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was cultivated by both Babylonians and Egyptians, and that they made but
very limited attainments. The early Greek philosophers, who visited
Egypt and the East in search of knowledge, found very little to reward
their curiosity or industry; not much beyond preposterous claims to a
high antiquity, and an esoteric wisdom which has not yet been revealed.
They approximated to the truth in reference to the solar year, by
observing the equinoxes and solstices, and the heliacal rising of
particular stars. Plato and Eudoxus spent thirteen years in Heliopolis
for the purpose of extracting the scientific knowledge of the priests,
but they learned but little beyond the fact that the solar year was a
trifle beyond three hundred and sixty-five days. No great names have
come down to us from the priests of Babylon or Egypt. No one gained an
individual reputation. The Chaldean and Egyptian priests may have
furnished the raw material of observation to the Greeks, but the latter
alone possessed the scientific genius by which indigested facts were
converted into a symmetrical system. The East never gave valuable
knowledge to the West. It gave only superstition. Instead of astronomy,
it gave astrology; instead of science, it gave magic and incantations
and dreams - poison which perverted the intellect. [Footnote: Sir G. G.
Lewis, _Hist. of Anc. Astron._, p. 293.] They connected their
astronomy with divination from the stars, and made their antiquity reach
back to two hundred and seventy thousand years. There were soothsayers
in the time of Daniel, and magicians, exorcists, and interpreters of
signs. [Footnote: Dan. i. 4, 17, 20.] They were not men of scientific
research, seeking truth. It was power they sought, by perverting the
intellect of the people. The astrology of the East was founded on the
principle that a star or constellation presided over the birth of an
individual, and either portended his fate, or shed a good or bad
influence upon his future life. The star which looked upon a child at
the hour of his birth, was called the horoscopus, and the peculiar
influence of each planet was determined by professors of the genethliac
art. The superstitions of Egypt and Chaldea unfortunately spread both
among the Greeks and Romans, and these were about all that the western
nations learned from the boastful priests of occult science. Whatever
was known of real value among the ancients, is due to the earnest
inquiries of the Greeks.

[Sidenote: Researches of the Greeks.]

And yet their researches were very unsatisfactory until the time of
Hipparchus. The primitive knowledge, until Thales, was almost nothing.
The Homeric poems regarded the earth as a circular plain, bounded by the
heaven, which was a solid vault or hemisphere, with its concavity turned
downwards. And this absurdity was believed until the time of Herodotus,
five centuries after; nor was it exploded fully in the time of
Aristotle. The sun, moon, and stars, were supposed to move upon, or
with, the inner surface of the heavenly hemisphere, and the ocean was
thought to gird the earth around as a great belt, into which the
heavenly bodies sunk at their setting. [Footnote: _Il_., vii. 422;
_Od_., iii. i. xix. 433.] Homer believed that the sun arose out of
the ocean, ascending the heaven, and again plunging into the ocean,
passing under the earth, and producing darkness. [Footnote: _Il_.
viii. 485.] The Greeks even personified the sun as a divine charioteer
driving his fiery steeds over the steep of heaven, until he bathed them
at evening in the western waves. Apollo became the god of the sun, as
Diana was the goddess of the moon. But the early Greek inquirers did not
attempt to explain how the sun found his way from the west back again to
the east. They merely took note of the diurnal course, the alternation
of day and night, the number of the seasons, and their regular
successions. They found the points of the compass by determining the
recurrence of the equinoxes and solstices; but they had no conception of
the ecliptic - of that great circle in the heaven, formed by the sun's
annual course, and of its obliquity when compared with the equator. Like
the Egyptians and Babylonians, they ascertained the length of the year
to be three hundred and sixty-five days; but perfect accuracy was
wanting for want of scientific instruments, and of recorded observations
of the heavenly bodies. The Greeks had not even a common chronological
era for the designation of years. Thus Herodotus informs us that the
Trojan War preceded his time by eight hundred years: [Footnote:
_Il_, ii. 53.] he merely states the interval between the event in
question and his own time; he had certain data for distant periods. Thus
the Greeks reckoned dates from the Trojan War, and the Romans from the
building of their city. And they divided the year into twelve months,
and introduced the intercalary circle of eight years, although the
Romans disused it afterwards until the calendar was reformed by Julius
Caesar. Thus there was no scientific astronomical knowledge worth
mentioning among the primitive Greeks.

