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HERSCHEL, SIR F

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Originally appearing in Volume V13, Page 393 of the 1911 Encyclopedia Britannica.
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HERSCHEL, See also:SIR F . W. invented for the construction of telescopic mirrors; the See also:man who had the hardihood to undertake polishing them doomed himself to walk leisurely and uniformly See also:round an upright See also:post for many See also:hours, without removing his hands from the See also:mirror, until his See also:work was done. On these occasions Herschel received his See also:food from the hands of his faithful See also:sister. But his See also:reward was nigh. In May 1786 his first two papers containing some results of his observations on the variable See also:star " Mira " and the mountains of the See also:moon were communicated to the Royal Society through the influential introduction of Dr See also:William See also:Watson. Herschel had made his acquaintance in a characteristic manner. In See also:order to obtain a sight of the moon the astronomer had taken his See also:telescope into the See also:street opposite his See also:house; the celebrated physician happening to pass at the See also:time, and seeing his See also:eye removed for a moment from the See also:instrument, requested permission to take his See also:place. The mutual courtesies and intelligent conversation which ensued soon ripened this casual acquaintance into a solid and enduring regard. The phenomena of variable stars were examined by Herschel as a See also:guide to what might be occurring in our own See also:sun. The sun, he knew, rotated on its See also:axis, and he knew that dark spots often exist on its photosphere; the questions that he put to himself were— Are there dark spots also on variable stars? Do the stars also rotate on their axes? or are they sometimes partially eclipsed by the intervention of opaque bodies?

And he went on to enquire, What are these singular spots upon the sun? and have they any See also:

practical relation to the inhabitants of this See also:planet? To these questions he applied his telescopes and his thoughts; and he communicated the results to the Royal Society in no less than six See also:memoirs, occupying very many pages in the Philosophical Transactions, and extending in date from 178o to 18or. It was in the latter See also:year that these remarkable papers culminated in the inquiry whether any relation could be traced in the recurrence of sun-spots, regarded as evidences of See also:solar activity, and the varying seasons of our planet, as exhibited by the varying See also:price of See also:corn. Herschel's reply was inconclusive; nor has a final See also:solution of the related problems yet been obtained. In 1781 he communicated to the Royal Society the first of a See also:series of papers on the rotation of the See also:planets and of their several satellites. The See also:object which he had in view was not so much to ascertain the times of their rotation as to discover whether those rotations are strictly See also:uniform. From the result he expected to gather, by See also:analogy, the See also:probability of an alteration in the length of our own See also:day. These inquiries occupy the greater See also:part of seven memoirs extending from 1781 to 1797. While engaged on them he noticed the curious See also:appearance of a See also:white spot near to each of the poles of the planet See also:Mars. On investigating the inclination of its axis to the See also:plane of its See also:orbit, and finding that it differed little from that of the See also:earth, he concluded that its changes of See also:climate also would resemble our own, and that these white patches were probably polar See also:snow. See also:Modern researches have See also:con-firmed his conclusion. He also discovered that, as far as his observations extended, the times of the rotations of the various satellites round their axes conform to the analogy of our moon by equalling the times of their revolution round their primaries.

Here again we perceive that his discoveries arose out of the systematic and comprehensive nature of his investigation. Nothing with such a man is accidental. In the same year (1781) Herschel made a See also:

