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CHAPTER I.

SYSTEM OF THE UNIVERSE.

1. WE find it recorded in the Sacred History of the Creation, That God made Lights in the firmament of the heaven to give light upon the earth;-to divide the day from the night, and to be for signs, and for seasons, and for days and years:-He made the greater light to rule the day, and the lesser light to rule the night; He made the stars also1.

2. These Celestial Lights are rendered subservient to the purposes for which they were created by certain established laws of Motion, according to which they either really move, or seem to us to move. As the Divine Wisdom has not thought proper to reveal to us what these laws of Motion are, there have been certain conjectures made concerning them. These conjectures are called Systems, from a Greek word (ovviornμ) denoting the harmoniously placing or arranging of certain bodies with respect to one another; they are also named Hypotheses or suppositions (from brоrin), because it can not be asserted concerning even the most probable of them, that the heavenly bodies do so move. But it is reasonable to suppose that they do move according to one of these Systems rather than in any other way, because upon such a supposition their phænomena or appearances (from paivouai) may be fairly solved and explained. It is the business of a particular Science to explain these systems and phænomena, and hence it is called Astronomy, from two Greek words (aorpov astrum and vóμos lex) denoting the knowledge of the laws of the stars or heavenly bodies.

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CHAPTER I.

SYSTEM OF THE UNIVERSE.

1. WE find it recorded in the Sacred History of the Creation, That God made Lights in the firmament of the heaven to give light upon the earth;-to divide the day from the night, and to be for signs, and for seasons, and for days and years:-He made the greater light to rule the day, and the lesser light to rule the night; He made the stars also1.

2. These Celestial Lights are rendered subservient to the purposes for which they were created by certain established laws of Motion, according to which they either really move, or seem to us to move. As the Divine Wisdom has not thought proper to reveal to us what these laws of Motion are, there have been certain conjectures made concerning them. These conjectures are called Systems, from a Greek word (ovvíornju) denoting the harmoniously placing or arranging of certain bodies with respect to one another; they are also named Hypotheses or suppositions (from brоrin), because it can not be asserted concerning even the most probable of them, that the heavenly bodies do so move. But it is reasonable to suppose that they do move according to one of these Systems rather than in any other way, because upon such a supposition their phænomena or appearances (from paivouai) may be fairly solved and explained. It is the business of a particular Science to explain these systems and phænomena, and hence it is called Astronomy, from two Greek words (orpov astrum and vópos lex) denoting the knowledge of the laws of the stars or heavenly bodies.

1

Again the Almighty spake, "Let there be lights

High in the expanse of heaven, to divide

The day from night; and let them be for signs,
For seasons, and for days and circling years;
And let them be for lights as I ordain

Their office in the firmament of heaven,

To give light on the earth."

Milton, Par, Lost, Book VII. 339.

B

3. There are four remarkable and well-known Systems or Hypotheses connected with the Sun and Planets; viz. the Pythagorean or Copernican, the Ptolemaic, the Tychonic, and the Newtonian. The last of these is now generally received by the learned from its having been established by Sir Isaac Newton on an immovable foundation: it is also called the Solar, or Planetary System. It derives the former of these names from Sol, or the Sun, which is made it's centre; and the latter from the word Planet by which all those bodies moving round the Sun are designated. The name Planet is from the Greek λavirns which signifies wanderer; and inasmuch as these celestial lights never preserve for any length of time the same relative situation, they may be said to be always straying or wandering from each other. The ancients were acquainted with six such Planets; viz. Mercury next the Sun; then follow successively Venus, the Earth, Mars, Jupiter and Saturn which last was the outermost of the whole: modern astronomers have added five others to this number, but from their (apparently) diminutive size, they are much less important than the preceding. It is concerning the motions of the Planets with respect to the Sun and to each other, that there was such a difference of opinion until Newton explained their phenomena after the most simple and uniform manner.

