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ASTRONOMY.

the fame nature with our earth, and detined for the like purpoes. For they are olid opaque globes, capable of upporting animals and vegetable. Some of them are larger, ome les, and ome much about the ize of our earth. They all circulate round the un, as the earth does, in a horter or longer time, according to their repective ditances from him; and have, where it would not be inconvenient, regular returns of ummer and winter, pring and autumn. They have warmer and colder climates, as the various productions of our earth require: And, in uch as afford a poibility of dicovering it, we oberve a regular motion round their axes like that of our earth, cauing an alternate return of day and night; which is neceary for labour, ret, and vegetation, and that all parts of their urfaces may be expoed to the rays of the un.

Such of the planets as are farthet from the un, and therefore enjoy leat of his light, have that deficiency made up by everal moons, which conlantly accompany and revolve about them, as our moon revolves about the earth. The remotet planet has, over and above, a broad ring encompaing it; which like a lucid zone in the heavens reflects the un’s light very copiouly on that planet; o that if the remoter planets have the un’s light fainter by day than we, they have an addition made to it morning and evening by one or more of their moons, and a greater quantity of light in the night-time.

On the urface of the moon, becaue it is nearer us than any other of the celetial bodies are, we dicover a nearer reemblance of our earth. For, by the aitance of telecopes, we oberve the moon to be full of high mountains, large valleys, and deep cavities. Thee imilarities leave us no room to doubt, but that all the planets and moons in the ytem are deigned as commodious habitations for creatures endued with capacities of knowing and adoring their beneficent Creator.

Since the fixed tars are prodigious pheres of fire like our un, and at inconceivable ditances from one another as well as from us, it is reaonable to conclude they are made for the ame purpoes that the un is ; each to betow light, heat, and vegetation, on a certain number of inhabited planets, kept by gravitation within the phere of its activity.

II.

The planets and comets which move round the un as their centre, contitute the Solar Sytem. Thoe planets which are near the un not only finih their circuits ooner, but like wie move fater in their repective orbits, than thoe which are more remote from him. Their motions are all performed from wet to eat, in orbits nearly circular. Their names, difiances, bulks, and periodical revolutions, are as follow.

The Sun, an immene globe of fire, is placed near the common centre, or rather in the lower focus, of the orbits of all the planets and comets; and turns round his axis in 25 days 6 hours, as is evident by the motion of pots een on his urface. His diameter is computed to be 763,000 miles; and, by the various attractions of the circumvolving planets, he is agitated by a mall motion round the centre of gravity of the ytem. All the planets, as een from him, move the ame way, and according to the order of igns in the graduated circle 'V5 V U -2c> Plate XL. fig. 2. which repreents the great ecliptic the heavens: But, as een from any one planet, the ret appear ometimes to go backward, ometimes forward, and ometimes to tand till; not in circles nor ellipes, but in looped curves which never return into themelves. The comets come from all parts of the heavens, and move in all forts of directions.

The axis of a planet is a line conceived to be drawn through its centre, about which it revolves as on a real axis. The extremities of this line, terminating in oppoite points of the planet’s urface, are called its That which points towards the northern part of the heavens, is called the  and the other, pointing towards the outhern part, is called the  A bowl whirled from one’s hand into the open air turns round uch a line within itelf, whilt it moves forward; and uch are the lines we mean, when we peak of the axes of the heavenly bodies.

Let us uppoe the earth’s orbit to be a thin, even, olid plane; cutting the un through the centre, and extended out as far as the tarry heavens, where it will mark the great circle called the This circle we uppoe to be divided into 12 equal parts, called ; each ign into 30 equal parts, called ; each degree into 60 equal parts, called ; and every minute into 60 equal parts, called  So that a econd is the 60th part of a minute; a minute the 60th part of a degree; and a degree the 360th part of a circle, or 30th part of a ign. The planes of the orbits of all the other planets likewie cut the un in halves; but, extended to the heavens, form circles different from one another, and from the ecliptic; one half of each being on the north ide, and the other on the outh ide of it. Conequently the orbit of each planet croes the ecliptic in two oppoite points, which are called the planet’s Thee nodes are all in different parts of the ecliptic; and therefore, if the planetary tracks remained viible in the heavens, they would in ome meaure reemble the different ruts of waggon-wheels croing one another in different parts, but never going far aunder. That node, or interection of the orbit of any planet with the earth’s, orbit, from which the planet acends northward above the ecliptic, is called the of the planet; and the other, which is directly oppoite thereto, is called its  Saturn’s acending node is in 21 deg. 13 min. of Cancer 05-, Jupiter's in 7 deg. 29 min. of the ame ign, Mars’s in 17 deg. 17 min. of Taurus, Venus’s in 13 deg. 59 min. of Gemini II, and Mercury’s in I4 deg. 43 min. of Taurus. Here we conider the earth’s orbit as the tandard, and the orbits of all the other planets as oblique to it.

When we peak of the planets orbits, all that is meant is their paths through the open and unreiting pace in which they move, and are kept in, by the attractive power of the un, and the projectile force impreed upon