Epicurus thinks that bodies are not to be limited; but the first bodies, which are simple bodies, and all those composed of them, all acknowledge gravity; that all atoms are moved, some perpendicularly, some obliquely; some are carried aloft either by direct impulse or with vibrations. CHAPTER XIII. OF THOSE THINGS THAT ARE LEAST IN NATURE. Empedocles, precedent to the four elements, introduceth the most minute bodies which resemble elements; but they did exist before the elements, having similar parts and orbicular. Heraclitus brings in the smallest fragments, and those indivisible. CHAPTER XIV. OF FIGURES. A figure is the exterior appearance, the circumscription, and the boundary of a body. The Pythagoreans say that the bodies of the four elements are spherical, fire being in the supremest place only excepted, whose figure is conical. CHAPTER XV. OF COLORS. Color is the visible quality of a body. The Pythagoreans called color the outward appearance of a body. Empedocles, that which is consentaneous to the passages of the eye. Plato, that they are fires emitted from bodies, which have parts harmonious for the sight. Zeno the Stoic, that colors are the first figurations of matter. The Pythagoreans, that colors are of four sorts, white and black, red and pale; and they derive the variety of colors from the diversity of the elements, and that seen in animals also from the variety of food and the air in which they live and are bred. CHAPTER XVI. OF THE DIVISION OF BODIES. The disciples of Thales and Pythagoras grant that all bodies are passible and divisible unto infinity. Others hold that atoms and indivisible parts are there fixed, and admit not of a division into infinity. Aristotle, that all bodies are potentially but not actually divisible into infinity. CHAPTER XVII. HOW BODIES ARE MIXED AND CONTEMPERATED ONE WITH ANOTHER. The ancient philosophers held that the mixture of elements proceeded from the alteration of qualities; but the disciples of Anaxagoras and Democritus say it is done by apposition. Empedocles composes the elements of still smaller bulks, those which are the most minute and may be termed the elements of elements. Plato assigns three bodies (but he will not allow these to be elements, nor properly so called), air, fire, and water, which are mutable into one another; but the earth is mutable into none of these. CHAPTER XVIII. OF A VACUUM. All the natural philosophers from Thales to Plato rejected a vacuum. Empedocles says that there is nothing of a vacuity in nature, nor any thing superabundant. Leucippus, Democritus, Demetrius, Metrodorus, Epicurus, that the atoms are infinite in number; and that a vacuum is infinite in magnitude. The Stoics, that within the compass of the world there is no vacuum, but beyond it the vacuum is infinite. Aristotle,[42] that the vacuum beyond the world is so great that the heaven has liberty to breathe into it, for the heaven is fiery.