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Airy, Adams, Challis and the Cambridge Philosophical Society
We give below details of Airy, Adams, Challis and the Cambridge Philosophical Society which is a slightly edited version built from two sources: Handley Carr Glyn Moule, Some Memories of William Peveril Turnbull, One of His Majesty's Inspectors of Schools (G Bell, 1919) and A Rupert Hall, The Cambridge Philosophical Society: A History 1819-1969 (Cambridge Philosophical Society, 1969).
George Biddell Airy (1801-92) was elected Plumian Professor and given direction of St John's College Observatory in 1828. His first paper - on silvered telescope mirrors, one of the great technical steps - was read by Peacock to the Cambridge Philosophical Society when Airy was still a Scholar of Trinity (November, 1822). This was the first of a long series, in which incidentally Airy described for the first time (1825) the visual defect, astigmatism, which he had discerned in his own eyes, and its correction. After his removal to Greenwich in 1835 Airy became one of the greatest Astronomers Royal. Airy, like his successor in Cambridge astronomy James Challis (1803-82), figured unfortunately in connection with the work of John Couch Adams; Challis was the Cambridge Philosophical Society's President at the critical time (1845-47). Director of the Cambridge Observatory for twenty-five years after 1836, and Plumian Professor from the same date to the end of his life, if Challis did not win great fame it was not through lack of vigour. He was a prolific author, devoting the later years of his life to relating the known laws of gravity, light, heat, electromagnetism etc. to the action of a single aether. He lectured steadily on practical astronomy from 1843 to 1879, when the course was printed, but the papers he had published by the Society were mostly on fluid mechanics. Unfortunately, he was less active in following up Adams's indications of the position of a hypothetical new planet, which might be disturbing the motions of Uranus. As a result (in his own words) "I lost the opportunity of announcing the discovery, by deferring the discussion of the observations, being much occupied with reductions of comet observations, and little suspecting that the indications of theory were accurate enough to give a chance of discovery in so short a time." In fact neither Challis at Cambridge nor Airy at Greenwich paid much attention to the indications for a search given them by Adams in September, 1845, until the following July when they read papers by U J J Leverrier who had independently reached - and more wisely, published - a similar prediction. Challis began elaborately to plot all the stars in the likely area of the sky - but in fact missed the new planet, though it was later ascertained that he had twice recorded Neptune in his registers, without realising that this was the object he was seeking. Galle at Berlin, primed by a letter from Leverrier (September, 1846), within an hour spotted a body not shown in Bremiker's atlas. This on subsequent examination proved to be Neptune.
John Couch Adams (1819-92), who was thus disappointed, went on to become Lowndean Professor (1858) and, in succession to Challis, Director of the Observatory (1861). He had the curious double distinction of refusing a knighthood, and having a University Prize founded under his name during his own lifetime, when the ingenuity of his solution to the inverse problem of perturbations had won the esteem it merited. [It should be noted, however, that the real characteristics of Neptune's orbit differ markedly from those predicted by both Leverrier and Adams. Both had relied on 'Bode's Law' as a guide to Neptune's mean distance from the Sun - Challis wrote a paper in the Transactions (III, 1830) on the extension of 'Bode's Law' to planetary satellites - but Neptune's orbit falsifies 'Bode's Law'.] He presided over the Cambridge Philosophical Society from 1861 to 1863. Before this, however, in 1853, Adams had made another important contribution by showing that the Sun's part in the Moon's secular acceleration could not amount to more than per century, about half the observed value; much later the phenomenon of tidal friction was invoked to account for the remainder. Rather similarly Adam's proof (1867) that the Leonid meteor shower has a period of about 33 years enabled the hypothesis to be entertained that such meteors represent the debris of a former comet (Proceedings, 2, 1867).
