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Title: Herschel
Author: Macpherson, Hector Copland (1888-1956)
Illustrator: Abbott, Lemuel Francis (1760?-1802)
Photographer [of Abbott's portrait]: Walker, Emery (1851-1933)
Date of first publication: 1919
Edition used as base for this ebook:
   London: Society for Promoting Christian Knowledge;
   New York: Macmillan, 1919
   [Pioneers of Progress. Men of Science.]
   [first edition]
Date first posted: 4 July 2012
Date last updated: 4 July 2012
Project Gutenberg Canada ebook #963

This ebook was produced by
David T. Jones, Ross Cooling, Walter MacDonald
& the Online Distributed Proofreading Canada Team
at http://www.pgdpcanada.net

This ebook was produced from images generously made
available by the Internet Archive






  PIONEERS
  OF
  PROGRESS

[Illustration]

  MEN OF SCIENCE

  HERSCHEL

  HECTOR MACPHERSON




[Illustration:

  L.F. Abbott, pinxit      Emery Walker, photographer

  SIR WILLIAM HERSCHEL, K.H., F.R.S.

  From the picture in the National Portrait Gallery]




  PIONEERS OF PROGRESS

  MEN OF SCIENCE
  Edited by S. CHAPMAN, M.A., D.Sc., F.R.S.

  HERSCHEL

  BY THE REV.
  HECTOR MACPHERSON
  M.A., F.R.A.S., F.R.S.E.

  AUTHOR OF
  "ASTRONOMERS OF TO-DAY," "A CENTURY'S PROGRESS IN ASTRONOMY"
  "THE ROMANCE OF MODERN ASTRONOMY," ETC. ETC.

  LONDON:
  SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE
  NEW YORK: THE MACMILLAN COMPANY
  1919




  CONTENTS.


  CHAP.                                           PAGE

     I. Early Years                                  5

    II. Herschel as Amateur Astronomer              15

   III. Herschel as Professional Astronomer         25

    IV. Solar and Planetary Studies                 36

     V. The Construction of the Heavens             46

    VI. Stellar Researches                          55

   VII. Closing Years                               61

  VIII. Personality and Influence                   70




  CHAPTER I.

  EARLY YEARS.


"Universal history--the history of what man has accomplished in this
world," says Carlyle, "is at bottom the history of the great men who
have worked here." It must be admitted that Carlyle under-estimated the
labours of the innumerable lesser workers in all departments of human
activity, that he overlooked the part played by mighty world-movements
in the realm both of thought and of action and the influence, even on
great men, of what has been called the "time-spirit". Still, Carlyle's
dictum--slightly qualified--is fundamentally true. A great personality
is a creative force; he gives more to his age and to posterity than he
receives from his age or the ages before him.

The history of astronomical science has been dominated in a remarkable
degree by great creative personalities--pioneers of astronomical
discovery. In the front rank of these distinguished men, posterity has
placed the name of William Herschel.

The illustrious astronomer came of an old German family, and was
descended from one of three brothers, who, on account of steadfast
devotion to the principles of Protestantism, were driven out of Moravia
in the early part of the seventeenth century and compelled to seek
refuge in Saxony. Hans Herschel, one of these brothers, settled at Pirna
in Saxony. His second son, Abraham, born in 1651, acquired some
distinction as a landscape-gardener. He learned gardening in the
Elector's gardens at Dresden, and was afterwards employed, until his
death in 1718, at the country-seat of Hohentziatz, in the principality
of Anhalt-Zerbst, near Magdeburg. According to the short account of the
family given by his illustrious grandson, "he had also a good knowledge
of arithmetic, writing, drawing, and music". The last-named talent he
bequeathed to his youngest son, Isaac, born at Hohentziatz on 14th
January, 1707. In a brief review of his life which he left behind him,
Isaac explains that it was the desire of his parents that he should
follow in his father's line of life. After the death of his father, his
elder brother Eusebius procured for him a situation in the gardens at
Zerbst. But he had, in his own words, "lost all interest in gardening".
"As I had already at Hohentziatz procured a violin and learned to play
it by ear, I took proper lessons at Zerbst from an hautboy-player in the
court-band. I also bought an hautboy, and was never so happy as when I
could occupy myself with music." At the age of twenty-one, having
decided to follow out music as his life-work, he went to Berlin to
study. Finding "the Prussian service as a bandsman very bad and
slavish," he went to Potsdam and took lessons for a year. From Potsdam
he made his way to Brunswick, and thence to Hanover, where in August,
1731, he was engaged as hautboy-player in the Foot-guards. Hanover was
destined to be his home, and in 1732 he married Anna Ilse Moritzen, the
daughter of a citizen of the neighbouring town of Wenstadt. They had a
family of ten, of whom six--four sons and two daughters--reached
maturity. Of these, the third, Friedrich Wilhelm, born at Hanover on
15th November, 1738, became one of the greatest astronomers--indeed, one
of the greatest men of science--of all time.

Isaac Herschel seems to have been not only a man of high musical talent,
but also of wide general culture. And despite the mother's dislike to
learning and her lack of interest in intellectual things, all the
members of the family--with the exception of the elder daughter,
Sophia--inherited something of their father's ability. All four
sons--Jacob, William, Alexander, and Dieterich--were eminent musicians;
and the younger daughter, Caroline Lucretia, born 16th March, 1750, also
accomplished in music, has earned a distinction only second to that of
her distinguished brother, whose life-work she shared.

In her memoirs, written in old age, Caroline Herschel has given some
interesting reminiscences of her father. "My father," she says, "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."

Despite his remarkable abilities, Isaac Herschel's whole life was spent
in straitened circumstances: the post of bandsman in the Hanoverian
Guards was not a lucrative one, and he was forced to augment his income
by private tuition. In addition, his poverty was aggravated by chronic
ill-health. After the battle of Dettingen in 1743, the Guards remained
all night in the field. Isaac Herschel lay in a wet furrow, and as a
result of that night's exposure, he contracted an asthmatical affection
which impaired his health permanently and ultimately caused his
premature death on 22nd March, 1767. Having no worldly goods to bequeath
to his children, he sought to educate them as completely as his limited
means would allow. From their earliest days, their father instructed
them in music. William Herschel, in the short account of his life
already referred to, tells us that his father "taught me to play on the
violin as soon as I was able to hold a small one made on purpose for me.
. . . Being also desirous of giving all his children as good an
education as his very limited circumstances would allow, I was at a
proper time sent to a school where, besides religious instructions, all
the boys received lessons in reading, writing, and arithmetic; and as I
very readily learned every task assigned me, I soon arrived at such a
degree of perfection, especially in arithmetic, that the master of the
school made use of me to hear younger boys say their lessons and to
examine their arithmetical calculations."

At the age of fourteen and a half, young William Herschel entered the
band of the Hanoverian Guards, on 1st May, 1753. His school life was at
an end, but his education was only beginning. For over two years he
received private lessons from a teacher named Hofschlger, who
afterwards filled an important post at Hamburg. These lessons included
languages, logic, ethics, and metaphysics. In those early years
Herschel's thirst for knowledge seems to have been insatiable.
"Although," he wrote in after years, "I loved music to excess and made
considerable progress in it, I yet determined with a sort of enthusiasm
to devote every moment I could spare to the pursuit of knowledge, which
I regarded as the sovereign good, and in which I resolved to place all
my future views of happiness in life."

This intellectual keenness was undoubtedly stimulated by the home
environment. The mother, it is true, was hostile to intellectual
ambition; she was a typical German _Hausfrau_, with no sympathy for
aspirations; but, as before mentioned, Isaac Herschel encouraged his
sons to talk and think on scientific and philosophical subjects.
Caroline Herschel, then a little girl about five years of age, has given
a very interesting glimpse into this period. "My brothers," she says,
"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 home from
a concert, or conversations on philosophical subjects which lasted
frequently till morning. . . . 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 Leibniz, 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."

The family circle was temporarily dispersed in the end of 1755. The
times were stormy: the Seven Years' War was raging: a French invasion of
England was expected, and the Hanoverian Guards were drafted across the
North Sea. Accordingly, Isaac Herschel and his two sons left Hanover
with the regiment. Embarking at Cuxhaven in the end of March 1756, they
reached Chatham after a passage of sixteen days. The Guards were
encamped successively at Maidstone, Coxheath, and Rochester. The
Herschels' sojourn in England was by no means profitless. At Coxheath as
well as at Maidstone, Herschel tells us, "my father, my eldest brother
and myself made several valuable acquaintances with families that were
fond of music, and which, on mine and my brother's return to England,
proved of great service to us". At Maidstone, too, young William
Herschel purchased a copy of Locke's "Essay on the Human Understanding".
The perusal of this volume--the only thing he took with him from
England--not only stimulated his interest in philosophy, but
familiarised him with the English language.

In the end of 1756, the Guards were ordered back to Hanover, owing to
the French threat to the country. Early in the following year, the
regiment went into the campaign which culminated in the disastrous
battle of Hastenbeck, 26th July, 1757. During the campaign they were
many times forced to encamp in the wet furrows of ploughed fields. At
Hastenbeck, the band was almost within reach of gunshot. Accordingly,
Isaac Herschel advised his son to consider his own safety. Young
Herschel thereupon, in his own words, "left the engagement and took the
road to Hanover, but when I arrived there, I found that having no
passport I was in danger of being pressed for a soldier". At that time
Herschel was not technically a soldier, but a member of the band.
Accordingly, he returned to the regiment, only to find that "nobody had
time to look after the musicians--they did not seem to be wanted". The
forced marches in the hot weather told on the lad's health, and his
father advised him to leave the service. "In September, my father's
opinion was, that as on account of my youth I had not been sworn in when
I was admitted to the Guards, I might leave the military service.
Indeed, he had no doubt but that he could obtain my dismission, and this
he after some time actually procured (in 1762) from General Sprcken,
who succeeded General Sommerfeld."

The formal discharge paper is in existence and was printed for the first
time in the "Collected Scientific Papers of Sir William Herschel,"
published in 1912. Dr. Dreyer, in his introductory sketch of Herschel's
life, gives it as his opinion that "the existence of this formal
discharge paper puts an end to the legend, too long and too readily
believed, that he deserted from the army and that he received a formal
pardon for this offence from George III on the occasion of his first
audience in 1782". Whether Herschel was technically a deserter or not,
it is very difficult to determine. In some notes furnished in later
years to the editor of a Gttingen scientific periodical, Herschel said:
"In my fifteenth year, I enlisted in military service, only remaining in
the army, however, until my nineteenth year, when I resigned and went
over to England." On the other hand, as already noted, he gives it as
his father's view that he was not really a soldier at all. The formal
discharge paper is dated 29th March, 1762, so that if William Herschel
was ever actually a unit of the army, the discharge paper merely
registered an accomplished fact: he had been out of the army and out of
the country for four and a half years. Whether or not he was _ipso
facto_ a soldier by virtue of his position in the band, there can be no
doubt that his departure for England was actuated by the desire to avoid
being recalled to the colours. The evidence of his sister Caroline, then
a little girl of seven, is decisive on this point. "I can now
comprehend," she says, "the reason why we little ones were continually
sent out of the way, and why I had only by chance a passing glimpse of
my brother as I was sitting at the entrance of a street door, when he
glided like a shadow along, wrapped in a greatcoat, followed by my
mother with a parcel containing his accoutrements. After he had
succeeded in passing unnoticed beyond the last sentinel at Herrenhausen,
he changed his dress. . . . My brother's keeping himself so carefully
from all notice was undoubtedly to avoid the danger of being pressed, as
all unengaged young men were forced into the service. Even the clergy,
unless they had livings, were not exempted."

At Hamburg, William Herschel was joined by his brother Jacob, and they
embarked together for England. Arriving in London, they were greatly
assisted by the friends whom they had made on the occasion of their
previous visit. Nevertheless, they seem to have had a hard struggle.
William Herschel had not half a guinea in his possession when he arrived
in London. He went into a music shop and asked if he could be of any use
in copying music. An opera was placed in his hands, and his promptitude
in returning the copy so impressed the master of the shop that he kept
him in his employment for a considerable time. Jacob Herschel contrived
to gain a livelihood by teaching music. At length, the brothers found
that they could not make a living in London. Accordingly, Jacob decided
to return to Hanover in the autumn of 1759 to compete for a place in the
court orchestra, which he was successful in gaining. For a time, William
was, in his own words, "involved in great difficulties". Fortunately,
however, he succeeded in procuring an appointment in Yorkshire. The Earl
of Darlington, Colonel of the Durham militia, was desirous of obtaining
a good musician as leader of the band. Herschel's name was brought to
his notice, and he received the offer of the post, which he accepted and
held for two years. These two years appear to have been very crowded.
The brief entries in his diary record the composition of various
symphonies, and he seems to have travelled a great deal over the north
of England. In 1761 he applied for an important post in Edinburgh--"the
manager of the concerts intending to leave that place"--and in
anticipation of receiving the appointment, he terminated his engagement
with Lord Darlington. However, Herschel was disappointed, as the concert
manager altered his plans and decided to remain at his post. On arriving
in Edinburgh, he records in his diary: "I was introduced to Mr. Hume,
the metaphysician, and a few days after, at one of their regular
concerts, I was appointed to lead the band of musicians, while some of
my symphonies and solo concerts were performed. Mr. Hume, who patronised
my performance, asked me to dine with him, and accepting of his
invitation, I met a considerable company."

