CHAPTER X.

WRITINGS AND EXPERIMENTAL INVESTIGATIONS.

Could the whole of Sir John Herschel’s astronomical career be obliterated, and the whole of his contributions to pure mathematics be forgotten, he would still merit celebrity as a physicist. Experimental optics, above all, engaged his attention. “Light,” he himself said, “was his first love,” and he was never wholly forgetful of it. In 1830 he described himself as “forcibly drawn aside from his optical studies” by the claims of nebulæ and double stars. How strong he felt those claims to be, can best be understood by considering the firmness with which he averted his mind, out of regard to them, from the intricate and bewitching subject of his early devotion.

“I understand from Peacock,” Dr. Whewell wrote to him, June 19, 1818, “that you are untwisting light like whipcord, examining every ray that passes within half a mile, and putting the awful question, ‘Polarised, or not polarised?’ to thousands that were never before suspected of any intention but that of moving in a straight line.” These interrogatories brought out a remarkable diversity in the action upon light of quartz, and other similar substances, corresponding with the two different modes of crystallisation belonging to each of them. Here, in Lord Kelvin’s phrase, is “one of the most notable meeting-places between natural history and natural philosophy.”

The nascent science of spectrum analysis was materially promoted by Herschel. He noticed in 1819 the distinctive light-absorbing qualities of coloured media, studied the spectra of various flames, adverted to the definiteness and individuality of the bright lines composing them, and recommended their employment for purposes of chemical identification.

A year later, he developed and modified Brewster’s explanation of the colours of mother-of-pearl. They do not, like the iridescence of a fly’s wing, result from the interference of waves of light reflected from two closely adjacent surfaces, but from interference brought about by the finely striated texture of the shell’s surface, and a cast of the rainbow-tinted surface in black sealing-wax will display the same sheen of colour as the original. Herschel detected, however, a second more closely striated structure which cannot be impressed upon plastic matter.

Up to this time he accepted unreservedly the emission theory of light. But a candid study of Young’s and Fresnel’s writings produced a fundamental change in his opinions; and in an article on “Light,” written for the “Encyclopædia Metropolitana” in 1827, he expounded the undulatory theory with all the ardour of a neophyte. He brought thereby one of the grandest generalisations of science into universal currency, and enforced its acceptance by the cogency of his arguments, the logical order of his method, and the lucidity of his style. The treatise was translated into French by Quetelet; and no reader, Professor Pritchard remarked, “could escape the charm of the half-suppressed enthusiasm which carried him along.”

Whewell ranked him “among the _very_ small number of those who, in the singularly splendid and striking researches of physical optics, had both added important experimental laws to those previously known, and weighed the relations of these discoveries to the refined and recondite theory towards which they seemed to point.” He contributed to the same Encyclopædia scarcely less brilliant essays on Heat, Sound, and Physical Astronomy.

“Do not observe too much in cold weather,” Miss Herschel advised her nephew, in anticipation of the winter of 1831–2; “write rather books to make folks stare at your profound knowledge.”

He followed the positive part of her counsel. Indeed, his “Preliminary Discourse on the Study of Natural Philosophy” had made its appearance in the previous year, as the introductory volume to Lardner’s “Cabinet Cyclopædia.” It was greeted with a chorus of approbation. Gauss reviewed it in the _Gelehrte Anzeigen_, Whewell in the _Quarterly Review_. Translated into French, German, and Italian, it delighted “all sorts and conditions” of readers with the justice and breadth of the views set forth in it agreeably, easily, and without pretension to superiority. The book included a survey of the actual state of scientific knowledge, and a philosophy of its augmentation. Students derived from it, Gauss remarked, both information as to how accepted results had been obtained, and guidance for their personal investigations. Herschel was exceptionally qualified, Whewell wrote, “to expound the rules and doctrines of that method of research to which modern science has owed its long-continued, steady advance, and present flourishing condition.” He had the knowledge, without the narrowness, of a specialist in almost every department of experimental physics. “With singular alacrity,” he came to the front wherever there seemed a chance of pushing back the barriers of ignorance. A disciple of Bacon, he had the advantage over his master of being habitually conversant with the practical working of inductive methods. The treatise was styled by Whewell “an admirable comment on the ‘Novum Organum.’” One, however, possesses the indefinable quality of _greatness_; it stands out from the centuries a solid structure, clothed with visionary magnificence; the other is elegant, attractive, wise, acute, even profound, but not in any degree, or from any point of view, _great_.

It was followed, in 1833, by “A Treatise on Astronomy,” published in the same series. An “Edinburgh Reviewer” (doubtless Brougham once more) perused it with regret. “The proper position of Sir John Herschel” he considered to be “at the head of those who are nobly, though it may be silently and without notice, endeavouring to extend the present limits of human knowledge,” rather than among “the ranks of those whose office it is to herald the triumphs of science, and point out its treasures and results to the admiration of the vulgar.” This ostensibly flattering estimate was made the basis for an imputation of vanity. 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 new truths to “find their way to the drawing-room as best they might.” The whole tenour of his life refuted these insinuations.

