The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science. Richard Holmes

       2 Herschel on the Moon

      1

      Shortly after his election as President of the Royal Society in 1778, Joseph Banks began to hear rumours of an unusually gifted amateur astronomer working away on his own in the West Country. These rumours first reached him through the Society’s official Secretary, Sir William Watson, whose brilliant and unconventional son, a young physician based in Somerset, was a moving spirit behind the newly founded Bath Philosophical Society. Watson (junior) began sending accounts to his father of a strange maverick who owned enormously powerful telescopes (supposedly built by himself), and was making extravagant claims about the moon.

      The initial reports that reached Banks were strange and somewhat sketchy. The man was called Wilhelm Hershell or William Herschel, possibly a German Jew from Dresden or Hanover.¹ One winter night in 1779 young Watson had found this Herschel in Bath, standing alone in a cobbled backstreet, viewing the moon through a large telescope. Though tall and well-dressed, and wearing his hair powdered, he was clearly an eccentric. He spoke with a strong German accent, and had no manservant accompanying him. Watson asked if he might take a look through the instrument, which he noticed was a reflector telescope, not the usual refractor used by amateurs. It was large-seven feet long-and mounted on an ingenious folding wooden frame. The whole thing was evidently home-made. To his surprise he found its resolution was better than any other telescope he had ever used. He had never seen the moon so clearly.²

      They fell into slightly halting conversation. Watson was immediately taken by Herschel’s humorous and modest manner, and soon realised that it disguised an acute unconventional intelligence. Herschel’s knowledge of astronomy, though obviously self-taught, was impressive. Though he had no university education, and said he had very little mathematics, he had mastered John Flamsteed’s great atlas of the constellations, read the textbooks of Robert Smith and James Ferguson, and knew a great deal about French astronomy. Above all he knew about the construction of telescopes, and the making of specula-mirrors. Though in his early forties, he talked of the stars with a quick, boyish enthusiasm, that betrayed intense and almost unnerving passion. Watson was so struck that he asked if he might call round to see him the very next morning.

      The house at 19 Rivers Street, in the lower, unfashionable section of Bath, was modest, and clearly Herschel was not a gentleman of leisure. The lower rooms were cluttered with astronomical equipment, but the front parlour was dominated by a harpsichord and piled high with musical scores.³ It emerged that Herschel was a professional musician, held the post of organist at the Bath Octagon Chapel, and made ends meet by giving music lessons. He also composed, and was fascinated by the theory of musical harmony. His domestic situation was odd. He was poor, and unmarried, but Watson noticed that he spoke tenderly of a sister, who was not only his housekeeper but also his ‘astronomical assistant’.⁴

      Watson invited his new acquaintance to join the Bath Philosophical Society. Herschel responded with alacrity. Though hesitant to speak in public, he started submitting papers through Watson. Many of them were strange ventures into speculative cosmology and the philosophy of science. They included such subjects as ‘What becomes of Light?’, ‘On the Electrical Fluid’ and ‘On the Existence of Space’.⁵

      Proud of his new discovery, Watson sent what he considered the best of these early papers to his father, Sir William, at the Royal Society in London. Herschel was modestly worried that his English would not be up to the mark, and Watson tactfully corrected each paper. It was not their plain literary style, however, which caused controversy, but their content. The very first of them, ‘Observations on the Mountains of the Moon’, was so unconventional that it caused an unaccustomed stir when it was published in the Society’s august journal Philosophical Transactions in spring 1780. In it Herschel claimed that with his home-made telescopes he had observed ‘forests’ on the lunar surface, and that the moon was ‘in all probability’ inhabited.

      Nevil Maskelyne, the Astronomer Royal and leading cosmological light of the Royal Society, was more than a little outraged by these apparently absurd claims. He had himself established that the moon had no life-sustaining atmosphere, based on the sharpness with which it occults starlight at its edge.⁶ But he was intrigued by the minute detail of Herschel’s observational sketches of the moon’s surface, and the apparently fantastic power of his reflector telescope. He wrote a challenging letter to Watson in Bath, questioning the seriousness of Herschel’s work, and his views on the moon. It was now that Joseph Banks, always on the lookout for new and unusual scientific talent, began to pay attention.

      Watson forwarded what he tactfully called ‘Dr Maskelyne’s extremely obliging letter’ to Herschel. Clearly anxious that Herschel might take offence at the implied criticism, he urged a diplomatic response in a covering note of 5 June 1780: ‘I think you would do right (pardon my giving you advice) either to add the desired improvements, or to write over again the Paper, and send it to Dr Maskelyne, who, as he is Astronomer Royal, will be pleased, I believe, with the compliment paid him, and he will present it anew to the Society.’⁷

      To his relief, Herschel wrote back to the Astronomer Royal with apparent modesty on 12 June: ‘I beg leave to observe Sir, that my saying that there is an absolute certainty of the Moon’s being inhabited, may perhaps be ascribed to a certain Enthusiasm which an observer, but young in the Science of Astronomy, can hardly divest himself of when he sees such Wonders before him. And if you promise not to call me a Lunatic I will transcribe a passage from some observations begun 18 months ago, which will show my real sentiments on the subject.’⁸

      The views that Herschel now expressed must have taken Maskelyne aback. Far from retracting his opinions, he emphasised his belief that ‘from analogy’ with the earth, and its likely conditions of heat, light and soil, the moon was ‘beyond doubt’ inhabited by life ‘of some kind or other’. Even more provocatively, he thought that the terrestrial view of matters gave undue importance to the earth. ‘When we call the Earth by way of distinction a planet and the Moon a satellite, we should consider whether we do not, in a certain sense, mistake the matter. Perhaps-and not unlikely-the Moon is the planet and the Earth the satellite! Are we not a larger moon to the Moon, than she is to us?…What a glorious view of the heavens from the Moon! How beautifully diversified with [her] hills and valleys!…Do not all the elements seem at war here, when we compare the earth with the Moon?’

      That Herschel was writing somewhat mischievously to the Astronomer Royal becomes clear towards the end of his letter. Poetry gently creeps up on astronomy: ‘The Earth acts the part of a Carriage, a heavenly waggon to carry about the more delicate Moon, to whom it is destined to give a glorious light in the absence of the Sun. Whereas we, as it were, travel on foot and have but a small lamp to give us light in our dark nights, and that too often extinguished by clouds.’ The teasing wit in Herschel’s final sally was unmistakeable: ‘For my part, were I to choose between the Earth and the Moon, I should not hesitate a moment to fix upon the Moon for my habitation!’⁹

      Maskelyne