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He finds, its apparent Motion was not made in a Just great Circle, but deviating considerably from it; and conceives, that every Comet falls to this deviation, when this apparent Motion grows slow, and the Star becomes Stationary (which, as he saith, it doth in respect of the Ecliptick, not its own Orbite.) Here he observes, That from Decemb. 313; to Decem. 30. Jan. 9. its course was almost in a great Circle: but, that then it began to deflect from that Circle towards the North; so that afterwards, with a very notable and conspicuous Curvity, it directed its course towards Primam Arietis: Of which deflection, he ventures to assign the cause from the Cometical Matter, the various position and distance of the Comet from the Earth and the Sun, the annual Motion of the Earth; and the impressed Motion, and the inclination of the discus of the Cometical Body.
He is pretty positive, that without the annual Motion of the Earth, no rational Account can be given of any Comet, but that all is involved with perplexities, and deform'd by absurdities.
He inquires, since all Comets have their peculiar Ingenite Motion; what kinde of Line it is, they describe by that Motion of their own? whether circular, or streight, or curve, or partly streight and partly curve? And if curve, Whether regular or irregular? if regular, whether Elliptic, or Parabolar or Hyperbolical? He answers, That this Motion is Conical; and judgeth, that by the Conick path all the Phænomena of Comets can, without any inconveniency, be readily solved; even of that, which (by History) in fifty days, passed through more then the 10 Signs of the Zodiack: And of that, which in two days run through eight Signs: and of another, which in 48 days posted through all the Signs, contra seriem. Which how it can be explicated upon the supposition of the Earths standing still, and upon the denying of the annual Motion thereof, he understands not at all.
