Agnes M. Clerke

“ The stars came out well, and no sooner had he got hold of Saturn than a sixth satellite stood revealed to view! Its “younger brother” was detected September 17th; and the two could be seen, on favourable opportunities, threading their way, like beads of light, along the lucid line of the almost vanished ring. Herschel named them Enceladus and Mimas, and found, on looking up his former observations of Saturn, that Enceladus, the exterior and brighter object, had been unmistakably seen with the twenty-foot, August 19th, 1787. Mimas is a very delicate test of instrumental perfection. ”

“ Yet there are to be found in every quarter of the world men imbued with William Herschel’s sublime ambitions. Success swells the ranks of an invading army; and the march of astronomy has, within the last decade, assumed a triumphal character. The victory can never be completely won; the march can never reach its final goal; but spoils are meanwhile gathered up by the wayside113 which eager recruits are crowding in to share. ”

“ No one of distinction in science came to Hanover without calling upon her. Humboldt, Gauss, Mädler, Encke, Schumacher, paid her their respects, personally or by letter, if not in both ways. “Next to listening to the conversation of learned men,” she told the younger Lady Herschel, “I like to hear about them; but I find myself, unfortunately, among beings who like nothing but smoking, big talk on politics, wars, and such-like things.” ”

“ But for this moral purpose, he might have squandered time in a multiplicity of partial researches. So late as 1830 he told Sir William Rowan Hamilton: “I find it impossible to dwell for very long on one subject, and this renders my pursuit of any branch of science necessarily very desultory.” His nebulæ and double stars saved him from being “everything by turns, and nothing long.” Their collection and revisal, begun as a duty, grew to be irresistibly attractive, and John Herschel pledged himself definitively to astronomy. ”

“ Music is the most exclusive of arts. In turning aside, after half a lifetime spent in its cultivation, to seek his ideal elsewhere, Herschel took an unparalleled course. And his choice was final. Music was long his pursuit, astronomy his pastime; a fortunate event enabled him to make astronomy his pursuit, while keeping music for a pastime. ”

“ One needs not be a “tailor of Breslau,” or a Siberian savage, to see it. The little star is unmistakably more luminous than of old.
An inversion of brilliancy between Castor and Pollux, and between the two leading stars in the Whale, is further generally admitted to have taken place during the eighteenth century. The prevalence of such vicissitudes was deeply impressive to Herschel, especially through their bearing upon the past and future history of our own planet. ”

“ The discovery of binary stars was, in Arago’s phrase, “one with a future.” In itself an amazing revelation, it marked the beginning of a series of investigations of immense variety and importance. By it, a science of sidereal mechanics was shown to be possible; the sway of gravitation received an unlimited extension; and the perception of order, which is the precursor of knowledge, ranged at once over the whole visible creation. Herschel, it is true, had not the means of formally proving that stellar orbits are described in obedience to the Newtonian law. ”

“ In the same manner we pass by gentle steps from a coarse cluster to an object such as the nebula in Orion, where we are still inclined to remain in the once adopted idea of stars exceedingly remote and inconceivably crowded, as being the occasion of that remarkable appearance. It seems, therefore, to require a more dissimilar object to set us right again. A glance like that of the naturalist, who casts his eye from the perfect animal to the perfect vegetable, is wanting to remove the veil from the mind of the astronomer. ”

“ From his earliest childhood William Herschel’s nerves and brain had been specially educated to discriminate impressions of sound, and his muscles to the peculiar agility needed for their regulated and delicate production; while, up to the age of thirty-five, he had used his eyes no more purposefully than other people. The eye, nevertheless, requires cultivation as much as the ear. “You must not expect to see at sight,” he told Alexander Aubert, of Loam Pit Hill, in 1782. And he wrote to Sir William Watson: “Seeing is in some respects an art which must be learnt. ”

“ He secured a post in Linley’s orchestra for his younger brother Alexander, in 1771; and he himself fetched his sister Caroline to Bath in 1772. Both were of very considerable help to him in his musical and other enterprises, the latter of which gradually gained ground over the former.
Music was never everything to William Herschel. He cultivated it with ardour; composed with facility in the prevalent graceful Italian style; possessed a keen appreciation and perfect taste. But a musical career, however brilliant, did not satisfy him. The inner promptings of genius told him to look beyond. ”

“ The general appearance to ourselves of the Milky Way leaves it uncertain whether it represents the projection upon the heavens of an immense stratum of equally scattered stars, or a ring-like accumulation, towards the middle of which our sun is situated. Herschel gave his preference, to begin with, to the former hypothesis, and then, with astonishing boldness and ingenuity, attempted to put it experimentally to the proof. ”

“ The appellation “Georgium Sidus,” bestowed in honour of his patron, George III.,25 never crossed the Channel, and has long since gone out of fashion amongst ourselves. Lalande tried to get the new planet called “Herschel;” but the title “Uranus,” proposed by Bode, of Berlin, was the “fittest,” and survived.
This discovery made the turning-point of Herschel’s career. It transformed him from a music-master into an astronomer. Without it his vast abilities would probably have been in great measure wasted. No man could long have borne the strain of so arduous a double life as he was then leading. ”

