PART II. THE SOLAR SYSTEM. GENERAL CHAPTER I. PHENOMENA OF THE SOLAR SYSTEM, HISTORY, &o. 307. OUR attention has hitherto been directed to those bodies which we see scattered everywhere throughout the whole celestial concave. These bodies, as has been shown, twinkle with a reddish and variable light, and appear to have always the same position with regard to each other. We know that their num ber is very great, and that their distance from us is immeasurable. We are also acquainted with their comparative brightness, and their situation. In a word, we have before us their few visible appearances, to which our knowledge of them is well-nigh limited; almost all our reasonings in regard to them being founded on conparatively few and uncertain analogies. Accordingly, our chief business thus far has been to detail their number, to describe their brightness and positions, and to give the names by which they have been designated. 308. There now remain to be considered certain other celestial bodies, all of which, from their remarkable appearance and changes, and some of them from their intimate connection with the comfort, convenience, and even existence of man, must have always attracted especial observation, and been objects of the most intense contemplation and the deepest interest. Most of these bodies are situated within the limits of the Zodiac. The most important of them are, the SUN, so superior to all the heavenly bodies for its apparent magnitude, for the light and heat which it imparts, for the marked effects of its changes of position with regard to the Earth; and the MOON, so conspicuous among the bodies which give light by night, and from her 307. Subject of Part II.? Of our investigations hitherto? How distinguished? Then nuraber, distance, &c.? What has been our chief business thus far? 308. What now remains to be considered? How situated? Which the most important of them? soft and silvery brightness, so pleasing to behold; remarkable not only for changes of position, but for the varied phases or appearances which she presents, as she waxes from her crescent form through all her different stages of increase to a full orb, and wanes back again to her former diminished figure. 309. The partial or total obscuration of these two bodies, which sometimes occurs, darkness taking place even at mid-day, and the face of night, before lighted up by the Moon's beams, being suddenly shaded by their absence, have always been among the most striking astronomical phenomena, and so powerful in their influence upon the beholders, as to fill them with perplexity and fear. 310. If we observe these two bodies, we shall find that, besides their apparent diurnal motion, across the heavens, they exhibit other phenomena, which must be the effect of motion. The Sun during one part of the year will be seen to rise every day farther and farther toward the north, to continue longer and longer above the horizon, to be more and more elevated at midday, until he arrives at a certain limit; and then, during the other part, the order is entirely reversed. 311. Again; if the Sun's motions be attentively observed, he will be found to have another motion, opposite to his apparent diurual motion from east to west. This may be perceived distinctly, if we notice, on any clear evening, any bright star which is first visible after sunset, near the place where he sunk below the horizon. The following evening, the star will not be visible on account of the approach of the Sun, and all the stars on the east of it will be successively eclipsed by his rays, until he shall have made a complete apparent revolution in the heavens. These are the most obvious phenomena exhibited by these two bodies. 312. The Moon sometimes is not seen at all; and then, when she first becomes visible, appears in the west, not far from the setting Sun, with a slender crescent form; every night she appears at a greater distance from the setting Sun, increasing in size, until at length she is found in the east, just as the Sun is sinking below the horizon in the west. 313. There are also situated within the limits of the Zodia certain other bodies, which, at first view and on a superficial examination, are scarcely distinguishable from the fixed stars 809 What said of their obscuration? 810. Of their motions? 811. Has the Sru an apparent eastward motion? 312. What said of the Moon's motions and phase. i 218. What other bodies and their motions? What called, and why? But, observed more attentively, they will be seen to shine with a milder and steadier light, and, besides being carried round with the stars, in the apparent revolution of the great celestial concave, they will seem to change their places in the concave itself. Sometimes they are stationary; sometimes they appear to be moving from west to east, and sometimes to be going back again from east to west; being seen at sunset sometimes in the east, and sometimes in the west, and always apparently changing their position with regard to the earth, each other, and the other heavenly bodies. From their wandering, as it were, it this manner through the heavens, they were called by the Greeks πλavηTαι, planets, which signifies wanderers. 314. There also sometimes appear in the heavens, bodies of a very extraordinary aspect, which continue visible for a considerable period, and then disappear from our view; and nothing more is seen of them, it may be, for years, when they again present themselves, and take their place among the bodies of the celestial sphere. They are distinguished from the planets by a dull and cloudy appearance, and by a train of light. As they approach the sun, however, their faint and nebulous light becomes more and more brilliant, and their train increases in length until they arrive at their nearest point of approximation, when they shine with their greatest brilliancy. As they recede from the Sun, they gradually lose their splendor, resume their faint and nebulous appearance, and their train diminishes, until they entirely disappear. They have no well-defined figure; they seem to move in every possible direction, and are found in every part of the heavens. From their train they were called by the Greeks Koun raι, comets, which signifies bearded, or having long hair. The causes of these various phenomena must have early constituted a very natural subject of inquiry. Accordingly, we shall find, if we examine the history of the science, that in very early times there were many speculations upon this subject, and that different theories were adopted to account for these celestial appearances. 315. The Egyptians, Chaldeans, Indians, and Chinese, early possessed many astronomical facts, many observations of important phenomena, and many rules and methods of astronomical calculation; and it has been supposed, that they had the ruins of a great system of astronomical science, which in the earliest ages of the world had been carried to a great degree of perfec tion, and that while the principles and explanations of the pho Is it 314. Any other bodies described? How distinguished? What called, and why? probable that these phenomena were early observed? 