Title: A discourse on comets. Containing, a brief description of the true system of the world, And An Enumeration of all the Discoveries which have been yet made concerning those temporary Appearances, With respect to their Orbits, Forms, Velocity, Magnitudes, Distances, Tails, &c. Particularly that whose Return is expected in this or the following Year. Extracted from the writings of Sir Isaac Newton, and other astronomers. To which is added, the opinion of that illustrious author, concerning the use of comets, the origin of matter; and his definition of the supreme being of the universe. Collected by J. L. Cowley, Mathematician.