The “Treatise on Astronomy” was enlarged in 1849 into the deservedly famous “Outlines of Astronomy.” Twelve editions of this book were published, the last in 1873; it was translated into Chinese and Arabic, as well as into most European languages, including Russian; it made a profound and lasting impression upon the public mind. No science has perhaps ever received so masterly a general interpretation. Methodical in plan, inspiriting in execution, it demands readers willing to share some part of the pains, for the sake of partaking in the high pleasures of the writer. For it is popular in the sense of eschewing mathematical formulæ, not in the sense of evading difficulties.

The work fittest to be set by its side is the “Exposition du Système du Monde.” But Laplace restricted his view to the sun’s domain, while Herschel excluded from his no part of the sidereal universe. Laplace was, besides, a geometer in the first, an astronomer only in the second place. The movements of the heavenly bodies interested him because they afforded opportunities for analytical triumphs. Their intricacy notwithstanding, he was elated to find that they could not baffle his ingenuity in constructing formulæ to correspond. Their balance, their harmony, their obedience to a single and simple law, gratified the orderly instincts of his powerful yet frigid mind. Where he could not explain, however, he did not admire. Mystery had no attraction for him. Knowledge, to _be_ knowledge in his eyes, should have definite, clear-cut outlines. His scheme of the universe was like the map of the world laid down by Hecatæus, neatly finished off with a circumfluent ocean-stream; it included no intimations of a _beyond_. Herschel’s, on the contrary, might be compared to the map of Herodotus, in which some details were filled in, while the external boundary had been abolished. The most essential part of the progress made in the interval consisted in leaving verge and scope for the unknown. Next to nothing remained to be learned of the heavens, as they presented themselves to the author of the “Mécanique Céleste”; while Herschel saw everywhere only beginnings, possibilities of discovery, and dim prospects of “ultimate attainments,” as to the realisation of which “it would be unwise to be sanguine, and unphilosophical to despair” (Playfair). At the head of very many of his chapters he might, without presumption, have written: “Quorum pars magna fui.” They gave largely the results of his personal investigations, and were vivified by immediate acquaintanceship with the objects described. Hence the unsought picturesqueness of his descriptive epithets, and the sublimity of trains of thought communicated to him direct from the unveiled heavens.

Herschel invented in 1825, jointly with Babbage, the “astatic,” or neutralised magnetic needle--a little instrument which was no sooner available than it was found to be indispensable. “Nihil tetigit quod non ornavit.” And many and various were the things touched by his versatile genius. He had a narrow escape of becoming for life a chemist. At the very outset of his career he applied for the vacant chair of that science at Cambridge; but was left, as he himself humorously expressed it, “in a glorious minority of one.” The chemical inquiries, nevertheless, which he carried on at Slough brought to his notice one set of relations of no trifling importance. This was the solvent effect upon salts of silver of the hyposulphites of soda, potash, etc. The discovery was turned to account by himself in 1840 for the “fixing” of photographic images. It secured the future of the embryo art. By the agency of hyposulphite of soda in washing away the unaffected chloride of silver, while leaving untouched the parts of the deposit decomposed and darkened by exposure, permanent light-pictures, capable of indefinite multiplication, were at length secured.

On March 14th, 1839, unaware that he had been anticipated by Fox Talbot, Herschel presented to the Royal Society twenty-three prints made by the sensitised paper process. A memoir communicated in 1840 was full of suggestive novelties. In it he described experiments on “the chemical analysis of the solar spectrum,” pointing out that the character and amount of the action exercised by the various rays depend mainly upon the nature of the substance acted upon. He made a start, too, with spectral photography, and his detection of the “lavender-grey” effect to the eye of the ultra-violet section might be said to have added a new note to the prismatic gamut. In the opposite, or infra-red end, by simply letting the solar spectrum fall upon a strip of paper moistened with alcohol, he detected, through the different rates of drying where they fell, some of the “cold bands,” by which the invisible heat-rays are furrowed. The photo-spectroscopic apparatus devised for the purpose of these researches formed part of the Loan Collection of Scientific Instruments exhibited at South Kensington in 1876.

Still more essential was the improvement of substituting for paper, glass plates spread with a sensitive film. A photograph of the old forty-foot telescope, taken by this method in 1839, and preserved in the South Kensington Museum, is of unrivalled antiquarian value as regards the history of photography. The terms “positive” and “negative” received in this remarkable paper their now familiar photographic meaning. Its merits were acknowledged in 1840 by the award of a Royal Medal.