4. All the heavenly bodies are spheres (or nearly so), but in consequence of their enlightened parts only being seen by us, they appear by reason of their great distance as plane surfaces; and hence these apparent surfaces are sometimes called discs, from the Latin word discus, as resembling a flat round dish. A straight line passing through the centre of a circle and cutting the circumference in two parts, is called its diameter, because it (diaperper) measures through it: now if a circle be supposed to turn completely round on this diameter, it will form a solid figure called a Sphere. A Hemisphere (from pove dimidius and opaipa sphæra) is a half-sphere cut through the centre by a right line in any direction; thus we say the Northern and Southern Hemispheres, the Eastern and Western Hemispheres, the Upper and Lower Hemispheres, and so on.

5. There is no doubt about the Chaldæans and Egyptians having been the first people in the world who were acquainted with astronomy; the Greeks borrowed it from the latter people, and like them derived from it a great part of their mythological fables. Thales is the first Greek who is mentioned as having laid the foundations of astronomy amongst his countrymen (B. c. 600); he was so well

2 And ye five other wandering fires, that move
In mystic dance not without song, resound
His praise, who out of darkness call'd up light.

Milton, Par. Lost, Book V. 177.

acquainted with the motions of the heavenly bodies that he not only explained the eclipses but actually predicted one; he taught that the earth was round, which most of his countrymen (both before and after his time) looked upon as only a plane; he likewise showed the causes of solstices and equinoxes, and divided the year into 365 days. His opinions were afterwards maintained, though with occasional alterations for the worse, by Anaximander, Anaximenes, Anaxagoras and others. But the most remarkable of his disciples was Pythagoras who is conjectured to have been well acquainted with the annual and diurnal revolution of the earth round the sun, though he only professed these opinions in private to his pupils: one of these named Philolaus was the first who taught openly the doctrines of his master, (about 450 B. C.), in which he was followed by Nicetas, Plato, Archimedes, Eratosthenes, Hipparchus &c.; but this true system of the universe was lost during the reign of the Peripatetic philosophy, and was first retrieved by Copernicus, about 300 years ago. (See Plate I. fig. 2.)

6. The Ptolemaic System was so named from the famous geographer and mathematician Claudius Ptolemæus who flourished at Pelusium in Egypt during the reigns of the Roman emperors Hadrian and Antoninus Pius. He taught that the earth was at rest in the centre of the universe, and that the heavens revolved round it from East to West in twenty-four hours, carrying all the heavenly bodies, stars and planets along with them: but as there were many difficulties in his system he endeavoured to account for some of the motions of the heavenly bodies by the introduction of cycles and epicycles which though they were exceedingly ingenious, were almost unintelligible. These doctrines were subsequently universally believed and maintained by the learned of all nations till they were refuted by Copernicus and Newton. (See Plate I. fig. 3.)

7. Nicholas Copernicus (born A. D. 1473 at Thorn a town of Prussia) the author of the Copernican System, unable to reconcile the confused and perplexing hypothesis of Ptolemy with his own observations, or with those notices concerning the heavenly bodies which he found scattered over the works of the earlier philosophers, set about to reform it's absurdity. But so firmly had the 1400 years which had elapsed from the time of Ptolemy to his own days rooted the error, that to confute it was incurring the imputation of heresy; and for this, about a century afterwards, Galileo, who made many improvements in the system of Copernicus, suffered the severest punishments. Copernicus taught (as Pythagoras had done before him) that the sun occupied the centre of the universe and that the planets moved round him3 in elliptical orbits proportioned to their size: this system established by the new arguments and discoveries of Galileo, Kepler and Newton, has finally prevailed over the prejudices against the earth's motion, encouraged as they were by the threats of ignorant bigots and the terror of the inquisition. (See Plate I. fig. 2.)

8. The Tychonic System was so called from Tycho Brahe a noble Dane (born A. D. 1546), who partly revived the old system of Ptolemy concerning the earth remaining at rest whilst the other heavenly bodies moved round it: he is said to have been induced to establish this hypothesis from an attachment to the popular superstition concerning the motionless state of the earth, which was founded not only on the plausible nature of such an arrangement, but on the erroneous interpretation of

Herod. I. 74.

3 What if the Sun

Be centre to the world; and other stars,

By his attractive virtue and their own

Incited, dance about him various rounds?

Their wandering course now high, now low, then hid,

Progressive, retrograde, or standing still,

In six thou seest; and what if seventh to these

The planet Earth, so stedfast though she seem,
Insensibly three different motions move?

Milton, Par. Lost, Book VIII. 122.

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