Immense research and learning have been expended by modern critics, to
show the state of scientific astronomy among the Greeks. I am equally
amazed at the amount of research, and its comparative worthlessness,
for what addition to science can be made by an enumeration of the
puerilities and errors of the Greeks, and how wasted and pedantic the
learning which ransacks all antiquity to prove that the Greeks adopted
this or that absurdity. [Transcriber's Note: Lengthy footnote relocated
to chapter end.]

[Sidenote: Thales.]

[Sidenote: Anaximander and Anaximenes.]

But to return. The earliest historic name associated with astronomy in
Greece was Thales, the founder of the Ionic school of philosophers, born
639 B.C. He is reported to have predicted an eclipse of the sun, to have
made a visit to Egypt, to have fixed the year at three hundred and
sixty-five days, and to have determined the course of the sun from
solstice to solstice. He attributed an eclipse of the moon to the
interposition of the earth between the sun and moon; and an eclipse of
the sun to the interposition of the moon between the sun and earth.
[Footnote: Sir G. G. Lewis, _Hist. of Astron._, p. 81.] He also
determined the ratio of the sun's diameter to its apparent orbit. As he
first solved the problem of inscribing a right-angled triangle in a
circle, [Footnote: Diog. Laert, i. 24.] he is the founder of geometrical
science in Greece. He left, however, nothing to writing, hence all
accounts of him are confused. It is to be doubted whether in fact he
made the discoveries attributed to him. His speculations, which science
rejects, such as that water is the principle of all things, are
irrelevant to a description of the progress of astronomy. That he was a
great light, no one questions, considering the ignorance with which he
was surrounded. Anaximander, who followed him in philosophy, held to
puerile doctrines concerning the motions and nature of the stars, which
it is useless to repeat. His addition to science, if he made any, was in
treating the magnitudes and distances of the planets. He attempted to
delineate the celestial sphere, and to measure time by a sun-dial.
Anaximenes of Miletus taught, like his predecessors, crude notions of
the sun and stars, and speculated on the nature of the moon, but did
nothing to advance his science on true grounds, except the construction
of sun-dials. The same may be said of Heraclitus, Xenophanes,
Parmenides, Anaxagoras. They were great men, but they gave to the world
mere speculations, some of which are very puerile. They all held to the
idea that the heavenly bodies revolved around the earth, and that the
earth was a plain. But they explained eclipses, and supposed that the
moon derived its light from the sun. Some of them knew the difference
between the planets and the fixed stars. Anaxagoras scouted the notion
that the sun was a god, and supposed it to be a mass of ignited stone,
for which he was called an atheist.

[Sidenote: Socrates.]

[Sidenote: Pythagoras.]

Socrates, who belonged to another school, avoided all barren
speculations concerning the universe, and confined himself to human
actions and interests. He looked even upon geometry in a very practical
way, so far as it could be made serviceable to land measuring. As for
the stars and planets, he supposed it was impossible to arrive at a true
knowledge of them, and regarded speculations upon them as useless. The
Greek astronomers, however barren were their general theories, still
laid the foundation of science. Pythagoras, born 580 B.C., taught the
obliquity of the ecliptic, probably learned in Egypt, and the identity
of the morning and evening stars. It is supposed that he maintained that
the sun was the centre of the universe, and that the earth revolved
around it. But this he did not demonstrate, and his whole system was
unscientific, assuming certain arbitrary principles, from which he
reasoned deductively. "He assumed that fire is more worthy than earth;
that the more worthy place must be given to the more worthy; that the
extremity is more worthy than the intermediate parts; and hence, as the
centre is an extremity, the place of fire is at the centre of the
universe, and that therefore the earth and other heavenly bodies move
round the fiery centre." But this was no heliocentric system, since the
sun moved like the earth, in a circle around the central fire. This was
merely the work of the imagination, utterly unscientific, though bold
and original. Nor did this hypothesis gain credit, since it was the
fixed opinion of philosophers, that the earth was the centre of the
universe, around which the sun and moon and planets revolved. But the
Pythagoreans were the first to teach that the motions of the sun, moon,
and planets, are circular and equable. Their idea that they emitted a
sound, and were combined into a harmonious symphony, was exceedingly
crude, however beautiful. "The music of the spheres" belongs to poetry,
as well as the speculations of Plato.

