[56] Lockyer, _Dawn of Astronomy_, p. 196.
------------------------------------------------------------------------
It will be seen from the above that only two of these fifteen
brightest stars of Ptolemy’s still bear their Greek names, Arcturus,
and Procyon; but most of the other modern names are direct translations,
either into Latin or Arabic, of Ptolemy’s description or name for the
star, while Vega and Aldebaran have preserved their original Arabic
names (much corrupted), and Canopus and Sirius are derived from the
Egyptian. Regulus-Basiliskos apparently comes from Babylon, for the
name of this star on tablets of the second century B.C. was Shar-ru,
which means “royal.”
Ptolemy’s “Last of the River” was taken by his Arab and other
commentators to be the first-magnitude star which consequently they
named Achernar, but this was too far south to be visible at Alexandria,
though possibly he heard of it or saw it himself at Syene, where it
rose over the horizon in his times. Delambre thinks it is the same as
Fomalhaut, which already belongs to two other constellations in the
star catalogue; Brown suggests it was Theta Eridani, which may have
been brighter sixteen centuries ago. Perhaps it was the star we now
call Alpha in the Phoenix, for this lies between the last bend of the
River and the Water of Aquarius, and its magnitude is between first and
second. The stars of the Southern Cross are included by Ptolemy in the
stars about the hind feet of the Centaur, though it is difficult to
identify each one with certainty: the positions are not very accurately
given.
Ptolemy wrote also on Astrology, or as it was then called Judicial
Astronomy, and his work on the subject, which is in four books,
received the name of the _Tetrabiblios_. It seems that astrology was
not very much believed in by the Greeks, for he protests that the
influences of the stars are real, and can be known and predicted, but
allows that this part of astronomy is much more difficult than the
mathematical part, with which he had dealt in the _Syntax_, and that
it has not yet been perfected, and therefore it is sometimes slandered
as untrue. Astrologers sometimes make mistakes, like doctors, yet both
astrology and medicine are useful arts. He mentions especially the
Egyptians as practising it.
Only second in importance to the _Almagest_, and even better known in
old days, was Ptolemy’s work on Geography. In this he shows how the
size of the earth and the latitudes and longitudes of places on Earth,
can be discovered by observations of the heavens. For Earth’s diameter
he adopts the value found by Poseidonius. His terrestrial globe had a
moveable half-circle attached to the poles, which was divided into 90°
from the equator in both directions, so that by placing this against
any spot on the globe, its latitude north or south of the equator
could be immediately read off. Only half the equator was marked on
this globe, and divided into 180°, for the known part of the earth
all lay within these limits. The parallels of latitude marked were
not the same as we use, though the most northerly fell very close to
the Arctic Circle: it showed the latitude of the Island of Thule, far
away “towards the Bears,” as Ptolemy expresses it, meaning that it lay
under the constellations near the North Pole. The most southerly was
not far below the equator, and others were marked between these which
divided the known Earth into “climates,” according to the height of the
Pole and the length of the longest day in each. Among the many towns
which figured on this globe we may mention Alexandria, Rome, Athens,
Jerusalem, Florence, Cadiz, Paris, Strasburg, London, Bath. Meridians
were marked at every 5 degrees. From this globe Ptolemy shows how a
plane map may be constructed. He took Rhodes as the central meridian,
because it had a nearly central position among the “climates,” and was
the place in which Hipparchus had observed.
Ptolemy also wrote books on Optics, on the theory and construction of
Dials, and on Music!
V. RETROSPECT.
The _Almagest_ is the last word of Greek astronomy. We have seen how
from the dawn of Greek history, as far as we can trace it back in
literature, the Greeks were familiar with the skies, and how the most
ancient of their philosophers had tried, chiefly by abstract reasoning,
to discover the cause of the circling motions—never changing, never
ceasing—of sun and stars. When the seemingly unruly movements of the
planets were known, they still felt sure that there must be some
underlying principle which would bring all into harmony. Inspired by
Plato, and helped by the Egyptians, Eudoxus took the first step towards
finding this principle by careful study of the planetary motions,
and at last, after many generations of observers and mathematicians,
Ptolemy was able to describe these motions as accurately as was
possible with the methods available.
At first the heavenly bodies had been thought of as gods, then as
worlds like our own, then as spheres of ethereal fire. They were
swept round by a mighty wind, they ran on wheels, they floated in the
ether, they were set in crystal spheres; the controlling force was
the principle of number or harmony, an all-pervading World-Soul, a
host of immaterial intellectual Beings subject to one eternal First
Mover. It was also suggested that the greater part of the motions were
apparent only, that Earth was really in motion, spinning on her axis,
revolving round a Central Fire, or revolving round the Sun. But these
ideas had not enough evidence to support them when suggested. Had a
great imaginative thinker, a Pythagoras or an Aristarchus, arisen
after Ptolemy, he could have shown in detail how by assuming these
two motions the phenomena could be more simply accounted for, and he
could have made out a very good case for their probability.[57] But the
time was past then for such bold originality, and the explanation of
Aristotle was universally adopted. He, as we saw, placed the abode of
the gods, the rulers of the universe, beyond the outermost sphere, and
found the principle for which all were seeking, which should be the key
to all celestial motions, in the law of circular motion.
------------------------------------------------------------------------
[57] The changing latitudes of the planets, for instance, which gave
Ptolemy much trouble, are much more easily explained when it is granted
that they partly depend upon Earth’s motion in an orbit whose plane is
slightly inclined to the planes of their orbits.
------------------------------------------------------------------------
The Greeks had at first thought that the earth was a disc, under a
tent-like sky; then it was a cylinder, with the sky in tiers above;
then a huge hemisphere filling half the universe. But they discovered
that it was a sphere, surrounded on every side by the heavens; and they
found its true size, and that the portion of it which was known to
them was less than a quarter of its whole extent. They explained the
marvel of Earth’s remaining unsupported in space by the known facts of
gravity, arguing that the falling of every particle of earth towards
Earth’s centre proved that it was also the centre of the Universe, and
that every heavy thing tended thither by a law of nature.
They also knew the size and the distance of the moon; they realized
that the planets were all immeasurably remote, and the stars vastly
more distant still. They believed that there were great intervals
between the planets, corresponding to the differences in their periods
of revolution, but the stars were always thought of as set in a great
sphere, and therefore all at the same distance from Earth at its
centre. The relative positions of the stars on this great sphere,
and times of rising and setting of many of them had been known in
a rough way for many ages, through the familiar appearance of the
constellations, named we know not by whom; but Hipparchus measured
their positions in degrees, and was able to foretell where any star
would be in the sky for any place or time. He also discovered the
Precession of the Equinoxes, and this was thought to prove a slow
rotation of the star sphere.
Astrology was learned by the Greeks in Egypt and the East, but was
never practised with the enthusiasm shown by their teachers.
As regards the division of time, the Greeks adopted from the
Babylonians the twenty-four hour day which we still use, and their
months began with the young moon. Their year therefore had to contain
a whole number of months, and it had sometimes twelve, and sometimes
thirteen, as with the ancient Babylonians, but the system by which
this was arranged was quite different, as they did not depend upon
observations of the stars, but counted the number of days between
equinox and equinox by means of gnomons. Great difficulties were
found in trying to reconcile the lunar and solar periods. The ancient
12-month year, used in the time of Hesiod, was found to be much too
short, and alternate years of 12 and 13 months made the period too
long; then an eight-year cycle was invented, but this had to be
constantly corrected, which led to great confusion. As we have seen how
carefully Meton and Euctemon had determined the length of the tropical
year, even before the days of Eudoxus, surprise may be felt that a
calendar year was not fixed to correspond accurately with the movements
of the sun, ignoring the irreconcileable movements of the moon, but it
is difficult for us to realize in these days how wrong and strange it
seemed if a new moon occurred in the middle or at the end of a month,
instead of at the beginning. In Aristophanes’ play of _The Clouds_,
which was acted in B.C. 423, the moon was said to grumble because men
would not keep the months as she showed them:—
“Yet you will not mark your days
As she bids you, but confuse them, jumbling them all sorts of ways,
And she says the gods in chorus shower reproaches on her head,
When in bitter disappointment they go supperless to bed,
Not obtaining festal banquets duly on the festal day.”
Then Meton made his celebrated discovery that nineteen tropical years
correspond almost exactly with 235 synodic months (the difference is
in fact only a few hours), and a cycle of 19 years was arranged, which
was adopted by all Greek states and dependencies. Some of the years had
twelve and some thirteen months, and some of the months 29 and others
30 days, but all followed in a regular order, and when one cycle was
completed another was begun. The total number of days in each cycle
was 6940, and as this is only 9½ hours longer than 19 true tropical
years, it follows that the average year in the Metonic cycle was only
half an hour longer than it should have been.[58] The average month was
not quite two minutes longer than the true synodic month.
------------------------------------------------------------------------
[58] It therefore really approached more nearly the sidereal year,
although the cycle was based on the tropical year.
------------------------------------------------------------------------
An improvement even on Meton’s cycle was made by Calippus, who
proposed to correct its too great length by quadrupling the period,
and then deducting one day from the whole. This would have given a
cycle of 76 calendar years, in which the average year was 365¼ days, or
only 11¼ minutes too long. It does not seem, however, to have been ever
brought into actual use as a calendar, but Ptolemy often refers to the
Calippic epoch as a date from which to calculate celestial phenomena.
[Sidenote: Theon of Alexandria _c._ 380 A.D.]
After Ptolemy, the Alexandrian school of astronomy produced only
copyists and commentators, the last of whom was Theon, who saw his
daughter Hypatia murdered and the library burned by fanatical mobs. It
only remains for us to see how the Greek system of astronomy, brought
to so great perfection in the _Almagest_, was neglected for many
centuries, and by whom it was at length rediscovered and made to live
again.
_VI. ASTRONOMY UNDER IMPERIAL AND CHRISTIAN ROME._
B.C. 46 TO A.D. 1000.
_Vos O clarissima mundi_
_Lumina labentem cœlo quæ ducitis annum._
Georgic I.
No new school of astronomy arose under the Roman Empire, nor do we even
know of one Roman who devoted his life to the science. The genius of
this people lay in other directions, and Dante truly says:—
‘“Nature ordained in the world a place and a people
for universal command ... to wit, Rome and her
citizens or people. The which our poet too has
touched upon right subtly in the sixth [Virgil, in
the sixth book of the Æneid], introducing Anchises
admonishing Æneas, the father of the Romans, thus:—
“Others shall beat out the breathing bronze more
softly, I do well believe it! And shall draw the
living features from the marble; shall plead causes
better, and trace with the rod the movements of the
sky, and tell of the rising stars. Roman! do thou
be mindful how to sway the peoples with command.
These be thy arts: to lay upon them the custom of
peace, to spare the subject and fight down the
proud.”’[59]
------------------------------------------------------------------------
[59] _De Mon._ II. vii., “Temple Classics” edition.
------------------------------------------------------------------------
Yet there were some enthusiastic amateur astronomers in Rome, for
Cicero tells us of one who had felt old age to be no burden because he
was so eager over his astronomical studies, sitting up sometimes all
night to finish his calculations, and delighted when an eclipse he had
foretold came to pass.[60] This ardent amateur, Sulpicius Gallus by
name, had found such knowledge of practical value in his younger days,
when he was with the legions in Macedonia, for he had been able to
persuade the troops not to be alarmed by an eclipse of the moon which
was about to happen, explaining how it was due to natural causes; and
while the soldiers in the opposite camp were shrieking and moaning,
believing that the eclipse portended the death of their king, the Roman
soldiers remained quite calm. This was on the eve of the battle of
Pydna, in B.C. 168, a little before the time of Hipparchus.
------------------------------------------------------------------------
[60] _De Senectute._
------------------------------------------------------------------------
[Sidenote: Ovid B.C. 43-A.D. 17.]
[Sidenote: Virgil B.C. 70-19.]
[Sidenote: Manilius _c._ A.D. 10.]
[Sidenote: Cicero B.C. 106-43.]
In Cicero’s own life-time, and throughout the early days of the Empire,
it was the fashion to have at least a smattering of Greek astronomy.
