The Age of Wonder

by Richard Holmes

  Maskelyne nevertheless stoutly confirmed his opinion to Banks that their dark horse, the ‘musician of Bath’, had made a revolutionary discovery, and had ‘much merit’. Yet he could not suppress a touch of rueful irony. ‘Mr Herschel is undoubtedly the most lucky of Astronomers in looking accidentally at the fixt stars with a 7 foot reflecting telescope magnifying 227 times to discover a comet of only 3’ [seconds of arc] diameter, which if he had magnified only 100 times he could not have known from a fixt star … Perhaps accident may do more for us than design could; and this makes one wish that the number of astronomers was multiplied in order to increase our chance of new discoveries.’123 This suggestion that the discovery had been ‘accidental’, and that he had been ‘lucky’, was to grow increasingly disturbing to Herschel.124

  Maskelyne had made public his support of Herschel just in time. On 29 April Messier wrote directly to ‘Monsieur Hertsthel at Bath’ from Paris, congratulating him — ‘this discovery does you much honour’ — and giving his opinion that this was very likely to be the seventh planet in the solar system. Messier had himself, he said modestly, discovered no fewer than eighteen comets in his lifetime, and this resembled none of them: it was ‘a little planet with a diameter of 4 to 5 seconds, a whitish light like that of Jupiter, and having the appearance when seen with glasses of a star of the 6th magnitude’. He signed ‘with consideration and respect’ as ‘Astronomer to the Navy of France, of the Academy of Sciences, France’.

  As Maskelyne and Banks were only too aware, Messier’s congratulations would soon carry the weight of the entire French Académie des Sciences.125 Throughout the spring and summer months of 1781, more and more astronomers — in France, Britain, Germany, Italy and Sweden – observed the tiny moving speck, and took the view that it was indeed a planet circling in a massive ellipse beyond Saturn. These included Jacques Cassini, Henry Cavendish and Pierre Méchain. In October Anders Lexell, the celebrated Russian mathematician, wrote from his observatory far away in St Petersburg, sending a fully computed orbit and adding his congratulations. Using a series of parallax readings, he calculated that the planet was large and unbelievably remote, over sixteen times further from the sun than the earth, and twice as far out as Saturn. The size of the solar system had been doubled. Jérôme Lalande, who also computed the orbit, later said that this was the moment when the Académie des Sciences finally accepted the new planet — seven months after it had been sighted. Lalande himself suggested it should be christened ‘Herschel’.

  It is suggestive that it was mathematical calculation, rather than astronomical observation, which finally convinced the scientific community that a seventh planet really did exist. One of the things Lexell’s calculation showed was that Herschel’s vivid impression that the planet was increasing in apparent diameter throughout March and April (and therefore approaching the earth) must have been the product of his growing concentration and excitement, since it was actually getting smaller and moving away. Lexell continued to work patiently for several years on his calculations, and later came up with the revised figure of 18.93 times the distance from the earth, impressively close to the modern computer-generated figure of 19.218. (In fact, as the planet’s orbit is elliptical not circular, the distance varies: at its closest it is 18.376 and at its furthest it is 20.083.)

  In May, Watson proudly took Herschel up to London to meet his father Sir William, and to renew his now extremely cordial relations with Nevil Maskelyne. Together with the wealthy Deptford astronomer Alexander Aubert, they all dined with Sir Joseph Banks at the Mitre Club, the tavern much favoured by Dr Johnson. This was Herschel’s first meeting with the inner circle of British astronomers, and it was a great success. There was an air of suppressed triumph and excitement. Banks, in high spirits, seized his hand, congratulated him on ‘the great discovery’, and announced that he was to be elected to the Royal Society and awarded the Copley Gold Medal forthwith — within the next fortnight!126 He claimed it as a decisive British victory over French astronomy, and the eminence of Messier, Pierre Laplace and Lalande, who had hitherto dominated European astronomy.

