indivisible Atoms, and that the simple Particles of Light are Atoms of that kind. Discoveries continued. Chapter XI Of the Rainbow; that Phenomenon a necessary Effect of the Laws of Refrangibility. Chapter XII New Discoveries touching the Cause of Colours, which confirm the preceding Doctrine; Demonstration that Colours are occasioned by the Density and Thickness of the Parts of which Bodies are composed (or the Thickness of the Parts that compose the Surfaces only). Chapter XIII Consequences of these Discoveries. The mutual Action of Bodies upon Light. Chapter XIV Of the Resemblance between the seven Primitive Colours and the seven Notes in Musick. Chapter XV Introductory Ideas concerning Gravity and the Laws of Attraction: That the Opinion of a subtil Matter, Vortices, and a Plenitude, ought to be rejected (But not that subtile Aether which Sir Isaac makes the Cause of Attraction, Refraction, Animal Motion, &c. which pervades the Universe). Chapter XVI That the Vortices and Plenitude of Descartes are impossible, and consequently that there is some other Cause of Gravity. Chapter XVII What is meant by Vacuity and Space, without which there could be neither Gravity nor Motion. Chapter XVIII Gravitation demonstrated from the Discoveries of Galileo and Newton: That the Moon revolves in her Orbit by the Force of this Gravitation. Chapter XIX That Gravitation and Attraction direct all the Planets in their Courses. Chapter XX Demonstrations of the Laws of Gravitation, drawn from the Rules of Kepler: That one of these Laws of Kepler demonstrates the Motion of the Earth. Chapter XXI New Proofs of Attraction. That the Inequalities of the Motion and Orbit of the Moon are necessarily the Effects of Attraction. Chapter XXII New Proofs and New Effects of Gravitation. That this Power is in every Particle of Matter. Discoveries dependent on this Principle. Chapter XXIII The Theory of our Planetary World. Chapter XXIV Of the Zodiacal Light, the Comets, and the fixed Stars. Chapter XXV Of the second Inequalities of the Motion of the Satellites, and the Phaenomena that depend thereon. Glossary Explanations of the hard Words used in this Treatise. References External links 1738 books Works by Voltaire