142 PHILOSOPHICAL TRANSACTIONS. [anNO I667. 



quae in Collo Ceti ante annos aliquot visa est. Alterum, de Nebulosa in An- 

 dromedas 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 time. 



As to the former of these stars he affirms, that, as it has 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 larger ; and that about the end 

 of the same month, if the crepuscle do not hinder, the greatest phasis of it will 

 appear, if it keep the same analogy of motions and periods, which it observed 

 from An. l638 to An. l664. Where he takes notice of the causes, why its 

 two greatest appearances could not be seen An. l664, l665, 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 every year an- 

 ticipate by 32 or 33 days; 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. 1662, about the end 

 of August, &c. so that this year it must be in March, if the former analogy 

 hold. 



He collects also from the observations, that one period from the greatest 

 phasis to the next consists of about 333 days: but that the interval of the time 

 between the times of its beginning to appear equal to the stars of the sixth 

 magnitude, and of its ending to do so, consists of about 120 days : And that its 

 greatest appearance lasts about 1 5 days : All which yet he would have under- 

 stood with some latitude. 



This done, he proceeds to the investigation of the causes of the vicissitudes 

 in the emersion and disappearance of this star, and having remarked, that the 

 apparent increase and decrease of every lucid body, proceeds either from its 

 changed distance from the eye of the observer, or from its various site and posi- 

 tion in respect of him, by which the angle of vision is changed ; or from the in- 

 crease or diminution of the bulk of the lucid body itself ; and having also de- 

 became a celebrated astronomer and mathematician, and tlie author of several ingenious books on 

 those sciences] particularly, 1. Philolaus, era Treatise on the true System of the World j 2. Astrono- 

 mia Philolaica; 3. A Treatise on Spiral Linesj 4. The two Admonitions noticed in the above Article; 

 5. His Arithmetic of Infinites, published in l6'82, being a diffuse amplification of Dr. Wallis's treatise 

 on the same subject. Bulliald was the inventor of a useful correction of Bishop Ward's approximating 

 hypothesis. 



