CHAPTER II.

THE GENERATION OF COSMICAL HEAT. 11 Conservation of Force—Indestructibility of Force—Its Convertibility into Heat—Dawn of the Doctrine—Mayer’s Deductions—Joule’s Experiments—Mechanical Equivalent of Heat—Gravitation the Source of Cosmical Heat—Calculations of Mayer and Helmholtz—The Moon as an Incandescent Sphere—Not necessarily Burning—Loss of Heat by Radiation—Cooling of External Crust—Commencement of Selenological History