The year of Saturn is completed when he has had his circulation in the space of thirty solar years; of Jupiter in twelve; of Mars in two, of the sun in twelve months; in so many Mercury and Venus, the spaces of their circulation being equal; of the moon in thirty days, in which time her course from her prime to her conjunction is finished. As to the great year, some make it to consist of eight years solar, some of nineteen, others of fifty-nine. Heraclitus, of eighteen thousand. Diogenes, of three hundred and sixty-five such years as Heraclitus assigns. Others there are who lengthen it to seven thousand seven hundred and seventy-seven years. BOOK III. In my two precedent treatises having in due order taken a compendious view and given an account of the celestial bodies, and of the moon which divides between them and the terrestrial, I must now convert my pen to discourse in this third book of Meteors, which are beings above the earth and below the moon, and are extended to the site and position of the earth, which is supposed to be the centre of the sphere of this world; and from thence will I take my beginning. CHAPTER I. OF THE GALAXY, OR THE MILKY WAY. It is a cloudy circle, which continually appears in the air, and by reason of the whiteness of its colors is called the galaxy, or the milky way. Some of the Pythagoreans say that, when Phaëton set the world on fire, a star falling from its own place in its circular passage through the region caused an inflammation. Others say that originally it was the first course of the sun; others, that it is an image as in a looking-glass, occasioned by the sun’s reflecting its beams towards the heavens, and this appears in the clouds and in the rainbow. Metrodorus, that it is merely the solar course, or the motion of the sun in its own circle. Parmenides, that the mixture of a thick and thin substance gives it a color which resembles milk. Anaxagoras, that the sun moving under the earth and not being able to enlighten every place, the shadow of the earth, being cast upon the part of the heavens, makes the galaxy. Democritus, that it is the splendor which ariseth from the coalition of many small bodies, which, being firmly united amongst themselves, do mutually enlighten one another. Aristotle, that it is the inflammation of dry, copious, and coherent exhalations, by which the fiery train, whose seat is beneath the ether and the planets, is produced. Posidonius, that it is a combination of fire, of rarer substance than the stars, but denser than light. CHAPTER II. OF COMETS AND SHOOTING FIRES, AND THOSE WHICH RESEMBLE BEAMS.