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one of the hundreds and thousands of stars which exist elsewhere
in space. Indeed, we may say at once that this little object was
not a star at all; it was a planet. That such was its true nature
was confirmed, after a little further observation, by perceiving
that the body was shifting its place on the heavens relatively to
the stars. The organist at the Octagon Chapel at Bath had,
therefore, discovered a new planet with his home-made telescope.
I can imagine some one will say, “Oh, there was nothing so
wonderful in that; are not planets always being discovered? Has
not M. Palisa, for instance discovered about eighty of such
objects, and are there not hundreds of them known nowadays?” This
is, to a certain extent, quite true. I have not the least desire
to detract from the credit of those industrious and sharp-sighted
astronomers who have in modern days brought so many of these
little objects within our cognisance. I think, however, it must
be admitted that such discoveries have a totally different
importance in the history of science from that which belongs to
the peerless achievement of Herschel. In the first place, it must
be observed that the minor planets now brought to light are so
minute that if a score of them were rolled to together into one
lump it would not be one-thousandth part of the size of the grand
planet discovered by Herschel. This is, nevertheless, not the
most important point. What marks Herschel’s achievement as one of
the great epochs in the history of astronomy is the fact that the
detection of Uranus was the very first recorded occasion of the
discovery of any planet whatever.
For uncounted ages those who watched the skies had been aware of
the existence of the five old planets-Jupiter, Mercury, Saturn,
Venus, and Mars. It never seems to have occurred to any of the
ancient philosophers that there could be other similar objects as
yet undetected over and above the well-known five. Great then was
the astonishment of the scientific world when the Bath organist
announced his discovery that the five planets which had been known
from all antiquity must now admit the company of a sixth. And
this sixth planet was, indeed, worthy on every ground to be
received into the ranks of the five glorious bodies of antiquity.
It was, no doubt, not so large as Saturn, it was certainly very
much less than Jupiter; on the other hand, the new body was very
much larger than Mercury, than Venus, or than Mars, and the earth
itself seemed quite an insignificant object in comparison with
this newly added member of the Solar System. In one respect, too,
Herschel’s new planet was a much more imposing object than any one
of the older bodies; it swept around the sun in a majestic orbit,
far outside that of Saturn, which had previously been regarded as
the boundary of the Solar System, and its stately progress
required a period of not less than eighty-one years.
King George the Third, hearing of the achievements of the
Hanoverian musician, felt much interest in his discovery, and
accordingly Herschel was bidden to come to Windsor, and to
bring with him the famous telescope, in order to exhibit the new
planet to the King, and to tell his Majesty all about it. The
result of the interview was to give Herschel the opportunity for
which he had so long wished, of being able to devote himself
exclusively to science for the rest of his life.
[PLATE: VIEW OF THE OBSERVATORY, HERSCHEL HOUSE, SLOUGH.]
The King took so great a fancy to the astronomer that he first, as
I have already mentioned, duly pardoned his desertion from the
army, some twenty-five years previously. As a further mark of his
favour the King proposed to confer on Herschel the title of his
Majesty’s own astronomer, to assign to him a residence near
Windsor, to provide him with a salary, and to furnish such funds
as might be required for the erection of great telescopes, and
for the conduct of that mighty scheme of celestial observation on
which Herschel was so eager to enter. Herschel’s capacity for
work would have been much impaired if he had been deprived of the
aid of his admirable sister, and to her, therefore, the King also
assigned a salary, and she was installed as Herschel’s assistant
in his new post.
With his usually impulsive determination, Herschel immediately cut
himself free from all his musical avocations at Bath, and at once
entered on the task of making and erecting the great telescopes at
Windsor. There, for more than thirty years, he and his faithful
sister prosecuted with unremitting ardour their nightly scrutiny
of the sky. Paper after paper was sent to the Royal Society,
describing the hundreds, indeed the thousands, of objects such as
double stars; nebulae and clusters, which were first revealed to
human gaze during those midnight vigils. To the end of his life
he still continued at every possible opportunity to devote himself
to that beloved pursuit in which he had such unparalleled success.
No single discovery of Herschel’s later years was, however, of the
same momentous description as that which first brought him to
fame.
[PLATE: THE 40-FOOT TELESCOPE AS IT WAS IN THE YEAR 1863,
HERSCHEL HOUSE, SLOUGH.]
Herschel married when considerably advanced in life and he lived
to enjoy the indescribable pleasure of finding that his only
son, afterwards Sir John Herschel, was treading worthily in his
footsteps, and attaining renown as an astronomical observer,
second only to that of his father. The elder Herschel died in
1822, and his illustrious sister Caroline then returned to
Hanover, where she lived for many years to receive the respect and
attention which were so justly hers. She died at a very advanced
age in 1848.
LAPLACE.
