The Astronomy of Milton's 'Paradise Lost'
by Thomas Nathaniel Orchard · English · Gutenberg #28434 · 517,778 chars · public domain (US)
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Title: The Astronomy of Milton's 'Paradise Lost'
Author: Thomas Nathaniel Orchard
Release date: March 29, 2009 [eBook #28434]
Language: English
Other information and formats: www.gutenberg.org/ebooks/28434
Credits: Produced by David Edwards, Nigel Blower and the Online
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*** START OF THE PROJECT GUTENBERG EBOOK THE ASTRONOMY OF MILTON'S 'PARADISE LOST' ***
Produced by David Edwards, Nigel Blower and the Online
Distributed Proofreading Team at http://www.pgdp.net (This
file was produced from images generously made available
by The Internet Archive/American Libraries.)
TRANSCRIBER'S NOTE
Greek letters used to identify stars (Bayer designation), are replaced
with the full name of the Greek letter, e.g. Alpha Centauri.
The single Greek word in the text is transliterated within braces, {kome}.
Minor punctuation and hyphenation inconsistencies have been corrected.
The spelling "Bernices" for "Berenices" has been retained throughout.
The following minor typographical errors have been corrected:
p75: "establish" changed to "established"
p99: "Firmanent" changed to "Firmament"
p111: "they thoughts" changed to "thy thoughts"
p120: "suen" changed to "seuen"
p134: "consequenc" changed to "consequence"
p146: "geographieal" changed to "geographical"
p167: "Lyrae" changed to "Lyrae" for consistency
p286: Removed redundant word "degrees" following the degree symbol
THE ASTRONOMY
OF
MILTON'S 'PARADISE LOST'
[Illustration: A TYPICAL SUN-SPOT]
THE ASTRONOMY
OF
MILTON'S 'PARADISE LOST'
BY
THOMAS N. ORCHARD, M.D.
MEMBER OF THE BRITISH ASTRONOMICAL ASSOCIATION
_These are thy glorious works, Parent of good,
Almighty! thine this universal frame,
Thus wondrous fair: Thyself how wondrous then!
Unspeakable._
LONGMANS, GREEN, AND CO.
LONDON, NEW YORK, AND BOMBAY
1896
All rights reserved
CONTENTS
CHAPTER PAGE
I. A Short Historical Sketch of Astronomy 1
II. Astronomy in the Seventeenth Century 45
III. Milton's Astronomical Knowledge 81
IV. Milton and Galileo 113
V. The Seasons 140
VI. The Starry Heavens 152
VII. The Starry Heavens 200
VIII. Description of Celestial Objects Mentioned in 'Paradise Lost' 244
IX. Milton's Imaginative and Descriptive Astronomy 306
ILLUSTRATIONS
_PLATES_
A Typical Sun-spot _Frontispiece_
Venus on the Sun's Disc _To face page_ 66
Cluster in Hercules " 218
Great Nebula in Orion " 230
A Portion of the Moon's Surface " 268
_IN TEXT_
FIG. PAGE
1. The Ptolemaic System of the Universe 86
2. Milton's Division of Universal Space 96
3. A Binary Star System--70 Ophiuchi 184
4. The Orbits of the Components of Gamma Virginis 189
5. Apparent Orbit of the Companion of Sirius 190
6. A Sun-spot Magnified 247
7. The Corona during the Eclipse of May 1883 254
8. A Portion of the Milky Way 289
PREFACE
Many able and cultured writers have delighted to expatiate on the
beauties of Milton's 'Paradise Lost,' and to linger with admiration over
the lofty utterances expressed in his poem. Though conscious of his
inability to do justice to the sublimest of poets and the noblest of
sciences, the author has ventured to contribute to Miltonic literature a
work which he hopes will prove to be of an interesting and instructive
character. Perhaps the choicest passages in the poem are associated with
astronomical allusion, and it is chiefly to the exposition and
illustration of these that this volume is devoted.
The writer is indebted to many authors for information and reference,
and especially to Miss Agnes M. Clerke, Professors Masson and Young, Mr.
James Nasmyth, Mr. G. F. Chambers, and Sir Robert Ball. Also to the
works of the late Mr. R. A. Proctor, Sirs W. and J. Herschel, Admiral
Smyth, Professor Grant, Mr. J. R. Hind, Sir David Brewster, Rev. A. B.
Whatton, and Prebendary Webb.
Most of the illustrations have been supplied by the Publishers: Messrs.
Macmillan and W. Hunt & Co. have kindly permitted the reproduction of
some of their drawings.
MANCHESTER, _March 1896_.
CHAPTER I
A SHORT HISTORICAL SKETCH OF ASTRONOMY
Astronomy is the oldest and most sublime of all the sciences. To a
contemplative observer of the heavens, the number and brilliancy of the
stars, the lustre of the planets, the silvery aspect of the Moon, with
her ever-changing phases, together with the order, the harmony, and
unison pervading them all, create in his mind thoughts of wonder and
admiration. Occupying the abyss of space indistinguishable from
infinity, the starry heavens in grandeur and magnificence surpass the
loftiest conceptions of the human mind; for, at a distance beyond the
range of ordinary vision, the telescope reveals clusters, systems,
galaxies, universes of stars--suns--the innumerable host of heaven, each
shining with a splendour comparable with that of our Sun, and, in all
likelihood, fulfilling in a similar manner the same beneficent purposes.
The time when man began to study the stars is lost in the antiquity of
prehistoric ages. The ancient inhabitants of the Earth regarded the
heavenly bodies with veneration and awe, erected temples in their
honour, and worshipped them as deities. Historical records of astronomy
carry us back several thousand years. During the greater part of this
time, and until a comparatively recent period, astronomy was associated
with astrology--a science which originated from a desire on the part of
mankind to penetrate the future, and which was based upon the supposed
influence of the heavenly bodies upon human and terrestrial affairs. It
was natural to imagine that the overruling power which governed and
directed the course of sublunary events resided in the heavens, and that
its decrees might be understood by watching the movements of the
heavenly bodies under its control. It was, therefore, believed that by
observing the configuration of the planets and the positions of the
constellations at the instant of the birth of an individual, his
horoscope, or destiny, could be foretold; and that by making
observations of a somewhat similar nature the occurrence of events of
public importance could be predicted. When, however, the laws which
govern the motions of the heavenly bodies became better known, and
especially after the discovery of the great law of gravitation,
astrology ceased to be a belief, though for long after it retained its
power over the imagination, and was often alluded to in the writings of
poets and other authors.
In the early dawn of astronomical science, the theories upheld with
regard to the structure of the heavens were of a simple and primitive
nature, and might even be described as grotesque. This need occasion no
surprise when we consider the difficulties with which ancient
astronomers had to contend in their endeavours to reduce to order and
harmony the complicated motions of the orbs which they beheld circling
around them.
The grouping of the stars into constellations having fanciful names,
derived from fable or ancient mythology, occurred at a very early
period, and though devoid of any methodical arrangement, is yet
sufficiently well-defined to serve the purposes of modern astronomers.
Several of the ancient nations of the earth, including the Chaldeans,
Egyptians, Hindus, and Chinese, claim to have been the earliest
astronomers. Chinese records of astronomy reveal an antiquity of near
3,000 years B.C., but they contain no evidence that their authors
possessed any scientific knowledge, and they merely record the
occurrence of solar eclipses and the appearances of comets.
It is not known when astronomy was first studied by the Egyptians; but
what astronomical information they have handed down is not of a very
intelligible kind, nor have they left behind any data that can be relied
upon. The Great Pyramid, judging from the exactness with which it faces
the cardinal points, must have been designed by persons who possessed a
good knowledge of astronomy, and it was probably made use of for
observational purposes.
It is now generally admitted that correct astronomical observations were
first made on the plains of Chaldea, records of eclipses having been
discovered in Chaldean cities which date back 2,234 years B.C. The
Chaldeans were true astronomers: they made correct observations of the
risings and settings of the heavenly bodies; and the exact orientation
of their temples and public buildings indicates the precision with which
they observed the positions of celestial objects. They invented the
zodiac and gnomon, made use of several kinds of dials, notified
eclipses, and divided the day into twenty-four hours.
To the Greeks belongs the credit of having first studied astronomy in a
regular and systematic manner. THALES (640 B.C.) was one of the earliest
of Greek astronomers, and may be regarded as the founder of the science
among that people. He was born at Miletus, and afterwards repaired to
Egypt for the purpose of study. On his return to Greece he founded the
Ionian school, and taught the sphericity of the Earth, the obliquity of
the ecliptic, and the true causes of eclipses of the Sun and Moon. He
also directed the attention of mariners to the superiority of the Lesser
Bear, as a guide for the navigation of vessels, as compared with the
Great Bear, by which constellation they usually steered. Thales believed
the Earth to be the centre of the universe, and that the stars were
composed of fire; he also predicted the occurrence of a great solar
eclipse.
Thales had for his successors Anaximander, Anaximenes, and Anaxagoras,
who taught the doctrines of the Ionian school.
The next great astronomer that we read of is PYTHAGORAS, who was born at
Samos 590 B.C. He studied under Thales, and afterwards visited Egypt and
India, in order that he might make himself familiar with the scientific
theories adopted by those nations. On his return to Europe he founded
his school in Italy, and taught in a more extended form the doctrines of
the Ionian school. In his speculations with regard to the structure of
the universe he propounded the theory (though the reasons by which he
sustained it were fanciful) that the Sun is the centre of the planetary
system, and that the Earth revolves round him. This theory--the accuracy
of which has since been confirmed--received but little attention from
his successors, and it sank into oblivion until the time of Copernicus,
by whom it was revived. Pythagoras discovered that the Morning and
Evening Stars are one and the same planet.
Among the famous astronomers who lived about this period we find
recorded the names of Meton, who introduced the Metonic cycle into
Greece and erected the first sundial at Athens; Eudoxus, who persuaded
the Greeks to adopt the year of 365-1/4 days; and Nicetas, who taught
that the Earth completed a daily revolution on her axis.
The Alexandrian school, which flourished for three centuries prior to
the Christian era, produced men of eminence whose discoveries and
investigations, when arranged and classified, enabled astronomy to be
regarded as a true theoretical science. The positions of the fixed stars
and the paths of the planets were determined with greater accuracy, and
irregularities of the motions of the Sun and Moon were investigated with
greater precision. Attempts were made to ascertain the distance of the
Sun from the Earth, and also the dimensions of the terrestrial sphere.
The obliquity of the ecliptic was accurately determined, and an arc of
the meridian was measured between Syene and Alexandria. The names of
Aristarchus, Eratosthenes, Aristyllus, Timocharis, and Autolycus, are
familiarly known in association with the advancement of the astronomy of
this period.
We now reach the name of HIPPARCHUS of Bithynia (140 B.C.), the most
illustrious astronomer of antiquity, who did much to raise astronomy to
the position of a true science, and who has also left behind him ample
evidence of his genius 'as a mathematician, an observer, and a
theorist.' We are indebted to him for the earliest star catalogue, in
which he included 1,081 stars. He discovered the Precession of the
Equinoxes, and determined the motions of the Sun and Moon, and also the
length of the year, with greater precision than any of his predecessors.
He invented the sciences of plane and spherical trigonometry, and was
the first to use right ascensions and declinations.
The next astronomer of eminence after Hipparchus was PTOLEMY (130 A.D.),
who resided at Alexandria. He was skilled as a mathematician and
geographer, and also excelled as a musician. His chief discovery was an
irregularity of the lunar motion, called the '_evection_.' He was also
the first to observe the effect of the refraction of light in causing
the apparent displacement of a heavenly body from its true position.
Ptolemy devoted much of his time to extending and improving the theories
of Hipparchus, and compiled a great treatise, called the 'Almagest,'
which contains nearly all the knowledge we possess of ancient astronomy.
Ptolemy's name is, however, most widely known in association with what
is called the Ptolemaic theory. This system, which originated long
before his time, but of which he was one of the ablest expounders, was
an attempt to establish on a scientific basis the conclusions and
results arrived at by early astronomers who studied and observed the
motions of the heavenly bodies. Ptolemy regarded the Earth as the
immovable centre of the universe, round which the Sun, Moon, planets,
and the entire heavens completed a daily revolution in twenty-four
hours. After the death of Ptolemy no worthy successor was found to
occupy his place, the study of astronomy began to decline among the
Greeks, and after a time it ceased to be cultivated by that people.
The Arabs next took up the study of astronomy, which they prosecuted
most assiduously for a period of four centuries. Their labours were,
however, confined chiefly to observational work, in which they
excelled; unlike their predecessors, they paid but little attention to
speculative theories--indeed, they regarded with such veneration the
opinions held by the Greeks, that they did not feel disposed to question
the accuracy of their doctrines. The most eminent astronomer among the
Arabs was ALBATEGNIUS (680 A.D.). He corrected the Greek observations,
and made several discoveries which testified to his abilities as an
observer. IBN YUNIS and ABUL WEFU were Arab astronomers who earned a
high reputation on account of the number and accuracy of their
observations. In Persia, a descendant of the famous Genghis Khan erected
an observatory, where astronomical observations were systematically
made. Omar, a Persian astronomer, suggested a reformation of the
calendar which, if it had been adopted, would have insured greater
accuracy than can be attained by the Gregorian style now in use. In
1433, Ulugh Beg, who resided at Samarcand, made many observations, and
constructed a star catalogue of greater exactness than was known to
exist prior to his time. The Arabs may be regarded as having been the
custodians of astronomy until the time of its revival in another quarter
of the Globe.
After the lapse of many centuries, astronomy was introduced into Western
Europe in 1220, and from that date to the present time its career has
been one of triumphant progress. In 1230, a translation of Ptolemy's
'Almagest' from Arabic into Latin was accomplished by order of the
German Emperor, Frederick II.; and in 1252 Alphonso X., King of Castile,
himself a zealous patron of astronomy, caused a new set of astronomical
tables to be constructed at his own expense, which, in honour of his
Majesty, were called the 'Alphonsine Tables.' Purbach and Regiomontanus,
two German astronomers of distinguished reputation, and Waltherus, a man
of considerable renown, made many important observations in the
fifteenth century.
The most eminent astronomer who lived during the latter part of this
century was Copernicus. NICOLAS COPERNICUS was born February 19, 1473,
at Thorn, a small town situated on the Vistula, which formed the
boundary between the kingdoms of Prussia and Poland. His father was a
Polish subject, and his mother of German extraction. Having lost his
parents early in life, he was educated under the supervision of his
uncle Lucas, Bishop of Ermland. Copernicus attended a school at Thorn,
and afterwards entered the University of Cracow, in 1491, where he
devoted four years to the study of mathematics and science. On leaving
Cracow he attached himself to the University of Bologna as a student of
canon law, and attended a course of lectures on astronomy given by
Novarra. In the ensuing year he was appointed canon of Frauenburg, the
cathedral city of the Diocese of Ermland, situated on the shores of the
Frisches Haff. In the year 1500 he was at Rome, where he lectured on
mathematics and astronomy. He next spent a few years at the University
of Padua, where, besides applying himself to mathematics and astronomy,
he studied medicine and obtained a degree. In 1505 Copernicus returned
to his native country, and was appointed medical attendant to his uncle,
the Bishop of Ermland, with whom he resided in the stately castle of
Heilsberg, situated at a distance of forty-six miles from Frauenburg.
Copernicus lived with his uncle from 1507 till 1512, and during that
time prosecuted his astronomical studies, and undertook, besides, many
arduous duties associated with the administration of the diocese; these
he faithfully discharged until the death of the Bishop, which occurred
in 1512. After the death of his uncle he took up his residence at
Frauenburg, where he occupied his time in meditating on his new
astronomy and undertaking various duties of a public character, which he
fulfilled with credit and distinction. In 1523 he was appointed
Administrator-General of the diocese. Though a canon of Frauenburg,
Copernicus never became a priest.
After many years of profound meditation and thought, Copernicus, in a
treatise entitled 'De Revolutionibus Orbium Celestium,' propounded a new
theory, or, more correctly speaking, revived the ancient Pythagorean
system of the universe. This great work, which he dedicated to Pope Paul
III., was completed in 1530; but he could not be prevailed upon to have
it published until 1543, the year in which he died. In 1542 Copernicus
had an apoplectic seizure, followed by paralysis and a gradual decay of
his mental and vital powers. His book was printed at Nuremberg, and the
first copy arrived at Frauenburg on May 24, 1543, in time to be touched
by the hands of the dying man, who in a few hours after expired. The
house in which Copernicus lived at Allenstein is still in existence, and
in the walls of his chamber are visible the perforations which he made
for the purpose of observing the stars cross the meridian.
Copernicus was the means of creating an entire revolution in the science
of astronomy, by transferring the centre of our system from the Earth to
the Sun. He accounted for the alternation of day and night by the
rotation of the Earth on her axis, and for the vicissitudes of the
seasons by her revolution round the Sun. He devoted the greater part of
his life to meditating on this theory, and adduced several weighty
reasons in its support. Copernicus could not help perceiving the
complications and entanglements by which the Ptolemaic system of the
universe was surrounded, and which compared unfavourably with the simple
and orderly manner in which other natural phenomena presented themselves
to his observation. By perceiving that Mars when in opposition was not
much inferior in lustre to Jupiter, and when in conjunction resembled a
star of the second magnitude, he arrived at the conclusion that the
Earth could not be the centre of the planet's motion. Having discovered
in some ancient manuscripts a theory, ascribed to the Egyptians, that
Mercury and Venus revolved round the Sun, whilst they accompanied the
orb in his revolution round the Earth, Copernicus was able to perceive
that this afforded him a means of explaining the alternate appearance of
those planets on each side of the Sun. The varied aspects of the
superior planets, when observed in different parts of their orbits, also
led him to conclude that the Earth was not the central body round which
they accomplished their revolutions. As a combined result of his
observation and reasoning Copernicus propounded the theory that the Sun
is the centre of our system, and that all the planets, including the
Earth, revolve in orbits around him. This, which is called the
Copernican system, is now regarded as, and has been proved to be, the
true theory of the solar system.
TYCHO BRAHE was a celebrated Danish astronomer, who earned a deservedly
high reputation on account of the number and accuracy of his
astronomical observations and calculations. The various astronomical
tables that were in use in his time contained many inaccuracies, and it
became necessary that they should be reconstructed upon a more correct
basis. Tycho possessed the practical skill required for this kind of
work.
He was born December 14, 1546, at Knudstorp, near Helsingborg. His
father, Otto Brahe, traced his descent from a Swedish family of noble
birth. At the age of thirteen Tycho was sent to the University of
Copenhagen, where it was intended he should prepare himself for the
study of the law.
The prediction of a great solar eclipse, which was to happen on August
21, 1560, caused much public excitement in Denmark, for in those days
such phenomena were regarded as portending the occurrence of events of
national importance. Tycho looked forward with great eagerness to the
time of the eclipse. He watched its progress with intense interest, and
when he perceived all the details of the phenomenon occur exactly as
they were predicted, he resolved to pursue the study of a science by
which, as was then believed, the occurrence of future events could be
foretold. From Copenhagen Tycho Brahe was sent to Leipsic to study
jurisprudence, but astronomy absorbed all his thoughts. He spent his
pocket-money in purchasing astronomical books, and, when his tutor had
retired to sleep, he occupied his time night after night in watching the
stars and making himself familiar with their courses. He followed the
planets in their direct and retrograde movements, and with the aid of a
small globe and pair of compasses was able by means of his own
calculations to detect serious discrepancies in the Alphonsine and
Prutenic tables. In order to make himself more proficient in calculating
astronomical tables he studied arithmetic and geometry, and learned
mathematics without the aid of a master. Having remained at Leipsic for
three years, during which time he paid far more attention to the study
of astronomy than to that of law, he returned to his native country in
consequence of the death of an uncle, who bequeathed him a considerable
estate. In Denmark he continued to prosecute his astronomical studies,
and incurred the displeasure of his friends, who blamed him for
neglecting his intended profession and wasting his time on astronomy,
which they regarded as useless and unprofitable.