Sir John Herschel would, doubtless, at that time have set aside as a chimera the notion that the art he was engaged in promoting was destined, in large measure, to supersede visual methods in astronomy; that the great telescopes of the future would find their most useful employment in concentrating the rays of celestial objects upon sensitive plates. He soon perceived, however, the importance of photography as an adjunct to direct observation, and recommended, in 1847, the automatic self-registration of sun-spots. This hint--emphasised in 1848--was acted upon in 1858, when the regular collection of documentary evidence as to the sun’s condition was begun at Kew with De la Rue’s “photoheliograph.”

In 1845 he published the first effective investigation of “fluorescence,” called by him “epipolic,” or superficial, “dispersion.” This curious phenomenon consists in the illumination to the eye of certain substances, such as sulphate of quinine and canary glass, under the play of _invisible_ light. Sir George Stokes showed in 1852 that the impinging rays have their undulations actually lengthened by the action of such kinds of matter, so as to become degraded in the spectrum, and thus brought within the range of vision.

The Herschelian theory of the sun was adopted, and long retained by Sir John. He believed in a cool, solid interior globe sheltered by a succession of aërial envelopes, rent, locally and temporarily, by tornadoes of fire. The presence of inhabitants on the globe so circumstanced was credible to him, although he abstained from dwelling upon the advantages of their state. He carefully followed, however, the progress of solar science, and in 1864 explained his altered views in the _Quarterly Journal of Science_. He now regarded the sun as a wholly gaseous mass--a conclusion in which he was anticipated only by Father Secchi. He added that it must be largely composed of matter kept in an intermediate condition between liquid and vaporous by “high temperature and enormous pressure.” The spot-period, he suggested, might be that of a revolving meteoric ring with condensations.

He was vividly interested in the “willow-leaf” controversy, raised in 1862 by Nasmyth’s misinterpreted observations. The objects seen were simply Sir William Herschel’s “nodules”--the luminous elements of the sun, held by Sir John in 1867 “to be permanently solid matter, having that sort of fibrous or filamentous structure which fits them, when juxtaposed by drifting about, and jostling one against another, to collect in flocks as _flue_ does in a room.” He concluded with the remarkable assertion that the sun has no real surface, “the density diminishing from that below the photosphere to _nil_ in the higher regions, where the pressure is _nil_.”

Herschel’s “Cape Observations” stands alone in astronomical literature for the wide and permanent interest of its contents. They are exceedingly various. Chapters on Halley’s Comet, on Sun-spots, the Satellites of Saturn, Astrometry, the Constitution of the Southern Galaxy, are associated with discussions on the nature and distribution of nebulæ, with monographs of two, and incidental notes on many of these enigmatical objects. The volume is illustrated with over sixty beautiful steel engravings of nebulæ and clusters, of sun-spots, and of the comet.

The speculations it includes regarding the nature of nebulæ, deserve even now to be remembered. Sir John was, at the outset, an unwavering adherent of the theory developed by his father in 1811. They were composed, he held in 1825, of a “self-luminous; or phosphorescent material substance, in a highly dilated or gaseous state, but gradually subsiding, by the mutual gravitation of its molecules, into stars and sidereal systems.” His personal experience, however, ran counter to this view. In 1833 he had become convinced that a nebula is, in general, “nothing more than a cluster of discrete stars.”

The successful resolution into stars, with the great Parsonstown specula, of many nebulæ until then called irresolvable, carried him still further in the same direction. To him, as to other thinkers, the presence in space of a self-luminous cosmic fluid became more than doubtful. In his Presidential Address to the British Association in 1845, he dwelt with enthusiasm on the completion of the Rosse reflector--“an achievement of such magnitude, that I want words to express my admiration of it.” He regarded “as one of the grand fields open for discovery with such an instrument, those marvellous and mysterious bodies, or systems of bodies, the nebulæ.” Their frequent resolution, actual or indicated, with increased optical power, led him to attribute recalcitrance in this respect to the smallness and closeness of the stars of which they consist; he held them, in short, to be “optically, and not physically, nebulous.”

A new consideration was thus introduced into discussions on nebulæ. The whole burthen of accounting for their varieties in telescopic aspect need no longer be thrown upon differences of remoteness; diversities in the size and closeness of nebular _molecules_ would answer the same purpose. So that pulverulent agglomerations, it was thought, might pass by insensible gradations into collections of truly sun-like bodies. All distinction between nebulæ and clusters was then abolished, the members of both classes consisting, like the sun’s photosphere, of shining granules, supported in an obscure medium, varying in real magnitude from _floccules_ to great globes, while each vast compound body rotated _en masse_ on an axis. Whatever the merits of this scheme, it at least harmonises with the now prevalent opinion that nebulæ and clusters belong to one unbroken cosmical series. “They are divided,” Mr. Cowper Ranyard wrote in 1893, “by no hard and fast line. The larger nebulæ may be described as groups of stars surrounded by bright nebulosity, and star-clusters as groups of stars surrounded by faint nebulosity.”

