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Title: Sir William Herschel: His Life and Works

Author: Edward Singleton Holden

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Language: English

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SIR WILLIAM HERSCHEL

HIS LIFE AND WORKS




[Illustration: Sir William Herschel]

SIR WILLIAM HERSCHEL


HIS LIFE AND WORKS

BY

EDWARD S. HOLDEN

UNITED STATES NAVAL OBSERVATORY, WASHINGTON

[Illustration: Coelis Exploratis]



NEW YORK
CHARLES SCRIBNER'S SONS
743 AND 745 BROADWAY
1881



COPYRIGHT, 1880,
BY CHARLES SCRIBNER'S SONS.



PRESS OF J. J. LITTLE & CO.,

NOS. 10 TO 20 ASTOR PLACE, NEW YORK.




Please see the end of the text for TRANSCRIBER'S NOTES




PREFACE.


In the following account of the life and works of Sir WILLIAM HERSCHEL,
I have been obliged to depend strictly upon data already in print--the
_Memoir_ of his sister, his own scientific writings and the memoirs and
diaries of his cotemporaries. The review of his published works will, I
trust, be of use. It is based upon a careful study of all his papers in
the _Philosophical Transactions_ and elsewhere.

A life of HERSCHEL which shall be satisfactory in every particular can
only be written after a full examination of the materials which are
preserved at the family seat in England; but as two generations have
passed since his death, and as no biography yet exists which approaches
to completeness, no apology seems to me to be needed for a
conscientious attempt to make the best use of the scanty material which
we do possess.

This study will, I trust, serve to exhibit so much of his life as
belongs to the whole public. His private life belongs to his family,
until the time is come to let the world know more of the greatest of
practical astronomers and of the inner life of one of its most profound
philosophers,--of a great and ardent mind, whose achievements are and
will remain the glory of England.




CONTENTS.

                                                  PAGE
CHAPTER I.

EARLY YEARS; 1738-1772,                              1


CHAPTER II.

LIFE IN BATH; 1772-1782,                            33


CHAPTER III.

LIFE AT DATCHET, CLAY HALL, AND SLOUGH; 1782-1822,  68


CHAPTER IV.

REVIEW OF THE SCIENTIFIC LABORS OF HERSCHEL,       118


BIBLIOGRAPHY,                                      215


INDEX OF NAMES,                                    235




LIFE AND WORKS

OF

WILLIAM HERSCHEL.




CHAPTER I.

EARLY YEARS; 1738-1772.


Of the great modern philosophers, that one of whom least is known, is
WILLIAM HERSCHEL. We may appropriate the words which escaped him when
the barren region of the sky near the body of _Scorpio_ was passing
slowly through the field of his great reflector, during one of his
sweeps, to express our own sense of absence of light and knowledge:
_Hier ist wahrhaftig ein Loch im Himmel._

HERSCHEL prepared, about the year 1818, a biographical memorandum, which
his sister CAROLINA placed among his papers.

This has never been made public. The only thoroughly authentic sources
of information in possession of the world, are a letter written by
HERSCHEL himself, in answer to a pressing request for a sketch of his
life, and the _Memoir and Correspondence of CAROLINE HERSCHEL_ (London,
1876), a precious memorial not only of his life, but of one which
otherwise would have remained almost unknown, and one, too, which the
world could ill afford to lose. The latter, which has been ably edited
by Mrs. MARY CORNWALLIS HERSCHEL,[1] is the only source of knowledge in
regard to the early years of the great astronomer, and together with the
all too scanty materials to be gained from a diligent search through the
biography of the time, affords the data for those personal details of
his life, habits, and character, which seem to complete the distinct,
though partial conception of him which the student of his philosophical
writings acquires.

The letter referred to was published in the Göttingen Magazine of
Science and Literature, III., 4, shortly after the name of HERSCHEL had
become familiar to every ear through his discovery of _Uranus_, but
while the circumstances of the discovery, and the condition of the
amateur who made it, were still entirely unknown.

The editor (LICHTENBERG) says:

    "Herr HERSCHEL was good enough to send me, some time since, through
    Herr MAGELLAN, copies of his Dissertations on Double Stars, on the
    Parallax of the Fixed Stars, and on a new Micrometer. In the letter
    which conveyed to him my thanks for his gift, I requested him to
    note down a few facts in regard to his life, for publication in this
    magazine, since various accounts, more or less incorrect, had
    appeared in several journals. In answer, I received a very obliging
    letter from him and what follows is that portion of it relating to
    my request, which was sent me with full permission to make it
    public."


                                                "DATCHET, NEAR WINDSOR,
                                                _Nov. 15, 1783._

    "I was born in Hanover, November, 1738. My father, who was a
    musician, destined me to the same profession, hence I was
    instructed betimes in his art. That I might acquire a perfect
    knowledge of the theory as well as of the practice of music, I was
    set at an early age to study mathematics in all its
    branches--algebra, conic sections, infinitesimal analysis, and the
    rest.

    "The insatiable desire for knowledge thus awakened resulted next in
    a course of languages; I learned French, English, and Latin, and
    steadfastly resolved henceforth to devote myself wholly to those
    sciences from the pursuit of which I alone looked for all my future
    happiness and enjoyment. I have never been either necessitated or
    disposed to alter this resolve. My father, whose means were limited,
    and who consequently could not be as liberal to his children as he
    would have desired, was compelled to dispose of them in one way or
    another at an early age; consequently in my fifteenth year I
    enlisted in military service, only remaining in the army, however,
    until I reached my nineteenth year, when I resigned and went over to
    England.

    "My familiarity with the organ, which I had carefully mastered
    previously, soon procured for me the position of organist in
    Yorkshire, which I finally exchanged for a similar situation at Bath
    in 1766, and while here the peculiar circumstances of my post, as
    agreeable as it was lucrative, made it possible for me to occupy
    myself once more with my studies, especially with mathematics. When,
    in the course of time, I took up astronomy, I determined to accept
    nothing on faith, but to see with my own eyes everything which
    others had seen before me. Having already some knowledge of the
    science of optics, I resolved to manufacture my own telescopes, and
    after many continuous, determined trials, I finally succeeded in
    completing a so-called Newtonian instrument, seven feet in length.
    From this I advanced to one of ten feet, and at last to one of
    twenty, for I had fully made up my mind to carry on the improvement
    of my telescopes as far as it could possibly be done. When I had
    carefully and thoroughly perfected the great instrument in all its
    parts, I made systematic use of it in my observations of the
    heavens, first forming a determination never to pass by any, the
    smallest, portion of them without due investigation. This habit,
    persisted in, led to the discovery of the new planet (_Georgium
    Sidus_). This was by no means the result of chance, but a simple
    consequence of the position of the planet on that particular
    evening, since it occupied precisely that spot in the heavens which
    came in the order of the minute observations that I had previously
    mapped out for myself. Had I not seen it just when I did, I must
    inevitably have come upon it soon after, since my telescope was so
    perfect that I was able to distinguish it from a fixed star in the
    first minute of observation.

    "Now to bring this sketch to a close. As the king had expressed a
    desire to see my telescope, I took it by his command to Greenwich,
    where it was compared with the instruments of my excellent friend,
    Dr. MASKELYNE, not only by himself, but by other experts, who
    pronounced it as their opinion that my instrument was superior to
    all the rest. Thereupon the king ordered that the instrument be
    brought to Windsor, and since it there met with marked approval, his
    majesty graciously awarded me a yearly pension, that I might be
    enabled to relinquish my profession of music, and devote my whole
    time to astronomy and the improvement of the telescope. Gratitude,
    as well as other considerations specified by me in a paper presented
    to the Royal Society, of which I am a member, has induced me to call
    the new planet _Georgium Sidus_.

        "'Georgium Sidus.--jam nunc assuesce vocari.'--(_Virgil._)

    And I hope it will retain the name."

We know but little of the family of HERSCHEL. The name is undoubtedly
Jewish, and is found in Poland, Germany, and England. We learn that the
ancestors of the present branch left Moravia about the beginning of the
XVIIth century, on account of their change of religion to Protestantism.
They became possessors of land in Saxony. HANS HERSCHEL, the
great-grandfather of WILLIAM, was a brewer in Pirna (a small town near
Dresden). Of the two sons of HANS, one, ABRAHAM (born in 1651, died
1718), was employed in the royal gardens at Dresden, and seems to have
been a man of taste and skill in his calling. Of his eldest son,
EUSEBIUS, there appears to be little trace in the records of the family.
The second son, BENJAMIN, died in infancy; the third, ISAAC, was born in
1707 (Jan. 14), and was thus an orphan at eleven years of age. ISAAC was
the father of the great astronomer.

He appears to have early had a passionate fondness for music, and this,
added to a distaste for his father's calling, determined his career. He
was taught music by an oboe-player in the royal band, and he also
learned the violin. At the age of twenty-one he studied music for a year
under the Cappelmeister PABRICH, at Potsdam, and in August, 1731, he
became oboist in the band of the Guards, at Hanover. In August, 1732, he
married ANNA ILSE MORITZEN. She appears to have been a careful and busy
wife and mother, possessed of no special faculties which would lead us
to attribute to her care any great part of the abilities of her son.
She could not herself write the letters which she sent to her husband
during his absences with his regiment. It was her firm belief that the
separations and some of the sorrows of the family came from too much
learning; and while she could not hinder the education of the sons of
the family, she prevented their sisters from learning French and
dancing. It is but just to say that the useful accomplishments of
cooking, sewing, and the care of a household, were thoroughly taught by
her to her two daughters. The father, ISAAC, appears to have been of a
different mould, and to him, no doubt, the chief intellectual
characteristics of the family are due. His position obliged him to be
often absent from Hanover, with his regiment, but his hand appears to
have been always present, smoothing over difficulties, and encouraging
his sons to such learning and improvement as was to be had.

His health was seriously injured by the exposures of the campaigns,
and he was left, after the Seven Years' War, with a broken constitution.

After his final return home, in 1760, his daughter gives this record of
him--

    "Copying music employed every vacant moment, even sometimes
    throughout half the night. . . . With my brother [DIETRICH]--now a
    little engaging creature of between four and five years old--he was
    very much pleased, and [on the first evening of his arrival at home]
    before he went to rest, the Adempken (a little violin) was taken
    from the shelf and newly strung, and the daily lessons immediately
    commenced. . . . I do not recollect that he ever desired any other
    society than what he had opportunities of enjoying in many of the
    parties where he was introduced by his profession, though far from
    being of a morose disposition; he would frequently encourage my
    mother in keeping up a social intercourse among a few acquaintances,
    whilst his afternoon hours generally were taken up in giving lessons
    to some scholars at home, who gladly saved him the troublesome
    exertion of walking. . . . He also found great pleasure in seeing
    DIETRICH'S improvement, who, young as he was, and of the most lively
    temper imaginable, was always ready to receive his lessons, leaving
    his little companions with the greatest cheerfulness to go to his
    father, who was so pleased with his performances that he made him
    play a solo on the Adempken in RAKE'S concert, being placed on a
    table before a crowded company, for which he was very much applauded
    and caressed, particularly by an English lady, who put a gold coin
    in his little pocket.

    "It was not long before my father had as many scholars as he could
    find time to attend. And when they assembled at my father's to make
    little concerts, I was frequently called to join the second violin
    in an overture, for my father found pleasure in giving me sometimes
    a lesson before the instruments were laid by, after practising with
    DIETRICH, for I never was missing at those hours, sitting in a
    corner with my knitting and listening all the while."

Here, as in all her writing, CAROLINA is simple, true, direct to
awkwardness, and unconsciously pathetic even in joy.

The family of ISAAC and ANNA HERSCHEL consisted of ten children. Six of
these lived to adult age. They were:

    1. SOPHIA ELIZABETH; born 1733, married GRIESBACH, a musician in the
       Guard, by whom she had children. Five of her sons were afterwards
       musicians at the court, in England, where they obtained places
       through the influence of WILLIAM.

    2. HENRY ANTON JACOB; born 1734, November 20.

    4. FREDERIC WILLIAM (the astronomer) born 1738, November 15.

    6. JOHN ALEXANDER; born 1745, November 13.

    8. CAROLINA LUCRETIA; born 1750, March 16.

    10. DIETRICH; born 1755, September 13.

Of this family group, the important figures to us are WILLIAM,
ALEXANDER, and CAROLINA.

JACOB was organist at the Garrison Church of Hanover in 1753, a member
of the Guards' band in 1755, and first violin in the Hanover Court
Orchestra in 1759. Afterwards he joined his brother WILLIAM in Bath, but
again returned to Hanover. In 1771 he published in Amsterdam his Opus
I., a set of six quartettes, and later, in London, he published two
symphonies and six trios. He appears to have been a clever musician, and
his letters to his younger brother WILLIAM are full of discussion on
points of musical composition, etc. He died in 1792.

DIETRICH, the youngest brother, shared in the musical abilities of his
family, and when only fifteen years old was so far advanced as to be
able to supply his brother JACOB'S place in the Court Orchestra, and to
give his lessons to private pupils. There is no one of the family,
except the eldest daughter, whom we do not know to have possessed marked
ability in music, and this taste descended truly for four generations.
In the letters of Chevalier BUNSEN,[2] he describes meeting, in 1847,
the eldest granddaughter of WILLIAM HERSCHEL, who, he says, "is a
musical genius."

Three members of the family, WILLIAM, ALEXANDER, and CAROLINA, formed a
group which was inseparable for many years, and while the progress of
the lives of ALEXANDER and CAROLINA was determined by the energy and
efforts of WILLIAM, these two lent him an aid without which his career
would have been strangely different. It is necessary to understand a
little better the early life of all three.

The sons of the HERSCHEL family all attended the garrison school in
Hanover until they were about fourteen years old. They were taught the
ordinary rudiments of knowledge--to read, to write, to cipher--and a
knowledge of French and English was added. WILLIAM especially
distinguished himself in his studies, learning French very rapidly, and
studying Latin and arithmetic with his master out of hours. The
household life seems to have been active, harmonious, and intelligent,
especially during the presence of the father, who took a great delight
in the rapid progress of all his sons in music, and who encouraged them
with his companionship in their studies and in their reading on all
intellectual subjects.

From the _Memoir_ of CAROLINA, on which we must depend for our
knowledge of this early life, we take the following paragraph:

    "My brothers were often introduced as solo performers and assistants
    in the orchestra of the court, and I remember that I was frequently
    prevented from going to sleep by the lively criticism on music on
    coming from a concert, or by conversations on philosophical subjects,
    which lasted frequently till morning, in which my father was a
    lively partaker and assistant of my brother WILLIAM, by contriving
    self-made instruments. . . . Often I would keep myself awake that
    I might listen to their animating remarks, for it made _me so happy_
    to see _them so happy_. But generally their conversation would
    branch out on philosophical subjects, when my brother WILLIAM and my
    father often argued with such warmth that my mother's interference
    became necessary, when the names LEIBNITZ, NEWTON, and EULER
    sounded rather too loud for the repose of her little ones, who
    ought to be in school by seven in the morning. But it seems that
    on the brothers retiring to their own room, where they shared
    the same bed, my brother WILLIAM had still a great deal to say; and
    frequently it happened that when he stopped for an assent or reply,
    he found his hearer was gone to sleep, and I suppose it was not till
    then that he bethought himself to do the same.

    "The recollection of these happy scenes confirms me in the belief,
    that had my brother WILLIAM not then been interrupted in his
    philosophical pursuits, we should have had much earlier proofs of
    his inventive genius. My father was a great admirer of astronomy,
    and had some knowledge of that science; for I remember his taking
    me, on a clear frosty night, into the street, to make me acquainted
    with several of the most beautiful constellations, after we had been
    gazing at a comet which was then visible. And I well remember with
    what delight he used to assist my brother WILLIAM in his various
    contrivances in the pursuit of his philosophical studies, among
    which was a neatly turned 4-inch globe, upon which the equator and
    ecliptic were engraved by my brother."

The mechanical genius was not confined to WILLIAM, for we read that
ALEXANDER used often to "sit by us and amuse us and himself by making
all sorts of things out of pasteboard, or contriving how to make a
twelve-hour cuckoo clock go a week." This ability of ALEXANDER'S was
turned later to the best account when he became his brother WILLIAM'S
right hand in the manufacture of reflectors, eye-pieces, and stands in
England. His abilities were great, and a purpose which might otherwise
have been lacking was supplied through the younger brother's ardor in
all that he undertook.

His musical talent was remarkable; he played "divinely" on the
violoncello. He returned to Hanover in 1816, where he lived in
comfortable independence, through the never-failing generosity of his
brother, until his death in 1821. A notice of him in a Bristol paper
says: "Died, March 15, 1821, at Hanover, ALEXANDER HERSCHEL, Esqr., well
known to the public of Bath and Bristol as a performer and elegant
musician; and who for forty-seven years was the admiration of the
frequenters of concerts and theatres of both those cities as principal
violoncello. To the extraordinary merits of Mr. HERSCHEL was united
considerable acquirement in the superior branches of mechanics and
philosophy, and his affinity to his brother, Sir WILLIAM HERSCHEL, was
not less in science than in blood."

We shall learn more of the sister, CAROLINA, as time goes on. Now in
these early years she was a silent and persistent child, growing up with
a feeling that she was uncared for and neglected, and lavishing all her
childish affection, as she did all that of her womanly life, on her
brother WILLIAM. Throughout her long life, "my brother" was WILLIAM,
"my nephew" _his_ son.

The brothers JACOB and WILLIAM were, with their father, members of the
band of the Guards in 1755, when the regiment was ordered to England,
and they were absent from Hanover a year.

WILLIAM (then seventeen years old) went as oboist, and out of his
scanty pay brought back to Hanover, in 1756, only one memento of his
stay--a copy of LOCKE _On the Human Understanding_.

He appears to have served with the Guard during part of the campaign of
1757. His health was then delicate, and his parents "determined to
remove him from the service--a step attended by no small
difficulties."[3]

This "removal" was hurriedly and safely effected, so hurriedly that the
copy of LOCKE was not put in the parcels sent after him to Hamburg by
his mother; "she, dear woman, knew no other wants than good linen and
clothing."

Thus, at last, the young WILLIAM HERSCHEL, the son of an oboe-player in
the King's Guard, is launched in life for himself, in the year 1757, at
the age of nineteen.

All his equipment is the "good linen and clothing," a knowledge of
French, Latin, and English, some skill in playing the violin, the organ,
and the oboe, and an "uncommon precipitancy" in doing what there is to
be done.

A slender outfit truly; but we are not to overlook what he said of
himself on another occasion. "I have, nevertheless, several resources in
view, and do not despair of succeeding pretty well in the end."

From 1757 to 1760--three years--we know nothing of his life. We can
imagine what it was. His previous visit to England had given him a good
knowledge of the language, and perhaps a few uninfluential
acquaintances. On his return he would naturally seek these out, and, by
means of his music, he could gain a livelihood. We first hear of him as
charged with the organization of the music of a corps of the militia of
Durham, under the auspices of the EARL OF DARLINGTON. "La manière dont
il remplit cette mission, le fit connaître avantageusement."[4] The
nature of the service of these militia corps, which were then forming
all over England, is well described in the Autobiography of GIBBON.
Every county-gentleman felt constrained to serve his country,
and the regimental mess-rooms were filled with men of rank and fashion.

In 1760 we hear of him again. He has attracted the notice of those about
him.

    "About the year 1760, as MILLER[5] was dining at Pontefract with
    the officers of the Durham militia, one of them, knowing his love of
    music, told him they had a young German in their band as a performer
    on the hautboy, who had only been a few months in England, and yet
    spoke English almost as well as a native, and who was also an
    excellent performer on the violin; the officer added that if MILLER
    would come into another room, this German should entertain him with
    a solo. The invitation was gladly accepted, and MILLER heard a solo
    of GIARDINI'S executed in a manner that surprised him. He afterwards
    took an opportunity of having some private conversation with the
    young musician, and asked him whether he had engaged himself for any
    long period to the Durham militia. The answer was, 'Only from month
    to month.' 'Leave them, then,' said the organist, 'and come and live
    with me. I am a single man, and think we shall be happy together;
    and, doubtless, your merit will soon entitle you to a more eligible
    situation.' The offer was accepted as frankly as it was made, and
    the reader may imagine with what satisfaction Dr. MILLER
    must have remembered this act of generous feeling when he hears
    that this young German was HERSCHEL, the Astronomer. 'My humble
    mansion,' says MILLER, 'consisted, at that time, but of two rooms.
    However, poor as I was, my cottage contained a library of
    well-chosen books; and it must appear singular that a foreigner who
    had been so short a time in England should understand even the
    peculiarities of the language so well as to fix upon SWIFT for his
    favorite author.'

    "He took an early opportunity of introducing his new friend at
    Mr. CROPLEY'S concerts; the first violin was resigned to him; 'and
    never,' says the organist, 'had I heard the concertos of CORELLI,
    GEMINIANI, and AVISON, or the overtures of HANDEL performed more
    chastely, or more according to the original intention of the
    composers, than by Mr. HERSCHEL. I soon lost my companion; his fame
    was presently spread abroad; he had the offer of pupils, and was
    solicited to lead the public concerts both at Wakefield and Halifax.
    A new organ for the parish church of Halifax was built about this
    time, and HERSCHEL was one of the seven candidates for the
    organist's place. They drew lots how they were to perform in
    succession. HERSCHEL drew the third, the second fell to Dr.
    WAINWRIGHT of Manchester, whose finger was so rapid that old
    SNETZLER, the organ-builder, ran about the church exclaiming:
    '_Te tevel! te tevel! he run over te keys like one cat; he will
    not give my piphes room for to shpeak._' 'During Mr. WAINWRIGHT'S
    performance,' says MILLER, 'I was standing in the middle aisle with
    HERSCHEL. 'What chance have you,' said I, 'to follow this man?' He
    replied, 'I don't know; I am sure fingers will not do.' On which he
    ascended the organ loft, and produced from the organ so uncommon a
    fulness, such a volume of slow, solemn harmony, that I could by no
    means account for the effect. After this short _ex tempore_
    effusion, he finished with the Old Hundredth psalm-tune, which he
    played better than his opponent.

    "'_Ay, ay_,' cried old SNETZLER, '_tish is very goot, very goot
    indeet; I vil luf tish man, for he gives my piphes room for to
    shpeak._' Having afterwards asked Mr. HERSCHEL by what means, in the
    beginning of his performance, he produced so uncommon an effect, he
    replied, 'I told you fingers would not do!' and producing two pieces
    of lead from his waistcoat pocket, 'one of these,' said he,
    'I placed on the lowest key of the organ, and the other upon the
    octave above; thus by accommodating the harmony, I produced the
    effect of four hands, instead of two.'"[6]

The dates in this extract are not so well defined as might be wished.
HERSCHEL had certainly been more than a few months in England at the
time of his meeting with Dr. MILLER, which was probably about 1760. The
appointment as organist at Halifax was in 1765, and the pupils and
public concerts must have filled up the intervening five years. During a
part of this time he lived in Leeds, with the family of Mr. BULMAN, whom
he afterwards provided with a place as clerk to the Octagon Chapel, in
his usual generous manner.

All during his life he was placing some of the less fortunate and
energetic members of his family.

We cannot be too grateful to Dr. MILLER, who, seeing his opportunity,
used it. Their frank friendship does honor to both. HERSCHEL'S
organ-playing, which no doubt had been begun when his brother was the
organist of the garrison chapel at Hanover, must have been perfected at
this time, and it was through his organ-playing that he was able to
leave the needy life in Yorkshire.

He was sure to have emerged sooner or later, but every year spared to
him as a struggling musician was a year saved to Astronomy.

During all this period, a constant correspondence was maintained
between the family at Hanover and the absent son.

Many of WILLIAM'S letters were written in English, and addressed to his
brother JACOB, and treated of such subjects as the Theory of Music, in
which he was already far advanced.

His little sister was still faithful to the memory of her _dearest_
brother, and his father, whose health was steadily declining, became
painfully eager for his return. In 1764 (April 2), he returned to
Hanover on a very brief visit. He was attached to England, he was
prospering there, and he had no inclination towards returning to a life
in Hanover. His sister says:

    "Of the joys and pleasures which all felt at this long-wished-for
    meeting with my--let me say my _dearest_--brother, but a small
    portion could fall to my share; for with my constant attendance at
    church and school, besides the time I was employed in doing the
    drudgery of the scullery, it was but seldom I could make one in the
    group when the family were assembled together.

    "In the first week, some of the orchestra were invited to a concert,
    at which some of my brother WILLIAM'S compositions, overtures, etc.,
    and some of my eldest brother JACOB'S were performed, to the great
    delight of my dear father, who hoped and expected that they would
    be turned to some profit by publishing them, but there was no
    printer who bid high enough.

    "Sunday, the 8th, was the--to me--eventful day of my confirmation,
    and I left home not a little proud and encouraged by my dear brother
    WILLIAM'S approbation of my appearance in my new gown."

The engagement of HERSCHEL at Halifax did not long continue. In 1766 he
obtained an advantageous engagement as oboist at Bath, and soon after
the position of organist at the Octagon Chapel was offered to him and
accepted. This was a great and important change.

Bath was then, as now, one of the most beautiful cities in England, and
the resort of the fashion and rank of the kingdom, who came to take the
waters. It is beautifully situated on both sides of the Avon, and has
many fine walks and public buildings. The aspect of the city is markedly
cheerful and brilliant, owing to the nature of the white stone of which
the principal houses are built, and to the exquisite amphitheatre of
hills in which they lie.

The society was then gay and polite, and HERSCHEL was at once thrown
into a far more intelligent atmosphere than that he had just left in
Yorkshire. It was easy to get new books, to see new faces, to hear new
things. The Assembly Rooms (built in 1771) were noted for their size and
elegance; the theatre was the best out of London.

His position as organist of the fashionable chapel placed him in the
current. His charming and engaging manners made him friends. His talents
brought him admirers and pupils, and pupils brought him money.[7]

He began in 1766 a life of unceasing activity, which continued. In 1768
he published in London a symphony (in C) for two violins, viola, bass,
two oboes, and two horns, and in the same year two military concertos
for two oboes, two horns, two trumpets, and two bassoons.[8] He wrote
pieces for the harp, glees, "catches," and other songs for the
voice. One of these, the _Echo Catch_, was published and had even
considerable vogue.

    A competent musical critic writes to me of this work: "The
    counterpoint is clear and flowing, and is managed with considerable
    taste and effect. It would be difficult to explain the great
    cleverness shown in the construction of the _Catch_ without diagrams
    to illustrate the movements of the parts. It is certainly an
    ingenious bit of musical writing."

When he left Bath (in 1782), many of these musical writings were lost,
in his great haste to take up his new profession. One, specially, his
sister remembers to have written out for the printer, "but he could not
find a moment to send it off, nor answer the printer's letters." This
was a four-part song, "In thee I bear so dear a part." He wrote very
many anthems, chants, and psalm-tunes for the excellent cathedral choir
of the Octagon Chapel. Unfortunately, most of this music is now not to
be found.

A notice of HERSCHEL'S life which appeared in the _European Magazine_
for 1785, January, gives a very lively picture of his life at this
time, and it is especially valuable as showing how he appeared to his
cotemporaries.

    "Although Mr. HERSCHEL loved music to an excess, and made a
    considerable progress in it, he yet determined with a sort of
    enthusiasm to devote every moment he could spare from business to
    the pursuit of knowledge, which he regarded as the sovereign good,
    and in which he resolved to place all his views of future happiness
    in life.". . .

    "His situation at the Octagon Chapel proved a very profitable one,
    as he soon fell into all the public business of the concerts, the
    Rooms, the Theatre, and the oratorios, besides many scholars and
    private concerts. This great run of business, instead of lessening
    his propensity to study, increased it, so that many times, after a
    fatiguing day of fourteen or sixteen hours spent in his vocation, he
    would retire at night with the greatest avidity to _unbend the
    mind_, if it may be so called, with a few propositions in
    MACLAURIN'S _Fluxions_, or other books of that sort."

It was in these years that he mastered Italian and made some progress
in Greek.

    "We may hazard a natural conjecture respecting the course of
    HERSCHEL'S early studies. Music conducted him to mathematics, or,
    in other words, impelled him to study SMITH'S _Harmonics_. Now this
    ROBERT SMITH was the author of _A Complete System of Optics_,
    a masterly work, which, notwithstanding the rapid growth of that
    branch of the science, is not yet wholly superseded. It seems to us
    not unlikely that HERSCHEL, studying the _Harmonics_, conceived a
    reverence for the author, who was at that time still living, so that
    from the _Philosophy of Music_ he passed to the _Optics_, a work on
    which SMITH'S great reputation chiefly rested; and thus undesignedly
    prepared himself for the career on which he was shortly about to
    enter with so much glory."[9]

There is no doubt that this conjecture is a true one. The _Optics_ of
Dr. SMITH is one of the very few books quoted by HERSCHEL throughout his
writings, and there is every evidence of his complete familiarity with
its conclusions and methods; and this familiarity is of the kind which a
student acquires with his early text-books. One other work he quotes in
the same way, LALANDE'S _Astronomy_, and this too must have been deeply
studied.

During the years 1765-1772, while HERSCHEL was following his profession
and his studies at Bath, the family life at Hanover went on in much the
same way.

In 1765 his father ISAAC had a stroke of paralysis, which ended his
violin-playing forever, and forced him to depend entirely upon pupils
and copying of music for a livelihood. He died on March 22, 1767,
leaving behind him a good name, and living in the affectionate
remembrance of his children and of all who knew him.

CAROLINA had now lost her best friend, and transferred to her brother
WILLIAM the affection she had before divided between him and her father.

    "My father wished to give me something like a polished education,
    but my mother was particularly determined that it should be a rough,
    but at the same time a useful one; and nothing farther she thought
    was necessary but to send me two or three months to a sempstress to
    be taught to make household linen. . . . My mother would not consent
    to my being taught French, and my brother Dietrich was even denied a
    dancing-master, because she would not permit my learning along with
    him, though the entrance had been paid for us both; so all my father
    could do for me was to indulge me (and please himself) sometimes
    with a short lesson on the violin, when my mother was either in
    good humor or out of the way. Though I have often felt myself
    exceedingly at a loss for the want of those few accomplishments of
    which I was thus, by an erroneous though well-meant opinion of my
    mother, deprived, I could not help thinking but that she had cause
    for wishing me not to know more than was necessary for being useful
    in the family; for it was her certain belief that my brother WILLIAM
    would have returned to his country, and my eldest brother not have
    looked so high, if they had had a little less learning.

          *       *       *       *       *

    But sometimes I found it scarcely possible to get through with the
    work required, and felt very unhappy that no time at all was left
    for improving myself in music or fancy work, in which I had an
    opportunity of receiving some instruction from an ingenious young
    woman whose parents lived in the same house with us. But the time
    wanted for spending a few hours together could only be obtained by
    our meeting at daybreak, because by the time of the family's rising
    at seven, I was obliged to be at my daily business. Though I had
    neither time nor means for producing anything immediately either for
    show or use, I was content with keeping samples of all possible
    patterns in needlework, beads, bugles, horse-hair, etc., for I could
    not help feeling troubled sometimes about my future destiny; yet I
    could not bear the idea of being turned into an Abigail or
    housemaid, and thought that with the above and such like
    acquirements, with a little notion of music, I might obtain a place
    as governess in some family where the want of a knowledge of French
    would be no objection."