Not caring to remain among his relatives, Tycho Brahe returned to
Germany, and arrived at Wittenberg in 1566. Whilst residing here he had
an altercation with a Danish gentleman over some question in
mathematics. The quarrel led to a duel with swords, which terminated
rather unfortunately for Tycho, who had a portion of his nose cut off.
This loss he repaired by ingeniously contriving one of gold, silver, and
wax, which was said to bear a good resemblance to the original. From
Wittenberg Tycho proceeded to Augsburg, where he resided for two years.
Here he made the acquaintance of several men distinguished for their
learning and their love of astronomy. During his stay at Augsburg he
constructed a quadrant of fourteen cubits radius, on which were
indicated the single minutes of a degree; he made many valuable
observations with this instrument, which he used in combination with a
large sextant.
In 1571 Tycho returned to Denmark, where his fame as an astronomer had
preceded him, and was the means of procuring for him a hearty welcome
from his relatives and friends. In 1572, when returning one night from
his laboratory--for Tycho studied alchemy as well as astronomy--he
beheld what appeared to be a new and brilliant star in the
constellation Cassiopeia, which was situated overhead. He directed the
attention of his companions to this wonderful object, and all declared
that they had never observed such a star before. On the following night
he measured its distance from the nearest stars in the constellation,
and arrived at the conclusion that it was a fixed star, and beyond our
system.
This remarkable object remained visible for sixteen months, and when at
its brightest rivalled Sirius. At first it was of a brilliant white
colour, but as it diminished in size it became yellow; it next changed
to a red colour, resembling Aldebaran; afterwards it appeared like
Saturn, and as it grew smaller it decreased in brightness, until it
finally became invisible. In 1573 Tycho Brahe married a peasant-girl
from the village of Knudstorp. This imprudent act roused the resentment
of his relatives, who, being of noble birth, were indignant that he
should have contracted such an alliance. The bitterness and mutual
ill-feeling created by this affair became so intense that the King of
Denmark deemed it advisable to endeavour to bring about a
reconciliation.
After this Tycho returned to Germany, and visited several cities before
deciding where he should take up his permanent residence.
His fame as an astronomer was now so great that he was received with
distinction wherever he went, and on the occasion of a visit to
Hesse-Cassel he spent a few pleasant days with William, Landgrave of
Hesse, who was himself skilled in astronomy.
Frederick II., King of Denmark, having recognised Tycho Brahe's great
merits as an astronomer, and not wishing that his fame should add lustre
to a foreign Court, expressed a desire that he should return to his
native country, and as an inducement offered him a life interest in the
island of Huen, in the Sound, where he undertook to erect and equip an
observatory at his own expense; the King also promised to bestow upon
him a pension, and grant him other emoluments besides.
Tycho gladly accepted this generous offer, and during the construction
of the observatory occupied his time in making a magnificent collection
of instruments and appliances adapted for observational purposes. This
handsome edifice, upon which the King of Denmark expended a sum of
20,000_l._, was called 'Uranienburg' ('The Citadel of the Heavens').
Here Tycho resided for a period of twenty years, during which time he
pursued his astronomical labours with untiring energy and zeal, and made
a large number of observations and calculations of much superior
accuracy to any that existed previously, which were afterwards of great
service to his successors. During his long residence at Huen, Tycho was
visited by many distinguished persons, who were attracted to his island
home by his fame and the magnificence of his observatory. Among them was
James VI. of Scotland, who, whilst journeying to the Court of Denmark
on the occasion of his marriage to a Danish princess, paid Tycho a
visit, and enjoyed his hospitality for a week. The King was delighted
with all that he saw, and on his departure presented Tycho with a
handsome donation, and at his request composed some Latin verses, in
which he eulogised his host and praised his observatory.
The island of Huen is situated about six miles from the coast of
Zealand, and fourteen from Copenhagen. It has a circumference of six
miles, and consists chiefly of an elevated plateau, in the centre of
which Tycho erected his observatory, the site of which is now marked by
two pits and a few mounds of earth--all that remains of Uranienburg. All
went well with Tycho Brahe during the lifetime of his noble patron; but
in 1588 Frederick II. died, and was succeeded by his son, a youth eleven
years of age.
The Danish nobles had long been jealous of Tycho's fame and reputation,
and on the death of the King an opportunity was afforded them of
intriguing with the object of accomplishing his downfall. Several false
accusations were brought against him, and the Court party made the
impoverished state of the Treasury an excuse for depriving him of his
pension and emoluments granted by the late King.
Tycho was no longer able to bear the expense of maintaining his
establishment at Huen, and fearing that he might be deprived of the
island itself, he took a house in Copenhagen, to which he removed all
his smaller instruments.
During his residence in the capital he was subjected to annoyance and
persecution. An order was issued in the King's name preventing him from
carrying on his chemical experiments, and he besides suffered the
indignity of a personal assault. Tycho Brahe resolved to quit his
ungrateful country and seek a home in some foreign land, where he should
be permitted to pursue his studies unmolested and live in quietness and
peace. He accordingly removed from the island of Huen all his
instruments and appliances that were of a portable nature, and packed
them on board a vessel which he hired for the purpose of transport, and,
having embarked with his family, his servants, and some of his pupils
and assistants, 'this interesting barque, freighted with the glory of
Denmark,' set sail from Copenhagen about the end of 1597, and having
crossed the Baltic in safety, arrived at Rostock, where Tycho found some
old friends waiting to receive him. He was now in doubt as to where he
should find a home, when the Austrian Emperor Rudolph, himself a liberal
patron of science and the fine arts, having heard of Tycho Brahe's
misfortunes, sent him an invitation to take up his abode in his
dominions, and promised that he should be treated in a manner worthy of
his reputation and fame.
Tycho resolved to accept the Emperor's kind invitation, and in the
spring of 1599 arrived at Prague, where he found a handsome residence
prepared for his reception.
He was received by the Emperor in a most cordial manner and treated with
the greatest kindness. An annual pension of three thousand crowns was
settled upon him for life, and he was to have his choice of several
residences belonging to his Majesty, where he might reside and erect a
new observatory. From among these he selected the Castle of Benach, in
Bohemia, which was situated on an elevated plateau and commanded a wide
view of the horizon.
During his residence at Benach Tycho received a visit from Kepler, who
stayed with him for several months in order that he might carry out some
astronomical observations. In the following year Kepler returned, and
took up his permanent residence with Tycho, having been appointed
assistant in his observatory, a post which, at Tycho's request, was
conferred upon him by the Emperor.
Tycho Brahe soon discovered that his ignorance of the language and
unfamiliarity with the customs of the people caused him much
inconvenience. He therefore asked permission from the Emperor to be
allowed to remove to Prague. This request was readily granted, and a
suitable residence was provided for him in the city.
In the meantime his family, his large instruments, and other property,
having arrived at Prague, Tycho was soon comfortably settled in his new
home.
Though Tycho Brahe continued his astronomical observations, yet he could
not help feeling that he lived among a strange people; nor did the
remembrance of his sufferings and the cruel treatment he received at the
hands of his fellow-countrymen subdue the affection which he cherished
towards his native land. Pondering over the past, he became despondent
and low-spirited; a morbid imagination caused him to brood over small
troubles, and gloomy, melancholy thoughts possessed his mind--symptoms
which seemed to presage the approach of some serious malady. One
evening, when visiting at the house of a friend, he was seized with a
painful illness, to which he succumbed in less than a fortnight. He died
at Prague on October 24, 1601, when in his fifty-fifth year.
The Emperor Rudolph, when informed of Tycho Brahe's death, expressed his
deep regret, and commanded that he should be interred in the principal
church in the city, and that his obsequies should be celebrated with
every mark of honour and respect.
Tycho Brahe stands out as the most romantic and prominent figure in the
history of astronomy. His independence of character, his ardent
attachments, his strong hatreds, and his love of splendour, are
characteristics which distinguish him from all other men of his age.
This remarkable man was an astronomer, astrologer, and alchemist; but in
his latter years he renounced astrology, and believed that the stars
exercised no influence over the destinies of mankind.
As a practical astronomer, Tycho Brahe has not been excelled by any
other observer of the heavens. The magnificence of his observatory at
Huen, upon the equipment and embellishment of which it is stated he
expended a ton of gold; the splendour and variety of his instruments,
and his ingenuity in inventing new ones, would alone have made him
famous. But it was by the skill and assiduity with which he carried out
his numerous and important observations that he has earned for himself a
position of the most honourable distinction among astronomers. In his
investigation of the Lunar theory Tycho Brahe discovered the Moon's
_annual equation_, a yearly effect produced by the Sun's disturbing
force as the Earth approaches or recedes from him in her orbit. He also
discovered another inequality in the Moon's motion, called the
_variation_. He determined with greater exactness astronomical
refractions from an altitude of 45 deg. downwards to the horizon, and
constructed a catalogue of 777 stars. He also made a vast number of
observations on planets, which formed the basis of the 'Rudolphine
Tables,' and were of invaluable assistance to Kepler in his
investigation of the laws relating to planetary motion.
Tycho Brahe declined to accept the Copernican theory, and devised a
system of his own, which he called the 'Tychonic.' By this arrangement
the Earth remained stationary, whilst all the planets revolved round
the Sun, who in his turn completed a daily revolution round the Earth.
All the phenomena associated with the motions of those bodies could be
explained by means of this system; but it did not receive much support,
and after the Copernican theory became better understood it was given
up, and heard of no more.
We now arrive at the name of KEPLER, one of the very greatest of
astronomers, and a man of remarkable genius, who was the first to
discover the real nature of the paths pursued by the Earth and planets
in their revolution round the Sun. After seventeen years of close
observation, he announced that those bodies travelled round the Sun in
elliptical or oval orbits, and not in circular paths, as was believed by
Copernicus. In his investigation of the laws which govern the motions of
the planets he formulated those famous theorems known as 'Kepler's
Laws,' which will endure for all time as a proof of his sagacity and
surpassing genius. Prior to the discovery of those laws the Sun, though
acknowledged to be the centre of the system, did not appear to occupy a
central position as regards the motions of the planets; but Kepler, by
demonstrating that the planes of the orbits of all the planets, and the
lines connecting their apsides, passed through the Sun, was enabled to
assign the orb his true position with regard to those bodies.
JOHN KEPLER was born at Weil, in the Duchy of Wurtemberg, December 21,
1571. His parents, though of noble family, lived in reduced
circumstances, owing to causes for which they were themselves chiefly
responsible. In his youth Kepler suffered so much from ill-health that
his education had to be neglected. In 1586 he was sent to a monastic
school at Maulbronn, which had been established at the Reformation, and
was under the patronage of the Duke of Wurtemberg. Afterwards he studied
at the University of Tubingen, where he distinguished himself and took a
degree. Kepler devoted his attention chiefly to science and mathematics,
but paid no particular attention to the study of astronomy. Maestlin,
the professor of mathematics, whose lectures he attended, upheld the
Copernican theory, and Kepler, who adopted the views of his teacher,
wrote an essay in favour of the diurnal rotation of the Earth, in which
he supported the more recent astronomical doctrines. In 1594, a vacancy
having occurred in the professorship of astronomy at Gratz consequent
upon the death of George Stadt, Kepler was appointed his successor. He
did not seek this office, as he felt no particular desire to take up the
study of astronomy, but was recommended by his tutors as a man well
fitted for the post. He was thus in a manner compelled to devote his
time and talents to the science of astronomy. Kepler directed his
attention to three subjects--viz. 'the number, the size, and the motion
of the orbits of the planets.' He endeavoured to ascertain if any
regular proportion existed between the sizes of the planetary orbits, or
in the difference of their sizes, but in this he was unsuccessful. He
then thought that, by imagining the existence of a planet between Mars
and Jupiter, and another between Venus and Mercury, he might be able to
attain his object; but he found that this assumption afforded him no
assistance. Kepler then imagined that as there were five regular
geometrical solids, and five planets, the distances of the latter were
regulated by the size of the solids described round one another. The
discovery afterwards of two additional planets testified to the
absurdity of this speculation. A description of these extraordinary
researches was published, in 1596, in a work entitled 'Prodromus of
Cosmographical Dissertations; containing the cosmographical mystery
respecting the admirable proportion of the celestial orbits, and the
genuine and real causes of the number, magnitude, and periods of the
planets, demonstrated by the five regular geometrical solids.' This
volume, notwithstanding the fanciful speculations which it contained,
was received with much favour by astronomers, and both Tycho Brahe and
Galileo encouraged Kepler to continue his researches. Galileo admired
his ingenuity, and Tycho advised him 'to lay a solid foundation for his
views by actual observation, and then, by ascending from these, to
strive to reach the causes of things.' Kepler spent many years in these
fruitless endeavours before he made those grand discoveries in search of
which he laboured so long.
The religious dissensions which at this time agitated Germany were
accompanied in many places by much tumult and excitement. At Gratz the
Catholics threatened to expel the Protestants from the city. Kepler, who
was of the Reformed faith, having recognised the danger with which he
was threatened, retired to Hungary with his wife, whom he had recently
married, and remained there for near twelve months, during which time he
occupied himself with writing several short treatises on subjects
connected with astronomy. In 1599 he returned to Gratz and resumed his
professorship.
In the year 1600 Kepler set out to pay Tycho Brahe a visit at Prague, in
order that he might be able to avail himself of information contained in
observations made by Tycho with regard to the eccentricities of the
orbits of the planets. He was received by Tycho with much cordiality,
and stayed with him for four months at his residence at Benach, Tycho in
the meantime having promised that he would use his influence with the
Emperor Rudolph to have him appointed as assistant in his observatory.
On the termination of his visit Kepler returned to Gratz, and as there
was a renewal of the religious trouble in the city, he resigned his
professorship, from which he only derived a small income, and, relying
on Tycho's promise, he again journeyed to Prague, and arrived there in
1601. Kepler was presented to the Emperor by Tycho, and the post of
Imperial Mathematician was conferred upon him, with a salary of 100
florins a year, upon condition that he should assist Tycho in his
observatory. This appointment was of much value to Kepler, because it
afforded him an opportunity of obtaining access to the numerous
astronomical observations made by Tycho, which were of great assistance
to him in the investigation of the subject which he had chosen--viz. the
laws which govern the motions of the planets, and the form and size of
the planetary orbits.
As an acknowledgment of the Emperor's great kindness, the two
astronomers resolved to compute a new set of astronomical tables, and in
honour of his Majesty they were to be called the 'Rudolphine Tables.'
This project pleased the Emperor, who promised to defray the expense of
their publication. Logomontanus, Tycho's chief assistant, had entrusted
to him that portion of the work relating to observations on the stars,
and Kepler had charge of the part which embraced the calculations
belonging to the planets and their orbits. This important work had
scarcely been begun when the departure of Logomontanus, who obtained an
appointment in Denmark, and the death of Tycho Brahe in October 1601,
necessitated its suspension for a time. Kepler was appointed Chief
Mathematician to the Emperor in succession to Tycho--a position of
honour and distinction, and to which was attached a handsome salary,
that was paid out of the Imperial treasury. But owing to the continuance
of expensive wars, which entailed a severe drain upon the resources of
the country, the public funds became very low, and Kepler's salary was
always in arrear. This condition of things involved him in serious
pecuniary difficulties, and the responsibility of having to maintain an
increasing family added to his anxieties. It was with the greatest
difficulty that he succeeded in obtaining payment of even a portion of
his salary, and he was reduced to such straits as to be under the
necessity of casting nativities in order to obtain money to meet his
most pressing requirements.
In 1609 Kepler published his great work, entitled 'The New Astronomy;
or, Commentaries on the Motions of Mars.' It was by his observation of
Mars, which has an orbit of greater eccentricity than that of any of the
other planets, with the exception of Mercury, that he was enabled, after
years of patient study, to announce in this volume the discovery of two
of the three famous theorems known as Kepler's Laws. The first is, that
all the planets move round the Sun in elliptic orbits, and that the orb
occupies one of the foci. The second is, that the radius-vector, or
imaginary line joining the centre of the planet and the centre of the
Sun, describes equal areas in equal times. The third law, which relates
to the connection between the periodic times and the distances of the
planets, was not discovered until ten years later, when Kepler, in 1619,
issued another work, called the 'Harmonies of the World,' dedicated to
James I. of England, in which was contained this remarkable law. These
laws have elevated astronomy to the position of a true physical science,
and also formed the starting-point of Newton's investigations which led
to the discovery of the law of gravitation. Kepler's delight on the
discovery of his third law was unbounded. He writes: 'Nothing holds me.
I will indulge in my sacred fury. I will triumph over mankind by the
honest confession that I have stolen the golden vases of the Egyptians
to build up a tabernacle for my God far away from the confines of Egypt.
If you forgive me, I rejoice; if you are angry, I can bear it. The die
is cast; the book is written, to be read either now or by posterity I
care not which. It may well wait a century for a reader, as God has
waited six thousand years for an observer.'
When Kepler presented his celebrated book to the Emperor, he remarked
that it was his intention to make a similar attack upon the other
planets, and promised that he would be successful if his Majesty would
undertake to find the means necessary for carrying on operations. But
the Emperor had more formidable enemies to contend with nearer home than
Jupiter and Saturn, and no funds were forthcoming to assist Kepler in
his undertaking.
The chair of mathematics in the University of Linz having become vacant,
Kepler offered himself as a candidate for the appointment, which he was
anxious to obtain; but the Emperor Rudolph was averse to his leaving
Prague, and encouraged him to hope that the arrears of his salary would
be paid. But past experience led Kepler to have no very sanguine
expectations on this point; nor was it until after the death of Rudolph,
in 1612, that he was relieved from his pecuniary embarrassments.
On the accession of Rudolph's brother, Matthias, to the Austrian throne,
Kepler was reappointed Imperial Mathematician; he was also permitted to
hold the professorship at Linz, to which he had been elected. Kepler was
not loth to remove from Prague, where he had spent eleven years harassed
by poverty and other domestic afflictions. Having settled with his
family at Linz, Kepler issued another work, in 1618, entitled 'Epitome
of the Copernican Astronomy,' in which he gave a general account of his
astronomical observations and discoveries, and a summary of his opinions
with regard to the theories which in those days were the subject of
controversial discussion. Almost immediately after its publication it
was included by the Congregation of the Index, at Rome, in the list of
prohibited books. This occasioned Kepler considerable alarm, as he
imagined it might interfere with the sale of his works, or give rise to
difficulties in the issue of others. He, however, was assured by his
friend Remus that the action of the Papal authorities need cause him no
anxiety.
The Emperor Matthias died in 1619, and was succeeded by Ferdinand III.,
who not only retained Kepler in his office, but gave orders that all the
arrears of his salary should be paid, including those which accumulated
during the reign of Rudolph; he also expressed a desire that the
'Rudolphine Tables' should be published without delay and at his cost.
But other obstacles intervened, for at this time Germany was involved in
a civil and religious war, which interfered with all peaceful
vocations. Kepler's library at Linz was sealed up by order of the
Jesuits, and the city was for a time besieged by troops. This state of
public affairs necessitated a considerable delay in the publication of
the 'Tables.'
The 'Rudolphine Tables' were published at Ulm in 1627. They were
commenced by Tycho Brahe, and completed by Kepler, who made his
calculations from Tycho's observations, and based them upon his own
great discovery of the ellipticity of the orbits of the planets. They
are divided into four parts. The first and third parts contain
logarithmic and other tables for the purpose of facilitating
astronomical calculations; in the second are tables of the Sun, Moon,
and planets; and in the fourth are indicated the positions of one
thousand stars as determined by Tycho. Kepler made a special journey to
Prague in order to present the 'Tables' to the Emperor, and afterwards
the Grand Duke of Tuscany sent him a gold chain as an acknowledgment of
his appreciation of the completion of this great work.
Albert Wallenstein, Duke of Friedland, an accomplished scholar and a man
fond of scientific pursuits, made Kepler a most liberal offer if he
would take up his residence in his dominions. After duly considering
this proposal, Kepler decided to accept the Duke's offer, provided it
received the sanction of the Emperor. This was readily given, and
Kepler, in 1629, removed with his family from Linz to Sagan, in Silesia.