[Sidenote: Eudoxus.]

Eudoxus, who was born 406 B.C., may be considered the founder of
scientific astronomical knowledge among the Greeks. He is reputed to
have visited Egypt with Plato, and to have resided thirteen years in
Heliopolis, in constant study of the stars, communing with the Egyptian
priests. His contribution to the science was a descriptive map of the
heavens, which was used as a manual of sidereal astronomy to the sixth
century of our era. He distributed the stars into constellations, with
recognized names, and gave a sort of geographical description of their
position and limits, although the constellations had been named before
his time. He stated the periodic times of the five planets visible to
the naked eye, but only approximated to the true periods.

The error of only one hundred and ninety days in the periodic time of
Saturn, shows that there had been, for a long time, close observations.
Aristotle, whose comprehensive intellect, like that of Bacon, took in
all forms of knowledge, condensed all that was known in his day in a
treatise concerning the heavens. [Footnote: Delambre, _Hist. de
l'Astron. Anc._, tom. i. p. 301.] He regarded astronomy as more
intimately connected with mathematical science than any other branch of
philosophy. But even he did not soar far beyond the philosophers of his
day, since he held to the immobility of the earth - the grand error of
the ancients. Some few speculators in science, like Heraclitus of Pontus
and Hicetas, conceived a motion of the earth itself upon its axis, so as
to account for the apparent motion of the sun, but they also thought it
was in the centre of the universe.

[Sidenote: Meton.]

The introduction of the gnomon and dial into Greece advanced
astronomical knowledge, since they were used to determine the equinoxes
and solstices, as well as parts of the day. Meton set up a sun-dial at
Athens in the year 433 B.C., but the length of the hour varied with the
time of the year, since the Greeks divided the day into twelve equal
parts. Dials were common at Rome in the time of Plautus, 224 B.C.;
[Footnote: Ap. Gell., _N. A._, iii. 3.] but there was a difficulty
of using them, since they failed at night and in cloudy weather, and
could not be relied on. Hence the introduction of water-clocks instead.

[Sidenote: Aristarchus.]

Aristarchus is said to have combated (280 B.C.) the geocentric theory so
generally received by philosophers, and to have promulgated the
hypothesis "that the fixed stars and the sun are immovable; that the
earth is carried round the sun in the circumference of a circle of which
the sun is the centre; and that the sphere of the fixed stars having the
same centre as the sun, is of such magnitude that the orbit of the earth
is to the distance of the fixed stars, as the centre of the sphere of
the fixed stars is to its surface." [Footnote: Lewis, p. 190.] This
speculation, resting on the authority of Archimedes, was ridiculed by
him; but if it were advanced, it shows a great advance in astronomical
science, and considering the age, was one of the boldest speculations of
antiquity. Aristarchus also, according to Plutarch, [Footnote: Plut.,
_Plac. Phil._, ii. 24.] explained the apparent annual motion of the
sun in the ecliptic, by supposing the orbit of the earth to be inclined
to its axis. There is no evidence that this great astronomer supported
his heliocentric theory with any geometrical proof, although Plutarch
maintains that he demonstrated it. [Footnote: _Quaest. Plat._, viii.
1.] This theory gave great offense, especially to the Stoics, and
Cleanthes, the head of the school at that time, maintained that the
author of such an impious doctrine should be punished. Aristarchus has
left a treatise "On the Magnitudes and Distances of the Sun and Moon,"
and his methods to measure the apparent diameters of the sun and moon,
are considered sound by modern astronomers, [Footnote: Lewis, p. 193.]
but inexact owing to defective instruments. He estimated the diameter of
the sun at the seven hundred and twentieth part of the circumference of
the circle, which it describes in its diurnal revolution, which is not
far from the truth; but in this treatise he does not allude to his
heliocentric theory.

[Sidenote: Archimedes.]

[Sidenote: Eratosthenes.]

