Anaxagoras, Democritus, and Cleanthes say that all the stars have their motion from east to west. Alcmaeon and the mathematicians, that the planets have a contrary motion to the fixed stars, and in opposition to them are carried from the west to the east. Anaximander, that they are carried by those circles and spheres on which they are placed. Anaximenes, that they are turned under and about the earth. Plato and the mathematicians, that the sun, Venus, and Mercury hold equal measures in their motions. CHAPTER XVII. WHENCE DO THE STARS RECEIVE THEIR LIGHT? Metrodorus says that all the fixed stars derive their light from the sun. Heraclitus and the Stoics, that earthly exhalations are those by which the stars are nourished. Aristotle, that the heavenly bodies require no nutriment, for they being eternal cannot be obnoxious to corruption. Plato and the Stoics, that the whole world and the stars are fed by the same things. CHAPTER XVIII. WHAT ARE THOSE STARS WHICH ARE CALLED THE DIOSCURI, THE TWINS, OR CASTOR AND POLLUX? Xenophanes says that those which appear as stars in the tops of ships are little clouds brilliant by their peculiar motion. Metrodorus, that the eyes of frighted and astonished people emit those lights which are called the Twins. CHAPTER XIX. HOW STARS PROGNOSTICATE, AND WHAT IS THE CAUSE OF WINTER AND SUMMER. Plato says that the summer and winter indications proceed from the rising and setting of the stars, that is, from the rising and setting of the sun, the moon, and the fixed stars. Anaximenes, that the rest in this are not at all concerned, but that it is wholly performed by the sun. Eudoxus and Aratus assign it in common to all the stars, for thus Aratus says:-- Thund'ring Jove stars in heaven hath fixed, And them in such beauteous order mixed, Which yearly future things predict. CHAPTER XX. OF THE ESSENCE OF THE SUN.