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have been transmitted us. However, all personswho have considered Comets before the time ofTycho Brake, the great Restorer of Astronomy, ima-gining they were nearer the Earth than the Moon,little regarded them, esteeming them as Vapors.

But in 1577, Tycho * applying assiduouslyto the study of the Stars, and having collectedlarge Instruments for measuring arcs of the Hea-vens with greater accuracy than the ancients couldpretend to, there appeared a Comet conspicuousenough, which Tycho observed strictly, and foundby many and just Experiments, that it had no sen-sible diurnal Parallax -f~, and consequently was so

B far

* Tycho Brake, born at Knudflorp in Denmark, December 1546,died Nov. 1601, at Prague, aged 54 Years, 9 Months, 19 Days.He was a Knight, and made Observations on the Stars a longtime at Uraniberg, in the I lie of Hucn, in the Sound, havingfabricated curious instruments for that purpose at the expenceof Chrijiian III. King of Denmark. When he left Denmarkhe was entertained at the Court of the Emperor Rodolph: Hehad great intimacy with IVMiam Prince of Heffe: His workscompleat were publifh’d at Frankfort, 1648.

f What is meant by Parallax is, that supposing the Cometwas observed from Uraniberg, and its distance from some fix’dStar noted : Again, suppose the same Comet was observed fromPrague, and its distance from the same fix’d Star noted like-wise; then if these two distances from the fix’d Star were thefame in appearance, then would the Comet be said to haveno sensible Parallax, which Astronomers conclude to be a De-monstration drawn from the Laws . of Optics, that they arehigher than the Moon ; for that Planet, view’d from thosetwo places before-mentioned, wou’d appear to have two diffe-rent distances from the same fix’d Star.

Sir Isaac Newton takes another method of shewing thatComets are solid bodies, and not vapors; by instancing, thatthe Comet of 1680 came within a sixth part of the Sun’s ■Diameter to his Surface, and therefore might, if a solid body,have contracted a heat 2000 times greater than red-hot iron;now had the Comet been vapor alone, the whole must have

been