INTRODUCTION.

PRELIMINARY OBSERVATIONS AND DEFINITIONS.

CHAPTER I.

ORIGIN AND HISTORY OF THE SCIENCE.

1. SCIENCE is knowledge systematically arranged, so as to be conveniently taught, easily learned, and readily applied.

2. ASTRONOMY is the science of the heavenly bodiesthe Sun, Moon, Planets, Comets, and Fixed Stars.

The term astronomy is from the Greek astron, a star, and nomos, a law; and signifies the laws or science of the stars.

3. Astronomy is divided into Descriptive, Physical, and Practical.

Descriptive Astronomy includes the mere facts of the science, irrespective of the causes of the phenomena observed, or of the means by which the facts were ascertained.

Physical Astronomy explains the causes of the various phenomena observed, as of Day and Night, the Seasons, Eclipses, Tides, &c.

Practical Astronomy relates to the means for acquiring astronomical knowledge by the use of instruments, and by mathematical calculations.

These three departments have arisen, one after the other, in the order in which they are here stated. At first a few facts and phenomena were observed, but the causes were unknown. Next some of the causes were investigated one by one; and, finally, instruments were invented for measuring distances, altitudes, &c.; data for calculations were obtained; and thus arose the department of Practical Astronomy.

1. Define the term Science.

2. What is Astronomy? (From what is the term derived ?)

3. How is astronomy divided? Descriptive? Physical? Practical? (State the order in which these departments have arisen.)

4. Astronomy has long been regarded as the most sublime of the sciences, eminently calculated to illustrate the wisdom, power, and goodness of God; to elevate and expand the human mind, and to fill it with exalted views of the Creator

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The glorious Architect who built the skies."

1. "The greatest men of all ages have pronounced this science to be the most sublime and surpassing of all that can be tested by human genius, and to be worthy of a life of study."-Smyth's Celestial Cycle.

2. "Our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above the low-contracted prejudices of the vulgar, and our understandings clearly convinced, and affected with the conviction of the existence, wisdom, power, goodness, and superintendency of the SUPREME BEING!"-Ferguson.

3. So remarkably does this science exhibit the glory and majesty of God, by its astounding revelations of His works, that it almost necessarily tends to fill the mind with awe and reverence. It was in view of this tendency that the poet Young said,

"An undevout astronomer is mad."

4. To the moral influence of the contemplation of the heavens, we have frequent reference in the sacred Scriptures. "The heavens declare the glory of God; and the firmament showeth his handy-work." (Psalm xix. 1.) "When I consider thy heavens, the work of thy fingers; the moon and stars, which thou hast ordained; what is man, that thou art mindful of him? and the son of man, that thou visitest him?" (Psalm viii. 8, 4.)

5. Astronomy is probably the most ancient of all the sciences. Some of the Chaldean observations date as far back as 2,250 years before Christ, or only 98 years. after the Flood! Laplace speaks confidently of Chinese observations 1,100 B. c.; and Mr. Bailly, an English astronomer, fixes the time of a conjunction of Mars, Jupiter, Saturn, and Mercury, mentioned in Chinese records, at 2,449 years before Christ.

1. The ancient Chinese astronomers and mathematicians were held to a fearful responsibility for the correctness of their calculations. In the reign of the Emperor Choukang, his two chief astronomers, Ho and Hi, were condemned to death for neglecting to announce the precise time of a solar eclipse, which took place B. C. 2,169.

2. The Holy Scriptures, some parts of which are very ancient, contain several allusions to the science of astronomy. In the first chapter of Genesis we have an account of the creation of the Sun, Moon, and Stars. "And God said, Let there be lights in the firmament of the heaven, to divide the day from the night, and let them be for signs, and for seasons, and for days and years. And let them be for lights in the firmament of the heaven, to give light upon the earth: and it was so. And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also." Verses 14-16.

8. In the book of Job, written 1,500 years before Christ, we read of several constellations that bear the same names now that they did three thousand years ago. "Which maketh Arcturus, Orion, and Pleiades, and the chambers of the south." (ix. 9.) Again: "Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion? Čanst thou bring forth Mazzaroth in his season? or canst thou guide Arcturus with his sons ?" (Chap. xxxviii. 31, 32.)

4. How astronomy regarded? (Smyth? Ferguson? Young? Scriptures?) 5. What of antiquity of astronomy? Chaldean and Chinese observations (Responsibility of Chinese astronomers? Ancient Scriptural allusions?)

6. The first astronomers were shepherds and herdsmen, who were led to this study by observing the movements of the sun, moon, and stars, while watching their flocks from year to year in the open fields.

ANCIENT ASTRONOMERS OBSERVING THE HEAVENS.

7. Thales, one of the seven wise men of Greece, was the first regular teacher of Astronomy, B. c. 600. The next was Anaximander, a disciple of Thales, who suc'ceeded him as head of the school at Miletus, B. c. 548. He asserted the true figure of the earth, and seems to have had some idea of its daily revolution.

Anaximander is supposed to have been the first who constructed globes and maps. He taught that the moon shines by reflection, and in several other respects advanced beyond the knowledge imparted by his distinguished tutor.

