Great Astronomers
by
R. S. Ball
Part 4 out of 5
of Provosts, Proctors, Bursars, and other College dignitaries:--In
1793 the Board ordered two of the clocks at the observatory to be
sent to Mr. Crosthwaite for repairs. Seven years later, in 1800, Mr.
Crosthwaite was asked if the clocks were ready. This impatience was
clearly unreasonable, for even in four more years, 1804, we find the
two clocks were still in hand. Two years later, in 1806, the Board
determined to take vigorous action by asking the Bursar to call upon
Crosthwaite. This evidently produced some effect, for in the
following year, 1807, the Professor had no doubt that the clocks
would be speedily returned. After eight years more, in 1815, one of
the clocks was still being repaired, and so it was in 1816, which is
the last record we have of these interesting timepieces. Astronomers
are, however, accustomed to deal with such stupendous periods in
their calculations, that even the time taken to repair a clock seems
but small in comparison.
The long tenure of the chair of Astronomy by Brinkley is divided into
two nearly equal periods by the year in which the great circle was
erected. Brinkley was eighteen years waiting for his telescope, and
he had eighteen years more in which to use it. During the first of
these periods Brinkley devoted himself to mathematical research;
during the latter he became a celebrated astronomer. Brinkley's
mathematical labours procured for their author some reputation as a
mathematician. They appear to be works of considerable mathematical
elegance, but not indicating any great power of original thought.
Perhaps it has been prejudicial to Brinkley's fame in this direction,
that he was immediately followed in his chair by so mighty a genius
as William Rowan Hamilton.
After the great circle had been at last erected, Brinkley was able to
begin his astronomical work in earnest. Nor was there much time to
lose. He was already forty-five years old, a year older than was
Herschel when he commenced his immortal career at Slough. Stimulated
by the consciousness of having the command of an instrument of unique
perfection, Brinkley loftily attempted the very highest class of
astronomical research. He resolved to measure anew with his own eye
and with his own hand the constants of aberration and of nutation. He
also strove to solve that great problem of the universe, the
discovery of the distance of a fixed star.
These were noble problems, and they were nobly attacked. But to
appraise with justice this work of Brinkley, done seventy years ago,
we must not apply to it the same criterion as we would think right to
apply to similar work were it done now. We do not any longer use
Brinkley's constant of aberration, nor do we now think that
Brinkley's determinations of the star distances were reliable. But,
nevertheless, his investigations exercised a marked influence on the
progress of science; they stimulated the study of the principles on
which exact measurements were to be conducted.
Brinkley had another profession in addition to that of an
astronomer. He was a divine. When a man endeavours to pursue two
distinct occupations concurrently, it will be equally easy to explain
why his career should be successful, or why it should be the
reverse. If he succeeds, he will, of course, exemplify the wisdom of
having two strings to his bow. Should he fail, it is, of course,
because he has attempted to sit on two stools at once. In Brinkley's
case, his two professions must be likened to the two strings rather
than to the two stools. It is true that his practical experience of
his clerical life was very slender. He had made no attempt to
combine the routine of a parish with his labours in the observatory.
Nor do we associate a special eminence in any department of religious
work with his name. If, however, we are to measure Brinkley's merits
as a divine by the ecclesiastical preferment which he received, his
services to theology must have rivalled his services to astronomy.
Having been raised step by step in the Church, he was at last
appointed to the See of Cloyne, in 1826, as the successor of Bishop
Berkeley.
Now, though it was permissible for the Archdeacon to be also the
Andrews Professor, yet when the Archdeacon became a Bishop, it was
understood that he should transfer his residence from the observatory
to the palace. The chair of Astronomy accordingly became vacant.
Brinkley's subsequent career seems to have been devoted entirely to
ecclesiastical matters, and for the last ten years of his life he did
not contribute a paper to any scientific society. Arago, after a
characteristic lament that Brinkley should have forsaken the pursuit
of science for the temporal and spiritual attractions of a bishopric,
pays a tribute to the conscientiousness of the quondam astronomer,
who would not even allow a telescope to be brought into the palace
lest his mind should be distracted from his sacred duties.
The good bishop died on the 13th September, 1835. He was buried in
the chapel of Trinity College, and a fine monument to his memory is a
familiar object at the foot of the noble old staircase of the library.
The best memorial of Brinkley is his admirable book on the "Elements
of Plane Astronomy." It passed through many editions in his lifetime,
and even at the present day the same work, revised first by Dr. Luby,
and more recently by the Rev. Dr. Stubbs and Dr. Brunnow, has a large
and well-merited circulation.
JOHN HERSCHEL.
This illustrious son of an illustrious father was born at Slough,
near Windsor, on the 7th March, 1792. He was the only child of Sir
William Herschel, who had married somewhat late in life, as we have
already mentioned.
[PLATE: ASTRONOMETER MADE BY SIR J. HERSCHEL to compare the light
of certain stars by the intervention of the moon.]
The surroundings among which the young astronomer was reared afforded
him an excellent training for that career on which he was to enter,
and in which he was destined to attain a fame only less brilliant
than that of his father. The circumstances of his youth permitted
him to enjoy one great advantage which was denied to the elder
Herschel. He was able, from his childhood, to devote himself almost
exclusively to intellectual pursuits. William Herschel, in the early
part of his career, had only been able to snatch occasional hours for
study from his busy life as a professional musician. But the son,
having been born with a taste for the student's life, was fortunate
enough to have been endowed with the leisure and the means to enjoy
it from the commencement. His early years have been so well
described by the late Professor Pritchard in the "Report of the
Council of the Royal Astronomical Society for 1872," that I venture
to make an extract here:--
"A few traits of John Herschel's boyhood, mentioned by himself in his
maturer life, have been treasured up by those who were dear to him,
and the record of some of them may satisfy a curiosity as pardonable
as inevitable, which craves to learn through what early steps great
men or great nations become illustrious. His home was singular, and
singularly calculated to nurture into greatness any child born as
John Herschel was with natural gifts, capable of wide development. At
the head of the house there was the aged, observant, reticent
philosopher, and rarely far away his devoted sister, Caroline
Herschel, whose labours and whose fame are still cognisable as a
beneficent satellite to the brighter light of her illustrious
brother. It was in the companionship of these remarkable persons,
and under the shadow of his father's wonderful telescope, that John
Herschel passed his boyish years. He saw them, in silent but
ceaseless industry, busied about things which had no apparent concern
with the world outside the walls of that well-known house, but which,
at a later period of his life, he, with an unrivalled eloquence,
taught his countrymen to appreciate as foremost among those living
influences which but satisfy and elevate the noblest instincts of our
nature. What sort of intercourse passed between the father and the
boy may be gathered from an incident or two which he narrated as
having impressed themselves permanently on the memory of his youth.
He once asked his father what he thought was the oldest of all
things. The father replied, after the Socratic method, by putting
another question: 'And what do you yourself suppose is the oldest of
all things?' The boy was not successful in his answers, thereon the
old astronomer took up a small stone from the garden walk: 'There, my
child, there is the oldest of all the things that I certainly know.'
On another occasion his father is said to have asked the boy, 'What
sort of things, do you think, are most alike?' The delicate,
blue-eyed boy, after a short pause, replied, 'The leaves of the same
tree are most like each other.' 'Gather, then, a handful of leaves of
that tree,' rejoined the philosopher, 'and choose two that are
alike.' The boy failed; but he hid the lesson in his heart, and his
thoughts were revealed after many days. These incidents may be
trifles; nor should we record them here had not John Herschel
himself, though singularly reticent about his personal emotions,
recorded them as having made a strong impression on his mind. Beyond
all doubt we can trace therein, first, that grasp and grouping of
many things in one, implied in the stone as the oldest of things;
and, secondly, that fine and subtle discrimination of each thing out
of many like things as forming the main features which characterized
the habit of our venerated friend's philosophy."
John Herschel entered St. John's College, Cambridge, when he was
seventeen years of age. His university career abundantly fulfilled
his father's eager desire, that his only son should develop a
capacity for the pursuit of science. After obtaining many lesser
distinctions, he finally came out as Senior Wrangler in 1813. It
was, indeed, a notable year in the mathematical annals of the
University. Second on that list, in which Herschel's name was first,
appeared that of the illustrious Peacock, afterwards Dean of Ely, who
remained throughout life one of Herschel's most intimate friends.
Almost immediately after taking his degree, Herschel gave evidence of
possessing a special aptitude for original scientific investigation.
He sent to the Royal Society a mathematical paper which was published
in the PHILOSOPHICAL TRANSACTIONS. Doubtless the splendour that
attached to the name he bore assisted him in procuring early
recognition of his own great powers. Certain it is that he was made
a Fellow of the Royal Society at the unprecedentedly early age of
twenty-one. Even after this remarkable encouragement to adopt a
scientific career as the business of his life, it does not seem that
John Herschel at first contemplated devoting himself exclusively to
science. He commenced to prepare for the profession of the Law by
entering as a student at the Middle Temple, and reading with a
practising barrister.
But a lawyer John Herschel was not destined to become. Circumstances
brought him into association with some leading scientific men. He
presently discovered that his inclinations tended more and more in
the direction of purely scientific pursuits. Thus it came to pass
that the original intention as to the calling which he should follow
was gradually abandoned. Fortunately for science Herschel found its
pursuit so attractive that he was led, as his father had been before
him, to give up his whole life to the advancement of knowledge. Nor
was it unnatural that a Senior Wrangler, who had once tasted the
delights of mathematical research, should have been tempted to devote
much time to this fascinating pursuit. By the time John Herschel was
twenty-nine he had published so much mathematical work, and his
researches were considered to possess so much merit, that the Royal
Society awarded him the Copley Medal, which was the highest
distinction it was capable of conferring.
At the death of his father in 1822, John Herschel, with his tastes
already formed for a scientific career, found himself in the
possession of ample means. To him also passed all his father's great
telescopes and apparatus. These material aids, together with a
dutiful sense of filial obligation, decided him to make practical
astronomy the main work of his life. He decided to continue to its
completion that great survey of the heavens which had already been
inaugurated, and, indeed, to a large extent accomplished, by his
father.
The first systematic piece of practical astronomical work which John
Herschel undertook was connected with the measurement of what are
known as "Double Stars." It should be observed, that there are in
the heavens a number of instances in which two stars are seen in very
close association. In the case of those objects to which the
expression "Double Stars" is generally applied, the two luminous
points are so close together that even though they might each be
quite bright enough to be visible to the unaided eye, yet their
proximity is such that they cannot be distinguished as two separate
objects without optical aid. The two stars seem fused together into
one. In the telescope, however, the bodies may be discerned
separately, though they are frequently so close together that it
taxes the utmost power of the instrument to indicate the division
between them.
The appearance presented by a double star might arise from the
circumstance that the two stars, though really separated from each
other by prodigious distances, happened to lie nearly in the same
line of vision, as seen from our point of view. No doubt, many of
the so-called double stars could be accounted for on this
supposition. Indeed, in the early days when but few double stars
were known, and when telescopes were not powerful enough to exhibit
the numerous close doubles which have since been brought to light,
there seems to have been a tendency to regard all double stars as
merely such perspective effects. It was not at first suggested that
there could be any physical connection between the components of each
pair. The appearance presented was regarded as merely due to the
circumstance that the line joining the two bodies happened to pass
near the earth.
[PLATE: SIR JOHN HERSCHEL.]
