« PreviousContinue »
of its orbit nearest the star, than it seemed to be when the earth was at the most diftant part of its orbit, or 190 millions of miles farther removed from the same ftar. The star nearest us, and consequently the largest in appearance, is the dog.ftar, or Sirius. Modern discoveries make it probable that each of those fixed stars is a fün, having planets and comets revolving round it, as our sun has the earth and other planets revolving round him. (Now the dog-itar appears 27,000 times less than the sup: and, as the distance of the stars must be greater in proportion as they seem less, mathematicians have computed the distance of Sirius from us to be two billions and two hundréd thousand millions of miles. A ray of light, therefore, though its motion is so quick as to be commonly thought' instantaneous, takes up more time in travelling from the stars to us than we do in making a Weft-India voyage. A found, which, next to light, is considered as the quickest body we are acquainted with, would not arrive to us from thence in 50,000 years. And a cannon-ball, flying at the rate of 480 miles an hour, would not reach us in 700,000 years.
The stars, being at such immense dittances from the fun, cannot possibly receive from him so strong a light as they seem to have, nor any brightness fufficient to make them visible to us, For the sun's rays must be lo scattered and dissipated before they reach such remote objects, that they can never be transmitted back to our eyes, so as to render those objeds visible by reflection. The stars, therefore, shine with their own native and unborrowed luftre, as the sun does; and since each particular ftar, as well as the sun, is confined to a particular portion of space, it is evident that the ftars are of the same nature with the sun.
It is far from probable that the Almighty, who always acts with in finite wisdom, and does nothing in vain, thould create so many glorious suns, fit for so many important purposes, and place them at such distances from each other, without proper objects near enough to be benefited by their influences. Whoever imagines that they were created only to give a faint glimmering light to the inhabitants of this globe, must have a very superficial knowledge of astronomy *, and a mean opinion of the divine wisdem; since, by an infinitely less exertion of creating power, the Deity could have given our earth much more light by one single additional moon.
Initead then of cne fun and one world only, in the universe, as the unskilful in astronomy imagine, that science discovers to us such an incon. ceivable number of suns, fyftenis, and worlds, dispersed through boundless space, that if our fun, with all the planets, moons, and comets beo longing to it, were annihilated, they would be no more milled by an eye that could take in the whole creation, than a grain of sand from the seaThore; the space they posless being comparatively so fmall, that it would fcarcely be a fenfible blank in the universe, although the Georgium Sidus, the outermoft of our planets, revolves about the fun in an orbit of 10,830 millions of miles in circumference, and fome of our comets make excurfions upwards of ten thousand miilions of miles beyond the orbit of the Georgium Sidus; and yet, at that amazing distance, they are incomparably nearer to the sun than to any of the itars, as is evident from their keeping clear of the attracting power of all the stars, and returning periodically by virtue of the fun's attračtion.
* Especially fince there are many stars which are not visible without the affiAtance of a good telescope ; and, therefore, instead of giving light to this world, can only be seen by a few aftronomers.
From what we know of our own system, it may be reasonably coneluded that all the rest are with equal wisdom contrived, fituated, and provided with accommodations for rational inhabitants. For although there is an almost infinite variety in the parts of the creation which we have opportanities of examining, yet there is a general analogy running through and connecting all the parts into one scheme, one design, one whole.
Since the fixed Itars are prodigious spheres of fire, like our fun, and at inconceivable distances from each other as well as from us, it is reasonable to conclude they are made for the fame purposes that the sun is, each to bestow light, heat, and vegetation, on a certain number of inhabited planets, retained by gravitation within the sptere of its activity.
What a sublime idea does this suggest to the human imagination, li. mited as are its powers, of the works of the Creator! Thousands and thousands of suns, multiplied without end, and ranged all around us, at immense distances from each other, attended by ten thousand times ten thousand worlds, all in rapid motion, yet calm, regular and harmonious, invariably keeping the paths prescribed them and these worlds peopled with myriads of intelligent þeings, formed for endless progresfion in perfection and felicity!
If so much power, wisdom, goodness, and magnificence, is displayed in the inaterial creation, which is the least confiderable part of the universe, how great, how wise, how good, muft HE be, who made and governs the whole!
THE CONSTELLATIONS.] The first people who gave much attention to the fixed stars, were the shepherds in the beautiful plains of Egypt and Babylon ; who, partly for amusement, and partly with a view to direct them in travelling during the night, observed the fituation of these ce lestial bodies. Endowed with a lively fancy, they divided the stars into different assemblages or constellations, each of which they supposed to represent the image of some animal, or other terrestrial object. The peasants in our own country do the same, for they distinguish that great northern constellation, which astronomers call Ursa Major, by the name of the Plough, the figure of which it certainly may represent, with a very little aid from the fancy. The constellations in general have preserved the names which were given them by the ancients; by whom they were reckoned 21 northern and 12 southern : but the moderns have increased the number of the northern to 36, and that of the southern to 32. Belides these, there are the 12 signs or constellations in the Zodiac, as it is called from the Greek word swor, an animal, because each of these 12 is supposed to represent some animal. This is a great circle which divides the heavens into two equal parts, of which we fall speak hereafter. In the mean time we shall conclude this section with an account of the rise and progress of astronomy, and the revolutions which have taken place in that science.
