CONTENTS. 



INTRODUCTION 



SECTION I. 



Attraction of a Sphere Form of Celestial Bodies Terrestrial Gravi- 

 tation retains the Moon in her Orbit The Heavenly Bodies move in 

 Conic Sections Gravitation Proportional to Mass Gravitation of 

 the Particles of Matter Figure of the Planets How it affects the 

 Motions of their Satellites Rotation and Translation impressed by the 

 same Impulse Motion of the Sun and Solar System ...... 4 



SECTION II. 



Elliptical Motion Mean and True Motion Equinoctial Ecliptic 

 Equinoxes Mean and True Longitude Equation of Centre In- 

 clination of the Orbits of Planets Celestial Latitude Nodes 

 Elements of an Orbit Undisturbed or Elliptical Orbits Great In- 

 clination of the Orbits of the New Planets Universal Gravitation the 

 Cause of Perturbations in the Motions of the Heavenly Bodies Problem 

 of the Three Bodies Stability of Solar System depends upon the Pri- 

 mitive Momentum of the Bodies 8 



SECTION III. 



Perturbations, Periodic and Secular Disturbing Action equivalent to 

 three Partial Forces Tangential Force the cause of the Periodic In- 

 equalities in Longitude, and Secular Inequalities in the Form and Position 

 of the Orbit in its own Plane Radial Force the cause of Variations in 

 the Planet's Distance from the Sun It combines with the Tangential 

 Force to produce the Secular Variations in the Form and Position of the 

 Orbit in its own Plane Perpendicular Force the cause of Periodic 

 Perturbations in Latitude, and Secular Variations in the Position of the 

 Orbit with regard to the Plane of the Ecliptic Mean Motion and 

 Major Axis Invariable Stability of System Effects of a Resisting 

 Medium Invariable Plane of the Solar System and of the Universe 

 G reat Inequality of Jupiter and Saturn , 13 



b 3 



