hath this periodic motion I am speaking of. For it is manifeft, that either the fun and the planets move about the earth, the one in the space of a year, and the reft in other times; or that the earth and the other planets move about the fun in fuch times. But let us (as I have all along done) fuppofe the latter, that the fun is fixt in the centre, without any other but its diurnal rotation in 254 days; in this cafe we fhall have the feveral primary planets revolving round the fun in an excellent and due order, by the exacteft rules of fuch a noble ftructure, fuch an admirable oeconomy, and that is in times (as L faid) in fquare proportion to the cubes of their distances. So that we fee Mercury to perform its period in near 88 days: Venus (the next in order to the fun) its period in fomewhat above 224 days: then the earth, with its companion the moon, in 365 days: then Mars in about 687 days: next him Jupiter in about 4333 days: and laftly, Saturn in fomewhat above 10759 days.

To this fo ftrict an order of the periods of those planets, we may add the confideration of the different paths of their periodical and diurnal motion that they lie not in a very different plane, as quite a crofs, or the like: nor exactly

and 1688, and perhaps by Bayer long before, as alfo Hevelius and others.

Of these new ftars, there is reafon to imagine there may be many, by reafon they are not confined to any one part of the heavens, but appear and disappear in divers conftellations, and divers parts of thofe conftellations, as in Caffiopeia, the fwan, the great bear, Andromeda, Eridanus, the whale, the fhip, and divers other parts of the heavens.

What these new stars are, is hard to determine. Meteors they cannot be, because they are of long continuance, and much too far off, for bodies that emit fo little light as metors do, to be feen by us. And as for other opinions about them, they are too many, and too frivolous (fome of them to be named) f, except one or two of the moft probable. Among which, one is of fome

fmall and that it grew bigger and bigger, fo as on October 23, to be feen with the naked eye, untill having arrived to its greatest magnitude, it again became less and lefs, and at last invifible even in a telescope. By frequent obfervations, he difcovered its motion to be very regular, and its period to be 404 days.

If the reader hath a mind to see a variety of these opinions, he may find them largely enough handled in Riccioli's Almageft. ubi fupra, c. 17.

perfons

perfons that think they may be such stars as have one fide darker than the other, as one of Saturn's fatellites is fuppofed to have, and fo appear only when the bright fide is turned towards us, and difappear as the darker takes place. Some think they may be fixt stars that expire in light and vapours 5, and are again rekindled, and recruited by the accefs of comets. Others take them to be comets themselves. But if I may be admitted to speak what was formerly my own opinion, I rather took them to be erratick of fome kind or other, and that for these reasons :

1. From fome of them, as I thought, feeming to change their places, and appearing fometimes farther off, and fometimes nearer unto other ftars as I have faid in the preface, p. 41.

2. From that increase and decrease of their light and magnitudes which is constantly obferyed in them, they being at firft obfcure, and hardly difcernible, but by degrees growing brighter and brighter, till fome of them equal the light of Venus; and others the light of the fixt stars, of the first, second, and third magnitudes and then again as gradually grow lefs and lefs, till they utterly disappear.

This is what Sir Ifaac Newton furmifes in his Princip. I. iii. Prop. 42.

Q4

3. From

CHA P. V.

OF THE PERIODICAL MOTION OF THE SECONDARY

PLANETS.

HAVING

WAVING confidered the periods of the primary planets, let us next caft our eye upon thofe of the secondaries. And among these we shall find the fame compleat order and harmony as among the laft. Thus Saturn's five moons, and Jupiter's four, and our own about the earth, have each of them their determinate times; fome longer, fome fhorter intervals of time; in the fame due proportion, as I fpake of among the primaries.

Befides which, there is another thing very confiderable in this periodical motion of thofe fecondary planets, and that is, that it is mixed with a kind of cochleous direction towards one or other pole of the primary planet; by which means every fatellite, by gentle degrees, makes its vifits towards each pole of its primary. This is well known among the Circumjovials, for instance,

planets revolving round fuch funs, as caft a much fiercer and more vigorous light than the fun doth and that thefe their planets might be more denfe than ours, and have furfaces more strongly reflecting light, and perhaps be much larger too. But notwithstanding that planetary reflected light may be fent to very great diftances by thefe means, yet without extravagant fuppofitions of this naturę, it may be doubted whether it would reach us, fo far off as the fixt stars are. And befides this, another doubt is, that although there are divers ftars near those new ftars of greater magnitudes than any of those new stars are, (which I have had the fortune to fee); yet I can scarce think them big enough, to conclude them to be the funs about which thofe new ftars (if planets) move. And therefore being uncertain what to determine in fo intricate a matter, I fhall leave it to future better obfervations (which the late long dark weather hath hindered me in the profecution of) which I hope may afford us fo good light, as may lead us into a much greater knowledge of those rare phæno

mena.

But whatever thofe new ftars are, they are a farther demonftration of God's power and glory: and that there are many more of the grand

works