HISTORY OF ASTRONOMY.

In the ancient Hindoo writings, many sublime sentiments occur on the subject of creation; and they contain various accounts which bear a close resemblance to the Mosaic history. Thus we are told that the universe first existed only in the divine idea; and that the sole self-existing power expanded this idea, and made the world visible with five elements and other principles of nature. Then He, whom the mind alone can perceive, whose essence eludes the external organs, who has no visible parts, and who exists from eternity, even He, the soul of all beings, whom no one can comprehend, shone forth in person. He framed all things. Then He whose powers are incomprehensible, having created this universe, was again absorbed in the spirit, changing the time of energy for the time of repose.

The Chaldean cosmogony, when divested of its allegorical form, seems to amount to this,- that darkness and water existed from eternity; that Bel divided the humid mass and gave birth to creation; and that the human mind is an emanation from the divine nature.

In the cosmogony of the ancient Persians, appear two eternal principles, -the one good, called Oromosdes or Ormuzd; and the other evil, called Ariman. These two principles contend with each other in the creation and government of the world. Each has his province, which he strives to enlarge, and Mithra is the mediator to moderate their contentions.

CHAPTER XIII.
History of Astronomy.

25

It is impossible to trace the history of astronomy back to its very earliest state of infancy. Perhaps this science is as old as society itself, and we may regard the rude observations of shepherds and herdsmen as exhibiting a step in its progress. The invenThe Egyptian cosmogony, according to the account tion of astronomy as a science has been ascribed to given of it by Plutarch, bears a strong resemblance to various nations, as the Chaldeans, the Egyptians, the that of Sanchoniathon. In this system, there was an Chinese, and the Hindoos. It is at least certain, that eternal chaos, and an eternal spirit united with it, these people were very early observers of the motions whose agency at last arranged the discordant mate- and phenomena of the heavenly bodies, that they regrials, and produced the visible system of the universe. istered certain events, and by these means were able The Orphic Fragments, or verses ascribed to Orpheus, to discover the periods at which these phenomena affirm that everything existed in God and proceeded from him. This doctrine may be characterized as pantheistic, that is, to implying that the universe is God.

would return again. This is science in its rudest and most imperfect shape.

The Hebrew Scriptures, which are the most ancient writings extant, describe the visible objects of the universe just as they appear to the eye. The earth is represented as a flat plane resting on "foundations which can never be moved." The sun, moon, and stars are spoken of as mere lights hung up on high to shed their beams over the earth. The heavens are described as a firmament dividing the waters above from the waters below, and through the openings or windows of which the rain fell upon the earth. The ancient Hebrews, evidently, had no idea of astronomy as a science.

Plato supposed the world to be produced by the Deity uniting eternal, immutable ideas, or forms, to variable matter. Aristotle had no proper cosmogony, because he supposed the world to be without beginning and without end. According to the doctrine of the Stoics, the divine nature, acting on matter, first produced moisture, and then the other elements, which are reciprocally convertible. Epicurus held that the universe was formed by the concourse of atoms, without the intervention of a divine creator. The cosmogony of the barbarous nations of the North, as may be The Chaldeans appear to have made observations collected from the Edda, supposes an eternal principle on eclipses, at a period earlier than the commencewhich existed prior to the formation of the world. ment of written history. Their first notions of the These accounts are interesting and valuable, as sun and moon were, that these luminaries were on showing the difficulties which mankind have encoun- fire on one side, and dark on the other, and that tered in studying the system of the universe, and the eclipses were caused by their occasionally turning errors and absurdities into which they have been led round. Another belief was, that these bodies were by following mistaken systems of philosophy, or the carried round the heavens in chariots, close on all still more illusive guide of fancy. The advances sides except one, in which was a round hole; and that which have been made in modern times, not only in a total or partial eclipse was caused by the complete or the art by which truth is to be obtained, but in the partial shutting of this aperture. acquisition of knowledge, will be established in a brief view of the present state of science, respecting astronomy, geology, and geography, which we shall present to the notice of the reader.

