This book, authored by Prof. George D. Birkhoff, is a significant addition to the American Mathematical Society Colloquium Publications series. It covers the material presented in Prof. Birkhoff's 1920 Colloquium Lectures at Chicago, focusing on formal aspects of theoretical dynamics. The book introduces Lagrangian systems and discusses special integrals of equations, extending beyond Hamiltonian systems to include general Pfaffian equations. It also covers the normalization of equations, stability of periodic motions, and the existence of periodic motions near stable periodic motions. The final chapter addresses the "problem of three bodies." The book is rigorous and includes original contributions, making it a valuable resource in the field. By Prof. Léon Robin, this book is part of the "History of Civilisation" series and aims to systematize and make accessible modern research in social studies. It is praised for its erudition and clear expression, with a focus on discerning interpretation and rigorous characterization of doctrines and systems. The book highlights the contrasting influences of Plato and Aristotle, emphasizing the importance of critical inquiry over mere elaboration and presentation. By Prof. Dr. W. Swietoslawski, this volume is the seventh in a series on general chemistry. It covers experimental methods and the analysis of thermochemical data, particularly in organic compounds. The book includes sections on calorimetry, thermochemical measurements, and the thermochemistry of atomic linkages. The last section, which summarizes thermochemical data, is of particular interest to both organic and inorganic chemists. By John Gordon Thomson and Andrew Robertson, this manual is intended for medical professionals. It provides a clear and concise overview of protozoology, suitable for those without extensive research experience. The book is structured to be accessible and practical for medical practitioners.This book, authored by Prof. George D. Birkhoff, is a significant addition to the American Mathematical Society Colloquium Publications series. It covers the material presented in Prof. Birkhoff's 1920 Colloquium Lectures at Chicago, focusing on formal aspects of theoretical dynamics. The book introduces Lagrangian systems and discusses special integrals of equations, extending beyond Hamiltonian systems to include general Pfaffian equations. It also covers the normalization of equations, stability of periodic motions, and the existence of periodic motions near stable periodic motions. The final chapter addresses the "problem of three bodies." The book is rigorous and includes original contributions, making it a valuable resource in the field. By Prof. Léon Robin, this book is part of the "History of Civilisation" series and aims to systematize and make accessible modern research in social studies. It is praised for its erudition and clear expression, with a focus on discerning interpretation and rigorous characterization of doctrines and systems. The book highlights the contrasting influences of Plato and Aristotle, emphasizing the importance of critical inquiry over mere elaboration and presentation. By Prof. Dr. W. Swietoslawski, this volume is the seventh in a series on general chemistry. It covers experimental methods and the analysis of thermochemical data, particularly in organic compounds. The book includes sections on calorimetry, thermochemical measurements, and the thermochemistry of atomic linkages. The last section, which summarizes thermochemical data, is of particular interest to both organic and inorganic chemists. By John Gordon Thomson and Andrew Robertson, this manual is intended for medical professionals. It provides a clear and concise overview of protozoology, suitable for those without extensive research experience. The book is structured to be accessible and practical for medical practitioners.