Ovid tells legends of the constellations; Virgil, at his farm where he
lingered happily among his vines, his cattle, and his bees, studied the
varying aspects of the constellations in connection with the seasons
and the weather; Manilius wrote a long poem in five books on astronomy
and astrology; Cicero himself was quite learned in the subject, and
made a translation of Aratus, which had a great vogue.
Very popular also, both in classical and mediæval times, was his _Dream
of Scipio_, which was an imitation of Plato’s fable of the vision of
Er, in the _Republic_. The moral is that earthly fame is valueless,
since Earth itself is insignificant compared with the starry heavens,
but that those who practice virtue for its own sake shall return to
the stars whence their souls originally came. The youthful Scipio is
transported to the skies in a dream, and meets the souls of his father
and of the elder Scipio Africanus in “a radiant circle of dazzling
whiteness, which you have learned from the Greeks to call the Milky
Way.” There he sees “stars which we never saw from this place, and
their magnitudes were such as we never imagined, the smallest of which
was that which, placed upon the extremity of the heavens, but nearest
to the earth, shone with borrowed light.” But the shining globes of the
stars are so great that Earth seems to have contracted to a point, and
Scipio gazes at it, grieved.
“How long will your gaze be fixed on Earth?” cries Africanus. “Do you
not see into what temples you have entered?” and he points out nine
spheres which compose the whole universe. The outermost, in which
the stars are fixed, is most divine, and within this are seven, one
of which contains the planet called Saturn upon earth, the next the
glorious Jupiter, friendly and helpful to mankind, then Mars, ruddy
and terrible, and the next place in the middle region is held by the
sun, the leader, prince, and governor of all other luminaries, the soul
of the world, filling all things with his light. Venus and Mercury
follow him in their courses, like attendants, and in the lowest sphere
rolls the moon, kindled by his rays. Below this, all is mortal and
transitory, except the souls given to the human race by the grace of
the gods; above the moon all is eternal. Earth, which is at the centre
and forms the ninth sphere, is immoveable and below all the rest; and
all weights, by their natural gravitation, fall towards her.
Scipio then asks what is the sound which fills his ears, so loud and
yet so sweet? and he is told that he hears the music of the spheres,
which is too great for mortal ears, just as the sun is too bright for
human eyes to look upon. Yet those who make music upon Earth, with
strings or voice, like all others who follow heavenly pursuits, are
opening for themselves a path by which to return to the stars, the true
home of the soul.
[Sidenote: Strabo born _c._ B.C. 63.]
[Sidenote: Seneca B.C. 3-A.D. 65.]
[Sidenote: Pliny _c._ A.D. 23-79.]
[Sidenote: Proclus died _c._ 480 A.D.]
[Sidenote: Martianus Capella, 5th century A.D.]
[Sidenote: Simplicius 5th century A.D.]
Other famous Latin authors who wrote on astronomy were Strabo,
Seneca, and Pliny, who quote Eudoxus and Aristotle, Poseidonius, and
Hipparchus. When Ptolemy’s work was done there was no great writer to
popularize it. Three hundred years later Proclus writes a commentary
on it, and Martianus Capella mentions it, but Simplicius, in his
commentary on Aristotle’s _De Cœlo_, though he speaks of “the admirable
Ptolemy,” is evidently unacquainted with his work.
No Roman added anything new to astronomy, and the most precious parts
of their writings for the history of astronomy are some fragmentary
notes of early Greek astronomers whose original works are lost.
The practical use of astronomy for measuring time appealed, however,
to the Roman people. The most ancient Roman year (said to have been
introduced by Romulus) had only ten months, March being the first,
which explains why the ninth to the twelfth of our present months have
the names of September, October, November and December, as if they came
in the order of seventh to tenth. Two more months were added later,
and at some unknown date the old Octennial or 8-year Cycle was adopted
from the Greeks. This involved the use of intercalary months of varying
length, and the priests were entrusted with the business of arranging
them. But the priests thought it much more important that the length
of the year should suit their convenience than that it should conform
to the celestial movements, so they made it long or short according as
they approved or not of the persons holding office at the time; and by
the time of Julius Cæsar the calendar had fallen into such confusion
that March 25, which was supposed to be the date of the spring equinox,
came in the middle of winter!
[Sidenote: Julius Cæsar and Sosigenes B.C. 46.]
A drastic reform was necessary. Julius Cæsar called in the Alexandrian
astronomer Sosigenes, and gave the Empire the calendar which, with the
exception of one small reform made since, we still use. The moon was
thrown over altogether: there were to be no more intercalary months,
and every year was to be exactly like the last, except for the addition
of one day in every fourth year, so as to make the average year equal
to 365¼ days. Since the tropical solar year is only 11 minutes, 14
seconds shorter than this, many centuries would elapse before the
months of this calendar would depart from their proper seasons. March
25 was restored to the time of the vernal equinox, but the first
day of the new year was to be January 1, and Julius Cæsar gave his
own name to the old fifth month of Quintilis. Each month was to be
alternately of 31 and 30 days, except February, which would only have
its full complement of 30 days in the fourth year (Leap Year), and 29
every other year. This reform was regarded by some as an unwarrantable
interference by a despot. Cicero, when some one mentioned that the
constellation Lyra would rise at a certain hour, answered bitterly,
“Yes, if the edict allows it!”
Unfortunately, the simplicity of the scheme was a good deal spoiled
by the folly of Augustus, who could not bear that the month of his
predecessor should have 31 days while the next, the old Sextilis, which
he turned into August, named after himself, should have only 30. So he
made two months of 31 days come together, and took away a day from
February. Afterwards, Nero gave his name to April, and Domitian his to
October, but this was more than a long-suffering world could bear, and
the new names were gladly forgotten as soon as the tyrants were dead.
Although, therefore, Rome was obliged to apply to Alexandria, that is
to Greek astronomy, to carry out the project, it was Rome that gave us
the most correct and convenient calendar which exists, better in both
respects than that which had been used in Greece itself.[61]
------------------------------------------------------------------------
[61] The _average_ year was the same, 365¼ days, in the old 8-year
cycle of the Greeks, and also in the Calippic cycle, which did not come
into practical use. The average year of the Metonic cycle was longer,
and therefore departed further from the true tropical year.
------------------------------------------------------------------------
But alas! the celestial science, a willing servant as time-measurer for
the daily uses of humanity, a docile captive to adorn the triumph of
literature, was doomed to a baser servitude. It was in the early days
of the Empire, and all through the Middle Ages, that the pseudo-science
of Astrology was pursued with passion, and men spent their lives
in studying the paths of planets and positions of the stars, urged
solely by the delusive hope of being able therefrom to read the book
of fate and guide the lives of their superstitious clients. From
Chaldea, its ancient home, came the most famous astrologers, but their
art was soon learned in every country of Europe, and its professors
were sought after by peasants and kings—now reviled and banished as
impious and leagued with devils, now loaded with honours and rewards,
revered, hated, welcomed, forbidden, but always believed in. Although
when Christianity was established the seven planets could no longer
be regarded as great gods ruling over the lesser gods of the stars,
they were still thought to be mighty revealers of fate. Each had his
special attributes and influence over man: the fiery colour of Mars
no doubt suggested the warlike and hostile spirit ascribed from time
immemorial to this planet-god; the slow motion of Saturn in his distant
sphere gave an impression of a mournful morose being, the “frigida
Saturni stella” of Virgil; Venus was the planet of love; the sun, of
honour and power, and so forth. Each planet was also mysteriously
connected with a colour, and, the alchemists said, with a metal; the
sun with gold, the moon with silver, Saturn with pale heavy lead, etc.
Each also influenced a special part of the body: thus, if Mercury were
unfavourably placed at the moment of a child’s birth it would be liable
to suffer from lung-disease; the moon’s position affected the brain;
the sun’s the heart, etc.
As the planets had distinct and often contrary influences in different
positions, it was necessary, in determining a man’s fate, to consider
the aspect of the whole heavens, especially at the moment of his birth,
but horoscopes were also cast for any period in his career, past,
present, or to come, enabling him to guard against threatening evils
or bad tendencies, and to seize favourable opportunities. The method
was as follows: the sky-sphere, as it appeared at the given time and
place, was divided into twelve “houses,” by drawing meridians (called
“circles of position”) 30° apart. The house just about to rise on the
eastern horizon was called the “ascendant,” and was the first and most
important, planets situated there having more power than anywhere else;
but each house had its special significance, the second (just above the
eastern horizon) being the House of Riches, the seventh of Marriage,
the twelfth of Enemies, etc. The kind and the strength of each planet’s
influence depended mainly upon the house in which it happened to be,
and was strongest when the planet was in its own house and also in its
favourite zodiacal sign. The sun was considered to be most at home in
Leo, the moon in Cancer, and each of the other five planets owned two
of the remaining signs. Another important point was the “aspect” of the
planets with regard to one another, that is, their angular distance
apart on the sky-sphere. If Mars and Jupiter, for instance, were in
“opposition,” _i.e._ 180° apart, the portent was unfavourable, but in
“trine” or “sextile” aspect (120° or 60° apart), favourable.
It is evident that for casting horoscopes it was necessary to be able
to calculate for any given time or place the positions of the heavenly
bodies; and for this the skies must be watched, and the movements
known of the stars, of sun and moon, and of planets. To this extent,
therefore, an interest in genuine astronomy was kept alive; but on the
other hand, the system fostered belief in the overwhelming importance
of Earth in the Universe, and the existence of the heavenly bodies
for the sole purpose of ruling and foretelling human destinies: no
one cared to inquire what were the underlying laws, and what the real
nature, of the heavenly phenomena.
Closely allied to this superstitious belief in planetary influences,
was the dread of comets, meteors, and eclipses, which were everywhere
regarded as omens. It was in vain that Seneca urged the greater
importance of investigating the nature of the heavenly bodies about
which something was already known, and of trying to solve the problem
worthy of highest consideration, viz. whether the earth, as some had
asserted, was turning rapidly, or was stationary in a turning World.
His very protest, as well as his lengthy dissertation on comets, shows
how far less interesting, alike to philosophers and public, were the
ordered courses of stars and planets, than the startling apparition of
such rare objects as that great “hairy star” which, appearing suddenly
during the games instituted by Augustus after the assassination of
Julius Cæsar, was thought to be the soul of the dead Emperor. Augustus
erected a temple in its honour.
Rome, considered as the metropolis of the dominant temporal power,
failed to encourage astronomy; Rome as the centre of the spiritual
power directly discouraged it.
[Sidenote: Cosmas _c._ 540 A.D.]
[Sidenote: Augustine 354-430 A.D.]
In the fourth and fifth centuries after Christ “the old heathen
theory” that Earth is a sphere was opposed by some of the Fathers,
as inconsistent with certain expressions in the Bible; and in the
sixth an Egyptian monk, Cosmas Indicopleustes, formulated a scheme of
the Universe according to which the Jewish Tabernacle was a type and
pattern of the World. The earth is the flat oblong floor, surrounded
by four seas; these are enclosed by four massive walls which support
a roof (the firmament or sky), and above this live the angels, who
move the sun, moon, and stars across the firmament, and let down rain
through its window. This childish cosmogony, supposed to be in entire
accordance with Genesis, Isaiah, and the Psalms, bears a curious
similarity to one of the oldest “heathen theories” of all, born in the
land where Cosmas lived.[62] Saint Augustine, however, author of the
paralysing doctrine: “Nothing is to be accepted save on the authority
of Scripture,” does not seem to have considered belief in a spherical
Earth forbidden, but it was to him a matter of perfect indifference,
while he upheld as an article of faith that in no case could any
antipodean inhabitants exist. For they could not be descendants of
Adam, nor ever hear the Gospel, since everyone knew the torrid zone to
be an impossible barrier between north and south. Another favourite
Church doctrine was that Jerusalem was the centre of the earth: this
idea, which it will be remembered has a place in Dante’s cosmogony, was
based on the words in Ezekiel:[63] “This is Jerusalem: I have set it in
the midst of the nations and countries that are round about her.” Good
bishop Arculf, and other pilgrims, were shown a pillar “on the north
side of the holy places, and in the middle of the city,” which marked
the exact spot, and were told in proof of the assertion that at midday
at the summer solstice this pillar cast no shadow! How this proved its
central position is a mystery, and if true the pillar must have been
deplorably crooked, for the sun can never pass overhead in Jerusalem,
in a latitude of nearly 32° north.
