Page:Philosophical Transactions - Volume 001.djvu/398

Rh 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 33. 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. 1662, 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 some latitude.

This done, he proceeds to the investigation of the Causes of the Vicissitudes in the Emersion and Dis-appearance of this 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 body 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 its 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, Rh