natural ambition of a founder, desired to place in it a telescope of
more magnificent proportions than could be found anywhere else. The
Board gave a spirited support to this enterprise, and negotiations
were entered into with the most eminent instrument-maker of those
days. This was Jesse Ramsden (1735-1800), famous as the improver of
the sextant, as the constructor of the great theodolite used by
General Roy in the English Survey, and as the inventor of the
dividing engine for graduating astronomical instruments. Ramsden had
built for Sir George Schuckburgh the largest and most perfect
equatorial ever attempted. He had constructed mural quadrants for
Padua and Verona, which elicited the wonder of astronomers when Dr.
Maskelyne declared he could detect no error in their graduation so
large as two seconds and a half. But Ramsden maintained that even
better results would be obtained by superseding the entire quadrant
by the circle. He obtained the means of testing this prediction when
he completed a superb circle for Palermo of five feet diameter.
Finding his anticipations were realised, he desired to apply the same
principles on a still grander scale. Ramsden was in this mood when
he met with Dr. Ussher. The enthusiasm of the astronomer and the
instrument-maker communicated itself to the Board, and a tremendous
circle, to be ten feet in diameter, was forthwith projected.
Projected, but never carried out. After Ramsden had to some extent
completed a 10-foot circle, he found such difficulties that he tried
a 9-foot, and this again he discarded for an 8-foot, which was
ultimately accomplished, though not entirely by himself.
Notwithstanding the contraction from the vast proportions originally
designed, the completed instrument must still be regarded as a
colossal piece of astronomical workmanship. Even at this day I do
not know that any other observatory can show a circle eight feet in
diameter graduated all round.
I think it is Professor Piazzi Smith who tells us how grateful he was
to find a large telescope he had ordered finished by the opticians on
the very day they had promised it. The day was perfectly correct; it
was only the year that was wrong. A somewhat remarkable experience
in this direction is chronicled by the early reports of the visitors
to Dunsink Observatory. I cannot find the date on which the great
circle was ordered from Ramsden, but it is fixed with sufficient
precision by an allusion in Ussher's paper to the Royal Irish
Academy, which shows that by the 13th June, 1785, the order had been
given, but that the abandonment of the 10-foot scale had not then
been contemplated. It was reasonable that the board should allow
Ramsden ample time for the completion of a work at once so elaborate
and so novel. It could not have been finished in a year, nor would
there have been much reason for complaint if the maker had found he
required two or even three years more.
Seven years gone, and still no telescope, was the condition in which
the Board found matters at their first visitation in 1792. They had,
however, assurances from Ramsden that the instrument would be
completed within the year; but, alas for such promises, another seven
years rolled on, and in 1799 the place for the great circle was still
vacant at Dunsink. Ramsden had fallen into bad health, and the Board
considerately directed that "inquiries should be made." Next year
there was still no progress, so the Board were roused to threaten
Ramsden with a suit at law; but the menace was never executed, for
the malady of the great optician grew worse, and he died that year.
Affairs had now assumed a critical aspect, for the college had
advanced much money to Ramsden during these fifteen years, and the
instrument was still unfinished. An appeal was made by the Provost
to Dr. Maskelyne, the Astronomer Royal of England, for his advice and
kindly offices in this emergency. Maskelyne responds--in terms
calculated to allay the anxiety of the Bursar--"Mr. Ramsden has left
property behind him, and the College can be in no danger of losing
both their money and the instrument." The business of Ramsden was
then undertaken by Berge, who proceeded to finish the circle quite as
deliberately as his predecessor. After four years Berge promised the
instrument in the following August, but it did not come. Two years
later (1806) the professor complains that he can get no answer from
Berge. In 1807, it is stated that Berge will send the telescope in a
month. He did not; but in the next year (1808), about twenty-three
years after the great circle was ordered, it was erected at Dunsink,
where it is still to be seen.
The following circumstances have been authenticated by the signatures
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 time-pieces. 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.