The Duke of Friedland treated him with great kindness and liberality,
and through his influence he was appointed to a professorship in the
University of Rostock. Though Kepler was permitted to retain the pension
bestowed upon him by the late Emperor Rudolph, he was unable after his
removal to Silesia to obtain payment of it, and there was a large
accumulation of arrears. In a final endeavour to recover the amount
owing to him he travelled to Ratisbon, and appealed to the Imperial
Assembly, but without success. The fatigue which Kepler endured on his
journey, combined with vexation and disappointment, brought on a fever,
which terminated fatally. He died on November 15, 1630, when in the
sixtieth year of his age, and was interred in St. Peter's churchyard,
Ratisbon.
Kepler was a man of indomitable energy and perseverance, and spared
neither time nor trouble in the accomplishment of any object which he
took in hand. In thinking over the form of the orbits of the planets, he
writes: 'I brooded with the whole energy of my mind on this
subject--asking why they are not other than they are--the number, the
size, and the motions of the orbits.' But many fanciful ideas passed
through Kepler's imaginative brain before he hit upon the true form of
the planetary orbits. In his 'Mysterium Cosmographicum' he asserts that
the five kinds of regular polyhedral solids, when described round one
another, regulated the distances of the planets and size of the
planetary orbits. In support of this theory he writes as follows: 'The
orbit of the Earth is the measure of the rest. About it circumscribe a
dodecahedron. The sphere including this will be that of Mars. About
Mars' orbit describe a tetrahedron; the sphere containing this will be
Jupiter's orbit. Round Jupiter's describe a cube; the sphere including
this will be Saturn's. Within the Earth's orbit inscribe an icosahedron;
the sphere inscribed in it will be Venus's orbit. In Venus inscribe an
octahedron; the sphere inscribed in it will be Mercury's.'
The above quotation is an instance of Kepler's wild and imaginative
genius, which ultimately led him to make those sublime discoveries
associated with planetary motion which are known as 'Kepler's Laws.'
He describes himself as 'troublesome and choleric in politics and
domestic matters;' but in his relations with scientific men he was
affable and pleasant. He showed no jealousy of a rival, and was always
ready to recognise merit in others; nor did he hesitate to acknowledge
any error of his own when more recent discoveries proved that he was
wrong.
Some of his works contain passages, written in a jocular strain,
indicative of a bright and cheerful temperament. The following
characteristic paragraph refers to the opinions of the Epicureans with
regard to the appearance of a new star, which they ascribed to a
fortuitous concourse of atoms: 'When I was a youth, with plenty of idle
time on my hands, I was much taken with the vanity, of which some grown
men are not ashamed, of making anagrams by transposing the letters of my
name written in Latin so as to make another sentence. Out of Ioannes
Keplerus came _Serpens in akuleo_ (a serpent in his sting); but not
being satisfied with the meaning of these words, and being unable to
make another, I trusted the thing to chance, and, taking out of a pack
of playing-cards as many as there were letters in the name, I wrote one
upon each, and then began to shuffle them, and at each shuffle to read
them in the order they came, to see if any meaning came of it. Now, may
all the Epicurean gods and goddesses confound this same chance, which,
although I have spent a good deal of time over it, never showed me
anything like sense, even from a distance. So I gave up my cards to the
Epicurean eternity, to be carried away into infinity; and it is said
they are still flying about there, in the utmost confusion, among the
atoms, and have never yet come to any meaning. I will tell those
disputants, my opponents, not my own opinion, but my wife's. Yesterday,
when weary with writing, and my mind quite dusty with considering these
atoms, I was called to supper, and a salad I had asked for was set
before me. "It seems, then," said I aloud, "that if pewter dishes,
leaves of lettuce, grains of salt, drops of water, vinegar and oil, and
slices of egg, had been flying about in the air from all eternity, it
might at last happen by chance that there would come a salad." "Yes,"
says my wife, "but not so nice and well dressed as this of mine is."'
Notwithstanding the frequent interruptions which, owing to various
reasons, retarded his labours, Kepler was able to bring to a successful
completion the numerous and important works upon which he was engaged
during his lifetime, the voluminous nature of which may be imagined when
it is stated that he published thirty-three separate works, besides
leaving behind twenty-two volumes of manuscript.
During his researches on the motions of Mars, Kepler discovered that the
planet sometimes travelled at an accelerated rate of speed, and at
another time its pace was diminished. At one time he observed it to be
in advance of the place where he calculated it should be found, and at
another time it was behind it. This caused him considerable perplexity,
and, feeling convinced in his mind that the form of the planet's orbit
could not be circular, he was compelled to turn his attention to some
other closed curve, by which those inequalities of motion could be
explained.
After years of careful observation and study, Kepler arrived at the
conclusion that the form of the planet's orbit is an ellipse, and that
the Sun occupies one of the foci. He afterwards determined that the
orbits of all the planets are of an elliptical form.
Having discovered the true form of the planetary orbits, Kepler next
endeavoured to ascertain the cause which regulates the unequal motion
that a planet pursues in its path. He observed that when a planet
approached the Sun its motion was accelerated, and as it receded from
him its pace became slower.
This he explained in his next great discovery by proving that an
imaginary line, or radius-vector, extending from the centre of the Sun
to the centre of the planet 'describes equal areas in equal times.' When
near the Sun, or at perihelion, a planet traverses a larger portion of
its arc in the same period of time than it does when at the opposite
part of its orbit, or when at aphelion; but, as the areas of both are
equal, it follows that the planet does not always maintain the same rate
of speed, and that its velocity is greatest when nearest the Sun, and
least when most distant from him.
By the application of his first and second laws Kepler was able to
formulate a third law. He found that there existed a remarkable
relationship between the mean distances of the planets and the times in
which they complete their revolutions round the Sun, and discovered
'that the squares of the periodic times are to each in the same
proportion as the cubes of the mean distances.' The periodic time of a
planet having been ascertained, the square of the mean distance and the
mean distance itself can be obtained. It is by the application of this
law that the distances of the planets are usually calculated.
These discoveries are known as Kepler's Laws, and are usually classified
as follows:--
1. 'The orbit described by every planet is an ellipse, of which the
centre of the Sun occupies one of the foci.
2. 'Every planet moves round the Sun in a plane orbit, and the
radius-vector, or imaginary line joining the centre of the planet and
the centre of the Sun, describes equal areas in equal times.
3. 'The squares of the periodic times of any two planets are
proportional to the cubes of their mean distances from the Sun.'[1]
These remarkable discoveries do not embrace all the achievements by
which Kepler has immortalised his name, and earned for himself the proud
title of 'Legislator of the Heavens;' he predicted transits of Mercury
and Venus, made important discoveries in optics, and was the inventor of
the astronomical telescope.
GALILEO GALILEI, the famous Italian astronomer and philosopher, and the
contemporary of Kepler and of Milton, was born at Pisa on February 15,
1564.
His father, who traced his descent from an ancient Florentine family,
was desirous that his son should adopt the profession of medicine, and
with this intention he entered him as a student at the University of
Pisa. Galileo, however, soon discovered that the study of mathematics
and mechanical science possessed a greater attraction for his mind,
and, following his inclinations, he resolved to devote his energies to
acquiring proficiency in those subjects.
In 1583 his attention was attracted by the oscillation of a brass lamp
suspended from the ceiling of the cathedral at Pisa. Galileo was
impressed with the regularity of its motion as it swung backwards and
forwards, and was led to imagine that the pendulum movement might prove
a valuable method for the correct measurement of time. The practical
application of this idea he afterwards adopted in the construction of an
astronomical clock.
Having become proficient in mathematics, Galileo, whilst engaged in
studying the writings of Archimedes, wrote an essay on 'The Hydrostatic
Balance,' and composed a treatise on 'The Centre of Gravity in Solid
Bodies.' The reputation which he earned by these contributions to
science procured for him the appointment of Lecturer on Mathematics at
the University of Pisa. Galileo next directed his attention to the works
of Aristotle, and made no attempt to conceal the disfavour with which he
regarded many of the doctrines taught by the Greek philosopher; nor had
he any difficulty in exposing their inaccuracies. One of these, which
maintained that the heavier of two bodies descended to the earth with
the greater rapidity, he proved to be incorrect, and demonstrated by
experiment from the top of the tower at Pisa that, except for the
unequal resistance of the air, all bodies fell to the ground with the
same velocity.
As the chief expounder of the new philosophy, Galileo had to encounter
the prejudices of the followers of Aristotle, and of all those who
disliked any innovation or change in the established order of things.
The antagonism which existed between Galileo and his opponents, who were
both numerous and influential, was intensified by the bitterness and
sarcasm which he imparted into his controversies, and the attitude
assumed by his enemies at last became so threatening that he deemed it
prudent to resign the Chair of Mathematics in the University of Pisa.
In the following year he was appointed to a similar post at Padua, where
his fame attracted crowds of pupils from all parts of Europe.
In 1611 Galileo visited Rome. He was received with much distinction by
the different learned societies, and was enrolled a member of the
Lyncaean Academy. In two years after his visit to the capital he
published a work in which he declared his adhesion to the Copernican
theory, and openly avowed his disbelief in the astronomical facts
recorded in the Scriptures. Galileo maintained that the sacred writings
were not intended for the purpose of imparting scientific information,
and that it was impossible for men to ignore phenomena witnessed with
their eyes, or disregard conclusions arrived at by the exercise of their
reasoning powers.
The champions of orthodoxy having become alarmed, an appeal was made to
the ecclesiastical authorities to assist in suppressing this recent
astronomical heresy, and other obnoxious doctrines, the authorship of
which was ascribed to Galileo.
In 1615, Galileo was summoned before the Inquisition to reply to the
accusation of heresy. 'He was charged with maintaining the motion of the
Earth and the stability of the Sun; with teaching this doctrine to his
pupils; with corresponding on the subject with several German
mathematicians; and with having published it, and attempted to reconcile
it to Scripture in his letters to Mark Velser in 1612.'
These charges having been formally investigated by the Inquisition,
Cardinal Bellarmine was authorised to communicate with Galileo, and
inform him that unless he renounced the obnoxious doctrines, and
promised 'neither to teach, defend, or publish them in future,' it was
decreed that he should be committed to prison. Galileo appeared next day
before the Cardinal, and, without any hesitation, pledged himself that
for the future he would adhere to the pronouncement of the Inquisition.
Having, as they imagined, silenced Galileo, the Inquisition resolved to
condemn the entire Copernican system as heretical; and in order to
effectually accomplish this, besides condemning the writings of Galileo,
they inhibited Kepler's 'Epitome of the Copernican System,' and
Copernicus's own work, 'De Revolutionibus Orbium Celestium.'
Whether it was that Galileo regarded the Inquisition as a body whose
decrees were too absurd and unreasonable to be heeded, or that he
dreaded the consequences which might have followed had he remained
obstinate, we know that, notwithstanding the pledges which he gave, he
was soon afterwards engaged in controversial discussion on those
subjects which he promised not to mention again.
On the accession of his friend Cardinal Barberini to the pontifical
throne in 1623, under the title of Urban VIII., Galileo undertook a
journey to Rome to offer him his congratulations upon his elevation to
the papal chair. He was received by his Holiness with marked attention
and kindness, was granted several prolonged audiences, and had conferred
upon him several valuable gifts.
Notwithstanding the kindness of Pope Urban and the leniency with which
he was treated by the Inquisition, Galileo, having ignored his pledge,
published in 1632 a book, in dialogue form, in which three persons were
supposed to express their scientific opinions. The first upheld the
Copernican theory and the more recent philosophical views; the second
person adopted a neutral position, suggested doubts, and made remarks of
an amusing nature; the third individual, called Simplicio, was a
believer in Ptolemy and Aristotle, and based his arguments upon the
philosophy of the ancients.
As soon as this work became publicly known, the enemies of Galileo
persuaded the Pope that the third person held up to ridicule was
intended as a representation of himself--an individual regardless of
scientific truth, and firmly attached to the ideas and opinions
associated with the writings of antiquity.
Almost immediately after the publication of the 'Dialogues' Galileo was
summoned before the Inquisition, and, notwithstanding his feeble health
and the infirmities of advanced age, he was, after a long and tedious
trial, condemned to abjure by oath on his knees his scientific beliefs.
'The ceremony of Galileo's abjuration was one of exciting interest and
of awful formality. Clothed in the sackcloth of a repentant criminal,
the venerable sage fell upon his knees before the assembled cardinals,
and, laying his hand upon the Holy Evangelists, he invoked the Divine
aid in abjuring, and detesting, and vowing never again to teach the
doctrines of the Earth's motion and of the Sun's stability. He pledged
himself that he would nevermore, either in words or in writing,
propagate such heresies; and he swore that he would fulfil and observe
the penances which had been inflicted upon him.' 'At the conclusion of
this ceremony, in which he recited his abjuration word for word and then
signed it, he was conveyed, in conformity with his sentence, to the
prison of the Inquisition.'[2]
Galileo's sarcasm, and the bitterness which he imparted into his
controversies, were more the cause of his misfortunes than his
scientific beliefs. When he became involved in difficulties he did not
possess the moral courage to enable him to abide by the consequences of
his acts; nor did he care to become a martyr for the sake of science,
his submission to the Inquisition having probably saved him from a fate
similar to what befell Bruno. Though it would be impossible to justify
Galileo's want of faith in his dealings with the Inquisition, yet one
cannot help sympathising deeply with the aged philosopher, who, in this
painful episode of his life, was compelled to go through the form of
making a retractation of his beliefs under circumstances of a most
humiliating nature.
But the persecution of Galileo did not delay the progress of scientific
inquiry nor retard the advancement of the Copernican theory, which,
after the discovery by Newton of the law of gravitation, was universally
adopted as the true theory of the solar system.
Ferdinand, Duke of Tuscany, having exerted his influence with Pope Urban
on behalf of Galileo, he was, after a few days' incarceration, released
from prison, and permission was given him to reside at Siena, where he
remained for six months. He was afterwards allowed to return to his
villa at Arcetri, and, though regarded as a prisoner of the Inquisition,
was permitted to pursue his studies unmolested for the remainder of his
days.
Galileo died at Arcetri on January 8, 1642, when in the seventy-eighth
year of his age.
Though not the inventor, he was the first to construct a refracting
telescope and apply it to astronomical research. With this instrument
he made a number of important discoveries which tended to confirm his
belief in the truthfulness of the Copernican theory.
On directing his telescope to the Sun, he discovered movable spots on
his disc, and concluded from his observation of them that the orb
rotated on his axis in about twenty-eight days. He also ascertained that
the Moon's illumination is due to reflected sunlight, and that her
surface is diversified by mountains, valleys, and plains.
On the night of January 7, 1610, Galileo discovered the four moons of
Jupiter. This discovery may be regarded as one of his most brilliant
achievements with the telescope; and, notwithstanding the improvement in
construction and size of modern instruments, no other satellite was
discovered until near midnight on September 9, 1892, when Mr. E. E.
Barnard, with the splendid telescope of the Lick Observatory, added
'another gem to the diadem of Jupiter.'
The phases of Venus and Mars, the triple form of Saturn, and the
constitution of the Milky Way, which he found to consist of a countless
multitude of stars, were additional discoveries for our knowledge of
which we are indebted to Galileo and his telescope. Galileo made many
other important discoveries in mechanical and physical science. He
detected the law of falling bodies in their accelerated motion towards
the Earth, determined the parabolic law of projectiles, and
demonstrated that matter, even if invisible, possessed the property of
weight.
In these pages a short historical description is given of the progress
made in astronomical science from an early period to the time in which
Milton lived. The discoveries of Copernicus, Kepler, and Galileo had
raised it to a position of lofty eminence, though the law of
gravitation, which accounts for the form and permanency of the planetary
orbits, still remained undiscovered. Theories formerly obscure or
conjectural were either rejected or elucidated with accuracy and
precision, and the solar system, having the Sun as its centre, with his
attendant family of planets and their satellites revolving in majestic
orbits around him, presented an impressive spectacle of order, harmony,
and design.
CHAPTER II
ASTRONOMY IN THE SEVENTEENTH CENTURY
The seventeenth century embraces the most remarkable epoch in the whole
history of astronomy. It was during this period that those wonderful
discoveries were made which have been the means of raising astronomy to
the lofty position which it now occupies among the sciences. The
unrivalled genius and patient labours of the illustrious men whose names
stand out in such prominence on the written pages of the history of this
era have rendered it one of the most interesting and elevating of
studies. Though Copernicus lived in the preceding century, yet the names
of Tycho Brahe, Kepler, Galileo, and Newton, testify to the greatness of
the discoveries that were made during this period, which have surrounded
the memories of those men with a lustre of undying fame.
Foremost among astronomers of less conspicuous eminence who made
important discoveries in this century we find the name of Huygens.
CHRISTIAN HUYGENS was born at The Hague in 1629. He was the second son
of Constantine Huygens, an eminent diplomatist, and secretary to the
Prince of Orange. Huygens studied at Leyden and Breda, and became
highly distinguished as a geometrician and scientist. He made important
investigations relative to the figure of the Earth, and wrote a learned
treatise on the cause of gravity; he also determined with greater
accuracy investigations made by Galileo regarding the accelerated motion
of bodies when subjected to the influence of that force.
Huygens admitted that the planets and their satellites attracted each
other with a force varying according to the inverse ratio of the squares
of their distances, but rejected the mutual attraction of the molecules
of matter, believing that they possessed gravity towards a central point
only, to which they were attracted. This supposition was at variance
with the Newtonian theory, which, however, was universally regarded as
the correct one.
Huygens originated the theory by which it is believed that light is
produced by the undulatory vibration of the ether; he also discovered
polarization.
Up to this time the method adopted in the construction of clocks was not
capable of producing a mechanism which measured time with sufficient
accuracy to satisfy the requirements of astronomers. Huygens endeavoured
to supply this want, and applied his mechanical ingenuity in
constructing a clock that could be relied upon to keep accurate time.
Though the pendulum motion was first adopted by Galileo, he was unable
to arrange its mechanism so that it should keep up a continuous
movement. The oscillation of the pendulum ceased after a time, and a
fresh impulse had to be applied to set it in motion. Consequently,
Galileo's clock was of no service as a timekeeper.
Huygens overcame this difficulty by so arranging the mechanism of his
clock that the balance, instead of being horizontal, was directed
perpendicularly, and prolonged downwards to form a pendulum, the
oscillations of which regulated the downward motion of the weight. This
invention, which was highly applauded, proved to be of great service
everywhere, and was especially valuable for astronomical purposes.
Huygens next directed his attention to the construction of telescopes,
and displayed much skill in the grinding and polishing of lenses. He
made several instruments superior in power and accuracy to any that
existed previously, and with one of these made some remarkable
discoveries when observing the planet Saturn.
The telescopic appearance of Saturn is one of the most beautiful in the
heavens. The planet, surrounded by two brilliant rings, and accompanied
by eight attendant moons, surpasses all the other orbs of the firmament
as an object of interest and admiration. To the naked eye, Saturn is
visible as a star of the first magnitude, and was known to the ancients
as the most remote of the planets. Travelling in space at a distance of
nearly one thousand millions of miles from the Sun, the planet
accomplishes a revolution of its mighty orbit in twenty-nine and a half
years.
Galileo was the first astronomer who directed a telescope to Saturn. He
observed that the planet presented a triform appearance, and that on
each side of the central globe there were two objects, in close contact
with it, which caused it to assume an ovoid shape. After further
observation, Galileo perceived that the lateral bodies gradually
decreased in size, until they became invisible. At the expiration of a
certain period of time they reappeared, and were observed to go through
a certain cycle of changes. By the application of increased telescopic
power it was discovered that the appendages were not of a rounded form,
but appeared as two small crescents, having their concave surfaces
directed towards the planet and their extremities in contact with it,
resembling the manner in which the handles are attached to a cup.
These objects were observed to go through a series of periodic changes.
After having become invisible, they reappeared as two luminous straight
bands, projecting from each side of the planet; during the next seven or
eight years they gradually opened out, and assumed a crescentic form;
they afterwards began to contract, and on the expiration of a similar
period, during which time they gradually decreased in size, they again
became invisible. It was perceived that the appendages completed a cycle
of their changes in about fifteen years.
