Philosophical Transactions of the Royal Society of London
No. 22, pp. 381-383
I. ISMAELIS BULLIALDI ad Astronomos Monita duo:
Primum, De Stella Nova, quo in Collo Ceti ante annos aliquot visa est.
Alterum, De Nebulosa in Andromedæ Cinguli parte Borea,
ante biennium iterum orta. [1667]

I. ISMAELIS BULLIALDIad Astronomos Monita duo: 
Primum, De Stella Nova, quo in Collo Ceti ante annos aliquot visa est. 
Alterum, De Nebulosa in Andromedæ Cinguli parte Borea, ante biennium iterum orta.

The chief end of the Author in publishing this Tract, seems to be, To excite Astronomers to a diligent observation, both of that New Star in the Neck of the Whale, to be seen in February and March next; and of that other, in the Northern part of Andromeda's Girdle, to be seen at this very present. 

As to the former of these Stars, he affirms, that, as it hath appeared for many years in the said place, so it will in the beginning of March next appear equal to the Stars of the third Magnitude, or perhaps bigger; and that about the end of the same Month, if the Crepuscle do not hinder, the greatest Phasis of it will appear, if so be, that it keep the same Analogy of Motions and Periods, which it observed from An. 1638. to An 1664. Where he takes notice of the Causes, why its two greatest Appearances could not be seen, An. 1664, 1665, 1666; and how he comes to know, that in the beginning of March next, it will equal or even exceed the Stars of the Third Magnitude; noting that from the Observations hitherto made of this Star, it is manifest, that the greatest Phases thereof do every year anticipate by 32, or 31. dayes; forasmuch as An. 1660. its greatest Appearance was about the end of October and the beginning of November; An. 1661 about the end of September, or the beginning of October; An. 1661 about the end of August, &c. so that this year it must be in March if the former Analogy do hold. 

He collects also from the Observations, That one Period from the greatest Phasis to the next, consists of about 333. dayes: but that the interval of the time betwixt the times of its beginning to appear equal to the Stars of the Sixt Magnitude, and of its ending to do so, consists of about 120. dayes: And that its greatest appearance lasts about 15. dayes: All which yet he would have understood with home latitude. 

This done, he proceeds to the investigation of the Causes of the Vicissitudes in the Emersion and Dis-appearance of the Star, and having discoursed, That the apparent Increase and Decrement of every Lucid Body proceeds either from its changed distance from the Eye of the Observer; or from its various site and position in respect of him, whereby the angle of Vision is changed; or from the increase or diminution of the bulk of the lucid boy it self: and having also demonstrated it impossible, that this Star should move in a Circle, or in an Ellipsis; and proved it improbable that it should move in a Strait Line, he concludes that there can be no other genuin, or at least, no other more probable cause of its Emersion and Occultation, than this, That the bigger part of that round Body is obscure and inconspicuous to us, and its lesser part lucid, the whole Body turning about it own Center, and one Axe, whereby for one determinate space of time it exhibits its lucid part to the Earth, for another, subducts it:  it not being likely, that fires should be kindled in the Body of that Star, and that the matter thereof should at certain times take fire and shine, at other times be extinguisht upon the consumption of that matter. 

So far of that Star. As to the other in the Girdle of Andromeda, seen about the beginning of An. 1665; he relates, that, when in the end of 1664. the World beheld the then appearing Comet, Astronomers observed also that new Phenomenon, which was called by them Nebulosa in Cingulo Andromeda. Concerning which, he notes, that the same had been already seen many years before by Simon Marius, vid. An. 1612. when with a Telescope he search'd for the Satellits of Jupiter, and observed their motions; alledging for proof hereof, the said Authors own words, out of his own Book, De Mundo Joviali, publisht An. 1614. And farther shews, that it hath formerly appear'd (about 150. years ago) and been taken notice off by an expert, though Anonymous, Astronomer; whose words he cites out of the Manuscript, brought out of Holland by the Excellent Jacobus Augustus Thuanus, returning from his Embassy to Paris; wherein also was marked the Figure of that Phænomenon, represented in print by our Author: who from all this collects, that, whereas this Star hath been seen formerly, and that 150. years since, but yet neither observed by Hipparchus, nor any other of the Antients, that we can find; nor also in the former Age by Tycho Brahe, nor in our Age, by Bayerus; and appear'd also in the Month of November last (wherein he wrote this Tract) much lessened and obscure, after it had, two years ago, shone very bright; that therefore it must needs appear and dis-appear by turns, like those in the Necks of the Whale and Swan.