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After the death of Thales, Pythagoras started the idea, that the diurnal motion of the sun and stars was not real, but occasioned by the motion of the earth on its axis; and that all the planets turned round the great luminary, which, in respect to them, was at rest in the centre of the system.
After this time the study of astronomy was neglected for nearly two hundred years; and even when revived by the Ptolemys of Egypt, their ideas on the subject were by no means consonant with those of Pythagoras: their system however, though erroneous, served to give the observers of that age, a tolerable idea of the apparent course of the heavenly bodies, and enabled them to reduce the science of geography to some certain rules.
In the fifteenth century, Copernicus revived the ancient Pythagorean system; and in the year 1610, Gallileo, a native of Italy, introduced telescopes into the service of astronomy, by which means he discovered the spots in the Sun, and its revolution on its axis; the mountains on the Moon, the phases of Saturn, and Jupiter's satellites.
The great Sir Isaac Newton first demonstrated the laws that regulate the motions of the Earth and of the heavenly bodies; taught the cause of the proportion observed by the planets in their rotations round their centres; and contrived a new theory of the moon, to account for all her irregularities. Doctor Halley favoured the world with the astrono
my of comets, together with astronomical tables and a catalogue of the stars and the studies of Mr. Flamstead and Dr. Herschel have afforded much new and curious information on this truly fascinating subject.
The advantages resulting from the study of astronomy are equally numerous and impor tant-calculated to expand and dignify the mind, to correct and improve our ideas, and to raise our contemplations from earth to heaven, and from the creatures to the infinitely wise and adorable Creator. By means of this invaluable science, we discover the source of all the celestial motions, follow the immense works of the Deity through the wide regions of the firmament; trace the various causes which regulate the vast machine of the universe, and exclaim with the royal Psalmist, "The heavens declare the glory of God!" Astronomy, also, is calculated to obliterate from the mind the effects of timidity, and superstition, exposing in its true colours the ridiculous system of astrology, and teaching mankind to look with tranquillity and composure on those phenomena which were once considered portentous of the death of potentates, the destruction of empires, or the annihilation of the universe.-From the heavens we have obtained all our knowledge of the seasons, and the art of reckoning by certain periods of time, than which nothing is more necessary in the common affairs of life; and so intimately connected are the studies of the
astronomer with chronology, that without their assistance the historic page must have been completely disfigured and involved in obscurity. It may suffice to add, that astronomy affords the most interesting advantages to geography and navigation, and consequently should be considered as one of the most useful branches of polite literature, at the same time that it is the acknowledged handmaid of true religion.
Of the Solar System.....Fixed Stars....
THE solar system derives its name from Sol, the Sun, because the Sun is supposed to be at rest in the centre, while all the planets, with their moons and satellites revolve round it at various distances. By certain spots on its disk, however, the great luminary has been found to turn round on its axis in the course of 25 days, 6 hours; and it has likewise another motion round the centre of gravity of the whole system, occasioned by the different at tractions of the planets.
Various opinions have been formed respecting the nature of the sun, which is supposed to be about 763,000 miles in diameter; but,
from its appearances and effects, it seems most. natural to conclude, that it is no other than an elementary fire; or, perhaps, that it is the grand centre of attraction to all the elementary fire in the planetary system, and that there is, by one law of nature, a constant restoration of fire from the planets to the sun, precisely equivalent to that which is, by another law, incessantly effused from the sun upon the planets.
The bodies which move round the sun as their centre of motion are called planets; and the first seven of them have been distinguished by astronomers with the following characters and appellations :
Mercury; Venus; the Earth; Mars; Jupiter: h Saturn; Georgium Sidus, or Herschel.
MERCURY, the nearest planet to the sun, performs his revolution in about 87 days, 23 hours, which is the length of his year. His distance from the centre of the system is about 37,000,000 of miles; his diameter is computed at three thousand two hundred; and in his revolution round the sun he moves at the rate of a hundred and five thousand miles an hour.
This planet exhibits phases like the moon, which demonstrates that, notwithstanding his remarkable brilliancy, he shines only by borrowed light. The times of his appearance are a little before sun-rise and a little after sun set,
VENUS, the second planet in the system, is supposed to be 68,000,000 of miles from the sun, and by her mean motion of 76,000 miles an hour, she performs her annual revolution in 24 days 17 hours, which is the length of her year. Her diameter is 7,700 miles, and her diurnal rotation on her axis is performed in 23 hours 22 minutes. When Venus appears to the west of the sun she is called the morning star, and when she appears to the east of the sun, she is denominated an evening star; Occupying each situation alternately for about 290 days. If viewed through a telescope, she seems to have all the phases and appearances of the moon, and at her brightest times, she exhibits a more beautiful appearance than an any other of the heavenly bodies.
The EARTH, which we inhabit, is the next planet above Venus, sitriated at the distance of 95,000,000 of miles from the sun. Its diameter is 7.900 miles, the circumference of its orbit 598,000,000 and its mean annual motion 58,000 miles an hour, by which it performs its revolution in 365 days, 5 hours, and 49 minutes. It likewise turns round its axis every twenty-four hours, from west to east and thus occasions an apparent motion of all the heavenly bodies, from east to west in the same time. This planet is accompanied by one moon in its annual progress, for purposes most beneficial to its numerous inhabitants.