A change was soon to come in her life too; her brother WILLIAM wrote
to propose that she should join him at Bath--

    . . . "to make the trial, if, by his instruction, I might not become
    a useful singer for his winter concerts and oratorios; he advised my
    brother JACOB to give me some lessons by way of beginning; but that
    if, after a trial of two years, we should not find it answer our
    expectation, he would bring me back again. This at first seemed to
    be agreeable to all parties, but by the time I had set my heart upon
    this change in my situation, JACOB began to turn the whole scheme
    into ridicule, and, of course, he never heard the sound of my voice
    except in speaking, and yet I was left in the harassing uncertainty
    whether I was to go or not. I resolved at last to prepare, as far as
    lay in my power, for both cases, by taking, in the first place,
    every opportunity, when all were from home, to imitate, with a gag
    between my teeth, the solo parts of concertos, _shake and all_, such
    as I had heard them play on the violin; in consequence I had gained
    a tolerable execution before I knew how to sing. I next began to
    knit ruffles, which were intended for my brother WILLIAM, in case I
    remained at home--else they were to be JACOB'S. For my mother and
    brother D. I knitted as many cotton stockings as would last two
    years at least."

In August, 1772, her brother arrived at Hanover, to take her back to
England with him. The journey to London was made between August 16th and
26th, and soon after they went together to HERSCHEL'S house, No. 7 New
King's Street, Bath.

FOOTNOTES:

[1] Wife of Major JOHN HERSCHEL, of the Royal Engineers,
grandson of Sir WILLIAM.

[2] Page 127.

[3] _Memoir_ of CAROLINA HERSCHEL, p. 10. Sir GEORGE AIRY,
Astronomer Royal, relates in the _Academy_ that this "removal" was a
desertion, as he was told by the Duke of Sussex that on the first visit
of HERSCHEL to the king, after the discovery of the _Georgium Sidus_,
the pardon of HERSCHEL was handed to him by the king himself, written
out in due form.

[4] FÉTIS; _Biographie universelle des musiciens_, tome V.
(1839) p. 141.

[5] Dr. MILLER, a noted organist, and afterwards historian of
Doncaster.

[6] _The Doctor_; by ROBERT SOUTHEY, edition of 1848, p.
140.

[7] He frequently gave thirty-five and thirty-eight lessons a
week to pupils at this time.

[8] According to FÉTIS. A search for these in London has led
me to the belief that FÉTIS, who is usually very accurate, is here
mistaken, and that these writings are by JACOB HERSCHEL.

[9] _Foreign Quarterly Review_, volume 31.




                           CHAPTER II.

                    LIFE IN BATH; 1772-1782.


It was to a busy life in Bath that HERSCHEL took his sister CAROLINA,
then twenty-two years old. She was a perfectly untried girl, of very
small accomplishments and outwardly with but little to attract. The
basis of her character was the possibility of an unchanging devotion to
one object; for the best years of her life this object was the happiness
and success of her brother WILLIAM, whom she profoundly loved. Her love
was headstrong and full of a kind of obstinate pride, which refused to
see anything but the view she had adopted. As long as her life continued
to be with her dearest brother, all was well with her. She had a noble
aim, and her heart was more than full. Later on, this very singleness of
character brought her other years of wretchedness. It is necessary to
understand the almost spaniel-like allegiance she gave, in order to
comprehend the value which her services were to HERSCHEL. She supplied
him with an aid which was utterly loyal, entire, and devoted. Her
obedience was unquestioning, her reverence amounted almost to adoration.
In their relation, he gave everything in the way of incentive and
initiative, and she returned her entire effort loyally.

At first her business was to gain a knowledge of the language, and to
perfect herself in singing, so that she might become a soloist in the
concerts and oratorios which he was constantly giving.

In the beginning it was not easy.

    . . . "As the season for the arrival of visitors to the baths does
    not begin till October, my brother had leisure to try my capacity for
    becoming a useful singer for his concerts and oratorios, and being
    very well satisfied with my voice, I had two or three lessons every
    day, and the hours which were not spent at the harpsichord, were
    employed in putting me in the way of managing the family. . . .
    On the second morning, on meeting my brother at breakfast, he began
    immediately to give me a lesson in English and arithmetic, and
    showed me the way of booking and keeping accounts of cash received
    and laid out. . . . By way of relaxation we talked of astronomy and
    the bright constellations with which I had made acquaintance during
    the fine nights we spent on the postwagen travelling through Holland.

    "My brother ALEXANDER, who had been some time in England, boarded
    and lodged with his elder brother, and, with myself, occupied the
    attic. The first floor, which was furnished in the newest and most
    handsome style, my brother kept for himself. The front room,
    containing the harpsichord, was always in order to receive his
    musical friends and scholars at little private concerts or
    rehearsals. . . . Sundays I received a sum for the weekly expenses,
    of which my housekeeping book (written in English) showed the amount
    laid out, and my purse the remaining cash. One of the principal
    things required was to market, and about six weeks after coming to
    England I was sent alone among fishwomen, butchers, basket-women,
    etc., and I brought home whatever in my fright I could pick up. . . .
    My brother ALEX., who was now returned from his summer engagement,
    used to watch me at a distance, unknown to me, till he saw me safe
    on my way home. But all attempts to introduce any order in our
    little household proved vain, owing to the servant my brother then
    had. And what still further increased my difficulty was, that my
    brother's time was entirely taken up with business, so that I only
    saw him at meals. Breakfast was at seven o'clock or before--much too
    early for me, who would rather have remained up all night than be
    obliged to rise at so early an hour. . . .

    "The three winter months passed on very heavily. I had to struggle
    against _heimwehe_ (home sickness) and low spirits, and to answer my
    sister's melancholy letters on the death of her husband, by which
    she became a widow with six children. I knew too little English to
    derive any consolation from the society of those who were about me,
    so that, dinner-time excepted, I was entirely left to myself."

So the winter passed.

    "The time when I could hope to receive a little more of my brother's
    instruction and attention was now drawing near; for after Easter,
    Bath becomes very empty, only a few of his scholars, whose families
    were resident in the neighborhood, remaining. But I was greatly
    disappointed; for, in consequence of the harassing and fatiguing
    life he had led during the winter months, he used to retire to bed
    with a basin of milk or glass of water, and SMITH'S _Harmonics_ and
    _Optics_, FERGUSON'S _Astronomy_, etc., and so went to sleep buried
    under his favorite authors; and his first thoughts on rising were
    how to obtain instruments for viewing those objects himself of which
    he had been reading. There being in one of the shops a
    two-and-a-half-foot Gregorian telescope to be let, it was for some
    time taken in requisition, and served not only for viewing the
    heavens, but for making experiments on its construction. . . . It soon
    appeared that my brother was not contented with knowing what former
    observers had seen, for he began to contrive a telescope eighteen or
    twenty feet long (I believe after HUYGHENS' description). . . . I was
    much hindered in my musical practice by my help being continually
    wanted in the execution of the various contrivances, and I had to
    amuse myself with 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. . . . My brother wrote to inquire the price of a reflecting
    mirror for (I believe) a five or six foot telescope. The answer was,
    there were none of so large a size, but a person offered to make one
    at a price much above what my brother thought proper to give. . . .
    About this time he bought of a Quaker, resident at Bath, who had
    formerly made attempts at polishing mirrors, all his rubbish of
    patterns, tools, hones, polishers, unfinished mirrors, etc., but all
    for small Gregorians, and none above two or three inches diameter.

    "But nothing serious could be attempted, for want of time, till the
    beginning of June, when some of my brother's scholars were leaving
    Bath; and then, to my sorrow, I saw almost every room turned into a
    workshop. A cabinet-maker making a tube and stands of all
    descriptions in a handsomely furnished drawing-room; ALEX. putting
    up a huge turning machine (which he had brought in the autumn from
    Bristol, where he used to spend the summer) in a bedroom, for
    turning patterns, grinding glasses, and turning eye-pieces, etc. At
    the same time music durst not lie entirely dormant during the
    summer, and my brother had frequent rehearsals at home, where Miss
    FARINELLI, an Italian singer, was met by several of the principal
    performers he had engaged for the winter concerts."

Finally, in 1774, he had made himself a Gregorian telescope,[10] and
had begun to view the heavens. He was then thirty-six years old.

The writer in the _European Magazine_ describes this period:

    "All this time he continued his astronomical observations, and
    nothing now seemed wanting to complete his felicity, but sufficient
    leisure to enjoy his telescopes, to which he was so much attached,
    that at the theatre he used frequently to run from the harpsichord
    to look at the stars, during the time between the acts."

In an extract from his _Journal No. 1_, now at the rooms of the Royal
Society, may be seen a copy of his first observation of the Nebula of
_Orion_, on March 4, 1774. This was made with his five-and-a-half-foot
Gregorian reflector.

It was at this time (1775), between the acts of the theatre, that he
made his first review of the heavens, with a Newtonian telescope, of an
aperture of four and a half inches and a magnifying power of 222 times.
This telescope was one of the first made by himself. The review
consisted of the examination of every star in the sky of the first,
second, third, and fourth magnitudes, and of all planets visible. There
are no records of these observations now extant, and they are noteworthy
only as a preparation for more serious work.

He was carrying out his resolve to see everything for himself. His
assiduity may be judged of by the fact that between 1774 and 1781
HERSCHEL had observed a single object--the Nebula of _Orion_--no less
than fourteen times.

The success of his first telescopes incited him to new efforts. His
house became a complete _atelier_, where everything that could tend to
excellence in this manufacture was tried and re-tried a hundred
different ways. When a difficulty arose, experiments were begun which
continued till it was conquered. When a success was gained, it was
prosecuted to the utmost.

In 1775 the first seven-foot reflector was made, in 1777 a ten-foot was
finished, in 1778 a "very good" ten-foot took its place. It must not be
thought that the telescopes mentioned were the only ones completed. On
the contrary, they were but the best ones selected out of many.

In 1774 a new house had been engaged, which had "more room for
workshops," and whose roof gave space for observing. The grass-plat near
it was soon utilized to hold the stand of a twenty-foot telescope, which
he had even then projected. His projects were unending, no success was
final; his mind was at the height of activity; his whole effort was
thrown into every undertaking.

The mirrors for all these telescopes were made by hand. Every portion
of the grinding down to rough dimensions, the shaping to something near
the correct form, the polishing till the accurately exact curves were
obtained, all this must be done by hand. The machines for the purpose
were not invented until 1788.[11]

ALEXANDER and WILLIAM worked together at this, but most of the work was
done by the latter. The sister's part was to attend in the workshop and
lend a hand wherever and whenever it was needed.

    . . . "My time was taken up with copying music and practising, besides
    attendance on my brother when polishing, since by way of keeping him
    alive I was constantly obliged to feed him by putting the victuals by
    bits into his mouth. This was once the case when, in order to finish
    a seven-foot mirror, he had not taken his hands from it for sixteen
    hours together. In general he was never unemployed at meals, but was
    always at those times contriving or making drawings of whatever
    came in his mind. Generally I was obliged to read to him whilst
    he was at the turning-lathe, or polishing mirrors, _Don Quixote_,
    _Arabian Nights' Entertainment_, the novels of STERNE, FIELDING,
    etc.; serving tea and supper without interrupting the work with
    which he was engaged, . . . and sometimes lending a hand. I became,
    in time, as useful a member of the workshop as a boy might be to
    his master in the first year of his apprenticeship. . . . But as
    I was to take a part the next year in the oratorios, I had, for a
    whole twelvemonth, two lessons per week from Miss FLEMING, the
    celebrated dancing-mistress, to drill me for a gentlewoman (God
    knows how she succeeded). So we lived on without interruption.
    My brother ALEX. was absent from Bath for some months every summer,
    but when at home he took much pleasure in executing some turning or
    clockmaker's work for his brother."

News from Hanover put a sudden stop, for a time, to all these labors.
The mother wrote, in the utmost distress, to say that DIETRICH had
disappeared from his home, it was supposed with the intention of going
to India "with a young idler not older than himself." His brother
immediately left the lathe at which he was turning an eye-piece in
cocoa-nut, and started for Holland, whence he proceeded to Hanover,
failing to meet his brother, as he expected. Meanwhile the sister
received a letter to say that DIETRICH was "laid up very ill" at an inn
in Wapping. ALEXANDER posted to town, removed him to a lodging, and,
after a fortnight's nursing, brought him to Bath, where, on his brother
WILLIAM'S return, he found him being well cared for by his sister.

About this time another change was made to the house 19 New King Street,
which was the last move in Bath. It was here that the _Georgium Sidus_
was discovered.

The music still went on. The oratorios of the _Messiah_, _Judas
Maccabeus_, and _Samson_ were to be performed under HERSCHEL'S
direction, with an orchestra of nearly one hundred pieces. The scores
and vocal parts of these CAROLINA copied with her own hands, and the
_soprani_ were instructed by her, she being the leading soloist. Along
with the music went the astronomy. Not only were new telescopes made,
but they were made for immediate use.

The variable star _Mira Ceti_ was observed, and a long series of lunar
observations begun.

    "In 1779, 1780, and 1781 I measured the heights of about one hundred
    mountains of the moon, by three different methods.

    "Some of these observations are given in _Philosophical
    Transactions_, vol. LXX., but most remain uncalculated in my journal
    _till some proper opportunity."[12]_

While HERSCHEL was measuring these lunar mountains, in December, 1779,
he made by chance an acquaintance of much value to him. Dr. WILLIAM
WATSON, a Fellow of the Royal Society, distinguished for his researches
in electricity, happened to see him at his telescope, and this led to a
visit and an invitation to HERSCHEL to join the Philosophical Society of
Bath, then forming. This he gladly did, and it was of use to him in many
ways.

He there formed acquaintance with men of his own way of thinking, and he
himself became known. Better than all, he learned to measure himself
with other men, and by his early papers read to the Society, he gained
skill in putting his thoughts before his hearers. This skill he never
lost, and the merely literary art of his memoirs would make his papers
remarkable without their other merits. He is always clear, and in his
early papers especially, he appeals to his particular audience--the
Royal Society--in a way which shows that he is conscious of all its
weaknesses as well as of its dignity. Later, his tone slightly changed.
He became less anxious to win his audience, for he had become an
authority. This knowledge lent a quiet strength to his style, but never
induced the slightest arrogance of spirit or manner.

The Bath Philosophical Society has left no printed proceedings. HERSCHEL
was one of its earliest members, and many papers were communicated to it
by his hand. These appear to have been of a very miscellaneous nature.
Some of them at least would be of the highest interest to us now.

In the _Philosophical Transactions_ for 1789, p. 220, HERSCHEL tells us
that he communicated to that Society "certain mathematical papers"
relating to central forces other than the force of gravity, which are or
may be concerned in the construction of the sidereal heavens. This early
idea was still entertained by HERSCHEL in 1789, and the mathematical
papers referred to must be contained in the _Minutes_ of the Society,
which on its dissolution were torn from the Minute-book and returned to
the writers.

The earliest published writing of HERSCHEL is the answer to the prize
question in the "Ladies' Diary" for 1779, proposed by the celebrated
LANDEN, namely:

    "The length, tension, and weight of a musical string being given,
    it is required to find how many vibrations it will make in a given
    time, when a small given weight is fastened to its middle and
    vibrates with it."

In the _Philosophical Transactions_ of the Royal Society for 1780, are
two papers of his. The title of the first is, _Astronomical Observations
on the Periodical Star in Collo Ceti_, by Mr. WILLIAM HERSCHEL, of Bath.
This was communicated to the Society by Dr. WILLIAM WATSON, Jr., and
was read May 11, 1780, at the same time as the other paper on the
mountains of the moon. It is to be noted that HERSCHEL was at this time
plain "Mr. WILLIAM HERSCHEL, of Bath." It was only in 1786 that he
became "Dr. HERSCHEL," through the Oxford degree of LL.D.

Neither of these two papers is specially remarkable on its purely
astronomical side. The problems examined were such as lay open before
all, and the treatment of them was such as would naturally be suggested.

The second of these two contained, however, a short description of his
Newtonian telescope, and he speaks of it with a just pride: "I believe
that for distinctness of vision this instrument is perhaps equal to any
that was ever made." He was, at least, certain of having obtained
excellence in the making of his instruments.

In his next paper, however, read January 11, 1781, a subject is
approached which shows a different kind of thought. It is the first
obvious proof of the truth of the statement which he made long
afterwards (1811), when he said: "A knowledge of the construction of
the heavens has always been the ultimate object of my observations."

The title of this paper was _Astronomical Observations on the Rotation
of the Planets round their Axes, made with a view to determine whether
the Earth's diurnal motion is perfectly equable_. Here the question is a
difficult and a remote one, and the method adopted for its solution is
perfectly suitable in principle. It marks a step onward from mere
observations to philosophizing upon their results. In practical
astronomy, too, we note an advance. Not only are his results given, but
also careful estimates of the errors to be feared in them, and a
discussion of the sources of such errors. The same volume of the
_Philosophical Transactions_ which contains this paper, also contains
another, _Account of a Comet_, read April 26, 1781. This comet was the
major planet _Uranus_, or, as HERSCHEL named it, _Georgium Sidus_.
He had found it on the night of Tuesday, March 13, 1781. "In examining
the small stars in the neighborhood of H _Geminorum_, I perceived one that
appeared visibly larger than the rest; being struck with its uncommon
appearance, I compared it to H _Geminorum_ and the small star in the
quartile between _Auriga_ and _Gemini_, and finding it so much larger
than either of them, I suspected it to be a comet." The "comet" was
observed over all Europe. Its orbit was computed by various astronomers,
and its distance from the sun was found to be nineteen times that of our
earth. This was no comet, but a new major planet. The discovery of the
amateur astronomer of Bath was the most striking since the invention of
the telescope. It had absolutely no parallel, for every other major
planet had been known from time immemorial.[13]

The effect of the discoveries of GALILEO was felt almost more in the
moral than in the scientific world. The mystic number of the planets was
broken up by the introduction of four satellites to _Jupiter_. That
_Venus_ emulated the phases of our moon, overthrew superstition and
seated the Copernican theory firmly. The discovery of "an innumerable
multitude of fixed stars" in the Milky Way confounded the received
ideas. This was the great mission of the telescope in GALILEO'S hands.

The epoch of mere astronomical discovery began with the detection of the
large satellite of _Saturn_ by HUYGHENS, in 1655. Even then superstition
was not dead. HUYGHENS did not search for more moons, because by that
discovery he had raised the number of known satellites to six,[14] and
because these, with the six planets, made "the perfect number twelve."

From 1671 to 1684 CASSINI discovered four more moons revolving about
_Saturn_. Since 1684 no new body had been added to the solar system.
It was thought complete for nearly a century.

In England, the remarkable discoveries of BRADLEY (1727-62) had been in
the field of practical astronomy, and his example had set the key-note
for further researches. France was just about beginning the brilliant
period of her discoveries in mathematical astronomy, and had no
observatory devoted to investigations like HERSCHEL'S, with the possible
exception of DARQUIER'S and FLAUGERGUES'. The observatories of SCHROETER
and VON HAHN, in Germany, were not yet active. The field which HERSCHEL
was created to fill was vacant, the whole world over. It was especially
so in England. The Royal Observatory at Greenwich, under MASKELYNE,
a skilful observer, whose work was mostly confined to meridian
observations, was no rival to a private observatory like HERSCHEL'S. The
private observatories themselves were but small affairs; those of the
king, at Kew, of Dr. WILSON, at Glasgow, of Mr. AUBERT, at Loampit Hill,
of the Count VON BRUHL, in London, being perhaps the most important.
The whole field was open. What was perhaps more remarkable, there was in
England, during HERSCHEL'S lifetime, no astronomer, public or private,
whose talents, even as an observer, lay in the same direction.

It hardly need be said that as a philosopher in his science, he had then
no rival, as he has had none since. His only associates even, were
MICHELL and WILSON.[15]

Without depreciating the abilities of the astronomers of England, his
cotemporaries, we may fairly say that HERSCHEL stood a great man among a
group of small ones.

Let us endeavor to appreciate the change effected in the state of
astronomy not only in England but in the whole world, simply by the
discovery of _Uranus_. Suppose, for example, that the last planet in our
system had been _Saturn_. No doubt HERSCHEL would have gone on. In spite
of one and another difficulty, he would have made his ten-foot, his
twenty-foot telescopes. His forty-foot would never have been built, and
the two satellites which he found with it might not have been
discovered. Certainly _Mimas_ would not have been. His researches on the
construction of the heavens would have been made; those were in his
brain, and must have been ultimated. The mass of observations of
_Saturn_, of _Jupiter_, of _Mars_, of _Venus_, would have been made and
published. The researches on the sun, on the "invisible rays" of heat,
on comets and nebulæ--all these might have been made, printed, and read.

But these would have gone into the _Philosophical Transactions_ as the
work of an amateur astronomer, "Mr. HERSCHEL, of Bath." They would have
been praised, and they would have been doubted. It would have taken a
whole generation to have appreciated them. They would have been severely
tried, entirely on their merits, and finally they would have stood where
they stand to-day--unrivalled. But through what increased labors these
successes would have been gained! It is not merely that the patronage of
the king, the subsidies for the forty-foot telescope (£4,000), the
comparative ease of HERSCHEL'S life would have been lacking. It is more
than this. It would have been necessary for him to have created the
audience to which he appealed, and to have conquered the most persistent
of enemies--indifference.

Certainly, if HERSCHEL'S mind had been other than it was, the discovery
of _Uranus_, which brought him honors from every scientific society in
the world, and which gave him authority, might have had a hurtful
effect. But, as he was, there was nothing which could have aided his
career more than this startling discovery. It was needed for him. It
completed the solar system far more by affording a free play to a
profoundly philosophical mind, than by occupying the vacant spaces
beyond _Saturn_.

His opportunities would have been profoundly modified, though his
personal worth would have been the same.

    "The Star that from the zenith darts its beams,
    Visible though it be to half the earth,
    Though half a sphere be conscious of its brightness,
    Is yet of no diviner origin,
    No purer essence, than the One that burns
    Like an untended watchfire, on the ridge
    Of some dark mountain; or than those that seem
    Humbly to hang, like twinkling winter lamps,
    Among the branches of the leafless trees."

To show how completely unknown the private astronomer of Bath was at
this time, I transcribe a sentence from BODE'S account of the discovery
of _Uranus_.

    "In the _Gazette Littéraire_ of June, 1781, this worthy man is
    called MERSTHEL; in JULIUS' _Journal Encyclopédique_, HERTSCHEL;
    in a letter from Mr. MASKELYNE to M. MESSIER, HERTHEL; in another
    letter of MASKELYNE'S to Herr MAYER, at Mannheim, HERRSCHELL; M.
    DARQUIER calls him HERMSTEL. What may his name be? He must have been
    born a _German_."[16]

This obscurity did not long continue. The news spread quickly from
fashionable Bath to London. On the 6th of December, 1781, HERSCHEL was
elected a Fellow of the Royal Society, to which he was formally
"admitted" May 30, 1782. He was forty-three years old.

He also received the Copley medal in 1781 for his "discovery of a new
and singular star."[17]

    . . . "He was now frequently interrupted by visitors who were
    introduced by some of his resident scholars, among whom I remember
    Sir HARRY ENGELFIELD, Dr. BLAGDEN, and Dr. MASKELYNE. With the
    latter he was engaged in a long conversation, which to me sounded
    like quarrelling, and the first words my brother said after he was
    gone were: 'That is a devil of a fellow.'. . .

    "I suppose their names were often not known, or were forgotten; for
    it was not till the year 1782 or 1783 that a memorandum of the names
    of visitors was thought of.". . . "My brother now 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 before an intended
    thirty-foot telescope could be completed, for which, between whiles
    (not interrupting the observations with seven, ten, and twenty-foot,
    and writing papers for both the Royal and Bath Philosophical
    Societies), gauges, shapes, weight, etc., 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 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, etc., and sometimes whole papers which were lent him for his
    perusal. Among them was one by Mr. MICHELL 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, etc., or a fire to be kept up, or a dish of
    coffee necessary during a long night's watching, I undertook with
    pleasure what others might have thought a hardship. . . . Since the
    discovery of the _Georgium Sidus_ [March 13, 1781], I believe few
    men of learning or consequence left Bath before they had seen and
    conversed with its discoverer, and thought themselves fortunate in
    finding him at home on their repeated visits. Sir WILLIAM WATSON was
    almost an intimate, for hardly a day passed but he had something to
    communicate from the letters which he received from Sir JOSEPH
    BANKS, and other members of the Royal Society, from which it
    appeared that my brother was expected in town to receive the gold
    medal. The end of November was the most precarious season for
    absenting himself. But Sir WILLIAM WATSON went with him, and it was
    arranged so that they set out with the diligence at night, and by
    that means his absence did not last above three or four days, when
    my brother returned alone, Sir WILLIAM remaining with his father.

    "Now a very busy winter was commencing; for my brother had engaged
    himself to conduct the oratorios conjointly with RONZINI, and had
    made himself answerable for the payment of the engaged performers,
    for his credit ever stood high in the opinion of every one he had to
    deal with. (He lost considerably by this arrangement.) But, though
    at times much harassed with business, the mirror for the thirty-foot
    reflector was never out of his mind, and if a minute could but be
    spared in going from one scholar to another, or giving one the slip,
    he called at home to see how the men went on with the furnace, which
    was built in a room below, even with the garden.

    "The mirror was to be cast in a mould of loam, of which an immense
    quantity was to be pounded in a mortar and sifted through a fine
    sieve. It was an endless piece of work, and served me for many an
    hour's exercise; and ALEX. frequently took his turn at it, for we
    were all eager to do something towards the great undertaking. Even
    Sir WILLIAM WATSON would sometimes take the pestle from me when he
    found me in the work-room, where he expected to find his friend, in
    whose concerns he took so much interest that he felt much
    disappointed at not being allowed to pay for the metal. But I do not
    think my brother ever accepted pecuniary assistance from any one of
    his friends, and on this occasion he declined the offer by saying it
    was paid for already.

    "Among the Bath visitors were many philosophical gentlemen who used
    to frequent the levées at St. James's, when in town. Colonel WALSH,
    in particular, informed my brother that from a conversation he had
    had with His Majesty, it appeared that in the spring he was to come
    with his seven-foot telescope to the king. Similar reports he
    received from many others, but they made no great impression nor
    caused any interruption in his occupation or study, and as soon as
    the season for the concerts was over, and the mould, etc., in
    readiness, a day was set apart for casting, and the metal was in the
    furnace. Unfortunately it began to leak at the moment when ready for
    pouring, and both my brothers and the caster, with his men, were
    obliged to run out at opposite doors, for the stone flooring (which
    ought to have been taken up) flew about in all directions as high as
    the ceiling. Before the second casting was attempted, everything
    which could insure success had been attended to, and a very perfect
    metal was found in the mould.

    "But a total stop and derangement now took place, and nearly six or
    seven months elapsed before my brother could return to the
    undisturbed enjoyment of his instruments and observations. For one
    morning in Passion Week, as Sir WILLIAM WATSON was with my brother,
    talking about the pending journey to town, my eldest nephew arrived
    to pay us a visit, and brought the confirmation that his uncle was
    expected with his instrument in town. . . . We had not one night in
    the week, except Friday, but what was set apart for an oratorio either
    at Bath or Bristol. Soon after Easter, a new organ being erected in
    St. James's Church, it was opened with two performances of the
    'Messiah;' this again took up some of my brother's time.". . .

In May of 1782 HERSCHEL went to London.

    "But when almost double the time had elapsed which my brother could
    safely be absent from his scholars, ALEX., as well as myself, were
    much at a loss how to answer their inquiries, for, from the letters
    we received, we could learn nothing but that he had been introduced
    to the king and queen, and had permission to come to the concerts at
    Buckingham House, where the king conversed with him about
    astronomy."

It was during his absence at this time that the three following letters
were written and received:

    "DEAR LINA:--

    "I have had an audience of His Majesty this morning, and met with a
    very gracious reception. I presented him with the drawing of the
    solar system, and had the honor of explaining it to him and the
    queen. My telescope is in three weeks' time to go to Richmond, and
    meanwhile to be put up at Greenwich, where I shall accordingly carry
    it to-day. So you see, LINA, that you must not think of seeing me in
    less than a month. I shall write to Miss LEE myself; and other
    scholars who inquire for me, you may tell that I cannot wait on them
    till His Majesty shall be pleased to give me leave to return, or
    rather to dismiss me, for till then I must attend. I will also write
    to Mr. PALMER to acquaint him with it.

    "I am in a great hurry, therefore can write no more at present.
    Tell ALEXANDER that everything looks very likely as if I were to stay
    here. The king inquired after him, and after my great speculum. He
    also gave me leave to come to hear the GRIESBACHS play at the
    private concert which he has every evening. My having seen the king
    need not be kept a secret, but about my staying here it will be best
    not to say anything, but only that I must remain here till His
    Majesty has observed the planets with my telescope.

    "Yesterday I dined with Colonel WALSH, who inquired after you. There
    were Mr. AUBERT and Dr. MASKELYNE. Dr. MASKELYNE in public declared
    his obligations to me for having introduced to them the high powers,
    for Mr. AUBERT has so much succeeded with them that he says he looks
    down upon 200, 300, or 400 with contempt, and immediately begins
    with 800. He has used 2,500 very completely, and seen my fine double
    stars with them. All my papers are printing, with the postscript and
    all, and are allowed to be very valuable. You see, LINA, I tell you
    all these things. You know vanity is not my foible, therefore I need
    not fear your censure. Farewell.

                   "I am, your affectionate brother,

                                           "WM. HERSCHEL.


    "Saturday Morning,

         "probably _May 25, 1782_."

                    TO MISS HERSCHEL.

                                    "Monday Evening, _June 3, 1782._

    "DEAR LINA:--

    "I pass my time between Greenwich and London agreeably enough,
    but am rather at a loss for work that I like. Company is not always
    pleasing, and I would much rather be polishing a speculum. Last
    Friday I was at the king's concert to hear GEORGE play. The king
    spoke to me as soon as he saw me, and kept me in conversation for
    half an hour. He asked GEORGE to play a solo-concerto on purpose
    that I might hear him; and GEORGE plays extremely well, is very much
    improved, and the king likes him very much. These two last nights I
    have been star-gazing at Greenwich with Dr. MASKELYNE and Mr.
    AUBERT. We have compared our telescopes together, and mine was found
    very superior to any of the Royal Observatory. Double stars which
    they could not see with their instruments I had the pleasure to show
    them very plainly, and my mechanism is so much approved of that
    Dr. MASKELYNE has already ordered a model to be taken from mine,
    and a stand to be made by it to his reflector. He is, however, now
    so much out of love with his instrument that he begins to doubt
    whether it _deserves_ a new stand.

    "I am introduced to the best company. To-morrow I dine at Lord
    PALMERSTON'S, next day with Sir JOSEPH BANKS, etc., etc. Among
    opticians and astronomers nothing now is talked of but _what they
    call_ my great discoveries. Alas! this shows how far they are
    behind, when such trifles as I have seen and done are called
    _great_. Let me but get at it again! I will make such telescopes,
    and see such things--that is, I will endeavor to do so."


                         TO MISS HERSCHEL.

