Adams, Airy and the Discovery of Neptune in 1846

by Allan Chapman


Soon after Neptune was discovered in Berlin, in September 1846, using Le Verrier's Computed position, a furore broke out in Britain about the priority of John Couch Adams. Though Adams's claim had not been advanced until October 1846, when even the English astronomers were still speaking of "Le Verrier's Planet", it came to be realised that Adams had already arrived at a computed position for the Uranus-disturbing planet by the autumn of 1845. Adams, via a letter of introduction from Professor Challis in Cambridge, had applied to Professor George Biddell Airy, the Astronomer Royal for some kind of assistance, though he failed to secure an interview with Airy, and nothing further happened - until the New Planet was discovered in Berlin, nearly a year later.

Popular interpretations of this incident place a great deal of responsibility upon Airy, for not having taken the initiative to secure a British discovery. Yet this is unjust, and several key factors must be born in mind:

  1. It was not the job of the Astronomer Royal to undertake searches.

  2. As an extremely over-worked man, Airy cannot be blamed for being unavailable when Adams chanced to call upon him without first having made an appointment. He was abroad on the first occasion, and at dinner with his family on the second.

  3. After Adams left his figures for Neptune's place, when the Airy family were at dinner on October 21st, 1845, Airy was prompt in writing to Adams in Cambridge, requesting crucial pieces of mathematical information about the basis of his computations. Adams never replied to Airy's letter, nor supplied the requested information.

  4. Why was Adams not admitted when Airy was at dinner? We should bear in mind that at the time Mrs. Richarda Airy was within a week of giving birth to their ninth child. Her previous pregnancies had been difficult, and as Airy was deeply attached to his wife, he saw no reason to have their dinner interrupted by a stranger who wished to see him on a business matter. There is no evidence to suggest that Adams was willing to wait until the meal was over in spite of the fact that the Airy family dined not in the evening, but in the late afternoon.

  5. Airy's voluminous surviving correspondence makes it clear that everyone - from Cabinet Ministers and Admirals, down to servant-girls wanting to have their fortunes told - wrote to, and occasionally called-in upon the Astronomer Royal. A man who was so much in the public eye had to defend his privacy.

  6. While all of this was going on, the Royal Observatory was being rocked by the disclosure of an awful incident. A senior Greenwich Observatory Assistant, William Richardson, had just been exposed for having committed an appalling murder. From late October 1846, onwards, Airy and his Chief Assistant, the Revd Robert Main, made appearances before the courts at the beginning of Richardson's trial. Airy was acutely embarrassed by the regular appearance of his name, as Richardson's employer, in the newspaper columns reporting the details of a crime which hinged upon sex, incest, and the burial of a body in a shallow grave.

  7. And if this was not enough, the year 1845-1856 was probably the busiest in Airy's professional life. For in addition to astronomy, he was immersed in the business of the Railway Gauge Commission. As the Scientific Commissioner, he was travelling around Britain testing trains and interviewing engineers. It was this Commission, and Airy's scientific advice, which settled British (and, later American) railway gauges at the "Standard Gauge" of 4 feet 8 1/2 inches.

John Couch Adams, while a brilliant mathematician, was rather naive socially, and was said by a senior Cambridge colleague to have behaved, regarding Neptune, not "like a man who made a great discovery, but like a bashful boy." In 1846, however, the "bashful boy" was 27 years old.

Urbain Le Verrier, the French co-discovery of Neptune was an older, and much more business-like individual, and had the determination to see his computations put to effect. Yet even he was not able to find a French Observatory that was willing to undertake the search, and was forced to write to colleagues in Berlin. We often forget that the French scientific establishment let Le Verrier down no less than the British was accused of having let down Adams. Once the Berlin sighting had been made, however, the French were quick to turn it into a French National discovery.

But to blame Airy for not doing what was not his job anyway - to search for private individual's privately investigated planet - is very unjust, especially when one considers the pressures under which Airy was operating. And if poor Adams had bothered to make appointments before turning up for interviews, and had also bothered to answer the letter from the Astronomer Royal, then the discovery of Neptune might have gone differently.

Yet the real justice of the incident was done when Adams and Le Verrier, who were two very different types of men, met in 1847. They had the greatest admiration for each other's work, and became good friends.

Allan Chapman
Wadham College,
Oxford University,
England.
Copyright © 20th April 1996 Allan Chapman

Bibliography

Allan Chapman:
"Private research and public duty: G.B.Airy and the discovery of Neptune" Journal for the History of Astronomy, xix (1988) 121-139 [to be re-printed, July 1996, in A. Chapman's volume of Essays, 'Astronomical Instruments and their Users, Tycho Brahe to William Lassell'. Variorum Collected Studies, Aldershot, England.]

Patrick Moore: The Planet Neptune, An Historical Survey before Voyager, Praxis-Wiley, 2nd Edition, (Chichester & New York 1996)

Allan Chapman:
"The Discovery of Neptune: Was anyone Really to Blame?" Astronomy Now, Forthcoming, September, 1996


The Discovery of Neptune.

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