Herschel’s assimilation of nebulæ to clusters was not meant to apply to “those extraordinary objects resembling the wisps and curls of a cirrous cloud,” which confront the astronomer in Orion, Argo, and elsewhere. “The wildest imagination,” he said, “can conceive nothing more capricious than their forms. With their resolution,” he averred, “and that of elliptic nebulæ, the idea of a nebulous matter, in the nature of a shining fluid or condensible gas, would cease to derive any support from observation.” He, in fact, discarded it absolutely on the deceptive analysis into stars at Parsonstown and Harvard College of the Orion and Andromeda nebulæ. The discredited hypothesis was nevertheless triumphantly reinstated by Dr. Huggins’s spectroscopic observations in 1864.

One-third of the whole nebular contents of the heavens Herschel found to be collected into a broad, irregular patch, the central point of which in Virgo coincides almost precisely with the northern pole of the Milky Way. He compared it to a canopy surmounting the galactic zone. In the other hemisphere the arrangement, although less distinctly characterised, is on the same general plan. Plainly, then, nebular distribution has an opposite correspondence with stellar distribution, and the two partial systems are complementary one to another, Herschel, however, contented himself with the somewhat ambiguous statement that “the nebulous system is distinct from the sidereal, though involving and, to a certain extent, intermixed with it.”

His verdict as to the ground-plan of the sidereal edifice might be summed up in the phrase, “Not a stratum, but an annulus,” our own situation being in a relatively vacant interior space. Hence, the sun belongs, not to the Milky Way proper--as it should on the stratum theory--but to the system of which the Milky Way forms part. This conclusion was in itself a distinct advance towards the solution of an exorbitantly difficult problem. The grand question as to the remoteness of the star-clouds in that gleaming sky-girdle was definitely raised by it; and the question is not, in the nature of things, unanswerable. Herschel’s annulus was not a neat structure with a cylindrical section, but “a flat ring, or some other re-entering form of immense and irregular breadth and thickness.” It is cloven over one-third of its circumference; it is interrupted by huge chasms; it is bent, and shattered and broken, and probably set with tentacular appendages, giving rise, by their foreshortening, to very complex visual effects. All of which modifying circumstances Herschel implicitly recognised. He was the first to gather any direct intimations of the existence of that “solar cluster” which, guessed at by the elder Herschel, has of late assumed a sort of elusive reality. A zone of bright stars, including those of Orion, Canis Major, the Ship, the Cross, and the Centaur, struck him at once as a conspicuous feature in the scenery of the southern heavens. Its aspect led him to “suspect that our nearest neighbours in the sidereal system form part of a subordinate sheet, or stratum,” inclined at an angle of twenty degrees to the plane of the Milky Way. To Dr. Gould at Cordoba, in 1879, “few celestial phenomena” appeared “more palpable” than this projected star-belt; and, since it traces out a great circle on the sphere, the sun must be placed within it, and pretty accurately in its plane; yet the difficulty of associating it intimately with our particular star seems all but insurmountable.

Herschel’s minor and occasional writings were neither few nor unimportant. He contributed articles on “Isoperimetrical Problems” and “Mathematics” to Brewster’s _Edinburgh Cyclopædia_, and on “Meteorology,” “Physical Geography,” and “The Telescope,” to the eighth edition of the _Encyclopædia Britannica_. These last were printed separately as well. He edited in 1849 the Admiralty “Manual of Scientific Inquiry,” and criticised in the _Edinburgh_ and _Quarterly Reviews_ Mrs. Somerville’s “Mechanism of the Heavens,” Whewell’s “History of the Inductive Sciences,” Humboldt’s “Kosmos,” and Quetelet’s “Theory of Probabilities.” His addresses as President of the Royal Astronomical Society were models of their kind, and the same might be said of his memoirs of Baily and Bessel in the “Monthly Notices.” Most of them were collected in 1857, with his review articles, into a volume of “Essays;” and his attractive “Familiar Lectures on Scientific Subjects,” published in 1867, gave permanence to some popular discourses delivered in the school-house of Hawkhurst, as well as to articles from _Good Words_ on Light and other subjects. No less than 152 papers by him are included in scientific repertories.

He had a considerable faculty for translating poetry, and its exercise made one of his favourite recreations. Having adopted the literal theory of the art, he kept strictly to the original metres, and thus fettered, got over the ground with more grace and ease than might have been expected. His first attempt with English hexameters was in a version of Schiller’s “Walk,” privately printed in 1842. He had come to love the poem through its association in his mind with a favourite stroll up the side of Table Mountain; and a translation of it in the _Edinburgh Review_ leaving, as he thought, something to be desired, he tried his hand, and distributed the result “among his friends as his Christmas sugar plum.” The various acknowledgments made an amusing collection. One lady said that she “found it difficult to get into the _step_ of the _Walk_.” Another correspondent declared that the _Walk_ had got into a _Run_ through ceaseless borrowing. A third qualified his encomium upon the ideas by adding, “To the _verse_ I am _averse_.” Joanna Baillie, however, and her sister were delighted with both the substance and form of the poem, and it was included among Whewell’s “English Hexameter Translations” in 1847.