------------------------------------------------------------------------
[62] See p. 45.
[63] _Ezekiel_, v. 5.
------------------------------------------------------------------------
The Church, like the State, saw that astronomy had one use, and
applied, like the State, to Greek astronomy for a calendar. It was
necessary that the ecclesiastical calendar should be luni-solar, since
Easter, which corresponds with the Jewish passover, must fall on the
Sunday following the first full moon after the Vernal Equinox. By 325
A.D., when the Council of Nice was held, at which this question was
settled, the Vernal Equinox fell on March 21 instead of March 25,
owing to the neglected eleven minutes in the Julian year. March 21 was
therefore adopted by the Church as the date of the equinox, which was
assumed to remain constant; and the old luni-solar cycle of Meton was
used, and still is used in all churches which celebrate Easter, as a
basis for the ecclesiastical calendar.
The custom of reckoning years forwards and backwards from the birth of
Christ was first introduced by a Roman abbot, Dionysius Exiguus, in the
sixth century, but it did not become general in Christian countries
until the ninth century. Dionysius adopted as the first day of the
epoch, not January 1, but March 25, the old Roman date of the vernal
equinox. This was because it was Annunciation Day, and it was a belief
of the Middle Ages that the Annunciation and also the Crucifixion
actually took place on this day, and also that the Creation began on
the same date.
[Sidenote: Martianus Capella 5th cent. A.D.]
[Sidenote: Cassiodorus _c._ 530 A.D.]
[Sidenote: Boëthius died 525.]
At the break-up of the Roman Empire some fragments of classical
learning were saved from the wreck, mainly in the text-books of the
“heathen” writers, Capella, Cassiodorus, and Boëthius. These were
preserved by the Church, now the only repository of learning. The
secular instruction given to churchmen included astronomy, for while
the “Trivium” comprised the three elementary sciences of Grammar,
Rhetoric, and Dialectic, the “Quadrivium” comprised the four advanced
sciences of Arithmetic, Astronomy, Geometry, and Music. But only a
mere smattering of the “Quadrivium” was taught in this period, and
scarcely more of astronomy than was necessary for determining the date
of Easter. The intimate knowledge and ingenious theories of the Greeks
concerning the celestial motions interested no one any more.
[Sidenote: Charlemagne 732-814.]
[Sidenote: Isidore died 636.]
[Sidenote: Bede _c._ 673-735]
[Sidenote: Fergil, 745.]
[Sidenote: Dicuil, 825]
From the seventh century, however, the ignorance began to be less
dense. Charlemagne established many schools, and there were enlightened
monks here and there—Saint Isidore of Seville, the Venerable Bede,
and Irish scholars like Fergil and Dicuil—whose teachings show that
the elements of astronomy as taught by the Greeks were not totally
forgotten everywhere. From the beginning of the ninth century all
famous monasteries had schools for laymen as well as for monks.
In Italy the darkness was never quite so deep as in northern Europe,
for traditions of classical culture never quite died out. And although
throughout the long period from Ptolemy to the end of the tenth
century, astronomy had been almost completely neglected in Europe, the
way was slowly being made plain for a great revival. The ideal Empire,
governing the whole world from the Eternal City, and the ideal Church
making all men brothers, though neither has ever existed in fact, did
so in men’s minds, as we see clearly in Dante, and both exercised a
powerful influence. The Roman Empire and the Roman Church did impress
a kind of unity on Europe as it grew: there was one civilization, one
religion, one language in which new thoughts could be conveyed to all.
Thus the ground was prepared, and whenever a new school of astronomy
should arise or be imported, it would not remain the property of one
nation surrounded by barbarians, but might at once be shared in and
advanced by the whole of Europe.
_VII. ARAB ASTRONOMY._
A.D. 750 TO 1250.
ARAB ASTRONOMY.
Once more the scene changes. While European science is at low ebb,
if we look to the banks of the Tigris, not many miles from the ruins
of ancient Babylon, we find the centre of a new and famous school of
astronomy.
[Sidenote: Al Mansur 753-775 A.D.]
From the deserts of Arabia an immense empire had arisen, which in less
than a century spread eastwards as far as India, and westwards to
Morocco and Spain. Its first capital was Damascus, but in 755, after
the defeat of the Omeyyad dynasty, the new Caliph fixed his capital
at Baghdad, the wondrous city of the Thousand and one Nights. This
Caliph was the renowned Al Mansur. To his court there came one day a
scholar from India, who was skilled in the knowledge of the stars, and
he laid before the Caliph a book which treated of things celestial and
showed how to foretell eclipses. Al Mansur was profoundly interested,
and ordered a translation of the book to be made into Arabic. The
astronomical system of the Hindus was at that time very similar to the
Greek, and there can be no doubt that Greek astronomy had found its way
to India several centuries before this.
[Sidenote: Haroun al Raschid 786-809 A.D.]
Shortly after this the writings of Greek philosophers and astronomers
were brought to the court at Baghdad. They had been carefully
preserved, copied, and translated into Syriac, by Nestorian monks in
some of the many monasteries which were founded in Persia and other
countries of the East when these heretic Christians were driven out
of Europe in the fifth century; and many of the Court physicians of
Baghdad came from a Nestorian school of medicine. Haroun al Raschid,
son of Al Mansur, gave orders for Ptolemy’s _Syntax_ to be translated
into Arabic, and it now received its name of _Almagest_: several other
translations were made later, and Aristotle was eagerly studied. This
Caliph sent an embassy to Charlemagne, and among the presents sent by
the East to the West were an elephant and a clepsydra.
[Sidenote: Al Mamun 813-833 A.D.]
Al Mamun, son and successor of Haroun Al Raschid, is said to have
learned astronomy under a Persian teacher. He also added to his
father’s library, and one of the terms of a treaty he made with
Michael, the Greek emperor, was that a collection of Greek writings
should be made throughout the empire, and forwarded (originals or
copies) to Baghdad. Moreover, he was not content with merely reading
astronomy, Greek, Persian, or Hindu: he ordered Ptolemy’s estimate
of the size of the earth to be tested, by measuring an arc of a
meridian in his own country, and he founded a splendid observatory
in the province of Baghdad. The instruments were of the same kinds
as the Alexandrian, but they were larger, and better made, and the
circles were more accurately divided. The Arab astronomers were good
observers, and among them for the first time we hear of astronomers
winning fame by skill in instrument making. Their dials were superior
to those of any other race, and they made some important improvements
in mathematics, which were immensely useful to astronomers. One great
service was the introduction of the decimal notation, which they
learned from the Hindus.
Astrology is forbidden by the Koran, but it was practised eagerly,
nevertheless, by the Arabs, who constructed tables for this purpose,
and made improvements in the methods used.
Traces of Arab contributions to astronomy survive in our words “zenith”
and “nadir,” and “almanac”; our word for a “cipher” is the Arabic
“zifra,” and indicates the main advantage of the decimal notation in
arithmetic; while “sine” is the Latin translation of an Arabic word,
and reminds us of the great improvements made in trigonometry.[64]
------------------------------------------------------------------------
[64] Arabic _gib_ = Latin _sinus_, a fold; _i.e._ the chord folded in
two.
------------------------------------------------------------------------
[Sidenote: Alfraganus _c._ 840 A.D.]
[Sidenote: Albategnius _c._ 900 A.D.]
[Sidenote: Abul Wefa 940-998.]
Among the many names of Ptolemy’s successors at Baghdad, strange and
uncouth to our ears, the three most famous are Mohammed ebn Ketir
of Fargana, Mohammed ben Geber Albatani, and Mohammed Abul Wefa al
Buzjani, which became known to the West under the shortened forms of
Alfraganus, Albategnius, and Abul Wefa.
[Sidenote: Ebn Jounis died 1009.]
Egypt too had her Arab school of astronomy, as she had had her Greek.
A little later than Abul Wefa, Ebn Jounis drew up the famous Hakemite
Tables of the sun, moon, and planets, under the patronage of the Caliph
Hakem of Cairo.
At the western end of the Arab dominions there were centres of
intellectual activity in Morocco and southern Spain. Cordova, the city
of the marvellous mosque, had also, in the tenth century, an Academy,
and a library which rivalled that of Baghdad; and here, in the midst of
almost ceaseless public strife and agitation, in a strangely mingled
atmosphere of cultured refinement unknown to the rest of Europe, and
of ferocious barbarism, of tyranny and tolerance, heroic deeds of
chivalry and treacherous intrigues, there lived and dreamed and worked
men of science and philosophers, poets, and artists.
[Sidenote: Arzachel _c._ 1080.]
[Sidenote: Averroës 1126-1198.]
[Sidenote: Al Betrugi _c._ 1150.]
[Sidenote: Abul Hazan _c._ 1200.]
The best known of the Spanish Arabs whose names are connected with
astronomy are Arzachel, who drew up the Tables of Toledo; Averroës, the
great philosopher, author of _De Substantia Orbis_, and a commentary on
Aristotle’s Metaphysics, who saw “a black spot on the sun” on the day
he had predicted a transit of Mercury; and Al Betrugi (or Alpetragius)
who wrote on the Spheres. There was also a certain Abul Hazan, a
renowned geographer, who travelled across North Africa, and made a
catalogue of 240 stars, including some not given by Ptolemy.
Of all the astronomical writings of the Arabs, one of those which
became earliest and best known in Europe was the _Elements of Astronomy
and Chronology_ of Alfraganus. This was actually used by Dante as his
favourite text-book, and he mentions it in the _Convivio_. I shall
therefore give a short account of its contents, following the edition
of Golius, printed in Arabic and Latin at Amsterdam in 1669.
In the first chapter Alfraganus gives an account of the calendars used
by different nations—Arabs and Berbers, Syrians, Romans, Persians, and
Egyptians. After this he plunges at once into a description of the
Universe, as portrayed by Ptolemy, and follows his master so closely
that his book is almost a much-abridged and simplified _Almagest_, with
a few additions, and with all the mathematics left out.
It is accepted almost without dispute among learned men, says
Alfraganus, that the sky is spherical, and rotates on two fixed poles,
one north, one south. This is proved by the observed movements of the
stars. Equally undisputed among the learned is the fact that Earth and
water together form a globe, which is surrounded by air. The spherical
form of Earth is proved by the fact that phenomena such as lunar
eclipses and shooting stars are seen at a later hour by observers in
the East, and by the changing height of stars above the horizon as one
travels north or south. Earth is at the centre of the universe, and is
but a point compared with the heavens.
There are two principal celestial motions: (1) the “prime motion” which
causes the whole sky to revolve with every celestial body, and produces
day and night; (2) the proper motions of the sun and other stars in the
opposite direction and round other poles. The great circle of the first
motion Alfraganus calls the Equator of the Day; that of the second, the
Star-bearing Circle, _i.e._ the zodiac, or more precisely, the ecliptic.
The twelve zodiacal signs are then described, with the division of
each into degrees and minutes, the positions of the equinoxes at the
beginning of Aries and Libra, and of the solstices at the beginning of
Cancer and Capricorn. The Colure is described as a great circle cutting
the zodiac (_i.e._ ecliptic) and equator at the points where they are
furthest apart (_i.e._ at the solstices). This greatest difference
was found by Ptolemy to be 23° 51′ but according to the measurement
ordered to be made by Al Mamun of pious memory, which was carried out
by a number of experts, it is 23° 35′. This value is adopted and quoted
subsequently throughout the book of Alfraganus.
Alfraganus then proceeds to explain very clearly how the movements of
sun and stars appear from different latitudes on Earth—on the equator,
at stations further north, and finally at the pole. He shows how it
happens that on the equator day and night are always of equal length,
and the sun passes exactly overhead twice a year; whereas day and night
vary more and more in length, according to season, as one travels
further north, and the sun is lower; until at last at the pole the year
consists of one long day and one equally long night, the celestial pole
is in the zenith and the celestial equator on the horizon, so that the
sky revolves like a mill-stone (_i.e._ the stars do not rise and set,
but trace out horizontal circles, like a wheel which is not upright but
flat on the ground).
