Herschel, John Frederick William (DNB00)

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HERSCHEL, Sir JOHN FREDERICK WILLIAM (1792–1871), astronomer, only child of Sir William Herschel [q. v.], was born at Slough on 7 March 1792. He was educated at Dr. Gretton's school at Hitcham, Buckinghamshire, then for a few months at Eton, and afterwards at home by Mr. Rogers, a Scottish mathematician. He entered St. John's College, Cambridge, at the age of seventeen, graduated thence in 1813 as senior wrangler and first Smith's prizeman, and was immediately elected to a fellowship in his college. He was at this time described by the poet Campbell as ‘a prodigy in science, and fond of poetry, but very unassuming’ (Beattie, Life of Campbell, ii. 234). He proceeded M.A. on 3 July 1816, and in occasional residences at the university during the interval formed a lifelong intimacy with Whewell. Their Sunday mornings' ‘philosophical breakfasts’ in 1815 were long remembered (Todhunter, Account of the Writings of Dr. Whewell, i. 6). Herschel's youthful compact with George Peacock [q. v.] and Charles Babbage [q. v.] to ‘do their best to leave the world wiser than they found it’ began to be fulfilled by their formation in 1813 of the ‘Analytical Society of Cambridge.’ The first volume of its transactions was written exclusively by Herschel and Babbage. A joint translation by Herschel and Peacock of Lacroix's ‘Elementary Treatise on the Differential Calculus,’ Cambridge, 1816, with an appendix on finite differences by Herschel, styled by Professor Tait ‘one of the most charming mathematical works ever written,’ became a university text-book, and was succeeded in 1820 by two admirable volumes of ‘Examples’ by Herschel and Babbage. To these works was mainly due the restoration of mathematical science in England by introducing the differential notation and continental methods of analysis.

Herschel's first communication to the Royal Society, ‘On a Remarkable Application of Cotes's Theorem’ (Phil. Trans. ciii. 8), was dated from Slough, 6 Oct. 1812, and on 27 May 1813 he was elected a fellow of the society. Several papers on various points of analysis followed, distinguished by the award of the Copley medal in 1821. That of 1816 (ib. cvi. 25), supplemented by an essay on the summation of series in the ‘Edinburgh Philosophical Journal’ in 1819 (ii. 23), was devoted to promote the new calculus of operations.

Gently combating his father's preference for the church, Herschel chose the law as his profession, and was entered as a student of Lincoln's Inn on 24 Jan. 1814. The acquaintance of Dr. Wollaston and of Mr. (afterwards Sir James) South diverted him, however, finally to science. He left London, and failing to obtain the chair of chemistry at Cambridge, experimented at Slough in chemistry and physical optics. Some of his original results were embodied in papers ‘On the Optical Phenomena exhibited by Mother-of-Pearl’ (ib. ii. 114), ‘On the Absorption of Light by Coloured Media’ (Trans. Roy. Soc. of Edinburgh, ix. 445), and in various researches on the action of crystals upon polarised light (Phil. Trans. cx. 45; Trans. Cambr. Phil. Soc. i. 21, 43).

