The Age of Wonder

by Richard Holmes

  4

  Herschel Among the Stars

  1

  Sir Joseph Banks had predicted that British astronomy would go further than French ballooning. In the summer of 1785 William Herschel embarked on his revolutionary new project to observe and resolve the heavens with a telescope more powerful than ever previously attempted. His first move was to draft a preliminary technical specification for Banks to submit to the King. It was a monumental proposal.

  What he intended to build was a telescope ‘of the Newtonian form, with an octagon tube 40 foot long and five feet in diameter; the specula [mirrors] of which it would be necessary to have at least two, or perhaps three, should be from 36 or 48 or 50 inches in diameter’.1 The telescope would have to be mounted in an enormous wooden gantry, capable of being turned safely on its axis by just two workmen, but also susceptible to the finest and most minute fingertip adjustments by the observing astronomer. The mirrors would weigh about half a ton each, and cost between £200 and £500. They would have to be cast in London and shipped by barge up the Thames for polishing.2 Casting would be a major feat of technology, and twenty workmen would be required to effect a continuous process of polishing with newly designed machinery.

  The forty-foot would be higher than a house, extremely susceptible to wind, and very exposed to adverse weather conditions, especially frost, condensation and air-temperature changes, which could ‘untune’ the mirrors like musical instruments. The astronomer (Herschel was now approaching fifty) would be required to climb a series of ladders to a special viewing platform perched at the mouth of the telescope, from which a fall would almost certainly prove fatal. The assistant (Caroline) would have to be shut in a special booth below to avoid light pollution, where she would have her desk and lamp, celestial clocks, observation journals and coffee flasks. But she would see virtually nothing of the stars themselves.

  Astronomer and assistant would be invisible to each other for hours on end, shouting commands and replies, although eventually connected by a metal speaking-tube. It would be rather as if they were the tiny crew of some enormous ship, one up on the bridge, the other below in the chart room, intimately dependent on each other but physically isolated. Perhaps this was the premonition of a new kind of vessel: a spaceship flying through the starry night.3

  All this would require a new level of funding by the King. The estimate of expenses totalled £1,395, with an annual running cost of £150. This huge sum did not include Herschel’s annual salary of £200.4 When he submitted this enormous research-grant application, Herschel austerely did not promise any immediate results — more planets, more comets, more sightings of extraterrestrial life forms. Instead he tried to reassure Banks in the most sober terms: ‘The sole end of the work would be to produce an Instrument that should answer the end of inspecting the Heavens, in order more fully to ascertain their construction.’5

  It was one of Sir Joseph Banks’s most dramatic diplomatic coups that he had convinced the King to announce a grant by September 1785. The sum was a generous one: the entire construction costs and four years’ running expenses — a total of £2,000. The one implied proviso was that Herschel needed to come up with results by the end of 1789. In November 1785 Banks was already sending tactful enquiries through William Watson: ‘Sir Joseph Banks is come to Town, & expressed a wish to know from you what preparations you have made relating to the great Telescope, & how far you have proceeded in the work itself. He said that he was very desirous of knowing, that he might be enabled to give the King a history of your proceedings.’6

  In fact there was no immediate progress that autumn. To Caroline’s dismay, Herschel had decided that his grand project required a new house with larger grounds for constructing and erecting the telescope, and more outbuildings for workshops. A first move from Datchet to Clay Hall, nearer to Windsor, had proved abortive when their new landlady objected to the cutting down of trees, and sought to raise the rent on the ingenious grounds that Herschel’s monster telescope, if it were ever built, would count as an ‘improvement’ to the house. Herschel wondered mildly if each new astronomical discovery would increase the valuation, and thereafter require a corresponding increase in the rent.

  On 3 April 1786 they moved again (the Herschels’ third move in four years), to ‘The Grove’, a quite small and rather dilapidated country house on the edge of the tiny village of Slough, three miles north of Windsor. It was owned by a wealthy local family, the Baldwins, whose various relations also owned two local inns, the Dolphin and the Crown, and were extensive landowners in the district. The Crown was the main mail-coach halt on the London to Bath turnpike, now rerouted as the modern A4 through Slough. (The original sleepy road junction has become a pedestrianised section of the busy high street, though still known locally as ‘the Crown crossroads’.)