During the next few months, Herschel held temporary appointments at
Newcastle and Pontefract, and in April, 1762, he accepted a post as
manager of concerts at Leeds, where he remained for about four years.
During this time, his public engagements multiplied, and he was rapidly
acquiring a notable position as a teacher of music--in which he was
greatly aided by his friend, Dr. Miller, organist at Doncaster, who
advised him to compete for the post of organist at Halifax. In his
memorandum for 7th March, 1766, Herschel states that the "Messiah" was
performed at a private club of chorus singers in Halifax, where it was
agreed to rehearse the same oratorio every other Friday in order to
perform it in the church at the opening of a new organ erected there.
". . . I was a candidate for the place of organist, which, by the
interest of the Messrs. Bates and many musical families I attended, I
had great hopes to obtain". On 30th August, 1766, he was unanimously
chosen as organist, but he had already been asked to allow himself to be
nominated as organist of the Octagon Chapel at Bath, where a new organ
was in process of erection. On 30th November, he played the organ at
Halifax for the last time, and notes: "For the thirteen Sundays of my
being organist, I was paid thirteen guineas". On 9th December he arrived
at Bath; and on 4th October, 1767, the Octagon Chapel was opened, with
Herschel as organist. He now entered on a busy and successful musical
career. Pupils flocked to him, and sometimes his lessons numbered
thirty-five a week. In addition, he composed anthems and psalm-tunes.
Under the date 28th March, 1767, he noted, "Taken a house from 25th
March to 29th September in Beaufort Square". Herschel had at last a
settled home in England.

In his diary, under the date 5th April, Herschel notes: "Went into
mourning for the death of my father". The vicissitudes through which the
family passed have been graphically described by Caroline, who was, at
her father's death, a girl of seventeen. From her earliest years,
Caroline had two objects of idolatry--her father and her "dear brother
William"--"the best and dearest of brothers". Her mother was
unimaginative and unsympathetic, without interest in intellectual or
graceful accomplishments. "It was her certain belief," Caroline records,
"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." Accordingly, Caroline became virtually the Cinderella of the
family--from earliest years a little neglected maid-of-all-work. Her
eldest brother and sister showed her little attention, and all her love
was concentrated on the father who wished to give her "something like a
polished education," and on her brother William, who invariably showed
her kindness and affection.

After her father's death, she describes herself as having fallen into a
"state of stupefaction". She "could not help feeling troubled about her
future destiny". Her mother and her brother Jacob consistently
under-estimated her; and domestic service seemed to be the only future
in store for her. But William had not forgotten the little sister of
early years. In 1771 he wrote home proposing that she should join him in
Bath and become "a useful singer for his winter concerts and oratorios".
Despite the opposition of her mother and the ridicule of her brother
Jacob, the plan materialised. In the autumn of 1772 William Herschel
arrived in Hanover, and at the close of a fortnight's stay, set off for
England along with Caroline. They arrived in Bath on 28th August, 1772,
and Caroline was at once installed as her brother's housekeeper. She
received instruction in English and arithmetic as well as lessons in
music. Already, too, a new interest had crept into Herschel's life. "By
way of relaxation," his sister tells us, "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."




  CHAPTER II.

  HERSCHEL AS AMATEUR ASTRONOMER.


In his diary, under the date 1766, Herschel has the following entries:
"February 19th. Wheatley. Observation of Venus." "February 24th. Eclipse
of the Moon at 7 o'clock a.m. Kirby." These are the first indications of
his interest in astronomy. He had from early years inherited from his
father a taste for what might be called star-gazing, and along with this
he had had from youth a bent towards mathematical as well as
philosophical research. Even in his busiest years, he never ceased to
read and study in his leisure hours. During the first years of his stay
in England, his foremost care was to master the English language. Next
he acquired Italian, which he believed to be essential to his
profession. From this he passed on to the study of Latin and Greek. The
latter language, however, he dropped, "as leading me too far from my
other favourite studies by taking up too much of my leisure. The theory
of music being connected with mathematics induced me very early to read
in Germany all that had been written upon the subject of harmony; and
when, not long after my arrival in England, the valuable book of Dr.
Smith's 'Harmonics' came into my hands, I perceived my ignorance, and
had recourse to other authors for information, by which I was drawn on
from one branch of mathematics to another." After perusing Smith's
"Harmonics," he became possessed of a copy of the same author's "System
of Optics". The study of optics passed into that of astronomy, which
was stimulated by "Astronomy Explained upon Sir Isaac Newton's
Principles," by James Ferguson, the Scottish astronomer. Herschel's
early interest in the latter science seems to have been revived. So
enthusiastic did he become that, in his own words, "I resolved to take
nothing upon trust, but to see with my own eyes all that other men had
seen before". At the time of his sister's arrival at Bath, Herschel had
plunged in earnest into the study of astronomy. "He went to sleep," she
tells us, "buried under his favourite authors; and his first thoughts on
rising were how to obtain instruments for viewing these objects himself
of which he had been reading." In May, 1773, he procured some
object-glasses which he fitted into pasteboard tables. Caroline
Herschel, who at that time had no interest whatever in telescopic
astronomy, tells us: "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". At length,
Herschel completed this instrument, 4 feet long, which magnified forty
times. With this, he records, he observed Jupiter and its satellites.
Afterwards he made other two refractors--15 and 30 feet long
respectively. Herschel soon discovered for himself the great weakness of
the refracting telescope--the long tubes which were then necessary in
order to counteract the effect of chromatic aberration. Finding the long
tubes almost "impossible to manage," he turned his attention to the
reflecting telescope, and in September hired a two-foot Gregorian
reflector, which he found much more convenient. He decided to acquire a
mirror of his own, for a tube 5 or 6 feet long. On enquiry he found
there were none in the market of so large a size. "A person," his sister
tells us, "offered to make one at a price much above what my brother
thought proper to give." Herschel, however, was not discouraged. He
became acquainted with a Quaker resident in Bath, who had in his leisure
hours amused himself with efforts at the construction of mirrors. This
individual had apparently failed in his endeavours--"his knowledge,"
Herschel noted, in that indifferent English which characterised him
throughout his lifetime, "being very confined"--and had decided to
dispose of his tools and half-finished mirrors. Herschel accordingly
purchased his stock, and plunged at once into the work of
telescope-making.

All through the winter 1773-4 and the following spring and summer,
Herschel laboured at his new line of work, in the midst of his busy
professional life. By 21st October, he had succeeded in casting mirrors
for a two-foot reflector, and by the middle of December, "it became
necessary to think of mounting these mirrors". Early in the new year, he
placed a 5-foot mirror into a square wooden tube, but finding the
adjustment of the Gregorian telescope very troublesome, he decided to
have recourse to the Newtonian form. On 1st March, 1774, he made his
first entry in his astronomical journal, stating that he had viewed "the
lucid spot in Orion's sword belt" and the ring of Saturn, which appeared
"like two slender arms". The success of this instrument encouraged
Herschel to construct other telescopes of the Newtonian form, and at
length he succeeded in making a 7-foot telescope with "many different
object mirrors". On 1st May, 1776, he observed Saturn's ring and two
belts "with great perfection".

The memoirs of his sister give us some idea of his unflagging energy.
With sorrow, natural from the housekeeper's point of view, Caroline saw
almost every room in the house transformed into a workshop. A tube and
stand were set up in a handsomely-furnished drawing-room; while
Alexander Herschel, the younger brother, who had now come to reside in
Bath, erected a huge turning-machine in a bedroom, for turning
eye-pieces and grinding glasses. "Every leisure moment was eagerly
snatched at for resuming some work which was in progress, without taking
time for changing dress, and many a lace ruffle was torn or bespattered
by molten pitch." From now onwards, Caroline proved herself the devoted
assistant and helper of her brother, keeping house for him, assisting
him in music and in his work of telescope-making. "By way of keeping him
alive," she says, "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' Entertainments,' the novels of Sterne, Fielding, etc.; serving
tea and supper without interrupting the work with which he was engaged.
. . . and sometimes lending a hand. . . . My brother Alex. was absent
from Bath for some months every summer, but when at home he took much
pleasure to execute some turning or clockmaker's work for his brother."

Herschel was not content with the construction of one or two telescopes.
The work went on during the remainder of his stay in Bath. How he
contrived to continue the construction of telescopes while making
long-continued surveys of the heavens--all in the spare time which he
was able to snatch from his busy career as a professional musician--must
always remain more or less of a mystery.

His earliest observations were on the Moon and planets. In 1776 he made
a number of examinations of the lunar surface, and three years later was
engaged in measuring the heights of the lunar mountains. From 1774
onwards, he carefully observed Saturn, and in April, 1777, he commenced
to make sketches in pen and ink of the markings on the surface of Mars,
and in the following year of those on Jupiter. His attention was not
confined to the members of the Solar System, and in 1777 he commenced a
series of observations on the variable star, Omicron--or Mira--Ceti. As
early as 1778 he had conceived the idea of attempting to determine by
measures of close doubles the annual parallax or apparent displacement
of a star in the sky due to the earth's change of position as it moves
in its orbit. From this parallax, the distance of a star is determined.
Before Herschel's time, astronomers had made many attempts to measure
stellar parallax, but owing to the great distance of even the nearest
stars and the consequent smallness of the displacement, and also because
of the comparative imperfection of astronomical instruments, all these
efforts had failed. Herschel was particularly interested in the problem,
and made several attempts to solve it, but was unsuccessful. It was not
until 1838 that the first determinations of stellar parallax were made.
Herschel's attempts were not altogether in vain, however, for while
tackling the problem, he was led to the study of double stars, which
resulted, after many years, in one of his greatest discoveries. At the
same time he executed his first review of the heavens with his 7-foot
Newtonian reflector. The review only extended to the first four
magnitudes: it was in itself a mere beginning, but it was the
starting-point of his work on stellar distribution.

Herschel soon became known to the cultured public of Bath, not only as a
prominent musician, but also as an amateur astronomer of considerable
eminence. His introduction to literary and scientific circles in the
town was a somewhat unconventional one. In his diary, under the date
December, 1779, there occurs the following entry: "About the latter end
of this month, I happened to be engaged on a series of observations on
the lunar mountains, and the Moon being in front of my house late in the
evening, I brought my 7-foot reflector into the street, and directed it
to the object of my observations. While I was looking into the
telescope, a gentleman coming by the place where I was stationed stopped
to look at the instrument. When I took my eye off the telescope, he very
politely asked if he might be permitted to look in, and expressed great
satisfaction at the view. Next morning, the gentleman, who proved to be
Dr. Watson, jun. (now Sir William), called at my house to thank me for
my civility in showing him the Moon, and told me that there was a
Literary Society then forming at Bath and invited me to become a member,
to which I readily consented."

About the middle of January, 1780, this society--the Philosophical
Society of Bath--began its meetings. Herschel not only attended these,
but contributed a considerable number of papers--thirty-one in all--in
the course of the next two years. One or two of these dealt with
astronomical subjects, such as the height of the lunar mountains, and
the variable star Mira Ceti; but most of them were on metaphysical and
physical subjects, such as "The Utility of Speculative Enquiries," "On
the Existence of Space," and "Experiments in Light". These were nearly
all published in 1912 in the "Collected Scientific Papers of Sir William
Herschel". Through Dr. Watson's influence, Herschel was introduced to
scientific circles in London, and he forwarded four communications to
the Royal Society before he was elected a Fellow. These were, a paper on
"Mira Ceti," read 11th May, 1780; on the "Mountains of the Moon," read
the same day; on the "Rotation of the planets on their Axes, with a view
to determine whether the Earth's diurnal motion is perfectly
equable,"--a remarkable and ingenious paper bearing the stamp of his own
peculiar methods of investigation--read 11th January, 1781; and "Account
of a Comet," read 26th April, 1781.

The last-named paper gave an account of the discovery which marked the
turning-point in Herschel's career. On 17th August, 1779, he commenced
his second review of the heavens. This review was made with his 7-foot
telescope of 62 inches aperture, and included stars down to the eighth
magnitude; its main purpose was to register double stars. On Tuesday,
13th March, 1781, in the course of this review, he jotted down in his
journal the following note, in somewhat doubtful English: "In the
quartile near Zeta Tauri, the lowest of two is a curious either nebulous
star or perhaps a comet. A small star follows the comet at two-thirds of
the field's distance." In the paper afterwards communicated to the Royal
Society, he explained that he perceived a star which appeared "visibly
larger than the rest: being struck with its uncommon magnitude, 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,
suspected it to be a comet". On Saturday, 17th March, he wrote, "I
looked for the comet or nebulous star, and found that it is a comet, for
it has changed its place". By Monday, the 19th, he found that the
supposed comet "moves according to the order of the signs, and its orbit
declines but little from the ecliptic".

The discovery was soon communicated to the Observatories of Greenwich
and Oxford. Maskelyne, the Astronomer-Royal, wrote to Dr. Watson on the
4th April that he had observed the strange object, "very different from
any comet I ever read any description of or saw". On 23rd April he wrote
to Herschel: "It is as likely to be a regular planet moving in an orbit
nearly circular round the Sun as a comet moving in a very eccentric
ellipsis"; and he immediately notified the French astronomers of the
discovery. Messier, the most famous observer of comets, commenced
observations on 16th April, and his example was followed by Lalande,
Lemonnier, and other astronomers in France and by Bode in Germany.
Efforts were made to calculate its orbit, on the assumption that it
actually was a cometary body. Orbits were calculated by Mchain, De
Saron, Laplace, and others. These efforts were fruitless. On 8th May De
Saron announced that the "comet" was much more distant from the Sun than
had been supposed. Laplace independently reached a similar conclusion.
Meanwhile, Lexell, the St. Petersburg mathematician, who happened to be
in England when the discovery was made, informed the St. Petersburg
Academy that the object discovered by the Bath musician was probably not
a comet at all, but an exterior planet, revolving at twice the distance
of Saturn, thus confirming Maskelyne's sagacious surmise. Later it
transpired that the planet had been observed no fewer than seventeen
times between 1690 and 1781 by able observers such as Flamsteed,
Bradley, Lemonnier, and Meyer, all of whom failed to differentiate it
from an ordinary star, either in regard to its appearance or its motion.
Lemonnier, indeed, had the discovery almost within his grasp, for he
observed the planet on four consecutive days in January, 1769, but his
carelessness robbed him of the distinction of detecting a new celestial
body.

