Read Ebook: The Story of the Herschels a Family of Astronomers Sir William Herschel Sir John Herschel Caroline Herschel by Anonymous

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Herschel's parents--The two brothers--A musical family--An inventive genius--The brothers in England--Herschel as an organist--A laborious life--Mechanical ingenuity of William Herschel--Telescope-making--A Sunday misadventure--Constructing a twenty-foot telescope--A domestic picture--Discovery of a new planet--Herschel's combined musical and astronomical pursuits--A thirty-foot telescope--Casting the mirror--An explosion

The house at Datchet--Housekeeping details--A devoted sister--Life at Datchet--Herschel's astronomical observations--Testing and trying "eyepieces"--The colossal telescope--Miss Herschel's accident--Removed to Slough--Constructing a forty-foot telescope--Brother and sister--Heroic self-denial--Occupations at Slough--Royal liberality--An astronomer's triumphs--About the nebulae--Investigation of the sun's constitution--The solar spots, and their influence--Physical constitution of the moon--Lunar volcanoes--Arago's explanation--Herschel's study of the planets--Satellites of Saturn--Discovery of Uranus--And of its six satellites--Study of Pigott's comet and the comet of 1811--Description of the latter--An uneventful life--Herschel's marriage--His honours--Extracts from his sister's diary--Decaying strength--Herschel removes to Bath--Last days of an astronomer--Illustration of the ruling passion--Death of Sir William Herschel--His achievements

Birth and education of Sir John Herschel--Honours at Cambridge--First publication--Continues his scientific studies--His numerous literary contributions--His devotion to his father's reputation--The forty-foot telescope--Herschel's observations on the double and triple stars--On the refraction and polarization of light--Catalogue of nebulae and star-clusters--Voyage to Cape Town--Letter to Miss Herschel--Study of the southern heavens--Return to England--Distinctions conferred upon him--His "Familiar Lectures on Scientific Subjects"--His description of volcanoes and earthquakes--Continual changes in the configuration of the earth--Violent earthquakes--Phenomena of volcanic eruptions--In Mexico--In the island of Sumbawa--Herschel's theory of volcanic forces--His character

Caroline Herschel's devotion to her brother William--Her grief and solitariness at his death--Reflections on the mutability of human things--Aunt and nephew--A parsimonious government--Miss Herschel's gold medal--South on Sir William's discoveries--On Miss Herschel's devotion--Her own astronomical discoveries--Her life at Hanover--Her wonderful memory--Anecdotes of Sir John Herschel--Correspondence between aunt and nephew--The path of duty--Sir John's visit to Miss Herschel--Reminiscences of early years--A nonogenarian--A Christmas in Hanover--Last days of Caroline Herschel--Her death--Her epitaph

THE STORY OF THE HERSCHELS.

Now, this is the feeling which the study of Astronomy very certainly awakens. Every day the astronomer discovers something which quickens his curiosity to discover more. Every day he catches new glimpses of the Almighty Wisdom, which stimulate his desire for a further revelation. And all he learns, and all he anticipates learning, combine to produce in him an emotion of awe. What grandeur lies before him in that endless procession of worlds--in that array of suns and stars extending beyond the limits of the most powerful telescopic vision! How marvellous it is! How beautiful! Observe the combination of simplicity with power; note how a great principle of "law" underlies the apparent intricacy of eccentric and intersecting orbits. And then the field of inquiry is inexhaustible. The astronomer has no fear of feeling the satiety of an Alexander, when he lamented that he had no more worlds to conquer. What Newton said of himself is true of every astronomer,--he is but as a child on the sea-shore, picking up a shell here and a shell there, but unable to grasp a full conception of the mighty ocean that thunders in his ears!