Astronomy is first mentioned on 10 Sept. 1816, when he reported himself as ‘going under my father's direction to take up star-gazing.’ He then began a re-examination of his father's double stars, and executed in 1821–3 the revision of 380 pairs in conjunction with South, and at South's observatory in Blackman Street, Southwark. The instruments employed were a seven-foot and a five-foot refractor. The resulting catalogue (Phil. Trans. vol. cxiv. pt. iii.) was honoured by the bestowal of the Astronomical Society's gold medal, and of the Lalande prize for astronomy in 1825, for which Bessel, Struve, and Pons were competitors. Herschel took an active part in the foundation of the Royal Astronomical Society; he wrote its inaugural address, and was its first foreign secretary. He travelled in Italy and Switzerland with Babbage in 1821, making an ascent of Monte Rosa, and visited Holland with Grahame in 1822. After the removal of South's telescopes to Passy in 1824, he went abroad again with Babbage; and made a barometrical determination of the height of Etna on 3 July. He then traversed Germany, seeing some eminent astronomers, and visiting his aunt Caroline Herschel [q. v.] at Hanover. He experimented upon solar radiation from the summit of the Puy de Dôme in 1826. On his election in November 1824 as secretary of the Royal Society, a post filled by him during three years, he took up his residence at 56 Devonshire Street, Portland Place, London. On 18 April 1825 he wrote to his aunt, on receiving her zone catalogue of nebulæ: ‘These curious objects I shall now take into my especial charge, nobody else can see them.’ More than half of Sir William Herschel's 2,500 nebulæ were invisible with any existing telescope except the twenty-foot ‘front-view’ reflector constructed by Herschel with his father's aid in 1820. His first effective use of it was in executing a valuable drawing of the Orion nebula in February 1824 (Memoirs Astr. Soc. ii. 487), in observations of the second comet of 1825, and of the Andromeda nebula (ib. pp. 486, 495). His great review of the nebulæ visible in the northern hemisphere was carried out at Slough with its aid during 1825–33, and the results embodied in a catalogue of 2,307 nebulæ, of which 525 were discovered by himself, presented to the Royal Society on 1 July 1833 (Phil. Trans. cxxiii. 359). The memoir was accompanied by nearly one hundred elaborate drawings, and contained many valuable suggestions. Its importance was recognised in 1836 by medals from the Royal and Astronomical Societies.

In a paper read before the Royal Society on 9 March 1826 Herschel gave the first discussion of the changes of position-angle between two adjacent stars as a means of detecting annual parallax (ib. cxvi. 266). He was elected president of the Royal Astronomical Society in February 1827, and for two subsequent biennial periods. His discoveries of double stars meanwhile, which in 1832 numbered 3,346, were progressively communicated in six catalogues to the Royal Astronomical Society (Memoirs, vols. ii–ix.), besides two extensive lists of measures of known pairs. These were after 1828 executed with a refractor of five inches aperture and seven feet focal length, which had been the chief instrument in the Blackman Street observatory. A graphical method of investigating stellar orbits, described by him before the Royal Astronomical Society on 13 Jan. 1832 (ib. v. 171), was a contribution of primary importance to a new branch of gravitational astronomy, recognised by a medal from the Royal Society on 30 Nov. 1833.

In a memoir ‘On the Aberration of Compound Lenses and Object-Glasses,’ read before the Royal Society on 22 March 1821 (Phil. Trans. cxi. 222), Herschel presented a complete analytical theory of spherical aberration, deducing practical rules of easy application for the construction of lenses, a popular abstract of which appeared in the ‘Edinburgh Philosophical Journal’ (1822, vi. 361). He still accepted the emission theory of light, but the results of Young and Fresnel soon afterwards engaged his eager study and acquiescence, and were brilliantly expounded in his article on light, written in 1827 for the ‘Encyclopædia Metropolitana.’ This admirable treatise, translated into French by Quetelet, besides including many original discoveries, gave European currency to the undulatory theory of light. Lucidity and power were no less conspicuous in Herschel's treatment of the subjects sound, heat, and physical astronomy, in the same publication. His ‘Preliminary Discourse on the Study of Natural Philosophy,’ published in 1830 as the opening volume of Lardner's ‘Cabinet Cyclopædia,’ and styled by Whewell an ‘admirable comment on the “Novum Organum”’ (Quarterly Review, July 1831), captivated readers of all classes by the quiet charm of its style, and the justice and breadth of its views. It was translated into French, German, and Italian, and reprinted in English in 1851. To the same repertory in 1833 Herschel contributed ‘A Treatise on Astronomy,’ enlarged in 1849 into the deservedly famous ‘Outlines of Astronomy,’ perhaps the most completely satisfactory general exposition of a science ever penned. A twelfth edition appeared in 1873, and it was translated into Russian, Chinese, and Arabic, besides other languages.