discovery which completely altered the See also:character of his professional See also:life. In the course of a methodical See also:review of the heavens he lighted on See also:art object which at first he supposed to be a See also:comet, but which, by its subsequent motions and appearance, averred itself to be a new planet, moving outside the orbit of See also:Saturn. The name of Georgium Sidus was by him assigned to it, but has by See also:general consent been laid aside in favour of See also:Uranus. The object was detected with a 7-ft. reflector having an See also:aperture of 62 in.; subsequently, when he had provided himself with a much more powerful telescope, of 20 ft. See also:focal length, he discovered, as he believed, no less than six Uranian satellites. Modern observations. while abolishing four of these supposed attendants, have added two others apparently not observed by Herschel. Seven memoirs In 1752, at the See also:age of fourteen, he joined the See also:band of the Hanoverian guard, and with his detachment visited See also:England in 1755, accompanied by his See also:father and eldest See also:brother; in the following year he returned to his native See also:country; but the hardships of campaigning during the Seven Years' See also:War imperil-See also:ling his See also:health, his parents privately removed him from the See also:regiment, and on the 26th of See also:July 1757 despatched him to England. There, as might have been expected, the earlier part of his career was attended with formidable difficulties and much privation. We find him engaged in several towns in the See also:north of England as organist and teacher of See also:music, which were not lucrative occupations. But the See also:tide of his fortunes began to flow when he obtained in 1766 the See also:appointment of organist to the Octagon See also:chapel in See also:Bath, at that time the resort of the See also:wealth and See also:fashion of the See also:city. During the next five or six years he became the leading musical authority, and the director of all the See also:chief public musical entertainments at Bath.

His circumstances having thus become easier, he revisited See also:

Hanover for the purpose of bringing back with him his sister See also:Caroline, whose services he much needed in his multifarious undertakings. She arrived in Bath in See also:August 1772, being at that time in her twenty-third year. She thus describes her brother's life soon after her arrival: " He used to retire to See also:bed with a bason of See also:milk or a See also:glass of See also:water, with See also:Smith's Harmonics and See also:Ferguson's See also:Astronomy, &c., and so went to See also:sleep buried under his favourite authors; and his first thoughts on waking were how to obtain See also:instruments for viewing those See also:objects himself of which he had been See also:reading." It is not without significance that we find him thus reading Smith's Harmonics; to that study See also:loyalty to his profession would impel him; as a reward for his thoroughness this led him to Smith's See also:Optics; and this, by a natural sequence, again led him to astronomy, for the purposes of which the chief See also:optical instruments were devised. It was in this way that he was introduced to the writings of Ferguson and Keill, and subsequently to those of See also:Lalande, whereby he educated himself to become an astronomer of undying fame. In those days telescopes were very rare, very expensive and not very efficient, for the Dollonds had not as yet perfected even their beautiful little achromatics of 24 in. aperture. So Herschel was obliged to content himself with See also:hiring a small Gregorian reflector of about 2 in. aperture, which he had seen exposed for See also:loan in a tradesman's See also:shop. Not satisfied with this See also:implement, he procured a small See also:lens of about 18 ft. focal length, and set his sister to work on a pasteboard See also:tube to match it, so as to make him a telescope. This unsatisfactory material was soon replaced by See also:tin, and thus a sorry sort of See also:vision was obtained of See also:Jupiter, Saturn and the moon. He then sought in See also:London for a reflector of much larger dimensions; but no such instrument was on See also:sale; and the terms demanded for the construction of a reflecting telescope of 5 or 6 ft. focal length he regarded as too exorbitant even for the gratification of such desires as his own. So he was driven to the only alternative that remained; he must himself build a large telescope. His first step in this direction was to See also:purchase the debris of an See also:amateur's implements for grinding and polishing small mirrors; and thus, by slow degrees, and by indomitable perseverance, he in 1774 had, as he says, the See also:satisfaction of viewing the heavens with a Newtonian telescope of 6 ft. focal length made by his own hands. But he was not contented to be a See also:mere star-gazer; on the contrary, he had from the very first conceived the gigantic project of See also:surveying the entire heavens, and, if possible, of ascertaining the See also:plan of their general structure by a settled mode of See also:procedure, if only he could provide himself with adequate instrumental means.