In 1656, Huygens, with a telescope constructed by himself, was enabled
to solve the enigma which for so many years baffled the efforts of the
ablest astronomers. He announced his discovery in the form of a Latin
cryptograph which, when deciphered, read as follows:--
'Annulo cingitur, tenui plano, nusquam cohaerente, ad eclipticam
inclinatio.'
'The planet is surrounded by a slender flat ring everywhere distinct
from its surface, and inclined to the ecliptic.'
Huygens perceived the shadow of the ring thrown on the planet, and was
able to account in a satisfactory manner for all the phenomena observed
in connection with its variable appearance.
The true form of the ring is circular, but by us it is seen
foreshortened; consequently, when the Earth is above or below its plane,
it appears of an elliptical shape. When the position of the planet is
such that the plane of the ring passes through the Sun, the edge of the
ring only is illumined, and then it becomes invisible for a short
period. In the same manner, when the plane of the ring passes through
the Earth, the illumined edge of the ring is not of sufficient magnitude
to appear visible, but as the enlightened side of the plane becomes more
inclined towards the Earth, the ring comes again into view. When the
plane of the ring passes between the Earth and the Sun, the unillumined
side of the ring is turned towards the Earth, and during the time it
remains in this position it is invisible.
Huygens discovered the sixth satellite of Saturn (Titan), and also the
Great Nebula in Orion.
JOHANN HEVELIUS, a celebrated Prussian astronomer, was born at Dantzig
in 1611, and died in that city in 1687. He was a man of wealth, and
erected an observatory at his residence, where, for a period of forty
years, he carried out a series of astronomical observations.
He constructed a chart of the stars, and in order to complete his work,
formed nine new constellations in those spaces in the celestial vault
which were previously un-named. They are known by the names
Camelopardus, Canes Venatici, Coma Bernices, Lacerta, Leo Minor, Lynx,
Monoceros, Sextans, and Vulpecula. He also executed a chart of the
Moon's surface, wrote a description of the lunar spots, and discovered
the Libration of the Moon in Longitude.
On May 30, 1661, Hevelius observed a transit of Mercury, a description
of which he published, and included with it Horrox's treatise on the
first-recorded transit of Venus. This work, after having passed through
several hands, became the property of Hevelius, who was capable of
appreciating its merits. The manuscript was sent to him by Huygens, and
in acknowledging it he writes: 'How greatly does my Mercury exult in the
joyous prospect that he may shortly fold within his arms Horrox's long
looked-for and beloved Venus! He renders you unfeigned thanks that by
your permission this much-desired union is about to be celebrated, and
that the writer is able, with your concurrence, to introduce them both
together to the public.'
Hevelius made numerous researches on comets, and suggested that the
form of their paths might be a parabola.
GIOVANNI DOMENICO CASSINI was born at Perinaldo, near Nice, in 1625. He
studied at Genoa and Bologna, and was afterwards appointed to the Chair
of Astronomy at the latter University. He was a man of high scientific
attainments, and made many important astronomical discoveries.
In 1671 he became Director of the Royal Observatory at Paris, and
devoted a long life to trying and difficult observations, which in his
later years deprived him of his eyesight.
In 1644 Cassini proved beyond doubt that Jupiter rotated on his axis,
and also assigned his period of rotation with considerable accuracy. He
published tables of the planet's satellites, and determined their
motions from observations of their eclipses. He ascertained the periods
of rotation of Venus and Mars; executed a chart of the lunar surface,
and observed an occultation of Jupiter by the Moon.
Cassini discovered the dual nature of Saturn's ring, having perceived
that instead of one there are two concentric rings separated by a dark
space. He also discovered four of the planet's satellites--viz. Japetus,
Rhea, Dione, and Tethys. He made a near approximation to the solar
parallax by means of researches on the parallax of Mars, and
investigated some irregularities of the Moon's motion. Cassini
discovered the belts of Jupiter, and also the Zodiacal Light, and
established the coincidence of the nodes of the lunar equator and orbit.
JAQUES CASSINI, son of Giovanni, was born at Paris in 1677. He followed
in his father's footsteps, and wrote several treatises on astronomical
subjects. He investigated the period of the rotation of Venus on her
axis, and upheld the results arrived at by his father, which were
afterwards confirmed by observations made by Schroeter. Cassini made
some valuable researches with regard to the proper motion of the stars,
and demonstrated that their change of position on the celestial vault
was real, and not caused by a displacement of the ecliptic. He attempted
to ascertain the apparent diameter of Sirius, and made observations with
regard to the visibility of the stars. The Cassini family produced
several generations of eminent astronomers, whose discoveries and
investigations were of much value in advancing the science of astronomy.
OLAUS ROEMER, an eminent Danish astronomer, was born at Copenhagen
September 25, 1644. When Picard, a French astronomer, visited Denmark in
1671, for the purpose of ascertaining the exact position of
'Uranienburg,' the site of Tycho Brahe's observatory, he made the
acquaintance of Roemer, who was engaged in studying mathematics and
astronomy under Erasmus Bartolinus. Having perceived that the young man
was gifted with no ordinary degree of talent, he secured his services to
assist him in his observations, and, on the conclusion of his labours,
Picard was so much impressed with the ability displayed by Roemer, that
he invited him to accompany him to France. This invitation he accepted,
and took up his residence in the French capital, where he continued to
prosecute his astronomical studies.
In 1675 Roemer communicated to the Academy of Sciences a paper, in which
he announced his discovery of the progressive transmission of light. It
was believed that light travelled instantaneously, but Roemer was able
to demonstrate the inaccuracy of this conclusion, and determined that
light travels through space with a measurable velocity.
By diligently observing the eclipses of Jupiter's satellites, Roemer
perceived that sometimes they occurred before, and sometimes after their
predicted times. This irregularity, he discovered, depended upon the
position of the Earth with regard to Jupiter. When the Earth, in
traversing her orbit, moved round to the opposite side of the Sun,
thereby bringing Jupiter into conjunction, an eclipse occurred sixteen
minutes twenty-six seconds later than it did when Jupiter was in
opposition or nearest to the Earth. As there existed an impression that
light travelled instantaneously, it was believed that an eclipse
occurred at the moment it was perceived in the telescope. This, however,
was not so. Roemer, after a long series of observations, concluded that
the discrepancies were due to the fact that light travels with a
measurable velocity, and that it requires a greater length of time,
upwards of sixteen minutes, to traverse the additional distance--the
diameter of the Earth's orbit--which intervenes between the Earth and
Jupiter, when the planet is in conjunction, as compared with the
distance between the Earth and Jupiter, when the latter is in
opposition. This discovery of Roemer's was the means of enabling the
velocity of light to be ascertained, which, according to recent
calculations, is about 187,000 miles a second. As an acknowledgment of
the importance of his communication, Roemer was awarded a seat in the
Academy, and apartments were assigned to him at the Royal Observatory,
where he carried on his astronomical studies.
In 1681 Roemer returned to Denmark, and was appointed Professor of
Mathematics in the University of Copenhagen; he was also entrusted with
the care of the city observatory--a duty which his reputation as an
astronomer eminently qualified him to undertake. The transit
instrument--a mechanism of much importance to astronomers--was invented
by Roemer in 1690; it consists of a telescope fixed to a horizontal
axis, and adjusted so as to revolve in the plane of the meridian. It is
employed in observing the passage of the heavenly bodies across the
observer's meridian. To note accurately by means of the astronomical
clock the exact instant of time at which a celestial body crosses the
centre of the field of view is the essential part of a transit
observation. Small transit instruments are employed for taking the time
and for regulating the observatory clock, but large instruments are
used for delicate and exact observations of Right Ascensions and
Declinations of stars of different magnitudes. Meridian, and altitude
and azimuth circles, are important astronomical appliances, which owe
their existence to the inventive skill of this distinguished astronomer.
Roemer resided for many years at the observatory in the city of
Copenhagen, where he pursued his astronomical studies until the time of
his death, which occurred in 1710. He meritoriously attempted to
determine the parallax of the fixed stars; and it is said that the
astronomical calculations and observations which he left behind him were
so voluminous as to equal in number those made by Tycho Brahe, nearly
all of which perished in a great conflagration that destroyed the
observatory and a large portion of the city of Copenhagen in 1728.
Among other astronomers of this century whose names deserve recording
were Descartes and Gassendi, whose mathematical researches in their
application to astronomy were of much value; Fabricius, Torricelli, and
Maraldi, who by their observations and investigations added many facts
to the general knowledge of the science; and Bayer, to whom belongs the
distinction of having constructed the first star-atlas.
In our own country during this period astronomy was cultivated by a few
enthusiastic men, who devoted their time and talents to promoting the
advancement of the science. It, however, received no recognition as a
subject of study at any of the Universities, and no public observatory
existed in Great Britain.
Though it was not until towards the close of the century that the
attention of all Europe was directed to England in admiration of the
discoveries of the illustrious Newton, yet astronomy had its humble
votaries, and chief among those was a young clergyman of the name of
Horrox.
JEREMIAH HORROX was born at Toxteth, near Liverpool, in 1619--close on
three centuries ago. Little is known of his family. His parents have
been described as persons who occupied a humble position in life, but,
as they were able to give their son a classical education which fitted
him for one of the learned professions, it is probable they were not so
obscure as they have been represented to be.
Having received his early education at Toxteth, Horrox afterwards
proceeded to Cambridge, and was entered as a student at Emmanuel College
on May 18, 1632, when in his fourteenth year.
At the University he devoted himself to the study of classics,
especially Latin, which in those days was the language adopted by men of
learning, when engaged in writing works of a philosophical and
scientific character.
After having remained at Cambridge for three years, Horrox returned to
his native county, and was appointed curate of Hoole, a place about
eight miles distant from Preston. Hoole is described as a narrow
low-lying strip of land consisting largely of moss, and almost converted
into an island by the waters of Martin Mere on the south, and the Ribble
on the north; and, though doubtless an open and favourable situation for
astronomical observation, it could not have been attractive as a place
of residence. Yet it was here on November 24, 1639, that Horrox made his
famous observation of the first recorded transit of Venus, an occurrence
with which his name will be for ever associated.
It was while at Cambridge that Horrox first turned his attention to the
study of astronomy. His love of the sublime, and the captivating
influence exerted on his mind by the contemplation of the heavenly
bodies, induced him to adopt astronomy as a pursuit congenial to his
tastes, and capable of exercising his highest mental powers. Having this
object in view, he applied himself with much earnestness to the study of
mathematics; he had, however, to rely mainly upon his own exertions, for
at that time no branch of physical or mathematical science was taught at
Cambridge, and consequently he obtained no professional instruction.
It was so also with astronomy, which, as a science, was scarcely known
in this country; no regular record of astronomical observations was kept
by any individual observer, and no public observatory existed in England
or in France.
The disadvantages and obstacles which Horrox had to encounter may be
best described by quoting his own words. He writes: 'There were many
hindrances. The abstruse nature of the study, my inexperience and want
of means dispirited me. I was much pained not to have any one to whom I
could look for guidance, or indeed for the sympathy of companionship in
my endeavours, and I was assailed by the languor and weariness which are
inseparable from every great undertaking. What then was to be done? I
could not make the pursuit an easy one, much less increase my fortune,
and least of all imbue others with a love for astronomy; and yet to
complain of philosophy on account of its difficulties would be foolish
and unworthy. I determined, therefore, that the tediousness of study
should be overcome by industry; my poverty--failing a better method--by
patience; and that instead of a master I would use astronomical books.
Armed with these weapons I would contend successfully; and, having heard
of others acquiring knowledge without greater help, I would blush that
any one should be able to do more than I, always remembering that word
of Virgil's--
Totidem nobis animaeque manusque.
Having heard much praise bestowed upon the works of Lansberg, a Flemish
astronomer, Horrox thought it would be to his advantage to procure a
copy of his writings. This he succeeded in obtaining after some
difficulty, and devoted a considerable time to calculating Ephemerides,
based upon the Lansberg Tables, but after making a number of
computations he discovered that they were unreliable and inaccurate.
In the year 1636 Horrox made the acquaintance of William Crabtree, a
devoted astronomer, who lived at Broughton, a suburb of Manchester. A
close friendship soon existed between the two men, and they carried on
an active correspondence about matters relating to the science which
they both loved so well.
Crabtree, who was an unbeliever in Lansberg, urged Horrox to discard the
Flemish astronomer's works, and devote his talents to the study of Tycho
Brahe and Kepler. This advice led Horrox to make a more rigorous
examination of the Lansberg Tables, and after comparing them with the
observations made by Crabtree, which coincided with his own, he resolved
to renounce them. Acting on the advice of his friend, Horrox directed
his attention to the writings of Kepler. The youthful astronomer soon
realised their value, and was charmed with the accuracy of observation
and inductive reasoning displayed in the elucidation of those general
laws which constituted a new era in the history of astronomy.
The Rudolphine Tables, which were the astronomical calculations
commenced by Tycho Brahe, and completed by Kepler, were regarded by
Horrox as much superior to those of Lansberg; but it occurred to him
that they might be improved by changing some of the numbers, and yet
retaining the hypotheses. To this task he applied himself with much
earnestness and assiduity, and after close application and laborious
study he accomplished the arduous undertaking of bringing those tables
to a high state of perfection.
In his investigation of the Lunar theory, Horrox outstripped all his
predecessors, and Sir Isaac Newton distinctly affirms he was the first
to discover that the Moon's motion round the Earth is in the form of an
ellipse with the centre in the lower focus. Besides having made this
discovery, Horrox was able to explain the causes of the inequalities of
the Moon's motion, which render the exact computation of her elements so
difficult.
The Annual Equation, an irregularity discovered by Tycho Brahe, which is
produced by the increase and decrease of the Sun's disturbing force as
the Earth approaches or recedes from him in her orbit, had its value
first assigned by Horrox. This he calculated to be eleven minutes
sixteen seconds, which is within four seconds of what it has since been
proved to be by the most recent observations.
The Evection, an irregular motion of the Moon discovered by Ptolemy,
whereby her mean longitude is increased or diminished, was explained by
Horrox as depending upon the libratory motion of the apsides, and the
change which takes place in the eccentricity of the lunar orbit.
These discoveries were made by Horrox before he attained the age of
twenty years, and if his reputation had alone rested upon them his name
would have been honourably associated with those who have attained to
the highest eminence in astronomy.
Another achievement which adds lustre to Horrox's name consists in his
detection of the inequality in the mean motions of Jupiter and Saturn.
He also directed his attention to the study of cometary bodies, and
arrived at certain conclusions with regard to the nature of their
movements. At first, he believed like Kepler that comets were projected
in straight lines from the Sun; this supposition having been upheld on
account of the great elongation of their orbits. He next perceived that
their velocity increased as they approached the Sun, and decreased as
they receded from him. Afterwards he says, 'They move in an elliptic
figure or near it,' and finally he arrived at the conclusion that
'comets move in elliptical orbits, being carried round the Sun with a
velocity which is probably variable.' This theory has been verified by
numerous observations, and is now generally accepted by astronomers.
Horrox also made a series of observations on the tides. He notified the
extent of their rise and fall at different periods, and investigated
other phenomena associated with their ebb and flow. After having
continued his observations for some time, he wrote to his friend
Crabtree, and informed him that he had perceived many interesting
details which had not been previously described, and he hoped to be
able to arrive at some important conclusions with regard to their nature
and cause. Unfortunately, Horrox's writings on this subject, along with
many other important papers, have been lost or destroyed. We are
therefore ignorant of the result of his researches, which were the first
undertaken by any person for the purpose of scientific inquiry.
From his study of the Lansberg and Rudolphine Tables, Horrox arrived at
the conclusion that a transit of Venus would occur on November 24, 1639.
This transit was for some unaccountable reason overlooked by Kepler, who
predicted one in 1631, and the next not until 1761. The transit of 1631
was not visible in Europe.
We are indebted to Horrox for a description of the transit of 1639--the
first that was ever observed of which there is any record; and were it
not for the accuracy of his calculations, the occurrence of the
phenomenon would have been unperceived, and no history of the
conjunction would have been handed down to posterity. As soon as Horrox
had assured himself of the time when the transit would take place, he
wrote to Crabtree to inform him of the date, and asked him to make
observations with his telescope, and especially to examine the diameter
of the planet, which he thought had been over-estimated. He also
requested him to write to Dr. Foster of Cambridge, and inform him of the
expected event, as it was desirable that the transit should be observed
from several places in consequence of the possibility of failure, owing
to an overcast sky. His letter is dated October 26, 1639. He says: 'My
reason for now writing is to advise you of a remarkable conjunction of
the Sun and Venus on the 24th of November, when there will be a transit.
As such a thing has not happened for many years past, and will not occur
again in this century, I earnestly entreat you to watch attentively with
your telescope in order to observe it as well as you can.
'Notice particularly the diameter of Venus, which is stated by Kepler to
be seven minutes, and by Lansberg to be eleven, but which I believe to
be scarcely greater than one minute.'
In describing the method which he adopted for observing the transit,
Horrox writes as follows: 'Having attentively examined Venus with my
instrument, I described on a sheet of paper a circle, whose diameter was
nearly equal to six inches--the narrowness of the apartment not
permitting me conveniently to use a larger size. I divided the
circumference of this circle into 360 degrees in the usual manner, and
its diameter into thirty equal parts, which gives about as many minutes
as are equivalent to the Sun's apparent diameter. Each of these thirty
parts was again divided into four equal portions, making in all one
hundred and twenty; and these, if necessary, may be more minutely
subdivided. The rest I left to ocular computation, which, in such small
sections, is quite as certain as any mechanical division. Suppose,
then, each of these thirty parts to be divided into sixty seconds,
according to the practice of astronomers. When the time of the
observation approached, I retired to my apartment, and, having closed
the windows against the light, I directed my telescope--previously
adjusted to a focus--through the aperture towards the Sun, and received
his rays at right angles upon the paper already mentioned. The Sun's
image exactly filled the circle, and I watched carefully and unceasingly
for any dark body that might enter upon the disc of light.
'Although the corrected computation of Venus' motions which I had before
prepared, and on the accuracy of which I implicitly relied, forbade me
to expect anything before three o'clock in the afternoon of the 24th,
yet since, according to the calculations of most astronomers, the
conjunction should take place sooner--by some even on the 23rd--I was
unwilling to depend entirely on my own opinion, which was not
sufficiently confirmed, lest by too much self-confidence I might
endanger the observation. Anxiously intent, therefore, on the
undertaking through the greater part of the 23rd, and on the whole of
the 24th, I omitted no available opportunity of observing her ingress. I
watched carefully on the 24th from sunrise to nine o'clock, and from a
little before ten until noon, and at one in the afternoon, being called
away in the intervals by business of the highest importance, which for
these ornamental pursuits I could not with propriety neglect.[3] But
during all this time I saw nothing in the Sun except a small and common
spot, consisting as it were of three points at a distance from the
centre towards the left, which I noticed on the preceding and following
days. This evidently had nothing to do with Venus. About fifteen minutes
past three in the afternoon, when I was again at liberty to continue my
labours, the clouds, as if by divine interposition, were entirely
dispersed, and I was once more invited to the grateful task of repeating
my observations. I then beheld a most agreeable spectacle--the object of
my sanguine wishes; a spot of unusual magnitude and of a perfectly
circular shape, which had already fully entered upon the Sun's disc on
the left, so that the limbs of the Sun and Venus precisely coincided,
forming an angle of contact. Not doubting that this was really the
shadow of the planet, I immediately applied myself sedulously to observe
it.
'In the first place, with respect to the inclination, the line of the
diameter of the circle being perpendicular to the horizon, although its
plane was somewhat inclined on account of the Sun's altitude, I found
that the shadow of Venus at the aforesaid hour--namely, fifteen minutes
past three--had entered the Sun's disc about 62 deg. 30', certainly between
60 deg. and 65 deg., from the top towards the right. This was the appearance in
the dark apartment; therefore, out of doors, beneath the open sky,
according to the laws of optics, the contrary would be the case, and
Venus would be below the centre of the Sun, distant 62 deg. 30' from the
lower limbs or the nadir, as the Arabians term it. The inclination
remained to all appearances the same until sunset, when the observation
was concluded.