Curiously enough, one of the very few first-hand descriptions of a meeting of the Cambridge Philosophical Society at this early period relates to that of 18 March 1867 at which, after a short communication from Challis, Adams described this last piece of work. The writer was William Peveril Turnbull, father of the mathematician Herbert Westren Turnbull, and his essay was written for a club called the Parallelepiped:
It was gaslight. The general audience among these were Professors Arthur Cayley and William Hallows Miller, and a few ladies who would lend countenance to philosophy - were seated on tiers of benches, and below this general audience sat an audience fewer and more select; a more vital part of the Society, I suppose, whether by merit or by office. Among this lesser audience are Challis and Adams the chief speakers at the meeting, but awaiting as yet the conclusion of certain business of the society. The instrument or symbol of this business is a ballot-box which is carried round and presented in turn to several ἄριστοι by a man with a beard, and finally brought to the table at which, facing the assembly, the two or three headmost functionaries (there are four if we count him with the beard) sit in quiet state. Behind these worthies there is an array of large diagrams intended by Adams to illustrate his discourse. Challis also has something written out on a blackboard, and both the lecturers are accompanied (silently) by instruments. Distance and the careful closing of doors and windows keep out the noise and air of the world though the ventilation was not quite reduced to zero, till affairs had somewhat advanced. Two new members have speedily been admitted (William Kingdon Clifford of the Parallelepiped is one of them), and the President calls on Professor Challis for his promised communication. Accordingly this short but learned gentleman, armed with a pointer, and with the calmness of a veteran lecturer, takes his stand beside the blackboard and begins to talk. Both lecturers talked; oratory interferes with science. - And thus he began:
"As the subject on which Professor Adams is to speak is much more interesting than mine, I shall be as brief as possible. I desire to explain how the process of Triangulation is conducted; which process I employ in calculating the difference of Longitude between the Society's clock and the clock in the Observatory."
But not to run the risk of a calumniously oblique narrative, I will directly say that the Professor seemed to have poked about Cambridge and the Madingley Road in a most numerical state of mind. He had measured distances to the tenth part of an inch, finding it necessary "to go that exactness." He had, moreover, availed himself of one of the minarets of King's as an object visible from more than one of his points of station. Finally, the difference of longitude came out - not abiit, erupit, evasit, but came out, like a tedious enigmatical fish after half a day's angling for him, - five seconds and sixty-one hundredths of a second.
Applause, faint as from the scientific, greeted this announcement, and the lecturer sat down. Then followed a narration of Adams's lecture on the meteor display of 1866 and the conclusions which he drew from these phenomena conclusions which were questioned by his fellow scientists and again defended by Adams in the discussion which ensued.
I shall now offer a few remarks about what I saw and heard. And first when you go to a scientific meeting and hear scientific men discourse, though you may very dimly perceive what they are about, they yet exercise an influence upon you. Authority, that great source of human ignorance, is here a source of knowledge. There is such a planet as Neptune: how do I know that? I never saw the planet, but I know that Adams thought he had discovered it, and that Adams was by the scientific world thought to be right. I believe the fact on authority: - and so believing, I am the more inclined to think that Adams is right about the meteors. The operation of his mind I do not attempt to follow - it is enough that he has once gained a position in the scientific world, and that he now speaks with confidence. And I remember against Challis that he was not altogether propitious to the efforts of Adams on the former occasion. Had it not been for Challis, I suspect that England, and not France, would have had the glory (slight as it was) of priority in that discovery. Secondly I observed that Adams treated space as a reality: - He spoke definitely of a body's position in space. His answer to the question "Is there such a thing as Infinite Space?" would have been a decided Yes, with no metaphysical limitation. [Relativity, one of the newest scientific ideas of this century, is much concerned with this question.] The fixed stars had all their own proper motions, the meteors travelled about hither and thither, and all was not only conceived of, but actually was in space. The problem is simply that of ascertaining the actual motions of the earth and the other bodies in the universe. To this practical question we take rule and line. To Ezekiel it was given to stand by and watch the Angel take measurements of the Holy City; but the measuring-rod was given into St John's hands. Let not metaphysical meditation for ever paralyse, but let us apply our reason to any the first reality.
Once more: how alien is eloquence from the dissertations of science! This philosophic presence admits nought more human than an applausive murmur, or a stray pleasantry from Adams, as when he said that the list of observers in the diagram, a list beginning with his name, was not, as we might see, arranged in order of merit, but alphabetically. The speaker uses no action save a motion of his hands that sympathises with his reasoning mood or assists our conceptions of those celestial motions: - motions which he seems to see as comprehensively as if they were no bigger than a hand's breadth. Nor does he show any human affection save modesty, nor any material failing save a fault of utterance which the hearer is proud to ignore. The connection of Scientific research with the hearts of Scientific men is all understood. The virtues of such men are silent and passive. Forbearance in dispute, candour in acknowledging the claims of each other to the merit of a new discovery, and an absence of scorn for the unscientific mass of people. I would also point out the moderation that Adams must have exercised in using his own powers of body and mind. The effort he has made has not been brief and feverish, but periodic and sustained. Wonderful things have been done by overtaxing the present power of the workman; and such are, I should think, to be found among the writings of Keats; but if Milton be really the greater poet, may we not remember how he says that in study also there can be intemperance, and that Urania nightly inspired easy his unpremeditated verse. - Urania, like the other gods, approves depth and not the tumult of the soul.
Last Updated December 2025