In the early part of his career, Sir William Herschel seems to have
entertained the view then generally held by other astronomers with
regard to the nature of these stellar pairs. The great observer
thought that the double stars could therefore be made to afford a
means of solving that problem in which so many of the observers of
the skies had been engaged, namely, the determination of the
distances of the stars from the earth. Herschel saw that the
displacement of the earth in its annual movement round the sun would
produce an apparent shift in the place of the nearer of the two stars
relatively to the other, supposed to be much more remote. If this
shift could be measured, then the distance of the nearer of the stars
could be estimated with some degree of precision.
As has not unfrequently happened in the history of science, an effect
was perceived of a very different nature from that which had been
anticipated. If the relative places of the two stars had been
apparently deranged merely in consequence of the motion of the earth,
then the phenomenon would be an annual one. After the lapse of a
year the two stars would have regained their original relative
positions. This was the effect for which William Herschel was
looking. In certain of the so called double stars, he, no doubt, did
find a movement. He detected the remarkable fact that both the
apparent distance and the relative positions of the two bodies were
changing. But what was his surprise to observe that these
alterations were not of an annually periodic character. It became
evident then that in some cases one of the component stars was
actually revolving around the other, in an orbit which required many
years for its completion. Here was indeed a remarkable discovery. It
was clearly impossible to suppose that movements of this kind could
be mere apparent displacements, arising from the annual shift in our
point of view, in consequence of the revolution of the earth.
Herschel's discovery established the interesting fact that, in
certain of these double stars, or binary stars, as these particular
objects are more expressively designated, there is an actual orbital
revolution of a character similar to that which the earth performs
around the sun. Thus it was demonstrated that in these particular
double stars the nearness of the two components was not merely
apparent. The objects must actually lie close together at a distance
which is small in comparison with the distance at which either of
them is separated from the earth. The fact that the heavens contain
pairs of twin suns in mutual revolution was thus brought to light.
In consequence of this beautiful discovery, the attention of
astronomers was directed to the subject of double stars with a degree
of interest which these objects had never before excited. It was
therefore not unnatural that John Herschel should have been attracted
to this branch of astronomical work. Admiration for his father's
discovery alone might have suggested that the son should strive to
develop this territory newly opened up to research. But it also
happened that the mathematical talents of the younger Herschel
inclined his inquiries in the same direction. He saw clearly that,
when sufficient observations of any particular binary star had been
accumulated, it would then be within the power of the mathematician
to elicit from those observations the shape and the position in space
of the path which each of the revolving stars described around the
other. Indeed, in some cases he would be able to perform the
astonishing feat of determining from his calculations the weight of
these distant suns, and thus be enabled to compare them with the mass
of our own sun.
[PLATE: NEBULA IN SOUTHERN HEMISPHERE, drawn by Sir John Herschel.]
But this work must follow the observations, it could not precede
them. The first step was therefore to observe and to measure with
the utmost care the positions and distances of those particular
double stars which appear to offer the greatest promise in this
particular research. In 1821, Herschel and a friend of his, Mr.
James South, agreed to work together with this object. South was a
medical man with an ardent devotion to science, and possessed of
considerable wealth. He procured the best astronomical instruments
that money could obtain, and became a most enthusiastic astronomer
and a practical observer of tremendous energy.
South and John Herschel worked together for two years in the
observation and measurement of the double stars discovered by Sir
William Herschel. In the course of this time their assiduity was
rewarded by the accumulation of so great a mass of careful
measurements that when published, they formed quite a volume in the
"Philosophical Transactions." The value and accuracy of the work,
when estimated by standards which form proper criteria for that
period, is universally recognised. It greatly promoted the progress
of sidereal astronomy, and the authors were in consequence awarded
medals from the Royal Society, and the Royal Astronomical Society,
as well as similar testimonials from various foreign institutions.
This work must, however, be regarded as merely introductory to the
main labours of John Herschel's life. His father devoted the greater
part of his years as an observer to what he called his "sweeps" of
the heavens. The great reflecting telescope, twenty feet long, was
moved slowly up and down through an arc of about two degrees towards
and from the pole, while the celestial panorama passed slowly in the
course of the diurnal motion before the keenly watching eye of the
astronomer. Whenever a double star traversed the field Herschel
described it to his sister Caroline, who, as we have already
mentioned, was his invariable assistant in his midnight watches. When
a nebula appeared, then he estimated its size and its brightness, he
noticed whether it had a nucleus, or whether it had stars disposed in
any significant manner with regard to it. He also dictated any other
circumstance which he deemed worthy of record. These observations
were duly committed to writing by the same faithful and indefatigable
scribe, whose business it also was to take a memorandum of the exact
position of the object as indicated by a dial placed in front of her
desk, and connected with the telescope.
John Herschel undertook the important task of re-observing the
various double stars and nebulae which had been discovered during
these memorable vigils. The son, however, lacked one inestimable
advantage which had been possessed by the father. John Herschel had
no assistant to discharge all those duties which Caroline had so
efficiently accomplished. He had, therefore, to modify the system of
sweeping previously adopted in order to enable all the work both of
observing and of recording to be done by himself. This, in many
ways, was a great drawback to the work of the younger astronomer. The
division of labour between the observer and the scribe enables a
greatly increased quantity of work to be got through. It is also
distinctly disadvantageous to an observer to have to use his eye at
the telescope directly after he has been employing it for reading the
graduations on a circle, by the light of a lamp, or for entering
memoranda in a note book. Nebulae, especially, are often so
excessively faint that they can only be properly observed by an eye
which is in that highly sensitive condition which is obtained by long
continuance in darkness. The frequent withdrawal of the eye from the
dark field of the telescope, and the application of it to reading by
artificial light, is very prejudicial to its use for the more
delicate purpose. John Herschel, no doubt, availed himself of every
precaution to mitigate the ill effects of this inconvenience as much
as possible, but it must have told upon his labours as compared with
those of his father.
But nevertheless John Herschel did great work during his "sweeps." He
was specially particular to note all the double stars which presented
themselves to his observation. Of course some little discretion must
be allowed in deciding as to what degree of proximity in adjacent
stars does actually bring them within the category of "double
stars." Sir John set down all such objects as seemed to him likely
to be of interest, and the results of his discoveries in this branch
of astronomy amount to some thousands. Six or seven great memoirs in
the TRANSACTIONS of the Royal Astronomical Society have been devoted
to giving an account of his labours in this department of astronomy.
[PLATE: THE CLUSTER IN THE CENTAUR, drawn by Sir John Herschel.]
One of the achievements by which Sir John Herschel is best known is
his invention of a method by which the orbits of binary stars could
be determined. It will be observed that when one star revolves
around another in consequence of the law of gravitation, the orbit
described must be an ellipse. This ellipse, however, generally
speaking, appears to us more or less foreshortened, for it is easily
seen that only under highly exceptional circumstances would the plane
in which the stars move happen to be directly square to the line of
view. It therefore follows that what we observe is not exactly the
track of one star around the other; it is rather the projection of
that track as seen on the surface of the sky. Now it is remarkable
that this apparent path is still an ellipse. Herschel contrived a
very ingenious and simple method by which he could discover from the
observations the size and position of the ellipse in which the
revolution actually takes place. He showed how, from the study of
the apparent orbit of the star, and from certain measurements which
could easily be effected upon it, the determination of the true
ellipse in which the movement is performed could be arrived at. In
other words, Herschel solved in a beautiful manner the problem of
finding the true orbits of double stars. The importance of this work
may be inferred from the fact that it has served as the basis on
which scores of other investigators have studied the fascinating
subject of the movement of binary stars.
The labours, both in the discovery and measurement of the double
stars, and in the discussion of the observations with the object of
finding the orbits of such stars as are in actual revolution,
received due recognition in yet another gold medal awarded by the
Royal Society. An address was delivered on the occasion by the Duke
of Sussex (30th November, 1833), in the course of which, after
stating that the medal had been conferred on Sir John Herschel, he
remarks:--
"It has been said that distance of place confers the same privilege
as distance of time, and I should gladly avail myself of the
privilege which is thus afforded me by Sir John Herschel's separation
from his country and friends, to express my admiration of his
character in stronger terms than I should otherwise venture to use;
for the language of panegyric, however sincerely it may flow from the
heart, might be mistaken for that of flattery, if it could not thus
claim somewhat of an historical character; but his great attainments
in almost every department of human knowledge, his fine powers as a
philosophical writer, his great services and his distinguished
devotion to science, the high principles which have regulated his
conduct in every relation of life, and, above all, his engaging
modesty, which is the crown of all his other virtues, presenting such
a model of an accomplished philosopher as can rarely be found beyond
the regions of fiction, demand abler pens than mine to describe them
in adequate terms, however much inclined I might feel to undertake
the task."
The first few lines of the eulogium just quoted allude to Herschel's
absence from England. This was not merely an episode of interest in
the career of Herschel, it was the occasion of one of the greatest
scientific expeditions in the whole history of astronomy.
Herschel had, as we have seen, undertaken a revision of his father's
"sweeps" for new objects, in those skies which are visible from our
latitudes in the northern hemisphere. He had well-nigh completed
this task. Zone by zone the whole of the heavens which could be
observed from Windsor had passed under his review. He had added
hundreds to the list of nebulae discovered by his father. He had
announced thousands of double stars. At last, however, the great
survey was accomplished. The contents of the northern hemisphere, so
far at least as they could be disclosed by his telescope of twenty
feet focal length, had been revealed.
[PLATE: SIR JOHN HERSCHEL'S OBSERVATORY AT FELDHAUSEN,
Cape of Good Hope.]
But Herschel felt that this mighty task had to be supplemented by
another of almost equal proportions, before it could be said that the
twenty-foot telescope had done its work. It was only the northern
half of the celestial sphere which had been fully explored. The
southern half was almost virgin territory, for no other astronomer
was possessed of a telescope of such power as those which the
Herschels had used. It is true, of course, that as a certain margin
of the southern hemisphere was visible from these latitudes, it had
been more or less scrutinized by observers in northern skies. And
the glimpses which had thus been obtained of the celestial objects in
the southern sky, were such as to make an eager astronomer long for a
closer acquaintance with the celestial wonders of the south. The
most glorious object in the sidereal heavens, the Great Nebula in
Orion, lies indeed in that southern hemisphere to which the younger
Herschel's attention now became directed. It fortunately happens,
however, for votaries of astronomy all the world over, that Nature
has kindly placed her most astounding object, the great Nebula in
Orion, in such a favoured position, near the equator, that from a
considerable range of latitudes, both north and south, the wonders of
the Nebula can be explored. There are grounds for thinking that the
southern heavens contain noteworthy objects which, on the whole, are
nearer to the solar system than are the noteworthy objects in the
northern skies. The nearest star whose distance is known, Alpha
Centauri, lies in the southern hemisphere, and so also does the most
splendid cluster of stars.
Influenced by the desire to examine these objects, Sir John Herschel
determined to take his great telescope to a station in the southern
hemisphere, and thus complete his survey of the sidereal heavens. The
latitude of the Cape of Good Hope is such that a suitable site could
be there found for his purpose. The purity of the skies in South
Africa promised to provide for the astronomer those clear nights
which his delicate task of surveying the nebulae would require.
On November 13, 1833, Sir John Herschel, who had by this time
received the honour of knighthood from William IV., sailed from
Portsmouth for the Cape of Good Hope, taking with him his gigantic
instruments. After a voyage of two months, which was considered to
be a fair passage in those days, he landed in Table Bay, and having
duly reconnoitred various localities, he decided to place his
observatory at a place called Feldhausen, about six miles from Cape
Town, near the base of the Table Mountain. A commodious residence
was there available, and in it he settled with his family. A
temporary building was erected to contain the equatorial, but the
great twenty-foot telescope was accommodated with no more shelter
than is provided by the open canopy of heaven.
