But very different is the case with Jupiter, which is the largest of all the planets, and adorned by his belts, attended with his glorious retinue of four moons, comes next in order in the heavens. The magnitude of this stupendous planet is, indeed, said to be no less than 1400 times larger than the earth: his year is something less than twelve of ours, and he moves at the rate of 29,894 miles in an hour. In consequence of his distance from the sun, his light and heat are computed to be only about one twentyseventh of what the earth receives, but the former of these may be compensated by the number of his moons; by one or more of which, there is scarcely any part of this planet but what is enlightened during the whole night, except his poles, and there is no saying, but what has the appearance of Jupiter's belt, may be something of an atmospheric nature, so constituted as to imbibe, and considerably increase, the heat of the sun's rays. Jupiter, in the heavens, appears to the eye next in magnitude to Venus.

Beyond the orbit of Jupiter moves Saturn, attended by a retinue of no less than seven satellites or moons, and having his body surrounded by an interior and exterior ring. Although the diameter of this planet is not so large as Jupiter, his magnitude is said to be no less than 966 times that of the earth, and, moving at the rate of 22,072 miles in an hour, he completes the revolution of his wide circle in a period not much less than thirty of our years.

The light and heat which he receives from the sun, are computed to be about one hundredth part of what

the earth receives; but, to compensate for this, besides the rings and moons already mentioned, the. disk of this planet has been observed to be crossed by zones or belts, which may be analogous to, and answer the purposes of, those of Jupiter, Saturn is visible to the naked eye, and shines in the heavens with a pale, feeble light.

The Georgian, or Georgium Sidus, is the remotest of all the planets yet discovered, and was brought to notice so recently as the 13th of March, 1781, by that indefatigable astronomer, Dr Herschel, Six satellites have already been discovered attending on this distant planet Its magnitude is supposed to be upwards of eighty times that of the earth, and its periodical revolution performed in something more than eighty three of our years. Through a telescope of a small magnifying power, the Georgian appears like a star of the sixth or seventh magnitude, and is only visible to the naked eye, in the absence of the moon, in a clear night.

These planets, with their attendant satellites and other appendages, are carried round the sun in elliptical orbits, differing but little from circles; by which means the temperature of their seasons must be wisely proportioned, and pretty equally kept up. To prevent too frequent eclipses, they move not in the same planes; and that they may not interfere with each other, they revolve all in the same direction, from the east away westerly. The greater part of them are known, and the whole are supposed to turn round on their axis in the same manner that our earth

does, by which means they must also be favoured with the alternate succession of day and night; and as the revolution of the satellites of Jupiter is known to a nicety, there can be no doubt but those planets, which have such attendants, are equally benefitted by them. Of the spots of Venus and of Mars, the belts of Jupiter and rings of Saturn, we can say little; but let it be remembered that we are surrounded by an atmosphere, the appearance of which may not easily be accounted for by the inhabitants of those distant bodies. That the planets are inhabited, we have every reason to believe, from the provision that is made for their comfort, and other analogy they bear to our own inhabited globe. It is true, that our views and discoveries respecting those distant orbs, must be imperfect and limited in this present state; but what we know not now, we may, perhaps, know hereafter; although it is not to be supposed that our finite capacities, even in a more exalted state and enlarged sphere of vision, shall ever be able fully to comprehend the mighty works of the Creator of the Universe, or utter forth all His praise.

CHAP. XX.

COMETS.

"Hast thou ne'er seen the comet's flaming flight?"

BESIDES the planets and their satellites, there are other bodies called Comets, which revolve round the sun in very eccentric ellipsis, and in all manner of

directions. These comets, in one part of their orbit, called the perihelion, approach very near the sun, and appear all in a blaze: this appearance, however, they gradually lose, as they fly off, with inconceivable rapidity, to the opposite part of their orbit, called, by astronomers, their aphelion; there they are totally divested of their luminous tail, and, being at such an immense distance from the sun, it is concluded they must experience a degree of cold, of which we can have no adequate conception. There are a variety of opinions as to the number of comets belonging to our system: Riccioli enumerated 154; others assert that 450 had been seen previous to 1771: the tables of Berlin estimate them at 700, and some have even supposed that there are millions. And, as these bodies appear but seldom, and their stay is so short, it is not surprising that so much ignorance should prevail respecting them. It is, however, now sufficiently ascertained, that these, like the planets, shine not by their own, but by a reflected light; and, were it not for the sun, these bodies, instead of alarming our fears by their glaring magnificence, would move unseen and unheeded by us; for, however naturalists may have differed respecting the composition of their tails, it seems now to be pretty well understood that they possess nothing fiery or combustible in them, and may, with more propriety, be likened to the mild radiance that proceeds across the street from the illuminated glass in an apothecary's window in a dark night, than to any thing of a baneful or pestilential nature.

There is one thing to be remarked with regard to the tails of comets, that they appear always in a direction averted from, or contrary to, the sun; and this certainly, with the circumstance of the stars being visible through them, gives colouring to the supposition that they are nothing more than merely a condensation of the solar rays, by the refracting power of the comet and its atmosphere.

With regard to the purposes for which comets were created, "all is doubt, uncertainty, and conjecture." Some have supposed they are the means, appointed by the Almighty, for putting a period to the planetary world; others have imagined that comets, in their several revolutions, gradually approach the sun, till at last they fall into it, and become a supply of fuel to that luminary; and some of the learned world, Dr. Mavor remarks, are of opinion, that they are places of future punishment for tormenting the damned with eternal vicissitudes of heat and cold; "but when, on the other hand," as the Doctor goes on, "we reflect on the infinite power and goodness of the Deity, the latter inclining, the former enabling him to make creatures suited to all states and circumstances; that matter exists only. for the sake of intelligent beings; and that, wherever we find it, we always perceive it pregnant with life, or subservient to that purpose; when we consider the numberless species, the astonishing diversity of animals, in earth, air, water, and even on other animals; every blade of grass, every tender leaf, every natural fluid, swarming with life, and every one of these enjoying such