'In the second place, the distance between the centres of Venus and the
Sun I found by three observations to be as follows:--
The Hour. | Distance of the Centres.
|
At 3.15 by the clock | 14' 24''
" 3.35 " | 13' 30''
" 3.45 " | 13' 0''
" 3.50 the apparent sunset. |
The true setting being 3.45, and the apparent about 5 minutes later, the
difference being caused by refraction. The clock therefore was
sufficiently correct.
'In the third place I found after careful and repeated observation that
the diameter of Venus, as her shadow was depicted on the paper, was
larger indeed than the thirtieth part of the solar diameter, though not
more so than the sixth, or at the utmost the fifth of such a part.
Therefore let the diameter of the Sun be to the diameter of Venus as 30'
to 1' 12''. Certainly her diameter never equalled 1' 30'', scarcely
perhaps 1' 20'', and this was evident as well when the planet was near
the Sun's limb as when far distant from it.
[Illustration: VENUS ON THE SUN'S DISC.]
'This observation was made in an obscure village where I have long been
in the habit of observing, about fifteen miles to the north of
Liverpool, the latitude of which I believe to be 53 deg. 20', although by
common maps it is stated at 54 deg. 12', therefore the latitude of the
village will be 53 deg. 35', and longitude of both 22 deg. 30' from the
Fortunate Islands, now called the Canaries. This is 14 deg. 15' to the west
of Uraniburg in Denmark, the longitude of which is stated by Brahe, a
native of the place, to be 36 deg. 45' from these islands.
'This is all I could observe respecting this celebrated conjunction
during the short time the Sun remained in the horizon: for although
Venus continued on his disc for several hours, she was not visible to me
longer than half an hour on account of his so quickly setting.
Nevertheless, all the observations which could possibly be made in so
short a time I was enabled by Divine Providence to complete so
effectually that I could scarcely have wished for a more extended
period. The inclination was the only point upon which I failed to attain
the utmost precision; for, owing to the rapid motion of the Sun it was
difficult to observe with certainty to a single degree, and I frankly
confess that I neither did nor could ascertain it. But all the rest is
sufficiently accurate, and as exact as I could desire.'
Besides having ascertained that the diameter of Venus subtends an angle
not much greater than one minute of arc, Horrox reduced the horizontal
solar parallax from fifty-seven seconds as stated by Kepler to fourteen
seconds, a calculation within one and a half second of the value
assigned to it by Halley sixty years after. He also reduced the Sun's
semi-diameter.
Crabtree, to whom Horrox refers as 'his most esteemed friend and a
person who has few superiors in mathematical learning,' made
preparations to observe the transit similar to those already described.
But the day was unfavourable, dark clouds obscured the sky and rendered
the Sun invisible. Crabtree was in despair, and relinquished all hope of
being able to witness the conjunction. However, just before sunset there
was a break in the clouds, and the Sun shone brilliantly for a short
interval. Crabtree at once seized his opportunity, and to his intense
delight observed the planet fully entered upon the Sun's disc. Instead
of proceeding to take observations, he was so overcome with emotion at
the sight of the phenomenon, that he continued to gaze upon it with rapt
attention, nor did he recover his self-possession until the clouds again
hid from his view the setting Sun.[4]
Crabtree's observation of the transit was, however, not a fruitless one.
He drew from memory a diagram showing the exact position of Venus on the
Sun's disc, which corresponded in every respect with Horrox's
observation; he also estimated the diameter of the planet to be 7/200
that of the Sun, which when calculated gives one minute three seconds;
Horrox having found it to be one minute twelve seconds. This transit of
Venus is remarkable as having been the first ever observed of which
there is any record, and for this we are indebted to the genius of
Horrox, who by a series of calculations, displaying a wonderfully
accurate knowledge of mathematics, was enabled to predict the occurrence
of the phenomenon on the very day, and almost at the hour it appeared,
and of which he and his friend Crabtree were the only observers.
Having thought it desirable to write an account of the transit, Horrox
prepared an elegant Latin treatise, entitled 'Venus in Sole
Visa'--'Venus seen in the Sun;' but not knowing what steps to take with
regard to its publication, he requested Crabtree to communicate with his
bookseller and obtain his advice on the matter.
In the meantime Horrox returned to Toxteth, and arranged to fulfil a
long-promised visit to Crabtree, which he looked forward to with much
pleasure, as it would afford him an opportunity of discussing with his
friend many matters of interest to both. This visit was frustrated in a
manner altogether unexpected. For we read that Horrox was seized with a
sudden and severe illness, the nature of which is not known, and that
his death occurred on the day previous to that of his intended visit to
his friend at Broughton. He expired on January 3, 1641, when in the 23rd
year of his age.
His death was a great grief to Crabtree, who, in one of his letters,
describes it as 'an irreparable loss:' and it is believed that he only
survived him a few years.[5] Of the papers left by Horrox, only a few
have been preserved, and these were discovered in Crabtree's house after
his death. Among them was his treatise on the transit of Venus which,
with other papers, was purchased by Dr. Worthington, Fellow of Emmanuel
College, Cambridge, a man of learning, who was capable of appreciating
their value. Ultimately, the treatise fell into the possession of
Hevelius, a celebrated German astronomer, who published it along with a
dissertation of his own, describing a transit of Mercury.
Horrox did not live to see any of his writings published, nor was any
monument erected to his memory until nearly two hundred years after his
death. But his name, though long forgotten except by astronomers, is now
engraved on marble in Westminster Abbey. Had his life been spared, it
would have been difficult to foretell to what eminence and fame he might
have risen, or what further discoveries his genius might have enabled
him to make. Few among English astronomers will hesitate to rank him
next with the illustrious Newton, and all will agree with Herschel, who
called him 'the pride and the boast of British Astronomy.'
WILLIAM GASCOIGNE was born in 1612, in the parish of Rothwell, in the
county of York, and afterwards resided at Middleton, near Leeds.
He was a man of an inventive turn of mind, and possessed good abilities,
which he devoted to improving the methods of telescopic observation.
At an early age he was occupied in observing celestial objects, making
researches in optics, and acquiring a proficient knowledge of astronomy.
Among his acquaintances were Crabtree and Horrox, with whom he carried
on a correspondence on matters appertaining to their favourite study.
The measurement of small angles was found at all times to be one of the
greatest difficulties which astronomers had to contend with. Tycho Brahe
was so misled by his measurements of the apparent diameters of the Sun
and Moon, that he concluded a total eclipse of the Sun was impossible.
Gascoigne overcame this difficulty by his invention of the micrometer.
This instrument, when applied to a telescope, was found to be of great
service in the correct measurement of minute angles and distances, and
was the means of greatly advancing the progress of practical astronomy
in the seventeenth century. A micrometer consists of a short tube,
across the opening of which are stretched two parallel wires; these
being intersected at right angles by a third. The wires are moved to or
from each other by delicately constructed screws, to which they are
attached. Each revolution, or part of a revolution, of a screw indicates
the distance by which the wires are moved.
This apparatus, when placed in the focus of a lens, gives very accurate
measurements of the diameters of celestial objects. It was successfully
used by Gascoigne in determining the apparent diameters of the Sun,
Moon, and several of the planets, and the mutual distances of the stars
which form the Pleiades.
Crabtree, after having paid Gascoigne a visit in 1639, describes in a
letter to Horrox the impression created on his mind by the micrometer.
He writes: 'The first thing Mr. Gascoigne showed me was a large
telescope, amplified and adorned with new inventions of his own, whereby
he can take the diameters of the Sun or Moon, or any small angle in the
heavens or upon the earth, most exactly through the glass to a second.'
The micrometer is now regarded as an indispensable appliance in the
observatory; the use of a spider web reticule instead of wire having
improved its efficiency. Gascoigne was one of the earliest astronomers
who recognised the value of the Keplerian telescope for observational
purposes, and Sherburn affirms that he was the first to construct an
instrument of this description having two convex lenses. Whether this be
true or not, it is certain that he applied the micrometer to the
telescope, and was the first to use telescopic sights, by means of which
he was able to fix the optical axis of his telescope, and ascertain by
observation the apparent positions of the heavenly bodies.
Crabtree, in a letter to Gascoigne, says: 'Could I purchase it with
travel, or procure it with gold, I would not be without a telescope for
observing small angles in the heavens; or want the use of your device of
a glass in a cane upon the movable ruler of your sextant, as I remember
for helping to the exact point of the Sun's rays.'
It was not known until the beginning of the eighteenth century that
Gascoigne had invented and used telescopic sights for the purpose of
making accurate astronomical observations. The accidental discovery of
some documents which contained a description of his appliances was the
means by which this became known.
Townley states that Gascoigne had completed a treatise on optics, which
was ready for publication, but that no trace of the manuscript could be
discovered after his death. Having embraced the Royalist cause, William
Gascoigne joined the forces of Charles I., and fell in the battle of
Marston Moor on July 2, 1644.
The early death of this young and remarkably clever man was a severe
blow to the science of astronomy in England.
The invention of logarithms, by Baron Napier, of Merchistoun, was found
to be of inestimable value to astronomers in facilitating and
abbreviating the methods of astronomical calculation.
By the use of logarithms, arithmetical computations which necessitated
laborious application for several months could with ease be completed in
as many days. It was remarked by Laplace that this invention was the
means of doubling the life of an astronomer, besides enabling him to
avoid errors and the tediousness associated with long and abstruse
calculations.
THOMAS HARRIOT, an eminent mathematician, and an assiduous astronomer,
made some valuable observations of the comet of 1607. He was one of the
earliest observers who made use of the telescope, and it was claimed on
his behalf that he discovered Jupiter's satellites, and the spots on the
Sun, independently of Galileo. Other astronomers have been desirous of
sharing this honour, but it has been conclusively proved that Galileo
was the first who made those discoveries.
The investigations of Norwood and Gilbert, the mechanical genius of
Hooke, and the patient researches of Flamsteed--the first Astronomer
Royal--were of much value in perfecting many details associated with the
study of astronomy.
The Royal Observatory at Greenwich was founded in 1675. The building was
erected under a warrant from Charles II. It announces the desire of the
Sovereign to build a small observatory in the park at Greenwich, 'in
order to the finding out of the longitude for perfecting the art of
navigation and astronomy.' This action on the part of the King may be
regarded as the first public acknowledgment of the usefulness of
astronomy for national purposes.
Since its erection, the observatory has been presided over by a
succession of talented men, who have raised it to a position of eminence
and usefulness unsurpassed by any similar institution in this or any
other country. The well-known names of Flamsteed, Halley, Bradley, and
Airy, testify to the valuable services rendered by those past directors
of the Greenwich Observatory in the cause of astronomical science.
If we take a general survey of the science of astronomy as it existed
from 1608 to 1674--a period that embraced the time in which Milton
lived--we shall find that it was still compassed by ignorance,
superstition, and mystery. Astrology was zealously cultivated; most
persons of rank and position had their nativity or horoscope cast, and
the belief in the ruling of the planets, and their influence on human
and terrestrial affairs, was through long usage firmly established in
the public mind. Indeed, at this time, astronomy was regarded as a
handmaid to astrology; for, with the aid of astronomical calculation,
the professors of this occult science were enabled to predict the
positions of the planets, and by this means practised their art with an
apparent degree of truthfulness.
Although over one hundred years had elapsed since the death of
Copernicus, his theory of the solar system did not find many supporters,
and the old forms of astronomical belief still retained their hold on
the minds of the majority of philosophic thinkers. This can be partly
accounted for, as many of the Ptolemaic doctrines were at first
associated with the Copernican theory, nor was it until a later period
that they were eliminated from the system.
Though Copernicus deserved the credit of having transferred the centre
of our system from the Earth to the Sun, yet his theory was imperfect in
its details, and contained many inaccuracies. He believed that the
planets could only move round the Sun in circular paths, nor was he
capable of conceiving of any other form of orbit in which they could
perform their revolutions. He was therefore compelled to retain the use
of cycles and epicycles, in order to account for irregularities in the
uniformly circular motions of those bodies.
We are indebted to the genius of Kepler for having placed the Copernican
system upon a sure and irremovable basis, and for having raised
astronomy to the position of a true physical science. By his discovery
that the planets travel round the Sun in elliptical orbits, he was
enabled to abolish cycles and epicycles, which created such confusion
and entanglement in the system, and to explain many apparent
irregularities of motion by ascribing to the Sun his true position with
regard to the motions of the planets.
After the death of Kepler, which occurred in 1630, the most eminent
supporter of the Copernican theory was the illustrious Galileo, whose
belief in its accuracy and truthfulness was confirmed by his own
discoveries.
Five of the planets were known at this time--viz. Mercury, Venus, Mars,
Jupiter, and Saturn; the latter, which revolves in its orbit at a
profound distance from the Sun, formed what at that time was believed to
be the boundary of the planetary system. The distance of the Earth from
the Sun was approximately known, and the orb was observed to rotate on
his axis.
It was also ascertained that the Moon shone by reflected light, and that
her surface was varied by inequalities resembling those of our Earth.
The elliptical form of her orbit had been discovered by Horrox, and her
elements were computed with a certain degree of accuracy.
The cloudy luminosity of the Milky Way had been resolved into a
multitude of separate stars, disclosing the immensity of the stellar
universe.
The crescent form of the planet Venus, the satellites of Jupiter and of
Saturn, and the progressive motion and measurement of light, had also
been discovered. Observations were made of transits of Mercury and
Venus, and refracting and reflecting telescopes were invented.
The law of universal gravitation, a power which retains the Earth and
planets in their orbits, causing them year after year to describe with
unerring regularity their oval paths round the Sun, was not known at
this time. Though Newton was born in 1642, he did not disclose the
results of his philosophic investigations until 1687--thirteen years
after the death of Milton--when, in the 'Principia,' he announced his
discovery of the great law of universal gravitation.
Kepler, though he discovered the laws of planetary motion, was unable to
determine the motive force which guided and retained those bodies in
their orbits. It was reserved for the genius of Newton to solve this
wonderful problem. This great philosopher was able to prove 'that every
particle of matter in the universe attracts every other particle with a
force proportioned to the mass of the attracting body, and inversely as
the square of the distance between them.' Newton was capable of
demonstrating that the force which guides and retains the Earth and
planets in their orbits resides in the Sun, and by the application of
this law of gravitation he was able to explain the motions of all
celestial bodies entering into the structure of the solar system.
This discovery may be regarded as the crowning point of the science of
astronomy, for, upon the unfailing energy of this mysterious power
depend the order and stability of the universe, extending as it does to
all material bodies existing in space, guiding, controlling, and
retaining them in their several paths and orbits, whether it be a tiny
meteor, a circling planet, or a mighty sun.
The nature of cometary bodies and the laws which govern their motions
were at this time still enshrouded in mystery, and when one of those
erratic wanderers made its appearance in the sky it was beheld by the
majority of mankind with feelings of awe and superstitious dread, and
regarded as a harbinger of evil and disaster, the precursor of war, of
famine, or the overthrow of an empire.
Newton, however, was able to divest those bodies of the mystery with
which they were surrounded by proving that any conic section may be
described about the Sun, consistent with the law of gravitation, and
that comets, notwithstanding the eccentricity of their orbits, obey the
laws of planetary motion.
Beyond the confines of our solar system, little was known of the
magnitude and extent of the sidereal universe which occupies the
infinitude of space by which we are surrounded. The stars were
recognised as self-luminous bodies, inconceivably remote, and although
they excited the curiosity of observers, and conjectures were made as to
their origin, yet no conclusive opinions were arrived at with regard to
their nature and constitution, and except that they were regarded as
glittering points of light which illumine the firmament, all else
appertaining to them remained an unravelled mystery. Even Copernicus had
no notion of a universe of stars.
Galileo, by his discovery that the galaxy consists of a multitude of
separate stars too remote to be defined by ordinary vision, demonstrated
how vast are the dimensions of the starry heavens, and on what a
stupendous scale the universe is constructed. But at this time it had
not occurred to astronomers, nor was it known until many years after,
that the stars are suns which shine with a splendour resembling that of
our Sun, and in many instances surpassing it. It was not until this
truth became known that the glories of the sidereal heavens were fully
comprehended, and their magnificence revealed. It was then ascertained
that the minute points of light which crowd the fields of our largest
telescopes, in their aggregations forming systems, clusters, galaxies,
and universes of stars, are shining orbs of light, among the countless
multitudes of which our Sun may be numbered as one.
CHAPTER III
MILTON'S ASTRONOMICAL KNOWLEDGE
It would be reasonable to imagine that Milton's knowledge of astronomy
was comprehensive and accurate, and superior to that possessed by most
scientific men of his age. His scholarly attainments, his familiarity
with ancient history and philosophy, his profound learning, and the
universality of his general knowledge, would lead one to conclude that
the science which treats of the mechanism of the heavens, and especially
the observational part of it--which at all times has been a source of
inspiration to poets of every degree of excellence--was to him a study
of absorbing interest, and one calculated to make a deep impression upon
his devoutly poetical mind. The serious character of Milton's verse, and
the reverent manner in which celestial incidents and objects are
described in it, impress one with the belief that his contemplation of
the heavens, and of the orbs that roll and shine in the firmament
overhead, afforded him much enjoyment and meditative delight. For no
poet, in ancient or in modern times, has introduced into his writings
with such frequency, or with such pleasing effect, so many passages
descriptive of the beauty and grandeur of the heavens. No other poet,
by the creative effort of his imagination, has soared to such a height;
nor has he ever been excelled in his descriptions of the celestial orbs,
and of the beautiful phenomena associated with their different motions.
In his minor poems, which were composed during his residence at Horton,
a charming rural retreat in Buckinghamshire, where the freshness and
varied beauty of the landscape and the attractive aspects of the
midnight sky were ever before him, we find enchanting descriptions of
celestial objects, and especially of those orbs which, by their
brilliancy and lustre, have always commanded the admiration of mankind.
For example, in 'L'Allegro' there are the following lines:--
Right against the eastern gate
Where the great Sun begins his state,
Robed in flames and amber light,
The clouds in thousand liveries dight;
and in 'Il Penseroso'--
To behold the wandering Moon,
Riding near her highest noon,
Like one that had been led astray
Through the heaven's wide pathless way,
And oft as if her head she bowed,
Stooping through a fleecy cloud.
In the happy choice of his theme, and by the comprehensive manner in
which he has treated it, Milton has been enabled by his poetic genius to
give to the world in his 'Paradise Lost' a poem which, for sublimity of
thought, loftiness of imagination, and beauty of expression in metrical
verse, is unsurpassed in any language.
It is, however, our intention to deal only with those passages in the
poem in which allusion is made to the heavenly bodies, and to incidents
and occurrences associated with astronomical phenomena. In the
exposition and illustration of these it has been considered desirable to
adopt the following general classification:--
1. To ascertain the extent of Milton's astronomical knowledge.
2. To describe the starry heavens and the celestial objects mentioned in
'Paradise Lost.'
3. To exemplify the use which Milton has made of astronomy in the
exercise of his imaginative and descriptive powers.
In the earlier half of the seventeenth century the Ptolemaic theory--by
which it was believed that the Earth was the immovable centre of the
universe, and that round it all the heavenly bodies completed a diurnal
revolution--still retained its ascendency over the minds of men of
learning and science, and all the doctrines associated with this ancient
astronomical creed were still religiously upheld by the educated classes
among the peoples inhabiting the different civilised regions of the
globe. The Copernican theory--by which the Sun is assigned the central
position in our system, with the Earth and planets revolving in orbits
round him--obtained the support of a few persons of advanced views and
high scientific attainments, but its doctrines had not yet seriously
threatened the supremacy of the older system. Though upwards of one
hundred years had elapsed since the death of Copernicus, yet the
doctrines associated with the system of which he was the founder were
but very tardily adopted up to this time. There were several reasons
which accounted for this. The Copernican system was at first imperfect
in its details, and included several of the Ptolemaic, doctrines which
rendered it less intelligible, and retarded its acceptance by persons
who would otherwise have been inclined to adopt it. Copernicus believed
that the planets travelled round the Sun in circular paths. This
necessitated the retention of cycles and epicycles, which gave rise to
much confusion; nor was it until Kepler made his great discovery of the
ellipticity of the planetary orbits that they were eliminated from the
system.