                                                     "_July 3, 1782._"

    "DEAR CAROLINA:--

    "I have been so much employed that you will not wonder at my not
    writing sooner. The letter you sent me last Monday came very safe to
    me. As Dr. WATSON has been so good as to acquaint you and ALEXANDER
    with my situation, I was still more easy in my silence to you. Last
    night the King, the Queen, the Prince of Wales, the Princess Royal,
    Princess SOPHIA, Princess AUGUSTA, etc., Duke of MONTAGUE, Dr.
    HEBERDEN, M. DE LUC, etc., etc., saw my telescope, and it was a very
    fine evening. My instrument gave general satisfaction. The king has
    very good eyes, and enjoys observations with telescopes exceedingly.

    "This evening, as the king and queen are gone to Kew, the princesses
    were desirous of seeing my telescope, but wanted to know if it was
    possible to see without going out on the grass, and were much
    pleased when they heard that my telescope could be carried into any
    place they liked best to have it. About eight o'clock it was moved
    into the queen's apartments, and we waited some time in hopes of
    seeing _Jupiter_ or _Saturn_. Meanwhile I showed the princesses, and
    several other ladies who were present, the speculum, the
    micrometers, the movements of the telescopes, and other things that
    seemed to excite their curiosity. When the evening appeared to be
    totally unpromising, I proposed an artificial _Saturn_ as an object,
    since we could not have the real one. I had beforehand prepared this
    little piece, as I guessed by the appearance of the weather in the
    afternoon we should have no stars to look at. This being accepted
    with great pleasure, I had the lamps lighted up which illuminated
    the picture of a _Saturn_ (cut out in pasteboard) at the bottom of
    the garden wall. The effect was fine, and so natural that the best
    astronomer might have been deceived. Their royal highnesses and
    other ladies seemed to be much pleased with the artifice.

    "I remained in the queen's apartment with the ladies till about half
    after ten; when in conversation with them I found them extremely
    well instructed in every subject that was introduced, and they
    seemed to be most amiable characters. To-morrow evening they hope to
    have better luck, and nothing will give me greater happiness than to
    be able to show them some of those beautiful objects with which the
    heavens are so gloriously ornamented."

CAROLINA'S diary goes on:

    "Sir WILLIAM WATSON returned to Bath after a fort-night or three
    weeks' stay. From him we heard that my brother was invited to
    Greenwich with the telescope, where he was met by a numerous party
    of astronomical and learned gentlemen, and trials of his instrument
    were made. In these letters he complained of being obliged to lead
    an idle life, having nothing to do but to pass between London and
    Greenwich. Sir WILLIAM received many letters, which he was so kind
    as to communicate to us. By these, and from those to ALEXANDER or to
    me, we learned that the king wished to see the telescope at Windsor.
    At last a letter, dated July 2, arrived from THERESE, and from this
    and several succeeding ones we gathered that the king would not
    suffer my brother to return to his profession again, and by his
    writing several times for a supply of money we could only suppose
    that he himself was in uncertainty about the time of his return.

    "In the last week of July my brother came home, and immediately
    prepared for removing to Datchet, where he had taken a house with a
    garden and grass-plat annexed, quite suitable for the purpose of an
    observing-place. Sir WILLIAM WATSON spent nearly the whole time at
    our house, and he was not the only friend who truly grieved at my
    brother's going from Bath; or feared his having perhaps agreed to no
    very advantageous offers; their fears were, in fact, not without
    reason. . . . The prospect of entering again on the toils of teaching,
    etc., which awaited my brother at home (the months of leisure being
    now almost gone by), appeared to him an intolerable waste of time,
    and by way of alternative he chose to be royal astronomer, with a
    salary of £200 a year. Sir WILLIAM WATSON was the only one to whom
    the sum was mentioned, and he exclaimed, 'Never bought monarch honor
    so cheap!' To every other inquirer, my brother's answer was that the
    king had provided for him."

On the 1st of August, 1782, the family removed to Datchet. The last
musical duty was performed on Whit-Sunday, 1782, in St. Margaret's
Chapel, Bath, when the anthem for the day was of HERSCHEL'S own
composition.

The end of the introductory epoch of his life is reached. Henceforth he
lived in his observatory, and from his forty-fourth year onwards he only
left it for short periods to go to London to submit his classic memoirs
to the Royal Society. Even for these occasions he chose periods of
moonlight, when no observations could be made.

He was a private man no longer. Henceforth he belongs to the whole
world.

FOOTNOTES:

[10] Probably on the model of one of SHORT'S Gregorian
telescopes, which were then the best instruments of the kind.

[11] For a description of the main points of HERSCHEL'S
processes of making reflectors, which will illustrate his strong
mechanical talents, see _Encyclopædia Britannica_, eighth edition,
article _Telescope_.

[12] These have never been published, nor is it likely at this
day, when our measuring instruments are so greatly improved, that they
would be of any material value to science, although of interest as
giving the proofs of HERSCHEL'S assiduity and skill. He was always more
than the maker of telescopes, for he was never content until they were
applied to the problems of astronomy.

[13] ARAGO has implied that if HERSCHEL had directed his
telescope to _Uranus_ only eleven days earlier than he did, this
discovery would have escaped him, since at that time (March 2, 1781) the
planet was at its _station_, and had no motion relative to the star.
This is an entire misconception, since the new planet was detected by
its physical appearance, and not by its motion. Does any one suppose
that "a new and singular star" like this would have been once viewed and
then forgotten?

[14] Four of _Jupiter_, one of the earth, and one of _Saturn_.

[15] JOHN MICHELL had been a member of the Royal Society since
1760: he died in 1793. He was a philosophical thinker, as is shown by
his memoirs on the distances of the stars, and by his invention of the
method for determining the earth's density. It is not certain that he
was personally known to HERSCHEL, although his writings were familiar to
the latter.

ALEXANDER WILSON was Professor of Astronomy at Glasgow, and is chiefly
known to us by his theory of the nature of the solar spots, which was
adopted and enlarged by HERSCHEL. He died in 1786; but the families of
WILSON and HERSCHEL remained close friends.

[16] _Berliner Jahrbuch_, 1784, p. 211. In the _Connaissance
des Tems_ for 1784 he is called "HOROCHELLE."

[17] At the presentation Sir JOSEPH BANKS, the President of the
Royal Society, said: "In the name of the Royal Society I present to you
this gold medal, the reward which they have assigned to your successful
labors, and I exhort you to continue diligently to cultivate those
fields of science which have produced to you a harvest of so much honor.
Your attention to the improvement of telescopes has already amply repaid
the labor which you have bestowed upon them; but the treasures of the
heavens are well known to be inexhaustible. Who can say but your new
star, which exceeds _Saturn_ in its distance from the sun, may exceed
him as much in magnificence of attendance? Who knows what new rings, new
satellites, or what other nameless and numberless phenomena remain
behind, waiting to reward future industry and improvement?"




                             CHAPTER III.

            LIFE AT DATCHET, CLAY HALL, AND SLOUGH; 1782-1822.


The new house at Datchet, which was occupied from 1782 till 1785, was a
source of despair to CAROLINA HERSCHEL, who looked upon its desolate and
isolated condition with a housekeeper's eyes. This was nothing to her
brother, who gayly consented to live upon "eggs and bacon," now that he
was free at last to mind the heavens. The ruinous state of the place had
no terrors in his eyes, for was there not a laundry which would serve as
a library, a large stable which was just the place for the grinding of
mirrors, and a grass-plat for the small twenty-foot reflector?

Here they set to work at astronomy; the brother with the twenty-foot,
the sister aiding him, and at odd times sweeping for comets. In the
course of her life she discovered no less than eight, and five of these
were first seen by her.

       *       *       *       *       *

In 1787 HERSCHEL wrote his paper "On three Volcanoes in the Moon,"
which he had observed in April of that year. In this he mentions
previous observations of the same sort. I do not remember that the
following account of these has ever been put on record in English.
Baron VON ZACH writes from London to BODE:[18]

    "Probably you have heard also of the volcanoes in the moon, which
    HERSCHEL has observed. . . . I will give you an account of it as I
    heard it from his own lips. Dr. LIND, a worthy physician in Windsor,
    who has made himself known through his two journeys in China, and
    who is a friend of our HERSCHEL'S, was with his wife one evening on
    a visit to HERSCHEL in Datchet [1783, May 4]. On this evening there
    was to be an occultation of a star at the moon's dark limb. This was
    observed by HERSCHEL and Doctor LIND. Mrs. LIND wished also to see
    what was occurring, and placed herself at a telescope and watched
    attentively.

    "Scarcely had the star disappeared before Mrs. LIND thought she saw
    it again, and exclaimed that the star had gone in front of, and not
    behind the moon. This provoked a short astronomical lecture on the
    question, but still she would not credit it, because she _saw_
    differently. Finally HERSCHEL stepped to the telescope, and in fact
    he saw a bright point on the dark disc of the moon, which he
    followed attentively. It gradually became fainter and finally
    vanished.". . .

The life at Datchet was not free from its annoyances.

    "Much of my brother's time was taken up in going, when the evenings
    were clear, to the queen's lodge, to show the king, etc., objects
    through the seven-foot. But when the days began to shorten, this was
    found impossible, for the telescope was often (at no small expense
    and risk of damage) obliged to be transported in the dark back to
    Datchet, for the purpose of spending the rest of the night with
    observations on double stars for a second catalogue. My brother was,
    besides, obliged to be absent for a week or ten days, for the
    purpose of bringing home the metal of the cracked thirty-foot
    mirror, and the remaining materials from his work-room. Before the
    furnace was taken down at Bath, a second twenty-foot mirror, twelve
    inches diameter, was cast, which happened to be very fortunate, for
    on the 1st of January, 1783, a very fine one cracked by frost in the
    tube.

    . . . "In my brother's absence from home I was, of course, left alone
    to amuse myself with my own thoughts, which were anything but
    cheerful. I found 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, such as are commonly used in
    a 'finder,' was given me. I was 'to sweep for comets,' and I see, by
    my journal, that I began August 22d, 1782, to write down and
    describe all remarkable appearances I saw in my 'sweeps,' which were
    horizontal. But it was not till the last two months of the same year
    that I felt the least encouragement to spend the star-light 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 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, etc., and when I could have his assistance
    immediately if I found a nebula or cluster of stars, of which I
    intended to give a catalogue; but, at the end of 1783, I had only
    marked fourteen, when my sweeping was interrupted by being employed
    to write down my brother's observations with the large twenty-foot.
    I had, however, the comfort to see that my brother was satisfied
    with my endeavors 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, etc., etc., of which
    something of the kind every moment would occur. For the assiduity
    with which the measurements on the diameter of the _Georgium Sidus_,
    and observations of other planets, double stars, etc., etc., were
    made, was incredible, as may be seen by the various papers that were
    given to the Royal Society in 1783, which papers were written in the
    daytime, or when cloudy nights interfered. Besides this, the
    twelve-inch speculum was perfected before the spring, and many hours
    were spent at the turning-bench, as not a night clear enough for
    observing ever passed but that some improvements were planned for
    perfecting the mounting and motions of the various instruments then
    in use, or some trials were made of new constructed eye-pieces,
    which were mostly executed by my brother'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 (made in
    moonlight nights), 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.

    "The summer months passed in the most active preparation for getting
    the large twenty-foot ready against the next winter. The carpenters
    and smiths of Datchet were in daily requisition, and, as soon as
    patterns for tools and mirrors were ready, my brother went to town
    to have them cast, and, during the three or four months ALEXANDER
    could be absent from Bath, the mirrors and optical parts were nearly
    completed.

    "But that the nights after a day of toil were not given to rest, may
    be seen by the observations on _Mars_, of which a paper, dated
    December 1, 1783, was given to the Royal Society. Some trouble,
    also, was often thrown away, during those nights, in the attempt to
    teach me to remeasure double stars with the same micrometers with
    which former measures had been taken, and the small twenty-foot was
    given me for that purpose. . . . I had also to ascertain their places
    by a transit instrument lent for that purpose by Mr. DALRYMPLE; but,
    after many fruitless attempts, it was seen that the instrument was,
    perhaps, as much in fault as my observations."

In 1783 HERSCHEL says:

    "I have now finished my third review of the heavens. The first was
    made with a Newtonian telescope something less than seven feet focal
    length, a power of 222, and an aperture of four and a half inches.
    It extended only to stars of the first, second, third, and fourth
    magnitudes. My second review was made with an instrument much
    superior to the other, of 85.2 inches focus, 6.2 inches aperture,
    and power 227. It extended to all the stars of HARRIS'S maps and
    the telescopic ones near them, as far as the eighth magnitude. The
    Catalogue of Double Stars and the discovery of the _Georgium Sidus_,
    were the results of that review. The third was with the same
    instrument and aperture, but with a power of 460. This review
    extended to all the stars of FLAMSTEED'S Catalogue, together with
    every small star about them, to the amount of a great many thousands
    of stars. I have, many a night, in the course of eleven or twelve
    hours of observation, carefully and singly examined not less than
    400 celestial objects, besides taking measures, and sometimes
    viewing a particular star for half an hour together."

The fourth review began with the twenty-foot, in 1784.

    "My brother began his series of sweeps when the instrument was yet
    in a very unfinished state, and my feelings were not very
    comfortable when every moment I was alarmed by a crack or fall,
    knowing him to be elevated fifteen feet or more on a temporary
    cross-beam, instead of a safe gallery. The ladders had not even
    their braces at the bottom; and one night, in a very high wind, he
    had hardly touched the ground before the whole apparatus came down.
    Some laboring men were called up to help in extricating the mirror,
    which was, fortunately, uninjured, but much work was cut out for
    carpenters next day. I could give a pretty long list of accidents
    which were near proving fatal to my brother as well as myself. To
    make observations with such large machinery, where all around is in
    darkness, is not unattended with danger, especially when personal
    safety is the last thing with which the mind is occupied; even poor
    PIAZZI did not go home without getting broken shins by falling over
    the rack-bar.

    "In the long days of the summer months many ten and seven foot
    mirrors were finished; there was nothing but grinding and polishing
    to be seen. For ten-foot, several had been cast with ribbed backs,
    by way of experiment, to reduce the weight in large mirrors. In my
    leisure hours I ground seven-foot and plain mirrors from rough to
    fining down, and was _indulged_ with polishing and the last
    finishing of a very beautiful mirror for Sir WILLIAM WATSON.

    "An account of the discoveries made with the twenty-foot and the
    improvements of the mechanical parts of the instrument during the
    winter of 1785 is given with the catalogue of the first 1,000 new
    nebulæ. By which account it must plainly appear that the expenses of
    these improvements, and those which were yet to be made in the
    apparatus of the twenty-foot (which, in fact, proved to be a model
    of a larger instrument), could not be supplied out of a salary of
    £200 a year, especially as my brother's finances had been too much
    reduced during the six months before he received his _first_
    quarterly payment of _fifty pounds_ (which was Michaelmas, 1782).
    Travelling from Bath to London, Greenwich, Windsor, backwards and
    forwards, transporting the telescope, etc., breaking up his
    establishment at Bath and forming a new one near the court, all
    this, even leaving such personal conveniences as he had for many
    years been used to, out of the question, could not be obtained for a
    trifle; a good large piece of ground was required for the use of the
    instruments, and a habitation in which he could receive and offer a
    bed to an astronomical friend, was necessary after a night's
    observation.

    "It seemed to be supposed that enough had been done when my brother
    was enabled to leave his profession that he might have time to make
    and sell telescopes. The king ordered four ten-foot himself, and
    many seven-foot besides had been bespoke, and much time had already
    been expended on polishing the mirrors for the same. But all this
    was only retarding the work of a thirty or forty foot instrument,
    which it was my brother's chief object to obtain as soon as
    possible; for he was then on the wrong side of forty-five, and felt
    how great an injustice he would be doing to himself and to the cause
    of astronomy by giving up his time to making telescopes for other
    observers.

    "Sir WILLIAM WATSON, who often in the lifetime of his father came to
    make some stay with us at Datchet, saw my brother's difficulties,
    and expressed great dissatisfaction. On his return to Bath he met,
    among the visitors there, several belonging to the court, to whom he
    gave his opinion concerning his friend and his situation very
    freely. In consequence of this, my brother had soon after, through
    Sir J. BANKS, the promise that £2,000 would be granted for enabling
    him to make himself an instrument.

    "Immediately every preparation for beginning the great work
    commenced. A very ingenious smith (CAMPION), who was seeking
    employment, was secured by my brother, and a temporary forge erected
    in an upstairs room."

The sale of these telescopes of HERSCHEL'S must have produced a large
sum, for he had made before 1795 more than two hundred seven-feet, one
hundred and fifty ten-feet, and eighty twenty-feet mirrors. For many of
the telescopes sent abroad no stands were constructed. The mirrors and
eye-pieces alone were furnished, and a drawing of the stand sent with
them by which the mirrors could be mounted.

In 1785 the cost of a seven-foot telescope, six and four-tenths inches
aperture, stand, eye-pieces, etc., complete, was two hundred guineas, a
ten-foot was six hundred guineas, and a twenty-foot about 2,500 to 3,000
guineas. He had made four ten-foot telescopes like this for the king.
In 1787 SCHROETER got the mirrors and eye-pieces only for a
four-and-three-quarter-inch reflector for five guineas; those for his
seven-foot telescope were twenty-three guineas. Later a seven-foot
telescope, complete, was sold for one hundred guineas, and the
twenty-five-foot reflector, made for the Madrid observatory, cost them
75,000 francs = $15,000.[19] It was ordered in 1796, but not delivered
for several years, the Spanish government being short of money. For a
ten and a seven foot telescope, the Prince of Canino paid £2,310.

VON MAGELLAN writes to BODE concerning a visit to HERSCHEL:[20]

    "I spent the night of the 6th of January at HERSCHEL'S, in Datchet,
    near Windsor, and had the good luck to hit on a fine evening. He has
    his twenty-foot Newtonian telescope in the open air and mounted in
    his garden very simply and conveniently. It is moved by an
    assistant, who stands below it. . . . Near the instrument is a clock
    regulated to sidereal time. . . . In the room near it sits HERSCHEL'S
    sister, and she has FLAMSTEED'S Atlas open before her. As he gives
    her the word, she writes down the declination and right ascension
    and the other circumstances of the observation. In this way
    HERSCHEL examines the whole sky without omitting the least part. He
    commonly observes with a magnifying power of one hundred and fifty,
    and is sure that after four or five years he will have passed in
    review every object above our horizon. He showed me the book in
    which his observations up to this time are written, and I am
    astonished at the great number of them. Each sweep covers 2° 15' in
    declination, and he lets each star pass at least three times through
    the field of his telescope, so that it is impossible that anything
    can escape him. He has already found about 900 double stars and
    almost as many nebulæ. I went to bed about one o'clock, and up to
    that time, he had found that night four or five new nebulæ. The
    thermometer in the garden stood at 13° Fahrenheit; but, in spite of
    this, HERSCHEL observes the whole night through, except that he
    stops every three or four hours and goes in the room for a few
    moments. For some years HERSCHEL has observed the heavens every hour
    when the weather is clear, and this always in the open air, because
    he says that the telescope only performs well when it is at the same
    temperature as the air. He protects himself against the weather by
    putting on more clothing. He has an excellent constitution, and
    thinks about nothing else in the world but the celestial bodies. He
    has promised me in the most cordial way, entirely in the service of
    astronomy, and without thinking of his own interest, to see to the
    telescopes I have ordered for European observatories, and he will
    himself attend to the preparation of the mirrors."

It was at this time, 1783, May 8, that HERSCHEL married. His wife was
the daughter of Mr. JAMES BALDWIN, a merchant of the city of London, and
the widow of JOHN PITT, Esq. She is described as a lady of singular
amiability and gentleness of character. She was entirely interested in
his scientific pursuits, and the jointure which she brought removed all
further anxiety about money affairs. They had but one child, JOHN
FREDERICK WILLIAM, born March 7, 1792.[21]

       *       *       *       *       *

The house at Datchet became more and more unfit for the needs of the
family, and in June, 1785, a move was made to Clay Hall, in Old Windsor.
The residence here was but short, and finally a last change was made to
Slough on April, 3d, 1786.

The ardor of the work during these years can be judged of by a single
sentence from CAROLINA HERSCHEL'S diary:

    "The last night at Clay Hall was spent in sweeping till daylight,
    and by the next evening the telescope stood ready for observation at
    Slough."

From 1786 until his death, HERSCHEL remained at Slough; his life, truly
speaking, was in his observatory.

It is indeed true, as ARAGO has said in his eloquent tribute to him: "On
peut dire hardiment du jardin et de la petite maison de Slough, que
c'est le lieu du monde où il a été fait le plus de découvertes. Le nom
de ce village ne périra pas; les sciences le transmettront
religieusement à nos derniers neveux."

HERSCHEL'S first contribution to the _Philosophical Transactions_ was
printed in the volume for 1780, his last in that for 1818. Of these
thirty-nine volumes, there are only two (1813 and 1817) which contain no
paper from his hand, and many volumes contain more than one, as he
published no less than sixty-eight memoirs in this place.

And yet it must not be thought that his was an austere and grave
existence. Music, which he loved to enthusiasm, was still a delight to
him. All the more that his devotion was free. The glimpses which we get
of his life with his friends show him always cheerful, ardent, and
devoted. Even in his later years, he had not lost a "boyish earnestness
to explain;" his simplicity and the charm of his manner struck every
one.

"HERSCHEL, you know, and everybody knows, is one of the most pleasing
and well-bred natural characters of the present age," says Dr. BURNEY,
who had opportunity to know.

The portrait which is given in the frontispiece must have been painted
about this time (1788), and the eager, ardent face shows his inner life
far better than any words can do.

Even in his scientific writings, which everything conspired to render
grave and sober, the almost poetic nature of his mind shows forth. In
one of his (unpublished) note-books, now in the Royal Society's library,
I found this entry:

    "640th Sweep--November 28, 1786.--The nebula of _Orion_, which I saw
    by the front view, was so glaring and beautiful that I could not
    think of taking any place of its extent."

He was quite alone under the perfectly silent sky when this was written,
and he was at his post simply to make this and other such observations.
But the sky was beautiful to him, and his faithful sister, CAROLINA,
sitting below, has preserved for us the words as they dropped from his
lips.

On the 11th of January, 1787, HERSCHEL discovered two satellites to
_Uranus_.

After he had well assured himself of their existence, but before he
communicated his discovery to the world, he made this crucial test. He
prepared a sketch of _Uranus_ attended by his two satellites, as it
would appear on the night of February 10, 1787, and when the night
came, "the heavens displayed the original of my drawings, by showing in
the situation I had delineated them _the Georgian planet attended by two
satellites_. I confess that this scene appeared to me with additional
beauty, as the little secondary planets seemed to give a dignity to the
primary one which raises it into a more conspicuous situation among the
great bodies of the solar system.". . .

In a memoir of 1789, he has a few sentences which show the living way
in which the heavens appeared to him:

    "This method of viewing the heavens seems to throw them into a new
    kind of light.

    "They are now seen to resemble a luxuriant garden, which contains
    the greatest variety of productions in different flourishing beds;
    and one advantage we may at least reap from it is, that we can, as
    it were, extend the range of our experience to an immense duration.
    For is it not almost the same thing whether we live successively to
    witness the germination, blooming, foliage, fecundity, fading,
    withering, and corruption of a plant, or whether a vast number of
    specimens selected from every stage through which the plant passes
    in the course of its existence be brought at once to our view?"

The thought here is no less finely expressed than it is profound. The
simile is perfect, if we have the power to separate among the vast
variety each state of being from every other, and if the very luxuriance
of illustration in the heavens does not bewilder and overpower the mind.
It was precisely this discriminating power that HERSCHEL possessed in
perfection.

There is a kind of humor in the way he records a change of opinion:

    "I formerly supposed the surface of _Saturn's_ ring to be rough,
    owing to luminous points like mountains seen on it, till one of
    these was kind enough to venture off the edge of the ring and appear
    as a satellite."

In 1782 he replies with a certain concealed sharpness to the idea that
he used magnifying powers which were too high. There is a tone almost of
impatience, as if he were conscious he was replying to a criticism based
on ignorance:

    "We are told that we gain nothing by magnifying too much. I grant
    it; but shall never believe I magnify too much till by experience I
    find that I can see better with a lower power." (1782.)

By 1786, when he returns to this subject, in answer to a formal request
to explain his use of high magnifiers, he is quite over any irritation,
and treats the subject almost with playfulness:

    "Soon after my first essay of using high powers with the Newtonian
    telescope, I began to doubt whether an opinion which has been
    entertained by several eminent authors, 'that vision will grow
    indistinct when the optic pencils are less than the fiftieth part of
    an inch,' would hold good in all cases. I perceived that according
    to this criterion I was not entitled to see distinctly with a power
    of much more than about 320 in a seven-foot telescope of an aperture
    of six and four-tenths inches, whereas in many experiments I found
    myself very well pleased with magnifiers which far exceeded such
    narrow limits. This induced me, as it were, by way of apology to
    myself for seeing well where I ought to have seen less distinctly,
    to make a few experiments."

It is needless to say that these experiments proved that from the point
of view taken by HERSCHEL, he was quite right, and that his high powers
had numerous valuable applications. He goes on to say:

    "Had it not been for a late conversation with some of my highly
    esteemed and learned friends, I might probably have left the papers
    on which these experiments were recorded, among the rest of those
    that are laid aside, when they have afforded me the information I
    want."

The last sentence seems to be a kind of notice to his learned friends
that there is yet more unsaid. As a warning to those to whose criticisms
he had replied, he gives them this picture of the kind of assiduity
which will be required, if some of his observations on double stars are
to be repeated:

    "It is in vain to look for these stars if every circumstance is not
    favorable. The observer as well as the instrument must have been
    long enough out in the open air to acquire the same temperature. In
    very cold weather an hour at least will be required." (1782.)

We may gain some further insight into his character from the following
chance extracts from his writings:

    "I have all along had truth and reality in view as the sole object
    of my endeavors." (1782.)

    "Not being satisfied when I thought it possible to obtain more
    accurate measures, I employed [a more delicate apparatus]." (1783.)

    "To this end I have already begun a series of observations upon
    several zones of double stars, and should the result of them be
    against these conjectures, I shall be the first to point out their
    fallacy." (1783.)

    "There is a great probability of succeeding still farther in this
    laborious but delightful research, so as to be able at last to say
    not only how much the annual parallax _is not_, but how much it
    really _is_." (1782.)

The nature of his philosophizing, and the limits which he set to
himself, may be more clearly seen in further extracts:

    "By taking more time [before printing these observations] I should
    undoubtedly be enabled to speak more confidently of the _interior_
    _construction of the heavens_, and of its various _nebulous_ and
    sidereal strata. As an apology for this prematurity it may be said
    that, the end of all discoveries being communication, we can never
    be too ready in giving facts and observations, whatever we may be in
    reasoning upon them." (1785.)

    "In an investigation of this delicate nature we ought to avoid two
    opposite extremes. If we indulge a fanciful imagination, and build
    worlds of our own, we must not wonder at our going wide from the
    path of truth and nature. On the other hand, if we add observation
    to observation without attempting to draw not only certain
    conclusions but also conjectural views from them, we offend against
    the very end for which only observations ought to be made. I will
    endeavor to keep a proper medium, but if I should deviate from that,
    I could wish not to fall into the latter error." (1785.)

    "As observations carefully made should always take the lead of
    theories, I shall not be concerned if what I have to say contradicts
    what has been said in my last paper on this subject." (1790.)

No course of reasoning could be more simple, more exact, more profound,
and more beautiful than this which follows:

    "As it has been shown that the spherical figure of a cluster is
    owing to the action of central powers, it follows that those
    clusters which, _cæteris paribus_, are the most complete in this
    figure, must have been the longest exposed to the action of these
    causes. Thus the maturity of a sidereal system may be judged from
    the disposition of the component parts.

    "Hence planetary nebulæ may be looked on as very aged. Though we
    cannot see any individual nebula pass through all its stages of
    life, we can select particular ones in each peculiar stage." (1789.)

There is something almost grandiose and majestic in his statement of
the ultimate destiny of the Galaxy:

                  "To him the fates were known
             Of orbs dim hovering on the skirts of space."

    "--Since the stars of the Milky Way are permanently exposed to the
    action of a power whereby they are irresistibly drawn into groups,
    we may be certain that from mere clustering stars they will be
    gradually compressed, through successive stages of accumulation,
    till they come up to what may be called the ripening period of the
    globular form, and total insulation; from which it is evident that
    the Milky Way must be finally broken up and cease to be a stratum of
    scattered stars.

    "The state into which the incessant action of the clustering power
    has brought it at present, is a kind of chronometer that may be used
    to measure the time of its past and future existence; and although
    we do not know the rate of going of this mysterious chronometer, it
    is nevertheless certain that since the breaking up of the Milky Way
    affords a proof that it cannot last forever, it equally bears
    witness that its past duration cannot be admitted to be infinite."
    (1814.)

HERSCHEL'S relations with his cotemporaries were usually of the most
pleasant character, though seldom intimate. This peace was broken but by
one unpleasant occurrence. In the _Philosophical Transactions_ for 1792,
SCHROETER had communicated a series of observations made with one of
HERSCHEL'S own telescopes on the atmospheres of _Venus_, the Moon, etc.
It was not only an account of phenomena which had been seen; it was
accompanied by measures, and the computations based on these led to
heights and dimensions for mountains on _Venus_ which were, to say the
least, extravagant. The adjective will not seem too strong when we say
that the very existence of the mountains themselves is to-day more than
doubtful.

The appearances seen by SCHROETER were described by him in perfectly
good faith, and similar ones have been since recorded. His reasoning
upon them was defective, and the measures which he made were practically
valueless. This paper, printed in the _Transactions_ of the Royal
Society, to which SCHROETER had not before contributed, appears to have
irritated HERSCHEL.

No doubt there were not wanting members of his own society who hinted
that on the Continent, too, there were to be found great observers, and
that here, at least, HERSCHEL had been anticipated even in his own
field. I have always thought that the memoir of HERSCHEL which appeared
in the next volume of the _Transactions_ (1793), _Observations on the
Planet Venus_, was a rejoinder intended far more for the detractors at
home than for the astronomer abroad. The review is conceived in a severe
spirit. The first idea seems to be to crush an opposition which he
feels. The truth is established, but its establishment is hardly the
_first_ object.

It seems as if HERSCHEL had almost allowed himself to be forced into a
position of arrogance, which his whole life shows was entirely foreign
to his nature. All through the review he does not once mention
SCHROETER'S name. He says:

    "A series of observations on _Venus_, begun by me in April, 1777,
    has been continued down to the present time. . . . The result of my
    observations would have been communicated long ago if I had not
    flattered myself with the hope of some better success concerning the
    diurnal motion of _Venus_, which has still eluded my constant
    attention as far as concerns its period and direction. . . . Even at
    this present time I should hesitate to give the following extracts
    if it did not seem incumbent on me to examine by what accident I
    came to overlook mountains in this planet of such enormous height as
    to exceed four, five, or even six times the perpendicular height of
    Chimboraço, the highest of our mountains. . . . The same paper contains
    other particulars concerning _Venus_ and _Saturn_. All of which
    being things of which I have never taken any notice, it will not be
    amiss to show, by what follows, that neither want of attention, nor
    a deficiency of instruments, would occasion my not perceiving these
    mountains of more than twenty-three miles in height, this jagged
    border of _Venus_, and these flat, spherical forms on _Saturn_."