His success encouraged him, after twenty years, to undertake an indefinitely more difficult task. Pope’s Iliad he described happily as “a magnificent adumbration” of the original; but he aimed rather at producing a “fac-simile,” in

“Hexameters no worse than daring Germany gave us.”

His version should come as near as he could bring it to a photograph of a grand piece of architecture; and as a measure of its fidelity, he printed in italics all the words _not_ in the text. Whewell remarked that it was “curious to see how few he had managed to make them,” and preferred his translation to any other with which he was acquainted. But English hexameters were a hobby of the Master of Trinity, who accordingly viewed with partiality what Tennyson called the “burlesque barbarous experiment” of thus lamely rendering “the strong-wing’d music of Homer.”

De Morgan, too, was one of the “averse.” “Many thanks for the hexameters,” he wrote, on receiving an instalment of the Collingwood Iliad; “they are as good as they can be, but all the logic in the world does not make me feel them to be English metre, and they give satisfaction only by reminding one of the Greek: just as, mark you, a flute-player--which I have been these forty-five years--only plays Haydn and Mozart because he has the assistance of the orchestral accompaniment which arises in his head with the melody. The hexameter, it is clear, does not fix itself in the popular mind. The popular mind knows neither quantity nor accent, but that which is to last bites its own way in, without any effort.”

Yet Herschel’s translation is not without merit. It is disfigured neither by affectation nor by magniloquence, and it catches here and there something of the greatness of the unapproached original. Let us take two specimens; this from the “Shield of Achilles”:--

“There he depicted the earth, and the canopied sky, and the ocean; There the unwearied sun, and the full-orb’d moon in their courses. All the configured stars, which gem the circuit of heaven, Pleiads and Hyads were there, and the giant force of Orion. There the revolving Bear, which the Wain they call, was ensculptured, Circling on high, and in all its course regarding Orion; Sole of the starry train which refuses to bathe in the Ocean.”

The next likewise appeals to the astronomer. It is the famous simile from the end of the Eighth Book:--

“As when around the glowing moon resplendent in ether, Shines forth the heavenly host, and the air reposes in stillness; Gleams every pointed rock, stands forth each buttress in prospect; Shimmers each woodland vale; and from realms of unspeakable glory Op’ning, the stars are revealed; and the heart of the shepherd rejoices. Such, and so many the fires, by the Trojans kindled, illumined Eddying Xanthus’ stream, and the ships, and the walls of the city.”

Sir John Herschel corresponded with Mr. Proctor, during the last two years of his life, on the subject of sidereal construction; and his replies to the arguments put before him show that his mind retained, even then, its openness and flexibility. He had none of the contempt for speculative excursions which sometimes walls up the thinking-powers of observers. “In the midst of so much darkness,” he held that “we ought to open our eyes as wide as possible to any glimpse of light, and utilise whatever twilight may be accorded us, to make out, though but indistinctly, the forms that surround us.” “_Hypotheses fingo_ in this style of our knowledge,” he went on, “is quite as good a motto as Newton’s _non fingo_--provided always they be not hypotheses as to modes of physical action for which experience gives no warrant.” And again: “We may--indeed, must--form theories as we go along; and they serve as guides for inquiry, or suggestions of things to inquire; but as yet we must hold them rather loosely, and for many years to come keep looking out for side-lights.”

These were his last words on the philosophy of discovery: and they constituted his last advice to scientific inquirers. But, good as were his precepts, his example was better. There was no discrepancy between his work and his thought. Both combined to inculcate aloofness from prejudice, readiness of conviction in unequivocal circumstances, suspension of judgment in dubious ones, and in all, candour, sobriety, and an earnest seeking for truth.

INDEX.

Actinometer, J. Herschel’s, 152, 179, 180

Adams, J. C., at Collingwood, 188

Ages of heavenly bodies, 68, 94, 170

Alexander, the Czar, 49

Amici, of Modena, 148, 150

Apertures, method of, 61, 63

Apex, solar, 78, 80

Archbishop of Canterbury, and George III., 38

Argelander, 80, 106

Asteroids, 46, 90–1, 95, 100

Astrometer, J. Herschel’s, 177

Astronomical Society, 49, 152, 188

Aubert, Alexander, 16, 101, 124

Babbage, companionship with J. Herschel, 143–4, 149, 152; astatic needle, 208

Bailey, S. I., 169, 170

Baily, Francis, 164, 185, 186, 187

Barnard, diameters of asteroids, 91; nebulosities, 110–11; photographs of Milky Way, 174