And, therefore, because Astronomy cherishes the feelings of awe and reverence and praise, because it inspires a continual yearning after additional knowledge, because it reveals to us something of the character of God, we conceive that of all the sciences it affords the purest intellectual gratification. Certainly it is one of the most absorbing. Its attraction seems to be irresistible. Once an astronomer, always an astronomer; the stars, we may fancy, will not relax the spell they lay upon their votary. He willingly withdraws himself from the din and gaiety of social life, to shut himself up in his chamber, and, with the magic tube due to the genius of a Galileo, survey with ever-new delight the celestial wonders. So was it with Tycho Brah?, and Copernicus, and Kepler; so was it, as the following pages will show, with that remarkable family of astronomers--astronomers for three generations--the HERSCHELS.

In the quiet city of Hanover, nearly a century and a half ago, lived a professor of music, by name Isaac Herschel, a Protestant in religion, though presumably of Jewish descent. He had been left an orphan at the early age of eleven, and his friends wished him to adopt the vocation of a landscape-gardener; but being passionately fond of music, and having acquired some skill on the violin, he left Dresden, his birthplace, in order to seek his fortune; wandering from place to place, until at Hanover, in 1731, he obtained an engagement in the band of the Guards. Soon afterwards he married; and by his wife, Anna Ilse Moritzen, had ten children, four of whom died in infancy. Of the others, two--a brother and a sister--lived to distinguish themselves by their intellectual power; and all true lovers of science will regard with reverence the memories of William and Caroline Herschel.

Frederick William Herschel was born on the 15th of November 1738. Like his father, he displayed an innate musical ability, which was sedulously cultivated and constantly developed; while his general mental training was left to the care of the master of the garrison-school. Those who are gifted with a love and a capacity for music sometimes show to little advantage in other pursuits; but such was not the case with William Herschel, who progressed so rapidly in all his studies that the pupil soon outstripped the teacher. Although, we are told, four years younger than his brother Jacob, the two began French together, and William mastered the language in half the time occupied by his senior. His leisure time out of school, when not given up to practice on the oboe and the violin, was devoted to the acquisition, of Latin and arithmetic.

In 1755, the tranquil family circle was broken up--the Hanoverian regiment in whose band William and Jacob were engaged having been ordered to England. The parting was very sorrowful; for the invalid father had derived much support as well as enjoyment from the company of his sons. At first, the English experiences of the young Germans were somewhat severe. They endured all the pangs of poverty; pangs endured with heroic composure, while William relaxed not a whit in his devotion to the pursuit of knowledge. Happily, however, his musical proficiency attracted the attention of Lord Durham, who offered him the appointment of bandmaster to a militia regiment stationed in the north of England. In this position he gradually formed a connection among the wealthier families of Leeds, Pontefract, and Doncaster, where he taught music, and conducted the public concerts and oratorios with equal zeal and success. In 1764 he paid a brief but happy visit to his family, much to the joy of his faithful sister, Caroline. Returning to England, for which country he cherished a strong affection, he resumed his career of patient industry, and in 1765 was appointed organist at Halifax. He was now in receipt of an income which secured him due domestic comforts, and enabled him to remedy the defects of his early education. With the help of a grammar and a dictionary he mastered Italian. He also studied mathematics and the scientific theory of music, losing no opportunity of adding to his stores of knowledge.

In 1766 he obtained the lucrative post of organist to the Octagon Chapel at Bath. Increased emoluments, however, brought with them increased obligations. He was required to play almost incessantly, either at the oratorios or in the rooms at the Baths, at the theatre, and in the public concerts. When his sister Caroline joined him, in 1772, she found him immersed in his various labours. For the choir of the Octagon Chapel he composed anthems, chants, and complete morning and evening services. A part of every day was occupied in giving lessons to his numerous pupils. In truth, he was one of the busiest men in England; yet in all his arrangements he was so methodical that he found time for everything--and time, more particularly, for the studies in which his soul delighted. His life furnishes an admirable example of what may be accomplished by a man with a firm will and a strong purpose, who sets before himself an end to be attained, and controls all his efforts towards its attainment. He toiled so hard as a musician, because he wanted to be something more. Every spare moment of the day, and frequently many hours of the night, he gave up to the pursuits which were gradually leading him into the path best fitted for his genius. The study of mathematics proved but a preliminary to the study of optics; and an accident made him once for all an astronomer.