As the Ptolemaic system of the universe held complete sway over the
minds of men for upwards of twenty centuries, it was difficult to
persuade many persons to renounce the astronomical beliefs to which they
were so firmly attached, in favour of those of any other system; so that
the overthrow of this venerable theory required a lengthened period of
time for its accomplishment.
It was thus in his earlier years, when Milton devoted his time to the
study of literature and philosophy, which he read extensively when
pursuing his academic career at Christ's College, Cambridge, and
afterwards at Horton, where he spent several years in acquiring a more
proficient knowledge of the literary, scientific, and philosophical
writings of the age, that he found the beliefs associated with the
Ptolemaic theory adopted without doubt or hesitation by the numerous
authors whose works he perused. His knowledge of Italian enabled him to
become familiar with Dante--one of his favourite authors, whose poetical
writings were deeply read by him, and who, in the elaboration of his
poem, the 'Divina Commedia,' included the entire Ptolemaic cosmology.
In England the Copernican theory had few supporters, and the majority of
those who represented the intellect and learning of the country still
retained their adherence to the old form of astronomical belief. We
therefore find that Milton followed the traditional way of thinking by
adopting the views associated with the Ptolemaic theory.
According to the Ptolemaic system, the Earth was regarded as the
immovable centre of the universe, and surrounding it were ten
crystalline spheres, or heavens, arranged in concentric circles, the
larger spheres enclosing the smaller ones; and within those was situated
the cosmos, or mundane universe, usually described as 'the Heavens and
the Earth.' To each of the first seven spheres there was attached a
heavenly body, which was carried round the Earth by the revolution of
the crystalline.
1st sphere: that of the Moon.
2nd sphere: that of the planet Mercury.
3rd sphere: that of the planet Venus.
4th sphere: that of the Sun; regarded as a planet.
5th sphere: that of the planet Mars.
6th sphere: that of the planet Jupiter.
7th sphere: that of the planet Saturn.
8th sphere: that of the fixed stars.
[Illustration: FIG. 1]
The eighth sphere included all the fixed stars, and was called the
firmament, because it was believed to impart steadiness to the inner
spheres, and, by its diurnal revolution, to carry them round the Earth,
causing the change of day and night.
The separate motions of the spheres, revolving with different
velocities, and at different angles to each other, accounted for the
astronomical phenomena associated with the orbs attached to each.
According to Ptolemy's scheme, the eighth sphere formed the outermost
boundary of the universe; but later astronomers added to this system two
other spheres--a _ninth_, called the _Crystalline_, which caused
Precession of the Equinoxes; and a _tenth_, called the _Primum Mobile_,
or First Moved, which brought about the alternation of day and night, by
carrying all the other spheres round the Earth once in every twenty-four
hours. The Primum Mobile enclosed, as if in a shell, all the other
spheres, in which was included the created universe, and, although of
vast dimensions, its conception did not overwhelm the mind in the same
manner that the effort to comprehend infinitude does.
Beyond this last sphere there was believed to exist a boundless,
uncircumscribed region, of immeasurable extent, called the Empyrean, or
Heaven of Heavens, the incorruptible abode of the Deity, the place of
eternal mysteries, which the comprehension of man was unable to fathom,
and of which it was impossible for his mind to form any conception. Such
were the imaginative beliefs upon which this ancient astronomical theory
was founded, that for a period of upwards of two thousand years held
undisputed sway over the minds of men, and exercised during that time a
predominating influence upon the imagination, thoughts, and conceptions
of all those who devoted themselves to literature, science, and art. Of
the truthfulness of this assertion there is ample evidence in the
poetical, philosophical, and historical writings of ancient authors,
whose ideas and conceptions regarding the created universe were limited
and circumscribed by this form of astronomical belief. In the works of
more recent writers we find that it continued to assert its influence;
and among our English poets, from Chaucer down to Shakespeare, there are
numerous references to the natural phenomena associated with this
system, and most frequently expressed by poetical allusions to 'the
music of the spheres.'
The ideas associated with the Ptolemaic theory were gratifying to the
pride and vanity of man, who could regard with complacency the paramount
importance of the globe which he inhabited, and of which he was the
absolute ruler, fixed in the centre of the universe, and surrounded by
ten revolving spheres, that carried along with them in their circuit all
other celestial bodies--Sun, Moon, and stars, which would appear to have
been created for his delectation, and for the purpose of ministering to
his requirements. But when the Copernican theory became better
understood, and especially after the discovery of the law of universal
gravitation, this venerable system of the universe, based upon a pile of
unreasonable and false hypotheses, after an existence of over twenty
centuries, sank into oblivion, and was no more heard of.
Milton's Ptolemaism is apparent in some of his shorter pieces, and also
in his minor poems, 'Arcades' and 'Comus.' His 'Ode on the Nativity' is
written in conformity with this belief, and the expression,
Ring out ye crystal spheres,
indicates a poetical allusion to this theory. But as Milton grew older
his Ptolemaism became greatly modified, and there are good reasons for
believing that in his latter years he renounced it entirely in favour of
Copernicanism. When on his continental tour in 1638, he made the
acquaintance of eminent men who held views different from those with
which he was familiar; and in his interview with Galileo at Arcetri, the
aged astronomer may have impressed upon his mind the superiority of the
Copernican theory, in accounting for the occurrence of celestial
phenomena, as compared with the Ptolemaic.
On his return to England from the Continent, Milton took up his
residence in London, and lived in apartments in a house in St. Bride's
Churchyard. Having no regular vocation, and not wishing to be dependent
upon his father, he undertook the education of his two nephews, John and
Edward Phillips, aged nine and ten years respectively. From St. Bride's
Churchyard he removed to a larger house in Aldersgate, where he received
as pupils the sons of some of his most intimate acquaintances. In the
list of subjects which Milton selected for the purpose of imparting
instruction to those youths he included astronomy and mathematics,
which formed part of the curriculum of this educational establishment.
The text-book from which he taught his nephews and other pupils
astronomy was called 'De Sphaera Mundi,' a work written by Joannes
Sacrobasco (John Holywood) in the thirteenth century. This book was an
epitome of Ptolemy's 'Almagest,' and therefore entirely Ptolemaic in its
teaching. It enjoyed great popularity during the Middle Ages, and is
reported to have gone through as many as forty editions.
The selection of astronomy as one of the subjects in which Milton
instructed his pupils affords us evidence that he must have devoted
considerable time and attention to acquiring a knowledge of the facts
and details associated with the study of the science. In the attainment
of this he had to depend upon his own exertions and the assistance
derived from astronomical books; for at this time astronomy received no
recognition as a branch of study at any of the universities; and in
Britain the science attracted less attention than on the Continent,
where the genius of Kepler and Galileo elevated it to a position of
national importance.
We shall find as we proceed that Milton's knowledge of astronomy was
comprehensive and accurate; that he was familiar with the astronomical
reasons by which many natural phenomena which occur around us can be
explained; and that he understood many of the details of the science
which are unknown to ordinary observers of the heavens.
It is remarkable how largely astronomy enters into the composition of
'Paradise Lost,' and we doubt if any author could have written such a
poem without possessing a knowledge of the heavens and of the celestial
orbs such as can only be attained by a proficient and intimate
acquaintance with this science.
The arguments in favour of or against the Ptolemaic and Copernican
theories were well known to Milton, even as regards their minute
details; and in Book viii. he introduces a scientific discussion based
upon the respective merits of those theories. The configuration of the
celestial and terrestrial spheres, and the great circles by which they
are circumscribed, he also knew. The causes which bring about the change
of the seasons; the obliquity of the ecliptic; the zodiacal
constellations through which the Sun travels, and the periods of the
year in which he occupies them, are embraced in Milton's knowledge of
the science of astronomy. The motions of the Earth, including the
Precession of the Equinoxes; the number and distinctive appearances of
the planets, their direct and retrograde courses, and their satellites,
are also described by him. The constellations, and their relative
positions on the celestial sphere; the principal stars, star-groups, and
clusters, and the Galaxy, testify to Milton's knowledge of astronomy,
and to the use which he has made of the science in the elaboration of
his poem.
The names of fourteen of the constellations are mentioned in 'Paradise
Lost.' These, when arranged alphabetically, read as follows:--
Andromeda, Aries, Astrea, Centaurus, Cancer, Capricornus, Gemini, Leo,
Libra, Ophiuchus, Orion, Scorpio, Taurus, and Virgo. Milton's allusions
to the zodiacal constellations are chiefly associated with his
description of the Sun's path in the heavens; but with the celestial
sign Libra (the _Scales_) he has introduced a lofty and poetical
conception of the means by which the Creator made known His will when
there arose a contention between Gabriel and Satan on his discovery in
Paradise.
The Eternal, to prevent such horrid fray,
Hung forth in Heaven his golden scales, yet seen
Betwixt Astrea[6] and the Scorpion sign,
Wherein all things created first he weighed,
The pendulous round Earth with balanced air
In counterpoise, now ponders all events,
Battles and realms. In these he put two weights,
The sequel each of parting and of fight:
The latter quick up flew, and kicked the beam.--iv. 996-1004.
Orion, the finest constellation in the heavens, did not escape Milton's
observation, and there is one allusion to it in his poem. It arrives on
the meridian in winter, where it is conspicuous as a brilliant
assemblage of stars, and represents an armed giant, or hunter, holding a
massive club in his right hand, and having a shield of lion's hide on
his left arm. A triple-gemmed belt encircles his waist, from which is
suspended a glittering sword, tipped with a bright star. The two
brilliants Betelgeux and Bellatrix form the giant's shoulders, and the
bright star Rigel marks the position of his advanced foot. The rising of
Orion was believed to be accompanied by stormy and tempestuous weather.
Milton alludes to this in the following lines:--
When with fierce winds Orion armed
Hath vexed the Red Sea coast, whose waves o'erthrew
Busiris and his Memphian chivalry.--i. 305-7.
Andromeda is described as being borne by Aries, and in 'Ophiuchus huge'
Milton locates a comet which extends the whole length of the
constellation. It is evident that Milton possessed a precise knowledge
of the configuration and size of the constellations, and of the
positions which they occupy relatively to each other on the celestial
sphere.
Though Milton was conversant with the Copernican theory, and entertained
a conviction of its accuracy and truthfulness, and doubtless recognised
the superiority of this system, which, besides conveying to the mind a
nobler conception of the universe and of the solar system--though it
diminished the importance of the Earth as a member of it--was capable of
explaining the occurrence of celestial phenomena in a manner more
satisfactory than could be arrived at by the Ptolemaic theory.
Notwithstanding this, he selected the Ptolemaic cosmology as the
scientific basis upon which he constructed his 'Paradise Lost,' and in
its elaboration adhered with marked fidelity to this system. There were
many reasons why Milton, in the composition of an imaginative poem,
should have chosen the Ptolemaic system of the universe rather than the
Copernican. This form of astronomical belief was adopted by all the
authors whose works he perused and studied in his younger days,
including his favourite poet, Dante; and his own poetic imaginings, as
indicated by his early poems, were in harmony with the doctrines of this
astronomical creed, a long acquaintance with which had, without doubt,
influenced his mind in its favour. This system of revolving spheres,
with the steadfast Earth at its centre, and the whole enclosed by the
Primum Mobile, constituted a more attractive and picturesque object for
poetic description than the simple and uncircumscribed arrangement of
the universe expressed by the Copernican theory. It also afforded him an
opportunity of localising those regions of space in which the chief
incidents in his poem are described--viz. HEAVEN, or THE EMPYREAN,
CHAOS, HELL, and the MUNDANE UNIVERSE. Milton's Ptolemaism, with its
adjuncts, may be understood by the following:
All that portion of space above the newly created universe, and beyond
the Primum Mobile, was known as HEAVEN, or THE EMPYREAN--a region of
light, of glory, and of happiness; the dwelling-place of the Deity, Who,
though omnipresent, here visibly revealed Himself to all the multitude
of angels whom He created, and who surrounded his throne in adoration
and worship.
Underneath the universe there existed a vast region of similar
dimensions to the Empyrean, called CHAOS, which was occupied by the
embryo elements of matter, that with incessant turmoil and confusion
warred with each other for supremacy--a wild abyss--
The womb of Nature and perhaps her grave.--ii. 911.
The lower portion of this region was divided off from the remainder, and
embraced the locality known as HELL--the place of torment, where the
rebellious angels were driven and shut in after their expulsion from
Heaven.
As far removed from God and light of Heaven
As from the centre thrice to the utmost pole.--i. 73-74.
The NEW UNIVERSE, which included the Earth and all the orbs of the
firmament known as the Starry Heavens, was created out of Chaos, and
hung, as if suspended by a golden chain, from the Empyrean above; and
although its magnitude and dimensions were inconceivable, yet, according
to the Ptolemaic theory, it was enclosed by the tenth sphere or Primum
Mobile.
By this partitioning of space Milton was able to contrive a system which
fulfilled the requirements of his great poem.
The annexed diagram explains the relative positions of the different
regions into which space was divided.
Though there are traces of Copernicanism found in 'Paradise Lost,' yet
Milton has very faithfully adhered to the Ptolemaic mechanism and
nomenclature throughout his poem.
In his description of the Creation, the Earth is formed first, then the
Sun, followed by the Moon, and afterwards the stars, all of which are
described as being in motion round the Earth. Allusion is also made to
this ancient system in several prominent passages, and in the following
lines there is a distinct reference to the various revolving spheres.
[Illustration: FIG. 2]
They pass the planets seven, and pass the fixed,
And that crystalline sphere whose balance weighs
The trepidation talked, and that first moved.--iii. 481-83.
The seven planetary spheres are first mentioned; then the eighth sphere,
or that of the fixed stars; then the ninth, or crystalline, which was
believed to cause a shaking, or trepidation, to account for certain
irregularities in the motions of the stars; and, lastly, the tenth
sphere, or Primum Mobile, called the 'first moved' because it set the
other spheres in motion.
To an uninstructed observer, the apparent motion of the heavenly bodies
round the Earth would naturally lead him to conclude that, of the two
theories, the Ptolemaic was the correct one. We therefore find that
Milton adopted the system most in accord with the knowledge and
intelligence possessed by the persons portrayed by him in his poem; and
in describing the natural phenomena witnessed in the heavens by our
first parents, he adheres to the doctrines of the Ptolemaic system, as
being most in harmony with the simple and primitive conceptions of those
created beings.
To their upward gaze, the orbs of heaven appeared to be in ceaseless
motion; the solid Earth, upon which they stood, was alone immovable and
at rest. Day after day they observed the Sun pursue his steadfast course
with unerring regularity: his rising in the east, accompanied by the
rosy hues of morn; his meridian splendour, and his sinking in the west,
tinting in colours of purple and gold inimitable the fleecy clouds
floating in the azure sky, as he bids farewell for a time to scenes of
life and happiness, rejoicing in the light and warmth of his
all-cheering beams. With the advent of night they beheld the Moon, now
increasing, now waning, pursue her irregular path, also to disappear in
the west; whilst, like the bands of an army marshalled in loose array,
the constellations of glittering stars, with stately motion, traversed
their nocturnal arcs, circling the pole of the heavens.
By referring to Book viii., 15-175, we find an account of an interesting
scientific discussion, or conversation, between Adam and Raphael
regarding the merits of the Ptolemaic and Copernican systems, and of the
relative importance and size of the heavenly bodies. By it we are
afforded an opportunity of learning how accurate and precise a knowledge
Milton possessed of both theories, and in what clear and perspicuous
language he expresses his arguments in favour of or against the
doctrines associated with each.
We may, with good reason, regard the views expressed by Adam as
representing Milton's own opinions, which were in conformity with the
Copernican theory; and in the Angel's reply, though of an undecided
character, we are able to perceive how aptly Milton describes the
erroneous conclusions upon which the Ptolemaic theory was based.
In this scientific discussion, it would seem rather strange that Adam,
the first of men, should have been capable of such philosophic
reasoning, propounding, as if by intuition, a theory upon which was
founded a system that had not been discovered until many centuries after
the time that astronomy became a science. By attributing to Adam such a
degree of intelligence and wisdom, the poet has taken a liberty which
enabled him to carry on this discussion in a manner befitting the
importance of the subject.
In the following lines Adam expresses to his Angel-guest, in forcible
and convincing language, his reasons in support of the Copernican
theory:--
When I behold this goodly frame, this World,
Of Heaven and Earth consisting, and compute
Their magnitudes--this Earth, a spot, a grain,
An atom, with the Firmament compared
And all her numbered stars, that seem to roll
Spaces incomprehensible (for such
Their distance argues, and their swift return
Diurnal) merely to officiate light
Round this opacous Earth, this punctual spot,
One day and night, in all her vast survey
Useless besides--reasoning, I oft admire,
How Nature, wise and frugal could commit
Such disproportions, with superfluous hand
So many nobler bodies to create,
Greater so manifold, to this one use,
For aught appears, and on their Orbs impose
Such restless revolution day by day
Repeated, while the sedentary Earth,
That better might with far less compass move,
Served by more noble than herself, attains
Her end without least motion, and receives,
As tribute, such a sumless journey brought
Of incorporeal speed, her warmth and light;
Speed, to describe whose swiftness number fails.--viii. 15-38.
We are enabled to perceive that Milton had formed a correct conception
of the magnitude and proportions of the universe, and also of the
relative size and importance of the Earth, which he describes as 'a
spot, a grain, an atom,' when compared with the surrounding heavens. He
expresses his surprise that all the stars of the firmament, whose
distances are so remote, and whose dimensions so greatly exceed those of
this globe, should in their diurnal revolution have 'such a sumless
journey of incorporeal speed imposed upon them' merely to officiate
light to the Earth, 'this punctual spot;' and reasoning, wonders how
Nature, wise and frugal in her ways, should commit such disproportions,
by adopting means so great to accomplish a result so small, when motion
imparted to the sedentary Earth would with greater ease produce the same
effect.
The inconceivable velocity with which it would be necessary for those
orbs to travel in order to accomplish a daily revolution round the Earth
might be described as almost spiritual, and beyond the power of
calculation by numbers.
The Angel, after listening to Adam's argument, expresses approval of his
desire to obtain knowledge, but answers him dubiously, and at the same
time criticises in a severe and adverse manner the Ptolemaic theory.
To ask or search I blame thee not; for Heaven
Is as the Book of God before thee set,
Wherein to read his wondrous works, and learn
His seasons, hours, or days, or months, or years.
This to attain, whether Heaven move or Earth,
Imports not, if thou reckon right; the rest
From Man or Angel the Great Architect
Did wisely to conceal, and not divulge
His secrets, to be scanned by them who ought
Rather admire. Or, if they list to try
Conjecture, he his fabric of the Heavens
Hath left to their disputes, perhaps to move
His laughter at their quaint opinions wide
Hereafter, when they come to model Heaven,
And calculate the stars; how they will wield
The mighty frame; how build, unbuild, contrive
To save appearances; how gird the Sphere
With Centric and Eccentric scribbled o'er
Cycle and Epicycle, Orb in Orb.--viii. 66-84.
When, with the advancement of science, astronomical observations were
made with greater accuracy, it was discovered that uniformity of motion
was not always maintained by those bodies which were believed to move in
circles round the Earth. It was observed that the Sun, when on one side
of his orbit, had an accelerated motion, as compared with the speed at
which he travelled when on the other side. The planets, also, appeared
to move with irregularity: sometimes a planet was observed to advance,
then become stationary, and afterwards affect a retrograde movement.
Those inequalities of motion could not be explained by means of the
revolution of crystalline spheres alone, but were accounted for by
imagining the existence of a small circle, or epicycle, whose centre
corresponded with a fixed point in the larger circle, or eccentric, as
it was called. This small circle revolved on its axis when carried round
with the larger one, and round it the planet also revolved, which when
situated in its outer portion would have a forward, and when in its
inner portion a retrograde, motion.