Herschel married, on 3 March 1829, Margaret Brodie, second daughter of the Rev. Dr. Alexander Stewart of Dingwall, Ross-shire. The union was of unclouded happiness. Put forward in 1830 against the Duke of Sussex as the ‘scientific candidate’ for the presidency of the Royal Society, he was defeated by a narrow majority. In 1831 he was created by William IV a knight of the royal Hanoverian Guelphic order, and during a visit to his aunt at Hanover in June 1832 attended the Waterloo banquet in the Herrenhausen Palace. A project long cherished of completing his survey of the heavens in the southern hemisphere became feasible after his mother's death in January 1832; and on 13 Nov. 1833, having declined a free passage in a ship of war (as he subsequently declined the reimbursement by government of his expenses), he embarked with his family and instruments on board the Mountstuart Elphinstone for the Cape of Good Hope, and reached Table Bay on 15 Jan. A house was secured at Feldhausen, six miles from Cape Town, in ‘one of the most magnificent sites’ (Herschel wrote to Baily) ‘I ever saw.’ On 22 Feb. 1834 he observed the Argo nebula with his great reflector, and the equatorial (the seven-foot Slough refractor) was ready for work before June. Both were employed with extraordinary vigour and perseverance during the ensuing four years; commonly under highly advantageous circumstances as to definition, although in the hot season he found the stars to ‘tremble, swell, and waver most formidably.’ The rapid tarnishing of his mirrors would have rendered them useless in three months but for the provident exportation of a polishing machine.

Herschel's work at Feldhausen marked the commencement in a wide sense of southern sidereal astronomy. Although struck with the comparative paucity of close double stars, he discovered and measured 1,202 pairs; 1,708 nebulæ and clusters, 1,269 of them previously unseen, figured in his lists; his chart of the Argo nebula gave the places of 1,203 stars; he catalogued 1,163 objects in both Magellanic Clouds; ‘monographed’ the Orion and other great nebulæ; and determined micrometrically the components of the ‘jewelled’ cluster in Crux. ‘Gauging’ the skies on his father's principle, he concluded the Milky Way, from a count of some 69,000 stars in 2,299 fields, to be an annulus rather than a disc of stars. He set the example of employing an ‘artificial star’ in stellar photometry, and skilfully applied the ‘method of sequences’ to fix the relative lustre of nearly five hundred stars, thereby laying a sure foundation for stellar magnitudes. The object aimed at was to range all the lucid stars along a single scale of brightness; and in order to link together southern and northern skies, the work of estimation was carried on on board ship in varying latitudes. Several specimens of the actinometer (described in 1825 in Edinb. Journ. of Science, iii. 107), with which at the close of 1836 he made the first satisfactory measures of direct solar radiation, were shown at the Meteorological Society's exhibition of instruments in 1889. The numerous sun-spots of 1836–7 engaged his close attention, and he suggested, in a letter to Baily of 1 March 1837, the now established relation between solar and auroral activity. His observations of Halley's comet between 28 Oct. 1835 and 5 May 1836 (Memoirs Roy. Astr. Soc. x. 325) gave strong support to the theory of electrical repulsion. From a series of observations of Saturn's satellites he derived corrected elements for those bodies, and the first independent confirmation of his father's discovery of the two next the ring. These multiplied labours were accomplished with only the aid of a mechanic named John Stone; but they were lightened by the cordial sympathy of Sir Thomas Maclear [q. v.], then H.M. astronomer at the Cape.

The public interest in this expedition was shown by the grotesque announcements of lunar discoveries at Feldhausen, made satirically by R. A. Locke in the ‘New York Sun’ for September 1835 (The Moon Story, New York, 1852). The excellent system of national education prevailing in the colony was initiated by Herschel, and he set on foot a plan of simultaneous meteorological observations, developed in his ‘Instructions for Making and Registering Meteorological Observations at various Stations in South Africa,’ printed in 1838 among the ‘Professional Papers of the Royal Engineers’ (ii. 214). Numerous tidal observations were sent by him to Dr. Whewell from the Cape. A few days before his departure from the Cape the members of the South African Literary and Scientific Institution, over which he had presided, presented him with a gold medal; and on 15 Feb. 1842 an obelisk of Craigleath stone was erected on the site of his great reflector.