A common two-foot telescope falling into his hands, revealed to him the wonders of the heavens. His imagination was inspired by their contemplation; with ever-increasing enthusiasm he gazed on the revolving planets, on the flashing stars; he determined to fathom more profoundly the constellated depths. A larger instrument was necessary, and Herschel wrote to London for it; but the price demanded proved far beyond the resources of the sanguine organist. What should he do? He was not the man to be beaten back by a difficulty: as he could not buy a telescope, he resolved to make one; an instrument eighteen or twenty feet long, which would reveal to him the phases of the remotest planets. And straightway the musician entered on a multitude of ingenious experiments, so as to discover the particular metallic alloys that reflected light with the greatest intensity, the best means of giving the parabolic figure to the mirrors, the necessary degree of polish, and other practical details. In his eager pursuit he enlisted the services of his loving and intelligent sister. "I was much hindered in my musical practice," she writes, "by my help being continually wanted in the execution of the various contrivances; and I had to amuse myself by making the tube of pasteboard for the glasses which were to arrive from London--for at that time no optician had settled at Bath. But when all was finished, no one besides my brother could get a glimpse of Jupiter or Saturn, for the great length of the tube would not allow it to be kept in a straight line. This difficulty, however, was soon removed, by substituting tin tubes."

The work went on famously, as might be expected from so much ardour, perseverance, and ingenuity. Of a Quaker resident at Bath, the musician-astronomer purchased a quantity of patterns, tools, hones, polishers, and unfinished mirrors. Every room in the house was converted into a workshop. In a handsomely-furnished drawing-room might be seen a cabinetmaker constructing a tube and stands of all descriptions; while Herschel's brother Alex was engaged in a bedroom in putting up a gigantic turning-machine. Meantime, the claims of music could not be ignored: there were frequent rehearsals for the public concerts; lessons to pupils; the composition of glees and catches, and the like; the superintendence of the practice of the chapel choir; and the study of sonatas and concertos for public performance. But all the leisure that could be made or stolen was occupied in labours which proved their own reward. Straight from the concert-platform rushed the musician to his workshop, and many a lace ruffle was torn by nails or bespattered by molten pitch; to say nothing of the positive danger to which Herschel continually exposed himself by the precipitancy of his movements. For example: one Saturday evening, when the two brothers returned from a concert between eleven and twelve o'clock, William amused himself all the way home with the idea of being at liberty to spend the next day, except the few hours' duty at chapel, at the turning-bench; but recollecting that the tools wanted sharpening, they ran with them and a lantern to their landlord's grindstone in a public yard, where, very naturally, they did not wish to be seen on a Sunday morning. But William was soon brought back by his brother, almost swooning with the loss of one of his finger-nails.

This incident took place in the winter of 1775, at a house situated near Walcot turnpike, to which Herschel had removed in the summer of the previous year. Here, on a grass plot behind the house, he made active preparations for the erection of a twenty-foot telescope. So assiduous was his devotion to this work, that while he was engaged in polishing the mirror, his sister was constantly obliged to feed him by putting his victuals into his mouth. Otherwise he would have reduced himself to a condition of positive emaciation! Once, when finishing a seven-foot mirror, he did not take his hands from it for sixteen consecutive hours; for in these days machinery had not been devised as a substitute for manual toil. He was seldom unemployed at meals; but at such times employed himself in contriving or making drawings of whatever occurred to his fertile fancy. Usually his sister Caroline read to him while he was engaged at the turning-lathe, or polishing mirrors; choosing such books as "Don Quixote," the "Arabian Nights," the novels of Sterne and Fielding; and tea and supper were served without any interruption to the task in which Herschel was absorbed.

