One of the great masterpieces of theoretical physics, this classic work contains a comprehensive exposition of the kinetic theory of gases that is still relevant today, nearly 100 years after its first publication. Although the modifications of quantum mechanics have rendered some parts of the work obsolete, many of the topics dealt with still yield to the classical-mechanics approach outlined by Boltzmann; moreover, a variety of problems in aerodynamics, nuclear reactors, and thermonuclear power generation are best solved by Boltzmann's famous transport equation. The work is divided into two parts: Part I deals with the theory of gases with monatomic particles, whose dimensions are negligible compared to the mean free path. Topics include molecules as elastic spheres and as centers of force, external forces and visible motions of the gas and the repelling force between molecules. Part II covers van der Waals' theory, the principles of general mechanics needed for a gas theory, gases with compound molecules, derivation of van der Waals' equation by means of the virial concept, theory of dissociation and supplements to the laws of thermal equilibrium in gases with compound molecules. Combining rigorous mathematical analysis with pragmatic treatment of physical and chemical applications, Lectures on Gas Theory was the standard work on kinetic theory in the first quarter of the 20th century. It remains "one of the greatest books in the history of exact sciences." ― Mark Kac.