The reply of SCHROETER (1795) is temperate and just. It does him honor,
and he generously gives full justice to his critic.

It would hardly be worth while to mention this slight incident if it
were not that during these years there certainly existed a feeling
that HERSCHEL undervalued the labors of his cotemporaries.

This impression was fostered no doubt by his general habit of not
quoting previous authorities in the fields which he was working.

A careful reading of his papers will, I think, show that his definite
indebtedness to his _cotemporaries_ was vanishingly small. The work of
MICHELL and WILSON he alludes to again and again, and always with
appreciation. Certainly he seems to show a vein of annoyance that the
papers of CHRISTIAN MAYER, _De novis in coelo sidereo phænomenis_
(1779), and _Beobachtungen von Fixsterntrabanten_ (1778), should have
been quoted to prove that the method proposed by HERSCHEL in 1782 for
ascertaining the parallax of the fixed stars by means of observations of
those which were double, was not entirely original with himself.

There is direct proof that it was so,[22] and if this was not
forthcoming it would be unnecessary, as he has amply shown in his
Catalogue of Double Stars. One is reminded of his remarks on the use of
the high magnifying powers by the impatience of his comments.

His proposal to call the newly discovered minor planets _asteroids_
(1802) was received as a sign that he wished to discriminate between the
discoveries of PIAZZI and OLBERS and his own discovery of URANUS.[23]

He takes pains to quietly put this on one side in one of his papers,
showing that he was cognizant of the existence of such a feeling.

I am tempted to resurrect from a deserved obscurity a notice of
HERSCHEL'S _Observations on the Two Lately Discovered Celestial Bodies_
(_Philosophical Transactions_, 1802), printed in the first volume
of the _Edinburgh Review_, simply to show the kind of envy to which even
he, the glory of England, was subject.

The reviewer sets forth the principal results of HERSCHEL'S
observations, and, after quoting his definition of the new term
asteroid, goes on to say:

    "If a new name must be found, why not call them by some appellation
    which shall, in some degree, be descriptive of, or at least
    consistent with, their properties? Why not, for instance, call them
    _Concentric Comets_, or _Planetary Comets_, or _Cometary Planets_?
    or, if a single term must be found, why may we not coin such a
    phrase as _Planetoid_ or _Cometoid_?"

Then follows a general arraignment of HERSCHEL'S methods of expression
and thought, as distinguished from his powers of mere observation. This
distinction, it may be said, exists only in the reviewer's mind; there
was no such distinction in fact. If ever a series of observations was
directed by profound and reasonable thought, it was HERSCHEL'S own.

    "Dr. HERSCHEL'S passion for coining words and idioms has often
    struck us as a weakness wholly unworthy of him. The invention of a
    name is but a poor achievement for him who has discovered whole
    worlds. Why, for instance, do we hear him talking of the
    _space-penetrating power_ of his instrument--a compound epithet and
    metaphor which he ought to have left to the poets, who, in some
    future age, shall acquire glory by celebrating his name. The other
    papers of Dr. HERSCHEL, in the late volumes of the _Transactions_,
    do not deserve such particular attention. His catalogue of 500 new
    nebulæ, though extremely valuable to the practical astronomer, leads
    to no general conclusions of importance, and abounds with the
    defects which are peculiar to the Doctor's writings--a great
    prolixity and tediousness of narration--loose and often
    unphilosophical reflections, which give no very favorable idea of
    his scientific powers, however great his merit may be as an
    observer--above all, that idle fondness for inventing names without
    any manner of occasion, to which we have already alluded, and a use
    of novel and affected idioms.

       *       *       *       *       *

    "To the speculations of the Doctor on the nature of the Sun, we have
    many similar objections; but they are all eclipsed by the grand
    absurdity which he has there committed, in his hasty and erroneous
    theory concerning the influence of the solar spots on the price of
    grain. Since the publication of Gulliver's voyage to Laputa, nothing
    so ridiculous has ever been offered to the world. We heartily wish
    the Doctor had suppressed it; or, if determined to publish it, that
    he had detailed it in language less confident and flippant."

One is almost ashamed to give space and currency to a forgotten attack,
but it yields a kind of perspective; and it is instructive and perhaps
useful to view HERSCHEL'S labors from all sides, even from wrong and
envious ones.

The study of the original papers, together with a knowledge of the
circumstances in which they were written, will abundantly show that
HERSCHEL'S ideas sprung from a profound meditation of the nature of
things in themselves. What the origin of trains of thought prosecuted
for years may have been we cannot say, nor could he himself have
expressed it. A new path in science was to be found out, and he found
it. It was not in his closet, surrounded by authorities, but under the
open sky, that he meditated the construction of the heavens. As he says,
"My situation permitted me not to consult large libraries; nor, indeed,
was it very material; for as I intended to view the heavens myself,
Nature, that great volume, appeared to me to contain the best
catalogue."

His remarkable memoirs on the invisible and other rays of the solar
spectrum were received with doubt, and with open denial by many of the
scientific bodies of Europe. The reviews and notices of his work in this
direction were often quite beyond the bounds of a proper scientific
criticism; but HERSCHEL maintained a dignified silence. The discoveries
were true, the proofs were open to all, and no response was needed from
him. He may have been sorely tempted to reply, but I am apt to believe
that the rumors that reached him from abroad and at home did not then
affect him as they might have done earlier. He was at his grand
climacteric, he had passed his sixty-third year, his temper was less
hasty than it had been in his youth, and his nerves had not yet received
the severe strain from whose effects he suffered during the last years
of his life.

       *       *       *       *       *

We have some glimpses of his personal life in the reminiscences of him
in the _Diary and Letters_ of Madame D'ARBLAY, who knew him well:

    "1786.--In the evening Mr. HERSCHEL came to tea. I had once seen
    that very extraordinary man at Mrs. DE LUC'S, but was happy to see
    him again, for he has not more fame to awaken curiosity than sense
    and modesty to gratify it. He is perfectly unassuming, yet openly
    happy, and happy in the success of those studies which would render
    a mind less excellently formed presumptuous and arrogant.

    "The king has not a happier subject than this man, who owes it
    wholly to His Majesty that he is not wretched; for such was his
    eagerness to quit all other pursuits to follow astronomy solely,
    that he was in danger of ruin, when his talents and great and
    uncommon genius attracted the king's patronage. He has now not only
    his pension, which gives him the felicity of devoting all his time
    to his darling study, but he is indulged in license from the king to
    make a telescope according to his new ideas and discoveries, that is
    to have no cost spared in its construction, and is wholly to be paid
    for by His Majesty.

    "This seems to have made him happier even than the pension, as it
    enables him to put in execution all his wonderful projects, from
    which his expectations of future discoveries are so sanguine as to
    make his present existence a state of almost perfect enjoyment.
    Mr. LOCKE himself would be quite charmed with him.

    "He seems a man without a wish that has its object in the
    terrestrial globe. At night Mr. HERSCHEL, by the king's command,
    came to exhibit to His Majesty and the royal family the new comet
    lately discovered by his sister, Miss HERSCHEL; and while I was
    playing at piquet with Mrs. SCHWELLENBURG, the Princess AUGUSTA came
    into the room and asked her if she chose to go into the garden and
    look at it. She declined the offer, and the princess then made it to
    me. I was glad to accept it for all sorts of reasons. We found him
    at his telescope. The comet was very small, and had nothing grand or
    striking in its appearance; but it is the first lady's comet, and I
    was very desirous to see it. Mr. HERSCHEL then showed me some of his
    new discovered universes, with all the good humor with which he
    would have taken the same trouble for a brother or a sister
    astronomer; there is no possibility of admiring his genius more than
    his gentleness."

    "_1786, December 30th_.--This morning my dear father carried me to
    Dr. HERSCHEL. That great and very extraordinary man received us
    almost with open arms. He is very fond of my father, who is one of
    the council of the Royal Society this year, as well as himself. . . .
    At this time of day there was nothing to see but his instruments;
    those, however, are curiosities sufficient. . . . I wished very much
    to have seen his sister, . . . but she had been up all night, and
    was then in bed."

    "_1787, September_.--Dr. HERSCHEL is a delightful man; so
    unassuming with his great knowledge, so willing to dispense it to
    the ignorant, and so cheerful and easy in his general manners, that,
    were he no genius, it would be impossible not to remark him as a
    pleasing and sensible man."

    "_1788, October 3d_.--We returned to Windsor at noon, and Mrs. DE
    LUC sent me a most pressing invitation to tea and to hear a little
    music. Two young ladies were to perform at her house in a little
    concert. Dr. HERSCHEL was there, and accompanied them very sweetly
    on the violin; his new-married wife was with him, and his sister.
    His wife seems good-natured; she was rich, too! and astronomers are
    as able as other men to discern that gold can glitter as well as
    stars."


                    DR. BURNEY TO MADAME D'ARBLAY.

                                             "CHELSEA COLLEGE,

                                                 _September 28, 1798_.

    "*   *   *   *   *

    "I drove through Slough in order to ask at Dr. HERSCHEL'S door when
    my visit would be least inconvenient to him--that night or next
    morning. The good soul was at dinner, but came to the door himself,
    to press me to alight immediately and partake of his family repast;
    and this he did so heartily that I could not resist.

            *       *       *       *       *       *       *

    "I expected (not knowing that HERSCHEL was married) only to have
    found Miss HERSCHEL; but there was a very old lady, the mother, I
    believe, of Mrs. HERSCHEL, who was at the head of the table herself,
    and a Scots lady (a Miss WILSON, daughter of Dr. WILSON, of Glasgow,
    an eminent astronomer), Miss HERSCHEL, and a little boy. They
    rejoiced at the accident which had brought me there, and hoped I
    would send my carriage away and take a bed with them. They were
    sorry they had no stables for my horses.

    "We soon grew acquainted--I mean the ladies and I--and before dinner
    was over we seemed old friends just met after a long absence. Mrs.
    HERSCHEL is sensible, good-humored, unpretending, and well bred;
    Miss HERSCHEL all shyness and virgin modesty; the Scots lady
    sensible and harmless; and the little boy entertaining, promising,
    and comical. HERSCHEL, you know, and everybody knows, is one of the
    most pleasing and well-bred natural characters of the present age,
    as well as the greatest astronomer.

    "Your health was drunk after dinner (put that into your pocket), and
    after much social conversation and a few hearty laughs, the ladies
    proposed to take a walk, in order, I believe, to leave HERSCHEL and
    me together. We walked and talked round his great telescopes till it
    grew damp and dusk, then retreated into his study to philosophize.

       *       *       *       *       *

    "He made a discovery to me, which, had I known it sooner, would have
    overset me, and prevented my reading any part of my work.[24] He
    said that he had almost always had an aversion to poetry, which he
    regarded as the arrangement of fine words, without any useful
    meaning or adherence to truth; but that when truth and science were
    united to these fine words, he liked poetry very well."


                         1798, December 10.

                    DR. BURNEY TO MADAME D'ARBLAY.

    "HERSCHEL has been in town for short spurts, and back again two or
    three times, leaving Mrs. HERSCHEL behind (in town) to transact law
    business. I had him here two whole days."

    The reading of the manuscript of the _Poetical History of Astronomy_
    was continued, "and HERSCHEL was so humble as to confess that I
    knew more of the history of astronomy than he did, and had surprised
    him with the mass of information I had got together.

    "He thanked me for the entertainment and instruction I had given
    him. 'Can anything be grander?' and all this before he knows a word
    of what I have said of himself--all his discoveries, as you may
    remember, being kept back for the twelfth and last book."


                    DR. BURNEY TO MADAME D'ARBLAY.

                             "SLOUGH, _Monday morning._ _July 22, 1799_,
                                 in bed at Dr. HERSCHEL'S, half-past
                                 five, where I can neither sleep nor lie
                                 idle.

    "My Dear Fanny:--I believe I told you on Friday that I was going to
    finish the perusal of my astronomical verses to the great astronomer
    on Saturday.

       *       *       *       *       *

    "After tea Dr. HERSCHEL proposed that we two should retire into a
    quiet room in order to resume the perusal of my work, in which no
    progress has been made since last December. The evening was
    finished very cheerfully; and we went to our bowers not much out of
    humor with each other or the world. . . . After dinner we all agreed
    to go to the terrace [at Windsor]--Mr., Mrs., and Miss H., with
    their nice little boy, and three young ladies. Here I met with
    almost everybody I wished and expected to see previous to the
    king's arrival.

       *       *       *       *       *

    "But now here comes Will, and I must get up, and make myself up to
    go down to the perusal of my last book, entitled _Herschel_. So
    good-morrow."


                                                "CHELSEA, _Tuesday._

    "Not a moment could I get to write till now. . . . I must tell you
    that HERSCHEL proposed to me to go with him to the king's concert at
    night, he having permission to go when he chooses, his five nephews
    (GRIESBACHS) making a principal part of the band. 'And,' says he,
    'I know you will be welcome.'"

An intimacy was gradually established between HERSCHEL and Dr. BURNEY.
They saw each other often at the meetings of the Royal Society, and
HERSCHEL frequently stayed at the doctor's house. "On the first evening
HERSCHEL spent at Chelsea, when I called for my ARGAND lamp, HERSCHEL,
who had not seen one of those lamps, was surprised at the great effusion
of light, and immediately calculated the difference between that and a
single candle, and found it sixteen to one."[25]

In 1793 we find HERSCHEL as a witness for his friend JAMES WATT, in the
celebrated case of WATT _vs._ BULL, which was tried in the Court of
Common Pleas. And from MUIRHEAD'S Life of WATT, it appears that HERSCHEL
visited WATT at Heathfield in 1810.

A delightful picture of the old age of HERSCHEL is given by the poet
CAMPBELL,[26] whose nature was fitted to perceive the beauties of a
grand and simple character like HERSCHEL'S:


                                      "[BRIGHTON], _September 15, 1813_.

    . . . "I wish you had been with me the day before yesterday, when you
    would have joined me, I am sure, deeply in admiring a great, simple,
    good old man--Dr. HERSCHEL. Do not think me vain, or at least put up
    with my vanity, in saying that I almost flatter myself I have made
    him my friend. I have got an invitation, and a pressing one, to go
    to his house; and the lady who introduced me to him, says he spoke
    of me as if he would really be happy to see me. . . . I spent all
    Sunday with him and his family. His son is a prodigy in sciences,
    and fond of poetry, but very unassuming. . . . Now, for the old
    astronomer himself. His simplicity, his kindness, his anecdotes, his
    readiness to explain--and make perfectly conspicuous too--his own
    sublime conceptions of the universe are indescribably charming. He
    is seventy-six, but fresh and stout; and there he sat, nearest the
    door, at his friend's house, alternately smiling at a joke, or
    contentedly sitting without share or notice in the conversation.
    Any train of conversation he follows implicitly; anything you ask he
    labors with a sort of boyish earnestness to explain.

    "I was anxious to get from him as many particulars as I could about
    his interview with BUONAPARTE.[27] The latter, it was reported, had
    astonished him by his astronomical knowledge.

    "'No,' he said, 'the First Consul did surprise me by his quickness
    and versatility on all subjects; but in science he seemed to know
    little more than any well-educated gentleman, and of astronomy much
    less for instance than our own king. His general air,' he said, 'was
    something like affecting to know more than he did know.' He was
    high, and tried to be great with HERSCHEL, I suppose, without
    success; and 'I remarked,' said the astronomer, 'his hypocrisy in
    concluding the conversation on astronomy by observing how all these
    glorious views gave proofs of an Almighty Wisdom.' I asked him if he
    thought the system of LAPLACE to be quite certain, with regard to
    the total security of the planetary system from the effects of
    gravitation losing its present balance? He said, No; he thought by
    no means that the universe was secured from the chance of sudden
    losses of parts.

    "He was convinced that there had existed a planet between _Mars_
    and _Jupiter_, in our own system, of which the little asteroids, or
    planetkins, lately discovered, are indubitably fragments; and
    'Remember,' said he, 'that though they have discovered only four of
    those parts, there will be thousands--perhaps thirty thousand
    more--yet discovered.' This planet he believed to have been lost by
    explosion.

    "With great kindness and patience he referred me, in the course of
    my attempts to talk with him, to a theorem in NEWTON'S 'Principles
    of Natural Philosophy' in which the time that the light takes to
    travel from the sun is proved with a simplicity which requires but a
    few steps in reasoning. In talking of some inconceivably distant
    bodies, he introduced the mention of this plain theorem, to remind
    me that the progress of light could be measured in the one case as
    well as the other. Then, speaking of himself, he said, with a
    modesty of manner which quite overcame me, when taken together with
    the greatness of the assertion: 'I have looked _further into space
    than ever human being did before me_. I have observed stars, of
    which the light, it can be proved, must take two millions of years
    to reach this earth.'

    "I really and unfeignedly felt at this moment as if I had been
    conversing with a supernatural intelligence. 'Nay, more,' said he,
    'if those distant bodies had ceased to exist two millions of years
    ago, we should still see them, as the light would travel after the
    body was gone. . . .' These were HERSCHEL'S words; and if you had
    heard him speak them, you would not think he was apt to tell more
    than the truth.

    "After leaving HERSCHEL I felt elevated and overcome; and have in
    writing to you made only this memorandum of some of the most
    interesting moments of my life."

CAMPBELL'S conscientious biographer appears to have felt that the value
of this charming account of his interview with HERSCHEL was in its
report of astronomical facts and opinions, and he adds a foot-note to
explain that "HERSCHEL'S opinion never amounted to more than
_hypothesis_ having some degree of probability. Sir JOHN HERSCHEL
remembers his father saying, 'If that hypothesis were true, and _if_ the
planet destroyed were as large as the earth, there must have been at
least thirty-thousand such fragments,' but always as an hypothesis--he
was never heard to declare any degree of conviction that it was so."

For us, the value of this sympathetic account of a day in HERSCHEL'S
life is in its conception of the simplicity, the modesty, the "boyish
earnestness," the elevation of thought and speech of the old
philosopher; and in the impression made on the feelings, not the mind,
of the poet, then thirty-five years old.

In a letter to ALISON, CAMPBELL reverts with great pleasure to the day
spent with HERSCHEL:

                                         "SYDENHAM, _December 12, 1813_.

"MY DEAREST ALISON:--

       *       *       *       *       *

    "I spent three weeks with my family at Brighton, in charming
    weather, and was much pleased with, as well as benefited by, the
    place. There I met a man with whom you will stare at the idea of my
    being congenial, or having the vanity to think myself so--the great
    HERSCHEL. He is a simple, great being. . . . I once in my life
    looked at NEWTON'S _Principia_, and attended an astronomical class
    at Glasgow; wonderful it seemed to myself, that the great man
    condescended to understand my questions; to become apparently
    earnest in communicating to me as much information as my limited
    capacity and preparation for such knowledge would admit. He invited
    me to see him at his own abode, and so kindly that I could not
    believe that it was mere good breeding; but a sincere wish to see me
    again. I had a full day with him; he described to me his whole
    interview with BUONAPARTE; said it was not true, as reported, that
    BUONAPARTE understood astronomical subjects deeply, but affected
    more than he knew.

    "In speaking of his great and chief telescope, he said with an air,
    not of the least pride, but with a greatness and simplicity of
    expression that struck me with wonder, 'I have looked further into
    space than ever human being did before me. I have observed stars, of
    which the light takes _two millions_ of years to travel to this
    globe.' I mean to pay him a reverential visit at Slough, as soon as
    my book is out, this winter."

       *       *       *       *       *

In 1807 CAROLINA HERSCHEL has this entry in her diary:

    "_October_ 4.--My brother came from Brighton. The same night two
    parties from the Castle came to see the comet, and during the whole
    month my brother had not an evening to himself. As he was then in
    the midst of polishing the forty-foot mirror, rest became absolutely
    necessary after a day spent in that most laborious work; and it has
    ever been my opinion that on the 14th of October his nerves received
    a shock of which he never got the better afterwards."

In the spring of 1808 he was quite seriously ill; but in May the
observing went on again. In 1809 and 1810 his principal investigations
were upon physical subjects (NEWTON'S rings), and in 1811 the only long
series of observations was upon the comet of that year. After 1811 the
state of HERSCHEL'S health required that his observations should be
much less frequent. Much of the time after 1811 he was absent, and his
work at home consisted largely in arranging the results of his previous
labors, and in computations connected with them. All through the years
1814 to 1822, HERSCHEL'S health was very feeble. The severe winter of
1813-14 had told materially upon him. In 1814, however, he undertook to
repolish the forty-foot mirror, but was obliged to give it over.

He now found it necessary to make frequent little excursions for change
of air and scene. His faithful sister remained at home, bringing order
into the masses of manuscript, and copying the papers for the Royal
Society.

She was sick at heart, fearing that each time she saw her brother it
would be the last. In 1818 she says:

    "Feb. 11, I went to my brother and remained with him till the 23d.
    We spent our time, though not in idleness, in sorrow and sadness.
    He is not only unwell, but low in spirits."

In 1818 (December 16), HERSCHEL went to London to have his portrait
painted by ARTAUD. While he was in London his will was made.[28]

In 1819 there is a glimmer of the old-time light. In a note HERSCHEL
says:

    "LINA:--There is a great comet. I want you to assist me. Come to
    dine and spend the day here. If you can come soon after one o'clock,
    we shall have time to prepare maps and telescopes. I saw its
    situation last night. It has a long tail.

    "_July 4, 1819._"

This note has been carefully kept by his sister, and on it she has
written: "I keep this as a relic. Every line _now_ traced by the hand of
my dear brother becomes a treasure to me."

So the next three years passed away. Sir WILLIAM[29] was daily more and
more feeble. He spent his time in putting his works in order, but could
devote only a few moments each day to this. His sister says:

    "_Aug. 11th_, _12th_, _13th_, and _14th_ [1822], I went as usual to
    spend some hours of the forenoon with my brother.

    "_Aug. 15th._--I hastened to the spot where I was wont to find him,
    with the newspaper which I was to read to him. But instead I found
    Mrs. MONSON, Miss BALDWIN, and Mr. BULMAN, from Leeds, the grandson
    of my brother's earliest acquaintance in this country. I was
    informed my brother had been obliged to return to his room, whither
    I flew immediately. Lady H. and the housekeeper were with him,
    administering everything which could be thought of for supporting
    him. I found him much irritated at not being able to grant Mr.
    BULMAN'S request for some token of remembrance for his father. As
    soon as he saw me, I was sent to the library to fetch one of his
    last papers and a plate of the forty-foot telescope. But for the
    universe I could not have looked twice at what I had snatched from
    the shelf, and when he faintly asked if the breaking up of the Milky
    Way was in it, I said 'Yes,' and he looked content. I cannot help
    remembering this circumstance; it was the last time I was sent to
    the library on such an occasion. That the anxious care for his
    papers and workrooms never ended but with his life, was proved by
    his frequent whispered inquiries if they were locked and the key
    safe, of which I took care to assure him that they were, and the key
    in Lady HERSCHEL'S hands.

    "After half an hour's vain attempt to support himself, my brother
    was obliged to consent to be put to bed, leaving no hope ever to see
    him rise again."

On the 25th of August, 1822, HERSCHEL died peacefully at the age of
eighty-four years.

His remains lie in the little church at Upton, near Windsor, where a
memorial tablet has been erected by his son. The epitaph is as
follows:[30]

                             H. S. E.

                GULIELMUS HERSCHEL Eques Guelphicus
               Hanoviæ natus Angliam elegit patriam
               Astronomis ætatis suæ præstantissimis
                       Merito annumeratus
                  Ut leviora sileantur inventa
               Planetam ille extra Saturni orbitam
                          Primus detexit
                  Novis artis adjumentis innixus
                 Quæ ipse excogitavit et perfecit
                   Coelorum perrupit claustra
            Et remotiora penetrans et explorans spatia
                    Incognitos astrorum ignes
            Astronomorum oculis et intellectui subjecit
                    Qua sedulitate qua solertia
                      Corporum et phantasmatum
             Extra systematis nostri fines lucentium
                       Naturam indagaverit
                Quidquid paulo audacius conjecit
                  Ingenita temperans verecundia
                  Ultro testantur hodie æquales
                  Vera esse quæ docuit pleraque
           Siquidem certiora futuris ingeniis subsidia
                     Debitura est astronomia
                     Agnoscent forte posteri
                 Vitam utilem innocuam amabilem
         Non minus felici laborum exitu quam virtutibus
                     Ornatam et vere eximiam
               Morte suis et bonis omnibus deflenda
                    Nec tamen immatura clausit
                Die XXV Augusti A. D. CI[C]I[C]CCCXXII
                      Ætatis vero suæ LXXXIV.

FOOTNOTES:

[18] BODE'S _Jahrbuch_, 1788, p. 144.

[19] ZACH'S _Monatlich Correspondenz_, 1802, p. 56.

[20] BODE'S _Jahrbuch_, 1788, p. 161.

[21] Through Sir JOHN HERSCHEL there is preserved to us an
incident of his early boyhood, which shows the nature of the training
his young mind received in the household at Slough.

Walking with his father, he asked him "What was the oldest of all
things?" The father replied, after the Socratic manner, "And what do you
suppose is the oldest of all things?" The boy was not successful in his
answers, whereon the old astronomer took up a small stone from the
garden walk: "There, my child, there is the oldest of all the things
that I certainly know." On another occasion the father asked his son,
"What sort of things do you think are most alike?" The boy replied,
"The leaves of the same tree are most like each other." "Gather, then,
a handful of leaves from that tree," rejoined the philosopher,
"and choose two which are alike."--_Monthly Notices Royal Astronomical
Society_, vol. xxxii., page 123.

[22] _Memoir of CAROLINE HERSCHEL_, p. 42.

[23] "Of late years these expectations have been more than
accomplished by the discovery of no fewer than four planetary bodies,
almost all in the same place; but so small that Dr. HERSCHEL refuses to
honor them with the name of planets, and chooses to call them asteroids,
though for what reason it is not easy to determine, unless it be to
deprive the discoverers of these bodies of any pretence for rating
themselves as high in the list of astronomical discoverers as
himself."--_History of the Royal Society_, by THOMAS THOMSON, p. 358.
This work was published in 1812, and therefore during the lifetime of
HERSCHEL.

[24] _Poetical History of Astronomy_: this work was nearly
completed, but was never published. The whole of it was read to
HERSCHEL, in order that BURNEY might have the benefit of his criticism
on its technical terms.

[25] _Memoirs of Dr. BURNEY_, vol. iii., p. 264.

[26] Life and Letters of THOMAS CAMPBELL, edited by WILLIAM
BEATTIE, vol. ii., p. 234.

[27] This interview must have taken place in 1802, during
HERSCHEL'S journey to Paris. We have no other record of it.

[28] The will of HERSCHEL was dated December 17th, 1818.

"The personal effects were sworn under £6,000. The copyhold and other
lands and tenements at Upton-cum-Chalvey, in the County of Bucks, and at
Slough, he decrees to his son, with £25,000 in the 3 per cent. Reduced
Annuities. £2,000 are given to his brother JOHANN DIETRICH, and
annuities of £100 each to his brother JOHANN ALEXANDER and to his sister
CAROLINA; £20 each to his nephews and nieces, and the residue (with the
exception of astronomical instruments, telescopes, observations, etc.,
which he declares to have given, on account of his advanced age, to his
son for the purpose of continuing his studies) is left solely to Lady
HERSCHEL."--_Gentleman's Magazine_, vol. xcii., 1822, p. 650.

It is not necessary to say here how nobly Sir JOHN HERSCHEL redeemed the
trust confided in him. All the world knows of his Survey of the Southern
Heavens, in which he completed the review of the sky which had been
begun and completed for the northern heavens by the same instruments in
his father's hands. A glance at the Bibliography at the end of this book
will show the titles of several papers by Sir JOHN, written with the
sole object of rendering his father's labors more complete.

[29] He was created a knight of the Royal Hanoverian
Guelphic Order in 1816, and was the first President of the Royal
Astronomical Society in 1821, his son being its first Foreign
Secretary.

[30] BODE'S _Jahrbuch_, 1823, p. 222.




                               CHAPTER IV.

          REVIEW OF THE SCIENTIFIC LABORS OF WILLIAM HERSCHEL.


In this chapter I shall endeavor to give such explanations as will
enable the general reader to follow the course of discovery in each
branch of astronomy and physics, regularly through the period of
HERSCHEL'S life, and up to the state in which he left it.

A more detailed and precise account, which should appeal directly to the
professional astronomer, will not be needed, since ARAGO has already
fulfilled this want in his "_Analyse de la vie et des travaux de Sir
WILLIAM HERSCHEL_," published in 1842. The few misconceptions there
contained will be easily corrected by those to whom alone they are of
consequence. The latter class of readers may also consult the abstracts
of HERSCHEL'S memoirs, which have been given in "_A Subject-index and a
Synopsis of the Scientific Writings of Sir WILLIAM HERSCHEL_," prepared
by Dr. HASTINGS and myself, and published by the Smithsonian
Institution.

An accurate sketch of the state of astronomy in England and on the
Continent, in the years 1780-1820, need not be given. It will be enough
if we remember that of the chief observatories of Europe, public and
private, no one was actively devoted to such labors as were undertaken
by HERSCHEL at the very beginning of his career.

His observations on variable stars, indeed, were in the same line as
those of PIGOTT; FLAUGERGUES and DARQUIER, in France, had perhaps
preceded him in minute scrutiny of the sun's surface, etc.; but, even in
that department of observation, he at once put an immense distance
between himself and others by the rapid and extraordinary advances in
the size and in the excellence of his telescopes. Before his time the
principal aids to observation were the Gregorian and Newtonian
telescopes of SHORT, and the small achromatics of DOLLOND.[31]

We have seen, in what goes before, how his patient zeal had succeeded in
improving upon these. There was no delay, and no rest. Steadily the art
of making reflectors was urged forward, until he had finally in his
hands the forty-foot telescope.

It must be admitted that this was the limit to which the manufacture of
powerful telescopes could be pushed in his generation. The optical and
mechanical difficulties which prevented a farther advance required time
for their solution; and, indeed, some of these difficulties are scarcely
solved at this day. It may fairly be said that no reflector larger than
three feet in aperture has yet realized our expectations.


           _The Improvement of Telescopes and Optical Apparatus._

It will be of interest to give in this place some connected account of
the large forty-foot reflector, of four feet aperture, made by HERSCHEL.
Its history extends from 1785 to 1811. Its manufacture was considered by
his cotemporaries as his greatest triumph. As a machine, it was
extremely ingenious in all its parts, as may be seen from the elaborate
description and plates of it published in the _Philosophical
Transactions_ for 1795. One of its mirrors certainly had good
definition, for, by means of it, the two small satellites of _Saturn_
(_Mimas_ and _Enceladus_) were discovered, and these discoveries alone
would make it famous. Perhaps more was expected of it by the public in
general than it absolutely performed. Its merits were after a while
decried, and HERSCHEL even felt obliged to state why he did not always
employ it in his observations. His reasons were perfectly valid, and
such as any one may understand. The time required to get so large a
machine into working order was a serious tax; it required more
assistants than his twenty-foot telescope, and he says, "I have made it
a rule never to employ a larger telescope when a smaller will answer the
purpose."