Herschel's observation, on 16 Dec. 1837, of the sudden rise of the star η Argûs from the second to the first magnitude (Monthly Notices, iv. 121; Cape Results, p. 32) constituted him the virtual discoverer of its abnormal character. He sailed in the Windsor Castle in the middle of March 1838, and landed in England after nine weeks, in part occupied by the continuance of his photometric estimates. A baronetcy (reluctantly accepted) was conferred upon him at the queen's coronation; he was created D.C.L. of the university of Oxford on 12 June 1839. He declined to enter parliament as the representative of the sister university, and refused a proposal that he should succeed the Duke of Sussex as president of the Royal Society, but was elected in 1842 lord rector of Marischal College, Aberdeen, and acted as president of the British Association at Cambridge in 1845. Almost every learned society in Europe and several in America placed his name on their lists of members; he was made chevalier of the Prussian order ‘Pour le Mérite,’ and on 23 July 1855 was chosen, on the decease of Gauss, one of the eight foreign associates of the French Institute.

He paid his last visit to Miss Herschel at Hanover in July 1838, dining with Olbers at Bremen on his return, and attending the meeting of the British Association at Newcastle in August. He was here appointed a member of a committee for reducing Lacaille's stars, and wrote the preface to the catalogue of them published in 1847. The promotion of a scheme, then recently started by Humboldt and Gauss, for widespread magnetic observations mainly devolved upon him; he drew up a memorial to government on the subject, composed the instructions for Sir James Ross's southern expedition, and reported progress year after year at successive meetings of the British Association. Still more laborious was the task, first attacked at the Cape, of revising the nomenclature of southern stars. He prepared charts (presented to the Royal Astronomical Society in 1867, Monthly Notices, xxvii. 213, xxviii. 92) of all the lucid stars in both hemispheres, assigning the brightness of each within a third of a magnitude; communicated a large project of constellational reform to the Royal Astro- nomical Society in 1841 (Memoirs, xii. 201), and made his final report, recommending less stringent, but more practicable measures, to the British Association in 1844 (Report, p. 32).

Herschel discovered in 1840 the variability of α Orionis (Memoirs Roy. Astr. Soc. xi. 269), and was, on 17 March 1843, among the first observers in England of the great comet (Proceedings Roy. Soc. iv. 450). In a ‘Note on the Art of Photography’ he had explained before the Royal Society, on 14 March 1839, his independent invention of the photographic use of sensitised paper (ib. iv. 131); and an essay ‘On the Chemical Action of the Rays of the Solar Spectrum on Preparations of Silver and other Substances,’ read on 5 March 1840 (Phil. Trans. cxxx. 1), obtained the third royal medal bestowed upon him by that body. It announced the use as a fixing agent of hyposulphite of soda, the solvent power of which upon the salts of silver he had discovered in 1819 (Edinb. Phil. Journal, i. 8); it originated the application to photographic prints of the terms ‘positive’ and ‘negative,’ adverted to ‘lavender grey’ rays beyond the violet, and described experiments on the ‘chemical analysis of the solar spectrum,’ by which an important new field was thrown open to research. The apparatus employed in them formed part of the Loan Collection of Scientific Instruments at South Kensington in 1876. His efforts to obtain coloured photographs were only partially successful; but his reproduction in 1843 of an engraving of the Slough forty-foot reflector was the first example of a photograph on glass (Abney, Treatise on Photography, p. 5). His discovery in 1845 (Phil. Trans. cxxxv. 147) of the ‘epipolic dispersion’ of light produced by sulphate of quinine and some other substances, led the way to Sir George Stokes's explanation of the phenomena of fluorescence.