No little excitement was aroused by Herschel's achievement. It was the
first planetary discovery within the memory of man--Mercury, Venus,
Mars, Jupiter, and Saturn having been known from prehistoric times. More
wonderful still, the discovery had been made, not by the leading
astronomers of the day, but by an unknown amateur. At one bound Herschel
leaped from obscurity to fame. The Royal Society of London awarded him
the Copley Medal in November, 1781, and elected him a Fellow in
December, exempting him from payment of subscriptions, as a mark of
esteem. The discovery had caused a stir in still higher circles, and on
10th May, 1782, Herschel was informed that the King--George
III--expected to make his acquaintance. On 8th May he left Bath to join
his friend, Dr. Watson, at Lincoln's Inn Fields, taking with him his
instruments, star-catalogues, maps, tables, etc. In a letter to his
sister, dated 25th May, he stated that he had had an audience of the
King, to whom he presented a drawing of the Solar System. On 2nd July
Herschel noted in his diary: "I had the honour of showing the King and
Queen and the Royal Family the planets Jupiter and Saturn, and other
objects".

Herschel was now seriously considering the possibility of abandoning the
profession of music and devoting himself to astronomy. There can be
little doubt that after George III expressed interest in the discovery,
Herschel indicated that he was anxious to be made "independent of
music". The result of his interview with the King was his appointment as
King's Astronomer. The appointment is referred to by Herschel himself in
his journal in the following terms: "It was settled by His Majesty that
I should give up my musical profession and, settling somewhere in the
neighbourhood of Windsor, devote my time to astronomy". The salary
attached to the new office was fixed at 200--certainly not a large sum.
Indeed, when Herschel's intimate friend, Dr. Watson, was informed as to
the exact amount, he exclaimed, "Never bought monarch honour so cheap".
Writing to her nephew, Sir John Herschel, in April, 1827, Caroline
attributed the "close bargains" made between George III and her brother
to the "shabby, mean-spirited advisers" of the King. Undoubtedly
Herschel made a pecuniary sacrifice in accepting the offer, but "the
prospect of entering again on the toils of teaching, etc," his sister
tells us, "which awaited my brother at home, appeared to him an
intolerable waste of time". Doubtless Herschel believed it to be the
best policy to close with the King's offer and thus be free to devote
himself to the study which had become the master-passion of his life.
The meagreness of the allowance has been often commented upon, but it
must be remembered, in justice to George III, that, firstly, the
purchasing power of money was considerably greater then than now, and,
secondly, the regular duties attached to the office were at that time
very few. There is no doubt that George III, by his creation of this new
post, made possible Herschel's long career of investigation and
discovery: for no man, not even Herschel, could possibly have stood the
strain of a life of professional activity and scientific investigation
combined. As one of his biographers has well said, "The astronomer of
Slough was the gift to science of the poor mad king".




  CHAPTER III.

  HERSCHEL AS PROFESSIONAL ASTRONOMER.


On 1st August, 1782, William and Caroline Herschel, in accordance with
the obligation of the holder of the new office of King's Astronomer to
reside near Windsor, entered into occupation of a large house on Datchet
Common. The house was in a ruinous condition and the garden and grounds
were overgrown with weeds. Nevertheless there were, in Herschel's eyes,
compensating advantages. There were outhouses available for the work of
telescope-making; a large laundry capable of refitting as a library;
and, most important of all, a grass lawn where telescopes could be
erected. Despite the discomforts of the half-ruinous house, and the
separation from congenial friendships--most of all from Alexander
Herschel, who remained in Bath to continue his musical career--William
Herschel was in the best of health and spirits. "Much of my brother's
time," Caroline Herschel records, "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". Undoubtedly there was much exacting and irksome
duty of this kind, of which Caroline complains in her reminiscences
again and again. Yet despite this, and despite also the smallness of his
salary, Herschel always expressed gratitude for the King's generosity.
The personal relations between George III and his astronomer seem to
have been consistently congenial; and one cannot help feeling that
something more than expediency prompted Herschel in his choice of a
name for the new planet which he had discovered.

As early as May, 1782--before the King had appointed him as King's
Astronomer--Herschel was apparently of opinion that the new planet
should be named after George III. In a letter to Herschel, dated 10th
May, 1782, Colonel Walsh, evidently one in close touch with the court,
wrote: "In a conversation which I had the honour to hold with His
Majesty on 30th ult. concerning you and your memorable discovery of a
new planet, I took occasion to mention that you had a two-fold claim as
a native of Hanover and a resident of Great Britain, where the discovery
was made, to be permitted to name the planet from His Majesty". In a
letter to his friend Watson in July, Herschel suggested the name, "Sidus
Georgium". It was not until the following year, after he was settled at
Datchet, that Herschel addressed to Sir Joseph Banks, President of the
Royal Society, a letter concerning the name of the new planet. "In the
fabulous ages of ancient times," he said in the course of this letter,
"the appellations of Mercury, Venus, Mars, Jupiter, and Saturn were
given to the planets as being the names of their principal heroes and
divinities. In the present more philosophical era, it would hardly be
allowable to have recourse to the same method and to call on Juno,
Pallas, Apollo or Minerva for a name to our new heavenly body. The first
consideration in any particular event or remarkable incident seems to be
its chronology: if, in any future age, it should be asked _when_ this
last-found planet was discovered, it would be a very satisfactory answer
to say, 'In the reign of King George the Third'. As a philosopher, then,
the name of Georgium Sidus presents itself to me as an appellation which
will conveniently convey the information of the time and country where
and when it was brought to view." Herschel then proceeds to eulogise the
King as "the liberal protector of every art and science," and as his
own benefactor, and closes with these words: "By addressing this letter
to you, Sir, as President of the Royal Society, I take the most
effectual method of communicating that name to the Literati of Europe,
which I hope they will receive with pleasure".

Herschel's suggestion, however, did not meet with the approval of the
scientific world. As the late Sir Robert Ball happily expressed it, the
continental astronomers thought that the King of England would "seem
oddly associated with Jupiter and Saturn; perhaps also they considered
that the British dominions, on which the Sun never sets, were already
quite large enough without further extension to the celestial regions".
Lalande proposed the name of Herschel, and for a considerable time the
planet was thus known in France. Indeed the name was also adopted in
many circles in Great Britain. Bode of Berlin, the editor of the
"Astronomisches Jahrbuch" of the day and one of the leading German
astronomers, suggested "Uranus," in keeping with the old custom of
affixing mythological names to the celestial bodies. For years all three
names were in use. In the "Nautical Almanac" the name, "the Georgian,"
evidently preferred to "Georgium Sidus," was used officially until 1847.
By the middle of the century, however, the name "Uranus" had been
generally adopted, and there can be no doubt that the decision was
sound. Bode was right and Herschel wrong.

We can hardly suppress a feeling of regret that Herschel, with his great
mind and soul, could have made a suggestion which savoured of
sycophancy: but we must bear in mind the circumstances. No planetary
discoveries had been made since prehistoric times, and there was
something to be said for making a new departure. That Herschel's
suggestion was not made solely out of gratitude is obvious from the fact
that he had practically decided on the name before he was appointed to
the new office. As a matter of fact, Herschel seems to have undoubtedly
had for the King a high personal regard. They were both Hanoverians, and
thus there was a sentimental tie between them: and George III., whatever
condemnation we may pass on him as a monarch, seems undoubtedly to have
taken an intelligent interest in astronomy. In his early days he had
made observations at the private observatory at Kew. That he did take an
intelligent interest is obvious from a letter which Herschel wrote on
20th May, 1787, to an official at Windsor Castle, in which he requested
him to inform the King of the luminosity of a lunar crater, adding that
he would himself be at Windsor in the evening to see the King's 10-foot
telescope set up for observation.

Despite Herschel's own friendship for the King and his own silence as to
the smallness of his salary, there can be no doubt that he was at first
sorely handicapped by straitened circumstances. He had made a great
financial sacrifice in accepting the post of King's Astronomer. Had he
been able to avoid incurring expenses, he could have managed to live on
200 a year; but it was imperative for him to construct larger
instruments, and the instruments which he had were in constant need of
repair and readjustment. His salary, as has been well said by the late
Miss Clerke, "gave him the means of living, but not of observing as he
proposed to observe". Accordingly he plunged with enthusiasm into the
work of making telescopes for sale. "The goodness of my telescopes," he
wrote in his journal, "being already known, I was desired by the King to
get some made for those who wished to have them. . . . This business in
the end not only proved very lucrative, but also enabled me to make
extensive experiments for polishing mirrors by machinery."

Despite the strenuous work of telescope-making, Herschel, while at
Datchet, continued his nightly surveys of the sky. His third review of
the heavens, which had been commenced at Bath, was completed in
January, 1784. This review included all the stars of Flamsteed's
catalogue and the small stars near them. The work was carried through
with amazing rapidity. He would observe for ten or twelve hours at a
stretch, and as many as 400 stars were observed and measured in the
course of a night. Later in the same year, his attention was drawn to
star-clusters and nebulae by the appearance of Messier's famous
catalogue, and accordingly on 28th October, 1783, he began to "sweep the
heavens" for these objects with his new 20-foot reflector of 187 inches
aperture, and at the same time to "gauge" the depth of the sidereal
system. A number of experimental observations were made, and on 18th
December he commenced his systematic "sweeps," which were continued till
1802.

In this work he found his sister an invaluable helper. In 1782, she
tells us, her thoughts were "anything but cheerful". "I found I was to
be trained as 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'. . . . But it was not until 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. . . . 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 I
could have his assistance immediately when 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
20-foot." Caroline's observations are preserved in three volumes of
quarto and four of folio. These observations were at first not
unattended by danger. They were commenced when the mountings of the
telescopes were in a very unfinished state, and Herschel was "elevated
fifteen feet or more on a temporary cross-beam instead of a safe
gallery". Caroline Herschel herself met with a somewhat severe accident
on the last day of 1783, and she left it on record that the Italian
astronomer Piazzi--discoverer of the first asteroid--"did not go home
without getting broken shins by falling over the rack-bar".

By the summer of 1785, Herschel decided that the old house at Datchet
was impossible as a permanent residence. An attack of ague was found to
be due to its damp situation. Accordingly, early in June, the Herschels
removed to a house at Clay Hall, near Old Windsor, where observations
were at once commenced. But trouble arose with the landlady--"a
litigious woman who refused to be bound to reasonable terms"--and in the
following spring Herschel fixed upon a new home at Slough, near Windsor.
Thither his instruments and apparatus were transported on 3rd April,
1786, without the loss of a single hour's observation. "The last night
at Clay Hall," says Caroline, "was spent in sweeping till daylight and
by the next evening the telescope stood ready for observation at
Slough." This was the last removal. The remainder of Herschel's life was
spent at Slough--"the spot of all the world," said Arago, "where the
greatest number of discoveries have been made". Here for many years,
Herschel and his devoted sister worked from twilight to dawn, sweeping
for clusters and nebulae, counting the stars in limited regions of the
heavens, occasionally scrutinising the Moon and the planets. "If it had
not been," writes Caroline, "for the intervention of a cloudy or moonlit
night, I know not when he or I either would have got any sleep." In the
daytime, too, his activity was ceaseless. He had to attend to his
telescopes and to direct the army of workmen who were constantly
employed making repairs; in addition, he was actively employed
systematising his observations and co-ordinating his results, which
appeared in the long series of papers contributed to the "Philosophical
Transactions" of the Royal Society--collected and published in two
volumes in 1912.

It soon became apparent that the work of making telescopes for other
observers, though lucrative, was in many respects a waste of time.
Herschel had long contemplated the construction of a very large
telescope, but this was impossible so long as his spare time was given
to the manufacture of smaller instruments, the great majority of which
passed into the possession of royal or aristocratic dabblers in
astronomy and were practically mere ornaments. A few, however, were
supplied to continental astronomers. With a 7-foot, Schrter, the German
astronomer, practically inaugurated the systematic study of the Moon's
surface.

Caroline Herschel notes that it was her brother's chief object at this
time to construct a 30 or 40-foot instrument, "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". But nothing could be done
without a grant from the King; Herschel could not bear the expense of
constructing a great telescope for himself. After some preliminary
spade-work had been done in the proper quarters by his life-long friend,
Sir William Watson, Herschel requested Sir Joseph Banks, President of
the Royal Society, to make application for a grant from the King. In
September, 1785, a grant of 2000 was made, and preparations for the
making of the instrument were at once begun. Two years later a second
sum of 2000 was granted, and in addition Herschel received, over and
above his salary, 200 per annum for the up-keep of the telescope; while
a salary of 50 a year was bestowed on Caroline Herschel as her
brother's assistant. By this time her name was becoming famous in the
world of science. On 1st August, 1786, during Herschel's absence in
Germany, she discovered a comet, the first of eight similar objects to
her credit. The small annuity conferred upon her was a recognition--
painfully inadequate--of her own work in astronomical science.