8. Pythagoras, another Greek philosopher, who founded the school of Croton, B. c. 500, greatly enlarged the science. He first gave form to the vague ideas that the sun was in the center of the planetary orbits, that the earth floated unsupported in space, and that the distant stars were worlds, and probably inhabited.

"It was Pythagoras," says Smyth, "who taught, in fact, the system which now immortalizes the name of Copernicus." But he adds that his teachings were but "the conjectures of a sagacious mind, not possessed of the evidence requisite to give stability to its opinions." Pythagoras is said to have perished from hunger, in his old age.

6. Who were the first astronomers? How led to this study?

7. Who first regular teacher of this science? How early? Who next?and when? What correct notions did he seem to entertain? (For what else distinguished?)

8. Who next after Anaximander? What advances did he make in this study? (What does Smyth say of his teachings? What said of his death?)

9. Ptolemy, an Egyptian philosopher, taught astronomy in the second century of the Christian era. He adopted the theory that the earth was located in the center of the universe, that it was perfectly at rest, and that the sun, moon, and stars actually revolved around it, from east to west, as they appear to do, every twenty-four hours. This system is called, after its author, the Ptolemaic Theory.

1. Ptolemy supposed the earth to be in the center of a system of crystalline arches, or hollow spheres, arranged one within the other, as represented in the cut. It is thought by some that he understood the spherical figure of the earth, and the cut is constructed upon this supposition. Ptolemy further supposed that the sun, moon, and stars were fixed in these crystalline spheres, at different distances from our globe; that the Moon was in the first, Mercury in the second, Venus in the third, the Sun in the fourth, Mars,

9. Who was Ptolemy?-and when did he flourish? Describe his theory, (How locate sun, moon, &c.? What absurdity did it involve, as it respects

Jupiter, and Saturn in the next three, and the fixed stars in the eighth. The ancients had no knowledge of Uranus or Neptune. This ponderous machinery was supposed to revolve from east to west around the earth, carrying with it the sun, moon, and stars, every twenty-four hours; and the spheres being crystal, the distant stars were visible through them.

2. If the sun was designed to enlighten and warm the different sides of our globe, the Ptolemaic method of effecting this object is most unreasonable. To carry the sun around the earth, to warm and enlighten its different sides, instead of having the earth turn first one side and then the other to the sun, by a revolution on its axis, would be like carrying a fire around a person who was cold, and wished to be warmed, instead of his turning himself to the fire as he pleased.

8. The Ptolemaic theory would require a motion inconceivably rapid in all the heavenly bodies. As the sun is ninety-five millions of miles from the earth, the entire diameter of his sphere would be one hundred and ninety millions of miles, and its circumference about six hundred millions. Divide this distance by twenty-four--the number of hours in a day-and it gives twenty-five million miles an hour, or sixty-nine thousand four hundred and forty-four miles per second, as the velocity of the sun! This theory would require a still more rapid motion in the fixed stars. It would require the nearest of these to move at the rate of nearly fourteen thousand millions of miles per second, or seventy thousand times as swift as light, in order to accomplish their daily course. But with all these difficulties in its way, the Ptolemaic theory was generally believed till about the middle of the sixteenth century, or three hundred years ago.

THE COPERNICAN SYSTEM.

10. About the year 1510, the ancient theory of Pythagoras was revived and improved by Copernicus, a Prussian astronomer, and has since been called, after him, the Copernican System.

1. The investigations of Copernicus were conducted between the years 1507 and 1580. In the latter year he finished his tables of the planets, and his great work, The Revolution of the Celestial Orbs; but he did not venture to publish his views till thirteen years after, or 1543, when he received a copy of it only a few hours before his death, and consequently never read it in print. It contains the old philosophy, interspersed with his own original and acute conceptions, and was received under very considerable opposition.-Smyth, vol. 1, p. 38.

2. Copernicus is generally regarded as the discoverer of the system which bears his name, but this is a popular error. There is abundant proof, notwithstanding the loss of his writings, that Pythagoras understood the leading features of what is now called the Copernican Theory.

11. The first prominent feature of the Copernican system is, that the earth is a sphere or globe, inhabited on all sides.

The evidence that the earth is a sphere or globe may be arranged and stated as follows:

1. Admitting that the sun, moon, and stars are worlds, the fact that they are round, as we see them to be, affords ground for the presumption, at least, that the earth also is round.

2. Water falling from the clouds is gathered into little globes or drops; and melted lead poured from the summit of a high tower assumes the form of globes, which, when cooled, are called shot. And the same law would cause a larger mass of fluid matter, if left undisturbed in space, to assume the same shape. But the Bible teaches that the

light and heat? What in respect to the motions of the heavenly bodies? Was such a theory ever generally believed? Till how recently?)

10: Who was Copernicus? For what distinguished? About what time? (What of his investigations? His work? Its publication? Character? What popular error noticed?)

11. State the first leading feature of the Copernican theory. (What proofs of its correctness? The first? Second? Third Fourth? Fifth? Sixth? Seventh ?)