For this purpose he, his brother and his sister toiled for many years at the grinding and polishing of hundreds of specula, always retaining the best and recasting the others, until the most perfect of the earlier products had been surpassed. This was the work of the daylight in those seasons of the year when the fashionable visitors of Bath had quitted the place, and had thus freed the See also:

family from professional duties. After 1974 every available See also:hour of the See also:night was devoted to the See also:long-hopedfor See also:scrutiny of the skies. In those days no machinery had been on the subject were communicated by him to the Royal Society, extending from the date of the discovery in 1781 to 1815. A noteworthy peculiarity in Herschel's mode of observation led to the discovery of this planet. He had observed that the See also:spurious diameters of stars are not much affected by increasing the magnifying See also:powers, but that the See also:case is different with other See also:celestial objects; hence if anything in his telescopic See also:field struck him as unusual in aspect, he immediately varied the magnifying See also:power in order to decide its nature. Thus Uranus was discovered; and had a similar method been applied to See also:Neptune, that planet would have been found'at See also:Cambridge some months before it was recognized at See also:Berlin. We now come to the beginning of Herschel's most important series of observations, culminating in what ought probably to be regarded as his See also:capital discovery. A material part of the task which he had set himself embraced the determination of the relative distances of the stars from our sun and from each other. Now, in the course of his scrutiny of the heavens, he had observed many stars in apparently very See also:close contiguity, but often differing greatly in relative brightness. He concluded that, on the See also:average, the brighter star would be the nearer to us, the smaller enormously more distant; and considering that an astronomer on the earth, in consequence of its immense orbital displacement of some 18o millions of See also:miles every six months, would see such a pair of stars under different See also:perspective aspects, he perceived that the measurement of these changes should See also:lead to an approximate determination of the stars' relative distances. He therefore mapped down the places and aspects of all the See also:double stars that he met with, and communicated in 1782 and 1785 very extensive catalogues of the results.

Indeed, his very last scientific memoir, sent to the Royal Astronomical Society in the year 1822, when he was its first See also:

president and already in the eighty-See also:fourth year of his age, related to these investigations. In the memoir of 1782 he threw out the hint that these apparently contiguous stars might be genuine pairs in mutual revolution; but he significantly added that the time had not yet arrived for settling the question. Eleven years afterwards (1793), he re-measured the relative positions of many such couples, and we may conceive what his feelings must have been at finding his prediction verified. For he ascertained that some of these stars circulated round each other, after the manner required by the See also:laws of See also:gravitation, and thus demonstrated the See also:action among the distant members of the starry See also:firmament of the same See also:mechanical laws which bind together the harmonious motions of our solar See also:system. This See also:sublime discovery, announced in 1802, would of itself suffice to immortalize his memory. If only he had lived long enough to learn the approximate distances of some of these binary combinations, he would at once have been able to calculate their masses relative to that of our own sun; and the quantities being, as we now know, strictly comparable, he would have found another of his analogical conjectures realized. In the year 1782 Herschel was invited to See also:Windsor by See also:George III., and accepted the See also:king's offer to become his private astronomer, and henceforth devote himself wholly to a scientific career. His See also:salary was fixed at £2o0 per annum, to which an addition of £5o per annum was subsequently made for the astronomical assistance of his sister. Dr Watson, to whom alone the amount was mentioned, made the natural remark, " Never before was See also:honour See also:purchased by a monarch at so cheap a See also:rate." In this way the See also:great astronomer removed from Bath, first to Datchet and soon afterwards permanently to See also:Slough, within easy See also:access of his royal See also:patron at Windsor. The old pursuits at Bath were soon resumed at Slough, but with renewed vigour and without the former professional interruptions. The greater part, in fact, of the papers already referred to are dated from Datchet and Slough; for the magnificent astronomical speculations in which he was engaged, though for the most part conceived in the earlier portion of his philosophical career, required years of patient observation before they could be fully examined and realized. It was at Slough in 1783 that he wrote his first memorable See also:paper on the " See also:Motion of the Solar System in Space,"—a sublimespeculation, yet through his See also:genius realized by considerations of the utmost simplicity.

