If our Earth can claim pre-eminence of the fore-mention’d Planets, for having a Moon to attend upon it, (for its Magnitude can make but a ſmall difference) how much Superiour muſt Jupiter and Saturn be to thoſe three and the Earth alſo? For whether we conſider their Bulk, in which they far exceed all the others, or the Number of Moons that wait upon them, it’s very probable that they are the chief, the primary Planets in our Syſtem, in compariſon with which the other four are nothing, and ſcarce worth mentioning. For the eaſier Conception of their vaſt Diſparity, I have thought fit to add a Scheme of our Earth, with the Moon’s Orbit, and the Globe of the Moon itſelf, and the Syſtems of [Fig. 3.] Jupiter and Saturn, where I have drawn every thing as near the true Proportion as poſſible. Jupiter you ſee is adorned with four, and Saturn with five Moons, all placed in their reſpective Orbits. The Moons about Jupiter we owe to Galilæo, ’tis well known: and any one may imagine he was in no ſmall Rapture at the Diſcovery. The outermoſt but one, and brighteſt of Saturn’s, it chanc’d to be my lot, with a Teleſcope not above 12 foot long, to have the firſt ſight of in the Year 1655. The reſt we may thank the induſtrious Caſſini for, who uſed the Glaſſes of Joſ. Campanus’s grinding, firſt of 36, and afterwards of 136 foot long. He has often, and particularly in the Year 1672, ſhew’d me the Third and Fifth. The Firſt and Second he gave me notice of by Letters in the Year 1684; but they are ſcarce ever to be ſeen, and I can’t poſitively ſay, I had ever that Happineſs; but am as ſatisfied that they are there, as if I had; not in the leaſt ſuſpecting the Credit of that worthy Man. Nay, I am afraid there are One or Two more ſtill behind, and not without reaſon. For between the Fourth and Fifth there’s a Diſtance not at all proportionable to that between all the others: Here, for ought I know, there may be a Sixth; or perhaps there may be another without the Fifth that may yet have eſcaped us: for we can never ſee the Fifth but in that part of his Orbit, which is towards the Weſt: for which we ſhall give you a very good reaſon.