It still remains as a remarkable feat of engineering and an example of
great optical and mechanical skill. It led the way to the large
reflectors of Lord ROSSE, some sixty years later, and several of the
forty-foot telescopes of the present day even have done less useful
work. Its great feat, however, was to have added two satellites to the
solar system. From the published accounts of it the following is taken:

    "When I resided at Bath I had long been acquainted with the theory
    of optics and mechanics, and wanted only that experience so
    necessary in the practical part of these sciences. This I acquired
    by degrees at that place, where in my leisure hours, by way of
    amusement, I made several two-foot, five-foot, seven-foot, ten-foot,
    and twenty-foot Newtonian telescopes, beside others, of the
    Gregorian form, of eight, twelve, and eighteen inches, and two,
    three, five, and ten feet focal length. In this way I made not less
    than two hundred seven-foot, one hundred and fifty ten-foot, and
    about eighty twenty-foot mirrors, not to mention the Gregorian
    telescopes.[32]

    "The number of stands I invented for these telescopes it would not
    be easy to assign. . . . In 1781 I began to construct a thirty-foot
    aërial reflector, and having made a stand for it, I cast the mirror
    thirty-six inches in diameter. This was cracked in cooling. I cast
    it a second time, and the furnace I had built in my house broke."

Soon after, the Georgian planet was discovered, and this interrupted the
work for a time.

    "In the year 1783 I finished a very good twenty-foot reflector with
    a large aperture, and mounted it upon the plan of my present
    telescope. After two years' observation with it, the great advantage
    of such apertures appeared so clearly to me that I recurred to my
    former intention of increasing them still further; and being now
    sufficiently provided with experience in the work which I wished to
    undertake, the President of the Royal Society, who is always ready
    to promote useful undertakings, had the goodness to lay my design
    before the king. His Majesty was graciously pleased to approve of
    it, and with his usual liberality to support it with his royal
    bounty.

    "In consequence of this arrangement I began to construct the
    forty-foot telescope about the latter end of 1785.[33] The woodwork
    of the stand and machines for giving the required motions to the
    instrument were immediately put in hand. In the whole of the
    apparatus none but common workmen were employed, for I made drawings
    of every part of it, by which it was easy to execute the work, as I
    constantly inspected and directed every person's labor; though
    sometimes there were not less than forty different workmen employed
    at the same time. While the stand of the telescope was preparing, I
    also began the construction of the great mirror, of which I
    inspected the casting, grinding, and polishing, and the work was in
    this manner carried on with no other interruption than that
    occasioned by the removal of all the apparatus and materials from
    where I then lived, to my present situation at Slough.

    "Here, soon after my arrival, I began to lay the foundation upon
    which by degrees the whole structure was raised as it now stands,
    and the speculum being highly polished and put into the tube, I had
    the first view through it on February 19, 1787. I do not, however,
    date the completing of the instrument till much later. For the first
    speculum, by a mismanagement of the person who cast it, came out
    thinner on the centre of the back than was intended, and on account
    of its weakness would not permit a good figure to be given to it.

    "A second mirror was cast January 26, 1788, but it cracked in
    cooling. February 16 we recast it, and it proved to be of a proper
    degree of strength. October 24 it was brought to a pretty good
    figure and polish, and I observed the planet _Saturn_ with it. But
    not being satisfied, I continued to work upon it till August 27,
    1789, when it was tried upon the fixed stars, and I found it to give
    a pretty sharp image. Large stars were a little affected with
    scattered light, owing to many remaining scratches on the mirror.
    August the 28th, 1789, having brought the telescope to the parallel
    of _Saturn_, I discovered a _sixth_ satellite of that planet, and
    also saw the spots upon _Saturn_ better than I had ever seen them
    before, so that I may date the finishing of the forty-foot telescope
    from that time."

Another satellite of _Saturn_ was discovered with the forty-foot on the
17th of September (1789). It was used for various observations so late
as 1811. On January 19, of that year, HERSCHEL observed the nebula of
_Orion_ with it. This was one of his last observations.

The final disposition of the telescope is told in the following extract
from a letter of Sir JOHN HERSCHEL'S to Mr. WELD, Secretary of the Royal
Society:

                                       "COLLINGWOOD, _March 13, 1847_.

    . . . "In reply to your queries, respecting the forty-foot
    reflecting telescope constructed by my father, I have to state that
    King GEORGE III. munificently defrayed the _entire_ cost of that
    instrument (including, of course, all preparatory cost in the nature
    of construction of tools, and of the apparatus for casting, grinding,
    and figuring the reflectors, of which two were constructed), at a
    total cost of £4,000. The woodwork of the telescope being so far
    decayed as to be dangerous, in the year 1839 I pulled it down, and
    piers were erected on which the tube was placed, _that_ being of
    iron and so well preserved, that, although not more than
    one-twentieth of an inch thick, when in the horizontal position it
    sustained within it all my family, and continues to sustain inclosed
    within it, to this day, not only the heavier of the two reflectors,
    but also all the more important portions of the machinery. . . .
    The mirror and the rest of the polishing apparatus are on the
    premises. The iron grinding tools and polishers are placed
    underneath the tube, let into the ground, and level with the surface
    of the gravelled area in which it stands.". . .

The closing of the tube was done with appropriate ceremony on
New-Year's-Day, 1840, when, after a procession through it by the family
at Slough, a poem, written by Sir JOHN, was read, the machinery put into
its present position, and the tube sealed.

The memoir on the forty-foot telescope shows throughout that HERSCHEL'S
prime object was not the making of the telescope itself, but that his
mind was constantly directed towards the uses to which it was to be
put--towards the questions which he wished it to answer.

Again and again, in his various papers, he returns to the question of
the _limit of vision_. As BESSEL has said:

    "The naked eye has its limit of vision in the stars of the sixth
    magnitude. The light of fainter stars than these does not affect the
    retina enough for them to be seen. A very small telescope penetrates
    to smaller, and, in general, without doubt, to more distant stars.
    A more powerful one penetrates deeper into space, and as its power is
    increased, so the boundaries of the visible universe are widened,
    and the number of stars increased to millions and millions. Whoever
    has followed the history of the series of HERSCHEL'S telescopes will
    have observed this. But HERSCHEL was not content with the bare fact,
    but strove ever to know _how far_ a telescope of a certain
    construction and size could penetrate, compared with the naked and
    unassisted eye. These investigations were never for the discovery of
    new facts concerning the working of his instruments; it was for the
    knowledge of the distribution of the fixed stars in space itself
    that he strove. . . . HERSCHEL'S instruments were designed to aid
    vision to the last extent. They were only secondarily for the taking
    of measures. His efforts were not for a knowledge of the _motions_,
    but of the _constitution_ and _construction_ of the heavenly
    bodies."

Besides the stands for his telescopes, which were both ingenious and
convenient, HERSCHEL devised many forms of apparatus for facilitating
the art of observation. His micrometers for measuring position angles,
his lamp micrometer, the method of limiting apertures, and the methods
he used for viewing the sun may be mentioned among these.

Points in practical astronomy are considered all through the years of
observation. A reference to his original papers will show how numerous,
how varied, and how valuable these are. I cannot forbear quoting here
the account of a precaution observed during his examination of the belts
on _Saturn_ (1794).

It is the most striking example of how fully HERSCHEL realized that the
eye of the observer is a material part of the optical apparatus of
astronomy. Simple as this principle may appear, it was an absolute
novelty in his day.

In making these observations, he says:

    "I took care to bend my head so as to receive the picture of the
    belt in the same direction as I did formerly. This was a precaution
    that occurred to me, as there was a possibility that the vertical
    diameter of the retina might be more or less sensitive than the
    horizontal one."

Astronomers will recognize in this the first suggestion of the processes
which have led to important results in the hands of Dr. OTTO STRUVE and
others in the comparison of the measures of double stars by different
observers, each of whom has a personal habit of observation, which, if
not corrected, may affect his results in the way which HERSCHEL was
striving to avoid.


           _Researches on the Relative Brightness of the
                     Stars: Variable Stars._

No research of HERSCHEL'S was more laborious than the elaborate
classification of the stars according to their comparative brightness,
which he executed during the years 1796 to 1799. It was directly in the
line of his main work--to find out the construction of the heavens.

His first paper had been upon the variable star _Mira Ceti_. Here was a
sun, shining by its native brightness, which waxed and waned like the
moon itself. This star is periodic. It is for a long period invisible to
the unassisted eye. Then it can just be seen, and increases in
brightness for a little over a month, and attains a maximum brilliancy.
From this it decreases for nearly three months, and after becoming
invisible, remains so for five or six months. Its whole period is about
333 days. Are all other stars constant in brightness? The example of
_Mira Ceti_ and of other known variables makes this at least doubtful.
But the sun itself may vary for all that we know. It is a simple star
like the rest.

This question of variability in general is an important one, then.
It can only be tested by making accurate catalogues of the relative
brilliance of stars at various times, and by comparing these. No such
general catalogue existed before HERSCHEL'S time, and led by the
discrepancies in isolated cases, which he found between his own
estimates and those of his predecessors, he made from observation a
series of four catalogues, in which were set down the order of sequence
of the stars of each constellation.

The method adopted by HERSCHEL was perfectly simple in principle, though
most laborious in practice. Suppose any number of stars, A, B, C, D, E,
. . . etc., near enough to each other to be well compared. The process
consists simply in writing down the names of the stars, A, B, C, etc.,
in the order of their relative brightness. Thus if for a group of eight
stars we have found at one epoch A, B, C, D, E, F, G, H, and if at
another time the order was A, B, C, D, F, E, G, H, symptoms of
variability are pointed out. Repeated observations, where the same star
is found in different sequences, will decide the question. Thus, for the
stars visible to the naked eye, we know exactly the state of the sky in
HERSCHEL'S day, now nearly a century ago. Any material change cannot
escape us. These catalogues have been singularly overlooked by the
observers of our generation who have followed this branch of
observation, and it was not till 1876 that they received proper
attention and a suitable reduction (at the hands of Mr. C. S. PIERCE).

We owe to HERSCHEL the first trustworthy account of the stars visible
to the naked eye, and since the date of his labors (about 1800) we have
similar views published by ARGELANDER (1839), HEIS (1848), ARGELANDER
and SCHÖNFELD (1857), GOULD (1860 and 1872), and HOUZEAU (1875). Thus
his labors have been well followed up.

In the prosecution of this work HERSCHEL found stars whose light was
progressively diminishing, others which regularly increased, one star
whose light periodically varies (_[alpha] Herculis_), and at least
one star (55 _Herculis_) which has utterly disappeared. On October 10,
1781, and April 11, 1782, he observed this latter star, but in May,
1791, it had totally vanished. There was no trace remaining.

The discovery of the variability of _[alpha] Herculis_ was a more
important one than would at first sight appear. Up to that time the only
variable stars known were seven in number. Their periods were four
hundred and ninety-four, four hundred and four, three hundred and
thirty-four, seven, six, five, and three days. These periods seemed to
fall into two groups, one of from three hundred to five hundred days,
the other comparatively much shorter, of three to seven days.
_[alpha] Herculis_ came to occupy the middle place between these groups,
its period being about sixty days.

The cause of these strange and regular variations of brightness was
supposed by HERSCHEL to be the rotation of the star bodily on an axis,
by which revolution different parts of its surface, of different
brilliancy, were successively and periodically presented to us. This
explanation it might have been difficult to receive, when the periods of
the known variables were so markedly various in length. His own
discovery came to bridge over the interval, and quite confirmed him in
his belief. He returned to the subject of the revolution of stars about
their axes again and again, and connected it with the revolution of
satellites.

He found that the satellites of _Jupiter_ and one of _Saturn's_
periodically changed in brightness, and by quite simple means showed
that their periods of rotation were at least approximately the same as
their periods of revolution about their primaries. In this case, as in
every other, he considered a discovery in each and every one of its
possible bearings. There are no instances where he has singularly
overlooked the consequences of his observations.


                    _Researches on Double Stars._

The double stars were the subject of HERSCHEL'S earliest and of his
latest papers. In 1782 he published his "_Catalogue of Double Stars_,"
and his last published memoir (1822) was on the same subject.

The question of determining the parallax of stars first brought HERSCHEL
to the discovery of double stars. If two stars, A and B, appear very
close together, and if, in reality, the star B is very many times more
distant from the earth than A, although seen along the same line of
sight, then the revolution of the earth in its orbit will produce
changes in the relative situation of A and B, and, in fact, B will
describe a small orbit about A, due to this revolution. This idea had
been proposed by GALILEO, and measures on this plan had been made by
LONG, with negative results. But HERSCHEL, in reviewing their work,
declares that the stars chosen by LONG were not suitable to the purpose.
It is necessary, among other things, to the success of this method, that
it should be certain that the star B is really very much more distant
than the star A. The only general test of the distance of stars is their
brilliancy, and HERSCHEL decided to use only stars for this research
which had two components very greatly different in brightness. A must be
very bright (and presumably near to us), and B must be very close to A,
and very faint (and thus, presumably, very distant).

It was in the search for such pairs of stars that the _Catalogue of
Double Stars_ (1782) was formed. HERSCHEL'S first idea of a double star
made such pairs as he found, to consist of two stars _accidentally_ near
to each other. A was near to us, and appeared projected in a certain
place on the celestial sphere. B was many times more distant, but, by
chance, was seen along the same line, and made with A an _optical_
double. If the two stars were at the same distance from the earth, if
they made part of the same physical system, if one revolved around the
other, then this method of gaining a knowledge of their distance failed.
Even in his first memoir on the subject, a surmise that this latter
state might occur in some cases, was expressed by HERSCHEL. The notes on
some of the pairs declare that a motion of one of them was suspected.
But this motion might be truly orbital--of one star about the other as
a centre--or it might simply be that one star was moving by its own
_proper_ motion, and leaving the other behind. It was best to wait and
see. The first Catalogue of Double Stars contained two hundred and three
instances of such associations. These were observed from time to time,
and new pairs discovered. The paper of MICHELL, "An Inquiry into the
probable Parallax and Magnitude of the Fixed Stars, from the Quantity of
Light which they Afford, and the Particular Circumstances of their
Situation" (1767), was read and pondered. By 1802 HERSCHEL had become
certain that there existed in the heavens real pairs of stars, both at
the same distance from the earth, which were physically connected with
each other. The arguments of MICHELL have been applied by BESSEL to the
case of one of HERSCHEL'S double stars, in much the same order in which
the argument ran in HERSCHEL'S own mind, as follows:

The star _Castor_ (_[alpha] Geminorum_) is a double star, where A is of
the second, and B of the fourth, magnitude. To the naked eye these two
appear as one star. With a telescope this is seen to be two stars, some
5" apart. In the whole sky there are not above fifty such stars
as the brighter of the two, and about four hundred of the brilliancy of
B. These fifty and four hundred stars are scattered over the vault of
heaven, almost at random. No law has yet been traced by which we can say
that here or here there shall be a bright star like A, or a fainter one
like B. In general the distribution appears to be fortuitous. How then
can we account for one of the four hundred stars like B placed so close
to one of the fifty like A?

The chances are over four hundred thousand to one that the association
in position is not accidental. This argument becomes overwhelming when
the same association is found in many other cases. There were two
hundred and three doubles in the Catalogue of 1782 alone, and many
thousands are now known.

By a process like this, HERSCHEL reached his grand discovery of true
binary systems, where one sun revolves about another. For he saw that
if the two stars are near together in space, they could not stand still
in face of each other, but that they must revolve in true orbits. Here
was the discovery which came to take the place of the detection of the
parallaxes of the fixed stars.

He had failed in one research, but he was led to grand conclusions.
Was the force that these distant pairs of suns obeyed, the force of
gravitation? This he could not settle, but his successors have done so.
It was not till about 1827 that SAVARY, of the Paris Observatory, showed
that one of HERSCHEL'S doubles was subjected to the law of gravitation,
and thus extended the power of this law from our system to the universe
at large. HERSCHEL himself lived to see some of his double stars perform
half a revolution.

Of HERSCHEL'S discoveries, ARAGO thinks this has "le plus d'avenir."
It may well be so. The laws which govern our solar system have been
extended, through his researches, to regions of unknown distance. The
binary stars will afford the largest field for research into the laws
which govern them, and together with the clusters and groups, they will
give a firm basis by which to study the distribution of stars in
general, since here we have the great advantage of knowing, if not the
real distance of the two stars from the earth, at least that this
distance is alike for both.


                  _Researches on Planets and Satellites._

After HERSCHEL'S first publication on the mountains of the Moon (1780),
our satellite appears to have occupied him but little. The observation
of volcanoes (1787) and of a lunar eclipse are his only published ones.
The planets _Mercury_, _Venus_, _Mars_, and _Jupiter_, although they
were often studied, were not the subjects of his more important memoirs.
The planet _Saturn_, on the contrary, seems never to have been lost
sight of from the time of his first view of it in 1772.

The field of discovery always appears to be completely occupied until
the advent of a great man, who, even by his way of putting old and
familiar facts, shows the paths along which discoveries must come, if at
all. This faculty comes from profound reflection on the nature of the
subject itself, from a sort of transmuting power which changes the words
of the books into the things of reality. HERSCHEL'S paper on _Saturn_,
in 1790, is an admirable example of this.

HERSCHEL'S observations on _Saturn_ began in 1772. From 1790 to 1808 he
published six memoirs on the figure, the ring, and the satellites of
this planet. The spheroidal shape of the ball was first discovered by
him, and we owe much of our certain knowledge of the constitution of the
rings to his work. The sixth and seventh satellites, _Mimas_ and
_Enceladus_, were discovered by him in 1789. The periods of rotation of
the ball and of the ring were also fixed. In his conclusions as to the
real figure of the rings, there is a degree of scientific caution which
is truly remarkable, and which to-day seems almost excessive.

In his paper of 1792, HERSCHEL shows that the most distant satellite of
_Saturn_--_Japetus_--turns once on its axis in each revolution about its
primary, just as our moon does. He says of this:

    "I cannot help reflecting with some pleasure on the discovery of an
    analogy which shows that a certain uniform plan is carried on among
    the secondary planets of our solar system; and we may conjecture
    that probably most of the satellites are governed by the same law;
    especially if it be founded on such a construction of their figure
    as makes them more ponderous towards their primary planets."

I believe the last suggestion to have been the first statement of the
possible arrangement of matter in satellites, which was afterwards so
forcibly maintained by HANSEN in his theory of the moon. HANSEN'S
researches show the consequences of such an arrangement, although they
do not prove its existence.

It should be recorded that the explanation which is to-day received of
the belts and bands upon _Jupiter_, is, I believe, first found in
HERSCHEL'S memoir on _Venus_ (1793). His memoir of 1797, on the
changeable brightness of the satellites of _Jupiter_, has already been
referred to. The times of the rotation of the satellites on their axes
was first determined by HERSCHEL from these observations, which also
contain accounts of the curious, and as yet unexplained, phenomena
attending their appearances on the disc of the planet.

HERSCHEL discovered in January, 1787, the two brighter satellites of
_Uranus_, now called _Oberon_ and _Titania_. They are among the faintest
objects in the solar system. A later discussion of all his observations
led him to the belief that there were four more, and he gives his
observations and computations in full. He says that of the existence of
additional satellites he has no doubt. Of these four, three were
exterior to the most distant satellite _Oberon_, the other was
"interior" to _Titania_.

It was not until 1834 that even _Oberon_ and _Titania_ were again
observed (by Sir JOHN HERSCHEL) with a telescope of twenty feet, similar
to that which had discovered them, and not until 1847 was the true state
of this system known, when Mr. LASSELL discovered _Ariel_ and _Umbriel_,
two satellites interior to _Titania_, neither of which was HERSCHEL'S
"interior" satellite. In 1848 and later years Mr. LASSELL, by the aid of
telescopes constructed by himself, fully settled the fact that only
four satellites of this planet existed. In 1874 I examined the
observations of HERSCHEL on his supposed "interior" satellite, thinking
that it might be possible that among the very few glimpses of it which
he recorded, some might have belonged to _Ariel_ and some to _Umbriel_,
and that by combining rare and almost accidental observations of two
satellites which really existed, he had come to announce the existence
of an "interior" satellite which had no existence in fact. Such I
believe to be the case. In 1801, April 17, HERSCHEL describes an
interior satellite in the position angle 189°, distant 18" from
the planet. At that instant _Umbriel_, one of Mr. LASSELL'S satellites,
was in the position 191°, and distant 21" from _Uranus_, in the
most favorable position for seeing it. The observation of 1794, March
27, _may_ belong to _Ariel_. At the best the investigation is of passing
interest only, and has nothing to do with the question of the discovery
of the satellites. HERSCHEL discovered the two brighter ones, and it
was only sixty years later that they were properly re-observed by Mr.
LASSELL, who has the great honor of having added as many more, and who
first settled the vexed question of satellites _exterior_ to _Oberon_,
and this with a reflecting telescope made by himself, which is
unequalled by any other of its dimensions.


                    _Researches on the Nature of the Sun._

In the introduction to his paper on the _Nature and Construction of the
Sun and Fixed Stars_ (1795), HERSCHEL recounts what was known of the
nature of the sun at that time. NEWTON had shown that it was the centre
of the system; GALILEO and his successors had determined its rotation,
the place of its equator, its real diameter, magnitude, density,
distance, and the force of gravity on its surface. He says:

    "I should not wonder if, considering all this, we were induced to
    think that nothing remained to be added; and yet we are still very
    ignorant in regard to the internal construction of the sun." "The
    spots have been supposed to be solid bodies, the smoke of
    volcanoes, the scum floating on an ocean of fluid matter, clouds,
    opaque masses, and to be many other things." "The sun itself has
    been called a globe of fire, though, perhaps, metaphorically." "It
    is time now to profit by the observations we are in possession of.
    I have availed myself of the labors of preceding astronomers, but
    have been induced thereto by my own actual observation of the solar
    phenomena."

HERSCHEL then refers to the theories advanced by his friend, Prof.
WILSON, of Glasgow, in 1774. WILSON maintained that the spots were
depressions below the sun's atmosphere, vast hollows as it were, at the
bases of which the true surface of the sun could be seen.

The essence of his theory was the existence of two different kinds of
matter in the sun: one solid and non-luminous--the nucleus--the other
gaseous and incandescent--the atmosphere. Vacant places in the
atmosphere, however caused, would show the black surface of the solid
mass below. These were the spots. No explanation could be given of the
_faculæ_, bright streaks, which appear on the sun's surface from time
to time; but his theory accounted for the existence of the black
_nuclei_ of the spots, and for the existence of the _penumbræ_ about
these. The penumbra of a spot was formed by the thinner parts of the
atmosphere about the vacancy which surrounded the nucleus.

This theory of WILSON'S was adopted by HERSCHEL as a basis for his own,
and he brought numerous observations to confirm it, in the modified
shape which he gave to it.

According to HERSCHEL, the sun consisted of three essentially different
parts. First, there was a solid nucleus, non-luminous, cool, and even
capable of being inhabited. Second, above this was an atmosphere proper;
and, lastly, outside of this was a layer in which floated the clouds, or
bodies which gave to the solar surface its intense brilliancy:

    "According to my theory, a dark spot in the sun is a place in its
    atmosphere which happens to be free from luminous decompositions"
    above it.

The two atmospheric layers, which will be of varying thickness about a
spot, will account for all the shades of darkness seen in the penumbra.
Ascending currents from the solar surface will elevate certain regions,
and may increase the solar activity near by, and will thus give rise to
faculæ, which HERSCHEL shows to be elevated above the general surface.
It will not be necessary to give a further account of this theory. The
data in the possession of the modern theorist is a thousand-fold that to
be derived from HERSCHEL'S observations, and, while the subject of the
internal construction of the sun is to-day unsettled, we know that many
important, even fundamental, portions of his theory are untenable.
A remark of his should be recorded, however, as it has played a great
part in such theories:

    "That the emission of light must waste the sun, is not a difficulty
    that can be opposed to our hypothesis. Many of the operations of
    Nature are carried on in her great laboratory which we cannot
    comprehend. Perhaps the many telescopic comets may restore to the
    sun what is lost by the emission of light."

Arguments in favor of the habitability of both sun and moon are
contained in this paper; but they rest more on a metaphysical than a
scientific basis, and are to-day justly forgotten.


             _Researches on the Motion of the Sun and of
                    the Solar System in Space._

In 1782 HERSCHEL writes, in regard to some of his discoveries of double
stars:

    "These may serve another very important end. I will just mention it,
    though it is foreign to my present purpose. Several stars of the
    first magnitude have been observed or suspected to have a proper
    motion; hence we may surmise that our sun, with all its planets and
    comets, may also have a motion towards some particular point of the
    heavens. . . . If this surmise should have any foundation, it will show
    itself in a series of some years in a kind of systematical parallax,
    or change, due to the motion of the whole solar system."

In 1783 he published his paper _On the Proper Motion of the Solar
System_, which contained the proofs of his surmises of a year before.
That certain of the stars had in fact a _proper_ motion had been well
established by the astronomers of the eighteenth century. After all
allowances had been made for the effects of precession and other
displacements of a star's position which were produced by motions of the
earth, it was found that there were still small outstanding differences
which must be due to the motion of the star itself--its proper motion.
The quantity of this motion was not well known for any star when
HERSCHEL'S researches began. Before they were concluded, however,
MASKELYNE had deduced the proper motions of thirty-six stars--the
fundamental stars, so called--which included in their number _Sirius_,
_Procyon_, _Arcturus_, and generally the brightest stars.

It is _à priori_ evident that stars, in general, must have proper
motions, when once we admit the universality of gravitation. That any
fixed star should be entirely at rest would require that the attractions
on all sides of it should be exactly balanced. Any change in the
position of this star would break up this balance, and thus, in general,
it follows that stars must be in motion, since all of them cannot occupy
such a critical position as has to be assumed. If but one fixed star is
in motion, this affects all the rest, and we cannot doubt but that
every star, our sun included, is in motion by an amount which varies
from small to great. If the sun alone had a motion, and the other stars
were at rest, the consequence of this would be that all the fixed stars
would appear to be retreating _en masse_ from that point in the sky
towards which we were moving. Those nearest us would move more rapidly,
those more distant less so. And in the same way, the stars from which
the solar system was receding would seem to be approaching each other.
If the stars, instead of being quite at rest, as just supposed, had
motions proper to themselves, then we should have a double complexity.
They would still appear to an observer in the solar system to have
motions, and part of these motions would be truly proper to the stars,
and part would be due to the advance of the sun itself in space.

Observations can show us only the _resultant_ of these two motions.
It is for reasoning to separate this resultant into its two components.
At first the question is to determine whether the results of observation
indicate any solar motion at all. If there is none, the proper motions
of stars will be directed along all possible lines. If the sun does
truly move, then there will be a general agreement in the resultant
motions of the stars near the ends of the line along which it moves,
while those at the sides, so to speak, will show comparatively less
systematic effect. It is as if one were riding in the rear of a railway
train and watching the rails over which it has just passed. As we recede
from any point, the rails at that point seem to come nearer and nearer
together.

If we were passing through a forest, we should see the trunks of the
trees from which we were going apparently come nearer and nearer
together, while those on the sides of us would remain at their constant
distance, and those in front would grow further and further apart.

These phenomena, which occur in a case where we are sensible of our own
motion, serve to show how we may deduce a motion, otherwise unknown,
from the appearances which are presented by the stars in space.

In this way, acting upon suggestions which had been thrown out
previously to his own time by LAMBERT, MAYER, and BRADLEY, HERSCHEL
demonstrated that the sun, together with all its system, was moving
through space in an unknown and majestic orbit of its own. The centre
round which this motion is directed cannot yet be assigned. We can
only know the point in the heavens towards which our course is
directed--"the apex of solar motion."

By a study of the proper motions assigned by MASKELYNE to the brighter
stars, HERSCHEL was able to define the position of the solar apex with
an astonishing degree of accuracy. His calculations have been several
times repeated with the advantage of modern analytical methods, and of
the hundred-fold material now at our disposition, but nothing essential
has been added to his results of 1805, which were based upon such scanty
data; and his paper of 1782 contains the announcement of the discovery
itself.

His second paper on the _Direction_ and _Velocity_ of the solar system
(1805) is the best example that can possibly be given of his marvellous
skill in reaching the heart of a matter, and it may be the one in which
his philosophical powers appear in their highest exercise. For sustained
reflection and high philosophic thought it is to be ranked with the
researches of NEWTON in the _Principia_.


           _Researches on the Construction of the Heavens._

HERSCHEL'S papers on the Construction of the Heavens, as he named it,
extended over his whole scientific life. By this he specially means the
method according to which the stars, the clusters, the nebulæ, are
spread through the regions of space, the causes that have led to this
distribution, and the laws to which it is subjected.

No single astronomical fact is unimportant in the light which it may
throw on the scheme of the whole, and each fact is to be considered in
this light. As an instance: his discovery of the variable star
_[alpha] Herculis_, which has a period of sixty days, was valuable in
itself as adding one more to the number of those strange suns whose
light is now brighter, now fainter, in a regular and periodic order.
But the chief value of the discovery was that now we had an instance of
a periodic star which went through all its phases in sixty days, and
connected, as it were, the stars of short periods (three to seven days)
with those of very long ones (three hundred to five hundred days), which
two groups had, until then, been the only ones known. In the same way
all his researches on the parallaxes of stars were not alone for the
discovery of the distance of any one or two single stars, but to gain a
unit of celestial measure, by means of which the depths of space might
be sounded.

Astronomy in HERSCHEL'S day considered the bodies of the solar system as
separated from each other by distances, and as filling a cubical space.
The ideas of near and far, of up and down, were preserved, in regard to
them, by common astronomical terms. But the vast number of stars seemed
to be thought of, as they appear in fact to exist, lying on the surface
of a hollow sphere. The immediate followers of BRADLEY used these fixed
stars as points of reference by which the motions within the solar
system could be determined, or, like LACAILLE and LALANDE, gathered
those immense catalogues of their positions which are so indispensable
to the science. MICHELL and HERSCHEL alone, in England, occupied their
thoughts with the nature and construction of the heavens--the one in his
study, the other through observation.[34] They were concerned with all
three of the dimensions of space.

In his memoir of 1784, HERSCHEL says:

    "Hitherto the sidereal heavens have, not inadequately for the
    purpose designed, been represented by the concave surface of a
    sphere, in the centre of which the eye of an observer might be
    supposed to be placed.

    "It is true the various magnitudes of the fixed stars even then
    plainly suggested to us, and would have better suited, the idea of
    an expanded firmament of three dimensions; but the observations upon
    which I am now going to enter still farther illustrate and enforce
    the necessity of considering the heavens in this point of view. In
    future, therefore, we shall look upon those regions into which we
    may now penetrate by means of such large telescopes, as a naturalist
    regards a rich extent of ground or chain of mountains containing
    strata variously inclined and directed, as well as consisting of
    very different materials. The surface of a globe or map, therefore,
    will but ill delineate the interior parts of the heavens."

HERSCHEL'S method of study was founded on a mode of observation which he
called _star-gauging_. It consisted in pointing a powerful telescope
toward various parts of the heavens, and ascertaining by actual count
how thick the stars were in each region. His twenty-foot reflector was
provided with such an eye-piece that, in looking into it, he saw a
portion of the heavens about 15' in diameter. A circle of this size on
the celestial sphere has about one quarter the apparent surface of the
sun, or of the full moon. On pointing the telescope in any direction, a
greater or less number of stars were visible. These were counted, and
the direction in which the telescope pointed was noted. Gauges of this
kind were made in all parts of the sky, and the results were tabulated
in the order of right ascension.

