Observational Sciences. Judgment affected by Scale. Terrestrial Magnetism. Existence of Potential. Separation of internal and external Causes. Diurnal Variation. Magnetic Storms. Their causes. Solar In?uence. Theories of Secular Variation. Atmospheric Electricity. Negative Charge of Earth. Ionization of Air. Origin of Atmospheric Electricity. Electric Charge of Rain. Ebert's Theory. Cause of Thunderstorms. The Age of the Earth. Rigidity of Earth. Displace ment of Axis. Gravitation. Identity of Molecules of the same kind.