CONTENTS. xi 



SECTION X. 



Rotation of the Earth invariable Decrease in the Earth's mean Tempera- 

 ture Earth originally in a state of Fusion Length of Day constant 



Decrease of Temperature ascribed by Sir John Herschel to the varia- 

 tion in the Excentricity of the Terrestrial Orbit Difference in the 

 Temperature of the two Hemispheres erroneously ascribed to the Excess 

 in the Length of Spring and Summer in the Southern Hemisphere ; attri- 

 buted by Sir Charles Lyell to the Operation of existing Causes Three 

 principal Axes of Rotation Position of the Axis of Rotation on the 

 Surface of the Earth invariable Ocean not sufficient to restore the 

 Equilibrium of the Earth if deranged Its Density and mean Depth 



Internal Structure of the Earth Page 71 



SECTION XI. 



Precession and Nutation Their Effects on the Apparent Places of the 

 Fixed Stars 79 



SECTION XII. 



Mean and Apparent Sidereal Time Mean and Apparent Solar Time 

 Equation of Time English and French Subdivisions of Time Leap 

 Year Christian Era Equinoctial Time Remarkable Eras de- 

 pending upon the Position of the Solar Perigee Inequality of the 

 Lengths of the Seasons in the two Hemispheres Application of Astro- 

 nomy to Chronology English and French Standards of Weights and 

 Measures . . 83 



SECTION XIII. 



Tides Forces that produce them Origin and Course of Tidal Wave 

 Its Speed Three kinds of Oscillations in the Ocean The Semidiurnal 

 Tides Equinoctial Tides Effects of the Declination of the Sun and 

 Moon Theory insufficient without Observation Direction of the 

 Tidal Wave Height of Tides Mass of Moon obtained from her 

 Action on the Tides Interference of Undulations Impossibility of a 

 Universal Inundation Currents 91 



SECTION XIV. 



Molecular Forces Permanency of the ultimate Particles of Matter 

 Interstices Mossotti's Theory Rankin's Theory of Molecular Vor- 

 tices Gases reduced to Liquids by Pressure Gravitation of Particles 

 Cohesion Crystallization Cleavage Isomorphism Minuteness 

 of the Particles Height of Atmosphere Chemical Affinity Definite 

 Proportions and Relative Weights of Atoms Faraday's Discovery with 

 regard to Affinity Capillary Attraction 102 