As in his earlier researches at home, the attention of the great
astronomer at the Cape of Good Hope was chiefly directed to the
measurement of the relative positions and distances apart of the
double stars, and to the close examination of the nebulae. In the
delineation of the form of these latter objects Herschel found ample
employment for his skilful pencil. Many of the drawings he has made
of the celestial wonders in the southern sky are admirable examples
of celestial portraiture.
The number of the nebulae and of those kindred objects, the star
clusters, which Herschel studied in the southern heavens, during four
years of delightful labour, amount in all to one thousand seven
hundred and seven. His notes on their appearance, and the
determinations of their positions, as well as his measurements of
double stars, and much other valuable astronomical research, were
published in a splendid volume, brought out at the cost of the Duke
of Northumberland. This is, indeed, a monumental work, full of
interesting and instructive reading for any one who has a taste for
astronomy.
Herschel had the good fortune to be at the Cape on the occasion of
the periodical return of Halley's great comet in 1833. To the study
of this body he gave assiduous attention, and the records of his
observations form one of the most interesting chapters in that
remarkable volume to which we have just referred.
[PLATE: COLUMN AT FELDHAUSEN, CAPE TOWN, to commemorate Sir John
Herschel's survey of the Southern Heavens.]
Early in 1838 Sir John Herschel returned to England. He had made
many friends at the Cape, who deeply sympathised with his self-
imposed labours while he was resident among them. They desired to
preserve the recollection of this visit, which would always, they
considered, be a source of gratification in the colony. Accordingly,
a number of scientific friends in that part of the world raised a
monument with a suitable inscription, on the spot which had been
occupied by the great twenty-foot reflector at Feldhausen.
His return to England after five years of absence was naturally an
occasion for much rejoicing among the lovers of astronomy. He was
entertained at a memorable banquet, and the Queen, at her coronation,
made him a baronet. His famous aunt Caroline, at that time aged
eighty, was still in the enjoyment of her faculties, and was able to
estimate at its true value the further lustre which was added to the
name she bore. But there is reason to believe that her satisfaction
was not quite unmixed with other feelings. With whatever favour she
might regard her nephew, he was still not the brother to whom her
life had been devoted. So jealous was this vigorous old lady of the
fame of the great brother William, that she could hardly hear with
patience of the achievements of any other astronomer, and this
failing existed in some degree even when that other astronomer
happened to be her illustrious nephew.
With Sir John Herschel's survey of the Southern Hemisphere it may be
said that his career as an observing astronomer came to a close. He
did not again engage in any systematic telescopic research. But it
must not be inferred from this statement that he desisted from active
astronomical work. It has been well observed that Sir John Herschel
was perhaps the only astronomer who has studied with success, and
advanced by original research, every department of the great science
with which his name is associated. It was to some other branches of
astronomy besides those concerned with looking through telescopes,
that the rest of the astronomer's life was to be devoted.
To the general student Sir John Herschel is best known by the volume
which he published under the title of "Outlines of Astronomy." This
is, indeed, a masterly work, in which the characteristic difficulties
of the subject are resolutely faced and expounded with as much
simplicity as their nature will admit. As a literary effort this
work is admirable, both on account of its picturesque language and
the ennobling conceptions of the universe which it unfolds. The
student who desires to become acquainted with those recondite
departments of astronomy, in which the effects of the disturbing
action of one planet upon the motions of another planet are
considered, will turn to the chapters in Herschel's famous work on
the subject. There he will find this complex matter elucidated,
without resort to difficult mathematics. Edition after edition of
this valuable work has appeared, and though the advances of modern
astronomy have left it somewhat out of date in certain departments,
yet the expositions it contains of the fundamental parts of the
science still remain unrivalled.
Another great work which Sir John undertook after his return from the
Cape, was a natural climax to those labours on which his father and
he had been occupied for so many years. We have already explained
how the work of both these observers had been mainly devoted to the
study of the nebulae and the star clusters. The results of their
discoveries had been announced to the world in numerous isolated
memoirs. The disjointed nature of these publications made their use
very inconvenient. But still it was necessary for those who desired
to study the marvellous objects discovered by the Herschels, to have
frequent recourse to the original works. To incorporate all the
several observations of nebular into one great systematic catalogue,
seemed, therefore, to be an indispensable condition of progress in
this branch of knowledge. No one could have been so fitted for this
task as Sir John Herschel. He, therefore, attacked and carried
through the great undertaking. Thus at last a grand catalogue of
nebulae and clusters was produced. Never before was there so
majestic an inventory. If we remember that each of the nebulae is an
object so vast, that the whole of the solar system would form an
inconsiderable speck by comparison, what are we to think of a
collection in which these objects are enumerated in thousands? In
this great catalogue we find arranged in systematic order all the
nebulae and all the clusters which had been revealed by the diligence
of the Herschels, father and son, in the Northern Hemisphere, and of
the son alone in the Southern Hemisphere. Nor should we omit to
mention that the labours of other astronomers were likewise
incorporated. It was unavoidable that the descriptions given to each
of the objects should be very slight. Abbreviations are used, which
indicate that a nebula is bright, or very bright, or extremely
bright, or faint, or very faint, or extremely faint. Such phrases
have certainly but a relative and technical meaning in such a
catalogue. The nebulae entered as extremely bright by the
experienced astronomer are only so described by way of contrast to
the great majority of these delicate telescopic objects. Most of the
nebulae, indeed, are so difficult to see, that they admit of but very
slight description. It should be observed that Herschel's catalogue
augmented the number of known nebulous objects to more than ten times
that collected into any catalogue which had ever been compiled before
the days of William Herschel's observing began. But the study of
these objects still advances, and the great telescopes now in use
could probably show at least twice as many of these objects as are
contained in the list of Herschel, of which a new and enlarged
edition has since been brought out by Dr. Dreyer.
One of the best illustrations of Sir John Herschel's literary powers
is to be found in the address which he delivered at the Royal
Astronomical Society, on the occasion of presenting a medal to Mr.
Francis Baily, in recognition of his catalogue of stars. The passage
I shall here cite places in its proper aspect the true merit of the
laborious duty involved in such a task as that which Mr. Baily had
carried through with such success:--
"If we ask to what end magnificent establishments are maintained by
states and sovereigns, furnished with masterpieces of art, and placed
under the direction of men of first-rate talent and high-minded
enthusiasm, sought out for those qualities among the foremost in the
ranks of science, if we demand QUI BONO? for what good a Bradley has
toiled, or a Maskelyne or a Piazzi has worn out his venerable age in
watching, the answer is--not to settle mere speculative points in the
doctrine of the universe; not to cater for the pride of man by
refined inquiries into the remoter mysteries of nature; not to trace
the path of our system through space, or its history through past and
future eternities. These, indeed, are noble ends and which I am far
from any thought of depreciating; the mind swells in their
contemplation, and attains in their pursuit an expansion and a
hardihood which fit it for the boldest enterprise. But the direct
practical utility of such labours is fully worthy of their
speculative grandeur. The stars are the landmarks of the universe;
and, amidst the endless and complicated fluctuations of our system,
seem placed by its Creator as guides and records, not merely to
elevate our minds by the contemplation of what is vast, but to teach
us to direct our actions by reference to what is immutable in His
works. It is, indeed, hardly possible to over-appreciate their value
in this point of view. Every well-determined star, from the moment
its place is registered, becomes to the astronomer, the geographer,
the navigator, the surveyor, a point of departure which can never
deceive or fail him, the same for ever and in all places, of a
delicacy so extreme as to be a test for every instrument yet invented
by man, yet equally adapted for the most ordinary purposes; as
available for regulating a town clock as for conducting a navy to the
Indies; as effective for mapping down the intricacies of a petty
barony as for adjusting the boundaries of Transatlantic empires. When
once its place has been thoroughly ascertained and carefully
recorded, the brazen circle with which that useful work was done may
moulder, the marble pillar may totter on its base, and the astronomer
himself survive only in the gratitude of posterity; but the record
remains, and transfuses all its own exactness into every
determination which takes it for a groundwork, giving to inferior
instruments--nay, even to temporary contrivances, and to the
observations of a few weeks or days--all the precision attained
originally at the cost of so much time, labour, and expense."
Sir John Herschel wrote many other works besides those we have
mentioned. His "Treatise on Meteorology" is, indeed, a standard work
on this subject, and numerous articles from the same pen on
miscellaneous subjects, which have been collected and reprinted,
seemed as a relaxation from his severe scientific studies. Like
certain other great mathematicians Herschel was also a poet, and he
published a translation of the Iliad into blank verse.
In his later years Sir John Herschel lived a retired life. For a
brief period he had, indeed, been induced to accept the office of
Master of the Mint. It was, however, evident that the routine of
such an occupation was not in accordance with his tastes, and he
gladly resigned it, to return to the seclusion of his study in his
beautiful home at Collingwood, in Kent.
His health having gradually failed, he died on the 11th May, 1871, in
the seventy-ninth year of his age.
THE EARL OF ROSSE.
The subject of our present sketch occupies quite a distinct position
in scientific history. Unlike many others who have risen by their
scientific discoveries from obscurity to fame, the great Earl of
Rosse was himself born in the purple. His father, who, under the
title of Sir Lawrence Parsons, had occupied a distinguished position
in the Irish Parliament, succeeded on the death of his father to the
Earldom which had been recently created. The subject of our present
memoir was, therefore, the third of the Earls of Rosse, and he was
born in York on June 17, 1800. Prior to his father's death in 1841,
he was known as Lord Oxmantown.
The University education of the illustrious astronomer was begun in
Dublin and completed at Oxford. We do not hear in his case of any
very remarkable University career. Lord Rosse was, however, a
diligent student, and obtained a first-class in mathematics. He
always took a great deal of interest in social questions, and was a
profound student of political economy. He had a seat in the House of
Commons, as member for King's County, from 1821 to 1834, his
ancestral estate being situated in this part of Ireland.
[PLATE: THE EARL OF ROSSE.]
Lord Rosse was endowed by nature with a special taste for mechanical
pursuits. Not only had he the qualifications of a scientific
engineer, but he had the manual dexterity which qualified him
personally to carry out many practical arts. Lord Rosse was, in
fact, a skilful mechanic, an experienced founder, and an ingenious
optician. His acquaintances were largely among those who were
interested in mechanical pursuits, and it was his delight to visit
the works or engineering establishments where refined processes in
the arts were being carried on. It has often been stated--and as I
have been told by members of his family, truly stated--that on one
occasion, after he had been shown over some large works in the north
of England, the proprietor bluntly said that he was greatly in want
of a foreman, and would indeed be pleased if his visitor, who had
evinced such extraordinary capacity for mechanical operations, would
accept the post. Lord Rosse produced his card, and gently explained
that he was not exactly the right man, but he appreciated the
compliment, and this led to a pleasant dinner, and was the basis of a
long friendship.
I remember on one occasion hearing Lord Rosse explain how it was that
he came to devote his attention to astronomy. It appears that when
he found himself in the possession of leisure and of means, he
deliberately cast around to think how that means and that leisure
could be most usefully employed. Nor was it surprising that he
should search for a direction which would offer special scope for his
mechanical tastes. He came to the conclusion that the building of
great telescopes was an art which had received no substantial advance
since the great days of William Herschel. He saw that to construct
mighty instruments for studying the heavens required at once the
command of time and the command of wealth, while he also felt that
this was a subject the inherent difficulties of which would tax to
the uttermost whatever mechanical skill he might possess. Thus it
was he decided that the construction of great telescopes should
become the business of his life.
[PLATE: BIRR CASTLE.
PLATE: THE MALL, PARSONSTOWN.]
