Written by J. Willard Gibbs, the most distinguished American mathematical physicist of the nineteenth century, this book was the first to bring together and arrange in logical order the works of Clausius, Maxwell, Boltzmann, and Gibbs himself. The lucid, advanced-level text remains a valuable collection of fundamental equations and principles. Topics include the general problem and the fundamental equation of statistical mechanics, the canonical distribution of the average energy values in a canonical ensemble of systems, and formulas for evaluating important functions of the energies of a system. Additional discussions cover maximum and minimal properties of distribution in phase, a valuable comparison of statistical mechanics with thermodynamics, and many other subjects.