The following is an extract from the gauges, and gives the average
number of stars in each field at the points noted in right ascension and
north polar distance:

  ----------------------------------------------------------
              |    N. P. D.     ||           |    N. P. D.
      R. A.   |   78° to 80°.   ||   R. A.   |   92° to 94°.
              |  No. of Stars.  ||           | No. of Stars.
  ------------|-----------------||-----------|--------------
      H.  M.  |                 ||  H.  M.   |
      11   6  |       3.1       ||  15  10   |      9.4
      12  31  |       3.4       ||  15  22   |     10.6
      12  44  |       4.6       ||  15  47   |     10.6
      12  49  |       3.9       ||  16   8   |     12.1
      13   5  |       3.8       ||  16  25   |     13.6
      14  30  |       3.6       ||  16  37   |     18.6
  ----------------------------------------------------------

In this small table, it is plain that a different law of clustering or
of distribution obtains in the two regions. Such differences are still
more marked, if we compare the extreme cases found by HERSCHEL, as
R. A. = 19h 41m, N. P. D. = 74° 33', number of stars per field = 588;
and R. A. = 16h 10m, N. P. D. = 113° 4', number of stars = 1.1.

The number of stars in certain portions is very great. For example, in
the Milky Way, near _Orion_, six fields of view promiscuously taken gave
110, 60, 70, 90, 70, and 74 stars each, or a mean of 79 stars per field.
The most vacant space in this neighborhood gave 60 stars. So that as
HERSCHEL'S sweeps were two degrees wide in declination, in one hour
(15°) there would pass through the field of his telescope 40,000 or more
stars. In some of the sweeps this number was as great as 116,000 stars
in a quarter of an hour.

When HERSCHEL first applied his telescope to the Milky Way, he believed
that it completely resolved the whole whitish appearance into small
stars. This conclusion he subsequently modified. He says:

    "It is very probable that the great stratum called the Milky Way is
    that in which the sun is placed, though perhaps not in the very
    centre of its thickness.

    "We gather this from the appearance of the Galaxy, which seems to
    encompass the whole heavens, as it certainly must do if the sun is
    within it. For, suppose a number of stars arranged between two
    parallel planes, indefinitely extended every way, but at a given
    considerable distance from each other; and calling this a sidereal
    stratum, an eye placed somewhere within it will see all the stars in
    the direction of the planes of the stratum projected into a great
    circle, which will appear lucid on account of the accumulation of
    the stars, while the rest of the heavens, at the sides, will only
    seem to be scattered over with constellations, more or less crowded
    according to the distance of the planes, or number of stars
    contained in the thickness or sides of the stratum.

    "If the eye were placed somewhere without the stratum, at no very
    great distance, the appearance of the stars within it would assume
    the form of one of the smaller circles of the sphere, which would be
    more or less contracted according to the distance of the eye; and,
    if this distance were exceedingly increased, the whole stratum might
    at last be drawn together into a lucid spot of any shape, according
    to the length, breadth, and height of the stratum.

    "Suppose that a smaller stratum should branch out from the former in
    a certain direction, and that it also is contained between two
    parallel planes, so that the eye is contained within the great
    stratum somewhere before the separation, and not far from the place
    where the strata are still united. Then this second stratum will not
    be projected into a bright circle like the former, but it will be
    seen as a lucid branch proceeding from the first, and returning
    into it again at a distance less than a semicircle. If the bounding
    surfaces are not parallel planes, but irregularly curved surfaces,
    analogous appearances must result."

The Milky Way, as we see it, presents the aspect which has been just
accounted for, in its general appearance of a girdle around the heavens
and in its bifurcation at a certain point, and HERSCHEL'S explanation of
this appearance, as just given, has never been seriously questioned. One
doubtful point remains: are the stars scattered all through space? or
are they near its bounding planes, or clustered in any way within this
space so as to produce the same result to the eye as if uniformly
distributed?

HERSCHEL assumed that they were nearly equably arranged all through the
space in question. He only examined one other arrangement, _viz._, that
of a ring of stars surrounding the sun, and he pronounced against such
an arrangement, for the reason that there is absolutely nothing in the
size or brilliancy of the sun to cause us to suppose it to be the centre
of such a gigantic system. No reason, except its importance to us
personally, can be alleged for such a supposition. Every star will have
its own appearance of a Galaxy or Milky Way, which will vary according
to the situation of the star.

Such an explanation will account for the general appearances of the
Milky Way and of the rest of the sky, supposing the stars equally or
nearly equally distributed in space. On this supposition, the system
must be deeper where the stars appear most numerous.

HERSCHEL endeavored, in his early memoirs, to explain this inequality of
distribution on the fundamental assumption that the stars were nearly
equably distributed in space. If they were so distributed, then the
number of stars visible in any gauge would show the thickness of the
stellar system in the direction in which the telescope was pointed.
At each pointing, the field of view of the instrument includes all the
visible stars situated within a cone, having its vortex at the
observer's eye, and its base at the very limits of the system, the angle
of the cone (at the eye) being 15'. Then the cubes of the
perpendiculars let fall from the eye, on the plane of the bases of the
various visual cones, are proportional to the solid contents of the
cones themselves, or, as the stars are supposed equally scattered within
all the cones, the cube roots of the numbers of stars in each of the
fields express the relative lengths of the perpendiculars. A _section_
of the sidereal system along any great circle can be constructed from
the data furnished by the gauges in the following way:

The solar system is within the mass of stars. From this point lines are
drawn along the different directions in which the gauging telescope was
pointed. On these lines are laid off lengths proportional to the cube
roots of the number of stars in each gauge. The irregular line joining
the terminal points will be approximately the bounding curve of the
stellar system in the great circle chosen. Within this line the space is
nearly uniformly filled with stars. Without it is empty space. A similar
section can be constructed in any other great circle, and a combination
of all such would give a representation of the shape of our stellar
system. The more numerous and careful the observations, the more
elaborate the representation, and the 863 gauges of HERSCHEL are
sufficient to mark out with great precision the main features of the
Milky Way, and even to indicate some of its chief irregularities.

On the fundamental assumption of HERSCHEL (equable distribution), no
other conclusion can be drawn from his statistics but the one laid down
by him.

This assumption he subsequently modified in some degree, and was led to
regard his gauges as indicating not so much the _depth of the system_ in
any direction, as the _clustering power or tendency_ of the stars in
those special regions. It is clear that if in any given part of the sky,
where, on the average, there are ten stars (say) to a field, we should
find a certain small portion having 100 or more to a field, then, on
HERSCHEL'S first hypothesis, rigorously interpreted, it would be
necessary to suppose a spike-shaped protuberance directed from the
earth, in order to explain the increased number of stars. If many such
places could be found, then the probability is great that this
explanation is wrong. We should more rationally suppose some real
inequality of star distribution here. It is, in fact, in just such
details that the method of HERSCHEL breaks down, and a careful
examination of his system leads to the belief that it must be greatly
modified to cover all the known facts, while it undoubtedly has, in the
main, a strong basis.

The stars are certainly not uniformly distributed, and any general
theory of the sidereal system must take into account the varied tendency
to aggregation in various parts of the sky.

In 1817, HERSCHEL published an important memoir on the same subject, in
which his first method was largely modified, though not abandoned. Its
fundamental principle was stated by him as follows:

    "It is evident that we cannot mean to affirm that the stars of the
    fifth, sixth, and seventh magnitudes are really smaller than those
    of the first, second, or third, and that we must ascribe the cause
    of the difference in the apparent magnitudes of the stars to a
    difference in their relative distances from us. On account of the
    great number of stars in each class, we must also allow that the
    stars of each succeeding magnitude, beginning with the first, are,
    one with another, further from us than those of the magnitude
    immediately preceding. The relative magnitudes give only relative
    distances, and can afford no information as to the real distances at
    which the stars are placed.

    "A standard of reference for the arrangement of the stars may be had
    by comparing their distribution to a certain properly modified
    equality of scattering. The equality which I propose does not
    require that the stars should be at equal distances from each other,
    nor is it necessary that all those of the same nominal magnitude
    should be equally distant from us."

It consisted in allotting a certain equal portion of space to every
star, so that, on the whole, each equal portion of space within the
stellar system contains an equal number of stars. The space about each
star can be considered spherical. Suppose such a sphere to surround our
own sun. Its radius will not differ greatly from the distance of the
nearest fixed star, and this is taken as the unit of distance.

Suppose a series of larger spheres, all drawn around our sun as a
centre, and having the radii 3, 5, 7, 9, etc. The contents of the
spheres being as the cubes of their diameters, the first sphere will
have 3 × 3 × 3 = 27 times the volume of the unit sphere, and will
therefore be large enough to contain 27 stars; the second will have 125
times the volume, and will therefore contain 125 stars, and so on with
the successive spheres. For instance, the sphere of radius 7 has room
for 343 stars, but of this space 125 parts belong to the spheres inside
of it; there is, therefore, room for 218 stars between the spheres of
radii 5 and 7.

HERSCHEL designates the several distances of these layers of stars as
orders; the stars between spheres 1 and 3 are of the first order of
distance, those between 3 and 5 of the second order, and so on.
Comparing the room for stars between the several spheres with the number
of stars of the several magnitudes which actually exists in the sky, he
found the result to be as follows:

  --------------------------------------------------------
    Order of  |  Number of   |             |  Number of
    Distance. | Stars there  |  Magnitude. | Stars of that
              | is Room for. |             |  Magnitude.
  --------------------------------------------------------
    1........ |      26      |      1      |      17
    2........ |      98      |      2      |      57
    3........ |     218      |      3      |     206
    4........ |     386      |      4      |     454
    5........ |     602      |      5      |   1,161
    6........ |     866      |      6      |   6,103
    7........ |   1,178      |      7      |   6,146
    8........ |   1,538      |             |
  ---------------------------------------------------------

The result of this comparison is, that if the order of magnitudes could
indicate the distance of the stars, it would denote at first a gradual
and afterward a very abrupt condensation of them, at and beyond the
region of the sixth-magnitude stars.

If we assume the brightness of any star to be inversely proportional to
the square of its distance, it leads to a scale of distance different
from that adopted by HERSCHEL, so that a sixth-magnitude star on the
common scale would be about of the eighth order of distance according to
this scheme--that is, we must remove a star of the first magnitude to
eight times its actual distance to make it shine like a star of the
sixth magnitude.

On the scheme here laid down, HERSCHEL subsequently assigned the _order_
of distance of various objects, mostly star-clusters, and his estimates
of these distances are still quoted. They rest on the fundamental
hypothesis which has been explained, and the error in the assumption of
equal intrinsic brilliancy for all stars affects these estimates. It is
perhaps probable that the hypothesis of equal brilliancy for all stars
is still more erroneous than the hypothesis of equal distribution, and
it may well be that there is a very large range indeed in the actual
dimensions and in the intrinsic brilliancy of stars at the same order of
distance from us, so that the tenth-magnitude stars, for example, may be
scattered throughout the spheres which HERSCHEL would assign to the
seventh, eighth, ninth, tenth, eleventh, twelfth, and thirteenth
magnitudes. However this may be, the fact remains that it is from
HERSCHEL'S groundwork that future investigators must build. He found the
whole subject in utter confusion. By his observations, data for the
solution of some of the most general questions were accumulated, and in
his memoirs, which STRUVE well calls "immortal," he brought the
scattered facts into order and gave the first bold outlines of a
reasonable theory. He is the founder of a new branch of astronomy.


            _Researches for a Scale of Celestial Measures.
                        Distances of the Stars._

If the stars are _supposed_ all of the same absolute brightness, their
brightness to the eye will depend only upon their distance from us. If
we call the brightness of one of the fixed stars at the distance of
_Sirius_, which may be used as the unity of distance, 1, then if it is
moved to the distance 2, its apparent brightness will be one-fourth; if
to the distance 3, one-ninth; if to the distance 4, one-sixteenth, and
so on, the apparent brightness diminishing as the square of the distance
increases. The distance may be taken as an order of magnitude. Stars at
the _distances_ two, three, four, etc., HERSCHEL called of the second,
third, and fourth magnitudes.

By a series of experiments, the details of which cannot be given here,
HERSCHEL determined the space-penetrating power of each of his
telescopes. The twenty-foot would penetrate into space seventy-five
times farther than the naked eye; the twenty-five foot, ninety-six
times; and the forty-foot, one hundred and ninety-two times. If the
seventh-magnitude stars are those just visible to the naked eye, and if
we still suppose all stars to be of equal intrinsic brightness, such
seventh-magnitude stars would remain visible in the forty-foot, even if
removed to 1,344 times the distance of _Sirius_ (1,344 = 7 × 192).
If, further, we suppose that the visibility of a star is strictly
proportional to the total intensity of the light from it which strikes
the eye, then a condensed cluster of 25,000 stars of the 1,344th
magnitude could still be seen in the forty-foot at a distance where each
star would have become 25,000 times fainter, that is, at about 158 times
the distance of _Sirius_ (158 × 158 = 24,964). The light from the
nearest star requires some three years to reach the earth. From a star
1,344 times farther it would require about 4,000 years, and for such a
cluster as we have imagined no less than 600,000 years are needed. That
is, the light by which we see such a group has not just now left it.
On the contrary, it has been travelling through space for centuries and
centuries since it first darted forth. It is the ancient history of such
groups that we are studying now, and it was thus that HERSCHEL declared
that telescopes penetrated into time as well as into space.

Other more exact researches on the relative light of stars were made by
HERSCHEL. These were only one more attempt to obtain a scale of
celestial distances, according to which some notion of the limits and of
the interior dimensions of the universe could be gained. Two telescopes,
_exactly equal_ in every respect, were chosen and placed side by side.
Pairs of stars which were _exactly equal_, were selected by means of
them. By diminishing the aperture of one telescope directed to a bright
star, and keeping the other telescope unchanged and directed to a
fainter star, the two stars could be equalized in light, and, from the
relative size of the apertures, the relative light of this pair of stars
could be accurately computed, and so on for other pairs. This was the
first use of the method of _limiting apertures_. His general results
were that the stars of the first magnitude would still remain visible to
the naked eye, even if they were at a distance from us _twelve_ times
their actual distance.

This method received a still further development at his hands. He did
not leave it until he had gained all the information it was capable of
giving. He prepared a set of telescopes collecting 4, 9, 16, etc.
(2 × 2, 3 × 3, 4 × 4, etc.), times as much light as the naked eye.
These were to extend the determinations of distance to the telescopic
stars. For example, a certain portion of the heavens which he examined
contained no star visible to the naked eye, but many telescopic stars.
We cannot say that no one of these is as bright in itself as some of our
first-magnitude stars. The smallest telescope of the set showed a large
number of stars; these must, then, be _twice_ as far from us, on the
average, as the stars just visible to the naked eye. But first-magnitude
stars, like _Sirius_, _Procyon_, _Arcturus_, etc., become just visible
to the eye if removed to twelve times their present distance. Hence the
stars seen in this first telescope of the set were between twelve and
twenty-four times as far from us as _Arcturus_, for example.

"At least," as HERSCHEL says, "we are certain that if stars of the size
and lustre of _Sirius_, _Arcturus_, etc., were removed into the
profundity of space I have mentioned, they would then appear like the
stars which I saw." With the next telescope, which collected nine times
more light than the eye, and brought into view objects three times more
distant, other and new stars appeared, which were then (3 × 12)
thirty-six times farther from us than _Arcturus_. In the same way, the
seven-foot reflector showed stars 204 times, the ten-foot 344 times,
the twenty-foot 900 times farther from us than the average
first-magnitude star. As the light from such a star requires three years
to reach us, the light from the faintest stars seen by the twenty-foot
would require 2,700 years (3 × 900).

But HERSCHEL was now (1817) convinced that the twenty-foot telescope
could not penetrate to the boundaries of the Milky Way; the faintest
stars of the Galaxy must then be farther from us even than nine hundred
times the distance of _Arcturus_, and their light must be at least 3,000
years old when it reaches us.

There is no escaping a certain part of the consequences established by
HERSCHEL. It is indeed true that unless a particular star is of the same
intrinsic brightness as our largest stars, this reasoning does not apply
to it; in just so far as the average star is less bright than the
average brightness of our largest stars, will the numbers which HERSCHEL
obtained be diminished. But for every star of which his hypothesis is
true, we may assert that his conclusions are true, and no one can deny,
with any show of reason, that, on the whole, his suppositions must be
valid. On the whole, the stars which we call faint are farther from us
than the brighter ones; and, on the whole, the brilliancy of our
brightest and nearest stars is not very far from the brilliancy of the
average star in space. We cannot yet define the word _very_ by a
numerical ratio.

The _method_ struck out by HERSCHEL was correct; it is for his
successors to look for the special cases and limitations, to answer the
question, At a certain distance from us, what are the variations which
actually take place in the brilliancy and the sizes of stars? The answer
to this question is to be found in the study of the clusters of regular
forms, where we _know_ the stars to be all at the same distance from us.


                    _Researches on Light and Heat, Etc._

Frequently in the course of his astronomical work, HERSCHEL found
himself confronted by questions of physics which could not be
immediately answered in the state of the science at that time. In his
efforts to find a method for determining the dimensions of the stellar
universe, he was finally led, as has been shown, to regard the
brightness of a star as, in general, the best attainable measure of its
distance from us. His work, however, was done with telescopes of various
dimensions and powers, and it was therefore necessary to find some law
for comparing the different results among themselves as well as with
those given by observations with an unassisted eye. This necessity
prompted an investigation, published in 1800, in which, after drawing
the distinction between absolute and intrinsic brightness, HERSCHEL gave
an expression for the _space-penetrating power_ of a telescope. The
reasoning at the base of this conception was as follows.

The ratio of the light entering the eye when directed toward a star, to
the whole light given out by the star, would be as the area of the pupil
of the eye to the area of the whole sphere having the star as a centre
and our distance from the star as a radius. If the eye is assisted by a
telescope, the ratio is quite different. In that case the ratio of the
light which enters the eye to the whole light, would be as the area of
the mirror or object-glass to the area of the whole sphere having the
star as a centre and its distance as a radius. Thus the light received
by the _eye_ in the two cases would be as the area of the pupil is to
the area of the object-glass. For instance, if the pupil has a diameter
of two-fifths of an inch, and the mirror a diameter of four inches, then
a hundred times as much light would enter the eye when assisted by the
telescope as when unarmed, since the _area_ of the pupil is
one-hundredth the _area_ of the objective.

If a particular star is just visible to the naked eye, it will be quite
bright if viewed with this special telescope, which makes it one hundred
times more brilliant in appearance. If we could move the star bodily
away from us to a distance ten times its present distance, we could thus
reduce its brightness, as seen with the telescope, to what it was at
first, as seen with the eye alone, _i. e._, to bare visibility. Moving
the star to ten times its present distance would increase the surface of
the sphere which it illuminates a hundred-fold. We cannot move any
special star, but we can examine stars of all brightnesses, and thus
(presumably) of all distances.

HERSCHEL'S argument was, then, as follows: Since with such a telescope
one can see a star ten times as far off as is possible to the naked eye,
this telescope has the power of penetrating into space ten times farther
than the eye alone. But this number ten, also, expresses the ratio of
the diameter of the objective to that of the pupil of the eye,
consequently the general law is that the _space-penetrating power_ of a
telescope is found by dividing the diameter of the mirror in inches by
two-fifths. The diameter of the pupil of the eye (two-fifths of an inch)
HERSCHEL determined by many measures.

This simple ratio would only hold good, however, provided no more light
were lost by the repeated reflections and refractions in the telescope
than in the eye. That light must be so lost was evident, but no data
existed for determining the loss. HERSCHEL was thus led to a long series
of photometric experiments on the reflecting powers of the metals used
in his mirrors, and on the amount of light transmitted by lenses.
Applying the corrections thus deduced experimentally, he found that the
space-penetrating power of his twenty-foot telescope, with which he made
his star-gauges, was sixty-one times that of the unassisted eye, while
the space-penetrating power of his great forty-foot telescope was one
hundred and ninety-two times that of the eye. In support of his
important conclusions HERSCHEL had an almost unlimited amount of
experimental data in the records of his observations, of which he made
effective use.

By far the most important of HERSCHEL'S work in the domain of pure
physics was published in the same year (1800), and related to radiant
heat. The investigation of the space-penetrating powers of telescopes
was undertaken for the sole purpose of aiding him in measuring the
dimensions of the stellar universe, and there was no temptation for him
to pursue it beyond the limits of its immediate usefulness. But here,
though the first hint leading to remarkable discoveries was a direct
consequence of his astronomical work, the novelty and interest of the
phenomena observed induced him to follow the investigation very far
beyond the mere solution of the practical question in which it
originated.

Having tried many varieties of shade-glasses between the eye-piece of
his telescope and the eye, in order to reduce the inordinate degree of
heat and light transmitted by the instrument when directed towards the
sun, he observed that certain combinations of colored glasses permitted
very little light to pass, but transmitted so much heat that they could
not be used; while, on the other hand, different combinations and
differently colored glasses would stop nearly all the heat, but allow an
inconveniently great amount of light to pass. At the same time he
noticed, in the various experiments, that the images of the sun were of
different colors. This suggested the question as to whether there was
not a different heating power proper to each color of the spectrum. On
comparing the readings of sensitive thermometers exposed in different
portions of an intense solar spectrum, he found that, beginning with the
violet end, he came to the maximum of light long before that of heat,
which lay at the other extremity, that is, near the red. By several
experiments it appeared that the maximum of illumination, _i. e._, the
yellow, had little more than half the heat of the full red rays; and
from other experiments he concluded that even the full red fell short of
the maximum of heat, which, perhaps, lay even a little beyond the limits
of the visible spectrum.

    "In this case," he says, "radiant heat will at least partly, if not
    chiefly, consist, if I may be permitted the expression, of invisible
    light; that is to say, of rays coming from the sun, that have such a
    momentum[35] as to be unfit for vision. And admitting, as is highly
    probable, that the organs of sight are only adapted to receive
    impressions from particles of a certain momentum, it explains why
    the maximum of illumination should be in the middle of the
    refrangible rays; as those which have greater or less momenta are
    likely to become equally unfit for the impression of sight."

In his second paper on this subject, published in the same year,
HERSCHEL describes the experiments which led to the conclusion given
above. This paper contains a remarkably interesting passage which
admirably illustrates HERSCHEL'S philosophic method.

    "To conclude, if we call light, those rays which illuminate objects,
    and radiant heat, those which heat bodies, it may be inquired
    whether light be essentially different from radiant heat? In answer
    to which I would suggest that we are not allowed, by the rules of
    philosophizing, to admit two different causes to explain certain
    effects, if they may be accounted for by one. . . . If this be a true
    account of the solar heat, for the support of which I appeal to my
    experiments, it remains only for us to admit that such of the rays
    of the sun as have the refrangibility of those which are contained
    in the prismatic spectrum, by the construction of the organs of
    sight, are admitted under the appearance of light and colors, and
    that the rest, being stopped in the coats and humors of the eye, act
    on them, as they are known to do on all the other parts of our body,
    by occasioning a sensation of heat."

We now know that the reasoning and conclusion here given are entirely
correct, but they have for their basis only a philosophical conception,
and not a series of experiments designed especially to test their
correctness. Such an experimental test of this important question was
the motive for a third and last paper in this department of physics.
This paper was published in volume ninety of the _Philosophical
Transactions_, and gave the results of two hundred and nineteen
quantitative experiments.

Here we are at a loss to know which to admire most--the marvellous skill
evinced in acquiring such accurate data with such inadequate means, and
in varying and testing such a number of questions as were suggested in
the course of the investigation--or the intellectual power shown in
marshalling and reducing to a system such intricate and apparently
self-contradictory phenomena. It is true that this discussion led him to
a different conclusion from that announced in the previous paper, and,
consequently, to a false conclusion; but almost the only escape from his
course of reasoning lay in a principle which belongs to a later period
of intellectual development than that of HERSCHEL'S own time.

HERSCHEL made a careful determination of the quantitative distribution
of light and of heat in the prismatic spectrum, and discovered the
surprising fact that not only where the light was at a maximum the heat
was very inconsiderable, but that where there was a maximum exhibition
of heat, there was not a trace of light.

    "This consideration," he writes, "must alter the form of our
    proposed inquiry; for the question being thus at least partly
    decided, since it is ascertained that we have rays of heat which
    give no light, it can only become a subject of inquiry whether some
    of these heat-making rays may not have a power of rendering objects
    visible, superadded to their now already established power of
    heating bodies. This being the case, it is evident that the _onus
    probandi_ ought to lie with those who are willing to establish such
    an hypothesis, for it does not appear that Nature is in the habit of
    using one and the same mechanism with any two of our senses. Witness
    the vibration of air that makes sound, the effluvia that occasion
    smells, the particles that produce taste, the resistance or
    repulsive powers that affect the touch--all these are evidently
    suited to their respective organs of sense."

It is difficult to see how the fallacy of this argument could have been
detected by any one not familiar with the fundamental physiological law
that the nature of a sensation is in no wise determined by the character
of the agent producing it, but only by the character of the nerves acted
upon; but, as already intimated, this law belongs to a later epoch than
the one we are considering. HERSCHEL thus finally concluded that light
and radiant heat were of essentially different natures, and upon this
supposition he explained all of the phenomena which his numerous
experiments had shown him. So complete and satisfactory did this work
appear to the scientific world, that for a long time the question was
looked upon as closed, and not until thirty-five years later was there
any dissent. Then the Italian physicist, MELLONI, with instrumental
means a thousand times more delicate than that of HERSCHEL, and with a
far larger store of cognate phenomena, collected during the generation
which had elapsed, to serve as a guide, discovered the true law. This,
as we have seen, was at first adopted by HERSCHEL on philosophical
grounds, and then rejected, since he did not at that time possess the
key which alone could have enabled him to properly interpret his
experiments.

It is well to summarize the capital discoveries in this field made by
HERSCHEL, more particularly because his claims as a discoverer seem to
have been strangely overlooked by historians of the development of
physical science. He, before any other investigator, showed that radiant
heat is refracted according to the laws governing the refraction of
light by transparent media; that a portion of the radiation from the sun
is incapable of exciting the sensation of vision, and that this portion
is the less refrangible; that the different colors of the spectrum
possess very unequal heating powers, which are not proportional to their
luminosity; that substances differ very greatly in their power of
transmitting radiant heat, and that this power does not depend solely
upon their color; and that the property of diffusing heat is possessed
to a varying degree by different bodies, independently of their color.
Nor should we neglect to emphasize, in this connection, the importance
of his measurements of the intensity of the heat and light in the
different portions of the solar spectrum. It is the more necessary to
state HERSCHEL'S claims clearly, as his work has been neglected by those
who should first have done him justice. In his "History of Physics,"
POGGENDORFF has no reference to HERSCHEL. In the collected works of
VERDET, long bibliographical notes are appended to each chapter, with
the intention of exhibiting the progress and order of discovery. But all
of HERSCHEL'S work is overlooked, or indexed under the name of his son.
One little reference in the text alone shows that his very name was not
unknown. Even in the great work of HELMHOLTZ on physiological optics,
HERSCHEL'S labors are not taken account of.

It is easy to account for this seemingly strange neglect. HERSCHEL is
known to this generation only as an astronomer. A study of his memoirs
will show that his physical work alone should give him a very high rank
indeed, and I trust that the brief summaries, which alone can be given
here, will have made this plain.

       *       *       *       *       *

We may conclude from the time expended, the elaborate nature of the
experiments involved, and the character of the papers devoted to their
consideration, that the portion of HERSCHEL'S researches in physics
which interested him to the greatest degree, was the investigation of
the optical phenomena known as NEWTON'S rings. In 1792 he obtained the
two object-glasses of HUYGHENS, which were in the possession of the
Royal Society, for the purpose of repeating NEWTON'S experiments, and in
1810 he read the last of his three papers on the subject.

Sir ISAAC NEWTON had given some of his most vigorous efforts to the
study of the phenomena of interference of light, which are exemplified
in the colors of thin and of thick plates. The colors of thin plates are
most conveniently studied in the regular form which they present when
produced by a thin plate of air, limited on one side by a plane
polished surface, and on the other by a spherical surface of long
radius, such as the exterior surface of a convex lens, for example.
The colors are then arranged in concentric circles, and, though others
had so produced them before NEWTON, these rings have, ever since the
publication of his remarkable work, been known by his name.

To explain the phenomena, NEWTON was obliged to supplement his theory of
the corpuscular nature of light, by supposing that the inconceivably
minute particles constituting light are not always equally susceptible
of reflection, but that they have periodically recurring "fits of easy
reflection" and of "easy transmission." This conception, though by no
means unphilosophical, seemed to HERSCHEL too artificial and improbable
for ready acceptance, and his effort was to supply a more probable
explanation.

The developments of optical science have justified HERSCHEL in his
objections, but we cannot accord to him must any considerable part in
making clear the true nature of the phenomenon. Indeed, it must be
recognized that his position was distinctly less advanced than that of
NEWTON. That great philosopher announced the true law governing the
relation between the color and the thickness of the film. HERSCHEL did
not recognize such a relation. NEWTON showed exactly how the phenomenon
depended upon the obliquity at which it was viewed. HERSCHEL found no
place in his theory for this evident variation.

In the series of experiments described in the first paper on this
subject, HERSCHEL mistook the locus of a certain set of rings which he
was observing. This mistake, though so slight as hardly to be detected
without the guidance of the definite knowledge acquired in later times,
not only vitiated the conclusion from the experiments, but gave an
erroneous direction to the whole investigation. To him these experiments
proved that NEWTON'S conception of a periodic phenomenon was untenable.
Thus cut loose from all hypothesis, his fertility in ideas and ingenuity
in experimentation are as striking as ever. He tried the effect of
having a polished metal as one of the surfaces limiting the thin plate
of air. Observing the so-called "blue bow" of NEWTON at the limit of
total reflection in a prism, he was led to the discovery of its
complement, the "red bow" by refraction. Here he thought he had found
the solution of his problem, and attributed the rings to the reflection
of the light which passed through in the red bow. Though mistaken, he
had presented to the world of science two experiments which have since
played very prominent parts in the undulatory theory of light, namely,
the rings formed upon polished metal, and the bands produced by a thin
plate near the critical angle.

As in his later researches upon the nature of radiant heat, he was wrong
in his conclusions, and perhaps with less excuse. His experiments were
skilfully devised and most ingenious. His philosophizing was distinctly
faulty. We can see not only that he was wrong, but exactly where he
began to go wrong. Yet these papers are full of interest to the
physicist, and by no means deserve the neglect into which they have
fallen.