In the centre of Ireland, seventy miles from Dublin, on the border
between King's County and Tipperary, is a little town whereof we must
be cautious before writing the name. The inhabitants of that town
frequently insist that its name is Birr, * while the official
designation is Parsonstown, and to this day for every six people who
apply one name to the town, there will be half a dozen who use the
other. But whichever it may be, Birr or Parsonstown--and I shall
generally call it by the latter name--it is a favourable specimen of
an Irish county town. The widest street is called the Oxmantown
Mall. It is bordered by the dwelling-houses of the chief residents,
and adorned with rows of stately trees. At one end of this
distinctly good feature in the town is the Parish Church, while at
the opposite end are the gates leading into Birr Castle, the
ancestral home of the house of Parsons. Passing through the gates
the visitor enters a spacious demesne, possessing much beauty of wood
and water, one of the most pleasing features being the junction of
the two rivers, which unite at a spot ornamented by beautiful
timber. At various points illustrations of the engineering skill of
the great Earl will be observed. The beauty of the park has been
greatly enhanced by the construction of an ample lake, designed with
the consummate art by which art is concealed. Even in mid-summer it
is enlivened by troops of wild ducks preening themselves in that
confidence which they enjoy in those happy localities where the sound
of a gun is seldom heard. The water is led into the lake by a tube
which passes under one of the two rivers just mentioned, while the
overflow from the lake turns a water-wheel, which works a pair of
elevators ingeniously constructed for draining the low-lying parts of
the estate.
* Considering the fame acquired by Parsonstown from Lord Rosse's
mirrors, it may be interesting to note the following extract from
"The Natural History of Ireland," by Dr. Gerard Boate, Thomas
Molyneux M.D., F.R.S., and others, which shows that 150 years ago
Parsonstown was famous for its glass:--
"We shall conclude this chapter with the glass, there having been
several glasshouses set up by the English in Ireland, none in Dublin
or other cities, but all of them in the country; amongst which the
principal was that of Birre, a market town, otherwise called
Parsonstown, after one Sir Lawrence Parsons, who, having purchased
that lordship, built a goodly house upon it; his son William Parsons
having succeeded him in the possession of it; which town is situate
in Queen's County, about fifty miles (Irish) to the southwest of
Dublin, upon the borders of the two provinces of Leinster and Munster;
from this place Dublin was furnished with all sorts of window and
drinking glasses, and such other as commonly are in use. One part of
the materials, viz., the sand, they had out of England; the other,
to wit the ashes, they made in the place of ash-tree, and used no
other. The chiefest difficulty was to get the clay for the pots to
melt the materials in; this they had out of the north."--Chap. XXI.,
Sect. VIII. "Of the Glass made in Ireland."
Birr Castle itself is a noble mansion with reminiscences from the
time of Cromwell. It is surrounded by a moat and a drawbridge of
modern construction, and from its windows beautiful views can be had
over the varied features of the park. But while the visitors to
Parsonstown will look with great interest on this residence of an
Irish landlord, whose delight it was to dwell in his own country, and
among his own people, yet the feature which they have specially come
to observe is not to be found in the castle itself. On an extensive
lawn, sweeping down from the moat towards the lake, stand two noble
masonry walls. They are turreted and clad with ivy, and considerably
loftier than any ordinary house. As the visitor approaches, he will
see between those walls what may at first sight appear to him to be
the funnel of a steamer lying down horizontally. On closer approach
he will find that it is an immense wooden tube, sixty feet long, and
upwards of six feet in diameter. It is in fact large enough to admit
of a tall man entering into it and walking erect right through from
one end to the other. This is indeed the most gigantic instrument
which has ever been constructed for the purpose of exploring the
heavens. Closely adjoining the walls between which the great tube
swings, is a little building called "The Observatory." In this the
smaller instruments are contained, and there are kept the books which
are necessary for reference. The observatory also offers shelter to
the observers, and provides the bright fire and the cup of warm tea,
which are so acceptable in the occasional intervals of a night's
observation passed on the top of the walls with no canopy but the
winter sky.
Almost the first point which would strike the visitor to Lord Rosse's
telescope is that the instrument at which he is looking is not only
enormously greater than anything of the kind that he has ever seen
before, but also that it is something of a totally different nature.
In an ordinary telescope he is accustomed to find a tube with lenses
of glass at either end, while the large telescopes that we see in our
observatories are also in general constructed on the same principle.
At one end there is the object-glass, and at the other end the
eye-piece, and of course it is obvious that with an instrument of
this construction it is to the lower end of the tube that the eye of
the observer must be placed when the telescope is pointed to the
skies. But in Lord Rosse's telescope you would look in vain for
these glasses, and it is not at the lower end of the instrument that
you are to take your station when you are going to make your
observations. The astronomer at Parsonstown has rather to avail
himself of the ingenious system of staircases and galleries, by which
he is enabled to obtain access to the mouth of the great tube. The
colossal telescope which swings between the great walls, like
Herschel's great telescope already mentioned, is a reflector, the
original invention of which is due of course to Newton. The optical
work which is accomplished by the lenses in the ordinary telescope is
effected in the type of instrument constructed by Lord Rosse by a
reflecting mirror which is placed at the lower end of the vast tube.
The mirror in this instrument is made of a metal consisting of two
parts of copper to one of tin. As we have already seen, this mixture
forms an alloy of a very peculiar nature. The copper and the tin
both surrender their distinctive qualities, and unite to form a
material of a very different physical character. The copper is tough
and brown, the tin is no doubt silvery in hue, but soft and almost
fibrous in texture. When the two metals are mixed together in the
proportions I have stated, the alloy obtained is intensely hard and
quite brittle being in both these respects utterly unlike either of
the two ingredients of which it is composed. It does, however,
resemble the tin in its whiteness, but it acquires a lustre far
brighter than tin; in fact, this alloy hardly falls short of silver
itself in its brilliance when polished.
[PLATE: LORD ROSSE'S TELESCOPE. From a photograph by W. Lawrence,
Upper Sackville Street, Dublin.]
The first duty that Lord Rosse had to undertake was the construction
of this tremendous mirror, six feet across, and about four or five
inches thick. The dimensions were far in excess of those which had
been contemplated in any previous attempt of the same kind. Herschel
had no doubt fashioned one mirror of four feet in diameter, and many
others of smaller dimensions, but the processes which he employed had
never been fully published, and it was obvious that, with a large
increase in dimensions, great additional difficulties had to be
encountered. Difficulties began at the very commencement of the
process, and were experienced in one form or another at every
subsequent stage. In the first place, the mere casting of a great
disc of this mixture of tin and copper, weighing something like three
or four tons, involved very troublesome problems. No doubt a casting
of this size, if the material had been, for example, iron, would have
offered no difficulties beyond those with which every practical
founder is well acquainted, and which he has to encounter daily in
the course of his ordinary work. But speculum metal is a material of
a very intractable description. There is, of course, no practical
difficulty in melting the copper, nor in adding the proper proportion
of tin when the copper has been melted. There may be no great
difficulty in arranging an organization by which several crucibles,
filled with the molten material, shall be poured simultaneously so as
to obtain the requisite mass of metal, but from this point the
difficulties begin. For speculum metal when cold is excessively
brittle, and were the casting permitted to cool like an ordinary
copper or iron casting, the mirror would inevitably fly into pieces.
Lord Rosse, therefore, found it necessary to anneal the casting with
extreme care by allowing it to cool very slowly. This was
accomplished by drawing the disc of metal as soon as it had entered
into the solid state, though still glowing red, into an annealing
oven. There the temperature was allowed to subside so gradually,
that six weeks elapsed before the mirror had reached the temperature
of the external air. The necessity for extreme precaution in the
operation of annealing will be manifest if we reflect on one of the
accidents which happened. On a certain occasion, after the cooling
of a great casting had been completed, it was found, on withdrawing
the speculum, that it was cracked into two pieces. This mishap was
eventually traced to the fact that one of the walls of the oven had
only a single brick in its thickness, and that therefore the heat had
escaped more easily through that side than through the other sides
which were built of double thickness. The speculum had,
consequently, not cooled uniformly, and hence the fracture had
resulted. Undeterred, however, by this failure, as well as by not a
few other difficulties, into a description of which we cannot now
enter, Lord Rosse steadily adhered to his self-imposed task, and at
last succeeded in casting two perfect discs on which to commence the
tedious processes of grinding and polishing. The magnitude of the
operations involved may perhaps be appreciated if I mention that the
value of the mere copper and tin entering into the composition of
each of the mirrors was about 500 pounds.
In no part of his undertaking was Lord Rosse's mechanical ingenuity
more taxed than in the devising of the mechanism for carrying out the
delicate operations of grinding and polishing the mirrors, whose
casting we have just mentioned. In the ordinary operations of the
telescope-maker, such processes had hitherto been generally effected
by hand, but, of course, such methods became impossible when dealing
with mirrors which were as large as a good-sized dinner table, and
whose weight was measured by tons. The rough grinding was effected
by means of a tool of cast iron about the same size as the mirror,
which was moved by suitable machinery both backwards and forwards,
and round and round, plenty of sand and water being supplied between
the mirror and the tool to produce the necessary attrition. As the
process proceeded and as the surface became smooth, emery was used
instead of sand; and when this stage was complete, the grinding tool
was removed and the polishing tool was substituted. The essential
part of this was a surface of pitch, which, having been temporarily
softened by heat, was then placed on the mirror, and accepted from
the mirror the proper form. Rouge was then introduced as the
polishing powder, and the operation was continued about nine hours,
by which time the great mirror had acquired the appearance of highly
polished silver. When completed, the disc of speculum metal was
about six feet across and four inches thick. The depression in the
centre was about half an inch. Mounted on a little truck, the great
speculum was then conveyed to the instrument, to be placed in its
receptacle at the bottom of the tube, the length of which was sixty
feet, this being the focal distance of the mirror. Another small
reflector was inserted in the great tube sideways, so as to direct
the gaze of the observer down upon the great reflector. Thus was
completed the most colossal instrument for the exploration of the
heavens which the art of man has ever constructed.
[PLATE: ROMAN CATHOLIC CHURCH AT PARSONSTOWN.]
It was once my privilege to be one of those to whom the illustrious
builder of the great telescope entrusted its use. For two seasons in
1865 and 1866 I had the honour of being Lord Rosse's astronomer.
During that time I passed many a fine night in the observer's
gallery, examining different objects in the heavens with the aid of
this remarkable instrument. At the time I was there, the objects
principally studied were the nebulae, those faint stains of light
which lie on the background of the sky. Lord Rosse's telescope was
specially suited for the scrutiny of these objects, inasmuch as their
delicacy required all the light-grasping power which could be
provided.
One of the greatest discoveries made by Lord Rosse, when his huge
instrument was first turned towards the heavens, consisted in the
detection of the spiral character of some of the nebulous forms.
When the extraordinary structure of these objects was first
announced, the discovery was received with some degree of
incredulity. Other astronomers looked at the same objects, and when
they failed to discern--and they frequently did fail to discern--the
spiral structure which Lord Rosse had indicated, they drew the
conclusion that this spiral structure did not exist. They thought it
must be due possibly to some instrumental defect or to the
imagination of the observer. It was, however, hardly possible for
any one who was both willing and competent to examine into the
evidence, to doubt the reality of Lord Rosse's discoveries. It
happens, however, that they have been recently placed beyond all
doubt by testimony which it is impossible to gainsay. A witness
never influenced by imagination has now come forward, and the
infallible photographic plate has justified Lord Rosse. Among the
remarkable discoveries which Dr. Isaac Roberts has recently made in
the application of his photographic apparatus to the heavens, there
is none more striking than that which declares, not only that the
nebulae which Lord Rosse described as spirals, actually do possess
the character so indicated, but that there are many others of the
same description. He has even brought to light the astonishingly
interesting fact that there are invisible objects of this class which
have never been seen by human eye, but whose spiral character is
visible to the peculiar delicacy of the photographic telescope.