"My brother applied himself to perfect his mirrors, erecting in his garden a stand for his twenty-foot telescope: many trials were necessary before the required motions for such an unwieldy machine could be contrived. Many attempts were made by way of experiment against a mirror before an intended thirty-foot telescope could be completed, for which, between whiles , gauges, shapes, weights, &c, of the mirror were calculated, and trials of the composition of the metal were made. In short, I saw nothing else and heard nothing else talked of but about these things when my brothers were together. Alex was always very alert, assisting when anything new was going forward; but he wanted perseverance, and never liked to confine himself at home for many hours together. And so it happened that my brother William was obliged to make trial of my abilities in copying for him catalogues, tables, &c, and sometimes whole papers which were lent him for his perusal. Among them was one by Mr. Michel, and a catalogue of Christian Mayer in Latin, which kept me employed when my brother was at the telescope at night. When I found that a hand was sometimes wanted when any particular measures were to be made with the lamp micrometer, or a fire to be kept up, or a dish of coffee necessary during a night's long watching, I undertook with pleasure what others might have thought a hardship."

But before this well-deserved good fortune fell to him, Herschel continued his industrious career as both musician and astronomer. During the concert season, which lasted five or six months, he had never a night disengaged, but was conducting oratorios at Bath or Bristol, arranging for public concerts, attending rehearsals, and superintending the performances of his choir. As soon as a lull came, the indomitable man, assisted by his faithful sister, returned to his astronomical pursuits. To gain a fuller and clearer knowledge of the starry worlds scattered over the vast fields of space, Herschel from the first had seen that instruments of much greater power were necessary than any hitherto used by astronomers. He set to work, therefore, on the construction of a thirty-foot telescope; the metallic mirror of which must, of course, be of proportionate dimensions. This huge mirror was to be cast in a mould of loam prepared from horse-dung, of which an immense quantity was to be pounded in a mortar, and sifted through a fine sieve; an arduous and almost endless task, undertaken by Caroline Herschel and her brother Alex. Then a furnace was erected in a back-room on the ground-floor; and every preparation having been made, a day was set apart for the casting. The day came, and Herschel and his collaborateurs looked forward to the consummation of their hopes. The metal was placed in the furnace; but, unfortunately, just when it was ready for pouring in a molten stream into the mould, it began to leak, and both the Herschels, and the caster with his men, were compelled to fly from the apartment, the stone flooring exploding, and flying about in all directions, as high as the ceiling. The astronomer, exhausted with heat and exertion, fell on a heap of brickbats; exhausted, but not dismayed. The work was renewed; and a second casting being attempted, it proved entirely successful, and a very perfect metal was formed in the mould.

In August 1782 the Herschels removed to Datchet. Their new home was "a large neglected place; the house in a deplorably ruinous condition, the garden and grounds overgrown with weeds." Nor were the domestic arrangements more favourable. For a fortnight the little family were without a female servant; and an old woman, the gardener's wife, showed Miss Herschel the shops, where the high prices of every article, from coals to butcher's meat, appalled her. But of these inconveniences Herschel took no account. Enough for him that he was released from the drudgery of teaching, and free thenceforth to devote himself to the heavens and their wonders. A man whose thoughts are always with the stars can hardly be expected to trouble himself about the price of tallow-candles! Were there not capacious stables in which mirrors of any size could be ground; and a roomy laundry capable of easy conversion into a library, with one door opening on a large lawn, where the "small twenty-foot" was to take its stand? Compared with advantages such as these, what mattered the scarcity of "butcher's meat"? Herschel laughingly assured his sister that they could live on eggs and bacon; which, he confidently asserted, would cost next to nothing, now that they were really in the country!

