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.