The theory of eccentrics and epicycles was sufficient for a time to
account for the inequalities of motion already described, and by this
means the Ptolemaic system was enabled to retain its ascendency for a
longer period than it otherwise would have done. But more recent
discoveries brought to light discrepancies and difficulties which were
explained away by adding epicycle to epicycle. This created a most
complicated entanglement, and hastened the downfall of a system which,
after an existence of many centuries, sank into oblivion, and is now
remembered as a belief of bygone ages.
The devices which the upholders of this system were compelled to adopt,
in order 'to save appearances,' with 'centric and eccentric,' cycle and
epicycle, 'orb in orb,' are in this manner appropriately described by
Milton, as indicating the confusion arising from a theory based upon
false hypotheses.
Continuing his reply, the Angel says:--
Already by thy reasoning this I guess,
Who art to lead thy offspring, and supposest
That bodies bright and greater should not serve
The less not bright, nor Heaven such journies run,
Earth sitting still, when she alone receives
The benefit. Consider, first, that great
Or bright infers not excellence. The Earth,
Though, in comparison of Heaven, so small,
Nor glistering, may of solid good contain
More plenty than the Sun that barren shines,
Whose virtue on itself works no effect,
But in the fruitful Earth; there first received,
His beams, inactive else, their vigour find,
Yet not to Earth are those bright luminaries
Officious, but to thee, Earth's habitant.
And, for the Heaven's wide circuit, let it speak
The Maker's high magnificence, who built
So spacious, and his line stretched out so far,
That Man may know he dwells not in his own--
An edifice too large for him to fill,
Lodged in a small partition; and the rest
Ordained for uses to his Lord best known,
The swiftness of those Circles attribute,
Though numberless, to his Omnipotence,
That to corporeal substances could add
Speed almost spiritual. Me thou think'st not slow,
Who since the morning-hour set out from Heaven
Where God resides, and ere midday arrived
In Eden--distance inexpressible
By numbers that have name. But this I urge,
Admitting motion in the Heavens, to show
Invalid that which thee to doubt it moved;
Not that I so affirm, though so it seem
To thee who hast thy dwelling here on Earth.
God, to remove his ways from human sense,
Placed Heaven from Earth so far, that earthly sight,
If it presume, might err in things too high,
And no advantage gain.--viii. 85-122.
Notwithstanding the Angel's severe criticism of the Ptolemaic system, he
does not unreservedly support the conclusions arrived at by Adam, but
endeavours to show that his reasoning may not be altogether correct. He
questions the validity of his argument that bodies of greater size and
brightness should not serve the smaller, though not bright, and that
heaven should move, while the Earth remained at rest. He argues that
great or bright infers not excellence, and that the Earth, though small,
may contain more virtue than the Sun, that 'barren shines,' whose beams
create no beneficial effect, except when directed on the fruitful
Earth. He reminds Adam that those bright luminaries minister not to the
Earth, but to himself, 'Earth's habitant,' and directs his attention to
the magnificence and extent of the surrounding universe, of which he
occupies but a small portion. The diurnal swiftness of the orbs that
move round the Earth he attributes to God's omnipotence, that to
material bodies 'could add speed almost spiritual.'
The Angel, after alluding to his rapid flight through space, suggests
that God placed heaven so far from Earth that man might not presume to
inquire into things which it would be of no advantage for him to know.
He then suddenly changes to the Copernican system, which he lucidly
describes in the following lines:--
What if the Sun
Be centre to the World, and other stars
By his attractive virtue and their own
Incited, dance about him various rounds?
Their wandering course, now high, now low, then hid,
Progressive, retrograde, or standing still,
In six thou seest; and what if, seventh to these
The planet Earth, so steadfast though she seem,
Insensibly three different motions move?
Which else to several spheres thou must ascribe,
Moved contrary with thwart obliquities,
Or save the Sun his labour, and that swift
Nocturnal and diurnal rhomb supposed
Invisible else above all stars, the wheel
Of day and night; which needs not thy belief,
If Earth, industrious of herself, fetch day
Travelling east, and with her part averse
From the Sun's beam meet night, her other part
Still luminous by his ray. What if that light,
Sent from her through the wide transpicuous air,
To the terrestrial Moon be as a star,
Enlightening her by day, as she by night
This Earth--reciprocal, if land be there,
Fields and inhabitants? Her spots thou seest
As clouds, and clouds may rain, and rain produce
Fruits in her softened soil, for some to eat
Allotted there; and other Suns, perhaps,
With their attendant Moons, thou wilt descry,
Communicating male and female light--
Which two great sexes animate the World,
Stored in each orb perhaps with some that live.
For such vast room in Nature unpossessed
By living soul, desert and desolate,
Only to shine, yet scarce to contribute
Each orb a glimpse of light, conveyed so far
Down to this habitable, which returns
Light back to them, is obvious to dispute.--viii. 122-58.
The Copernican theory, which is less complicated and more easily
understood than the Ptolemaic, is described by Milton with accuracy and
methodical skill.
The Sun having been assigned that central position in the system which
his magnitude and importance claim as his due, the planets circling in
orbits around him have their motions described in a manner indicative of
the precise knowledge which Milton acquired of this theory. At this time
the law of gravitation was unknown, and, although the ellipticity of the
orbits of the planets had been discovered by Kepler, the nature of the
motive force which guided and retained them in their paths still
remained a mystery. It was believed that the planets were whirled round
the Sun, as if by the action of magnetic fibres; a mutual attractive
influence having been supposed to exist between them and the orb,
similar to that of the opposite poles of magnets.
Milton alludes to this theory in the following lines:--
They, as they move
Their starry dance in numbers that compute
Days, months, and years, towards his all-cheering lamp
Turn swift their various motions, or are turned
By his magnetic beam.--iii. 579-83.
An important advance upon this theory was made by Horrox, who, in his
study of celestial dynamics, attributed the curvilineal motion of the
planets to the influence of two forces, one projective, the other
attractive. He illustrated this by observing the path described by a
stone when thrown obliquely into the air. He perceived that its motion
was governed by the impulse imparted to it by the hand, and also by the
attractive force of the Earth. Under these two influences, the stone
describes a graceful curve, and in its descent falls at the same angle
at which it rose. Hence arises the general law: 'When two spheres are
mutually attracted, and if not prevented by foreign influences, their
straight paths are deflected into curves concave to each other, and
corresponding with one of the sections of a cone, according to the
velocity of the revolving body. If the velocity with which the revolving
body is impelled be equal to what it would acquire by falling through
half the radius of a circle described from the centre of deflection, its
orbit will be circular; but if it be less than that quantity, its path
becomes elliptical.'
Newton afterwards embraced this law in his great principle of
gravitation, and demonstrated that the force which guides and retains
the Earth and planets in their orbits resides in the Sun. By the orb's
attractive influence a planet, after having received its first impulse,
is deflected from its original straight path, and bent towards that
luminary, and by the combined action of the projective and attractive
forces is made to describe an orbit which, if elliptical, has one of its
foci occupied by the Sun. So evenly balanced are those two forces, that
one is unable to gain any permanent ascendency over the other, and
consequently the planet traverses its orbit with unerring regularity,
and, if undisturbed by external influences, will continue in its path
for all time.
Milton describes the position of the planets in the sky as--
Now high, now low, then hid;
and their motions--
Progressive, retrograde, or standing still.
It is evident that Milton was familiar with the apparently irregular
paths pursued by the planets when observed from the Earth. He knew of
their stationary points, and also the backward loopings traced out by
them on the surface of the sphere.
If observed from the Sun, all the planets would be seen to follow their
true paths round that body; their motion would invariably lie in the
same direction, and any variation in their speed as they approached
perihelion or aphelion would be real. But the planets, when observed
from the Earth, which is itself in motion, appear to move irregularly.
Sometimes they remain stationary for a brief period, and, instead of
progressing onward, affect a retrograde movement. This irregularity of
motion is only apparent, and can be explained as a result of the
combined motions of the Earth and planets, which are travelling together
round the Sun with different velocities, and in orbits of unequal
magnitude.
In his allusion to the Copernican system the 'planet' 'Earth' is
described by Milton as seventh. This is not strictly accurate, as only
five planets were known--viz. Mercury, Venus, Mars, Jupiter, and Saturn;
but to make up the number Milton has included the Moon, which may be
regarded as the Earth's planet.
The three motions ascribed to the Earth are--(1) The diurnal rotation on
her axis; (2) her annual revolution round the Sun; (3) Precession of the
Equinoxes.
The rotation of the Earth on her axis may be likened to the spinning
motion of a top, and is the cause of the alternation of day and night.
This rotatory motion is sustained with such exact precision that, during
the past 2,000 years, it has been impossible to detect the minutest
difference in the time in which the Earth accomplishes a revolution on
her axis, and therefore the length of the sidereal day, which is 3
minutes 56 seconds shorter than the mean solar day, is invariable. In
this motion of the Earth we have a time-measuring unit which may be
regarded as absolutely correct.
The Earth completes a revolution of her orbit in 365-1/4 days. In this
period of time she accomplishes a journey of 580 millions of miles,
travelling at the average rate of 66,000 miles an hour. The change of
the seasons, and the lengthening and shortening of the day, are natural
phenomena, which occur as a consequence of the Earth's annual revolution
round the Sun. Precession is a retrograde or westerly motion of the
equinoctial points, caused by the attraction of the Sun, Moon, and
planets on the spheroidal figure of the Earth. By this movement the
poles of the Earth are made to describe a circular path in that part of
the heavens to which they point; so that, after the lapse of many years,
the star which is known as the Pole Star will not occupy the position
indicated by its name, but will be situated at a considerable distance
from the pole. These motions, Milton says, unless attributed to the
Earth, must be ascribed to several spheres crossing and thwarting each
other obliquely; but the Earth, by rotating from west to east, will of
herself fetch day, her other half, averted from the Sun's rays, being
enveloped in night. Thus saving the Sun his labour, and the 'primum
mobile,' 'that swift nocturnal and diurnal rhomb,' which carried all the
lower spheres along with it, and brought about the change of day and
night.
Milton's allusion to the occurrence of natural phenomena in the Moon
similar to those which happen on the Earth is in keeping with the
opinions entertained regarding our satellite, Galileo having imagined
that he discovered with his telescope continents and seas on the lunar
surface, which led to the belief that the Moon was the abode of
intelligent life.
... and other suns, perhaps,
With their attendant moons, thou wilt descry
Communicating male and female light.--viii. 148-50.
Milton in these lines refers to Jupiter and Saturn, and their
satellites, which had been recently discovered; those of the former by
Galileo, and four of those of the latter by Cassini. The existence of
male and female light was an idea entertained by the ancients, and which
is mentioned by Pliny. The Sun was regarded as a masculine star, and the
Moon as feminine; the light emanating from each being similarly
distinguished, and possessing different properties.
Milton supposes that, as the Earth receives light from the stars, she
returns light back to them. But in his time little was known about the
stars, nor was it ascertained how distant they are.
The Angel, in bringing to a conclusion his conversation with Adam, deems
it unadvisable to vouchsafe him a decisive reply to his inquiry
regarding the motions of celestial bodies, and in the following lines
gives a beautifully poetical summary of this elevated and philosophic
discussion:--
But whether thus these things, or whether not,
Whether the Sun, predominant in Heaven,
Rise on the Earth, or Earth rise on the Sun;
He from the east his flaming round begin,
Or she from west her silent course advance
With inoffensive pace that spinning sleeps
On her soft axle, whilst she paces even,
And bears thee soft with the smooth air along--
Solicit not thy thoughts with matters hid.--viii. 159-67.
In this scientific discourse between Adam and Raphael, in which they
discuss the structural arrangement of the heavens and the motions of
celestial bodies, we are afforded an opportunity of learning what exact
and comprehensive knowledge Milton possessed of both the Ptolemaic and
Copernican theories. The concise and accurate manner in which he
describes the doctrines belonging to each system indicates that he must
have devoted considerable time and attention to making himself master of
the details associated with both theories, which in his time were the
cause of much controversy and discussion among philosophers and men of
science.
The Ptolemaic system, with its crystalline spheres revolving round the
Earth, the addition to those of cycles and epicycles, and the heaping of
them upon each other, in order to account for phenomena associated with
the motions of celestial bodies, are concisely and accurately described.
The unreasonableness of this theory, when compared with the Copernican,
is clearly delineated by Milton where Adam is made to express his views
with regard to motion in the heavens. His argument, declared in logical
and persuasive language, demonstrates how contrary to reason it would be
to imagine that the entire heavens should revolve round the Earth to
bring about a result which could be more easily attained by imparting
motion to the Earth herself. The inconceivable velocity with which it
would be necessary for the celestial orbs to travel in order to
accomplish their daily revolution is described by him as opposed to all
reason, and entailing upon them a journey which it would be impossible
for material bodies to perform. None the less accurate is Milton's
description of the Copernican system. He describes the Sun as occupying
that position in the system which his magnitude and supreme importance
claim as his sole right, having the planets with their satellites,
That from his lordly eye keep distance due.--iii. 578,
circling in majestic orbits around him, acknowledging his controlling
power, and bending to his firm but gentle sway. Their positions, their
paths, and their motions, real and apparent, are described in flowing
and harmonious verse.
CHAPTER IV
MILTON AND GALILEO
After the death of his mother, which occurred in 1637, Milton expressed
a desire to visit the Continent, where there were many places of
interest which he often longed to see. Having obtained the consent of
his kind and indulgent father, he set out on his travels in April 1638,
accompanied by a single man-servant, and arrived in Paris, where he only
stayed a few days. During his residence in the French capital he was
introduced by Lord Scudamore, the English Ambassador at the Court of
Versailles, to Hugo Grotius, one of the most distinguished scholars and
philosophic thinkers of his age. From Paris Milton journeyed to Nice,
where he first beheld the beauty of Italian scenery and the classic
shores of the Mediterranean Sea. From Nice he sailed to Genoa and
Leghorn, and after a short stay at those places continued his journey to
Florence, one of the most interesting and picturesque of Italian cities.
Situated in the Valley of the Arno, and encircled by sloping hills
covered with luxuriant vegetation, the sides of which were studded with
residences half-hidden among the foliage of gardens and vineyards,
Florence, besides being famed for its natural beauty, was at that time
the centre of Italian culture and learning, and the abode of men eminent
in literature and science. Here Milton remained for a period of two
months, and enjoyed the friendship and hospitality of its most noted
citizens, many of whom delighted to honour their English visitor. He was
warmly welcomed by the members of the various literary academies, who
admired his compositions and conversation; the flattering encomiums
bestowed upon him by those learned societies having been amply repaid by
Milton in choice and elegant Latin verse.
Among those who resided in the vicinity of Florence was the illustrious
Galileo, who in his sorrow-stricken old age was held a prisoner of the
Inquisition for having upheld and taught scientific doctrines which were
declared to be heretical. After his abjuration he was committed to
prison, but on the intervention of influential friends was released
after a few days' incarceration, and permitted to return to his home at
Arcetri. He was, however, kept under strict surveillance, and forbidden
to leave his house or receive any of his intimate friends without having
first obtained the sanction of the ecclesiastical authorities. After
several years of close confinement at Arcetri, during which time he
suffered much from rheumatism and continued ill-health, aggravated by
grief and mental depression consequent upon the death of his favourite
daughter, Galileo applied for permission to go to Florence in order to
place himself under medical treatment. This request was granted by the
Pope subject to certain conditions, which would be communicated to him
when he presented himself at the office of the Inquisition at Florence.
These were more severe than he anticipated. He was forbidden to leave
his house or receive any of his friends there, and those injunctions
were so strictly adhered to that during Passion Week he had to obtain a
special order so that he might be able to attend mass. At the expiration
of a few months Galileo was ordered to return to Arcetri, which he never
left again.
An affliction, perhaps the most deplorable that can happen to any human
being, was added to the burden of Galileo's misfortunes and woes. A
disorder which had some years previously injured the sight of his right
eye returned in 1636. In the following year the left eye became
similarly affected, with the result that in a few months Galileo became
totally blind. His friends at first hoped that the disease was cataract,
and that some relief might be afforded by means of an operation; but it
was discovered to be an opacity of the cornea, which at his age was
considered unamenable to treatment. This sudden and unexpected calamity
was to Galileo a most deplorable occurrence, for it necessitated the
relinquishment of his favourite pursuit, which he followed with such
intense interest and delight. His friend Castelli writes: 'The noblest
eye is darkened which Nature ever made; an eye so privileged, and gifted
with such rare qualities that it may with truth be said to have seen
more than all of those eyes who are gone, and to have opened the eyes of
all who are to come.' Galileo endured his affliction with patient
resignation and fortitude, and in the following extract from a letter by
him he acknowledges the chastening hand of a Divine Providence: 'Alas!
your dear friend and servant Galileo has become totally blind, so that
this heaven, this earth, this universe, which with wonderful
observations I had enlarged a hundred and a thousand times beyond the
belief of bygone ages, henceforward for me is shrunk into the narrow
space which I myself fill in it. So it pleases God; it shall then please
me also.' The rigorous curtailment of his liberty which prompted Galileo
to head his letters, 'From my prison at Arcetri,' was relaxed when total
blindness had supervened upon the infirmities of age. Permission was
given him to receive his friends, and he was allowed to have free
intercourse with his neighbours.
Milton, during his stay at Florence, visited Galileo at Arcetri. We are
ignorant of the details of this eventful and interesting interview
between the aged and blind astronomer and the young English poet, who
afterwards immortalised his name in heroic verse, and who in his
declining years suffered from an affliction similar to that which befel
Galileo, and to which he alludes so pathetically in the following
lines:--
Thee I revisit safe,
And feel thy sovran vital lamp; but thou
Revisitest not these eyes, that roll in vain
To find thy piercing ray, and find no dawn;
So thick a drop serene hath quenched their orbs,
Or dim suffusion veiled.--iii. 21-26.
We can imagine that Galileo's astronomical views, which at that time
were the subject of much discussion among scientific men and professors
of religion, and on account of which he suffered persecution, were
eagerly discussed. It is also probable that the information communicated
by Galileo, or by some of his followers, may have persuaded Milton to
entertain a more favourable opinion of the Copernican theory. The
interesting discoveries made by Galileo with his telescope without doubt
formed a pleasant subject of conversation, and Milton enjoyed the
privilege of listening to a detailed description of these from the lips
of the aged astronomer. The telescope, its principle, its mechanism, and
the method of observing, were most probably explained to him; and we can
believe that an opportunity was afforded him of examining those in
Galileo's observatory, and of perhaps testing their magnifying power
upon some celestial object favourably situated for observation. Though
Milton has not favoured us with any details of his visit to Galileo, yet
it was one which made a lasting impression upon his mind, and was never
afterwards forgotten by him. 'There it was,' he writes, 'I found and
visited the famous Galileo, grown old, a prisoner of the Inquisition for
thinking in astronomy otherwise than the Franciscan and Dominican
licensers thought.' In years long after, when Milton, himself feeble
and blind, sat down to compose his 'Paradise Lost,' the remembrance of
the Tuscan artist and his telescope was still fresh in his memory.
By the invention of the telescope and its application to astronomical
research, a vast amount of information and additional detail have been
learned regarding the bodies which enter into the formation of the solar
system; and by its aid many new ones were also discovered. On sweeping
the heavens with the instrument, the illimitable extent of the sidereal
universe became apparent, and numberless objects of interest were
brought within the range of vision the existence of which had not been
previously imagined.