In his earlier years, Lord Rosse himself used to be a diligent
observer of the heavenly bodies with the great telescope which was
completed in the year 1845. But I think that those who knew Lord
Rosse well, will agree that it was more the mechanical processes
incidental to the making of the telescope which engaged his interest
than the actual observations with the telescope when it was
completed. Indeed one who was well acquainted with him believed Lord
Rosse's special interest in the great telescope ceased when the last
nail had been driven into it. But the telescope was never allowed to
lie idle, for Lord Rosse always had associated with him some ardent
young astronomer, whose delight it was to employ to the uttermost the
advantages of his position in exploring the wonders of the sky. Among
those who were in this capacity in the early days of the great
telescope, I may mention my esteemed friend Dr. Johnston Stoney.
Such was the renown of Lord Rosse himself, brought about by his
consummate mechanical genius and his astronomical discoveries, and
such the interest which gathered around the marvellous workshops at
Birr castle, wherein his monumental exhibitions of optical skill were
constructed, that visitors thronged to see him from all parts of the
world. His home at Parsonstown became one of the most remarkable
scientific centres in Great Britain; thither assembled from time to
time all the leading men of science in the country, as well as many
illustrious foreigners. For many years Lord Rosse filled with marked
distinction the exalted position of President of the Royal Society,
and his advice and experience in practical mechanical matters were
always at the disposal of those who sought his assistance. Personally
and socially Lord Rosse endeared himself to all with whom he came in
contact. I remember one of the attendants telling me that on one
occasion he had the misfortune to let fall and break one of the small
mirrors on which Lord Rosse had himself expended many hours of hard
personal labour. The only remark of his lordship was that "accidents
will happen."
The latter years of his life Lord Rosse passed in comparative
seclusion; he occasionally went to London for a brief sojourn during
the season, and he occasionally went for a cruise in his yacht; but
the greater part of the year he spent at Birr Castle, devoting
himself largely to the study of political and social questions, and
rarely going outside the walls of his demesne, except to church on
Sunday mornings. He died on October 31, 1867.
He was succeeded by his eldest son, the present Earl of Rosse, who
has inherited his father's scientific abilities, and done much
notable work with the great telescope.
AIRY.
In our sketch of the life of Flamsteed, we have referred to the
circumstances under which the famous Observatory that crowns
Greenwich Hill was founded. We have also had occasion to mention
that among the illustrious successors of Flamsteed both Halley and
Bradley are to be included. But a remarkable development of
Greenwich Observatory from the modest establishment of early days
took place under the direction of the distinguished astronomer whose
name is at the head of this chapter. By his labours this temple of
science was organised to such a degree of perfection that it has
served in many respects as a model for other astronomical
establishments in various parts of the world. An excellent account
of Airy's career has been given by Professor H. H. Turner, in the
obituary notice published by the Royal Astronomical Society. To this
I am indebted for many of the particulars here to be set down
concerning the life of the illustrious Astronomer Royal.
The family from which Airy took his origin came from Kentmere, in
Westmoreland. His father, William Airy, belonged to a Lincolnshire
branch of the same stock. His mother's maiden name was Ann Biddell,
and her family resided at Playford, near Ipswich. William Airy held
some small government post which necessitated an occasional change of
residence to different parts of the country, and thus it was that his
son, George Biddell, came to be born at Alnwick, on 27th July, 1801.
The boy's education, so far as his school life was concerned was
partly conducted at Hereford and partly at Colchester. He does not,
however, seem to have derived much benefit from the hours which he
passed in the schoolroom. But it was delightful to him to spend his
holidays on the farm at Playford, where his uncle, Arthur Biddell,
showed him much kindness. The scenes of his early youth remained
dear to Airy throughout his life, and in subsequent years he himself
owned a house at Playford, to which it was his special delight to
resort for relaxation during the course of his arduous career. In
spite of the defects of his school training he seems to have
manifested such remarkable abilities that his uncle decided to enter
him in Cambridge University. He accordingly joined Trinity College
as a sizar in 1819, and after a brilliant career in mathematical and
physical science he graduated as Senior Wrangler in 1823. It may be
noted as an exceptional circumstance that, notwithstanding the
demands on his time in studying for his tripos, he was able, after
his second term of residence, to support himself entirely by taking
private pupils. In the year after he had taken his degree he was
elected to a Fellowship at Trinity College.
Having thus gained an independent position, Airy immediately entered
upon that career of scientific work which he prosecuted without
intermission almost to the very close of his life. One of his most
interesting researches in these early days is on the subject of
Astigmatism, which defect he had discovered in his own eyes. His
investigations led him to suggest a means of correcting this defect
by using a pair of spectacles with lenses so shaped as to counteract
the derangement which the astigmatic eye impressed upon the rays of
light. His researches on this subject were of a very complete
character, and the principles he laid down are to the present day
practically employed by oculists in the treatment of this
malformation.
On the 7th of December, 1826, Airy was elected to the Lucasian
Professorship of Mathematics in the University of Cambridge, the
chair which Newton's occupancy had rendered so illustrious. His
tenure of this office only lasted for two years, when he exchanged it
for the Plumian Professorship. The attraction which led him to
desire this change is doubtless to be found in the circumstance that
the Plumian Professorship of Astronomy carried with it at that time
the appointment of director of the new astronomical observatory, the
origin of which must now be described.
Those most interested in the scientific side of University life
decided in 1820 that it would be proper to found an astronomical
observatory at Cambridge. Donations were accordingly sought for this
purpose, and upwards of 6,000 pounds were contributed by members of
the University and the public. To this sum 5,000 pounds were added
by a grant from the University chest, and in 1824 further sums
amounting altogether to 7,115 pounds were given by the University for
the same object. The regulations as to the administration of the new
observatory placed it under the management of the Plumian Professor,
who was to be provided with two assistants. Their duties were to
consist in making meridian observations of the sun, moon, and the
stars, and the observations made each year were to be printed and
published. The observatory was also to be used in the educational
work of the University, for it was arranged that smaller instruments
were to be provided by which students could be instructed in the
practical art of making astronomical observations.
The building of the Cambridge Astronomical Observatory was completed
in 1824, but in 1828, when Airy entered on the discharge of his
duties as Director, the establishment was still far from completion,
in so far as its organisation was concerned. Airy commenced his work
so energetically that in the next year after his appointment he was
able to publish the first volume of "Cambridge Astronomical
Observations," notwithstanding that every part of the work, from the
making of observations to the revising of the proof-sheets, had to be
done by himself.
It may here be remarked that these early volumes of the publications
of the Cambridge Observatory contained the first exposition of those
systematic methods of astronomical work which Airy afterwards
developed to such a great extent at Greenwich, and which have been
subsequently adopted in many other places. No more profitable
instruction for the astronomical beginner can be found than that
which can be had by the study of these volumes, in which the Plumian
Professor has laid down with admirable clearness the true principles
on which meridian work should be conducted.
[PLATE: SIR GEORGE AIRY.
From a Photograph by Mr. E.P. Adams, Greenwich.]
Airy gradually added to the instruments with which the observatory
was originally equipped. A mural circle was mounted in 1832, and in
the same year a small equatorial was erected by Jones. This was made
use of by Airy in a well-known series of observations of Jupiter's
fourth satellite for the determination of the mass of the great
planet. His memoir on this subject fully ex pounds the method of
finding the weight of a planet from observations of the movements of
a satellite by which the planet is attended. This is, indeed, a
valuable investigation which no student of astronomy can afford to
neglect. The ardour with which Airy devoted himself to astronomical
studies may be gathered from a remarkable report on the progress of
astronomy during the present century, which he communicated to the
British Association at its second meeting in 1832. In the early
years of his life at Cambridge his most famous achievement was
connected with a research in theoretical astronomy for which
consummate mathematical power was required. We can only give a brief
account of the Subject, for to enter into any full detail with regard
to it would be quite out of the question.
Venus is a planet of about the same size and the same weight as the
earth, revolving in an orbit which lies within that described by our
globe. Venus, consequently, takes less time than the earth to
accomplish one revolution round the sun, and it happens that the
relative movements of Venus and the earth are so proportioned that in
the time in which our earth accomplishes eight of her revolutions the
other planet will have accomplished almost exactly thirteen. It,
therefore, follows that if the earth and Venus are in line with the
sun at one date, then in eight years later both planets will again be
found at the same points in their orbits. In those eight years the
earth has gone round eight times, and has, therefore, regained its
original position, while in the same period Venus has accomplished
thirteen complete revolutions, and, therefore, this planet also has
reached the same spot where it was at first. Venus and the earth, of
course, attract each other, and in consequence of these mutual
attractions the earth is swayed from the elliptic track which it
would otherwise pursue. In like manner Venus is also forced by the
attraction of the earth to revolve in a track which deviates from
that which it would otherwise follow. Owing to the fact that the sun
is of such preponderating magnitude (being, in fact, upwards of
300,000 times as heavy as either Venus or the earth), the
disturbances induced in the motion of either planet, in consequence
of the attraction of the other, are relatively insignificant to the
main controlling agency by which each of the movements is governed.
It is, however, possible under certain circumstances that the
disturbing effects produced upon one planet by the other can become
so multiplied as to produce peculiar effects which attain measurable
dimensions. Suppose that the periodic times in which the earth and
Venus revolved had no simple relation to each other, then the points
of their tracks in which the two planets came into line with the sun
would be found at different parts of the orbits, and consequently the
disturbances would to a great extent neutralise each other, and
produce but little appreciable effect. As, however, Venus and the
earth come back every eight years to nearly the same positions at the
same points of their track, an accumulative effect is produced. For
the disturbance of one planet upon the other will, of course, be
greatest when those two planets are nearest, that is, when they lie
in line with the sun and on the same side of it. Every eight years a
certain part of the orbit of the earth is, therefore, disturbed by
the attraction of Venus with peculiar vigour. The consequence is
that, owing to the numerical relation between the movements of the
planets to which I have referred, disturbing effects become
appreciable which would otherwise be too small to permit of
recognition. Airy proposed to himself to compute the effects which
Venus would have on the movement of the earth in consequence of the
circumstance that eight revolutions of the one planet required almost
the same time as thirteen revolutions of the other. This is a
mathematical inquiry of the most arduous description, but the Plumian
Professor succeeded in working it out, and he had, accordingly, the
gratification of announcing to the Royal Society that he had detected
the influence which Venus was thus able to assert on the movement of
our earth around the sun. This remarkable investigation gained for
its author the gold medal of the Royal Astronomical Society in the
year 1832.
In consequence Of his numerous discoveries, Airy's scientific fame
had become so well recognised that the Government awarded him a
special pension, and in 1835, when Pond, who was then Astronomer
Royal, resigned, Airy was offered the post at Greenwich. There was
in truth, no scientific inducement to the Plumian Professor to leave
the comparatively easy post he held at Cambridge, in which he had
ample leisure to devote himself to those researches which specially
interested him, and accept that of the much more arduous observatory
at Greenwich. There were not even pecuniary inducements to make the
change; however, he felt it to be his duty to accede to the request
which the Government had made that he would take up the position
which Pond had vacated, and accordingly Airy went to Greenwich as
Astronomer Royal on October 1st, 1835.