And so he settled down to a life of quiet, industry at Datchet; his admirable sister being formally adopted as his assistant and secretary. Never had master a more devoted, a more enthusiastic, or a more intelligent servant! She shared in all his night-watches, with her eye constantly on the clock, and the pencil in her hand; with unerring accuracy she made all the complex calculations so frequently required; she made three or four copies of every observation in separate registers, co-ordinating, classifying, and analyzing them. If the scientific world, says Arago, saw with astonishment the unexampled rapidity with which Herschel's works succeeded one another for many years, they were greatly indebted for this affluence of production to the affectionate ardour of his sister Caroline. Her enthusiasm never failed; her industry knew no check; and her brother's fame was dearer to her than life.

In one of her letters she describes with graphic simplicity the "interior" at Datchet:--

"I found that I was to be trained for an assistant-astronomer; and by way of encouragement, a telescope adapted for 'sweeping' , consisting of a tube with two glasses, was given me. I was to 'sweep for comets;' and I see by my journal that I began August 22nd, 1782, to write down and describe all remarkable appearances I saw in my 'sweeps.' But it was not till the last two months of the same year that I felt the least encouragement to spend the starlit nights on a grass-plot covered with dew or hoar-frost, without a human being near enough to be within call. I knew too little of the real heavens to be able to point out every object so as to find it again without losing too much time by consulting the Atlas. But all these troubles were removed when I knew my brother to be at no great distance, making observations with his various instruments on double stars, planets, and the like; and I could have his assistance immediately when I found a nebula, or cluster of stars, of which I intended to give a catalogue. I had the comfort to see," she continues, "that my brother was satisfied with my endeavours to assist him when he wanted another person either to run to the clocks, write down a memorandum, fetch and carry instruments, or measure the ground with poles,--of which something of the kind every moment would occur."

The conscientious care and assiduous industry with which Herschel made his measurements of the diameter of the Georgium Sidus , and his interesting observations of other planets, of double stars with their coloured light, of cometary and nebulous appearances, were truly remarkable; as may be seen by the various papers which he wrote at this time for the Royal Society. In addition to all this labour, he perfected a twelve-inch speculum of vast magnifying power before the spring of 1784; and many hours were spent at the turning-bench, as not a night clear enough for observing ever passed without the devising of improvements in the mounting and motion of the various instruments then in use, or the test and trial of newly-constructed "eyepieces," most of which were executed by Herschel's own hands. "Wishing to save his time, he began to have some work of that kind done by a watchmaker, who had retired from business, and lived on Datchet Common; but the work was so bad, and the charges so unreasonable, that he could not be employed. It was not till some time afterwards, in his frequent visits to the meetings of the Royal Society , that he had an opportunity of looking about for mathematical workmen, opticians, and founders. But the work seldom answered expectation, and it was kept to be executed with improvements by Alexander during the few months he spent with us."

In July 1783 Herschel began his observations with his large twenty-foot telescope, though it was in an unfinished state; and his sister watched and waited with much apprehension when she knew him to be elevated some fifteen feet or more on a temporary crossbeam instead of a safe gallery. Here it is needful to explain, perhaps, that these huge astronomical telescopes are not used like ordinary glasses, to one end of which the observer applies his eye; the objects towards which the tube is directed being thrown upon a large mirror, which is attached to it externally at some distance from the ground. The observer, therefore, needs to be mounted on an elevated platform or gallery, from which he can conveniently inspect the mirror. One night, in a very high wind, Herschel had scarcely descended from his station before the whole apparatus came down; and his sister was in continual apprehension of some serious accident. One such, indeed, occurred, and to herself. The evening of the 31st of December had been cloudy, but as a few stars shone forth about ten o'clock, hurried preparations were made for observing. Herschel, standing at the front of the telescope, directed his sister to make a certain alteration in the lateral motion, which was done by machinery, on which the point of support of the tube and mirror rested. At each end of the machine or trough was an iron hook, such as butchers use for suspending their joints of meat; and having to run in the dark across ground covered a foot deep with melting snow, Miss Herschel fell on one of these hooks, which entered her right leg above the knee. To her brother's injunction, "Make haste!" she could answer only by a pitiful cry, "I am hooked!" He and the workmen hastened immediately to her assistance, but they could not disentangle her without leaving nearly two ounces of her flesh behind. For some weeks she was an invalid, and at one time it was feared that amputation might be necessary.