The circumference of Earth, as determined by Al Mamun of glorious
memory, is 20,400 miles, and the diameter, therefore, is nearly
6500.[65] Alfraganus deduces from this the area of the whole Earth and
also of the habitable portion of Earth. The latter extends only from
the equator to 66° 25′ North, and its longitude at the equator is equal
to 180° or 10,200 miles, at the northern limit to 4080 miles. This is
divided into seven “Climates,“ as in Ptolemy’s Geography, the first
lying a little north of the equator. Alfraganus gives for each the
length of the longest day, the height of the pole above the horizon,
the extent of territory, and the principal regions and towns comprised.
He admits that south of the first climate as far as 0° is some land,
surrounded by sea, and sparsely inhabited, and north of the seventh
climate are a few towns, but these are of no account.
------------------------------------------------------------------------
[65] The Arabian mile was equal to 4000 “black cubits,” and if this is
the Egyptian and Babylonian cubit, the values are rather too large,
being in round numbers 26,500 and 8,500 English miles, instead of
25,000 and 8000.
------------------------------------------------------------------------
Our author treats next of the risings and settings of the zodiacal
signs, and of the division of the day into 24 equal or 24 “temporary”
hours (see p. 26).
After this, the unanimous opinion of wise and learned men concerning
the spheres is duly set forth in seven chapters; how there are eight
great Orbs, the smaller enclosed within the greater, the star sphere
being the outermost and largest of all; how epicycles are fixed in
these; how only the star sphere has its centre exactly in Earth,
the others being slightly eccentric; what are the positions of the
poles and centres of the great spheres and the small epicycles, their
relative sizes, and their different velocities as they turn; finally,
how well the system represents the movements of sun, moon, stars, and
planets. The moon’s mean daily motion, resulting from a wonderful
combination of five circular motions, amounts to about 13° 11′; the
sun’s is 59′, and he completes a revolution in 365¼ days “less an
insignificant fraction.” (This being a popular treatise Alfraganus
apparently thinks it unnecessary to state the length of the year
more precisely). The sluggish motion (“motus tardissimus”) of the
star sphere, which is communicated to all the rest in addition to their
own motions, is 1° in a century, according to Ptolemy, so that it
completes a revolution in 36,000 years.
Coming now to the fixed stars, their number, and brightness, Alfraganus
does not copy Ptolemy’s great catalogue, but informs us that learned
men (“sapientes”) did number all the fixed stars as far south as they
could see in the 3rd climate, and divided them according to magnitude
into six classes. “To the first class they assigned the bright and
shining stars such as Canis (Sirius) and Procyon, Vultur Cadens (Vega)
and Cor Leonis (Regulus). Stars a little less bright they called second
magnitude: such are Alfarcatein and Benet Naax,” Arab constellations
which the Latin version describes as the two bright stars of Ursa
Minor, and those brilliant ones in the tail of Ursa Major. Thus they
proceeded with the other magnitudes, the smallest measured being of the
sixth magnitude. The number of stars in each class is given, and the
total of 1022;[66] then a list of the 15 first-magnitude stars, which
are the same as Ptolemy’s (See p. 155). This is followed by a list of
the Arab “Mansions of the moon.”
------------------------------------------------------------------------
[66] The Catalogue of Hipparchus is said to have contained 1080 stars,
but Ptolemy’s has only 1022.
------------------------------------------------------------------------
[Illustration: Fig. 36. Method (erroneous) of estimating planetary
distances, described by Alfraganus.
The distance _E A_ being known, and _E p_ being assumed equal to it,
the distance _E a_ can be calculated from the known ratio _E a_: _p a_.]
So far (with the exception of the mansions of the moon) the Arab
writer has followed the Greek, but we have now reached a point where
he diverges. Ptolemy, he says, only tells us the distances and sizes
of the sun and moon, and said nothing about the other heavenly bodies;
but if we suppose the greatest distance of the moon to be the same as
the least distance of Mercury, and from this calculate his greatest
distance (for the ratio is known), and if we proceed in the same way
with Mercury and Venus, we shall find that the greatest distance
of Venus equals the least distance of the sun as given by Ptolemy.
Ptolemy’s least distance for the sun, which was totally wrong, was
1160 Earth-radii: the greatest distance of Venus, calculated in this
way from Ptolemy’s figures, was 1150. Alfraganus takes this unlucky
coincidence as an indication that there is only just sufficient space
between each sphere and the next to allow their respective epicycles
to pass one another, and upon this entirely erroneous assumption he
proceeds to lay down the distances of each planet from the earth,
and finally of the stars, which are all supposed to be at the same
distance, equal to the greatest distance of Saturn.
Who first suggested this method of estimating distances we do not know:
the first mention of it occurs in Europe in the fifth century A.D. The
following table shows the distances obtained in this way:—
GREATEST DISTANCE.
_In Semi-Diameters of Earth._
Moon 64⅛
Mercury 167
Venus 1120
Sun 1220
Mars 8876
Jupiter 14,405
Saturn and Stars 20,110
In this, the moon’s distance is approximately correct, but the sun’s
is not much more than one-twentieth of its true value. To set the
stars at a distance of only twenty thousand times Earth’s semi-diameter
seems to us to bring them very close,[67] but they would still be
beyond measurement by naked eye methods, so it is no contradiction to
Alfraganus’ earlier statement that Earth is a point compared with the
heavens.
------------------------------------------------------------------------
[67] Earth’s diameter, and even Earth’s distance from the sun, is too
small a unit. Light, travelling 186,000 miles a second, takes 4¼ years
to reach us from the nearest star.
------------------------------------------------------------------------
The Arabs also believed that they had succeeded in measuring the
apparent diameters of the planets and even of the points of light which
are all we can see of stars, so Alfraganus gives the accepted sizes of
all. I give them below in descending order of size. The modern values
in the third column show how false were the results obtained by this
mistaken method.
DIAMETER: EARTH = 1.
_Alfraganus. Modern Values._
Sun 5½ 109½
The 15 first-magnitude { Arcturus, Sirius,
stars 4¾ { Spica, and others, much
{ larger than the sun.
Jupiter 4⁹/₁₆ 11
Saturn 4½ 9
Other stars, in order of { Various. Some certainly
magnitude, 2nd to 6th ... { larger than the sun.
Mars 1⅛ ½
Earth 1 1
Venus ³/₁₀ ⁹/₁₀
Moon ⁵/₁₇ ¼
Mercury ¹/₁₈ ⅓
In the above table the size of the moon (whose parallax had been found
by the Greeks) is the only one which is nearly right. The sun is far
too small, and so are the stars. We cannot yet know with certainty the
diameter of any star, but they are all comparable with the sun, and
many are enormously larger.[68] As their distances are all different,
some of the brightest may be comparatively small, and some of the
faintest the largest of all.
------------------------------------------------------------------------
[68] It is impossible to measure the diameter of any star, even with
the help of the most powerful telescopes, but in the case of a double
star at a known distance the movement of the components as they
travel round their common centre of gravity enables us to determine
the gravitational force they exercise on each other, and thus their
combined mass; and their spectra give some idea of their density. For
instance, the mass of the double star Alpha Centauri is nearly twice
that of our sun; and as the components appear to be about equal to
each other, and both show a spectrum resembling that of the sun, we
may conclude that Alpha Centauri consists of two stars, each of which
has about the same diameter as our sun. Arcturus has a diameter far
greater, some say ten times, some not less than twenty-five times as
great as the sun!
------------------------------------------------------------------------
The Arabs took a backward step in adopting these imaginary
measurements, for Hipparchus had recognized that only the moon was near
enough to measure, and although Ptolemy accepted Aristarchus’ value for
the sun, he distinctly stated that the planets had no parallaxes and he
could not tell their distances.
The next four chapters describe briefly the risings, settings, and
meridian transits of stars as seen from different latitudes on Earth;
the heliacal risings and settings and the conjunctions with the sun
of planets, stars, and moon: the phases of the moon and the direction
of her horns at different times of the year. Parallax is then clearly
defined and discussed.
A description follows of the earth’s shadow, thrown by the sun into
space—its tapering form, its position, always pointing away from the
sun, its width at the distance of the moon, and its length according
to Ptolemy. This is stated to be 268 times Earth’s semi-diameter,
which is nearly correct,[69] for although Alfraganus believed (from
Ptolemy’s erroneous parallax) that the sun, was much nearer than it
really is, it followed from this—since the size was deduced from
the distance—that he also thought it much smaller, and the length of
a shadow thrown by any dark body is longer the nearer it is to the
light-source, but shorter, the smaller is the light-source.
------------------------------------------------------------------------
[69] The mean length of Earth’s shadow (which varies a little with
her distance from the sun,) is 857,000 miles, or 216 times her
semi-diameter.
------------------------------------------------------------------------
[Illustration: Fig. 37. Earth’s Shadow.]
The two last chapters are devoted to eclipses, lunar and solar, and
Alfraganus points out that, unlike lunar eclipses, eclipses of the sun
vary in duration and magnitude according to the place on Earth from
which they are viewed.
The book concludes: “Enough having now been said concerning the
eclipses of sun and moon, by the goodness of God we have been enabled
to bring this writing to an end; and for this _Deo Laus et Gloria_.”
The time at which Alfraganus lived is not precisely known, but it seems
to have been in the first half of the 9th century, since from internal
evidence he wrote after, but probably not much after, the death of
Al Mamun. His name indicates that he was a native of the beautiful
and fertile country, shut in by lofty mountains, which lies on either
side of the ancient river Jaxartes. He was surnamed the Calculator,
and wrote on sun dials and the astrolabe, but we do not know of any
observational work of his.
Later Arab writers although they all continued to base their work on
that of Ptolemy, improved on some of his estimates. Albategnius began
his book “On the Number and Motions of the Stars” by saying that having
studied Ptolemy’s _Syntax_ and mastered the Greek methods, and having
noticed some errors in the positions of the stars, he felt impelled
to add to Ptolemy’s observations, as the latter had added to those of
Abrachis (Hipparchus), for it is not given to man to attain perfection.
He gives a much more accurate value for precession than Alfraganus had
done, who merely copied Ptolemy, for he makes it 54½ seconds yearly,
or one degree in 66 instead of in 100 years. His tropical year,
too, is only two minutes shorter than the modern value, so that he
improved upon Hipparchus in this respect; and he made the discovery
which Ptolemy missed, the motion of the sun’s apogee. He merely notes,
however, that the position found by himself differed from that given in
the _Almagest_, so it is doubtful whether he realized his discovery, or
merely thought that a large error had been made.
Although some of Ptolemy’s values were thus corrected by the Baghdad
astronomers, no change was made in his theory of epicycles and
eccentrics, which all accepted as having a concrete existence, partly
because at first they did not distinguish between these and the spheres
discussed by Aristotle, which he had described as formed of the same
material as the planets. As Ptolemy does not explicitly state that his
circles were only symbols, this is not surprising. They are formed, say
the Arabs, of the fifth essence al-acir (the æther); and they conceived
the epicycle as gliding over the outer surface of the deferent, like a
small soap-bubble on the back of a big one. This notion, coupled with
Ptolemy’s erroneous distance of the sun, misled them, as we have seen,
into their imaginary discovery of planetary distances.
[Sidenote: Tabit ben Korra 826-901.]
It was also partly due to Ptolemy’s unfortunate habit of adopting
the doubtful or merely provisional results of his predecessors, and
representing them as well established and confirmed by himself, that
they fell into another error. Tabit ben Korra, noting the discrepancy
between the Greek and the Arab value of precession, investigated
the question, and put forward a theory that the motion varies both
in amount and direction. In his book “On the Motion of the Eighth
Sphere” he describes an elaborate apparatus which he had invented to
account for this variation, but he is very modest about it, and after
narrating the results obtained by others, and how they had left them to
be judged by posterity, he adds “And this is what we have done, with
God’s blessing.” Then follow his figures and tables. This imaginary
discovery was accepted by some of the Arab school, and it appears in
many mediæval tables, instead of precession, under the name of the
“trepidation.”
The belief in the material reality of the spheres caused the Arabs
to add a ninth sphere to the eighth of Ptolemy and Alfraganus, for
they thought it was enough to demand of the eighth that it should
carry all the stars and give them their slow movement of precession
(or trepidation). This ninth sphere, therefore, enveloped the whole
universe: upon it were fixed no epicycles, no stars, no planets, but it
originated the “prime motion” by turning once in a day and night, and
communicating this revolution to all the inner spheres. It became known
in mediæval astronomy as the Primum Mobile or first moving.
