This book describes the evolution of the scientific theory of gearing from the pre-Eulerian period to the present day. It presents systematically the main achievements in this field of mechanical engineering, i.e., to discuss each significant achievement in the kinematic geometry of gearing and to associate each achievement with the name of the gear scientist who first to discovered the corresponding achievement. The book examines three periods in the development of gear theory and technology: The pre-Eulerian period of the development of art of designing gears The time when Leonhard Euler obtained the first fundamental result in the gear theory The post-Eulerian period in the development of the gear science The discussion concludes with a preliminary chronology of the development of the scientific theory of gearing. Provides thorough contextual explanation of the scientific theory of gearing Covers all known significant achievements in the field of kinematic geometry of gearing Maximizes reader understanding of gear manufacturing and the state of the art of gear design at the in the 21st century.