  The youngest member of the family, Mary Baldwin, was a considerable heiress, and had married a retired London merchant, John Pitt, who was some twenty years older than herself. They decided to lead an easy-going country life, and had their own large, comfortable house less than a mile away from The Grove at the little village of Upton. They proved hospitable and friendly neighbours, and soon got to know the Herschels socially. John was in ‘a declining state of health, so William would walk over at weekends, and sit talking to him in his well-appointed library. Caroline seems to have got on rather well with the Pitts’ son Paul, an only child who had just started at nearby Eton College.7

  The Grove stood in secluded grounds, 200 yards south of the Crown Inn, on the east side of the road to Windsor. Though it was surrounded by trees, the ground dropped away sharply to the south, offering a good observational platform. It was also ideal for rapid communications with London and Maskelyne’s observatory at Greenwich, as well as remaining close to the King’s residence. Indeed the turrets of Windsor Castle could be seen from the terraced walk on the south of the property, a constant reminder of the expectations of the royal patron.8 The house itself was not large: four bedrooms and a servants’ attic. But it had extensive sheds and stables which were gradually converted into workshops and laboratories, and a wash house that became a forge. Above the stables were a series of haylofts which could be converted into a separate apartment. Caroline claimed these for her own. She had them roughly whitewashed, and put into use as a bedroom and a writing room, with a small outside staircase leading up to a flat roof from which she hoped to carry out her comet ‘sweeps’ in security and independently. This became her ‘cottage’ and occasional residence, a first step towards domestic independence at the age of thirty-six.

  The Grove also had a large flat area of rough gardens in front of it, ideal for levelling and laying the extensive circular brick foundations of the wooden gantry for the forty-foot telescope. The brickwork was capped with Portland stone, though later this was cracked by frost and had to be sheathed in oak.9 As work progressed, Herschel had all the surrounding trees cut down, including a magnificent row of ancient elms, ‘to the grief of everyone who knew that sweet spot’, as one neighbour observed. Characteristically, Herschel took no notice of their objections.10 This scattered collection of buildings would later become known as Observatory House’, and Herschel’s telescope would be marked on the first edition of the Ordnance Survey map for Berkshire in 1830.11

  The launch of the new project changed the quiet rhythm of the Herschels’ lives. The spring of 1786 was ‘a perfect Chaos of business’, as Caroline put it with a certain relish: ‘If it had not been sometimes for the intervention of a cloudy or a moonlight night [bad for stellar observation], I know not when my Brother (or I neither) should have got any sleep; for with the morning came also the workpeople of which there were no less than between 30 or 40 at work for upwards of 3 months together, some employed with felling and rooting out trees, some digging and preparing the ground for the Bricklayers who were laying the foundation for the telescope, and the carpenter in Slough with all his men.’12

  News of the proposed monster telescope brought a
steady stream of visitors to Slough: men of science, academics from the universities, foreign tourists, and too many dignitaries from the Court. Caroline would grow increasingly impatient at their tendency to interrupt Herschel’s work. She developed her own laconic way of registering this impatience: ‘Professor Sniadecky often saw some objects through the 20 foot Telescope, among others the Georgian satellites. He had taken lodgings in Slough for the purpose of seeing and hearing my Brother whenever he could find him at leisure. Himself was a very silent man.’13 She was always happy, however, to welcome old friends like William Watson and Nevil Maskelyne, and new supporters from the Royal Society like Charles Burney (who was also in favour of hot-air balloons). Americans were notably well-received.