By the end of 1842 he had performed without assistance the computations necessary for the publication of his Cape observations. In September 1843 the letterpress was ‘fairly begun,’ and after some delays the work appeared in 1847, at the cost of the Duke of Northumberland, in a large quarto volume, entitled ‘Results of Astronomical Observations made during the years 1834–8 at the Cape of Good Hope.’ Besides the catalogues of nebulæ and double stars, it included profound discussions of various astronomical topics, and was enriched with over sixty exquisite engravings. He insisted in it upon the connection of sun-spots with the sun's rotation, and started the ‘cyclonic theory’ of their origin. He investigated graphically the distribution of nebulæ, but fluctuated in his views as to their nature. Regarding them in 1825 as probably composed of ‘a self-luminous or phosphorescent substance, gradually subsiding into stars and sidereal systems’ (Memoirs Royal Astronomical Society, ii. 487), he ascribed to them later a stellar constitution, and finally inclined to suppose them formed of ‘discrete luminous bodies floating in a non-luminous medium’ (Results, &c. p. 139). Herschel stands almost alone in his attempt to grapple with the dynamical problems presented by star-clusters, and his analysis of the Magellanic Clouds was decisive as to the status of nebulæ. For these labours he received the Copley medal in 1847, and a special testimonial from the Royal Astronomical Society in 1848.

In April 1840 Herschel removed from Slough to a more commodious residence, named Collingwood, at Hawkhurst in Kent, and in December 1850 accepted the post of master of the mint, on its conversion from a ministerial into a permanent office. The reorganisation of the establishment devolved upon him, and the duties connected with it were rendered the more uncongenial by the partial separation from his family which their fulfilment required. He was one of the jury for scientific instruments at the Great Exhibition, and a member of the royal commission appointed in 1850 to inquire into the course of study at the universities of Oxford and Cambridge. His health suffered, and his resignation of his position at the mint was unwillingly accepted in 1855.

Herschel afterwards led a retired life at Collingwood. The collection and revisal of his father's and his own labours was an arduous task, partially completed by the presentation to the Royal Society on 16 Oct. 1863 of a ‘Catalogue of 5,079 Nebulæ and Clusters’ (all then known), reduced to the common epoch 1860 (Phil. Trans. cliv. 1). He next undertook the amalgamation into a catalogue of his father's ‘classes’ of double stars, and on 14 Dec. 1866 read before the Royal Astronomical Society a ‘Synopsis of all Sir William Herschel's Micrometrical Measures of the Double Stars described by him’ (Memoirs, xxxv. 21). The autograph observations of the 812 pairs catalogued accompanied the paper, and are deposited in the library of the society. Herschel's general and descriptive catalogue of double stars was his last great undertaking. He finished before his death the arrangement in right ascension of 10,320 composite objects, with the synoptical history of two-fifths of them; and from his papers bequeathed to the Royal Astronomical Society the incomplete cata- logue in the fortieth volume of the society's ‘Memoirs’ was posthumously published, with a few indispensable additions, under the editorship of Mr. Main and Professor Pritchard.

‘Every day of Herschel's long and happy life,’ it was remarked by Professor Tait, ‘added its share to his scientific services.’ His recommendation in 1854 of photography for the registration of sun-spots (Monthly Notices, xv. 158) bore fruit in his lifetime. He published in 1864 a weighty contribution to solar physics (Quarterly Journal of Science, i. 233), urged in the ‘willow-leaf’ debate the ‘filamentous’ structure of the solar floccules (Monthly Notices, xxv. 152), observed and assigned a ‘radiant’ to the meteoric shower of 13 Nov. 1866 (ib. xxvii. 19), and pointed out with conclusive force the improbability of certain alleged changes in the Argo nebula (ib. xxviii. 225). He amused himself with translating poetry. His translation of Schiller's ‘Walk’ was printed for private circulation in 1842, and included in 1847 among Whewell's ‘English Hexameter Translations.’ He also translated Bürger's ‘Lenore,’ and in 1866 the ‘Iliad’ in ‘English accentuated hexameters.’ The first book was published with a defence of the adopted metre in the ‘Cornhill Magazine’ for May 1862. A version by Herschel in terza rima of the first canto of Dante's ‘Inferno’ appeared in the ‘Cornhill Magazine’ for July 1868.