[Sidenote: Nasir-ed-din 1201-1274.]
[Sidenote: Alfonso 1223-1284.]
The Baghdad school of astronomy came to an end with Abul Wefa in
998, and the Spanish schools died out when Seville and Cordova were
captured by the Christians in the thirteenth century; but the impetus
given to the study of Greek astronomy and astronomical observation was
carried on by other nations. In Persia a fine observatory was founded
by Nasir-ed-din; in Spain the Christian king, Alfonso X, ordered tables
to be drawn up to replace those of Arzachel, and the _Libros de Saber_
to be compiled. The movement in Persia was short-lived, but in Europe
the revival of astronomy had begun.
_VIII. THE RETURN OF GREEK ASTRONOMY TO EUROPE._
A.D. 1000 TO 1300.
“He hath made everything beautiful in His time; also He hath set
the infinite in their heart.”
In the whole cycle of the changing year there is no moment so wonderful
in northern climes as that which comes in early February, when winter
is not yet past, but for the first time the promise of spring is felt
in the air. Not a leaf has unfolded its green, but the swelling buds on
the trees make a purple flush all over the woods, the blackbird sings
an exultant strain, and in some sheltered copse you may find a delicate
daring primrose already in bloom.
Such a moment in the history of Europe was the year 1000 Anno Domini.
After the apathy, the ignorance, the despair of the Dark Ages, a new
spirit began to breathe hope into the hearts of men. A love of beauty,
a new religious fervour, a passionate desire for knowledge took
possession of them. Yet it was nearly a hundred years before the great
universities which were one expression of this new spirit sprang up
in Paris, Bologna, Oxford, to be followed later by similar centres of
intellectual activity in all parts of Europe.
By the end of the twelfth century it is said that there were 100,000
students in Bologna. A large number were foreigners from many lands,
for as Latin was the universal tongue in education, all nations could
understand each other, and scholars often wandered from one university
to another, attracted by the fame of some great master. Similarly the
doctors would teach first in one town and then another. Men of all
ages and classes met together, for among the students were young boys
and elderly ecclesiastics, poor scholars who begged their bread, and
rich nobles who came with a tutor, a chaplain, and a whole suite of
servants. There were no colleges or even lecture-halls: the students
joined together in small groups to take a house and share expenses, and
the professor lectured in his own house, or in a hired room, or, if the
audience was large, in a city square, speaking from an open-air pulpit.
All were united in the ardent pursuit of learning, and none complained
if the floors were merely covered with straw, and the lectures, which
often lasted three hours, began before sunrise on winter mornings in
rooms which had no light and no fire. Was it not enough that when
leaving at the end of university life one was technically said to be
“going home a wise man”?
One cause of this intellectual fervour was the influence of Arab
culture, with which Europe came into contact through the crusades,
and through the Saracens in Sicily, and the Moors in Spain. For this
reason astronomy and astrology took a high rank among the new studies.
To distinguish between the two is quite a modern idea, and in mediæval
times either name was used indifferently to cover both subjects. In
Bologna university in the thirteenth century an important school of
medicine and arts arose, through Arab influence, and the Arab doctors
of medicine introduced the system of astronomy which they had learned
from the Greeks. “A doctor without astrology,” it was said, “is like
an eye that cannot see;” and before prescribing for a patient it was
thought quite as important to determine the positions of the planets,
as the nature of the disease. By the beginning of the fourteenth
century there were salaried professors of astrology in Bologna, and
they were more highly esteemed than any other professors except those
of philosophy.
[Illustration: A MEDIÆVAL ASTRONOMER. [_To face p. 200._
_From a painting by Gerard Dow._]
[Sidenote: Cecco d’Ascoli _d_. 1327.]
One of their duties was to provide “judgments” (_i.e._ to cast the
horoscope) gratis for students. But the dignity was a perilous one.
Legitimate prediction by astrology bordered close on necromancy, which
was banned by the Church, and one of Bologna’s most famous professors
in astrology, the learned Cecco d’Ascoli, was burned at the stake in
Florence in 1327 for the crime of sorcery.
Astronomy, like other subjects, was taught chiefly by lectures and
“repetitions,” or classes for catechizing the students on what they had
already heard. Books could also be had, though they were dear, on hire
or purchase, from the university “stationers” or librarians.
The first books on Greek astronomy which found their way into European
universities were Latin translations of Arabic commentaries and
paraphrases of Aristotle, which travelled from Moorish academies in
Spain to Paris. The astronomical treatises with strange technical terms
in Arabic were hard work to translate, especially when they had already
passed through several languages, as often happened. Thus it was
possible to possess a work of Aristotle which was a Latin translation
of a Hebrew translation of a commentary upon an Arabic translation of a
Syriac translation of the original Greek text!
[Sidenote: Urban IV., pope 1261-1264.]
But meanwhile some of Aristotle’s works in the Greek entered Italy from
the East, as a result of the crusading conquest of Constantinople in
1204. The first translations of these into Latin were very poor, but
later on St. Thomas Aquinas, with the help of Pope Urban IV., had a
better version made.
[Sidenote: Frederick II. 1194-1250.]
[Sidenote: Sacrobosco died _c._ 1256.]
[Sidenote: Roger Bacon _c._ 1214 to _c._ 1294.]
It was long before a good Latin version of Ptolemy’s _Almagest_ could
be obtained. A translation was made from the Arabic in 1230, at the
bidding of the Emperor Frederick II., who did much, at his Sicilian
court, to encourage Arab literature, but this translation was not
much known or used.[70] The teachings of the _Almagest_ became known
chiefly through popular expositions such as those of Alfraganus,
Albategnius, and John Halifax of Holywood, an English monk who became
famous under his Latinized name of Sacrobosco. He was not an astronomer
but had studied Greek and Arab writings, and finding that the study of
astronomy was neglected because books on the subject were difficult
both to procure and to understand, he compiled a useful handbook, which
became widely popular and remained so for several centuries. Several
other writers, notably Roger Bacon, wrote on the spheres, on the use of
astrolabes, and on astrology. The books prescribed in Bologna for the
course in Astrology and Mathematics were as follows:—
------------------------------------------------------------------------
[70] It was also translated from Arabic into Latin at Toledo, in 1175.
------------------------------------------------------------------------
A work on Arithmetic or Algebra.
Euclid, with a thirteenth century commentary.
The “Theorica Planetarum,” which was either a free translation
of Ptolemy’s _Almagest_ or an exposition of its principles.
The Alfonsine Tables.
The Canons of De Lignières (of Amiens, 1330 A.D.),
_i.e._ rules for the use of astronomical tables to determine
the motions of the heavenly bodies.
Portions of the Canon of Avicenna (the Arab philosopher).
A treatise on the Astrolabe by a Jewish astrologer of the
ninth century.
A treatise on the Quadrant.
The astrological works of Ptolemy, with a commentary.
A book by Alchabicius (fl. _c._ 850 A.D.),
probably his work on astrology.
A book on astrological medicine.
[Sidenote: Alfonso X. 1223-1284.]
From the above we gather that a past master in Astrology would
understand the elements of mathematics, and all the astronomy that
Ptolemy’s translator or commentator could teach; that he had learned—at
least in theory—the use of astronomical instruments and tables, and
a good deal of astrology, including its use in medical practice.
The tables were intended mainly for astrological predictions. The
standard Alfonsine Tables had been drawn up in 1252 by Christians,
Jews, and Moors, under the direction of Alfonso X. king of Castile.
They contained lists of positions of the planets, dates of Easter
moons, “golden numbers” and “dominical letters” of the ecclesiastical
calendar, times and other details of eclipses, together with methods
for finding the places of planets, and for casting horoscopes. This
is the Alfonso who was so much shocked at the complexity of Ptolemy’s
multitudinous circles that “the ointment of his name is marred,” says
Fuller, “with the dead fly of his atheisticall speech”: “If only the
Creator had consulted me, when He made the world, I would have given
some good advice!”
[Sidenote: Sylvester II. (Gerbert) Pope, 999-1003.]
Not one of all these books pretended to add any new discovery
to astronomy: all intellectual energy was absorbed in eagerly
assimilating the knowledge stored by Greeks and Arabs. Nor were any
great observatories founded in Europe yet, in imitation of Alexandria,
Rhodes, or Baghdad. The instruments in use were celestial globes and
small portable astrolabes and quadrants for determining positions
and angular distances between the heavenly bodies. The learned pope,
Sylvester II., who had studied astronomy among the Moors in Spain, was
so skilful in making astrolabes that some accused him of gaining the
art by selling his soul to the devil!
[Sidenote: Albertus Magnus 1193-1280.]
[Sidenote: Aquinas 1225-1274.]
When Aristotle first came to Paris (about 1200 A.D.), in Oriental
dress, and accompanied by Moslem authors, the Council of Paris
denounced him as an infidel; yet in less than fifty years all his works
were placed on the list of books prescribed in the university course.
This was brought about by the Dominicans. In six of his twenty-one
ponderous volumes the German friar Albertus Magnus paraphrased the
whole of Aristotle’s works, and stripping his philosophy of the
pantheistic and materialistic garb in which the Spanish Arab Averroës
had clothed it, presented the Greek philosopher as an ally of
Christianity. The Italian saint, Thomas Aquinas, pupil of Albertus,
in his much more readable commentaries and treatises, popularized
this idea so successfully that Aristotle—_the_ Philosopher, as he was
called—speedily became as great an authority on every other subject as
he had always been on logic.
It was a mutual victory. Aquinas captured the Greek for the Christian
faith; Aristotle won the western world to accept his theories. No
longer was the doctrine of a spherical Earth called “an old heathen
theory”: it was almost an integral part of the Catholic faith.
Aristotle’s demonstration that there must be a First Mover, himself
unmoved, became an argument for the existence of the Christian Deity;
the intelligences which preside over the celestial movements were
interpreted as the nine hierarchies of angels whose existence was
taught by the Church. To the eight spheres of the Greeks and the
Primum Mobile of the Arabs, the thirteenth-century Christians added
the all-embracing heaven of heavens, the Empyrean, to be the abode of
the Creator and blessed spirits. Within the central immoveable earth
they placed Purgatory and the fires of Hell. They accepted the limits
of the habitable earth as laid down by Ptolemy, but kept Jerusalem as
the centre by asserting that it was situated 90° from the Pillars of
Hercules, and 90° from the mouths of the Ganges. Eden, the earthly
paradise of Adam and Eve, was represented on contemporary maps as in
the extreme East, separated by sea from the eastern boundary of the
inhabited earth.
Thus theology and science supported one another. All learning was
sacred, and all that man’s mind is capable of understanding he might
aspire to know, for the search if rightly pursued would lead at last
to the perfect bliss of beholding with unveiled eyes the Source of all
Truth.
_SECOND PART._
THE ASTRONOMY OF DANTE.
I. POPULAR ASTRONOMY IN ITALY IN DANTE’S TIME.
In the first part of this book we have sketched the story of man’s
thoughts about the stars, from primitive days until the thirteenth
century of our era. We have seen what a wealth of imagination and
invention the Greeks brought to bear on the purely empirical science of
Egypt and Babylon and Homeric Greece, and how out of all the systems
devised by them between 600 B.C. and 100 B.C. one survived, which
was completed and expounded by Ptolemy in the second century after
Christ in his great _Syntax_ or _Almagest_. Its fundamental principles
were that Earth is a sphere, at rest in the centre of the Universe,
surrounded on all sides by spherical heavens, and that the movements
of all the heavenly bodies are explained by a combination of uniform
circular movements.
In the succeeding centuries there were few who could appreciate his
work, and during the Dark Ages it was scarcely known in Europe, but
was preserved by Nestorian Christians in schools and monasteries of
Persia, whence it was unearthed by Mahomedan princes, five centuries
after Ptolemy’s death; and when another five centuries had passed it
was brought back to Europe, tinged with Oriental thought, and almost
immediately became immensely popular among scholars.
Then there arose one of the world’s greatest poets, and, a thousand
years after Ptolemy’s death, immortalized his work, writing in a tongue
unknown to Ptolemy, and for nations which in his day were only just
struggling into existence. As Homer reflects to us man’s primitive
conceptions of the Universe, so Dante reflects the ideas of Ptolemy and
his school.