The Egyptians, previous to the birth of science among the Greeks, had some correct notions as to the length of the year, and had made some advances towards a knowledge of the obliquity of the ecliptic, although they were indebted to Thales of Miletus for the art of measuring the height of their pyramids from the length of their shadows. The Chinese are said to

26

PRESENT STATE OF KNOWLEDGE IN RESPECT TO ASTRONOMY-SOLAR SYSTEM.

have calculated eclipses more than 2000 years before Christ. Of their general notions of astronomy at this time, however, we know nothing.

which are now regarded as the true foundation of the solar system.

Galileo invented the telescope in 1610, and by the Thales is regarded as the founder of astronomy help of this instrument, made the first discovery of the among the Greeks. He flourished about 600 years satellites of Jupiter. He also discovered the phases before Christ. He supposed the stars to be fire, and of Venus. The Catholic church, which had long that the moon received her light from the sun. He defended with intolerent bigotry the Ptolemaic sysunderstood the earth to be round, but supposed it to tem, compelled Galileo to renounce his opinions. But be placed in the centre of the universe. The heavens, the progress of scientific truth was not checked by this in his system, were divided into five circles,-the persecution. equator, the two tropics, and the arctic and antarctic circles. He fixed the length of the year at 365 days. Thales is also said to have predicted the celebrated eclipse of the sun which caused the termination of the war between the Medes and Lydians.

Herschel discovered in 1781 the planet which at first bore his name, and afterwards that of Georgiam Sidas, but which is now called Uranus. The asteroids were discovered at various times, from 1801 to 1847. The most remarkable of astronomical discoveries was that of Neptune, the most distant known planet of our system. The existence of this body was demonstrated in 1846, by a series of mathematical calculations, made by Le Verrier, a Frenchman, and Adams, an Englisherally ascribed to the former. The present state of the science of astronomy deserves particular notice, as it presents to the mind the most sublime objects of contemplation, and is calculated to exalt our estimate of those powers bestowed upon us by the Creator. A brief view of this subject is, furthermore, a fit preliminary to the study of the history of man, inasmuch as it points out his relation to the universe, and shows the immeasurable scope of that system of which every individual is a part.

Anaximander, Anaximanes, and Anaxagores, the successors of Thales, within a century of his time, contributed much to the advancement of astronomy. The last taught that the moon was habitable, and consisted of hills, valleys, and waters, like the earth. man-though the honor of the discovery is more genPythagoras, who flourished about 540 B. C., added greatly to the science of astronomy. He taught that the universe was composed of four elements, and that the sun was in the centre; that the earth was round, and that we had antipodes; that the moon reflected the rays of the sun; that the stars were worlds containing earth, air, and ether; that the moon was inhabited like the earth, and that the comets were wandering stars, disappearing in the superior parts of their orbits, and becoming visible in the lower parts. The white color of the milky way he ascribed to the brightness of a great number of small stars. He supposed the distances of the moon and planets from the earth to be in certain harmonic proportion to one another. He was the first observer who ascertained that the planet Venus is both the morning and evening star.

CHAPTER XIV.

omy-The Solar System.

Hipparchus, who flourished in the second century Present State of Knowledge in respect to Astronbefore Christ, carried astronomy to still higher perfection. He fixed the length of the year at 365 days, 5 hours, and 53 minutes, which is within four minutes and three seconds of the truth. He discovered a method of computing with triangles, and established the theory of the sun's motion. A new star made its appearance in his time, and this suggested to him the scheme of forming a catalogue of the stars, for the purpose of enabling future astronomers to ascertain whether the general picture of the heavens remained always the same.

Ptolemy of Alexandria, in the second century after Christ, established a theory of astronomy which still bears his name. He taught that the earth was immovable, and that the sun and planets revolved round it. The science of astronomy had reached its highest point amongst the Greeks, and began to decline. The Saracens, about the middle of the seventh century, dispersed the men of science and destroyed the libraries which had been collected at Alexandria. Astronomy was cultivated by these people after they had settled themselves peaceably in the countries which they had conquered.

