Heraclides, native of Pontus, that it is a lofty cloud inflamed by a sublime fire.

The like causes he assigns to the bearded comet, to those circles that are seen about the sun or stars, or those meteors which resemble pillars or beams, and all others which are of this kind.

This way unanimously go all the Peripatetics, holding that these meteors, being formed by the clouds, do differ according to their various configurations.

Epigenes, that a comet arises from a rising of spirit or wind, mixed with an earthy substance and set on fire.

Boethus, that it is a phantasy presented to us by fiery air.
Diogenes, that comets are stars.