“ HERSCHEL’S SPECIAL INVESTIGATIONS. Double stars were, when Herschel began to pay attention to them, regarded as mere chance productions. No suspicion was entertained that a real, physical bond united their components. Only the Jesuit astronomer, Christian Mayer, maintained that bright stars were often attended by faint ones; and since his observations were not such as to inspire much confidence, his assertions counted for very little. “In my opinion,” Herschel wrote in 1782, “it is much too soon to form any theories of small stars revolving round large ones.” ”

“ In January, 1781, there came an essay stamped with the peculiar impress of his genius, entitled “Astronomical Observations on the Rotation of the Planets round their Axes, made with a view to determine whether the earth’s diurnal motion is perfectly equable.” It embodied an attempt to apply a definite criterion to the time-keeping of our planet. But the prospect is exceedingly remote of rating one planet-clock by the other. Herschel’s methods of inquiry are, however, aptly illustrated in this curiously original paper. His speculations always invited the control of facts. ”

“ Pointing two similar telescopes upon two unequal stars, he equalised them to the eye by stopping down the aperture of the instrument directed towards the brighter object. Assuming each to emit the same quantity of light, their respective distances would then be inversely as the diameters of the reflecting surfaces by which they were brought to the same level of apparent lustre. But the enormous real diversities of stellar size and brightness render this plan of action wholly illusory. Even for average estimates, proper motion is apparently a safer criterion of distance than magnitude. ”

“ On June 1st, 1821, he inserted into the50 tube with thin and trembling hands the mirror of the twenty-foot telescope, and took his final look at the heavens. All his old instincts were still alive, only the bodily power to carry out their behests was gone. An unparalleled career of achievement left him unsatisfied with what he had done. Old age brought him no Sabbath rest, but only an enforced and wearisome cessation from activity. His inability to re-polish the four-foot speculum was the doom of his chef d’œuvre. ”

“ This prodigious appurtenance was, in grade of luminosity, an exact match for the Milky Way. That comets wear out by the waste of their substance at perihelion, he thought very probable; the extent of their gleaming appendages thus serving as a criterion of their antiquity. They might, indeed, arrive in the solar system already shorn of much of their splendour by passages round other suns than ours ”

“ He, indeed, probably even then, suspected that close equal stars formed genuine couples; but he waited, if so, for evidence of the connection. The chief subject of his experiments on parallax was Epsilon Boötis, an exquisitely tinted, unequal pair. But he soon became aware that either stellar parallax was elusively small, or that he was on the wrong track for detecting it. And, since his favourite stars have proved to be a binary combination, it was, of course, drawing water in a sieve to make one the test of perspective shifting in the other. ”

“ On nights meteorologically quite fine, the dismayed astronomer not uncommonly sees the stars “walking about” in the field of view; and a mere handful of cloud will, at other times, with incredible swiftness, spread over the whole face of the sky. Still, compensation is, sooner or later, sure to come in a run of magnificent observing weather. This was Herschel’s experience. ”

“ Herschel’s sun is to us moderns a wholly fabulous body. Still, there is a fantastic magnificence about the conception so strongly realised by his powerful imagination. Moreover, its scientific value was by no means inconsiderable. It represented the first serious effort to co-ordinate solar phenomena; it implied the spontaneous action of some sort of machinery for the production of light and heat. Spots were associated with a circulatory process; the photosphere was portrayed under its true aspect. ”

“ The “flying synods of worlds” formed by them must gravitate one towards another as if concentrated at their several centres of gravity. Accordingly, “a star, or sun, such as ours, may have a proper motion within108 its own system of stars, while the whole may have another proper motion totally different in quantity and direction.” We may thus, he continued, “arrive in process of time, at a knowledge of all the real, complicated motions of the planet we inhabit; of the solar system to which it belongs; and even of the sidereal system of which the sun may possibly be a member.” ”

“ The inducements, according to the critic, were strong “to descend from the airy summits of abstract science to the level at which the great body of the reading public can appreciate and applaud. Philosophers, like other writers, naturally wish to be read, and to have reputation; and reputation, as was remarked by d’Alembert, depends more upon the number than the merit of those who praise.” Sir John Herschel would have been better employed in pursuing the track of original discoveries, leaving new207 truths to “find their way to the drawing-room as best they might.” ”

“ The earth is heated from the outside, and therefore unequally;179 hence the air rushes along, turning westward as it goes, from the chilly poles to the torrid zone of vertical sunshine. No reason is, however, apparent why the solar equator should be hotter than the solar poles. That adduced by Herschel is certainly inadequate. He supposed that, by a retention of heat at the equator due to the accumulation there, consequent upon his rotation, of the sun’s absorbing atmosphere, a difference of temperature might be maintained sufficient to keep the solar trade-winds blowing. ”

“ A royal grant of £2,000 for the construction of the designed giant telescope, followed by another of equal amount, together with an annual allowance of £200 for its repairs, removed the last obstacle to his success. The wide distribution of first-class instruments might, indeed, have been thought to promise more for the advancement of astronomy than the labours of a single individual. No mistake could be greater. Not an observation worth mentioning was made with any of the numerous instruments sent out from Datchet or Slough, save only those acquired by Schröter and Pond. ”