               _Researches on the Dimensions of the Stars._

HERSCHEL examined a number of bright stars, using extremely high
magnifying powers, in order to determine whether the stars have sensible
dimensions. In a good telescope stars present round and pretty uniformly
illuminated disks. If these disks really represent the angular diameter
of the stars, they should admit of magnifying, like other objects; but,
instead of this, HERSCHEL found that they appeared smaller as the
telescopic power was increased. He accordingly called the disk of light
seen in the telescope a spurious disk. This singular phenomenon gave its
discoverer a ready criterion for determining whether a small bright body
has an appreciable size, or only impresses the sense of sight by virtue
of its intrinsic brightness. If the first were the case, the apparent
size would increase with increased magnifying power, while, if the
angular dimensions were inappreciable, the apparent size would, on the
contrary, diminish with additional magnifying. An occasion for using
this criterion came in the first years of this century, with the
discovery of three small planets having orbits lying between those of
_Mars_ and _Jupiter_. HERSCHEL gave the name _Asteroids_ to these
bodies. As the appropriateness of this term had been violently assailed,
the discovery of _Juno_, in 1804, the third one of the group, led to a
careful experimental study of the defining power of the telescope used,
and of the laws governing the phenomena of spurious disks.

With a telescope of about nine inches in aperture, HERSCHEL found that
if _Juno_ subtended an angle greater than a quarter of a second of arc,
a certain indication of the fact would have shown itself in the course
of the experiments. This conclusion was a justification of the name
Asteroid, since the appearance of the new planet was strictly stellar.
On other grounds, a better name might have been selected.

In the paper giving the results of the experiments, the phenomena of the
spurious disks are very completely described; but they did not attract
the attention which they deserved, and they only became an object of
especial interest to students of physics when they were again studied by
the famous German optician FRAUNHOFER, a generation later.

Incidentally the experiments are of interest, as yielding us a measure
of the excellence of HERSCHEL'S telescopes, and a measure which is quite
independent of the keenness of his vision. From them we may be sure that
the efficiency of the nine-inch mirror used was not sensibly less than
that of the highest theoretically attainable excellence. In this
connection, too, we may refer to the _Philosophical Transactions_ for
1790, pp. 468 and 475, where HERSCHEL gives observations of both
_Enceladus_ and _Mimas_ seen in contact with the ball of _Saturn_.
I have never seen so good definition, telescopic and atmospheric, as he
must have had on these occasions.


              _Researches on the Spectra of the Fixed Stars._

The spectroscope was applied by SECCHI to the study of the spectra of
the fixed stars visible to the naked eye in the years 1863 to 1866.
He examined the nature of the spectrum of each of the larger stars,
and found that these stars could be arranged in three general classes or
_types_. His results have been verified and extended by other
astronomers, and his classification has been generally accepted.
According to SECCHI, the lucid stars may be separated into three groups,
distinguished by marked differences in their spectra. SECCHI'S Type I.
contains stars whose spectra are like those of _Sirius_, _Procyon_, and
_[alpha] Lyræ_; his Type II. stars like _Arcturus_ and _Aldebaran_;
his Type III. stars like _[alpha] Orionis_.

HERSCHEL also made some trials in this direction. In the _Philosophical
Transactions_ for 1814 (p. 264), he says:

    "By some experiments on the light of a few of the stars of the first
    magnitude, made in 1798, by a prism applied to the eye-glasses of my
    reflectors, adjustable to any angle and to any direction, I had the
    following analyses:

    "The light of _Sirius_ consists of red, orange, yellow, green, blue,
    purple, and violet. _[alpha] Orionis_ contains the same colors,
    but the red is more intense, and the orange and yellow are less
    copious in proportion than they are in _Sirius_. _Procyon_ contains
    all the colors, but proportionately more blue and purple than
    _Sirius_. _Arcturus_ contains more red and orange, and less yellow
    in proportion than _Sirius_. _Aldebaran_ contains much orange and
    very little yellow. _[alpha] Lyræ_ contains much yellow, green,
    blue, and purple."

Here the essential peculiarities of the spectrum of each of the stars
investigated by HERSCHEL is pointed out, and if we were to use his
observations alone to classify these stars into types, we should put
_Sirius_ and _Procyon_ into one type of stars which have "all the
colors" in their spectra; _Arcturus_ and _Aldebaran_ would represent
another group of stars, with a deficiency of yellow and an excess of
orange and red in the spectrum; and _[alpha] Orionis_ would stand as
a type of those stars with an excess of red and a deficiency of orange.
_[alpha] Lyræ_ would represent a sub-group of the first class.

HERSCHEL'S immediate object was not classification, and his observations
are only recorded in a passing way. But the fact remains that he
clearly distinguished the essential differences of the spectra of these
stars, and that he made these observations in support of his statement
that the fixed stars, "like the planets, also shine with differently
colored light. That of _Arcturus_ and _Aldebaran_, for instance, is as
different from the light of _Sirius_ and _Capella_ as that of _Mars_ and
_Saturn_ is from the light of _Venus_ and _Jupiter_."

Of course, no special discovery can be claimed for him on these few
instances. We can see, however, a good example of the manner in which he
examined a subject from every side, and used the most remote evidence
exactly in its proper place and time.


          _Researches on the Variable Emission of Light
                  and Heat from the Sun._

It is certainly a remarkable fact that HERSCHEL was the first observer
to recognize the real importance of the aperture or diameter of a
telescope. Before his time it was generally assumed that this element
only conditioned the amount of light transmitted to the eye, or, in
other words, merely determined the brightness of the image. Hence the
conclusion that if an object is sufficiently bright, the telescope may
be made as small as desired without loss of power. Thus, in observing
the sun, astronomers before HERSCHEL had been accustomed to reduce the
aperture of their telescopes, in order to moderate the heat and light
transmitted. SCHEINER, it is true, nearly two centuries before the time
we are considering, had invented a method for observing the sun without
danger, still employing the full aperture. This was by projecting the
image of the sun on a white screen beyond the eye-piece, the telescope
being slightly lengthened. For special purposes this ingenious method
has even been found useful in modern times, though for sharpness of
definition it bears much the same relation to the more usual manner of
observing, that a photographic picture does to direct vision.

Although HERSCHEL saw the advantages of using the whole aperture of a
telescope in such observations, the practical difficulties in the way
were very great. We have noted his attempts to find screens which would
effectively cut off a large portion of the heat and light without
impairing vision, and have considered, somewhat in detail, the
remarkable discoveries in radiant heat to which these attempts led him.
His efforts were not unsuccessful. A green glass smoked, and a glass
cell containing a solution of black writing ink in water--were found to
work admirably.

Thus provided with more powerful instrumental means than had ever been
applied to the purpose, HERSCHEL turned his attention to the sun. In a
very short time he exhausted nearly all there was to be discovered, so
that since the publication of his last paper on this subject, in 1801,
until the present time, there has been but a single telescopic
phenomenon, connected with the physical appearance of the sun, which was
unknown to HERSCHEL. That phenomenon is the frequent occurrence of a
darker central shade or kernel in large spots, discovered by DAWES about
1858.

HERSCHEL, though observing a hundred and ninety years after the earliest
discovery of sun spots, seems to have been the first to suspect their
periodic character. To establish this as a fact, and to measure the
period, was left for our own times and for the indefatigable observer
SCHWABE. The probable importance of such a period in its relation to
terrestrial meteorology was not only clearly pointed out by HERSCHEL,
but he even attempted to demonstrate, from such data as were obtainable,
the character of this influence.

Perhaps no one thing which this great philosopher has done better
exhibits the catholic character of his mind than this research. When the
possible connection of solar and terrestrial phenomena occurred to him
as a question to be tested, there were no available meteorological
records, and he could find but four or five short series of
observations, widely separated in time. To an ordinary thinker the task
would have seemed hopeless until more data had been collected. But
HERSCHEL'S fertile mind, though it could not recall lost opportunities
for solar observations, did find a substitute for meteorological records
in the statistics of the prices of grain during the various epochs.
It is clear that the price of wheat must have depended upon the supply,
and the supply, in turn, largely upon the character of the season.
The method, as ingenious as it is, failed in HERSCHEL'S hands on account
of the paucity of solar statistics; but it has since proved of value,
and has taken its place as a recognized method of research.


                    _Researches on Nebulæ and Clusters._

When HERSCHEL first began to observe the nebulæ in 1774, there were
very few of these objects known. The nebulæ of _Orion_ and _Andromeda_
had been known in Europe only a little over a hundred years.

In 1784 MESSIER published a list of sixty-eight such objects which he
had found in his searches for comets, and twenty-eight nebulæ had been
found by LACAILLE in his observations at the Cape of Good Hope. In the
mere discovery of these objects HERSCHEL quickly surpassed all others.
In 1786 he published a catalogue of one thousand new nebulæ, in 1789 a
catalogue of a second thousand, and in 1802 one of five hundred. In all
he discovered and described two thousand five hundred and eight new
nebulæ and clusters. This branch of astronomy may almost be said to be
proper to the HERSCHELS, father and son. Sir JOHN HERSCHEL re-observed
all his father's nebulæ in the northern hemisphere, and added many new
ones, and in his astronomical expedition to the Cape of Good Hope he
recorded almost an equal number in the southern sky.

Of the six thousand two hundred nebulæ now known the HERSCHELS
discovered at least eight-tenths. The mere discovery of twenty-five
hundred nebulæ would have been a brilliant addition to our knowledge of
celestial statistics.

HERSCHEL did more than merely point out the existence and position of
these new bodies. Each observation was accompanied by a careful and
minute description of the object viewed, and with sketches and diagrams
which gave the position of the small stars in it and near it.[36]

As the nebulæ and clusters were discovered they were placed in classes,
each class covering those nebulæ which resembled each other in their
general features. Even at the telescope HERSCHEL'S object was not
discovery merely, but to know the inner constitution of the heavens.
His classes were arranged with this end, and they are to-day adopted.
They were:

  CLASS I. "Bright nebulæ (288 in all).
       II. "Faint nebulæ (909 in all).
      III. "Very faint nebulæ (984 in all).
       IV. "Planetary nebulæ, stars with burs, with milky chevelure,
              with short rays, remarkable shapes, etc. (79 in all).
        V. "Very large nebulæ (52 in all).
       VI. "Very compressed and rich clusters of stars (42 in all).
      VII. "Pretty much compressed clusters (67 in all).
     VIII. "Coarsely scattered clusters of stars" (88 in all).

The lists of these classes were the storehouses of rich material from
which HERSCHEL drew the examples by which his later opinions on the
physical conditions of nebulous matter were enforced.

As the nebulæ were discovered and classified they were placed upon a
star-map in their proper positions (1786), and, as the discoveries went
on, the real laws of the distribution of the nebulæ and of the clusters
over the surface of the sky showed themselves more and more plainly. It
was by this means that HERSCHEL was led to the announcement of the law
that the spaces richest in nebulæ are distant from the Milky Way, etc.
By no other means could he have detected this, and I believe this to
have been the first example of the use of the graphical method, now
become common in treating large masses of statistics.

It is still in his capacity of an observer--an acute and wise one--that
HERSCHEL is considered. But this was the least of his gifts. This vast
mass of material was not left in this state: it served him for a
stepping-stone to larger views of the nature and extent of the nebulous
matter itself.

His views on the nature of nebulæ underwent successive changes. At first
he supposed all nebulæ to be but aggregations of stars. The logic was
simple. To the naked eye there are many groups of stars which appear
nebulous. _Praesepe_ is, perhaps, the best example. The slightest
telescopic power applied to such groups alters the nebulous appearance,
and shows that it comes from the combined and confused light of discrete
stars. Other groups which remain nebulous in a seven-foot telescope,
become stellar in a ten-foot. The nebulosity of the ten-foot can be
resolved into stars by the twenty-foot, and so on. The nebulæ which
remained still unresolved, it was reasonable to conclude, would yield to
higher power, and generally a nebula was but a group of stars removed to
a great distance. An increase of telescopic power was alone necessary to
demonstrate this.[37]

    "Nebulæ can be selected so that an insensible gradation shall take
    place from a coarse cluster like the _Pleiades_ down to a milky
    nebulosity like that in _Orion_, every intermediate step being
    represented. This tends to confirm the hypothesis that all are
    composed of stars more or less remote."

So, at first, HERSCHEL believed that his twenty-foot telescope was of
power sufficient to fathom the Milky Way, that is, to see through it and
beyond it, and to reduce all its nebulosities to true groups of stars.

In 1791 he published a memoir on _Nebulous Stars_, in which his views
were completely changed. He had found a nebulous star, the sixty-ninth
of his Class IV., to which his reasons would not apply. In the centre of
it was a bright star; around the star was a halo gradually diminishing
in brightness from the star outward, and perfectly circular. It was
clear the two parts, star and nebula, were connected, and thus at the
same distance from us.

There were two possible solutions only. Either the whole mass was,
_first_, composed of stars, in which case the nucleus would be
enormously larger than the other stars of its stellar magnitude
elsewhere in the sky, or the stars which made up the halo indefinitely
small; or, _second_, the central nucleus was indeed a star, but a star
surrounded with "a shining fluid, of a nature totally unknown to us."

The long strata of nebulæ, which he had before described under the name
of "telescopic Milky Ways," might well be accounted for by masses of
this fluid lying beyond the regions of the seventh-magnitude stars. This
fluid might exist independently of stars. If it is self-luminous, it
seems more fit to produce a star by its condensation, than to depend
upon the star for its own existence. Such were a few of the theorems to
which his discovery of this nebula led him. The hypothesis of an elastic
_shining fluid_ existing in space, sometimes in connection with stars,
sometimes distinct from them, was adopted and never abandoned. How well
the spectroscope has confirmed this idea it is not necessary to say.
We know the shining fluid does exist, and in late years we have seen the
reverse of the process imagined by HERSCHEL. A star has actually, under
our eyes, become a planetary nebula, and the cycle of which he gave the
first terms is complete.

In five separate memoirs (1802, 1811, 1814, 1817, and 1818) HERSCHEL
elaborated his views of the sidereal system. The whole extent of his
views must be gained from the extended memoirs themselves. Here only the
merest outline can be given.

In 1802 there is a marshaling of the various objects beyond our solar
system. The stars themselves may be _insulated_, or may belong to
_binary_ or _multiple_ systems, to _clusters_ and groups, or to grand
groups like the Milky Way. Nebulæ may have any of the forms which have
been described; and, in 1811, he gives examples of immense spaces in the
sky covered with diffused and very faint nebulosity. "Its abundance
exceeds all imagination."[38] These masses of nebular matter are the
seats of attracting forces, and these forces must produce condensation.
When a nebula has more than one preponderating seat of attracting
matter, it may in time be divided, and the double nebulæ have had such
an origin. When nebulæ appear to us as round masses, they are in reality
globular in form, and this form is at once the effect and the proof of a
gravitating cause.

The central brightness of nebulæ points out the seat of the attraction;
and the completeness of the approximation to a spherical form points out
the length of time that the gravitating forces have been at work. Those
nebulæ (and clusters) which are most perfect in the globular form, have
been longest exposed to central forces. The planetary nebulæ are the
oldest in our system. They must have a rotatory motion on their axes.

By progressive condensation planetary nebulæ may be successively
converted into bright stellar nebulæ, or into nebulous stars, and these
again, by the effects of the same cause, into insulated or double stars.
This chain of theorems, laid down in the memoir of 1811, is enforced in
1814 with examples which show how the nebulous appearance may grow into
the sidereal. HERSCHEL selects from the hundreds of instances in his
note-books, nebulæ in every stage of progress, and traces the effect of
condensation and of clustering power through all its course, even to the
final breaking up of the Milky Way itself.

The memoirs of 1817 and 1818 add little to the general view of the
physical constitution of the heavens. They are attempts to gain a scale
of celestial measures by which we may judge of the distances of the
stars and clusters in which these changes are going on.

There is little to change in HERSCHEL'S statement of the general
construction of the heavens. It is the groundwork upon which we have
still to build. Every astronomical discovery and every physical fact
well observed is material for the elaboration of its details or for the
correction of some of its minor points. As a scientific conception it is
perhaps the grandest that has ever entered into the human mind. As a
study of the height to which the efforts of one man may go, it is almost
without a parallel. The philosopher who will add to it to-day, will have
his facts and his methods ready to his hands. HERSCHEL presents the
almost unique example of an eager observer marshaling the multitude of
single instances, which he himself has laboriously gathered, into a
compact and philosophic whole. In spite of minor errors and defects, his
ideas of the nature of the sidereal universe have prevailed, and are
to-day the unacknowledged basis of our every thought upon it. Some of
its most secret processes have been worked out by him, and the paths
which he pointed out are those along which our advances must be made.

In concluding this condensed account of HERSCHEL'S scientific labors,
it behoves us to remember that there was nothing due to accident in his
long life. He was born with the faculties which fitted him for the
gigantic labors which he undertook, and he had the firm basis of energy
and principle which kept him steadily to his work.

As a practical astronomer he remains without an equal. In profound
philosophy he has few superiors. By a kindly chance he can be claimed as
the citizen of no one country. In very truth his is one of the few names
which belong to the whole world.

FOOTNOTES:

[31] JAMES SHORT, F.R.S. (1710-1768), and JOHN DOLLOND, F.R.S.
(1706-1761), were the most celebrated makers of telescopes of their day.
The six-foot Newtonian reflectors of SHORT (aperture 9.4 inches), and
the forty-six-inch achromatics of DOLLOND (aperture 3.6 inches), were
highly esteemed. The Royal Observatory of Greenwich possessed, in 1765,
one of each class. In a comparative trial of SHORT'S telescope, at
Greenwich, and one of HERSCHEL'S first telescopes, the latter was
adjudged greatly superior.

[32] At least _one_ of these telescopes had the principal
mirror made of glass instead of metal.--_Philosophical Transactions_,
1803.

[33] The following extract from FOURIER'S _Éloge_ of HERSCHEL
is of interest in this connection. The sum first appropriated by the
king was £2,000. This was afterwards raised to £4,000, and a sum of £200
yearly was given for maintenance.

"L'histoire doit conserver à jamais la réponse de ce prince à un
étranger célèbre [LALANDE?] qui le remerciait des sommes considérables
accordées pour les progrès de l'astronomie. 'Je fais les dépenses de la
guerre,' dit le roi, 'parcequ'elles sont nécessaires; quant à celles des
sciences, il m'est agréable des les ordonner; leur objet ne coûte point
des larmes, et honore l'humanité.'"

LALANDE'S own account is a little different. He says the king exclaimed:
"Ne vaut-il pas mieux employer son argent à cela qu'à faire tuer des
hommes?"

[34] The memoirs on the parallaxes of stars, written by various
astronomers from 1750 to 1800, were mainly directed to the improvement
of the methods, or to the discovery of the parallax of some particular
star. For example, LACAILLE'S observations of _Sirius_, at the Cape of
Good Hope, had resulted in a parallax of 9" for that star--a
quantity over forty times too large.

[35] HERSCHEL accepted, as did all his cotemporaries, the
Newtonian or corpuscular theory of light.

[36] Thus the position of small stars critically situated in
the centre, or on the edges of the nebulæ was always noted. Many of the
descriptions are given in the published papers, but the publication of
the diagrams would be an immense help to this branch of astronomy.
D'ARREST in his reduction of HERSCHEL'S nebula observations (1856)
writes: "Gewiss wäre es vom höchsten Interesse für die Entwickelung,
welche hoffentlich auch dieser Zweig der beobachtenden Astronomie
zukünftig erhalten wird, wenn die HERSCHEL'Schen Beobachtungen in der
Ausführlichkeit in welcher sie, verschiedenen Andeutungen zufolge,
_handschriftlich_ vorhanden sind, veröffentlicht würden. Es schliesst
sich dieser Wunsch in Betreff der Nebelflecken lebhaft an den an,
welcher, schon vor einem Jahrzehnt nach Veröffentlichung der 400 noch
unedirten _star-gauges_ von gewichtigerer Seite her geäussert wurde."
In this all must agree who have a knowledge of the direction in which we
must look for advances in the difficult and important questions of the
distance, the motions, and the changes of the nebulæ. Almost the only
aid to be looked for from the older observations must come from such
diagrams, and we may safely say that the publication of this priceless
material, just as it stands, would carry our exact data back from 1833
to 1786, or no less than forty-seven years.

[37] Long after HERSCHEL had abandoned this idea, it continued
current among astronomers. The successes of Lord ROSSE'S telescope
perpetuated to the middle of the nineteenth century an erroneous view
which HERSCHEL had given up in 1791.

[38] These have never been re-observed. They should be sought
for with a powerful refractor, taking special precautions against the
illumination of the field of view from neighboring bright stars.
HERSCHEL'S reflectors were specially open to illusions produced in this
way. His observations probably will remain untested until some large
telescope is used in the way he adopted, _i. e._, in sweeping.




                             BIBLIOGRAPHY.


I.--LIST OF THE PUBLISHED WRITINGS OF WILLIAM HERSCHEL ON ASTRONOMICAL
    SUBJECTS.

                       [In chronological order.]

_N.B.--In general, translations and abstracts of those which appeared
in periodicals are not noticed here. I have made exceptions in the
more important cases._

[Solution of a prize question. _See_ this book, page 46.]
                              _Ladies' Diary_, 1779.


Astronomical observations on the periodical star in _Collo Ceti_.
                              _Phil. Trans._, 1780, p. 338.


Astronomical observations relating to the mountains of the moon.
                              _Phil. Trans._, 1780, p. 507.


Astronomical observations on the rotation of the planets round their
axes, made with a view to determine whether the earth's diurnal motion
is perfectly equable.
                              _Phil. Trans._, 1781, p. 115.


Account of a comet. [Dated 13th March, 1781. This was _Uranus_.]
                              _Phil. Trans._, 1781, p. 492.


On the parallax of the fixed stars.
                              _Phil. Trans._, 1782, p. 82.


Catalogue of double stars.
                       _Phil. Trans._, 1782, p. 112: translation in
                         _Bode's Jahrbuch_, 1786, p. 187.


Description of a lamp micrometer and the method of using it.
                              _Phil. Trans._, 1782, p. 163.


A paper to obviate some doubts concerning the great magnifying powers used.
                              _Phil. Trans._, 1782, p. 173.


A letter from WILLIAM HERSCHEL, Esq., F.R.S., to Sir JOSEPH BANKS,
_Bart._, P.R.S.
                              _Phil. Trans._, 1783, p. 1.


Aus einem Schreiben des Hrn. HERSCHEL an mich [BODE], datirt London, den
13ten August, 1783.
[This is a letter forwarding HERSCHEL'S memoir on the Parallax of the
Fixed Stars, etc.]
                              _Bode's Jahrbuch_, 1786, p. 258.


On the diameter and magnitude of the _Georgium Sidus_, with a
description of the dark and lucid disk and periphery micrometers.
                              _Phil. Trans._, 1783, p. 4.


On the proper motion of the sun and solar system, with an account of
several changes that have happened among the fixed stars since the time
of Mr. FLAMSTEED.
                              _Phil. Trans._, 1783, p. 247.
                              _Bode's Jahrbuch_, 1787, p. 194, p. 224.


Astronomische Nachrichten und Entdeckungen, aus einem französischen
Schreiben desselben an mich [BODE], datirt Datchet, nahe bey Windsor,
den 18. Mai, 1784.

[This letter is on the subject of the use of high magnifying powers, and
gives a _résumé_ of his recent papers.]
                              _Bode's Jahrbuch_, 1787, p. 211.


On the remarkable appearances at the polar regions of the planet _Mars_,
the inclination of its axis, the position of its poles and its
spheroidical figure; with a few hints relating to its real diameter and
atmosphere.
                              _Phil. Trans._, 1784, p. 233.


Account of some observations tending to investigate the construction of
the heavens.
                              _Phil. Trans._, 1784, p. 437.


[_Bode's Jahrbuch_, 1788, p. 246, has a summary of this paper by Baron
VON ZACH. See, also, _Bode's Jahrbuch_, 1794, p. 213.]


Catalogue of double stars.
                              _Phil. Trans._, 1785, p. 40.


On the construction of the heavens.
                              _Phil. Trans._, 1785, p. 213.
                              _Bode's Jahrbuch_, 1788, p. 238.
                      See, also, _same_, 1787, p. 213, and 1794, p. 213.


Aus einem Schreiben des Hrn. HERSCHEL an mich [BODE], datirt Clay Hall,
nahe bey Windsor, den 20. Jul., 1785.
[This is a letter forwarding two memoirs, and giving the prices of
telescopes]
                              _Bode's Jahrbuch_, 1788, p. 254.


Catalogue of one thousand new nebulæ and clusters of stars.
                              _Phil. Trans._, 1786, p. 457.
                              _Bode's Jahrbuch_, 1791, p. 157,
                              and _same_, 1794, p. 213.


Investigation of the cause of that indistinctness of vision which has
been ascribed to the smallness of the optic pencil.
                              _Phil. Trans._, 1786, p. 500.


Remarks on the new comet [1786, II.].
                              _Phil. Trans._, 1787, p. 4.


[Letter from HERSCHEL to BODE on the discovery of two satellites to
_Uranus_, dated Slough, 1787, Feb. 11.]
                              _Bode's Jahrbuch_, 1790, p. 253.


An account of the discovery of two satellites revolving round the
_Georgian planet_.
                              _Phil. Trans._, 1787, p. 125.
                              _Bode's Jahrbuch_, 1791, p. 255.


An account of three volcanoes in the moon.
                              _Phil. Trans._, 1787, p. 229.
                              _Bode's Jahrbuch_, 1791, p. 255.


Note on M. MÉCHAIN'S comet. [1787, I.] [Added to preceding paper.]
                              _Phil. Trans._, 1787, p. 232.


On the _Georgian planet_ and its satellites.
                              _Phil. Trans._, 1788, p. 364.
                              _Bode's Jahrbuch_, 1793, p. 104.


Observations on a comet [1788, II.].
                              _Phil. Trans._, 1789, p. 151.


Catalogue of a second thousand of new nebulæ and clusters of stars, with
a few introductory remarks on the construction of the heavens.
                              _Phil. Trans._, 1789, p. 212.
                              _Bode's Jahrbuch_, 1793, p. 104.
                              Also, _same_, 1794, p. 150.


Account of the discovery of a sixth and seventh satellite of the planet
_Saturn_, with remarks on the construction of its ring, its atmosphere,
its rotation on an axis, and its spheroidical figure.
                              _Phil. Trans._, 1790, p. 1.
                              _Bode's Jahrbuch_, 1793, p. 239;
                              _same_, 1796, p. 88; 1797, p. 249.


On the satellites of the planet _Saturn_, and the rotation of its ring
on an axis.
                              _Phil. Trans._, 1790, p. 427.


On nebulous stars properly so called.
                              _Phil. Trans._, 1791, p. 71.
                              _Bode's Jahrbuch_, 1801, p. 128.


On the ring of _Saturn_ and the rotation of the fifth satellite upon its
axis.
                              _Phil. Trans._, 1792, p. 1.
                              _Bode's Jahrbuch_, 1796, p. 88.


Miscellaneous observations.

[Account of a comet], p. 23 [1792, I.].

[On the periodical appearance of omicron Ceti], p. 24.

[On the disappearance of the 55th _Herculis_], p. 26.

[Remarkable phenomenon in an eclipse of the moon], p. 27.
                              _Phil. Trans._, 1792, p. 23.


Observations on the planet _Venus_.
                              _Phil. Trans._, 1793, p. 201.


Observations of a quintuple belt on the planet _Saturn_.
                              _Phil. Trans._, 1794, p. 28.
                              _Bode's Jahrbuch_, 1798, p. 90.


Account of some particulars observed during the late eclipse of the sun.
[1793, September 5th.]
                              _Phil. Trans._, 1794, p. 39.


On the rotation of the planet _Saturn_ upon its axis.
                              _Phil. Trans._, 1794, p. 48.
                              _Bode's Jahrbuch_, 1798, p. 74.


On the nature and construction of the sun and fixed stars.
                             _Phil. Trans._, 1795, p. 46.
                             _Bode's Jahrbuch_, II. Suppl. Band, p. 65.


Description of a forty-foot reflecting telescope.
                             _Phil. Trans._, 1795, p. 347.
                             _Bode's Jahrbuch_, III. Suppl. Band, p. 238.


Additional observations on the comet. [1796, I.]
                              _Phil. Trans._, 1796, p. 131.


On the method of observing the changes that happen to the fixed stars;
with some remarks on the stability of the light of our sun. To which is
added a catalogue of comparative brightness for ascertaining the
permanency of the lustre of stars.
                              _Phil. Trans._, 1796, p. 166.
                              _Bode's Jahrbuch_, 1809, p. 201.


On the periodical star _[alpha] Herculis_; with remarks tending to
establish the rotatory motion of the stars on their axes; to which is
added a second catalogue of the comparative brightness of the stars.
                              _Phil. Trans._, 1796, p. 452.
                              _Bode's Jahrbuch_, 1809, p. 201.


A third catalogue of the comparative brightness of the stars, with an
introductory account of an index to Mr. FLAMSTEED'S observations of the
fixed stars, contained in the second volume of the Historia Coelestis.
To which are added several useful results derived from that index.
                              _Phil. Trans._, 1797, p. 293.
                              _Bode's Jahrbuch_, 1810, p. 143.


Observations of the changeable brightness of the satellites of
_Jupiter_, and of the variation in their apparent magnitudes, with a
determination of the time of their rotatory motions on their axes. To
which is added a measure of the diameter of the second satellite, and an
estimate of the comparative size of all the four.
                              _Phil. Trans._, 1797, p. 332.
                              _Bode's Jahrbuch_, 1801, p. 103.


On the discovery of four additional satellites of the _Georgium Sidus_.
The retrograde motion of its old satellites announced, and the cause of
their disappearance at certain distances from the planet explained.
                              _Phil. Trans._, 1798, p. 47.
                              _Bode's Jahrbuch_, 1801, p. 231.


A fourth catalogue of the comparative brightness of the stars.
                              _Phil. Trans._, 1799, p. 121.
                              _Bode's Jahrbuch_, 1810, p. 143.


On the power of penetrating into space by telescopes, with a comparative
determination of the extent of that power in natural vision, and in
telescopes of various sizes and constructions, illustrated by select
observations.
                              _Phil. Trans._, 1800, pp. 49-85.
                              _Bode's Jahrbuch_, 1804, p. 231.


Investigation of the powers of the prismatic colors to heat and
illuminate objects, with remarks that prove the different refrangibility
of radiant heat. To which is added an inquiry into the method of viewing
the sun advantageously with telescopes of large apertures and high
magnifying powers.
                              _Phil. Trans._, 1800, pp. 255-283.
                              _Bode's Jahrbuch_, 1804, p. 89.


Experiments on the refrangibility of the invisible rays of the sun.
                              _Phil. Trans._, 1800, pp. 284-292.
                              _Bode's Jahrbuch_, 1804, p. 89.


Experiments on the solar and on the terrestrial rays that occasion heat,
with a comparative view of the laws by which light and heat, or rather
the rays that occasion them, are subject, in order to determine whether
they are the same or different.
                               _Phil. Trans._, 1800, pp. 293-326, 437-538.
                               _Gilbert Annal._, X. (1802), pp. 68-78;
                               _same_, XII. (1803), pp. 521-546.


Observations tending to investigate the nature of the sun, in order to
find the causes or symptoms of its variable emission of light and heat,
with remarks on the use that may possibly be drawn from solar
observations.
                       _Phil. Trans._, 1801, pp. 265-318.
                       _Bode's Jahrbuch_, 1805, p. 218, and 1806, p. 113.


Ueber den 7 Nebelfleck der 1sten classe des Herschel'schen Verzeichniss,
und ueber _Ceres_ und _Pallas_, vom Herrn Doctor HERSCHEL, aus zwey
Briefen desselben.
                              _Bode's Jahrbuch_, 1805, p. 211.