The construction of the great telescope occupied nearly four years. The
erection of this immense instrument took up a great deal of Herschel's
attention. His sister asserted that "there is not one screwbolt about
the whole apparatus but what was fixed under the immediate eye of my
brother. I have seen him lie stretched many an hour in a burning sun,
across the top beam while the iron-work for the various motions was
being fixed. At one time, no fewer than twenty-four men (twelve and
twelve relieving each other) kept polishing day and night; my brother,
of course, never leaving them all the while, taking his food without
allowing himself time to sit down to table."

This ceaseless industry bore fruit when in August, 1789, the great
telescope was ready for use. Herschel's former telescopes had been
Newtonians, with small secondary mirrors. In January, 1787, however, he
made a novel experiment with his 20-foot telescope. In order to save the
light lost by the second reflection, Herschel removed the small mirror
and slightly tilted the tube. The result more than justified
expectations, and the experiment resulted in the discovery of two
satellites of Uranus. Accordingly, he decided to make the 40-foot
telescope on this "front-view" principle. This particular form of the
reflector is known as the Herschelian.

Herschel was very proud of his large telescope and in 1795 sent a
description of it to the Royal Society. Yet, on the whole, its
performances were disappointing. Immediately it was erected Herschel
succeeded in confirming the existence of two new satellites of Saturn:
and to the ringed planet he turned his great instrument on numerous
occasions. But it was cumbersome and difficult to manipulate, and the
speculum on which so much care had been bestowed preserved its original
polish for no more than two years. In Herschel's later years, he rarely
made use of it, although it remained standing until seventeen years
after its maker's death. In 1839, it was dismantled by Sir John
Herschel, and laid in a horizontal position, which it occupied for many
years, until a falling tree destroyed all but ten feet of the tube.

The completion of the 40-foot was the climax of Herschel's career as a
maker of telescopes. The fame of the great instrument spread over the
world. Princes, dukes, and courtiers visited Slough in order to view one
of the wonders of the age. Astronomers, too, came from all parts of the
world--Lalande, Mchain, Legendre, Cassini from Paris, Oriani from
Milan, Piazzi from Palermo, Sniadecki from Cracow. Slough became a place
of pilgrimage, not only for astronomers, but also for large numbers who
had only a slight interest in, or curiosity about, the science. Herschel
did not abandon telescope-making altogether but it was not now so
necessary for pecuniary reasons. On 8th May, 1788, Herschel was married
to Mrs. Pitt, widow of John Pitt, Esq., and daughter of Mr. Adee
Baldwin, a London merchant. Miss Burney, the novelist, has left on
record her meeting with Herschel and his wife soon after the marriage.
"His newly-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." Whether or not
there is any ground for this hint as to a motive for Herschel's
marriage, there can be no doubt that he was now relieved from all
financial care. There can be no doubt either that the marriage was a
very happy one, and that the relations between his wife and his sister
were all that could be desired. From this time onwards, however,
Caroline Herschel resided in lodgings in the village of Slough.

In the earlier part of his career, Herschel rarely went from home except
on business. On 3rd July, 1786, accompanied by his brother Alexander, he
started for Gttingen, in order to convey to the University one of his
10-foot reflectors as a gift from George III. This was his last visit to
his native country. In 1792, he made an extensive tour in England and
Scotland, in the company of a Polish friend, General Komarzewski. Visits
were paid to the principal factories in the middle and north of England,
and Herschel seems to have taken a 7-foot telescope with him in order to
treat his hosts to views of the heavens. The tour embraced Coventry,
Birmingham--where he dined with James Watt--Bangor, Carnarvon, and
Manchester, then via Liverpool, Preston and Carlisle to Glasgow. Here he
received the freedom of the city and the degree of LL.D. from the
University. From Glasgow the friends proceeded to Edinburgh, from whose
University Herschel had received the same degree six years earlier. In
Edinburgh he met numerous literary and scientific men, including
Principal Robertson and Dr. Hutton, and, in addition, inspected the
Observatory. The return journey was made by Sunderland, Durham and
Richmond in Yorkshire.

At the close of the eighteenth century, Herschel was at the zenith of
his powers and at the height of his prosperity. Honorary degrees were
conferred upon him and learned societies enrolled his name among their
members. He accepted these recognitions of his genius, but put little
stress upon them. Miss Burney, who along with her father visited him on
numerous occasions, described Herschel as "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. . . . He seems a man
without a wish that has its object in the terrestrial globe."




  CHAPTER IV.

  SOLAR AND PLANETARY STUDIES.


One result of Herschel's fame as the founder of stellar astronomy has
been that his greatness as an observer and student of the Sun and
planets has been largely overlooked. Nevertheless his work in solar and
planetary astronomy alone would have gained for him the highest position
among the astronomical observers of the day. "Among the celestial
bodies," he wrote in 1799, "the Sun is certainly the first which should
attract our notice." From an early date he was attracted by solar
phenomena, and in the course of his career contributed several papers on
the Sun to the Royal Society. In the first of these, "On the Nature and
Construction of the Sun and Fixed Stars," read 18th December, 1794, he
propounded his hypothesis of the Sun's constitution, to which he adhered
throughout his lifetime.

Before Herschel's time, the Sun had been observed by Galileo, Scheiner,
Fabricius, Hevelius, Cassini and others. Sun-spots had been observed for
over a century and a half and many important details had been detected,
but concerning their nature controversy had raged and uncertainty
prevailed. In 1774, just at the beginning of Herschel's career as an
observer, the well-known theory of sun-spots was propounded by Alexander
Wilson, Professor of Astronomy in the University of Glasgow. A series of
observations convinced him that the spots were depressions beneath the
general surface of the Sun; not mountains, as many observers had
supposed, but cavities in the glowing surface through which the darker
interior was visible. "Is it not reasonable," he asked, "to think that
the great and stupendous body of the Sun is made up of two kinds of
matter, very different in their qualities: that by far the greater part
is solid and dark and that this immense and dark globe is encompassed
with a thin covering of that resplendent substance from which the Sun
would seem to derive the whole of his revivifying heat and energy?"
Herschel's earliest observations were confirmatory of Wilson's
conclusions. In 1783 he closely followed a large spot, noticing that "it
was plainly depressed below the surface of the Sun: and that it had very
broad shelving sides". He was soon led to adopt Wilson's view of the
solar constitution, which he developed in his first paper on the Sun in
1794.

His observations of the great spot of 1774 led him to conclude that he
viewed "the real solid body of the Sun itself, of which we rarely see
more than its shining atmosphere." This interpretation of sun-spot
observations was the foundation-stone of his theoretical edifice. He
concluded, in agreement with, but independently of, Wilson, that the
solar globe was dark and solid, surrounded by a glowing atmosphere
composed of various "elastic fluids that are more or less lucid and
transparent". This lucid fluid, named by Schrter the "photosphere,"
Herschel believed to be generated in the Sun's atmosphere. An analogy,
he said, might be drawn from the generation of clouds in the terrestrial
atmosphere. In his paper of 1801, Herschel concluded that there are "two
different regions of solar clouds, like those upon our globe. In that
case their light is only the uniform reflection of the surrounding
superior self-luminous region."

"The solid body of the Sun beneath these clouds," Herschel said,
"appears to be nothing else than a very eminent, large and lucid planet,
evidently the first, or in strictness of speaking, the only primary one
of our systems; all others being truly secondary to it." This solid
body, he believed to be protected from the great heat of the elastic
fluid of its own atmosphere by dense planetary clouds; it was
diversified by mountains and valleys, and was in every way analogous to
the Earth and the other planets. "We need not hesitate to admit," he
said in 1794, "that the Sun is richly stored with inhabitants." In 1801,
after further close study, he claimed that all his former arguments had
been confirmed.

Herschel's theory met with general acceptance for many years. It
harmonised with the trend of later eighteenth century thought,
which--possibly as a result of the reaction from narrow theological
views of the Earth's supreme place in nature--shrank from the idea of
empty worlds. It was not until the invention of the spectroscope that
the theory was universally abandoned. Untenable though it was, it was
the first serious attempt to co-ordinate the isolated facts ascertained
concerning phenomena of the solar disc.

The fallacious nature of his theory should not blind us to Herschel's
great work as an observer of solar phenomena. In his paper of 1794 he
noted the existence of "elevated bright places" which, after Hevelius,
he named faculae. "I see these faculae extended . . . over about
one-sixth part of the Sun. . . . Towards the north and south I see no
faculae; there is all over the Sun a great unevenness in the surface,
which has the appearance of a mixture of small points of an unequal
light; but they are evidently an unevenness or roughness of high and low
parts." Very few details of the solar surface escaped his persistent
scrutiny. His paper of 1801 described the process of spot-formation with
a wonderful accuracy of detail. Curiously enough, Herschel--although he
devoted attention to the prevalence or absence of spots--failed to
notice the sun-spot period. Probably he would have done so, had his
attention to the Sun been more exclusive.

Herschel's solar work was not purely telescopic. His investigations on
light and heat occupied a great deal of his time at the beginning of
the century; and he contributed to the Royal Society on these subjects
four papers in rapid succession. He was led to the inquiry by his search
for the most suitable dark glasses for solar observation, in the course
of which he found that some materials were opaque to light and others to
heat. His papers have been called "the first exposition worth mentioning
of the principles of radiant heat". In this exposition he showed that
radiant heat obeyed the laws of reflection, refraction and dispersion.
His investigation of the infra-red heat rays led to one of his greatest
discoveries--that of the invisible portions of the solar spectrum.

Early in his career, Herschel paid considerable attention to the Moon.
His second paper in 1780 dealt with his measures of the height of the
lunar mountains. In 1783 a sensation was caused in scientific circles by
the news that Herschel had seen lunar volcanoes in violent eruption. In
a letter to Magellan, a Portuguese amateur astronomer, he stated that on
4th May, he "perceived in the dark part of the Moon a luminous spot. It
had the appearance of a red star of about the fourth magnitude." In 1787
he communicated a paper to the Royal Society, in which he announced the
appearance of other three volcanoes, and in which he promised the
Society an account of the eruption of 4th May, 1783. This account was
never forthcoming. The leading French astronomers were inclined to the
view that the appearances were actually due to earth-shine. It is
possible that Lalande, who visited Slough in 1788, may have converted
Herschel to this view. At all events, nothing further was published
concerning the supposed volcanoes.

Herschel believed the Moon to be both habitable and inhabited. Yet he
laid it down in 1794 "that we perceive no large seas in the Moon, that
its atmosphere (the existence of which has even been doubted by many) is
extremely rare and unfit for the purposes of animal life; that its
climates, its seasons, and the length of its days totally differ from
ours; that without dense clouds (which the Moon has not) there can be no
rain; perhaps no rivers, no lakes". His belief in the habitability of
our satellite arose from the view that its inhabitants "are fitted to
their conditions as well as we on this globe are to ours".

Of the planets, Mercury alone was neglected by Herschel; he studied it
only when in transit across the solar disc. His observations on
Venus--"an object," he said, "that has long engaged my particular
attention"--were commenced in April, 1777, and were continued for
sixteen years. Herschel had four objects in view--to measure the
rotation period of the planet, to ascertain the presence or absence of
an atmosphere, to determine accurately the planet's diameter, and to
give "attention to the construction of the planet with regard to
permanent appearances". He satisfied himself that Venus did rotate, but
the diurnal motion, he said, "on account of the density of the
atmosphere of this planet, has still eluded my constant attention, as
far as concerns its period and direction". The spots which Herschel
discovered on the planet's surface were faint and ill-defined. His
observations on Venus were in direct contradiction to those of Schrter.
The German astronomer had not only estimated the planet's rotation
period at 23 hours, but had announced the existence of mountains on
Venus, whose height exceeded five or six times the perpendicular
elevation of Chimborazo. "As to the mountains on Venus," said Herschel,
"I may venture to say that no eye which is not considerably better than
mine, or assisted by much better instruments, will ever get a sight of
them." Herschel's negative conclusions have been on the whole confirmed
by later astronomers.

Herschel may be safely called the founder of Martian astronomy. In 1777
he commenced observations on Mars, and he early satisfied himself that
"the constant and determined shape" of the spots "as well as remarkable
colour, show them to be permanent and fastened to the body of the
planet". The spots which chiefly attracted his attention were the white
polar caps. On 17th April, 1777, he noted, "There are two remarkable
bright spots on Mars". These spots had been noticed by Maraldi early in
the century, but Herschel was the first to investigate their nature and
to chronicle their periodical variation in size. "I may well be
permitted to surmise," he wrote in 1784, ". . . that the bright polar
spots are owing to the vivid reflection of light from frozen regions;
and that the reduction of these spots is to be ascribed to their being
exposed to the Sun. In the year 1781, the south polar spot was extremely
large, which we might well expect, since that pole had but lately been
involved in a whole twelve months' darkness and absence of the Sun: but
in 1783 I found it considerably smaller than before." Herschel's
sagacious surmise has been abundantly confirmed by all subsequent
observers. In addition, he determined the rotation period with
considerable accuracy. In 1781 he announced it to be 24 hours, 39
minutes, 2167 seconds; he also ascertained the axial inclination and
equatorial diameter. The general conclusion which he reached as a result
of his observations was that "the analogy between Mars and the Earth is,
perhaps, by far the greatest in the whole solar system. Their diurnal
motion is nearly the same; the obliquity of their respective ecliptics,
on which the seasons depend, not very different." The planet, he
concluded, "has a considerable but moderate atmosphere, so that its
inhabitants probably enjoy a situation in many respects similar to
ours".