Bates, Joah, anecdote of W. Herschel, 12

Bath, centre of fashion, 12; Herschel’s residences there, 17, 26, 47

Beckedorff, Mrs., 126, 127, 160; Miss, 138

Bessel, solar movement, 80; estimate of W. Herschel, 109; Halley’s comet, 177; at Collingwood, 187; memoir of, 216

Biot, estimate of J. Herschel, 201

Bonaparte, Lucien, 33, 44

Bonaparte, Napoleon, Herschel’s interview with, 47

Bradley, observation of Castor, 76

Brougham, Lord, 53, 88, 90, 207

Burney, Dr., notices of W. Herschel, 12, 44, 45–6; walk through forty-foot, 38; notices of Caroline and J. Herschel, 125, 142

Burney, Miss, meetings with W. Herschel, 38–9; with Mrs. and Miss Herschel, 44, 124, 125, 127

Burnham, double stars, 103; planetary nebulæ, 155

Campbell, Thomas, admiration for W. Herschel, 47–8; notice of his son, 145

Cavendish, anecdote of, 100

Clay Hall, 36

Climate, changes of, 82

Comet, of October 1806, 48; of 1811, 94; Encke’s, 124, 175; of 1819, 128–9; Biela’s, 153; Halley’s, 175–6, 180, 211

Comets, decay of, 94; Miss Herschel’s, 124, 125

Common, Dr., five-foot reflector, 99

Construction of the Heavens, 53, 60, 113–114, 214–15

Dante and the “Divina Commedia,” 15

Datchet, house at, 32, 36

Dawes, sun-spot nuclei, 83

De la Rue, photoheliograph, 210

De Morgan, letter to Captain Smyth, 188–9; Herschel and the coinage, 191; friendship with, 197; dislike to hexameters, 217

Dreyer, Catalogue of Nebulæ, 192

Easton, Milky Way structure, 106

Edgeworth, Miss, at Slough and Collingwood, 192–3

Feldhausen, 163, 180, 181

Flamsteed, British Catalogue, 80, 123, 126

Galileo, double-star method of parallaxes, 55

Gauss, 151, 201, 205

George III., patronage of Herschel, 10, 24, 28–9, 30, 32, 33; taste for astronomy, 30, 47; walk through great telescope, 38

Gill, Dr., Herschel’s micrometers, 103; photographic catalogue, 106; photographs of Argo nebula, 167; of Omega Centauri, 169

Gordon, Lady, portrait of Sir J. Herschel, 202

Gould, Dr., solar cluster, 107, 215

Grahame, James, 149

Gravitation, extension of to stellar systems, 77, 148

Gregorian reflectors, 20, 29

Griesbach, Mrs., 10, 116; her sons, 10, 28, 29

Halley, list of nebulæ, 19; stellar motions, 77

Hamilton, Sir W. R., communications with J. Herschel, 146, 152, 158, 173, 188; speech by, 182; at Collingwood, 193; quaternions, 194–5

Haydn, visit to Slough, 44

Heat-rays in solar spectrum, 95–6

Herschel, Alexander, assisted his brother, 13, 21, 27, 120; accompanied him to Göttingen, 37; supported by him, 51; care for his sister, 118

Herschel, Professor Alexander, meteoric researches, 201

Herschel, Caroline, fetched to Bath, 15, 118; help in speculum making, 15, 20, 124; a singer, 21, 117, 119; remarks, 25, 27, 34, 49; letters from W. Herschel, 28, 29, 30, 129; household cares, 32, 118, 121; reminiscences, 35, 36, 37, 39, 48, 50, 68; annuity, 51, 131; birth and childhood, 115–16; education, 115, 118, 121; visits to London, 121, 127; discoveries of nebulæ, 122; of comets, 124–5, 139; her brother’s assistant, 122–3, 125; catalogues nebulæ, 123, 132; Index to Flamsteed’s observations, 126; royal attentions, 126, 127, 133, 135, 139; anxiety about her brother’s health, 128–9; return to Hanover, 130–1; Gold Medals bestowed on, 132, 138; joy in her nephew’s career, 134–5, 159; his visits, 135–36, 159; Recollections and Journals, 137, 138; death, 139; personality, 139–41; anecdotes of J. Herschel’s childhood, 142; his letters to her, 151, 152, 153, 162–3, 164, 175, 176, 187; her portrait, 196; her advice to him, 205