THE heavenly bodies are to be regarded as comThe revival of astronomy in Europe is referred to posed of the Sun and its attendant orbs, called the the time of Copernicus, though he was preceded by solar system; and the fixed stars, which are supposed some others, who prevented the last traces of Grecian to be other suns, and centres of troops of planets revolvand Arabic science from being effaced, by preserving ing around them. The former are to us by far the and studying such works as the dark ages had spared. most interesting, as they are not only so near as to be Copernicus was born in the latter part of the 15th cen- within reach of investigation, but they are of that tury. He placed the sun in the centre of the revolv- sisterhood of worlds of which our own earth is a ing planets, and laid down those general principles member.

PRESENT STATE OF KNOWLEDGE IN RESPECT TO ASTRONOMY-SOLAR SYSTEM.

27

density is little more than that of water, it would weigh 3360 planets such as Saturn, 1067 planets such as Jupiter, 329,000 globes such as the Earth, and more than 2,000,000 of globes such as Mercury, although its density is nearly equal to that of lead."

The Solar System is composed of a great central to pass along every square mile on its surface, at the luminary, the Sun, and a number of comparatively rate of thirty miles every day, it would require more small bodies, the planets, comets, &c., which re- than two hundred and twenty millions of years before volve around it in various periods. The relative the survey of this vast globe could be completed. size of these bodies, and their respective distances "It would contain within its circumference more from each other, may be estimated by the follow-than thirteen hundred thousand globes as large as the ing illustration. On a level field, place a globe, Earth, and a thousand globes of the size of Jupiter, two feet in diameter; this will represent the SUN. which is the largest planet of the system. It is more MERCURY will be represented by a grain of mustard- than five hundred times larger than all the planets, seed, on the circumference of a circle 164 feet in di- satellites, and comets belonging to our system, vast ameter; VENUS, by a pea, on a circle 284 feet in and extensive as some of them are. Although its diameter; the EARTH, a somewhat larger pea, on a circle of 430 feet; MARS, a large pin's head, on a circle of 654 feet; JUNO, CERES, VESTA, and PALLAS, grains of sand, in orbits of from 1000 to 1200 feet; JuPITER, an orange, in an orbit of nearly half a mile across; SATURN, a small orange, in an orbit of four The most obvious apparent motion of the Sun is, fifths of a mile; and URANUS, a cherry, on the circum- that it seems to rise in the morning in the east, to ference of a circle more than a mile and a half in traverse the heavens in a westerly direction, and at diameter. We shall now proceed to give a more par- last, to disappear beneath the horizon. But it is now ticular account of these members of the solar system.well understood that the Sun is quiescent, and that The Sun, when viewed with a telescope, presents the seeming motion we have described is occasioned the appearance of an enormous globe of fire, frequently by the daily rotation of the Earth on its axis. But in a state of violent agitation or ebullition. Black although the Sun is fixed in the centre of the system spots, of irregular form, rarely visible to the naked of planets, it appears that it revolves on its axis like eye, sometimes pass over his disk, in a space of about the other heavenly bodies, and that it completes its fourteen days; one was measured by Sir W. Herschel, revolution in twenty-five days and ten hours. Every in 1779, and found to be 30,000 miles in breadth. A part of its equator moves at the rate of 4352 miles spot, when first seen on the eastern edge, appears like an hour. It is also considered probable that the Sun, a line, progressively extending in breadth, till it attended by its troop of planets, makes a vast journey reaches the middle, when it begins to contract, and in space, but whether in a straight line, or in an ultimately disappears at the western edge. In some immense circle, is still matter of conjecture. rare instances, spots reappear on the eastern side, and are even permanent for two or three revolutions; but they generally change their aspect in a few days, and disappear.