The planet Jupiter did not claim so much of Herschel's attention as
either Mars or Saturn. Nevertheless, his short study of the giant world
marked an epoch. In his paper of 1781 on the "Rotation of the Planets
round their Axes," he put forward as a suggested explanation of the
atmospheric condition of Jupiter what has been known as the "trade-wind"
theory. "As the principal belts on Jupiter are equatorial, and as we
have certain constant winds upon our planet that regularly, for certain
periods, blow the same way, it is easily supposed that they may form
equatorial belts by gathering together the vapours which swim in our
atmosphere and carrying them about in the same direction. This will by
analogy account for all the irregularities of Jupiter's revolutions."
Herschel devoted no other paper to Jupiter, but in 1797 he communicated
to the Royal Society his "Observations of the Satellites of Jupiter,
with a Determination of their Rotation". From his determinations of
their variable brightness, he concluded that the rotation periods of all
four satellites coincided with their periods of revolution round
Jupiter--a conclusion confirmed by subsequent research. Herschel also
made the first attempt to measure the diameters of the satellites. His
conclusion--also confirmed by later observers--was "that the third
satellite is considerably larger than any of the rest; that the first is
a little larger than the second and nearly of the size of the fourth;
and that the second is a little smaller than the first or fourth or the
smallest of them all".

"The planet Saturn," Herschel wrote, "is perhaps one of the most
engaging objects that astronomy offers to our view. As such it drew my
attention as early as the year 1774." And it received more of Herschel's
attention than any of the other planets. Six of his papers to the Royal
Society dealt with Saturn, the first in 1789 and the last in 1805. He
concluded in 1789 that the planet had an atmosphere of considerable
density; and from the appearance of the belts he inferred that it "turns
upon an axis which is perpendicular to the ring," and this view was
confirmed by his detection of a considerable polar flattening. In
December, 1793, he stated that the period of rotation "is probably not
of a long duration"; and in the following year he confirmed his
suspicion, and announced the period of rotation as 10 hours 16 minutes.

Five satellites of Saturn were known when Herschel commenced his study
of the planet. His discovery of two exceedingly faint inner satellites,
rendered fainter still by their proximity to the bright disc and ring of
Saturn, was the result of long and continued investigation. He had
entertained "strong suspicions" of the existence of a sixth satellite
for a considerable time; and on 19th August, 1787, using the 20-foot
reflector as a "front view," he noticed an object which he marked down
as possibly a sixth moon. The possibility was rendered a certainty when
on 28th August, 1789, he turned the new 40-foot on Saturn. Six
satellites were manifestly visible, sharing in the planet's motion. On
17th September, he detected another satellite, still fainter, and closer
to the ring, revolving in less than one terrestrial day. These moons
were named Enceladus and Mimas. Two years later he announced that the
fifth satellite--Japetus--performs its rotation, like the moons of
Jupiter and our moon, in a period coincident with its revolution. These
conclusions led him to an important generalisation, that "a certain
uniform plan is carried on among the secondaries of our solar system;
and we may conjecture that probably most of the moons of all the planets
are governed by the same law".

The ring-system fascinated Herschel. In 1789 he suspected its division
into two, and this suspicion was confirmed in 1791. "Its division into
two very unequal parts can admit of no doubt." He appears to have seen
the inner dusky or "crape" ring, but he did not recognise it as a
portion of the system. In common with Laplace and contemporary
astronomers, he believed the rings to be solid structures. In August,
1815, Herschel made his last observations of the planet, with both the
40-foot and the 20-foot telescopes.

As was to be expected, the planet Uranus was an object of special
interest to its discoverer. In 1783 he communicated the results of his
preliminary study of the new planet to the Royal Society. He then
estimated that "the real diameter of the planet must be between four and
five times that of the Earth". In a later paper, in 1788, he announced
the diameter as 34,217 miles--a remarkably accurate measure. He
commenced soon after the discovery to search for Uranian satellites. At
first he was continually disappointed and gave over the attempt.
Resuming his observations, however, with the front-view method, he
detected on 11th January, 1787, two very faint stars. After careful
search of these objects in motion he tells us that he deferred a final
judgment as to their nature till 10th February. "And in order to put my
theory of these two satellites to a trial, I made a sketch on paper to
point out beforehand their situation with respect to the planet and its
parallel of declination. The long-expected evening came on, and
notwithstanding the most unfavourable appearance of dark weather, it
cleared up at last, and the heavens now displayed the original of my
drawing by showing in the situation I had delineated them, _the Georgian
planet attended by two satellites_."

He determined the times of revolution of these moons; estimated their
size as probably not less than that of the satellites of Jupiter; and
noted the great inclination of their orbits. In 1797 Herschel announced
the discovery of four additional satellites, but this was never
confirmed, and there can be little doubt that what he actually observed
were small faint stars; although it is just possible that he may have
glimpsed the very faint inner pair detected in 1847. A suspicion that
Uranus was encircled by a ring similar to Saturn was finally negatived
by his investigations in 1792, which he described as "very decisive
against the existence of a ring".

Herschel never discovered a comet. This branch of astronomy he left to
his sister, who detected no fewer than eight during the course of her
observing career. The first of these, discovered 1st August, 1786, was
the subject of a short communication to the Royal Society. Other comets,
too, seem to have been closely studied by him. The great comet of 1811
called forth a long communication to the Royal Society. In this paper,
he emphasised the transient nature of comets.

Herschel missed discovering the first four asteroids, which were
detected by Piazzi, Olbers and Harding, when the great astronomer of
Slough was at the height of his powers as an observer. He closely
studied them after their discovery and endeavoured to measure their
discs, but his measures were not very exact. In a paper read before the
Royal Society, on "Observations on the two lately discovered celestial
bodies," he suggested the name "asteroids" for the new worlds. Brougham
in the "Edinburgh Review" took exception to the name, and insinuated
that Herschel had deliberately coined it for the purpose of keeping the
discoveries of Piazzi and Olbers on a lower level than his own discovery
of Uranus, Herschel made no direct reply to the attack. He merely
referred to the fact that he had "incurred the illiberal criticism of
the 'Edinburgh Review,'" and in 1804, in a subsequent paper on the
asteroids, after the discovery of Juno, he said that "the specific
difference between planets and asteroids appears now, by the addition of
a third individual of the latter species, to be more fully established,
and that circumstance, in my opinion, has added more to the ornament of
our system than the discovery of another planet could have done".




  CHAPTER V.

  THE CONSTRUCTION OF THE HEAVENS.


"A knowledge of the construction of the heavens," Herschel wrote in
1811, "has always been the ultimate object of my observations." All his
other investigations--solar, planetary and stellar--were secondary to
this great aim. Before the commencement of his career as an astronomer,
the stars attracted very little attention. Star-catalogues had been
formed, but, nevertheless, the stars were regarded chiefly as convenient
reference-points for observations of the Moon and planets. A few double
and variable stars and several star-clusters and nebulae had been
discovered; theories of stellar distribution had been outlined by one or
two obscure non-professional astronomers, such as Wright and Lambert.
But there was little interest among astronomers in the study of the
stars for their own sakes; and no great systematic effort had been made
to discover the laws of stellar distribution and motion.

The field of sidereal astronomy, therefore, was virtually untrodden
when, shortly after the beginning of his telescopic work, Herschel began
his first review of the heavens. His second review, commenced in 1779,
included stars down to the eighth magnitude. By-products of this review
were the discovery of Uranus and the formation of his first catalogue of
double stars. In December, 1781, he commenced his third review, which he
completed in January, 1784, and which resulted in the publication of a
second double-star catalogue. The problem which confronted Herschel was
two-fold: (1) the scale, and (2) the structure of the stellar system. In
1781 he had written a paper on the parallaxes of the fixed stars, but
his investigation only yielded a negative result. Accordingly he
concentrated on the question of the structure of the universe and the
arrangement of its component parts.

In 1783 the publication of Messier's first catalogue directed Herschel's
attention to the star-clusters and nebulae. As soon as it came into his
hands, he says, he applied his 20-feet reflector to the nebulae, "and
saw with the greatest pleasure that most of the nebulae which I had an
opportunity of examining in proper situations yielded to the force of my
light and power and were resolved into stars". Accordingly, Herschel
decided to "sweep" the heavens with two main objects in view: (1) to
search systematically for new nebulae, and (2) to gauge the extent of
the sidereal system by counting the number of stars visible in different
regions of the heavens. In 1784, in his preliminary paper on the
construction of the heavens, he described his method of star-gauging,
which, he said, "consists in repeatedly taking the number of stars in
ten fields of view of my reflector very near each other, and by adding
their sums and cutting off one decimal on the right, a mean of the
contents of the heavens, in all the parts which are thus gauged, is
obtained".

In his paper on "The Construction of the Heavens," dated 1st January,
1785, Herschel gave the results of his preliminary investigations and
outlined his theory of the stellar system. "That the Milky Way," he
said, "is a most extensive stratum of stars of various sizes admits no
longer of the least doubt, and that our Sun is actually one of the
heavenly bodies belonging to it is evident. I have now viewed and gauged
this shining zone in almost every direction, and find it composed of
stars whose number, by the account of these gauges, constantly
increases and decreases in proportion to its apparent brightness to the
naked eye." In the most crowded part of the Galaxy, Herschel
occasionally counted as many as 588 stars in a field of view, and in
quarter of an hour's time no fewer than 116,000 stars were thus
enumerated, while other fields were almost destitute of stars. Herschel
made two important assumptions--(1) that the stars were, roughly
speaking, of the same size, and (2) that they were scattered throughout
space with some approach to uniformity. As a result of his star-gauges,
he was enabled on these two assumptions to estimate the possible extent
and shape of the sidereal system. He sketched it as a cloven disc of
irregular outline, extending much further in the direction of the Milky
Way than in that of the galactic poles, the cleft representing the
famous division in the Milky Way. The Milky Way was regarded as more or
less an optical phenomenon, as a vastly extended portion of the stellar
system.

Herschel's gauges led him to the view that the galactic system was
strictly limited in extent. "It is true," he said, "that it would not be
consistent confidently to affirm that we were on an island unless we had
actually found ourselves everywhere bounded by the ocean, and therefore
I will go no further than the gauges will authorise; but considering the
little depth of the stratum in all those places which have been actually
gauged, to which must be added all the intermediate parts that have been
viewed and found to be much like the rest, there is but little room to
expect a connection between our nebula and any of the neighbouring
ones." The stellar system which he designated as "our nebula" was in his
view an island universe--"a very extensive branching, compound congeries
of many millions of stars". The majority of nebul and clusters he
believed to be independent stellar units. He divided these nebul, or
milky ways--for at this time the two terms were interchangeable in his
vocabulary--into four "forms," our "nebula" being regarded as of the
third. In 1785 Herschel informed Miss Burney that he had discovered
fifteen hundred universes,--"fifteen hundred whole sidereal systems,
some of which might well outvie our Milky Way in grandeur".

Such was the famous "disc-theory" and its corollary--the hypothesis of
island universes. For many years this theory was expounded in text-books
of astronomy and popular science manuals as if it had been the outcome
of Herschel's matured views on the stellar universe. The late R. A.
Proctor, who was one of the first close students of Herschel's papers,
truly remarked that "It seems to have been supposed that his papers
could be treated as we might treat such a work as Sir J. Herschel's
'Outlines of Astronomy'; that extracts might be made from any part of
any paper without reference to the position which the paper chanced to
occupy in the entire series". The consequence of this method of
expounding Herschel's views was that for many years astronomers were
hardly aware of his gradual change of opinion.

The disc-theory and its corollary were, as already noted, based on the
assumption of an equal scattering of stars in the Milky Way and involved
the belief that all nebul were stellar clusters which would ultimately
be resolved into stars. The first of these views was never held very
confidently by Herschel. In his paper of 1785 he admitted that "in all
probability there may not be two or three of them in the heavens, whose
mutual distance shall be equal to that of any other two given stars, but
it should be considered that when we take all the stars collectively
there will be a mean distance which may be assumed as the general one".
Even in the paper of 1785 Herschel remarked that it would not be
difficult to point to two or three hundred gathering clusters in our
system. Indeed, his classification of so-called "nebul" was based on
his view that condensation gave evidence of age. Accordingly, he
foresaw, as a result of "clustering power," the breaking-up of the
galactic system into many small independent nebul. More and more
evidences of this "clustering power" came to his notice until in 1802 he
said of the Galaxy: "This immense starry aggregation is by no means
uniform. The stars of which it is composed are very unequally scattered
and show evident marks of clustering together into many separate
allotments." He was coming gradually to the view that the fundamental
assumption underlying his disc-theory--that of an average equality of
scattering--was untenable. In his paper of 1811 he said: "I must freely
confess that by continuing my sweeps of the heavens, my opinion of the
arrangement of the stars and their magnitudes and of some other
particulars has undergone a gradual change; and, indeed, when the
novelty of the subject is considered, we cannot be surprised that many
things formerly taken for granted should, on examination, prove to be
different from what they were generally but incautiously supposed to be.
For instance, an equal scattering of stars may be admitted in certain
calculations; but when we examine the Milky Way, or the
closely-compressed clusters of stars, of which my catalogues have
recorded so many instances, this supposed equality must be given up."
With the abandonment of this general assumption, the disc-theory became
untenable.