  Sometime in the summer of 1786 the fifty-year-old John Adams, graduate of Harvard University, man of science and future second President of the United States, turned up one morning uninvited at The Grove. He was shown round all Herschel’s new telescopes, and they embarked on an impassioned discussion of the possibility of extraterrestrial life, and the moral implications of there being a ‘plurality of worlds’. This was the sort of metaphysical debate that Herschel had once had with his brother Jacob, touching on the speculations of European authors like Fontenelle and Huygens, but which he tended to avoid with his English contemporaries. Neither Herschel nor Caroline recorded exactly what was said, but it is clear from his own diaries that Adams would have put lively and unorthodox views: ‘Astronomers tell us that not only all the Planets and Satellites in our Solar system, but all the unnumbered Worlds that revolve round the fixt Stars are inhabited … If this is the case all Mankind are no more in comparison [with] the whole rational Creation of God, than a point in the orbit of Saturn.’

  Like the poet Shelley a generation later, Adams liked to press this argument one stage further. If astronomy discovered extraterrestrial civilisations, then surely the earth-based doctrines of Christian redemption became absurd, or at least mighty inconvenient for the Lord. ‘I ask a Calvinist, whether he will subscribe to this alternative: EITHER God Almighty must assume the respective shapes of all these different Species, and suffer the penalties of their Crimes, in their stead; OR ELSE all these Beings must be consigned to everlasting Perdition?’14 ♣

  Amidst all the bustle of visitors and workmen, Herschel was despatched by royal command in July 1786 to deliver and erect one of his ten-foot telescopes, as King George’s special gift to the University of Göttingen, which was fast becoming the centre of scientific studies in Germany. His brother Alexander was to accompany him as business manager. This was both a great honour and a great inconvenience, and for the first time in her life Caroline was left wholly in charge of both the construction work on the forty-foot and the continuing observation programme of nebulae and double stars. Currently they had completed 572 sweeps, identified 1,567 nebulae, and found two tiny new moons orbiting Georgium Sidus (a discovery that particularly amused the King).15

  Caroline’s first response was thoroughly domestic. She started a new day book, neatly headed it ‘Book of Work Done’, drew a careful set of parallel columns, and recorded her inventory of tasks.

  July 3rd 1786. My Brothers William and Alex left Slough to begin their journey to Germany … By way of not suffering too much by sadness, I began with bustling work. I cleaned the brass work for the 7 and 10 feet telescopes and put curtains before the shelves to hinder the dust from settling upon it again. I cleaned and put the [mirror] polishing room in order and made the gardener clean the work-yard, put everything in safety and mend the Fences.

  She would not tolerate idling among the workmen, who evidently caused difficulties. The gardener was reprimanded for lolling about the lawns: ‘he gave me the name of “Stingy —” in the village, because I objected to his being there when not wanted’.16 It would be interesting to know what the ‘—’ stood for: the fact that Caroline was female, foreign, diminutive, unmarried, disciplined, or brilliantly gifted perhaps?

  That afternoon she did needlework and went shopping in Windsor; when she got back she was mortified to find ‘there had been four foreign Gentlemen looking at the instruments in the garden, but did not leave their names’. Later unannounced visitors that month included Nevil Maskelyne and his wife, three members of the great Dolland telescope family, the Duke of Saxe-Gotha, Tiberius Cavallo (the balloon expert from the Royal Society), her friend Dr James Lind, the Prince Resonico and the Plumian Professor of Astronomy at Cambridge, Dr Antony Shepherd. The question of visitors became more awkward as July progressed, and for the first time made Caroline aware of the social anomaly of her position. ‘I was often put into great perplexity by such self-inviting visitors; for I could only look upon myself as an individual who was neither Mistress of her Brother’s house, nor of her Time, and for that reason neither could, nor would, ever give invitations.’ She also found the endless ‘gossipings’ of Alexander’s pretty but ‘foolish’ new wife, who came over from Bath, intolerable.17

  By the end of July Caroline had decided that the only way to remedy this situation was to insist on her own quite separate regime. She would be an astronomer, not a housekeeper. She would check over the calculations of William’s nebulae by day, and make her own sweeps up on the roof by night. She would go to bed late (often just before dawn light, around 4 a.m.) and get up late (but always in time to pay the workmen after breakfast). She even wrote William a little imaginary letter about this in her ‘Book of Work Done’. In this case it was to be work she would not do. ‘I find I cannot go fast enough with the registering of sweeps to be serviceable to the Catalogue of Nebulua. Therefore I will begin immediately to recalculate them, and hope to finish them before you return. Besides I think the consequences will be bad of registering the sweeps backwards.’18 Thus liberated from the nightly duty of William’s sweeps, her ‘Book of Work Done’ began to fill with her own astronomical observations. Symbolically she recorded on 30 August winding up the ‘Sidereal Time Piece’, the big brass chronometer used to fix stellar positions.