And because he lived just at this time he was able to write with
perfect confidence, quoting Ptolemy and the Catholic Faith side by
side as infallible authorities in astronomy. Had he lived in the early
Christian centuries he would have been obliged to choose between
classical and orthodox views; had he been born three centuries later,
he would have found Copernicus and Galileo ranged against Ptolemy and
the Church. Even Milton writing a hundred years after the death of
Copernicus, could not make up his mind which system to adopt, and the
astronomy of _Paradise Lost_ is a curious jumble of ancient, modern,
and transitional ideas. He describes the Primum Mobile as a “firm
opacous globe”[71] on which Satan alights and walks about, yet later on
tells us that we need not believe in its existence if Earth is turning
on her axis;[72] the archangel Raphæl describes to Adam the Creation,
at which he was present, yet declares that he himself does not know
whether the sun circles round Earth, or Earth round the sun. This the
great Architect had wisely concealed from man and angel,
------------------------------------------------------------------------
[71] _Paradise Lost_, II. 418.
[72] _Paradise Lost_, VIII. 34-38.
“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.”[73]
[73] _Paradise Lost_, VIII. 77-84.
------------------------------------------------------------------------
Such inconsistencies are not found in Dante’s work, and nothing could
have been further from his thoughts than to imagine the Creator mocking
at man’s mistakes and ignorance. Like the angelic doctor, Thomas
Aquinas, he considered man’s desire for knowledge as one of his highest
attributes, and believed that it had been given to him in order to be
satisfied.
But before we examine Dante’s writings, it will be interesting to form
an idea of the spirit in which astronomy was generally regarded by his
fellow-countrymen, and what were his opportunities of studying it.
Dante Alighieri was born in Florence in or about the year 1265, and
died in 1321. There can be no doubt that the part of star-lore which
appealed most to the general public in Italy at this time, educated and
ignorant alike, was the art of the astrologers. The movements of the
heavenly bodies were regarded not merely as omens, but as the actual
instruments by which every event on Earth was brought to pass. Every
class of plants, every race of animals, was thought to be under the
protection of some planet or constellation; so if it was a bad year for
certain fruits, or if an epidemic broke out among the cattle, this was
because the guardian planet was unfavourably placed, or an evil planet
was in the protecting constellation. Floods and drought, prosperity and
death, properties of minerals such as the lodestone’s attraction for
iron or the emerald’s alleged power of blinding serpents, the instincts
of animals and the impulses of men, all were subject to the influences
of the stars; and naturally the men who understood and interpreted
their movements were held in great repute.
Some of them were unscrupulous quacks, like the one-eyed prophet of
Brescia, mentioned by the gossiping friar Salimbene.[74] He “called
himself an astrologer and diviner,” and received daily “ten great
pennies of silver, and nightly three great Genoese candles of the
purest wax” from a political party in Modena, as a recompense for
advising them how to act. On one occasion he prophesied a victory for
them, but he had little faith in his own words, for being threatened
with violence if his prophecy should fail, he “carried off all that
he had gained and went his way without saluting his hosts.” “Then,”
adds the friar, “the men of Sassuolo began to mock them, as men who
sacrifice to devils and not to God, as it is written in Deuteronomy.”
------------------------------------------------------------------------
[74] All quotations from Salimbene’s Chronicle are taken from Coulton’s
_From Saint Francis to Dante_.
------------------------------------------------------------------------
But most of these men, like Asdente of Parma, sincerely believed in
their own ability to foretell events, and they usually combined some
other favourite forms of soothsaying, as well as a little alchemy,
with astrology. Asdente is described by Salimbene as “a poor working
cobbler, pure and simple, and fearing God, and courteous and urbane;
illiterate, but with great illumination of mind.” His proper name
was Master Benvenuto, but he was “commonly called Asdente, that is,
toothless, by way of contrary, for he hath great and disordered teeth
and an impediment in his speech, yet he understands and is understood
well. He dwells at the bridge-head of Parma, hard by the city moat
and the well, along the street which goes to Borgo San Donnino.” This
humble prophet was said by Dante to be the best known citizen of all
Parma (_Conv._, IV. xvi. 65-71): he was asked to dinner by a bishop,
and consulted by the warring factions of Reggio and Parma. He was said
to have foretold the death of two popes, and a naval defeat of Pisa by
Genoa.
The greatest generals of the day governed their tactics by the advice
of astrologers who regularly accompanied them to the field and the
camp. The famous Ghibelline, Guido of Montefeltro, who is called
by Villani the cleverest soldier of his times[75] retained Guido
Bonatti[76] in his service and was believed to have gained his great
victory at Forli (in 1282) through the advice of this astrologer.
Bonatti is diversely described as a tiler and a lawyer, but whatever
his original occupation may have been he found that the position of
private astrologer brought him both more fame and more money. He wrote
a book on Judicial Astronomy, and Vincent de Beauvais describes him as
celebrated throughout the western world for his knowledge of the art.
------------------------------------------------------------------------
[75] _Croniche Fiorentine_, Bk. VII. par. 80.
[76] _Inf._ xx. 118.
------------------------------------------------------------------------
But Bonatti’s fame was faint and fugitive compared with that of the
wizard Michael Scot. He is one of the picturesque figures of the
thirteenth century, round whom so many legends have gathered that the
facts of his life are difficult to glean. It seems that he was born
in Fifeshire of a noble Scottish family, at the end of the twelfth or
beginning of the thirteenth century, that he studied in Oxford and
Paris, and then spent some time in Toledo. Here he learned Arabic,
and probably also astrology, for it was so commonly practised there,
especially among the Arabs and the Jews, that it was sometimes called
the Toletan art. Afterwards he went to Germany, and was discovered by
Frederick II., who took him to Italy. His great learning earned the
admiration of Pope Gregory IX., who speaks of him quite affectionately
in a letter to the Archbishop of Canterbury; and it is said that
Honorius II. would have liked to make him an archbishop. But Sir
Michael the Scot found Frederick’s court more congenial. The Emperor,
who was himself a poet, was a munificent patron of literature and art,
and attracted to himself men of talent from all parts of the world. The
culture of both East and West met at that brilliant Sicilian court[77]
which was his for fifteen years before the title of Emperor was added
to that of King of Naples and Sicily. Indeed it was his “fellowship
with Saracens”[78] which was one great reason for the accusation of
heresy on account of which Dante placed him among the Epicureans in the
_Inferno_. He knew Arabic, as well as French, German, Italian, Latin,
and Greek. Michael Scot’s acquaintance with Moorish literature and
language was a bond of sympathy between them; he became astrologer to
Frederick, and at the Emperor’s wish he superintended a new translation
of Aristotle’s works from Arabic into Latin. His taste for astronomy is
evidenced by the fact that out of these he chose to translate the _De
Cœlo_ himself.
------------------------------------------------------------------------
[77] _V. E._, I. xii. 20-35.
[78] Villani, _Croniche Fiorentine_, VI. 1 and 24.
------------------------------------------------------------------------
An absurd story is told by Salimbene about Frederick and Michael
Scot, which, however, shows what was believed of his capabilities as
an astronomer. The Emperor one day asked him, when they were in the
palace together, how far they were from the sky, and the astrologer
told him the distance. They then took a long journey together, during
which the palace was secretly lowered, and on their return Frederick
asked casually whether the sky could really be so distant as Michael
had said. “Whereupon he made his calculations, and made answer that
certainly either the sky had been raised or the earth lowered; and then
the Emperor knew that he spake truth.”
Michael Scot is said to have warned Frederick that he would die in
Florence, for which reason the Emperor would not enter that city;
but having thoughtlessly gone to a town called Florentiola he died
there; “for this,” adds the historian, “is almost always the way, the
devil tricks one by a play upon words.” It is curious to contrast
this remark, attributing Michael’s prophecy to the evil powers, with
Salimbene’s quotation from him, in exactly the same spirit as if he
were quoting from an Old Testament prophet:—“that the word of Michael
Scot may be fulfilled in them, which he wrote in his verses wherein he
predicted the future, ‘And the factions at Reggio shall hold ill words
together.’” The same author brackets him with others who have foretold
the future, in a list which reads curiously to us—“Abbot Joachim,
Merlin, Methodius and the Sybil, Isaiah, Jeremiah, Hosea, Daniel, and
the Apocalypse, and Michael Scot who was astrologer to the deposed
Emperor Frederick II.”
Besides these prophetic verses, Michael wrote several books which treat
almost exclusively of astrology, alchemy, and other occult “sciences,”
and even in the fifteenth century it was said that his magic books
could not be opened without danger, because of the fiends who were
thereby invoked! He seems to have returned to his native Scotland to
die, but the date is very uncertain. We do not know whether Dante’s
picture of him is drawn from memory, or hearsay of some who had seen
the lanky Scotsman among the southerners, by nature taller and thinner
than they, and worn by his prolonged studies.
“Quell’ altro che ne’ fianchi è così poco
Michele Scotto fu, che veramente
Delle magiche frode seppe il gioco.”[79]
(_Inf._ xx. 115-117).
------------------------------------------------------------------------
[79]
“That other, round the loins
So slender of his shape, was Michael Scot,
Practised in every sleight of magic wile.”
_Carey._
------------------------------------------------------------------------
It was perhaps the winning personality or the prudence of the canny
Scot which enabled him to bring a brilliant career to a peaceful close,
favoured by the Church as well as by the excommunicated Emperor,
although his studies were of so dubious a nature, and he was intimate
with heretic Mahomedans and Jews. Cecco d’Ascoli was not so fortunate.
This learned Italian received the high and honoured post of professor
of astrology in Bologna, where he lectured and cast horoscopes for his
students. He was well versed in natural science, but the shady side of
astrology had a fatal attraction for him: he fell under suspicion as a
sorcerer, was condemned, and burned at the stake in Florence in 1327
(six years after Dante’s death).
The reputations achieved by these and other thirteenth-century
astrologers in Italy, belonging to such different ranks of life, show
what an immense importance was attached to their art by the general
public. Yet we shall be greatly mistaken if we think that it was only
to acquire skill in this fascinating pursuit that men thronged to hear
Cecco lecture, or pored over Latin manuscripts. The intense ardour for
knowledge which marks this period made them eager to understand the
world around them and the sky above their heads.
[Illustration: ASTRONOMY.
_From a fresco in the Spanish Chapel of Santa Maria Novella, Florence._
[_To face p. 217._}]
It would be a shame, writes one, to live in a house and not know how
it is built or what shape it has, never to examine the walls, and
floors, and ceilings, nor to consider the use of the wooden beams used
in its construction. In like manner we should not be content without
understanding the form and structure of the Universe in which we live.
Man, with his upright attitude and his head held high, unlike the
animals, was designed by his Creator to look and listen, to know and
comprehend this marvellous Universe, and especially that noblest part
of it above him, the heavens and their wonderful movements. For thus
alone can he learn to know God Himself, the great Architect of the
World.
In writing thus, Ristoro, the monk of Arezzo, was not only echoing
the thoughts of Plato and Cicero, he was expressing the feeling for
astronomy as a noble and elevating study which was general among
thoughtful men of his time. It was expressed also in contemporary art.
Visitors to the “Spanish Chapel” in the cloisters of a Florentine
church will remember seeing on the frescoed walls the figure of
Astronomy as she was personified in Tuscany in the fourteenth century.
She sits among her peers, the sciences of the Trivium and Quadrivium,
the only one who wears a crown; her fair hair frames a spiritual face,
one hand is lifted heavenwards, the other holds a celestial sphere, on
which the broad band of the zodiac crosses the “equator of the day.” At
her feet sits a kingly figure in flowing robes, also crowned, and with
a face of singular beauty and refinement; he gazes up into the skies
with a rapt expression, and on his knee is a book in which he writes
what he sees.
This nameless figure was identified doubtfully by Ruskin as Zoroaster,
who was considered by many as the inventor of astrology, but surely
it can be no other than Ptolemy with his _Almagest_. For Ptolemy, the
prince of astronomers, was often and naturally confused with the royal
race who had patronized astronomy at Alexandria; as for instance by
Omons, a thirteenth-century writer, who says in his _Image du Monde_
that “Ptolemy king of Egypt” wrote the _Almagest_. The curious mode
of dressing the hair and beard may have been thought by the artist to
represent an ancient Egyptian fashion.