Not satisfied with the magnifying power of any of the instruments he had hitherto constructed, Herschel resolved, in 1784, to attempt a forty-foot telescope. Such a work, however, was far beyond his limited private resources; and he did not venture to undertake it until promised a royal bounty of ?2000. Then he removed from Datchet to Clay Hall, Old Windsor; and again, in 1786, to Slough, where he finally settled, and succeeded in erecting a commodious and well-equipped observatory. "We may confidently assert," says Arago, "relative to the little house and garden of Slough, that it is the spot of all the world where the greatest number of discoveries have been made. The name of that village will never perish: science will transmit it religiously to our latest posterity."

At Slough, as at Datchet, prevailed the most enthusiastic industry; and the house was soon as full of well-ordered labour as a bee-hive. Smiths were kept constantly at work on different parts of the new telescopic leviathan; and a whole troop of labourers was engaged in grinding the tools required for shaping and polishing its mirror. Had not a cloudy or moonlight night sometimes intervened, Herschel and his sister must have died of sheer exhaustion, for they toiled with unremitting ardour both day and night. With the morning came the workpeople, of whom no fewer than between thirty and forty were at work for upwards of three months together: some employed in felling and rooting out trees, some digging and preparing the ground for the bricklayers, who were laying the foundation for the telescope. Then there were the carpenter and his men; and, meanwhile, the smith was converting a wash-house into a forge, and manufacturing complete sets of tools for his own share of the labour. In short, the place was at one time a complete workshop for the manufacture of optical instruments; and it was a pleasure to enter it for the purpose of observing the fervour of the great astronomer, and the reverent attention given to his orders.

It is impossible not to refer here to the sisterly devotion of Caroline Herschel, who was in every respect worthy of her noble-minded, tender-hearted, and enthusiastic brother.

To Miss Herschel's diary we again refer, for a glimpse of the occupations of her brother and herself at Slough in the first two years of their residence. These two years, to use an apt expression of her own, were spent in a perfect chaos of business. The garden and workrooms swarmed with labourers and workmen--smiths and carpenters speeding to and fro between the forge and the forty-foot machinery; and so incessant was the vigilance of Herschel, that not a screw-bolt in the whole apparatus was fixed except under his eye. "I have seen him," writes his sister, "lying stretched many an hour in the burning sun, across the top beam, whilst the iron-work for the various motions was being fixed." At one time no fewer than twenty-four men, in relays of twelve each, were engaged in grinding and polishing day and night; and Herschel never left them, taking his food without allowing himself time to sit down to table.

In recognition of his scientific triumphs, the honorary degree of LL.D was conferred upon Herschel, in 1786, by the University of Oxford. They were triumphs that well merited such a recognition. He had already made some important observations on the nature of double stars, on the dimensions of the telescopic planets, and had begun his famous investigations into the composition of the nebulae,--those clusters of stars and nebulous matter which had previously proved such a problem to astronomers. The remarkable phenomenon of a periodical change of intensity in certain stars, which wax and wane in radiance like a revolving light, had also excited his attention. Further, he had entered upon the experiments which ultimately showed that the Sun positively moves; that in this, as in other respects, the magnificent orb of day must be ranged among the stars; that the apparently inextricable irregularities of numerous sidereal proper motions arise in great part from the displacement of the Solar System; that, in short, the point of space toward which Earth and its sister planets are annually advancing, is situated in the constellation of Hercules.

"Let us," says a French writer, "to these immortal labours add the ingenious ideas that we owe to Herschel on the nebulae, on the constitution of the Milky Way, on the Universe as a whole,--ideas which almost by themselves constitute the actual history of the formation of the worlds,--and we cannot but have a deep reverence for that powerful genius that scarcely ever erred, notwithstanding the ardour of its imagination."