Additional observations tending to investigate the symptoms of the
variable emission of the light and heat of the sun, with trials to set
aside darkening glasses by transmitting the solar rays through liquids,
and a few remarks to remove objections that might be made against some
of the arguments contained in the former paper.
                              _Phil. Trans._, 1801, pp. 354-362.


Observations on the two lately discovered celestial bodies
[_Ceres and Pallas_].
                  _Phil. Trans._, 1802, pp. 213-232.
                  _Nicholson Journal_, IV. (1808), pp. 120-130, 142-148.


Catalogue of five hundred new nebulæ, nebulous stars, planetary nebulæ,
and clusters of stars, with remarks on the construction of the heavens.
                              _Phil. Trans._, 1802, pp. 477-528.
                              _Bode's Jahrbuch_, 1807, p. 113.


Observations of the transit of _Mercury_ over the sun's disk, to which
is added an investigation of the causes which often prevent the proper
action of mirrors.
                              _Phil. Trans._, 1803, pp. 214-232.


Account of the changes which have happened during the last twenty-five
years in the relative situation of double stars, with an investigation
of the cause to which they are owing.
                              _Phil. Trans._, 1803, pp. 339-382.
                              _Bode's Jahrbuch_, 1808, pp. 154-178.


Continuation of the account of the changes that have happened in the
relative situation of double stars.
                              _Phil. Trans._, 1804, pp. 353-384.
                              _Bode's Jahrbuch_, 1808, p. 226.


Aus einem Schreiben des Herrn Doctor HERSCHEL, datirt Slough, bey
Windsor, den 31. May, 1804.

[Relates to his theory of the relation between the solar radiation and
the price of wheat.]
                              _Bode's Jahrbuch_, 1808, p. 226.


Experiments for ascertaining how far telescopes will enable us to
determine very small angles, and to distinguish the real from the
spurious diameters of celestial and terrestrial objects, with an
application of the results of those experiments to a series of
observations on the nature and magnitude of Mr. HARDING'S lately
discovered star [_Juno_ (1804),].
                              _Phil. Trans._, 1805, pp. 31-70.


On the direction and velocity of the motion of the sun and solar system.
                              _Phil. Trans._, 1805, pp. 233-256.
                              _Bode's Jahrbuch_, IV. Suppl. Band, p. 67.


Observations on the singular figure of the planet _Saturn_.
                              _Phil. Trans._, 1805, pp. 272-280.
                              _Bode's Jahrbuch_, 1809, p. 197.


On the quantity and velocity of solar motion.
                              _Phil. Trans._, 1806, pp. 205-237.
                              _Bode's Jahrbuch_, 1811, p. 224.


Observations and remarks on the figure, climate, and atmosphere of
_Saturn_ and its ring.
                              _Phil. Trans._, 1806, pp. 455-467.
                              _Gilbert Annal._, XXXIV. (1810), pp. 82-105.
                              _Bode's Jahrbuch_, 1810, p. 228.


Experiments for investigating the cause of the colored concentric rings
discovered by Sir I. NEWTON between two object-glasses laid one upon
another.
                   _Phil. Trans._, 1807, pp. 180-233.
                   _Annal. de Chimie_, LXX., 1809, pp. 154-181, 293-321;
                   _same_, LXXI., 1809, pp. 5-40.


Observations on the nature of the new celestial body [_Vesta_]
discovered by Dr. OLBERS, and of the comet which was expected to appear
last January in its return from the sun. [1806, II.]
                              _Phil. Trans._, 1807, pp. 260-266.


Observations of a comet [1807, I.] made with a view to investigate its
magnitude and the nature of its illumination, to which is added an
account of a new irregularity lately perceived in the apparent figure of
the planet _Saturn_.
                        _Phil. Trans._, 1808, pp. 145-163.
                        _Gilbert Annal._, XXXVI. (1810), pp. 389-393.
                        _Zach, Monat. Corresp._, XX. (1809), pp. 512-514.


Continuation of experiments for investigating the cause of colored
concentric rings and other appearances of a similar nature.
                              _Phil. Trans._, 1809, pp. 259-302.


Supplement to the first and second part of the paper of experiments for
investigating the cause of colored concentric rings between
object-glasses, and other appearances of a similar nature.
                              _Phil. Trans._, 1810, pp. 149-177.
                              _Gilbert Annal._, XLVI., 1814, pp. 22-79.


Astronomical observations relating to the construction of the heavens,
arranged for the purpose of a critical examination, the result of which
appears to throw some new light upon the organization of the celestial
bodies.
                           _Phil. Trans._, 1811, pp. 269-336.
                           _Journ. de Phys._, LXXV., 1812, pp. 121-167.


Observations of a comet, with remarks on the construction of its
different parts [1811, I.].
           _Phil. Trans._, 1812, pp. 115-143.
           _Journ. de Phys._, LXXVII., 1813, pp. 125-135.
           _Zach, Monat. Corresp._, XXVIII., 1813, pp. 455-469, 558-568.
           _Bode's Jahrbuch_, 1816, p. 185.


Observations of a second comet, with remarks on its construction
[1811, II.].
                           _Phil. Trans._, 1812, pp. 229-237.
                           _Nicholson Journ._, XXXV., 1813, pp. 193-199.
                           _Bode's Jahrbuch_, 1816, p. 203.


Astronomical observations relating to the sidereal part of the heavens,
and its connection with the nebulous part, arranged for the purpose of a
critical examination.
                              _Phil. Trans._, 1814. pp. 248-284.
                              _Bode's Jahrbuch_, 1818, pp. 97-118.


A series of observations of the satellites of the _Georgian planet_,
including a passage through the node of their orbits, with an
introductory account of the telescopic apparatus that has been used on
this occasion, and a final exposition of some calculated particulars
deduced from the observations.
                              _Phil. Trans._, 1815, pp. 293-362.
                              _Bode's Jahrbuch_, 1819, p. 232-242.


Astronomical observations and experiments tending to investigate the
local arrangement of the celestial bodies in space, and to determine the
extent and condition of the Milky Way.
                              _Phil. Trans._, 1817, pp. 302-331.
                              _Bode's Jahrbuch_, 1821, p. 149.


Astronomical observations and experiments selected for the purpose of
ascertaining the relative distances of clusters of stars, and of
investigating how far the power of our telescopes may be expected to
reach into space, when directed to ambiguous celestial objects.
                              _Phil. Trans._, 1818, pp. 429-470.


On the places of one hundred and forty-five new double stars (1821).
                            _Mem. Roy. Ast. Soc._, 1, 1822, pp. 166-181.



II.--LIST OF WORKS RELATING TO THE LIFE AND WRITINGS OF WILLIAM
HERSCHEL.

                 [Arranged alphabetically by authors.]

_N.B.--In general, the notices of his life to be found in Encyclopædias
of Biography, etc., are not included here._


ARAGO (F.)
    Analyse de la vie et des travaux de Sir WILLIAM HERSCHEL [from
_Annuaire du Bureau des Longitudes_, 1842]. Paris, 1843. 18mo.
        [See also the _Annuaire_ for 1834, for an account of HERSCHEL'S
        work on double stars.]


ARAGO (F.)
    Biographies of Distinguished Scientific Men. Translated by Admiral
      W. H. SMYTH, Rev. B. POWELL, and ROBERT GRANT, Esq. HERSCHEL.
        First series, p. 258. Boston, 1859. 8vo.


ARAGO (F.)
    HERSCHEL. [Translated from the French.]
        Smithsonian Report. 1870. p. 197. 8vo.


AUWERS (A.)
    WILLIAM HERSCHEL'S Verzeichnisse von Nebelflecken und Sternhaufen
      bearbeitet von A. AUWERS.
        From the _Königsberg Observations_. 1862. Folio.


BESSEL (F. W.)
    Sir WILLIAM HERSCHEL. [From the _Königsberger Allgemeine Zeitung_, 1,
      1843, No. 37, _et seq._, reprinted in his] _Abhandlungen_, vol iii.,
      p. 468. Leipzig, 1876. 4to.


D'ARREST (H. L.)
    Verzeichniss von Sir WILLIAM HERSCHEL'S Nebelflecken _erster_ und
      _vierter_ Classe, aus den Beobachtungen berechnet und auf 1850
      reducirt.
        _Abhandlungen der Math. Phys. Classe der K. Sächs Gesells. d.
          Wissenschaften_, Band iii. [1857], p. 359.


DUNKIN (E.)
    Obituary Notices of Astronomers, p. 86. Sir WILLIAM HERSCHEL,
      K.C.H., F.R.S., 1738-1822.
        London, 1879. 12mo.


FÉTIS (F. J.)
    Biographie universelle des Musiciens [Article HERSCHEL].
        Paris, 1835-37. 8vo.


FORBES (J. D.)
    Sir WILLIAM HERSCHEL [being § 2 of Dissertation vi.].
        Encyclopædia Britannica, eighth edition.
        Vol. i.,_Dissertations_, p. 838.


FOURIER (J.)
    Éloge historique de Sir WILLIAM HERSCHEL, prononcé dans la séance
      publique de l'Académie royale des sciences le 7 Juin, 1824.

       _Historie de l'Académie Royale des Sciences de l'Institut de France_,
         _tome_ vi., _année_ 1823, p. lxi.


HARDING (C. L.)
    Des Herrn Dr. HERSCHEL'S Untersuchungen über die Natur der
      Sonnenstrahlen, aus dem englischen übersetzt. Erstes Heft.
      [Translations from _Phil. Trans._, 1800.] Celle, 1801. 16mo.


HASTINGS (C. S.)
    See HOLDEN _and_ HASTINGS.


HERSCHEL (Carolina.)
    An Account of a new Comet. [1786, II.]
        _Phil. Trans._, 1787, vol. LXXVII., p. 1.


HERSCHEL (Carolina.)
    An Account of the Discovery of a Comet. [1793, I.]
        _Phil. Trans._, 1794, vol. LXXXIV., p. 1.


HERSCHEL (Carolina.)
    Account of the Discovery of a Comet. [1795, II.]
        _Phil. Trans._, 1796, vol. LXXXVI., p. 131.


HERSCHEL (Carolina.)
    Catalogue of Stars taken from FLAMSTEED'S observations contained in
      the second volume of his _Historia Coelestis_, and not inserted
      in the British Catalogue; to which is added a collection of errata
      which should be noticed in the same volume; with remarks by W.
      HERSCHEL. London, 1798. Folio.


HERSCHEL (Carolina.)
    Verzeichniss von 74 Sternen FLAMSTEEDS von denen keine beobachtungen
      in der _Hist. Coel. Brit._ vorkommen.
        _Bode's Jahrbuch_, 1806, p. 255


[HERSCHEL (Carolina.)]
    [Notice of her Life.]
        _Monthly Notices Roy. Ast. Soc._, vol. 8, p. 64; _also_, _Memoirs
          Roy. Ast. Soc._, vol. 17, p. 120.


[HERSCHEL (Carolina.)]
    Memoir and Correspondence of CAROLINE HERSCHEL. By Mrs. JOHN
      HERSCHEL. With portraits. London, 1876. 12mo.


HERSCHEL (J. F. W.)
    Article _Telescope_, in Encyclopædia Britannica, eighth edition.
      [This article (illustrated) gives most of the important features of
      Sir WILLIAM HERSCHEL'S manner of grinding and polishing specula.]


HERSCHEL (J. F. W.)
    Catalogue of Nebulæ and Clusters of Stars. [General and systematic
      reduction of all Sir W. HERSCHEL'S observations brought into
      connection with all other similar ones.]
        _Phil. Trans._, 1864. Page 1. 4to.


HERSCHEL (J. F. W.)
    A Synopsis of all Sir WILLIAM HERSCHEL'S Micrometrical Measurements,
      etc., of Double Stars, together with a Catalogue of those Stars . . .
      for 1880.
        _Mem. Roy. Ast. Soc._, vol. 35, p. 21. Lond., 1867. 4to.

HERSCHEL (J. F. W.)
    Additional Identifications of Double Stars in the Synoptic
      Catalogues of Sir WILLIAM HERSCHEL'S Micrometrical Measurements,
      etc.
        _Monthly Notices Roy. Ast. Soc._, vol. 28, p. 151. London, 1868.
         8vo.


HERSCHEL (Mrs. John.)
    Memoir and Correspondence of CAROLINE HERSCHEL. With portraits.
        London, 1876. 12mo.


HERSCHEL (W.)
    [Solution of a prize question. _See_ this book, page 46.]
        _Ladies' Diary_, 1779.


HERSCHEL (W.)
    The favorite Eccho Catch . . . and the preceding Glee [by S. LEACH].
      To which is added the . . . Catch Sung by Three Old Women . . .
      in the Pantomime called "The Genius of Nonsense" [by H. HARINGTON].
        London, 1780(?). Obl. folio. [A MS. copy of this was kindly
        furnished me by Dr. R. GARNETT, of the British Museum.]



HERSCHEL (W.)
    _Göttingen Magazin der Wissenschaften und Literatur_ (1783), vol.
      iii., p. 4. LICHTENBERG and FORSTER, Editors.
        [Letter from HERSCHEL, giving a brief account of his life. _See_
        this book, page 3.]


HERSCHEL (W.)
    I. _Manuscripts in possession of the Royal Society._

       1. A series of register sheets in which are entered up _all_ the
          observations of _each_ nebula, copied _verbatim_ from the
          sweeps. 2. A similar set of register sheets for MESSIER'S nebulæ.
          3. A general index of the 2,508 nebulæ of W. HERSCHEL; given the
          class and number, to find the general number. 4. An index list;
          given the general number, to find the class and number.
          5. A more complete list like 4. 6. A manuscript catalogue of
          all the nebulæ and clusters, reduced to 1,800, and arranged
          in zones of 1° in polar distance; by Miss CAROLINA HERSCHEL.
          7. The original sweeps with the 20-foot reflector at Slough,
          in three small 4to and four folio vols. of MS.


II. _Manuscripts in possession of the Royal Astronomical Society._

        This library contains "the whole series of autograph observations
          of each double star [observed by HERSCHEL], brought together on
          separate sheets by Sir WILLIAM HERSCHEL and Miss CAROLINA
          HERSCHEL."


[HERSCHEL (W.)]
    Some Account of the Life and Writings of WILLIAM HERSCHEL, Esq.
      [With a Portrait.]
        The _European Magazine and London Review_ for January, 1785. 8vo.


[HERSCHEL (W.)]
        _Edinburgh Review_, vol. i., p, 426.
            [A review of HERSCHEL'S memoir, "Observations on the two
            lately discovered bodies," from _Phil. Trans._, 1802. _See_
            this book, page 96.]


[HERSCHEL (W.)]
        "Sir WILLIAM HERSCHEL, from a London paper."

        [This is a short obituary notice "furnished by a gentleman well
          acquainted with Sir WILLIAM and his family, and its accuracy may
          be relied on."]

        _Niles' Register_, vol. 23, p. 154. Nov. 9, 1822. 8vo.


[HERSCHEL (W.)]
    Obituary: Sir WILLIAM HERSCHEL, Knt., LL.D., F.R.S.
        _The Gentleman's Magazine and Historical Chronicle_, vol. xcii.,
          1822, p. 274. 8vo.


[HERSCHEL (W.)]
        _Annual Register_, 1822, p. 289. 8vo.


[HERSCHEL (W.)]
    W. HERSCHEL'S Sämmtliche Schriften, Erster Band.
        Ueber den Bau des Himmels. Mit 10 Kupfertafeln.
          [Edited by J. W. PFAFF. A second edition was published in 1850.]
          Dresden and Leipzig, 1828. 8vo.


[HERSCHEL (W.)]
        _New York Mirror_, vol. vi., 1829-30, p. 388.


[HERSCHEL (W.)]
        _Living Age_, vol. ii., p. 125 (1844). 8vo.
        [Reprinted from _Chambers' Journal_.]


[HERSCHEL (W.)]
        _Foreign Quarterly Review_, vol. 31, p. 438. 8vo.

        [Review of ARAGO'S "Analyse de la vie et des travaux de Sir WILLIAM
          HERSCHEL."]


[HERSCHEL (W.)]
    ARAGO'S Life of HERSCHEL.

        _Eclectic Museum_, vol. ii., p. 556. [Reprinted from the _Foreign
          Quarterly Review_, vol. 31.]


HOLDEN (E. S.)
    On the Inner Satellites of _Uranus_. [Reduction of Sir WILLIAM
      HERSCHEL'S observations.]

        _Proceedings Amer. Assn. Adv. Science_, _August_, 1874, p. 49.
         8vo.


HOLDEN (E. S.)
    Index Catalogue of Books and Memoirs relative to nebulæ, clusters,
      etc. _Smithsonian Miscellaneous Collections_, No. 311, pp. 19-38.
    [Abstracts of Sir WILLIAM HERSCHEL'S memoirs (on nebulæ) in the
      _Philosophical Transactions_.]

        Washington, 1877. 8vo.


HOLDEN (E. S.) and C. S. HASTINGS.
    A Subject-index and a Synopsis of the scientific writings of Sir
      WILLIAM HERSCHEL. [Reprinted from the _Report_ of the Smithsonian
      Institution (1879).]

        Washington, 1881. 8vo.


KRAFFT (J. G. F.)
    Kurze Nachricht von dem berühmten Astronomen HERSCHEL und einigen
      seiner Entdeckungen.

        Bayreuth, 1787. 8vo.

PEIRCE (C. S.)
    Photometric Researches. [A reduction of HERSCHEL'S observations on
      the comparative brightness of the stars.] _Annals Harvard College
      Observatory_, vol. ix.

        Leipzig, 1878. 4to.


SOMMER (G. M.)
    WILLIAM HERSCHEL . . . ueber den Bau des Himmels; drei abhandlungen
      aus dem englischen uebersetzt, nebst einem authentischen Auszug
      aus KANTS allgemeiner Naturgeschichte und Theorie des Himmels.

        Koenigsberg, 1791. 8vo.


STRUVE (W.)
    Études d'astronomie stellaire. Sur la voie lactée et sur la distance
      des étoiles fixes. [P. 24 _et seq._ contains an elaborate review
      of the construction of the heavens according to HERSCHEL.] St.
      Petersburg, 1847. 8vo.


WOLF (R.)
    WILLIAM HERSCHEL. Zurich, 1867. 8vo.


ZACH (F. von.)
    Dr. WILLIAM HERSCHEL [translated from _Public Characters_ and
      printed in ZACH'S _Monatlich Correspondenz_, 1802, part i., p. 70
      _et seq._]


III.--LIST OF THE PUBLISHED PORTRAITS OF WILLIAM HERSCHEL.

_Artist_, MME. DUPIERY. _Engraver_, THÖNERT. 8vo. Early portrait. Some
  copies in red. Profile.

_Artist_, F. REHBURG. _Engraver_, F. W. BOLLINGER. 8vo. Late portrait.

_Artist_, ----? _Engraver_, C. WESTERMAYR. 8vo. Medallion.

_Artist_, C. BRAND. _Engraver_, ----? 8vo. Lithograph.

_Artist_, ----? _Engraver_, J. SEWELL. 8vo. Profile, 1785.

_Artist_, ----? _Engraver_, ----? 8vo. Profile.

_Artist_, F. BONNEVILLE. _Engraver_, F. BONNEVILLE. 8vo. Profile.

_Artist_, J. RUSSELL, R.A. _Engraver_, E. SCRIVEN. 8vo. Engraved from a
  crayon in the possession of his son, and published by the S. D. U. K.
  in the _Gallery of Portraits_, vol. 5.

_Artist_, ----? _Engraver_, ----? 8vo. _European Magazine_, Jan., 1785.
  This is a bust in profile, showing the left side of the face.

_Artist_, ----? _Engraver_, THOMSON. 8vo. Published by Caxton, 1823.
This must have been engraved before 1816 since the legend is WILLIAM
HERSCHEL, LL.D., F.R.S.

_Artist_, Lady GORDON. From the painting by ABBOTT in the National
Portrait Gallery. _Engraver_, JOSEPH BROWN. 8vo. Published in memoir of
CAROLINE HERSCHEL. This is of the date 1788, or thereabouts. _See_
frontispiece.

_Artist_, ----? _Engraver_, C. MÜLLER. 4to. Medallion, 1785(?).

_Artist_, ----? _Engraver_, H. PINHAS. 4to. Legend in Russian.

_Artist_, BAISCH. _Engraver_, ----? 4to. Lithograph.

_Artist_, H. GRÉVEDON. _Engraver_, ----? Fol. Lithograph.

_Artist_, ----? _Engraver_, F. MÜLLER. Fol.

_Artist_, ABBOTT. _Engraver_, RYDER. Fol. 1788.

_Artist_, J. BOILLY. _Engraver_, ----? Fol. 1822. Lithograph.

_Artist_, ----? _Engraver_, J. GODBY. Fol.


R. W. S. LUTWIDGE, Esq., F.R.A.S., has an original seal with a head of
Sir WILLIAM HERSCHEL, which is shown on the title-page of this work. A
cut of it has been courteously furnished me by JOHN BROWNING, Esq.,
F.R.A.S., etc.

In 1787 a bust of HERSCHEL was made by LOCKIE for Sir WILLIAM WATSON.

A picture of HERSCHEL was painted by Mr. ARTAUD about the beginning of
1819. A portrait of HERSCHEL by ABBOTT is in the National Portrait
Gallery, London. There are no doubt many other paintings in England,
though I can find notices of these only. The Royal Society of London has
nearly a hundred portraits of its most distinguished members, but owns
none of Sir WILLIAM HERSCHEL.




                            INDEX OF NAMES.


_N.B.--This index is intended to refer to the proper names occurring in
the body of the work only, and not to the Bibliography._


  Airy (Sir George), 17.

  Alison (Sir Archibald), 111.

  Arago (François), 49, 81, 139.

  Artaud (M.), 114.

  Aubert (Alexander), 52, 62, 63.


  Baldwin (Miss), 115.

  Banks (Sir Joseph), 56, 58, 64.

  Bessel (F. W.), 127, 137.

  Blagden (Dr.), 57.

  Bonaparte (Napoleon), 108, 111.

  Bradley (James), 51, 153.

  Bruhl (Count von), 52.

  Bulman (Mr.), 22, 115, 116.

  Bunsen (Chevalier), 12.

  Burney (Dr.), 82, 101, 102, 104, 105, 106.


  Campbell (Thomas), 107.

  Cassini (J. D.), 51.

  Cropley (Mr.), 20.


  Dalrymple (Mr.), 73.

  D'Arblay (Madame), 100 _et seq._

  Darlington (Earl of), 18.

  Darquier, 51, 119.

  D'Arrest (H. L.), 204.

  Dawes (W. R.), 200.

  De Luc (M.), 64.

  De Luc (Mrs.), 100, 102.

  Dollond (J.), 120.


  Engelfield (Sir Harry), 57.


  Farinelli (Miss), 38.

  Flaugergues (H.), 51, 119.

  Fleming (Miss), 42.

  Fourier (J.), 124.

  Frauenhofer (J.), 195.


  Galileo, 50, 135.

  George III., 64, 77, 124, 126.

  Griesbach (George), 63.

  Griesbachs (the), 62, 106.


  Hansen (P. A.), 142.

  Hastings (C. S.), 119.

  Heberden (Dr.), 64.

  Helmholtz (H.), 188.

  Herschel (Abraham) [1651-1718], 6.

  Herschel (Alexander) [1745-1821], 10, 12, 14, 15, 35, 38, 41, 57, 61,
    62, 66, 72, 73, 114.

  Herschel (Benjamin), 7.

  Herschel (Carolina) [1750-1848], 2, 10, 11, 12, 16, 23, 29, 33, 41, 43,
    68;
    discovers five comets, 69, 70, 78, 83, 103, 105, 112, 113, 114, 115.

  Herschel (Carolina), her _Memoir_ quoted, 2, 9, 13, 23, 29, 31, 34, 36,
    41, 57, 61, 63, 64, 65, 70, 74.

  Herschel (Dietrich), 9, 10, 11, 29, 42, 114.

  Herschel (Eusebius), 7.

  Herschel (Hans) [_circa_ 1600], 6.

  Herschel (Isaac) [1707-1767], 7, 8, 29.

  Herschel (Jacob) [1734-1792], 10, 11, 16, 23, 30.

  Herschel (Sir John Frederick William) [1792-1871], 80, 103, 105, 114,
    126, 127, 143, 203.

  Herschel (Lady), 80, 102, 103, 105, 114.

  Herschel (Major John), 2.

  Herschel (Mrs. Mary Cornwallis), 2.

  Herschel (Sophia Elizabeth), b. 1733, married Griesbach, 10.

  Herschel (William), born 1738, November 15; 10.
    oboist in the band of the Guards (1755), and goes to England for the
      first time, returning in 1756, 16.
    deserts from the Guards and goes to England (1757), 17.
    organizes the band of the Durham militia (1760), 18.
    leaves the band and lives with Dr. Miller, 19.
    leads the public concerts at Wakefield and Halifax, 20.
    organist at Halifax (1765), 22.
    organist of the Octagon Chapel at Bath (1766), 24.
    his musical writings, 26.
    studies Smith's harmonies and optics, 28.
    visits Hanover, August, 1772, 32.
    hires a small telescope, 37.
    makes his first telescope (1774), 38.
    visits Hanover (1775?), 42.
    1st review of the heavens, 39, 73.
    2d review of the heavens, 73.
    3d review of the heavens (1783), 73.
    4th review of the heavens (1785), 74.
    manufacture of telescopes, 40, 59, 75, 77, 120, 121, 122, 123, 124,
      125, 126, 127.
    moves to 19 New King St., Bath, 43.
    conducts oratorios of Handel, 43.
    begins astronomical _measures_ (1779), 44.
    joins Philosophical Society of Bath, 45.
    first published scientific writing (1779), 46.
    first communication to the Royal Society (1780), 47.
    discovery of _Uranus_ (1781, March 13), 49.
    its effect on his career, 53.
    elected a member of the Royal Society (1781), and receives the
      Copley medal, 56.
    attempts a thirty-foot reflector, 59.
    goes to London, 1782 (May, June, July), 61.
    appointed Royal Astronomer (£200), 1782, 67.
    removes to Datchet, 1782, August 1, 67.
    his assiduity, 72, 77, 79, 81.
    his mechanical genius, 14, 41, 121.
    cost of his telescopes, 77.
    marries Mrs. John Pitt, _née_ Baldwin (1783), 80.
    only child born (1792), 80.
    removes to Slough (1786), 81.
    LL.D. (_Oxon._), 1786, 47.
    his account of the discovery of _Uranus_ (1781, March 13), 4.
    discovers two satellites to _Uranus_, 1787, Jan. 11, 84.
    discovers two satellites to _Saturn_, 1789, August-September, 125.
    invents machines for making reflectors (1788), 41.
    began forty-foot telescope, 1785, finished it, 1789, 121.
    biographical letter (1783), 3.
    list of published portraits of him, 232.
    value of his sister's assistance to him, 34.
    letters to Carolina Herschel, 61, 63, 64, 114.
    his personal character (1786-1800), 100 _et seq._
    his relations to his cotemporaries, 85, 86, 87, 91, 94, 95, 96, 97,
      98, 99.
    list of writings relating to him and to his works, 225.
    his literary skill, 45.
    examples of his style, 83 _et seq._
    failure of health, 112 _et seq._
    created a Knight of the Royal Hanoverian Guelphic Order (1816), 115.

  Herschel (Sir William), first president of the Royal Astronomical Society
       (1821), 115.
    his will, 114.
    his death, August 25th, 1822, 116.
    his epitaph, 117.
    list of his scientific writings, 215.
    review of his scientific labors, 118.
    the improvement of telescopes and apparatus, 121.
    the relative brightness of the stars; variable stars, 130.
    researches on double stars, 134.
    researches on planets and satellites, 140.
    researches on the nature of the sun, 145, 186, 198.
    the motion of the solar system in space, 149.
    researches on the construction of the heavens, 154.
    scale of celestial measures; distances of the stars, 170.
    researches on light, heat, etc., 176.
    researches on the dimensions of the stars, 193.
    on the spectra of the fixed stars, 195.
    on the variable emission of light and heat from the sun, 198.
    researches on nebulæ and clusters, 202.

  Huyghens (C.), 50, 189.


  King George III., 64, 77, 124, 126.


  Lacaille (N. L.), 156, 202.

  Lalande (Jerome), 28, 124, 156.

  Lambert (J. H.), 153.

  Lassell (W.), 143.

  Lee (Miss), 61.

  Lichtenberg (Herr), 3.

  Lind (Dr. and Mrs.), 69.

  Long (Dr.), 135.


  Magellan (Herr), 3, 78.

  Maskelyne (Nevil), 5, 51, 57, 62, 63, 150, 153.

  Mayer (Christian), 94, 153.

  Melloni (M.), 186.

  Messier (C.), 202.

  Michell (John), 52, 94, 137, 156.

  Miller (Dr.), 19, 20, 21, 22.

  Monson (Mrs.), 115.

  Moritzen (Anna Ilse), m. Isaac Herschel, 7, 8.


  Napoleon I., 108, 111.

  Newton (Sir Isaac), 189, 190, 191, 192.


  Olbers (William), 95.


  Pabrich (Cappelmeister), 7.

  Palmerston (Lord), 64.

  Piazzi (Joseph), 75, 95.

  Pierce (Charles S.), 132.

  Pigott (J.), 119.

  Poggendorff (J. G.), 188.


  Ronzoni (Signor), 59.

  Rosse (Lord), 122, 207.


  Savary (M.), 139.

  Secchi (Angelo), 195, 196.

  Scheiner (C.), 199.

  Schroeter (J. H.), 51, 77, 91, 92, 93.

  Schwabe (H.), 201.

  Short (James), 120.

  Smith (Dr. Robert), 28.

  Snetzler (Herr), 20, 21.

  Struve (Otto von), 129.


  Thomson (Thomas), 95.


  Verdet (E.), 188.


  Wainwright (Dr.), 20.

  Walsh (Colonel), 62.

  Watson (Sir William), 44, 58, 60, 64, 65, 66, 67, 75, 76.

  Watt (James), 106.

  Weld (R.), 126.

  Wilson (Alexander), 52, 94, 146.


  Zach (Baron von), 69.




THE END.




START OF TRANSCRIBER'S NOTES:

I have used [alpha] to represent the greek letter used in the text.


  page line  In the Original text, left as is.
  227    3   übersetzt
  231   29   uebersetzt
   18   24   Biographie universelle des musiciens
  226   24   Biographie universelle des Musiciens
  231   33   Koenigsberg, 1791. 8vo.
  226    9   Königsberger Allgemeine Zeitung
  195    4   Fraunhofer
  235 index  Frauenhofer (J.), 195.
  226   29   Vol.  (all other occurances are) vol.
  238 index  Ronzoni (Signor), 59.
   58   26   Ronzini


  Original
  page line  Original text                    Replaced with
   65   23   ornamented.                      ornamented."
  117   31   [C] for letter C reversed        CI[C]I[C]CCCXXII
  216   25   den 18. May                      den 18. Mai
  219   23   Suppl. Band., p. 238.            Suppl. Band, p. 238.


END OF TRANSCRIBER'S NOTES:






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