315. What said of the Egyptians Chaldeans, &c.? Of the Chinese in particular? O. the In Haus and Chaldeans? nomena were lost, the isolated, unconnected facts, rules of calculation, and phenomena themselves, remained. Thus, the Chinese, who, it is generally agreed, possess the oldest authentic observations on record, have recorded in their annals, a conjunction of five planets at the same time, which happened 2461 years before Christ, or 100 years before the flood. By mathe matical calculation, it is ascertained that this conjunction really occurred at that time The first observation of a solar eclipse of which the word has any knowledge, was made by the Chinese, 2128 years before Christ, or 220 years after the deluge. It seems, also, that the Chinese understood the method of calculating eclipses; for, it is said, that the emperor was so irritated against the great officers of state for neglecting to predict the eclipse, that he caused them to be put to death. The Chinese have, from time imemorial, considered Solar Eclipses and conjunctions of the planets, as prognostics of importance to the Empire, and they have been predicted as a matter of state policy. The astronomical epoch of the Chinese, according to Bailly, commenced with Fohi, their first emperor, who flourished 2952 years before the Christian era, or about 350 years before the deluge. If it be asked how the knowledge of this antediluvian astronomy was preserved and transinitted, it is said that the columns on which it was registered have survived the deluge, and that those of Egypt are only copies which have become originals, now that the others have been forgotten. The Indians, also, profess to have many celestial observations of a very early date. The Chaldeans have been justly cele brated in all ages for their astronomical observations. When Alexander took Babylon, his preceptor, Callisthenes, found a series of Chaldean observations, made in that city, and extending back, with little interruption, through a period of 1903 years preceding that event. This would carry us back to at least 2234 years before the birth of Christ, or to about the time of the dispersion of mankind by the confusion of tongues. 316. The Greeks, in all probability, derived many notions in regard to this science, and many facts and observations, from Egypt, the great fountain of ancient learning and wisdom, and many were the speculations and hypotheses of their philosophers The first of the Greek philosophers who taught Astronomy was Thales, of Miletus. He flourished about 640 years before the Christian era. Then followed Anaximander, Anaximenes Anaxagoras, Pythagoras, Plato. Some of the doctrines maintained by these philosophers were, that the Earth was round, that it had two motions, a diurnal motion on its axis, and an annual motion around the Sun, that the Sun was a globe of fire, that the Moon received her light from the Sun, that she was habitable, contained mountains, seas, &c.: that her eclipses wer. caused by the Earth's shadow, that the planets were not designed merely to adorn our heavens, that they were worlds of themselves, and that the fixed stars were centers of distant systems. Some of them, however, maintained that the Earth was flat, and others Chat, though round, it was at rest in the center of the universe. 317. When that distinguished school of philosophy was established at Alexandria, in Egypt, by the munificence of the sovereigns to whom that portion of Alexander's empire had fallen, astronomy recived a new impulse. It was now, in the second century after Christ, that the first complete system or treatise of astronomy of which we have any knowledge, was formed. All before had been unconnected and incomplete. Ptolemy, with the opinions of all antiquity, and of all the philosophers 816. Of the Greeks? Who first taught astronomy among them? Date? Who next? State some of their doctrines? 317. What record of this science? What of Itoicing and his works? who had preceded him, spread out before him, composed a work in thirteen books, called the Meyaλn Evvтağıç, or Great System. 318. Rejecting the doctrine of Pythagoras, who taught that the Sun was the center of the universe, and that the Earth had a diurnal motion on its axis and an annual motion around the Sun, as contrary to the evidence of the senses, Ptolemy endeavored to account for the celestial phenomena, by supposing the Earth to be the center of the universe, and all the heavenly bodies to revolve around it. He seems to have entertained an idea, in regard to the supposition, that the Earth revolved on its axis, similar to one which some entertain even at the present day. "If," says he, "there were any motion of the Earth common to it and all other heavenly bodies, it would certainly precede them all by the excess of its mass being so great; and animals and a certain portion of heavy bodies would be left behind, riding upon the air, and the earth itself would very soon be completely carried out of the heavens." 319. In explaining the celestial phenomena, however, upon his hypothesis, he met with a difficulty in the apparently stationary attitude and retrograde motions which he saw the planets sometimes have To explain this, however, he supposed the planets to revolve in small circles, which he called epicycles, which were, at the same time, carried around the Earth in larger circles, which he called deferents, or carrying circles. In following out his theory, and applying it to the explanation of different phenomena, It became necessary to add new epicycles, and to have recourse to other expedients, until the system became unwieldy, cumbrous, and complicated. This theory, although astronomical observations continued to be made, and some distinguished astronomers appeared fron time to time, was the prevailing theory until the middle of the 15th century. It was not, however, always received with implicit confidence; nor were its difficulties alwayr entirely unappreciated. Alphonso X., king of Castile, who flourished in the 13th century, when contemplating the doctrine of the epicycles, exclaimed, "Were the universe thus constructed, if the Deity had called me to his councils at the creation of the world, I could have given him good advice." He did not, however, mean any impiety or irreverence, except what was directed against the system of Ptolemy. 320. About the middle of the 15th century, Copernicus, a native of Thorn in Prussia, conceiving a passionate attachment to the study of astronomy, quitted the profession of medicine, and devoted himself with the most intense ardor to the study of this science. "His mind," it is said, "had long been imbued with the idea that simplicity and harmony should characterize the arrangements of the planetary system. In the complication. and disorder which he saw reigned in the hypothesis of Ptolemy, he perceived insuperable objections to its being considered as a representation of nature." 819. What 320. What dis 318. His system of astronomy? What singular idea and reasoning? difficulty did he meet with, and how explain it ? What further difficulty? How long did this theory prevail? What anecdote of the King of Castile? tinguished student of astronomy now arose? His impressions in regard to the Ptolemaic theory? His own earlier convictions? What other theories did he study? |