Herschel's daring attempt to formulate a cosmology proved abortive. In
place of this he was led to evolve a cosmogony. He appears to have been
unaware of Kant's nebular hypothesis; indeed, he seems to have had, at
the beginning of his career, no conception of evolutionary development
among the celestial bodies. The dim, misty-looking nebul were all
believed to be external galaxies, which increased telescopic power could
resolve into their component stars. He was led to question and then to
reject this generalisation by his study of a nebulous star of the
eighth magnitude in the constellation Taurus, surrounded by a
faintly-luminous atmosphere of considerable extent. The results of his
investigations and reflections were contained in his remarkable paper
"On nebulous stars properly so-called," dated 1st January, 1791. In
regard to the nebulous star in Taurus, he said: "Our judgment will be
that the nebulosity about the star is not of a starry nature". If, he
pointed out, the nebulosity consisted of very remote stars, which appear
nebulous on account of great distance, "then what must be the enormous
size of the central point which outshines all the rest in so superlative
a degree as to admit of no comparison?" If, however, the star is of
average size, the smaller points composing the nebulosity must be almost
infinitesimal. "We therefore either have a central body which is not a
star, or have a star which is involved in a shining fluid of a nature
totally unknown to us. I can adopt no other sentiment than the latter."
And with characteristic caution he added in the same paper: "If
therefore this matter is self-luminous, it seems more fit to produce a
star by its condensation than to depend on the star for its existence".

This was in 1791, five years before Laplace suggested his classical
hypothesis at the close of the "Systeme du Monde". The germ of the
nebular theory, therefore, was present in the mind of Herschel at this
early stage. In the paper of 1791, Herschel proceeded to apply his new
view to the various nebulous regions all over the heavens. He concluded
that he had been too hasty in his former surmise that all nebul were
distant clusters. If the "shining fluid" can exist without stars, "we
may with great facility explain that very extensive telescopic
nebulosity" in the constellation Orion. "What a field of novelty is here
opened to our conceptions!"

In 1802 Herschel dealt with the subject again in his "Catalogue of 500
new nebul". But it was not till 1811, in another epoch-making paper on
the construction of the heavens, that Herschel enunciated his nebular
hypothesis. In this paper he gave a complete list of nebul which he had
discovered and studied, "assorting them into as many classes as will be
required to produce the most gradual affinity between the individuals
contained in any one class with those contained in that which precedes
and that which follows it". Those contained in one class and those in
the next class in order, he declared, have not so much difference
between them, in his own suggestive remark, "as there would be in an
annual description of the human figure, were it given from the birth of
a child till he comes to be a man in his prime". He traced the
evolutionary sequence from extensive diffused nebulosities, through
irregular nebul, "nebul a little brighter in the middle," "nebul a
little brighter" and "much brighter in the middle," nebul showing the
progress of condensation, planetary nebul and stellar nebul, to
"nebul nearly approaching to the appearance of stars". He declared it
highly probable that "every succeeding state of the nebulous matter is
the result of the action of gravitation upon it while in a foregoing
one, and by such steps the successive condensation of it has been
brought up to the planetary condition. From this the transit to the
stellar form, it has been shown, requires but a very small additional
compression of the nebulous matter." In 1814 he drew attention to double
nebul joined by nebulosity between them. "It seems," he said, "as if we
had these double objects in three different successive conditions: first
as nebul; next as stars with remaining nebulosity; and lastly as stars
completely free from nebulous appearance". Herschel's nebular hypothesis
has never received in text-books of astronomy the attention it deserves.
It was the result of long years of patient study, and is one of the most
perfect examples of inductive reasoning in the history of science.

Herschel, as has been already remarked, had sought a cosmology and he
had found a cosmogony. Nevertheless, he did not abandon his attempt to
discover the structure of the sidereal system. In 1817 and 1818, when
nearly eighty years of age, he communicated two remarkable papers to the
Royal Society on the extent and condition of the Milky Way and on the
relative distances of clusters of stars. In these papers Herschel
explained his new method of star-gauging, which some writers have
confused with his first. The two methods, however, were quite distinct.
In the first, one telescope was used in different regions of the
heavens; whereas in the second, various telescopes were turned on the
same region. The new method assumed the distribution of the stars to
approximate to a certain properly-modified equality of scattering, and
also a certain equality of real brightness. In the paper of 1817 he
applied this new principle to the Milky Way, and in the paper of 1818 to
star-clusters, assuming that the relative distances of "globular and
other clusters" can be determined by the telescopic powers necessary to
reveal and resolve them, provided that the component stars are,
generally speaking, comparable to Sirius in size. Proctor, writing in
1872, contended that "the principle is unsound and that Herschel himself
would have abandoned it had he tested it earlier in his observing
career". Most writers have agreed with his estimate: yet recent work on
star-clusters[1] would seem to indicate that Herschel's second method
was not so unsound as has been generally believed. Herschel propounded
no hypothesis to take the place of the disc-theory. Indeed, his later
view was that the sidereal system was much more extended in the plane of
the Galaxy than he had previously believed. "The utmost stretch of the
space-penetrating power of the 20-foot telescope could not fathom the
profundity of the Milky Way." In 1817, he gave expression to the view
that "not only our sun, but all the stars we can see with the eye are
deeply immersed in the Milky Way and form a component part of it".
Nevertheless, in the paper of 1818, he held that some of the nebulae,
not obviously composed of true nebulous matter, which he called
"ambiguous objects" are "clusters of stars in disguise, on account of
their being so deeply immersed in space that none of the gauging powers
of our telescopes have hitherto been able to reach them". Obviously, he
still clung to the view that some of these dim, misty objects were
"island universes".

The paper of 1818 was the last which Herschel wrote on the construction
of the heavens. He failed in the object of his search, but countless
others have failed since his day, and at the present time astronomers
are still groping after the solution of the great problem. Herschel did
not labour in vain: his papers on the structure of the universe form the
foundation of all subsequent research. In the eloquent words of the late
Miss Clerke: "One cannot reflect without amazement that the special
life-task set himself by this struggling musician--originally a
penniless deserter from the Hanoverian Guard--was nothing less than to
search out the construction of the heavens. He did not accomplish it,
for that was impossible; but he never relinquished it, and, in grappling
with it, laid deep and sure the foundations of sidereal science."

[Footnote 1: By Dr. Harlow Shapley, at Mount Wilson Observatory,
California.]




  CHAPTER VI.

  STELLAR RESEARCHES.


Herschel did not attain to the knowledge of the ultimate structure of
the Universe to which he aspired; but in the course of his long career
as an observer and thinker he was led to several discoveries of the
greatest importance. The discovery of nebul was, of course, one of the
objects of his long-continued series of "sweeps" of the heavens. He
communicated his first catalogue of 1000 new nebul and clusters of
stars to the Royal Society in 1788; this was followed three years later
by a second catalogue of 1000 similar objects, while in 1802 he drew up
a catalogue of 500 "new nebul, nebulous stars, planetary nebul and
clusters of stars". He was equally devoted to the study of double stars.
These objects, as already mentioned,[2] first attracted his attention
because of their suitability for determination of relative stellar
parallaxes. But Herschel soon realised that the measurement of the
annual parallax of stars was beyond the power of his instruments. His
quest for parallaxes from the study of double stars led him to another
discovery altogether.

On 10th January, 1782, he communicated to the Royal Society a catalogue
of 269 double stars, of which 227 had been discovered by himself; this
was succeeded by a second list of 434 in December, 1784. From the
beginning of his study of these stellar pairs, he seems to have had a
suspicion as to their nature. In the postscript to his first catalogue
he said: "In my opinion, it is much too soon to form any theories of
small stars revolving round large ones". It was, of course, obvious that
double stars might be optical only--caused by two stars happening to lie
in the same line of vision. Nevertheless, despite his caution, he kept a
careful watch on the relative positions of the components of double star
systems for twenty years. In the paper accompanying his catalogue of 500
new nebul, read 1st July, 1802, Herschel expressed the view that
"casual situations will not account for the multiplied phenomena of
double stars," and announced that he was about to communicate a series
of observations, from which it would be evident that "many of them have
actually changed their situation with regard to each other, in a
progressive course, denoting a periodical revolution round each other;
and that the motion of some of them is direct, while that of others is
retrograde". These observations were tabulated in two papers on "the
changes that have happened in the relative situation of double stars,"
read in 1803 and 1804 respectively. In the first paper, Herschel brought
forward evidence in regard to the orbital motions of Alpha Geminorum
(Castor), Gamma Leonis, Epsilon Bootis, Zeta Herculis, Delta Serpentis,
and Gamma Virginis. The second paper gave details concerning other fifty
stars. Herschel also assigned periods to several of the more prominent
binaries. These investigations, Herschel claimed, went to prove that
many double stars are "not merely double in appearance, but must be
allowed to be real binary combinations of two stars intimately held
together by the bond of mutual attraction".

The importance of the discovery of binary stars may be realised when we
recollect that previously there was no scientific proof of the
prevalence of the law of gravitation outside of the Solar System. There
were, of course, strong reasons for believing the law to be universal;
and John Michell, a man of remarkable sagacity, had argued before
Herschel began his observations, that many double stars were certainly
binaries. But there was no direct proof until Herschel, after twenty
years of patient study, announced his results in 1802. The discovery
gave scientific proof of the unity of the Cosmos and of the universal
validity of the Newtonian law.

Another brilliant discovery, made almost casually, was announced in 1783
in a paper entitled "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". Halley had in 1718 announced
that a number of the brighter stars, so far from being "fixed," in
reality were moving through space with considerable velocity. Herschel
gave it as his view that "there is not, in strictness of speaking, one
fixed star in the heavens". "Now, if the proper motion of the stars in
general be once admitted, who can refuse to allow that our Sun, with all
its planets and comets, that is, the Solar System, is no less liable to
such a general agitation as we find to obtain among all the rest of the
celestial bodies?" The idea had occurred to several contemporary
astronomers, Wilson, Lalande, and Mayer, but no one had succeeded in
attacking the problem practically. It was plainly obvious that the
motion of the Sun could only be detected through the resulting apparent
motion of the stars, just as the orbital motion of the Earth is
reflected in the planetary motions. If the Sun is moving in a certain
direction, the stars in front will appear to disperse, while those
behind will seem to draw closer together. But the problem is complicated
by the individual motions of the stars; and these motions--themselves
very minute--have to be decomposed into two parts, the real motions of
the stars themselves and the apparent motion resulting from the
translation of the Solar System. "We ought, therefore," said Herschel,
"to resolve that which is common to all the stars, which are bound to
have what is called a proper motion, into a single real motion of the
Solar System, as far as that will answer the known facts, and only to
attribute to the proper motion of each particular star the deviations
from the general law the stars seem to follow in those movements."

Herschel treated the problem in the simplest manner. Dealing with the
proper motions of seven bright stars--Sirius, Castor, Procyon, Pollux,
Regulus, Arcturus, and Altair--he separated their real from their
apparent motions by simple geometrical methods, and reached the
conclusion that the Solar System was moving towards a point in the
constellation Hercules, the "apex" of the solar motion being marked by
the star Lambda Herculis. "We may," he said, "in a general way estimate
that the solar motion can certainly not be less than that which the
Earth has in her annual orbit." In 1805, Herschel again attacked the
problem, making use of Maskelyne's table of the proper motions of
thirty-six stars. His result was in the main confirmatory of his earlier
conclusions, the "apex" being again located in the constellation
Hercules.

Herschel's brilliant discovery was regarded with considerable
incredulity by several of his contemporaries and successors. They seemed
to feel that the data on which he worked were too slender for a
trustworthy result to be deduced. Bessel, the greatest practical
astronomer of the next generation, maintained that there was no evidence
in favour of a motion towards a point in Hercules; and even Sir John
Herschel rejected his father's conclusions. In 1837, Argelander attacked
the question from a study of the motion of 390 stars. The result of his
investigation was to confirm abundantly Herschel's conclusions. Since
Argelander's time, determination after determination has been made, by
many illustrious mathematicians of each generation. Every refinement has
been exhausted, "only," in the striking words of Ball, "to confirm the
truth of that splendid theory which seems to have been one of the
flashes of Herschel's genius".

The light of the stars, no less than their motions, was a favourite
subject of study with Herschel. His first communication to the Royal
Society dealt with the famous variable star Mira Ceti; and several other
papers dealt with the brilliancy of the stars. The problem of stellar
variation fascinated him. "Dark spots, or large portions of the surface
less luminous than the rest, turned alternately in certain directions,
either towards or from us," he wrote in 1796, "will account for all the
phenomena of periodical changes in the lustre of the stars so
satisfactorily that we certainly need not look for any other cause." But
he was aware of other variations--the gradual increase or decrease of
the light of certain stars in the course of years or centuries. He
regarded as a problem of great practical interest the stability or
otherwise of the brilliance of the Sun. His interest in the question of
stellar brightness and variation led to his determination of the
relative brightness of the stars. Four catalogues of comparative
brightness of stars were communicated to the Royal Society--the first on
25th February, 1796, the fourth on 21st February, 1799. The observations
on which these catalogues were based were made in the years 1795-97, and
Herschel seems to have attached so much importance to the work that for
three years he discontinued his "sweeping" of the heavens. Two other
catalogues were left unpublished at the time of his death, and were
first issued in the collected edition of his works. The observations he
himself described as "difficult and laborious". He mentioned in the
paper accompanying his first catalogue the various causes of error which
had to be guarded against, such as moonlight, the different altitudes at
which a star might be viewed, the uncertainty of flying cloud, the
scintillation of the stars, the zodiacal light, the aurora borealis, and
"dew or damp upon the glasses or specula when a telescope is used".
Nevertheless, Herschel completed his catalogues, and left behind him a
work of imperishable value. For a hundred years the work was
under-estimated by astronomers, until, at the close of the nineteenth
century, the catalogues were reduced and discussed by the late Professor
E. C. Pickering, of Harvard, who gave the following estimate of the
value of Herschel's work: "Herschel furnished observations of nearly
3000 stars, from which their magnitudes a hundred years ago can now be
determined with an accuracy approaching that of the best modern
catalogues. The average difference from the photometric catalogues is
only  016, which includes the actual variations of the stars during a
century, as well as the errors of both catalogues. The error of a single
comparison but little exceeds a tenth of a magnitude."