  In fact Banks’s enthusiasm had rather got the better of him. The Copley Medal and the fellowship election had to go through the Society’s plodding bureaucratic procedures, which took another six months. Maskelyne used the interval to write warmly to Herschel in August: ‘I hope you will do the astronomical world the favour to give a name to your new planet, which is entirely your own, and which we are so much obliged to you for the discovery of.’127

  It was subsequently shown that ‘Georgium Sidus’ had actually been observed and recorded at least seventeen times between 1690 and 1781, and was even catalogued by Flamsteed. But it had always been dismissed as a minor ‘fixed’ star. It was only Herschel’s observational genius — and the quality of his seven-foot reflector — which identified it as a large, steadily moving body in regular orbit round the sun: a true planet. And it was Maskelyne who, by promptly supporting Herschel and bringing his observations to the attention of other leading European astronomers, confirmed the discovery and had it accepted by the scientific community at large. It later became clear that Uranus was a weird blue ice giant (not ‘little’ as Messier thought), twice the distance of Saturn, and taking 84.3 years to complete a solar orbit. It is the only planet in the solar system which is tilted ‘on its side’, so its axis of rotation, or spin, is horizontal to its solar orbit.♣

  In November Banks wrote a friendly and characteristically droll letter to Herschel, asking him for details of how he made the discovery that famous night, and all the difficulties ‘etc etc’ it caused him. He wanted to refer to these when presenting him to the assembled members of the Royal Society in London the following month: ‘Sir, The Council of the Royal Society have ordered their Annual Prize Medal to be presented to you in reward for your discovery of the new star. I must request that (as it is usual for me on that occasion to say something in commendation of the discovery) you will furnish me with such anecdotes of the difficulties you experienced etc etc … as you may think proper to assist me in giving due praise to your industry and ability.’

  Banks, in high good humour, also enjoyed putting Herschel on his mettle. ‘Some of our astronomers here incline to the opinion that it is a Planet, and not a Comet. If you are of that opinion, it should forthwith be provided with a name, or our nimble neighbours, the French, will certainly save us the trouble of Baptizing it.’128

  Herschel, again advised by Watson, asked Banks if he could name the planet after the King, ‘Georgium Sidus’, a sound and self-effacing diplomatic stroke from a fellow Hanoverian.129 But he was less easy about the continuing murmurs in some quarters of the Royal Society that his discovery had been in some sense ‘accidental’. This struck at his very notion of scientific method. He wrote insistently, even angrily, to Banks just before the ceremony on 19 November: ‘The new star could not have been found out even with the best telescopes had I not undertaken to examine every star in the heavens including such as are telescopic, to the amount of at least 8 or 10 thousand. I found it at the end of my second review after a number of observations … The discovery cannot be said to be owing to chance only it being almost impossible that such a star should escape my notice … The first moment I directed my telescope to the new star, I saw with a power of 227 that it differed sufficiently from other celestial bodies; and when I put on the higher powers of 460 and 932 was quite convinced it was not a fixt star.’130

  This claim was to become a point of honour with Herschel, often repeated. In September 1782 he wrote to Lalande in Paris, stating emphatically that the discovery ‘was not owing to chance’. Since he was embarked on a regular review of the sky, ‘it must sooner or later fall into my way, and as it was that day the turn of the stars in that neighbourhood to be examined, I could not very well overlook it’.131 The following year he wrote to the German astronomer Georg Christoph Lichtenberg at Göttingen, repeating that it was ‘not by accident’, and adding: ‘when
I came to Astronomy as a branch of [mathematics] I resolved to take nothing upon trust but see with my own eyes all what other men had seen before’.132 Lichtenberg replied enthusiastically (in German): ‘Mein Gott! If I had only known, when I was for a few days in Bath in October 1775, that such a man lived there! As I am no friend of tea rooms, nor of cards or balls, I was much ennuyéd and spent my time at the top of the [cathedral] tower with a field glass…’