DIFFERENT SYSTEMS OF THE UNIVERSE.] Mankind must have made a very confiderable improvement in observing the motions of the heavenly bodies, before they could so far disengage themselves from the prejudices of sense and popular opinion, as to believe that the earth upon which we live was not fixed and immoveable . We find, accordingly, that Thales
, the Milesian, who, about 580 years before Christ, first taught astronomy in Eorope, had made a fufficient progress in this science to calculate eclipses, or interpositions of the moon beiween the earth and the sun, ar of the earth between the sun and the moon (the nature of which may be easily understood from what we have already observed). Pythagoras
, a native
of Samos, Aourished about 50 years after Thales, and was, no doubt, equally well acquainted with the motion of the heavenly bodies. He conceived an idea, which there is no reason to believe had ever been thought of before, namely, that the earth itself was in motion, and that, the fun was at reft. He found that it was impossible, in any other way, to explain consistently the heavenly motions. His system, however, was so extremely opposite to all the prejudices of sense and opinion, that it Devet made great progress, nor was ever widely diffused in the ancient world. The philosophers of antiquity, despairing of being able to overcome ignorance by reason, endeavoured to adapt the one to the other, and in fome measure to reconcile them. Ptolemy, an Egyptian philosopher, who flourished 138 years before Christ, supposed, with the vulgar, that the earth was fixed immoveably in the centre of the universe, and that the seven planets, considering the moon as one of the primaries, were placed near to it. Above them he placed the firmament of fixed stars, then the crystalline orbs, then the primum mobile, and last of all, the cælum empyreum, or heaven of heavens. All these vafi orbs he imagined to move round the earth once in 24 hours, and, besides that, in certain ftated and periodical times. To account for these motions, he was obliged to conceive a number of circles, called eccentrics and epicycles, crosting and interfering with each other. This system was universally maintained by the peripatetic philosophers, who were the most confiderable fect in Europe, from the time of Ptolemy to the revival of learning in the fixe teenth century.
At length, Copernicus, a native of Poland, a bold and original genius, adopted the Pythagorean or true system of the universe, and published it to the world in the year 1530. This doctrine had remained so long in ob(curity, that the restorer of it was considered as the inventor; and the fyftem obtained the name of the Copernican philofophy, though only revived by that great man.
Europe, however, was still immersed in ignorance; and the general ideas of the world were not able to keep pace with those of a refined phiJosophy. Copernicus therefore had few abettors, but many opponents. Tycho Brahe, in particular, a noble Dane, sensible of the defects of the Ptolemaic fyftem, but unwilling to acknowledge the motion of the earth, endeavoured, about the year 1586, to establish a new system of his own, which was ftill more perplexed and embarrassed than that of Prolemy. It allows a monthly motion to the moon round the earth, as the centre of its orbit; and makes the fun to be the centre of the orbits of Mercury, Venus, Mars, Jupiter, and Saturn. The fun, however, with all the planets, is supposed to be whirled round the carth in a year, and even once in the twenty-four hours. This fyftem, notwithstanding its absurdity, met with many advocates. Longomontanus, and others, fo far refined upon it, as to admit the diurnal motion of the carth, though they indsted that it had no annual motion.
About this time, after a darkness of many successive ages, the fil dawn of learning and taste began to appear in Europe. Learned men in different countries began to cultivate astronomy. Galilen, a Florentine, about the year 1610), introduced the use of telelcopes, which furnished new arguments in support of the motion of the earth, and conta firmed the old ones. The fury and bigotry of the clergy, indeed, had almoft ftifleri the science in its infancy; and Galileo was obliged to renounce the Copernican system, as a damnable heresy. The happy reformation in religion, however, placed a great part of Europe beyond
the reach of the papal thunder. It taught mankind that the Scriptures were not given for explaining systems of natural philofophy, but ‘for a: much nobler purpose, -to render us just, virtuous, and humane; that, instead of opposing the word of God, which, in speaking of natural things, fuits itself to the prejudices of weak mortals, we employed our faculties in a manner highly agreeable to our Maker, in tracing the nature of his works, which, the more they are considered, afford us the greater reason to admire his glorious attributes of power, wisdom, and goodness. From this time, therefore, noble discoveries were made in all the branches of astronomy. Not only the motions of the heavenly bodies were clearly explained, but the general law of nature, according to which they moved, was discovered and illustrated by the immortal Newron. This law is called Gravity or Attraction, and is the same by which any body falls to the ground, when disengaged from what supported it. It has been demonstrated, that this same law, which keeps the sea in its channel, and the various bodies which cover the surface of this earth from flying off into the air, operates throughout the universe, retains the planets in their orbits, and preserves the whole fabric of nature from confufions and disorder.
OF THE SPHERE.
AVING, in the foregoing section, treated of the UNIVERSE in general, in which the earth has been considered as a planet, we now proceed to the doctrine of the Sphere, which ought always to precede that of the globe or earth, as we shall see in the next tection. In treating this subject we shall consider the earth as at rest, and the heavenly bodies as performing their revolutions around it. This method cannot lead the reader into any mittake, since we have previously explained the true fyftem ct the universe, from which it appears, that it is the real motion of the earth which occasions the apparent motion of the heavenly bodies. It is besides attended with this advantage, that it perfe&tly agrees with the information of our senses. The imagination therefore is not put on the stretch ; the idea is ealy and familiar; and, in delivering the elements of science, this objeet cannot be too much attended to.
N. B. In order more clearly to comprehend what follows, the reader may occasionally turn his eye to the figure of the artificial sphere on the opposite page.
The ancients obserred, that all the stars turned (in appearance) round the earth, from east to west, in twenty-four hours; that the circles which they described in those revolutions were parallel to cach other, but not of the fame magnitude; those palling over the middle of the earth beo ing the largest, while the rest diminished in proportion to their distance from it. They also observed, that there were two points in the heavens which always preserved the same fituation. Thele points they termed celestial poles, because the heavens seemed to turn round them. In order to imitate these motions, they invented what is called the Artificial Sphere, through the centre of which they drew a wire or iron rod, called an Aris, whose extremities were fixed to the immoveable points called Poles. They further observed, that, on the 20th of March and