| XXX | (435) | XXX |
435 A S T R O N O M Y. the fame nature with buriearth, and deftined for the circumvolving planets, he is agitated by a fmall motion like purpofes. For they are folid opaque globes, capa- round the centre of gravity of the fyftem. All the plable of fupporting animals and vegetable. Some of them nets, as feen from him, move the fame way, and acto the order of figns in the graduated circle are larger, fome lefs, and fome much about the fize of cording our earth. They all circulate round the fun, as the 'V5 V U -2c> fig. 2. which the great eclipticPlatein XL. the heavens: But, asreprefeen earth does, in a fhorter or longer time, according to their fents refpebtive diftances from him; and have, where it would from any one planet, the refi appear fometimes to go not be inconvenient, regular returns mf fummer and win- backward, fometimes forward, and fometimes to Hand ter, fpring and autumn. They,have warmer and cold- ftiil; not in circles nor ellipfes, but in looped curves er climates,, as.the various productions of our earth re- which never return into themfelves. The comets come quire : And, in fuch as afford a pollibiJity of difcovering from all parts of the heavens, and move in all forts of it, we obferve a regular motion round their axes like directions. that of our earth, caufing an alternate return of day The axis of a planet is a line conceived to be drawn and night; which is neceifary for labour, reft, and ve- through its centre, about which it revolves as on a real getation, and that all parts of their furfaces may be axis. The extremities of this line, terminating in opexpofed to the rays of the fun. pofite points of the planet’s furface, are called its poles. Such of the planets as are fartheft from the fun, and That which points towards the northern part of the heatherefore enjoy leaft of his light, have that deficiency vens, is called the north pole; and the other, pointing made up by feveral moons, which conflantly accompany towards the fouthern part, is called the fouth pole. A and revolve about them, as our moon revolves about the bowl whirled from one’s hand into the open air turns earth. The remoteft planet has, over and above, a round fuch a line within itlelf, whilft it moves forward ; broad ring encompafling it; which like a lucid zone in and fuch are ths lines we mean, when we fpeak of the the heavens refleds the fun’s light very copioufly on that axes of the heavenly bodies. planet; fo that if the remoter planets have the fun’s Let us fuppofe the earth’s orbit to be a thin, even, folight fainter by day than we,' they have an addition lid plane ; cutting the fun through the centre, and exmade to it morning and evening by one or more of their tended out as far as the ftarry heavens, where -it will moons, and a greater quantity of light in the night-time. mark the great circle called the ecliptic. This circle we On the furface of the moon, becaufe it is nearer us fuppofe to be divided into 12 equal parts, calledfigns-, than any other of the celeftial bodies are, we difcover a each fign into 30 equal parts, called degrees-, each denearer refemblance of our earth. For, by the alfiftance gree into 60 equal parts, called minutes-, and every rniof telefcopes, we obferve the moon to be full of high nute into 60 equal parts, called feconds : So that a iemountains, large valleys, and deep cavities. Thefe fi- cond is the 60th .part of a minute; a minute the 60th milarities leave us no room to doubt, but that all the part of a degree; and a degree the 360th part of a cirplanets and moons in the fyftem are defigned as commo- cle, or 30th part of a fign. The planes of the orbits of dious habitations for creatures endued with capacities of all the other planets like wife cut the fun in halves; bur, knowing and adoring their beneficent Creator. extended to th? heavens, form circles different from one Since the fixed ftars are prodigious fpheres of fire like another, and from the ecliptic; one half of each being our fun, and at inconceivable diftances from one another on the north fide, and the other on the fouth fide of it" as well as from us, it is reafonable to conclude they are Confequently the orbit of each planet croffes the ecliptic made for the fame purpofes that the fun is ; each to be- in two oppofite points, which are called the planet’s llow light, heat, and vegetation, on a certain number of nodes. Thefe nodes are all in different parts of the eInhabited planets,, kept by gravitation within the fphere chptic; and therefore, if the planetary tracks remained of its activity.. vifible in the heavens, they would in fome meafure referable the different ruts of waggon-wheels crofiing one another in different parts, but never going far afunder. Chap. II. Of the Solar System. That node, or interfeflion of the orbit of any planet with the earth’s, orbit, from which the planet afcends The planets and comets which move round the fun as above the ecliptic, is called the ajcendine their centre, conflitute the Solar Syftem. Thofe planets northward node of the planet ; and the other, which is diredly opwhich are near the fun not only finifh their circuits foon- pofite thereto, its defending node. Saturn’s er, but like wife move fafler in their refpeCtive orbits, afctndipg node isis incalled 21 deg. 13 min. of Cancer 05-, Juthan thofe which are more remote from him. Their piter' s in 7 deg. 29 min. fame fign, Mars’s in motinns are all performed from well to eafl, in orbits 17 deg. 17 min. of Taurus,of theVenus’s in 13 deg. nearly circular. Their names, difiances, bulks, and min. of Gemini n, and Mercury’s in I 4 deg. 43 mi59nperiodical revolutions, are as follow. of Taurus. Here we confider the earth’s orbit as the The Sun an immenfe globe of fire, is placed near fiandard, and the orbits of all the other planets as obthe common centre, or rather in the lower focus, of the lique to it. orbits o.f all the planets and comets; and turns round his When we fpeak.of the planets orbits, all that is meant axis in 25 days 6 hours, as is evident by the motion of their paths through the.open and unrefifting fjhice in fpots feen on-his furface. His diameter is computed to iswhich and are kept in, by the attrae.ive be 763,000 miles; and, by the various attractions of the power oftheythe move, fun, and the projedile force impreffed up-
