Based on author's American Mathematical Society Colloquium lectures, September 5-8, 1920.
Revised by Jurgen Moser, with new bibliographical references and an addendum.
Includes bibliographical references and index.
Physical aspects of dynamical systems -- Variational principles and applications -- Formal aspects of dynamics -- Stability of periodic motions -- Existence of periodic motions -- Application of Poincaré's geometric theorem -- General theory of dynamic systems -- The case of two degrees of freedom -- The problem of three bodies.