Astronomers inform us, that sometimes 50 spots are seen at once on the Sun's surface. From 1611 to 1629, it was hardly free from spots; while, from 1650 to 1670, scarcely any were to be seen. The same irregularity has been frequently noticed. In October, 1827, 150 spots were noticed at one time.

Sometimes, several small spots unite into a large one; again, a large one separates into smaller ones, which soon vanish. These phenomena induced Herschel to suppose the Sun to be a solid, dark nucleus, surrounded by a vast atmosphere, almost always filled with luminous clouds, occasionally opening and disclosing the opaque mass within.

The planet Mercury is 37,000,000 miles from the Sun, and is the nearest that has yet been discovered. It is seldom seen by the naked eye; its daily revolu-, tion is performed in 24 hours, 5 minutes, and 20 seconds. It revolves round the Sun in the space of 87 days and 23 hours. When viewed with the telescope, it presents the various phases of the moon, from a crescent to the full, round orb.

The diameter of Mercury is 3200 miles. Its surface contains 32,000,000 of square miles. It is about one fifteenth the size of the Earth. In its revolution round the Sun, its motion is swifter than that of any other planet, being 109,800 miles every hour, 1830 miles every minute, and more than 30 miles during each beat of the pulse. The density of matter composing Mercury is twice that of the Earth, yet it would require two millions of globes, of the same size, to make one of the size and density of the Sun.

The speculations of Laplace were different; he imagined the solar orb to be a mass of fire, and that the The planet Venus, with the exception of the Sun violent effervescences and explosions, seen on its sur- and moon, is the most splendid of the heavenly bodies. face, are occasioned by the eruption of elastic fluids It appears like a shining lamp amid the lesser orbs of formed in its interior; and that the spots are enor- night; and, at particular seasons, ushers in the mornmous caverns, like the craters of our volcanoes. The ing dawn and the evening twilight. But if such is theory of Herschel, however, is that most generally its appearance to the naked eye, it becomes a still received by learned men. more interesting object, when viewed with the telesThe magnitude of this vast luminary is an object cope of the astronomer. It passes through all the which overpowers the imagination. Its diameter phases of the moon, from the crescent to the gibbous is 880,000 miles; its circumference, 2,764,600 miles; form; and formerly several dark spots were noticed its surface contains 2,432,800,000,000 of square miles, upon its surface. Its daily rotation is performed in 23 which is twelve thousand three hundred and fifty hours and 20 minutes. Several mountains have been times the area of the terraqueous globe, and nearly discovered, and one of them is nearly twenty miles fifty thousand times the extent of all the habitable parts of the earth. Were its centre placed over the earth, it would fill the whole orbit of the moon, and reach 200,000 miles beyond it on every hand. Were a person to travel over the surface of the Sun, so as

high, or five times the height of Chimborazo. It possesses an atmosphere supposed to be about three miles in height, and is supposed to have a satellite, or moon; but this is not determined with certainty.

The diameter of Venus is 7800 miles, being a little

PRESENT STATE OF THE SCIENCE OF ASTRONOMY.

less than that of the Earth. It does not appear that is very limited. The deepest mine does not extend any great quantity of water exists upon it. Its quan- more than a mile from the surface; and this depth, tity of light is about twice that of the Earth. It re- compared with the diameter of the Earth, is not more volves in an orbit of 433,800,000 miles, in the space than the scratch of a pin upon the surface of an artiof 224 days and 16 hours. Its distance from the Sun ficial globe. What materials are to be found within is 68,000,000 miles; and from the Earth, when near- the bowels of the Earth, will be forever beyond the est to us, about 27,000,000 miles. Its matter is in a slight degree less dense than that of the Earth.

Present State of the Science of Astronomy, con- size. The diurnal revolution of the Earth is per

PRESENT STATE OF THE SCIENCE OF ASTRONOMY.