Archimedes, born 287 B.C., is stated to have measured the distance of
the sun, moon, and planets, and he constructed an orrery in which he
exhibited their motions. But it was not in the Grecian colony of
Syracuse, but of Alexandria, that the greatest light was shed on
astronomical science. Here Aristarchus resided, and also Eratosthenes,
who lived between the years 276 and 196 B.C. He was a native of Athens,
but was invited by Ptolemy Euergetes to Alexandria, and placed at the
head of the library. His great achievement was the determination of the
circumference of the earth. This was done by measuring on the ground the
distance between Syene, a city exactly under the tropic, and Alexandria
situated on the same meridian. The distance was found to be five
thousand stadia. The meridional distance of the sun from the zenith of
Alexandria, he estimated to be 7 degrees 12', or a fiftieth part of the
circumference of the meridian. Hence the circumference of the earth was
fixed at two hundred and fifty thousand stadia, not far from the truth.
The circumference being known, the diameter of the earth was easily
determined. The moderns have added nothing to this method. He also
calculated the diameter of the sun to be twenty-seven times greater than
of the earth, and the distance of the sun from the earth to be eight
hundred and four million stadia, and that of the moon seven hundred and
eighty thousand stadia - a very close approximation to the truth.

[Sidenote: Hipparchus.]

[Sidenote: Greatness of Hipparchus.]

Astronomical science received a great impulse from the school of
Alexandria, and Eratosthenes had worthy successors in Aristarchus,
Aristyllus, Apollonius. But the great light of this school was
Hipparchus, whose lifetime extended from 190 to 120 years B.C. He laid
the foundation of astronomy upon a scientific basis. "He determined,"
says Delambre, "the position of the stars by right ascensions and
declinations; he was acquainted with the obliquity of the ecliptic. He
determined the inequality of the sun, and the place of its apogee, as
well as its mean motion; the mean motion of the moon, of its nodes and
apogee; the equation of the moon's centre, and the inclination of its
orbit; he likewise detected a second inequality, of which he could not,
for want of proper observations, discover the period and the law. His
commentary on Aratus shows that he had expounded, and given a
geometrical demonstration of, the methods necessary to find out the
right and oblique ascensions of the points of the ecliptic and of the
stars, the east point and the culminating point of the ecliptic, and the
angle of the east, which is now called the nonagesimal degree. He could
calculate eclipses of the moon, and use them for the correction of his
lunar tables, and he had an approximate knowledge of parallax."
[Footnote: Delambre, _Hist. de l'Astron. Anc._, tom. i. p. 184.]
His determination of the motions of the sun and moon, and method of
predicting eclipses, evince great mathematical genius. But he combined,
with this determination, a theory of epicycles and eccentrics, which
modern astronomy discards. It was, however, a great thing to conceive of
the earth as a solid sphere, and reduce the phenomena of the heavenly
bodies to uniform motions in of circular orbits. "That Hipparchus should
have succeeded in the first great steps of the resolution of the
heavenly bodies into circular motions is a circumstance," says Whewell,
"which gives him one of the most distinguished places in the roll of
great astronomers." [Footnote: _Hist. Ind. Science_, vol. i. p.
181.] But he even did more than this. He discovered that apparent motion
of the fixed stars round the axis of the ecliptic, which is called the
Precession of the Equinoxes, one of the greatest discoveries in
astronomy. He maintained that the precession was not greater than fifty-
nine seconds, and not less than thirty-six seconds. Hipparchus framed a
catalogue of the stars, and determined their places with reference to
the ecliptic, by their latitudes and longitudes. Altogether, he seems to
have been one of the greatest geniuses of antiquity, and his works imply
a prodigious amount of calculation.

[Sidenote: Posidonius.]

[Sidenote: The Roman Calendar.]