Such was Herschel's explanation of the mode of formation of the solar spots; and allowing it to be well-founded, we must expect to find--what is, indeed, the case--that the Sun does not always and regularly pour forth equal quantities of light and heat. It is true that Herschel's hypothesis has been modified by later astronomers; but his is the credit of having directed them into the right course of inquiry and observation.

The physical constitution of the Moon was a subject which also engaged the attention of our indefatigable enthusiast. As early as 1780 he attempted the measurement of the lunar mountains, and came to the conclusion that few of them exceeded 2600 feet in height. Later research, however, has proved these figures to be inadequate. Next he addressed himself to a study of the lunar volcanoes, three of which he declared to be in a state of ignition; two of them apparently on the decline, the third still active. He was so convinced of the reality of the phenomenon, that on the 20th of April 1787 he wrote:--"The volcano burns with greater violence than it did last night." The real diameter of the volcanic light he estimated at 16,400 feet. Its intensity he described as superior to that of the nucleus of a comet then flashing across our system. The objects situated near the crater were fully illuminated by the glare of its burning matter.

It may seem strange that, after observations so exact and minute, few astronomers now admit the existence of active volcanoes in the Moon. The reasons for their incredulity are thus stated:--

The various parts of the Moon do not all reflect with the same intensity. Here, that intensity may be dependent on the form; elsewhere, on the nature of the materials. Those persons who have examined the lunar orb with telescopes, know how very considerable the difference arising from these two causes may be,--with how much keener and stronger a radiance one point of the Moon will sometimes shine than those around it. Well, it would seem to be obvious that the ratio of intensity between the brilliant parts and the faint parts must always be the same, whatever the origin of the illuminating light. In that portion of the lunar sphere which receives the glow and glory of the sun, we know that some points exist, the brightness of which is extraordinary compared with the feeble flickering gleam of those around them. And these same points, when seen in the dim reflection of the Earth, will still predominate in intensity over the neighbouring regions. In this way Arago and others explain the observations of Herschel, without admitting the existence of active volcanoes in the Moon. That volcanoes there are, is a familiar fact; but they would seem to have exhausted their activity in long-past ages. The lunar surface is now a dreary waste of rugged lava and ashes, covered with the matter ejected from craters once in a state of furious eruption. The Moon, in fact, is a world which has burned itself out. How strange the thought that in a far-back period the inhabitants of Earth, had Earth then been inhabited, might have seen the glare of countless volcanoes diffused, lurid and threatening, over the face of their satellite! How strange the thought that the once active fires should all have died away, and the Moon have thus been prepared for the better reception and reflection of the solar radiance in order to illuminate the nights of Earth!

The planets, needless to say, were the objects of Herschel's assiduous attention. Mercury was the one which least interested him; but he ascertained the perfect circularity of its disc. With respect to Venus, he endeavoured to determine the time of its rotation from 1777. We owe to him the discovery of the true shape of the "red planet Mars,"--that, like the Earth, it is an oblate spheroid, or flattened at the poles. After Piazzi, Olbers, and Harding had discovered the small planets, Ceres, Pallas, Juno, and Vesta, he applied himself to the measurement of their angular diameters. His researches led him to the conclusion that these four new bodies could not properly be ranked with the planets, and he proposed to call them Asteroids--a name now generally adopted. Since Herschel's time, the number of these minor planets known to astronomers has increased to upwards of one hundred.

With respect to Jupiter, our astronomer arrived at some important facts in connection with the duration of its rotation. He also made numerous observations on the intensities and comparative magnitudes of its satellites.

