here we shall find a no lefs admirable fcene of the great CREATOR's Care and Wisdom, than we difcovered in the Earth and Moon. In Mars indeed, we can difcern a great fimilitude with the Earth in its Opacity and Spots, but we have not yet been able to perceive any attendance of Moons, as in the other fuperiour Planets; not fo much probably because there are none, but because they are fmall, or they reflect a weak light, and are at a great distance from us. And as for Venus and Mercury, there may be no occafion for any Attendants, by reason of their proximity to the Sun. But in the two highest, or more distant Planets, Jupiter and Saturn, we have a very noble and entertaining scene of the CREATOR's Glory. For whereas thofe two Planets are at a much greater diftance than any of the other Planets,from their Fountain of Light

and

and Heat, the Sun Sun; and as confequently their Heat and Light are abated in proportion to the square of their Distances; so to make them amends they are surrounded with a more grand Retinue of Secondary Planets, or Moons; Jupiter with four, Saturn with five, as 'tis imagined, and probably more (1).

(1) Mr. Huygens in his Cofmotheoros p. 99. gives this account of the difcovery of the Satellites of Jupiter and Saturn, That it is well known the discovery of the Circumjovials is owing to Galilæo; that the brightest, and outermoft Circumfaturnial be happened to fee with a 12 foot Glass in the year 1655; that the rest are owing to Caffini, who first faw them with a Glafs of Campani's grinding of 36 feet,and afterwards with one of as many feet above 100. That the 2d and 5th Caffi hewed him in 1672, and afterwards oftener. That Caffini acquainted him by Letter afterwards with bi difcovery of the First and Second in 1684. That these nuo last are not easily difcerned, and be cannot say be ever faw them. That befide thefe be fufpects there may be one or more lye concealed. Of which fee chap. 7. following.

AND

AND an admirable remedy this is, not only for the great distance of thefe two Planets from the Sun, but alfo for the tardity of their periodick motion in their refpective Orbits. t whereas Saturn revolves round

Sun but once in near thirty years, an upiter but once in near 12, it con. o pass that the places near the two s of those Planets have a Night of near 15 years in Saturn, and 6 in Jupiter, fuppofing their Axes inclined to the Planes of their Orbits, as it is in our own Globe. But fuppofing (as it is imagined) that their Axes are not fo much inclined, and that their Days and Nights, their Winters and Summers are nearly equal; in this refpect the cafe would be worfe than in the long Nights in the other cafe: but in both cafes the Polar parts of both those Planets would be difmal regions of darkness, when so long detained from the

But an ad

kindly vifits of the Sun. mirable remedy is found, and a glorious scene of the great CREATOR's Works appears therein, as will be manifeft by confidering particulars in each of those two Superiour Planets,

CHAP. VI.

Of Jupiter's Moons, Days and Seafons.

IN

speaking concerning the fuperior Planets in particular, I fhall begin with Jupiter. The Distance of this Planet from the Sun, is reckoned to be 343 millions of miles farther from the Sun than we are; and by that means the Sun's Light and Heat are 27 times lefs there than with us, and its apparent Diameter

five

.

five times lefs (1) And confidering how vaft a Globe Jupiter is, having its fuperficies 100 times, yea (accor ding to Mr. Huygens's computations) 400 times bigger than that of the Earth; in this cafe, what vaft tracts of that Globe muft needs lie in profound darkness and defolation, had no remedy been provided! But there are divers provided. One is by the frequent Rotations of Jupiter round his own Axis; which being performed in less than 10 hours, it comes to pass that what is wanting in the ftrength and degree of Light and Heat, is compenfated by the frequent Returns thereof.

THE other Remedy is by the Increase of the number of Moons about

hi(1) Gregorii Aftron. L. 6. Prop. 5. Mr. Huygens makes the Light and Heat but 25 times lefs and the apparent Diameter 5 times. Cofmoth. S P. 103.