Herschel died at Collingwood on 11 May 1871, and was buried on 19 May in Westminster Abbey, near the grave of Sir Isaac Newton. His cordial encouragement of rising men sustained his popularity to the last. Mr. Nasmyth puts him ‘supremely at the head’ of all the scientific men of his acquaintance for knowledge, simplicity, and humility. Biot, when asked by Professor Pritchard, after the death of Laplace, whom he thought his worthiest successor, replied, ‘If I did not love him so much, I should unhesitatingly say, John Herschel.’ His private life was one unbroken tenour of domestic affection and unostentatious piety, but he shrank from active participation in worldly affairs. Love of truth was in him absolutely untainted by the egotism of the discoverer, his quiet candour being nowhere more apparent than in his correspondence with R. A. Proctor on the subject of sidereal construction in 1869–71 (Proctor, Other Suns, 1887, p. 393).

Herschel, without the soaring genius of his father, had a wider range and a more catholic mind. He was led to astronomy by filial piety, in opposition to a spontaneous preference for chemistry and optics. ‘Light,’ he used to say, ‘was his first love.’ Yet his position as a celestial explorer is unique. He was an unsurpassed observer, and his breadth of knowledge and power of vividly describing what he saw added incalculably to the value of his observations. His books hence take high rank among the elevating influences of this century. He never lost his taste for simple amusements; was in his element with children, loved gardening, and took interest in all technical arts. His unpublished correspondence on scientific subjects is of historical interest; his letters to intimate friends are full of genial and tender sentiments. His wife died on 3 Aug. 1884. He was succeeded in the baronetcy by his eldest son, Sir William James Herschel; his second son, Professor Alexander Stewart Herschel, is well known as an astronomer and physicist; Colonel John Herschel, his third son, was elected a fellow of the Royal Society in 1871, in recognition of his spectroscopic examination of southern nebulæ. Eight of Herschel's nine daughters are still (1891) living.

Besides the works already mentioned, he wrote in 1817–18 the articles ‘Isoperimetrical Problems’ and ‘Mathematics’ for Brewster's ‘Edinburgh Cyclopædia;’ and for the eighth edition of the ‘Encyclopædia Britannica,’ those on ‘Meteorology,’ ‘Physical Geography,’ and the ‘Telescope’—all three published apart as well. The first issue of the admiralty ‘Manual of Scientific Inquiry’ (London, 1849) was edited and the section on meteorology (separately printed from the third edition in 1859) written by him. He contributed several articles to the ‘Edinburgh’ and ‘Quarterly’ reviews, including critiques of Mrs. Somerville's ‘Mechanism of the Heavens,’ Whewell's ‘History and Philosophy of the Inductive Sciences,’ Humboldt's ‘Kosmos,’ and Quetelet's ‘Theory of Probabilities’ (the last prefixed in 1862 to the second edition of Quetelet's ‘Physique Sociale’). These with his addresses in presenting the medals of the Royal Astronomical Society, his ‘Memoir of Francis Baily,’ and some poetical pieces were collected in 1857 into a volume of ‘Essays,’ followed after ten years by ‘Familiar Lectures on Scientific Subjects.’ Three discourses ‘On Earthquakes and Volcanoes,’ ‘On the Sun,’ and ‘On Comets,’ delivered in the parish school-house of Hawkhurst, and printed in ‘Good Words,’ originated this delightful book; the chief remaining contents were popular articles from the same periodical ‘On the Weather and Weather Prophets,’ ‘On Celestial Weighings and Measurings,’ and ‘On Light.’

