The Motion of the late Comet prædicted.
There was lately sent to one of the Secretaries of the Royal Society a Packet, containing some Copies of a Printed Paper, Entituled, The Ephemerides of the Comet, made by the same Person, that sent it, called Monsieur Auzout, a French Gentleman of no ordinary Merit and Learning, who desired, that a couple of them might be recommended to the said Society, and one to their President, and another to his Highness Prince Rupert, and the rest to some other Persons, nominated by him in a Letter that accompanied this present, and known abroad for their singular abilities and knowledge in Philosophical Matters. The end of the Communication of this Paper was, That, the motion of the Comet, that hath lately appeared, having been prædicted by the said Monsieur
Auzout, after he had seen it (as himself affirms) but 4 or 5 times: the Virtuosi of England, among others, might compare also their Observations with his Ephemerides, either to confirm the Hypothesis, upon which the Author had before hand calculated the way of this Star, or to undeceive him, if he be in a mistake. The said Author Dedicateth these his conceptions to the most Christian King, telling him, that he presents Him with a design, which never yet was undertaken by any Astronomer, all the World having been hitherto perswaded, that the motions of Comets were so irregular, that they could not be reduced to any Laws, and men having contented themselves, to observe exactly the places, through which they did pass; but no man, that he knows, having been so bold as to venture to foretel the places, through which they should pass, and where they should cease to appear: Whereas he exhibites here the Ephemerides, determining day by day, in what place of the Heavens this Comet shall be, at what hour it shall be in its Meridian, and at what hour it shall set; untill its too great remoteness, or the approach of the Sun, hide it from our eyes. Descending to particulars, he saith, that this Star, being disengaged from the beams of the Sun might have been observed, if his conjectures be good, ever since it hath been of 17 or 18 degrees Southern Latitude, and that about the middle of November last, and sooner, unless it have been too small: That however it hath been seen in Holland ever since the 2d. of December last, at which time, according to his reckoning, the Diurnal motion of the Comet should already amount to 17 or 18 minutes. He finds, that this Star moveth just enough in the Plan of a Great Circle, which inclineth to the Equinoctial about 30 degrees, and to the Ecliptick about 49d. or 49½ cutting the Equator at about 45d½, and the Ecliptick at the 28d of Aries, or a little more. He saith just enough, because he thinks, there may perhaps be some parallaxe, which he wisheth could be determined.
Hence, (so he goes on) every one who pleaseth, may see, in tracing the Comet upon the Globe, through, or by which Stars it hath passed and shall pass; adding, that there will be neither cause to wonder, that having descended to about 6. deg. beneath the Tropick of Capricorn, he hath remounted afterwards, and shall go
on ascending so, as to pass the Æquinoctial, and perhaps proceed to 15. degrees Northern Declination, if it do not disappear before that time, by reason of its remoteness: Nor to believe, that there have been two Comets, upon its being seen again the 31. of December; since, according to him, it ought to have been so, if it continue to move in a Great Circle.
Having hereupon shewed, how the motion is to be traced upon the Globe, he finds, that, according to his Calculation, this Comet was to pass the Tropick of Capricorn about the 16 of December, and being entred into the Sign of Virgo on the 20. of the same month, and having been in Quadrat with the Sun, it should still descend, until the 26 of December in the morning, and then enter into Leo; that having entred, the 28. of the same month, into Cancer, and been, a little after that time, in its greatest Inclination to the Ecliptick, vid in the 28. degree of Leo, it was to repass the Southern Tropick, over against the little Dogg, on the 29. of December about 9 or 10 of the clock in the morning, after it had been opposite to the Sun 2. or 3. hours before; and that on the 29. of December in the evening it should be in Gemini; and at the very beginning of the New year, enter into Taurus.
After this, our Author finds, that this Comet, according to his account, should pass the Æquator, on the 4. of January before noon, and that about 5. or 6. of the clock in the evening of that day it was to come into the jaw of the Whale, and the 9. of the same, at 6. of the clock it should come close to the small Star of the Whale, which is in its way, a little below. At length he finds that it was to enter into Aries on the 12. of January, and to cut the Ecliptick on the 16. of the same month about noon, at which time it was to be again in Quadrat with the Sun, whence drawing a little to above the Northern Line of Pisces, it should in his opinion cease to appear a little beyond that place, without going as far as to the middle of Aries, if so be that its remoteness make it not disappear sooner.
He continueth, and saith, that this Comet shall not arrive to the place over against the Line of Pisces till the 10 of February, & that then its Diurnal motion shall not exceed 8 minutes, and not 5 minutes about the 20 of the same month: and that in the
beginning of March, if we see it so long, the said motion shall not exceed 4 minutes, and so shall be still diminishing; except the Comet become Retrograde, which, as very important, he would have well observed; as also, whether its motion will be about the end more or less swift, than he hath calculated it.
He subjoyneth, that the greatest way, which this Star could make in 24. hours, hath been 13. d. 25′; and in one houre, about 34′; and thinking it probable, that about the time, when it made so much way, it should be nearest to the Earth, he concludeth that its motion in 24. hours must be, in its least distance from the Earth, as about 3. to 14, or 1. to 4⅔, and that its motion in one hour was to be to the same least distance, as about 1. to 1021/7.