  When he came to write an autobiographic sketch for his friend Dr Hutton in 1809, Herschel was more insistent than ever: ‘It has generally been supposed that it was a lucky accident which brought this star to my view; this is an evident mistake. In the regular manner I examined every star of the heavens, not only of that magnitude but many far inferior, it was that night its turn to be discovered. I had gradually perused the great Volume of the Author of Nature and was now come to the seventh Planet. Had business prevented me that evening, I must have found it the next, and the goodness of my telescope was such that I perceived its planetary disk as soon as I looked at it; and by application of my micrometer, I determined its motion in a few hours.’133

  This claim is not entirely borne out by his original Observation Journal. His first sweep or ‘review’ of double stars, begun in 1779, had not revealed the Georgium Sidus, so discovery on the second was not inevitable. Nor was recognition instant when it came. The journal reveals no precise Eureka ‘first moment’ on 13 March, only the hardening suspicion drawn out over five days to Saturday, 17 March that the strange body had ‘proper motion’, but was neither a ‘nebulous star’ nor a ‘comet’, and so was very probably a new planet. But it was Nevil Maskelyne who was the first to say so explicitly in writing, in April.

  Nevertheless, Herschel’s discovery was an astonishing feat. It became his professional signature, and a historic moment for cosmology. It is hardly surprising that over the years he continued romantically to refine the story, and compressed his discovery into a single wondrous night, the inspired work of a glorious ‘few hours’. Caroline never commented on this, although it seems clear that she was present during the critical nights of measuring between 21 March and 6 April 1781. The effect of this account was to present an engagingly romantic image of science at work: the solitary man of genius pursuing the mysterious moment of revelation.

  Joseph Banks’s presentation speech, when awarding the prestigious Copley Gold Medal for the best work in any scientific field during the year 1781, in front of the assembled Fellows of the Royal Society, was unreservedly complimentary to Herschel. The discovery of the new planet was the first great success of Banks’s new presidency. In his most expansive and jovial mood, he accordingly projected a visionary future for Herschel’s astronomy: ‘Your attention to the improvement of telescopes has already amply repaid the labour which you bestowed upon them; but the treasures of heaven are well known to be inexhaustible. Who can say but your new star, which exceeds Saturn in its distance from the sun, may exceed him as much in magnificence of attendance? Who can say what new rings, new satellites, or what other nameless and numberless phenomena remain behind, waiting to reward future industry?’134

  The award set the seal on Herschel’s reputation, and reignited the general fascination with astronomy. The discovery of the seventh planet began a revolution in the popular conception of cosmology. It was widely reported in the gazettes, journals and year books published in London, Paris and Berlin at the end of 1782. Yet although all orreries were instantly out of date, it took some time for Uranus to enter into the popular imagery and iconography of the solar system.

  One of the best of the new wave of popular astronomy books was John Bonnycastle’s Introduction to Astronomy in Letters to his Pupil, which first appeared in 1786 (and went on to new expanded editions in 1788, 1811 and 1822). Bonnycastle gave the discovery of Uranus its own chapter: ‘Of all the discoveries in this science, none will be thought more singular than that which has lately been made by Dr Herschell … This is a Primary Planet belonging to the solar system, which till 13th of March 1781, when it was first seen by Dr Herschell, had escaped the observation of every other astronomer, both ancient and modern …’ Yet he still treated it as a puzzling novelty, its significance yet to be developed. ‘This discovery, which at first appears more curious than useful, may yet be of great service to astronomy … and may produce many new discoveries in the celestial regions, by which our knowledge of the heavenly bodies, and of the immutable laws that govern the universe, will become much more extended: which is the great object of the science …’135

  Bonnycastle’s book was a thoroughly Romantic production, which included a good deal of ‘illustrative’ cosmological poetry from Milton, Dryden and Young. It also sported an engraved frontispiece by Henry Fuseli. This showed the goddess of astronomy, Urania, in a diaphanous observation-dress, pointing seductively to her new star while instructing a youthful male pupil. The publisher was Joseph Johnson of St Paul’s Churchyard, also the publisher of William Blake, William Godwin and Mary Wollstonecraft; and later of Wordsworth and Coleridge.