Ptolemy, we know, was universely acknowledged at the time to be “Master
of Astronomy,” as Brunetto Latini calls him. His _Almagest_ was only
known indirectly, but it was believed to contain all that could be
known about the movements and the nature of the heavens. Some minor
additions and corrections had been made, as we have seen, by the Arab
astronomers, but the system was accepted as a complete and satisfactory
explanation of all celestial phenomena. Hence no professional
astronomer was expected to make discoveries; he was simply well versed
in the work of those who went before him, skilful in the use of a few
simple instruments and tables, and practised in applying the principles
of astrology.
A general notion of the Ptolemaic system was widely diffused. For
those who could not read Latin there were encyclopædic works written
in the vernacular and in a popular style, such as the _Trésor_ of
Brunetto Latini, and these always contained a section on astronomy.
The average educated man probably had only vague ideas about epicycles
and eccentrics, and perhaps had never heard of the Arab estimates of
the sizes of the planets; but he would know that astronomy taught
that Earth is a globe, motionless at the centre of the universe, and
smaller than any of the stars; he would know the names of the seven
planets (including among these the sun and moon), and probably also
their colours, their periods, and their astrological significance; the
zodiacal constellations would be familiar, especially as they were
often used decoratively; and he would believe that stars and planets
are set in crystalline transparent spheres.
Moreover, he would often be more of an astronomer than he knew, for he
would learn almost unconsciously many things of which modern men are
ignorant. The ill-lighted streets and the dangers of night journeys
would force him to be better acquainted with the motions and phases
of the moon than most of us are to-day; he would know when and where
to look for different stars; and the want of a watch would make it
necessary for him to be able to take his time from the sun at any
season of the year. He could, however, sometimes consult a sundial on
a church wall or in a private garden, and the church chimes rang out
at tierce, and nones, and vespers. These were heard at intervals which
were much longer in summer than in winter, for the system of “temporary
hours” was used by the Church, and the service of tierce was held
halfway between sunrise and noon (or nones), and vespers was halfway
between noon and sunset.
_II. DANTE’S STUDIES._
DANTE’S STUDIES.
Dante was far above the level of the average educated man. Not that
his scientific ideas were in advance of his age: on the contrary, one
special interest that they have for us is that they illustrate, like
his political and religious views, the beliefs and feelings of the
period. His authorities were the authorities of all, but he had studied
them and made their thoughts his own, as few others did, except some
churchmen and professed scholars. The extent and depth of his reading
is evident from his own writings, and his great learning is noted with
admiration by all his biographers. Giovanni Villani, in the earliest
account we possess of Dante, says that he was “a great scholar in
almost every branch of learning, although he was a layman.” Boccaccio
would have us believe that while still a child, so young that he might
be expected to spend his time playing with other children or sitting
on his mother’s knee, he gave the whole of his time to reading and
learning. Lionardo Bruni, however, assures us that though he was an
ardent student, and showed unusual powers at an early age, he by no
means tried to “sever himself from the world, but living and moving
about amongst other young men of his age, he approved himself gracious
and skilful in every youthful exercise.” It was wonderful, he says, how
Dante maintained all his social and civic intercourse while he pursued
his studies so fervently.
In truth, the poet’s troubled life was far removed from that life of
calm retirement which one thinks suitable for a scholar. In his early
youth he experienced a passionate love and sorrow; a year before the
death of Beatrice he was fighting for Florence in the great battle of
Campaldino, nor was it the first time he had borne arms; in 1296 he
spoke in the council of the Hundred; in 1300 he was ambassador for the
Tuscan League to San Gemignano, and was elected to the highest office
a citizen could hold in his native city, that of Prior; in 1301 he
was ambassador to the Pope in Rome, and in the year following he was
exiled. After this he was always wandering, often in great poverty,
dependent on first one patron and then another, always hoping that some
turn of affairs would restore him to Florence, always taking a keen and
active interest in Italian politics, until he died, still in exile, at
Ravenna. Add to this the difficulties common to all scholars of his
day, viz. absence of printed books, public libraries, and journals,
etc., and we must marvel how he ever found the opportunities and the
serenity of mind for his prolonged studies.
Boccaccio adds another obstacle—his wife! To console him for the death
of Beatrice, his friends and relatives persuaded him to marry a wife of
their choosing with melancholy results:—
“Dante formerly had been used to spend his time
over his precious studies whenever he was inclined,
and would converse with kings and princes, dispute
with philosophers, and frequent the company of
poets.... Now, whenever it pleased his new mistress
he must at her bidding quit this distinguished
company, and bear with the talk of women, and to
avoid a worse vexation must not only assent to
their opinions, but against his inclination must
even approve them. He who, whenever the presence of
the vulgar herd annoyed him, had been accustomed
to retire to some solitary spot, and there to
speculate on the motions of the heavens, or the
source of animal life, or the beginnings of created
things, or may be to indulge some strange fancy, or
to compose somewhat which after his death should
make his name live into future ages, he now, as
often as the whim took his new mistress, must
abandon all such sweet contemplation, and go in
company with those who had little mind for such
things.”[80]
------------------------------------------------------------------------
[80] Boccaccio’s _Vita di Dante_; Translation from Toynbee’s _Dante
Alighieri_ (Oxford Biographies), pp. 92, 93.
------------------------------------------------------------------------
However, after a long tirade against wives, Boccaccio owns that as far
as concerns Dante the picture is entirely imaginary. He believes the
marriage was an unhappy one, because after his exile Dante and his
wife never met again, but we have no evidence whatever that while they
were together their life was as Boccaccio depicts it. Doubtless family
life and the care of four children interfered to some extent with
Dante’s studies, but the one detail Boccaccio affirms as fact among his
fancies, namely that the poet refused for nineteen years to see his
wife, seems rather to imply that one thing poor Gemma did know how to
do was to leave her husband in peace when he did not desire her company.
When and where Dante began to study astronomy seriously it is not easy
to say. His favourite study in his youth was poetry, but his parents
(says Bruni) gave him a good general education, engaging such teachers
as could be found in Florence, where as yet there was no university.
But seeing how clever the boy was, his relatives and friends helped and
encouraged him, and among the latter Bruni mentions Brunetto Latini.
This famous Florentine was a very learned lawyer, who during Dante’s
infancy and boyhood held high offices of state in the city. It is not
possible, therefore, that he should have had pupils at this time, and
he cannot have been Dante’s master in any strict sense of the word, as
Vasari affirms, and as many commentators have assumed on the strength
of the moving interview between these two in the _Inferno_.[81]
Dante’s affectionate greeting mingled with reverence, and the fatherly
solicitude of Brunetto, suggest just such a connection as Bruni
indicates. The elderly man had taken an interest in the budding genius
of the boy, and had held inspiring conversations with him from time
to time on serious subjects, and by his own example had encouraged
the youth to win fame through his pen. For Dante was no doubt well
acquainted with Brunetto’s _Tesoretto_, and his more ambitious and
voluminous _Trésor_, which Brunetto specially commends to his care.[82]
This was a compendium of knowledge, a small part of which was devoted
to the elements of astronomy, and it may well be that this short
epitome was Dante’s first introduction to the science.
------------------------------------------------------------------------
[81] _Inf._ xv. 23 _et seq._
[82] _Inf._ xv. 119.
------------------------------------------------------------------------
Some have thought that Brunetto’s advice to Dante to follow his star
“Se tu segui tua stella ...,”[83] indicates that he had cast the poet’s
horoscope; but there is no evidence that Brunetto had ever practised
astrology, or even that he took special interest in it above other
branches of learning.
------------------------------------------------------------------------
[83] “If thou follow thy star,” _Inf._ xv. 55.
------------------------------------------------------------------------
Villani and other biographers tell us that after his banishment from
Florence, therefore in middle age, Dante went to the University at
Bologna, but they seem to have made this statement rather because of
its probability than because they knew it for fact. It is, however,
quite possible that he spent a couple of years there, between 1304
and 1306. He probably left his “primo rifugio”[84] at Verona when
Bartolommeo della Scala[85] died in March 1304, and we know nothing of
his whereabouts till August 1306, when he was in Padua, as is proved by
a fifteenth century document.[86] Now in 1306 a number of Ghibelline
students and professors left Bologna for Padua; and we know that Dante
had friends among the Bolognese professors, for later on he seems to
have corresponded with Cecco d’ Ascoli,[87] and Del Virgilio entreated
him to come and receive the laurel crown, an invitation which the poet
refused in one of his Latin Eclogues. Bologna and the Bolognese are
referred to several times in Dante’s works, and the friar Catalano is
no doubt alluding to the school of theology at the University when he
says in _Inf._ xxiii. 142-144 that he used to hear at Bologna much
about the wickedness and the lies of the Devil. One vivid passage can
hardly be anything but a personal reminiscence of the Carisenda, the
leaning tower at Bologna. The poet compares his fear when he saw the
giant Antæus stooping over Virgil and himself to the sensation of
looking up at the Carisenda from beneath the leaning side, when a cloud
is passing over it, and the spectator feels that the tower is about to
fall upon him.[88] (The tower was much higher in Dante’s day than it
is now, part having been pulled down in the middle of the fourteenth
century).
------------------------------------------------------------------------
[84] “First refuge,” _Par._ xvii. 70.
[85] _Par._ xvii. 71, 72.
[86] Imbriani, _Dante a Padova_.
[87] “_Torno a Ravenna e de lì non mi parto_ (I am going back to
Ravenna, and shall not leave it again), is a line in the _Acerba_ which
Cecco d’ Ascoli puts into the mouth of Dante, as though from a letter
written to himself from the divine poet at the time” (about the year
1319). _Dante and Giovanni del Virgilio_, by Wicksteed and Gardner, p.
84.
[88] _Inf._ xxxi. 136-141.
------------------------------------------------------------------------
The University at Padua was also famous, and as it was originally an
offshoot from Bologna and modelled on the same plan, it is sure to
have included astronomy in its curriculum. But Dante does not seem to
have stayed here more than a few months.
There is also a tradition that he went to Paris, the greatest
intellectual centre of his times, and that he himself heard those
lectures of Sigieri, the philosopher, in the Street of Straw, of
which he makes mention in _Par._ x. 137. This is possible, but quite
uncertain; the allusion to Sigieri is no proof, since it has lately
been discovered that he died in Italy, and his story was well known
there.
After sifting all the evidence available, we can only echo Boccaccio,
and say of Dante that “As it was at divers ages that he studied and
learned the divers sciences, so likewise it was at divers places of
study that he mastered them under divers teachers.”
_III. BOOKS ON ASTRONOMY USED BY DANTE._
BOOKS ON ASTRONOMY USED BY DANTE.
We shall probably be right if we conclude that Dante’s knowledge of
astronomy was principally gained from independent reading, and from
conversation and discussion with learned men. Like a true scholar,
he was learning all his life, for in the _Paradiso_ he corrects the
opinion expressed earlier in the _Convivio_ about the origin of the
markings in the moon.
Boccaccio’s description of his planning out a course of study and
attacking some subjects alone in his youth agrees with his own
account of his lonely struggles with Latin authors;[89] and it is
quite credible that he suffered heat and cold, and went without food
and sleep in his eagerness to learn, since he himself mentions quite
casually that at one time he injured his sight by constant reading, so
that the stars appeared blurred to him, until by rest and bathing with
cold water it became strong again.[90]
------------------------------------------------------------------------
[89] _Conv._ II. xiii. 22-26.
[90] _Conv._ III. ix. 146-157.
------------------------------------------------------------------------
His diligence must have been great, and his memory wonderful, judging
from the numerous quotations from classical and contemporary authors
to be found in his writings. They seem to be chiefly from memory,
and it is not likely that he can often have had many books by him
when writing. If he gives a reference it is often a vague one, and
occasionally wrong: his authorities on astronomical questions are
sometimes “the mathematicians,” “the astrologers,” or “the sages of
Egypt,” by whom he means the Alexandrian astronomers.
One does not, of course, expect mediæval writers to verify their
references, or to have our modern scruples about quoting other authors
without acknowledgement: in those days they were only too glad to get
their information wherever they could, often at second or third hand,
and to make it their own by storing it in their memories. Nevertheless,
from a careful study of Dante’s direct quotations, and his allusions
and reminiscences, which are sometimes unconscious, a good idea may be
gained of his range of reading, and of the books and authors on whom he
chiefly relied for his astronomical data.