He returned to the same subject with See also:

fuller details in 1805. It was also after his removal to Slough that he published his first memoir on the construction of the heavens, which from the first had been the inspiring See also:idea of his varied toils. In a long series of remarkable papers, addressed as usual to the Royal Society, and extending from the year 1784 to 1818, when he was eighty years of age, he demonstrated the fact that our sun is a star situated not far from the bifurcation of the Milky Way, and that all the stars visible to us See also:lie more or less in clusters scattered throughout a comparatively thin, but immensely extended stratum. At one time he imagined that his powerful instruments had pierced through this stellar stratum, and that he had approximately determined the See also:form of some of its boundaries. In the last of his memoirs, having convinced himself of his See also:error, he admitted that to his telescopes the Milky Way was " fathomless." On either See also:side of this assemblage of stars, presumably in ceaseless motion round their See also:common centre of gravity, Herschel discovered a See also:canopy of discrete nebulous masses, such as those from the condensation of which he supposed the whole stellar universe to have been formed, —a magnificent conception, pursued with a force of genius and put to the practical test of observation with an See also:industry almost incredible. Hitherto we have said nothing about the great reflecting telescope, of 40 ft. focal length and 4 ft. aperture, the construction of which is often, though mistakenly, regarded as his chief performance. The full description of this celebrated instrument will be found in the 85th See also:volume of the Transactions of the Royal Society. On the day that it was finished (August 28, 1789) Herschel saw at the first view, in a grandeur not witnessed before, the Saturnian system with six satellites, five of which had been discovered long before by C. See also:Huygens and G. D. See also:Cassini, while the See also:sixth, subsequently named Enceladus, he had, two years before, sighted by glimpses in his exquisite little telescope of 62 in. aperture, but now saw in unmistakable brightness with the towering See also:giant he had just completed. On the 17th of See also:September he discovered a seventh, which proved to be the nearest to the globe of Saturn.

It has since received the name of Mimas. It is somewhat remarkable that, notwithstanding his long and repeated scrutinies of this planet, the eighth See also:

satellite, See also:Hyperion, and the See also:crape See also:ring should have escaped him. Herschel married, on the 8th of May 1788, the widow of Mr See also:John See also:Pitt, a wealthy London See also:merchant, by whom he had an only son, John See also:Frederick William. The See also:prince See also:regent conferred a Hanoverian See also:knighthood upon him in 1816. But a far more valued and less tardy distinction was the See also:Copley See also:medal assigned to him by his associates in the Royal Society in 1781. He died at Slough on the 25th of August 1822, in the eighty-fourth year of his age, and was buried under the See also:tower of St Laurence's See also:Church, Upton, within a few See also:hundred yards of the old site of the 4o-ft. telescope. A mural tablet on the See also:wall of the church bears a Latin inscription from the See also:pen of the See also:late Dr Goodall, See also:provost of See also:Eton See also:College. See Mrs John Herschel, Memoir of Caroline Herschel (1876); E. S. See also:Holden, Herschel, his Life and See also:Works (1881) A. M. See also:Clerke, The Herschels and Modern Astronomy (1895); E.

S. Holden and C. S. See also:

Hastings, Synopsis of the Scientific Writings of Sir William Herschel (See also:Washington, 1881) ; See also:Baron See also:Laurier, Eloge historique, See also:Paris Memoirs (1823), p. lxi. ; F. See also:Arago, Analyse historique, Annuaire du See also:Bureau See also:des Longitudes (1842), p. 249; Arago, See also:Biographies of Scientific Men, p. 167; Madame d'Arblay's See also:Diary, passim; Public Characters (1798-1799), p. 384 (with portrait); J. Sime, William Herschet'and his Work (1900). Herschel's photometric Star Catalogues were discussed and reduced by E. C.

See also:

Pickering in Harvard See also:Annals, vols. xiv. p. 345, See also:xxiii. p. 185, and See also:xxiv. (C. P.; A. M.

End of Article: HERSCHEL, SIR F

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