  Bonnycastle was a great friend of the philosopher Godwin, and besides including poetry to illustrate his astronomical explanations, he considered the imaginative impact of the new astronomy. The ‘Babylonian’ writers of Egypt had increased the Biblical estimate of the earth’s age from 6,000 to 400,000 years, but Bonnycastle pointed out that ‘the best modern astronomers’ had increased this to ‘not less than 2 million years’. He thought that viewing the stars through a telescope both liberated the imagination and produced a certain kind of wonder, mixed with disabling awe or terror: ‘Astronomy has enlarged the sphere of our conceptions, and opened to us a universe without bounds, where the human Imagination is lost. Surrounded by infinite space, and swallowed up in an immensity of being, man seems but as a drop of water in the ocean, mixed and confounded with the general mass. But from this situation, perplexing as it is, he endeavours to extricate himself; and by looking abroad into Nature, employs the powers she has bestowed upon him in investigating her works.’136

  Uranus slowly became a symbol of the new, pioneering discoveries of Romantic science. An unfathomably larger universe was steadily opening up, and this gradually transformed popular notions of the size and mystery of the world ‘beyond the heavens’. Indeed, the very terms ‘world’, ‘heaven’ and ‘universe’ began to change their meanings. It was the psychological breakthrough that Kant had predicted in his Universal Natural History and Theory of the Heavens back in 1755: ‘We may cherish the hope that new planets will perhaps yet be discovered beyond Saturn.’137

  Erasmus Darwin would eventually celebrate Herschel’s new astronomy in his poem The Botanic Garden (1791), notably in the spectacular opening section of Canto 1. The discovery of Uranus inspired Darwin to evoke many other possible ‘solar systems’, each with its own sun and planetary family, spontaneously exploding into being after an initial ‘big bang’. Here Darwin was using Newton’s celestial mechanics (based on Kepler’s three laws of planetary motion), but dramatising the new notion of an endless sequential creation as implied by Herschel. The creative cosmic force is ‘Love’ (as in the classical cosmology of Lucretius), while the Biblical God now seems content simply to initiate what is, in effect, a vast cosmological experiment, and then sit back as a passive observer.

  When Love Divine, with brooding wings unfurl’d,

  Call’d from the rude abyss the living World,

  ‘Let there be Light!’, proclaimed the Almighty Lord,

  Astonish’d Chaos heard the potent word;

  Through all his realms the kindling ether runs

  And the mass starts into a million Suns.

  Earths round each Sun with quick explosions burst,

  And second Planets issue from the first;

  Bend as they journey with projectile force,

  In bright ellipses their reluctant course;

  Orbs wheel in orbs, round centres centres roll,

  And form, self-balanced, one revol
ving whole.

  – Onward they move, amid their bright abode,

  Space without bound, the bosom of their God!

  To this shimmering and kinetic passage, which seems to anticipate in language the music of Haydn’s Creation (1796-98), Darwin added a long, admiring Note on ‘Mr Herschel’s sublime and curious account of the construction of the heavens’.138 ♣

  Astronomers from all over Europe (especially France, Germany and Sweden) began to write to Herschel in Bath, asking for details about his metal specula, his high-magnification eyepieces and his observational techniques. In England there continued to be much scepticism about both his abilities and his telescopes. His replies tended to be formal, but occasionally he relaxed a little with astronomers whom he trusted, and whose skills he admired. He light-heartedly described the pains he took to set up, tune and even ‘humour’ his telescopes. He gave them a life of their own, and implied that he treated them like so many concert prima donnas (perhaps remembering La Farinelli, who had saved him at the Pump Room). To Alexander Aubert in London he wrote one of his most whimsical accounts on 9 January 1782, when enclosing his new catalogue of double stars. ‘These instruments have played me so many tricks that I have at last found them out in many of their humours, and have made them confess to me what they would have concealed, if I had not with such perseverance and patience, courted them. I have tortured them with powers, flattered them with attendance to find out the critical moments when they would act, tried them with Specula of a short and long focus, a large aperture and a narrow one. It would be hard if they had not proved kind to me at last!’139