TRAJECTORY

, a term often used generally for the path of any body moving either in a void, or in a medium that resists its motion; or even for any curve passing through a given number of points. Thus Newton, Princip. lib. 1, prob. 22, proposes to describe a Trajectory that shall pass through five given points.

Trajectory of a Comet, is its path or orbit, or the line it describes in its motion. This path, Hevelius, in his Cometographia, will have to be very nearly a right line; but Dr. Halley concludes it to be, as it really is, a very excentric ellipsis; though its place may often be well computed on the supposition of its being a parabola.—Newton, in prop. 41 of his 3d book, shews how to determine the Trajectory of a comet from three observations; and in his last prop. how to correct a Trajectory graphically described.