We come next in order to Saturn, the gloomy planet which the ancient astrologers regarded with so much dislike. Here, too, we find traces of Herschel's labours. Not only has he enlarged our knowledge of its equatorial compression, of its physical constitution, and of the rotation of its luminous belt or ring, but he added two to the number of its satellites. Five only of these were known at the close of the seventeenth century; of which Cussiric discovered four, and Huygens one. It was universally believed that the subject was exhausted.

But, on the 28th of August 1780, Herschel's colossal tube revealed to his delighted gaze a satellite nearer to the Saturnian ring than those previously observed. And a few days later, on the 17th of September, a seventh and last satellite crossed his field of vision. It was situated between the former and the ring; that is, it is the nearest to it of the seven.

But the most remarkable of Herschel's achievements was the discovery of the planet Uranus, and the detection of its satellites.

Those singular meteors, the comets, which flash through heaven with long trails of light, and of old astonished the nations as if they were harbingers of some overwhelming calamity, were also the frequent subjects of our astronomer's investigations. He brought some of his fine and powerful instruments to bear on a comet discovered by Mr. Pigott in 1807, and closely and carefully investigated its physical constitution.

The same writer adds:--

"The light of the head had a bluish-green tint." Was this a real tint, or did the central reddish body, only through contrast, make the surrounding vapour appear to be coloured? Herschel did not examine the question from this point of view.

"The head of the comet appeared to be enveloped at a certain distance, on the side towards the Sun, by a brilliant narrow zone, embracing about a semicircle, and of a yellowish colour. From the two extremities of the semicircle arose, towards the region away from the Sun, two long luminous streaks which limited the tail. Between the brilliant circular semi-ring and the head, the cometary substance appeared to be dark, of great rarity, and very diaphanous.

"The luminous self-ring floated: one day it seemed to be suspended in the diaphanous atmosphere by which the head of the comet was surrounded, at a distance of 322,000 English miles from the nucleus.

"This distance was not constant. The matter of the semi-annular envelope seemed even to be precipitated by slow degrees through the diaphanous atmosphere; finally, it reached the nucleus; the earlier appearances vanished; the comet was reduced to a globular nebula.

"During its period of dissolution, the ring appeared sometimes to have several branches.

"The luminous shreds of the tail apparently underwent rapid, frequent, and considerable variations of length. Herschel discerned symptoms of a rotatory movement both in the comet and its tail; a movement which carried unequal shreds from the centre towards the border, and the border towards the centre. On examining at intervals the same region of the tail--the border, for example--sensible changes of length must have been perceptible; which, however, had no reality in them. Herschel thought that both the comet of 1811 and that of 1807 were self-luminous. The second comet of 1811 appeared to him to shine only by borrowed light. It must be acknowledged that these conjectures did not rest on anything demonstrative.

"In attentively comparing the comet of 1807 with the beautiful comet of 1811, relative to the changes of distance from the Sun, and the modifications resulting thence, Herschel put it beyond doubt that these modifications have something individual in them,--something relative to a special state of the nebulous matter. On one celestial body the changes of distance produce an enormous effect, on another the modifications are insignificant."

We have reproduced these observations by a distinguished French astronomer, in order to show the reader what was the nature, and how great was the importance, of Herschel's labours, and in how remarkable and comprehensive a manner he conducted his survey of the celestial phenomena. We now return to our brief narrative of his life.

Such a life, absorbed in tranquil and incessant studies, presents no curious, romantic, or surprising incidents. It was the life of a reverent, patient, gentle, and devoted man of genius, who dedicated himself to the task of making known the "wondrous works of God" to his fellow-men, and who in all his social and domestic relations was without blot or stain.

It is said, by the highest of all authority, that a prophet is not honoured in his own country. But our astronomer was not without the reward of his work, even in his lifetime. The University of Oxford conferred upon him the illustrious honorary degree of D.C.L. In 1816 he received the Guelphic order of knighthood; and in 1820 he was chosen the first president of the Astronomical Society.

From his sister's diary we gather a few particulars illustrative of his mode of life.

On the 4th of October 1806 she writes:--

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