Comet, a member of the solar system under control of the sun, consisting of a bright nucleus within a nebulous envelope, generally extended into a tail on the rear of its orbit, which is extremely eccentric, pursuing its course with a velocity which increases as it approaches the sun, and which diminishes as it withdraws from it; these bodies are very numerous, have their respective periods of revolution, which have been in many cases determined by observation.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Comenius, John Amos * Comines