press.

    ‘The Neptune File’

    This is a two-inch thick wad of relevant documents collated by Airy, and, as Turner commented in 1904:

    ‘The letters reproduced in this [i.e., Turner;’s] "account" are still in the Observatory at Greenwich, pinned together just as Airy left them’ (p.48).


    The file has returned from a clandestine journey to Australia and Chile, c.1965-1999, and now resides quietly in the Cambridge University Library (see "Eggen Takes the Papers"). Only three of the above accounts allude to this file. Turner's account quoted from various letters, eleven of them, all cited in Airy's Account. He abbreviated them just as Airy had done, and as Airy omitted phrases, so did he. In the July 9th letter of Airy to Challis, Airy had omitted the key phrase 'a possible shadow of':

    'You know that I attach importance to the examination of that part of the heavens in which there is ... reason for suspecting the existence of a planet exterior to Uranus.'

    No historian would, given the choice, reiterate so crucial an act of censorship. These things suggest that in 1904 Turner had no access to the RGO's Neptune file. Clearly, however, he had seen it! This suggests that it enjoyed a highly secretive status, as not subject to prying eyes. Allan Chapman’s 1988 article was the first after Turner to refer to it, as missing.

    William Smart’s account in 1946 cites a letter to Airy from Sedgwick, then surmises: ‘Airy evidently replied on 1846 December 8, to this letter, as may be gathered from,’(p.74) indicating that he did not have access to the complete file. Morton Grosser’s book written in 1962 did not allude to the file either in its text, where he was unaware of the intense correspondence of seven letters between Airy and Sedgwick over December 2-9th 1846, nor in its extensive bibliography. Tom Standage, who wrote ‘The Neptune File’ soon its recovery, appears to have been the first person who both saw the file and used it to give a historical account - which is curious. Whether he fully apprehended its implications, before rather quickly re-telling the traditional story, is another matter.


    The Essential Illusion

    Glaisher’s account (1896) fifty years after the discovery reiterated Airy’s bogus claim, made brazenly before the Royal Astronomical Society on November 13th 1846, that
    ‘The position thus assigned by Le Verrier to the disturbing planet differed by only 1 degree from that given by Adams in the paper which he had left at the Royal Observatory more than seven months before.’ (p.xviii)

    They differed by over four degrees. One here needs to compare true helio longitudes, at the same epoch (see "Within one Degree"). The ‘within one degree’ concept was a vital part of the myth built up of Adams’ prediction, and had the advantage that persons re-telling the story did not have to bother about the confusing astronomical details.

    To some extent, the confusion resulted from Adams’ ‘predictions’ being given as mean rather than true helio longitude. Owing to the large eccentricities involved, the Equation of Centre which converts mean helio long. to true required four terms in its expansion, which would no doubt have been hard work. The relevant calculations were however given in John Herschel’s Outline of Astronomy 1852, which Glaisher would have consulted.

    Journeys of the Neptune-Papers

    Sir Donald MacAlister collected and preserved the diaries, letters and papers of Adams, whom he knew well. In 1907 MacAlister became employed at Glasgow University and so the papers went North, then they journeyed South again when he retired back to Cambridge. He there copied out many of the other Neptune-discovery manuscripts, which is fortunate as his handwriting is now more legible than the faded originals. On his death in 1929 the papers passed to William Smart, who obtained a position at Glasgow university so the papers went North again. When in 1959 they returned South, they were presented to St John’s College archive. They remained, surprisingly inaccessible to scholars, in 19 unsorted boxes. In 1990 MacAlister’s niece presented some more papers to St John’s, which she had found in her attic. The 150th anniversary in 1996 focussed sufficient interest on the subject, for a comprehensive computer-indexing to take place at John’s , as was completed early in 1999.

    This website shows a fragment of Adams’ diary for 1846, which I obtained in 1999 merely by asking for it at St John’s library archives (see:"Adams’ forgotten Diary"). No previous scholar (it would appear) had seen it! Equally, MacAlister’s copy of the rather censored letter by Airy of December 8th Sedgwick, was available on request, although top Neptune-discovery scholars Allan Chapman and Dennis Rawlins had earlier been unable to obtain it. The recovery of Britain’s Neptune-file synchronously with the becoming-accessible of the Adams Archives at John’s, both in the year 1999, means that, at last, one can begin to tell the story!