The Galilean telescope was invented in 1609. But the magnifying power of
certain lenses, and their combination in producing singular visual
effects, are alluded to in the writings of several early authors. The
value of single lenses as an aid to sight had been long known, and
spectacles were in common use in the fourteenth century. Several
mathematicians have described the wonderful optical results obtained
from glasses concave and convex, of parabolic and circular forms, and
from 'perspective glasses,' in which were embodied the principle of the
telescope. It is asserted that our countryman, Roger Bacon (1214), had
some notion of the properties of the telescope; but among those familiar
with the combination of lenses the two men who made the nearest approach
to the invention of the instrument were Baptista Porta and Gerolamo
Fracastro. The latter, who died in 1553, writes as follows: 'For which
reason those things which are seen at the bottom of water appear greater
than those which are at the top; and if anyone look through two
eye-glasses, one placed upon the other, he will see everything much
larger and nearer.' It is doubtful if Fracastro had any notion of
constructing a mechanism which might answer the purpose of a telescopic
tube. Baptista Porta (1611) is more explicit in what he describes. He
writes: 'Concave lenses show distant objects most clearly, convex those
which are nearer; whence they may be used to assist the sight. With a
concave glass distant objects will be seen, small, but distinct; with a
convex one, those near at hand, larger, but confused; if you know
_rightly_ how to combine one of each sort, you will see both far and
near objects larger and clearer.' He then goes on to say: 'I shall now
endeavour to show in what manner we may continue to recognise our
friends at the distance of several miles, and how those of weak sight
may read the most minute letters from a distance. It is an invention of
great utility, and grounded on optical principles; nor is at all
difficult of execution; but it must be so divulged as not to be
understood by the vulgar, and yet be clear to the sharp-sighted.' After
this, he proceeds to describe a mechanism the details of which are
confusing and unintelligible, nor did it appear to bear any resemblance
to a telescopic tube.
In a work published by Thomas Digges in 1591, he makes the following
allusion to his father's experiments with the lenses: 'My father, by his
continuall painfull practices, assisted with demonstrations
mathematicall, was able, and sundry times hath by proportionall glasses,
duely situate in convenient angles, not only discouered things farre
off, read letters, numbered peeces of money with the verye coyne and
superscription thereof cast by some of his freends of purpose, upon
downes in open fields; but also seuen miles off, declared what hath beene
doone at that instant in priuate places.' It must be admitted that if
Leonard Digges had not constructed a telescope, he knew how to combine
lenses by the aid of which a visual effect was created similar to that
produced by the use of the instrument.
The inventor of the telescope was a Dutchman named Hans Lippershey, who
carried on the business of a spectacle-maker in the town of Middelburg.
His discovery was purely accidental. It is said that the
instrument--which was directed towards a weather-cock on a church spire,
of which it gave a large and inverted image--was for some time exhibited
in his shop as a curiosity before its importance was recognised. The
Marquis Spinola, happening to see this philosophical toy, purchased it,
and presented it to Prince Maurice of Nassau, who imagined it might be
of service for the purpose of military reconnoitring. The value of the
invention was, however, soon realised, and in the following year
telescopes were sold in Paris. In 1609, Galileo, when on a visit to a
friend at Venice, received intelligence of the invention of an
instrument by a Dutch optician which possessed the power of causing
distant objects to appear much nearer than when observed by ordinary
vision. The accuracy of this information was confirmed by letters which
he received from Paris; and this general report, Galileo asserted, was
all he knew of the subject. Fuccarius, in a disparaging letter, says
that one of the Dutch telescopes had been brought to Venice, and that he
himself had seen it. This statement is not incompatible with Galileo's
affirmation that he had not seen the original instrument, and knew no
more about it than what had been communicated to him in the letters from
the French capital. It was insinuated by Fuccarius that Galileo had seen
the telescope at Venice, but, as he denied this, we should not hesitate
to believe in his veracity.
Immediately after his return to Padua, Galileo began to think how he
might be able to contrive an instrument with properties similar to the
one of which he had been informed; and in the following words describes
the process of reasoning by which he arrived at a successful result: 'I
argued in the following manner. The contrivance consists either of one
glass or of more--one is not sufficient, since it must be either convex,
concave, or plane. The last does not produce any sensible alteration in
objects; the concave diminishes them. It is true that the convex
magnifies, but it renders them confused and indistinct; consequently,
one glass is insufficient to produce the desired effect. Proceeding to
consider two glasses, and bearing in mind that the plane causes no
change, I determined that the instrument could not consist of the
combination of a plane glass with either of the other two. I therefore
applied myself to make experiments on combinations of the two other
kinds, and thus obtained that of which I was in search.' Galileo's
telescope consisted of two lenses--one plano-convex, the other
plano-concave, the latter being held next the eye. These he fixed in a
piece of organ pipe, which served the purpose of a tube, the glasses
being distant from each other by the difference of their focal lengths.
An exactly similar principle is adopted in the construction of an
opera-glass, which can be accurately described as a double Galilean
telescope. Galileo must be regarded as the inventor of this kind of
telescope, which in one respect differed very materially from the one
constructed by the Dutch optician. If what has been said with regard to
the _inverted_ weather-cock be true, then Lippershey's telescope was
made with two convex lenses, distant from each other by the sum of their
focal lengths, and all objects observed with it were seen inverted.
Refracting astronomical telescopes are now constructed on this
principle, it having been discovered that for observational purposes
they possess several advantages over the Galilean instrument. When
Galileo had completed his first telescope he returned with it to
Venice, where he exhibited it to his friends. The sensation created by
this small instrument, which magnified only three times, was most
extraordinary, and almost amounted to a frenzy. Crowds of the principal
citizens of Venice flocked to Galileo's house in order that they might
see the magical tube about which such wonderful reports were circulated;
and for upwards of a month he was daily occupied in describing his
invention to attentive audiences. At the expiration of this time the
Doge of Venice, Leonardo Deodati, hinted that the Senate would not be
averse to receive the telescope as a gift. Galileo readily acquiesced
with this desire, and, as an acknowledgment of his merits, a decree was
issued confirming his appointment as professor at Padua for life, and
increasing his salary from 500 to 1,000 florins. The public excitement
created by the telescope showed no signs of abatement. Sirturi mentions
that, having succeeded in constructing an instrument, he ascended the
tower of St. Mark's at Venice, hoping to be able to use it there without
interruption. He was, however, detected by a few individuals, and soon
surrounded by a crowd, which took possession of his telescope, and
detained him for several hours until their curiosity was satisfied.
Eager inquiries having been made as to where he lodged, Sirturi, fearing
a repetition of his experience in the church tower, decided to quit
Venice early next morning, and betake himself to a quieter and less
frequented neighbourhood.
The instrument was at first called Galileo's tube; the double eye-glass;
the perspective; the trunk; the cylinder. The appellation _telescope_
was given it by Demisiano.
Galileo next directed his attention to the construction of telescopes,
and applied his mechanical skill in making instruments of a larger size,
one of which magnified _eight_ times. 'And at length,' he writes,
'sparing neither labour nor expense, he completed an instrument that was
capable of magnifying more than _thirty_ times.'
Galileo now commenced an exploration of the celestial regions with his
telescope, and on carefully examining some of the heavenly bodies, made
many wonderful discoveries which added greatly to the fame and lustre of
his name.
The first celestial object to which Galileo directed his telescope was
the Moon. He was deeply interested to find how much her surface
resembled that of the Earth, and was able to perceive lofty mountain
ranges, the illumined peaks of which reflected the sunlight, whilst
their bases and sides were still enveloped in dark shadow; great plains
which he imagined were seas, valleys, elevated ridges, depressions, and
inequalities similar to what are found on our globe. Galileo believed
the Moon to be a habitable world, and concluded that the dark and
luminous portions of her surface were land and water, which reflected
with unequal intensity the light of the Sun. The followers of Aristotle
received the announcement of these discoveries with much displeasure.
They maintained that the Moon was perfectly spherical and smooth--a vast
mirror, the dark portions of which were the reflection of our
terrestrial mountains and forests--and accused Galileo 'of taking a
delight in distorting and ruining the fairest works of Nature.' He
appealed to the unequal condition of the surface of our globe, but this
was of no avail in altering their preconceived notions of the lunar
surface.
Perhaps the most important discovery made by Galileo with the telescope
was that of the four moons of Jupiter. On the night of January 7, 1610,
when engaged in observing the planet, his attention was attracted by
three small stars which appeared brighter than those in their immediate
neighbourhood. They were all in a straight line and parallel with the
ecliptic; two of them were situated to the east, and one to the west of
Jupiter. On the following night he was surprised to find all three to
the west of the planet, and nearer to each other. This caused him
considerable perplexity, and he was at a loss to understand how Jupiter
could be east of the three stars, when on the preceding night he was
observed to the west of two of them. Galileo was unable to reconcile the
altered positions of those bodies with the apparent motion of Jupiter
among the fixed stars as indicated by the astronomical tables. The next
opportunity he had of observing them was on the 10th, when two stars
only were visible, and they were to the east of the planet. As it was
impossible for Jupiter to move from west to east on January 8 and from
east to west on the 10th, he concluded that it was the motion of the
stars and not that of Jupiter which accounted for the observed
phenomena. Galileo watched the stars attentively on successive evenings
and discovered a fourth, and on observing how they changed their
positions relatively to each other he soon arrived at the conclusion
that the stars were four moons which revolved round Jupiter after the
manner in which the Moon revolves round the Earth. Having assured
himself that the four new stars were four moons that with periodical
regularity circled round the great planet, Galileo named them the
Medicean Stars in honour of his patron, Cosmo de' Medici, Grand Duke of
Tuscany. He also published an essay entitled 'Nuncius Sidereus,' or the
'Sidereal Messenger,' which contained an account of this important
discovery.
The announcement of Galileo's discovery of the four satellites of
Jupiter created a profound sensation, and its significance became at
once apparent. Aristotelians and Ptolemaists received the information
with much disfavour and incredulity, and many persons positively refused
to believe Galileo, whom they accused of inventing fables. On the other
hand, the upholders of the Copernican theory hailed it with
satisfaction, as it declared that Jupiter with his four moons
constituted a system of greater magnitude and importance than that of
our globe with her single satellite, and that consequently the Earth
could not be regarded as the centre of the universe.
When Kepler heard of this remarkable discovery, he wrote to Galileo and
expressed himself in the following characteristic manner: 'I was sitting
idle at home thinking of you, most excellent Galileo, and your letters,
when the news was brought me of the discovery of four planets by the
help of the double eye-glass. Wachenfels stopped his carriage at my door
to tell me, when such a fit of wonder seized me at a report which seemed
so very absurd, and I was thrown into such agitation at seeing an old
dispute between us decided in this way, that between his joy, my
colouring, and the laughter of both, confounded as we were by such a
novelty, we were hardly capable, he of speaking, or I of listening.... I
am so far from disbelieving in the existence of the four circumjovial
planets, that I long for a telescope to anticipate you, if possible, in
discovering two round Mars (as the proportion seems to me to require),
six or eight round Saturn, and perhaps one each round Mercury and
Venus.' The intelligence of Galileo's discoveries was received by his
opponents in a spirit entirely different from that manifested by Kepler.
The principal professor of philosophy at Padua, when requested to look
at the Moon and planets through Galileo's glass, persistently declined,
and did his utmost to persuade the Grand Duke that the four satellites
of Jupiter could not possibly exist. Francesco Sizzi, a Florentine
astronomer, argued that, as there are seven apertures in the head,
seven known metals, and seven days in the week, so there could only be
seven planets. To these absurd remarks Galileo replied by saying that,
'whatever their force might be as a reason for believing beforehand that
no more than seven planets would be discovered, they hardly seemed of
sufficient weight to destroy the new ones when actually seen.' Another
individual, named Christmann, writes: 'We are not to think that Jupiter
has four satellites given him by Nature in order, by revolving round
him, to immortalize the name of the Medici, who first had notice of the
observation. These are the dreams of idle men, who love ludicrous ideas
better than our laborious and industrious correction of the heavens.
Nature abhors so horrible a chaos, and to the truly wise such vanity is
detestable.' Martin Horky, a _protege_ of Kepler's, issued a pamphlet in
which he made a violent attack on Galileo. He says: 'I will never
concede his four new planets to that Italian from Padua though I die for
it.' He then asks the following questions, and replies to them himself:
(1) Whether they exist? (2) What they are? (3) What they are like? (4)
Why they are? 'The first question is soon disposed of by Horky's
declaring positively that he has examined the heavens with Galileo's own
glass, and that no such thing as a satellite about Jupiter exists. To
the second, he declared solemnly that he does not more surely know that
he has a soul in his body than that reflected rays are the sole cause of
Galileo's erroneous observations. In regard to the third question, he
says that these planets are like the smallest fly compared to an
elephant; and, finally, concludes on the fourth, that the only use of
them is to gratify Galileo's "thirst of gold," and to afford himself a
subject of discussion.'[7] Galileo did not condescend to take any notice
of this scurrilous production; but Horky, who imagined that he had done
something clever, sent a copy of his pamphlet to Kepler. In a few days
after he called to see him, and was received with such a storm of
indignation that he begged for mercy and implored his forgiveness.
Kepler forgave him, but insisted on his making amends. He writes: 'I
have taken him again into favour upon this preliminary condition, to
which he has agreed--that I am to show him Jupiter's satellites, _and he
is to see them_, and own that they are there.'
The evidence in support of the existence of Jupiter's satellites became
so conclusive that the opponents of Galileo were compelled to renounce
their disbelief in those bodies, whether real or pretended. The Grand
Duke, preferring to trust to his eyes rather than believe in the
arguments of the professor at Padua, observed the satellites on several
occasions, along with Galileo, at Pisa, and on his departure bestowed
upon him a gift of one thousand florins. Several of Galileo's enemies,
as a result of their observations, now arrived at the conclusion that
his discovery was incomplete, and that Jupiter had more than four
satellites in attendance upon him. Scheiner counted five, Rheita nine,
and other observers increased the number to twelve. But it was found to
be quite as hazardous to exceed the number stated by Galileo as it was
to deny the existence of any; for, when Jupiter had traversed a short
distance of his path among the fixed stars, the only bodies that
accompanied him were his four original attendants, which continued to
revolve round him with unerring regularity in every part of his orbit.
Galileo did not afford his opponents much time to oppose or controvert
with argument the discoveries made by him with the telescope before his
announcement of a new one attracted public attention from those already
known. He, however, exercised greater caution in disclosing the results
of his observations, as other persons laid claim to having made similar
discoveries prior to the time at which his were announced. He therefore
adopted a method in common use among astronomers in those days, by which
the letters in a sentence announcing a discovery were transposed so as
to form an anagram.
Galileo announced his next discovery in this manner, and which read as
follows:--
Smaismrmilme poeta leumi bvne nugttaviras.
This, when deciphered, formed the sentence:--
Altissimum planetam tergeminum observavi.
I have observed that the remotest planet is triple.
Galileo perceived that Saturn presented a triform appearance, and that,
instead of one body, there were three, all in a straight line, and
apparently in contact with each other, the middle one being larger than
the two lateral ones. In a letter to Kepler he remarked: 'Now I have
discovered a Court for Jupiter, and two servants for this old man, who
aid his steps and never quit his side.' Kepler, who excelled as an
imaginative writer, replied: 'I will not make an old man of Saturn, nor
slaves of his attendant globes; but rather let this tricorporate form be
Geryon--so shall Galileo be Hercules, and the telescope his club, armed
with which he has conquered that distant planet, and dragged him from
the remotest depths of Nature, and exposed him to the view of all.'
Continuing his observations, Galileo perceived that the two lateral
objects gradually decreased in size, and at the expiration of two years
entirely disappeared, leaving the central globe visible only. He was
unable to assign any reason for this peculiar occurrence, which caused
him much perplexity, and he expresses himself thus: 'What is to be said
concerning so strange a metamorphosis? Are the two lesser stars consumed
after the manner of the solar spots? Have they vanished and suddenly
fled? Has Saturn, perhaps, devoured his own children? Or were the
appearances, indeed, illusion or fraud, with which the glasses have so
long deceived me, as well as many others to whom I have shown them? Now,
perhaps, is the time to revive the well-nigh withered hopes of those
who, guided by more profound contemplations, have discovered the fallacy
of the new observations, and demonstrated the utter impossibility of
their existence. I do not know what to say in a case so surprising, so
unlooked-for, and so novel. The shortness of the time, the unexpected
nature of the event, the weakness of my understanding, and the fear of
being mistaken, have greatly confounded me.' After a certain interval
those bodies reappeared; but Galileo's glass was not sufficiently
powerful to enable him to ascertain their nature nor solve the mystery,
which for upwards of half a century perplexed the ablest astronomers.
The elucidation of this inexplicable phenomenon was reserved for
Christian Huygens, who, with an improved telescope of his own
construction, was able to declare that Saturn's appendages were portions
of a ring which surrounds the planet, and is everywhere distinct from
its surface.
Galileo next directed his attention to the planet Venus, and as a result
of his observations was led to communicate to the public another
anagram:--
Haec immatura a me jam frustra leguntur oy.
This, when rendered correctly, reads:--
Cynthiae figuras aemulatur mater amorum.
Venus rivals the appearances of the Moon.
The phases of Venus were one of the most interesting of Galileo's
discoveries with the telescope. When observed near inferior conjunction
the planet presents the appearance of a slender crescent, resembling
the Moon when a few days old. Travelling from this point to superior
conjunction, the illumined portion of her disc gradually increases,
until it becomes circular, like the full Moon. This changing appearance
of Venus afforded Galileo irresistible proof that the planet is an
opaque body, which derives its light from the Sun, and that it circles
round the orb--convincing evidence of the accuracy and truthfulness of
the Copernican theory.
It was in this manner that Galileo announced his discovery of the phases
of Venus, the peerless planet of our morning and evening skies, whose
slender crescent forms such a beautiful object in the telescope, and
who, as she traverses her orbit, exhibits all the varied changes of form
presented by the Moon in her monthly journey round the Earth. These
varying aspects of Venus were not unknown to Milton; and, indeed, he may
have been informed of them by Galileo in his conversation with him at
Arcetri; nor has he failed to introduce an allusion to this beautiful
phenomenon in his poem. In his description of the Creation, after the
Sun was formed, he adds:--
Hither, as to their fountain, other stars
Repairing, in their golden urns draw light,
And hence the morning planet gilds her horns.--vii. 364-66.
Galileo also discovered that the planet Mars does not always present the
appearance of a circular disc. When near opposition the full disc of the
planet is visible, but at all other times it is gibbous, and approaches
nearest to that of a half-moon when at the quadratures.
In the year 1610, on directing his telescope to the Sun, Galileo
detected dark spots on the solar disc. Similar spots, sufficiently large
to be distinguished by the naked eye, had been observed from time to
time for centuries prior to the invention of the telescope, but nothing
was known of their nature. In 1609 Kepler observed a spot on the Sun,
which he thought was the planet Mercury in conjunction with the orb; the
short time during which it was visible, in consequence of clouds having
obscured the face of the luminary, prevented him from being able to
determine the accuracy of his surmise, but since then it has been
ascertained that no transit of Mercury took place at that time, and
Kepler afterwards acknowledged that he had arrived at an erroneous
conclusion. Galileo was much puzzled in trying to find out the true
nature of the spots. At first he was led to imagine that planets like
Mercury and Venus revolved round the Sun at a short distance from the
orb, and that their dark bodies, travelling across the solar disc, gave
rise to the phenomenon of the spots. After further observation, he
ascertained that the spots were in actual contact with the Sun; that
they were irregular in shape and size, and continued to appear and
disappear. Sometimes a large spot would break up into several smaller
ones, and at other times three or four small spots would unite to form a
large one. They all had a common motion, and appeared to rotate with
the Sun, from which Galileo concluded that the orb rotated on his axis
in about twenty-eight days. Galileo believed that the spots were clouds
floating in the solar atmosphere, and that they intercepted a portion of
the light of the Sun.
The Milky Way, that wondrous zone of light which encircles the heavens,
remained for many ages a source of perplexity to ancient astronomers and
philosophers, who, in their endeavours to ascertain its nature, had
arrived at various absurd and erroneous conclusions. On directing his
telescope to this luminous tract, Galileo discovered, to his
inexpressible admiration, that it consists of a vast multitude of stars,
too minute to be visible to the naked eye. He also discerned that its
milky luminosity is created by the blended light of myriads of stars, so
remote as to be incapable of definition by his telescope. In his
'Nuncius Sidereus' he gives an account of his observations of the Galaxy
and expresses his satisfaction that he has been enabled to terminate an
ancient controversy by demonstrating to the senses the stellar structure
of the Milky Way. When engaged in exploring the celestial regions with
his telescope, Galileo observed a marked difference in the appearance of
the fixed stars, as compared with that of the planets. Each of the
latter showed a rounded disc resembling that of a small moon, but the
stars exhibited no disc, and sho
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