Herschel, Dietrich, 20–1, 51, 127–8, 130, 131

Herschel, Sir John, dismantling of great telescope, 43; catalogues of nebulæ, 132, 155, 191–2; visits to Hanover, 135–6, 151, 159–60, 184; nebular observations, 136, 153, 154–7, 165–7; Cape Expedition, 135, 159–2, 181–2; birth and childhood, 142; university career, 143–5; medals awarded to, 145, 148, 149, 157, 187, 201; work on double stars, 134, 146–48, 157; method for computing orbits, 148–9; general catalogue, 192; ascents of Monte Rosa and Etna, 149–50; explorations in Auvergne, 152; experiments on solar radiation, 151–2, 179; visit to Ireland, 152; cometary observations, 153, 175–6, 180, 189; telescopes, 153, 158, 164, 183; discovery of star in Orion-trapezium, 158; marriage, 159; Feldhausen, 163, 180–1; Cape climate, 164; Magellanic Clouds, 165–6; Argo nebula, 167; Eta Argûs, 168–9; globular clusters, 169–71, 213; star-gauging, 171–2; comets, 175–6; stellar photometry, 177; solar theory, 178–9, 211; Saturnian satellites, 180; magnetic work, 184, 189, 208; constellational reform, 185; removal to Collingwood, 186; Cape Results, 186–7, 211–12; President Astronomical Society, 188; Master of the Mint, 190–1; guests at Collingwood, 188, 193, 195; sonnet, 194; family life, 195–6; death, 197; powers and character, 198–201; books, 205–8; photographic experiments, 209–10; nature of nebulæ, 212–14; solar cluster, 215; poetical performances, 216–18; philosophy of discovery, 219

Herschel, Colonel John, examination of nebular spectra, 201

Herschel, Isaac, 9, 21, 115, 116

Herschel, Jacob, 116, 117, 128

Herschel, Lady, the elder, 44, 50, 152, 160

Herschel, Lady, the younger, 159, 192, 194, 201

Herschel, Sir William, birth, 9; musical career, 10–16, 21, 26, 121; telescope, making, 14–15, 17, 19, 20, 22; thirty-foot, 26–8, seven-foot, 28–9; for sale, 33; forty-foot, 34, 37, 38, 41–3, 49, 50, 100, 137, 210; twenty-foot, 35–6, 40, 50; front-view telescopes, 40, 41, 102, 153; space-penetrating power of, 61, 98; reviews of the heavens, 19, 20, 26, 35, 36, 42, 46; early papers, 22–3; discovery of Uranus, 24–5, 120; observations of double stars, 26, 49, 55–6, 75; interviews with the king, 28–30; royal astronomer, 30, 32–3; mode of observing, 30, 122; discovery of Uranian satellites, 40, 93, 153; of Saturnian satellites, 41, 43, 92; marriage, 44; aversion to poetry, 45–6; interview with Bonaparte, 47; observations of comets, 48, 94, 128–9; failure of health, 49–50, 128–9; death and character, 51; construction of the heavens, 53–4, 60, 114; star distances, 54–5, 57, 60–1, 64, 75; star-gauging, 57–8, 113; nature of the Milky Way, 57–9, 62–3; chasms in, 68; method of apertures, 61; catalogues of nebulæ, 64; varieties, 65; island universes, 66–7, 72; development, 67–8; nebulous fluid, 69–70; condensation into stars, 71–2, 109; nebular distribution, 73; discovery of binary stars, 76–7, 147; transport of the solar system, 77, 80, 108; stellar photometry, 80–2, 174–5; theory of the sun, 83–6, 211; sun spots and weather, 87–8; observations of Venus, 88; of Mars, 89; of the asteroids, 90; of Saturn, 91; law of satellite-rotation, 92; lunar volcanoes, 93; detection of infra-red heat-rays, 95–7; use of high powers, 101–2; micrometers, 103; photometric enumeration, 106; solar cluster, 107–8; diffused nebulosities, 110–11; a founder of sidereal astronomy, 112

Herschel, Sir William J., 49, 136, 183, 201

Huggins, Dr., spectra of nebulæ, 109, 214; of stars, 113

Humboldt, 133, 138, 170, 184

Huygens, improvement of telescopes, 17

Jacob, southern Milky Way, 172

Japetus, rotation of, 92

Jupiter, trade wind theory of, 91; rotation of satellites, 93

Kapteyn, solar cluster, 107

Knipping, Mrs., 137, 138

Lacaille, southern nebulæ, 19

Langley, bolometer, 95; atmospheric absorption, 152, 179

Laplace, 18, 47, 91, 201, 207

Lassell, Uranian satellites, 93; reflectors, 99; observation of Mimas, 180

Le Verrier, 187, 188

Lexell, orbit of Uranus, 24

Maclear, Sir Thomas, 162, 168, 176, 181

Magellan, Von, accounts of William and Caroline Herschel, 40, 122

Magellanic clouds, 165–6

Magnitudes, stellar, 81, 104–5, 177

Mars, analogy with the earth, 89

Maskelyne, 25, 29, 76

Mayer, Christian, satellite-stars, 75

Mayer, Tobias, solar translation, 77, 78

Michell, revolving stars, 75; solar group, 107

Micrometer, lamp, 24, 103; wire, 56, 103

Milky Way, rifts in, 50, 67–8, 173, 175, 215; structure, 57–59, 62, 173–4, 214–15; spectral peculiarity, 105; distance, 106, 173, 214; splendour in southern hemisphere, 172; photographic portrayal, 174–5

Miller, Dr., 11, 12

Mitchell, Miss, visit to Collingwood, 195–6

Monck, stellar spectroscopic distribution, 107

Moon, mountains of, 22, 23; volcanoes, 93–4.

