Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/38

Rh parabolic curves. Then ee how eaily he may account for the deflexion of the tone above poken of. The tone, ays he, floats in this ubtile fluid, and following its motion, can't chue but decribe the ame figure. But the fluid moves in parabolic curves; and therefore the tone mut move in a parabola of coure. Would not the acutenes of this philoopher be thought very extraordinary, who could deduce the appearances of nature from mechanical caues, matter and motion, o clearly that the meanet man may undetand it? Or indeed hould not we mile to ee this new Galileo taking o much mathematical pains to introduce occult qualities into philoophy, from whence they have been o happily excluded? But I am ahamed to dwell o long upon trifles.

The um of the matter is this; the number of the Comets is certainly very great; their motions are perfectly regular; and oberve the ame laws with thoe of the Planets. The orbits in which they move are conic ections, and thoe very eccentric. They move every way towards all parts of the Heavens, and pas through the planetary regions with all poible freedom, and their motion is often contrary to the order of the igns. Thee phænomena are mot evidently confirmed by atronomical obervations, 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; unles the celetial paces 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 urround every Planet mut be of the ame denity with the Planet, as was hewn above.