Herschel's observations of starlight were not only visual and
telescopic. In 1798 he passed the light of a few stars of the first
magnitude through a prism applied to the eye-glasses of his reflectors.
He found that the light of Sirius consisted of red, orange, yellow,
green, blue, purple, and violet: that Betelgeux contained the same
colours, but that the red was more intense than in Sirius; that Procyon
contained more blue and purple, and Arcturus more red and orange than
Sirius; that Aldebaran contained much orange; and Vega much yellow,
green, blue and purple. Of course, Herschel was unable to discern the
dark lines in these spectra, but his observation deserves to be
remembered as the first application of the prism to starlight.

It is difficult to know whether to admire most the observational skill
or the intellectual grasp displayed in these subsidiary researches; and
we cannot but feel, with Arago, "a deep reverence for that powerful
genius that has scarcely ever erred".

[Footnote 2: Chapter II., p. 19.]




  CHAPTER VII.

  CLOSING YEARS.


By the beginning of the nineteenth century, Herschel's extraordinary
activity began somewhat to abate. Not that his mind had become less
acute, or his interest in astronomy less marked. But it was physically
impossible for any man to maintain the standard of activity which had
been his for thirty years. He had now completed his comprehensive
surveys of the heavens, and accordingly his studies became more and more
specialised. The Sun and Saturn, the newly-discovered asteroids, and
several comets, and last but not least, his experiments on light,
occupied more and more of his time. But he now allowed himself intervals
of rest between his investigations; he found more time for music, always
one of his chief delights, and in addition he gave himself more
opportunities for holidays. In July, 1801, accompanied by his wife and
his son John, then a lad of nine, he visited Paris. Here he made the
acquaintance of Laplace, with whom he had many important conversations,
and was introduced to Napoleon, then First Consul. At 7 o'clock on 8th
August the Minister of the Interior conducted Herschel, along with
Laplace and Count Rumford, to Napoleon's palace at Malmaison. Herschel
records in his journal that the First Consul, who met the party in the
garden, politely put some questions on astronomical subjects. It was
reported at the time that Napoleon's astronomical knowledge had
astonished Herschel. Such was apparently not the case. Twelve years
later, in conversation with the poet Campbell, Herschel contradicted
this report. "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 was something
like affecting to know more than he did know. I remarked his hypocrisy
in concluding the conversation on astronomy by observing how all these
glorious views gave proofs of an Almighty wisdom." With his keen, quick
intuition, Herschel perceived the incongruity of the man of overweening
pride and vainglory taking the Divine name upon his lips and simulating
a mock piety. The chief result of Herschel's visit to Paris was his
election in 1802 as one of the eight foreign associates of the French
Institute.

Summer holidays were usually spent at Dawlish, with his lifelong friend,
Sir William Watson, and at Tunbridge Wells, Brighton, and Ramsgate.
Nevertheless, his health began to fail by gradual stages. His duties as
King's Astronomer, nominal so far as scientific work was concerned, were
somewhat exacting, and as he grew older he was less able to spend
several hours in an evening explaining the heavenly bodies to groups of
royal and aristocratic visitors. In October, 1806, the appearance of a
bright comet attracted a large number of visitors to Slough. On the
evening of the 4th, Caroline Herschel narrates, "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
40-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 from which he never got the
better afterwards; for on that day (in particular) he had hardly
dismissed his troop of men, when visitors assembled, and from the time
it was dark till past midnight, he was on the grass-plot surrounded by
between fifty and sixty persons without having time for putting on
proper clothing or for the least nourishment passing his lips. Among the
company, I remember, were the Duke of Sussex, Prince Galitzin, Lord
Darnley, a number of officers, Admiral Boston, and some ladies." This
tremendous strain told on Herschel, and the result was that in the
spring he became dangerously ill. Caroline tells us that on 26th
February, 1807, he was so ill that even she was not allowed to see him,
and until 8th March his recovery was despaired of. However, he rallied
and recovered, but his health was permanently impaired. But his mind was
as clear as ever, and some of his most remarkable papers were written
after his illness--that of 1811, in which he developed the nebular
hypothesis, and those of 1814, 1817, and 1818, on the construction of
the heavens. Physically, however, he was unequal to the task of
attending to his great telescopes. On 30th September, 1815, his sister
recorded that "his strength is now, and has for the last two or three
years, not been equal to the labour required for polishing 40-foot
mirrors. And it was only by little excursions and absences from his
workrooms he for some time recovered from the effects of over-exertion".
During these last years, Caroline's diaries make sad reading, for they
record little more than the gradual decay of health and vigour in the
"best and dearest of brothers". His inability to repolish his great
mirror was a bitter disappointment to him, and he became depressed and
sorrowful. She afterwards recorded that "when all hopes for the return
of vigour and strength necessary for resuming the unfinished task was
gone, all cheerfulness and spirits had also forsaken him. . . . Every
nerve of the dear man had been unstrung by over-exertion," so that "a
further attempt at leaving the work complete became impossible". In
1819, before his departure for a holiday at Bath, "the last moments
before he stepped into the carriage were spent in walking through his
library and workrooms, pointing with anxious looks to every shelf and
drawer, desiring me to examine all and to make memorandums of them as
well as I could. He was hardly able to support himself, and his spirits
were so low that I found difficulty in commanding my voice so far as to
give him the assurance he should find on his return that my time had not
been misspent."

But Herschel was not always, even in extreme old age, depressed and
gloomy. A German visitor to Slough, in 1819, thus described the great
astronomer: "While we were standing by the great telescope, which we
more admired than comprehended, its master appeared, a cheerful old man
aged eighty-one. How unassumingly did he make his communications! How
lightly did he ascend the steps to the gallery! With what calm pleasure
did he seem to enjoy the success of his efforts in life. All accounts
from his native country seemed to please him, although the German
language had become somewhat less familiar to his ear. After a short
conversation, we took our leave, charged with friendly greetings to all
beyond the sea who might still remember him."

On 5th April, 1816, he received the first mark of recognition from the
British Government--the third class of the Hanoverian Guelphic Order. In
the following month he was created a Knight of the same Order. In 1820,
when the Astronomical Society of London--now the Royal Astronomical
Society--was founded, Herschel was elected as the first President. His
health did not permit him to attend the meetings, but he communicated
his last paper--on double stars--to its "Memoirs" in 1821.

Caroline Herschel's Memoirs record the agony of soul through which she
passed as her brother became weaker and weaker. In 1819 he sent a note
across to her lodgings, notifying her of the appearance of a "great
comet". She preserved this, with the comment, "I keep this as a relic!
Every line _now_ traced by the hand of my dear brother becomes a
treasure to me." Her own health was seriously impaired, and she
sometimes expected to pass away before him. But a different fate was in
store for her. The hot summer of 1822 told heavily upon Herschel, but
apparently no imminent danger was anticipated, for his son John, then a
graduate of Cambridge, started on the 8th of August for a tour on the
continent. On the 15th, "after half-an-hour's vain attempt to support
himself," the faithful chronicler relates, "my brother was obliged to
consent to be put to bed, leaving no hope ever to see him rise again".
Ten days later, 25th August, 1822, he passed away, within three months
of completing his eighty-fourth year. He was buried in the church of St.
Lawrence at Upton, near Slough. The long Latin inscription claims for
him that "coelorum perrupit claustra"--"He broke through the barriers of
the skies".

The end was not unexpected, but to his devoted sister--the companion and
co-worker of a lifetime--the loss was irreparable. After his death, she
tells us, there was but one comfort left her, "that of retiring to the
chamber of death, there to ruminate without interruption on my isolated
situation. Of this last solace I was robbed on the 7th September, when
the dear remains were consigned to the grave." Her own life, she felt,
was finished; she had no further interests. And so she decided to leave
England and return to Hanover and the scenes of her girlhood, there to
spend the evening of her days. There was another reason for her
decision. Only one of her brothers now survived; Alexander had died a
year before William, and sentimental reasons impelled her to make her
home with Dieterich. In the midst of her deep sorrow she had made over
to Dieterich--shiftless and impecunious as ever--her little capital sum
of 500; in her own words, "I gave myself, with all I was worth, up to
my brother Dieterich and his family". No sooner had she arrived in
Hanover, in October, 1822, than she realised her great mistake. She
found herself among uncongenial company. "In the last hope of finding in
Dieterich a brother to whom I might communicate all my thoughts of past,
present and future," she wrote to her nephew in 1827, "I saw myself
disappointed the very first day of our travelling on land. For let me
touch on what topic I would, he maintained the contrary, which I soon
saw was done merely because he would allow no one else to know anything
but himself." The old lady could find no congeniality in the company of
a soured, fractious old man, and among people who could not enter in the
slightest into her scientific interests. "From the moment I set foot on
German ground," she said, "I found I was alone." She described herself
as leading a "solitary and useless" life--"not finding Hanover or anyone
in it like what I left when the best of brothers took me with him to
England in August, 1772".

Solitary her life was, so far as congeniality went, but by no means
useless. Soon after her settlement in Hanover, she formed a catalogue of
all her brother's nebul and clusters, arranged in zones. In April,
1825, she forwarded this to her nephew, John Herschel, then engaged in
his review of these objects. This catalogue was described by Sir David
Brewster, as "an extraordinary monument of the unextinguished ardour of
a lady of seventy-five in the cause of abstract science". It was
rewarded by the presentation to her of the Gold Medal of the Royal
Astronomical Society, in 1828--an honour by which, with characteristic
modesty, she said she was "more shocked than gratified". In 1835 she was
elected an honorary member of the Royal Astronomical Society, membership
of which was not then open to women; and in 1838 the Royal Irish Academy
enrolled her name among its members. These honours sat very lightly on
her. "Saying too much of what I have done," she said in 1826, "is
saying too little of him, for he did all. I was a mere tool which he had
the trouble of sharpening and adapting for the purpose he wanted it, for
lack of a better."

As the years passed, and her vitality ebbed, all her affection became
concentrated in the one being whom she felt understood her and with whom
she had community of interests--her nephew John. She followed his career
with pride, as a worthy sequel to that of his father; his visits to
Hanover were to her oases in the desert of her experience; he and his
wife were her principal correspondents. She wrote her last letter to her
nephew, December 3rd, 1846: she was then ninety-six, and had survived
her brother for twenty-four years. During 1847, tenderly nursed by her
niece, Mrs. Knipping, the only one of Dieterich's family who really
sought to care for her, she slowly sank, and on 9th January, 1848, she
passed away--within two months of completing her ninety-eighth year. She
was buried beside her parents in the churchyard of the Gartengemeinde at
Hanover. Her epitaph, composed by herself, records that "the eyes of her
who is glorified were here below turned to the starry heavens. Her own
discoveries of comets and her participation in the immortal labours of
her brother, William Herschel, bear witness of this to future ages."

Future ages are not likely to forget Caroline Herschel. Her own original
work was, it is true, comparatively small; but her self-sacrificing
devotion to her brother, her performance of the countless small petty
drudgeries of his scientific life, her tender care for his welfare and
comfort, give her an honourable place among women of lasting fame. As
long as William Herschel is remembered, his sister Caroline will not be
forgotten. As has been truly said, "she shines and will continue to
shine by the reflected light that she loved".

The career of the younger Herschel was, in many respects, the sequel
to, and completion of, that of his father. John Frederick William
Herschel, born "within the shadow of the great telescope," on 7th March,
1792, was educated at Hitcham, Eton and Cambridge. At the University he
was a distinguished student, particularly in mathematics, and graduated
as Senior Wrangler in 1813. He was in no hurry to choose his life-work,
nor was there any need. Since his father's marriage, the family had been
in easy, if not affluent circumstances. His father had destined him for
the Church, but he preferred the study of law. He never practised at the
Bar, however, and at last decided for a scientific career. In 1816 he
informed a correspondent that he was "going under his father's
directions to take up star-gazing". He had at first no definite
inclination in that direction, but he decided to complete his father's
work. During his father's lifetime, he re-examined many binary stars, in
conjunction with Sir James South, and for these observations he received
the Lalande Prize of the French Academy and the Gold Medal of the
Astronomical Society.