Nasmyth, opinion of J. Herschel, 196–7; solar willow leaves, 211

Nebula, Orion, 15, 43, 65, 70, 71, 110, 111, 153, 167, 214; Dumb-bell, 157; Argo, 167; Andromeda, 214

Nebulæ, catalogues, 19, 64, 123, 132, 191–2; discoveries, 35, 64, 122, 165; nature, 66, 212–4; development, 67, 69, 109–10; distribution, 73, 214

Nebulæ, annular, 65, 157, 165

Nebulæ, double, 72, 156

Nebulæ, planetary, 65, 67, 71; spectrum, 109; satellites to, 155; colour, 165

Nebulæ, rifted, 157

Nebular theory, 71–2, 109

Newton, law of gravitation, 17, 77; reflectors, 20, 23; mode of investigation, 23, 206

Olbers, origin of asteroids, 90; comet of 1819, 129; light extinction, 174; visit from J. Herschel, 184

Orange, Prince of, enquiries at Slough, 39

Papendick, Mrs., remarks on William and Caroline Herschel, 39, 44, 125

Peacock, Dean, 143, 194, 203

Photography, of stellar spectra, 104, 107; of nebulæ, 110–11, 113, 166–7; star charting by, 113, 172, 199; of clusters, 169–70, 171; of solar spectrum, 209; of sun-spots, 210

Photometric enumeration, 60, 106, 107, 114; catalogues, 80

Photometry, stellar, 81, 104, 177; photographic, 105

Piazzi, visit to Slough, 39, 150

Pickering, E. C. and W. H., photographs of Orion nebula, 111

Pouillet, solar radiation, 179

Pritchard, Dr., 143, 192, 201, 204

Proctor, star-drift, 108; estimate of Sir J. Herschel, 199, 200; correspondence with, 218

Ranyard, A. C., changes in nebulæ, 168; clusters, 213

Roberts, Dr., photographs of nebulæ, 157, 165

Rosse reflector, 99, 212

Russell, H. C., photographs of Magellanic clouds, 166; of Argo nebula, 167; of Milky Way, 175

Saturn, artificial, 30; satellites, 41, 43, 91, 92, 180; rings, 91–2

Savary, stellar orbits, 148, 149

Schröter, 34, 84, 88–9

Secchi, 113, 211

See, Dr., double nebulæ, 156

Sirius, brilliancy, 42, 168; standard star, 58, 61, 63, 80

Slough, W. Herschel’s residence at, 36, 44; birthplace of J. Herschel, 142

Sniadecki, stay at Slough, 39

Solar cluster, 107, 215

Solar radiation, 151–2, 179

Somerville, Mrs., 132

South, Sir James, 146, 147, 149

Spectrum analysis, 84, 204, 209

Spencer, unity of sidereal system, 166

Stanley, Dean, on J. Herschel, 199

Star-clusters, 49, 59, 63, 67, 72, 169–71, 213

Star-gauging, 57–8, 113, 171–2

Stars, binary, 72, 156; discovery, 76–7, 147; orbits, 147–9

Stars, double, observations of, 55–6, 103, 146–8, 157; colours, 56, 112, 156; nebular relations, 155

Stars, distribution of, 58–9, 60, 73, 81, 106, 171–2

Stars, movements of, 77, 107–8

Stars, nebulous, 69, 70, 71

Stars, spectra of, 83, 105

Stars, spectroscopic binary, 104

Stars, temporary, 66–7

Stars, variable, 23, 81–2, 168–9

Stokes, Sir G., fluorescence, 210

Stone, Herschel’s assistant, 180

Struve, W., 148, 158, 188

Sun, translation, 77–80, 108; vicissitudes, 82, 87, 88; constitution, 83–6, 178–9, 211

Sussex, Duke of, 158

Telescopes, Improvement of, 17, 19, 20, 24–6, 33, 36, 98–100

Uranus, discovery of, 24–5, 26, 120; satellites, 40, 93, 153

Watson, Sir W., 16, 22, 27, 30, 47, 124

Watt, James, 47

Whewell, Dr., unity of sidereal system, 76, 166; friendship with J. Herschel, 145, 163, 191, 200; tidal data, 181; articles in Quarterly Review, 186, 205–6; Geological Society, 189; on optical enquiries, 203–4; hexameters, 217

Wolf, Dr. Max, photographs of nebulæ, 111; of Milky Way, 175

Wollaston, 145, 177

Worlds, inhabited, 85, 86, 89, 147.

PRINTED BY CASSELL & COMPANY, LIMITED, LA BELLE SAUVAGE PRINTING WORKS, LONDON, E.C.

Transcriber’s Notes

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