Herschel's discovery of a correspondence between the crystallographical and optical peculiarities of quartz (Trans. Cambridge Phil. Society, i. 43) was designated by Sir William Thomson ‘one of the most notable meeting-places between natural history and natural philosophy’ (British Association Report, 1871, p. lxxxv). He improved the objectives of microscopes (Phil. Trans. cxi. 246), delivered in 1824 the Bakerian lecture ‘On certain Motions produced in Fluid Conductors when transmitting the Electric Current’ (ib. cxiv. 162), and joined Babbage in a remarkable set of experiments on the magnetisation of rotating metallic plates (ib. cxv. 467). He gave the earliest discussion (in 1830) of the influence upon climate of the earth's orbital eccentricity (Trans. Geological Society, iii. 293), and on 23 Sept. 1832 made the curious observation of a knot of faint stars through great part of the substance of Biela's comet (Monthly Notices, ii. 117). First after his father, he caught sight in 1828 of the Uranian satellites, and corrected their periods from observations in 1830–2 (Memoirs Royal Astron. Soc. viii. 1). An arrangement casually described by him for viewing the sun by first-surface reflection (Cape Observations, p. 436) proved of material use in helioscopic researches. For many years he was an active member of the council of the Royal Society and of the board of visitors to the Royal Observatory; he was a trustee of the British Museum, and sat on the royal commission on standards in 1838–43. One hundred and fifty-two contributions by him are enumerated in the Royal Society's ‘Catalogue of Scientific Papers.’ A list of his works down to 1861, drawn up by himself, appeared at Cambridge, United States, in the ‘Mathematical Monthly Magazine’ (iii. 220), accompanied by an excellent engraving from a photograph sent by Lady Herschel to Miss Maria Mitchell of Nantucket.

St. John's College, Cambridge, possesses a portrait in oils of Herschel by Pickersgill, and his bust executed by Baily about 1852. A small painting by Thomas Webster, R.A., from a photograph taken in 1871, and Mrs. Cameron's life-size photographs are good likenesses. The best representation of his later aspect is, however, in a painting by his eldest daughter, Caroline, wife of Sir Alexander Hamilton. A life-size sketch of him by Watts, taken about 1852, remains with the artist.

[Family papers and information from Miss Herschel; Mrs. John Herschel's Memoir of Caroline Herschel; Royal Astronomical Society's Monthly Notices, xxxii. 122 (Pritchard); the same in German in Almanach der Kaiserlichen Akademie, Vienna, 1873, p. 147; Proceedings Royal Society, xx. xvii (T. Romney Robinson); Proceedings Royal Society of Edinburgh, vii. 543 (Tait); Nature, iv. 69; Dunkin's Obituary Notices, p. 47; Report Brit. Assoc. 1871, p. lxxxv (Sir W. Thomson); Forbes in Encycl. Brit. i. 861 (8th edit.); Quarterly Journal of Science, v. 186 (with portrait); Proctor's Essays on Astronomy; Smithsonian Rep. 1871, p. 109; Proceedings American Acad. viii. 461, 1872; Proceedings American Phil. Society, xii. 217, Philadelphia, 1873; Mailly's Mémoires couronnés par l'Acad. de Bruxelles, vol. xxiii. pt. ii. p. 109, 1873 (8vo ser.); Bulletin de l'Acad. de Bruxelles, 2nd ser. xxxi. 478 (Quetelet); E. Kondor in Mathematical Memoirs of Budapest Acad. of Sciences, vol. iii. No. 3, 1874 (in Magyar); Revue Britannique, January 1837, p. 175 (letter written from the Cape by Herschel to Sir W. Hamilton); Century Magazine, June 1885, October 1889; Grant's Hist. of Physical Astronomy; Clerke's Popular Hist. of Astronomy; Mädler's Geschichte der Himmelskunde, vol. ii.; Mémoires de la Société Physique de Genève, xxi. 586 (Gautier); Times, 13 May 1871.]

A. M. C.