4 a jDdif :tllanea Curio fa. 



almoft Four times higher than Saturn&vA whofc 

 Velocity, tho' encreafed but a very little, would 

 be fufficient to change its Orbit, from an Ellip- 

 tical to a Parabolical one. This, moreover, 

 confirms me in my Opinion of its being the 

 fame \ that in the Year 1456. in the Summer 

 time, a Comet was feen pafling Retrograde 

 between the Earth and the Sun, much after 

 the fame Manner : Which, tho' no Body made 

 Obfervations upon it, yet from its Period, and 

 the Manner of its Tranfit, I cannot think dif* 

 ferent from thofe I have juft now mention'd. 

 Hence I dare venture to foretell, That it will 

 return again in the Year 1758. And, if it 

 Ihould then return, we fhall have no Reafon 

 to doubt but the reft muft return too : There- 

 fore Aftronomers have a large Field to exercife 

 themfelves in for many Ages, before they 

 will be able to know the Number of thefe many 

 and great Bodies revolving about the common 

 Center of the Sun , and reduce their Motions 

 to certain Rules. I thought, indeed, that the 

 Comet which appear'd in the Year 1532. might 

 be the fame with that obferv'd by Hevclius in the 

 Year 1661. But Jpans Obfervations, which are 

 the only ones we have concerning the firft of 

 thefe Comets, are too rude and unskilful, for 

 any thing of Certainty to be drawn from them, 

 in fo nice a Matter. I defign to treat of all 

 thefe Things in a larger Volume, and contribute 

 my utmoft for the Promotion of this Part of 

 Aftronomy, if it fhall pleafe God to continue 

 my Life and Health. 



In the mean time, thofe that defire to know 

 how to conltruft Geometrically the Orb of a 

 Comet, by Three accurate Obfervations given, 



may 