In 1828 he succeeded in rediscovering the genuine satellites of Uranus,
and in the same year commenced his review of his father's nebul and
star-clusters. The completion of this work was signalised by knighthood.
Then, in 1833, after his mother's death, he decided to extend his
father's surveys to the southern hemisphere. He transported his great
telescope to Cape Colony, and at Feldhausen, near Cape Town, from 1834
to 1838, he swept the southern skies, cataloguing double stars, clusters
and nebul; and after nine years of arduous labour, the monumental
volume known as "Results of Astronomical Observations at the Cape of
Good Hope" was published. Meanwhile, honours were showered thick and
fast upon the astronomer; he was created a baronet after his return from
South Africa, many degrees were conferred upon him, and learned
societies vied with each other in enrolling his name among their
members. On his return to England, he did not re-erect his telescopes;
and his career as an observer was closed. During the latter part of his
life he was regarded as the greatest English astronomer of his day, and
on his death on 5th May, 1871, at his home at Collingwood in Kent, he
was interred in Westminster Abbey, close to the grave of Newton.

Sir John Herschel was survived by three sons, of whom only the eldest,
Sir William James Herschel (1832-1917), did not inherit the family taste
for astronomy. The second son, Alexander Stewart Herschel (1836-1907),
Professor at Durham College, devoted considerable attention to meteoric
astronomy, while the younger son, Colonel John Herschel, in his earlier
days undertook a spectroscopic examination of southern nebul. The names
of a grand-daughter and of a great grandson of Sir William
Herschel--Miss Francesca Herschel and Rev. J. C. W. Herschel--appear on
the roll of Fellows of the Royal Astronomical Society, to testify that
the family is still distinguished by love of the oldest of the
sciences.




  CHAPTER VIII.

  PERSONALITY AND INFLUENCE.


Scientific biographies are sometimes painful reading--painful because in
them we are occasionally brought face to face with the flaws in great
characters, the pettinesses of great minds. The biography of Herschel
does not belong to that class. The character which shines through his
writings, through his sister's memoirs, and through the correspondence
and comments of contemporaries is that of a genial, kindly, earnest man.
In private life he was a good husband and father, a loving brother and a
devoted son. His less fortunate relatives found in him a ready and
willing helper: he maintained his brother Alexander after his retirement
until his death in 1821. Even to Dieterich, the shiftless member of the
family, he was unfailingly kind and sympathetic, bequeathing to him a
sum of 2000. From earliest years he was to Caroline "the best and
dearest of brothers," and that his care for her did not close with his
death is evident from his bequest to her of an annuity. Alike in times
of adversity and prosperity, he was ever helpful and kind.

He had none of that aloofness which has often characterised men of
science. He was at all times ready to reply to correspondents and to
answer inquiries. He was always accessible and never pedantic. The poet
Campbell has given us a charming word-picture of the astronomer in
private life. Writing to a friend on 15th September, 1813, Campbell
said: "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. . . . 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 labours
with a sort of boyish earnestness to explain. . . . 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'."

Herschel's close friendships were few but enduring. Sir William Watson,
Sir Joseph Banks, Dr. Maskelyne, and Mr. Aubert, were intimate friends
and correspondents of many years' standing. Among continental
astronomers, Lalande, Bode, and Schrter, were the most frequent
correspondents. With men of science his relations were as harmonious as
with humble amateurs or anxious inquirers. No acrimonious controversies
disturbed the even tenor of his scientific career. The nearest approach
to heat was in his paper of 1793, when he made his spirited refutation
of Schrter's alleged discovery of high mountains in Venus; and on that
occasion his words were probably written more in the spirit of banter
than controversy. At least, Schrter seems to have so regarded them, for
the two astronomers continued to be friendly correspondents.

His mind was many-sided, and to the end his interests were varied. His
love for music never left him, nor did that early interest in
metaphysical and logical reasoning which prompted the seventeen-year-old
musician to spend all his earnings on a copy of Locke's "Essay on the
Human Understanding". His early contributions to the Bath Literary
Society included a number of philosophical papers. One of these dealt
with the "utility of speculative inquiries". In this there occurs the
following passage, which gives us some idea of the catholicity of his
mind and also an insight into the secret of his success as a man of
science: "It was said that speculation and metaphysics were of little
use to mankind. This I deny. The perfection of our nature is evidently
to be looked for in the superior powers of reason and speculation. What
would all experiments avail if we should stop there and not argue upon
them so as to draw general conclusions? And how can we argue and draw
conclusions if the superior intellectual powers are not improved by
frequent exercise in speculative researches? Half a dozen experiments
made with judgment by a person who reasons well are worth a thousand
random observations of insignificant matters of fact. But setting aside
the very obvious consequences of improved faculties, the subjects of
mere speculative knowledge are of the highest concern to those who love
wisdom. By metaphysics we are enabled to prove the existence of a First
Cause, the Infinite Author of all dependent beings. By mathematics we
come to have a just idea of the superlative perfection of His works. By
logic we can prove them to others. By ethics we are made sensible of our
duty towards the Author of our existence and to our fellow-creatures."

This full-orbed conception of the world seems to have saved Herschel
from falling under the influence of the spirit of scepticism then
prevalent among men of science. In his mind--keen and logical as it
was--there seems to have been no conflict between the scientific and
religious instincts. In a letter to a correspondent, dated 1st January,
1794, he said, quite simply and without affectation: "It is certainly a
very laudable thing to receive instruction from the great Workmaster of
Nature, and for that reason all experimental philosophy is instituted".

In his paper on the "Construction of the Heavens," in 1785, he wrote,
"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." This
principle he maintained throughout his life. We can trace its operation
through all the wonderful series of papers which he communicated to the
Royal Society. In regard to the Milky Way, to island universes, to the
nature of nebul, to double stars, to the Sun and planets, we see him
collecting facts, framing hypotheses to account for these facts, and
testing them by further facts. He had no fear of propounding theories,
nor had he hesitation in withdrawing them. Theories were to him means to
an end--the discovery of truth.

The career of Herschel marked an epoch in astronomy. His powerful genius
directed the course of the science in the nineteenth century; and modern
astronomy still bears the impress of his massive mind. When he began his
long career as an observer, astronomy had become more or less a branch
of applied mathematics. Such was not to be wondered at; the immediate
task of the eighteenth century was the proof of the universal validity
of the Newtonian law--a task carried forward to a triumphant conclusion
by Lagrange and Laplace. But one result of the concentration of energy
on the mathematical side of the science was that the study of the
physical condition of the Sun, Moon, and planets was largely neglected;
while the stellar branch of astronomy was virtually non-existent.

As a result of his development of the powers of the telescope, Herschel
was enabled to take the whole field of observational astronomy for his
province. He enormously extended knowledge of the Sun; and his solar
theory, untenable though it proved, was the first attempt to systematise
and co-ordinate the known facts concerning the Sun. His work on the
various worlds of the Solar System marked the foundation of modern
planetary topography. His paper on Mars in 1784 constituted Martian
astronomy a distinct branch of the science. The scientific study of the
Saturnian system may be said to have begun with him; he was the author
of the first serious attempt to explain the atmospheric phenomena on
Jupiter. He not only discovered Uranus--and thus prepared the way for
the discovery of Neptune--but he persistently scrutinised its disc until
he ascertained its size and mass. His discoveries of satellites did not
exhaust his work on the secondary systems. His remarkable intuition that
the rotation periods of satellites are equal to their times of
revolution was one of the flashes of his genius.

In stellar astronomy he discovered binary stars, and thus proved what
others had suspected--that the law of gravitation was of universal
application. With consummate skill and audacity he attacked the highly
difficult and elusive problem of the solar motion, and successfully
measuring its rate and direction, he demonstrated further the essential
kinship of Sun and stars. His efforts to know the construction of the
heavens were unsuccessful, but he laid the foundation of a new branch of
astronomy--that dealing with the distribution and motions of the stars;
and in addition discovered suns and worlds in process of formation.
Herschel was the first student of nature to point to evolution in
progress and to classify natural objects in evolutionary array.

Above all, Herschel enormously widened the mental horizon of man. His
researches extended the universe both in space and time--in very truth,
"he broke through the barriers of the skies". He revealed to the
wondering gaze of his contemporaries star upon star, system upon system,
cluster upon cluster. Speaking of these revelations Horace Walpole said:
"If there are twenty millions of worlds, why not as many and as many and
as many more? Oh, one's imagination cracks!" His researches revealed the
Earth in its true light--one revolving globule chained to a tiny star; a
dust-grain in the infinite.

Every branch of observational astronomy bears to this day the impress of
Herschel's powerful personality. Since his death, the science has
greatly advanced; its horizons have widened, and innumerable new facts
have been brought to light. Yet, even to-day, we cannot but agree with
the verdict of a prominent American astronomer[3] that Herschel "was so
far in advance of his age that we are just now beginning to appreciate
his genius," and we may safely say that in the annals of astronomical
science the name of William Herschel, pioneer of modern astronomy, will
shine with increasing lustre as the years roll on. To him, indeed, we
may apply, with peculiar fitness, the beautiful words of Longfellow:--

  Were a star quenched on high,
    For ages would its light,
  Still travelling downwards from the sky,
    Shine on our mortal sight.

  So when a great man dies;
    For years beyond our ken
  The light he leaves behind him lies
    Upon the paths of men.

[Footnote 3: Prof. T. J. J. See.]




  APPENDIX.


  I. CHIEF DATES IN HERSCHEL'S LIFE.

  Born at Hanover, 15th November, 1738.
  Settled in England, 1757.
  Appointed organist of Octagon Chapel in Bath, 1766.
  First recorded astronomical observation, 19th February, 1766.
  Began to construct telescopes, 1773.
  First recorded telescopic observation, 1st March, 1774.
  Discovery of Uranus, 13th March, 1781.
  Elected Fellow of the Royal Society, December, 1781.
  Appointed as King's Astronomer, 1782.
  Discovery of Proper Motion of Solar System, 1783.
  First paper on the Construction of the Heavens, 1784.
  Disc-theory of the Universe propounded, 1785.
  Marriage, 8th May, 1788.
  Investigation of nebulous stars, 1791.
  Discovery of revolving double stars, 1802.
  Abandonment of disc-theory and enunciation of nebular hypothesis, 1811.
  Last paper published, 1821.
  Died at Slough, 25th August 1822.


  II. BIBLIOGRAPHY.

The following works may be recommended for those who desire a closer
acquaintance with Herschel's life and work:--


  (i) _Standard sources of information._

    The Collected Scientific Papers of Sir William Herschel--with
    Biographical introduction by Dr. J. L. E. Dreyer--in two volumes
    (published by the Royal Society and the Royal Astronomical
    Society).

    Memoir and Correspondence of Caroline Herschel, by Mrs. John
    Herschel (John Murray).


  (ii) _Popular Biographies._

    The Herschels and Modern Astronomy, by Agnes M. Clerke (Cassell
    & Co.).

    William Herschel and His Work, by James Sime (T. & T. Clark).

    Sir William Herschel: His Life and Works, by E. S. Holden.

    Biographies of Distinguished Scientific Men, by Franois Arago.


  (iii) _Historical Works, dealing with Herschel's place in Modern
  Astronomy._

    History of Physical Astronomy, by Robert Grant (Baldwin).

    History of Astronomy during the Nineteenth Century, by Agnes M.
    Clerke (A. & C. Black).

    A History of Astronomy, by Arthur Berry (John Murray).

    A Century's Progress in Astronomy, by Hector Macpherson
    (Blackwood).

    A History of Astronomy, by W. W. Bryant (Methuen).


  ABERDEEN: THE UNIVERSITY PRESS




  PIONEERS OF PROGRESS

  MEN OF SCIENCE

  Edited by S. CHAPMAN, M.A., D.Sc., F.R.S. With Portrait.
  Paper, 1s.; cloth, 2s. net.


HERSCHEL.
    By Hector Macpherson, F.R.A.S.

JOSEPH PRIESTLEY.
    By D. H. Peacock.

JOSEPH DALTON HOOKER.
    By F. O. Bower, Sc.D., F.R.S.

GALILEO.
    By W. W. Bryant, F.R.A.S., Royal Observatory, Greenwich.

MICHAEL FARADAY.
    By J. A. Crowther, D.Sc.

ALFRED RUSSELL WALLACE.
    The Story of a great Discoverer. By Lancelot T. Hogben, B.A., B.Sc.

  (_Others in preparation._)


A VOYAGE IN SPACE.

    A Course of Six Lectures "adapted to a Juvenile Auditory," by H.
    H. Turner, D.Sc., D.C.L., F.R.S., Savilian Professor of
    Astronomy in the University of Oxford. With over 130
    Illustrations. Cloth boards, 6s. net.

THE WONDERS OF WIRELESS TELEGRAPHY.

    Explained in simple terms for the non-technical reader. By J. A.
    Fleming, M.A., D.Sc., F.R.S., University Professor of Electrical
    Engineering in the University of London, etc. With numerous
    Diagrams. Cloth boards.

COAL AND WHAT WE GET FROM IT.

    A Romance of Applied Science. By Raphael Meldola, F.R.S.,
    F.I.C., sometime Professor of Chemistry in Finsbury Technical
    College. Illustrated. Cloth, 2s. 6d. net.


  S. P. C. K., LONDON.


=Transcriber's Notes:=
- hyphenation, spelling and grammar have been preserved as in the
  original (other than as listed below)
- various places, nebul and nebulae both used, and left as is
Page 7, wordly goods to bequeath ==> worldly goods to bequeath
Page 9, Leibnitz ==> Leibniz
Page 11, After he had suceeeded ==> After he had succeeded
Page 26, "Sidus Georginum" ==> "Sidus Georgium"
Page 38, in every way analagous ==> in every way analogous
Page 43, with its revolution, ==> with its revolution.
Page 64, After a short comversation ==> After a short conversation
Page 69, Westminister Abbey ==> Westminster Abbey




[End of Herschel, by the Rev. Hector Macpherson]