29

must thus alternate would destroy human life, even on | farthest, 240,000,000 miles. This fact will explain, the supposition that vegetation could be maintained. what most persons have noticed, that this planet is at The moon, like all other heavenly bodies, appears one time almost imperceptible, and at another seems to rise in the east and set in the western part of the to vie with Jupiter in magnitude and splendor. The horizon. Its real motion, however, is in a contrary diurnal revolution of Mars is performed in 24 hours, direction- that is, from west to east, or in the same 39 minutes, 29 seconds. Its orbit is 900,000,000 direction in which all the planets move round the Sun. miles in circumference. It performs this circuit in 1 It is a dark body, deriving its light from the Sun, and year and 322 days. Its rate of motion is 54,649 occasionally a faint light, by reflection of the Sun's miles every hour, which is more than a hundred times rays, from the Earth. It is about 240,000 miles from greater than the utmost velocity of a cannon-ball. the centre of the Earth, and pursues its course around When viewed through a telescope, this planet prethis planet at the rate of 2300 miles an hour. It sents a variety of dark spots and belts, though of difperforms its revolution in 29 days, 12 hours, and 44 ferent forms and shades. Luminous spots, and zones, minutes. It is a curious fact, that the revolution on have also been discovered, which frequently change its axis is performed in the same time as its revolu- their appearance, and alternately disappear and return. tion round the Earth. Accordingly, it always presents The latter are supposed to be occasioned by snow; the the same face to the Earth, so that we never see more former are conjectured to be occasioned by a distributhan one side of it. tion of the surface of the planet into land and water. It is supposed that one third of the surface is occupied by the latter. It is probable that the diversities in the appearance of Mars, as seen through a telescope, are in part occasioned by clouds.

The moon appears nearly as large as the Sun; but it is but about one fiftieth the size of the Earth, and it would take 63,000,000 of globes, of the size of the moon, to make one of the Sun.

An Eclipse of the Sun.

Mars has a variety of seasons, similar to ours, and it bears a closer resemblance to the Earth than any other planet. It is 4200 miles in diameter, a little more than half that of our globe. No moon or satellite has been discovered, as attendant upon it.

Ceres, Pallas, Juno, and Vesta.-The immense interval which lies between the orbits of Mars and Jupiter had led astronomers to surmise that some planet, of considerable magnitude, might possibly exist within this limit. But instead of one, four small orbs have been recently discovered, which bear the above names. The first, called Ceres, was discovered by Piazzi, in Sicily, on the first day of the present century. Pallas was discovered in March, 1802, by Olbers; Juno by Harding, in September, 1804, and Vesta by Olbers, in March, 1807.

These four planets are invisible to the naked eye, When the Earth comes between the Sun and moon, and we are, therefore, indebted to the telescope for a it casts its shadow upon the latter, which is then said knowledge of their existence. It is conjectured, and to be eclipsed. An eclipse of the Sun is occasioned not without reason, that these four planets were once by the moon coming between the Earth and the Sun, united in one, and that by some mighty force they thus cutting off its rays. An eclipse of the moon have been sundered, and thrown into their present always occurs at the time of its full; eclipses of the orbits. Their diameter has not been ascertained with Sun occur at the time of the new moon. It is one precision. Herschel reckons that the largest does not of the triumphs of science, that these sublime phe- exceed 500 miles in circumference. nomena, formerly so fruitful a source of superstitious fear and ominous prediction, are now the subject of the most exact calculation, and are as much divested of every mysterious attribute as the common events of sunrise and sunset.

Telescopic Views of Jupiter.

We now come to one of the most splendid orbs in the planetary system. Jupiter is 495,000,000 miles from the Sun, and the circumference of its orbit is 3,110,000,000 of miles. Around this orbit it moves in 11 years, and 315 days, at the rate of about 30,000 The planet Mars.-The Earth is placed, in the miles an hour. Its nearest approach to the Earth is solar system, between the orbits of Venus and Mars. about 600,000,000 miles. A cannon-ball, flying at the The latter is 145,000,000 miles from the Sun. When rate of 500 miles an hour, would reach it in a little less nearest the Earth, its distance is 50,000,000; when than a hundred years. The daily rotation of Jupiter