Astronomy made no progress for three hundred years, although it was
expounded by improved methods. Posidonius constructed an orrery, which
exhibited the diurnal motions of the sun, moon, and five planets.
Posidonius calculated the circumference of the earth to be two hundred
and forty thousand stadia by a different method from Eratosthenes. The
barrenness of discovery, from Hipparchus to Ptolemy, in spite of the
patronage of the Ptolemies, was owing to the want of instruments for the
accurate measure of time, like our clocks, to the imperfection of
astronomical tables, and to the want of telescopes. Hence the great
Greek astronomers were unable to realize their theories. Their theories
were magnificent, and evinced great power of mathematical combination;
but what could they do without that wondrous instrument by which the
human eye indefinitely multiplies its power? - by which objects are
distinctly seen, which, without it, would be invisible? Moreover, the
ancients had no accurate almanacs, since the care of the calendar
belonged to the priests rather than to the astronomers, who tampered
with the computation of time for temporary and personal objects. The
calendars of different communities differed. Hence Julius Caesar rendered
a great service to science by the reform of the Roman calendar, which
was exclusively under the control of the college of pontiffs. The Roman
year consisted of three hundred and fifty-five days, and, in the time of
Caesar, the calendar was in great confusion, being ninety days in
advance, so that January was an autumn month. He inserted the regular
intercalary month of twenty-three days, and two additional ones of
sixty-seven days. These, together of ninety days, were added to three
hundred and sixty-five days, making a year of transition of four hundred
and forty-five days, by which January was brought back to the first
month in the year after the winter solstice. And to prevent the
repetition of the error, he directed that in future the year should
consist of three hundred and sixty-five and one quarter days, which he
effected by adding one day to the months of April, June, September, and
November, and two days to the months of January, Sextilis, and December,
making an addition of ten days to the old year of three hundred and
fifty-five. And he provided for a uniform intercalation of one day in
every fourth year, which accounted for the remaining quarter of a day.
[Footnote: Suet., _Caesar_, 49; Plut., _Caesar_, 59.]

"Ille moras solis, quibus in sua signa rediret,
Traditur exactis disposuisse notis.
Is decies senos tercentum et quinque diebus
Junxit; et pleno tempora quarta die.
Hic anni modus est. In lustrum accedere debet
Quae consummatur partibus, una dies."

[Footnote: Ovid, _Fast._, iii.]

[Sidenote: Caesar's labors.]

Caesar was a student of astronomy, and always found time for its
contemplation. He is said even to have written a treatise on the motion
of the stars. He was assisted in his reform of the calendar by
Sosigines, an Alexandrian astronomer. He took it out of the hands of the
priests, and made it a matter of pure civil regulation. The year was
defined by the sun, and not, as before, by the moon.

Thus the Romans were the first to bring the scientific knowledge of the
Greeks into practical use; but while they measured the year with a great
approximation to accuracy, they still used sun-dials and water-clocks to
measure diurnal time. And even these were not constructed as they should
have been. The hours on the sun-dial were all made equal, instead of
varying with the length of the day, so that the hour varied with the
length of the day. The illuminated interval was divided into twelve
equal parts, so that, if the sun rose at five A.M. and set at eight
P.M., each hour was equal to eighty minutes. And this rude method of
measurement of diurnal time remained in use till the sixth century. But
clocks, with wheels and weights, were not invented till the twelfth
century.

The earlier Greek astronomers did not attempt to fix the order of the
planets; but when geometry was applied to celestial movements, the
difference between the three superior planets and the two inferior was
perceived, and the sun was placed in the midst between them, so that the
seven movable heavenly bodies were made to succeed one another in the
following order: 1. Saturn; 2. Jupiter; 3. Mars; 4. The Sun; 5. Venus;
6. Mercury; 7. The Moon. Archimedes adopted this order, which was
followed by the leading philosophers. [Footnote: Lewis, p. 247.]

[Sidenote: Ptolemy and his system.]

The last great light among the ancients in astronomical science was
Ptolemy, who lived from 100 to 170 A.D. in Alexandria. He was acquainted
with the writings of all the previous astronomers, but accepted
Hipparchus as his guide. He held that the heaven is spherical and
revolves upon its axis; that the earth is a sphere, and is situated
within the celestial sphere, and nearly at its centre; that it is a mere
point in reference to the distance and magnitude of the fixed stars, and
that it has no motion. He adopted the views of the ancient astronomers,
who placed Saturn, Jupiter, and Mars next under the sphere of the fixed
stars, then the sun above Venus and Mercury, and lastly the moon next to
the earth. But he differed from Aristotle, who conceived that the earth
revolves in an orbit round the centre of the planetary system, and turns
upon its axis - two ideas in common with the doctrines which Copernicus
afterward unfolded. But even he did not conceive the heliocentric theory
that the sun is the centre of the universe. Archimedes and Hipparchus
both rejected this theory.

In regard to the practical value of the speculations of the ancient
astronomers, it may be said that, had they possessed clocks and
telescopes, their scientific methods would have sufficed for all
practical purposes. The greatness of modern discoveries lies in the



Online LibraryJohn LordThe Old Roman World, : the Grandeur and Failure of Its Civilization → online text (page 30 of 50)