  Three summers previously William had built Caroline a special two-foot Newtonian reflector, mounted within an ingenious wooden box-frame. Because of its large aperture, its tube appeared much fatter, heavier and stubbier than normal reflectors of this type: a rotund, almost jovial presence, but not in the least awkward to handle. Suspended from a pivot at the top of the box-frame, the telescope could be precisely raised or lowered by a system of pulleys operated by a large brass winding handle at the bottom. These adjustments were easy to make, and extremely fine. The whole ‘contrivance’ was set on a solid portable wooden stand, constructed like a three-legged stool, and exactly carpentered to bring the Newtonian viewing lens precisely to the level of Caroline’s eye. It also allowed a workman (or Caroline herself) to carry the telescope and stand in two sections, and position it wherever required, downstairs in the garden or upstairs on the flat roof.19

  This beautiful instrument was designed specifically for its huge light-gathering power and its wide angle of vision. The mirror was 4.2 inches in diameter (the size more usually placed in the seven-foot reflectors), with a large observational field of over two degrees. The magnification was comparatively low at twenty-four times. As with modern binoculars, this combination of low power with a large viewing field allowed the observer to see faint stellar objects very brightly, while placing them within a comparatively wide context of surrounding stars. In effect, Herschel had constructed for Caroline a hunter’s telescope.

  It was a deliberate challenge. The instrument was not suitable for deep space, but it was perfectly designed to spot any strange or unknown object moving through the familiar field of ‘fixed stars’. It was designed to find wanderers and messengers coming into the solar system. In other words, to catch new planets or new comets. It eventually became famous as ‘Miss Herschel’s small sweeper’, and would be joined within two years by ‘Miss Herschel’s large sweeper’.20

  On 1 August 1786, only two nights after starting her new sweep
s, Caroline thought she had spotted an unknown stellar object moving through Ursa Major (the Great Bear constellation). It appeared to be descending, but barely perceptibly, towards a triangulation of stars in the beautifully named Coma Berenices (‘Berenice’s Hair’, as celebrated in Pope’s poem ‘The Rape of the Lock’). To find something so quickly, and in such a familiar place (the Great Bear or Big Dipper being the first stop of every amateur stargazer wanting to locate the Pole Star), seemed wildly unlikely. Caroline’s Observation Book conveys meticulous caution, but also remarkable certainty.

  Unable to calculate the mathematical coordinates of the object, she accompanied her observations with a series of three neat drawings or figures, over an eighty-minute time lapse. These showed the circular viewing field of her telescope, with an asterisk shape very slightly changing position relative to three known fixed stars.

  August 1st 1786. 9 hours 50 mins. I saw the object in the center of fig. 1 like a star out of focus while the others were perfectly clear. The sec. star is very faint but the weather is hazy, and in a clearer night undoubtedly some more will be visible. … 11 hours 10 mins. I think the situation is now like in Fig.3 but it is so hazy that I could only imagine I saw the second star & the preceding I could not see at all. The comet is about half way between 53 and 54 Ursa maj. and some stars which I found after looking over the map at leisure to be 14, 15, and 16 Coma Berenices … 21

  Caroline does not remark that her comet was moving from a male to a female constellation, a fact which might have well have struck her as peculiarly appropriate. But the account written into the ‘Book of Work Done’ catches something of her growing excitement. The drudgery of daytime calculation in her study was overtaken by the tantalising expectations and frustrations of the nights up on the flat roof.