parabolic curves. Then ſee how eaſily he may account for the deflexion of the ſtone above ſpoken of. The ſtone, ſays he, floats in this ſubtile fluid, and following its motion, can't chuſe but deſcribe the ſame figure. But the fluid moves in parabolic curves; and therefore the ſtone muſt move in a parabola of courſe. Would not the acuteneſs of this philoſopher be thought very extraordinary, who could deduce the appearances of nature from mechanical cauſes, matter and motion, ſo clearly that the meaneſt man may undeſtand it? Or indeed ſhould not we ſmile to ſee this new Galileo taking ſo much mathematical pains to introduce occult qualities into philoſophy, from whence they have been ſo happily excluded? But I am aſhamed to dwell ſo long upon trifles.
The ſum of the matter is this; the number of the Comets is certainly very great; their motions are perfectly regular; and obſerve the ſame laws with thoſe of the Planets. The orbits in which they move are conic ſections, and thoſe very eccentric. They move every way towards all parts of the Heavens, and paſs through the planetary regions with all poſſible freedom, and their motion is often contrary to the order of the ſigns. Theſe phænomena are moſt evidently confirmed by aſtronomical obſervations, and cannot be accounted for by vortices. Nay indeed they are utterly irreconcilable with the vortices of the Planets. There can be no room for the motions of the Comets; unleſs the celeſtial ſpaces be entirely cleared of that fictitious matter.
For if the Planets are carried about the Sun in vortices; the parts of the vortices which immediately ſurround every Planet muſt be of the ſame
denſity with the Planet, as was ſhewn above. There-