His supreme authority was of course Ptolemy. But it would only be by a
rare chance that he could see the _Almagest_, even in a translation,
and all the evidence that we can find in his own writings points to
its being entirely unknown to him. On each of the three occasions that
he quotes Ptolemy’s opinion on subjects dealt with in the _Almagest_
he is wrong: once it is Ptolemy’s view on the physical nature of
the Galaxy,[91] as to which none had been expressed, although its
appearance was carefully described; in another case he implies that
Ptolemy discovered precession, and says that he added a ninth heaven
to account for it,[92] and this double mistake was apparently copied
from Albertus Magnus or Averroës.[93] As we know, it was Hipparchus
who discovered precession, and Ptolemy gives him the credit for in the
_Almagest_; it was the Arabian astronomers who added the ninth sphere.
------------------------------------------------------------------------
[91] _Conv._ II. xv. 73-77.
[92] _Conv._ II. iii. 36-52, _V. N._ xxx.
[93] Averroës, in his commentary on Aristotle’s _De Cœlo_, says
that the ancients believed the eighth, or starry, heaven, to be the
outermost, but that Ptolemy assumed a ninth, “because he said that he
had discovered a slow motion along the signs of the zodiac in the fixed
stars.” Albertus Magnus, in his _De Cœlo et Mundo_, Book II., says also
that the ancients, including Aristotle, believed that there were only
eight heavens, but that Ptolemy, so far as he can understand, believed
in ten, on philosophical not mathematical grounds (compare _Conv._
II. iii. 40, 41). Albertus accepted the theory of “trepidation,” and
thought this was the only movement which ought to be assigned to the
star sphere; there remained, therefore, two motions, which affect all
the planetary spheres and the star sphere, for which two more spheres
must be assumed, a ninth sphere for precession, and a tenth, the primum
mobile, for the diurnal motion. Outside all was the Empyrean. Dante
never mentions trepidation, and evidently did not believe in it: he
needed only nine moving spheres, therefore, but counts the Empyrean as
a tenth heaven.
------------------------------------------------------------------------
On the other hand Dante quotes twice quite correctly from the
_Tetrabiblios_, which was more widely known.[94] He may, therefore,
possibly have read it, and he alludes to it in the _Convivio_, though
by a curious slip he does not give its name, thinking he has done so
already: “Tolommeo dice nello allegato libro....”[95] This is in the
fourteenth chapter of the second treatise, but so far from having just
quoted any special work by Ptolemy he has said nothing at all about
him since the third chapter, and then it was only his opinion and name
that were mentioned. I have not been able to trace the quotation given
in the _Quæstio de Aqua et Terra_ (xxi. 29-31), where Ptolemy is said
to have asserted that things on earth resemble things in heaven, but
this probably comes also (or was supposed to come), from the “judicial
astronomy” of the _Tetrabiblios_. It is not taken from the _Almagest_.
------------------------------------------------------------------------
[94] _Conv._ II. xiv. 198-202. _Ibid._ 249-253.
[95] “Ptolemy says in the book above cited.”
------------------------------------------------------------------------
The elements of Ptolemy’s system, however, could be learned indirectly,
and it seems that Dante had recourse to the excellent epitome of the
Arab astronomer Alfraganus. It is true that his name is only mentioned
once, and his book once; but nearly all Dante’s astronomical data
appear to have been taken from him, and his very expressions are
sometimes repeated.
One of the most striking examples of borrowing from the _Elementa
Astronomica_ of Alfraganus occurs in the _Paradiso_, where Dante likens
twenty-four spirits to as many brilliant stars.[96] He makes up the
number by taking fifteen specially bright stars from different parts
of the sky, and adding to them the stars of Ursa Major and two stars
of Ursa Minor. The seven chief stars of Ursa Major are well known,
but Beta and Gamma Ursæ Minoris are not conspicuous nor specially
familiar; and why, if he takes fifteen unnamed, should he name any of
the twenty-four? Turning to chapter 19 of Alfraganus’ book, we find
that he follows Ptolemy in enumerating fifteen first-magnitude stars in
different parts of the sky, and then he gives as examples of the second
magnitude (_i.e._ next in brightness) Benet Naax and Alfarcatein, Arab
constellations which correspond with the tail of Ursa Major, and Beta
and Gamma of Ursa Minor.
------------------------------------------------------------------------
[96] _Par._ xiii. 1-13.
------------------------------------------------------------------------
There is no reason to suppose that Dante knew Arabic, but there were
several versions of Alfraganus in Latin, and it is even possible to
determine with some certainty which of them he used. Speaking of
the movements of the planet Venus, he says that they may be found,
summarized from the best demonstrations of the astrologers, in the
_Book of the Collection of the Stars_:—
“Li quali, secondochè nel _Libro dell’ Aggregazione
delle Stelle_ epilogato si trova, dalla migliore dimostrazione
degli astrologi ....”
(_Conv._ II. vi. 133-136).
Although the usual name for the book of Alfraganus in Latin was
_Elementa Astronomica_, the version for which mediæval students
were indebted to the indefatigable translator Gerard of Cremona
bears in the MSS. the title _Alfragani liber de aggregationibus
Scientiæ Stellarum et de principiis cœlestium motuum_. It is this
book, therefore, that Dante means, though he has translated the title
somewhat inaccurately.[97]
------------------------------------------------------------------------
[97] See Schiaparelli’s letter in Lubin’s _Dante e gli Astronomi
Italiani_. The name is, however, also used as a sub-title in the
printed edition of Christmann, Frankfort, 1590, which was based not
on the translation of Gerard but of Johannes Hispalensis of Seville;
and Toynbee thinks that this Frankfort edition represents most nearly
the version of Alfraganus used by Dante. It is the only one of the
five printed editions which gives the same figure for the diameter of
Mercury as that quoted by Dante. See Toynbee, “Dante’s Obligations to
Alfraganus” in _Romania_ xxiv. 95, and Moore, _Studies in Dante_ iii.
p. 3, _note_.
------------------------------------------------------------------------
There were several other books known to Dante from which he must have
gleaned information about Ptolemy’s system, but Alfraganus we may
regard as his standard reference book. Many versions of Alfraganus are
still extant, and it is pleasant to feel that we can hold in our own
hands Dante’s text-book on astronomy. The best known is the printed
edition of Golius, published in Amsterdam in 1669: it is in both Latin
and Arabic, and opening in the middle we may turn the pages backwards
to see the beautiful Arabic letters of Alfraganus’ own language, which
is written from right to left, or forwards to look at the Latin in
which he became known to Dante.
Next in importance to Alfraganus among Dante’s authorities on astronomy
was Aristotle. We have seen how overwhelming his authority became in
natural science in the second half of the thirteenth century, and how
for some time scholars failed to distinguish between the system of
spheres devised by Eudoxus, which was the scheme upheld by Aristotle,
and the epicycles and eccentrics of Ptolemy. Among all Aristotle’s
admirers none was more devoted than Dante: for him Aristotle is not
only “Il Filosofo,” the Philosopher _par excellence_, as he was
generally called in that age; he is “quello glorioso filosofo al
quale la Natura più aperse li suoi segreti,” his intellect was “quasi
divino,” and his words are of “somma e altissima autoritade.”[98]
Throughout Dante’s own writings his references to Aristotle are so
frequent that Dr. Moore observes: “The amount and variety of Dante’s
knowledge of the contents of the various works of Aristotle is nothing
less than astonishing.”[99]
------------------------------------------------------------------------
[98] “That glorious philosopher to whom Nature most fully revealed her
secrets,” _Conv._ III. v. 54-56; “almost divine,” _Conv._ IV. vi. 133;
“supreme and highest authority,” _Ibid._ 52.
[99] Moore, _Studies in Dante_ I. (Scripture and Classical Authors in
Dante), from which much of the information in this chapter has been
taken.
------------------------------------------------------------------------
He does not, however, consider Aristotle infallible as regards the
details of astronomy, for in these the philosopher was only following
the observers and mathematicians;[100] but in all matters which depend
upon first principles, in which Dante would include the form of the
earth, Aristotle’s authority may not be called in question.[101] In
cosmical physics, such as the doctrine of the four elements, and in
meteorology, Dante follows “il mio Maestro”[102] implicitly, and it is
also largely from the _De Cælo_ that he gained his knowledge of early
Greek speculations regarding the universe.
------------------------------------------------------------------------
[100] _Conv._ II. iii. 19-21.
[101] _Conv._ III. v. 62-65.
[102] “My master.”
------------------------------------------------------------------------
Dante knew little more of Greek than of Arabic. His occasional use of
Greek words is enough to prove this—for example when he discusses the
Pythagorean theory of “Antictona,” using the accusative as if it were a
nominative.[103] In several passages he implies that the language was
not known to him, and he distinctly states that he used translations of
Aristotle’s works. Here again we are able to identify the versions he
used. In _Conv._ II. xv. 59-73 he complains that it is impossible to
know what Aristotle believed about the Milky Way, because in the “old
translation” he is made to say one thing, and in the “new translation”
quite another. From his quotations of these two conflicting opinions,
we are able to deduce that the “old translation” was that which Michael
Scot made from the Arabic, and the “new translation” that of Aquinas,
which was made direct from the Greek.
------------------------------------------------------------------------
[103] _Conv._ III. v. 32.
------------------------------------------------------------------------
He had access, therefore, to more than one Latin translation of
Aristotle; and beside this, his quotations seem to have been often
taken from commentators and compilers of his own times, especially
Aquinas and Albertus Magnus. This was frequently the case with the
_Meteorologica_ of Aristotle, for the _De Meteoris_ of Albertus Magnus
seems to have been much used by Dante in place of Aristotle’s own work.
Dante quotes it by name as _Meteora_ in _Conv._ II. xiv. 169, and also
in _Conv._ IV. xxiii. 125-126, where he mentions “Alberto” as the
author.
These two, then, the Arab Alfraganus and the Greek Aristotle, were
Dante’s chief authorities in astronomy, both in Latin translations.
Besides these, there is evidence in his writings that he was familiar
with several classical authors who treated of astronomy. He quotes
frequently from many of Cicero’s works, and we find echoes, in two
passages, of the _Dream of Scipio_,[104] which he is almost certain to
have read, since it was a favourite book in his time. There are several
references to Seneca, but the only time that an astronomical phenomenon
recorded by him is mentioned[105] Dante is evidently quoting at
second-hand from Albertus Magnus. With all the works of Virgil, and
with the _Metamorphoses_ of Ovid (from which he took his astronomical
myths)[106] he was evidently very familiar; and Lucan is one of his
authorities for the position of the earth’s equator. In this case the
name of the author and the number of the book are precisely stated.[107]
------------------------------------------------------------------------
[104] _Inf._ ii. 76-78; _Par._ xxii. 134-138.
[105] _Conv._ ii. xiv. 174-176.
[106] Phaëthon, _Conv._ II. xv. 53-55, _Purg._ xxix. 118-120; Latona,
_Purg._ xx. 130-132; the Horses of the Sun, _Conv._ IV. xxiii. 134-139,
etc., etc.
[107] _Conv._ III. v. 115-117.
------------------------------------------------------------------------
Dante had a great reverence for Plato, whom he calls “uomo
eccellentissimo,”[108] and of whom he repeats the mediæval legend that
he was a prince who gave up all for the sake of acquiring wisdom.[109]
Of his writings he only knew the _Timaeus_, probably the Latin
translation and commentary of Chalcidius, which was widely known. Or he
may have been acquainted with Aquinas’ commentary, which has since been
lost. He also knew something of Plato’s teachings through Aristotle and
Cicero, Albertus Magnus, and Aquinas, and perhaps St. Augustine. When
he feels obliged to dissent from the great philosopher’s doctrine that
the souls of men come from the stars, he does so with reluctance and
great gentleness.[110]
------------------------------------------------------------------------
[108] “A man of supreme excellence.” _Conv._ II. v. 21, 22.
[109] _Conv._ III. xiv. 76-79.
[110] _Par._ iv. 22-24, 49-60.
------------------------------------------------------------------------