Printed By Spottiswoode AND CO. NEW-STREET SQUARE AND PARLIAMENT STREET SIXTH EDITION, VOL. 1. LONDON: LONGMANS, GREEN, AND CO. 1879. All rights reserved. PREFACE TO THE SIXTH EDITION. VOL. I. INORGANIC NATURE. I. THE CONSTITUTION OF NATURE. II. RADIATION. 1. Visible and Invisible Radiation. 2. Origin and Character of Radiation. The Aether. 3. The Atomic.