He immediately began with his usual energy to organise the systematic
conduct of the business of the National Observatory. To realise one
of the main characteristics of Airy's great work at Greenwich, it is
necessary to explain a point that might not perhaps be understood
without a little explanation by those who have no practical
experience in an observatory. In the work of an establishment such
as Greenwich, an observation almost always consists of a measurement
of some kind. The observer may, for instance, be making a
measurement of the time at which a star passes across a spider line
stretched through the field of view; on another occasion his object
may be the measurement of an angle which is read off by examining
through a microscope the lines of division on a graduated circle when
the telescope is so pointed that the star is placed on a certain mark
in the field of view. In either case the immediate result of the
astronomical observation is a purely numerical one, but it rarely
happens, indeed we may say it never happens, that the immediate
numerical result which the observation gives expresses directly the
quantity which we are really seeking for. No doubt the observation
has been so designed that the quantity we want to find can be
obtained from the figures which the measurement gives, but the object
sought is not those figures, for there are always a multitude of
other influences by which those figures are affected. For example,
if an observation were to be perfect, then the telescope with which
the observation is made should be perfectly placed in the exact
position which it ought to occupy; this is, however, never the case,
for no mechanic can ever construct or adjust a telescope so perfectly
as the wants of the astronomer demand. The clock also by which we
determine the time of the observation should be correct, but this is
rarely if ever the case. We have to correct our observations for
such errors, that is to say, we have to determine the errors in the
positions of our telescopes and the errors in the going of our
clocks, and then we have to determine what the observations would
have been had our telescopes been absolutely perfect, and had our
clocks been absolutely correct. There are also many other matters
which have to be attended to in order to reduce our observations so
as to obtain from the figures as yielded to the observer at the
telescope the actual quantities which it is his object to determine.
The work of effecting these reductions is generally a very intricate
and laborious matter, so that it has not unfrequently happened that
while observations have accumulated in an observatory, yet the
tedious duty of reducing these observations has been allowed to fall
into arrear. When Airy entered on his duties at Greenwich he found
there an enormous mass of observations which, though implicitly
containing materials of the greatest value to astronomers, were, in
their unreduced form, entirely unavailable for any useful purpose.
He, therefore, devoted himself to coping with the reduction of the
observations of his predecessors. He framed systematic methods by
which the reductions were to be effected, and he so arranged the work
that little more than careful attention to numerical accuracy would
be required for the conduct of the operations. Encouraged by the
Admiralty, for it is under this department that Greenwich Observatory
is placed, the Astronomer Royal employed a large force of computers
to deal with the work. BY his energy and admirable organisation he
managed to reduce an extremely valuable series of planetary
observations, and to publish the results, which have been of the
greatest importance to astronomical investigation.
The Astronomer Royal was a capable, practical engineer as well as an
optician, and he presently occupied himself by designing astronomical
instruments of improved pattern, which should replace the antiquated
instruments he found in the observatory. In the course of years the
entire equipment underwent a total transformation. He ordered a
great meridian circle, every part of which may be said to have been
formed from his own designs. He also designed the mounting for a
fine equatorial telescope worked by a driving clock, which he had
himself invented. Gradually the establishment at Greenwich waxed
great under his incessant care. It was the custom for the
observatory to be inspected every year by a board of visitors, whose
chairman was the President of the Royal Society. At each annual
visitation, held on the first Saturday in June, the visitors received
a report from the Astronomer Royal, in which he set forth the
business which had been accomplished during the past year. It was on
these occasions that applications were made to the Admiralty, either
for new instruments or for developing the work of the observatory in
some other way. After the more official business of the inspection
was over, the observatory was thrown open to visitors, and hundreds
of people enjoyed on that day the privilege of seeing the national
observatory. These annual gatherings are happily still continued,
and the first Saturday in June is known to be the occasion of one of
the most interesting reunions of scientific men which takes place in
the course of the year.
Airy's scientific work was, however, by no means confined to the
observatory. He interested himself largely in expeditions for the
observation of eclipses and in projects for the measurement of arcs
on the earth. He devoted much attention to the collection of magnetic
observations from various parts of the world. Especially will it be
remembered that the circumstances of the transits of Venus, which
occurred in 1874 and in 1882, were investigated by him, and under his
guidance expeditions were sent forth to observe the transits from
those localities in remote parts of the earth where observations most
suitable for the determination of the sun's distance from the earth
could be obtained. The Astronomer Royal also studied tidal
phenomena, and he rendered great service to the country in the
restoration of the standards of length and weight which had been
destroyed in the great fire at the House of Parliament in October,
1834. In the most practical scientific matters his advice was often
sought, and was as cheerfully rendered. Now we find him engaged in
an investigation of the irregularities of the compass in iron ships,
with a view to remedying its defects; now we find him reporting on
the best gauge for railways. Among the most generally useful
developments of the observatory must be mentioned the telegraphic
method for the distribution of exact time. By arrangement with the
Post Office, the astronomers at Greenwich despatch each morning a
signal from the observatory to London at ten o'clock precisely. By
special apparatus, this signal is thence distributed automatically
over the country, so as to enable the time to be known everywhere
accurately to a single second. It was part of the same system that a
time ball should be dropped daily at one o'clock at Deal, as well as
at other places, for the purpose of enabling ship's chronometers to
be regulated.
Airy's writings were most voluminous, and no fewer than forty-eight
memoirs by him are mentioned in the "Catalogue of Scientific
Memoirs," published by the Royal Society up to the year 1873, and
this only included ten years out of an entire life of most
extraordinary activity. Many other subjects besides those of a
purely scientific character from time to time engaged his attention.
He wrote, for instance, a very interesting treatise on the Roman
invasion of Britain, especially with a view of determining the port
from which Caesar set forth from Gaul, and the point at which he
landed on the British coast. Airy was doubtless led to this
investigation by his study of the tidal phenomena in the Straits of
Dover. Perhaps the Astronomer Royal is best known to the general
reading public by his excellent lectures on astronomy, delivered at
the Ipswich Museum in 1848. This book has passed through many
editions, and it gives a most admirable account of the manner in
which the fundamental problems in astronomy have to be attacked.
As years rolled by almost every honour and distinction that could be
conferred upon a scientific man was awarded to Sir George Airy. He
was, indeed, the recipient of other honours not often awarded for
scientific distinction. Among these we may mention that in 1875 he
received the freedom of the City of London, "as a recognition of his
indefatigable labours in astronomy, and of his eminent services in
the advancement of practical science, whereby he has so materially
benefited the cause of commerce and civilisation."
Until his eightieth year Airy continued to discharge his labours at
Greenwich with unflagging energy. At last, on August 15th, 1881, he
resigned the office which he had held so long with such distinction
to himself and such benefit to his country. He had married in 1830
the daughter of the Rev. Richard Smith, of Edensor. Lady Airy died
in 1875, and three sons and three daughters survived him. One
daughter is the wife of Dr. Routh, of Cambridge, and his other
daughters were the constant companions of their father during the
declining years of his life. Up to the age of ninety he enjoyed
perfect physical health, but an accidental fall which then occurred
was attended with serious results. He died on Saturday, January 2nd,
1892, and was buried in the churchyard at Playford.
HAMILTON.
William Rowan Hamilton was born at midnight between the 3rd and 4th
of August, 1805, at Dublin, in the house which was then 29, but
subsequently 36, Dominick Street. His father, Archibald Hamilton,
was a solicitor, and William was the fourth of a family of nine. With
reference to his descent, it may be sufficient to notice that his
ancestors appear to have been chiefly of gentle Irish families, but
that his maternal grandmother was of Scottish birth. When he was
about a year old, his father and mother decided to hand over the
education of the child to his uncle, James Hamilton, a clergyman of
Trim, in County Meath. James Hamilton's sister, Sydney, resided with
him, and it was in their home that the days of William's childhood
were passed.
In Mr. Graves' "Life of Sir William Rowan Hamilton" a series of
letters will be found, in which Aunt Sydney details the progress of
the boy to his mother in Dublin. Probably there is no record of an
infant prodigy more extraordinary than that which these letters
contain. At three years old his aunt assured the mother that William
is "a hopeful blade," but at that time it was his physical vigour to
which she apparently referred; for the proofs of his capacity, which
she adduces, related to his prowess in making boys older than himself
fly before him. In the second letter, a month later, we hear that
William is brought in to read the Bible for the purpose of putting to
shame other boys double his age who could not read nearly so well.
Uncle James appears to have taken much pains with William's
schooling, but his aunt said that "how he picks up everything is
astonishing, for he never stops playing and jumping about." When he
was four years and three months old, we hear that he went out to dine
at the vicar's, and amused the company by reading for them equally
well whether the book was turned upside down or held in any other
fashion. His aunt assures the mother that "Willie is a most sensible
little creature, but at the same time has a great deal of roguery."
At four years and five months old he came up to pay his mother a
visit in town, and she writes to her sister a description of the
boy;--
"His reciting is astonishing, and his clear and accurate knowledge of
geography is beyond belief; he even draws the countries with a pencil
on paper, and will cut them out, though not perfectly accurate, yet
so well that a anybody knowing the countries could not mistake them;
but, you will think this nothing when I tell you that he reads Latin,
Greek, and Hebrew."
Aunt Sydney recorded that the moment Willie got back to Trim he was
desirous of at once resuming his former pursuits. He would not eat
his breakfast till his uncle had heard him his Hebrew, and he
comments on the importance of proper pronunciation. At five he was
taken to see a friend, to whom he repeated long passages from
Dryden. A gentleman present, who was not unnaturally sceptical about
Willie's attainments, desired to test him in Greek, and took down a
copy of Homer which happened to have the contracted type, and to his
amazement Willie went on with the greatest ease. At six years and
nine months he was translating Homer and Virgil; a year later his
uncle tells us that William finds so little difficulty in learning
French and Italian, that he wishes to read Homer in French. He is
enraptured with the Iliad, and carries it about with him, repeating
from it whatever particularly pleases him. At eight years and one
month the boy was one of a party who visited the Scalp in the Dublin
mountains, and he was so delighted with the scenery that he forthwith
delivered an oration in Latin. At nine years and six months he is
not satisfied until he learns Sanscrit; three months later his thirst
for the Oriental languages is unabated, and at ten years and four
months he is studying Arabic and Persian. When nearly twelve he
prepared a manuscript ready for publication. It was a "Syriac
Grammar," in Syriac letters and characters compiled from that of
Buxtorf, by William Hamilton, Esq., of Dublin and Trim. When he was
fourteen, the Persian ambassador, Mirza Abul Hassan Khan, paid a
visit to Dublin, and, as a practical exercise in his Oriental
languages, the young scholar addressed to his Excellency a letter in
Persian; a translation of which production is given by Mr. Graves.
When William was fourteen he had the misfortune to lose his father;
and he had lost his mother two years previously. The boy and his
three sisters were kindly provided for by different members of the
family on both sides.
It was when William was about fifteen that his attention began to be
turned towards scientific subjects. These were at first regarded
rather as a relaxation from the linguistic studies with which he had
been so largely occupied. On November 22nd, 1820, he notes in his
journal that he had begun Newton's "Principia": he commenced also the
study of astronomy by observing eclipses, occultations, and similar
phenomena. When he was sixteen we learn that he had read conic
sections, and that he was engaged in the study of pendulums. After
an attack of illness, he was moved for change to Dublin, and in May,
1822, we find him reading the differential calculus and Laplace's
"Mecanique Celeste." He criticises an important part of Laplace's
work relative to the demonstration of the parallelogram of forces. In
this same year appeared the first gushes of those poems which
afterwards flowed in torrents.
