Kinetic Theory, Volume I: The Nature of Gases and of Heat deals with kinetic theory and the nature of gases and heat. A comprehensive account of the life, works, and historical environment of a number of scientists such as Robert Boyle and Hermann von Helmholtz is presented. This volume is comprised of 11 chapters and begins with an overview of the caloric theory, the principle of conservation of energy, the ""virial theorem,"" and atomic magnitudes. The discussion then turns to the qualitative atomic theory of the ""spring"" of the air, proposed by Robert Boyle; Isaac Newton's repulsion theory; Daniel Bernoulli's thery on the properties and motions of elastic fluids, especially air; and George Gregory's theory on the existence of fire. Subsequent chapters focus on Robert Mayer's theory on the forces of inorganic nature; James Joule's theory on matter, living force, and heat; Hermann von Helmholtz's theory on the conservation of force; and Rudolf Clausius's theory on the nature of heat. James Clerk Maxwell's dynamical theory of gases is also examined. This book is written primarily for students and research workers in physics, as well as for historians of science.