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far from being a Vapor, that it was much higherthan the Moon ; and in short, that no reason couldbe given that it might not be a Planet, notwith-standing the contrary assertions of the Pretendersto Learning of those Times.

The sagacious Kepler * followed, and by the helpof J'ycho s labours, found 'out the true and natu-ral System of the World, and immensely increasedthe Science of Astronomy : Shewing, that all thePlanets revolv’d in Planes passing thro’ the Centerof the Sun, describing elliptic Curves in such man-ner, that equal Areæ of elliptical Segments (theCenter of the Sun being plac’d in the Focus of theEllipsis) are always described in equal times, inwhich the Areas are described. He also found,that the Cubes of the distances of Planets fromthe Sun were as the squares of their periodic times.Two Comets appeared to this skilful Artist one moreremarkable than the other: And from the Obser-vations Kepler made on these, and by many Disco-veries of an annual Parallax, he concluded, that

been dispersed by so .intense a heat. He concludes therefore,that Comets are solid bodies, and that their tails are vapors,emitted from them by the great heat of the Sun, as steem isfrom water when heated by a great fire, and all the ap-pearances agree perfectly with this sentiment.

* John Kepler , born at IKwl, in the country of JKirtemherg ,in 1571. Tycho Brcihe having settled in Bohemia , and obtainedall manner of conveniences from the Emperor Rodolph forperfecting Astronomy, prevail’d on Kepler to leave the Uni-versity of Glatz and to come to him, which he did with hisfamily and library in 1600; but Tycho dying in 1601, Keplerenjoyed the title of Mathematician to the Emperor all hi$life, who ordered him to finish the Tables of Tycho Brake ,which were to be called Rodclphine , which he publifh’d in 1627.He died at RaiiJhon t where he was sollicking the arrears of hispension.

Comets