The author of the “Mecanique Celeste” was born at Beaumont-en-Auge, near Honfleur, in 1749, just thirteen years later than his
renowned friend Lagrange. His father was a farmer, but appears to
have been in a position to provide a good education for a son who
seemed promising. Considering the unorthodoxy in religious
matters which is generally said to have characterized Laplace in
later years, it is interesting to note that when he was a boy the
subject which first claimed his attention was theology. He was,
however, soon introduced to the study of mathematics, in which he
presently became so proficient, that while he was still no more
than eighteen years old, he obtained employment as a mathematical
teacher in his native town.
Desiring wider opportunities for study and for the acquisition of
fame than could be obtained in the narrow associations of
provincial life, young Laplace started for Paris, being provided
with letters of introduction to D’Alembert, who then occupied
the most prominent position as a mathematician in France, if not
in the whole of Europe. D’Alembert’s fame was indeed so
brilliant that Catherine the Great wrote to ask him to undertake
the education of her Son, and promised the splendid income of a
hundred thousand francs. He preferred, however, a quiet life of
research in Paris, although there was but a modest salary attached
to his office. The philosopher accordingly declined the alluring
offer to go to Russia, even though Catherine wrote again to say:
“I know that your refusal arises from your desire to cultivate
your studies and your friendships in quiet. But this is of no
consequence: bring all your friends with you, and I promise you
that both you and they shall have every accommodation in my
power.” With equal firmness the illustrious mathematician
resisted the manifold attractions with which Frederick the Great
sought to induce him, to take up his residence at Berlin. In
reading of these invitations we cannot but be struck at the
extraordinary respect which was then paid to scientific
distinction. It must be remembered that the discoveries of such
a man as D’Alembert were utterly incapable of being appreciated
except by those who possessed a high degree of mathematical
culture. We nevertheless find the potentates of Russia and
Prussia entreating and, as it happens, vainly entreating, the
most distinguished mathematician in France to accept the
positions that they were proud to offer him.
It was to D’Alembert, the profound mathematician, that young
Laplace, the son of the country farmer, presented his letters of
introduction. But those letters seem to have elicited no reply,
whereupon Laplace wrote to D’Alembert submitting a discussion on
some point in Dynamics. This letter instantly produced the
desired effect. D’Alembert thought that such mathematical talent
as the young man displayed was in itself the best of introductions
to his favour. It could not be overlooked, and accordingly he
invited Laplace to come and see him. Laplace, of course,
presented himself, and ere long D’Alembert obtained for the rising
philosopher a professorship of mathematics in the Military School
in Paris. This gave the brilliant young mathematician the opening
for which he sought, and he quickly availed himself of it.
Laplace was twenty-three years old when his first memoir on a
profound mathematical subject appeared in the Memoirs of the
Academy at Turin. From this time onwards we find him publishing
one memoir after another in which he attacks, and in many cases
successfully vanquishes, profound difficulties in the application
of the Newtonian theory of gravitation to the explanation of the
solar system. Like his great contemporary Lagrange, he loftily
attempted problems which demanded consummate analytical skill for
their solution. The attention of the scientific world thus became
riveted on the splendid discoveries which emanated from these two
men, each gifted with extraordinary genius.
Laplace’s most famous work is, of course, the “Mecanique
Celeste,” in which he essayed a comprehensive attempt to carry out
the principles which Newton had laid down, into much greater
detail than Newton had found practicable. The fact was that
Newton had not only to construct the theory of gravitation, but he
had to invent the mathematical tools, so to speak, by which his
theory could be applied to the explanation of the movements of the
heavenly bodies. In the course of the century which had elapsed
between the time of Newton and the time of Laplace, mathematics
had been extensively developed. In particular, that potent
instrument called the infinitesimal calculus, which Newton had
invented for the investigation of nature, had become so far
perfected that Laplace, when he attempted to unravel the movements
of the heavenly bodies, found himself provided with a calculus far
more efficient than that which had been available to Newton. The
purely geometrical methods which Newton employed, though they are
admirably adapted for demonstrating in a general way the
tendencies of forces and for explaining the more obvious phenomena
by which the movements of the heavenly bodies are disturbed, are
yet quite inadequate for dealing with the more subtle effects of
the Law of Gravitation. The disturbances which one planet
exercises upon the rest can only be fully ascertained by the aid
of long calculation, and for these calculations analytical methods
are required.
With an armament of mathematical methods which had been perfected
since the days of Newton by the labours of two or three
generations of consummate mathematical inventors, Laplace essayed
in the “Mecanique Celeste” to unravel the mysteries of the
heavens. It will hardly be disputed that the book which he has
produced is one of the most difficult books to understand that has
ever been written. In great part, of course, this difficulty
arises from the very nature of the subject, and is so far
unavoidable. No one need attempt to read the “Mecanique Celeste”
who has not been naturally endowed with considerable mathematical
aptitude which he has cultivated by years of assiduous study. The
critic will also note that there are grave defects in Laplace’s
method of
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