His somewhat discursive studies had, however, now to give place to a
more definite course of reading in preparation for entrance to the
University of Dublin. The tutor under whom he entered, Charles
Boyton, was himself a distinguished man, but he frankly told the
young William that he could be of little use to him as a tutor, for
his pupil was quite as fit to be his tutor. Eliza Hamilton, by whom
this is recorded, adds, "But there is one thing which Boyton would
promise to be to him, and that was a FRIEND; and that one proof he
would give of this should be that, if ever he saw William beginning
to be UPSET by the sensation he would excite, and the notice he would
attract, he would tell him of it." At the beginning of his college
career he distanced all his competitors in every intellectual
pursuit. At his first term examination in the University he was
first in Classics and first in Mathematics, while he received the
Chancellor's prize for a poem on the Ionian Islands, and another for
his poem on Eustace de St. Pierre.
There is abundant testimony that Hamilton had "a heart for friendship
formed." Among the warmest of the friends whom he made in these
early days was the gifted Maria Edgeworth, who writes to her sister
about "young Mr. Hamilton, an admirable Crichton of eighteen, a real
prodigy of talents, who Dr. Brinkley says may be a second Newton,
quiet, gentle, and simple." His sister Eliza, to whom he was
affectionately attached, writes to him in 1824:--
"I had been drawing pictures of you in my mind in your study at
Cumberland Street with 'Xenophon,' &c., on the table, and you, with
your most awfully sublime face of thought, now sitting down, and now
walking about, at times rubbing your hands with an air of
satisfaction, and at times bursting forth into some very heroical
strain of poetry in an unknown language, and in your own internal
solemn ventriloquist-like voice, when you address yourself to the
silence and solitude of your own room, and indeed, at times, even
when your mysterious poetical addresses are not quite unheard."
This letter is quoted because it refers to a circumstance which all
who ever met with Hamilton, even in his latest years, will remember.
He was endowed with two distinct voices, one a high treble, the other
a deep bass, and he alternately employed these voices not only in
ordinary conversation, but when he was delivering an address on the
profundities of Quaternions to the Royal Irish Academy, or on
similar occasions. His friends had long grown so familiar with this
peculiarity that they were sometimes rather surprised to find how
ludicrous it appeared to strangers.
Hamilton was fortunate in finding, while still at a very early age, a
career open before him which was worthy of his talents. He had not
ceased to be an undergraduate before he was called to fill an
illustrious chair in his university. The circumstances are briefly
as follows.
We have already mentioned that, in 1826, Brinkley was appointed
Bishop of Cloyne, and the professorship of astronomy thereupon became
vacant. Such was Hamilton's conspicuous eminence that,
notwithstanding he was still an undergraduate, and had only just
completed his twenty-first year, he was immediately thought of as a
suitable successor to the chair. Indeed, so remarkable were his
talents in almost every direction that had the vacancy been in the
professorship of classics or of mathematics, of English literature or
of metaphysics, of modern or of Oriental languages, it seems
difficult to suppose that he would not have occurred to every one as
a possible successor. The chief ground, however, on which the
friends of Hamilton urged his appointment was the earnest of original
power which he had already shown in a research on the theory of
Systems of Rays. This profound work created a new branch of optics,
and led a few years later to a superb discovery, by which the fame of
its author became world-wide.
At first Hamilton thought it would be presumption for him to apply
for so exalted a position; he accordingly retired to the country, and
resumed his studies for his degree. Other eminent candidates came
forward, among them some from Cambridge, and a few of the Fellows
from Trinity College, Dublin, also sent in their claims. It was not
until Hamilton received an urgent letter from his tutor Boyton, in
which he was assured of the favourable disposition of the Board
towards his candidature, that he consented to come forward, and on
June 16th, 1827, he was unanimously chosen to succeed the Bishop of
Cloyne as Professor of Astronomy in the University. The appointment
met with almost universal approval. It should, however, be noted
that Brinkley, whom Hamilton succeeded, did not concur in the general
sentiment. No one could have formed a higher opinion than he had
done of Hamilton's transcendent powers; indeed, it was on that very
ground that he seemed to view the appointment with disapprobation.
He considered that it would have been wiser for Hamilton to have
obtained a Fellowship, in which capacity he would have been able to
exercise a greater freedom in his choice of intellectual pursuits.
The bishop seems to have thought, and not without reason, that
Hamilton's genius would rather recoil from much of the routine work
of an astronomical establishment. Now that Hamilton's whole life is
before us, it is easy to see that the bishop was entirely wrong. It
is quite true that Hamilton never became a skilled astronomical
observer; but the seclusion of the observatory was eminently
favourable to those gigantic labours to which his life was devoted,
and which have shed so much lustre, not only on Hamilton himself, but
also on his University and his country.
In his early years at Dunsink, Hamilton did make some attempts at a
practical use of the telescopes, but he possessed no natural aptitude
for such work, while exposure which it involved seems to have acted
injuriously on his health. He, therefore, gradually allowed his
attention to be devoted to those mathematical researches in which he
had already given such promise of distinction. Although it was in
pure mathematics that he ultimately won his greatest fame, yet he
always maintained and maintained with justice, that he had ample
claims to the title of an astronomer. In his later years he set
forth this position himself in a rather striking manner. De Morgan
had written commending to Hamilton's notice Grant's "History of
Physical Astronomy." After becoming acquainted with the book,
Hamilton writes to his friend as follows:--
"The book is very valuable, and very creditable to its composer. But
your humble servant may be pardoned if he finds himself somewhat
amused at the title, `History of Physical Astronomy from the Earliest
Ages to the Middle of the Nineteenth Century,' when he fails to
observe any notice of the discoveries of Sir W. R. Hamilton in the
theory of the 'Dynamics of the Heavens.'"
The intimacy between the two correspondents will account for the tone
of this letter; and, indeed, Hamilton supplies in the lines which
follow ample grounds for his complaint. He tells how Jacobi spoke of
him in Manchester in 1842 as "le Lagrange de votre pays," and how
Donkin had said that, "The Analytical Theory of Dynamics as it exists
at present is due mainly to the labours of La Grange Poisson,
Sir W. R. Hamilton, and Jacobi, whose researches on this subject
present a series of discoveries hardly paralleled for their elegance
and importance in any other branch of mathematics." In the same
letter Hamilton also alludes to the success which had attended the
applications of his methods in other hands than his own to the
elucidation of the difficult subject of Planetary Perturbations.
Even had his contributions to science amounted to no more than these
discoveries, his tenure of the chair would have been an illustrious
one. It happens, however, that in the gigantic mass of his
intellectual work these researches, though intrinsically of such
importance, assume what might almost be described as a relative
insignificance.
The most famous achievement of Hamilton's earlier years at the
observatory was the discovery of conical refraction. This was one of
those rare events in the history of science, in which a sagacious
calculation has predicted a result of an almost startling character,
subsequently confirmed by observation. At once this conferred on the
young professor a world-wide renown. Indeed, though he was still
only twenty-seven, he had already lived through an amount of
intellectual activity which would have been remarkable for a man of
threescore and ten.
Simultaneously with his growth in fame came the growth of his several
friendships. There were, in the first place, his scientific
friendships with Herschel, Robinson, and many others with whom he had
copious correspondence. In the excellent biography to which I have
referred, Hamilton's correspondence with Coleridge may be read, as
can also the letters to his lady correspondents, among them being
Maria Edgeworth, Lady Dunraven, and Lady Campbell. Many of these
sheets relate to literary matters, but they are largely intermingled
With genial pleasantry, and serve at all events to show the affection
and esteem with which he was regarded by all who had the privilege of
knowing him. There are also the letters to the sisters whom he
adored, letters brimming over with such exalted sentiment, that most
ordinary sisters would be tempted to receive them with a smile in the
excessively improbable event of their still more ordinary brothers
attempting to pen such effusions. There are also indications of
letters to and from other young ladies who from time to time were the
objects of Hamilton's tender admiration. We use the plural
advisedly, for, as Mr. Graves has set forth, Hamilton's love affairs
pursued a rather troubled course. The attention which he lavished on
one or two fair ones was not reciprocated, and even the intense
charms of mathematical discovery could not assuage the pangs which
the disappointed lover experienced. At last he reached the haven of
matrimony in 1833, when he was married to Miss Bayly. Of his married
life Hamilton said, many years later to De Morgan, that it was as
happy as he expected, and happier than he deserved. He had two sons,
William and Archibald, and one daughter, Helen, who became the wife
of Archdeacon O'Regan.
[PLATE: SIR W. ROWAN HAMILTON.]
The most remarkable of Hamilton's friendships in his early years was
unquestionably that with Wordsworth. It commenced with Hamilton's
visit to Keswick; and on the first evening, when the poet met the
young mathematician, an incident occurred which showed the mutual
interest that was aroused. Hamilton thus describes it in a letter to
his sister Eliza:--
"He (Wordsworth) walked back with our party as far as their lodge,
and then, on our bidding Mrs. Harrison good-night, I offered to walk
back with him while my party proceeded to the hotel. This offer he
accepted, and our conversation had become so interesting that when we
had arrived at his home, a distance of about a mile, he proposed to
walk back with me on my way to Ambleside, a proposal which you may be
sure I did not reject; so far from it that when he came to turn once
more towards his home I also turned once more along with him. It was
very late when I reached the hotel after all this walking."
Hamilton also submitted to Wordsworth an original poem, entitled
"It Haunts me Yet." The reply of Wordsworth is worth repeating:--
"With a safe conscience I can assure you that, in my judgment, your
verses are animated with the poetic spirit, as they are evidently the
product of strong feeling. The sixth and seventh stanzas affected me
much, even to the dimming of my eyes and faltering of my voice while
I was reading them aloud. Having said this, I have said enough. Now
for the per contra. You will not, I am sure, be hurt when I tell you
that the workmanship (what else could be expected from so young a
writer?) is not what it ought to be. . .
"My household desire to be remembered to you in no formal way.
Seldom have I parted--never, I was going to say--with one whom after
so short an acquaintance I lost sight of with more regret. I trust
we shall meet again."
The further affectionate intercourse between Hamilton and Wordsworth
is fully set forth, and to Hamilton's latest years a recollection of
his "Rydal hours" was carefully treasured and frequently referred
to. Wordsworth visited Hamilton at the observatory, where a
beautiful shady path in the garden is to the present day spoken of as
"Wordsworth's Walk."
It was the practice of Hamilton to produce a sonnet on almost every
occasion which admitted of poetical treatment, and it was his delight
to communicate his verses to his friends all round. When Whewell was
producing his "Bridgewater Treatises," he writes to Hamilton in
1833:--
"Your sonnet which you showed me expressed much better than I could
express it the feeling with which I tried to write this book, and I
once intended to ask your permission to prefix the sonnet to my book,
but my friends persuaded me that I ought to tell my story in my own
prose, however much better your verse might be."
The first epoch-marking contribution to Theoretical Dynamics after
the time of Newton was undoubtedly made by Lagrange, in his discovery
of the general equations of Motion. The next great step in the same
direction was that taken by Hamilton in his discovery of a still more
comprehensive method. Of this contribution Hamilton writes to
Whewell, March 31st, 1834:--
"As to my late paper, a day or two ago sent off to London, it is
merely mathematical and deductive. I ventured, indeed, to call it
the 'Mecanique Analytique' of Lagrange, 'a scientific poem'; and
spoke of Dynamics, or the Science of Force, as treating of 'Power
acting by Law in Space and Time.' In other respects it is as
unpoetical and unmetaphysical as my gravest friends could desire."
It may well be doubted whether there is a more beautiful chapter in
the whole of mathematical philosophy than that which contains
Hamilton's dynamical theory. It is disfigured by no tedious
complexity of symbols; it condescends not to any particular problems;
it is an all embracing theory, which gives an intellectual grasp of
the most appropriate method for discovering the result of the
application of force to matter. It is the very generality of this
doctrine which has somewhat impeded the applications of which it is
susceptible. The exigencies of examinations are partly responsible
for the fact that the method has not become more familiar to students
of the higher mathematics. An eminent professor has complained that
Hamilton's essay on dynamics was of such an extremely abstract
character, that he found himself unable to extract from it problems
suitable for his examination papers.
The following extract is from a letter of Professor Sylvester to
Hamilton, dated 20th of September, 1841. It will show how his works
were appreciated by so consummate a mathematician as the writer:--
"Believe me, sir, it is not the least of my regrets in quitting this
empire to feel that I forego the casual occasion of meeting those
masters of my art, yourself chief amongst the number, whose
acquaintance, whose conversation, or even notice, have in themselves
the power to inspire, and almost to impart fresh vigour to the
understanding, and the courage and faith without which the efforts of
invention are in vain. The golden moments I enjoyed under your
hospitable roof at Dunsink, or moments such as they were, may
probably never again fall to my lot.
"At a vast distance, and in an humble eminence, I still promise myself
the calm satisfaction of observing your blazing course in the
elevated regions of discovery. Such national honour as you are able
to confer on your country is, perhaps, the only species of that
luxury for the rich (I mean what is termed one's glory) which is not
bought at the expense of the comforts of the million."
The study of metaphysics was always a favourite recreation when
Hamilton sought for a change from the pursuit of mathematics. In the
year 1834 we find him a diligent student of Kant; and, to show the
views of the author of Quaternions and of Algebra as the Science of
Pure Time on the "Critique of the Pure Reason," we quote the
following letter, dated 18th of July, 1834, from Hamilton to Viscount
Adare:--
"I have read a large part of the 'Critique of the Pure Reason,' and
find it wonderfully clear, and generally quite convincing.
Notwithstanding some previous preparation from Berkeley, and from my
own thoughts, I seem to have learned much from Kant's own statement
of his views of 'Space and Time.' Yet, on the whole, a large part of
my pleasure consists in recognising through Kant's works, opinions,
or rather views, which have been long familiar to myself, although
far more clearly and systematically expressed and combined by him.
. . . Kant is, I think, much more indebted than he owns, or, perhaps
knows, to Berkeley, whom he calls by a sneer, `GUTEM Berkeley'. . .
as it were, `good soul, well meaning man,' who was able for all that
to shake to its centre the world of human thought, and to effect a
revolution among the early consequences of which was the growth of
Kant himself."
At several meetings of the British Association Hamilton was a very
conspicuous figure. Especially was this the case in 1835, when the
Association met in Dublin, and when Hamilton, though then but thirty
years old, had attained such celebrity that even among a very
brilliant gathering his name was perhaps the most renowned. A
banquet was given at Trinity College in honour of the meeting. The
distinguished visitors assembled in the Library of the University.
The Earl of Mulgrave, then Lord Lieutenant of Ireland, made this the
opportunity of conferring on Hamilton the honour of knighthood,
gracefully adding, as he did so: "I but set the royal, and therefore
the national mark, on a distinction already acquired by your genius
and labours."
The banquet followed, writes Mr. Graves. "It was no little addition
to the honour Hamilton had already received that, when Professor
Whewell returned thanks for the toast of the University of Cambridge,
he thought it appropriate to add the words, 'There was one point
which strongly pressed upon him at that moment: it was now one
hundred and thirty years since a great man in another Trinity College
knelt down before his sovereign, and rose up Sir Isaac Newton.' The
compliment was welcomed by immense applause."
A more substantial recognition of the labours of Hamilton took place
subsequently. He thus describes it in a letter to Mr. Graves of 14th
of November, 1843:--
"The Queen has been pleased--and you will not doubt that it was
entirely unsolicited, and even unexpected, on my part--'to express
her entire approbation of the grant of a pension of two hundred
pounds per annum from the Civil List' to me for scientific services.
The letters from Sir Robert Peel and from the Lord Lieutenant of
Ireland in which this grant has been communicated or referred to have
been really more gratifying to my feelings than the addition to my
income, however useful, and almost necessary, that may have been."
The circumstances we have mentioned might lead to the supposition
that Hamilton was then at the zenith of his fame but this was not
so. It might more truly be said, that his achievements up to this
point were rather the preliminary exercises which fitted him for the
gigantic task of his life. The name of Hamilton is now chiefly
associated with his memorable invention of the calculus of
Quaternions. It was to the creation of this branch of mathematics
that the maturer powers of his life were devoted; in fact he gives us
himself an illustration of how completely habituated he became to the
new modes of thought which Quaternions originated. In one of his
later years he happened to take up a copy of his famous paper on
Dynamics, a paper which at the time created such a sensation among
mathematicians, and which is at this moment regarded as one of the
classics of dynamical literature. He read, he tells us, his paper
with considerable interest, and expressed his feelings of
gratification that he found himself still able to follow its
reasoning without undue effort. But it seemed to him all the time as
a work belonging to an age of analysis now entirely superseded.
In order to realise the magnitude of the revolution which Hamilton
has wrought in the application of symbols to mathematical
investigation, it is necessary to think of what Hamilton did beside
the mighty advance made by Descartes. To describe the character of
the quaternion calculus would be unsuited to the pages of this work,
but we may quote an interesting letter, written by Hamilton from his
deathbed, twenty-two years later, to his son Archibald, in which he
has recorded the circumstances of the discovery:--
"Indeed, I happen to be able to put the finger of memory upon the year
and month--October, 1843--when having recently returned from visits
to Cork and Parsonstown, connected with a meeting of the British
Association, the desire to discover the laws of multiplication
referred to, regained with me a certain strength and earnestness
which had for years been dormant, but was then on the point of being
gratified, and was occasionally talked of with you. Every morning in
the early part of the above-cited month, on my coming down to
breakfast, your (then) little brother William Edwin, and yourself,
used to ask me, 'Well papa, can you multiply triplets?' Whereto I
was always obliged to reply, with a sad shake of the head: 'No, I
can only ADD and subtract them,'
"But on the 16th day of the same month--which happened to be Monday,
and a Council day of the Royal Irish Academy--I was walking in to
attend and preside, and your mother was walking with me along the
Royal Canal, to which she had perhaps driven; and although she talked
with me now and then, yet an UNDERCURRENT of thought was going on in
my mind which gave at last a RESULT, whereof it is not too much to
say that I felt AT ONCE the importance. An ELECTRIC circuit seemed
to CLOSE; and a spark flashed forth the herald (as I FORESAW
IMMEDIATELY) of many long years to come of definitely directed
thought and work by MYSELF, if spared, and, at all events, on the
part of OTHERS if I should even be allowed to live long enough
distinctly to communicate the discovery. Nor could I resist the
impulse--unphilosophical as it may have been--to cut with a knife on
a stone of Brougham Bridge as we passed it, the fundamental formula
which contains the SOLUTION of the PROBLEM, but, of course, the
inscription has long since mouldered away. A more durable notice
remains, however, on the Council Books of the Academy for that day
(October 16, 1843), which records the fact that I then asked for and
obtained leave to read a Paper on 'Quaternions,' at the First General
Meeting of the Session; which reading took place accordingly, on
Monday, the 13th of November following."
Writing to Professor Tait, Hamilton gives further particulars of the
same event. And again in a letter to the Rev. J. W. Stubbs:--
"To-morrow will be the fifteenth birthday of the Quaternions. They
started into life full-grown on the 16th October, 1843, as I was
walking with Lady Hamilton to Dublin, and came up to Brougham
Bridge--which my boys have since called Quaternion Bridge. I pulled
out a pocketbook which still exists, and made entry, on which at the
very moment I felt that it might be worth my while to expend the
labour of at least ten or fifteen years to come. But then it is fair
to say that this was because I felt a problem to have been at that
moment solved, an intellectual want relieved which had haunted me for
at least fifteen years before.
"But did the thought of establishing such a system, in which
geometrically opposite facts--namely, two lines (or areas) which are
opposite IN SPACE give ALWAYS a positive product--ever come into
anybody's head till I was led to it in October, 1843, by trying to
extend my old theory of algebraic couples, and of algebra as the
science of pure time? As to my regarding geometrical addition of
lines as equivalent to composition of motions (and as performed by
the same rules), that is indeed essential in my theory but not
peculiar to it; on the contrary, I am only one of many who have been
led to this view of addition."
Pilgrims in future ages will doubtless visit the spot commemorated by
the invention of Quaternions. Perhaps as they look at that by no
means graceful structure Quaternion Bridge, they will regret that the
hand of some Old Mortality had not been occasionally employed in
cutting the memorable inscription afresh. It is now irrecoverably
lost.
It was ten years after the discovery that the great volume appeared
under the title of "Lectures on Quaternions," Dublin, 1853. The
reception of this work by the scientific world was such as might have
been expected from the extraordinary reputation of its author, and
the novelty and importance of the new calculus. His valued friend,
Sir John Herschel, writes to him in that style of which he was a
master:--
"Now, most heartily let me congratulate you on getting out your
book--on having found utterance, ore rotundo, for all that labouring
and seething mass of thought which has been from time to time sending
out sparks, and gleams, and smokes, and shaking the soil about you;
but now breaks into a good honest eruption, with a lava stream and a
shower of fertilizing ashes.
"Metaphor and simile apart, there is work for a twelve-month to any
man to read such a book, and for half a lifetime to digest it, and I
am glad to see it brought to a conclusion."
We may also record Hamilton's own opinion expressed to Humphrey
Lloyd:--
"In general, although in one sense I hope that I am actually growing
modest about the quaternions, from my seeing so many peeps and vistas
into future expansions of their principles, I still must assert that
this discovery appears to me to be as important for the middle of the
nineteenth century as the discovery of fluxions was for the close of
the seventeenth."
Bartholomew Lloyd died in 1837. He had been the Provost of Trinity
College, and the President of the Royal Irish Academy. Three
candidates were put forward by their respective friends for the
vacant Presidency. One was Humphrey Lloyd, the son of the late
Provost, and the two others were Hamilton and Archbishop Whately.
Lloyd from the first urged strongly the claims of Hamilton, and
deprecated the putting forward of his own name. Hamilton in like
manner desired to withdraw in favour of Lloyd. The wish was strongly
felt by many of the Fellows of the College that Lloyd should be
elected, in consequence of his having a more intimate association
with collegiate life than Hamilton; while his scientific eminence was
world-wide. The election ultimately gave Hamilton a considerable
majority over Lloyd, behind whom the Archbishop followed at a
considerable distance. All concluded happily, for both Lloyd and the
Archbishop expressed, and no doubt felt, the pre-eminent claims of
Hamilton, and both of them cordially accepted the office of a
Vice-President, to which, according to the constitution of the
Academy, it is the privilege of the incoming President to nominate.
In another chapter I have mentioned as a memorable episode in
astronomical history, that Sir J. Herschel went for a prolonged
sojourn to the Cape of Good Hope, for the purpose of submitting the
southern skies to the same scrutiny with the great telescope that his
father had given to the northern skies. The occasion of Herschel's
return after the brilliant success of his enterprise, was celebrated
by a banquet. On June 15th, 1838, Hamilton was assigned the high
honour of proposing the health of Herschel. This banquet is
otherwise memorable in Hamilton's career as being one of the two
occasions in which he was in the company of his intimate friend De
Morgan.
In the year 1838 a scheme was adopted by the Royal Irish Academy for
the award of medals to the authors of papers which appeared to
possess exceptionally high merit. At the institution of the medal
two papers were named in competition for the prize. One was
Hamilton's "Memoir on Algebra, as the Science of Pure Time." The
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